Implants in Clinical Dentistry 2002 - Palmer

Implants in Clinical Dentistry

Implants in ClinicalDentistry

Richard M Palmer PhD, BDS, FDS, RCS (Eng), FDS RCS (Ed)Professor of Implant Dentistry and Periodontology, Guy’s, Kings and St Thomas’ Hospitals Medical and Dental Schools, London, SE1 9RT, UK

Brian J Smith BDS, MSc, FDS RCS (Eng)Consultant in Restorative Dentistry, Unit of Restorative Dentistry,Guy’s and St Thomas’ Hospitals Trust, London, SE1 9RT, UK

Leslie C Howe BDS, FDS RCS (Eng)Consultant in Restorative Dentistry, Guy’s and St Thomas’ Hospitals Trusts and Specialist in Restorative Dentistry and Prosthodontics, 21 Wimpole Street, London W1M 7AD, UK

Paul J Palmer BDS, MSc, MRD RCS (Eng)Specialist in Periodontics, 21 Wimpole Street, London W1M 7AD andPostgraduate Tutor in Implant Surgery, Guy’s, Kings and St Thomas’ Hospitals Medical and Dental Schools, London, SE1 9RT, UK

M A RT I N D U N I T Z

Preface vii

Acknowledgements ix

Part I—Overview

1 Overview of implant dentistry 3

Part II—Planning

2 Treatment planning: general considerations 27

3 Single tooth planning in the anterior region 35

4 Single tooth planning for molar replacements 47

5 Fixed bridge planning 53

6 Diagnosis and treatment planning for implant dentures 69

Part III—Surgery

7 Basic factors in implant surgery 85

8 Flap design for implant surgery 97

9 Surgical placement of the single tooth implant in the anterior maxilla 105

10 Implant placement for fixed bridgework 115

11 Immediate and early replacement implants 123

12 Grafting procedures for implant placement 131

Part IV—Prosthodontics

13 Single tooth implant prosthodontics 157

14 Fixed bridge prosthodontics 183

15 Implant denture prosthodontics 215

Part V—Complications and Maintenance

16 Single tooth and fixed bridge 235

17 Implant dentures 251

Index 263

C O N T E N T S

vi CONTENTS

This book is based upon our combined experi-ences of working together in the treatment ofpatients with dental implant prostheses at Guy'sHospital and in private practice over the last 10years. While the chapters are not attributed tospecific authors, the surgical chapters are mainlythe work of Richard and Paul Palmer; the implantdenture chapters, Brian Smith; and the fixedprosthodontics, Leslie Howe. Our initial experi-ences were with the Brånemark system, whichestablished a benchmark in implant treatment,with high success rates using meticulous tech-niques. It was immensely valuable to use thissystem at a time when it rapidly developed toallow sophisticated treatment of the completeclinical spectrum. Working in an academic institute

we felt that it was essential to gain experience inother leading implant systems to allow compari-son and to educate ourselves and our students.We were thus able to appreciate some of thefeatures of other systems such as single stageimplant surgery and the development of implantsurfaces which gave the potential for more rapidosseointegration and earlier loading. We were alsoone of the initial teams to evaluate the Astra TechST implant. We believe that the four implantsystems (Astra Tech, Brånemark/Nobel Biocare,Frialit and ITI Straumann) described in this bookcover most of the important features of modernimplant design and that the information containedwithin this text could apply to many more systemsthat are available today.

Richard M Palmer PhD, BDS, FDS RCS(Eng), FDS RCS(Ed)

Brian J SmithBDS, MSc, FDS RCS(Eng)

Leslie C HoweBDS, FDS RCS(Eng)

Paul J PalmerBDS, MSc, MRD RCS(Eng)

P R E FA C E

We would like to thank the following people andpublishers:

Dr David Radford for producing the scanningelectron microscopy images in figures 1.9, 1.10and 1.11.

Dr Michael Fenlon for help with the case illus-trated in figure 5.5.

Dr Claire Morgan for providing figure 15.19.

Dr Paul Robinson for help with the maxillofacialsurgical aspects of treatment in the case illus-trated in figure 12.14.

The UK subsidiaries of Astra Tech, Frialit, NobelBiocare and ITI Straumann for providing illustra-tions of some components illustrated in chapter1.

Munksgaard International Publishers Ltd, Copen-hagen, Denmark, for permission to reproducefigure 1.24 which was taken from Cawood JI andHowell RA, International Journal of Oral andMaxillofacial Surgery, 20:75, 1991.

The British Dental Journal and MacmillanPublishers for permission to reproduce figures2.1, 2.4, 5.7, 5.20 and 10.1 from A Clinical Guideto Implants in Dentistry (ed RM Palmer).

Image Diagnostic Technology, London, UK forFigures 5.8, 5.9 and 5.10.

The highly skilled technical staff at Guy's Hospi-tal, Kedge and Quince London W1 and Brookerand Hamill, London W1.

A C K N O W L E D G E M E N T S

PA R T I

Overview

Introduction

The development of endosseous osseointegrateddental implants has been very rapid over the lasttwo decades and there are now many implantsystems available that will provide the clinicianwith:

• a high degree of predictability in the attain-ment of osseointegration

• versatile surgical and prosthodontic protocols• design features that facilitate ease of treat-

ment and aesthetics• a low complication rate and ease of mainte-

nance• published papers to support the manufactur-

ers’ claims• a reputable company with good customer

support

There is no perfect system and the choice maybe bewildering. It is easy for a clinician to beseduced into believing that a new system isbetter or less expensive. All implant treatmentdepends upon a high level of clinical training andexperience. Much of the cost of treatment is notsystem dependent but relates to clinical time andlaboratory expenses.

There are a number of published versions ofwhat constitutes a successful implant or implantsystem. For example, Albrektsson et al. (1986)proposed the following criteria for minimumsuccess:

1. An individual, unattached implant is immobilewhen tested clinically.

2. Radiographic examination does not revealany peri-implant radiolucency.

3. After the first year in function, radiographicvertical bone loss is less than 0.2 mm perannum.

4. The individual implant performance is charac-terized by an absence of signs and symptomssuch as pain, infections, neuropathies, paraes-thesia, or violation of the inferior dental canal.

5. As a minimum, the implant should fulfil theabove criteria with a success rate of 85% atthe end of a 5-year observation period and80% at the end of a 10-year period.

The most definitive criterion is that the implantis not mobile (criterion 1). By definition, osseoin-tegration produces a direct structural andfunctional union between the surrounding boneand the surface of the implant. The implant istherefore held rigidly within bone without anintervening fibrous encapsulation (or periodontalligament) and therefore should not exhibit anymobility or peri-implant radiolucency (criterion2). However, in order to test the mobility of animplant supporting a fixed bridge reconstruction,the bridge has to be removed. This fact haslimited the use of this test in clinical practice andin many long-term studies. Radiographic bonelevels are also difficult to assess because theydepend upon longitudinal measurements from aspecified landmark. The landmark may differwith various designs of implant and is more diffi-cult to visualize in some than others. Forexample, the flat top of the implant in theBrånemark system is easily defined on a well-aligned radiograph and is used as the landmarkto measure bone changes. In most designs ofimplant, some bone remodelling is expected inthe first year of function in response to occlusalforces and establishment of the normal dimen-sions of the peri-implant soft tissues. Subse-quently the bone levels are usually stable on themajority of implants over many years. A smallproportion of implants may show some boneloss and account for the mean figures of boneloss that are published in the literature.

1Overview of implant dentistry

Progressive or continuous bone loss is a sign ofpotential implant failure. However, it is difficultor impossible to establish agreement betweenresearchers/clinicians as to what level of bonedestruction constitutes failure, therefore mostimplants described as failures are those thathave been removed from the mouth. Implantsthat remain in function but do not match thecriteria for success are described as ‘surviving’.

Implants placed in the mandible (particularlyanterior to the mental foramina) enjoy a veryhigh success rate, such that it would be difficultor impossible to show differences between rivalsystems. In contrast, the more demanding situa-tion of the posterior maxilla, where implants ofshorter length are placed in bone of softerquality, may reveal differences between successrates. This remains to be substantiated incomparative clinical trials. Currently there are nocomparative data to recommend one systemover another, but certain design features mayhave theoretical advantages (see section onimplant design).

Patient factors

There are few contraindications to implant treat-ment. The main potential problem areas toconsider are:

• Age• Untreated dental disease• Severe mucosal lesions• Tobacco smoking, alcohol and drug abuse• Poor bone quality• Previous radiotherapy to the jaws• Poorly controlled systemic disease such as

diabetes• Bleeding disorders

Age

The fact that the implant behaves as anankylosed unit restricts its use to individuals whohave completed their jaw growth. Placement ofan osseointegrated implant in a child will resultin relative submergence of the implant restora-tion with growth of the surrounding alveolar

process during normal development. It is there-fore advisable to delay implant placement untilgrowth is complete, this is generally earlier infemales than males, but considerable variationexists. It is usually acceptable to treat patients intheir late teens. Although some growth potentialmay remain in patients in their early twenties,this is less likely to result in an aestheticproblem.

There is no upper age limit to implant treat-ment provided that the patient is fit enough andwilling to be treated. For example, elderlyedentulous individuals can experience consider-able quality of life and health gain with implanttreatment to stabilize complete dentures (seeChapter 6).

Untreated dental disease

The clinician should ensure that all patients arecomprehensively examined, diagnosed andtreated to deal adequately with concurrent dentaldisease.

Severe mucosal lesions

Caution should be exercised before treatingpatients with severe mucosal/gingival lesionssuch as erosive lichen planus or mucousmembrane pemphigoid. When these conditionsaffect the gingiva they are often more problem-atic around the natural dentition and the discom-fort compromises plaque control, adding to theinflammation. Similar lesions can arise aroundimplants penetrating the mucosa.

Tobacco smoking and drug abuse

It is well established that tobacco smoking is avery important risk factor in periodontitis andthat it affects healing. This has been demon-strated extensively in the dental, medical andsurgical literature. A few studies have shown thatthe overall mean failure rate of dental implantsin smokers is approximately twice that in non-smokers. Smokers should be warned of this

4 IMPLANTS IN CLINICAL DENTISTRY

association and encouraged to quit the habit.Protocols have been proposed that recommendsmokers to give up for at least two weeks priorto implant placement and for several weeksafterwards. Such recommendations have notbeen tested adequately in clinical trials and norhas the compliance of the patients. The chanceof the quitter relapsing is disappointingly highand some patients will try to hide the fact thatthey are still smoking. It should also be notedthat reported mean implant failure rates are notevenly distributed throughout the patient popula-tion. Rather, implant failures are more likely tocluster in certain individuals. In our experiencethis is more likely in heavy smokers who have ahigh intake of alcohol. In addition, failure is morelikely in those who have poor-quality bone,which is a possible association with tobaccosmoking. It should be noted also that smokersfollowed in longitudinal studies have beenshown to have more significant marginal boneloss around their implants than non-smokers.Most of these findings have been reported fromstudies involving the Brånemark system, proba-bly because it is one of the best-documented andwidely used systems to date. More data involv-ing other systems would be useful.

Drug abuse may affect the general health ofindividuals and their compliance with treatmentand may therefore be an important contraindica-tion.

Poor bone quality

This is a term often used to denote regions ofbone in which there is low mineralization or poortrabeculation. It is often associated with a thin orabsent cortex and is referred to as type 4 bone(see section on bone factors). It is a normal variantof bone quality and is more likely to occur in theposterior maxilla. Osteoporosis is a condition thatresults in a reduction of the bone mineral densityand commonly affects postmenopausal females,having its greatest effect in the spine and pelvis.The commonly used DEXA (Dual Energy X-RayAbsorptiometry) scans for osteoporosis assess-ment do not generally provide useful clinicalmeasures of the jaws. The effect of osteoporosison the maxilla and mandible may be of littlesignificance in the majority of patients. Many

patients can have type 4 bone quality, particularlyin the posterior maxilla, in the absence of anyosteoporotic changes.

Previous radiotherapy to the jaws

Radiation for malignant disease of the jawsresults in endarteritis, which compromises bonehealing and in extreme cases can lead to osteo-radionecrosis following trauma/infection. Thesepatients requiring implant treatment should bemanaged in specialist centres. It can be helpfulto optimize timing of implant placement inrelation to the radiotherapy and to provide acourse of hyperbaric oxygen treatment. Thelatter may improve implant success particularlyin the maxilla. Success rates in the mandiblemay be acceptable even without hyperbaricoxygen treatment, although more clinical trialsare required to establish the effectiveness of therecommended protocols.

Poorly controlled systemic diseasesuch as diabetes

Diabetes has been a commonly quoted factor toconsider in implant treatment. It does affect thevasculature, healing and response to infection.Although there is limited evidence to suggesthigher failure of implants in well-controlleddiabetes, it would be unwise to ignore this factorin poorly controlled patients.

Bleeding disorders

Bleeding disorders are obviously relevant to thesurgical delivery of treatment and require advicefrom the patient’s physician.

Osseointegration

Osseointegration is basically a union betweenbone and the implant surface (Figure 1.1). It isnot an absolute phenomenon and can be

OVERVIEW OF IMPLANT DENTISTRY 5

measured histologically as the proportion of thetotal implant surface that is in contact with bone.Greater levels of bone contact occur in corticalbone than in cancellous bone, where marrowspaces are often adjacent to the implant surface.Therefore bone with well-formed cortices anddense trabeculation offers the greatest potentialfor a high degree of bone to implant contact. Thedegree of bone contact may increase with time.The precise nature of osseointegration at amolecular level is not fully understood. At thelight microscope level there is a very close

adaptation of the bone to the implant surface. Atthe higher magnifications possible with electronmicroscopy, there is a gap (approximately100 nm wide) between the implant surface andthe bone. This is occupied by an interveningcollagen-rich zone adjacent to the bone and amore amorphous zone adjacent to the implantsurface. Bone proteoglycans may be important inthe initial attachment of the tissues to theimplant surface, which in the case of titaniumimplants consists of a titanium oxide layer,which is defined as a ceramic.


Figure 1.1

(A) Histological section of osseointegration. At the light microscope level the bone appears to be in intimate contact withthe titanium implant surface over a large proportion of the area. Small marrow spaces are visible where bone is not incontact with the implant surface. (B) Higher power micrograph showing almost total bone to implant contact.

A B

It has been proposed that the biologicalprocess leading to and maintaining osseointe-gration is dependent upon the following factors,which will be considered in more detail in thesubsequent sections:

• Biocompatibility• Implant design• Submerged and non-submerged protocols• Bone factors• Loading conditions• Prosthetic loading considerations

Biocompatibility

Most current dental implants (including allsystems considered in this book) are made ofcommercially pure titanium. Titanium has estab-lished a benchmark in osseointegration againstwhich few other materials compare. Relatedmaterials such as niobium are able to produce ahigh degree of osseointegration and, in addition,successful clinical results are reported withtitanium–aluminium–vanadium alloys. The titan-ium alloys have the potential disadvantage ofionic leakage of aluminium into the tissues butthey have the potential to enhance the physi-cal/mechanical properties of the implants. Thiswould be of greater significance in narrow-diameter implants.

Hydroxyapatite-coated implants have thepotential to allow more rapid bone growth ontheir surfaces and they have been recommendedfor use in situations of poorer bone quality. Thereported disadvantages are delamination of thecoating and corrosion with time. More recently,resorbable coatings have been developed thataim to improve the initial rate of bone healingagainst the implant surface, followed by resorp-tion within a short time frame to allow estab-lishment of a bone to metal contact. Hydroxy-apatite-coated implants are not consideredwithin this book because the authors have noexperience of them.

All the implant systems used by the authorsand illustrated in this book are made fromtitanium and therefore are highly comparable inthis respect. The main differences in the systemsare in the design, which is considered in the nextsection.

Implant design

Implant design usually refers to the design of theintraosseous component (the endosseous dentalimplant). However, the design of the implantabutment junction and the abutments is ex-tremely important in prosthodontic managementand maintenance and will be dealt with in aseparate section.

The implant design has a great influence oninitial stability and subsequent function in bone.

The main design parameters are:

• Implant length• Implant diameter• Implant shape• Surface characteristics

Implant length

Implants are generally available in lengths fromabout 6 mm to as much as 20 mm. The mostcommon lengths employed are between 8 and 15mm, which correspond quite closely to normalroot lengths. There has been a tendency to uselonger implants in systems such as Brånemarkcompared with, for example, Straumann. TheBrånemark protocol advocated maximizingimplant length, where possible, to engage bonecortices apically as well as marginally in order togain high initial stability. In contrast, the conceptwith Straumann was to increase the surface areaof shorter implants by design features (e.g.hollow cylinders) or surface treatments (seesection on surface characteristics).

Implant diameter

Most implants are approximately 4 mm indiameter. A diameter of at least 3.25 mm isrecommended to ensure adequate implantstrength. Diameters up to 6.5 mm are available,which are considerably stronger and have amuch higher surface area. They may also engagelateral bone cortices to enhance initial stability.However, they may not be so widely usedbecause sufficient bone width is not commonlyencountered in most patients’ jaws.


Implant shape

Various shapes are used by different manufac-turers:• Brånemark implants are solid screws (3.3, 3.75,

4, 5 or 5.5 mm in diameter) with a thread pitchof 0.6 mm (Figures 1.2 and 1.3). The implants

can be self-tapped owing to the fact that theyhave a cutting end. The original design of theBrånemark implant was not a self-tapper, andin good-quality bone the implant site neededto be tapped prior to implant insertion. Insofter bone (type 4 and possibly type 3) theimplant will develop its own thread passagewithout prior tapping. The original design (andprotocol) is preferred by the authors eventhough it may be slightly more time consum-ing. This is because the self-tapper design hasquite pronounced cutting flutes that do notallow as smooth an entry into the bone site(This feature has been improved in the latestMark 3 design: Nobel Biocare AB, Göteborg,Sweden; Figure 1.2.) Pre-tapping ensures thatthe implant will readily seat to the desiredlevel. If self-tapping implants are used in densebone, the site may have to be made wider witha larger diameter twist drill (or pre-tapped asin the original protocol).

• AstraTech implants are parallel-sided self-tapping solid screws (basically 3.5 mm or4 mm in diameter) with a thread pitch of0.6 mm (Figure 1.4). To allow for successfulseating of the implant, the bone preparationis made with twist drills 0.3 mm less in diame-ter in normal quality bone and 0.15 mmnarrower in hard or dense bone. The singletooth (ST: Astra Meditec AB, Mölndal,


Figure 1.2

The latest design of Nobel Biocare implant (based on theoriginal Brånemark concept) has a self-tapping end. Thestandard implants are 3.75 mm in diameter and availablein a range of lengths from 7 to 20 mm.

Figure 1.3

A narrow-diameter (3.3 mm) Nobel Biocare implant beinginstalled in a narrow maxillary lateral incisor space.

Figure 1.4

AstraTech implants showing the various diameters anddesigns available. The standard implants of 3.5 and4.0 mm are on the left and the single tooth (ST) implantson the right. The ST implants have identical bodies to thestandard implants but have a microthreaded conical collarthat houses an internal anti-rotational double-hexagonelement.

Sweden) implant has a different design in thatthe top part has a microthreaded conicalcollar, which is claimed to distribute stress atthe marginal bone more favourably.

• Straumann implants used to be available ashollow screws, hollow cylinders or solidscrews. The hollow cylinders greatly increasethe available surface area for bone contact butare now only available in a pre-angled design


Figure 1.5

An angled hollow-cylinderStraumann implant specifi-cally recommended foranterior maxillary singletooth replacement. Thisimplant has a titanium-plasma-sprayed surface.

Figure 1.6

A 4.1-mm diameter solid-screw Straumann implant.This particular implant is anaesthetic line implant thathas a reduced height ofpolished collar (1.8 mm, asopposed to 2.8 mm on thestandard implant). Thesurface has been sand-blasted and acid etched.The top of the polishedcollar expands to a diameterof 4.8 mm.

Figure 1.7

The Frialit 2 implants are stepped cylinders and thereforeare more like tapered root forms. The implant on the righthas threads on each of the steps and is recommendedwhere greater stability at placement is required, such asimmediate placement into extraction sockets.

Figure 1.8

The matched drills for the stepped Frialit 2 implants, withlengths of 11, 13 and 15 mm and diameters of 3.8, 4.5,5.5 and 6.5 mm.

for single anterior tooth replacement (Figure1.5). Hollow screws are no longer available (ahigher rate of fracture was observed in hollowdesigns). The solid screws are the only designused by the authors (Figure 1.6). They areavailable in diameters of 3.2, 4.1 and 4.8 mmand have a coarse-thread pitch.

• Frialit implants (Figures 1.7 and 1.8) aretapered, stepped cylinders (3.8, 4.5, 5.5 and6.5 mm diameter at the top). They are there-fore more ‘root form’, with the various diame-ters designed to replace teeth of corres-ponding dimensions. Most implants of thisdesign are pushed or tapped into place. Analternative design has self-tapping threads onthe steps, which requires that the implant isgiven three rotations to seat it.

Surface characteristics

The degree of surface roughness varies greatlybetween different systems. Surfaces that aremachined, grit-blasted, plasma sprayed andcoated are available:

• Brånemark implants have a machined surfaceas a result of the cutting of the screw thread.This has small ridges when viewed at highmagnification (Figure 1.9) and this degree ofsurface irregularity was claimed to be close toideal because smoother surfaces fail toosseointegrate and rougher surfaces are moreprone to ion release and corrosion. This claimis disputed and the other implants listed belowhave rougher surfaces that may favour osseoin-tegration. The 3i implants that were based onthe Brånemark design are available with anacid-etched surface on the threads apical to thefirst 2 mm. Brånemark implants are now alsoavailable with a treated surface (TiUnite).

• AstraTech implants have a roughened surfaceproduced by ‘grit blasting’, in this case withtitanium oxide particles. The resulting surfacehas approximately 5-µm depressions over theentire intraosseous part of the implant. Thissurface has been termed ‘TiO blasted’ (Figure1.10). Comparative tests in experimentalanimals have demonstrated a higher degreeof bone to implant contact and higher torqueremoval forces than machined surfaces.

• Straumann – surfaces were originally plasmasprayed (Figure 1.11). Molten titanium issprayed onto the surface of the implant toproduce a rougher surface than a blasted one.The available surface area is much larger andthis may have advantages in lower qualitybone and enhanced performance of short(under 10 mm) implants. Straumann havedeveloped a newer surface called the SLA(Sand blasted–Large grit–Acid etched: InstitutStraumann AG, Waldenburg, Switzerland;Figure 1.12). This surface has large irregular-ities with smaller ones superimposed on top.It is claimed to have an advantage over theplasma-sprayed surface, with a reduction inhealing time to achieve osseointegration. AllStraumann implants have a highly polishedcollar (2.8 mm long in the standard implant)to allow soft-tissue adaptation because theywere originally designed as a non-submergedsystem (see section on submerged and non-submerged protocols).


Figure 1.9

Electron micrograph of a ‘machined’ implant surface.There are ridges and grooves produced during the machin-ing. The macroscopic appearance can be seen in Figures1.2 and 1.3.


Figure 1.10

(A) AstraTech TiO-blasted surface. This scanning electronmicrograph shows the numerous pits of approximately5 µm.

Figure 1.10

(B) Lower power view showing the TiO-blasted surface onthe thread profiles.

A

B

Figure 1.11

Scanning electron micrograph of the Straumann plasma-sprayed surface at the junction with the polished collar(top).

Figure 1.12

(A) The Straumann SLA surface produces a complex oflarge and small pits providing a large area for osseointe-gration.

A

• Frialit – implants are available in both plasma-sprayed surfaces and acid-etched and grit-blasted/acid-etched surfaces (Figures 1.12 and1.13). The top collar is polished to allow softtissue adaptation.

The optimum surface morphology has yet tobe defined, and some may perform better insome circumstances. By increasing the surfaceroughness there is the potential to increase thesurface contact with bone, but this may be at theexpense of more ionic exchange and surfacecorrosion. Bacterial contamination of the implantsurface also will be affected by the surfaceroughness if it becomes exposed within the

mouth. The current trend is therefore towardsslightly roughened surfaces (blasted/etched).

Implant/abutment design

Most implant systems have a wide range ofabutments for various applications (e.g. singletooth, fixed bridge, overdenture) and techniques(e.g. standard manufactured abutments,prepable abutments, cast-to abutments; seeChapters 13 and 14). However, the design of theimplant abutment junction varies considerably:

• Brånemark – this junction is described as aflat-top external hexagon (Figure 1.14). Thehexagon was designed to allow rotation (i.e.screwing-in) of the implant during placement.It is an essential design feature in single tooth(ST) replacement as an anti-rotational device.The design proved to be very useful in thedevelopment of direct recording of impres-sions of the implant head rather than theabutment, thus allowing evaluation andabutment selection in the laboratory (seeChapter 13). The abutment is secured to theimplant with an abutment screw. The jointbetween implant and abutment is precise butdoes not produce a seal, a feature that doesnot appear to result in any clinical disadvan-tage. The hexagon is only 0.6 mm high and itmay be difficult for the inexperienced clinicianto determine whether the abutment isprecisely located on the implant. The fit istherefore normally checked radiographically,which also requires a good parallelingtechnique for adequate visualization of thejoint. Similar designs of external hexagonimplants have increased the height of thehexagon to 1 mm, making abutment connec-tion easier. However, newer abutment designsfor multiple-connected units (which do notrequire an anti-rotational property) haveabandoned the female part of the hexagon toallow easier connection and avoid problems ofmalalignment (Nobel Biocare multi-unitabutment). The original design concept wasthat the weakest component of the systemwas the small gold screw (prosthetic screw)that secured the prosthesis framework to theabutment, followed by the abutment screw


Figure 1.12

(B) Scanning electron micrograph of the Frialit grit-blastedand acid-etched surface.

Figure 1.13

Scanning electron micrograph of the acid-etched surfacein the Frialit system.

B

and then the implant (Figure 1.15). Thus,overloads leading to component failure shouldbe dealt with more readily (see Chapter 16).

• AstraTech – this design incorporates a conicalabutment fitting into the conical head of theimplant, described by the manufacturers as a‘conical seal’ (Figure 1.16). The taper of thecone is 11°, which is greater than a morsetaper (6°). The abutments self-guide intoposition and are easily placed even in verydifficult locations. It is not usually necessaryto check the localization with radiographs.This design produces a very secure, strongunion. The standard abutments are solid one-piece components, whereas the ST abutmentsand customizable abutments are two-piecewith an abutment screw. The ST implant andabutments feature an internal hexagon anti-rotation design (Figure 1.17).

• Straumann – this implant has a transmucosalcollar, a feature that many of the other sys-tems incorporate in the abutment design. Theabutment/implant junction is therefore oftensupramucosal and the connection and check-


Figure 1.14

The external hexagon at the top of the Brånemark implantshown here immediately after implant placement. Thehexagon was originally used to rotate the implant intoplace, but Nobel Biocare have recently developed a newinserting mechanism within the internal thread.

Figure 1.15

A section through the ‘original’ Brånemark implant stack.At the top, a small gold screw secures the prosthetic goldcylinder to the abutment screw, which in turn holds theabutment onto the implant.

Figure 1.16

Section through an AstraTech stack showing a very goodfit between the abutment and the implant. The interfaceis an internal cone with an angle of 11°.

ing of the fit of the components are easierthan most systems. The aesthetic line implanthas a shorter collar (1.8 mm) to allow submu-cosal placement of the abutment/prosthesisunion but the connection is still easy due tothe internal tapered conical design with anangle of 8° (Figure 1.18).

• Frialit – this has some of the features of thepreviously described systems. Basically, theabutment fits within the implant head but isparallel sided (Figures 1.19 and 1.20). Itfeatures an internal hexagon anti-rotationalsystem and an abutment screw, which alsosecures the prosthesis in screw-retained fixedbridge designs. The junction seal is improvedwith a silicone washer within the assembly(not to be confused with the intra-mobileelement of the IMZ system, which is notconsidered in this book).

Submerged and non-submergedprotocols

The terms submerged and non-submergedimplant protocols were at one time clearly appli-cable to different implant systems. The classicsubmerged system was the original protocol asdescribed by Brånemark. Implants were installedwith the head of the implant (and cover-screw)level with the crestal bone and the muco-


Figure 1.17

A selection of AstraTech single tooth (ST) abutments ofvarious lengths. The lower part shows the anti-rotationalhexagon which fits within the collar of the ST implant. Theconical sides of the abutment fit within the internal coneof the implant head. The top part has an octagonal anti-rotation design to accept the ST crown.

Figure 1.18

The left ‘cut-away’ picture shows the head of the standardsolid-screw Straumann implant, featuring an internalconical design (and anti-rotational grooves) that allows avery precise fit with the solid abutments shown on theright.

Figure 1.19

The internal hexagon of the Frialit 2 (Friatec AG,Mannheim, Germany) implant. The abutments are shownin Figure 1.20.

Figure 1.20

Frialit 2 abutments showing the hexagons that engage the‘hex’ in the implant head.

periosteal flaps closed over the implants and leftto heal for several months (Figure 1.14). This hadseveral theoretical advantages:

1. Bone healing to the implant surface occurredin an environment free of potential bacterialcolonization and inflammation.

2. Epithelialization of the implant–bone interfacewas prevented.

3. The implants were protected from loadingand micromovement, which could lead tofailure of osseointegration and fibrous tissueencapsulation.

The submerged system requires a secondsurgical procedure after a period of bone healingto expose the implant and attach a transmucosalabutment. The initial soft-tissue healing phasewould then take a further period of approxi-mately 2–4 weeks. Abutment selection wouldtake into account the thickness of the mucosaand the type of restoration.

The best example of a non-submerged system

is the Straumann implant. In this case theimplant is designed with an integral smoothcollar that protrudes through the mucosa, allow-ing the implant to remain exposed from the timeof insertion (Figures 1.21). The most obviousadvantage is the avoidance of a second surgicalprocedure and more time for maturation of thesoft-tissue collar at the same time as the bonehealing is occurring. Although this protocol doesnot comply with the three theoretical advantagesenumerated above, the results are equallysuccessful.

However, clinical development and commer-cial competition have lead to many systemsbeing used in either a submerged or non-submerged fashion even though they wereprimarily designed for one or the other. This can,therefore, be somewhat confusing and there maybe some advantage in using a system in themanner for which it was originally devised, i.e. ifyou wish to use a non-submerged protocol whynot choose a system that was designed for thispurpose?


Figure 1.21

(A) A 4.1 mm standard Straumann solid-screw implant has been placed so that the polished collar is above the crest ofthe bone. (B) A closure screw has been placed on top of the implant and the flaps sutured around the collar to leave theimplant exposed. This implant was designed to be used in this ‘non-submerged’ fashion.

A B

Another difference between systems designedfor these protocols is the level of theimplant/abutment junction in relation to thebone. Brånemark, AstraTech and Frialit implants(all primarily submerged systems) are placedwith the head of the implant at the level of thebone. At the time of abutment connection theinterface with the implant is at the same level.

Brånemark implants

During the first year of loading, the bone level inthe Brånemark system recedes to the level of thefirst thread where it should stabilize (Figure 1.22).Three possible reasons for this have beenproposed:

1. The threads of the implant provide a betterdistribution of forces to the surrounding bonethan the parallel-sided head of the implant.

2. The establishment of a biological width forthe investing soft tissues. The junctionalepithelium is relocated on the implant and noton the abutment.

3. The interface between the abutment andimplant is the apposition of two flat surfaces(flat-top implant) that are held together by anabutment screw. This arrangement does notform a perfect seal and may allow leakage ofbacteria or bacterial products from within theabutment/restoration, thereby promoting asmall inflammatory lesion that may affect theapical location of the epithelial attachment.

AstraTech implants

In the AstraTech system the bone marginrecedes slightly apically in the first year in muchthe same way as it does with the Brånemarksystem. However, in other cases, and particularlywith the AstraTech ST implant, the bone mayremain at the level of the implant head (Figure1.23). The biological implication of this is that thejunctional epithelium must be superficial to thisand therefore located on the abutment. Thepossible reasons for this arrangement in contrastto the explanations given above for the loss ofmarginal bone are:

1. The surface of the implant maintains boneheight more effectively in the collar region.This may be due to the blasted surface (TiOblast) or the presence of microthreading (asimilar machined conical head in an oldBrånemark design loses bone to the firstthread).

2. The implant/abutment junction is a conicaljunction – a cone fitting within a cone – that


Figure 1.22

Radiograph of two Brånemark implants after 1 year infunction, showing the bone level to be at the first threadof the implants.

provides a tighter seal, thereby eliminatingmicrobial contamination/leakage at the inter-face and also producing a more mechanicallysound union with no chance of micromove-ment. The stability of the junction may facili-tate positional stability of the junctionalepithelium.

Straumann implantsThe Straumann implant/abutment interface isconceptually different to those described above.The integral smooth transmucosal collar of theimplant is either 2.8 mm (with the standardimplant) or 1.8 mm (with the aesthetic line plusimplant) in length. The implant/abutmentjunction may be submucosal or supramucosal,depending upon the length of the transmucosalcollar, the thickness of the mucosa and the depthto which the implant has been placed. The endof the smooth collar coincides with the start ofthe roughened endosseous portion, which isdesigned to be located at the level of the boneat the implant placement. There is, therefore,potential space for location of the junctionalepithelium and connective tissue zone on thecollar or neck of the implant at a level apical tothe abutment implant junction. Moreover, theimplant/ abutment junction is a highly effectiveconical seal. This should prevent any movementbetween the components and the interface,which would prevent bacterial ingress.

The preceding considerations of the differentimplant systems reveal a number of basic differ-ences:

1. The designed level of the implant/abutmentinterface.

2. The design characteristics at the implantabutment interface in terms of mechanicalstability and seal.

3. The macroscopic features of the implant andits surface characteristics.

4. The level of transition of the surface charac-teristics on the implant surface.

This multitude of features has an impact onthe level of the bone crest and the position ofthe junctional epithelium/connective tissuezone. Despite what appears to be a large andfundamental difference, the bone levelcomparison between the systems is clinicallyand radiographically very small (less than1 mm at baseline values) and the maintenanceof bone levels thereafter is very similar, withall systems reporting highly effective long-term maintenance of bone levels. The differ-ences reported in longitudinal trials are notsufficient to recommend one system overanother.


Figure 1.23

Radiograph of an AstraTech ST implant after 1 year infunction, showing the bone crest at the level of the top ofthe microthreaded collar.

Bone factors

When an implant is first placed in the bonethere should be a close fit to ensure stability.The space between implant and bone is initiallyfilled with a blood clot and serum/boneproteins. Although great care is taken to avoiddamaging the bone, the initial response to thesurgical trauma is resorption, which is thenfollowed by bone deposition. There is a criticalperiod in the healing process at approximately2 weeks post-implant insertion when boneresorption will result in a lower degree ofimplant stability than that achieved initially.

Subsequent bone formation will result in anincrease in the level of bone contact and stabil-ity. The stability of the implant at the time ofplacement is very important and is dependentupon bone quantity and quality as well as theimplant design features considered above. Theedentulous ridge can be classified in terms ofshape (bone quantity) and bone quality.Following the loss of a tooth, the alveolar boneresorbs in width and height (Figure 1.24).

In extreme cases, bone resorption proceeds toa level that is beyond the normal extent of thealveolar process and well within the basal boneof the jaws. Determination of bone quantity is


Figure 1.24

(A) Classification of jaw resorption as described by Cawood and Howell (1991), showing cross-sectional profiles throughdifferent regions: 1 = anterior mandible; 2 = posterior mandible; 3 = anterior maxilla; 4 = posterior maxilla. (B) Exampleof an edentulous maxilla that would be clinically classified as class lll in both the anterior and posterior regions. Althoughthe ridges appear broad, there may be little bone in the posterior region due to extension of the maxillary air sinuses. (C)Example of a severely resorbed edentulous mandible that would be classified as class V or Vl. Confirmation would requireradiographic examination.

A

B

C

1

2

3

4

considered in the clinical and radiographicsections of the treatment planning chapters(Chapters 2–6). Assessing bone quality is rathermore difficult. Plain radiographs can be mislead-ing and sectional tomograms provide a betterindication of medullary bone density (seeChapter 2). In many cases the bone quality canbe confirmed only at surgical preparation of thesite. Bone quality can be assessed by measuringthe cutting torque during preparation of theimplant site. The initial stability (and subsequentstability) of the implant can be quantified usingresonance frequency analysis, which to date hasbeen used mainly in experimental trials.

The simplest categorization of bone quality isthat described by Lekholm and Zarb (1985) astypes 1–4. Type 1 bone is predominantly corticaland may offer good initial stability at implantplacement but is more easily damaged byoverheating during the drilling process, especiallywith sites over 10 mm in depth. Types 2 and 3 arethe most favourable quality of jaw bone forimplant treatment. These types have a well-formedcortex and densely trabeculated medullary spaces(type 2 has more cortex/denser trabeculation thantype 3). Type 4 bone has a thin or absent corticallayer and sparse trabeculation, it offers poor initialimplant stability and fewer cells with goodosteogenic potential to promote osseointegration,and therefore has been associated with higherrates of implant failure.

Healing resulting in osseointegration is highlydependent upon a surgical technique that avoidsheating the bone. Slow drilling speeds, the useof successive incrementally larger sharp drillsand copious saline irrigation aim to keep thetemperature below that at which bone tissuedamage occurs (approximately 47°C for 1 min).Further refinements include cooling the irrigantand using internally irrigated drills. Methods bywhich these factors are controlled are consideredin more detail in the surgical sections (Chapters7–11). Factors that compromise bone quality areinfection, irradiation and heavy smoking, whichhave been dealt with earlier in this chapter.

Loading conditions

Osseointegrated implants lack the viscoelasticdamping system and proprioceptive mecha-

nisms of the periodontal ligament, which effec-tively dissipate and control forces. However,proprioceptive mechanisms may operate withinbone and associated oral structures. Forcesdistributed directly to the bone are usuallyconcentrated in certain areas, particularly aroundthe neck of the implant. Excessive forces appliedto the implant may result in remodelling of themarginal bone, i.e. apical movement of the bonemargin with loss of osseointegration. The exactmechanism of how this occurs is not entirelyclear but it has been suggested that microfrac-tures may propagate within the adjacent bone.Bone loss caused by excessive loading may beslowly progressive. In rare cases it may reach apoint where there is catastrophic failure of theremaining osseointegration or fracture of theimplant. Excessive forces may be detected priorto this stage through radiographic marginal boneloss or mechanical failure of the prosthodonticsuperstructure and/or abutments (see Chapter 16).

It has been shown that normal/well-controlledforces result in increases in the degree of bone toimplant contact and remodelling of adjacenttrabecular structures to dissipate the forces.Adaptation is therefore possible, although osseoin-tegration does not permit movement of theimplant in the way that a tooth may be orthodon-tically repositioned. Therefore, the osseointegratedimplant has proved itself to be a very effectiveanchorage system for difficult orthodontic cases.

Loading protocols

Loading protocols, i.e. the duration of timebetween implant insertion and functional loading,have been largely empirical. The time allowed foradequate bone healing should be based uponclinical trials that test the effects of factors suchas bone quality, loading factors, implant type, etc.However, there are very limited data on theeffects of these complex variables and currentlythere is no accurate measure that precisely deter-mines the optimum period of healing beforeloading can commence. This has not limited thevariety of protocols advocated, including:

• Delayed loading (for 3–6 months)• Early loading (e.g. at 6 weeks)• Immediate loading


Delayed loading

This has been the traditional approach and hasmuch to commend it because it is tried, testedand predictable. Following installation of animplant, all loading is avoided during the earlyhealing phase. Movement of the implant withinthe bone at this stage may result in fibroustissue encapsulation rather than osseointegra-tion. In partially dentate subjects it may be desir-able to provide temporary/provisional pros-theses that are tooth supported. However, inpatients who wear mucosally supporteddentures it has been recommended that theyshould not be worn over the implant area for 1–2weeks. In the edentulous maxilla we wouldnormally advise that a denture is not worn for 1week, and in the mandible for 2 weeks, becauseof the poorer stability of the soft-tissue woundand smaller denture-bearing surface. The origi-nal Brånemark protocol then advised leavingimplants unloaded and buried beneath themucosa for approximately 6 months in themaxilla and 3 months in the mandible, duemainly to differences in bone quality. There aremany data to support the cautious approachadvocated by Brånemark in ensuring a high levelof predictable implant success. However, theoriginal Straumann protocol did not differentiatebetween upper and lower jaw, a 3–monthhealing period being recommended for both.

Early loading

A number of systems now advocate a healingperiod of just 6 weeks before loading. This hasbeen tested by 3i with an implant that has anacid-etched surface (and with a design basedupon the Brånemark implant) and by Straumannwith their SLA surface-treated implants. Somecaution is recommended in that the implantsshould be placed in good-quality bone in situa-tions that are not subjected to high loads. Inthese favourable circumstances the results aregood.

Immediate loading

It has been demonstrated also that immediateloading is compatible with subsequent success-

ful osseointegration, provided that the bonequality is good and the functional forces can becontrolled adequately. In studies on ST restora-tions, the crowns are usually kept out of contactin intercuspal and lateral excursions, therebyalmost eliminating functional loading until adefinitive crown is provided. In contrast, fixedbridgework allows connection of multiple im-plants, providing good splinting and stabiliza-tion, and therefore has been tested in immediateloading protocols, with some success. However,the clinician should have a good reason to adoptthe early/immediate loading protocols particu-larly as they are likely to be less predictable.

The long-term functional loading of theimplant-supported prosthesis is a further impor-tant consideration that will be dealt with in thefollowing section.

Prosthetic loading

considerations

Carefully planned functional occlusal loading willresult in maintenance of osseointegration andpossibly increased bone to implant contact. Incontrast, excessive loading may lead to boneloss and/or component failure. Clinical loadingconditions are largely dependent upon thefactors described below, which are dealt with inmore detail in Chapters 13–15.

The type of prostheticreconstruction

This can vary from an ST replacement in thepartially dentate case to a full arch reconstruc-tion in the edentulous individual. Implants thatsupport dentures may present particularproblems with control of loading because theymay be largely mucosal supported, entirelyimplant supported or a combination of the two.

The occlusal scheme

The lack of mobility in implant-supported fixedprostheses requires the provision of shallow


cuspal inclines and careful distribution of loads inlateral excursions. With ST implant restorations itis important to develop initial tooth contacts onthe natural dentition and to avoid guidance inlateral excursions on the implant restoration.Loading will also depend upon the opposingdentition, which could be natural teeth, anotherimplant-supported prosthesis or a conventionalremovable prosthesis. Surprisingly high forcescan be generated through removable prostheses.

The number, distribution,orientation and design of implants

The distribution of load to the supporting bonecan be spread by increasing the number anddimensions (diameter, surface topography,length) of the implants. The spacing andthree–dimensional arrangement of the individualimplants will also be very important, and is dealtwith in detail in Chapter 5.

The design and properties ofimplant connectors

Multiple implants are usually joined by a rigidframework. This provides good splinting anddistribution of loads between implants. It isequally important that the framework has apassive fit on the implant abutments so thatstresses are not set up within the prostheticconstruction.

Dimensions and location ofcantilever extensions

Some implant reconstructions are designed withcantilever extensions to provide function (andappearance) in areas where provision ofadditional implants is difficult. This may be dueto practical or financial considerations.Cantilever extensions have the potential tocreate high loads, particularly on the implantadjacent to the cantilever. The extent of theleverage of any cantilever should be consideredin relation to the anteroposterior distance

between implants at the extreme ends of thereconstruction. This topic is dealt with in moredetail in Chapter 5.

Patient parafunctional activities

Great caution should be exercised in treatingpatients with known parafunctional activities.

Choice of an implant system

In routine cases it may not matter which systemis chosen; this is particularly the case with treat-ment in the anterior mandible. However, in ourexperience the choice of a system in any partic-ular case depends upon:

• The aesthetic requirements• The available bone height, width and quality

(including whether the site has been grafted)• Perceived restorative difficulties• Desired surgical protocol

Therefore, we would suggest the following:

• In the aesthetic zone, choose an implantwhere the crown contour can achieve goodemergence from the soft tissue with a readilymaintainable healthy submucosal margin.

• Choose an implant of the appropriate lengthand width for the existing crestal morphology.Ensure that choice of a reduced width implantdoes not compromise strength in the particu-lar situation.

• If the site will only accommodate a shortimplant or if the bone quality is poor orgrafted, then choose an implant with a rough-ened surface rather than a machined surface.

• If there are likely to be difficulties withprosthodontic construction due to difficultangulation of the implants, choose a systemthat is versatile enough to cope with thesedifficulties, i.e. has a good range ofsolutions/components.

• If you wish to use a submerged or non-submerged protocol, then choose a systemthat has a proven published record with thatparticular protocol.


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PA R T I I

Planning

Introduction

This chapter provides an overall view of treat-ment planning. The reader should consult thechapters on planning for single tooth restora-tions, fixed bridges and implant dentures formore detailed considerations. The treatment planshould begin with a clear idea of the desired endresult of treatment, which should fulfil thefunctional and aesthetic requirements of thepatient. It is important that these treatment goalsare realistic, predictable and readily maintain-able: realistic means that the end result can bereadily achieved and is not unduly optimistic;

predictable means that there is a very highchance of success of achieving the end resultand that the prosthesis will function satisfactorilyin the long term; and readily maintainable meansthat the prosthesis does not compromise thepatient’s oral hygiene and that the ‘servicing’implications for the patient and the dentist areacceptable.

In this chapter it will be assumed that treat-ment options other than implant-retainedrestorations have been considered and there areno relevant contraindications (see Chapter 1).Evaluation begins with a patient consultation andassessment of the aesthetic and functional

2Treatment planning: generalconsiderations

Figure 2.1

(A) In normal function this patient reveals the incisal halfof the anterior teeth. (B) The same patient smiling revealsmost of the crowns of the teeth, but not the gingivalmargin. (C) The patient with the lips retracted showing agross discrepancy of the gingival margins that is not visiblein normal function and smiling.

C

A B


Figure 2.2

(A) A patient smiling who just reveals the gingival margins and is therefore aesthetically more demanding than the patientin Figure 2.1. (B) The same patient with the lips retracted. The upper right central and lateral incisors are implant-retainedrestorations. The interdental papilla between the two implants has been replaced with prosthetic ‘gum work’ becausethe soft-tissue deficiency was impossible to correct surgically. The aesthetics is satisfactory and the patient is able toadequately clean the area.

A B

C

A BFigure 2.3

(A) A patient with missing maxillary lateral incisor, canineand premolar teeth. The ridge has resorbed in a verticaldirection and towards the palate, resulting in loss ofnormal arch form. (B) The existing prosthesis reveals thatthe apparently large space only accommodates two teeth,and prosthetic gum work is required to make good theridge deficiency. (C) The ridge form at surgery prior tografting shows the vertical loss of bone. The ridge is quitebroad but palatally located.

requirements, and proceeds to more detailedplanning with intraoral examination, diagnosticset-ups and appropriate radiographic examina-tion. At all stages in this process it is importantto establish and maintain good communication(verbal and written) with the patients to ensurethat they understand the proposed treatmentplan and the alternatives.

Aesthetic considerations assume great impor-tance in most patients with missing anteriorteeth. This is an increasing challenge for theclinician and is related to:

1. the degree of coverage of the anterior teeth(and gingivae) by the lips during normalfunction and smiling (Figures 2.1 and 2.2)

2. the degree of ridge resorption, both verticallyand horizontally (Figure 2.3)

3. provision of adequate lip support (Figure 2.4)

The appearance of the planned restoration canbe judged by producing a diagnostic set-up onstudy casts or providing a provisional diagnosticprosthesis. The latter usually proves to be moreinformative for patients because they can judgethe appearance in their own mouths and evenwear the prosthesis for extended periods of time

to adequately assess it. Both diagnostic castsand provisional prosthesis can serve as a modelfor the fabrication of:

1. a radiographic stent to assess tooth positionin relation to the underlying ridge profile(Figure 2.5)

2. a surgical stent (or guide) to assist thesurgeon in the optimal placement of theimplants (Figure 2.6)

3. a transitional restoration during the treatmentprogramme

Ideally, patients should be examined with andwithout their current or diagnostic prosthesis(Figure 2.7) to assess:

• facial contours• lip support• tooth position• how much of the prosthesis is revealed

during function• occlusal relationships

The diagnostic set-up should then be adjusted, ifnecessary. to fulfil the requirements of the desiredend result before proceeding with treatment.

TREATMENT PLANNING: GENERAL CONSIDERATIONS 29

Figure 2.4

(A) Profile of a patient wearing a removable denture with a labial flange to provide lip support. (B) Profile of the samepatient showing poorer lip support following removal of the labial flange.

A B


Figure 2.5

A sectional tomogram taken on a Scanora™ (Soredex Orion,Helsinki, Finland), showing the ridge profile in relation to aradiographic outline of the proposed tooth position (T*) froma radiopaque stent that the patient was wearing.

Figure 2.6

A surgical stent being used to guide the surgeon duringthe implant surgery. This stent is a rigid plastic blow-downmade on a duplicate cast of the diagnostic wax-up. It fitson the adjacent teeth and reproduces the labial contour ofthe tooth that is to be replaced.

Figure 2.7

(A) A young patient with developmentally missing maxil-lary lateral incisors. (B) The same patient wearing an exist-ing partial denture allows assessment of the aestheticsand tooth position. (C) The completed result with twosingle tooth implants replacing the lateral incisors.

A

B

C

Reduced or insufficient function is a commoncomplaint for patients who have removabledentures or who have lost many molar teeth.Functional inadequacy is often a perceivedproblem of the patient and is assessed by inter-view rather than any specific clinical measure.The variation between individuals with regard tohow they perceive this problem is large. A short-ened dental arch extending to the first molar orsecond premolar may provide adequate functionand appearance for some patients. However,missing maxillary premolars (and occasion-ally first molars) often presents an aestheticproblem.

Provisional dentures can be used to clarifythese needs.

Initial clinical examination

Thorough extraoral and intraoral clinical exami-nations should be carried out on all patients toensure the diagnosis of all existing dental andoral disease. The diagnosis and management ofcaries, periodontal disease and endodonticproblems is not the remit of this book and thereader is referred to other more relevant texts.Factors of more specific relevance to implanttreatment are dealt with here and in the relatedmore detailed chapters on single teeth, fixedbridges and implant dentures (Chapters 3–6).

Evaluation of the edentulous spaceor ridge

The height, width and contour of the edentulousridge can be assessed visually and carefullypalpated. The presence of concavities/depres-sions (especially on the labial aspects) is usuallyreadily detected. However, accurate assessmentof the underlying bone width is difficult,especially where the overlying tissue is thick andfibrous. This occurs particularly on the palate,where the tissue may be very thick, and canresult in a very false impression of the boneprofile. The thickness of the soft tissue can bemeasured by puncturing the soft tissue with acalibrated probe after administering local anaes-thetic (ridge mapping).

The profile/angulation of the ridge and itsrelation to the opposing dentition are also impor-tant. The distance between the edentulous ridgeand the opposing dentition should be measuredto ensure that there is adequate room for theprosthodontic components (Figure 2.8).Proclined ridge forms will tend to lead toproclined placement of the implants, which couldaffect loading and aesthetics. Large horizontal orvertical discrepancies (Figure 2.9) between thejaws must be recognized and managementappropriately planned.

The clinical examination of the ridge also allowsassessment of the soft-tissue thickness, which is


Figure 2.8

(A) A patient with missing maxillary anterior teeth in whomthe lower incisors nearly touch the soft-tissue ridge incentric occlusion. The space available for implant compo-nents will also depend upon the level of placement of theimplant heads in the underlying bone. (B) The same patientwith their existing partial denture. The prosthetic teethhave been ridge lapped and no labial flange has beenprovided. This provides further evidence that there hasbeen minimal ridge resorption since loss of the teeth.

A

B

important for the attainment of good aesthetics.Keratinized tissue that is attached to the edentu-lous ridge will also generally provide a better peri-implant soft tissue than non-keratinized mobilemucosa. The length of the edentulous ridge canbe measured to give an indication of the possiblenumber of implants that could be accommodated.This is best done with callipers and a millimetrerule. The space should be measured between thetips of the crowns, the maximum contour of thecrowns and at the level of the edentulous ridge.However, this also requires reference to:

1. radiographs, to allow a correlation with avail-able bone

2. the diagnostic set-up for the proposed toothlocation

3. the edentulous ridges bound by the teeth; theavailable space will also be affected byangulation of adjacent tooth roots, which maybe palpated and assessed radiographically

Initial radiographic screening

A screening radiograph should give the clinicianan indication of:

1. overall anatomy of the maxilla and mandibleand potential vertical height of available bone

2. anatomical anomalies or pathological lesions3. sites where it may be possible to place

implants without grafting, and sites thatwould require grafting

4. restorative and periodontal status of remain-ing teeth

In most instances the dental panoramictomograph (DPT) is the radiograph of choice(Figure 2.10). It provides an image within a pre-defined focal trough of both upper and lowerjaws that gives a reasonable approximation ofbone height, the position of the inferior dentalneurovascular bundle, the size and position ofthe maxillary antra and any pathological condi-tions that may be present. It is therefore an idealview for initial treatment planning and forproviding patient information, because itpresents the image in a way that many patientsare able to understand. Some areas may not beimaged particularly well, but this can beminimized by ensuring that the patient ispositioned correctly in the machine and that theappropriate programme is selected. It providesmore information about associated anatomicalstructures than periapical radiographs but withless fine-detail of the teeth. It should be remem-bered that all DPTs are magnified images (atapproximately �1.3). Distortion also occurs inthe anteroposterior dimension, reducing theirusefulness when planning implant spacing/numbers. The initial screening radiograph allowsselection of the most appropriate radiographicexamination for definitive planning (see Chapters3–6 for single teeth, fixed bridgework andimplant dentures).

Study casts and diagnostic

set-ups

Articulated study casts allow measurements ofmany of the factors considered in the previoussection. The proposed replacement teeth can bepositioned on the casts using either dentureteeth or teeth carved in wax (Figure 2.11). Theformer have the advantage that they can beconverted into a temporary restoration that canbe evaluated in the mouth by clinician andpatient. The diagnostic set-up therefore deter-mines the number and position of the teeth to


Figure 2.9

This patient has suffered extensive loss of mandibularbone following a road traffic accident that resulted in afractured mandible and osteomyelitis. There is now amarked vertical and horizontal discrepancy between thejaws.


Figure 2.10

A dental panoramictomogram provides avery good screeningradiograph to show themajor anatomicalfeatures of the jaws inrelation to the existingteeth. This patient haslarge maxillary airsinuses, resorption ofsome molar teeth,periodontitis andimpacted lower thirdmolars. He requires agreat deal of prepara-tory work beforeimplants can beconsidered.

Figure 2.11

(A) A patient with missing maxillary central incisors following loss of a bridge that had extended from tooth 12 to tooth21. The bridge was sectioned at tooth 12 and tooth 21 was extracted. (B) The intraoral view showing good ridge heightat tooth 11 but loss of vertical height at tooth 21, which was extracted following an endodontic infection. (C) The patientwith a diagnostic denture in place with the lips at rest. (D) The intraoral appearance of the diagnostic denture. There isno labial flange and the discrepancy in ridge height between teeth 11 and 21 is less obvious. This patient was treatedwithout ridge augmentation.

C D

A B

be replaced and their occlusal relationship withthe opposing dentition.

Once the diagnostic set-up has been agreed bythe patient and clinician, it can be used toconstruct a stent (or guide) for radiographicimaging and surgical placement of the implants.The stent/guide can be positioned on the origi-nal cast and, with reference to the radiographs,the clinician can decide upon the optimumlocation, number and type of implants (seeChapter 5).

Basic treatment order

Deciding on the treatment order may be verystraightforward in some circumstances and inothers extremely difficult, particularly for thosecases involving transitional restorations.

A traditional plan may include the following:

1. Examination – clinical and initial radiographic.2. Diagnostic set-up, provisional restoration and

specialized radiographs, if required.3. Discussion of treatment options with the

patient and decision on final restoration.4. Completion of any necessary dental treat-

ment, including:• Extraction of hopeless teeth• Periodontal treatment• Restorative treatment, new restorations

and/or endodontics as required.5. Construction of provisional or transitional

restorations, if required.6. Construction of surgical guide or stent.7. Surgical placement of implants.8. Allow adequate time for healing/osseointe-

gration according to protocol, bone qualityand functional demands.

9. Prosthodontic phase.

Conclusion

It is imperative to consider all treatment optionswith the patient, and during detailed planning itmay become apparent that an alternative solutionis preferred. In all cases the implant treatment

should be part of an overall plan to ensure thehealth of any remaining teeth and soft tissues.Once the goal or end point has been agreed, itshould be possible to work back to formulate thetreatment sequence. The cost of the proposedtreatment plan is also of great relevance. Thegreater the number of implants placed, the higherwill be the cost, and this may therefore place limitson treatment options. In difficult cases it is betterto place additional implants to the minimumnumber required, to take account of possible failureand improved predictability and biomechanics.

Bibliography

Budtz-Jorgensen E (1996). Restoration of the partiallyedentulous mouth—a comparison of overdentures,removable partial dentures, fixed partial dentures andimplant treatment. J Dent 24: 237–44.

Ekestubbe A (1993). Reliability of spiral tomographywith the Scanora technique for dental implantplanning. Clin Oral Implants Res 4: 195–202.

Garber DA (1996). The esthetic implant: letting restora-tion be the guide. J Am Dent Assoc 126: 319–25.

Grondahl K, Lekholm U (1997). The predictive value ofradiographic diagnosis of implant instability. Int J OralMaxillofac Implants 12: 59–64.

Kent G, Johns R (1994). Effects of osseointegratedimplants on psychological and social well-being: acomparison with replacement removable prostheses.Int J Oral Maxillofac Implants 9: 103–6.

McAlarney ME, Stavropoulos DN (1996). Determinationof cantilever length to anterior–posterior spread ratioassuming failure criteria to be the compromise of theprosthesis retaining screw–prosthesis joint. Int J OralMaxillofac Implants 11: 331–9.

Oikarinen K, Raustia AM, Hartikainen M (1995). Generaland local contraindications for endosseal implants—anepidemiological panoramic radiograph study in 65 yearold subjects. Commun Dent Oral Epidemiol 23: 114–18.

Wennstrom J, Bengazi F, Lekholm U (1994). The influenceof the masticatory mucosa on the peri-implant soft-tissuecondition. Clin Oral Implants Res 5: 1–8.

Wise M (1995). Failure in the Restored Dentition:Management and Treatment. Chicago: QuintessencePublishing.


Introduction

Single tooth restorations are often thought to bethe most demanding implant restorations, partic-ularly from the aesthetic viewpoint. Achievementof an ideal result is dependent upon:

1. the status of the adjacent teeth2. the ridge and soft-tissue profile3. planning and precise implant placement4. sympathetic surgical handling of the soft

tissue5. a high standard of prosthetics

The assessment and planning is dealt with in thischapter and surgical and prosthodontic factors insubsequent chapters.

Clinical examination

Examination should start with an extraoralassessment of the lips and the amount of toothor gingiva that is exposed when the patientsmiles (Figure 3.1A). A high smile line exposinga lot of gingiva is the most demanding aestheti-cally with both conventional and implantprosthodontics. The appearance of the soft tissueand particularly the height and quality of thegingival papillae on the proximal surfaces of theteeth adjacent to the missing tooth are particu-larly important in these cases (Figure 3.1B). Ifthere has been gingival recession this should benoted. Exposure of root surface on the adjacentteeth labial surfaces may be correctable withperiodontal mucogingival plastic surgery proce-dures, but recession on proximal surfaces is notusually correctable. The patient needs to bemade aware of the limitations (which are the

same as those that apply to tooth-supportedfixed bridgework). It is always easier to judge theaesthetic problems if the patient has an existingreplacement, preferably one without prostheticreplacement of soft tissue. A simple ‘gum-fitted’removable partial denture that has a satisfactoryappearance is very helpful (Figure 3.1C). Theheight of the edentulous ridge and its width andprofile should be assessed by careful palpation.Large ridge concavities are usually readilydetected. Ridge mapping is advocated by someclinicians. In this technique the area under inves-tigation is given local anaesthesia and the thick-ness of the soft tissue is measured by puncturingit to the bone, using either a graduated periodon-tal probe or specially designed callipers. Theinformation is transferred to a cast of the jawthat is sectioned through the ridge. This methodgives a better indication of bone profile thansimple palpation but is still prone to error.Whenever the clinician is in doubt about thebone width and contour, it is advisable torequest a radiographic examination to achievethis (see section on sectional tomography).

One of the most important assessments ismeasurement of the tooth space at the level ofthe crown, at the soft-tissue margin and betweenthe roots. The first is important for the aesthet-ics and is best judged by measuring the width ofthe crown in comparison to the contralateralnatural tooth, if present. The available width atthe root level determines whether an implantand abutment can be accommodated withoutcompromising the adjacent tooth roots and softtissue. A commonly quoted minimal dimensionis 6 mm, both in the mesiodistal and buccolin-gual plane. This allows for an average implant of4 mm in diameter to have a margin of 1 mm ofbone surrounding it. The mesiodistal dimensionis commonly compromised in the maxillary

3Single tooth planning in the anteriorregion

lateral incisor region and the lower incisorregion, where the natural teeth are small (Figures3.2 and 3.3). In the case of young patients withdevelopmentally missing maxillary incisors, it isadvisable to liaise with the treating orthodontiststo agree space requirements and to check thatadequate space has been achieved beforeremoval of the orthodontic appliance. Theadjacent root alignment can sometimes bepalpated but usually requires verification radio-graphically. Spaces that are 5 mm widemesiodistally may be amenable to treatmentwith a narrow-diameter implant/abutment (e.g.3.3 mm rather than 4 mm in diameter) providedthat the forces it is subjected to are not too high.For example, utilization of narrow implantswould be contraindicated in a patient with aparafunctional activity such as bruxism.

On the other hand, patients with a spaceddentition have excess mesiodistal space.Provided that the ridge has an adequate bucco-lingual width, the clinician could plan to place a

wider diameter implant that more closelymatches the root of the tooth that is beingreplaced (Figures 3.4 and 3.5). The selection ofthe most appropriate implant diameter has agreat bearing on the aesthetics and surgery. Thisis dealt with in more detail in the surgical section(Chapter 9), which also compares some of theimplant systems available.

Examination of the occlusion

This usually can be accomplished by simple clini-cal examination. The adjacent tooth contacts (andthat of the pre-existing prosthetic replacement ifavailable) should be examined in centric occlu-sion, retruded contact and protrusive and lateralexcursions. Occlusal contacts on the single toothimplant restoration should be designed such thatcontacts occur first on adjacent teeth. This takesaccount of the normal physiological mobility of


Figure 3.1

(A) This patient, who has tooth 11 replaced with a singletooth implant, does not expose any gingival tissue whenhe smiles. (B) An intraoral view of the single tooth implantat position 11. Note that the adjacent incisors have smallamounts of gingival recession on the labial and proximalaspects, which was present before treatment. This loss ofattachment on the proximal surfaces affects papillaryheight and is very difficult or impossible to regain. (C) Thesame patient before treatment, confirming the position ofthe gingival margins on the natural teeth. The prosthesisis a simple ‘gum-fitted spoon denture’, which providesacceptable aesthetics but poor function. It is a usefuldiagnostic aid.

A B

C

SINGLE TOOTH PLANNING IN THE ANTERIOR REGION 37

Figure 3.2

(A) Replacement of a small upper lateral incisor with asingle tooth implant showing good soft-tissue form andaesthetics. (B) Radiograph of the single tooth implantwhich in this case is a narrow-diameter (3.3 mm) NobelBiocare (Brånemark design) implant. This is a good choicefor narrow spaces and low load situations.

Figure 3.3

(A) Replacement of lower incisors (in this case the lowerright central incisor) can be particularly challengingbecause of the limited space available. (B) Radiograph ofthe narrow-diameter (3.3 mm) Nobel Biocare implantreplacing the lower central incisor. A standard abutmenthas been used, which further compromises the availablespace. A customized narrower abutment could have beenused.

A

B

A

B

the teeth compared with the rigid osseointe-grated implant. Difficulties can arise when replac-ing canines in a canine-guided occlusion. Underthese circumstances attempts should be made toachieve group function and light contacts on theimplant restoration. Similar precautions arerequired with central and lateral incisor replace-ments in Class 2 Divison 2 incisor relationshipswith deep overbites (Figure 3.6).

Radiographic examination

Radiography for single tooth replacement inindividuals with little bone loss normally can beaccomplished by intraoral radiographs takenwith a long cone paralleling technique. However,it must be remembered that an overall evalua-tion of the mouth should be made for a fullassessment of treatment needs. Image quality isof the utmost importance and the clinicianshould ensure that all relevant anatomical struc-tures are shown on the image being used andthat any allowances for distortion of the imageare made. It can be surprisingly difficult to obtainaccurate radiographic mesiodistal measurementsof spaces at sites in the arch such as the maxil-lary lateral incisors/canines and the mandibularcanines. This is due to the curvature of the archand the difficulty of achieving parallel film align-ment with the space. The clinical measures canbe checked against the radiographic measures toobtain a more accurate estimate.

Sectional tomography

Although some clinicians use computed tomog-raphy (CT) scans for single tooth planning, wewould consider this to be in excess of what isnormally required. The CT scans, however, maybe very important aids with more complex casesand they are therefore dealt with in the chapteron fixed bridge planning (see Chapter 5). Manymodern dental panoramic tomograph (DPT)machines now offer sectional tomography forimplant planning (see below).

In order to optimize the information providedby these more advanced radiographic tech-niques, it is advisable to provide information


Figure 3.4

(A) The maxillary canine has been replaced by anAstraTech single tooth (ST) implant, which has a 4.5-mmor 5.5-mm diameter top. The latter is the more suitable fora canine replacement. (B) Radiograph of the AstraTech STimplant with the bone margin at the top of the implant.The implant/abutment junction is an internal cone thatgives considerable strength and stability, both of which areimportant requirements for canine replacements.

B

A


Figure 3.5

(A) The second bicuspid has been replaced with a 4.5-mm diameter Frialit 2 implant. (B) Radiograph of the Frialit 2 implant(push-fit, stepped cylinder design), which shows a very good match between the size of the crown and the diameter ofthe implant. (C) The upper right central incisor has been replaced with a 5-mm diameter Nobel Biocare implant. (D)Radiograph of the wide-diameter implant, which more closely matches the diameter of the natural tooth root and crown.However, in many cases there is insufficient bone width buccolingually in the incisor region to accommodate wideimplants, therefore implants of about 4 mm diameter are more commonly used.

C

DB

A

about the planned final restoration. A suitableexisting partial denture or a customized stentthat mimics the desired tooth set-up isconstructed and radiographic markers incorpo-rated. The radiopaque marker can be placed inthe cingulum area of the tooth if a screw-retainedcrown is planned, to indicate the access hole forthe screw. Alternatively, the labial surface of thestent can be painted with a radiopaque varnishto show the labial profile and cervical margin ofthe planned crown in relation to the underlyingbone ridge (Figure 3.7). Simpler types of stentinvolve placing radiopaque markers (e.g. ballbearings of various diameters or twisted wireshapes) into a baseplate, designed to help deter-mine mesiodistal distortion and location.

Scanora™ (Soredex Orion, Helsinki, Finland) isan example of the new generation oftomographic machines with facilities to generatehigh-quality sectional images. In contrast to CTscanning, where the sectional images aresoftware generated, the Scanora produces atomographic image directly onto film. It usescomplex broad-beam spiral tomography and isable to scan in multiple planes. The scans arecomputer controlled with automatic execution.They rely on good patient positioning andexperience in using the machine. The patient’s

head is carefully aligned within the device andthis position is recorded with skin markers andlight beams. A conventional DPT image is


Figure 3.6

The upper lateral incisor has been replaced by anAstraTech single implant tooth 6 years before this photo-graph. There has been complete stability and no compli-cations despite the difficult Class 2 Division 2 incisorrelationship.

A

B

Figure 3.7

(A) Dental pantomogram taken on a Scanora at �1.7magnification. The young patient has a large number ofdevelopmentally missing teeth, including maxillary lateralincisors and canines. (B) Sectional tomogram of theanterior ridge, which is angled labially and is thin.

produced and the sites that require sectionaltomographs are determined. The patient isrepositioned in exactly the same alignment andthe appropriate tomographic programme isselected for the chosen region of the jaw.

The Scanora magnification is �1.3 or �1.7 forroutine DPTs but is �1.7 for all sectional images.Tomographic sections are normally 2 or 4 mm inthickness. As with all tomograms, the image

produced includes adjacent structures that arenot within the focal trough, which thereforeappear blurred and out of focus.

In order to facilitate planning using images atdifferent magnifications, transparent overlaysdepicting implants of various lengths and diame-ters at the corresponding magnifications can besuperimposed directly on the radiograph. Theseprovide a simple method of assessing implant


(C) A transparent overlay of a 4-mm diameter implant has been superimposed on the ridge profile. There is insufficientwidth of bone to accommodate this implant, and not even a 3.3-mm diameter implant. This site needs to be made wider.(D) The sectional profile of the tooth (T*) to be replaced can be visualized by coating the radiographic stent with radiopaquevarnish. The Scanora section of this wider ridge profile has been assessed using a transparent overlay of the appropriateimplant design, which can be accommodated within the available bone volume. The red dashed line shows that the angleof the implant would pass through the labial face just apical to the incisal tip. A cemented restoration would be satis-factory.

C D

sites and implant placement at different angula-tions.

Diagnostic set-ups

Patients with aesthetically acceptable provisionalrestorations may not require diagnostic wax-ups.There are considerable advantages in using thepre-existing prosthesis or a new provisionalrestoration that can be worn by the patient toprovide a realistic potential end result. This canbe agreed upon between patient and clinicianand recorded. Wax-ups are difficult for thepatient to judge and computer-manipulatedimages may not be entirely realistic or achiev-

able. We routinely use simple acrylic removableprostheses for this purpose (see section onremovable partial dentures). The set-up shouldestablish the emergence profile of the crown andestimate the level of emergence from the soft-tissue at the planned cervical/gingival margin.

Cemented or screw-retained

crowns

The preceding information should provide the clini-cian with sufficient information to indicate whetherit is possible and/or desirable to provide acemented or screw-retained crown. This is dealt


Figure 3.8

(A) The upper right canine has been replaced by a single tooth implant in an ideal position giving a very good buccalemergence profile. (B) The palatal view of the crown at the upper right canine shows that it is a cemented crown witha very nice contour. The angle of the implant was close to the long axis, passing close to the cusp tip.

A B

with in some detail in the surgical chapter on singleteeth (Chapter 9), but needs to be considered here.Nowadays, most anterior single tooth crowns arecemented. This produces very good aestheticswithout a visible screw hole on the palatal surface,even though this can be restored carefully withtooth-coloured restorative material. An optimumlabial contour and emergence profile is achievedwith an implant that is angled with its long axispassing through the incisal tip or slightly labial toit. This restoration cannot be screw-retained (Figure3.8). However, in cases where there has been fairlyextensive ridge resorption that has not beencorrected by bone grafting, the position and angleof the implant may be more palatal. This allowsscrew retention through the palatal surface,

permits full retrievability of the crown and wouldmake it possible to retighten a loose abutmentshould it occur. The disadvantage is that it isusually associated with a ridge-lap labial margin(Figure 3.9). The above mainly applies to the upperincisors and canines. In the premolar zone theimplant is normally in the long axis of the crown,allowing either cementation or screw retention,according to the clinician’s preference.

Provisional restorations

In the majority of treatment plans the provisionalrestoration is an essential component. It helps toestablish the design of the final reconstruction and


C D

(C) In contrast, the single tooth implant replacing the canine on the patient’s left side has a more ridge-lapped buccalprofile. (D) The palatal view shows the cemented crown with a much more bulbous palatal contour because the implantis palatally placed and the angle of the implant goes through the cingulum area.

is used by the patient throughout the treatmentstages. The following provisional restorations aremost commonly used for single tooth restorations.

Removable partial dentures

Although it has been suggested that denturesshould not be worn for 1 or 2 weeks followingimplant surgery, this does not usually apply tothe single tooth cases. Single tooth or short-spandentures usually can be worn immediately aftersurgery. The denture can be adjusted so thatlittle or no pressure is transmitted at the site ofthe implant. Acrylic dentures are simple andinexpensive to construct and allow easy adjust-ment to accommodate any changes in tissueprofile following implant placement and thetransmucosal abutments when they are fitted.When used as an immediate replacement follow-ing tooth extraction the shape of the gum-fittedpontic can be adjusted to develop a goodemergence profile and soft-tissue contour.

Adhesive bridgework

Many patients prefer the idea of a fixed provi-sional restoration. Adhesive bridgework is

normally retained by a single adjacent retainerthat should permit removal by the clinician.Therefore, the Rochette design is recommendedas drilling out the composite lugs within theframework holes should allow removal.However, this occasionally proves to be moredifficult than one might expect and the removaland replacement of adhesive bridges consider-ably adds to the treatment time, particularly inthe restorative phase. It is worth making theprosthetic tooth from acrylic or composite, toallow more rapid adjustment when the bridge isrecemented over a protruding abutment. Thefixed restoration has considerable advantages incases where it is important to avoid any loadingof the ridge/mucosa, e.g. where grafting orregenerative techniques have been used(Chapter 12).

Treatment schedules

The treatment schedule for single tooth replace-ment in most cases should be relatively simple:

1. Initial consultation, clinical evaluation andradiographic examination

2. Agreement of aesthetic/functional demands


Figure 3.9

(A) The single tooth implant replacing the upper left central incisor is very palatally placed, resulting in a marked ridge-lap of the crown. (B) A palatal view of the restoration shows that there is a hole in the cingulum that gives direct accessto the abutment screw (i.e. the long axis of the implant), making the restoration retrievable (although the crown iscemented to the abutment).

A B

using existing prosthesis or diagnostic set-up/new provisional prosthesis

3. Treatment of related dental problems thatcould compromise implant treatment

4. Surgical placement of the implant and provi-sion of temporary prosthesis

5. Healing phase to allow osseointegrationaccording to established protocol

6. Abutment choice and connection7. Prosthodontic treatment

However, there are a number of situations thatwill need modification:

1. Immediate replacement following extraction(see Chapter 11)

2. Soft tissue or bone augmentation prior toimplant placement (see Chapter 12).

3. Early loading or immediate loading protocols.Provided that bone quality and implant stabil-ity are good, early loading (e.g. 6 weeksfollowing implant placement) should notcompromise success. Promising results havebeen shown with immediate loading, butfailure rates can be higher, particularly whereloading is difficult to control (see Chapter 1).

Conclusion

This chapter has dealt with most of the basicplanning issues of anterior single tooth replace-ment. However, many of the more detailedissues are best considered in the surgical chapter(Chapter 9) and the prosthodontic chapter(Chapter 13).

Bibliography

Andersson B, Odman P, Carlsson GE (1995). A study of184 consecutive patients referred for single toothreplacement. Clin Oral Implants Res 6: 232–7.

Engquist B, Nilson H, Astrand P (1995). Single toothreplacement by osseointegrated Brånemark implants.Clin Oral Implants Res 6: 238–45.

Hess D, Buser D, Dietschi D, Grossen G, SchonbergerA, Belser U (1998). Esthetic single-tooth replacementwith implants: a team approach. Quintessence Int 29:77–86.

Kemppainen P, Eskola S, Ylipaavalniemi P (1997). Acomparative prospective clinical study of two single-tooth implants: a preliminary report of 102 implants. JProsth Dent 77: 382–7.

Millar BJ, Taylor NG (1995). Lateral thinking: themanagement of missing upper lateral incisors. Br DentJ 179: 99–106.


Introduction

The considerations for replacement of singlemolars are not primarily aesthetic as in thepreceding chapter on anterior teeth, but themechanical considerations are far more impor-tant. It is not generally recommended to replacea molar by a single implant of 4 mm diameter orless because of the potentially large cantileverforces that it could be subjected to (Figure 4.1),resulting in biomechanical failure. The basicalternatives are therefore placement of twostandard implants or a single wide-diameterimplant. The space requirements and potentialcosts are quite different.

Two-implant solutions

Molar spaces of 11 mm mesiodistal width can,theoretically, be treated by placement of two 4-mm diameter implants. This requires extremecare and skill to avoid damage to adjacent toothroots. Also, the space between the two implantsmay prove to be too small to allow a properlycontoured restoration and an adequate bone andsoft-tissue zone (Figure 4.2).

In most cases the space should be at least13 mm to allow the two-implant solution (Figure4.3). The space has to be measured at the levelof the crestal bone and the adjacent tooth rootsmust not converge within the space.

4Single tooth planning for molarreplacements

Figure 4.1

Alternative implant solutions for a single molar. The sizediscrepancy between a single 4-mm implant (A) and thenormal occlusal table of a molar may subject it to leverageforces that are too high and biomechanical failure. Thesituation is considerably improved by using two implants(B) or a single wide implant (C).

Figure 4.2

An 11-mm space at the level of the crestal bone couldtheoretically accommodate two 4-mm diameter implantsand allow a space of 1 mm between them and theadjacent teeth.

It is important also to measure the space avail-able at the occlusal plane, particularly if there istilting of the adjacent teeth. Under these circum-stances an unfavourable path of insertion ofprosthodontic components may prevent the

reconstruction, or the implant abutments maytouch. The choice of implant diameter, implantsystem and implant abutment will have a markedimpact on the available space as illustrated inFigures 4.4–4.7.


Figure 4.3

A 13-mm space at crestal level allows placement of two4-mm diameter implants. A safer margin between implantsand teeth (1.5 mm) is provided and a minimum of 2 mmbetween implants.

Figure 4.4

The space at the level of the occlusal surface is reduceddue to tilting of the distal molar, although there is morebone width available apically. The surgery may be easierbut the prosthodontics could be compromised or, insevere cases, made impossible.

Figure 4.5

Two 4-mm diameter implants have been placed with widermargins between them and the adjacent teeth. Theabutments that flare to a wider diameter may touch orleave insufficient space for a healthy soft-tissue collar. Thiscould be improved by using narrower abutments.

Figure 4.6

When space is limited the selection of an alternativeimplant system can help enormously. This figure illustratesplacement of two AstraTech implants. Selection of the 3.5-mm diameter implant rather than the 4-mm implant wouldprovide an additional saving of 1 mm. The AstraTechabutments are narrower than the implant heads andprovide space saving for the superstructure and softtissue.

SINGLE TOOTH PLANNING FOR MOLAR REPLACEMENTS 49

Figure 4.7

(A) Radiograph of a mandibular molar space, suggestingadequate room for two implants. (B) Radiograph with trans-parent overlay of two standard diameter implants, confirmingadequate mesiodistal space. The implants are no longer thanthe adjacent natural roots and are above the inferior dentalcanal. (C) Radiograph of two AstraTech 4-mm standardimplants used to replace the mandibular first molar. The twoimplants have been joined together with a gold casting fabri-cated on two cast-to abutments. The abutments are narrowerthan the implants at the level of the implant head and theshape of the casting facilitates soft-tissue contour and plaquecontrol. (D) Occlusal view of the screw-retained casting onthe two implants. (E) Lingual clinical mirror view of thecompleted restoration. A porcelain-fused-to-metal crown hasbeen cemented onto the gold substructure. (F) Buccal viewof the completed restoration. The space between theimplants has been contoured to facilitate oral hygiene with abottle brush. (G) Occlusal view of the completed cementedcrown without access to the abutment screws.

A

B

C

D

E

F

G

Single implant solutions withwide-diameter implants

Many molar spaces are less than 12 mm, andeconomic considerations often indicate the use

of single implant replacements. Wider diameterimplants are available in most systems, and inall the systems described in this book (Table 4.1).

The mechanical advantages of a wide-diameter implant for molar replacement are:


Figure 4.8

(A) A mandibular molar space showing a single tooth implant healing abutment with good soft-tissue width both mesiallyand distally. (B) Radiograph of the mandibular molar replaced by a 10-mm long Nobel Biocare 5-mm diameter wide-platformimplant. There would have been adequate space for two 4-mm implants but at much greater cost. (C) Clinical photographof the mandibular first molar replaced by a single wide-diameter implant. The appearance and soft-tissue contours aregood. (D) Occlusal view of the completed restoration. The crown has been cemented to a standard abutment. However,an access hole (filled with composite) has been fabricated to allow the crown to be retrievable. This allows tightening ofthe abutment screw if it should become loose due to the considerable occlusal forces in the molar region.

A

B

C

D

1. Better force distribution with reduction ofleverage forces because implant diametermore closely matches that of the crown.

2. The implant is stronger and less likely tofracture.

3. The abutments and abutment screws areusually bigger and stronger.

4. The surface area of the abutment is usuallylarger and will provide more retention.

SINGLE TOOTH PLANNING FOR MOLAR REPLACEMENTS 51

Table 4.1 Examples of wider diameter implants availablefrom various companies

Make Type Diameter

AstraTech Single tooth (ST) 5 mmNobel Biocare Brånemark regular 5 and 5.5 mm

and wide platformFrialit Frialit 2 stepped 5.5 and 6.5 mm

cylinderITI/Straumann Wide body, solid 4.8 and 6.5 mm

screw and wide neck3i Brånemark type 5 and 6 mm

3i: Implant Innovations, West Palm Beach, FL, USAAstraTech: Astra Meditec AB, Mölndal, SwedenNobel Biocare: Nobel Biocare AB, Göteborg, SwedenFrialit: Friatec AG, Mannheim, GermanyITI/Straumann: Institut Straumann AG, Waldenburg, Switzerland

Figure 4.9

(A) Radiograph of a maxillary first molar with failedendodontic treatment and a broken-down crown. Theadjacent teeth have small restorations. (B) The first molarhas been replaced by a single tooth implant: a 5-mmdiameter wide platform Nobel Biocare. The implant is10 mm in length and extends just into the maxillary sinus.Insufficient mesiodistal space was available for a two-implant option.

B

A

Figure 4.10

(A) The maxillary molar is missing. The maxillary secondpremolar is a single tooth implant. (B) Radiograph showingthat the second premolar has been replaced by a Frialit 2implant (4.5-mm diameter screw design). The maxillarysinus has extended into the molar space, making implantplacement impossible without sinus grafting. The secondmolar has a questionable prognosis. If this tooth is lost, asinus graft would allow replacement of both molars.

B

A

The mesiodistal molar width should alwaysprovide sufficient space for a wide-diameterimplant (Figure 4.8 and 4.9). However, this is notalways the case in the buccolingual dimension.Narrow ridges occur in both posterior maxillaand mandible, often only allowing placement ofnormal-diameter implants without recourse tografting. In many cases (particularly shortly afterloss of the molar) there is sufficient buccolingualwidth and the wide-diameter implant should beideal. The increased surface area that it providesalso has a distinct advantage in the molarregions, where bone height is often limited byexpansion of the maxillary sinus and the positionof the inferior alveolar nerve (Figure 4.10). Theminimal length of implant recommended wouldbe 8 mm, although 10 mm would be preferred inmost cases. The selection of an implant with asurface that has been treated to increase furtherits area and improve the rate and quality ofosseointegration is preferred in these circum-stances. Unfortunately, there are no large-scalelongitudinal trials of molar replacements tosubstantiate these opinions.

Conclusions

If space and economics allow, choose the two-implant option. In other cases ensure that thebuccolingual width will accommodate a wide-diameter implant (assuming that the mesiodistalspace is adequate). Caution should be exercisedin patients with bone height less than 10 mm,poor bone quality or high functional demands.

Bibliography

Andersson B, Odman P, Carlsson GE (1995). A study of184 consecutive patients referred for single toothreplacement. Clin Oral Implants Res 6: 232–7.

Bahat O, Handelsman M (1996). Use of wide implantsand double implants in the posterior jaw: a clinicalreport. Int J Oral Maxillofac Implants 11: 379–86.

Balshi TJ, Hernandez RE, Pryszlak MC, Rangert B(1996). A comparative study of one implant versus tworeplacing a single molar. Int J Oral Maxillofac Implants11: 372–8.

Becker W, Becker BE (1995). Replacement of maxillaryand mandibular molars with single endosseousimplant restorations. J Prosth Dent 74: 51–5.

Langer B, Langer L, Herrmann I, Jorneus L (1993). Thewide fixture: a solution for special bone situations anda rescue for the compromised implant. Int J OralMaxillofac Implants 8: 400–8.


Introduction

Planning for implant-supported fixed bridgesfollows the lines described in the previouschapters. The chapter on single tooth replace-ment in the anterior region (Chapter 3) dealt withthe aesthetic demands and the chapter on molarreplacements (Chapter 4) with some of theloading and spacing considerations. Extensivebridgework in partially dentate and edentulousjaws involves planning for placement of multipleimplants in sites that may be more demandingsurgically (see Chapters 10 and 12). The number

and distribution of implants is a complexvariable and is dealt with below.

Clinical examination anddiagnostic set-ups

Patients requiring extensive fixed bridgeworkoften need more detailed examination andconsideration of treatment alternatives thanthose requiring more simple restorations.

In partially dentate patients the following shouldbe evaluated:

5Fixed bridge planning

Figure 5.1

(A) Clinical appearance of a patient who has an extensivemaxillary bridge and very few mandibular teeth. Themandibular arch appears to be ideally suited to implanttreatment. (B) Radiograph of the same patient showinggood bone height in the anterior mandible. However, themaxillary teeth have a poor prognosis and are affected byadvanced untreated periodontal disease, endodonticlesions and caries. Loss of all the maxillary teeth places adifferent perspective on the management of the lowerjaw.

A

B

1. Examination of the restorative, endodonticand periodontal status of the remaining teeth.This should reveal treatment needs and anidea of the prognosis of the teeth (Figure 5.1).This is extremely important because theimplant restoration should have a good long-term prognosis and adjacent teeth or oppos-ing teeth should, for the most part, offer acomparable prognosis. This is not always thecase and the patient should be made aware

of the potential prognosis of the natural denti-tion and the possibilities for future replace-ment, should this become necessary. A goodexample would be replacement of first and


B

Figure 5.2

(A) Patient with lips at rest, showing less lip support onthe right than on the left. (B) Intraoral view of the samepatient who has been provided with a diagnostic partialacrylic removable denture without a labial flange. Thecervical aspects of teeth 13, 12 and 11 are more palatallyplaced because of extensive resorption of the labial bone.This results in the incisal tips being cantilevered forward,to establish a relationship with the opposing teeth. Thisset-up may be unfavourable mechanically and aestheticallyfor implant treatment, and grafting should be considered.

A

Figure 5.3

A patient with missing lower molars and moderate resorp-tion of the ridge. The interocclusal space is increased andthe prosthesis would require long crowns. The amount ofbone height above the inferior dental canal is often limited,and implant lengths of about 10 mm are commonly used.Shorter implants may produce very unfavourableimplant/crown ratios and an onlay graft may be indicatedto provide enough bone for longer implants and to reducethe interocclusal space.

Figure 5.4

A patient who has been treated with implant-supportedbridges on both sides of the maxilla distal to the centralincisors. The bridges have long crowns because of theextensive vertical resorption of bone following tooth loss.Sufficient bone was present to provide implants of 10 and13 mm in length. The lip coverage was favourable and theteeth have been treated for periodontal disease.

second molars in one jaw opposing the teethin the other jaw that have a limited prog-nosis. Replacement of the opposing teethmay be straightforward with conventional

dentistry or implants. In contrast, replacementmay be impossible without implants involvingmajor bone grafting, a treatment that thepatient may not be willing to undergo.

FIXED BRIDGE PLANNING 55

Figure 5.5

(A) An edentulous patient who had been treated with maxillary and mandibular fixed implant-supported bridges 6 yearsprior to these photographs. There is adequate lip support and good aesthetics during normal function. (B) The lip supportin profile at rest. (C) The exposure of the maxillary bridge on smiling. (D) The intraoral appearance, showing the bridgesthat were constructed along the principles of Brånemark. The standard abutments protrude above the mucosa to allowgood access for oral hygiene. The superstructure consists of a rigid gold casting and the prosthetic teeth and ‘gumwork’are acrylic.

A

B D

C

2. The degree of ridge resorption. It is importantto recognize not only the degree of resorptionthat would compromise implant placementbut also that which would compromiseaesthetics because of a high lip line or insuf-ficient lip support (Figure 5.2). These factorsshould be assessed further using diagnosticwax-ups and diagnostic removable prosthe-ses, as described previously.

3. Centric jaw relationship and protrusive andlateral excursions of the lower jaw. The verticalheight within the existing and planned occlusalvertical dimension is another important factor.There may be insufficient height to accommo-date the prosthesis from the implant head dueto overeruption of the opposing teeth. Theother extreme is where there is a large verticalspace to be restored that would produce anunfavourable prosthesis/implant ratio (cf.crown/root ratio in natural dentition; Figures 5.3and 5.4). The forces on the planned prosthesisare also increased where the prosthesis is likelyto be cantilevered, either distally in a free endsaddle (see Figure 5.14) or anteriorly where thejaw has resorbed relative to the required toothposition (see Figure 5.2). These factors assumegreater importance in patients who exhibitparafunctional activities and who have limitedbone volume and/or quality.

Additionally, in edentulous patients the degreeof ridge and jaw resorption affecting soft-tissuesupport and maxillary/mandibular relationshipsshould be evaluated (Figure 5.5). With progres-sive resorption, patients are more likely toacquire a pseudo class 3 jaw relationship andvery poor lip support. The potential solutions tothis problem are extensive bone grafting/osteotomy (Chapter 12) or provision of overden-tures, which is dealt with in detail in Chapter 6.

Other points to remember in severely resorbedcases:

• A fixed bridge prosthesis will almost certainlyrequire the addition of prosthetic gingivae(Figure 5.6).

• The restoration/implant height ratio is morelikely to be unfavourable.

• Resorption of the ridge produces a smaller arcof bone to support the implants than therequired arc to provide a functional andaesthetic prosthesis.

Diagnostic set-ups

These should follow the principles described inthe chapters on general planning (Chapter 2) andsingle tooth planning (Chapter 3). The larger therestoration, the more complex the evaluation.We would advocate the use of removabledentures with gum-fitted teeth (and labial flangesfor comparison) to allow both the clinician andthe patient to assess the potential end result(Figure 5.7).


Figure 5.6

(A) A patient with a full-arch maxillary implant bridge. (B)The intraoral appearance of the maxillary bridge, showingthat the residual ridge is very resorbed and the implantheads are palatally placed in a smaller arc. Adequate lipsupport and aesthetics are provided by the position of theteeth and the provision of prosthetic ‘gumwork’.

A

B

Radiographic examination

In some situations the simpler radiographictechniques of dental panoramic tomographs(DPTs) and conventional film tomography will beentirely adequate (see Chapter 4). However,complex cases often demand computed tomog-raphy (CT) scans, which can offer detailed multi-format images for detailed planning. They areparticularly useful for cases involving:

1. Posterior mandible sites, particularly bilateralcases that are imaged by the same scan.

2. Large-span edentulous spaces in the maxil-lary arch. In the anterior region, thin ridgesmay be revealed where DPT images havesuggested adequate bone height; in theposterior region, more detailed images ofmaxillary sinus extension are often required.

Computed tomography uses X-rays to producesectional images, as in conventional tomography.


Figure 5.7

(A) A patient with extensive anterior tooth loss. (B) Theremovable partial denture that the patient had beenwearing had a large labial flange to provide lip support (seeFigure 5.7D). (C) A ‘diagnostic denture’ to determine thechange in appearance with removal of the labial flange,and the position of the teeth in relation to ridge and poten-tial implant placement. This denture can be duplicated toprovide radiographic and surgical stents. (D) Lip supportwith the denture, including the labial flange. (E) Slight lossof lip support without the labial flange.

A

B

C

E

D

High-resolution images are achieved by initiallyscanning in an axial plane, keeping the sectionsthin, and by making the scans contiguous oroverlapping. The scans should be limited to thearea of interest and avoid radiosensitive tissuessuch as the eyes. The patient’s head is alignedin the scanner with light markers, and a scoutview is obtained that gives an image similar to alateral skull film. The radiation dose of this scoutview is low and can be repeated if the alignmentis incorrect. Generally, the mandible is scannedwith slices parallel to the occlusal plane and the

maxilla, using the same plane or one parallel tothe floor of the nose. Deviation from this align-ment will result in the cross-sectional slices notbeing in the same direction as the proposedimplant placement (see pp. 38–42). In place ofconventional film the radiation is detected byhighly sensitive crystal or gas detectors and isthen converted to digital data. These data can bestored and manipulated by computer software toproduce the image. The software then allowsmultiplane sections to be reconstituted, thequality of which are dependent on the original


Figure 5.8

SIM/Plant™ (Columbia Scientific Inc, Maryland, USA) software view showing ‘mock’ implant placement in the maxilla.The images on the left numbered 35–46 are cross-sectional images. An implant has been placed and appears in sections38–40. The mesiodistal position of the implant can be seen in the panoramic view (bottom right) and axial view above(CT Axial 19). The top right shows the alignment view (scout view), and a box which displays bone density values.(Courtesy of Image Diagnostic Technology, London, UK.)

scan section thickness and integers betweensuccessive sections.

Images can be produced as:

1. Standard radiographic negative images onlarge sheets.

2. Images on photographic paper, often in bookform.

3. Images for viewing on a computer monitor.

Heavy metals will produce a scatter-like inter-ference pattern if they are present in the slice

under examination and the interference willtherefore appear in all the generated sectionalimages. Extensive artefacts may render a CTscan unreadable and can be produced by largeposts in root canals or heavily restored teethwhere the plane of examination passes throughsuch a tooth as well as an area of critical inter-est.

In some instances, therefore, either a compro-mise has to be made in the direction of scanningor a different method of examination chosen (e.g.conventional tomography as described in


Figure 5.9

SIM/Plant™ (Columbia Scientific Inc, Maryland, USA) software view showing ‘mock’ implant placement in the mandible.The images on the left numbered 48–56 are cross-sectional images. An implant has been ‘placed’ and appears in sections51–53 with its apex about 3 mm above the inferior dental canal and mental foramen (section 53). The mesiodistal positionof the implant can be seen in the panoramic view (bottom right, which clearly shows the path of the inferior dental canal)and axial view above (CT Axial 24). The top right displays bone density values in relation to the implant. (Courtesy ofImage Diagnostic Technology, London, UK.)

Chapter 3). Consideration should also be given toremoving the offending metal prior to examina-tion if appropriate in the overall treatment plan.

The various scan images can be measured forselection of implant length and diameter.Although the nominal magnification of theimages is 1:1, some machines and camerasproduce images where the magnification mayvary. A scale is usually incorporated alongsidethe various groups of images and the real magni-fication can be determined from this. A correc-tion factor then can be applied to measurementstaken directly from the films.

In contrast to hard copies of the scans, one ofthe advantages of the computer-based imagesoftware programmes (e.g. SIM/Plant™) is that itis possible to produce images of implants (andtheir restorative components) that can be‘placed’ within the CT scan (Figures 5.8–5.10).This enables the clinician to evaluate therelationships between the proposed implantsand ridge morphology, anatomical features andadjacent teeth. When used in conjunction with aradiographic stent, the possibility of reproducingthe orientation envisaged at the planning stageis greatly increased.


Figure 5.10

The new ‘Surgicase’ interactive software (Surgicase, Materialise NV, Leuven, Belgium) has additional three-dimensionalcapabilities. Implants can be placed and manipulated in this view and, as illustrated, the nerve can be highlighted withinthe jaw, using a transparency tool (courtesy of Image Diagnostic Technology, London, UK).

Planning implant numbers anddistribution

In planning fixed bridgework supported byimplants there are recommendations regarding

the minimum number of implants that would berequired (Table 5.1). Increasing the number ofimplants allows for failure of an implant (or morethan one) and may provide improved long-termpredictability.


Table 5.1 Guide for implant numbers in various circumstances

Examples of types of replacement required Suggested number of implants and prosthetic solution

Full-arch bridges in edentulous maxilla At least five or six implants – preferably extending to second premolarregion. Additional implants in molar regions recommended by manyclinicians

Full-arch bridges in edentulous mandible At least four or five implants in the region between the mental foramina.Additional implants in molar regions recommended by many clinicians

Missing molars Two missing molars normally require three standard-diameter implants.Two wide-diameter implants could be used to support a bridge or twosingle tooth molar units.

Three missing maxillary anterior teeth Two or three implants supporting a bridge. If there is sufficient space forthree implants, consider three single tooth units

Four missing maxillary anterior teeth Four upper incisors would normally require a minimum of three implants tosupport a bridge. If there is sufficient space for four implants, considerfour single tooth units

Four missing mandibular incisors Four lower incisors could be replaced using two implants and a fixedbridge. There is usually not enough room for more implants. The samesolution may be adequate to replace mandibular canines and incisors(which is not usually the case in the maxilla)

Figure 5.11

(A) An example of six implants arranged in the lower jaw in the region between the mental foramina, with the most distalimplant in the first premolar site. In this case the anteroposterior distance between implants shown by the dashed linesis not very great because of the shape of the jaw. (B) In contrast, in this example the six implants have been arrangedso that the most distal implants have been placed distal to the first premolars. The anteroposterior distance betweenimplants has been increased greatly, providing an improved biomechanical arrangement. This arrangement could moreadequately support distal cantilever extensions.

A B

Configuration and angulation ofimplantsThe configuration of the implant sites, theangulation of the implant sites and the angula-tion of the implants have considerable impact onthe structural/load-bearing capacity of the pros-

thesis. In edentulous full-arch cases it is impor-tant to distribute implants throughout the curveof the arch and to place implants distal to thecanine sites (Figures 5.11–5.13). The possibility ofextending the implant placement beyond thepremolar zone into the molar zone depends uponthe amount of available bone. Unfortunately,


Figure 5.12

(A) Placement of seven implants in a maxilla that has been treated previously with buccal onlay grafts. The implantsextend distally as far as the maxillary sinuses would allow. (B) The casting for the same patient, showing a single distalcantilever unit on each side.

A B

Figure 5.13

(A) A patient with a completed full-arch maxillary implant bridge. Where there was more resorption the teeth are moreridge lapped and there are small amounts of prosthetic gumwork (patient’s left side). In other areas (patient’s right side)the emergence profiles of the crowns are better. (B) An occlusal view of the full-arch bridge, which is screw-retained. Itcan be seen that the implant screw holes on the patient’s left side are more palatally placed than on the right side, wherethey are close to the incisal edge.

A B

adequate bone in these zones is not alwayspresent in completely edentulous jaws andpresents the clinician with two choices:

1. Surgery to create sufficient bone (see Chapter12).

2. Not utilizing the area for implant placement.

The latter situation may be overcome by distalcantilevering of a prosthesis but there are limitsto this strategy (Figure 5.14).

In extensive edentulous zones in the partiallydentate individual, the configuration of implantsassumes the same degree of importance. It isgenerally recommended to avoid placement of


Figure 5.14

(A) A mandibular full-arch bridge (ad modum Brånemark) viewed from the undersurface, showing the distribution and archform of the implant positions. One cantilever unit has been provided on each side. (B) Maxillary full-arch bridge (ad modumBrånemark) viewed from the undersurface, showing the distribution and arch form of the implant positions. Two cantileverunits have been provided on each side, in this case, to improve aesthetics (see Figure 5.11).

A B

Figure 5.15

Two implants are always in a straight line! This arrange-ment may be entirely adequate for replacing the four lowerincisors using two implants, and with favourable conditionscould apply to the four upper incisors or the six loweranterior teeth (incisors and canines). However, it is gener-ally considered an inadequate number for replacing twomolar teeth with standard-diameter implants, where theadvantage of a three-implant tripodization arrangement isrecommended.

Figure 5.16

Three implants have been placed to support two molarunits. The lower part of the figure represents a plan viewwith the middle implant offset slightly to produce a tripodarrangement (dashed lines) and improved biomechanicalproperties.

multiple implants in a straight line (Figures 5.15and 5.16). In the situation where three implantsare provided, offsetting one implant to producea tripod arrangement is normally recommended(Figure 5.16). This will improve the situation evenif the offset is minor, which is often the case inthe posterior mandible and maxilla (Figure 5.17).

The angulation of the implant sites more orless mimics the angulation of the natural teeth,with modifications according to the design of thefinal prosthesis and the degree of ridge resorp-tion. A surgical stent provides important guid-ance. If the final prosthesis is designed to beretrievable/screw-retained, the ideal angle of theimplant passes through the cingulum area of theanterior teeth and the occlusal surfaces of thepremolar/molar teeth (Figures 5.13 and 5.17). Ina non-retrievable cemented prosthesis theangulation would be the same in the posteriorteeth because this is also consistent with loadingthe implants through the long axis (Figure 5.18).However, in the anterior zone the angulation canbe more labially inclined through the incisal tipor towards the labial surface, potentially improv-ing the emergence aesthetics (see Chapter 9).However, force transmission through theanterior implants may be less favourablebecause it will be far removed from axialloading. Further consideration of the angulationand spacing of different implant designs is givenin the surgical chapters (Chapters 9 and 10).


Figure 5.17

(A) A three-unit screw-retained maxillary bridge with thescrew holes in the middle of the occlusal surfaces. Theimplants are not in a straight line. However, the degree oftripodization is small because of the width of availablebone and the other prosthetic demands of implant place-ment. (B) Radiograph showing the three Nobel Biocare(Brånemark) implants supporting the bridge.

B

A

Figure 5.18

Forces directed through implants placed in the posteriorjaw will usually be in the same long axis as the premolarand molar teeth. Labial angulation of the anterior implantsmeans that normal forces are not directed down the longaxis.

Fixed bridges or multiple singleunits

There is a trend to place an implant for eachindividual missing tooth, in which case it wouldbe possible to restore each as a separate singletooth unit. This approach, although first appear-ing very logical, is difficult to achieve in practiceand may not be as predictable in its outcome.There are a number of potential problems withthis approach:

1. Some teeth, such as lower incisors, have asmall mesiodistal dimension that is less thanmost implants.

2. Teeth can function perfectly well with verysmall amounts of intervening hard and softtissue (less than 1 mm), unlike implants.

3. As teeth are lost and the jaws resorb, theperimeter of the arch decreases, thus reduc-ing the space for implant placement. Theimplant spacing requirements are naturallyaffected by the system selected.


Figure 5.19

(A) The abutments show that there is labial angulation of the three implants in the right maxilla, which has undergoneconsiderable resorption and lost some of its arch form. (B) A palatal view showing the same features. (C) The completedbridge has been cemented to the abutments (screw retention would have required angled abutments – see Chapter 14).The crowns are slightly cantilevered to the labial/buccal side. (D) An occlusal view of the completed bridge. No screwholes are visible because the bridge is cemented.

A

B

C

D

4. The angulation of natural roots in the healthyalveolus may be impossible to mimic in theresorbed jaw. Proclination of natural anteriorteeth and anatomical variations such ascrown/root angulations are difficult to mimicwith implants.

5. Tapering of normal root forms may allowmore teeth within a given area of jaw bone.Tapered implants may have an advantage incertain cases, although few designs mimic thepronounced tapering seen in some naturalteeth.

6. Failure of a single implant in a multiple single-unit case requires replacement of that unit.The fixed bridge solution may still beworkable with one implant less (Figure 5.20).

7. Provision of a fixed bridge with fewerimplants than the teeth that are beingreplaced is more economical/cost effective.

8. The splinting afforded by the fixed bridgemay improve the biomechanical properties.

The potential advantages of multiple singleunits are :

• More natural appearance• No need for complex casting for precise

fitting of multiple abutments• Simpler prosthodontic procedures• Patient can floss between units

But there are additional disadvantages:

• Multiple cementation of units• Multiple paths of insertion and contact points

Provisional restorations

Removable dentures

The most simple provisional prosthesis is acomplete or partial removable denture. Whenconstructed in acrylic they provide an inexpen-sive and readily adjustable prosthesis that can bemodified to produce a radiographic stent orduplicated and modified to produce a surgicalstent. In cases where the implant surgery hasbeen extensive, e.g. placement of four or moreimplants in an edentulous jaw, it is commonlyrecommended to avoid wearing the denture for


Figure 5.20

(A) A patient with loss of teeth 13,12,11 and 21. There isgood ridge height and profile. (B) The patient’s existingremovable partial denture replaces the missing four teethin a spaced arrangement. This implant solution wouldrequire four single tooth units. (C) The same patient witha diagnostic denture bearing five teeth to close thediastemas. This solution would require provision of a fixedbridge based on three implants. The siting of the implantsunder the teeth to be replaced would be quite differentfrom the arrangement in (B).

A

B

C

a period of at least 1 week. This avoids earlytransmucosal loading of the implants and allowsadequate reduction of postsurgical oedema totake place, facilitating proper adaptation of thedenture. A complete upper denture can usuallybe relined and refitted after 1 week, but theatrophic edentulous lower jaw often requires aperiod of 2 weeks of healing before a completedenture can be worn satisfactorily.

Fixed bridgeworkProvisional fixed bridgework retained by full-coverage restorations may be the treatment ofchoice, particularly for patients having extensivetreatment who are not prepared to undergo aperiod of time without a fixed restoration. Thisassumes the presence of a sufficient number ofteeth to support the provisional or transitional


Figure 5.21

(A) This patient was very unhappy about the appearance of her natural teeth. (B) Intraoral examination revealed advancedperiodontitis. The remaining teeth had a very poor prognosis. The patient did not wish to wear removable dentures atany time. (C) The majority of the teeth were extracted and periodontal treatment provided for the few remaining teeth.These teeth were used to support provisional/transitional bridges made of gold and composite. Implants were installedin the edentulous areas and, following a period of osseointegration, used to support new full-arch implant bridges. (D)The completed full-arch maxillary and mandibular implant bridges.

A B

C D

bridge (Figure 5.21) or utilization of one of thetransitional implant systems (these are verynarrow-diameter implants that are placedbetween the definitive implants and are removedbefore the final prostheses is constructed). Fixedprovisional bridgework enables ridge augmenta-tion procedures to be carried out without the riskof transmucosal loading and the associatedmicro- movement affecting the healing, andshould reduce complications. The bridgeworkmay have to remain in place some considerabletime, with frequent removal and replacement.Abutment teeth must be prepared adequately toallow for the casting of a metal framework ofsufficient strength and rigidity and for theacrylic/composite. Allowance should be made forthe fact that the bridge will have to be modifiedfollowing abutment connection.

Treatment schedules

These are usually far more complex than thosedescribed for single teeth, but follow the sameprinciples:

1. Initial consultation, clinical evaluation andradiographic examination, which ofteninvolves tomography.

2. Agreement of aesthetic/functional demandsusing existing prosthesis or diagnostic set-up/new provisional prosthesis. Decision onwhether to provide a fixed bridge or animplant denture (see Chapter 6).

3. Treatment of related dental problems thatcould compromise implant treatment, includ-ing timing of further extractions and relation-ship to implant placement (see Chapter 11).

4. Planning number, type and location ofimplants in relation to planned prosthesis andavailable bone. Decision as to whether boneor soft-tissue augmentation is required priorto implant placement (see Chapter 12).

5. Arranging type of anaesthesia – local anaethe-sia, local anaesthesia plus sedation or generalanaesthesia.

6. Surgical placement of the implants and provi-sion of temporary prosthesis.

7. Healing phase to allow osseointegrationaccording to established protocols andcomplexity of case.

8. Abutment connection and modification ofprosthesis or construction of new implant-borne provisional prosthesis.

9. Number of appointments for prosthodontictreatment (see Chapter 14).

Conclusion

The treatment planning for extensive bridgeworkhas a far greater number of variables to contendwith and a number of alternative solutions. Thepatient needs to be made aware of these, but inany case will have to rely upon the treating clini-cian for guidance. Good recording, documenta-tion and communication are required to maintaina good patient/clinician relationship. Patientsshould also realize that the maintenance require-ments of extensive prostheses are likely to bemuch higher than those described for singletooth restorations.

Bibliography

Bahat O (1993). Treatment planning and placement ofimplants in the posterior maxillae: a report of 732consecutive Nobelpharma implants. Int J OralMaxillofac Implants 8: 151–61.

Brånemark PI, Svensson B, van Steenberghe D (1995).Ten-year survival rates of fixed prostheses on four orsix implants ad modum Brånemark in full edentulism.Clin Oral Implants Res 6: 227–31.

Hebel K, Gajjar R (1997). Cement retained versus screwretained implant restorations: achieving optimal occlu-sion and aesthetics in implant dentistry. J Prosth Dent77: 28–35.

Naert I, Quirynen M, van Steenberghe D, Darius P(1992). A six-year prosthodontic study of 509 consecu-tively inserted implants for the treatment of partialedentulism. J Prosth Dent 67: 236–45.

Rangert BR, Jemt T, Jorneus L (1989). Forces andmoments on Brånemark implants. Int J Oral MaxillofacImplants 4: 241–7.

Reddy S, Mayfield-Donahoo T, Vanderven FJJ, JeffcoatMK (1994). A comparison of the diagnostic advantagesof panoramic radiography and computed tomographyscanning for placement of root form dental implants.Clin Oral Implants Res 5: 229–38.


Introduction

This chapter will describe the diagnosis andtreatment planning of patients for implantdentures. These prostheses can be defined ascomplete or partial dentures, supported, retainedor stabilized by one or more dental implants. Inthis book, the term ‘denture’ refers to a patient-removable prosthesis rather than, as in NorthAmerica, a fixed or removable prosthesis.

The consequences of total tooth loss are wellknown and include bone resorption, changes inorofacial morphology and psychological effects.Treatment with conventional complete dentureshas been shown to be reasonably successfulwhen the residual alveolar ridges are favourable,when the dentures have been well made andwhen the patient is reasonably philosophicalabout wearing dentures (Fenlon et al., 2000).Such treatment has not been so successful,however, when:

1. The residual alveolar ridges are resorbed andeven well-made dentures have poor supportand stability.

2. Where movement of the dentures leads todiscomfort, pain and poor function. This maybe compounded by poor neuromuscularcontrol in, for example, Parkinson’s disease orfollowing a stroke.

3. Where the dentures are not well toleratedbecause of emotional reasons or because ofa strong gag reflex.

4. Where a single denture has poor stabilitybecause of opposing natural teeth. The worstcombination is remaining maxillary teethopposing a mandibular denture on a severelyresorbed residual ridge.

These difficulties can be overcome by the useof osseointegrated implants to support, retain

and stabilize dentures, and such treatment hasbeen shown to be effective in longitudinalstudies (Mericske-Stern, 1990; Mericske-Sternand Zarb, 1993; Jemt et al., 1996; Makkonen etal., 1997). Many of the principles of treatmentwith implant dentures are identical to those oftreatment with conventional dentures.

Indications for implant denturesas definitive treatment

There are three main indications for implantdentures:

1. Where complete dentures have been wornsuccessfully for many years but severeresorption (Figures 6.1 and 6.2) or loss ofneuromuscular control now limits retention orstability, causing movement of one or bothdentures; where the patient has accepted thetooth loss and does not really mind wearingdentures.

6Diagnosis and treatment planning forimplant dentures

Figure 6.1

Resorbed mandibular residual ridge. The patient wasexperiencing discomfort and poor function owing to thepoor support and poor stability of the mandibular denture.

2. Where a fixed restoration cannot providesufficient replacement of resorbed hard andsoft-tissues to produce an acceptable appear-ance.

3. Where remaining natural teeth have anunfavourable distribution for retention andsupport of a removable partial denture (Figure6.3).

Where conventional complete or partialdentures are not well tolerated because ofemotional reasons, the patient may not acceptimplant dentures because these prostheses arestill patient-removable and may still carry the‘stigma’ of false teeth. In this situation, thepatient may wish to settle for nothing less thana completely fixed implant bridge. Whereconventional dentures are not well toleratedbecause of a strong gag reflex, it may be possi-ble to provide a maxillary implant denture withreduced palatal coverage. If sufficient numbersof implants can be placed, with grafting if neces-sary, it may be preferable to plan for an implantbridge at the outset. In the mandible, as few asthree implants in good quality bone have beenused to retain implant bridges (Brånemark et al.,1999).

Where the complaint is of lack of confidenceand fear of movement of the denture, implantstabilization of the denture may be indicated

even though ridge resorption may not be severe.Where the residual ridges have undergone littleresorption, however, there may be a shortage ofvertical space for implant components.

Many alternative treatment plans in practiceare developed because the patient finds the idealtreatment plan too expensive. This can lead todissatisfaction in implant treatment because theapparently lower cost option may be denture-based whereas the ideal treatment is a fixedrestoration. In reality, implant dentures requireconsiderable maintenance (see Chapter 17). Notonly do the dentures need repairing, relining orreplacing but the various attachment mecha-nisms between the implants and the denturesare also subject to wear, fracture and loss and itis time consuming to replace them. The cost ofthis maintenance must be included in anycomparison between the costs of fixed andremovable implant restorations.

Indications for implant denturesas provisional prostheses

In those situations where a fixed implant bridgehas been planned but some implants have failed,it may be necessary to provide a provisionalimplant denture until further implants can be


Figure 6.2

Dental panoramic tomograph (DPT) radiograph of samepatient showing severe resorption of mandible.

Figure 6.3

Partially dentate patient with posteriorly placed abutmentteeth. Four AstraTech implants have been placed tosupport and retain the long span anterior base of a partialdenture since a fixed restoration could not provide suffi-cient replacement of the resorbed tissues.

placed. If the original clinical problem indicateda fixed solution, then that should be pursued.However, in such emergency situations, a failurerate of 72% for the remaining implants has beenreported (Palmqvist et al, 1994).

Assessment of the patient

The commonest denture complaints are aboutlooseness, pain or discomfort, inability to eat,poor appearance and poor speech. Fortunately,a strong gag reflex is not common and themajority of patients have come to terms with theloss of their teeth. A patient may still be embar-rassed about the problem, however, and reportan ‘acceptable’ concern. This may be one that isdifficult to assess, such as vague discomfort,general looseness or difficulty in eating. Forexample, some patients may consider them-selves rather vain if they complain about theappearance of the dentures and so tell you thatthey cannot eat. It should be possible to elicit thereal problem, however, by a series of questionsabout the similarity of the present denture teethto the original natural teeth.

The recommended method of history-taking iswell covered in standard textbooks aboutconventional complete dentures and so will notbe repeated here. What you are trying to find outis whether or not the patient’s clinical situationcomes under the indications mentioned aboveand whether or not the patient would benefitfrom implant treatment. Problems caused byfaults in denture construction are generallyresolved by better conventional dentures andthese should certainly be attempted prior toimplants unless it is evident that implant treat-ment is also indicated. Complaints about poorappearance cannot be resolved by implant treat-ment per se but by setting the denture teeth ina more natural position with reference tophotographs of original teeth when available. Ofcourse, if a patient has had teeth extractedbecause of unhappiness with their appearance,you will not be thanked if you suggest restora-tion of the original appearance!

The medical history should be discussed,although there are very few contraindications toconventional complete dentures because they,and the treatment stages required to make them,

are among the least invasive of any dental proce-dure. Some patients consider dentures as themost invasive dental procedure, being inextrica-bly related to the extraction of the natural teeth.Psychological problems caused by the latter maybe helped by implant treatment but the outcomemay be uncertain: unresolved conflict over theloss of the teeth may lead to an irrationalresponse to treatment.

Putting implants into bone is a surgical pro-cedure and contraindications to surgery havebeen discussed in Chapter 1. Prosthodonticcontraindications would include lack of space inwhich to place components and parafunctionalforces greater than those that the componentscan bear. However, if the implants themselvescan withstand these forces, then you and thepatient must accept that there will be moremaintenance and repairs of the dentures thannormal. The alternative is greater potential forpain and bone resorption with conventionalcomplete dentures. The patient must beinformed prior to treatment so that any subse-quent explanation as to why bits keep breakingoff the dentures is not perceived to be a lameexcuse.

Severe mental illness has generally beenincluded in lists of contraindications for implanttreatment because of the difficulties of reason-able informed consent. However, the mentalproblems that lead to severe denture intoleranceand failure to come to terms with the loss of theteeth are the same as those that would pose diffi-culties were implant treatment to fail. Forpatients in this group, it is crucial to know thelikely response to failure of treatment. It is a diffi-cult area to judge and referral to a clinicalpsychologist or psychiatrist may be necessary.

Examination of the patient and

the existing dentures

The face and mouth should be examined in asystematic manner for pathological conditions.Extraorally, the amount of lip and cheek supportprovided by the existing dentures should benoted, as well as the occluding vertical relation-ship with the dentures in place. Intraorally, theresorption of the residual alveolar ridges should

DIAGNOSIS AND TREATMENT PLANNING FOR IMPLANT DENTURES 71

be recorded as mild, moderate or severe. Thesulci should be examined for displaceability,width and depth. A ball-ended burnisher is usefulfor examination of displaceable tissue andfibrous replacement of ridges. The vibrating lineof the palate should be graded as being a broadarea or sharply demarcated, and the depth of thehamular notches should be noted. The positionof the coronoid process should be noted becauseit sometimes occludes the pterygomaxillaryfossa in lateral movements of the mandible. Themucosa should be examined carefully and anyinflammation, ulceration, sinuses, retained roots,etc. noted. The quantity and quality of salivashould be assessed.

The existing dentures should be examined forbasic details such as:

1. Extension2. Occluding vertical relationship3. Occlusal plane4. Anterior and posterior tooth position5. How the teeth meet and slide over each other6. Shape and colour of the denture teeth7. Contour and colour of the denture base

material

It is generally accepted that the occluding verti-cal relationship of conventional completedentures must allow for sufficient freeway spaceand that the denture teeth should meet evenlywhen the patient closes in the retruded position.

Examination of the dentures out of the mouthwill reveal whether or not there may be sufficientspace for components should implant treatmentbe considered and give an approximate idea ofwhere the implants should be placed. This isobviously easier the better the technical qualityof the dentures. If they have been made at thecorrect vertical relationship with a correctocclusal plane, then the thickness of the denturecan be measured with a calliper. This is themaximum space available from which somethingmust be subtracted to allow for denture teeth.

Where existing dentures have too manytechnical errors to be useful in assessing theproposed implant position, a trial set-up (Figure6.4) will be needed as part of the special inves-tigations. When grafting is planned, such a trialset-up will indicate how much space is availablefor the graft when the space for the componentsand teeth is subtracted (Figures 6.5, 6.6).


Figure 6.4

Completed trial set-up of denture teeth on casts which hadbeen mounted on articulator using facebow record andinterocclusal record.

Figure 6.5

DPT radiograph of patient with severe resorption of maxillanecessitating grafting in order to place implants.

Figure 6.6

Articulated diagnostic casts showing space available forgraft, prosthodontic components, and teeth.

By this stage you have listened to your patientand examined the mouth and existing dentures,and it should be possible for you to arrive at aprovisional diagnosis. This may include:

1. Moderate or severe alveolar ridge resorption2. Unstable dentures3. Incorrectly constructed dentures with one or

more errors of base extension, tooth position,occlusion, etc.

4. Poor adaptation to dentures after loss of teeth5. Pathological conditions such as retained

roots, denture ulcers, hyperplasia, etc.

Other special investigations may include radio-graphs to complete the diagnosis and referralsto specialists for suspicious ulcers, etc. If theclinical situation comes under the indicationsmentioned earlier, you will certainly be thinkingof implant treatment and a radiographic exami-nation will be needed.

Radiographic assessment

The standard view is the dental pantomogramwith some way of working out the magnification.This can be done by taping a trident device withknown tine lengths to the skin in the area to beassessed (Figure 6.7). The bone height on thefilm then can be calculated by reference to theknown enlargement of the image of the trident.Many dental panoramic tomograph (DPT)machines now produce films to a known magni-fication and the bone dimension can bemeasured directly using a ruler supplied by themanufacturer. Alternatively, transparent overlayswith printed images of different length implantsto known magnifications can be used to selectproposed implant size directly. There is somehorizontal distortion with all DPT machines.

A lateral skull view can be useful for theanterior maxilla and mandible (Figure 6.8). But toassess accurately the amount of bone in otherareas a sectional tomogram will be required. Forexample, a Scanora machine (Soredex Orion,Helsinki, Finland) will provide sections or a fullcomputed tomography (CT) scan can be used. Astent with radiographic markers is required tomatch the films with the clinical sites.


Figure 6.7

DPT radiograph showing image of trident with tines ofknown length.

Figure 6.8

Lateral skull radiograph showing midline of mandible. Thethickness and density of the cortical bone and the cancel-lous bone can be clearly seen.

Figure 6.9

Lateral skull radiograph of patient who has had onlay graftsto anterior maxilla to increase width of available bone. Thegrafts were taken from the anterior mandible and aresecured by titanium screws to the existing maxillary bone.

For mandibular implant dentures, a DPT filmwill probably suffice because the implants needonly be placed in the canine region. This film willalso indicate whether or not grafting will berequired for lack of ridge height but it is lessuseful for assessing ridge thickness. Palpation ofthe ridge thickness is useful in the anteriormandible but can be very misleading in themaxilla where the palatal mucosa is thick.

The sections, either from a lateral skull view orfrom tomograms, will indicate the quality andquantity of bone available for implant placement.In our experience, grafting is rarely needed in themandible but is needed in the maxilla when eitherthe vertical height or width is insufficient. It isbeyond the scope of this section to go into detailabout grafting (see Chapter 12) but, in outline,bone grafts for implant dentures may be onlay orinterpositional. For maxillary implant dentures forpatients with severe bone resorption, onlay grafts(Figure 6.9) are generally sufficient: there is noneed to reposition the alveolar ridge to improveappearance because the denture flange can beused to restore the soft-tissue contour.

Diagnosis and treatmentplanning

By this stage, sufficient information should beknown to confirm the diagnosis and to decide

what treatment is appropriate. If the patient’sclinical situation comes under the indicationcategories mentioned above, you can decidewhether or not implant treatment is indicated,whether or not there is sufficient bone of goodquality and whether or not there are anycontraindications to the treatment. The outcomemay be that new conventional dentures areindicated and that there is no real indication forimplant treatment. Having said that, it could beargued that all edentulous patients would benefitfrom two implants in the mandible to support thedenture and to prevent further bone resorption.Certainly, if there were evidence of fairly rapidbone resorption even though the patient was notsuffering any problem, it would be good clinicalpractice to inform the patient of the fact andsuggest treatment. The effect of implant treat-ment in the mandible on a conventional maxil-lary complete denture must also be consideredand it may be necessary to consider implants inboth jaws. Fixed implant bridges may beindicated with or without grafting; these restora-tions are covered in Chapter 5.

Once treatment has been decided, the nextstep is to plan the sequence of the stages. Unlessthe existing dentures are technically correct, atrial set-up is essential to decide proposed toothposition (Figure 6.4) and to confirm the amountof space for the components. Once toothposition is confirmed, a stent can be made fromthe trial denture (Figure 6.10) or duplicate of theexisting denture (Figure 6.11). Guide holes arethen cut in the stent to indicate the proposedimplant position and opened out buccally orlingually so that the guide pins used duringimplant placement can be directly observed(Figure 6.12). In general, the proposed implantposition should be that which allows the compo-nents to be sited in the thickest part of thedenture resin and within the normal contour.

Prosthodontic components

available

Nobel Biocare

This manufacturer offers various bars and ballattachments for implant dentures. The original 2-mm diameter round bar and small clip system


Figure 6.10

The mandibular trial denture shown in Figure 6.4 has beenduplicated in clear acrylic resin. Guide holes have been cutin the canine region of the stent and opened out buccally.

has been expanded to now include macro andmicro ovoid bars and macro and micro U-shapedbars, all with clips that can be cut to the requiredlength (Figures 6.13–6.16).

These preformed gold bars can be soldered togold cylinders, 3 and 4 mm in height, that arescrewed to standard abutments ranging in lengthfrom 3 to 10 mm. Fixture head gold alloy cylin-ders (Figures 6.17 and 6.18) and titanium alloycylinders also are now available. These wereintroduced with single-stage implants, where theexternal hex is placed supramucosally to reduce


Figure 6.11

A stent has been made from a duplicate of an existingdenture.

Figure 6.12

Mandibular stent in place during implant placement. Theguide pins placed into the implants can be seen emergingin the intended position.

Figure 6.13

NobelBiocare 2-mm diameter round bar soldered buccallyto gold cylinders on two mandibular implants to avoidencroachment on lingual sulcus.

Figure 6.14

Fitting surface of denture showing two clips forNobelBiocare round bar.

Figure 6.15

NobelBiocare Macro-Ovoid bar on four maxillary implants.

the overall height of the supramucosal compo-nents. They are very useful, however, for rathersuperficially placed implants to obtain a low barprofile.

The original standard ball attachment consistedof a ball-headed titanium screw and a 3–5.5-mmsleeve similar to the standard abutment sleeve(Figure 6.19). The matrix consisted of a plasticcap (with rubber O-ring), 5.5 mm high and7.2 mm in diameter, that was processed into thedenture. The ball-headed titanium screw has now


Figure 6.16

Fitting surface of mandibular denture showing customlength clips for NobelBiocare Macro-Ovoid bar.

Figure 6.17

Mandibular cast with three NobelBiocare fixture head goldalloy cylinders. These cylinders can be adjusted to obtainlowest profile for bar.

Figure 6.18

Mandibular cast with low profile bar constructed onNobelBiocare fixture head gold alloy cylinders.

Figure 6.19

NobelBiocare standard ball attachment. A mandibularimplant denture has been sectioned through a retentioncap in the canine region and a ball attachment with sleeveplaced in position. The ball attachment is screwed into theimplant and the sleeve fits around the external hex. Thedriver engages an internal hexagon on the top of the ballattachment.

Figure 6.20

NobelBiocare 2.25-mm ball attachments in place on twomandibular implants. The ball attachment is screwed intothe implant retaining the sleeve around the external hex.The driver engages the flat surfaces on the collar of theball attachment.

been replaced with a gold alloy screw but the ballattachment is only available for regular platformimplants. Some years later, Nobel Biocare intro-duced a 2.25-mm ball attachment (Figure 6.20)with a six-tined adjustable gold alloy matrix or atitanium alloy matrix with replaceable stainless-steel circlip. The circlip can be replaced byunscrewing the cover. The gold matrix is 2.3 mmhigh and 3.7 mm in diameter. The titanium alloymatrix is 3.1 mm high and 3.7 mm in diameter.The gold matrix is processed into the acrylic resinof the denture base. Only the retention portion of

the titanium alloy matrix is processed into theacrylic resin, positioned by a mounting sleeve.The circlip and cover are attached after thedenture is finished. The 2.25-mm ball attach-ments are available for narrow and regularplatform implants.

AstraTech

This manufacturer supplies a 1.9-mm diameterround gold alloy bar, 50 mm in length, with smallriders (clips) manufactured by Cendres and


Figure 6.21

AstraTech 1.9-mm diameter round gold alloy bar solderedto gold alloy cylinders on four maxillary implants (photo-graph courtesy of Mrs C Morgan).

Figure 6.22

AstraTech ball attachments on two mandibular implants.These attachments are solid and are screwed into theinternal cone of the AstraTech implants via the flatsurfaces just below the ball.

Figure 6.23

AstraTech magnet system. The TiN coated keepers havebeen screwed into 45° uni-abutments in four maxillaryimplants. A driver engages the flat surfaces of thekeepers.

Figure 6.24

AstraTech magnet system. The fitting surface of the maxil-lary denture showing four titanium encapsulated steel alloymagnets.

Metaux. The bar is soldered to gold alloy cylindersthat are screwed to 20° or 45° uni-abutmentsranging in length from 0 to 6.0 mm. There is asmall ball abutment (Figure 6.22), in lengths of0–6.0 mm, with an adjustable four-tine gold alloymatrix that is processed into the acrylic resin of thedenture. There is also a magnet system that has aTiN-coated keeper that screws into a 45° uni-abutment with a titanium-encapsulated steel alloymagnet in the denture (Figures 6.23 and 6.24).

ITI/Straumann

This manufacturer supplies mini and regular egg-shaped gold alloy bars and clips (Dolder bars:manufactured by Cendres and Metaux, Biel-Bienne, Switzerland). The bar is soldered to agold alloy coping that is screwed to the Octa(now SynOcta, Institut Straumann, Waldenburg,Switzerland) abutment. ITI/Straumann alsosupply mini and regular titanium bars and clipsfor laser welding to titanium copings as well asplastic burn-out patterns for casting titanium barsand copings. There is a small ball attachment(Figure 6.25: listed as a retentive anchor) thatscrews directly into the ITI/Straumann implant(there is no abutment as such) with an adjustablefour-tine gold alloy matrix and a titanium alloymatrix with replaceable stainless-steel circlip thatappears identical to the Nobel Biocare matrix.

3i

This manufacturer provides a range of compo-nents that fit other manufacturers’ implants. Theirsmall ball attachment was available a year beforethe Nobel Biocare 2.25-mm ball attachment andhas a very low profile matrix with rubber ringrequiring as little as 3 mm of vertical space(Figures 6.26 and 6.27). The matrix is attached to


Figure 6.26

3i ball attachments have been screwed into NobelBiocareimplants. The matrices are in place on the ball attachmentsand are attached to the denture with autopolymerizingresin via an intraoral procedure. The red O-rings are fittedto the matrices for this procedure and are removed andreplaced with the white O-rings.

Figure 6.27

Fitting surface of maxillary denture. The red O-rings havebeen replaced with the white O-rings. The rubber O-ringsare easily removed and replaced with a flat plastic instru-ment.

Figure 6.25

ITI/Straumann retentive anchor. The ball attachmentscrews into the implant with the driver engaging the flatsurfaces.

the denture by autopolymerizing resin as anintraoral procedure. There is also a castable ballattachment for use on non-parallel implants inconjunction with a UCLA (University of Californiaat Los Angeles) abutment. A preformed roundgold alloy bar and clips is supplied as well as theHader bar and plastic clip system.

Other manufacturers

There are several other manufacturers who offerbar/clip systems and ball attachments, e.g.Friatec and IMZ.

Choosing the implant systemand retentive device

Mandibular dentures

In general, two to four implants placed betweenthe mental foramina have been suggested, withthe denture being retained by clips onto a barjoining the implants, by ball attachments ontothe individual implants or by magnets. Bars havebeen round or ovoid to allow some rotation ofthe denture but it has been shown that the barconfiguration does not appear to be significant(Wright and Watson, 1998).

The results from medium- and long-termstudies, however, have shown that two implantsplaced in the canine region are sufficient tostabilize a mandibular denture (Mericske-Stern,1990; Chan et al., 1995). Moreover, two ballattachments have been shown to be as effectiveas a bar and clip system (Naert et al., 1998). Theimplants for ball attachments should be parallelfor best results, although manufacturers statethat divergences of up to 10° are acceptable. The3i’s system has a castable ball so that divergentimplants can still be used for ball attachments.

The major systems that we have used (NobelBiocare, AstraTech, ITI/Straumann) have all beenshown to be effective in stabilizing mandibulardentures, whether by bar and clip systems, byball attachments, or by magnets (Mericske-Stern,1990; Jemt et al., 1996; Makkonen et al., 1997;Davis and Packer, 1999). Ball attachments have

been shown to be as effective as bar and clipsystems, so they should be the first choicebecause they are simple to use, require lesslaboratory work and produce no dead spacespace for overgrowth of soft tissue.

We have no particular recommendations as towhich implant system should be used in themandible: all three major systems appear equallyeffective. The ITI/Straumann implant has a slightdisadvantage in that no compensation is possibleif the implant is placed too superficial. The othersystems have varying lengths of abutments. TheNobel Biocare system has implant head gold ortitanium cylinders that enable a very low profilefor their bar/clip system.

If there is sufficient space, the standard NobelBiocare ball attachments appear to be thesimplest and the most durable. The implantshould be placed so that the retention cap willbe sited within the thickest part of the acrylicresin and within the normal contour of thedenture (Figure 6.19).

Where the implants are divergent, a bar andclip system can be used or the 3i castable ball.The amount of space available must be sufficientfor both the bar and the clip to lie within thecontour of the denture. The final decision as tothe exact position of the bar should be madeafter the final set-up of the implant denture teeth.It may be necessary to solder the bar lingual orbuccal to the gold cylinders to enable the clip tobe positioned within the contour of the dentureor to avoid encroaching on the lingual sulcus(Figure 6.13). The original Nobel Biocare roundbar worked well but the small clips sometimesfractured. The later ovoid bars, both micro andmacro, come supplied with long clips that can becut to size. Occasionally, these clips come out ofthe acrylic resin entirely. The ITI/Straumann barand clip (the Cendres and Metaux Dolder bar)appears to be the most durable bar/clip combi-nation and we have occasionally used this bar onother manufacturers’ gold cylinders.

A disadvantage of any bar and clip system isthat there will be a dead space in the denture intowhich soft tissue can proliferate. Various sugges-tions have been made to reduce the dead space,including the lowest possible profile of bar or theuse of silicone rubber inserts to fit around the bar.The amount of space available will be shown bythe trial set-up and the appropriate system canbe selected.


Maxillary dentures

The consensus appears to be that the minimumnumber of implants in the maxilla for an overden-ture is four and that they should be splinted by abar. The retention device can be a clip or clipsdirectly onto the bar, or studs or other attach-ments can be soldered to the bar with matricesin the denture. Most studies show higher failurerates for implants in the maxilla but they had toomany variables to enable comparisons to bemade between various retention systems. Onestudy followed 49 patients for up to 10 years,comparing the Nobel Biocare round bar and clipsystem with the Nobel Biocare standard ballattachments, and found no difference betweenthe two retention systems (Bergendal andEngquist, 1998). What appeared to be moresignificant was the quality of the bone, becausethe bulk of failures occurred in poor quality bone.It would seem sensible to place four or moreimplants in poor quality bone and join themtogether. For the maxilla, it may be more impor-tant to select an implant system with the bestsuccess rate in poor quality bone, such as onewith implants that have a roughened surface.

For bar and clip systems, the implants need tobe spaced so that there is room for clips betweenthe implants. Most manufacturers have clips thatcan be adjusted for length. Clips can be placedon cantilevered bars but the added strain willlead to occasional solder joint failure and ahigher rate of clip fracture or dislodgement.

Owing to the greater difficulties experienced inproviding maxillary overdentures on singleattachment systems, some clinicians advocateplacement of as many implants as possible, withthe provision of a milled or spark-eroded bar tosupport a removable bridge with a flange. Thisis one of the most technically demanding andexpensive prosthetic options and is not coveredin this book.

Single-stage or two-stage

implants

There are no real advantages or disadvantagesof either approach from a prosthodontic point ofview. Certainly, the patient will get the finishedimplant denture in a slightly shorter time but the

existing denture may have to be highly modifiedin order for it to be worn safely while theimplants are deemed to be integrating. If thedenture can be modified with an appropriate softmaterial, it will probably be more stable overhealing abutments after a single-stage procedurethan over the edentulous ridge following theimplant placement in a two-stage procedure.Single-stage implant placement has been shownto be effective for mandibular implant dentures(Cooper et al., 1999).

Bibliography

Bergendal T, Engquist B (1998). Implant-supportedoverdentures: a longitudinal prospective study. Int JOral Maxillofac Implants 13: 253–62.

Brånemark PI, Engstrand P, Ohrnell LO, Grondahl K,Nilsson P, Hagberg K, Darle C, Lekholm U (1999).Brånemark Novum: a new treatment concept forrehabilitation of the edentulous mandible. Preliminaryresults from a prospective clinical follow up study. ClinImplant Dent and Related Research 1: 2–16.

Chan MFW-Y, Johnston C, Howell RA, Cawood JI(1995). Prosthetic management of the atrophicmandible using endosseous implants and overden-tures: a six year review. Br Dent J 179: 329–37.

Cooper LF, Scurria MS, Lang LA, Guckes AD, MoriartyJD, Felton DA (1999). Treatment of edentulism usingAstraTech implants and ball abutments to retainmandibular overdentures. Int J Oral MaxillofacImplants 14: 646–53.

Davis D, Packer M (1999). Mandibular overdenturesstabilised by AstraTech implants with either ball attach-ments or magnets. Int J Prosthod 12: 222–9.

Fenlon MR, Sherriff M, Walter JD (2000). An investiga-tion of factors influencing patients’ use of newcomplete dentures using structural equation modellingtechniques. Comm Dent Oral Epidemiol 28: 133–40.

Jemt T, Chai J, Harnett J, Heath MR, Hutton JE, JohnsRB, McKenna S, McNamara DC, van Steenberghe D,Taylor R, Watson RM, Herrman I (1996). A 5-yearprospective multicentre follow-up report on overden-tures supported by osseointegrated implants. Int J OralMaxillofac Implants 11: 291–8.

Makkonen TA, Homberg S, Niemi L, Olsson C,Tammisalo T, Peltola J (1997). A 5-year prospectiveclinical study of AstraTech dental implants supportingfixed bridges or overdentures in the edentulousmandible. Clin Oral Implants Res 8: 469–75.


Mericske-Stern R (1990). Clinical evaluation of overden-ture restorations supported by osseointegratedtitanium implants: a retrospective study. Int J OralMaxillofac Implants 5: 375–83.

Mericske-Stern R, Zarb GA (1993). Overdentures: analternative implant methodology for edentulouspatients. Int J Prosthod 6: 203–8.

Naert I, Gizani S, Vuylsteke M, van Steenberghe D(1998). A 5-year randomised clinical trial on the influ-ence of splinted and unsplinted oral implants in

mandibular overdenture therapy. Part 1: Peri-implantoutcome. Clin Oral Implants Res 9: 170–7.

Palmqvist S, Sondell K, Swartz B (1994). Implant-supported maxillary overdentures: outcome in plannedand emergency cases. Int J Oral Maxillofac Implants 9:184–90.

Wright PS, Watson RM (1998) Effect of prefabricatedbar design with implant-stabilized prostheses on ridgeresorption: a clinical report. Int J Oral MaxillofacImplants 13: 77–81.


PA R T I I I

Surgery

Introduction

After planning, the surgical execution of implantplacement is the next critical procedure in theattainment of successful osseointegrated im-plants. The most important factors to control inimplant surgery are:

1. A sterile technique avoiding contamination ofthe implant surface.

2. Avoiding damage to the bone by thermalinjury during the drilling process.

3. Careful preparation of the bone site so thatthe implant is stable at placement.

4. Placement of the implant in an aestheticallyand functionally acceptable position.

5. Avoidance of excessive loading in the healingperiod. Some protocols advocate no loadingfor 3–6 months. Newer protocols that allowimmediate loading depend upon very carefulcontrol of the magnitude of loading (seeChapter 1).

Poor control of these factors can lead to failureof osseointegration, which may be manifestedsubsequently as:

1. Infection at the implant site.2. Implant mobility or the implant may be

rotated when attempting to detach or attacha component.

3. Pain from inflammation in the bone surround-ing the implant. This may be manifested aspain on pressure on the implant.

4. A radiolucent space surrounding the implantthat is consistent with fibrous encapsulation.However, a failed implant may have a normalradiographic appearance.

Under these circumstances the failed implant

would have to be removed and treatment recom-menced or an alternative sought.

Avoidance of thermal injury tothe bone

Bone cells will be damaged irreversibly if thetemperature is raised in the bone to 47°C formore than 1 min. Bone cell death will result inmore extensive resorption and failure of osseoin-tegration. This is avoided by:

• careful cooling of the bone and drills withcopious sterile saline

• use of sharp drills• control of the cutting speed

Coolant is applied to the external surface of thedrills or via the internal aspect in speciallydesigned internal irrigation drills. The harder andmore dense the bone, the more difficult it is tomaintain adequate cooling. In situations wherethe bone is dense, the surgeon runs the risk ofoverheating the bone as the depth of the drillingincreases. This can be minimized by acceptingshorter implant preparations as advocated in theStraumann system or by improving the coolingefficiency of the bone preparation. The Frialit 2system (Friatec AG, Mannheim, Germany), unlikethe other systems described in this text, usesinternally irrigated drills in addition to externalirrigation (Figure 7.1). The drills are extremelyefficient at cutting bone and the likelihood ofburning the bone must be low, provided that thedrills are replaced regularly (20 preparations) andcare is taken to ensure that the irrigant solutionis not blocked in its passage to the working tip.

7Basic factors in implant surgery


A B

C D

BASIC FACTORS IN IMPLANT SURGERY 87

Figure 7.1

A series of photographs illustrating surgical preparationand placement of an implant with the Frialit 2 system. Atall stages the drilling procedure is cooled by internal andexternal irrigation with sterile saline. (A) Buccal and palatalflaps have been raised to expose the bone at the uppersecond premolar site. (B) A 2-mm diameter twist drill isused to establish the initial angulation and depth of thesite. The drill has cross-cut grooves showing the length ofpreparation. In most cases the site is started with a roundbur that readily penetrates the outer cortex of bone. (C) A3-mm diameter twist drill enlarges the site and confirmsthe depth to accept a 13-mm long Frialit 2 implant. (D) Thefirst of the stepped Frialit drills enlarges the site to accepta 4.5-mm diameter implant. (E) The second of the Frialitstepped drills is used to enlarge the site to accept a 5.5-mm diameter implant. (F) A 13-mm long, 5.5-mm diame-ter Frialit 2 implant has been pushed into the site with theplacement head (ball-shaped device on top of the implant).It is then gently but firmly tapped into place until all theplasma-sprayed surface is within bone. (G) The placementhead is simply removed to reveal the sealing screw, whichprotects the inner part of the implant during the healingprocess.

E F

G


Figure 7.2

A series of photographs illustrating surgical preparation and placement of two implants with the Brånemark system (NobelBiocare AB, Göteborg, Sweden). At all stages the drilling procedure is cooled by external irrigation with sterile saline. (A)Flaps have been raised to reveal the bone ridge. The initial entry point of the site has been achieved with a round bur.A 2-mm twist drill is used to establish the angulation and depth of the site. The drill is marked with black bands at theimplant lengths. (B) The position and angulation of the two implant sites is verified with direction indicators. These shouldbe viewed from various angles and checked against the surgical stent and the opposing teeth (by asking the patient toclose and gently touch the indicators – they should be directed to the buccal cusps of the lower teeth). The angles canbe adjusted slightly at this stage. (C) Provided that the position and angulation are satisfactory, the sites can be enlargedwith a 3-mm twist drill following the same line. The surgeon is helped by reference to an indicator retained in the adjacentsite and by using a pilot drill that enlarges the top part of the site from 2 mm to 3 mm. (D) Both sites have been drilledto 3 mm in diameter. A direction indicator is in the distal site and a measuring probe is being used to verify the depthof the anterior site. (E) The bone cortex is countersunk to accept the implant level with the bone crest. The level ofcountersinking is varied according to many factors, including available bone height, bone quality, interocclusal space,aesthetic demands and emergence profile of the planned restoration. It is helpful to judge this against the surgical stent.(F) The threaded implant is inserted using slow revolutions of the handpiece and is cooled with sterile saline irrigation.The implant is either a ‘self-tapper’ or the site is pre-tapped according to bone hardness and operator preference. (G) The

A B

C D


implants in place. They have at least 2 mm of interveningbone and about the same between the anterior implantand the adjacent tooth. (H) Cover screws have been placedon the implant heads to protect the inner aspect of theimplant during healing. They are level with the surround-ing bone. (I) The flaps are closed and the implants leftburied for 3–6 months in the classical Brånemark two-stage submerged protocol.

E F

G H

I

In all systems the implant site is prepared withsmall-diameter drills in the first place and thenthe site is gradually made larger with increasing-diameter drills (Figures 7.1 and 7.2). In additionto minimizing heat production, the initial use ofsmall-diameter drills also allows modifications tothe initial angle or site of preparation whenrequired. The drills should be sharp. This iseasier to ensure using new disposable drills foreach case, as in the Nobel Biocare/Brånemarkprotocol, compared with the other systemsconsidered in this book. However, the sophisti-cated design of the step-shaped internallyirrigated drills in the Frialit system (see Figure7.1) would be expensive to fabricate in a dispos-able form, therefore a record of the number ofsites prepared (and the hardness of the bone) isuseful in determining when drills should bereplaced. This also applies to the Straumann andAstra systems.

The cutting speed of the drills during the mainpreparation of the sites is approximately1500–2000 rpm. The flutes of twist drills may beclogged up with bone debris, and therefore it isimportant to withdraw them from the prepara-tion site at regular intervals during the prepara-tion process to wash away the debris and coolthe drill. If the site needs to be tapped, as in theoriginal Brånemark protocol, this is done atspeeds comparable with those used to insertscrew-threaded implants (approximately 20 rpm).

Ensuring good initial stability ofthe implant

The surgical preparation aims to provide animplant that feels stable following insertion. Thiscan be judged by:

• simple clinical evaluation (dependent uponoperator experience)

• torque insertion forces – these can be set onthe drilling unit and are usually between 10and 45 Ncm. Some units record the torqueand provide a printout

• periotest values – the mobility can bemeasured with an electronic instrument thatwas originally designed to measure toothmobility

• resonance frequency analysis – this latestdevice measures the stiffness of the implantwithin the bone through electronic vibrationand recording

The last two methods have been used mainly inexperimental studies but could find a clinicalapplication. An implant that is loose within theprepared site will not osseointegrate. In the earlyphases of healing the implant must not besubjected to forces that will cause movement ofthe implant, even if the movement is small. It hasbeen suggested that micromovement up to100 µm may be compatible with healing byosseointegration, but beyond this fibrous encap-sulation is more likely to occur. It is not possibleto offer comparative data between implants inthis respect. However, various approaches canbe adopted to ensure a stable implant with thedifferent implant systems. Initial stability of theimplant depends upon:

1. Length of the implant2. Diameter of the implant3. Design of the implant4. Surface configuration of the implant5. Thickness of the bone cortex and how many

cortices the implant engages6. Density of the medullary bone trabeculation7. Dimensions of the preparation site compared

with that of the implant

The philosophy of what constitutes adequateimplant length varies between systems. Theoriginal Brånemark concept was that of bicorticalstabilization. This required that an implantextended from the superficial cortex of theedentulous ridge to the inferior cortex of theanterior mandible or the nasal floor or floor ofthe antrum in the maxilla. This is clearly notpossible in the posterior mandible because of thepresence of the inferior dental canal and in thissituation shorter implants with unicorticalfixation are used. Bicortical fixation is probablyonly advantageous in areas of poor bone qualityin the medullary space. The Straumann systemroutinely uses shorter implants of 8–12 mm inlength, and fixation and surface area areimproved by using solid screws (hollow screwnow only available for single tooth replacement)with surface treatments of either plasma-sprayedtitanium or sand blasting and acid etching (see


Chapter 1). This type of implant may be a goodchoice for bridgework in the posterior mandibleand posterior maxilla, where there may be littleheight of available bone.

There is one other important proviso aboutimplant length, and that is to ensure that thereis adequate vertical space when the patientopens his/her mouth to permit insertion of theplanned length of implant together with its inser-tion device. The latter could include thehandpiece head, handpiece connector andimplant mount. Although many systems offerlow-profile versions of these components, thelength of the implant may be the most criticalfeature. This is not usually a problem for theanterior region of the mouth but is very impor-tant in the molar regions. Some systems such asStraumann have a gauge that can be used toassess this factor (Figure 7.3).

Most systems produce implants in widerdiameters to improve stability and strength (seeChapter 4). The increased diameter provides anoverall greater surface area and theoreticallymay provide the equivalent of bicortical stabi-lization by engaging both buccal and lingualcortices.

The Brånemark system implant has also beenmodified as an alternative approach to improvestabilization in areas of limited bone height andlimited bone quality. The modification to theimplant for poor quality bone has been to producea slightly tapered implant with a double helicalthread. This means that it requires half the numberof rotations to seat it and it will cut more efficientlyin softer bone. The surface of the implant is likethe rest of the Brånemark system – machined –and therefore the response of the bone to thesurface will presumably be the same, the onlydifference being a higher degree of initial stability.

The Frialit 2 system provides a differentapproach to this problem. The surface area of theimplants is increased considerably by having astepped cylinder design, a range of differentdiameters and a surface that is treated. The Frialit2 push-fit implant can be used in practically allsituations and may have advantages over a screwdesign in soft bone. The Frialit 2 is also availablein a screw design. Each of the stepped cylindershas an individual thread and it only requires threerotations to ensure full seating of the implant.The threaded implant may have better initialstability in bone that is more dense and is partic-

ularly recommended in immediate replacementprotocols (see Chapter 11).

The initial stability of an implant can beimproved easily by inserting an implant into asite that is prepared smaller than the implant.This approach is used in the AstraTech systemto good effect (see Chapter 10, Figure 10.1).Therefore, when using a 3.5-mm diameterimplant the site is routinely prepared to a diame-ter of 3.2 mm and the implant is self-tapped intoposition. If, however, the bone at the site is verydense, the surgeon is advised to prepare the siteto a diameter of 3.35 mm. Similar recommenda-tions are given with the 4-mm. diameterAstraTech implant, with twist drills of 3.7 and


Figure 7.3

The Straumann measuring device is used to check thatthere is adequate inter-arch space to accommodate thehandpiece and drill.

3.85 mm according to the available bone density.The AstraTech implant surface is blasted (withtitanium oxide giving a 5-µm rough surface),which may do little to improve initial stability buthas been shown to achieve higher bone-to-implant contact in the healing period comparedwith a machine surface. This is also true of theplasma-sprayed surfaces (Frialit and Straumann)and the SLA (Sand blasted–Large grit–Acidetched) surface of the Straumann.

Placement of the implant in an

acceptable position

This is dealt with in considerable detail in thechapters on single teeth (Chapter 9) and fixedbridges (Chapter 10). Problems should beavoided by:

1. Careful planning2. Use of surgical stents3. Reviewing each stage of the preparation

process

Surgical stents should be constructed using thediagnostic set-ups or provisional prosthesis.They should be rigid enough to prevent distor-tion and stable to minimize movement (Figure7.4). Stents constructed in cold-cure acrylic using

adjacent teeth for stability are ideal. The stenthelps the surgeon with the mesiodistal position-ing of the implant (avoiding placement in theembrasure spaces) and the buccolingualpositioning and angulation. In replacing anteriorteeth it is particularly important to provide theprofile of the buccal aspect of the prosthesis,including the cervical margin, to give theplanned emergence profile (Figure 7.5) in orderto optimize aesthetics.


Figure 7.4

A rigid cold-cure acrylic stent reproducing the labial facesof the missing central incisors. Direction indicators havebeen placed in the initial preparation sites to assessagainst the stent.

Figure 7.5

(A) A clear plastic ‘blow down’ stent constructed on a castfrom the diagnostic set-up. It has been trimmed to followthe cervical margins of the teeth. With short edentulousspans these stents are rigid and stable enough, but theplastic is generally too flexible for longer spans. Directionindicators show the initial preparation sites. (B) An occlusalview of the stent, with direction indicators showing thatthe angle of the sites is through the cingulum region ofthe crowns, allowing screw retention of the restorations.

A

B


Figure 7.6

A series of photographs illustrating surgical preparation andplacement of Straumann implants in a mandibular denturecase. (A) The atrophic mandibular ridge with little keratinizedmucosa. (B) A cold-cure acrylic stent has been constructedand tried in the mouth. The stent is a duplicate of thepatient’s denture, with slots cut in the regions of plannedimplant placement (right and left canine). At this stage ithelps to plan the location and extent of the incisions. (C)Flaps have been raised and the sites started using a roundbur to penetrate the hard cortex. The incision preserveskeratinized tissue on the labial and lingual aspects. A midlinelabial incison helps initial reflection and reduces tension. (D)The stent in position with a depth gauge/indicator post inthe patient’s right side and a twist drill on the left side. Thestent is removed to allow complete preparation of the sitebut is inserted at different stages to check on position andalignment. (E) The right site is being tapped and there is adepth indicator on the left side. Both show a depth of10 mm, which is the planned insertion length of the solid-screw 4.1-mm diameter implants. (F) The implants havebeen placed with the polished collars above the bone crest.(G) Closure screws have been attached to the implants andthe flaps have been sutured.D

C

B

A

E

F

G

It is more difficult to provide a stable stent inan edentulous jaw. Under these circumstancesthe stent needs to be extended onto stablemucosa (which is more readily accomplishedusing the palate) but still allow access and retainstability once the mucoperiosteal flaps areraised. In completely edentulous jaws and long-span edentulous spaces it is important toconstruct stents in a material that is sufficientlyrigid to retain its shape; if it was flexible it wouldcompromise implant positioning (Figure 7.6).

The stages of placement can be reviewedusing indicator posts in the prepared sites. Thesecan be evaluated against the surgical stent(Figures 7.5 and 7.6). It is recommended that thesurgeon reviews the angles of the indicator postsfrom various aspects. Failure to do so can leadto surprising errors.

The position of the indicator posts should alsobe reviewed in relation to the opposing dentition.In the buccal segments in a patient with a normalbuccopalatal relationship, the maxillary indicatorshould be directed towards the buccal cusps ofthe lower teeth and the mandibular indicatorstowards the palatal cusps of the maxillary teeth.This ensures that the implant is placed in thecentral fossa area of the tooth and forces aredirected down the long axis.

The level of the head of the implant should beplaced to allow adequate vertical space from theopposing dentition and to produce good aesthet-ics. These important issues are dealt with indetail in the following chapters.

Preoperative care, anaesthesia

and analgesia

Basic preoperative care should include:

1. Antiseptic rinsing of the oral cavity and perio-ral skin. Chlorhexidine gluconate (2% or 1.2%proprietary rinses for 1 min) is recommended.

2. Administration of analgesics. Oral analgesics(such as 200 or 400 mg of ibuprofen or acomparable alternative) are usually sufficientin most outpatient cases. Control of pain ismore effective if analgesics are given prior tosurgery and the levels maintained to preventdevelopment of severe pain.

3. Administration of antibiotics. This used to bea routine procedure. Placement of one or afew implants under ideal circumstancesprobably does not warrant antibiotics. Whereantibiotics are indicated (e.g. multipleimplants where bone is exposed for longperiods of time or grafting is carried out), theclinician could use a standard protocol (e.g.3 g of amoxicillin preoperatively, followed bya 5-day course).

Antibiotic and analgesic regimes will differaccording to the status of the patient, theviewpoint of the clinician and the country wherethe treatment is being carried out. It is thereforebeyond the remit of this book.

Anaesthesia

Many cases can be managed satisfactorily withlocal anaesthesia, depending upon the skill andexperience of the surgeon and the attitude of thepatient. The magnitude and duration of implantsurgery are considerably increased with multipleimplant placement, especially where more thanone quadrant is involved. As a general indication,it is worthwhile considering sedation techniquesin procedures likely to exceed 1 h (e.g. the equiv-alent of the placement of three implants or morefor the experienced operator). Prolonged difficultprocedures and those requiring extensive graft-ing may require general anaesthesia.

Local anaesthesia has advantages over generalanaesthesia. In particular the conscious patient isable to cooperate by performing normal jawmovements in centric and lateral excursions tohelp verify the appropriate implant positioning.The vasoconstrictor in the local anaesthetic isuseful in providing improved haemostasis andprolonged analgesia. Longer acting local anaes-thetics may be particularly useful in this type ofsurgery.

Basic flap design and soft-tissue

handling

Some surgical texts describe implant placementwithout flap elevation but this can readily lead to


lateral perforation of the bone in inexperiencedhands. It is more suited to single implant place-ment directly into extraction sockets, and this isconsidered in Chapter 11. Flap design (seeChapter 8) and elevation should achieve com-plete exposure of the edentulous ridge, includingany bone concavities and identification of impor-tant anatomical structures. The flap also shouldbe closed easily with sutures under minimumtension, with incision lines based upon soundbone as in any good surgical practice.

Elevation of flaps is best accomplished usingperiosteal elevators with a fairly sharp edge,especially where the bone ridge is uneven.Fibrous and muscle attachments that tether theflap margins may need to be released by sharpdissection. Flaps should be elevated to allowgood visualization of the ridge form but notexcessive in opening tissue spaces unnecessar-ily. However, good reflection of the soft tissueson the lingual aspect of the lower premolars isadvised because implant preparations in thisarea may inadvertently perforate the lingualplate in a natural concavity and damage a branchof the sublingual artery. This can result in exten-sive bleeding in the unreflected tissue that is notnoticed by the surgeon and results in a deep-seated sublingual haematoma. This may presentsome time within 24 h postoperatively and hasbeen reported to threaten the patient’s airway.

Before closure of the flaps it is important tocheck that there is no residual bone debris or clotbeneath the flaps by careful irrigation with sterilesaline and inspection with suction. The flaps arecarefully closed with sutures of the surgeon’schoice, either non-resorbable or resorbable. Inmost cases, simple interrupted no. 4/0 black silksutures are satisfactory. Vertical mattress suturesare recommended by some operators where amore secure seal is required, e.g. over a graftedsite. Finer no. 7/0 polypropylene sutures (as usedin plastic surgery) are recommended by others,in which case a larger number are required andfine suturing instruments are mandatory. How-ever, the most important factor is to ensure thatthe wound closure is free of tension. In difficultcases requiring flap advancement, periostealreleasing incisions, vertical relieving incisionsand stabilizing sutures remote from the woundedges can be helpful. Firm pressure with moistpacks should be applied to re-adapt the flaps andcontrol bleeding.

Basic postoperative care

Patients should be prescribed appropriateanalgesics, antibiotics if indicated and achlorhexidine mouthrinse. They should beadvised to use ice packs to reduce swelling andbruising, which does not usually occur withsimple cases. Postoperative pain should not besevere. Pain should not arise from the bonebecause this would indicate poor technique anddamage, possibly leading to failure. Surgeryclose to the inferior dental nerve may result intransient altered sensation and the patientshould be made aware of this possibility.

In many cases patients are advised not to weartheir removable dentures for 1–2 weeks in order toavoid pressure on the wound and implants. Thisrequirement is probably still valid with implantsurgery in the edentulous mandible. It is accept-able for the patient to wear a removable dentureafter surgery with placement of a small number ofimplants, where swelling is less likely and there isgood wound and denture stability. However, thedenture normally needs to be relieved and a softlining added. The patient should be seen 1 weeklater for suture removal and further adjustment totheir denture if required. Patients who areprovided with a fixed provisional prosthesis havean advantage in this respect, but may need adjust-ment to the undersurface of the pontics to accom-modate soft-tissue changes.

Bibliography

Brånemark PI, Zarb GA, Albrektsson T, eds (1985).Osseointegration in Clinical Dentistry. Chicago:Quintessence Publishing.

ten Bruggenkate CM, Krekeler G, Kraaijenhagen HA,Foitzik C, Osterbeek HS (1993). Haemorrhage of thefloor of the mouth resulting from lingual perforationduring implant placement: a clinical report. Int J OralMaxillofac Implants 8: 329–34.

Eriksson RA, Albrektsson T (1984). The effect of heaton bone regeneration: an experimental study in therabbit using the bone growth chamber. J OralMaxillofac Surg 42: 705–11.

Eriksson RA, Adell R (1986). Temperatures duringdrilling for the placement of implants using theosseointegration technique. J Oral Maxillofac Surg 44:4–7.


Ivanoff CJ, Sennerby L, Lekholm U (1996). Influence ofinitial implant mobility on the integration of titaniumimplants: an experimental study in rabbits. Clin OralImplants Res 7: 120–7.

Jaffin R, Berman C (1991). The excessive loss ofBrånemark fixtures in type IV bone. J Periodontol 62:2–4.

Lekholm U (1998). Surgical considerations and possi-ble shortcomings of the host sites. J Prosth Dent 79:43–8.

Meredith N (1998). Assessment of implant stability asa prognostic determinant. Int J Prosthod 11: 491–501.


Introduction

This chapter deals primarily with flap design forpartially dentate cases, describing most ex-amples in the aesthetic zone for single implantplacement. The same principles are applicable tolarger edentulous spaces. The last section brieflydescribes some aspects of flap design in theedentulous jaw.

Flap design in the aestheticzone

Some surgical texts describe implant placementwithout flap elevation but this can readily lead tolateral perforation of the bone in inexperiencedhands. It is more suited to single implant place-ment directly into extraction sockets, which isconsidered in Chapter 11. Flap design and eleva-tion should achieve adequate exposure of theridge, including any bone concavities, andidentify important anatomical structures. Theflap also should be closed easily with suturesunder minimum tension, with incision linesbased upon sound bone as in any good surgicalpractice.

A midcrestal incision can be employed in mostcases. The incision can be extended within thegingival crevices of adjacent teeth (Figure 8.1A)and the mucoperiosteum can be elevated quiteextensively in an apical direction to allowadequate visualization of the bone contour.

However, in most cases we advocate the useof relieving incisions to aid flap reflection andexposure (Figure 8.2). The relieving incisionsnext to teeth require particular attention. Theincisions can be kept vertical and parallel overly-ing sound bone so that, on closure, the flap’s

8Flap design for implant surgery

Figure 8.1

(A) An incision on the crest of the edentulous ridge isextended in the gingival crevices of the adjacent teeth toallow adequate exposure of the ridge. (B) A normal incisorspace with a midcrestal incision. The vertical relievingincisions on sound bone are flared at their apical extent.The relieving incisions extend a short distance into thepalatal mucosa to allow adequate elevation.

B

A

nutrition is not compromised. The apical extentcan be flared if improved in visualization of theapical bone contour is needed. It is important toavoid placing obliquely inclined relievingincisions over prominent root surfaces, becausethe wound can break down if there are underly-ing bone dehiscences and gingival recession canresult (Figure 8.1B).

On placing relieving incisions or reflecting theflaps, care should be taken to protect importantanatomical structures such as the mental nerve.Elevation of flaps over the incisive canal regionhas minimal consequences in terms of resultingparaesthesia, and bleeding is seldom a problem.Short relieving incisions into the palate are alsohelpful and do not need to be extended so far asto cut any major vessels.

Where there is little keratinized tissue it issometimes useful to locate the crestal incisiontowards the palatal aspect in the maxillary arch,which has considerably more keratinized tissueas it extends onto the palate (Figure 8.3). Thisdesign is also a useful strategy in cases wherebone augmentation procedures may be requiredon the labial aspect, to ensure adequate woundclosure remote from any implant surfaces, graftmaterials or GBR membranes. However, in theselatter cases it is probably prudent to place reliev-

ing incisions at least one tooth, lateral to the areaof augmentation treatment (Figure 8.4).

The main controversy in flap design for singletooth implants is whether to involve and reflect


Figure 8.2

(A) It is advised to avoid placing oblique relieving incisions over prominent root surfaces because recession may result ifthere is an underlying bony dehiscence. A broad base to the flap is not necessary for survival because the blood supplyand nutrient bed for mucosal flaps are excellent. (B) A midcrestal incision leaving papillae in situ. The oblique relievingincisions do not pass over the adjacent root surfaces.

A B

Figure 8.3

The crestal incision has been made on the palatal aspectof the ridge. Reflection of the flap may be slightly moredifficult and the wound margins are more remote from theimplant head. This was once considered to be importantin submerged implant surgery.

FLAP DESIGN FOR IMPLANT SURGERY 99

Figure 8.4

If augmentation procedures are thought to be required, itis prudent to base incision lines more remotely to avoidexposure of grafted materials. The relieving incisions havetherefore been made one tooth wide, laterally on eachside, and the crestal incision has been made towards thepalatal side.

Figure 8.5

(A) The wide central incisor space allows an adequatewidth flap to be developed in the middle of the space,while allowing preservation of the papillae. (B) A clinicalexample showing preservation of the papillae on theadjacent teeth in this wide central incisor space. The flapdesign and reflection have provided good visualization ofthe bone during implant insertion. (C) The same case withthe flap nicely approximated with just two crestal sutures.Relieving incisions may require suturing if they tend togape.

CB

A

the adjacent papillae or not. Avoidance of papillareflection aims to preserve the aesthetics ofthese structures which are difficult or impossibleto reconstruct if lost (Figure 8.5).

However, in many cases the single tooth spaceis narrow mesiodistally and elevation of thepapillae may be unavoidable (Figure 8.6). If onecan only preserve a narrow strip of soft tissue onthe proximal surfaces of the adjacent teeth, itmay have its blood supply compromised to suchan extent that full reflection of the tissue wouldbe no more damaging. The present authors haveroutinely elevated papillae as in the flap designshown in Figures 8.1 and 8.5, with no detrimentto the soft-tissue profile subsequently. We wouldtherefore recommend:

1. In sites that are less than or equal to 7 mmmesiodistally, to reflect the papillae.

2. In sites that are 8 mm or greater, a mesiodis-tal crestal incision of 5–6 mm will allow non-reflection of an adequate width of papillarytissue to recommend the technique.


Figure 8.6

(A) The narrower incisor space (as is often the case withlateral incisors) does not allow an adequate width of flapand avoidance of disturbing the proximal papillae, whichare routinely raised in this flap design. (B) A narrow maxil-lary lateral incisor is being replaced with a narrow-platform3.3-mm diameter Nobel Biocare implant. The flap designhas elevated all the soft tissue in the space and the paral-lel labial relieving incisions are at the line angles of theadjacent teeth.

A

B

Figure 8.7

Where the soft tissue of the ridge is thick, a split-thick-ness incision can be employed that produces a ‘halvingjoint’. This is designed to minimize the chance of break-down of the incision but can only be made in thick tissuewhere this problem is less likely to occur anyway.

3. If doubt exists as to the need to exposeanatomical structures such as the incisivenerve or if augmentation techniques may beindicated, then the wider flap design incorpo-rating papillae is again recommended.

The incisions described above are simple in-cisions through epithelium, connective tissueand periosteum down to bone. More sophisti-cated incision lines can be used where the tissueis thick in order to produce overlapping flapmargins rather than a simple butt joint (Figure8.7). This requires incision through the epithe-lium at one point, horizontal extension of theincision in the midzone of the connective tissueand a vertical incision down through the perios-teum. The resulting ‘halving joint’ may providemore secure coverage in areas where boneaugmentation is planned.

Additional considerations inedentulous jaws

As described in the previous section, a midcre-stal incision can be employed in most cases.Where there is little keratinized tissue, e.g. in thecase of the resorbed edentulous mandible, it is

recommended that the incision is made in themiddle of this tissue to retain some keratinizedmucosa on each side of the wound. The maxil-lary arch has considerably more keratinizedtissue as it extends onto the palate, and it issometimes useful to locate the crestal incisiontowards the palatal aspect. This strategy can beused to relocate more keratinized tissue on thebuccal surface of the non-submerged implant (orthe same at abutment connection surgery).

In the edentulous maxilla or mandible, amidline labial relieving incision extending intothe sulcus enables the surgeon to elevate underthe periosteum more easily, especially where thecrest of the ridge is knife-edged or uneven. Therelieving incision also reduces tension on thebuccal flap, making retraction much easier(Figure 8.8).

Flap design in abutmentconnection surgery

Flap design for abutment connection surgery isimportant because it gives the surgeon a chanceto modify the soft-tissue profiles. Many of thepoints raised also apply to handling of the flapsin single-stage non-submerged implant surgery.


Figure 8.8

(A) Flap design in the edentulous maxilla being treated with non-submerged Straumann implants. The crestal incision hasbeen made towards the palatal aspect of the planned placement site. This allows retention of more keratinized tissue onthe buccal aspects of the implants. A midline labial relieving incision helps flap reflection and lengthens the flap marginto improve adaptation around the implant collars. (B) The flaps are sutured with simple re-adaptation and no resection oftissue.

A B

In general, incisions are made directly over theimplant heads unless the surgeon wishes torelocate some of the available keratinized tissuemore on one aspect than the other. In severelyresorbed jaws with minimal keratinized tissue itis important to preserve it all, and in some casessoft-tissue grafting may be required. Small crestalincisions over the implant head and minimal soft-tissue reflection to allow abutment connectionare easier with systems that have an internalabutment/implant connection such as AstraTech(Figure 8.9). In the Brånemark system, we wouldgenerally advocate more extensive exposure ofthe implant head to facilitate abutment connec-tion, and to allow visual checking of the fit priorto radiographic verification. In some cases bonegrows over the implant head and this has to beremoved with small hand chisels (our prefer-ence), burs or purpose-designed mills, takingcare not to damage the implant. More flap reflec-tion is required if bone removal is needed, includ-ing the use of relieving incisions. It is importantto have relieving incisions remote from the edgesof the transmucosal abutment (or collar of a non-submerged implant) where the wound may breakdown at these points because the flap marginsare not based upon sound tissue (Figure 8.10).

In some circumstances the initial straight-lineincision can be closed around the abutmentswithout resecting/reshaping tissue, provided thata good soft-tissue profile is achieved. This iseasier where the mucosa is relatively thin orelastic. In other circumstances the flaps need tobe reshaped by making curved incisions tomatch the shape of the abutments. Instead ofsimply excising this tissue, it is often worthwhileadopting the strategy described by Palacci, ofretaining the attachment of this tissue at one endand rotating it around the abutment to ensure


Figure 8.9

Small incisions over an AstraTech implant allow connec-tion of a healing abutment. The implant to the right hasthe cover screw exposed.

Figure 8.10

(A) The relieving incisions are made at the line angles ofthe abutments and may subsequently break down. (B) Themore remote relieving incisions are more likely to healuneventfully and do not generally compromise the papil-lary form.

A

B

good coverage of the bone (Figure 8.11). Thiswill aid the soft-tissue profile but will not neces-sarily produce papillary height between adjacentabutments as originally described. Papillary formis more dependent on the presence of naturaladjacent teeth with good gingival attachment onthe proximal surface and careful development ofadjacent emerging crown profiles.

The healing abutment length should be chosenso that it just emerges through the soft tissueand does not require too much modification of

the provisional prosthesis. There has been avogue for advocating different width healingabutments to match the size of the tooth beingreplaced, thereby developing a more appropriatesoft-tissue form at an early stage. However, thewidth of the healing abutment can be extremeand can compromise the soft-tissue profile. Wewould advocate using healing abutments thatare slightly narrower than the tooth beingreplaced and then ‘stretching’ the tissue with thefinal or provisional prosthesis.


Figure 8.11

A series of clinical illustrations of abutment connection surgery. (A) A crestal incision over the heads of the implantsextends just into the crevice of the adjacent teeth. (B) Good flap reflection has allowed removal of bone, which has grownover the cover screws, with a hand chisel. (C) The flaps are re-adapted around healing abutments. The flaps are reshapedand the tissue that would normally be excised is preserved and rotated between the healing abutments. (D) The flapsare closed with simple interrupted sutures.

A B

C D

Conclusion

This chapter has simply dealt with the issue offlap design. Suturing and postoperative carewere dealt with in Chapter 7. The followingchapters deal with the finer points of implantplacement.

Bibliography

Palacci P, Ericsson I (2000). Esthetic implant dentistry:soft and hard tissue management. Chicago: Quin-tessence Publishing.

Introduction

This chapter deals with some of the most impor-tant issues of implant placement that are directlyapplicable to Chapter 10 on fixed bridgework.Single tooth restorations may be the mostaesthetically demanding of all implant restora-tions because they are most frequently used toreplace maxillary anterior teeth where they canbe judged against adjacent natural teeth. In orderto produce the optimum aesthetics the restora-tion should emerge from the soft tissue at thesame level and contour as the natural teeth. Thisis facilitated by good pre-existing soft tissue andbone contours, meticulous planning, precisepositioning of the implant at surgery and a highstandard of prosthodontics. The ideal situation iswhere there has been no or minimal bone lossand the soft tissues are perfectly contouredaround the adjacent natural teeth.

Controlling variables in implantplacement

All implant placement relies upon a good three-dimensional perspective by the operator. Thereare relatively few variables that affect this:

1. Mesiodistal positioning2. Buccolingual positioning3. Angulation of the long axis of the implant4. Vertical positioning of the implant head

All of these variables are easier to consider whenjudged against a surgical stent that providesinformation on the position and shape of the

labial face of the restoration. A typical sequenceof single tooth implant surgery is illustrated inFigure 9.1.

Mesiodistal and buccolingualpositioning

These are decided upon with the initial penetra-tion of the drill into the bone site (Figure 9.1D).The mesiodistal positioning is relatively straight-forward and in most instances will be in themiddle of the single tooth gap (Figure 9.2),unless there is planned spacing to accommodatea wider diastema on one side of the restoration.

However, in many instances bone resorptionwill affect the buccolingual position of the ridgeand the angulation, factors that are more difficultto cope with, especially for the inexperiencedclinician (Figure 9.3). The site also may beaffected by localized ridge defects or thepresence of anatomical structures such as theincisive canal (Figure 9.4).

Buccolingual angulation of theimplant

The implant can be placed in the same long axisas the crown. This is shown in the clinical series(Figure 9.5) and diagrammatically in Figure 9.6A,where the implant/crown has been placed at theaverage angle from the Frankfurt plane of 110°.The long axis of the implant and abutmentpasses through the incisal tip of the crown. Thisis a common situation and dictates that the

9Surgical placement of the singletooth implant in the anterior maxilla


Figure 9.1

A series of photographs showing the placement of two AstraTech single tooth (ST) implants to replace both maxillary centralincisors. (A) The preoperative situation showing good ridge form. (B) Buccal and palatal flaps have been elevated. (C) A cold-cure acrylic stent has been tried to assess the position of the labial faces of the central incisors to the underlying ridge. (D)The outer cortex of the ridge is penetrated with a round bur in the appropriate mesiodistal and buccolingual positions. (E)The angulation of the sites is developed with twist drills of increasing dimensions. This is the first twist drill of 2.5 mm in

A B

C D

E F

SURGICAL PLACEMENT OF THE SINGLE TOOTH IMPLANT IN THE ANTERIOR MAXILLA 107

diameter. Changes to the angulation can be made at the early stages of drilling. Reference should be made using directionindicators (in patient’s right site) and the stent. (F) and (G) Direction indicators (with safety sutures attached) placed in bothsites. (H) After establishing that the site positions and angulations are satisfactory, the sites are enlarged with a 3.2-mmtwist drill. (I) The sites are prepared with a conical drill to accept the conical head of the ST implant. (J) The ST implant isinserted, initially by hand on the implant inserter and then using a handpiece at slow revolutions. (K) The implants have beenplaced with their heads just below the crest of the bone. This is to allow a good emergence profile of the central incisors,which are quite wide compared with the implant head (4.5 mm). (L) Closure of the flaps in this submerged two-stage protocol.

G

H

I J

K L

crown is cemented to the abutment. In somecases the profile of the bone ridge dictates amore labial inclination of the implant.

In Figure 9.6B the implant has been angled afurther 10° labially, with the crown maintainingits previous position/angulation. The long axisnow passes labial to the incisal edge andproduces a slight crown/implant angulation thatmimics the crown/root angulation seen in manynatural incisor teeth. This angulation mayproduce very good aesthetics, giving a naturalform and prominence to the labial cervicalmargin similar to the adjacent teeth, i.e. anoptimum emergence profile (Figures 9.7 and 9.8).Increased labial angulation (Figure 9.6C) by afurther 10° will still produce a restorableaesthetic solution, but beyond this the restora-tive problems will increase to a point where itmay be impossible to provide an acceptablerestoration (Figure 9.6D).

In contrast, resorption of the bone ridgetowards the palate may promote more palatalangulation of the implant. Figure 9.9 showsprogressive 10° angulations of the implanttowards the palate. Up to 10° palatal angulation

there is little compromise, although there will bea tendency towards a less favourable buccalcervical contour/emergence profile. As thepalatal angulation increases there will be a needto make up the loss of cervical contour byprogressive ridge lapping of the restoration. Thisresults in a restoration that does not emergefrom the soft tissues but a ridge lap that ‘sits’ onthe tissues in a similar way to a conventionalpontic in fixed prosthodontics (Figure 9.10). Theonly advantage of the palatally angled implant isthe possibility of access to the abutment screwthrough the cingulum of the restoration permit-ting a screw-retained restoration rather than acemented one. The screw-retained design ofsingle tooth restoration is less important than itused to be because of lower incidences ofabutment screw loosening (through betterdesign and adequate tightening of abutmentscrews using controlled torque devices).

Figures 9.6 and 9.9 would suggest that anacceptable angle would be between 20°proclined and 10° retroclined to the ‘ideal/normal’ long axis. Angulations outside theseparameters will compromise the aesthetics and


Figure 9.2

The implant is placed in the middle of the gap of the toothit is replacing, in the same position as the root would havebeen. This is also indicated in the lateral view in this ideal-istic situation where minimal or no bone loss has occurred.

Figure 9.3

The diagram on the left shows an implant in the long axisof the root in an ideal situation. The more common situa-tion is illustrated in the diagram on the right, where theimplant has been positioned palatally as the ridge hasresorbed in this direction. The angulation of the implanthas been maintained and now passes through the cingu-lum of the incisor such that a screw-retained retrievablerestoration would be possible. There is, however, suffi-cient bone volume to allow proclination of the implant sothat the angle passes through the incisal tip.

test the skills of the prosthodontist to the limitwhere the implant is unrestorable or aestheti-cally unacceptable. The following points shouldhelp to avoid this situation:

1. Good preoperative assessment and planning2. Grafting of sites where these difficulties are

predicted3. Utilization of surgical stents and guide pins at


A B

C

D

Figure 9.4

A series of photographs illustrating the effects of palatalplacement of the implant. (A) A patient with a missingmaxillary central incisor. (B) Flaps have been raised and theimplant site prepared in the available bone. It is slightlypalatal because of loss of labial bone, and slightly distalbecause of the presence of a prominent incisive nervecanal. (C) The completed result showing satisfactoryaesthetics, but with the implant crown slightly ridge lappedto compensate for the palatal placement. (D) A radiographof the completed case showing bone levels at the top ofthis AstraTech single tooth (ST) implant.


Figure 9.5

A series showing replacement of a maxillary lateral incisorwith an AstraTech single tooth (ST) implant where theimplant angle is through the incisal tip. (A) Initial presen-tation showing that left and right maxillary lateral incisorshad been replaced previously with resin-retained bridges.The left bridge had failed and is being replaced with animplant restoration. (B) Preparation of the site is complete.There has been little labial resorption, allowing very goodplacement and an angulation that passes close to theincisal tip. (C) The completed case showing good aesthet-ics and emergence profile of the implant crown. (D) Palatalview of the cemented implant crown, showing normalcontour and a small vent hole to allow escape of excesscement. (E) Radiograph of completed case, showing boneat the top of the implant and the good emergence profileof the restoration.

A B

C D

E


Figure 9.6

Implants drawn at various angles from the Frankfurt plane,with 110° considered to be the average root angulation ina class I incisor relationship. The crown of the restorationhas not had its angulation changed, and in each case theimplant and abutment have been progressively labiallyinclined by 10° increments.

Figure 9.7

A series showing replacement of a maxillary lateral incisor with labial angulation of the implant. (A) The wide missinglateral incisor space. (B) The stent in place, with a direction indicator in the initially prepared site. (C) The implant hasbeen inserted and the inserting device is still connected. The midlabial part of the implant shows a very small (1-mm)dehiscence and the proximal sides are just below the crest of the interdental bone. (D) A side view of the implant insertershowing quite marked labial angulation of the implant, corresponding to a line through the midlabial point of the crown.It is also apparent that the natural teeth have a pronounced crown/root angulation. (E) The completed result showinggood aesthetics of this cemented implant crown.

D E

A B C

each stage of the preparation to check onangulation and vertical positioning of theimplant head

The above guidelines are approximate (andrelatively crude 10° increments) and each caseshould be judged on its own merits, particularlywith regard to patients who have pronouncednatural crown root angulations and/or class 2 or3 incisal relationships.

A difficult angulation problem encountered atthe time of surgery may be reduced by prepar-ing the initial entry site of the implant towardsthe palatal, which would allow a change inangulation and keep the implant preparationwithin the bone contour.

An alternative strategy is available with theStraumann system, which produces an implantwith an angle at the head of the implant of 15°that mimics a natural crown/root angulation (seeChapter 1). This implant is a push-fit design sothat the angled aspect can be positioned at theexact required plane.

Vertical positioning of the implanthead

Figure 9.2 shows a frontal view of the idealarrangement of the implant in the middle of thespace in the long axis of the tooth with the head


Figure 9.8

Replacement of both maxillary lateral incisors in a young patient. (A) This photograph shows the impression copings onthe implants during the prosthodontic phase. There is a labial angulation of both implants compared with the adjacentnatural teeth. (B) The completed result showing good emergence profiles.

A B

Figure 9.9

Implants are drawn at various angles from the Frankfurtplane, with 110° considered to be the average root angula-tion in a class I incisor relationship. The crown of therestoration has not had its angulation changed, and in eachcase the implant and abutment have been progressivelypalatally inclined by 10° increments.


Figure 9.10

A series showing marked palatal positioning of an implant replacing a maxillary central incisor.(A) Occlusal view of the ridge form showing labial concavity. (B) Elevation of the flaps revealsa large incisive canal, further compromising the site. (C) The site has been prepared in the avail-able bone volume without compromising adjacent structures. (D) An AstraTech single tooth(ST) implant has been placed. (E) The completed result showing compromised aestheticsbecause of the palatal positioning of the implant. The crown is ridge lapped. The area wouldhave required a moderate-sized graft to overcome this. The patient was prepared to accept thecompromise, particularly as the cervical area did not show during normal function. (F) Palatalview of the completed case, showing the access hole to the abutment screw. The crown iscemented to a standard abutment, but the crown/abutment assembly could be removed or theabutment screw tightened through this access hole. (G) Radiograph of completed case showinggood contour/mergence in this plane, concealing the ridge lap profile in the buccopalatal plane.

A B

C D

E F

G

of the implant 3 mm apical to the cervical/gingi-val margin of the restoration. There should belittle variation in the angle of the implant in thisplane and most of the variation relates to thevertical level of the head of the implant. Thedistance of 3 mm between implant head andadjacent tooth cement/enamel junction is quotedbecause it usually allows a smooth transition ofrestoration profile from an implant of averagediameter (4 mm) to the natural crowncontour/dimensions of maxillary central incisorsor canines (Figure 9.5E). An implant head that istoo close to the crown (Figure 9.11A) will neces-sitate an abrupt, highly angulated profile and thepossibility of unaesthetic exposure of theabutment or implant head. An implant head thatis located further apically will allow a very

smooth transition profile (Figures 9.11B and9.1K), but if this is too extreme it will produceless favourable restoration/implant height ratios.The deeply placed implant head may be moredifficult for the prosthodontist to deal with andfailure to maintain soft-tissue height will compro-mise the aesthetics.

The emergence profile therefore dependsupon:

1. The size of the crown to be replaced2. The diameter of the implant/abutment3. The vertical distance between implant and

crown cervical margin

In systems such as the Frialit 2, an implantdiameter can be selected to match more closelythe size of the tooth it is replacing. The verticallevel of the implant is still very important tomaintain soft-tissue aesthetics.

Conclusions

It should be clear from the preceding discussionsand diagrams that the angulation, buccolingualposition and the vertical level of the implanthead have a marked effect on the contour andaesthetics of the single tooth restoration. It isvery important that the clinician who is surgicallyplacing the implant has a thorough appreciationof these factors. The utilization of a stent indicat-ing the labial aspect of the planned restorationwill help to avoid many of the potentialproblems, particularly for the inexperiencedoperator. The placement of an implant in anunrestorable or unaesthetic position must beavoided and in situations where the bone profile,position or quantity is compromised, graftingshould be carried out to correct this, ideally as aseparate procedure prior to implant placement(see Chapter 12).


Figure 9.11

Labial view of emergence profile contours from implantsplaced at different vertical levels apical to the desiredrestoration. (A) Very abrupt profile. (B) The more idealprofile. (C) The profile has been altered by maintaining thevertical level but increasing the diameter of the head ofthe implant.

A B C

Introduction

The planning and placement of implants for fixedbridgework follows the basic rules set out forthose described in the chapter on single teeth(Chapter 9) but with more complications of siteselection, the relationship between adjacentimplants and their relationship to the plannedprosthesis. Ideally all of these factors will havebeen resolved in the planning phase, with carefulmatching of the radiographic data, diagnosticset-ups and clinical verification. However,despite the most careful planning there areoccasions when modifications have to be madeat surgery and it is under these circumstancesthat it is advantageous if the surgeon has knowl-edge of the prosthodontic implications, eitherthrough his/her own experience or through thatof an attending prosthodontic specialist.

The requirements for surgical stents, anaes-thesia, flap design and soft-tissue handling aredealt within the chapter on basic surgery(Chapter 7).

Implant positioning andinstallation

When placing multiple implants it is especiallyhelpful to be able to refer to a written plan of sitelocation, estimated implant length and implantdiameter and relevant radiographs and studycasts. Following elevation of the flaps the surgi-cal stent is tried in and referred to at variousstages during the site development. Theproposed sites of the implants are marked in thecortical bone with a round bur. The initial

positioning is checked against adjacent teeth andanatomical structures, tooth positions on thestent, bone contour at the site and implantspacing. Spacing is required between adjacentimplants (and implants and teeth) for anadequate width of bone (at least 1 mm andpreferably 2 mm) and an adequate zone of softtissue (2–3 mm). The angulation of the site isthen developed with a twist drill. Remember thatmodifications to the position and angle can bemade only at the early stages of the preparationprocess (e.g. the 2-mm twist drill stage). Thelength of the site is then established and thesystem protocol is followed with increasingdiameters of drills until the preparation iscomplete and the implant can be placed (Figure10.1).

Implant spacing in multiple

implant placement

This was dealt with in some detail in theplanning chapters (Chapters 4 and 5) but it ishelpful to remind the surgeon with appropriateillustrations. The spacing requirements will varywith the system being used. In cases treated withthe Brånemark system (Figure 10.2), the standardimplants used are 3.75 or 4 mm in diameter inthe threaded portion and 4 mm in diameter atthe implant head. The routine recommendationis to place implants at a 7-mm centre-to-centrespacing, which would allow a 3-mm bone widthbetween the outer surfaces of the implants. Asdescribed above, this can be reduced to as littleas 1 mm at the bone level. However, this maynot give sufficient soft-tissue width in many

10Implant placement for fixedbridgework


Figure 10.1

A series of photographs illustrating placement of AstraTech implants in the anterior mandible in a patient with severehypodontia. (A) The preoperative view of the anterior mandible. (B) Flaps have been raised buccally and lingually to revealthe ridge form. The location of the mental nerve is checked radiographically and clinically. (C) The four implant sites areprepared with a 2.5-mm twist drill, following perforation of the cortex with a round bur. Direction indicators are placedsequentially in the prepared sites to help the surgeon maintain an acceptable degree of parallelism. The direction indica-tor posts should be checked against the stent and the opposing dentition. The widths of the indicator posts also giveinformation about the diameter of the implants and the spacing between them. (D) Once the surgeon is satisfied withthe location and angulation of the initial preparation, the sites can be enlarged with the next diameter of twist drill, inthis case 3.2 mm. The direction indicator posts still give important guidance to maintain the angulation at the individualsites. (E) A 3.5-mm diameter implant is inserted into the prepared site. (F) All implants have been placed and cover screwsinserted. The flaps are then closed with sutures.

A B

C D

E F

cases, especially as the manufactured abutmentshave a wider diameter than the implant head(Figure 10.3). The standard Estheticone (NobelBiocare, Göteborg, Sweden) abutment is themost commonly used manufactured componentand has a width of 4.5 mm. Therefore, with a 1-mm spacing at the bone level two adjacentabutments will touch, leaving no space for a soft-tissue cuff. In most instances, therefore, thestandard 7-mm spacing recommendation ismuch safer.

The spacing problem may be eased by utiliza-tion of a system where the abutment is narrowerthan the implant head. This the case with theAstraTech system illustrated in Figure 10.1.Standard implants are either 3.5 or 4 mm indiameter at the implant head but the conicalabutment fits within the head of the implant. Thereduced width of the abutment at the implanthead expands to a maximum diameter thatmatches the implant diameter at a distance of2 mm above the head of the implant. This conicalprofile allows a good soft-tissue cuff to beformed and therefore permits slightly closerpositioning of the implants than is the case forthe Brånemark system when using standardmanufactured abutments.

The Straumann system (Figure 10.4) requiresdifferent considerations. A standard 4.1-mmdiameter implant (measured in the endosseouspart) has a transmucosal collar that enlarges to

IMPLANT PLACEMENT FOR FIXED BRIDGEWORK 117

Figure 10.2

Placement of Brånemark implants in the anterior maxilla. (A) The sites have been prepared to a 3-mm diameter and thedirection indicators have been placed to review the angulation and spacing. There is ample space in this case, with centre-to-centre spacing between implants of about 8 mm. (B) The implants have been placed and transfer copings attached tothem. An impression recording the position of the implants was then taken to allow construction of a provisional bridgethat could be fitted at the abutment connection surgery 6 months later.

A B

Figure 10.3

An example of Brånemark implants that were placed tooclose together. The implants in the central incisor sites(those with abutments connected) have good spacingbetween them, in contrast to the minimal space betweenthe implants in the lateral incisor sites (cover screws inplace).

4.8 mm in diameter at the top. The implantsshould be placed so that there is at least a 1-mmgap between adjacent collars at their maximumwidth, which gives an additional soft-tissuespace apical to this (and in turn an adequatedimension of bone). As with the AstraTechsystem, the abutments have a narrower diame-ter than the implant head and therefore do notencroach upon the space further.

The Frialit system requires a differentapproach. In this system the implant sites arefirst prepared to an acceptable final depth (Figure

10.5). The sites are then widened with successivestepped conical drills that exactly match therange of implants of diameters 3.8, 4.5, 5.5 and6.5 mm, therefore the initial siting of the implantcentres is very dependent upon the planneddiameter of the final implant. If there is a miscal-culation and it appears that the implants of theplanned diameter will be too close, then anarrower preparation and implant would have tobe utilized. Unlike the previously describedsystems, the Frialit implants are tapered apicallyand therefore it is easier to provide adequate


Figure 10.4

A series of photographs showing the installation ofStraumann implants. (A) Two Straumann implants havebeen inserted in the maxilla distal to the canine. (B) Anocclusal view of the implants showing a gap of about2 mm between the outer aspect of the polished collarsand the same gap between the anterior implant and thetooth. (C) A radiograph of the implants with closure screwsin place. The shape of the implants means that there ismore space between them at the bone level than at thesoft-tissue level.

A B

C

bone between implants in the apical zone.However, this is not so much of a problem as thecoronal aspect where the breach in the epithe-lium occurs, where complications are far morelikely in terms of inflammation or aesthetics.

The other factor to remember is to allowadequate space between the implant and anadjacent tooth (Figures 10.4B and 10.5C–F). Theinitial selection of the site has to take intoaccount:

• the planned diameter of the implant• the proximal contour of the tooth• allowance of a minimum of 1 mm of bone

between implant and root• allowance of adequate space for the proximal

soft-tissue papilla• a path of insertion of the implant that is not

affected by the tooth contour.

Implant angulation

Guide pins placed in the developing implant sitesshould be checked against the surgical stent andthe opposing dentition, and modifications madeas necessary. The angulation of the implant sitesmore or less mimics the angulation of the naturalteeth, with modifications according to the designof the final prosthesis and the degree of ridgeresorption. If the final prosthesis is designed tobe retrievable/screw-retained, the ideal angle ofthe implant passes through the cingulum area ofthe anterior teeth and the occlusal surfaces of thepremolar/molar teeth. In a non-retrievablecemented prosthesis the angulation would bethe same in the posterior teeth because this isalso consistent with loading the implantsthrough the long axis. However, in the anteriorzone the angulation can be inclined more labiallythrough the incisal tip or towards the labialsurface, potentially improving the emergenceaesthetics (see Chapter 9 on single toothimplants). However, the force transmissionthrough the implants may be less favourablebecause it will be far removed from axial loading(Figure 10.6). Therefore, within a given zone ofthe jaw the implants are placed more or lessparallel to one another. Placement of multipleguide pins is very helpful and should preventunacceptable angulation of the implants (Figures

10.1C, D and 10.2A). Manufactured abutmentsallow quite large angular variations betweenimplants, and customizable abutments can beused if these values are exceeded (Chapter 14).For example, implants may be angled more thanusual to engage more bone length at sites nextto the maxillary sinus (see Chapter 12).

Level of the implant head

The last factor to consider in implant placementis the level of the implant head. This level willdictate:

1. available vertical space to the occlusal planeor incisal plane for abutments and restoration

2. vertical space for the emergence profile of therestoration

Submerging the implant head may provide muchneeded space to accommodate abutments andrestoration in individuals with little verticalspace, for instance patients with minimal ridgeresorption. More often, ridge resorption is tosuch an extent that submergence of the implanthead is not required other than to optimize theemergence profile and aesthetics. The deeper theimplant head, the easier it is to make a gradualsmooth transition to the emerging crown. Incontrast, it will have an adverse effect on theratio of the height of the restoration to theimplant length (equivalent of the crown/rootratio). This can therefore produce unfavourableforce distribution and leverage.

It is perhaps easiest to contrast the effects ofimplant head level between submerged systemssuch as the Brånemark or AstraTech with that of a non-submerged system such as theStraumann. In the prescribed use of theBrånemark implants, the implant head iscountersunk to a point that allows the coverscrew (which protects the external hexagon) tobe level with the crest of the bone ridge. Thisfacilitates soft-tissue coverage and minimizes thechance of subsequent wound dehiscence andimplant loading. However, in order to achievethis the implant site is countersunk and thisplaces the implant head either within the super-ficial cortex or below this if the cortex is thin.This may therefore negate one of the prime aims



E F

A B

C

D


Figure 10.5

A series of photographs showing the installation of four Frialit 2 implants in the posterior maxilla. (A) The edentulousposterior maxilla prior to surgery. (B) Buccal and palatal flaps have been raised to expose the ridge adequately. (C) Anacrylic stent in place to evaluate the position and direction of the mesial site that has been prepared with the 2-mmdiameter drill. (D) The mesial site preparation is completed with a 3.8-mm diameter stepped drill. (E) The 3.8-mm diame-ter stepped screw implant has been inserted level with the crest of the ridge. The ‘dot’ on the inserting device shouldbe on the buccal aspect to facilitate the prosthodontic procedure. (F) An occlusal view of the mesial implant in place—note the space between it and the tooth. Initial preparation of the distal sites has been started. (G) The distal site iscompleted with a 4.5-mm stepped drill (colour code blue). (H) All four implants have been inserted. The three distalimplants are 4.5 mm in diameter (blue) and the mesial implant is 3.8 mm in diameter (yellow). (I) Abutment connectionsurgery with healing abutments. (J) Suturing of the flaps around the healing abutments.

G

H

I J

of bicortical stabilization with this system.Countersinking could therefore be viewed asbeing destructive for the cortical anchorage,which could be critical in areas of poor bonequality, such as the posterior maxilla. It is evenmore pertinent when one considers that in thefirst year of loading the implant there is boneresorption to the level of the first thread, furtheraccentuating loss of previous cortical bone.However, the advantage of countersinking is thatthe abutment implant junction is placed suffi-ciently far apically to allow a good emergenceprofile of the restoration and an aesthetic subgin-gival placement of the restoration margin. Thedesign of the AstraTech system allows place-ment of the implant head at the level of thecrestal bone without countersinking and therebypreserves cortical bone. This is because the

standard implant head has nearly the samediameter as the main threaded portion of theimplant and the cover screw fits within theimplant head. This system is therefore veryuseful in the resorbed maxilla, which may havelittle crestal cortex, because it can be used toutilize fully the limited bone height and maintaincortical anchorage.

The standard design of the Straumann implanthas a smooth transmucosal collar that is 2.8 mmin length. In areas of thin mucosa the implanthead will be above the mucosa and the aesthet-ics may be compromised. However, theStraumann aesthetic line has a reduced height oftransmucosal collar because the plasma-sprayed/SLA surface coating extends further onto thecollar area. The interface is placed at the level ofthe cortical bone (or countersunk further) toproduce a submucosal implant/ abutmentjunction.

Conclusion

The surgeon must be very familiar with thesystem that he/she is using in multiple implantplacement because of the large number ofvariables. The dimensional comparisons of thevarious implant systems used in this book aredescribed in Chapter 1 and an appreciation oftheir differences and respective dimensions isvital to the clinician planning the treatment andthose providing the surgical and prosthodonticphases of treatment. The surgeon may have tomodify the plan during surgery and can only dothis if he/she has an extensive range of implantsat his/her disposal and knowledge of theprosthodontic requirements.


Figure 10.6

Forces directed through implants placed in the posteriorjaw will usually be in the same long axis as the premolarand molar teeth. Labial angulation of the anterior implantsmeans that normal forces are not directed down the longaxis.

Introduction

In many cases implants are placed at sites whereteeth have been lost many months or yearspreviously. Traditional implant surgical protocolssuch as that described by Brånemark advocatedleaving extraction sites for 12 months to allowcomplete healing and maturation of bone.However, the resorption of bone over extendedtime periods often led to a situation where therewas insufficient bone for routine implant place-ment. Protocols have therefore developed inwhich implants are placed at the time of extrac-tion of the tooth, or soon after, before significantbone resorption occurs.

Timing of implant placement

There are various recommendations regardingtiming of implant placement following toothextraction. Basically the implant can be placedimmediately following extraction during thesame surgical procedure (‘immediate implantplacement’) or following a delay of a few weeks,in which case it has often been referred to as

‘delayed-immediate’. This latter term is ratherclumsy and this protocol will be referred to as‘early placement’ in this text. The differencesbetween ‘immediate’ and ‘early’ placement aresummarized in Table 11.1.

The ‘early’ protocol errs on the side of cautionand is therefore possibly more predictable,although there are no comparative studies tosupport this statement. It may offer an advantagewhen it is used with submerged implant proto-cols because the soft-tissue healing that occursbetween extraction and implant placement facil-itates flap coverage. The choice of protocol alsodepends upon the difficulty of the case.

The ‘immediate’ protocol is more applicable ifan anterior tooth is being replaced. The extrac-tion should be relatively straightforward, thesocket not too large to compromise implantstability (Figures 11.1 and 11.2) and the provisionof a temporary restoration should be simple. Incontrast, a case requiring multiple and/or difficultextractions and temporization may be besthandled in a separate dedicated surgical opera-tion to that of implant placement. Most of thefollowing considerations apply to anterior toothreplacement, because the situation with multi-rooted teeth is usually far more compromised

11Immediate and early replacementimplants

Table 11.1 Summary of immediate and early implant placement

Immediate placement Early placement

Timing

Advantages

Disadvantages

Implant placement at the same surgicalprocedure as tooth extraction• Reduced number of surgical procedures• Optimizes visualization of extraction socket• Flap elevation may be unnecessary• Contraindicated if overt infection is present• Caution required if extraction sufficiently

traumatic to complicate healing process

Implant placement 2–6 weeks following toothextraction• Allows resolution of any infection• Allows soft-tissue healing to cover socket• May allow early healing of bone (woven bone)• Additional surgical procedure required• May be insufficient bone to achieve primary

stability of the implant

owing to the larger extraction sockets and lessbone apical to the socket.

Assessment

The assessment for immediate/early placementfollows the same guidelines as discussed inprevious sections but with additional featuresrelated to the effect of the extraction socket onthe implant placement. It has been stated alreadythat the area should be free of overt infectionand if any doubt exists the implant surgeryshould be delayed and, if necessary, appropriateantibiotics given.

The main factors to assess are obtained fromgood-quality radiographs of known magnifica-tion and include:

1. Size and shape of roots (Figure 11.1)• length• width• taper• number of roots in the case of molars

2. Bone support (Figures 11.2 and 11.3)• height of marginal bone supporting the

tooth root• distance between apex of root and anatom-

ical limit of bone (e.g. floor of nose, maxil-lary sinus, inferior dental neurovascularbundle)

3. Difficulty of extraction procedure• simple elevation/forceps• surgical procedure involving bone removal

Tooth/root extraction

It is essential to carry out the tooth/root extrac-tion as atraumatically as possible in order toprevent:

1. Fracture of the socket walls2. Loss of the labial plate of bone


Figure 11.1

The central incisor root is longer and wider than the lateralincisor. The distance between the apex of the root and thefloor of the nose varies considerably. The bone apical tothe root may be important to secure initial stability of theimplant.

Figure 11.2

A standard 4-mm diameter implant of the same length asthe central incisor root may only just attain stability in theapical portion. A longer implant could be used.

Figure 11.3

A longer 4-mm diameter implant has been placed moreapically in a site prepared apical to the apex of the socketclose to the floor of the nose. The apical bone providesgood stability for the implant. There is a reduction in thespace between the implant and the socket walls., Thealternative strategies are illustrated in Figures 11.6 and11.7.

3. Excessive trauma to the socket wall that couldlead to necrosis of bone or a localized osteitis.

In most cases it is recommended to use gradualand careful loosening and elevation of the rootswith specifically designed periotomes (Figure11.4). These allow gradual dilatation of thecoronal part of the socket and severance/ruptureof the periodontal ligament fibres. The periotomeshould be worked circumferentially around theroot, working gradually deeper until the tooth iselevated with little force. Careful forceps extrac-tion is also permissible, particularly if smallrotational movements are effective and leverageagainst the labial plate of bone can be avoided.In some cases exposure of the alveolus throughflap elevation is necessary, which allows inspec-tion of the bone and effect of the transmittedforces upon it. Surgical bone removal should bekept to a minimum and performed with copiousirrigation if burs are used.

Following successful removal of the root, anygranulation tissue should be curetted from thesocket and any inflamed periodontal pockettissue should be excised. Some clinicians recom-mend routine curettage of the socket wall toremove residual periodontal ligament fibres,although there is little evidence to support thisprotocol (and it is not performed by the presentauthors). Implant placement should bepostponed if any doubts exist regarding thelikelihood of persistent infection or the possibil-ity of osteitis due to traumatic removal of thetooth root. Under these circumstances and inplanned early-placement protocols the soft tissueshould be closed as much as possible with

sutures. Soft-tissue closure can be facilitated byflap advancement following releasing incisionsand incision of the periosteal surface of the flap.Antibiotics should be given where appropriate.

Implant placement

Preparation of implant sites within extractionsockets may not be as easy as it first appears. Inimmediate placement the socket will have beencuretted as necessary. With the early-placementprotocol the soft tissue is elevated to allow re-inspection of the socket and removal of anyingrowth of soft tissue. Any woven bone shouldbe left undisturbed. The surgical preparation(with drills matched to the system being utilized)more or less follows the angulation of the socket,provided that the tooth was in a satisfactoryposition and that an implant angle through theincisal tip or labial to it is acceptable (Figures 11.2and 11.3). However, in some cases involving themaxillary anterior teeth the bone on the palatalaspect of the socket is the best to provide a goodsite preparation to secure implant stability (Figure11.5). It may also provide more palatal angulationof the implant to facilitate screw retention of theprosthesis if this is desirable. It is helpful if theinitial preparation of the site is started with around bur, which readily penetrates the socketwall. Drilling into an angled surface within a

IMMEDIATE AND EARLY REPLACEMENT IMPLANTS 125

Figure 11.4

Periotomes with different-designed ends to allow dilatationof the socket and atraumatic extraction.

Figure 11.5

At times, the most suitable bone to secure stability of theimplant is on the palatal aspect of the socket, especiallywhere the labial plate is very thin or has been lost.However, the implant will be palatally placed and aesthet-ics may be compromised. A thin labial plate may becompressed to reduce the volume of the residual socket.

socket is more difficult than into a relatively flatcrestal platform of bone. A standard sequence ofdrills follows the round bur and the angulation ofthe site is checked against the stent and oppos-ing teeth. It is usually more difficult to check theangulation with the standard indicators present inmost surgical kits because they are too short andunstable within the socket. The angulation canalways be checked with a twist drill removedfrom the handpiece.

In most cases it is essential to prepare the siteapical to the natural socket to ensure implantstability and predictable osseointegration intomature bone (Figure 11.3). In situations wherethere is little or no bone available apical to thesocket, then a wider diameter implant has to beselected or the procedure delayed to allowadequate bone healing of the socket. The levelof the implant head is usually placed just withinthe socket or slightly apical, according to theaesthetic requirements as discussed in Chapters3 and 9. A more apically placed implant headoften reduces the size of gap between implantsurface and socket wall (Figure 11.3), but there isa limit to this compensatory strategy.

Implant selection

It is very helpful to overlay the radiograph withtransparent outlines of the implant design to beconsidered in the various lengths and diametersavailable. Ideally the implant should be slightlybigger than the root it is replacing, to ensure agood fit in the prepared site within the socketand hence a high degree of initial stability. Thisis one of the claimed advantages of a systemspecifically designed for this purpose, such asFrialit. The Frialit 2 has a stepped cylinder designof various diameters to make it easier to achievethese objectives (Figure 11.6). The other implantsystem that is good in these situations is theAstraTech single tooth (ST) implant (Figure 11.7).This has a wider conical collar (available in 4.5-and 5-mm diameters at the top) that gives agood fit in most anterior tooth sockets, and theapical threaded portion gives good initial stabil-ity, especially if it can be extended into boneapical to the socket. This latter feature is themain way of achieving good stability with paral-lel screw-threaded design implants. Ideally there

should be 4-5 mm of sound bone apical to thesocket to prepare and engage with an implant ofsufficient length. With implants of a parallel-sided design there is often a gap between thecoronal part of the socket and the implantsurface (Figure 11.2 and 11.3). The size of the gapis critical. A gap of 1–2 mm should fill with boneand osseointegration should occur. Where thegap is larger, this may be grafted, preferablyusing autogenous bone collected from the sitepreparation or an adjacent area of suitable donorbone. In addition, it is often possible to reducethe size of the gap by compressing the walls ofthe socket using finger pressure or by gentlefracturing of the thin coronal walls of the socket


Figure 11.6

A stepped cylinder implant (Frialit 2) developed for immedi-ate replacement has a wide enough diameter and lengthto almost obliterate the socket. This implant also has aseries of threads to help stability in the immediate replace-ment situation.

Figure 11.7

An AstraTech ST implant has an apical threaded portionthat can be used to engage bone apical to the socket andprovide good stability. The conical microthreaded collar iswider at the top (4.5 or 5 mm) and reduces the deadspace.


Figure 11.8

A series of photographs showing immediate implant place-ment for replacement of maxillary central incisors withAstraTech ST implants. (A) Preoperative photographshowing aesthetic natural teeth. (B) Radiograph showingfractures of roots in the cervical third. (C) Flaps have beenraised and the roots carefully elevated. The sites are beingprepared within the sockets. A stent (not shown) has beenused to check the position of the guide pin in the partiallyprepared site. (D) The AstraTech ST implants have beenplaced. Stability is achieved by extending the implantlength apical to the natural socket. There is only a smallvoid on the labial aspect of the implants that will fill in withbone without recourse to grafting. (E) The area has healedvery well 2 weeks after surgery. There is complete soft-tissue coverage. The implants were left buried for 6months. The abutment connection surgery for this case isillustrated in Chapter 8 (Figure 8.11). (F) The completedresult 2 years after crown cementation on prep-ableabutments.F

D

C

A

B

E


Figure 11.9

A series of photographs showing immediate replacement of a maxillary canine in a patient with dentinogenesis imper-fecta, using the Frialit 2 system. (A) The crown of the maxillary canine has fractured and worn after many years with aconventional restoration. The flap design is evident. (B) The root has been carefully elevated. (C) The initial preparationof the socket with the twist drill. The length of the preparation is established and then increasing widths of stepped drillsare used according to the final diameter of the implant that can be accommodated at this site. (D) The chosen implant:a 4.5-mm diameter threaded stepped cylinder (Frialit 2). This design achieves very good stability by preparing the lateralwalls of the socket and is aided by the threads. (E) The implant completely fills the prepared site without any voids. (F)The healed soft tissue showing complete closure at 2 weeks post-surgery.

A B

C

E F

D


Figure 11.10

A series of photographs showing early placement of two Brånemark implants to replace the maxillary central incisors. (A)The maxillary central incisors have drifted and are very mobile due to extensive root resorption. (B) Four weeks follow-ing extraction of the incisors, soft-tissue healing of the sockets is good. The patient has been wearing a Rochette provi-sional bridge, which has been removed to allow installation of the implants. (C) Buccal and palatal flaps have been raised

A B

C D

E F

continued overleaf

with a suitable instrument. Most of the forego-ing discussion is mainly applicable to placementinto an anterior single root socket and it is notusually possible with molar sites.

The sequence of implant placement in extrac-tion sockets is shown in Figures 11.8–11.10,which illustrates some of the points mentionedabove and how the different systems cope withthis situation.

Conclusion

Immediate and early implant placement proto-cols can offer highly predictable results, which inclinical trials have been shown to be as good oreven better than traditional protocols. However,there are many potential factors that have to beappreciated and accounted for if one is toemulate these success rates.

Bibliography

Becker W, Becker B (1990). Guided tissue regenerationfor implants placed into extraction sockets and forimplant dehiscences. Surgical techniques and casereports. Int J Period and Rest Dent 10: 376–91.

Gomez-Roman G, Schulte W, d’Hoedt B, Axman-Krcmar D (1997). The Frialit-2 implant system: five-yearclinical experience in single tooth and immediatelypostextraction applications. Int J Oral MaxillofacImplants 12: 299–309.

Rosenquist B, Grenthe B (1996). Immediate placementof implants into extraction sockets: implant survival. IntJ Oral Maxillofac Implants 11: 205–9.

Salama H, Salama M (1993). The role of orthodonticextrusive remodelling in the enhancement of soft andhard tissue profiles prior to implant placement: asystematic approach to the management of extractionsite defects. Int J Period and Rest Dent 13: 312–33.


and residual soft tissue has been removed from the sockets. A plastic stent, based upon a diagnostic set-up and provi-sional Rochette, is stabilized on the adjacent teeth. The measuring indicator, held palatally, has a width of 7 mm (corre-sponding to the recommended centre-to-centre distance between two Brånemark 3.75-mm implants). (D) A 2-mm twistdrill is used to prepare the initial implant angulation. (E) A guide pin is placed in the right central incisor socket and theleft site is being enlarged from 2 to 3 mm in diameter. (F) The guide pins show the position and angle of the preparedsites within the sockets in relation to the stent. (G) The implants have been placed and the cover screws connected. Theimplants are towards the palatal aspect of the sockets. The small voids labially were grafted with osseous coagulumcollected from the drilling process. (H) The completed result showing the two single tooth implants in an acceptableaesthetic position.

G H

Introduction

The overriding requirement for successfulimplant placement is to have enough bonevolume of sufficient density to enable an implantof the appropriate size to be placed in a desir-able position and orientation. Many of the graft-ing procedures described in this chapter havebeen developed as localized procedures toovercome small anatomical limitations. There isalso a need occasionally to employ morecomplex techniques to change the entire alveo-lar ridge form that may additionally involve anassociated change in skeletal base.

As well as the obvious osseous component tothis problem there are also many situationswhere the soft tissue in the area of proposedimplant placement is deficient. The soft tissuesplay a vital role in maintaining the peri-implantenvironment, long-term health and alsocontribute greatly to the resulting aesthetics,particularly in the anterior region. The peri-implant soft tissues must be able to maintaintheir structural integrity during normal functionand oral hygiene procedures.

Grafts therefore may be employed to:

• enable implant placement• enhance aesthetics and improve soft tissues• change the pre-existing jaw relationship

The initial planning stages as described in previ-ous chapters take on even greater levels ofimportance in potential graft cases. By their verynature they are more difficult to plan and executeand the end result may fall short of both the clini-cian’s and patient’s expectations. It is importantthat all the alternatives are considered and

presented to the patient so that they can makean informed decision with regard to their treat-ment. In particular, it is important to considerwhether a compromise solution using prosthetictechniques may be more desirable and achiev-able as well as more predictable in the long term.Another alternative is to consider whether theutilization of the various implant designs mayovercome the problem.

Bone graft materials

The degree of bone grafting required forimplant placement varies from localized defi-ciencies to cases where there is a need tochange the entire arch form and/or jaw relation-ship. There exist, therefore, a great manytechniques and materials to facilitate such graft-ing procedures, many of which may be used incombination. The interaction between the graftand the surrounding host bone is very impor-tant and is the subject of much research.Although some grafts will act merely as spacefillers, the ideal graft will be osseoconductiveand osseoinductive. Osseoconduction is theproperty of promoting bone growth from thesurrounding host bone onto the surface of thegraft material, using the graft as a framework.The graft material in such cases may beresorbed or remain virtually intact, dependingon the material used. Osseoinduction is theability to promote de novo bone formationremote from the host bone even within non-calcified tissues. Bone morphogenetic proteinsand other bone-promoting factors have thislatter property.

12Grafting procedures for implantplacement

Autogenous bone grafts

The ready availability of autogenous bone hasalways meant that it is the first choice of bonegrafting material for many clinicians. However,patient acceptance of autogenous bone harvest-ing may be low, given the potential morbidityassociated with such techniques. Although agreat amount of research and clinical time hasbeen spent over many years to develop substi-tutes for autogenous bone, it remains the goldstandard by which all other materials are judgedand is the material of choice for the presentauthors. Its main advantages are:

• Availability• Sterility• Biocompatibility• Osseoinductive potential• Osseoconductive potential• Ease of use

The graft acts as a scaffold for the ingrowth ofblood vessels and as a source of osteoprogeni-tor cells and bone-inducing molecules. The graftis eventually resorbed as part of the normalturnover of bone.

Other graft materials

Although the gold standard for bone graftingremains the patient’s own bone, the limitations onthe amounts available (particularly from sites otherthan the iliac crest) mean that there remains a greatdemand for alternative graft materials. Xenograftsare derived from another species, allogenic grafts(allografts) from a member of the same speciesand alloplasts are synthetic materials.

The macro- and microstructure of these graftshave an enormous influence on their efficacy.The pore diameter and volume are therefore ofgreat importance. The ideal characteristics of asubstitute bone graft material have beendescribed (Hammerle, 1999) as:

• Sterile• Non-toxic• Non-immunogenic• Osteoconductive or osteoinductive• Favorable clinical handling

• Resorption and replacement by host bone• Synthetic• Available in sufficient quantities• Low in cost

Allogenic grafts

Bone derived from cadavers has been usedwidely in orthopaedics and implant dentistry aswell as periodontics. The graft may be freeze-dried or decalcified freeze-dried bone allograft(DFDBA), both of which are thought to be a goodsource of bone morphogenetic protein. It isharvested from donors with well-documentedmedical histories and tested for the commoninfective antigens. It is therefore considered to bea reasonably safe source of grafting material.The grafts are produced as particulates with areasonably uniform grain size or as sheets andlarge blocks. They are osteoconductive, provid-ing a framework for new bone growth, andshould be resorbed as part of the normalturnover of bone but some particles appear toremain intact for some time after the graft hasbeen placed. The ability of DFDBA to induce newbone (osteoinductive) formation has been thesubject of a great amount of research withconflicting results. This is thought to be duepartly to the differences in the way humans reactto graft materials as opposed to animal models,and partly to the differences in the source andprocessing of DFDBA grafts.

Demineralized laminar bone sheets are avail-able in varying thicknesses of 20–700 µm, andthose of 100–300 µm have similar physicalproperties to Gore-Tex™ (WL Gore andAssociates, Flagstaff, AZ, USA), allowing them tobe used as membranes for guided bone regen-eration (GBR) procedures.

Despite the rigorous testing of the donorsthere remains the possibility of some cross-infec-tion from the graft and the development of othersources of graft materials is likely to reduce thedemand for allografts in the future.

Deproteinized bovine bone mineral

Deproteinized bovine bone mineral (Bio-Oss®,Geistlich Pharma, Wolhusen, Switzerland) hassimilar properties to human cancellous bone,


both in its macrostructure and its crystallinecontent. The physical properties are also close tothose of the bone that it is used to replace. As apurely mineral graft it is osseoconductive and isthought to undergo resorption, although this hasbeen found to be variable. When used in a partic-ulate form it is mixed with the patient’s bloodand packed into the defect. Some authors havedescribed improved results when combining thiswith a membrane to protect the clot. Because itis available in large quantities it has been usedin sinus lift procedures instead of autografting(Yildirim, 2000). The particles also may be usedas a filler to increase the volume of autogenousgraft material. In addition, the graft material isavailable as thin sheets of bone to cover andprotect defects while retaining their shape asdescribed above for allografts. The use of bovinematerial, albeit in a purely mineral and non-antigenic form, may not be completely accept-able to some clinicians or indeed some patients.

Alloplastic graft materials

Synthetically produced materials have theadvantage of having no risk of cross-infectionbut may still give rise to an antigenic response.Their physical properties can be manipulated toa great degree and they may be used also incombination with bone-promoting molecules toenhance their effectiveness. They act as a frame-work for bone formation on their surface and aretherefore osseoconductive. They include:

• Hydroxyapatite• Calcium Phosphate• Tricalcium Phosphate (TCP)• Bioactive Glasses• Calcium Carbonate

Guided bone regeneration

Guided bone regeneration (GBR) membraneswere originally developed to promote new tissuegrowth within a protected volumetric defect forperiodontal regeneration. The desire to promotenew bone growth without resorting to graftingprocedures led to widespread use of thistechnique in implant surgery. The main aim is to

allow ingress of bone cells to promote boneformation within the defect. The originalmembranes were expanded polytetrafluoroethy-lene (PTFE, Gore-Tex™). It is a non-resorbablematerial that requires removal at second-stagesurgery. The need for removal led to the devel-opment of resorbable membranes made ofsynthetic polymers such as polylactate andpolyglycolic acid, as well as collagenmembranes. Resorbable materials should befunctional for between 3 and 6 months afterinsertion. However, they may be resorbed or losetheir shape too quickly and limit the amount ofbone regeneration achieved.

The creation and maintenance of a volumetricdefect is critical and this may be improved byreinforcing PTFE membranes with titanium strips.Further enhancement of the space-maintainingproperties is achieved by the use of fixation pinsand screws that serve to ‘tent’ the membrane(Figure 12.1). This can be achieved also byplacing small bone chips within the defect, whichwill also act as osseoconductive/osseoinductivegrafts (Figure 12.2). Cortical bone within thedefect is perforated with surgical burs to promoteosteogenic cells to occupy the space created(Figure 12.3).

GRAFTING PROCEDURES FOR IMPLANT PLACEMENT 133

Figure 12.1

The use of screws or pins may be advocated in theabsence of autogenous bone to retain the shape of thedefect and stabilize the membrane, thus optimizinghealing. Here, a Memfix™ (Institut Straumann, Walden-burg, Switzerland) tenting screw has been placed in themiddle of the defect to prevent the soft tissues fromcollapsing, thereby reducing the volume of bone created.

Guided bone regeneration is also commonlyused at the time of implant placement to repairsmall fenestrations and dehiscences aroundimplants (see Figure 12.18A). It should beremembered that any such bone created will notfunction to stabilize the implant at the time ofplacement and that initial implant stabilityremains the overriding priority. The amount ofnew bone created can be quite substantial butthe degree to which it becomes osseointegratedis variable. The amount of bone to implantcontact of the newly generated bone is thoughtto change with time and loading. Guided boneregeneration is most predictable when attempt-ing to increase the buccolingual dimension, butincreasing the vertical dimension using thistechnique is very difficult and unpredictable.

Although membranes are designed to allow thepassage of nutrients, they nonetheless tend tocompromise the blood supply to the overlyingsoft tissues. This can result in breakdown of thesoft tissues, exposure of the membrane andinfection. This may result in a net loss of bone inthe surgical area or failure of implants to osseoin-tegrate. It is important that all incisions are keptas remote from the grafted area as possible andthat the wound is sutured hermetically andwithout undue tension. Supporting the tissues

with sutures that take large bites and ‘sling’ theflaps can reduce tension at the wound edges.

Intraoral harvesting and graftingof autogenous bone

Autogenous bone grafts may be taken astrephine or block specimens both from intra- andextraoral sites. Fairly large grafts may be takenfrom the interforaminal region of the mandible.This procedure can be performed under local


Figure 12.2

Small bone chips have been placed under a PTFEmembrane to maintain the volume of the graft site; theunderlying cortical bone also has been perforated with asmall round surgical bur.

Figure 12.3

Perforation of the host bed with surgical drills allows prolif-eration of bone cells and vascular tissue underneathmembranes and between the donor site and grafted bonematerial.

anaesthesia. Great care is required in order toavoid compromising the nerve/blood supply tothe anterior teeth. Careful radiographic assess-ment of the region is important preoperatively inorder to ascertain the amount of bone available.Once the mucoperiosteal flap has been raised viaa sulcular incision to give wide exposure of themandible, the graft can be outlined leaving atleast 3 mm of clear bone below the apices of theincisor teeth (Figure 12.4).

The root contours often can be visualized directlyonce the alveolus is exposed. For harvesting blocksof bone the surgeon has a number of choices:

• Fissure burs• Oscillating saws• Rotating discs• Trephines

The authors prefer the use of high-speeddiamond discs in either straight or contra-angledhandpieces when obtaining large bone blocks(Figure 12.5). These have the advantage of limit-ing the depth of cut to 2–3 mm, as well as havingexcellent guards to prevent soft-tissue trauma.Copious saline irrigation is required throughoutthis procedure. It is vital to cut completelythrough the outer cortex so that the graft can becleaved from the underlying cancellous bone(Figure 12.6).


Figure 12.4

By using a wide-based flap close to the mucogingivaljunction, a large portion of the anterior mandible may beexposed. Owing to a thick labial plate, the roots of thelower teeth are not visible and care must be taken to avoidtraumatizing the teeth.

Figure 12.5

Contra-angled and straight handpieces for the use ofdiamond discs for bone grafting (FRIOS MicroSaws,Friatec, Mannheim, Germany). Owing to the guards, thesemay be used in fairly confined spaces without traumatiz-ing the adjacent soft tissues.

Figure 12.6

The diamond discs cut very fine lines at a controlled depth,minimizing the chance of causing damage to adjacentstructures. It is important to ensure that the cuts meet ateach corner to allow elevation of the block. Bleeding fromthe depths of each cut indicates that the cuts arecompletely through the cortex and into the cancellousbone. Attempting to elevate the block while the corticallayer is intact will cause fracture of the graft.

A

B

In some areas the initial cuts may have to bedeepened using standard fissure pattern burs tothe desired depth. Care is required to limit the cutsto within the body of the mandible because lingualperforation may lead to haemorrhage of the lingualsoft tissues, which can be difficult to arrest. Oncethe outline cuts have been completed the graft canbe elevated using osteotomes or curved chiselsspecifically designed for that purpose. Large blocksthat extend across the midline can prove difficult toelevate and may need to be divided and deliveredin two pieces (Figure 12.7).

Trephine specimens also may be harvested fromthe chin and there are many different sizes oftrephine available for this purpose (Figure 12.8D).


Figure 12.7

In order to harvest a large graft from the anterior mandible,the blocks are taken in two pieces, enabling outfracturewithout using too much force and reducing the risk ofbreaking the blocks. Note the depth of the graft sites,which have been deepened by harvesting of the underly-ing cancellous bone.

A

B

C

D

Figure 12.8

(A,B) Trephine donor sites from the lower retromolar area.This region can yield good-quality bone grafts but the sizeof the grafts can be limited. By increasing the size of theaccess flap, the ascending ramus may be used as a donorsite—in such cases the use of diamond discs may be easierand the size of the graft is increased. (C) The amount ofbone available from trephine specimens is variable; indense bone the graft may be largely cortical as shown. Inareas of low density, such as the maxillary tuberosity, theremay be little bone recovered. (D) Trephines of various sizesare available to allow for different graft sizes as well aslimitations of access in certain regions. It is useful to havedepth indication lines on the outer aspect to allow thesurgeon to judge the depth of the cut being made.

Access to this region with fairly unwieldyhandpieces and large trephines can make this amore difficult procedure than taking blocks, unlessextensive soft-tissue reflection has been achieved.Once the corticocancellous block has beenremoved, further harvesting of cancellous chipscan be undertaken from the graft bed as well ascortical chips from the wound edge. Control of anybony haemorrhage is important before soft-tissueclosure, and for this the authors prefercarboxymethylcellulose mesh packed into the graftbed, although bone wax may be preferred bysome operators. Others advocate packing thedefect with bone substitutes held in place withbarrier membranes in order to minimize anypotential change in the bony profile. Good closureof the soft tissue at the donor site is criticalbecause the tendency for wound breakdown isquite high and a hermetic-type wound closureshould be aimed for.

Other intraoral harvesting sites are availablebut may be more limited in the amount of boneavailable. Trephine specimens taken from themandibular retromolar area can provide good-sized grafts of high-density bone (Figures12.8A,B); the maxillary tuberosities also may beused but the bone density in this region may bepoor. Larger blocks may be gained from theascending ramus and external obliqueridge/coronoid process, as well as the buccalaspect of the body of the mandible, using thediamond discs described.

The amount of bone harvested from any sitewhile using cutting instruments can be increasedby employing harvesting sieves within thesuction apparatus (Figure 12.9). These collect theosseous coagulum produced during drilling,which is considered to have good osseoinductivepotential. Owing to aeration and hydrationduring cutting, the volume of coagulumproduced can be significant, particularly if fairlycoarse rotary instruments have been used. Thecoagulum forms a paste-like substance that isreadily manipulated and can be placed in anyresidual voids between graft and recipient bed.Where a change in alveolar profile is sought, thegraft needs protection with a space-creatingmembrane or mesh.

Intraoral bone harvesting has become morepopular with the introduction of some of thetechniques above and is particularly attractive inthat the dental surgeon is working in a familiar

environment. The fact that these procedures canbe performed under local anaesthesia with arelatively low morbidity also makes them thetreatment of choice for small grafts. However, ifthere is a need for larger blocks of bone, extra-oral donor sites are required. Historically the siteof choice has been the iliac crest because boneis readily available in large volumes (Figure12.10). However, this requires an appropriatelytrained surgeon, a general anaesthetic (unlesstrephine specimens are considered adequate)and the procedure is associated with a significantmorbidity.

Once the graft material has been harvested, itcan be shaped to fill the defect with irrigatedburs or hand instruments such as rongeurs andchisels. Ideally the graft should be adapted togive a close fit to the recipient bed, with anysmall residual deficiencies made good with bonechips and osseous coagulum. The recipient bedshould be perforated with round surgical burs topromote bleeding from the underlying cancel-lous bone, to encourage vascularization andunion of the graft.

The success of the graft, like that of theimplants, is dependent on the stability of thegraft and the associated blood clot. The graftshould, therefore, be held firmly in position


Figure 12.9

A bone trap used for harvesting bone chips and osseouscoagulum during bone preparation with rotary instruments.The white plastic filter collects the bone, which then canbe used to pack small voids; this part is disposable. Fairlylarge quantities of material may be collected using thismethod, particularly when using fairly coarse cutting instru-ments such as twist drills.

using wires or titanium screws (Figure 12.11B).Further stability and protection of the graft maybe achieved by using titanium mesh or barriermembranes to cover the graft. These may bestabilized using small screws or tacks. The useof barrier membranes in particular has beenadvocated to reduce the amount of resorption ofthe graft that occurs in the healing phase, whichmay be as much as 50% over 6 months(Hammerle, 1998). However, the use ofmembranes also poses an increased risk of infec-tion, particularly if this becomes exposed. The

present authors do not advocate the use ofmembranes with block grafts but accept thatthey may be necessary with particulate/milledgrafts.

Wound closure at the grafted site must becomplete, with great emphasis on achieving ahermetic seal with as little tension on the soft-tissue flaps as possible. This can be difficult toachieve with large changes in bone profile andmay require further soft-tissue reflection andperiosteal relief to advance the soft tissues. Dueconsideration should be given to the potentialproblems of closure and in particular placingrelieving incisions remote from the grafted sitewhen gaining surgical access. The potential forwound breakdown over grafted areas is higherand carries with it a high morbidity. Patientsshould receive appropriate pre- and postopera-tive antibiotics to minimize the risk of infection.


A

B

Figure 12.10

(A) The favoured extraoral site for bone harvesting remainsthe iliac crest, from where substantial blocks of bone andsignificant amounts of cancellous chips may be harvested.(B) A bone mill can be used to fragment large bone graftsto produce a particulate graft that is more readily packed intovoids and awkward or confined spaces. Such grafts may beuseful in sinus lift procedures using a delayed implant inser-tion protocol (see section on sinus lift procedures).

Figure 12.11 (right)

(A) View of the upper jaw showing the left canine regionrequiring grafting prior to implant placement. The crestalridge profile appears to be of adequate dimensions on theright but there is a significant buccal concavity present onthe left. (B) Two cortico-cancellous blocks have beentrimmed to shape and secured using 2.0-mm diametertitanium screws which engage the residual ridge. Prior tothis the host site cortical plate is perforated with a smallsurgical drill (See Figure 12.3.) The grafts are larger thanthe required ridge profile to allow for some resorptionduring healing. Any spaces between the grafts and thehost bed are packed with cancellous bone chips andosseous coagulum. Further osseous coagulum is packedbetween and over the grafts to produce a smoother profileto the grafted site. (C) Three months later there has beenlittle resorption of the grafts but this underlines the impor-tance of placing larger grafts than are ultimately required.Protection of the grafts with membranes or titanium meshmay reduce the amount of resorption but can increase therisk of infection and total loss of graft material. (D) A direc-tion indicator in place after drilling with a 2.5-mm twist drillto show the planned implant orientation and adequateavailable bone on the buccal aspect. (E) Placement of animplant in an ideal orientation without any dehiscences orfenestrations has been facilitated by the use of the grafts.


A

C

D

E

B

The length of time between grafting andimplant placement has been the subject of muchcontroversy. When using onlay grafts theauthors prefer a time interval of 3 months,whereas in GBR techniques it may be better todelay implant placement for up to 6 months.Screws and membrane tacks are readilyremoved at the time of implant placement butthe complete removal of PTFE membranes canbe difficult to achieve. When placing implants inareas that have recently undergone an onlaygraft, great care is required not to cleave thegraft off the underlying alveolus. Incrementaldrilling procedures and low forces at placementare therefore mandatory.

Surgical management of largealveolar defects

More demanding ridge defects arise from long-standing tooth loss and denture wearing, as wellas trauma and as a result of some pathologicalconditions. Grafting in such cases may be under-taken to allow implant placement but also tochange the profile of the alveolus to enable place-ment of implants in a more ideal orientation.Long-standing tooth loss can lead to a consider-able change in skeletal relationships (pseudo-class III jaw relation) that may need correction.Treatment of cases with gross loss of verticalheight of the alveolar ridge without graftingwould necessitate the use of short implants,which may be considered undesirable because itresults in a poor crown/prosthesis to implant ratiothat may cause biomechanical failure in the longterm (Figure 12.12). Bone grafting techniquesshould not only increase the volume of bone butalso create an implant bed of good-quality boneto ensure long-term implant success.

Large grafts taken from the iliac crest can befashioned to produce an entire new alveolarform. This technique is favoured in cases wherethere is a skeletal base discrepancy or where alarge change in the vertical component of theridge is required, particularly where there is adesire to reduce the height of the prosthesis.Onlay grafting can be performed as a one- ortwo-stage procedure, with the implants used tosecure the graft in the one-stage approach(Figure 12.13). This requires that there is enough

residual basal bone to secure the implants andgraft. In full-arch cases at least six implants arerequired to achieve this. In the two-stageapproach, implant placement should take placearound 3 months after the graft procedure.

In cases where the vertical height of the maxil-lary ridge is inadequate, inlay grafts may be thetreatment of choice. Large inlay grafts spanningthe entire maxillary complex in combination witha Le Fort 1 down-fracture have been usedsuccessfully, particularly in cases where achange in skeletal relationship is desirable. Thistechnique preserves the intraoral ridge profilebut allows substantial gains in available verticalheight for implant placement (Figure 12.14).

Sinus lift procedures

Loss of alveolar ridge height, particularly incombination with pneumatization of the edentu-lous posterior maxilla, means that there isfrequently a lack of bone height for implantplacement. It is also often the case that any resid-ual bone in this area is of poor quality. Sinusfloor grafting procedures were developed byTatum in the late 1970s to overcome these


Figure 12.12

Placing implants into the residual ridge will require the useof short implants and a poor implant/crown ratio. An onlaygraft would increase the bone volume, allowing the use oflonger implants as well as reducing the height of theprosthesis (see Figure 12.13).

problems and have been used with great successworldwide following the principles described byhim. There is little evidence of disturbances tosinus drainage following this procedure.

In the classic approach, a bony window ortrapdoor is created in the buccal sinus wall togain access to the sinus. It is vital that clearradiographs are available preoperatively to showthe topography of the sinus, particularly thepresence of any bony butresses or septa thatprevent elevation of the window (Figure 12.15A).In addition, it is useful to ascertain the bucco-palatal dimension of the sinus to ensure that thetrapdoor created will have space to rotateupwards within the sinus cavity (Figure 12.15B).The presence of any sinus disease or a historyof recurrent sinus infections are contraindica-tions to this procedure.

The procedure can be carried out under localanaesthesia, and the use of infraorbital blocks isadvocated. Good access is obtained through awide-based soft-tissue incision with its bound-aries remote from the proposed point of entry tothe sinus. Commonly, the sinus wall is thin andthe sinus cavity can be seen as a bluish grey areaon the bone surface. This is helpful in delineat-ing the trapdoor, which must be cut over thesinus cavity or it will be impossible to elevate.

Where the sinus wall is thick the surgeon has torely on the preoperative radiographs orcomputed tomography (CT) scans to mark outthe shape of the window. The window shouldextend mesiodistally as far as the proposedimplant sites. If a pronounced bony septum ispresent, it may be necessary to create twoseparate windows or use an alternative approach(see next section). The outline is preferablycreated with diamond-coated surgical burs usingcopious irrigation, with great care taken not toperforate the underlying sinus membrane.

The inferior and lateral cuts are takencompletely through the bone but the superior cutmay be partially perforated to allow the windowto be infractured, leaving the superior aspect asa hinge. Once the cuts are complete the surgeonshould be able to move the window inwards withfairly gentle pressure.

As the trapdoor is elevated, the sinusmembrane is gently lifted off the surroundingbone. It is important to keep the sinus membraneintact throughout this procedure because it isexceedingly difficult or impossible to suture tearsin the membrane. Small perforations may bepatched with resorbable membranes orcarboxymethylcellulose. Large tears may dictatethat the procedure is abandoned, particularly ifthe intention is to graft the sinus with a particu-late graft material rather than a corticocancellousblock. The elevation continues until the desiredsize of void has been created, with the sinusmembrane pushed medially and superiorly alongwith the trapdoor. The degree to which the sinusfloor may be lifted is also dictated by the positionof the osteon on the medial wall, which allowsdrainage of the sinus. Once the space has beencreated within the sinus, two differentapproaches may be taken. If there is enoughresidual alveolar bone to accept and stabilizeimplants (usually at least 5 mm in height), thenthey may be placed immediately, with any resid-ual voids being packed with graft material. Iflarge blocks of bone are being placed into thesinus these may be stabilized by placing theimplants through both the alveolus and the graft(Figure 12.15I). In cases where there is littleresidual alveolar bone the void is first graftedand implants are then placed 3 months later.This latter technique is probably the preferredoption, with more predictable results in all cases.The preferred graft material is autogenous bone.


Figure 12.13

Onlay grafts may be secured to the residual alveolusprovided that there is enough bone to stabilize theimplants. Soft-tissue closure may be difficult in these situa-tions.


D

B

C

A

Figure 12.14

(A,B) This patient has a severe skeletal base discrepancy, aswell as many developmentally absent teeth. A combinationof bone grafting and maxillary osteotomy using a Le Fort 1down-fracture and advancement is required to alter the skele-tal relationship. Additionally, large maxillary sinuses dictate theuse of short implants, unless bone grafts are placed. (C)Intraoral view showing degree of oligodontia (postosteotomy).(D) Lateral cephalogram showing the skeletal profile after LeFort 1 osteotomy and iliac crest inlay graft. (Orthognathicsurgery by Dr Paul Robinson.)

continued


Figure 12.14 continued

(E) Dental panoramic tomograph showing implants in place in the maxilla with the completed implant-retained bridge inthe mandible. The increased available alveolar height provided by the inlay graft allows placement of long implants witha favourable implant/prosthesis ratio. (F) The final result with bridges in place. Despite the grafting procedure, the alveo-lar orientation dictated the placement of labially inclined implants and buccal access holes for the bridge screws. (G)Lateral cephalogram showing the final bridgework in situ. Note the improved facial profile and the orientation of the maxil-lary implants. (H) Clinical photograph showing the final result, with good profile and facial height.

E F

G H


A

B

C

Figure 12.15

(A) Dental panoramic tomo-graph of a patient requiringimplants in the posteriormaxilla. The alveolar ridge hasa good intraoral height but theextension of the maxillarysinus on the left side makes itimpossible to place more thanone implant without using agrafting procedure. There isno indication of sinus pathol-ogy or fluid levels/mucosalthickening. Additionally therewould appear to be no bonysepta running across thelateral wall. The proposed sitefor a cortico-cancellous graftfrom the chin is also outlined.(B) Sectional tomograms ofthe patient shown in Figure15A allow evaluation of thespace available to elevate thetrap door (shown by theyellow line). An indication ofthe likely volume of graftrequired can be ascertainedas well as the length ofimplant that may eventuallybe placed. The amount ofresidual alveolus in this casewould not be enough tostabilise the implant at thesinus grafting stage. Implantswould be placed as a separateprocedure three months later.(C) Placement of a singleimplant into the residualalveolous distal to the upperleft cuspid is possible for thepatient shown in Figure 15A.This may be enough inpatients with a restrictedsmile line or in low load situa-tions but is rarely the treat-ment of choice unless solelyreplacing the upper secondbicuspid.

continued


DE

F

G


(D) A trapdoor has been outlined in the posterior maxilla by careful bone removal with a surgical bur. (E) The trapdoorhas been elevated and the sinus membrane has remained intact during this stage. There is not enough residual alveolous(5 mm) to allow simultaneous sinus lift and implant placement, therefore a graft will be placed into the void created. (F)Residual space within the cavity is packed with autogenous bone material including osseous coagulum. The graft maybe covered with a resorbable membrane to ensure it remains within the void. The flap is then sutured back into place.(G) Pre-operative radiograph showing limited bone height in the posterior maxilla. (H) Post-operative radiograph after asinus lift has been performed in the upper left quadrant. The new level of the sinus floor in relation to the installedimplants can be seen. Enough residual alveolous was present in the upper right quadrant to allow implant placementwithout grafting. (I) Large blocks of corticocancellous graft material may be stabilised by placing implants through boththe residual alveolous and the graft. Ideally the graft should be orientated so that the cortical plate is superior allowinggood fixation of the apices of the implants.

I

H

Care should be taken when using particulategraft materials to ensure that the membrane isintact or that any tears are well sealed andprotected. Once the graft material and/or theimplants are in place and the trapdoor is held inits elevated position, closure of the wound isstraightforward with no need for the placementof a GBR membrane over the buccal aspect ofthe original trapdoor.

Transalveolar sinus floor elevation

Implants are often placed with their apicesextending into the sinus cavity by a fewmillimetres when attempting bicortical stabi-lization in the maxilla without any associatedproblems. Attempts to lift the sinus membranethrough the osteotomy site have beendescribed and bone apposition around theapices of the implants also has been shown. Amore refined technique has been described bySummers, using specific osteotomes to drivebone apically through the osteotomy site but toretain it under the sinus membrane (Figure12.16). Implants may be inserted immediatelywith this technique as long as the minimum5 mm of alveolar ridge height pre-exists to givethe implants initial stability.

Other techniques

Management of extraction sites

Teeth requiring extraction and subsequent implantplacement may be dealt with in several ways. Itshould be remembered that the majority of extrac-tion sites heal uneventfully with good bone fill ofthe socket, particularly when only one tooth isinvolved and there are adjacent standing teeth.

Preservation of the tooth socket is a prerequi-site for predictable bone fill and this is bestachieved using an atraumatic extraction method,in particular, the use of a Periotome®

(Friedrichsfeld GmbH, Mannheim, Germany) orluxators can be useful in achieving this (Figure12.17). Difficult extractions requiring boneremoval and associated soft-tissue involvementmay be aided in healing by good wound closure,particularly soft-tissue advancement to effectprimary closure. Placing graft material into theextraction socket as well as the use of occlusivemembranes have been advocated to improvebone fill. Problems may arise, however, if thesocket and graft/membrane subsequently becomeinfected, resulting in more bone loss than wouldhave occurred without the graft procedure.


Figure 12.16

The floor of the sinus may be elevated at each osteotomysite using Summers’ technique. By pushing a plug of boneapically with osteotomes, the floor may be infractured toleave the sinus membrane intact.

Figure 12.17

Luxators have much larger blades than the Periotome®

(see Chapter 11, Figure 11.4) and tend to expand thesocket more than sever the periodontal ligament. They aresupplied with a sharpening stone (shown at the bottom ofthe picture) and if they are maintained in their originalsharp-edged condition they may be used readily to extractteeth and preserve alveolar form.

Dehiscences and fenestrations

Small defects created at the time of implantplacement, such as marginal dehiscences orfenestrations, may require grafting, depending ontheir shape, size and location (Figure 12.18). Therationale for such procedures must, however, bequestioned because grafts placed in such defectsas well as bone created using GBR techniques areunable to contribute to the initial stability of theimplant and the bone may not ever integrate withthe surface of the implant. Repair of such defectsmay be useful in situations where the overlyingmucosa is thin and there is a risk of the implantshowing through the gingiva.

Crest splitting and dilation

Placement of an implant into a ridge that isslightly narrower than the implant diameter canbe achieved by increasing the crest width usingone of two techniques. Dilation of a site can beachieved in its simplest form by allowing theimplant to expand the ridge as it is inserted. This

can be achieved where the bone is thin and softenough to allow this. Formal dilation of the ridgeis achieved using osteotomes, such as Summers’osteotomes or those for specific systems, e.g.


Figure 12.18

(A) Small fenestrations such as this are often created at the time of implant placement. The need to graft such defects or toemploy GBR techniques is questionable. The implant has good initial stability and the majority of it is in good bone; placementof a membrane could lead to infection and loss of bone. (B) Larger dehiscences such as that on the lower left implant mayrequire grafting to encourage bone coverage of the exposed threads. Because the threads are outside the labial cortex, amembrane would tend to collapse onto the threads, thus reducing the amount of bone formed. Support for the membrane tomaintain volume should be sought, therefore, by the use of a titanium-reinforced membrane or preferably using bone chipsunder the membrane.

Figure 12.19

Osteotomes for dilation of implant sites have been devel-oped and are useful particularly in the softer maxillarybone. They all have markings along their length to corre-spond with the different implant lengths available.

A

B

Friatomes® (Friatec, Mannheim, Germany) (Figure12.19). This technique is dependent on therebeing enough cancellous bone present betweenthe cortical plates to allow initial site develop-ment with a surgical drill. By gentle manipulationand the use of osteotomes of slightly increasingdiameters, reasonable expansion of the ridge canbe achieved, enabling implant placement.

Total expansion of a ridge can be performedusing bladed osteotomes or ridge splittingsets, e.g. Crestosplit® (J van Straten MedischeTechniek, Nieuwegein, The Netherlands) (Figure12.20). Again, there must be some cancellousbone present within the ridge to allow for anatural plane of cleavage. Care must be takento limit the area of expansion by placing limit-ing cuts at each end of the ridge. The dangerof fracturing one cortical plate from the otheris not to be ignored and considerable practiceis required to master this technique. In partic-ular, caution should be exercised in sites with

brittle bone, especially in older individuals andsmokers. A combination of ridge splitting andindividual site dilation can allow markedchanges in the ridge profile. Once the ridgehas been expanded, implants, bone graft or acombination of the two can be placed in thevoid. Immediate placement of implants intosites that have been ridge split may be compli-cated by an inability to achieve initial stabilityof the implants.

A limiting factor for these techniques is thatthey do not allow for any change in orientationof the ridge and therefore the implant. In areaswhere implant angulation is important and theridge does not allow such orientation, othertechniques are required to augment bone at thedesired location.

Distraction osteogenesis

The use of bone plates secured either side of asurgically created fracture line, which are thenmechanically separated incrementally on a dailybasis, has been described both in orthopaedicsand maxillofacial surgery to increase bone


Figure 12.20

The Crestosplit® osteotomes allow a combination ofdilation at specific implant sites along with ridge expan-sion mesially and distally. Great care is required using thistechnique and case selection is very important.

Figure 12.21

With restricted height available above the inferior dentalcanal, the use of multiple short implants may beadvocated. Achieving initial implant stability in such situa-tions can be difficult to achieve because there is oftenpoor cancellous bone and it is not possible to engage theapices of the implants in cortical bone. The need to leavea safe margin of error between the length of the drills andthe canal usually means leaving the implants 3 mm shortof the canal, in contrast to the distal implant in the figure.

length. Miniature distraction sets have now beendeveloped to allow ridge height augmentationover limited spans and subsequent implantplacement.

Nerve transpositioning/obliteration

Loss of alveolar height in the posterior mandiblewill eventually compromise implant placementunless the mandible is wide buccolingually andspace exists to place an implant to one side ofthe nerve. In the majority of cases this is notpossible and the operator is left with severaloptions. Placement of multiple short implantsmay provide enough support without compro-mising the restoration biomechanically. Gainingstability of the implants may be difficult becausethe cancellous bone is often sparse (Figure12.21). Placing implants anterior to the mentalforamen and cantilevering distally has been usedwith great success and is appropriate in caseswith well-spaced implants of good length and inthe presence of a favourable occlusion. Onlaygrafts also may be used in this situation and actto improve the implant/crown ratio (Figure12.22).

The alternative is to surgically expose theinferior dental bundle and to move it buccally toallow implant placement through the bulk of the

mandible and thus achieve bicortical stabiliza-tion. This is a difficult procedure and the poten-tial morbidity, in particular anaesthesia orparaesthesia of the mental nerve should beexplained fully to the patient. Good exposure ofthe mandible is required, with complete dissec-tion of the mental nerve as it exits from the bodyof the mandible. The buccal plate is then gentlyremoved with burs and irrigation to facilitatemoving the nerve to the buccal aspect over therequired distance. The implants can be placedand the nerve placed back in close proximity tothem.

The only other neurovascular bundle thatcommonly compromises implant placement isthe incisive nerve in the premaxilla. This canbe very large and can limit ideal placement ofan implant in either of the central incisorspaces. Removal of the bundle and packing ofthe canal with bone graft can render this siteamenable to treatment after a 3-month healingperiod.

Soft-tissue grafting techniques

The soft tissues around implants serve afunctional role as well as an aesthetic one.Aesthetic problems are commonly diagnosed atthe planning stage of treatment and theirmanagement may be carried out alongside theimplant treatment. Functional problems oftenappear once the implant prosthesis is in situ andare frequently managed as a separate entity.

Functional soft-tissue problems

The peri-implant soft tissues have the samefunctional demands placed upon them as thosearound the natural dentition. They are thereforerequired to withstand the trauma of oral hygienepractices and the forces placed upon them duringmastication. It is therefore preferable to haveimplants emerging through non-mobile keratinizedmucosa. The severely resorbed edentulousmandible is frequently devoid of attached mucosa,and implants in such cases are prone to soft-tissueinflammation and reactive hyperplasias. Recurrentproblems associated with mobile and inflamed


Figure 12.22

The use of an onlay graft allows the placement of longerimplants and reduces the height of the prosthesis. Theimplants engage another layer of cortical bone and aretherefore easier to make stable at implant placement.


A B

C D

E

Figure 12.23

(A) The lack of attached gingiva around the abutment ofthe upper right lateral incisor presents an aestheticproblem for the patient (despite a low smile line) butalso prevents good oral hygiene due to the thin friablenature of the mucosa; a soft-tissue graft is thereforeindicated. (B) A split-thickness flap is raised to includea sound margin of tissue for the graft bed, leaving thepapillae intact. (C) The connective-tissue graft isharvested from the palate and trimmed to the correctshape and size. Some shrinkage should be allowed forand so the graft should be kept slightly larger than isrequired for the final result. By harvesting via an epithe-lial longitudinal incision, a cuff of epithelial tissue can beincorporated into the graft. (D) The graft is laid intoposition and held in place with sutures, ensuring goodcoverage of the abutment. Note that the epithelializedcuff has been placed around the abutment, with theconnective tissue extending apically. (E) Two weekspostoperatively, the increase in bulk of the tissues isobvious. The increased width of attached gingiva andcoverage of the abutment has been achieved. Furthermaturation will result in a smoother overall gingivalprofile.

soft tissues are best treated by the placement offree gingival grafts taken from the palate andsutured to a prepared vascular bed around theimplant in the same way as would be performedaround a tooth.

Care must be taken to immobilize the graftduring healing, which can be difficult to achievein sites with a shallow sulcus. The use of inter-positional connective-tissue grafts may alsoprovide a more stable and robust gingivalmargin around the implant. Free gingival andconnective-tissue grafts (Figure 12.23) may beused in this way at any stage of implant treat-ment: pre-implant placement, at abutmentconnection or once the prosthesis is in place. If

grafting is required after the prosthetic phase iscomplete, it may be necessary to remove theprosthesis, bury the implant and graft the siteand then bring the abutment through theattached mucosa once healing has taken place.

Aesthetic soft-tissue problems

Small soft-tissue defects, which may also have abone deficiency, may be considered unaestheticat the initial evaluation and treatment planningstage but it should be remembered that suchdefects often will be rectified once the prosthetic


A

B

C

Figure 12.24

(A) Gross loss of buccal hard and soft tissues of the upperright canine dictates that grafting of this site is required toachieve an acceptable aesthetic result. The loss of softtissue is the biggest problem in such cases, particularlythe entire loss of the attached gingiva. Placement of aconnective-tissue graft at the time of extraction willreplace the lost tissues. (B) Connective-tissue grafts arereadily obtained from the palatal soft tissues by employinga filleting technique via a limited incision. (C) Two monthspostoperatively there is a good width of attached gingiva.The height of the adjacent tissues will retain the profileduring the healing phase. Once an implant is emergingthrough the gingival complex, further restoration of thebuccal profile will be achieved.

components are emerging through the mucosa.Soft-tissue maturation occurs around implants,particularly around lone-standing single toothimplants with adjacent natural teeth. This isoptimized by good implant placement, allowinga natural emergence profile of the restoration aswell as careful soft-tissue handling at all stagesof treatment.

Larger defects need to be rectified surgicallyand this can be achieved readily using free gingi-val grafts and interpositional connective-tissuegrafts in combination with hard-tissue augmenta-tion for the more severe defects. Such techniquesare usually best performed before or at the timeof implant placement in order to achieve the bestresults (Figure 12.24). Once again, the use of thepatient’s own tissue is preferable to any of theother graft materials available.

Papillary preservation or interdental papillaryregeneration has been widely advocated; thedegree to which this is possible is open toquestion, but the basis of the technique, carefulsoft-tissue manipulation and the preservation ofas much keratinized tissue as possible, willundoubtedly maximize the soft-tissue healingpotential (Figure 12.25). Healthy peri-implant softtissues are more likely to respond favourably togood prosthetic work with anatomical emer-gence form.

Bibliography

Andersson B, Odman P, Widmark G, Waas A (1993).Anterior tooth replacement with implants in patientswith a narrow alveolar ridge form. A clinical studyusing guided tissue regeneration. Clin Oral ImplantsRes 4: 90–8.

Balshi T, Lee HY, Hernandez R (1995). The use of ptery-gomaxillary implants in the partially edentulouspatient: a preliminary report. Int J Oral MaxillofacImplants 10: 89–98.

Becker W, Becker B (1990). Guided tissue regenerationfor implants placed into extraction sockets and forimplant dehiscences: surgical techniques and casereports. Int J Period and Rest Dent 10: 377–91.

Bloomqvist JE, Alberius P, Isaksson S (1996).Retrospective analysis of one stage maxillary sinusaugmentation with endosseous implants. Int J OralMaxillofac Implants 11: 512–21.

Dahlin C, Andersson L, Linde A (1991). Bone augmen-tation at fenestrated implants by an osteopromotivemembrane technique. A controlled clinical study. ClinOral Implants Res 2: 159–69.

Hammerle CHF, Karring T (1998). Guided bone regen-eration at oral implant sites. Periodontol 2000 17:151–75.

Hammerle CHF (1999). Membranes and bone substi-tutes in guided bone regeneration. Proceedings of the3rd European Workshop on Periodontology-ImplantDentistry. Ed. by Niklaus P Lang. Quintessence Publ.468–99.


A B

Figure 12.25

(A) By careful manipulation of the soft tissues at stage II surgery, the gingival morphology may be optimized and theattached gingiva preserved. (B) Suturing of the flaps allows for healing by primary intention. The use of vertical mattresssutures, as shown in the midline papilla, maintains the height of the papillary tissues.

Kahnberg KE, Nilsson P, Rasmusson L (1999). Le FortI osteotomy with interpositional bone grafts andimplants for the rehabilitation of the severely resorbedmaxilla: a 2-stage approach. Int J Oral MaxillofacImplants 14: 571–8.

Lundgren S, Moy P, Johansson C, Nilsson H (1996).Augmentation of the maxillary sinus floor with particulatemandible: a histomorphometric study. Int J OralMaxillofac Implants 11: 760–6.

Nyman E, Kahnberg KE, Gunne J (1993). Bone graftsand Brånemark implants in the treatment of theseverely resorbed maxilla: a 2 year longitudinal study.Int J Oral Maxillofac Implants 8: 45–53.

Palmer RM, Floyd PD, Palmer PJ, Smith BJ, JohanssonCB, Albrektsson T (1994). Healing of implant dehis-cence defects with and without expanded polytetraflu-oroethylene membranes: a controlled clinical andhistological study. Clin Oral Implants Res 5: 98–104.

Sigurdsson TJ, Fu E, Takakis DN, Rohrer MD, WikesjoUME (1997). Bone morphogenetic protein-2 for peri-implant bone regeneration and osseointegration. ClinOral Implants Res 8: 367–74.

Simion M, Baldoni M, Rossi P, Zaffe D (1994). Acomparative study of the effectiveness of e-PTFEmembranes with and without exposure during thehealing period. Int J Period and Rest Dent 14: 167–80.

Tidwell JK, Blijdorp PA, Stoelinga PJW, Brouns JB,Hinderks F (1992). Composite grafting of the maxil-lary sinus for placement of endosteal implants—apreliminary report of 48 patients. Int J Oral MaxillofacSurg 21: 204–9.

Tong DC, Rioux K, Drangsholt M, Beirne OR (1998). Areview of survival rates for implants in grafted maxil-lary sinuses using meta-analysis. Int J Oral MaxillofacImplants 13: 175–82.

Yildirim M, Spiekermann H, Biesterfeld S, Edelhoff D(2000). Maxillary sinus augmentation using xenogenicbone substitute material Bio-Oss® in combination withvenous blood. A histologic and histomorphometricstudy in humans. Clin Oral Implants Res 11: 217–29.


PA R T I V

Prosthodontics

Introduction

Prosthodontic treatment is not just restricted to thefinal stage of implant treatment. The treatmentplanning chapter (Chapter 2) will have demon-strated the need for the correct decision to betaken regarding the suitability of implant treatmentover conventional techniques and the desirabilityfor a clear view of the desired end result prior toimplant placement. The importance of realisticdiagnostic wax-ups or restorations and surgicalstents cannot be overemphasized. It is also essen-tial that provisional restorations that can functionand be adapted during the stages of implant place-ment and exposure be provided. Whether oneoperator provides the implant treatment from startto finish or different dentists are undertaking thesurgical and prosthodontic stages, prosthodonticinput from the start is mandatory.

In many respects the prosthodontic treatmentfor a single tooth is straightforward if theplanning and placement of the implant is correct.However, with poor implant positioning orplanning, prosthodontic correction of the error toachieve an acceptable result can be impossible.Restoration of single tooth implants thereforecan be the easiest and the most demanding ofall implant restorations. The choice of the appro-priate single tooth abutment is one of the mostimportant prosthodontic factors and this is dealtwith in subsequent sections.

Abutment types

All manufacturers produce a variety of abutmentssuitable for single tooth restorations. Abutmentsattach the crown to the implant and preventrotation between components. Many differenttypes are required to allow for variations in such

factors as implant position, angulations, depthand soft-tissue contours and still achieve anaesthetic end result. The final restoration needsthe correct emergence profile in order to supportand contour the soft tissue. This may require atransition from a standard 4-mm diameterimplant to the 7-mm wide neck of a centralincisor tooth within the vertical dimension of onlya few millimetres (Figure 13.1). The abutmentneeds to resist conventional compressive andtensile loads and rotational forces, because it willnot be joined to other implants or teeth. There

13Single tooth implant prosthodontics

Figure 13.1

Selection of abutment height. In (A), a short abutment collarplaces the margin deeper in the soft tissues but allowsmore height for the development of a suitable emergenceangle compared with a longer abutment collar height (B).

A B

are few situations in which it is acceptable for asingle tooth restoration to show metal at thegingival margin and so there must be adaptabil-ity in the abutment design to allow for anaesthetic margin placement. Most anterior singletooth restorations will be cemented onto theabutment and this will get over any problemsthere may be with labial paths of insertion.

Abutments for single tooth restorations fallinto the following categories (see Table 13.1):

• Standard abutments• Prepable abutments• Fully customized abutments• Computer-generated abutments• Ceramic abutments• Abutments for screw-retained crowns

Standard abutments

Most implant types have a pre-made abutment,normally made of titanium. There are usually twopieces, with an abutment that fits onto theimplant head and a separate abutment screw thatcan be titanium alloy or gold alloy. A variety ofheights are offered, with a smooth collar thatextends from the implant head to the margin forthe crown (see Chapter 1, Figures 1.17–1.20).Matched impression copings, temporary copings,laboratory analogues and gold and porcelaincylinders are produced to ease manufacture. Thestandard technique is illustrated in Figure 13.2.

For the Nobel Biocare implant the CeraOneabutment fits onto the flat top and engages theraised hexagon to give anti-rotation for theabutment. As with all flat-top implant designs, it isessential that the abutment properly seats onto theimplant head and so a verification radiograph isrequired (Figure 13.3). The abutment is retained tothe implant by a gold alloy screw that is torquedinto position at 32 N.cm for a regular platformimplant, once seating has been confirmed. Toachieve this exact level of torque a mechanicaldevice such as an electronic torque controller isessential and the abutment needs to be held with acounter-torque. Narrow-platform implant abutmentscrews are tightened to 20 N.cm and wide-platformabutment screws to 45 N.cm.

The conical-headed implant (AstraTech, Frialitand Straumann) abutments have a matchedconical fit surface but also an anti-rotational


Table 13.1 Abutment types for single tooth restorations

Type Name Manufacturer

Standard abutment CeraOne Nobel BiocareST abutment AstraTechAbutment MH6/A0 (A15) FrialitSolid abutment Straumann

Prepable abutment TiAdapt, CerAdapt Nobel BiocareProfile BI abutment AstraTechAbutment MH6/A0, CeraBase FrialitSolid abutment Straumann

Fully customized abutment AurAdapt Nobel BiocareCast-to abutment AstraTechAuroBase Frialit

Computer-generated abutment Procera Nobel BiocareScrew-retained crown abutment Internal Hexed EsthetiCone Nobel Biocare

SynOcta Straumann

AstraTech: Astra Meditec AB, Mölndal, Sweden; Frialit: Friatec AG, Mannheim, Germany; Nobel Biocare: Nobel Biocare AB, Göteborg,Sweden; Straumann: Institut Straumann AG, Waldenburg, Switzerland.

Figure 13.2

Missing central incisor tooth replaced by an AstraTech STimplant with a standard prosthodontic approach:

(A) standard ST abutment in place; (B) abutment mounted onholder prior to placement—note the conical design withhexagonal anti-rotation base; (C) abutment and holder areseated and the abutment screw is tightened; the pencil markon the holder aligns the position of the abutment in theimplant; (D) impression coping seated onto abutment; (E)impression coping picked up in an impregum impression; (F)a laboratory information sheet gives technical instructions; (G)a Polaroid clinical photograph with the chosen shade guide inposition provides further information for the technician;

SINGLE TOOTH IMPLANT PROSTHODONTICS 159

A E

F

G continued

B

C

D



(H) the completed crown on the working model—note thesoft-tissue replica; (I) the completed crown, where themetal margin has been formed from the pre-made semi-burnout gold cylinder provided by the manufacturer; (J)internally the crown will have a precise, retentive and non-rotational fit; (K) the abutment screw hole is sealed withgutta percha; (L) the crown is cemented into place; (M)the end result is highly aesthetic.

H K

L

M

I

J

element to give the abutment resistance torotational forces. This element is found at theend of the cone in the deepest part of the implantand it is essential that the abutment is held androtation attempted prior to tightening the screwto ensure that the abutment is fully seated. Averification radiograph is not usually requiredbut may be used if there is any doubt that theabutment has not seated properly.

The coronal part of single tooth abutments needsto provide adequate retention and resistance formfor the crown to be retained by cement to theabutment. They are usually cylindrical in shape,

either parallel sided or with a slight taper. A flatfacet is required to provide resistance to rotation.The Nobel Biocare CeraOne abutment is a parallel-sided hexagonal cylinder, which delivers consider-able retention and stability to rotational forces tothe crown. The precision of fit for these restora-tions, particularly when using the matched goldcylinders, is such that difficulty can be encounteredwhen cementing them into position and cementswith a low viscosity or the provision of a vent holemay be required. Other designs such as the AstraTech ST (single tooth) have space between theabutment and crown to allow for cement release.Tapered abutment heads, such as the Straumannsolid abutment or Frialit 2 abutment MH 6, shouldnot offer as much resistance to seating as parallel-sided abutments.

The matched impression copings for all designsare simple push-fit plastic that can be picked up inan impression material. The gold cylinders providedare designed to have wax built up to a contournecessary for a conventional metal–ceramic crown.Alternatively, plastic ‘burn-out’ copings are availablethat produce a similar result. Some manufacturersproduce porcelain copings onto which conventionalporcelain can be fired.

Advantages/indications of standardabutments

• Simple to use.• Minimal chairside and laboratory time.• Predictable fit and retention for crown.• Use in ‘straightforward’ cases where optimal

space and implant orientation have beenachieved.

Disadvantages/contraindications ofstandard abutments

• Margin for crown does not follow gingivalcontour.

• Cannot be customized for implant orientationor anatomical features—particularly not suitedto very labially inclined implants.

Prepable abutmentsThe connection to implant with these abut-ments is the same as for standard abutments


Figure 13.3

A periapical radiograph demonstrating the failure to correctlyseat a CeraOne abutment onto a Nobel Biocare implant.

and an outline of the technique is illustrated inFigure 13.4. The retentive element for the crownis a block of metal that can be customized toachieve an ‘ideal’ preparation contour. Theabutments come in a variety of diametersroughly corresponding to the dimensions ofupper lateral and lower incisors (4–4.5 mm),upper central incisors, canines and premolars(5.5 mm) and molar teeth (6.5–7 mm). A smoothcollar extends from the implant head to thisdimension. An impression is taken of theimplant head and a model is made with asilicone soft-tissue replica (see later section onlaboratory techniques). The abutment isprepared using high-speed instrumentationeither by the dentist or the dental technician.The metal can be cut back to achieve a prepa-ration comparable with a conventional crownpreparation. The gingival margin can followgingival contours and be placed subgingivallyon the labial and proximal sides but can besupragingival palatally. Enough space must becreated to allow sufficient space for the crown.

The metal surface that will be covered by thecrown can be left with a coarse finish to aidretention and does not need to be polished, butany metal that will be in contact with the softtissue should be as smooth as possible.

A major advantage of this approach is theability to change orientation for the crownrelative to the implant (Figure 13.5). This isnormally required to rectify a labial inclination ofthe implant. The correct transverse shape for thecrown also can be achieved. With a conventionalabutment the whole restoration is circular incross-section at the implant head and throughthe abutment. The ideal contour is developedonly from the start of the crown. With a prepableabutment, the abutment itself can be modified toresemble more accurately the cross-sectionalshape of a natural tooth. For example, an uppercentral incisor tooth is roughly triangular inshape at the gingival level with a flat labialsurface. If a circular abutment is put in positionthis will tend to be under-contoured mesiodis-tally or, if a larger size is used, it will push down


Figure 13.4

Missing central incisor tooth where an AstraTech STimplant has a minor labial angulation: (A) On presenta-tion, the healing abutment has been cut back topreserve labial soft tissue; (B) following an impressionof the implant head, a cast is prepared using an implantanalogue and a soft-tissue replica; (C) the Profile BIabutment try-in kit; (D) abutment analogues can be triedon the cast to assist in the correct choice of abutmentheight and width; (E) the amount of preparation requiredand residual abutment can be visualized; (F) the preparedabutment in place—note the poorly formed gingivalcontour at this stage; (G) following provisional cementa-tion of the crown the gingiva is healthy and wellcontoured; the abutment screw access hole has beenfilled with gutta percha; (H) the completed restoration;(I) a post-cementation periapical radiograph.

B

A


C

D

E

H

IF

G

the labial gingival margin in the centre. Aprepable abutment can be cut back on the labialsurface in the centre but still keep adequatewidth mesiodistally and affect a good emergenceprofile with more ease (Figure 13.6).

Prepable abutments should be prepared out ofthe mouth. Small changes can be made intra-orally with an air-rotor under copious irrigation,but are best avoided. They can be prepared intwo ways. The first way is to produce theabutment and final crown in one stage. This isacceptable for restorations where minor changes

are being made to the implant orientation andthe soft tissue is healthy and will remain stable.This technique ensures a good marginal fitbetween abutment and crown because it doesnot require a second impression. There is the riskof a poor long-term result if the gingival marginis only placed just subgingivally, because if thereis some recession of the gingival margin follow-ing cementation, then some metal will show. Amargin for error with a slightly deeper marginplacement is recommended. It is often wise tocement the crown temporarily to allow for soft-tissue resolution prior to final cementation.

The second way is to prepare the abutment andprovisional crown as a first stage. Then a secondimpression is taken with the abutment in place anda final conventional crown made. More stages arerequired for this approach but a more predictableresult may be obtained. However, it can be diffi-cult to take an impression of an abutment inposition and deep margins pose a problembecause gingival retraction cord is hard to use.Acrylic copings can be made in advance and apick-up technique employed. Alternatively, oncethe abutment has been deemed acceptable, it canbe removed from the mouth and the crown frame-work can be produced directly on the abutment.Minor changes to the margin carried out in themouth can result in gingival bleeding, so it is bestto remove the abutment and place it back onto theimplant head model for chairside adjustment.

This second technique is particularly useful if theemergence and profile of the soft tissue need to bemodified significantly. A prepable abutment isproduced with a provisional crown that partly satis-fies the desired end contour. Following temporarycementation, the soft tissue will be deformed andthen re-modelled to the new shape. The contourcan be modified over successive visits by additionto the provisional crown until the desired contourand gingival emergence have been achieved. Animpression of the abutment and adjacent softtissue will allow for production of the final crown.

Advantages/indications of prepableabutments

• the technique will suit almost every situation• copes with angulation changes• allows for soft-tissue remodelling and good

emergence profiles


Figure 13.5

When the desired crown is in the same long axis as theimplant, a standard abutment will achieve a good result(A). If the implant has a more labial angulation, as in (B)and (C), and the path of insertion of the crown needs tobe different to that of the implant, a prepable abutmentmay be indicated. The crown in (B) will be too thin on thelabial aspect and the prepable abutment (C) allows morespace for the crown.

Figure 13.6

An upper central incisor tooth is essentially triangular incross-section (A). Choosing an implant diameter that isnarrower than the tooth (B) will allow the emergence tobe developed through the contour of the abutment andcrown. An oversized implant (C) will not allow a suitableemergence to be developed.

A B C

A B C

Disadvantages/contraindications ofprepable abutments

• more complex laboratory technique• may require second intraoral impression• precision of fit of crown to abutment is less

predictable

Fully customized abutmentsThese abutments share many properties withprepable abutments but they can be produced witheven more allowances for compromised implantpositioning. The basic procedure is illustrated inFigure 13.7. Following an implant head impression


Figure 13.7

Restoration of an AstraTech ST implant that is close to theadjacent tooth. There was a large incisive canal that influ-enced implant placement. (A) From the implant headmodel, the lack of space between the implant head andthe adjacent tooth can be seen. Use of an abutment andseparate crown would therefore be difficult. (B) Using acast-to abutment, a one-piece abutment and crown hasbeen produced. The abutment is completely customizableusing a conventional wax pattern and casting technique.(C) The resulting restoration eliminates the need forcementation and is retained by the abutment screw. (D)On initial insertion, the crown causes blanching to the softtissues. (E) Removal of the restoration 4 weeks laterdemonstrates a healthy contoured gingival cuff. (F) Thecompleted crown.

A

B C

D

E

F

the abutment pattern is placed in position on theworking model. Some designs have a preciousmetal base that provides the accuracy and detail ofthe fit surface to the implant; other designs repro-duce the fit surface in the burn-out pattern. Theabutment shape is waxed onto the pattern andthen cast in precious metal. With this process it ispossible for an abutment to be produced to accom-modate significant changes in angulation betweenimplant and crown and also to move the apparentlong axis of the final restoration to a differentposition on the implant long axis, although this islimited by the need to retain adequate retentiveform for the final crown.

The extra complexities of this process restrictits use to difficult situations that can be resolvedonly by full customization. Where the fit surfaceof the abutment has been cast rather thanmanufactured, the quality of fit may not be asgood. Conventional abutment screws retain theabutments and the rest of their use is the sameas for prepable abutments.

Computer-generated abutmentsUsing the Procera system, it is possible forcustomized abutments to be produced using afactory process. Head of implant impressions aretaken and the working model is placed in ascanner. Readings are taken of the implantposition and angulation relative to the desiredrestoration. Using computer software, an ‘ideal’abutment shape can be generated and viewed inthree dimensions. The position of the gingivalmargin can be superimposed on the image andthe information sent to a specialized centrewhere the abutment is produced in titanium.

The end result of these abutments is verysimilar to prepable abutments. With highly skilledtechnicians, who are experienced in the scanningtechnique, the process is straightforward, but thetechnique is limited to laboratories with thoseskills. The remaining process to complete therestoration is the same as for prepable abutments.

Ceramic abutmentsThese are essentially the same as prepableabutments and are used in the same way(Figures 13.8 and 13.9). They are made from


A

B

C

Figure 13.8

Nobel Biocare implants restored with porcelain CerAdaptabutments. The implant heads were close to the surfaceand conventional abutments could not be hidden. (A) Theprepared abutments in position; the abutment screwaccess holes are sealed with a tooth-coloured material. (B)The abutment screws are torqued carefully into placeusing an electronic torque controller and a counter-torqueto prevent overstressing the implant. (C) The completedProcera crowns cemented with a tooth-coloured compos-ite resin cement.

dense porcelain and clinical trials have demon-strated good success rates, although the numberof trials is limited in number and there is littlelong-term data. The restorations can be highlyaesthetic; the final crown should be all-porcelainin construction and cemented with a tooth-coloured lute to achieve optimal results. Ceramicabutments are not suitable for situations wheresignificant angulation changes need to be made,

because the porcelain remaining following prepa-ration will be at risk of fracture if it is too thin.

Abutments for screw-retainedcrownsThe desirability for screw retention has alreadybeen discussed. The normal way to achieve a


Figure 13.9

Two Nobel Biocare implants restored with CerAdaptabutments. The gingival tissues were thin and, to preventshine-through of the metal abutments, porcelainabutments were chosen. (A) Healing abutments in place.(B) Implant head impression copings in position prior toimpression taking. (C) On the cast, the abutments areprepared. (D) All porcelain crowns are produced directly onthe abutments. (E) The completed restorations.

A

C D

E

B

screw-retained crown is to use an abutmentdesigned for bridges (EsthetiCone from NobelBiocare or Octa from Straumann) but to use agold cylinder that has an internal surface withfacets that engage the abutment (Figures 13.10and 13.11). If the abutment does not have thistype of surface, such as the Uni-abutment(AstraTech), then there will be nothing to resistrotational forces other than the gold screw.

Systems such as the Frialit have componentsspecifically for screw retention where the screwdoes not seat into the abutment in the long axis,but has a lateral retaining screw that can bepositioned on the palatal or lingual aspect of thecrown. As long as there is sufficient space forthis, it can produce an aesthetic retrievable crownwith no screw hole on the occlusal surface.

Generally, screw-retained crowns are moreapplicable to premolar and molar regions whereocclusal screw access may be less of anaesthetic problem and in situations where theremay be more of a need to remove restorations(e.g. to tighten the abutment screw) or joinimplants to further implants in the future.

Impressions and abutmentselection

The previous section described in detail thevarious abutments and techniques available.However, before an abutment is selected, achoice needs to be made between two alternative


Figure 13.10

A missing central incisor tooth with a Nobel Biocare implant in place. (A) An EsthetiCone abutment has been placed. Thepatient expressed a desire for the restoration to be easily retrievable, so a screw-retained crown has been chosen. (B)The internal contour of the gold cylinder used will engage the anti-rotational features of the abutment. (C) Palatal viewof the final restoration in place shows the position of the retaining screw in the cingulum of the crown. (D) The completedrestoration.

A B

C D


Figure 13.11

A single Straumann implant placed for a missing uppersecond premolar tooth: (A) the working cast with a replicaof the implant; (B) completed crown – the screw accesshole is centrally placed; (C) buccal view of the crown inposition—the upper teeth are in cross bite with the lowerteeth; (D) periapical radiograph of the completed restora-tion; (E) a similar case of a missing first premolar toothalso with a Straumann implant; the abutment is protectedwith a healing cap; (F) occlusal view of the implant priorto abutment connection;

continued

A

D E

F

B C



(G) the completed crown, occlusal view; (H) the completed restoration.

G H

C

A B

Figure 13.12

Four Nobel Biocare implants to be restored in singlerestorations: (A) CeraOne abutment impression copings inplace; (B) a stock tray has been modified to allow thecopings to project; (C) an impression taken in Impregum—note the finger marks over the copings due to the opera-tor holding the copings down to prevent their movementwhile the impression material sets.

techniques: abutment impressions or implanthead impressions.

Abutment impressions

The conventional approach for single toothrestorations using standard manufacturer-madecomponents is to choose the abutment and placeit into position. An impression is made of theabutment and a working model is producedusing ready-made components (Figure 13.12).The abutment can be left in position and coveredwith a temporary cover or a temporary crowncan be built up using conventional crown andbridge techniques (with a temporary componentfrom the manufacturer).

Alternatively, the abutment can be removedfollowing impression taking and stored for use atthe next appointment. The healing abutment istherefore replaced. This technique requires lesschairside time and the original provisional restora-tion (denture or resin bonded bridge) can be re-fitted. It is important that the abutment is storedin a sterile container and care must be taken toensure that it will go back into exactly the sameposition next time. With the CeraOne system, forexample, the abutment will seat back onto theimplant in a reproducible way each time becausethe components are symmetrical and matched.With some systems, such as the AstraTech ST,there is a difference between the number of facetson components, i.e. the abutment could reseatinto a different position next time. Many compo-nents are made in this way because it allowsmore positions of the abutment on first seating. Ifthe abutment is to be removed, it needs to re-orientate in the correct position. Marking theabutment holder prior to removal of the abutmentand leaving it in the holder until the next appoint-ment will achieve this (see Figure 13.2C).Whichever of these alternatives is followed, thistechnique requires that the abutment is chosen inthe mouth and an error in choice can be costly.

Implant head impressions

This technique is mandatory for all abutmenttypes other than conventional abutments and

has much to recommend it as the approach ofchoice. An impression is recorded of the implanthead using an impression coping (see Chapter 14for more detail), which is cast with an analogueof the implant head to produce a working model(Figure 13.13). The abutment can be selected andseated onto the model. Choice of the abutmentoutside of the mouth ensures that the correctdecision can be made more easily without takingup clinical time. Any of the abutment types canbe used in this way. Care must be taken not todamage the abutment assembly, particularly thescrew, and therefore a laboratory screw shouldbe used and the clinical screw stored until theabutment is seated into the mouth. The abut-ment should be sterilized before placement inthe mouth.

Some prosthodontists prefer to choose theabutment using this technique but then place theabutment into the mouth and re-take the impres-sion.

Choosing the abutment

Abutment selection is based on several features.

Depth of soft tissue

The vertical height from implant head to thegingival margin is measured at the shallowestpoint on the labial surface. This can be measuredintraorally with a periodontal measuring probeor with various devices provided by manufactur-ers that fit onto the implant head and indicate thedepth. To ensure that the metal collar of theabutment does not show, the abutment ischosen so that the labial margin is at least 1 mmsubgingival. Care must be taken to ensure thatchoosing abutments to suit the labial margindoes not result in an excessively deep marginelsewhere. The authors find that margins morethan 3 mm deep result in restorations that aredifficult to seat and removal of excess cementmay be impossible. In situations where there isa marked discrepancy between the gingivalheights around the margin, a prepable abutmentis indicated because it allows the margin to beplaced in relation to the gingival contour. Thistechnique assumes that the chosen abutment



Figure 13.13

Restoration of an AstraTech ST implant with a Profile BI abutment: (A) Missing upper lateral incisor tooth; (B) healingabutment removed; (C) implant head impression coping in place; (D) the working cast—the gingival replica has beenremoved; (E) the prepared abutment; (F) there has been more labial reduction to allow for the desired crown contours;

continued

A B

C D

E F

has a diameter close to that of the cervicalmargin of the tooth to be replaced.

Emergence profile

It is easier to create a good emergence profile ifthere is at least 3 mm of vertical space fromimplant head to gingival margin (Figure 13.14).This allows a transition from an implant head,which is often at least 2–3 mm less in diameterthan the cervical margin of the proposed restora-tion. If it is necessary to flare from the implanthead to a wide-necked restoration in a shortvertical space, it is most readily achieved usinga wide-diameter prepable abutment. This can



(G) the completed crown and abutment—note the contour that has been achieved; (H) the completed restoration on themaster cast; (I) the abutment in place; the gingival blanching is normal due to the difference in contour between thehealing abutment and the definitive abutment; (J) the completed restoration.

G H

I J

Figure 13.14

Selection of a shorter abutment (B,C) allows more verticalspace for possible alterations in labial angulation withstandard abutments compared with a normal selection (A)where the crown margin has been placed just subgingival.

A B C

create a dramatic change in little vertical space,but care must be taken not to excessivelyovercontour this region, which then may be diffi-cult to maintain. There may be a desire to createa final restoration with a wide gingival dimen-sion especially where the interdental gingivalpapillae have been lost to leave ‘black triangles’,which will spoil the final appearance.

Orientation

Ideally the implant will have been placed closeto the long axis of the missing tooth crown andadjacent clinical crowns. Implant placement withthe long axis of the implant through the incisaltip or just to the palatal surface is easiest torestore and any of the abutments can work inthis situation. It is a common scenario, however,for the implant to have a slight or evenpronounced labial inclination. There are severalreasons why this may be the case, including:

• The bony contour following resorption fromtooth loss often results in an alveolus whichdictates implant placement in a more labialinclination.

• As a result of the natural curvature of theoriginal and adjacent teeth, the roots may beorientated at a different angle to the clinicalcrown.

Small degrees of labial angulation (see Chapters3, 4 and 9) can therefore be desirable and easilyaccommodated by standard abutments. Ifstandard abutments are used in situations withmore labial angulation, they may result in eitheran excessively overcontoured labial surface or aporcelain surface that is too thin to mask themetal structure underneath. Starting the restora-tion more apical by using a shorter abutment willhelp (Figure 13.14). A better result can beachieved by using prepable abutments or fullycustomized abutments, because the path ofinsertion of the crown can be different to thelong axis of the implant. Changes of between 30°and 40° can be made; the limiting factors arenormally the need to retain some abutmentstructure around the abutment screw hole andthe need to provide adequate retention for thecrown. To assist with the correct abutmentchoice, the best approach is to determine the

correct labial contour using either the provisionalrestoration or from a diagnostic wax-up. Asilicone putty labial mask can be produced fromthis and placed either in the mouth or, ideally,on a working implant head model. The trueorientation of the implant relative to the labialsurface is then clear and the correct abutmentchoice can be made.

Interocclusal space

The space from implant head to the opposingtooth needs to be assessed. The shorteststandard abutments require a minimum verticalspace of 6–7 mm. If less space exists a prepableabutment may be indicated, although verticalspaces less than 5 mm are difficult to restore andalternative conventional dental techniques, suchas increasing the vertical dimension of the occlu-sion or the use of ‘Dahl’ appliances, should havebeen considered. Once again, correct planningand a deeper implant placement can avoid thisproblem. Excessive vertical dimensions can berestored using any of the abutment types.Standard abutments are available in variousheights and they have adequate retention andresistance form to support restorations withconsiderable vertical height. The implant crownneeds to be made so that the porcelain iscorrectly supported by the metal work.

Retrievability

A screw-retained restoration will be easier toremove at a later stage if it is envisaged that thiswill be required. A cemented crown, even placedon a standard abutment with a temporarycement, can be very difficult to remove. Ingeneral, a restoration can only be made screwretained if the path of insertion for the screw willbe on the palatal or occlusal aspect. Specificabutments for single teeth are available or astandard abutment can have the crowncemented onto the abutment out of the mouthand a larger access hole made through thecrown to fit the restoration onto the implant withthe abutment screw. Screw retention can beuseful in situations where there is limited spacebetween adjacent teeth. Access for the cementa-tion process can be limited and the space needed


for the abutment, cement lute and crown takesup more space than a one-piece screw-retainedrestoration (see Figure 13.7).

Special aesthetic requirements

The techniques already outlined aim to providean aesthetic restoration with no metal showing.Problems can arise if the implant head is closeto the surface or if the labial gingival tissue isthin so that the metal abutment shows throughthe gingiva, causing greying and a poor appear-ance. This can be determined by attaching animplant head impression coping and looking fora colour change. A porcelain abutment such asthe CerAdapt from Nobel Biocare can allow foran aesthetic restoration to be achieved.

Final restoration

Before a single tooth implant abutment ischosen, the type of final restoration requiredmust be considered because this will have abearing on the abutment selection. When usingmetal abutments there is little reason for avoid-ing the use of metal ceramic restorations. Allporcelain restorations cemented onto metalabutments need to be quite thick to avoid themetal showing through and resulting in a greyrestoration. Problems can arise when singletooth implants are being matched to adjacentteeth that are already restored with porcelaincrowns or porcelain veneers. It is often best toreplace adjacent restorations so that they can bereconstructed together in the same materials.Alternatively, more space needs to be created inthe abutment to accommodate the all-ceramiccrown.

Abutment selection kits

Several manufacturers produce abutment selec-tion kits that are exact replicas of the differentabutments available (Figure 13.4C). They arenormally used on an implant head cast but canalso be used intraorally. Because it can be diffi-cult to visualize an abutment in position and anincorrect choice can be very costly, their use is

highly recommended (see Chapter 14 for moredetail).

Having chosen the abutment and decidedupon the final restoration, the clinical techniquescan now be outlined.

Abutment connection

Deep soft-tissue tunnels will make abutmentseating a purely tactile process. It may also bean uncomfortable process for the patient, partic-ularly if the soft tissue is still in a fragile state. Itis essential that healing abutments are not leftout for any length of time because the soft tissuewill quickly collapse into the space and will bepainful to push back. Local anaesthetic maytherefore be required. A degree of soft-tissueblanching is to be expected, but patients shouldfeel the area return to normal within a fewminutes.

If the abutment is to be placed in the mouthand left in place, the abutment screw will needto be tightened to the manufacturer’s recom-mendations. Electronic and hand torque devicesare available, with and without counter-torques.It is essential that the abutment is fully seatedand in the correct position before torquing thescrew because the fit surfaces will be damagedand it can be difficult to remove if incorrect, orthe screw may fracture.

The complications of removing abutmentsonce impressions have been taken and reseatingthem in the same position have been discussedalready.

Impressions

For standard abutments, plastic push-on impres-sion copings are seated onto the abutment(Figure 13.15). These are often a tight fit andhydrostatic pressure can build up inside suchthat they tend to lift up from the abutment ifseating pressure is released. If it is obvious thatthe coping is not stable, it should be leftuntrimmed and a hole cut in the impression trayso that finger pressure can be exerted on thecoping while the impression material is setting.A retentive impression coping is trimmed so that



Figure 13.15

A Frialit 2 implant placed to replace a missing upper central incisor tooth: (A) healing abutment in position; (B) the impres-sion coping; (C) the coping is seated into the implant—the metal part will stay in the implant following removal of theimpression; (D) the blue plastic component is picked up in the impregum impression; the metal coping that remainedattached to the implant will reseat accurately back into this; (E) working cast with abutment in position; (F) the metalcoping for crown manufacture;

continued

A B

C D

E F

it does not interfere with an impression tray.Conventional crown and bridge techniques canbe employed. A stock tray that is rigid enough tosupport medium- or heavy-bodied impressionmaterial is used. The impression material usedneeds to be rigid enough when set to hold theimpression coping without tearing. Light-bodiedmaterials are therefore not suitable. Putty consis-tency materials alone are also not suitable,because they will not flow around the copings.Single-phase materials such as polyethers andaddition-cured silicones (medium- or heavy-bodied pastes) are recommended.

Impression material is syringed around thecoping and the tray is seated. A full-arch impres-sion is recommended. Once set, the impressionshould retain the coping and it should be tested

carefully for looseness with tweezers. If there isany doubt that the coping may have moved inthe impression, it is best to re-take the impres-sion. The impression should also record theadjacent teeth and their gingival margins, as wellas the articular surfaces of all the teeth in thearch. The abutment analogue needs to beattached to the impression coping ready for thelaboratory to cast the impression.

Good quality opposing impressions andocclusal records are required. For a single toothrestoration it is normally not necessary formodels to be fully articulated, but similarrequirements to conventional crown work shouldbe followed and a complex occlusal relationshipthat needs to be copied may indicate full articu-lation on a suitable articulator.


G H

I J


(G) completed crown on cast; (H) internally, the use of a pre-made coping ensures an accurate fit; (I) abutment seated;(J) the crown immediately after cementation; the gingival blanching will resolve in a short time.

For a prepable abutment to be used, animpression of the implant head is required toallow the abutment to be modified on a modelin the laboratory. A ‘pick up’ impressiontechnique is followed, with an impressioncoping held into position with a guide pin. Thepin needs to be unscrewed before the impres-sion is removed from the mouth (see Chapter14 for more detail). Once a prepable abutmenthas been placed, a secondary impression of theabutment in position and the gingival contourmay be required. If the gingival margin of theabutment is only just subgingival, it may bepossible to record the margin using a conven-tional impression technique, syringing light-bodied material into the gingival crevice.Deeper margins or situations where there issome gingival bleeding make the use of agingival retraction cord necessary (Figure13.16). This needs to be packed with carebecause it must not be pushed below thewidest contour of the abutment, otherwise itwill be difficult to remove. It is important thatthe margin of the abutment is checked after theimpression has been removed to ensure thatfragments of material have not torn from theimpression and remain trapped under the

convexity of the abutment. If an impression isproving difficult to take, it is better to replace awell-fitting provisional restoration and allowthe soft tissue to improve and then try again,or alternatively to consider removing theabutment and directly waxing up the frame-work on the abutment or to construct an acryliccoping of the abutment that can be picked upin a secondary impression.

Temporary restorations

Short-term temporary crowns can be constructedat the chairside using plastic copings supplied tofit on conventional single tooth abutments.These can be time consuming to make and oftenit is best to remove the abutment and replace theprovisional restoration. Temporary crowns canbe constructed from the diagnostic wax-up usingeither a putty or vacuum-formed mould in crownand bridge temporary acrylic materials. Thetemporary crown will need to extend down tothe margin of the coping and the material willnot flow subgingivally. The temporary restora-tion needs to be contoured carefully to have anacceptable emergence profile and this is bestcompleted out of the mouth using light-curedcomposite.

Longer term provisional crowns to be placedon prepable abutments or to be used for soft-tissue moulding techniques (see earlier) are bestconstructed in the laboratory in advance.Temporary crowns can be cemented usingconventional materials such as zinc oxide/eugenol or temporary cements.

Shade taking and laboratoryprocedures

Ideally the shade should be taken with agree-ment of the dentist, patient and technician. Thedesign of the abutment also should be a jointresponsibility between dentist and technician.For single tooth restorations, the expectations ofthe patient are often very high and only thehighest quality aesthetics will be acceptable.


Figure 13.16

Gingival retraction cord placed around prepable abutmentsto assist in an accurate impression being taken of thesubgingival margins.

Laboratory techniques

Analogues for either the abutment or the implanthead are attached to the coping in the impression(Figure 13.17). A soft-tissue replica in a flexiblematerial needs to be incorporated into theworking model, because a hard model would notallow the restoration to extend subgingivally andcreate a good emergence. Several silicone materi-als are available and they are placed into theimpression around the laboratory replica beforedental stone is poured. The soft-tissue replica isremovable to allow access to the margin area.

Conventional techniques are followed forcrown construction, as already outlined.

Fitting the completedrestoration

Try-in

The restoration can be tried in prior to comple-tion. Straightforward cases can go to completionfrom the initial impression but where significantchanges have to be made to orientation or soft-tissue contours, a try-in is advised. The crowncan be seated with finger pressure but will often

rise up due to the gingiva being displaced. It isoften difficult for patients to see the exact resultat this time unless the crown is being firmly heldin. The contact points are checked with dentalfloss, as for conventional crowns.

Occlusion

The occlusal contacts should be checked prior toand after cementation. The ideal arrangement isfor the implant restoration to be in very lightcontact when the patient gently holds their teethtogether and to be in full contact only whenheavy load is applied. The best test is for theimplant restoration not to hold shimstock onlight contact, whereas the adjacent teeth do. Asmore pressure is exerted, the implant restorationcan start to hold shimstock.

This can be difficult to determine until therestoration is finally cemented. Prior to cemen-tation it is probably best to adjust and check theocclusion with occlusal indicator papers forgross overcontact. The crown should be adjustedso that it lightly marks and so that heavier marksare visible on adjacent teeth. The implant crownshould not be placed without occlusal contactbecause this could result in movement of theopposing teeth.


Figure 13.17

(A) An impregum impression of an abutment with the laboratory replica attached. (B) The soft gingival replica is pouredinto the impression

A B

The occlusal contacts are first checked in theintercuspal position (the position of maximumintercuspation). This may not be in the retrudedarc of closure and so the crown should bechecked in this position to ensure that it will notcreate an occlusal interference.

Next the crown is checked for protrusive andlateral contacts. In protrusive movement, if thecrown is to be in contact it should be shared withother teeth and not be the sole point of contact.In lateral movement, the crown should conformto the existing occlusal scheme: either a groupcontact or canine-guided. It is not desirable forthe implant restoration to act as the only guidingsurface for lateral movement.

Cementation

It may be prudent for the final restoration to becemented provisionally while the patient accom-modates to it, and to give time for the soft tissueto mature around the new shape. A modifiedtemporary cement should be used because well-fitting crowns can be difficult to remove later,especially as the smooth shape and lack of anaccessible margin can make it difficult to holdthe crown to remove it.

Prior to finally cementing the crown theabutment screw should be checked for tightnessand some gutta percha or similar soft materialplaced over the screw head so that it can befound easily and the head remain undamaged ifthe crown ever needs to be removed and theabutment taken out in the future.

Traditional cements such as zinc phosphateare often recommended but care has to be takento ensure that the viscosity of the cement is lowenough for the crown to be fully seated. Thequality of fit between abutment and restorationmeans that softer cements designed for tempo-rary cementation are adequate as the definitivecement.

Whatever cement is used, the crown does notneed to be filled completely with cementbecause excess cement extending down belowthe margin can be difficult to detect and remove.Ideally, exactly the right amount of cement toproduce no excess should be aimed for andthere are few complications to having an incom-plete cement lute compared with conventional

crown and bridgework. Many operators prefer tocreate a vent hole in the back of the crown toensure that excess cement comes out in acontrolled position. The hole can be sealed laterwith composite filling material (Figure 13.18).

It can often be difficult to seat the crown intoposition due to the deep position of the implant,the need to recontour the soft tissue byoverbuilding the proximal areas or due to bleed-ing from the soft tissues. Do not try to force thecrown down with permanent cement. Place itprovisionally first with a temporary cement andremove it and re-cement at a later stage once thegingiva have recontoured and matured.

Following cementation, a long cone periapicalradiograph should be taken to:

• verify seating of the restoration• check that no excess cement is present• act as a record of the marginal bone height

for comparison with follow-up images

Instructions to the patient

The patient must be armed with the knowledgeand ability to maintain the restoration. For singletooth restorations no special oral hygiene


Figure 13.18

Two single tooth implant-supported crowns with cementventing holes just visible above the gingival margin on thepalatal aspect. These have been restored with compositeresin.

techniques are required and the patient shouldbe able to follow the same cleaning techniquesthat they follow for their other teeth. Patientsshould be warned that the new implant restora-tion might feel ‘hard’ and ‘heavy’ to bite on fora few days, a feeling that soon passes. It is notnormal for patients to feel any discomfort fromsingle tooth restorations and they should beencouraged to return if they have any symptoms.The complications of single tooth restorationsare covered in Chapter 16.

Additional considerations

Multiple single tooth restorations

The process of providing multiple single toothrestorations next to each other raises the follow-ing issues:

• Is there adequate space, not just to place theimplants but also to place abutments andcrowns and to allow for adequate space forinterdental gingivae to develop? It is

sometimes better to place fewer implants andrestore the region with a bridge.

• A single tooth space normally has some inter-dental papillae left due to the presence ofadjacent teeth. If several teeth are lost, theridge often heals with a flat contour.Placement of individual crowns can result intriangular dark spaces interdentally. This canbe overcome to some extent by overcontour-ing the crowns (see Figure 13.19) but it maybe remedied better by placing linked crowns.Soft-tissue augmentation techniques areconsidered in Chapter 12.

Restorations from impressions atimplant placement

It is possible to provide an implant-supportedcrown from impressions taken at implant place-ment and to insert the abutment and a provi-sional crown at implant exposure. This willspeed up the process of provision of a restora-tion and, in particular, dispense with the need toadjust a temporary restoration to allow for


Figure 13.19

(A) Missing lateral incisor and canine teeth. The gingival contour, particularly between the two implants, is evident. (B)An acceptable aesthetic result has been obtained by producing crowns with a long contact area and overcontouring inter-dentally.

A B

healing abutments. This may be a particularadvantage where a temporary partial denture isthin due to the occlusal contacts. Furtherthinning of the denture to accommodate healingabutments can make the denture unusable. It isalso proposed that the soft-tissue contours formto the correct shape more speedily, although thiswill depend upon achieving a correct emergenceprofile and margin placement from the limitedinformation available from the first impression.On the whole, the disadvantages and extracomplexity of this technique make it only worthconsidering in exceptional situations.

An impression is taken at implant placement.Because the implant is not integrated at thisstage, care must be taken not to compromise theimplant. An impression coping is placed onto theimplant head and, rather than take a conven-tional impression, the coping is linked to a rigidsurgical stent using acrylic. The study model isthen adjusted to accept the stent, which isreplaced with the impression coping attached toan implant analogue. A new working model iscreated that will give a reasonably accuraterepresentation of the implant position but willnot reproduce the gingival contour around theimplant. A prepable abutment is adjusted to givean ideal emergence, and margin placement isdictated by the contours of adjacent teeth. Astandard abutment also can be used. An acrylicprovisional crown is made on the abutment. Atimplant exposure the abutment is seated, andthis can be verified visually. The provisionalcrown is cemented with temporary cement andthe soft tissue sutured around the crown.Following healing, a prepable abutment can beadjusted to ensure that the margins are in thecorrect position and an impression is taken forthe final crown.

Bibliography

Andersson B, Odman P, Carlsson L, Brånemark PI(1992). A new Brånemark single tooth abutment:handling and early clinical experiences. Int J OralMaxillofac Implants 7: 105–11.

Andersson B, Odman P, Lindvall AM, Brånemark PI(1998). Cemented single crowns on osseointegratedimplants after 5 years: results from a prospective studyon CeraOne. Int J Prosthod 11: 212–8.

Balfour A, O’Brien GR (1995). Comparative study ofantirotational single tooth abutments. J Prosth Dent73: 36–43.

Belser UC, Bernard JP, Buser D (1996). Implantsupported restorations in the anterior region.Prosthetic considerations, Pract Period Aesth Dent 8:875–83.

Jemt T (1998). Customized titanium single-implantabutments: 2 year follow-up pilot study. Int J Prosthod11: 312–6.

Jemt T, Laney W, Harris D, Henry PJ, Krogh PHJ,Polizzi G, Zarb GA, Herrmann I (1991). Osseointegratedimplants for single tooth replacement: a 1-year reportfrom a multicenter prospective study. Int J OralMaxillofac Implants 6: 29–36.

Jorneus L, Jemt T, Carlsson L (1992). Loads anddesigns of screw joints for single crowns supported byosseointegrated implants. Int J Oral MaxillofacImplants 7: 353–9.

Laney W, Jemt T, Harris D, Henry PJ, Krogh PHJ,Polizzi G, Zarb GA, Herrmann I (1994). Osseointegratedimplants for single tooth replacement: progress reportfrom a multicenter prospective study after 3 years. IntJ Oral Maxillofac Implants 6: 29–36.

Lewis S (1995). Anterior single-tooth implant restora-tions. Int J Period Rest Dent 15: 30–41.

Palmer RM, Smith BJ, Palmer PJ, Floyd PD (1997). Aprospective study of Astra single tooth implants. ClinOral Implants Res 8: 173–9.


Introduction

The chapters on treatment planning and surgeryhave emphasized the role of prosthodonticplanning prior to embarking on treatment. Forfixed bridges, it is essential that thoroughplanning has been undertaken to determine theend result required. From this, a surgical stentcan be produced to guide the surgery and goodprovisional restorations made that will be able tofunction during the stages of treatment until thefinal restoration is achieved.

A further complication of constructing bridgeson implants is the need for exact clinical andtechnical control to take impressions andconstruct the restoration so that it will fit with ahigh level of accuracy. With conventional bridge-work supported by teeth the displacement of theabutment teeth within the periodontal ligamentcan compensate for small errors in the fit of abridge. Placing a bridge onto implants demandsa higher level of accuracy in fit because thebridge needs to seat passively onto the rigidimplants. This requirement is increased if thebridge is to be screwed to the abutments ratherthan cemented.

Principles

Short-span and long-span bridges

The abutments and techniques used to constructimplant-supported bridges are the same whetherthe bridge just involves two implants linkedtogether or if the full jaw is to be restored with sixor more implants supporting one fixed bridge(Figure 14.1). The complexity of achieving anacceptable fit is, however, increased when multiple

implants are used. Linking implants in a fixedbridge has the following benefits:

• Shorter implants (under 10 mm) can beprotected from overload by the otherimplants, because the rigid structure willdistribute the load over the combined surfaceareas of the implants.

• Implants placed in areas of high potentialstress can be protected by linked structures.For example, linking to other implants canprotect the most distal implant in a posteriorreconstruction.

• Linked implants allow cantilever pontics to beincorporated into a bridge. This is particularlyuseful with distal extension bridges. It is oftendifficult to place adequate length implants indistal positions due to lack of bone andanatomical features. By linking implantsplaced anteriorly, the patient can be providedwith teeth in these regions.

Where several implants are available ofadequate dimensions it may be advisable todivide the restoration into separate bridges sothat it is easier to construct and maintain in thefuture if complications arise. Much debate hasarisen regarding the desirability of bridgesextending across the midline due to the poten-tial flexure (particularly of the mandible) duringloading. However, clinical trials have notdemonstrated this to be a clinical problem andthe authors do not see this as a potentialcomplication.

Distal cantilevers

Distal cantilevers may be indicated with freeend saddle restorations where it has not been

14Fixed bridge prosthodontics


Figure 14.1

Two Straumann implants have been placed in the missingpremolar teeth sites: (A) healing caps in position; (B)SynOcta bridge abutments have been placed; (C) impres-sion copings attached to the abutments; (D) impressioncopings removed in the impression; (E) metal frameworktried in with guide pins; (F) completed bridge—note thesubgingival margin placement for optimum aesthetics.

A D

B E

F

C

possible to place an implant as far distal asrequired for appearance and function. Theability to provide a cantilever depends uponseveral factors (see also Chapter 5):

• The potential load that might be placed on theextension. Natural opposing teeth or a patientwith a previous history of parafunctionrequires caution compared with a cantileveropposed by a removable restoration orpontic.

• The length and width of the most distalimplant, which will take the greatest compres-sive load.

• The length and position of the most anteriorimplant, which will take the greatest tensileload.

• The antero-posterior dimension measuredfrom a line drawn between the most distalimplant on either side, to the most anteriorimplant. The greater this distance the longerthe potential cantilever that can be placed asthe anterior implant will not be subject to asmuch stress as if the implants are placed in astraight line.

Some authorities have suggested that cantileversas long as 20 mm can be constructed safely. Theauthors would recommend that this figure betreated with caution and ideally distalcantilevers, even with several long implants in agood arch shape, should be restricted to10–15 mm (two premolar-sized pontics).

Screw-retained or cementedbridges

Attaching bridges to implants with screws allowsthe possibility of making the restoration easilyretrievable and free from the potential problemsof cementation, a concept that can offer consid-erable advantages over conventional bridgeworkbased on teeth. In the Brånemark system,abutments are chosen that locate onto theimplant head and are held into position with anabutment screw. The abutment is designed toaccept a smaller ‘bridge’ screw that will retainthe bridge. This screw passes through amachined gold cylinder that is incorporated intothe bridge structure and seats accurately onto

the abutment (Figure 14.2). The small bridgescrew that retains the restoration is designed tobe the weakest link in the implant assembly andshould be the part to fail if the restoration isoverloaded or subjected to trauma.

Variations exist with the other systems.AstraTech Uni-abutments (AstraTech: AstraMeditec AB, Mölndal, Sweden) and StraumannSynOcta abutments (ITI/Straumann: InstitutStraumann AG, Waldenburg, Switzerland) areone-piece. Frialit abutments have a single screwthat acts as the bridge screw and the abutmentscrew.

The screw-retained bridge needs to be apassive fit onto the abutments, confirming that itis in the same path of insertion and plane as theabutment head. If a bridge screw is tightenedinto an abutment and the gold cylinder is notseating evenly, the screw will be put undertension and not only will the bridge not beseating down properly and marginal gaps exist,but there is a high chance of the screw loosen-ing or fracturing with time. Each bridge goldcylinder needs to be in this exact relationshipand the complication of constructing a bridgewith multiple abutments lies in achieving thisdegree of accuracy. For many dentists, theadvantage of ease of removal of the bridge isoutweighed by these potential difficulties.

Cemented bridges do not necessarily demandsuch high standards of precision, because thecement lute will allow a bridge to seat withoutputting the structure under tension. This is not ajustification for poor technical or clinicalstandards but reflects a reality that perfection isnot reliably achieved. Cemented bridges areconstructed on abutments that are prepared inthe laboratory to resemble prepared teeth asrequired for conventional bridges (Figure 14.3).More laboratory time is often required than fortechniques that use standard manufacturer-madecomponents. The retrievability of cementedbridges can be controlled to some extent by theuse of temporary cements because these mayallow removal of bridges if required. The poten-tial for dissolution of cement from margins willnot result in caries as it can with conventionalbridges. Cemented bridges do not require anaccess hole for the gold screw through thebridge. Although this is rarely a problem for mostpatients, it can present complications if the screwhole has to be positioned in a visible area or at

FIXED BRIDGE PROSTHODONTICS 185


A B

C D

E F

Figure 14.2

Four Frialit implants have been placed to replace the missing premolar and molar teeth: (A) master cast producedfollowing implant head impressions—the different coloured implant analogues correspond to the diameter of implantplaced; (B) bridge cylinders are linked in a wax pattern ready for casting; (C) occlusal view showing access forabutment/bridge screws; (D) completed casting—the mesial handle is for production purposes and will be removedbefore final insertion; (E) casting from buccal side—note the precise fit; (F) the casting is tried in prior to porcelainplacement to verify the fit;

continued

a point of essential occlusal contact. Cementedbridges therefore are often indicated if implantshave not been placed in the long axis of thedesired restoration. For many dentists, the majoradvantage of cemented bridges is the similarityto conventional crown and bridge techniques.

The decision between screw-retained andcemented bridges also depends upon the ability

of the dental laboratory to construct an acceptablerestoration. The decision should be based on theclinical situation and articulated working modelsprior to abutment selection, and the techniquemost suited to the individual situation is chosen.Often the choice has been made at the treatmentplanning stage following discussion with thepatient.


G H

I

J


(G) the completed bridge; (H)adequate embrasure space hasbeen provided for oral hygienemeasures; (I) completed bridge fromthe occlusal surface; the retainingscrews eventually will be coveredwith a tooth-coloured restoration; (J)the metal collars of the abutmentsare visible only where the patient’slip line will cover the gingival marginon smiling.

Advantages of screw-retained bridges

• easily retrieved• complete seating of the restoration is more

readily ensured• utilizes manufactured components for all

fitting surfaces• no risk of cement retained at margin—allows

deep margin placement

Disadvantages of screw-retained bridges

• implant needs to be in long axis of restora-tion so screw hole is on occlusal surface orangled abutments need to be used

• screw hole may be visible or in an importantarea of the occlusal surface

• requires a ‘passive fit’ for each gold cylinderonto the abutments

• risk of bridge screw loosening or fracture

Advantages of cemented bridges

• ‘passive fit’ not as critical but is desirable• no screw access holes• similar to conventional bridge techniques• can easily overcome differences in angulation

between implants and restore implants withadverse angulations

Disadvantages of cemented bridges

• retrievability more difficult


A B

C D

Figure 14.3

A cemented full-arch bridge constructed on AstraTech implants and Profile BI abutments: (A) seven implants have been placed;(B) following head of implant impressions, the prepable abutments have been prepared to ensure parallelism, adequate reten-tion and the ideal bridge contours; in this case there has been more labial reduction of the anterior abutments to compensatefor a slight labial angulation of the implants; (C) the metal superstructure for the bridge; (D) the fit surface of the superstructure;

• more laboratory time required to produceprepared abutments and temporary bridges ifrequired

• cementation needs to be controlled,especially with subgingival margins

• difficult to ensure full seating of the bridge,especially with tight or deep gingival ‘collars’or if there is bleeding

• increased technical costs and chairside time iftemporary bridges are required

Abutment types

As with single tooth restorations, there areseveral types of abutments and the manufactur-ers versions are listed in Table 14.1.


E F

G H


(E) the abutments are in position; (F) the bridge superstructure is tried in to ensure the fit; (G) the bridge is completed;in the lower jaw a full-arch screw-retained bridge has also been constructed; (H) the completed restoration in themouth.

Table 14.1 Abutment types for fixed bridge restorations

Manufacturer Type Name

Nobel Biocare Screwed Standard abutmentEsthetiConeMirasConeMulti-abutmentAngled abutment

Cemented TiAdaptAurAdapt

AstraTech Screwed Uni-abutmentAngled abutment

Cemented Profile BI abutmentCast-to abutment

Frialit Screwed MH2 abutmentCemented Telescopic abutment

AuroBaseStraumann Screwed SynOcta abutment

Cemented SynOcta solid abutments

Nobel Biocare: Nobel Biocare AB, Göteborg, SwedenFrialit: Friatec AG, Mannheim, Germany

For screw-retained bridgesBridge abutments can be either one-piece ortwo-piece. As the abutments are to be linked,there is no need for the bridge cylinders to haveindividual anti-rotational features, because the

whole bridge structure will not be able to rotate.The individual abutments, however, mayengage into anti-rotational features in theimplant if present. For example, the NobelBiocare EsthetiCone abutment engages theexternal hexagon on the top of the implant so


Figure 14.4

Two Nobel Biocare implants have been placed to replacemissing premolar teeth. The mesial implant head is verysuperficial. (A) Working cast of implant heads. The distalimplant can receive a conventional bridge abutment(EsthetiCone). Mesially, the implant head is level with thegingival margin. (B) A fully customizable UCLA abutment(similar to AurAdapt) in place. This will allow the mesialabutment to be customized to allow for extension of theporcelain to the implant head without the metal collarrequired for conventional abutments. (C) The customizedabutment has been incorporated into the bridge casting. (D)The completed bridge shows a conventional bridge screwfor the distal abutment. The mesial abutment requires alarger access hole for the abutment screw, which willdirectly retain the bridge/abutment to the implant. (E) Thecompleted bridge in place; minimal metal is visible.

A

B

C

D

E

that the abutment is stable and cannot rotate.The abutment is in two parts and the separateabutment screw is tightened to 20 N.cm toprevent it from loosening. The top of theabutment is conical in contour with flat facets,on the side. By using a gold bridge cylinder thatdoes not engage the facets, the cylinders can belinked together without each abutment havingto be parallel to each other. The facets can beengaged with a hexed gold cylinder for a singletooth restoration where anti-rotation isrequired. Bridge abutments are designed tocope with differences in angulation betweenimplants. The EsthetiCone abutment has a 20°taper so that angulations up to 40° betweenimplants can be compensated for. The bridgeabutments with the Straumann SynOcta andFrialit MH2 systems are similar to the NobelBiocare design. The new multi-abutment fromNobel Biocare dispenses with the abutmentengaging the external hexagon of the implant(no anti-rotational feature) and this aids seatingof the abutments.

The bridge abutment for the AstraTechsystem is a one-piece abutment (Uni-abutment)so it does not have an anti-rotational compo-nent in its attachment to the implant, althoughonce the abutment is fully seated in the inter-nal cone of the implant it has a high level ofstability. The smooth-sided abutment head hasa matched bridge cylinder and the anti-rotational element for the system relies uponthe linkage of the components. Abutments aremade with 20° and 40° tapered tops to allowcompensation for even severe angulation differ-ences (40° and 80°).

The original Nobel Biocare standardabutment is a simple parallel-sided abutmentwith a flat top. The bridge construction starts atthe top of the abutment and this design lendsitself to reconstructions, particularly in thelower jaw, where considerable resorption hasoccurred and aesthetics are not demanding. Inareas with higher aesthetic demands, thedesigns already discussed allow the bridgeframework to cover the abutment so that it is,in effect, hidden under the bridge. Abutmentscome in a variety of collar heights to allow fordifferent soft tissue thickness. The collar heightis chosen to allow for a subgingival marginplacement if required (Figure 14.4). Variations indesign also allow for different abutment head

heights. In a situation where there may be littleintraocclusal space between the head of theimplant and the opposing tooth, a shorterabutment will be required. It is not normallypossible to restore an implant with a screw-retained bridge if there is less than 5–6 mm ofinterocclusal space. Ideally there needs to be atleast 2 mm of space beyond the bridge screwso that it can be covered with an aestheticrestoration. Cases with reduced intraocclusalspace are often better restored with a cementedrestoration, especially if appearance is para-mount.

Angled abutments

The access hole for the bridge screw ideallyneeds to emerge through the centre of theocclusal surface of the restoration. Angledabutments are designed to compensate for adifferent path of insertion for the bridge andbridge screw compared with the implant(Figure 14.5). Angled abutments are availablein the range 15–35°. Depending upon theposition in which the abutment is seated on theimplant it is also possible to use this angula-tion change to ‘move’ the bridge screw accessin a mesial or distal direction. Angledabutments still have the same top as conven-tional screw abutments and accept the samegold bridge cylinders. The angled design istherefore dependent upon a variation in theheight of the metal collar at the implant end ofthe abutment. Care should be taken therefore,to check if this higher metal collar will compro-mise the appearance, because angledabutments are not suited to situations with asuperficial implant head. Although it is possi-ble for the margin to be altered and the goldcylinder modified to cover the metal collar, thiswill decrease the quality of fit of the restora-tion.

When angled abutments are used, it isnormally necessary for the laboratory to providean acrylic jig to allow the clinician to orientatethe abutment to the correct position. This canrelate either to adjacent teeth or otherabutments. The jig should be kept for the futurein case the abutments ever need to be removedand replaced.


For cemented bridges

Prepable abutments

These abutments are the same as those alreadydiscussed in Chapter 13. They are abutments with

a solid head that can be prepared in the laboratoryso that they are retentive, have margins in anaesthetic position and have an acceptable degreeof parallelism to each other to be able to have aconventional bridge cemented onto them. Toconstruct a bridge using this approach, a head of


A B

C D

Figure 14.5

Two Nobel Biocare implants supporting an anterior bridge: (A) guide pins have been placed in the implant analoguesfollowing head of implant impressions; the path of insertion of the implants would dictate labial screw access holes ifconvention screw-retained abutments are used; (B) using angled abutments the screw access can be realigned to anacceptable position; (C) angled abutments in position—note the metal collar, which is just visible above the gingival margin;(D) the completed bridge; the bridge structure has been extended in front of the abutments to disguise the visible metal;

continued

implant impression should be taken and theabutments chosen to correspond to the toothbeing replaced. Manufacturers produce abutmentsin a variety of widths, normally in the range of4.5 mm corresponding to lower incisor and upperlateral incisor teeth, 5.5 mm corresponding toupper central incisors, canine and premolar teethand 7.0 mm for molars. Abutments also come in avariety of heights and some manufacturers alsoproduce angled prepable abutments.

Abutments are best chosen using a trial kit ofabutment analogues placed onto the workingmodel (see Figure 13.4C). They should be chosenso that:

• the dimension and height of the abutment asit sits on the implant allows for the plannedemergence of the restoration through thegingiva;

• there is adequate bulk of metal just below thegingival margin to allow for the abutment tobe prepared to accept an adequate thicknessof bridge margin subgingivally;

• there is adequate height of the abutment toallow it to support properly the bridge frame-work;

• there is adequate bulk of metal in regionswhere there may need to be significant reduc-tion of the abutment to allow for changes in


E F

G H


(E) the palatal screw access results in a bulky contour; (F) the same case restored with prepable (TiAdapt) abutments;the angulation change has been achieved by heavily preparing the abutments labially; (G) the bridge cemented to theabutments; it has not been possible to completely disguise the metal abutment margin; (H) the resulting palatal contourmore closely resembles natural contours than the previous screw-retained bridge.


A B

C D

E F

Figure 14.6

A complex case where implant placement was only possible in potentially compromised positions due to skeletal malfor-mation. A lower bridge supported by implants has already been placed. Nobel Biocare implants have been placed. (A)Fully customizable abutments have been prepared and are tried in prior to finalization to ensure that the correct shapehas been achieved. (B) A try-in of the proposed bridge in wax to confirm an acceptable result can be achieved. (C) Theabutments are cast and finished prior to placement. (D) A cemented bridge is produced to restore the missing teeth andsoft tissue. Space has been left for access to the implants for cleaning. (E) The abutments in place. (F) The completedcemented bridge. Surgical aspects of this case are illustrated in Figure 12.14.

angulation and orientation between implants;it is sometimes better to choose a largerabutment

Implants that have a feature in the design thatallows the abutment to seat into a predictableposition each time by engaging a hexagon or aninternal facet (Nobel Biocare, Frialit 2, AstraTechST and Straumann solid screw) can have theabutments prepared and the definitive bridgeconstructed from one original working model.However, if there is any degree of gingival re-contouring required or if implants do not havean indexing feature (standard AstraTechimplant), the abutment needs to be seated witha jig, although exact positioning cannot beguaranteed. It is best to place a provisionalbridge following insertion of the abutments andthen take a further impression of the abutmentsin position for construction of the definitivebridge.

Fully customized and computer-generatedabutments

Just as for single tooth applications, abutmentsfor cemented restorations can be produced usingcastable abutments or the computer-generatedProcera system. Cast abutments are indicatedwhen significant re-orientation of abutments isrequired, because they can be waxed up andthen cast to the desired angulation and dimen-sion (Figure 14.6). It is often a matter of famil-iarity and experience of the dental technicianwhen choosing between cast abutments orprepable abutments, because both can achievesimilar results.

The Procera system can provide correctlyorientated abutments for cemented bridgeconstruction from one master impression of theNobel Biocare implant heads, without signifi-cant laboratory time. The technician uses guidepins placed in the implant replicas and themodel is mounted into a scanner. Usingthree–dimensional imaging, the desired abut-ment shape can be developed and the informa-tion sent to a factory facility that will constructthe abutment in titanium. The abutments needfinal finishing of the margin position andocclusal surfaces in the laboratory prior to use.

Abutment selection andimpressions

Abutments can be selected either directly in themouth or an impression can be taken of theimplant head and the abutments chosen fromthe resulting model (Figure 14.7). Quitecommonly, it is not clear exactly which abutmentwill be required from a clinical examination. Theincorrect choice of abutment can be costly,especially if the error is not determined untilafter the restoration has been made. Before theabutment is finally chosen however, it is essen-tial that there is adequate information availableto know exactly what the shape and position thefinal restoration should be, so that the correctabutment is chosen to achieve that result. Thiscan be just as relevant for short-span bridgeswith only two or three implants as for extensivefull-arch reconstructions.

Implant head impressions

An impression of the implant head to produce alaboratory cast can be used to choose theabutment, allow preparation of prepableabutments and often to act as the workingmodel for complete bridge construction.Impressions copings are placed onto the implanthead (Figure 14.8). With a flat-top implant averification radiograph will be required toensure that the impression coping is fully seatedover the external hexagon. The impressioncoping is secured to the implant by a guide pinthat screws into the abutment screw hole. Thetop of the guide pin projects beyond the copingand should be longer than adjacent teeth. Animpression tray is modified so that the guide pinprojects through the tray without touching it (formore detail, see later in this chapter). Thecoping is picked up in an impression materialthat sets rigid and the guide pin is unscrewed.The coping should not move in the impressionand an analogue of the implant is attached tothe coping prior to pouring a cast. The castshould be produced with a soft tissue replicabecause the implant head will normally besubgingival and a rigid replica of the gingiva willnot allow access to the implant head. Using thismodel, the abutments can be selected.



A B

C D

E F

Figure 14.7

Upper and lower full-arch bridges constructed on AstraTech implants. (A) Upper cast following implant head impressions,implant analogues and soft tissue replicas are required. (B) By linking three impression copings in a rigid laboratorycomposite beam, a wax rim can be constructed. (C) The wax rim is trimmed and indexed to facilitate accurate jawrelations. (D) Trimmed occlusal rims are stable in the mouth. (E) The occlusal plane is checked. (F) A facebow record canbe taken. continued


G H

I J

K L


(G) A final interocclusal record is taken. (H) A full diagnostic set-up of tooth position is produced, supported by the compos-ite beams. (I) The set-up is tried in. The jaw relations and appearance are assessed and altered as required. The patientcan see the result and changes can be made easily at this stage. (J) Following approval of the tooth position a puttymask is made of the try-in. (K) The putty mask records tooth position. (L) It can be located onto the working model andthe correct abutment chosen to achieve the desired tooth position. continued


M

N O

P Q


(M) The chosen abutments (Uni-abutments) in place. (N)The completed bridges from the fit surface. The goldbridge cylinders can be seen clearly. The underside of thebridge is carefully contoured and polished to aid cleaning.(O) Occlusal view of the bridges showing the bridge screwaccess holes. (P) The completed bridges. (Q) On smiling,the appearance is excellent.

Evaluation using a diagnostic work-up

A guide is needed of the required tooth positionto relate the implant head model to the newrestoration. If the patient has a satisfactory exist-ing denture or bridge that is to be copied, animpression can be taken of it and a putty maskmade of the labial and incisal surfaces (Figures14.7J–L). This can be tried against the implanthead model and will demonstrate the relationshipbetween the tooth and implant. Alternatively, if adiagnostic wax-up has been carried out, from

which a surgical stent was provided, this can berelated to the new working model.

If no accurate guide is available and there is anydoubt as to the orientation of the implants, it isadvisable to produce a new diagnostic tooth set-upthat can be tried into the mouth and agreed withthe patient before the abutments are chosen. Thiscan be produced as a denture type set-up or ideallyas a fixed set-up. Temporary bridge cylinders arelinked together with acrylic or laboratory compos-ite resin on the working model and a diagnosticset-up is produced in wax or with denture teeth,


A B

C D

Figure 14.8

(A) AstraTech implant head pick-up impression copings have been screwed to the implants. (B) Impregum impressionmaterial is syringed around the copings. (C) The tray is seated over the copings. (D) The end of the copings is identifiedwith the fingers and the tray is stabilized until set. The screws are undone prior to removal of the impression.

which can be tried into the mouth secured to theimplants. It can give an exact idea as to the possi-ble complications that may be encountered beforeexpensive abutments and laboratory work havebeen undertaken. This information can be trans-ferred into a provisional bridge and the patientallowed to live with the restoration for a period oftime to ensure that it is satisfactory before the finalrestoration is made.

Abutment try-in kits

Many manufacturers produce replicas of theabutment types that can greatly assist abutment

selection (Figure 14.9). They can be used in themouth or more commonly, on an implant headcast. Made of aluminium they will not damagethe implant or implant replica and for ease ofrecognition they are often colour coded so thatdifferent sizes can be easily recognized. Theimplant head cast is related to the putty mask.Abutments can be tried in to get the best possi-ble screw access position, marginal height andemergence. The selected abutment then shouldbe related to the opposing model to check forinterocclusal clearance. Try-in kits are alsoproduced for prepable abutments.

Selection and seating for screw-retained bridges

In a straightforward situation where a short-spanscrew-retained bridge is to be constructed and itcan be certain that the implant is orientated suchthat the bridge screw will emerge through theocclusal surface (placement of a guide pin intothe implant will give a clearer view of theimplant’s orientation), the following steps can befollowed:

• Determine the distance from the implant headto the opposing tooth using a periodontalprobe or dividers. If there is going to be insuf-ficient space to allow coverage of the bridgescrew, reconsider a cemented approach.

• Using a periodontal measuring probe or amanufacturer’s depth-measuring device, deter-mine the abutment gingival collar height. Theplanned margin should be 1–2 mm below thegingival margin at its lowest point on thevisible surfaces.

• Place the abutment but do not tighten it.Check the orientation and the occlusal clear-ance. Seating may need to be verified radio-graphically.

• If the abutment is going to be left in positionand the temporary restoration can be placedover it, the abutment screw can be tightened.If the abutment is to be removed to allow thehealing abutment to be replaced betweenappointments, it should only be hand tight-ened.

• A transfer impression of the abutment can betaken.


Figure 14.9

(A) The Nobel Biocare abutment try-in kit. Replicas of theabutments can be tried on a cast or intraorally. (B)Examples of the analogues. The 17° and 30° angledabutments can be compared.

A

B

• A protective cap can be placed on theabutment if it is to be left in situ (Figure 14.10)and the temporary restoration can be modi-fied to accommodate the resulting dimen-sions.

If it is not possible for the abutment to be chosenfrom a clinical examination, an implant headimpression should be taken and the abutmentselected on the model as already outlined. Theimplant head model can be used as the workingmodel for the final bridge as long as it is accurateand shows sufficient detail of the rest of the arch.Many operators have proposed that for largebridges it is better to choose the abutments from

the implant head model and then re-take animpression with the abutments seated in themouth. The authors find that this is not neces-sary if the implant head impression is accurate.The chosen abutments are therefore seated ontothe implant head model and hand tightenedusing laboratory screws (because the gold ortitanium screws used in the mouth might bedamaged in the stainless-steel implantanalogues). The bridge is therefore constructedon the actual abutments, which will need to becleaned and sterilized before placement in themouth.

Abutment seating for flat-top implantsinvolves ensuring that the abutment is fully


A B

C D

Figure 14.10

(A) Nobel Biocare EsthetiCone bridge abutments in place. (B) Abutment protection caps used as the abutments will beleft in the mouth between appointments. (C) The complete denture is adjusted to accommodate the abutments and caps.(D) Soft re-line material is used to adapt the denture for use while the bridge is being constructed.

seated over the external hexagon by holdingthe abutment with the correct placement toolsto feel that it cannot rotate before the abutmentscrew is hand tightened. This can be difficult ifthe gingiva is thick, tight or bleeding and averification radiograph is essential to ensurethat the hexagon is properly engaged and nosoft tissue is trapped. This potential problemhas been reduced with the Nobel Biocare multi-abutments, which are easier to seat fullybecause the external hexagon is not engaged.Care should always be taken not to leave thehealing abutment out for any length of timebecause the gingiva will quickly contract and itwill be painful for the patient when it is pushedback. If the abutment is to be left on theimplant, it can be tightened into position follow-ing verification of seating. With the NobelBiocare EsthetiCone this involves torquing to 20N.cm and counter-torquing to prevent stressingof the implant. Straumann however, recom-mend the SynOcta abutment be torqued to32 N.cm without counter-torquing. Themanufacturer’s recommendations should befollowed. A ready-made protection cap coversthe abutment.

Abutments that are to be removed followingimpression-taking to allow the provisional restora-tion to be replaced should only be hand tighteneduntil the final stage of bridge construction.

Implant systems with an internal conicaldesign (Straumann/AstraTech) allow seating ofthe abutment in a more predictable way and averification radiograph is not usually required.

Impression trays

Custom-made trays are useful in a mouth withdifficult access or a complex or outsize shape orin cases with multiple implants where the chair-side time in modifying a stock tray is longer(Figure 14.11). They should be rigid in designand should be formed to support the impressioncoping along its full height. Spacing of at least2 mm is recommended.

Stock trays should be of a good quality sothat they will still be rigid following cutting ofan access hole for the guide pin. The stock traysize is chosen in the normal manner and theposition of emergence of the guide pin ismarked. Access holes are prepared to ensure


A

B

C

Figure 14.11

(A) A special tray constructed for impressions for a full-arch bridge. (B) The impression coping securing pins arevisible through the tray. (C) The EsthetiCone abutmentimpression copings are securely held in the impressionmaterial using this pick-up technique.

that the tray does not encroach on the impres-sion coping, because they should not touch thetray.

The access holes for the guide pins arecovered in wax to prevent the impressionmaterial flowing out through the hole (Figure14.8D).

Impression materials

Polyethers and silicone impression materialshave physical properties that make them suitablefor implant impressions:

• The material should set rigid enough tosupport the coping and prevent movement ofthe coping on removal from the mouth andcasting of the model.

• It should record enough fine detail to identifyproperly the gingival contours and other teethin the mouth.

• It should be dimensionally stable and notreact with materials used in model produc-tion, such as the gingival replica.

• It should accept disinfection techniques.

For these reasons it is not recommended thatlight-bodied impression materials be usedaround the impression copings because they willnot be strong enough and heavy putty materialswill not flow around the copings or record finedetails. One-phase medium-bodied paste systemsare preferred.

Some operators recommend splinting impres-sion copings together with acrylic prior toimpression-taking to ensure that the copings arestable relative to each other. There is nothing torecommend such extra complexity.

Pick-up impressions

The most reliable impression technique tofollow is the pick-up technique (Figure 14.12).As described already, the impression coping issecured to the abutment with a guide pin.These are available in a variety of lengths toensure the correct projection through theimpression tray while still having access witha screwdriver to the pin. The impressionmaterial is syringed around the coping and

the tray is filled. As the tray is seated in themouth, the guide pins can be felt by theoperators’ fingers through the wax over theaccess holes. If the pins are not felt, the trayshould be seated further while the impressionmaterial is still fluid. The tray is stabilized untilthe full set is reached and the guide pins arethen fully unscrewed. The impression copingswill be removed with the tray and so remainfully seated in the impression material at alltimes. The guide pins are used to locate andretain the abutment analogues for castproduction.

Reseating impressions

The reseating technique can be used in areas ofdifficult access where locating and unscrewingthe guide pins with an impression tray in themouth may be difficult. Impression copings,which have a retentive and distinctive patternon the surface, are fully screwed onto theabutment (Figures 14.13 and 14.14). They donot project beyond adjacent teeth and a trayshould be used with stops so that it will nottouch the copings when seated in the mouth.Access holes are not cut in the tray. Impressionmaterial is syringed around the coping and thetray is seated. Once set, the tray is removed andan impression will have been made of thecoping shape. The coping will stay in the mouthfollowing impression removal. The coping isthen unscrewed from the abutment and theabutment analogue is attached for modelproduction. The impression coping is reseatedinto the impression and its stability is checked.It is important that adequate material extendsaround the coping or it will not locate andremain stable.

For cemented restorations

Prepable abutments need to be selected andproduced on implant head casts and thetechnique described already should be followed.Once again, abutment selection kits are availablefrom some manufacturers. The preparedabutments need to be re-tried in the mouth withthe aid of a transfer jig to assist with correct


orientation. If a further impression of theabutments in position is required, conventionalbridge impression techniques are employed.Light-bodied materials are syringed around theabutment and a heavy-bodied material is used

for the bulk of the impression. Recording the finedetail of deep margins can be difficult. A gingi-val retraction cord does not retain well in thesulcus and care must be taken not to push itdown below the bulbosity of the abutment where


A B

C D

E

Figure 14.12

(A) MirasCone abutment impression copings have beensecured to the abutments. (B) The impression copingsrecord the position of the abutment as well as the softtissue contours. (C) A stock tray was used because accesswas straightforward. (D) Abutment replicas are secured tothe impression copings prior to cast construction. (E) Theworking model.


A

A B

B

C D

Figure 14.14

(A) AstraTech implant head reseating impression copings in place. (B) The impression of the copings. (C) The impressioncoping and analogue—the impression coping has a flat facet to ensure that it can be re-orientated correctly in the impres-sion. (D) The coping and analogue are reseated into the impression together.

Figure 14.13

(A) A reseating impres-sion using Nobel BiocareEsthetiCone impressioncopings. The ribbedcontour of the copingcan be seen clearly inthe impression. Thedistal coping andabutment replica havebeen re-inserted into theimpression. (B) Theimpression coping (topleft) and the abutmentanalogue (top right).When screwed together,the coping can bereseated into theimpression.

it may be difficult to remove (see Figure 13.16).Electrosurgery is completely contraindicated.The best results are achieved by careful removalof temporary restorations and treating the softtissue with great care so that marginal bleedingis avoided. Acrylic transfer copings can be madein advance in the laboratory at the time ofabutment preparation. These can be picked up ina new impression but are only useful if the gingi-val margins have not needed to be altered intra-orally.

Impression verification for all techniques

The impression is checked for:

• coping stability: each coping should be testedwith tweezers to ensure that no more thanvery limited movement occurs;

• adequate record of immediate gingivalcontours: at least 4–5 mm beyond the copingso that a proper gingival replica can be made;

• full record of adjacent teeth: to ensure propercontact point construction and harmoniousemergence profiles;

• full record of articular surfaces of whole arch:for accurate articulation of casts

Occlusal records

Good quality opposing casts are essential and itis recommended that these are made usingrubber base impression materials rather thanalginate. As for conventional bridgework, thereare no exact rules to follow but it is recom-mended that a semi-adjustable articulator beused as a minimum for all full-arch bridges andshorter span bridges where the occlusal schemeis likely to be changed by the bridge. Thisincludes all posterior extension designs andanterior bridges where incisal guidance may bealtered. If a short-span bridge is to beconstructed where adjacent teeth are presentand a conformative occlusal scheme is to beadopted, it may be acceptable for full articulationto be avoided. Unlike complete denture jawrelations where the stability of a wax rim can bedifficult, this is greatly simplified by constructionof a wax rim that is secured to the implants

(Figures 14.7B–G). The rim then can be trimmedto the correct vertical height of occlusion and aninterocclusal record taken. It is also useful tomark such features as the centreline and smileline.

Full information needs to be sent to the labora-tory including occlusal registration (with theabutments in position), records of provisionalrestorations if they need to be reproduced in thefinal bridgework and shade registration. If gingi-val-coloured material is to be used to mask longcrowns or interdental areas, this should also beshade matched.

Provisional bridges

The use of provisional bridges to ensure anacceptable appearance has been discussedalready. Manufacturers produce temporarycomponents that attach directly to the implanthead or can fit onto the abutments. Thesecomponents are either made of acrylic or metal.Although a provisional bridge is not usuallyindicated for long periods of time, it is still essen-tial that it has an accurate fit. A provisional struc-ture can damage implants if it is screwed downtightly when it does not fit properly. Provisionalbridges also can be used to determine toothposition and speech patterns before final bridgeconstruction. Patients who have worn dentures,particularly for missing maxillary anterior teeth,for many years may have problems in adaptingtheir speech. Placement and subsequent adapta-tion and modification of a provisional bridge thatcan be copied in the permanent restorationsmoothes this process.

Provisional bridges are commonly used withcemented bridges, where removal of thecustomized abutments between appointmentscan lead to errors occurring. Replicating theposition of the abutments is difficult if there is noanti-rotational (indexing) element in the implant/abutment junction, e.g. AstraTech standardimplant and Uni-abutment. A provisional bridge istherefore produced at the same time as theabutments are prepared. Following placement ofthe abutments, the provisional bridge is used toform the ideal gingival emergence and marginposition and, if necessary, the bridge can bealtered to change gradually the emergence


contour. Once the ideal contour has beenachieved, a conventional crown and bridgeimpression is taken of the abutments in position.

Laboratory procedures

The material chosen for the bridge constructionhas a significant effect on the design and clinicaltechniques followed. Original designs favouredrigid cast gold beams produced by waxingtogether manufactured gold cylinders supportingacrylic denture teeth embedded in pressure-cured pink denture acrylic. This had the greatadvantage of being a familiar technique and asthe superstructures were removable the problemof acrylic wear was not an issue as the bridgecould be refurbished easily. In a desire to makerestorations more aesthetic, clinicians movedtowards the use of porcelain on bonding gold oreven titanium frameworks. When constructinglarge bridges this involves a high level of techni-cal expertise, particularly to achieve a good fit aswell as good appearance. Some clinicians preferto undertake post-ceramic soldering or weldingto ensure that the porcelain firing process doesnot distort the metal substructure. Large metalceramic bridges are subject to a high incidenceof long-term porcelain fractures and so aresometimes divided into smaller units and madeeasily retrievable where possible.

The development of laboratory compositematerials has allowed the production of exten-sive bridges with a customized, durable andaesthetic surface similar to porcelain, without theneed for firing and possible distortion. Thesematerials are highly suitable for implant-supported bridges, because they are moreresilient than porcelain and can be more easilyrepaired. They are not as resistant to wear asporcelain, although evidence suggests that theywill wear at a rate similar to natural teeth andare particularly indicated if the opposing restora-tion is made of the same material. They will notretain their appearance as well as porcelain butfor longer span bridges they are clinically accept-able. Patients who are provided with extensiveimplant-supported fixed bridges in opposingjaws may report problems with ‘noise’ and thevery hard feeling from the porcelain surfacescontacting.

Titanium frameworks may offer considerableadvantages over the use of gold from the costand weight aspects. Titanium cannot be cast inthe conventional way but manufacturing pro-cesses can be employed to produce machinedframeworks.

The technical procedures for implant bridgesare similar to conventional crown and bridgetechniques, but the following features are ofnote:

• A soft gingival replica is essential to allow foraccess to subgingival implant heads andabutment margins. The gingival replica isremovable to check the marginal fit.

• The highest possible standard of metal frame-work production is required to achieve apassive fit.

• Care must be taken to ensure that no distor-tion of the framework occurs during firing ofthe porcelain. Damage to the framework fithas been reported following acrylic polishingof full-arch bridges if handled roughly.

• Frameworks should be cast in a high-gold-content metal compatible with the gold bridgecylinders provided by the manufacturers.Several laboratories are able to producetitanium frameworks that may offer advan-tages over conventional gold frameworks.

• The importance of relating the implantposition to the desired tooth position beforechoosing the abutment has been discussedalready. Of equal importance in the labora-tory is the relationship of the abutment tothe final tooth position so that the frameworkis the correct contour to support theaesthetic portion of the bridge and thecorrect occlusal form. Many dental techni-cians prefer to wax-up the whole bridge andthen cut the wax-up back to allow space forthe porcelain or resin to ensure this contour(Figure 14.2B).

Trying and fitting the restoration

Try-in

Larger span or short-span bridges should betried in before fit. Try-in can be carried out at thefollowing times:


• Before framework construction: the goldcylinders are linked together with a rigidmaterial such as laboratory composite resin.The accuracy of the impression can beverified by seating this in the mouth. Thereshould be no displacement of the frame whenscrewed down at either end and the resinconnection will normally crack if the structureis tried in and there is a poor fit. If this occursit is best to retake the impression. The linkedgold cylinders can be used for occlusalrecords by attaching a wax rim, and they canalso support a trial set-up of teeth if required.

• Following framework construction but beforeplacement of teeth: try-in at this time willallow for full evaluation of the fit of the frameand detection of errors before time is wastedcompleting a bridge that does not fit. Theframe is first seated down with fingerpressure and any gross error in fit is detectedby rocking of the framework. The bridgescrews are then tried in one at a time to seeif tightening a screw results in movement ofthe frame away from another abutment. Tightgingival cuffs or a framework pressing on softtissues can make this difficult. Finally, all ofthe screws are tightened and a misfit may berevealed as discomfort and a tight feeling bythe patient. An error in fit detected at thisstage is remedied either by retaking theimpression or by sectioning the frame andsplinting it in the mouth for it to be solderedor welded. A frame that has to be sectionedshould be tried in again before proceedingfurther.

• Finally a bridge can be tried in prior to polish-ing or at a biscuit bake if porcelain. This willallow for checks to be made on the appear-ance and the occlusion prior to completion.

Placing the bridge

If the definitive abutments have been removedbetween appointments they should be seatedand tightened as recommended, normally usinga torque device. The bridge is seated onto theabutments and the fit is verified as discussedabove. There is little point in trying to verifymarginal fit visually unless the margins aresupragingival. It is quite normal for there to be

some gingival blanching due to pressure on thesoft tissues from the new profile of the bridge.Patients should be reassured that this is a tempo-rary problem. If the fit is acceptable, the occlu-sion is checked.

Occlusion

If the bridge is being placed as a conformativerestoration (in a partially dentate patient), itshould be checked firstly in the retruded arc ofclosure to ensure that it does not create anocclusal interference. Next, the intercuspalposition should be checked. Ideally, the bridgeshould be only just in contact when the patientcloses lightly and should come fully into contactwhen the patient exerts heavy force. This willobviously depend upon how many natural teethremain and how good their occlusal contacts are.This degree of contact is difficult to quantify butthe best way of proceeding is to use occlusalindicator paper to get even contact betweenteeth and implants (Figure 14.15). Shimstockshould then be used and on light contact theimplant bridge should not hold the shimstock,but the teeth should. As the patient exerts moreforce so the implant bridge should hold theshimstock as well as the teeth. Ideally, the areasof contact should be located as close to thecentre of the implants as possible so that forcesare transmitted down the long axis of theimplant under loading. Cantilever pontics shouldbe loaded as little as possible.

The bridge is then checked in lateral andprotrusive movements. If a natural canineguidance is present, this will protect the bridgefrom lateral loading. If a group function occlu-sion exists, the implant bridge should be harmo-nious with this. If the canine tooth is beingreplaced as part of the bridge, it is normalpractice for the occlusion to be reorganized as agroup function occlusion if this can be achievedwithout sacrificing appearance. If lateralguidance has to be provided, this should beshallow, shared over several teeth if possibleand be centred on the strongest implant.

Protrusive guidance should have been deter-mined prior to construction because the anteriortooth position will dramatically alter this. Theprotrusive movement should be smooth and


spread over as many teeth as possible, onceagain ideally centred over the implants ratherthan on pontics.

If a reorganised occlusal scheme is to beadopted, such as a full-arch bridge, this wouldfollow normal crown and bridge and completedenture prosthodontics without the need for abalanced occlusion. The intercuspal occlusionshould be provided at the ideal vertical dimen-sion in the retruded arc of closure (retrudedcontact position), there should be an even andflat forwards movement of 1–2 mm, the lateralmovement should be a group function withmultiple contacts and the protrusive movementshould be shallow and even.

Bridge screw tightening

With short-span bridges the screws can be tight-ened to 10 N.cm of torque, either manually orwith a torquing device. Large implant-supportedbridges should be seated progressively to assistwith complete seating and prevent overtorquingthe bridge screws. The screws in the centreshould be hand-tightened first, moving distallyand alternating from side to side. When thebridge is first placed, the screw access holesshould be sealed with some cotton wool andtemporary filling material. There is a significantincidence of early screw loosening, particularlywith long bridges. The bridge therefore shouldbe checked after 1–2 weeks and the bridgescrews checked for tightness. Movement of ascrew by 90° or less is considered acceptable.Any screws more loose than this must bechecked a further 1–2 weeks later. It is unusualfor a screw not to retain its tightness for thesecond time and if this occurs it should bechecked carefully because it may indicate a poor


A

B

C

Figure 14.15

The occlusion is checked on a lower implant-supportedbridge: (A) Articulating paper is used to mark initialcontacts under light pressure. (B) The heaviest marks arepresent on the natural teeth, and the implant bridge (thesecond and third from the back) is only lightly touching.(C) Shimstock is used to confirm that the implant restora-tions are in contact under loading.

fit for the framework or that the bridge is beingoverloaded.

Once the screws have remained tight and thepatient has approved all aspects of the bridge,the screw access holes can be sealed perma-nently. In order to allow access in the futurewithout possible damage to the screw heads,they should be covered first with a layer ofsoftened gutta percha or similar material, whichwill seal the space but not set hard so it can beremoved easily if required. The occlusal portionof the screw access hole is best restored with acolour-matched light-cured composite resinfilling material and the occlusion re-checkedafterwards.

Bridge cementation

On completion of a cemented bridge a decisionneeds to be made regarding the type of cemen-tation required. With multiple parallelabutments the restoration does not require ahard (permanent) cement because this willmake the bridge difficult to seat fully and willmake it impossible to retrieve in the future.Implant bridges therefore can be ‘permanently’cemented with provisional cements as long asthey demonstrate good retention and stabilityat the try-in.

When the bridge is first completed, it isprudent to cement it provisionally to allow thepatient to ‘live with’ the bridge for a short whileand check on contour, appearance and speechbefore final cementation. Weakened or modifiedtemporary cement is all that will be required.Provisional seating also allows the gingiva toadapt to the new contour and will make finalcementation an easier technique, because thebridge will not be prevented from seating by atight gingival collar.

Prior to final cementation, the abutmentscrews are checked for tightness and the screwslots sealed with gutta percha. The chosencement is mixed and placed in the bridge, onlya thin layer will be necessary and the excesscement should be kept to a minimum to ease itsremoval. If hard cement such as zinc phosphatehas been chosen, this should not be mixed as aviscous material or the bridge will not fully seat.The margins must be checked very carefully to

ensure complete excess cement removal. Theocclusion must be re-checked following cemen-tation.

Instructions to the patient

On completion, long-cone periapical radiographsshould be taken for all implants to confirmseating and act as a future guide for marginalbone levels (Figure 14.16). If a cemented bridgehas been placed, excess cement should also bechecked for. The patient is given specific hygieneinstructions, particularly on how to access theareas between implants. They should be warnedto be careful with the new bridge duringfunction, because they are more likely to bitetheir inner cheek, lips or tongue as they get usedto having a fixed structure rather than a denture.Patients who have worn a denture long termprior to implant treatment experience moreproblems at the start, and these are bestdiscussed before problems arise in order toprevent the patient from becoming dissatisfied.

In particular, speech may be affected whenrestoring the upper anterior teeth. The perceptionof speech change is often more apparent to thepatient than to anyone else and usually returnsto normal after 1–2 weeks. Longer accommoda-tion times are, however, sometimes needed.

Follow-up

Following final completion of the new restorationit is wise to arrange for a review within 6months, particularly to check home maintenance.The marginal bone levels should be checked forstability with new long-cone periapical radio-graphs after 1 year and then approximately every2 years.

Additional considerations

Joining teeth and implants

Ideally, implants should not be linked to naturalteeth due to differential mobility. In particular, it


is not advisable for a tooth to be linked into abridge that is supported by several implants. Inthis situation, the bridge will be supported purelyby the implants and the tooth will be superflu-ous. With time, the tooth may unseat from thebridge and intrude into the alveolus. If design orother factors dictate retention of a tooth, it isadvisable that the tooth be protected by a goldcoping so that movement of the tooth from thebridge will not result in an unprotected toothbecoming carious.

Success in linking teeth and implants can beachieved if a single sound and non-mobile toothis linked to a single implant (Figure 14.17).Although there is still the differential in proper-ties between the two abutments, clinical trialshave shown high levels of success with noincreased bone loss or technical complications.Once again, it is advisable for the tooth to beprotected with a sub-bridge gold coping, whichshould be cemented with hard cement and thebridge with a weaker material. In the event of


A B

C

D

Figure 14.16

A posterior bridge supported by Straumann implants: (A) three healingabutments are visible; (B) the completed bridge; (C) occlusal view—screwretention has been used; (D) a periapical radiograph taken at the end oftreatment.

bridge cementation failure, the tooth will not beexposed to the potential of caries at the failedmargin. Such linked bridges are useful if there isonly enough bone volume for one implant to beplaced but the patient requires the provision oftwo extra teeth. Linking the implant to theadjacent tooth will allow for either a single-unitcantilever bridge or a fixed-fixed design with atooth and implant separated by a single missingunit. Provision of a joint as in conventionalbridgework is not advised, because the joint willstill allow the tooth to intrude from the bridge.

Bibliography

Arvidson K, Bystedt H, Frykholm A, von Konow L,Lothigius E (1992). A 3-year clinical study of Astradental implants in the treatment of edentulousmandibles. Int J Oral Maxillofac Implants 7: 321–9.

Arvidson K, Bystedt H, Frykholm A, von Konow L,Lothigius E (1998). Five year prospective follow upreport of the AstraTech implant system in the treat-ment of edentulous mandibles. Clin Oral Implants Res9: 225–34.

Cameron SM, Joyce A, Brosseau JS (1998). Radio-graphic verification of implant abutment seating. JProsth Dent 79: 298–303.

Cheshire PD, Hobkirk JA (1996). An in vivo quantitativeanalysis of the fit of Nobel Biocare implant super-structures. J Oral Rehab 23: 782–9.

Hellden LB, Derand T (1998). Description and evalua-tion of a simplified method to achieve passive fitbetween cast titanium frameworks and implants. Int JOral Maxillofac Implants 13: 190–6.

Hobkirk JA, Psarros KJ (1992). The influence of occlusalsurface material on peak masticatory forces usingossointegrated implant supported prostheses. Int JOral Maxillofac Implants 7: 345–52.

Jemt T (1994). Fixed implant supported prostheses in


A B

C

Figure 14.17

A three-unit bridge supported by a natural tooth and anAstraTech ST implant: (A) a Profile BI abutment (prepable)has been placed and the natural tooth prepared; (B) thetooth is protected with a gold coping; (C) the cementedbridge at completion.

the edentulous maxilla. Clin Oral Implants Res 5:142–7.

Jemt T (1995). Three dimensional distortion of goldalloy castings and welded titanium frameworks.Measurements of the precision of fit betweencompleted implant prostheses and the master casts inroutine edentulous situations. J Oral Rehab 22: 557–64.

Jemt T, Lekholm U (1993). Oral implant treatment inposterior partially edentulous jaws: a 5-year, follow-upreport. Int J Oral Maxillofac Implants 8: 635–40.

Jemt T, Book K (1996). Prosthesis misfit and marginalbone loss in edentulous implant patients. Int J OralMaxillofac Implants 11: 620–5.

Lundgren D, Laurell L (1994). Occlusal aspects offixed bridgework supported by endosseous

implants. In: Proceedings of the 1st EuropeanWorkshop on Periodontology, eds Lang NP andKarring T, pp. 326–44. London: QuintessencePublishing.

McAlarney ME, Stavropoulos DN (1996). Determinationof cantilever length to anterior–posterior spread ratioassuming failure criteria to be the compromise of theprosthesis retaining screw–prosthesis joint. Int J OralMaxillofac Implants 11: 331–9.

Olsson M, Gunne J, Astrand P, Borg K (1995). Bridgessupported by free standing implants versus bridgessupported by tooth and implant: a five year prospec-tive study. Clin Oral Implants Res 6: 114–21.

Schlumberger T, Bowley JF, Maze GI (1998). Intrusionphenomena in combination tooth implant restorations:a review of the literature. J Prosthet Dent 80: 190–203.


Introduction

This chapter will describe the clinical proceduresinvolved in the construction of implant dentures.Many of them are identical in principle to thoseused in the construction of conventionalcomplete dentures. It is assumed that the readerwill have a basic understanding of these latterprocedures and it is not intended that thischapter will cover every stage in great detail. Fora more detailed description of generic proce-dures, the reader is referred to textbooks cover-ing complete denture prosthodontics.

Manufacturers are constantly developing theirproducts and it is inevitable that some of them might not be included in this edition.Readers are referred to the individual manufac-turers’ catalogues for detailed descriptions oftheir products.

Selection of abutments or ballattachments

When a two-stage procedure has been carriedout, the patient should be seen about 4 weeksafter second-stage surgery for selection ofabutments or ball attachments and primaryimpressions. When a one-stage procedure hasbeen carried out, this prosthodontic stage wouldnormally be carried out about 3 months aftermandibular implant placement (6 months aftermaxillary implant placement with Nobel Biocareimplants).

The healing abutments are removed and thedistance from the top of the implant to themucosal surface can be measured with, forexample, a periodontal probe (Figure 15.1). Theaim is to achieve the lowest possible profilewhen selecting a transmucosal abutment for a

bar or magnet, or selecting a ball attachment sothat the prosthodontic components are withinthe intended contour of the denture. A generalidea of what is required should be apparent fromthe treatment planning and stent construction.However, it is necessary to make the final selec-tion after the mucosa has healed around theimplants.

Most manufacturers supply a range ofabutments in lengths up to 7 mm. The ITI/Straumann implant has the transmucosalelement already incorporated into the implant sono choice is possible at this stage: the decisionhas already been made at the time of placing theimplant. There is only one size of bar abutment(Figure 15.2) or ball attachment. The originalNobel Biocare standard abutment for bars andthe large ball attachment (Figure 15.3) had aminimum sleeve length of 3 mm so there was a

15Implant denture prosthodontics

Figure 15.1

A healing abutment over a Nobel Biocare implant has beenremoved. The distance from the top of the implant (exclud-ing the external hex) to the mucosa can be measured witha periodontal probe.

potential shortage of space with superficiallyplaced implants. The later Nobel Biocare 2.25-mm ball attachment has a minimum abutmentsleeve length of 1 mm (Figure 15.4). The NobelBiocare fixture-head gold coping, which fitsdirectly onto the implant, can be reduced inheight to allow the construction of a bar veryclose to the mucosa. The AstraTech uni-abutments for bars or magnets range in lengthup to 6 mm (Figure 15.5) and the ball attach-

ments have a similar range. The range of compo-nents is described more fully in Chapter 6.

Primary impressions

Once the measurements for abutments or ballattachments have been made, the healingabutments should be replaced and primary


Figure 15.2

Octa abutments (SynOcta®: Institut Straumann, Walden-burg, Switzerland) in place on ITI/Straumann implantsinserted at correct depth. Lowest profile for bar can beachieved.

Figure 15.4

Nobel Biocare 2.25-mm ball attachments with sleevelength selected to give lowest profile.

Figure 15.5

AstraTech 20° uni-abutments with appropriate cuff lengthto achieve lowest profile for bar or magnets.

Figure 15.3

Nobel Biocare standard ball attachments with sleevelength selected to give lowest profile.

impressions made. The purpose of these impres-sions, usually made with alginate impressionmaterial, is to produce casts upon which customtrays can be made.

A suitable stock impression tray is selectedthat will allow a minimum thickness of 3 mm ofalginate material and that extends to cover themajor landmark areas. In the mandible these arethe buccal, labial and lingual sulci, the retromo-lar pads and the retromylohyoid fossae; in themaxilla these are the buccal and labial sulci, thehamular notches and the palate. The imprints ofthe healing abutments are required for thecustom tray design.

The container of alginate impression materialshould be shaken to homogenize the powderparticles. The water and powder are dispensedusing the manufacturer’s measures and athermometer should be used to adjust thetemperature of the water. Warmer water can beused to accelerate the setting time for patientswho have a strong gag reflex. Once a satisfac-tory impression has been made (Figures 15.6 and15.7), it should be rinsed, disinfected, wrapped indamp gauze or tissue and placed in an airtightbox. A polythene sandwich box is ideal becauseit prevents the impression from drying out andis rigid to prevent the impression from beingcrushed during transportation to the dentallaboratory.

Custom tray construction andfinal impressions

A custom tray is made on the primary cast fromacrylic resin tray material or light-curing traymaterial. Polyether impression material is usedfor the final impressions because it is suffi-ciently rigid to hold the various prosthodonticcomponents that will be used during the impres-

IMPLANT DENTURE PROSTHODONTICS 217

Figure 15.6

Mandibular preliminary impression in alginate materialrecording major landmarks. Nobel Biocare standardabutments are already in place. The intended retentionsystem is a bar and clips.

Figure 15.7

Maxillary preliminary impression in alginate material.Healing abutments are in place.

Figure 15.8

Primary mandibular cast showing prescription for dentaltechnician: spacer thickness, extent and buccal shelfstops, window areas (healing abutment areas have hadplaster added to indicate eventual height of studs).

sion procedure. This material requires a 1.25-mm spacer, so a single sheet of baseplate waxis placed on the primary cast to the desiredoutline and areas are cut out for the tray stops(Figures 15.8). Extra wax or plaster is placedaround the abutments to ensure adequate clear-ance and the tray is constructed with windowsover the abutments; tray material is broughtvertically to enclose the intended impression

copings or ball attachments (Figures 15.9 and15.10).

The various manufacturers’ implant systemshave similar principles involved in making thefinal impressions for implant dentures. The origi-nal standard method for bar-retained implantdentures (and for AstraTech magnets) is shownin Figures 15.11–15.20 and involves the attach-ment of irregularly shaped impression copings


Figure 15.9

Typical mandibular custom tray with windows with suffi-cient clearance around implant.

Figure 15.10

Typical maxillary custom tray.

Figure 15.11

Standard bar impression technique: standard NobelBiocare abutments have been attached to the implants andstandard impression copings have been attached to theabutments.

Figures 15.12

Standard bar impression technique: the custom tray has awindow area through which the impression coping pinscan be accessed. The window is a single large windowbecause the implants are relatively close. A wax sheet hasbeen added over the window and the tray has been triedin the mouth. The imprints of the tops of the pins can beseen clearly on the underside of the wax sheet. The stopson the posterior part of the tray are visible.

by long pins to the selected abutments that havebeen attached to the implants. The custom trayhas a window through which the pins protrudewhen the impression is made. Once the materialhas set, the pins are loosened and the impres-sion is removed from the mouth with the impres-sion copings now firmly held in the impression.Then, laboratory replicas of the abutments areattached to the impression copings via the long

pins prior to boxing the impression and pouringthe cast. In the standard method, the position ofthe abutment is recorded via the coping ratherthan an impression being made of it.

With ball attachment systems, the abutmentscrew has a ball head and this is screwed intothe implant with the appropriate screwdriver.The large Nobel Biocare ball attachment is largeenough to have the screwdriver hole in the ball


Figure 15.13

Standard bar impression technique: the impression ismade using Impregum (Espe, D-82229 Seefeld, Germany)material. The tray has been placed so that the pins fit intothe imprints on the underside of the wax sheet.

Figure 15.14

Standard bar impression technique: the impressionmaterial has set and the wax sheet has been removed,revealing the tops of the impression coping pins. Thesepins can now be unscrewed so that the impression canbe removed from the mouth.

Figure 15.15

Standard bar impression technique: the final impressionshowing well-formed borders and impression copingssecurely held in material. The stops on the posterior ridgeareas are clearly demarcated – these areas will be adjustedwhen the denture is fitted.

Figure 15.16

Standard bar impression technique: the laboratory replicasof abutments have been attached to the impressioncopings with the impression coping pins.

head but all the others have drivers that enclosethe ball and engage suitable flats on the collar.The final impression is made of the ball attach-ments and laboratory replicas of them are placedin the impression prior to pouring the cast(Figures 15.21–15.29). The AstraTech ball attach-ment system has plastic impression copings thatare placed over the ball (Figure 15.30) prior tothe impression and remain in the impression

when it is removed from the mouth. The advan-tage of this coping is that the fit between it andthe laboratory replica is more precise than withthe small ball attachments of other manufactur-ers.

A later type of impression coping has beendeveloped for bar-retained implant dentures –the bar impression coping. Bar impressioncopings are attached to the abutment already


Figure 15.18

Standard bar impression technique: AstraTech impressioncoping, 20° squared.

Figure 15.17

Standard bar impression technique: the working cast withstainless-steel abutment replicas.

Figure 15.19

Standard bar impression technique: final maxillary impres-sion with AstraTech impression copings.

Figure 15.20

Standard bar impression technique: ITI/Straumann Octatransfer copings.


Figure 15.21

Final impression of Nobel Biocare 2.25-mm ball attach-ments (detail) showing driver flats.

Figure 15.22

Nobel Biocare 2.25-mm ball attachment replicas.

Figure 15.23

Final impression with the laboratory replicas placed intoimprints of ball attachments.

Figure 15.24

Final impression of three Nobel Biocare standard ballattachments.

Figure 15.25

Nobel Biocare standard ball attachment replicas in brass.Also available in stainless steel.

Figure 15.26

Working cast with two replicas of ball attachments.Spacers are supplied, which are inserted into the hole onthe top of the ball. These spacers ensure that the reten-tion cap is correctly aligned vertically.


Figure 15.27

Final impression of ITI/Straumann retentive anchors withanterior and buccal shelf stops demarcated.

Figure 15.28

ITI/Straumann transfer pin for retentive anchor.

Figure 15.29

Final impression with transfer pins placed into imprints ofretentive anchors.

Figure 15.30

AstraTech ball impression copings. These are picked upwith the final impression.

Figure 15.31

Nobel Biocare fixture head impression copings. These canbe used with slot-head pins in the standard bar impressiontechnique shown in Figures 15.11–15.17 except that areplica of the implant is attached to the copings before thecast is poured. They can also be used with round-headedpins in the bar impression coping method shown inChapter 17, Figures 17.24–17.28.

Figure 15.32

Protection caps on standard Nobel Biocare abutments.

attached to the implant and remain in the mouthwhen the impression is removed. The barimpression copings are then unscrewed from theabutment, attached to laboratory replicas of theabutments and then re-inserted into the impres-sion prior to pouring the cast (see Chapter 17,Figures 17.24–17.28).

Nobel Biocare have introduced fixture headimpression copings to complement the fixturehead copings mentioned earlier (Figure 15.31).These impression copings can be used with slot-headed pins in the standard method shown inFigures 15.11–15.20 or as bar impression copingsthat remain in the mouth after the impressionhas been removed (see Chapter 17, Figures17.24–17.28).

Once the final impressions have been made,the abutments or ball attachments can be left inplace on the implants but protection caps areessential for the former to prevent food debrisand calculus from entering the screw hole for thegold cylinders (Figure 15.32). The temporary softlining on the base of any denture that is beingworn will, of course, need to be changed toaccommodate the abutments and protectioncaps or ball attachments. Alternatively, theabutments or ball attachments can be removedand the healing abutments replaced until thenext stage. In this case, the temporary liningdoes not need to be changed.

Verification of final cast

It can be helpful to verify the accuracy of the finalcast, especially for intended bar-retained implantdentures, to avoid discovering errors late on inthe treatment. This can be done by linkingimpression copings with composite resin inexactly the same way as for extensive fixedrestorations (see Chapter 14).

Recording the maxillomandibular

relationship

For the construction of implant dentures, just aswith conventional complete dentures, the spatialrelationship between the maxilla and themandible is recorded by the use of occlusion

rims on temporary or processed bases. The rimsare shaped to prescribe the intended position ofthe anterior teeth and the occlusal plane, and areadjusted to meet evenly when the patient closesin the retruded position at a vertical relationshipthat allows for sufficient interocclusal distance(freeway space). A setting material is then intro-duced between the occlusal surfaces of the tworims to record their relationship.

The base of the occlusion rim can incorporateall or part of the impression coping to stabilizethe rim during the recording procedure for a bar-retained denture (Figure 15.33). For a ball-attach-ment-retained denture, the base of the rim canincorporate the actual retention caps. The smallretention caps of Nobel Biocare, AstraTech orITI/Staumann ball attachments are best incorpo-rated into a heat-cured acrylic resin basebecause they can be pulled out of a wax base(Figures 15.34). The large Nobel Biocare reten-tion caps have sufficient surface area to remainwithin a wax base.

The intended vertical relationship is deter-mined by establishing the resting verticalrelationship via a sliding calliper in almostuniversal use (a Willis gauge) or by the use ofdividers measuring between marks on thepatient’s nose and chin. By convention, 4 mm aresubtracted from the measurement of the restingvertical relationship to arrive at a proposedoccluding vertical relationship. This equates toabout 2 mm of interocclusal distance (freewayspace) at the first molar region. Whatever


Figure 15.33

Nobel Biocare impression copings in wax occlusion rim.


Figure 15.34

Nobel Biocare 2.25-mm gold alloy retention capsprocessed into heat-cured acrylic resin base.

Figure 15.35

Basic hand position for making interocclusal records: theleft index finger and thumb are stabilizing the maxillaryocclusion rim and posterior part of the mandibular rim; theright index finger is placed in front of the mandibularocclusion rim; the right second finger and thumb areplaced below the chin. The right hand guides the mandibleinto the retruded position. The facebow fork is in place tofacilitate the facebow transfer record when the interoc-clusal record material has set.

Figure 15.36

Automixed record material is injected onto the occlusalsurface of the mandibular rim. The left hand remains inposition to stabilize both rims and to prevent patientclosing.

Figure 15.37

Mandibular closure is guided until the occlusion rims touchgently. The operator’s fingers remain in position until thematerial has set.

method is used to assess these dimensions, ithas always been considered essential to havesufficient interocclusal distance for maximumcomfort for conventional complete dentures. It isnot clear whether or not the presence of implantsalters this requirement.

The method of locating the relative position ofone occlusion rim to the other is shown inFigures 15.35–15.37: a fluid-setting material isintroduced between the occlusal surfaces of theocclusion rims, with a working time sufficientlylong to allow an unhurried guided mandibularclosure into the retruded position, a setting timesufficiently short for the material to set soonafter this closure and sufficient durability for thematerial to remain intact after the occlusion rimsare removed from the mouth. A facebow trans-fer record can be made conveniently at the sametime as the interocclusal record by placing thefacebow fork into the maxillary rim before therecord is made. Once the interocclusal recordmaterial has set, the rims are then stabilized bythe patient keeping the rims together while thefacebow calliper is positioned over the fork andthe infraorbital pointer is adjusted (Figure 15.38).

After the facebow transfer record has beenmade, the entire assembly is removed from thepatient and disinfected. The maxillary cast isthen mounted on the upper member of a semi-adjustable articulator with low expansion mount-ing plaster and with the use of a facebow

support. The mandibular cast is mounted oncethe maxillary mounting plaster has set.

Selection of denture teeth

In general, the aim should be to select dentureteeth that resemble the original natural teeth andto arrange them in a similar way. This willusually produce the most natural-looking den-tures and the patient will adapt to them morequickly. Photographs (Figures 15.39 and 15.40) ofthe patient’s original teeth will help in this proce-dure but the denture teeth may need the incisaledges adjusted to simulate wear (Figure 15.41).

Posterior teeth should be selected with asmuch care as anterior teeth. For the mandibulardenture, the space available is from the distal


Figure 15.38

When the material has set, the facebow calliper is slid overthe fork and the locking device is tightened. The orbitalpointer is located and its locking device is tightened.

Figure 15.39

Photograph of patient with natural teeth.

surface of the proposed canine to thecommencement of any slope up to the retromo-lar pad. It may be possible to fit two premolarsand two molars into this space, but occasionallya second molar or a premolar may need to beomitted, especially in a patient with a Class 2 jawrelationship. In general, narrow occlusal surfacesare desirable to increase masticatory efficiency,but in patients with Class 2 or Class 3 skeletalrelationships wider occlusal surfaces may benecessary to develop and maintain occlusalcontact in a range of mandibular positions.

Confirmation of cast relationshipon articulator

The relationship of the casts on the articulator isconfirmed by setting up denture teeth (on

temporary wax or acrylic resin bases, or on heat-cured acrylic resin bases) in tight intercuspationand in the position prescribed by the occlusionrims (Figure 15.42). The trial dentures are thenplaced in the patient’s mouth and, using thehand position shown in Figure 15.35, the patientis guided into closure in the retruded position(Figure 15.43). If the denture teeth come togetherevenly with no movement of the trial denturebase, then the horizontal relationship of the castscan be considered confirmed. If this occlusionoccurs at an occluding vertical relationship witha demonstrable interocclusal distance, then thevertical relationship of the casts can be consid-ered confirmed.

If the denture teeth do not meet evenly whenthe patient closes in the retruded position (Figure15.44), the occlusion should be examined withthe trial dentures back on the articulator. If theteeth are not in tight intercuspation, they should


Figure 15.40

Denture teeth of implant denture have been selected andarranged to resemble those of pre-extraction photograph.

Figure 15.41

Denture teeth of maxillary implant denture have had incisaledges ground to simulate wear.

be reset and the trial dentures again placed inthe mouth. If the teeth still do not meet evenly,the cast relationship is incorrect and a newinterocclusal record will be necessary. This iscarried out by removing one set of posteriorteeth, marking the mandibular incisors with thedegree of overlap required when the new recordis being made (Figure 15.45) and then making anew record as described above. The mandibularcast is remounted using the new record, theposterior teeth are reset and the trial denturesare then replaced in the mouth to test the verac-ity of the cast relationship.


Figure 15.42

Working casts have been mounted on a semi-adjustablearticulator and denture teeth have been set in tight inter-cuspation.

Figure 15.43

Patient is guided into retruded closure with trial dentures.

Figure 15.44

These posterior teeth do not meet evenly when the patientis guided into retruded position. A new interocclusal recordwill be necessary.

Figure 15.45

A pencil mark can be made on the mandibular teeth priorto any new record, to indicate the amount of closurerequired: the right index finger can be placed so that duringclosure the maxillary teeth will touch the gloved fingernailand prevent further closure. Thus, the new record can bemade at the intended vertical relationship.

Occasionally, the denture teeth may meetevenly in the patient’s mouth but at a verticalrelationship that has insufficient or excessiveinterocclusal distance. If the amount is small, thenecessary adjustment can be made on the artic-ulator because a facebow record has been made.If the error is large, it is better to make a newinterocclusal record at the correct verticalrelationship because an arbitrary facebow record(as opposed to a hinge axis record) becomes lessaccurate with larger changes in vertical dimen-sion.

Confirmation of anterior tooth position isaccomplished by reference to anatomical land-marks such as the incisive papilla, pre-extractionrecords such as casts or photographs, speechsounds and direct patient feedback.

A protrusive interoccusal record is made toadjust the horizontal condylar guidance of semi-adjustable articulators but the lateral condylarguidance is usually adjusted arbitrarily becausesuch instruments do not accept all lateral interoc-clusal records.

The final step at this stage is to decide on theposterior limit of the maxillary denture if this hasnot already been done.

Completion of the implant

dentures

Where a bar and clip retention system is beingused, the bar is now constructed with referenceto anterior tooth position and the contour of thedenture (Figures 15.46 and 15.47). The barshould be tried in the mouth prior to completionof the dentures. If the bar does not fit theabutments in the mouth (Figure 15.48), it shouldbe examined carefully on the cast (Figure 15.49).If the bar does not fit the cast, it should be cutand resoldered or remade so that it does fit.Then it can again be tried in the mouth. If the bardemonstrates a passive fit on the abutments(Figure 15.50), then the denture can be finished.If the bar does not demonstrate a passive fit, thefinal impression must be at fault and will needto be repeated. If, however, the composite try-inmentioned earlier has been carried out, this canbe avoided.

Ideally, the posterior teeth should be set in abilateral balanced occlusion. Much has been


Figure 15.46

Once the final tooth position is confirmed, the bar can beconstructed.

Figure 15.47

The bar is in position on the working cast and has beencovered with plaster to block out all but the retentiveelements of the clips. The entire assembly is within thecontour of the denture after the tooth position has beenconfirmed.

Figure 15.48

The bar has been tried in mouth. There is a gap betweenthe gold cylinder and the standard abutment.

written about the advantages and disadvantagesof such an occlusion. It is certainly difficult toachieve with some manufacturers’ teeth. My ownexperience over 30 years in prosthodonticpractice is that dentures seem to be more stablewith a balanced occlusion but it is not clearwhether or not such an occlusion has any effecton implant success. However, where there isevidence of overloading of implants, it would

seem sensible to reduce the loading by reducingthe anterior guidance.

The implant dentures should now be finishedwith any clips attached to the bar over appropri-ate spacers and all but the retention elements ofthe clips blocked out with plaster prior to flask-ing, packing and processing in the usual way(Figures 15.51–15.57). Where ball attachmentsare being used, the retention caps are attached


Figure 15.49

The bar is back on the cast; the gap is present on the cast.The bar will need to be cut and resoldered.

Figure 15.50

The bar on maxillary standard abutments with passive fit.

Figure 15.51

Nobel Biocare clips attached to round bar, with spacersand all but retention tags covered with plaster. AstraTechbar and riders are similar.

Figure 15.52

ITI/Straumann Dolder bar and clips in place with spacers.Clips should be clear of gold cylinders to avoid anyimpingement during denture movement. In view of thelong bar, the denture is also supported on anterior goldcylinders.


Figure 15.53

Completed dentures showing Nobel Biocare Macro-Ovoidbar clips.

Figure 15.54

Completed mandibular denture showing ITI/Straumanntitanium alloy matrices.

Figure 15.55

Complete mandibular denture showing Nobel Biocarestandard ball attachment matrices.

Figure 15.56

Completed mandibular denture showing ITI/Straumanngold alloy matrices (similar to AstraTech and Nobel Biocare2.25-mm matrices). ITI/Straumann and AstraTech matriceshave four tines and Nobel Biocare matrices have six tines.

Figure 15.57

Completed maxillary denture with ITI/Straumann Dolderbar clips.

Figure 15.58

Completed maxillary implant denture with tinted gingivalacrylic resin to simulate melanin pigmentation.

to the laboratory replicas and again blocked outwith plaster. Where magnets are being used, themagnets are attached to the replicas withcyanoacrylate glue. Occasionally, gingival tintingwill be required where the patient has melaninpigmentation (Figure 15.58).

Insertion of the implant

dentures

Healing abutments that have been left in placein-between clinical stages should be unscrewed

and the definitive abutments for bars, magnetsor ball attachments should be placed. A torquedriver can be used, but hand tightening hasusually been sufficient for the components underimplant dentures. Bars should now be attachedwith appropriate screws (Figure 15.59).

The dentures should be coated with pressureindicator paste to identify pressure areas,especially those created by the tray stops. Theseareas should be adjusted with an acrylic resinbur, as well as any obvious sharp edges (Figures15.60 and 15.61).

A new interocclusal record and remounting ofthe dentures on an articulator for final occlusal


Figure 15.59

Radiograph of fitted maxillary Nobel Biocare Macro-Ovoidgold alloy bar (patient with onlay bone graft illustrated inFigure 6.9 of Chapter 6 and in Figure 15.50 above).

Figure 15.60

Pressure indicator paste applied to mandibular denture,showing posterior tray stop areas.

Figure 15.61

Pressure area over tray stop in original final impression.

Figure 15.62

Completed dentures have been remounted with newinterocclusal record and occlusion is adjusted using anextra-wide sheet of articulating paper in the forceps.

adjustments are always recommended for bestresults (Figure 15.62). Any small clinical errors orprocessing changes can be corrected by use ofthis procedure.

Once the dentures have been fitted, the patientshould ideally be seen within 48 h for any neces-sary adjustments. The patient should be warnedthat some soreness is likely. This may be causedby pressure areas in the final impression, overex-tension or faults in the occlusion. Use of pressureindicator paste and the remounting procedurewill reduce the prevalence of post-insertiondiscomfort. Occasionally, overextension will be

caused by the viscous nature of the polyetherimpression material if the custom tray was notextended correctly. In addition, it is very difficultto make impressions for implant dentures by anyother method than a static method: materialssuitable for functional impressions are not reallysuitable for picking up the components ofimplant dentures or rigid enough to hold thelaboratory replicas.

The patient should be seen regularly until thedentures are comfortable, and then reviewed atleast annually as part of a regular maintenanceprogramme.


PA R T V

Complications and Maintenance

Introduction

In order to measure treatment success and theincidence of complications, it has been suggestedthat longitudinal studies of implant systems shouldbe a minimum of 5 years (preferably prospectivestudies rather than retrospective), with adequateradiographic and clinical supporting data. Compli-cations should be rare and in most cases avoidableby careful attention to diagnosis, treatmentplanning, good surgical and prosthodontic trainingand experience and by following well-establishedprotocols that demonstrate high success andpredictability. However, complications can occur inthe early treatment phases, either surgical orprosthodontic, or following completion of treat-ment during the maintenance phase. Failure ofosseointegration of individual implants should berelatively rare, with most failures occurring duringthe initial healing period or following abutmentconnection and initial loading. Longer term compli-cations may be associated with:

• general wear and tear• inadequate attention to oral hygiene• poorly controlled occlusal forces• poor design of prostheses• utilization of an inadequately tested implant

system• soft-tissue deficiencies

The complications relating to surgery arecommon to all types of implant treatment andsystems and are considered together. Prostheticand late complications and maintenance aredealt with under separate sections for singletooth replacement and fixed bridges. Chapter 17deals with implant dentures.

Surgical sequelae andcomplications

It is important to warn patients about the mostcommon surgical/postoperative complications.Patients may experience some postoperativeswelling, bruising and discomfort, even withstraightforward single implant surgery. However,these sequelae are much more likely in casesinvolving placement of a large number ofimplants or grafting. These complications can beminimized with:

• gentle surgical manipulation of the hard andsoft tissues

• avoidance of over-reflection of flaps• preoperative and postoperative analgesics

(preferably those with anti-inflammatoryproperties such as the non-steroidal anti-inflammatory drugs, e.g. ibuprofen)

• recommendations to use ice packs to reduceswelling

• intravenous steroids in more major cases• pressure applied to the wound postopera-

tively to control haemostasis and avoidhaematoma formation

In our experience the majority of patientshave little or no postoperative swelling/bruis-ing/pain (Figure 16.1). The success of osseo-integration is dependent on minimal mechani-cal and thermal trauma to the bone and there-fore the patient should not experience pain inthe bone sites. Severe pain may suggest poortechnique and may coincide with early failure ofthe implant. A more controversial topic iswhether pre- and postoperative antibiotics arerequired to prevent infection and subsequent

16Single tooth and fixed bridge

failure of the implant. It was once routine toprescribe antibiotics. However, as implantsurgery is carried out under good surgicalconditions and a sterile implant is deliveredcarefully into the prepared site, the chance ofinfection should be low. It would be prudent touse antibiotics if:

• There has been a recent infection at the site.• Immediate replacement techniques are

used.• Multiple implants are placed where flaps have

been raised extensively or for a long periodof time.

• Augmentation and grafting are performed,including guided bone regeneration (GBR)membranes.

• The patient has a medical history thatsuggests a susceptibility to infection.

• The patient is a smoker.• The patient has hard bone (Type 1) that has

been difficult to cut and cool.• The implant placement has breached the

maxillary sinus floor.

In some cases patients experience infection inthe soft tissue if the surgeon has left debrisunder the flap margins or a large clot hasbecome infected. These cases are largely avoid-able.

Wound dehiscence

The soft tissue wound may break down in thefirst week following implant installation (e.g.particularly in the severely atrophic mandible).This used to concern clinicians when it led toimplant head exposure in submerged implantsystems, but because it has now been shown thatthese implants work in non-submerged protocolsit is not thought to be significant (Figure 16.2). Ifan implant head becomes exposed in a case thatwas planned to be submerged, it is important tokeep the area clean with antiseptic rinses (suchas 0.2/0.12% chlorhexidine) to prevent inflamma-tion and marginal bone loss. This situation maybe improved by changing the cover screw on theimplant for a healing abutment. Any breakdownof the soft tissue wound can lead to inflamma-tion/bone loss and is most critical in graftingprocedures where graft vitality and success canbe severely compromised.

Early implant failure

Most early surgical failures of osseointegration aredue to poor surgical technique or placement ofimplants into bone of very poor density, or in areaswith a lack of bone volume that has only allowed


Figure 16.1

Bruising near the chin and submandibular region 1 weekfollowing implant surgery to place six implants in the upperjaw.

Figure 16.2

Spontaneous exposure of a previously submerged implant.There is little or no inflammation of the soft tissue. Theimplant position is poor, having been placed in the middleof a two-tooth space.

utilization of very short implants (7 mm or less).Failure of osseointegration may not be obviousuntil the surgeon carries out abutment connectionsurgery or when the prosthodontist tries to load theimplant. It is sometimes difficult for the clinician toassess implant stability and occasionally a looseabutment may be misinterpreted as a failedimplant. The suspect abutment should be tightenedand the stability reassessed. Tightening of theabutment should not elicit discomfort/pain unlessthere is inflammation within the bone (consistentwith failure) or trapping of soft tissue betweenabutment and implant head. In most cases milddiscomfort soon resolves and there is no long-termcomplication. In other cases the discomfort is asign that there is a problem, and more obviousfailure of the osseointegration is revealed somedays or weeks later.

Damage to the bone resulting in necrosis, painand subsequent infection is more likely wherehard bone has been prepared with inadequatecooling and/or blunt drills (Figure 16.3). This ismore likely at deep preparation sites (e.g.> 13 mm). Such deep preparations are notusually necessary in good-quality bone andshould be avoided. The resultant pain can besevere and an infection that is likely to be deepseated can track through the soft tissues. In theanterior region of the mandible the infection maytrack to the external skin surface, producing a

disfiguring sinus tract, fibrosis and scarring(Figure 16.4).

Damage to neurovascular structures

Loss of sensation to the lower lip caused bytrauma to the inferior dental or mental nerve isa serious injury (Figure 16.5). Surgery close to

SINGLE TOOTH AND FIXED BRIDGE 237

Figure 16.3

Surgical exposure of an apical lesion of bone loss, probablycaused by inadequate cooling of the end of the drill duringpreparation of the site. The patient experienced pain andinfection for several months after the implant placement.

Figure 16.4

A sinus tract appearing on the skin at the lower border ofthe mandible. Inadequate cooling of an 18-mm implant sitein hard bone was the likely cause.

Figure 16.5

A panoral radiograph showing placement of implants in theposterior mandible with little or no regard to the positionof the inferior dental canal. The implants on the patient’sright breached the canal and resulted in mental anaesthe-sia; the implants on the left were placed so close to thenerve that paraesthesia resulted. (The clinician involved inthis case is not known to the authors.)

these structures is hazardous and great careshould be taken and the patient warned of thepossible consequences. The following pointsshould be appreciated to avoid this complication:

1. Avoid making relieving incisions in the areaof the mental nerve.

2. Do not place crestal incisions over the regionof a superficially located mental foramen inthe severely resorbed mandible.

3. Adequately expose, identify and protect thenerve when operating close to it.

4. Check for anterior loops of the inferior dentalnerve anterior to the mental foramen byradiography or by gentle probing of theforamen if utilizing this site.

5. Plan carefully with good tomographic orcomputed tomography (CT) images thatallow good visualization of the inferiordental canal and the superficial ridge.

6. Take careful measurements of the availableheight and width of the bone above thecanal.

7. In some circumstances it may be possible toplace an implant in a plane that safely avoidsthe canal, which could not be appreciatedusing two-dimensional radiography.

8. Use transparent transfers of the appropriateimplants at the correct magnification tooverlay on the radiographic images, or acomputer software program if this is avail-able to you.

9. Avoid thermal damage to the bone that isleft between the implant tip and the nervecanal.

10. Allow a safety margin for:• measurement error• a margin of bone between implant tip and

and canal, which we would suggest to beno less than 2 mm (although somesurgeons will place implants very close tothe canal)

• drill length at the cutting tip (differentdrills have various profiles and mayovercut 1–2 mm longer than the plannedimplant length)

• difficulty of surgical access, vision andcontrol of cutting pressure at the depth ofthe site

Patients are unlikely to complain followingdamage to the incisive nerve in the midline of

the anterior maxilla. Damage to the incisivebranch of the inferior dental nerve may gounnoticed in patients with no teeth in theanterior mandible. However in dentate patients,an implant placed in the canine or first premolarregion can sever or damage the incisive nervesupply to the remaining lower incisors. Thepatient may complain of paraesthesia or anaes-thesia of the lateral incisor periodontium and thiscan be distressing. The central incisor is notusually affected because of dual innervationacross the midline. Therefore it is wise to avoidviolation of the mandibular incisive canal indentate subjects.

A related problem can also occur when bonegrafts are taken from the chin in dentatesubjects. An osteotomy cut to close to theincisor or canine apices can result in alterationsof sensation or, worse, loss of pulp vitality. Asafety margin of 3 mm is recommendedbetween the osteotomy cut and the apices (seeChapter 12).

Fractures

The severely resorbed mandible can becompromised by implant placement such that afracture occurs at surgery or a short timefollowing this. Sectional tomograms should betaken to assess adequately the profile of theseverely resorbed mandible and to avoid theplacement of too many implants within zones oflow bone volume (e.g. mandibular first premo-lar region).

Prosthetic complications andmaintenance

Complications and maintenance requirementsvary widely between patients, depending on:

• susceptibility to caries and periodontaldisease in the dentate patients

• complexity and type of implant-supportedprostheses

• functional demands• the patient’s ability to maintain an adequate

standard of oral hygiene


It is generally recommended that patients treatedwith implant prostheses are seen at least on anannual basis, but in many cases they will alsorequire routine hygienist treatment at 3-, 4- or 6-month intervals, according to individual require-ments.

Single tooth units

Single tooth units should require little mainte-nance. The majority of single units arecemented and the integrity of the cementationshould be checked. Crown decementation ofsingle tooth units is unusual, even in caseswhere a relatively weak temporary cement hasbeen used. This is because of the close fit of the

abutment to the crown, and in some cases ahigh degree of parallelism between them, whichmay make separation difficult or impossible. Amore common complication is failure to seatthe crown at the original cementation becauseof failure to relieve hydraulic pressure withinthe crown using a cementation vent (Figure16.6). The resulting poor marginal fit andexposure of a large amount of cement lute mayresult in soft tissue inflammation because of theincreased bacterial plaque retention. A vent alsohelps to reduce excess cement from beingextruded at the crown margins, which can giverise to considerable inflammation, includingsoft tissue abscess and fistula formation. Plaqueretention and development of inflammationmay also be the initial sign of a loose abutment(see below).


Figure 16.6

(A) Radiograph of an AstraTech single tooth implant wherethere has been failure to seat the cemented crown fully.A gap can be seen between the crown and abutment. Thiscomplication is largely avoided by adequate venting of thecrown to allow excess cement to escape. (B) The clinicalappearance of the case in (A), showing very good softtissue health despite the unsatisfactory seating of thecrown.

A

B

Fixed prostheses

The prostheses should be checked for signs ofwear or breakage on a regular basis. Fixedrestorations should have the cementation orscrew fixation checked. This may includechecking the screws that retain the prostheses(Figure 16.7) and those that retain theabutments (see below). The occlusion shouldbe re-evaluated, particularly where there hasbeen occlusal wear of the prostheses orcoexisting natural dentition. It is not generallyrecommended to remove routinely the screw-retained bridge superstructures unless there isa suspicion that there is a problem with one ofthe implants/abutments. Fixed prostheses thathave proved difficult to clean by the patientmay require removal to allow adequate profes-sional cleaning, which is easier with screw-retained fixed prostheses than cementedtypes.

The screws retaining a prosthesis to theabutment are often covered with a layer ofrestorative material, such as composite or glassionomer, which may need replacing. Screws thatare accessible should be checked to ensure thatthey have not loosened. This is more likely tooccur in an ill-fitting prosthesis or where highloads have been applied.

Removable prostheses (dealt within detail in Chapter 17)

Removable prostheses need to be checked forretention and stability. In the case of prostheseswith combined implant and mucosal support itis important to check that the implants are notsuffering from overload caused by loss ofmucosal support due to further ridge resorption(Figure 16.8). It has been suggested that remov-able prostheses often require more mainte-nance in the form of adjustment and replace-ment of retentive elements such as clips and‘ball retainers’, compared with fixed prostheses.

Screw and abutment connections

Repeated chewing cycles may produce screwloosening, either at the bridge screw level orthe abutment level. Most single tooth restora-tions have cemented crowns with no directaccess to the abutment for screw tightening.Therefore, should this be required, removal ofthe crown is necessary. Abutment loosening


Figure 16.7

Radiograph of a posterior mandibular bridge. The loosebridge screw in the distal abutment is visible.

Figure 16.8

Implants joined by a bar used to support a maxillarydenture. The oral hygiene is poor and the loading has beenhigh, causing loss of osseointegration of the distal implant.

and development of a gap between abutmentand implant will manifest as a loose prosthesis(Figure 16.9). This can even appear as thoughthere has been failure at the implant level.Screw loosening can be prevented largely byattention to occlusal contacts and adequatetightening of the bridge and abutment screw, inthe first place by using specifically designedtorque wrenches/handpieces (see Chapters 13and 14). Some implant systems, e.g. NobelBiocare, suggest re-tightening of bridge screws2 weeks after initial fitting of the bridge super-structure. The design of the abutment/implantinterface may also reduce this complication.The internal abutment connection designsshould produce a more stable joint than the flattop designs. Even with the latter design, theoccurrence of screw loosening is low providedthat the correct torque has been applied. Screwloosening is often an important sign of overloaddue to:

• poorly fitting prosthesis/non-passive fit• poor design, e.g. overextension of a cantilever• poor implant/crown ratio• inadequate attention to occlusal contacts• too few implants/teeth to establish an adequate

occlusal table

• parafunctional activity

These factors require identification, correctionand proper management to avoid this complica-tion. Failure to deal with these problems, partic-ularly in patients who exhibit parafunctionalactivities, may predispose to screw fracture(retention screws or abutment screws), whichmanifests as a loose prosthesis and may bedetected radiographically (Figures 16.9 and16.10). The fractured screws need to be removedand replaced. In many instances the fracturedscrew can be unwound by engaging thefractured surface with a sharp probe and movingthe probe round in a counter-clockwise direction.Alternatively, a commercially designed retrievalkit may make this process easier. The screw thencan be replaced and attention given to correctthe cause of the problem in order to avoid arepeat of the problem and possibly ultimatefailure of the implant. In some instances removalof the fractured screw proves to be impossible.Fractured screws are difficult to remove bydrilling without causing considerable damage tothe implant. This may make subsequent restora-tion impossible unless it is feasible to constructa custom-made post that can be cemented withinthe implant.


Figure 16.9

A radiograph of a posterior mandibular bridge onBrånemark implants, showing failure to seat the distalabutment (prior to completion of the bridge) and a loosebridge screw.

Figure 16.10

The lower screw is a retrieved fractured Brånemarkabutment screw, compared with an intact screw above it.The fractured screw was removed from the case illus-trated in Figure 16.12.

Implant fractures

Fortunately, fracture of an implant is rare. It ismore likely to occur with:

• narrow diameter implants, particularly wherethe wall thickness is thin

• excessive load• marginal bone loss that has progressed to the

level of an inherent weakness of the implant(Figure 16.11), often the level where wallthickness is thin at the apical level of theabutment screw

Implant fracture is rarely retrievable, andrequires either burying the fractured componentbeneath the mucosa or its removal (Figure16.12). The latter can be difficult and traumatic,usually requiring surgical trephining that mayleave a considerable defect in the jaw bone.

Soft-tissue evaluation andproblems

The mucosa surrounding the implant abutmentsshould appear free of superficial inflammation.Gentle pressure on the exterior surface of thesoft tissue should not result in any bleeding orexudate and should produce minimal or nodiscomfort. Inflammation of the peri-implantmucosa has been termed ‘peri-implant mucosi-tis’ to differentiate it from the more destructivelesion involving bone loss, so-called ‘peri-implantitis’. Probing depths may be evaluatedand will depend upon the thickness of the origi-nal mucosa, any overgrowth of soft tissue andany loss of attachment/marginal bone loss that


Figure 16.11

The top of a fractured Straumann implant. This hollowcylinder implant had progressively lost bone to the levelwhere there were perforations in the implant cylinder, thelevel at which the implant fractured.

Figure 16.12

A radiograph of three Brånemark implants supporting amaxillary bridge that had been subjected to excessiveloading. The anterior implant (right) had previously suffereda fractured abutment screw, the top half of which wasremoved and replaced with a gold screw (moreradiopaque) but the apical part could not be removed. Thedistal implant (left) had a similar history that was followedby fracture of the implant at the level of the apex of theabutment screw. This latter situation usually requiresremoval or burial of the fractured implant.

may have occurred. Standard periodontalprobes with a tip diameter of approximately0.5 mm and a probing force of 25 g are recom-mended. Ideally probing depths should berelatively shallow (< 4 mm) with no or minimalbleeding. Studies have demonstrated thatprobing around implants is not dissimilar toprobing around the natural dentition. In generalthe junctional epithelium is quite delicate andcan be breached by the probe. The underlyingconnective tissue around implants is notconnected by well-formed fibre bundles to theabutment/implant surface and forms parallelcollagen fibre bundles. This offers less resis-tance to probing. In general the probe stopsshort of the bone margin by about 1 mm. Ifincreased probing depths, soft tissue prolifera-tion, copious bleeding, exudate or tenderness topressure are found, the area should be ex-amined radiographically (regardless of whetherradiographic re-evaluation is scheduled) todetermine whether there has been any loss ofmarginal bone or loss of osseointegration (seesection on peri-implantitis). In these circum-stances it may be advisable to dismantle a screwretained implant superstructure to allow ade-quate examination of individual abutments andimplants.

Most inflammatory conditions can becorrected with attention to oral hygiene andprofessional cleaning. The latter is also consid-erably facilitated if the prosthesis can be disman-tled and cleaned outside the mouth. However,there are a number of instances that may requiresurgical correction of the soft tissue problem:

• Soft-tissue overgrowth• Soft-tissue deficiencies• Persistent inflammation/infection• Continuing bone loss (see peri-implantitis)

Soft-tissue overgrowth

Soft-tissue proliferation may occur aroundbridges with poorly designed embrasures andunder supporting bars of implant dentures (seeChapter 17). It may require simple excision ifthere is adequate attached keratinized tissueapical to it, or an inverse bevel resection as usedin periodontal surgery to thin out the excess

tissue but preserve the keratinized tissue toproduce a zone of attached tissue around theabutment (see Figure 16.14).

Soft-tissue deficiencies

The transmucosal part of the implant restorationmay emerge through non-keratinized mucosa,particularly in situations where there has beensevere loss of bone, e.g. edentulous jaws. Non-keratinized mucosa looks redder and moredelicate than keratinized tissue and may lackattachment to the underlying bone. This can giverise to soreness and compromised plaquecontrol, particularly in implant denture cases.Persistent soreness and inflammation can beovercome by grafting keratinized mucosa to thesite in a procedure that is the same as free gingi-val grafting using donor tissue from the palate.In other situations it may give rise to compro-mised aesthetics (Figures 16.13 and 16.14).

Persistent inflammation

Persistent inflammation or discomfort may arisedue to poor implant positioning. It may requirerecontouring of the soft tissues to allow patientcleaning, and this may reveal the less than satis-factory aesthetics produced by poor planningand execution of treatment (Figure 16.14) Inother more severe cases the only remedy maybe to remove the implants or bury them perma-nently beneath the mucosa (Figure 16.15). Poorlydesigned or constructed protheses may need tobe replaced, but in some cases this would alsoinvolve correction of the implant position. Acompromise solution may therefore be sought.

Evaluation of marginal bonelevels

It is important to establish baseline radiographswhen the prosthesis is fitted. It would seemreasonable to radiograph annually for the first3–5 years, then bi-annually up to 10 years in theabsence of clinical signs or symptoms. In all


cases every effort should be made to minimizedistortion and produce comparable reproducibleimages to allow longitudinal assessment. Mostimplant systems report a small amount of boneloss in the first year following loading, followedby a steady state in subsequent years in themajority of implants. More marginal bone losshas been reported in patients who smoke. Ifprogressive bone loss is detected, the clinicianhas to decide whether this is most likely due toexcessive loading or bacteria-induced inflamma-tion (peri-implantitis).


Figure 16.13

(A) The maxillary central and lateral incisors were replacedwith single tooth implants. However, loss of interdentaltissue has produced a very unaesthetic result. The softtissue defect is difficult or impossible to correct surgically.(B) The crowns have been replaced with a splinted unitbearing a pink porcelain prosthetic ‘interdental papilla’. (C)The improvement in aesthetics is shown with the patientsmiling.

A

B

C

Figure 16.14

(A) This patient does not reveal the gingival margin whenshe smiles. (B) Retraction of the lips shows the unsatisfac-tory intraoral appearance of the receded soft tissue expos-ing the titanium abutments. The implants had been placedin the interdental zones and the patient had found it impos-sible to carry out adequate oral hygiene. Inflammation andsoft tissue overgrowth had occurred, which required surgi-cal resection resulting in this appearance.

A

B

Peri-implantitisThe incidence of peri-implantitis would appear tobe low. A diagnosis of peri-implantitis means thatan inflammatory lesion has caused obvious boneloss. Usually the marginal soft tissue will appearinflamed but this is not always the case becausethe lesion may be deep seated. Probing willsuggest loss of marginal bone and radiographs

will confirm this. It is quite possible that thebacteria implicated in periodontitis, such asPorphyromonas gingivalis, are also the majorpathogens in peri-implantitis. There is therefore apossibility of colonization or infection of theimplant surfaces from pre-existing periodonto-pathic bacteria. Therefore implants should not beplaced in patients with untreated periodontaldisease. The destruction of the supporting tissues


Figure 16.15

(A) Clinical appearance of a three-unitimplant-supported bridge replacing themaxillary right lateral incisor and bothcentral incisors. A small soft tissueabscess is visible at the right central incisorunit. Initially three implants had beeninserted to replace each of the missingteeth as single units. (B) A radiograph ofthe bridge shows that there is a buried(unused/unconnected) implant beneath theright central incisor unit, in very closeproximity to and in intraoral communicationwith the implant in the right lateral incisorregion. This had led to a submucosal infec-tion at the head of the buried implant. (C)The buried implant at the right centralincisor site had been deemed to beunrestorable as an individual unit, and itproved impossible to remove simply inorder to resolve the infection. Therefore,the coronal part of the implant wassectioned and removed, leaving the apicalpart in situ. (D) The healed result withresolution of the infection. The loss of softtissue contour necessitated addition to thebridgework. The bridge was then remade.This problem could have been avoided byplacement of only two implants in thelimited space, rather than placing implantstoo close together to allow restoration.

A D

B C

of teeth and implants has many similarities butthere are important differences due to the natureof the supporting tissues. This is particularlynoticeable with the different patterns of tissuedestruction observed. Peri-implantitis affects theentire circumference of the implant resulting in a‘gutter’ of bone loss filled with inflammatorytissue extending to the bone surface (Figure16.16). It would seem probable that destructiveinflammatory lesions affecting both teeth andimplants have stages in which the diseaseprocess is more rapid (burst phenomenon)followed by periods of relative quiescence.

Unfortunately there have been some very polar-ized views as to the incidence and nature of peri-implantitis. Some have contended that peri-implantitis only occurs at implants with roughsurfaces that allow bacterial colonization. Con-versely, bone loss at smoother implant surfaceswas held to be due to overload. Clearly this simplis-tic distinction is false and unhelpful and is reminis-cent of the debate about the importance of occlusaltrauma in periodontitis. It must be conceded thatthe destruction of the marginal bone in a bacteriallyinduced peri-implantitis may be difficult to differen-tiate from bone loss due to excessive forces.Moreover, the latter situation subsequently may be

prone to bacterially induced inflammation. It shouldbe clear that any lesion giving rise to marked boneloss should be evaluated for both occlusal andbacterial factors and treated appropriately. Occlusalfactors are more likely to be implicated in situationswhere there has been:

• a history of parafunction• a history of breakages of the superstructure

or retaining screws• breakages or loosening of screws• an angular/narrow pattern of bone loss• too few implants placed to replace the

missing teeth• excessive cantilever extensions

Bacterially induced factors are more likely tobe implicated where there is:

• poor oral hygiene• retention of cement in the subgingival area• macroscopic gaps between implant compo-

nents subgingivally• marked inflammation, exudation and prolifer-

ation of the soft tissue• wide saucerized areas of marginal bone loss

visible on radiographs


Figure 16.16

(A) A clinical photograph of asurgically exposed implant thathas suffered from peri-implan-titis. The inflammatory tissuehas been removed to revealbone loss that forms a circum-ferential gutter. (B) Radiographof the lesion showing the widesaucerized pattern of bone losstypical of peri-implantitis.

A B

Management of peri-implantitis

Occlusal factors that could result in implantoverload should be identified and corrected.Lesions that are thought to be due primarily tobacterial colonization or secondarily contami-nated by bacteria are currently managed in asimilar fashion to lesions of periodontitisaround teeth, by gaining surgical access to thelesion. The keratinized mucosa should bepreserved as much as possible, by employingan inverse bevel incision to separate it from theunderlying inflammatory tissue. Followingincision to bone, the soft tissue flaps should beelevated to expose normal adjacent bone. Theinflammatory tissue surrounding the implant isreadily removed (Figure 16.16A). The main diffi-culty is adequately disinfecting the implantsurface. This is more readily accomplished on arelatively smooth surface but may be almostimpossible on a very porous surface such as ahydroxyapatite coating. Therefore, roughsurfaces require more extensive debridementthan a smooth surface. Rougher surfaces mayrequire removal of the contaminated layer withburs. Contaminated surfaces may be disinfectedusing a topical antiseptic such as chlorhexidine,detergents or topical antibiotics. Peri-implantitislesions are not sufficiently common to haveallowed comparison of different methods ofcleaning. In many cases the soft tissue inflam-mation can be resolved and there may be somerepair of the bone. Some clinicians attempt toregenerate the lost bone using techniques suchas guided bone regeneration. In cases whereregenerative techniques have been used andbone fill has occurred, most research hasconcluded that re-osseointegration is unlikely tooccur.

Routine hygiene maintenancerequirements

Single tooth restorations

An individual with a healthy dentition and asingle tooth implant replacement should havethe simplest maintenance requirements and

few, if any, complications. The patient shouldbe able to maintain the peri-implant soft andhard tissues in a state of health equivalent tothat which exists around their natural teeth,almost without professional intervention(Figure 16.17). This can be achieved withroutine toothbrushing and flossing. However, insome circumstances, the contour of the singletooth restoration is not ideal and instead ofproducing a smooth readily cleansable emer-gence profile, poor positioning of the implantmay have resulted in a degree of ridge lapping.This will require modification of oral hygienetechniques to clean under the overhangingcrown morphology, with dental tape or super-floss passed or threaded under the overhang.Single tooth restorations rarely have calculusformation on their highly glazed porcelain orpolished gold surfaces. Professional scaling isnot therefore normally required.

Fixed bridges and removableprostheses

In patients with more complex fixed prosthe-ses, development of readily cleansable embra-sure spaces by the technician considerablyfacilitates patients’ oral hygiene. Difficultiesoccur with poor implant positioning, such asplacement in embrasure spaces and implantsplaced too close together (Figures 16.14 and16.15). The selection of abutments may have aconsiderable impact. Smooth titanium abut-ment surfaces are well tolerated by the softtissues. With cemented restorations it is advis-able to limit the subgingival extent of thecement junction to allow easier cementation,removal of excess cement and checking ofmarginal integrity.

Scaling of implant prostheses

Supragingival calculus deposition is mostfrequently seen in implants in the anteriormandible (often on implant denture abutments), inmuch the same pattern as natural teeth. Calculusshould be removed from titanium abutments withinstruments that will not damage the surface



Figure 16.17

A series of photographsshowing long-term mainte-nance of a single toothimplant restoration (AstraTech)replacing a maxillary lateralincisor. (A) Clinical appearanceof the left lateral incisor unit atcementation. (B) Radiographof the completed restorationat cementation. The bonelevels are at the top of theimplant. (C) The improvementof the soft tissue profile andexcellent healthy appearance6 years later. (D) Maintenanceof bone levels at the top of theimplant after 6 years.

A C

B D

Figure 16.18

A plastic-tipped curette for scaling titanium abutments toavoid damage to them.

(Figure 16.18), therefore the instruments areusually made of plastic. In most cases wherepatients are treated with prostheses that havebeen optimized to produce good aesthetics, theabutments used are low profile with no exposureof titanium supragingivally and minimal exposureof the titanium surface subgingivally, so thisproblem does not arise. Ultrasonic instrumentsand steel-tipped instruments are contraindicated.

Conclusion

Ideally all patients should be in a recall/mainte-nance programme. This is particularly importantin patients who have complex prostheses, whereservicing requirements may be greater. Somepatients fail to appreciate the importance offollow-up and complications may arise as a result.

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Introduction

This chapter will describe prosthodontic compli-cations and post-insertion maintenance of thecompleted implant dentures. Complications mayoccur before, during and after the prosthodonticphase of implant treatment; maintenance andrepairs of the dentures and components will berequired after the dentures are fitted. Variousstudies have shown different results for themaintenance requirements for implant dentures.Hemmings et al. (1994) concluded that implantdentures required less maintenance than fixedrestorations, but others (Chan et al., 1996;Watson and Davis, 1996; Watson et al., 1997)have pointed out the necessity for replacementof clips, adjustments and remakes.

Complications before theprosthodontic phase oftreatment

Placement of implants in anunplanned position

Implants may be inadvertently placed in anunplanned buccopalatal or buccolingual position,in an unplanned mesiodistal position, at anunplanned angulation or at an unplanned depth.Situations such as these are more likely when astent is not available but may still occur evenwhen a stent is used if there are unexpectedfindings during surgery.

Minor changes from the intended implantposition or angulation usually can be accommo-dated within an overdenture, although an alter-native attachment mechanism may have to beused, for instance, a smaller ball attachment maybe needed (Figure 17.1). Some manufacturers

provide a choice of sizes and these have beendescribed in Chapter 6.

Greater deviations from the intended implantposition will create an abnormal contour in thefinished denture. This may be uncomfortable forthe patient and may cause speech difficulties oreven soft-tissue proliferation (Figures 17.2 and17.3).

17Implant dentures

Figure 17.1

Maxillary implants placed too buccally. There is insufficientroom for a Nobel Biocare standard ball attachment reten-tion cap so a smaller 3i ball attachment is used instead.The figure shows a Nobel Biocare retention cap on theright implant and a 3i matrix on the left implant.

Figure 17.2

ITI/Straumann implants placed too superficially and the leftimplant placed too lingually. There is an unfavourable soft-tissue response around the left implant.

Where an implant has been placed in aposition that is too superficial, there may beinsufficient space for the prosthodontic compo-nents to be contained within the normal contourof the proposed denture. Even when there issufficient bulk of acrylic resin, and a bar and clipsystem is planned, the resulting bar may beseveral millimetres away from the mucosa(Figure 17.4). Although this, in itself, is only criti-cal when short implants are used and the lever-age is increased under loading, the amount of

so-called dead space is increased and there maybe tissue overgrowth beneath the bar.

Nobel Biocare have introduced fixture-headgold or titanium cylinders, originally designed tobe used with a single-stage surgery implantwhere the external hex is superficial to themucosa, to reduce the overall height of thesupramucosal components. These cylinders fitdirectly onto the implant and can be reduced inheight. They can be used instead of theabutment/gold cylinder system on a superficiallyplaced implant to enable a bar to be placed closeto the alveolar ridge mucosa (Figure 17.5).

A disadvantage of the one-piece ITI/Straumannimplant is that no compensation is possible foran implant that has been placed in a position thatis too superficial (Figure 17.2).

Where several implants have been placed tooclose together there may be insufficient space forclips between them. In such situations, cantileverextensions may be necessary but the clips aremore likely to fracture or be pulled out of theresin.

Failure of integration of one ormore implants

One or more implants may fail to integrate priorto the commencement of implant denture


Figure 17.3

Completed denture has unfavourable contour owing tounplanned implant placement.

Figure 17.4

Superficial placement of Nobel Biocare implants. Roundbar on 3-mm standard abutments is several millimetresaway from the ridge. Labial inclination has also necessi-tated soldering the bar to the lingual surfaces of gold alloycylinders to place clips in the thickest portion of thedenture.

Figure 17.5

Nobel Biocare Macro-Ovoid bar on fixture head gold alloycylinders enables a very low profile bar. The cast has beenscraped to permit close adaptation. The blanching in thefigure was evident only on immediate placement of thebar.

construction, leaving remaining implants in anunfavourable distribution. In the maxilla, aminimum of four implants ideally should beplaced. If one or two should fail, an implantdenture can still be made but the risks ofoverload are higher, particularly where there areopposing teeth in the mandible. If the remainingimplants are unilateral, the stability of theimplant denture will suffer.

In these situations, further implants should beplaced to achieve the planned implant distribu-tion. A transitional denture can be constructedbut the risks of overloading the remainingimplants must be considered.

Failure of bone graft, preventingimplant placement

If this happens, it is possible to repeat the proce-dure but, in our experience, the patients haveusually decided to remain with a conventionaldenture. A new denture is usually requiredbecause of the inevitable change of contour ofthe residual ridge after the surgery and, moreproblematically, because of the change of sulcuselasticity due to scarring.

Complications during theprosthodontic phase oftreatment

Complications include fracture of the existingdenture after removal of acrylic resin to allow forthe temporary soft lining, and loosening anddamage to healing abutments. Existing cobalt–chromium-based dentures, even when widely cutaway, are particularly hard on healing abut-ments, ball attachments or standard abutmentsthat remain in the mouth during the prosthodon-tic phase of treatment. It is always preferable tohave an acrylic-resin-based denture, especiallyas the soft lining materials adhere more securely.

Opposing teeth may damage healingabutments, standard abutments or ball attach-ments, particularly when a shearing or glancingcontact is possible. This possibility must be takeninto consideration during planning stages, even

to the extent of changing the retention system sothat such contacts are vertical onto a flat surfaceaway from a screw head. Where ball attachmentsare unavoidable, a soft PVC mouthguard can bemade for night-time wear (Figure 17.6).

Where a bar and clip system is being used, itis advisable to try the bar in the mouth beforethe denture is finished. If the bar does not fit, itshould be checked on the working cast. If it doesnot fit the working cast, it should be cut andresoldered, or remade, prior to trying it in themouth again. If the bar fits the cast but not themouth, the cast must be at fault and a new finalimpression will be required.

Dentures unable to be insertedover ball attachments

If one of the laboratory analogues was notinserted precisely into the impression, the errorin the working cast may prevent the completeddenture from being inserted. In such situations,retention caps can be removed and re-attachedusing autopolymerizing resin in an intraoralprocedure, but the procedure is not easy. Therelining/repairing procedure described later inFigures 17.21–17.35 is to be preferred.

IMPLANT DENTURES 253

Figure 17.6

Two 3i ball attachments opposing natural teeth. A soft PVCmouthguard has been made for the mandibular teeth.

Post-insertion complications and

maintenance

Failure of integration of one ormore implants

In common with most published studies, ourexperience has been that implant failure is veryrare in the mandible. Some failures are seen inthe maxilla, especially in smokers and wherethere have been opposing natural teeth. Wherea bar is the retention system, the bar will needto be unscrewed to remove the failed implantand then sectioned to reduce its length (Figures17.7 and 17.8), unless the failed implant isbetween two other quite close implants. Thelatter situation is quite unusual because mostfailures tend to be the most distal implants.

Fracture of ball attachment orimplant

Fractures of ball attachments may occur whenthey oppose natural teeth. The remaining portionof the fractured ball attachment can beunscrewed with a dental explorer or themanufacturer may provide a ‘rescue kit’. Inextremis, the portion can be drilled out but it isdifficult to avoid damaging the internal implantthreads. The Nobel Biocare rescue kit comes withminiature taps to tidy up the internal thread andshould probably be used whenever one of theirdamaged components is removed. Where animplant fails because of fracture, the denturemay still be reasonably stable with a singleremaining implant (Figures 17.9 and 17.10).

Fracture or wear of denture orcomponents

Once implant dentures have been made, somepatients appear to increase the force exertedupon the dentures during mastication or possi-bly parafunction. Although the implants may beable to withstand these forces, the prosthodon-tic components and the denture itself are morevulnerable. These increased forces may causeexcessive wear of the occlusal surfaces of the

teeth (Figure 17.11), perforation and fracture ofdenture base material (Figure 17.12), fracture ofdenture teeth (Figure 17.13), fracture of clips,dislodgement of clips from acrylic resin, wearand fracture of ball attachment matrices (Figure17.14) and wear of bars. Components can bereplaced using cold-cure acrylic resin as anintraoral procedure but extreme care is needed


Figure 17.7

Radiograph of failed right maxillary implant supporting bar.

Figure 17.8

The bar has been sectioned near to remaining left maxil-lary implants leaving space for one clip.


Figure 17.9

A dental panoramic tomograph (DPT) showing the apicalportion of a fractured implant in the right maxillary canineregion.

Figure 17.10

Implant in the right maxillary canine region has beenremoved, leaving one implant in the left canine region. Themaxillary denture is still reasonably stable.

Figure 17.11

Excessive wear of denture teeth on implant dentures after4 years of use.

Figure 17.12

Perforation of denture base and exposure of clip retainersin maxillary denture opposed by crowned mandibular teeth.

Figure 17.13

Fractured maxillary right lateral incisor of implant denture.

Figure 17.14

Fractured tines of Nobel Biocare gold alloy matrix for 2.25-mm ball attachment.

(Figures 17.15–17.17). When replacing clips withsuch an intraoral procedure, it is helpful forsome part of the denture to rest onto the barcomplex so that the denture can be locatedaccurately in the mouth. Some manufacturers’instructions have stated, however, that thedenture should not rest on the gold cylinders.Alternatively, the components can be replaced

using the relining procedure illustrated later(Figures 17.21–17.35).

The titanium alloy matrix available from NobelBiocare and ITI/Staumann consists of three parts:a retention part that is embedded in the acrylicresin of the denture, a stainless-steel circlip anda removable cover for the circlip. If the circlipneeds replacing, the cover can be unscrewed to


Figure 17.15

A Nobel Biocare clip has been positioned on round barwith spacer and wax used to block out bar.

Figure 17.16

The old clip has been removed from maxillary denture andan access hole has been made through to the palatalsurface of the denture.

Figure 17.17

The hole is enlarged until the denture can be seatedwithout disturbing the clip in place on the bar.Autopolymerizing resin is then fed through the hole toattach the retention elements of the clip to the denture.When this resin has set the denture can be removed fromthe mouth, additional resin is added around the clip andthen this is polymerized under pressure for maximumstrength.

Figure 17.18

Titanium alloy matrix available from Nobel Biocare andITI/Straumann. The removable cover can be unscrewed toreplace the circlip.

allow replacement of the circlip without disturb-ing the retention part (Figure 17.18).

Cobalt–chromium alloy bases can be used toprevent excessive wear of acrylic resin, particu-larly when opposing crowned teeth (Figure17.19) and also to prevent fracture of the basewhen this has been reduced in patients whohave a strong gag reflex (Figure 17.20).

Continued bone resorptionWhere there is evidence of continued boneresorption in the edentulous areas away from theimplants, implant dentures can be relined usingthe relining procedure illustrated in Figures17.21–17.35.


Figure 17.19

Cobalt–chromium alloy platform to oppose crownedmandibular teeth.

Figure 17.20

Cobalt–chromium alloy base for palateless maxillaryimplant denture.

Figure 17.21

A mandibular denture in which the two distal clips hadfractured from the resin.

Figure 17.22

Nobel Biocare Macro-Ovoid bar retaining the dentureshown in Figure 17.21.

Overgrowth of mucosa under bar

Overgrowth of mucosa beneath a bar can beremoved surgically if its presence causesdiscomfort or difficulty with cleaning.

Difficulty with speech

This is not uncommon with maxillary dentureswhere the palatal contour is bulky to accommo-date a bar and clip system. If the patient cannot


Figure 17.23

The bar is unscrewed from the standard abutments.

Figure 17.24

Bar impression copings are placed on the abutments. Thebar impression copings are used because standard impres-sion copings would require the pins to emerge through thedenture teeth. If a ball attachment-retained denture isbeing relined, no impression copings are normally used(except for AstraTech, which have ball attachment impres-sion copings).

Figure 17.25

The remaining clip is removed, space is created for theimpression copings and space is created for the impres-sion material except for the stops marked. For a ballattachment-retained denture, space is created for the ballattachment (and coping if using an AstraTech ball attach-ment) and impression material.

Figure 17.26

The impression is made using Impregum (Espe, D-8229Seefeld, Germany) impression material. This material issufficiently rigid to hold the prosthodontic components.The position of the denture is rehearsed before theimpression is made and is checked while the impressionis being made by reference to the opposing denture.


Figure 17.27

The bar impression copings are removed from theabutments and are attached to the abutment replicas.

Figure 17.28

The impression copings, attached to the laboratoryabutment replicas, are inserted into the impression. For aball attachment-retained denture, ball attachment replicasare inserted into the impression.

Figure 17.29

Plastic healing caps are attached to the standardabutments in the mouth to prevent food debris and calcu-lus from entering the internal thread or to prevent damagefrom opposing teeth when present. Ball attachmentsrequire no such caps. If a previous denture is available, itcan be modified to fit over the healing caps or ball attach-ments. The bar is retained for the laboratory procedure.

Figure 17.30

The impression is disinfected and boxed and the cast ispoured. The cast is mounted on the lower member of anarticulator and an overcast is attached to the uppermember to record the position of the occlusal surfaces.


Figure 17.31

The denture is separated from the cast and the bar isattached to the laboratory replicas.

Figure 17.32

The new clips are positioned on the bar with appropriatespacers. The replicas, bar and clips are covered withplaster, except for the retention tags. In the Nobel Biocaresystem, the denture does not rest on any part of the barassembly. With a ball attachment-retained denture, newretainers would be positioned on the replica and coveredwith plaster, except for the retention portion of theretainer. The titanium alloy matrix has a plastic insert sothat the circlip and cover are not flasked.

Figure 17.33

The impression material is removed from the denture basetogether with sufficient acrylic resin so that the denturecan be positioned via the overcast without any part of thedenture touching the clips or cast.

Figure 17.34

Once positioned, the borders of the denture are completedwith wax. Then the cast is removed from the articulatorcomplete with denture and flasked in the usual way. Thenew base is processed via a standard heat-curing method.

get used to the new contour after several weeks,a different retention system such as ball attach-ments or magnets may have to be considered.

Maintenance schedule

After all normal post-insertion adjustments havebeen carried out and the patient is comfortablewith the new implant dentures, the patient shouldbe seen at least once per year for review(Mericske-Stern et al, 1994). The patient shouldbe asked to make contact immediately if there areany sudden changes such as loosening of a baror ball attachment or loosening of the dentures.The latter may indicate fracture of a clip ormatrix, or deterioration of a rubber ring in a ballattachment retainer (Figures 17.36 and 17.37).

At the annual visit, dentures should be testedfor stability on the mucosa and any rockingshould be diagnosed, for example, bone resorp-tion or wear or fracture of a prosthodonticcomponent. Ball attachments should be checkedfor tightness using the appropriate screwdriver.Bars can be removed and individual abutmentschecked for tightness and implants checked forany mobility. With the bar off, any calculus canbe removed easily from the abutments and fromthe bar itself with a plastic instrument. The ballattachment retainers in the dentures should beinspected for any fractures of the tines or deteri-oration of rubber rings. It is probably wise tochange rubber rings at this visit, although therings in Nobel Biocare standard ball attachmentmatrices seem to last for years. Clips in denturesshould be checked for any fractures or loosenessin the resin.

If any repairs or replacements of the denturecomponents are required or the denture requiresrelining, the procedure illustrated in Figures17.21–17.35 can be used. Alternatively, ballattachment retainers or clips can be replaced asan intraoral procedure, as mentioned earlier.Replacement of the intraoral prosthodonticcomponents is usually a simple matter ofunscrewing the worn part and replacing with anew part. If a new bar is needed, the illustratedprocedure again can be used.

The implants themselves should be radio-graphed once per year using the same view(Batenburg et al., 1998), otherwise any changes


Figure 17.35

The relined denture showing the new clips. After the barhas been re-attached to the abutments, the denture isrefitted preferably using a remount procedure to eliminateprocessing changes and errors in positioning the dentureduring the impression procedure.

Figure 17.36

Two 3i O-rings that have deteriorated.

Figure 17.37

New 3i O-rings are easily placed with a suitable instru-ment.

may not be detected. Where bone levelchanges are visible, overloading may beresponsible and it may be worthwhile remount-ing the dentures and re-examining the lateralocclusion. The denture teeth can be adjusted toreduce the anterior guidance where necessary.

Bibliography

Batenburg RH, Meijer HJ, Geraets WG, vander Stelt PF(1998). Radiographic assessment of changes inmarginal bone around endosseous implants support-ing mandibular overdentures. Dentomaxillofac Radiol27: 221–4.

Chan MF, Johnston C, Howell RA (1996). A retrospec-tive study of the maintenance requirements associatedwith implant stabilized mandibular overdentures. Eur JProsthodont Rest Dent 4: 39–43.

Hemmings KW, Schmitt A, Zarb GA (1994).Complications and maintenance requirements for fixedprostheses and overdentures in the edentulousmandible: a five year report. Int J Oral MaxillofacImplants 9: 191–6.

Mericske-Stern R, Steinlin Schaffner T, Marti P,Geering AH (1994). Peri-implant mucosal aspects ofITI implants supporting overdentures. A five-yearlongitudinal study. Clin Oral Implants Res 5: 9–18.

Watson RM, Davis D (1996). Follow up and mainte-nance of implant supported prostheses: a comparisonof 20 complete mandibular dentures and 20 completefixed cantilever prostheses. Br Dent J 181: 321–7.

Watson RM, Jemt T, Chai J, Harnett J, Heath MR,Hutton JE, Johns RB, McKenna S, McNamara DC, vanSteenberghe D, Taylor R, Herman I (1997).Prosthodontic treatment, patient response, and theneed for maintenance of complete implant-supportedoverdentures: an appraisal of 5 years of prospectivestudy. Int J Prosthodont 10: 345–54.


Page numbers in italics denote figure legends. Wherethere is a textual reference to the topic on the samepage as a legend, italics have not been used.

3i components 78, 251

abutment analoguesfixed bridgework 204, 205implant dentures 219, 220, 223single tooth 162, 177

abutment impression copings 202–3, 204abutment impressions 171abutment protection caps 202, 210, 222, 223abutment screws 158, 166, 241

access 108, 114, 169, 186checking and sealing 180, 210loosening and fracture 240–1, 242

abutment selection kits see abutment try-in kitsabutment try-in kits 162, 175, 193, 200abutment types

fixed bridgework 189, 190–5single tooth restorations 157–68, 158

abutment–crown, one-piece 165abutments 7

angled design 191, 200angulation 65, 164, 166, 167, 193, 195for bridges 168, 196–206ceramic 166–7computer-generated 158, 166, 195connection 101–2, 103

fixed bridgework 68, 121single tooth implants 175, 176

emergence profile 173–4height 157and holder 158and hygiene 247for implant dentures 231and implant diameter 117, 193and impressions 195–6interocclusal space 174length 173, 174, 215loose 237, 239orientation 174for provisional crowns 182

retrievability 174–5seating 195selection of 168, 175, 215–16soft-tissue depth 171, 173, 191standard 158, 161titanium 158, 247, 248, 249see also fully customized abutments; healing

abutments; prepable abutments; see also under specific manufacturers

acid-etched implants 9, 12acrylic dentures 42, 44, 55, 66, 207, 253acrylic-resin denture repair 254, 255adhesive bridgework 44aesthetic assessment 30aesthetic zone flap design 97–101aesthetics 27, 28, 29, 175

and angulation 108, 110and ridge resorption 56

alginate impression material 217allografts/allogenic grafts 132alloplasts/alloplastic grafts 132, 133anaesthesia 68, 238

of mental nerve 149, 237analgesics 94, 95angled implants 9, 110, 111, 112angulation 43, 105–12, 111, 112, 174

and abutment choice 164, 166, 167, 193, 195after jaw resorption 65average root angulation 111and crest splitting 148development of 106–7, 115, 116of early placement sites 125–6, 130in fixed bridgework 117, 119, 191and force direction 64and indicator posts 94of single tooth implant 42and use of stents 92

antibiotics 94, 95, 138, 235–6for early placement 124, 125topical 247

anti-rotational devices 12, 14, 158, 160, 161for bridgework 190, 191, 206

antiseptic rinsing 94, 236articulating paper 209, 231articulation of models 177

Index

articulators 177, 226–8, 231semi-adjustable 206, 225, 227

assessment 35, 71, 124AstraTech system 122

abutmentsProfile BI 162, 172, 188ST 14, 158, 161, 171, 195Uni-abutments 185, 191, 198, 206, 216

ball attachments 77, 220, 223ball impression copings 222cylinders 78diameter of abutments 118implant–abutment junctions 13, 102implants 8, 49, 70, 91, 199, 206

and bone level 16–17for bridgework 188placement 116spacing 117ST 8–9, 38, 40, 105, 162, 165

for early placement 126, 127placement 109, 110, 113, 158, 172

surfaces 10, 11, 92impression copings 220magnet system 77, 78matrices 78narrow-diameter 48restoration maintenance 248round bar and small clip system 77–8, 229

augmentation see grafting/augmentationautogenous bone grafts 132, 134–40

in immediate/early placement 126for sinus lift procedure 141, 145

bacterial contamination 12, 245from implant–abutment junction 16–17

ball attachmentsfracture 254impression technique 219–20maintenance 261replicas 259rescue kits 254retention caps 223, 224, 229selection for implant dentures 215–16

bar and clips 76, 79, 79–80, 228fitting 253maintenance 261

bar impression copings 222, 223bicortical fixation 90biomechanical failure 47Bio-Oss 132–3blanching of soft-tissues 165, 173, 175, 177, 208,

252block bone harvesting 134, 135, 138bone

density 58, 59, 73deposition 18grafting see grafting/augmentation

hardness and thermal injury 85, 236, 237harvesting 134–8, 140healing 15, 18, 19–20height 32, 52, 148levels 3, 243–4, 261loss 243, 243–4, 245

gutter 246progressive/continuous 4vertical 28, 33, 140

quality 19, 74and implant dentures 80and loading protocols 20poor 5, 7, 122

quantity 18–19, 74removal 102, 103, 125resorption 18, 54, 74

continued 257and implant positioning 105

thickness 73visualization 97, 99

bone mill 138bone morphogenetic proteins 131, 132bone resorption

see also graft resorption; jaw resorption; ridgeresorption

bone to implant contact 6, 12bone wax 137bone width 31Brånemark protocol, original 20Brånemark system 5, 14

abutment connection 102, 241and bone level 16fixed bridges 185head level 119implant placement 117, 129implant–abutment junction 12–13implants 8, 10, 115, 117, 241length of implants 7radiographic definition 3tapered implants 91

Brånemark type bridges 55bridge screws 198, 209–10bridges

Brånemark type bridges 55cementation 210full arch see full-arch implant bridgesloss 33placement 208screw-retained or cemented 185, 188–9

buccolingual positioning 105, 106

calculus 247, 261cancellous bone 6, 135, 136, 148cantilever extensions 21, 252cantilever forces 47cantilever units 183, 208, 212

distal 62, 63, 183, 185

264 INDEX

cantilevered crowns 65caries 211, 212casts 196, 225

implant head 175, 190laboratory 195opposing 206primary 217study 29, 32, 34verification 223working 169, 176, 190, 220, 221, 253

cementation 180, 210, 239problems 161

cementation vents 110, 180, 239cemented bridges 185, 188–9

abutments 192–5, 203–6complex case 194provisional 206, 210selection/seating 203–4, 206, 210

cemented crowns 42–3, 50, 108, 110, 166temporary 178

Cendres and Metaux bars 78, 79Cendres and Metaux clips 77–8ceramic abutments 166–7, 175chin as graft donor site 136, 144, 238chlorhexidine mouthrinse 94, 95, 236, 247cleaning

professional 240, 243see also oral hygiene

clinical examination 35–8for fixed bridgework 53–6initial 31–2

closure screws 93, 118cobalt–chromium-based dentures 253, 257communication with patient 29, 68, 231–2complications 235–8, 238–42, 251–5computed tomography scans 38, 57–60, 73

artefacts 59and nerve damage 238and sinus lift procedure 141

computer software for CT 58–9computer-generated abutments 158, 166, 195concavity, labial 113conical abutment design 13, 14, 16, 17, 77, 158

and seating 202conical drills 107, 118conical implant head 107connective-tissue grafts 150, 151, 152copings 176, 211

acrylic 164fixture head 216, 222, 223plastic ‘burn out’ 161porcelain 161retained 177temporary 158transfer 206, 220

cortical anchorage 122cortical bone 6, 122, 133, 134, 135

countersinking 119, 122cover screws 116, 130, 236crest dilation/splitting 147–8Crestosplit 148cross-infection and grafts 132, 133crowns

all porcelain 167cantilevered 65cemented 42–3, 50, 108, 110, 166, 178linked 181retrievable 42–3, 50

custom trays 218construction 217–20, 223

cutting speed of drills 90cylinders 75, 76, 78

bridge 185, 186, 191, 198fixture head 252gold 161, 168, 229gold and porcelain 158

Dahl appliances 174dead space 79, 252decalcified freeze-dried bone allograft (DFDBA)

132decementation 239dehiscences 111, 119, 134, 147, 236

bone 98delayed loading 20dental disease 4, 245dental panoramic tomograph (DTP) 32, 33, 38, 40–1,

57for implant dentures 73

dentinogenesis imperfecta 128denture fitting 67denture support 69dentures

existing 71–3implant 69–80

definition 69diagnosis and planning 74indications for 69–70

mucosally supportedand delayed loading 20

selection of teeth 225deproteinized bovine bone mineral 132–3depth-measuring devices 200developmentally missing teeth 30, 36, 40, 142DEXA scans 5diagnostic casts, articulated 72diagnostic denture 33, 57diagnostic set-ups 29, 32, 34, 197

for fixed bridgework 53–6for single tooth 40, 42

diagnostic wax-ups 178, 199diagnostic work-ups 199diamond disc saws 135, 136diastemata 105

INDEX 265

direction indicators 92, 107, 111, 116, 117distraction osteogenesis 148–9divergent implants 79double helical threaded implant 91DPT see dental panoramic tomographdrills 90

conical 107, 118internally irrigated 19, 85record of usage 90stepped 87, 121, 128

Dual Energy X-ray Absorptiometry 5

early implant placement 123, 129early loading 20edentulous ridge 31–2, 35, 101emergence aesthetics 64emergence profiles 42, 43, 107, 110, 157

abutment selection 173–4factors influencing 114optimum 108removable dentures 44temporary restorations 178and use of stents 92

end of treatment 210, 211endarteritis 5endodontic status evaluation 54examination

clinical 31–2, 35–8, 53–6of existing dentures 71–3for implant dentures 71–3occlusion 36, 38radiographic 35, 38–42, 57–60, 73–4, 210,

261excursions of lower jaw 56extraction socket 123, 124

management 146preservation 146

extraction, tooth/root 124–5

facebow 224, 225record 196, 224, 225

fenestrations 134, 147fibrosis 237fibrous tissue encapsulation 15, 20, 90fitting of restoration 179–81fixed implant bridges 67–8, 70, 74, 117, 119

hygiene maintenance 247prosthodontics 183–212vs single units 65–6, 183

flaps 88buccal 106, 121, 129closure/suturing 93, 95, 97, 116, 121

re-adaptation 101in submerged protocol 89, 107

design 94–5, 128in abutment connection 101–3in aesthetic zone 97–101

elevation 87, 95, 97, 113for fixed bridgework 115

palatal 106, 121, 129reflection 97, 98, 102reshaping 101, 102, 103

follow-up 210, 232, 239, 249force direction 64, 119, 122force distribution 51fractured mandible 32, 238Frankfurt plane 105, 111, 112free gingival grafts 151, 152, 243freeway space 72, 223Friatec

abutmentsfor fixed bridges 191Frialit 2 14, 118

for fixed bridges 185MH 6 161

seating 195implant-abutment junctions 14implants 10, 118

bridgework 118, 121, 186early placement 126Frialit 2 9, 39, 51, 87, 128single tooth 114, 176surfaces 12, 92

irrigated drills 85, 87, 90matched drills 9screw-retained crown abutments 168stepped cylinder implants 91

Friatomes 148FRIOS MicroSaws 135full-arch bridges 62, 67, 188

mandibular 63maxillary 56, 62, 63

fully customized abutmentsfixed bridgework 119, 190, 194, 195single tooth 158, 165–6, 174

general anaesthesia 94, 137gingival contours 178gingival recession 36, 98gingival replicas 207gingival retraction cords 178, 204gingival tinting in dentures 230Gore-Tex 132, 133graft resorption 132, 133, 138grafting/augmentation 101, 131–52, 238

allografts 132alloplasts 132, 133and antibiotics 236autogenous grafts 126, 132, 134–40, 141, 145in crest splitting 148donor sites

chin 136, 144, 238iliac crest 137–8, 140palate 150, 151, 243

266 INDEX

failure 253and flap design 99host bed perforation 134and implant dentures 72, 74and implant placement 130, 140, 147inlay grafts 140, 142, 143of large alveolar defects 140materials 131–4

particulate 130, 145, 146bone chips 133, 134, 137, 138, 147

with maxillary osteotomy 142onlay grafts 54, 73, 74, 140, 149for progressive resorption 56sinus 51soft-tissue 149–52, 243

connective-tissue 150, 151, 152stability of graft 137–8, 147xenografts 132see also guided bone regeneration

grit-blasted implants 10, 12, 90guide pins 119, 130

for bridgework 184, 192, 195guided bone regeneration 132, 133–4, 236,

247and implant placement 134, 140

harvesting sieves 137healing abutments 102, 167, 236

damage from existing denture 253fixed bridgework 121, 211in impressions/casts 217length 103removal 175, 202, 215, 231single tooth implants 50, 176

healing caps 169, 184, 259heating see thermal injuryhexagon joints 12, 13, 14, 76hydroxyapatite-coated implants 7hygienist treatment 239

iliac crest bone harvesting 137–8, 140iliac crest inlay graft 142immediate loading 20immediate replacement protocols 91, 236implant analogues 162implant connectors 21implant dentures 79–80, 251–62

abnormal contours 251, 252completion 228–31complications

after prosthdontic stage 254–5before prosthodontic stage 251–3during prosthodontic stage 253

fracture/wear 254, 255, 256–7insertion 231–2maintenance 261–2mandibular 74, 79–80, 93

maxillary 80patient assessment for 71prosthodontics 215–32as provisional prostheses 70–1

implant fractures 242, 255implant head 107

casts 175, 190and flap design 102impressions 161, 195, 196

copings 167, 172, 182, 195level of 94, 119, 122models 201

implant surgery 85–95implant to bone contact 6, 12implant–abutment junction 7, 38, 241

bacteria from 16–17design 12–14level relative to bone 16, 17submucosal 122

implant/prosthesis ratio 56, 143, 149implants 5

configuration 62–4design 7–18diameter 7

selection 36, 37, 47, 48, 60, 114and emergence 164

dimensions 21, 60, 185distribution 21, 61–4, 253early placement 124, 126, 130failure 242, 252–3, 254, 255

early 235, 236–7rate 71

installation 115length 7, 60, 85, 90–1maxillary vs mandibular 4number 61, 61–4, 80placement 92–4, 109

after sinus lift 144, 145anterior teeth 105–14crest splitting 148by CT scan 60delayed-immediate 123early 125–6fixed bridgework 115–22Frialit 2 implants 87grafting and 130, 140, 147and guided bone regeneration 134, 140immediate 123, 127, 128immediate/early 124, 125–6multiple 115, 117–19, 148, 149onlay grafts 140, 149superficial 252timing 123–4

positioning 105, 115, 165preparation for 87, 88–9, 90, 93radiographic checks 261shapes 8–10

INDEX 267

implants (cont.)spacing 21, 80, 115, 117–19stability 90–2, 128, 147

and bone healing 18in crest splitting 148in fixed bridges 191

submerged, exposure of 236success 3, 4–5, 254surfaces 9, 16, 52, 80, 92

sprayed/coated 7, 10–12, 122and stability 90, 92

threaded 91, 126in unplanned position 251–2see also specific types and manufacturers

impregum 170, 179, 199, 219, 261impression coping pins 219impression copings 112, 158, 170

abutment 202–3, 204and abutment analogues 177bar 220, 223, 258, 259for fixed bridgework 184implant head 167, 172, 182, 195in impressions 218linked 196matched 158, 161in pick-up impression 178plastic push-on 175, 176, 220for reseating impressions 205in wax rims 223

impression materials 177, 203, 217–18see also impregum

impression technique 218–20impression trays

custom 217–20, 218, 223stock 170, 177, 202–3, 217

impressions 175, 177–8, 181–2abutment selection 168, 195–6

cemented bridges 203–6screw-retained bridges 196–203

final 217–20, 219, 221, 222, 223implant head 161, 195, 196primary 216–17, 217secondary 178verification 206

incisionscrestal 99, 102mid-crestal 97relieving 97–8, 99, 100, 101

angles 102for bone removal 102flared 97, 98

split thickness 100, 150incisive canal 109, 113, 238

flap reflection 98implant positioning 105, 165

incisive nerve 149, 238indicator posts 94

infection 19, 235, 236, 237bacterial 244, 245in bone grafting 134, 146and early placement 125

inferior dental bundle 32, 149, 237–8inferior dental canal 148inflammation 239, 242, 243, 244

persistent 243tissue removal 247

inflammatory lesions 16, 246inlay grafts 140, 142, 143intercuspal occlusion 209intercuspation 226, 227interdental papillary regeneration 152interocclusal records 197, 225, 226–8, 231

material 224, 225protrusive 228

interocclusal space 174, 225, 227see also freeway space

irradiation and bone quality 19irrigated drills 19, 85, 87–9irrigation, external 85, 87–9

for bone harvesting 135ITI/Straumann see Straumann

jaw relations 56, 72, 197, 223jaw resorption 65, 66, 122

see also ridge resorptionjigs for seating 191, 195junctional epithelium 16, 17

keratinized tissue 32, 101lack of 93, 98relocation 102

labial flanges 29, 31, 33, 54, 57laboratory procedures 179, 207landmark areas 217, 228lateral movements 180, 208, 209Le Fort 1 down-fracture 140, 142lesions 4, 16, 246lining, temporary 223linked crowns 181lip support 29, 54, 55, 56

from existing dentures 71with/without labial flange 57

load-bearing capacity 62loading 15, 19–21

transmucosal 67, 68local anaesthesia 94, 134–5, 146, 175long-span bridges 183luxators 146

machined surfaces 10, 91magnification of images 32, 41, 73maintenance 68, 238–42

of fixed bridgework 70implant dentures 232, 261–2

268 INDEX

marginal fit 164masticatory efficiency 226mattress sutures 152maxillomandibular relations see jaw relationsmeasurement for abutments 215measurement of scan images 60measuring gauges 91, 130, 223medical history 71melanin pigmentation 230membranes 146

bone grafting 137, 138, 147mental nerve 98, 116, 237–8mesh in grafting 137, 138mesiodistal positioning 105, 106micromovement 15, 68microthreaded implants 9, 16, 126MirasCone 204molar replacements 47–52molar space 49mouthguard, soft PVC 253mucosal grafts 149–52, 243mucosal lesions, severe 4multiple implant placement 115, 117–19, 148,

149multiple single-tooth units 65–6, 181, 183

natural dentition 54–5, 70necrosis 237nerve transpositioning 149neuromuscular control 69niobium 7Nobel Biocare

abutmentsCerAdapt 175CeraOne 158, 166, 167, 171

impression copings 170Estheticone 117, 168, 190–1, 202

impression copings 205multi-abutments 12, 191, 202seating 161, 171standard 191, 215–16, 218, 222

ball attachments 216, 219–202.25mm 77, 216, 221retention caps 223, 224, 251standard 76–7, 79, 80, 221

Brånemark style implants 64cylinders 75, 76drills 90

irrigated 88–9fixture head copings 216, 222, 223fixture head cylinders 252implant denture components 74–7implants 78, 161, 170

for fixed bridgework 190, 192, 194narrow-diameter 8, 37narrow-platform 100, 158regular platform 158

self-tapping 8wide-diameter 39, 50, 51, 158

matrices 77, 230, 255, 256, 261ovoid bar and clip system 75, 76, 252

Macro-Ovoid 230, 231, 252rescue kits 254round bar and small clip system 74, 75, 80, 229,

252U-shaped bars 75

non-resorbable membranes 133non-submerged systems 10, 14, 15–18, 21, 87, 119

and flap design 101

occluding relations 72occlusal contacts 36, 208

checking 179, 180occlusal factors in bone loss 246occlusal indicator papers 179occlusal plane 196occlusal records 206occlusal scheme 20–1occlusal surfaces 226occlusal wear 240occlusion 208–9

bilateral balanced 228–9of completed restoration 179examination 36, 38

occlusion adjustments 231–2, 261occlusion rims see wax rimsoligodontia 116, 142one-piece abutment–crown 165onlay grafts 54, 73, 74

implant placement 140, 149for longer implants 149

oral hygiene 210, 240, 243, 244considerations 187maintenance 247, 249soft-tissue problems 149, 150techniques 181

orientation 60, 162, 174O-rings 78, 261osseointegration 5–7, 19, 126, 134

failure 243, 252–3, 254factors 85, 90, 236

histological section 6and loading 20time reduced 10, 11, 52

osseous coagulum 130, 137, 138, 145osteitis 125osteoconduction 131, 132, 133osteoinduction 131, 132, 137osteomyelitis 32osteoporosis 5osteoprogenitor cells 132osteoradionecrosis 5osteotomes 146, 147, 148osteotomy 56, 142, 146, 238

INDEX 269

overcasts 259, 260overcontouring 181overdentures 56overextension 232overgrowth see under soft-tissueoverloading 183, 229, 240, 241, 244

checks for 261

pain 237postoperative 95, 235

Palacci strategy 102–3palatal coverage 70palatal donor sites 150, 151, 243papillae, gingival 35

disturbance of 100form 103preservation of 98, 99, 100, 152prosthetic 244

paraesthesia 149, 237, 238parafunctional activities 21, 71passive fit 228, 229patient instructions 180–1, 210perforation of cortical bone 133, 134perforation of recipient bed 137peri-implant mucositis 242peri-implantitis 242, 244, 245–7

management 247periodontal disease 4, 67, 245, 246periodontal measuring probe 171, 200, 215, 243periodontal pocket tissue 125periodontal status evaluation 54periodontitis 67, 246periotest values 90periotomes 125, 146pick-up impressions 178, 203

copings 199, 203planning

dentures, implant 68, 74fixed bridges 53–68single anterior teeth 35–45single molars 47–52

plaque retention 239plasma-sprayed implants 10, 11, 12, 122

and stability 90, 92plastic ‘burn out’ copings 161polished collars 10, 11, 12polyether impression material 217–18porcelain abutments 166–7, 175porcelain copings 161post-ceramic soldering/welding 207postoperative care 95preoperative care 94prepable abutments 158, 161–2, 166, 174

advantages/disadvantages 164–5in fixed bridges 188, 192–3, 195, 203and gingival contours 171impressions for 177

preparation 164and temporary restorations 178try-in kits 200

pressure areas 231pressure indicator paste 231, 232pre-tapping 8, 90probing depths 242, 243Procera 166, 195proclined ridge forms 31prognosis of natural dentition 54–5proliferation see under soft tissueprosthesis/implant ratio 56, 143, 149prosthetic gum work 28, 55, 56, 62, 244prosthodontics

components 74–9fixed bridges 183–212implant dentures 215–32single tooth units 157–82

proteoglycans 6protrusive movements 180, 208–9provisional/temporary bridges 67provisional/temporary prostheses 32, 42, 43–4, 66–8, 178

bridges 195, 200, 206–7diagnostic 29, 31implant dentures as 70–1tooth supported 20

psychological problems 71PTFE membranes 133, 140putty masks 197

radiographic examination 38–42fixed bridgework 57–60, 210implant dentures 73–4, 261ridge 35

radiographic markers 40radiographic screening 32radiographs

baseline 243–4bone quality assessment 19sinus lift procedure 141, 145

radiolucency, peri-implant 3radiotherapy 5recipient bed 137relining procedure 253, 256, 257removable dentures 44, 56, 66–7removable prostheses 42, 240, 247repairing procedure 253, 255–6replacement

of denture components 254of maxillary central incisors 106, 109of maxillary lateral incisors 110, 111, 112

rescue/retrieval kits 241, 254reseating impressions 203, 205resonance frequency analysis 19, 90resorption see bone resorption; graft resorption; jaw

resorption; ridge resorptionrestorative status evaluation 54

270 INDEX

retention caps 223, 224retrievability 50, 108, 174–5, 185ridge augmentation 68ridge defects 105ridge exposure 97, 121ridge mapping 31, 35ridge resorption 28, 29, 54

and angulation 108and denture type 69DPT scan 70evaluation/recording 56, 71–2and screw-retained crowns 43see also jaw resorption

ridge splitting sets 148ridge thickness assessment 74ridge width 52, 57ridge-lapped margins 43, 44ridge-lapped prostheses 31, 108, 109, 113

hygiene maintenance 247root size and shape 124root surface exposure 35root tapering 66rubber rings 78, 261

saddle restorations, free end 185safety margins 238sand-blasted implants 9, 10, 11, 92

see also grit-blasted implantssaucerized areas of bone loss 246scaling of prostheses 247, 249Scanora 30, 40, 73scarring 237, 253scout view 58screw fracture 241, 242screw loosening 240–1screw retrieval kits 241screw-retained bridges 62, 185, 186–7, 211

abutment selection 190–2, 196–203advantages/disadvantages 188selection and seating 200–3

screw-retained casting 49screw-retained crown abutments 158, 167–8screw-retained crowns 42–3screw-retained restorations 108sealing screws 87, 89, 93seating 161, 171, 210seating failure 239, 241self-tapping implants 8shade matching 158, 178

gingival material 206shimstock 179, 208, 209short-span bridges 183SIM/Plant software 58, 59, 60single tooth implants 8–9, 36, 42, 44

anterior 35–45, 105–14complications 239flap design for 98, 100

hygiene maintenance 247, 248molars 47–52multiple 65–6, 181, 183prosthodontics 157–82

single-implant molar replacement 50–2single-stage implants 80, 101, 215sinus graft 51sinus lift 138, 140–1, 144, 146

transalveolar 146sinus membrane 141, 145, 146sinus tracts 237skeletal malformation 142, 194small tooth spaces 36, 37smoking 19, 148, 236, 244

and implant success 4–5, 254soft tissues 44, 125, 131, 242–3

adaptation 10, 12augmentation 68breakdown 134depth 171, 173grafts 149–52, 243

connective-tissue 150, 151, 152manipulation 94–5, 152maturation 150, 152overgrowth/proliferation 79, 80

with bridges 243, 244with dentures 251, 252, 258

problems 243aesthetic 149, 150, 151–2functional 149, 151, 239

profiles 101, 103, 164replicas 55, 160, 162, 207

gumwork 28, 55, 56, 62, 244implant head impressions 195, 196

support see lip supportthickness 31–2, 191

solid-screw implants 8, 9space 47, 48

between adjacent teeth 174for implant dentures 71for molar replacements 47

speechand bridges 206, 210and implant dentures 251, 258, 261

spiral tomography 40stability

of dentures 69of grafts 137–8testing 210, 261

stabilization of dentures 70, 79standard abutments 158, 161standard bar impression technique 218–19, 220stents 34, 75, 111

acrylic 92, 93, 106, 107, 121in computed tomography 40in edentulous jaws 94plastic 130

INDEX 271

stents (cont.)plastic ‘blow-down’ 92radiographic 29, 30, 57, 60, 66, 73surgical 29, 30, 57, 64, 66, 92

fixed bridgework 115, 119, 199impression copings 182

stepped cylinder implants 9, 10, 39, 91, 121for immediate replacement 126, 128

stepped drills 87stock impression trays 177, 202–3, 217

modified 170Straumann protocol, original 20Straumann system

abutments 118, 161, 195Octa/SynOcta 78, 168, 184, 185, 191, 216tightening 202

ball attachments 78retention caps 223

bars and clipsDolder 229, 230egg-shaped 78, 79

components 78–9implant-abutment junctions 13–14, 17implants 117, 122, 169, 215

aesthetic line 14angled push-fit 112and bone level 17, 252for fixed bridges 184, 211and flap design 101fractured 242hollow 9–10installation of 118length of 7, 85, 90surfaces of 10, 11, 90, 92

matrices 230, 256measuring device 91non-submerged system 15retention anchors 78, 222transfer copings 220

studies 20, 80longitudinal 5, 17, 235

study casts 29, 32, 34submerged systems 14–18, 21, 88–9, 107,

119success 3, 4–5Summers’ technique 146surgical sequelae 235–8Surgicase interactive software 60sutures 95, 97

tapered implants 66, 91, 118see also stepped cylinder implants

tapping see pre-tapping; self-tappingteeth

coverage/exposure of 27, 28, 29assessment 35

natural 210–12, 225

temporary copings 158temporary prostheses see provisional/temporary

prosthesesthermal injury 19, 85, 90, 237, 238threaded implants 91, 126timing of denture fitting 67TiO blasted implants 10, 11, 16, 92titanium

abutments 158scaling 247, 248, 249

frameworks 207and osseointegration 6, 7sprayed on implants 10

titanium alloys 7titanium oxide 6

see also TiO blasted implantstobacco smoking see smokingtomograms, sectional 30, 38–42, 40–2, 73

bone quality assessment 19tomographic section thickness 41tomography, conventional 57, 238tooth space measurement 35torque devices 175, 231, 241

electronic 166, 175torque insertion forces 90torquing 202transalveolar sinus floor elevation 146transfer copings 206, 220transition profile 114transitional implant systems 68transitional restoration 29transmucosal collar 13, 17, 122transparent overlays 41, 73, 126, 238trapdoors 141, 145tray material, acrylic resin 223tray stops 231trays, impression see custom trays; impression trays;

stock impression traystreatment

planning 27–34schedules 34, 44–5, 68, 74

trephine harvesting 134, 136–7trephines 136trial set-ups 72tripod arrangement 63, 64try-in 179, 194, 207–8two-implant molar replacement 49two-stage implants 80, 89two-stage protocols 107, 215

vertical height 56, 174vertical positioning 112–14vertical space 70, 91, 173

wax rims 196, 206, 223wax-ups 178, 199wear simulation 225, 226

272 INDEX

Willis gauge 223working casts 169, 253

with abutment analogues 220with abutment connections 176with ball attachments 221implant heads 190

working models 160, 187, 204implant head impression copings 174, 182with soft-tissue replicas 179

wound breakdown 98, 138, 236wound closure 137, 138, 146

xenografts 132

young patients 36

INDEX 273

Implants in Clinical Dentistry 2002 - Palmer

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