CliniCal papers

1 Based on the tendency of a material to deform when opposing forces are applied as expressed by

the avg. elastic (Young’s) modulus values of the two materials (Titanium 110 GPa or PEEK 4GPa). 2 Kurtz, S (2012). “PEEK Biomaterials Handbook”. Edition 1, Oxford, Elsevier Inc.

dental prosthetiCsalternative to metalWhy dentists Choose JUvora™

moreshoCK aBsorption126x

Juvora Ltd Hillhouse International, Thornton Cleveleys, Lancashire FY5 4QD United Kingdom | +44 (0) 1253 897555 | info@juvoradental.com | www.juvoradental.com

• CAD/CAM dental disc made from PEEK-OPTIMA™, a high performance polymer

• An alternative to metal for long-term2 fixed and removable prosthetic frameworks

• More shock absorption1 than Titanium, addressing problems with parafunction

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60 Private Dentistry October 2015

The high-performance polymers (HPPs) are the uppermost class of plastics, possessing better temperature and chemical stability and mechanical properties than the commodity plastics, but typically being manufactured in lower volumes and costing more.

The family of HPPs that have entered dentistry are called the Polyarletherketones (‘PAEKs’), of which there are several members with varying chemical structures. Many of us in the dental industry are inadvertently familiar with the family member called PEEK (Polyetheretherketone), through its use in healing caps, temporary abutments and scan bodies.

However, the reason for the recent enthusiasm surrounding PAEKs has been their potential for use as a metal alternative in broader indications such as removable dentures (Figures 1 and 2) and implant borne prosthetics (Figure 3). It is here that

High performance polymers - part one

the shock absorbing characteristics of the material could be extremely interesting for immediate loading or long term frameworks (Figure 4).

In this first article of a series of six, the background to these materials will be described. This will be followed by a series of case studies describing their use in removable and implant-borne prosthetics.

The PAEK familyPEEK is the most well-known and most widely used PAEK family member. PEEK was invented in the UK in 1978 (ICI – now as Victrex plc) and was selected by aerospace, semiconductor, automotive and medical industries as a standard material of use in all these sectors. It is typically used as a metal replacement, due to its strength to weight ratio and corrosion resistance. Other family members also exist which are variations of the chemistry (eg PEK and PEKK), and these materials can also be filled with pigments or reinforcing agents. In their unaltered, unfilled state the materials are beige in colour.

PAEKs in MedicalSeveral of the properties of PEEK that were being exploited in industry (eg strength-to-weight ratio, chemical and wear resistance, radiolucency, and reduced stiffness versus metals) were naturally intriguing for medical use. The first published PEEK medical research came in the 1980s

(Williams et al., 1987) followed by the first implantable grade from Invibio Biomaterial Solutions in the 1990s (Victrex plc./Invibio Ltd, UK). Medical grades have a much tighter specification, and increased quality control than industrial grade materials, which is important in the wake of the silicone breast implant scandal (see http://www.nhs.uk/conditions/breast-implants/pages/pip-introduction.aspx). PEEK remained the only medical PAEK for many years.

Spine surgeons particularly adopted Invibio’s PEEK, liking the reduced Young’s Modulus (stiffness) of the material and the scatter-free CT and MRI imaging. PEEK has since become the standard alternative to titanium for load bearing spinal cage devices for the spine. Today, manufacturer Invibio claims PEEK has been used in around five million implantable devices, spanning some 500 separate US FDA 510k regulatory clearances. In more recent years, additional versions of PEEK and PEKK have appeared on the medical marketplace, but have been limited in use.

PAEKs in dentistryShort term devices such as temporary healing caps and abutments have been sold direct to dentists through the dental companies for many years. In these situations, either unfilled PEEK or PEEK with a 10% titanium dioxide pigment filler are typical and have been used in these

In the first of a series of articles, Professor Paul Tipton gives us an introduction to high performance polymers in dentistry. Here he discusses polyether ether ketone (PEEK), a new material for framework fabrication in prosthodontics

Professor Paul Tipton BDS MSc DGDP RCS is an internationally acclaimed Specialist in Prosthodontics who has worked in private practice for more than 30 years. He is the founder of Tipton Training Ltd, one of the UK’s leading private dental training academies and the author of over one 100 scientific articles for the dental press. He gained his Master’s Degree in 1989 from the Eastman Dental Hospital and London University and started teaching on the University of Manchester’s MSc in Restorative Dentistry. He is now Professor of Restorative and Cosmetic Dentistry at the City of London Dental School. His private dental training academy, Tipton Training, was founded in 1991 and to date over 3000 dentists have completed a one year course at the Academy. He practices at his clinics in Manchester, Watford and Harley St. London. All details can be found at www.drpaultipton.co.uk

Aims and objectives To explain the properties of PEEK materials and their recent and future use in dental prosthetics and devices.

Expected outcomes Correctly answering the CPD questions on page 78 will show the reader has understood the development and qualities of PEEK materials relevant to dentistry.

Verifiable CPD hours: 1

Clinical excellence with CPD

Private Dentistry October 2015 61

temporary devices for over a decade.In the case of customised prostheses, the

upstream material or shape becomes the ‘device’ and is regulated and cleared for use for a defined set of indications. Here, the PAEKs have appeared as materials for use in injection press systems or as discs for computer aided design/manufacture (CAD/CAM).

Types of PAEKs for prostheticsThere are now many brands of PAEK dental devices becoming available for use in prosthetic frameworks. The most common formulations of the PAEKs are:• Unfilled, pure 100% PEEK (eg JUVORA, Invibio/JUVORA Ltd). This is a beige material.• 80% PEEK with 20% nanoceramic filler (eg. BioHPP, Bredent GmbH). This is a white material.• 80% PEEK with 20% titanium dioxide filler (eg Dentokeep disc, NT Trading). This is a white material.

• 80% PEKK with 20% filler including titanium dioxide (eg Pekkton Ivory, Cendres and Mettaux). This is an off-white material.

Typically the particle size of these fillers (circa. 300-500 nanometers for the nanoceramic) is not likely to give significant reinforcing properties to the material, since they are not fibres. Instead the fillers act more as a pigment and alter surface topography. These levels of 20% filler will make the material stiffness slightly higher, but consequently also slightly increase brittleness. It should also be noted that the inclusion of titanium dioxide mean that these brands - BioHPP; Dentokeep and Pekkton should not be pitched as ‘metal free’ since this could be in breach of Advertising Standards and/or Governing Bodies. The reader should also take note as to the cleared indications for use as the different materials and forms may have varying clearances.

To date, PAEKs with these specific 20% fillers only have a limited history of use in dental and actually no prior medical history

in any other medical applications. Therefore it is fair to say that the jury is still out as to the effects of adding these levels of these specific fillers to the PAEKs and the author advises the use only of the pure material where there are long-term studies.

Methods of framework manufactureThere are two methods for laboratories to manufacture substructure frameworks from PAEKs. These are: (i) injection moulding or (ii) CAD/CAM.

(i) Industrial injection moulding machines process the polymer under very high speed and pressure (eg. 1000’s bar), which are typically two orders of magnitude higher than the typical bench top pressing machines available to the dental laboratory (eg. 10’s bar). This means that small scale injection moulding of PAEK is no mean feat, due to tight processing windows and design limitations. Also these re-melting of PAEKs can also increase the risk of unpredictable mechanical and physical

Figure 1: PAEK removeable denture

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62 Private Dentistry October 2015

properties (eg brittleness, flexibility, colour, warping) if the framework has not cooled and recrystallised correctly.

Finally, re-melting of PAEK materials can also cause degradation of the polymer (eg generation of phenol) unless very closely controlled using the correct equipment. This polymer degradation can be accentuated by the inclusion of fillers in the materials (such as reinforcing agents or

pigments). Therefore, melt processing of these materials should only be done by a competent laboratory and using the equipment recommended by the supplier.

(ii) The alternative manufacture route uses CAD/CAM technology. This manufacturing route avoids all of the risks mentioned previously for re-melting the polymer. The material properties remain consistent and the framework manufacture

can also benefit from the increase precision and reproducibility of a digital workflow. Although it does require a more significant capital investment by the laboratory, many laboratories are seeing that it is necessary to align with other industries and adopt digitisation to increase efficiencies.

PAEK materials further extend these CAD/CAM efficiencies when compared to milling metal substructures, since there is typically less tool wear and faster milling times and the capital equipment necessary to mill them does not need to be as expensive as machines for milling metal frameworks.

It is the author’s view that the optimum use of these materials only comes from the CAD/CAM milling process as opposed to the injection moulding process.

Polymer propertiesWhen handling a prosthetic framework made from a PAEK, a striking thing is the difference in weight. When identical full arch implant prosthetic substructure frameworks were made from four different materials, the results from weighing were: PAEK 4.9g, titanium 17g, zirconia 23g and cobalt chrome 33g.

However, it is the possibility to introduce shock absorption to a prosthesis that is perhaps the most exciting. This could have positive implications for patient comfort and for damage limitation. In my view, the most relevant mechanical property related to the aspect of shock absorption is not ultimately compressive strength (as is sometimes promoted), but actually flexural strength and elastic modulus.

Obtaining an increasingly stronger material becomes academic since clearly it would be simplistic to prefer the highest value.

Metals have very high compressive strengths relative to PAEKs but are not shock absorbing. Naturally, a design must also consider the influence of thickness and shape as well, but values for flexural strength and elastic modulus are more indicative of the stiffness of a material and how much it will deflect the load. Stiffer materials, like metals, have a high elastic modulus (see Table 1) meaning that metals require high loads to elastically deform them. Therefore, one can look at natural materials like bone for clues as to an ideal for stiffness. Common denture materials like PMMA have an elastic modulus range of 1.8-3.1 GPa, but limited strength. The

‘There are two methods for laboratories to manufacture substructure frameworks from PAEKs. These are: (i) injection moulding or (ii) CAD/CAM’

Figure 2: PAEK removeable denture

Figure 2: PAEK implant-

bourne prosthesis

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PAEKs have an elastic modulus closer to bone (4-5GPa) allowing the framework to be stiffer, yet still shock absorbing. However, PAEKs also additionally possess sufficient strength to be considered as a metal alternative.

ConclusionsThe high-performance polymers called PEEK and PEKK have exciting potential in dentistry as a metal alternative for removable and implant prosthetic frameworks. Their stiffness properties confer

promise as a substructure that could add an element of shock absorption. This may have benefits for patient comfort, addressing parafunction and damage limitation. In the following series of case studies, I shall describe the use of a PEEK high performance polymer as a framework for removable and implant prosthetics.

ReferencesWilliams, D.F., McNamara, A., and Tutner, R.M. (1987) Potential of polyetheretherketone (PEEK) and carbon-fibre-reinforced PEEK in medical applications. Journal of Material Science Letters. February 1987, volume 6, issue 2, pp 188-190.

Elastic modulus comparison of different dental materials and natural bone.

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Questions turn to page 78

Figure 4: Long-term framework in PAEK

68 Private Dentistry November 2015

Polyether ether ketone (PEEK) high-performance polymer has proven successful in many areas of medicine for a number of years and is also gaining an ever-increasing number of advocates in dentistry thanks to its good physical properties and chemical resistance. CAD/CAM processing of PEEK also opens new options. In the following article the authors demonstrate the

In the second article in this series, Professor Paul Tipton and Dr Bernd Siewert look at Polyether ether ketone (PEEK) - a new material for framework fabrication - and consider the processing methods, pressing vs milling and the findings regarding long-term use

High-performance polymers - part two

possibility of milling PEEK in the CAD/CAM procedure from industrially manufactured material blocks (Juvora dental disc) rather than injection moulding, and present long-term documentation of a case involving treatment of bruxism by means of a prosthetic restoration.

Injection-moulding techniqueIf industrially manufactured elements are used for an implant-borne prosthetic restoration they can be overmoulded (thermopress system) with PEEK. This eliminates the need for additional adhesive retention, which can be of particular advantage where little space is available, for example in the anterior region. Furthermore, the injection-moulding technique requires lower financial investment than CAD/CAM fabrication of PEEK frameworks.

The entire fabrication process of wax-up, investing and finishing is time consuming. The procedure with the thermopress system was not fully developed technically. In some cases visible voids and cracks were produced in the framework due to the familiar problems of injection moulding. In these cases the complete fabrication process had to be repeated. It was not always possible to maintain the surface contours of the wax-up exactly due to adjustments to

the surface which were occasionally necessary. This is counter productive, in particular with fully anatomically designed bridge frameworks.

The transition to the plastic phase (heating and subsequent cooling) impairs the material-technical properties, especially with high-performance polymers such as PEEK. There is the risk of changes in the crystal lattice structure. Despite these factors, which may result in a reduction in quality, no problems with regard to crack formation, material fatigue or even fracture have occurred.

CAD/CAM bridge frameworksIndustrially manufactured blanks with approval for permanent restorations have recently become available (Juvora dental disc, Juvora). This material has no additives - it is therefore highly pure - and has been used in medicine for many years (PEEK-OPTIMA, Invibio).

The advantage of CAD/CAM fabricated bridge frameworks is that the material is not adversely affected during the fabrication process, provided it is used correctly. Bridge frameworks, milled from a high-grade, industrially manufactured block (Figures 1-2), undergo no physical changes during the fabrication process and exhibit the same or possibly better material-

Aims and objectives To discuss the properties of PEEK polymers as used in a milled restoration designed by CAD/CAM to treat a bruxism patient.

Expected outcomes Correctly answering the CPD questions on page 88 shows that the reader has understood how the properties of PEEK materials can be best applied for dental applications.

Verifiable CPD hours: 1

Professor Paul Tipton BDS MSc DGDP RCS is an internationally acclaimed Specialist in Prosthodontics who has worked in private practice for more than 30 years. He is the founder of Tipton Training Ltd, one of the UK’s leading private dental training academies and the author of over one 100 scientific articles for the dental press. He gained his Master’s Degree in 1989 from the Eastman Dental Hospital and London University and started teaching on the University of Manchester’s MSc in Restorative Dentistry. He is now Professor of Restorative and Cosmetic Dentistry at the City of London Dental School. His private dental training academy, Tipton Training, was founded in 1991 and to date over 3000 dentists have completed a one year course at the Academy. He practices at his clinics in Manchester, Watford and Harley St. London. All details can be found at www.drpaultipton.co.uk

Dr Bernd Siewert studied at the Christian Albrecht University, Kiel, Germany from 1981 to 1986. He spent his two-year assistance time in a practice near Hamburg, Germany. In 1989 he gained a Dr. med. dent. doctorate before moving to Spain where he worked in private practice in Madrid and Malaga. Since 1996 Dr Siewert has his own private practice in Madrid and specialises in implant treatment. Since 2007 he has worked as an instructor at the International Training Center for Dental Implantology (IFZI), Nuremberg, Germany, lectures at a national and international level and is the author of numerous publications.

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Private Dentistry November 2015 69

technical properties (Figures 3-4).Advantages of CAD/CAM:

• High-quality bridge frameworks with no material faults• Precise manufacture• Reduced manufacturing time• Easily reproducible fabrication process.

The reworking required is limited to high-lustre polishing, provided a correct CAD/CAM chain is employed. This guarantees that the shape contoured during software-supported fabrication is retained exactly.

Bruxism in patientsIn our opinion the ideal method and materials have yet to be found in the search for an optimal prosthetic solution for bruxism patients. Acrylic teeth have a damping effect but are subject to abrasion. Metal or all-ceramic restorations are at risk

of fracture and do not provide any shock-absorbing effect to prevent overloading of the patient’s natural teeth and the implants.

Prosthetic restorationThis 55-year-old female patient, was referred to us for implant treatment and prosthetic restoration (Figure 5). She had previously been treated via a bar-supported denture placed on four implants (Figures 6-9).

After 13 years of use the overdenture was damaged due to severe bruxism and was no longer sufficient. It was replaced by a fixed, operator-removable, horizontally screw-retained bridge (Figures 10-12). The chrome-cobalt-molybdenum alloy telescope crowns on four implants and two molars were adhesively retained in a bridge framework fabricated using PEEK (BioXS, Bredent).

Figures 1-2: Framework (left: basal, right occlusal), Juvora dental disc fabricated in the CAD/CAM supported process

Figure 3: The veneered bridge on the master model (palatal view)

Figure 4: The bridge in the patient’s mouth after ten months in situ. The secondary telescope UL6 and bridge pontic UL5 have been designed fully anatomically. The shade of the non-veneered PEEK (Juvora dental disc) is acceptable for the occlusal surface in the posterior region. The gingival conditions are excellent

Figure 5: Initial situation, partially edentulous upper jaw with retained and displaced canines

Figures 7-9: At the time (1996) the patient was prosthetically treated with a bar-supported denture

Figure 6: After removal of the canines and placement of four implants

Figure 7 Figure 8 Figure 9

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70 Private Dentistry November 2015

After three years in situ the occlusal surfaces (veneers) had been abraded completely in the posterior region and later the veneers split off tooth UL2 due to the bruxism (Figures 13-14). A remake of the

prosthetic restoration was unavoidable. The BioXS PEEK framework material was completely intact. Following abrasion of the acrylic teeth, the framework surface was in direct occlusal contact and there were only

minimal signs of wear. No cracks or decementation were observed basally. Neither the implants nor the molars with the cemented primary crowns showed any clinical anomalies (Figure 15).

Figures 10-12: After 13 years the damaged denture was replaced by a fixed, operator-removable, horizontally screw-retained bridge

Figures 13-14: After three years in situ the veneers split off again (bruxism), the PEEK frameworks, however, show no signs of impairment

Figure 15 (right): Neither the implants nor the molars (primary crowns) show any clinical anomalies

Figure 10

Figure 11

Figure 12

Figure 15

Figure 14

Figure 13

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Private Dentistry November 2015 73

What appeared to be clear was that the composite bridge design of the PEEK bridge framework is also sufficiently resistant to withstand enormous masticatory forces, but that the acrylic teeth in the posterior region are the weak point in patients with bruxism.

Second prosthetic restorationIt was then decided on CAD/CAM-supported fabrication of a fully anatomical bridge framework for the remake of the prosthetic restoration. The material used was unfilled PEEK, Juvora dental disc, which can be used for fabricating highly precise restorations. The basal region was designed fully anatomically in a convex shape (Figures 16-19). The buccal aspects in the visible areas from premolar to premolar were veneered. As both the protrusive and lateral excursions were to be on the PEEK framework, no prefabricated laminate veneers were placed in this area but rather custom-milled composite veneers (Figures 18-19). The occlusal surfaces and guidance

pathways were not veneered.An occlusal screw-retained restoration

was fabricated as horizontal screw retention in combination with the telescope principle can be problematic from a hygiene point of view. To ensure that the bridge fitted passively, the four implant copings in the mouth were adhesively retained and then the new restoration fitted. The non-veneered Juvora dental disc is barely noticeable as an occlusal surface material. The grey-brown shade of the occlusal and oral sections was accepted by the patient without any problem (Figures 20-21).

In such cases where bruxism is a problem the focus is on producing a durable, functioning restoration. The shock-absorbing properties of the new design should protect the implants and the patient’s natural teeth against the destructive forces of bruxism. Juvora dental disc PEEK material is completely free of additives (eg barium sulphate) and is therefore not visible on anorthopantomogram; a detail that one has to become accustomed to (Figure 22).

Figures 18-19: The finished bridge. The Juvora dental disc framework was designed fully anatomically in the functionally critical areas

Figures 20-21: Finished bridge in situ

Figure 18

Figure 20

Figure 19

Figure 21

Figures 16-17: The implant-supported bridge was remade with CAD/CAM

Figure 16

Figure 17

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Private Dentistry November 2015 75

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Reference1. Siewert B, Parra M: Eine neue Werkstoffklasse in der Zahn,edizin. PEEK als Gerüstmaterial bei 12-gliedrigen implantatgetragenen Brücken (A new material class in dentistry. PEEK as a framework material with 12-unit, implant-supported bridges). Z Zahnärztl Implantol 2013;29:148-159.

DiscussionInvibio Optima PEEK has been tried and tested as a material for implants in the medical field for over ten years. Its high biocompatibility has been proven in several clinical studies (Siewert, 2013). The low specific weight, bone-like elasticity, metal-free character and toughness, combined with virtually non-existent material fatigue make it an ideal material for use in prosthetic dentistry. The CAD/CAM-supported processing of PEEK opens up new possibilities. The physical properties of the material described allow approximately the same design dimensions as those of metallic materials.

To date, approval of the Juvora dental disc covers removable restorations, implant-borne prosthetics and crowns and bridges. This means that cast-metal denture bases, secondary units, superstructures with fixed/removable restorations, implant-supported, posterior full crowns and (as demonstrated here) operator removable, screw-retained bridges can be fabricated using the material described. In the past, long-term clinical results were achieved in patients with bruxism and heavy pressing using a gold alloy on the occlusal surface. A material is now available for these indications, which has the effect of damping masticatory forces and, due to its greyish shade, can also be used for occlusal contours - metal free and biocompatible.

ConclusionThe positive clinical experiences using fully anatomical PEEK bridge frameworks, fabricated using the injection-moulding technique, can be transferred to CAD/CAM processing. This enables frameworks to be fabricated in a reliable, reproducible production procedure.

Consistent, optimum material quality is also guaranteed. The chemical properties of PEEK exclude any transparent versions. However, it may be possible in the future to add inorganic dyes to reproduce the shades on the Vita shade guide. Full crowns made from this material could then be used with confidence, including with regard to aesthetic parameters. A material has therefore been found that builds on the clinical experience of gold.

Figure 22: The X-ray image. The Juvora dental disc is highly pure and free of additives, and is therefore not visible on the X-ray

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Questions turn to page 88

1 Patient feedback from 92 cases July 2013 – March 2015

2 Based on the tendency of a material to deform when opposing forces are applied as expressed by the avg. elastic

(Young’s) modulus values of the two materials (Titanium 110 GPa or PEEK 4GPa).

3 Kurtz, S (2012). “PEEK Biomaterials Handbook”. Edition 1, Oxford, Elsevier Inc.

implant prosthetiCsalternative to metalWhy patients Choose JUvora™

rated highon Comfort199%

Juvora Ltd Hillhouse International, Thornton Cleveleys, Lancashire FY5 4QD United Kingdom | +44 (0) 1253 897555 | info@juvoradental.com | www.juvoradental.com

• CAD/CAM precision for tailored fit

• 26x more shock absorption2 than Titanium for superior comfort

• Made from PEEK-OPTIMATM, a high-performance polymer solution for long-term3 fixed and removable prosthetic frameworks

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PRIVATE DENTISTRY SEPTEMBER 2016

oday, it is widely believed that high-performance polymers have a great future potential with regard to their use as framework materials in restorative dentistry. While for a long time,

they have been exclusively used for temporary restorations, new application options are created due to the availability of innovative, optimised materials such as polyether ether ketone (PEEK). This material for example can be used successfully for the computer-aided production of long-span, implant-supported restorations.

MATERIAL PROPERTIESPEEK is an aromatic, semi-crystalline thermoplastic polymer that has been in use as a material for implants in different medical fields (eg in orthopedics and oral and

Professor Paul Tipton and Dr Bernd Siewert present a case study using polyether ether ketone (PEEK) for the production of an implant-supported All-on-Four

HIGH PERFORMANCE POLYMERS - PART 3

CLINICAL EXCELLENCEWITH CPD

T maxillofacial surgery) for more than ten years. The thermoplastic production procedure ensures that virtually no residual monomers are released. Due to its semi-crystalline character, the material remains mechanically stable even in an aggressive environment like the oral cavity.

Several years ago, PEEK was used for the first time in dentistry. Since September 2012, PEEK blanks for CAD/CAM production are available as well: Juvora Dental Discs (Juvora, Thornton-Cleveleys, UK). This material is no longer indicated for temporary restorations only. The blanks are sourced from Invibio Biomaterial Solutions that have been successfully used in medical technology for more than a decade. It is specified that the melting point of this material is high for polymers (340°C) and allows repeated sterilisation of frameworks. The modulus of

PROFESSOR PAUL TIPTON BDS MSC DGDP RCS

Professor Tipton is an internationally acclaimed Specialist in Prosthodontics who has worked in private practice for

more than 30 years. He is the founder of Tipton Training Ltd, one of the UK’s leading private dental training academies and the author of over one 100 scientific articles for the

dental press. He gained his Master’s Degree in 1989 from the Eastman Dental Hospital and London University and started

teaching on the University of Manchester’s MSc in Restorative Dentistry. He is now Professor of Restorative and Cosmetic Dentistry at the City of London Dental School. His private dental training academy, Tipton Training, was founded in 1991 and to date over 3000 dentists have completed a one

year course at the Academy. He practices at his clinics in Manchester, Watford and Harley St. London.

WEBSITE: www.drpaultipton.co.uk

DR BERND SIEWERT Dr Bernd Siewert studied at the Christian Albrecht University,

Kiel, Germany from 1981 to 1986. He spent his two-year assistance time in a practice near Hamburg, Germany. In 1989

he gained a DMD doctorate before moving to Spain where he worked in private practice in Madrid and Malaga. Since 1996 Dr Siewert has his own private practice in Madrid and specialises in implant treatment. Since 2007 he has worked

as an instructor at the International Training Center for Dental Implantology (IFZI), Nuremberg, Germany, lectures

at a national and international level and is the author of numerous publications.

WEBSITE: www.clinicasomosaguas.com

elasticity is similar to that of natural bone. Its flexural strength is 165 MPa, the elongation at break amounts to 40%, meaning that a sample breaks when it is stretched by 40% of its initial length. According to the manufacturer, the consequence is that the material is flexible under load without fracturing - a property that seems beneficial especially from a functional therapeutic perspective. Juvora Dental Discs made from PEEK are recommended for the production of (semi-)removable structures. These include telescope attachments, dentures with precision attachments, claps-retained dentures and implant-supported, screw-retained restorations.

CASE STUDYThis 67-year-old female patient was referred to us with pain in her lower jaw. She had a

Figure 1: Initial situation

Figure 3: The bridge after its removal

Figure 2: Situation after removal of the existing restoration

Figure 4: Result after extraction of the remaining front teeth and build up of the canines

66

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Figure 5: Virtual positioning of the implants taking into account the prosthetic possibilities and the anatomical structures

Figure 7: Model with implant analogsFigure 6: The drilling template

Figure 8: Temporary with framework made from chromium cobalt Figure 9: Impression posts in the patient’s mouth with transfer key

combined fixed and removable restoration consisting of a cemented metal-ceramic bridge on teeth LL3 to LR3 and a clasp-retained partial denture in the mandible (Figure 1). In addition, she had an asymmetric occlusion (Angle class II). All six remaining lower teeth could not be retained due to caries and

advanced periodontitis (Figure 2). Figure 3 shows the existing bridge after its removal.

The patient was informed about the treatment options and chose a fixed denture on four implants. The All-on-4 concept was used in this case. This involves the insertion of two anterior implants without angulation, while the

two distal implants in the posterior region are placed at an angle to allow for optimal use of the available bone and avoid damaging important anatomical structures (such as the alveolar inferior nerve).

In the present case, a minimally invasive implant insertion protocol using a drilling

67

PRIVATE DENTISTRY SEPTEMBER 2016

Figure 11: Model with laboratory analogs and artificial gingiva

Figure 12: Digitised master model with laboratory analogs and artificial gingiva Figure 13: Veneers in their desired position

Figure 10: Impression taking with an individual tray

template was planned. We also aimed at immediate loading of the implants with a metal-reinforced composite provisional that had been produced prior to the surgery and was to be screwed on the implants.

IMPLANT PLANNINGIn the first step, the teeth LL2, LR1 and LR2 were extracted. The canines received endodontic treatment and were stabilised with temporary screw in posts and composite (Figure 4). The old bridge with the crowns LL3 and LR3 that were isolated inside was used as a template for the build-up. It was important to temporarily retain the canines since they were to be used for exact intra-oral positioning and safe fixation of the drilling template during guided surgery. In this way, it was not necessary to insert three temporary implants with ball heads. In the next step, a wax set-up was created in order to determine the ideal arch relations and to establish the desired aesthetic appearance of the planned restoration together with the patient. On the basis of the resulting mock-up, a radiographic template was produced using material that contains barium sulphate. The template was subsequently positioned in the patient’s mouth and a three-dimensional X-ray was taken with Galileos (Sirona Dental, A-Salzburg).

The resulting DICOM data set with the

radiographic template was imported into the 3D planning software. With the software, the ideal position of the four implants was determined virtually. At this, the planned prosthetic restoration - abutments with an angulation of 0, 17.5 and 35 degrees are available for this purpose - and the anatomical structures were taken into account. Moreover, the implants were positioned in the middle of the alveolar process and an ideal angulation for the distal implants was determined. In general, they should emerge as distally as possible to create the best AP spread. At the same time, the required distance to critical anatomical structures, in this case the mandibular canal, has to be observed (Figures 5-6).

Experience suggests that the benefits of the digital workflow in implant planning primarily result from the chance of taking all required decisions regarding implant insertion prior to the surgical intervention. Moreover, a minimally invasive approach that ensures an accelerated healing process, a minimised duration of the operation and reduced post-operative discomfort is possible. In addition, a long-term temporary can be produced in the laboratory prior to the intervention, so that immediate placement is possible. This enables the designing of a more delicate provisional which allows for a better hygiene and control. Last but not least, the total treatment time is

drastically reduced.After completion of the virtual planning step,

the determined positions for the four implants were transferred to the radiographic template and drilling sleeves were integrated to create a drill guide (Figure 6).

PRROVISIONAL RESTORATIONIn the dental laboratory, four implant analogs were placed in the desired positions on the mandibular model (Figure 7). Afterwards, the provisional was produced on this cast in accordance with the wax up: the framework was made from chromium cobalt and veneered with acrylic polymer (Figure 8). The inner metal framework prevents the denture from fracturing and allows for a more delicate design than possible for bridges without any reinforcement. One of the four screw canals was integrated and used for pre-fixation in the patient’s mouth after implant insertion, while the other three canals were closed. The temporary had no distal free-end saddles to avoid overloading during osseointegration of the implants.

SURGERYIn the clinic the template was positioned on teeth LL3 and LR3. Then, the four implants with 16 mm length and a diameter of 4mm were inserted. Initially, the pilot holes in region LL2 and LR2 were prepared, the template removed

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Figure 14: Proposed framework design

Figure 16: Nested framework in the virtual blank

Figure 18: Milled framework prior to its removal from the blank

Figure 15: Veneers on the framework

Figure 17: Milling path calculation

Figure 19: Lateral view of the finalised bridge

and the remaining teeth extracted. Then, the template was repositioned and the pilot drills were inserted again in region LL2 and LR2 in order to fix the templates on them and continue the preparation process. After implant insertion, the abutments which had an angulation of 35° (implant in region LL5) and 17.5° (implant in region LR5) were placed and the provisional fixed.

The required chair time for the described

procedure of surgery and immediate restoration amounts to approximately two and a half hours. Usually, there are no post-surgery swellings or hematomas. Pain medication is administered during the first 24 hours only.

FINAL RESTORATIONAfter a four-month healing period, an impression was taken for the production of the final restoration. For this purpose, the four

screws were released and the provisional bridge was removed. Since so far, it is not possible to consistently implement the digital workflow for impression taking, the conventional procedure was adopted. A potential weakness of the available intra-oral scanners lies in the correct matching of single images resulting from the capture of large soft tissue areas. Impression copings were inserted (Figure 9) and a stable transfer key was produced using composite

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Figure 20: Occlusal view of the bridge after placement and before closure of the screw holes

Figure 21: Final restoration

material. The individual, open tray was fitted and an impression taken with a PVS material (Figure 10).

The master model was fabricated using polymer to avoid an expansion that is typical for gypsum. The laboratory analogs were also fixed on the model with a torque of 12 Ncm. On the complete arch, artificial gingiva was placed in order to ensure an error-free scanning of the analogs (Figure 11).

Figure 12 shows the virtual model after digitisation on the screen. With the model being mounted in the articulator, the pre-fabricated veneers were positioned in the predetermined way and in correct occlusion using wax and then scanned.

Figure 13 shows the positioned veneers on the 3D model. Having scanned them once, their geometries can be deposited in the software library. Afterwards, the PEEK framework was designed using the exocad DentalCAD software. Within this context, the software generated a full-contour design proposal which can be modified manually and was subsequently anatomically reduced (Figure 14).

Figure 15 shows the planned framework (blue) and the veneers which will be bonded on the framework in a special procedure (grey). It is possible to modify the shape and size of the framework manually, however, the user is warned if he falls below the recommended minimum wall thickness. In all, the designing with a computer enables the creation of precise full-contour designs with regard to the fit of the veneers, the convex shaping of the basal areas with ideal pressure on the gingiva and a direct design of the screw canals.

After completion of the design step, the data was sent to the CAM software for nesting in the virtual blank, positioning of the connectors (Figure 16) and milling path calculation (Figure 17). Finally, the framework was milled using the machine DWX-50 (Roland DG, D-Willich) in the production center PEEK-O-BELLO (E-Madrid).

RESTORATION PLACEMENTThe PEEK framework (Juvora Dental Disc) was removed from the blank (Figure 18). On the master model, a passive and precise fit was confirmed before the veneers were bonded with the PEEK framework using a special technique involving composite material. After finishing and addition of artificial gingiva (Figure 19), the restoration was tried in. Since a precise fit was obtained here as well and modifications were not required, the restoration was immediately screwed onto the four implants (Figures 20 and 21). The patient had a comfortable feeling during chewing and was highly satisfied with the appearance of the restoration.

CONCLUSIONSThis case description shows how Juvora Dental Discs are used within the digital workflow in order to produce precisely fitting implant-

supported restorations.Experience gained with PEEK during the

past six years suggests it is very well-suited as a framework material for the fabrication of complex semi-removable dentures. Due to the availability of Juvora Dental Discs for CAD/CAM processing, the benefits resulting from the positive material properties can be combined with those of the digital workflow, such as efficiency and precision. Thanks to the elasticity of the material that is similar to that of cancellous bone, chewing forces acting on the restoration are compensated. Due to its elasticity, PEEK thus serves as a shock absorber and imitates the periodontal ligament that is missing around implants. The clinical experience with this material has shown that the peri-implant bone remains stable over time.

And if a passive fit is not entirely achievable, the inaccuracies are balanced when the PEEK framework is screwed on the implants.

CPDAIMS AND OBJECTIVES

To demonstrate the process for manufacturing an implant supported full arch prosthesis using PEEK

materials and bonded veneers. EXPECTED OUTCOMES

Correctly answering the cPD questions on page 80 shows the reader understand the process and advantages of

combining PEEK materials with digital planning.VERIFIABLE CPD HOURS: 1

COMMENTS TO PRIVATE DENTISTRY@ThePDmag

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STUDI

1. Bernd Siewert, Polyetheretherketon (PEEK) A New Materiai for Framework Fabrication, ZAHNTECKNIK 2013

2. Bernd Siewert et al, PEEK A New Materiai for Metal Free Prosthetic Therapy, Ouintessenz ZT 2013

3. Ingrid Eiber-Fath et al, Innovative, Biocompatible & Radiolucent (Innovative Biocompatible and Radiolucent),ZWP 2013

4. Bernd Siewert, Production of lmplant Supported Bridges from PEEK Blanks, DZW 2014

5. Volker Zeibig, CAD/CAM-manufactured dental prosthesis made of the high-performance polymer PolyetherEther Ketone (PEEK) as a biocompatible denture materiai UMG 2014

6. Nicolas Torrents et al, Use of polyetheretherketone in the fabrication of a maxillary obturator prosthesis: Aclinica! report, Journal Prosthetic Dentistry 2014

7. Rolf Vollmer et al, Double crowns made of a new high performance polymer- CADCAM 2014

8. Carola Kolbeck et al, ln-vitro-examination of molar crowns with substructures made of differentPolyetheretherketones, IADR 2012

9. Lubica Hallmann et al, The improvement of adhesive properties of PEEK through different pre-treatments,Journal of Applied Surface Science 2012

Juvora STUDI

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STUDI

1 O. Carola Kolbeck et al, Biofilm Formation on Polyetheretherketone Surfaces and Cleaning Options, IADR 2013

11. Martin Rosentritt et al, Shear bond strength between veneering composite and PEEK, Clinica! Ora!lnvestigations Journal 2014

12. Carola Kolbeck et al, In-vitro investigation of differently shaped single crowns made frompolyetheretherketone-DG PRO 2014

13. Terry Whitty, PEEK A New Materiai for CADCAM Dentistry, eLABORATE 2014

Notes

Notes

The information contained herein is believed to be an accurate description of the typical characteristics and/or uses of Juvora product(s) and services. However, it is your ultimate responsibility to determine the performance, efficacy and safety of using Juvora product(s) and services for a specific application. Sugges-tions of uses should not be taken as inducements to infringe any particular patent or as a representation that the product is suitable for such uses.

Juvora makes no warranties, express or implied, including without limitation, a warranty of fitness for a particular purpose or of intellectual property non-infringement, including, but not limited to patent non-infringement, which are expressly disclaimed, whether express or implied, in fact or by law. Furthermore, Juvora makes no warranty to your customers or agents, and has not authorized anyone to make any repre-sentation or warranty other than as provided above.

Juvora shall in no event be liable for any general, indirect, special, consequential, punitive, incidental or similar damages, including without limitation, damages for harm to business, lost profits or lost savings, even if Juvora has been advised of the possibility of such damages, regardless to the form of action.

JUvOrA™ is a trademark of Juvora Ltd. All rights reserved. ©2016 Juvora Ltd.

Invibio™ and the Invibio (logo) are trademarks of Invibio Ltd. PEEK-Optima™ is a trademark of Invibio Ltd.

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