Selection of anterior teeths./ fixed orthodontics courses

Selection of patient for intraoral implants

INDIAN DENTAL ACADEMY

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Introduction

The use of dental implants to provide support for replacement of missing teeth is becoming an important component of modern dentistry. As a result of advances in research on implant design, materials, and techniques the use of these devices has increased dramatically in the past few years and is expected to expand further in the future. Many types of implants are now available for application to different clinical cases, and an increasing number of dentists have become involved in this form of treatment.

Many individuals with edentulism can be treated with partial or complete traditional removable dentures or fixed bridges. However, these prostheses are not satisfactory for a significant number of individuals who have lost the tooth-bearing portions of the bone and simply cannot manage removable prostheses, or are medically compromised and cannot properly masticate food. Moreover, there is a strong suggestion that a substantial number of patients prefer implant- supported prostheses over soft tissue supported prostheses.


Research advances in dental implantology have led to the development of several different types of implants, and it is anticipated that continued research will lead to improved devices. At present, continued evaluation is necessary to determine that appropriate implant devices are available to meet the therapeutic demands of the different portions of the jawbones and the unique needs of patients.

Criteria of success vary with different implant systems. Therefore, it is difficult to compare certain types of implants for which success criteria and indications may be different.

Dental implants may be classified by type as endosseous, subperiosteal, transosteal, intramucosal, endodontic, and bone substitutes



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These implant types are subdivided as follows: • Endosseous:

Root form. Blade (plate) form. Ramus frame.

• Subperiosteal: Complete. Unilateral. Circumferential.

• Transosteal: Staple. Single pin. Multiple pin.www.indiandentalacademy.com

For long-term successful performance of all dental implant types the following general factors should be considered:

•Biomaterials. •Biomechanics. •Dental evaluation. •Medical evaluation. •Surgical requirements.•Healing processes. •Prosthodontics. •Postinsertion maintenance.


All practitioners involved in patient care should be knowledgeable regarding these factors and their interrelationships. Standards of dental practice would suggest the following general contraindications for the above three categories of dental implants:

• Debilitating or uncontrolled disease. • Pregnancy. • Lack of adequate training of practitioner. • Conditions, diseases, or treatment that severely compromise healing, e.g., including radiation therapy. • Poor patient motivation. • Psychiatric disorders that interfere with patient understanding and compliance with necessary procedures. Unrealistic patient expectations. • Unattainable prosthodontic reconstruction. • Inability of patient to manage oral hygiene. • Patient hypersensitivity to specific components of the implant. www.indiandentalacademy.com

With regard to indications for a specific implant type, the bone available to support the implant is the primary factor after prosthodontic diagnosis and treatment plan. This bone is measured in width, height, length, anatomical contour, and density. These physiological and anatomical factors may be altered by either osteoplasty or augmentation of the bone. In addition, other factors affecting indications for implant type are the degree and location of the edentulism of the patient.


Indications for each implant type are specified below:

• ENDOSSEOUS, root form: o Adequate bone to support the implant with width and height being the primary dimensions of concern. o Maxillary and mandibular arch locations. o Completely or partially edentulous patients.

• ENDOSSEOUS, blade (plate) form: o Adequate bone to support the implant with width and length being the primary dimensions of concern. o Maxillary and mandibular arch locations. o Completely or partially edentulous patients.


• ENDOSSEOUS, ramus frame: oAdequate anterior bone to support the implant with width and height being the primary dimensions of concern. oMandibular arch location. oCompletely edentulous patients.

• SUBPERIOSTEAL, complete, unilateral, circumferential: oAtrophy of bone but with adequate bone to support the implant. oMaxillary and mandibular arch locations. oCompletely and partially edentulous patients. oStable bone for support.


• TRANSOSTEAL, staple, single pin, multiple pin: ο Adequate anterior bone to support the implant.o Lack of adequate training of practitioner. ο Conditions, diseases, or treatment that severely compromise healing, e.g., including radiation therapy. ο Poor patient motivation. ο Psychiatric disorders that interfere with patient understanding and compliance with necessary procedures. ο Unrealistic patient expectations. ο Unattainable prosthodontic reconstruction. ο Inability of patient to manage oral hygiene. o Patient hypersensitivity to specific components of the implant.


Implant treatment is delivered in several ways:(1) By multidisciplinary teams of dentists in which an oral

surgeon or periodontist performs the surgical component of the implant and a prosthodontist performs the prosthetic component;

(2) By individual implantologists with extensive training in both the surgical and prosthetic components who perform all aspects of the procedure;

Patient selection should be restricted to those patients who show a need and motivation for the implant procedures. The evaluation of the recipient should include a survey of adequate bone structure, medical history, and, where indicated, medical laboratory studies and consultation with the patient's physician. The use of computerized tomography for evaluation of maxillary and mandibular anatomy is suggested when more accurate information regarding implant placement is needed. The patient's dental evaluation also should include a psychosocial appraisal of his or her suitability for implant procedures when psychological symptoms are present. www.indiandentalacademy.com

Osseointegration is the direct structural and functional connection between ordered, living bone, and surface of a load carrying implant


Baseline vital signs of blood pressure. Pulse and temperature should be taken in the evaluation stage


The sequential multiple analyzer allows for analysis of specific blood components, which may be helpful in diagnosing underlying systemic diseases


Complete blood count is determined in the clinical laboratory


Urine analysis should precede Stage I surgery


Chest X-rays are taken if general anaesthesia is being considered.


Baseline E.C.G should be completed pre-operatively


A thorough clinical assessment should be undertaken for every patient before undergoing therapy


Assessment of any oral pathology


Assessment of TMJ function


In partially edentulous patients an evaluation of pocket depth should be made with a Michigan O Probe with Williams markings


Use of disclosing agents facilitates assessment of the plaque index


Presence of calculus should be noted


Mobility patterns may be ascertained by using a mirror handle and a periodontal probe handle placed at opposite ends of the tooth.


The patients past personal oral hygeine habits and periodontal health may be accurate predictors of his/her projected compliance in the maintenance of osseointegrated implants.


Intra oral and extra oral photographs should be taken pre-operatively, intra-operatively and post operatively


Diagnostic study models are helpful in treatment planning an projecting goals to the patient pre-operatively. They also aid in this retrospective analysis of the progress of therapy.


Pre-operative radiographic analysis is one of the most critical aspects of the clinical evaluation


Diagnostic wax up aids in the proper projection of functional and aesthetic goals


In planning the implant case we must think is reverse, i.e., we need to plan the final outcome prior to the placement of fixtures.


Diagnositc wax up may then be duplicated and appropriate surgical stents created.


The facebow fork with wax, compound or any other accurate recording medium is placed in the mouth and pressed against the maxillary arch. The facebow is centered on the face and then held in position and tightened.


A centric relation record is started by pressing wax against the maxillary teeth. The mandible is manipulated into centric relation position and guided into the wax.


Wax record is then trimmed through the buccal cusp tip of the maxillary teeth. The wax record is tried back in the mouth to verify its accuracy.


Wax record is floated in room temperature water to prevent distortion


The mounts are poured, trimmed and mounted in the conventional manner.


In partially edentulous situations, a complete radiographic survey should be done


Partially edentulous situation, the panoramic radiograph can be of value in radiographic assessment of gross osseous pathology, appropriate tooth position and some indication as to appropriate fixture site location and length.


The appropriate location of neurovascular bundle and fixture site locations may be projected.


The lateral cephalometric radiograph is of much greater diagnostic value for the fully edentulous patient.


A tomogram is used to evaluate the patients bony topography


Section of tomogram used to evaluate the bony topography in the posterior maxilla


Computerized tomography is an important part of the pre-operative radiological analysis.


Treatment sequence – Edentulous

•Diagnostic records

•Transitional prosthesis

•Surgery / fixture placement

•Surgery / abutment connection

•Definitive restoration

•Maintenance


In partially edentulous situation a diagnostic wax up has been completed utilizing denture teeth.


Metallic balls have been incorporated into the stent to allow for calculation of the magnification error


Radiological stents prepared for CT scans should be prepared with gutta percha radiographic markers rather than with stainless steel balls to prevent scatter.


Biomechanical considerationsThe purpose of inserting implants into the jaw bone is to establish long lasting support for the patients prosthetic teeth. From a mechanical point of view is it thus essential to consider the strength of the elements involved and load supplied in order to establish the desired long term function.

When placing the fixtures in the bone the surgeon establishes the base for the future function of the implant supported prosthesis. The number and positions of the fixture and anchorage quality are defined at the time the surgical procedure is carried out. An understanding of basic biomechanical relationships is therefore essential for the surgeon striving for long term success for the patient.


The following guidelines are valuable for minimizing the risk of overload as well as minimizing its possible consequences:

1. The lever arm principle is affective for estimating the distribution of forces between implants as well as on each individual implant.

2. The force direction to strive for is axial on the fixtures.3. The key factor for achieving axial load is spreading the

implant in both mesial / distal and buccal / lingual directions.4. Fixtures along the straight line such as two fixture solutions

may provide critical problems. Placements of at least one offset fixture is crucial in such cases.

5. Preservation of as much high quality cortical bone as possible at the coronal neck is essential for optimizing the biomechanical strength of the system

6. Bi-cortical anchorage of the fixture is advantageous for minimizing the stress level of the bone. www.indiandentalacademy.com

In the full arch prosthesis, the implants constitute bridge posts which share the applied prosthetic loads as axial forces between them. Placing the implants evenly along an arch enables this axial load distribution. In partial prosthesis with shorter span, this geometrical implant spread is not always possible. In such cases it is appropriate to look at the fixture as being an artificial tooth root rather than a bridge post, because it may have to withstand load in all direction from the connected prosthesis. Implant supported partial prosthesis are therefore more sensitive to the precise and detailed placement and anchorage of the fixtures than are full arch prosthesis.


SINGLE FREE STANDING FIXTURE

The single tooth replacement in the anterior part of the jaw means the replacement of a missing natural tooth with a fixture of approximately the same dimensions as the missing natural tooth. If the fixture in such a case is as long as the missing natural root and has the same bone support as the natural root once did, sufficient bone strength can be expected. Thus the load limits will not be defined by the bone in such a situation.

In the posterior part of the jaw, however, a single fixture does not correspond to the lost root support of a molar which ordinarily has multiple roots of approximately the same dimensions as a fixture. Extension of the prosthetic tooth beyond the outer diameter of the abutment introduces cantilever affects and fixture bending movement. Considering these factors in combination with the fact that loading factors are at their greatest in the posterior region of the mouth, it is easy to understand that a single fixture in the molar region may be subjected to excessive forces.


TWO FIXTURES

Two fixtures supporting the prosthesis will always define a line connecting the surface of the implant and around which the prosthesis load can cause a bending movement. Such a movement will occur if a vertical load is applied offset to this center line. Also a transverse force component will always be derived from occlusal contact force as a result of the inclination of the cusps. The transverse force will lead to a bending of the implant as well. If prosthesis has an extension the leverage will enhance any transverse force applied at the end of the extension.

Thus the two fixture solution makes bending movements on the implants all but inevitable and substantial stress magnification can be developed due to lever arm affects in some situations. In corresponding positions, natural teeth are always supported by multiple tooth roots, spread along the extension of the teeth. Unfortunately, the two fixture solution is incapable of giving such optimal support leading to high stress levels. Ins as much as this situation often occurs in the posterior part of the mouth where the occlusal forces are at their greatest, both proper support of the fixture threads in cortical bone and bi-cortical anchorage are essential to assure sufficient bone strength at the implant site. Bi-cortical anchorage may sometimes be achieved by buccally/lingually placed fixtures.


THREE OR MORE FIXTURES

To eliminate the risk of excessive bending at a partial implant supported prosthesis the placement of a third fixture is recommended. This third fixture makes it possible to spread the fixture support analogously. If three fixtures are anatomically possible they should be placed slightly out of line with an offset of a minimum of 2-3 mm. By doing so the prosthesis will be supported by a tripod and any offset axial force or any transverse force will be counter acted by axial forces on the fixtures. The placement of third offset fixture brings the situation back to the preferred vertical load distribution among the bridge posts supporting the prosthesis.


OVERDENTURE

Transverse forces and bending movement

The purpose of supporting an overdenture by implants is to retain the prosthesis and to stabilize its position. The stabilizing function means that transverse forces from biting or chewing will act in the posterior/anterior direction at the attachment level. Thus in the case of only two fixtures supporting the overdenture, the fixtures will be subjected to bending movements. If a third fixture is possible, and placed offset to the other two, it is possible to compensate for this transverse force by axial forces as in the partial cases. To benefit from this third fixture the implants have to be connected to each other by a bar or bridge.


Load magnitude and bone quality

Transverse forces in the case of an overdenture maybe of a large magnitude since the implants have to withstand the total transverse force applied to the prosthesis. Therefore, the anchorage of the fixtures in the bone is crucial in this form of treatment and long fixtures and short abutments are preferred. In weak bone the third fixture and a bar construction should be utilized in order to minimize the loading of the bone. The implant supported overdenture represents a therapy with potential high loads and should be carefully planned in situations with weak bone such as in the maxilla.


In completely edentulous patients a removable implant supported prosthesis offers several advantages over a fixed restoration:

1. Fewer implants are required

2. Prosthodontic appointments are shorter, components costs are decreased, prosthesis are less complicated and treatment is less expensive for the patient as a consequence.

3. Long term professional maintenance or treatment of complications is facilitated.

4. Daily home care is easier.

5. Patient aesthetics can be enhanced with labial flanges and denture teeth compared with customized metal or porcelain teeth. The labial contours can replace lost bone width and height and support the labial soft tissues without hygienic compromise.

6. The prosthesis can be removed at night to manage parafunction. www.indiandentalacademy.com

The patient should not be encouraged to accept a fixed prosthesis if a removable prosthesis can adequately satisfy the patients needs and desires. Ideally the fixed partial denture is completely implant supported rather than joining implants to teeth . This concept leads to the use of more implants in the treatment plan. Although this may be a cost disadvantage, there are significant advantages. The added implants in the edentulous site result in fewer pontics, more retentive units in the restoration, and less stress to the supporting bone. As a result, complications are minimized and implant and prosthesis longevity are increased.

The final restoration must be visualized at the onset. After this first importance to, the individual areas of abutment support are determined. If natural teeth are present in those areas, they are evaluated using the criteria of traditional prosthodontics. If no natural teeth are in the areas of primary support, the bone is evaluated to assess which type of implant may be placed to support the intended prosthesis. www.indiandentalacademy.com

BONE DENSITY

Available bone is particularly important in implant dentistry and is describes the external architecture or volume of the edentulous areas considered for implants. In addition, bone has an internal structure described in terms of quality or density which reflects the strength of the bone.

Following the standard surgical and prosthodontic protocol, Adell et al reported an approximate 10% greater success in the anterior mandible as compared to the anterior maxilla. Lower success rates were also noted in the posterior mandible as compared to the anterior mandible with the same protocol was followed by Schnitman et al. The highest clinical failure rates have been noted in the posterior maxilla.


BONE CLASSIFICATION SYSTEMS RELATED TO IMPLANT DENTISTRY

Linkow in 1970, classified bone density into three categories:

Class I bone structure: this ideal bone type consists of evenly spaced trabeculae with small cancellated spaces.

Class II bone structure: the bone has slightly larges cancellated spaces with less uniformity of the osseous pattern.

Class III bone structure: large marrow filled spaces exist between bone trabeculae.


Lakholm and Zarb, in 1985, listed four bone qualities found in anterior regions of the jaw bone.

Quality 1: composed of homogenous compact bone.

Quality 2: thick layer of compact bone surrounding a core of dense trabecular bone.

Quality 3: thin layer of cortical bone surrounding dense trabecular bone of favourable strength.

Quality 4: thin layer of cortical bone surrounding a core of low density trabecular bone.


Misch bone density classification (1988)

D1: Dense cortical bone

D2: Thick dense to porous cortical bone on crest and course trabecular bone within.

D3: Thin porous cortical bone on crest and fine trabecular bone within.

D4: Fine trabecular bone

D5: Immature, non-mineralized bone.

In order to communicate more broadly to the profession related to the tactile sense of different bone densities this classification is compared to materials of varying densities.


Drilling and placing implants into D1 bone is similar to drilling and into Oak or Maple wood.

D2 bone is similar to the tactile sensation of drilling into white pine or Spruce.

D3 bone is similar to drilling into Balsa wood.

D4 bone is similar to drilling into Styrofoam.


RADIOGRAPHIC BONE DENSITY

Periapical or panoramic radiographs are not very beneficial to determine bone density because the lateral cortical plates often obscure the trabecular bone density.

Bone density may be more precisely determined by tomographic radiographs, especially computerized tomograms. Ct produces axial images of the patients anatomy perpendicular to the long axis of the body. Each CT axial image has 260,000 pixels and each pixel has a CT number (Hounsfield unit) related to the density of the tissues within the pixel. In general the higher the CT number, denser the tissue.

D1: More than 1250 Hounsfield unit

D2: 850 –1250 Hounsfield unit

D3: 350-850 Hounsfield unit

D4: 150-350 Hounsfield unit

D5: less than 150 Hounsfield unitwww.indiandentalacademy.com

CROWN IMPLANT BODY RATIO

The crown implant body ratio impacts the appearance of the final prosthesis and the amount of movement of force on the implant and surrounding crestal bone. The crown height is measured from the occlusal or incisal plane to the crest of the ridge and the endosteal implant height from the crest of the ridge to its apex. The greater the crown height the greater the movement force of lever arm to lateral force. Aesthetically, the prosthesis is likely to replace the sole anatomic crowns of natural teeth when a greater crown implant ratio is present. As the crown implant ratio increases the number of implants and / or wider implants should be inserted to counter act the increase in stress.


AVAILABLE BONE HEIGHT

The minimum height of available bone for endosteal implants is in part related to the density of the bone. The more dense bone may accommodate a shorter implant and the least dense bone requires a longer implant. Once the minimum implant height is established for each implant design, the width is more important than additional length. The height of the available bone is measured from the crest of the edentulous ridge to the opposing landmark such as the maxillary sinus or mandibular canal in the posterior regions. The anterior regions are limited by the nasal nares or the inferior border of the mandible. The mandibular first premolar region may present reduced height of available bone compared with the anterior region because of the anterior loop of the mandibular canal as it passes below the foramen and proceeds superiorly then distally before it exits through the mental foramen.


AVAILABLE BONE WIDTH

The width of available bone is measured between the facial and lingual plates at the crest of the potential implant site. Once adequate height is available for implants, primary criteria affecting long term survival of endosteal implants is the width of the available bone. Root form implants of 4mm crestal diameter, usually require 5mm of bone width to ensure sufficient bone thickness and blood supply around the implant for predictable survival.


AVAILABLE BONE ANGULATION

Bone angulation is aligned with the forces of occlusion and is parallel to the long axis of the prosthodontic restoration. Alveolar bone angulation represents the root trajectory in relation to the occlusal plane. Rarely this bone angulation remains constant after the loss of teeth especially in the anterior edentulous maxillary arch. The limiting factor of angulation of force between the body and the abutment of an implant is correlated to the width of the bone. The implant body may be inserted so as to reduce the divergence of the abutments. Therefore, the acceptable bone anglation and the wider ridge may be as much as 30º.


PRE-IMPLANT CONSIDERATIONS

The pre-implant prosthodontic evaluation of the patients overall condition closely resembles traditional dentists. However, specific conditions may modify and hinder the course of implant treatment if overlooked and should be considered before a final treatment plan in presented to the patient.


The conditions include the following:

1. Existing occlusion

2. Existing occlusal plane, orientation

3. Interarch space

4. Existing vertical dimension of occlusion

5. Maxillomandibualr arch relationship

6. TMJ status

7. Existing prosthesis

8. Arch form

9. Implant ideal permucosal position

10. Missing teeth – location

11. Missing teeth - number

12. Lip line at rest and during speech

13. Mandibular flexion

14. Soft tissue support.


Centric occlusion is the tooth position of maximal intercupsation . Its relationship to centric relation is noteworthy to the restoring prosthodontist because of the potential need of occlusal adjustments to eliminate deflective tooth contours.

A proper curve of spee and curve of Wilson are indicated for proper aesthetics and to prevent posterior lateral interferences during excursions. The occlusal plane is evaluated in relationship to the final implant prosthesis. Odontoplasty, endodontic therapy and /or crowns are indicated to remedy tipping and /or extrusions of adjacent or opposing natural teeth. A pretreatment diagnostic wax-up is strongly suggested to evaluate these needed changes before implant placement.

The interarch space depends on the type of restoration and requires at least 7mm in the posterior regions and 8-10mm in the anterior regions of the mouth for fixed restorations. This permits enough space for occlusal material strength and aesthetics, abutment height retention and hygiene considerations.


Removable prosthesis often require 12mm or more of interarch space for denture teeth and acrylic base strength, attachments, bars and hygiene considerations.

Several conditions relate to arch relationship. Arch relationship often concerns the anterior regions of the maxilla and mandible. The anterior edentulous maxilla resorb towards the palate. The width of the alveolar ridge decreases 40% within a few years primarily at the expense of the labial plate. Consequently, implants are often placed lingual to the original tooth position. Final restoration is consequently over contoured to place the incisal 2/3rd in the ideal position for aesthetics. The incisal edge position is facial to the remaining bone. This results in a cantilevered force on the anterior implant body. An anterior cantilever on implants in the mandibular arch may correct and Angle’s Class II jaw relationship. Transversal arch relationships include the existence of posterior cross bites which occur frequently in implant dentistry. When mandibular sub-periosteal implants are used for implant support posterior teeth maybe placed in a cross bite to decrease the moment forces developing on the maxillary posterior teethwww.indiandentalacademy.com

Existing prosthesis are evaluated for proper design and function. A removable partial soft tissue supported restoration opposing the proposed implant supported prosthesis is of particular interest. The occlusal forces vary widely as the underlying bone remodels. The aesthetics of the existing prosthesis that will be replaced by implant supported restoration are evaluated. The contour, arrangement and position of the teeth in an acceptable restoration all influence the future implant prosthesis design.

The position of the implant abutment is of particular importance for prosthesis. An implant placed in improper position can compromise the final results in aesthetics, biomechanics and maintenance. The most compromising position for an implant is too facial resulting in compromised aesthetics, phonetics, lip support and function. An angulated abutment may help improve the condition if the improper placement is not severe. But the facial gingival contour remains compromised.


The number and location of missing tooth influence the prosthodontic treatment plan of the patient. For most cases the second molar is not replaced in posterior implant supported prosthesis. The mandibular first molar is designed to occlude with the marginal ridge of a natural second molar to prevent extrusion.

The lip positions are evaluated including resting lip line, maxillary high lip line and mandibular low lip line. The resting lip line is especially noted if maxillary anterior teeth are to be replaced.

Ridge parallelism is also evaluated. Having both ridges parallel to the occlusal plane is most favourable. If both ridges are divergent, stability of the denture will be greatly affected.


Review of literature

Jacob RF Reece GP Taylor TD Miller MJ Mandibular restoration in the cancer patient: microvascular surgeryand implant prostheses. (In: Tex Dent J (1992 Jun) 109(6):23-6)

This article deals with state of the art reconstruction and rehabilitation of the head and neck cancer patient who requires mandibular resection. The mandible can be reconstructed by microvascular free tissue transfer of bone and soft tissue from distant body sites. The dental units and missing soft tissue contours can be supported by osseointegrated implants placed in the grafted bone. This article discusses the rationale for patient selection and sequencing of this complex and rewarding rehabilitation.


Larsen PE Stronczek MJ Beck FM Rohrer M Osteointegration of implants in radiated bone with and withoutadjunctive hyperbaric oxygen. (In: J Oral Maxillofac Surg (1993 Mar) 51(3):280-7)

A study was undertaken to evaluate the integration of endosseous implants in rabbit tibias that had received a tumoricidal dose of radiation. The effect of hyperbaric oxygen on integration in this compromised situation was also evaluated. Despite clinical and radiographic evidence of success of all implants, there was a significant decrease in amount of histologic bony integration of implants placed in the tibias that had received radiation therapy when compared to contralateral control implants. Adjunctive hyperbaric oxygen therapy significantly improved the amount of histologic integration of implants placed within the radiated tibias evaluated at 10 and 16 weeks after placement. Hyperbaric oxygen was also associated with better soft tissue wound healing in the radiated surgical site. Increased integration time significantly improved the amount of histologic integration in the animals that did not receive hyperbaric oxygen.www.indiandentalacademy.com

Johnsson K Hansson A Granstrom G Jacobsson M Turesson I The effects of hyperbaric oxygenation on bone-titanium implantinterface strength with and without preceding irradiation.(In: Int J Oral Maxillofac Implants (1993) 8(4):415-9)

This study investigated the influence of a single 15-Gy dose of irradiation on the capacity of titanium screws to integrate in irradiated bone tissue. The biomechanical force necessary to unscrew the titanium implants 8 weeks after placement was 54% lower for implants in irradiated bone tissue compared to implants in nonirradiated bone tissue. Postirradiation use of hyperbaric oxygen treatment (2-hour daily treatments for 21 days) increased the biomechanical force necessary to unscrew the titanium implants by 44% in irradiated bone and by 22% in nonirradiated bone.


Franzen L Rosenquist JB Rosenquist KI Gustafsson I Oral implant rehabilitation of patients with oral malignancies treated with radiotherapy and surgery without adjunctive hyperbaric oxygen. (In: Int J Oral Maxillofac Implants (1995 Mar-Apr) 10(2):183-7)

Five patients treated with radiotherapy and surgery for oral malignant tumors had a total of 20 Brånemark implants placed in irradiated bone of the mandible. The radiotherapy dose varied between 25 and 64 Gy (mean 40.3 Gy) with a biologically effective dose varying between 33.4 and 106.9. One implant did not osseointegrate, but 19 remain stable after 3 to 6 years of observation. The oral surgery procedures were carried out without adjunct hyperbaric oxygen therapy, and the successful results support the view that such adjunctive measures are not always necessary in the oral rehabilitation after radiotherapy.


Esposito M, Hirsch JM, Lekholm U, Thomsen PBiological factors contributing to failures of osseointegrated oral implants. (I). Success criteria and epidemiology. (European Journal of Oral Sciences 106(1):527-51, 1998 Feb)

Radiographic examinations together with implant mobility tests seem to be the most reliable parameters in the assessment of the prognosis for osseointegrated implants. Biologically related implant failures calculated on a sample of 2,812 implants were relatively rare: 7.7% over a 5-year period (bone graft excluded). The predictability of implant treatment was remarkable, particularly for partially edentulous patients, who showed failure rates about half those of totally edentulous subjects. Analysis also confirmed (for both early and late failures) the general trend of maxillas, having almost 3 times more implant losses than mandibles, with the exception of the partially edentulous situation which displayed similar failure rates both in upper and lower jaws. Surgical trauma together with anatomical conditions are believed to be the most important etiological factors for early implant losses (3.60% of 16,935 implants). The low prevalence of failures attributable to peri-implantitis found in the literature together with the fact that, in general, partially edentulous patients have less resorbed jaws, speak in favour of jaw volume, bone quality, and overload as the three major determinants for late implant failures in the Branemark system. Conversely, the ITI system seemed to be characterized by a higher prevalence of losses due to peri-implantitis. These differences may be attributed to the different implant designs and surface characteristics.


Esposito M, Hirsch JM, Lekholm U, Thomsen PBiological factors contributing to failures of osseointegrated oral implants. (II). Etiopathogenesis. (Eur J Oral Sci 1998;106(3):721-64.)

The aim of the present review is to evaluate the English language literature regarding factors associated with the loss of oral implants. An evidence-based format in conjunction, when possible, with a meta-analytic approach is used. The review identifies the following factors to be associated with biological failures of oral implants: medical status of the patient, smoking, bone quality, bone grafting, irradiation therapy, parafunctions, operator experience, degree of surgical trauma, bacterial contamination, lack of preoperative antibiotics, immediate loading, nonsubmerged procedure, number of implants supporting a prosthesis, implant surface characteristics and design. Excessive surgical trauma together with an impaired healing ability, premature loading and infection are likely to be the most common causes of early implant losses. Whereas progressive chronic marginal infection (peri-implantitis) and overload in conjunction with the host characteristics are the major etiological agents causing late failures. Furthermore, it appears that implant surface properties (roughness and type of coating) may influence the failure pattern. Various surface properties may therefore be indicated for different anatomical and host conditions. Finally, the histopathology of implant losses is described and discussed in relation to the clinical findings.www.indiandentalacademy.com

Tong DC, Rioux K, Drangsholt M, Beirne ORA review of survival rates for implants placed in grafted maxillary sinuses using meta-analysis. (International Journal of Oral & Maxillofacial Implants 13(2):175-82, 1998 Mar-Apr)

A variety of materials and procedures are used to create adequate bone volume in the maxillary sinus for placement of endosseous implants in the posterior atrophic maxilla. This review used the structured method of meta-analysis to evaluate the survival of the implants placed into various materials that have been used in the maxillary sinus with the sinus lift procedure. A MEDLINE computer search of the English literature yielded 28 studies that reported using the maxillary sinus augmentation procedure to increase bone volume for placement of endosseous implants; only 10 of these met the inclusion criteria for meta-analysis. Data regarding immediate or delayed placement of implants were combined to simplify analysis. Implant survival was 90% for autogenous bone (484 implants in 130 patients followed for 6 to 60 months), 94% for the combination of hydroxyapatite (HA) and autogenous bone (363 implants in 104 patients followed for 18 months), 98% for the combination of demineralized freeze-dried bone (DFDB) and HA (215 implants in 50 patients followed for 7 to 60 months), and 87% for HA alone (30 implants in 11 patients followed for 18 months).


Lindh T, Gunne J, Tillberg A, Molin MA meta-analysis of implants in partial edentulism.Clinical Oral Implants Research 9(2):80-90, 1998 Apr

A meta-analytic technique was used to estimate the survival of implants supporting bridges or single crowns in partially edentulous patients. A survey of the literature revealed 66 studies, published between 1986 and 1996. Nine studies on single implants and 10 studies on fixed partial dentures met the inclusion criteria for the meta-analysis. Data from a total of 2686 implants, 570 single crowns (SC) and 2116 in fixed partial dentures (FPD), were analyzed. In order to calculate annual survival rates for individual studies a life-table analysis was conducted. Maximum follow-up time ranged between 1 and 8 years. After 1 year the success rate was calculated to be at least 85.7% for FPD and 97.2% for SC. When the results from the FPD studies were pooled the survival rate was 93.6% after 6-7 years. The corresponding value for SC was 97.5%.www.indiandentalacademy.com

Cochran DLA comparison of endosseous dental implant surfaces. (Journal of Periodontology 70(12):1523-39, 1999 Dec)

Endosseous dental implants are available with various surface characteristics ranging from relatively smooth machined surfaces to more roughened surfaces created by coatings, blasting by various substances, by acid treatments, or by combinations of the treatments. Meta-analyses were performed on all implants in all locations, on implants placed only in the maxilla or the mandible, and, finally, on implants placed in the maxilla compared to implants placed in the mandible. Evaluation of the data revealed that predictably high success rates can be achieved for implants with both rough and smooth titanium surfaces and for hydroxyapatite-coated implants. When studies were clustered by specific indications or patient populations, rough surfaced implants had significantly higher success rates compared to implants with more smooth surfaces except in the case of single tooth replacements where the success rates were comparable. In general, implants placed in the mandible had significantly higher success rates than implants placed in the maxilla. However, in the partially edentulous patient group, titanium implants with a rough surface had significantly higher success rates in the maxilla compared to the mandible and, in cases of single tooth replacement, success rates were similar in the maxilla and in the mandible as was the case for hydroxyapatite-coated implants. The documented advantage of implants with a roughened surface in animal and in vitro experiments has been demonstrated in clinical cases when studies were compared in which specific indications or patients were treated. Additionally, implants placed in the mandible have, in general, higher success rates than implants placed in the maxilla, with only a few exceptions noted. These data from human clinical experiences support the documented advantage of implants with a roughened surface in animal and in vitro experimentation and indicate that the magnitude of the advantage is significant for patient care.


Esposito M, Hirsch J, Lekholm U, Thomsen P.Differential diagnosis and treatment strategies for biologic complications and failing oral implants: a review of the literature.(Int J Oral Maxillofac Implants 1999;14(4):473-90)

The aim of this article was to review the literature on differential diagnosis and treatment of biologic complications and failing implants. All types of publications, with the exception of abstracts, published in English up to December 1998, were included. A multi-layered search strategy was used. Controlled clinical trials (CCTs) were searched in the Cochrane Oral Health Group's Specialized Register of Trials. This database contains all CCTs identified in MEDLINE and EMBASE. PubMed was searched using various key words and the "related articles" feature. All identified publications were obtained and none were excluded. Infection, impaired healing, and overload are considered the major etiologic factors for the loss of oral implants. Only a few clinical and animal investigations were found that tested the validity of the proposed therapeutic approaches. The treatment of failing implants is still based mainly on empirical considerations, often derived from periodontal research, from data extrapolated from in vitro findings, or from anecdotal case reports performed on a trial-and-error basis.www.indiandentalacademy.com

Ivanoff C-J. - Gröndahl K. - Bergström C. - Lekholm U. - Brånemark P-I. Influence of bicortical or monocortical anchorage on maxillary implant stability: A 15-year retrospective study of Brånemark system implants. (February 2000 - Int. J of Oral & Maxillofacial Implants - Vol. 15 No. 1 pp 103-110.)` Numerous factors relating to bone quality have been cited with respect to stress distribution at the bone-to-implant interface. One such factor is the role and influence of cortical fixation, both mono- (MCF) and bi-cortical fixation (BCF). To date BCF has been deemed by clinicians to be beneficial and experimentally it has been shown to yield increased torque resistance and an increase in percentage bone-to-implant contact. However calculations from Finite Element Analyses (FEA) and photoelastic studies have yielded conflicting results, indicating that BCF may be less than ideal, with an influence over the pattern of stress concentration which becomes located in the crestal regions. This has been associated with an under stimulation of the cancellous compartment. Few data exist from long-term clinical studies. To this end a retrospective assessment of data gathered over 15 years was undertaken to compare the outcome for implants placed in the maxilla benefiting from either MCF or BCF.


Creugers NH, Kreulen CM, Snoek PA, de Kanter RJA systematic review of single-tooth restorations supported by implants. (Journal of Dentistry 28(4):209-17, 2000 May)

A three-step inclusion/exclusion procedure was applied to identify papers that represented: good scientific practice (GSP), reported results of all patients, implants and crowns for more than 2years, and had sufficient data to generate life-table analyses. The outcomes were 'implant failure' and 'crown completion'. Nine studies survived. These data showed an overall mean GSP of 0.37 with a predicted 4year implant survival of 97% (n=459), and an uncomplicated crown maintenance of 83% (n=240). Single-tooth implants show an acceptable short-term survival of 4years, but crown complications are common.


Lee JJ, Rouhfar L, Beirne ORSurvival of hydroxyapatite-coated implants: a meta-analytic review. (Journal of Oral & Maxillofacial Surgery 58(12):1372-9; discussion 1379-80, 2000 Dec)

The survival rates reported for HA-coated implants were similar to the survival rates reported for uncoated titanium implants. If resorption of the HA coating causes late failure of implants, the yearly interval survival rates should have decreased with increased years of follow-up. This decrease was not observed in the longitudinal human clinical trials that met the selection criteria for this study. Detailed analysis of these clinical trials did not show that HA-coating compromises the long-term survival of dental implants.


Sadowsky SJMandibular implant-retained overdentures: a literature review.(Journal of Prosthetic Dentistry 86(5):468-73, 2001 Nov)

The implant-retained overdenture for the mandible has been shown to be a highly successful prosthetic treatment similar to the fixed implant denture. However, controversy persists as to its design and indications. Few literature reviews have been published on the topic. This article critically analyzes the existing mandibular implant overdenture literature relative to bone preservation, effect on antagonist jaw, number of implants required, anchorage systems, maintenance, and patient satisfaction. A MEDLINE search was completed (from 1987 to 2001), along with a manual search, to locate relevant English-language articles on mandibular implant overdentures. Twelve treatment concepts are elucidated from a distillation of the literature review.


Boioli LT, Penaud J, Miller NA meta-analytic, quantitative assessment of osseointegration establishment and evolution of submerged and non-submerged endosseous titanium oral implants.(Clinical Oral Implants Research 12(6):579-88, 2001 Dec)

Two implant placement methods are used in oral implantology: submerged (S, two-stage surgical procedure) and non-submerged (NS, one-stage surgery). However, a quantitative assessment of their influence on implant osseointegration, summarising the whole present experience, is not directly possible, owing to the lack of normalisation of the published results. To overcome this difficulty, selection criteria have been applied to the latter in a process of a meta-analysis of specialised literature, in order to authorise a pooled treatment with an adequate statistical method. Survival life tables are established (up to 15 and 10 years respectively for S and NS implants placed in normal situations) for extended samples (13049 S and 5515 NS implants). Early (before loading) failure rates and 95% confidence level ranges of cumulative implant survival rates are shown. For both categories, the quality of the placement stage remains critical to ensure optimal osseointegration behaviour. Both categories match current survival requirements, but with a quite different behaviour over time. NS implants, while osseointegrating better initially, are subject to causes of osseointegration loss, which persist over a longer period of time. Implant design characteristics (including the type of surface) seem to be more relevant than the placement procedure for the implant's behaviour. This is in agreement with recent histological and preliminary clinical results, and should be confirmed by further studies. www.indiandentalacademy.com

Quirynen M, De Soete M, van Steenberghe D.Infectious risks for oral implants: a review of the literature. (Clin Oral Implants Res. 2002 Feb;13(1):1-19)

The use of oral implants in the rehabilitation of partially and fully edentulous patients is widely accepted even though failures do occur. The chance for implants to integrate can for example be jeopardised by the intra-oral presence of bacteria and concomitant inflammatory reactions. The longevity of osseointegrated implants can be compromised by occlusal overload and/or plaque-induced peri-implantitis, depending on the implant geometry and surface characteristics. Animal studies, cross-sectional and longitudinal observations in man, as well as association studies indicate that peri-implantitis is characterised by a microbiota comparable to that of periodontitis (high proportion of anaerobic Gram-negative rods, motile organisms and spirochetes), but this does not necessarily prove a causal relationship. However, in order to prevent such a bacterial shift, the following measures can be considered: periodontal health in the remaining dentition (to prevent bacterial translocation), the avoidance of deepened peri-implant pockets, and the use of a relatively smooth abutment and implant surface. Finally, periodontitis enhancing factors such as smoking and poor oral hygiene also increase the risk for peri-implantitis. Whether the susceptibility for periodontitis is related to that for peri-implantitis may vary according to the implant type and especially its surface topography.


References

1. Jacob RF Reece GP Taylor TD Miller MJ Mandibular restoration in the cancer patient: microvascular surgery and implant prostheses. (In: Tex Dent J (1992 Jun) 109(6):23-6)

2. Larsen PE Stronczek MJ Beck FM Rohrer M Osteointegration of implants in radiated bone with and withoutadjunctive hyperbaric oxygen. (In: J Oral Maxillofac Surg (1993 Mar) 51(3):280-7)

3. Johnsson K Hansson A Granstrom G Jacobsson M Turesson I The effects of hyperbaric oxygenation on bone-titanium implantinterface strength with and without preceding irradiation. (In: Int J Oral Maxillofac Implants (1993) 8(4):415-9)


4. Franzen L Rosenquist JB Rosenquist KI Gustafsson I Oral implant rehabilitation of patients with oral malignancies treated with radiotherapy and surgery without adjunctive hyperbaric oxygen. (In: Int J Oral Maxillofac Implants (1995 Mar-Apr) 10(2):183-7)

5. Esposito M, Hirsch JM, Lekholm U, Thomsen P Biological factors contributing to failures of osseointegrated oral implants. (I). Success criteria and epidemiology. (European Journal of Oral Sciences 106(1):527-51, 1998 Feb)

6. Esposito M, Hirsch JM, Lekholm U, Thomsen P Biological factors contributing to failures of osseointegrated oral implants. (II). Etiopathogenesis. (Eur J Oral Sci 1998;106(3):721-64.)www.indiandentalacademy.com

7. Tong DC, Rioux K, Drangsholt M, Beirne OR A review of survival rates for implants placed in grafted maxillary sinuses using meta-analysis. (International Journal of Oral & Maxillofacial Implants 13(2):175-82, 1998 Mar-Apr)

8. Lindh T, Gunne J, Tillberg A, Molin M A meta-analysis of implants in partial edentulism. (Clinical Oral Implants Research 9(2):80-90, 1998 Apr)

9. Cochran DL A comparison of endosseous dental implant surfaces. (Journal of Periodontology 70(12):1523-39, 1999 Dec)

10. Esposito M, Hirsch J, Lekholm U, Thomsen P. Differential diagnosis and treatment strategies for biologic complications and failing oral implants: a review of the literature. (Int J Oral Maxillofac Implants 1999;14(4):473-90)


11. Ivanoff C-J. - Gröndahl K. - Bergström C. - Lekholm U. - Brånemark P-I. Influence of bicortical or monocortical anchorage on maxillary implant stability: A 15-year retrospective study of Brånemark system implants. (February 2000 - Int. J of Oral & Maxillofacial Implants - Vol. 15 No. 1 pp 103-110.)

12. Creugers NH, Kreulen CM, Snoek PA, de Kanter RJ A systematic review of single-tooth restorations supported by implants. (Journal of Dentistry 28(4):209-17, 2000 May)

13. Lee JJ, Rouhfar L, Beirne OR Survival of hydroxyapatite-coated implants: a meta-analytic review. (Journal of Oral & Maxillofacial Surgery 58(12):1372-9; discussion 1379-80, 2000 Dec)


14. Sadowsky SJ Mandibular implant-retained overdentures: a literature review. (Journal of Prosthetic Dentistry 86(5):468-73, 2001 Nov)

15. Boioli LT, Penaud J, Miller N A meta-analytic, quantitative assessment of osseointegration establishment and evolution of submerged and non-submerged endosseous titanium oral implants. (Clinical Oral Implants Research 12(6):579-88, 2001 Dec)

16. Quirynen M, De Soete M, van Steenberghe D. Infectious risks for oral implants: a review of the literature. (Clin Oral Implants Res. 2002 Feb;13(1):1-19)


17. Contemporary implant dentistry. Carl E. Misch Second Edition.

18. Implant therapy. Nevins. Second Edition

19. Dental Implants; Dental Clinics of North America, Jan 1998.

20. Brånemark System of Oral Reconstruction. Russmassan.

21. Surgical Manual of Oral Reconstruction. Brånemark


CONCLUSION

Patients who are partially or fully edentulous are better served with tissue integrated prosthesis rather than other classical forms of therapy. However, not all patients can or should be considered suitable for this procedure.

The first step in the clinical protocol is a thorough medical and dental evaluation to screen out those patients who can be better served by an alternate treatment modality.

The patient must be viewed in totality and the end result visualized prior to the surgery. The “reverse approach” means the anticipated prosthetic result should be determined prior to surgery.


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Selection of anterior teeths./ fixed orthodontics courses

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