Implants Now 2018 Edition by Professional Dentistry

The Implant Essential

The Implant E IMPLANTS NOW PROFESSIONAL DENTISTRY PRESENTS...

2018 Edition

The Implant Essential Clinically Proven Defense

Against Peri-Implantitis The Implant Essent The Implant Essential

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Clinically Proven Defens Against Peri-Implantitis Clinically Proven Defense Against Peri-Implantitis

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Contents...

1 Peri-implantitis: incidence, prevalence and treatment.......... 6

4 Recent implant research..................................................................... 44

Introduction.......................................................................................... 6 Risk factors............................................................................................ 8 Warning signs....................................................................................... 8 Peri-implantitis...................................................................................... 10 References........................................................................................... 19

How important is the choice of surgeon?........................................ 44 3D printing tested................................................................................ 45 Narrow diameter implants tested...................................................... 45 Does chronic infection affect placement? .................................... 46 Quality of life assessment.................................................................... 47 Implants and periodontal health....................................................... 47 Surface coatings................................................................................. 48 References........................................................................................... 49

2 Guidelines crowns, fixed bridges and dental implants........... 22

Introduction.......................................................................................... 22 Indications............................................................................................ 22 Hygiene maintenance........................................................................ 23 Alternatives to crowns and fixed prostheses.................................... 23 The rationale for the use of crowns................................................... 24 Definition of a fixed bridge................................................................. 24 Fixed bridges........................................................................................ 24 Aims ...................................................................................................... 25 Assessment........................................................................................... 26 The number and position of implants................................................ 27 Fixed bridge......................................................................................... 27 Overdenture......................................................................................... 27 Surgical protocols for implant placement........................................ 27 Dental implants single versus two-stage surgery............................. 28 Immediate placement....................................................................... 28 Immediate loading............................................................................. 29 Healing times........................................................................................ 29 Cemented or screw-retained restorations....................................... 29 Reference............................................................................................. 31

5 Diagnostic factors and treatment planning in posterior implants.............................................................................. 50

Treatment planning considerations Available space - Mesiodistal............................................................ 51 Buccolingual........................................................................................ 52 Occlusogingival................................................................................... 53 Implant number and position............................................................ 55 Occlusal considerations..................................................................... 56

6 Peri-implantitis aetiology and prevention..................................... 58

3 Treatment planning for implants in the aesthetic zone............ 32 Introduction.......................................................................................... 32 Systemic Factors - Age........................................................................ 32 Diabetes mellitus.................................................................................. 32 Head and neck cancer patients....................................................... 33 Metabolic bone diseases................................................................... 33 Corticosteroids..................................................................................... 33 Smoking................................................................................................ 34 Psycho-social wellbeing..................................................................... 34 Local factors - Oral hygiene............................................................... 34 Occlusion and parafunction.............................................................. 34 Soft tissue assessment - Smile line and lip line.................................. 36 Gingival biotype.................................................................................. 36 Keratinised tissue.................................................................................. 37 Position of the existing tooth.............................................................. 37 3D Spacing requirements................................................................... 37 3D osseous-gingival relationship........................................................ 39 Diagnostic imaging and further investigations................................ 39 Conclusion............................................................................................ 40 References........................................................................................... 40

Peri-implant mucositis and peri-implantitis....................................... 58 Diagnostic features of peri-implantitis............................................... 58 Probing.................................................................................................. 59 Bleeding on probing........................................................................... 60 Suppuration.......................................................................................... 60 Percussion............................................................................................. 60 Mobility.................................................................................................. 60 Radiographic features........................................................................ 61 Aetiology.............................................................................................. 61 Differential diagnosis........................................................................... 62 Operative factors................................................................................ 63 Abutment connection........................................................................ 63 Impressions and temporary restorations........................................... 64 Laboratory phase................................................................................ 64 Planning for screw or cement-retention........................................... 64 Designing for maintenance............................................................... 65 Decontamination................................................................................ 65 Fitting screw-retained restorations..................................................... 66 Fitting cement-retained restorations................................................. 66 References........................................................................................... 66

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Chapter 1

Peri-implantitis: incidence, prevalence and treatment By Michael Norton

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Introduction It is estimated that only 2 to 3% of the edentulous population has so far received dental implants. In the US approximately 500,000 implants are placed each year, whilst in the UK that figure was said to be around 140,000 back in 2010 but has substantially increased since then. The prevalence of peri-implantitis has been reported to be up to 29 %1 most notably in patients whose implants are placed within a partial dentition. This yields a potential incidence with possibly as many as 185,000 implants in the US and UK alone that might succumb to some form of periimplant disease on an annual basis. The bacteria found within peri-implant lesions are similar to those found in deeper periodontal pockets2,3, and cross infection by periodontopathogens as a primary aetiology has been implicated as a possible pathway. However the wide variety of implant designs, surfaces and prosthetic restorations etc. make the treatment of peri-implantitis much less predictable and subject to much greater variability than periodontal disease, where natural teeth present a known anatomy and well defined surface structure. In 2008 a systematic review4 of the literature regarding peri-implantitis using PubMed and the Cochrane library revealed little consensus on the treatment of this troublesome condition. One study reported on the efficacy of sub-mucosal debridement using ultrasonics or carbon fibre curettes5, while two others compared the effect of an Er:YAG laser against that of mechanical debridement and 2% chlorhexidine as a combined therapy6,7. The first found similar results between laser and combined therapies, while the second concluded that the laser effect was limited to a six month period. A further study compared combinations of oral hygiene instruction, mechanical debridement and topical minocycline with a similar regime which substituted 1% chlorhexidine as the antimicrobial8. The former seemed to confer some benefit while the latter showed limited or no clinical improvements. Finally, a study comparing two bone regeneration procedures reported clinically significant improvements mediated by both9.

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Nonetheless a multitude of other studies have also been published reporting on the efficacy of tetracycline10, CO2 laser11, and photocatalytic decontamination amongst others in the treatment of peri-implantitis12. Such a plethora of therapies makes it difficult for the clinician to choose a regimen that is both within the reach of the average clinician and has some documented reliability.

Risk factors There have been a number of risk factors cited for peri-implantitis. In a study published in the Journal of Clinical Periodontology a clear association was demonstrated through multi-level statistical analysis between risk of peri-implantitis and location, specifically the maxilla, while overt peri-implantitis was shown to be highly correlated to patients with a predisposing history of periodontitis and being male13. Surprisingly in this particular study no correlation was demonstrated with smoking, yet this has been a consistently cited risk factor in many other studies. Indeed in a study published in the Swedish Dental Journal in 2010, the percentage of implants with peri-implantitis was significantly increased for smokers compared to non-smokers (p = 0.04)14. Other factors that have been implicated include excess cement, poor oral hygiene, and prosthesis design which are of course inter-related with some prostheses making effective oral hygiene untenable, while others present deep margins that make removal of excess cement almost impossible.

Warning signs Peri-implantitis rarely presents unannounced unless of course the patient fails to be placed on a regular recall programme or fails to attend for regular review. Early signs are often apparent in the form of peri-implant mucositis. This condition is characterised by mucosal oedema, rubor and bleeding on probing (BOP). By definition it is not associated with bone loss15. However this condition is often asymptomatic to the patient and as such is typically only diagnosed at routine recall. Hence there is a need to recognise that when implant treatment is completed the patient should remain on annual reviews for at least the first five years, and thereafter once every two years. On presentation with mucositis or early peri-implantitis with limited bony involvement a combination of mechanical debridement and sub-mucosal decontamination and antimicrobial therapy are indicated. As stated above there are many different

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regimens recommended, but the author favours a so-called â&#x20AC;&#x2DC;Triple Therapyâ&#x20AC;&#x2122; which he has used with great success over a number of years. The treatment should be repeated three times within a two-week period and consists of the following protocol: 1.

Sub-mucosal irrigation with HybenX (Epien Medical Inc, USA) oral tissue

desiccant at the deepest level of the pocket on all sides of the implant for 10

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Sub-mucosal irrigation with 5-10mL chlorhexidine (0.2%) (Corsodyl, Omega

Pharma Manufacturing GmbH, Germany) per site, at the deepest level of the

pocket on all sides of the implant

Application of Minocycline Gel 2% (Dentomycin, Henry Schein Ltd, UK) at the

deepest level of the pocket on all sides of the implant.

However once peri-implant mucositis has taken hold it is unfortunate that it is often exacerbated by the design of implants today. The presence of a rough surface, taken to the top of an implant, and the application of micro-threads or grooves have been proposed as potential confounding factors for the advance of the lesion due to biofilm formation and bacterial contamination of the surface which leads to bone loss and further surface exposure. With advancing bone loss it often results in colonisation of the deeper pockets with well known periodontopathogens and infection ensues. This then is peri-implantitis.

Peri-implantitis Peri-implantitis is characterised by the presence of vertical or crater-like bone defects and spontaneous purulence and bleeding on palpation (Fig 1& 2). It is typically associated with deep peri-implant pocketing > 5mm.

Fig 1

Fig 2

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This condition is undoubtedly of increasing concern due to the following principle factors: •

The almost exclusive use of roughened implant surfaces

•

The treatment of partially dentate patients with a history of periodontal disease

•

The placement of implants with inadequate bone volume resulting in

facial dehiscences

•

The use of cement retained prostheses.

Implants with a micro-roughened surface texture have presented excellent longterm data and until recently there has been very little published in the literature demonstrating a susceptibility of these surfaces to this condition. However recent work by Albouy et al.16,17 has received widespread attention with concern for the evidence that suggests some modern micro-textured surfaces may be completely resistant to decontamination17. Such implants are unlikely to respond successfully to any treatment and their removal is inevitable. Ultimately, if left unchecked and untreated, it may become impossible to arrest the condition, leading to wholesale failure of the case (Figs 3 & 4). Such failures impose a tremendous strain and burden on the clinician (let alone the patient), destroying the confidence of a patient who has endured significant expense and trauma and occasionally results in a breakdown of communication between both parties that all too often sadly results in a legal claim of negligence. Such claims can be hard to defend for patients where no warnings and/or supportive periodontal/peri-implant therapy have been undertaken.

Fig 3

Fig 4

These radiographs demonstrate multiple advance crater-like defects, which are associated clinically with profuse purulence.

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Treatment typically requires surgical access to excise any fibrous capsule and for direct access to the implant for surface decontamination. The authorâ&#x20AC;&#x2122;s preference until now has been to use chlorhexidine and tetracycline solution for this purpose while others have reported the use of citric acid and hydrogen peroxide amongst others17. The use of lasers has also been extensively reported6,7,19-21. However in a recent systematic review, a meta-analysis could only be done for the Erbium YAG laser as the literature on all other laser types was weak or heterogenous22. The author recently completed a prospective closed-cohort study of 20 patients in an efficacy trial using ErbiumYAG water laser (Morita, AdvErl Evo, Kyoto, Japan.) and the results of this study showed great promise with notable resolution of both defect depth as well as percentage suppuration and BOP23. Indeed, promising data has already been published to date using this same machine24, 25. Nonetheless this methodology remains outside the reach of most general practitioners and has yet to be proven reproducibly effective. As such most attention therefore remains focused on physical debridement via surgical intervention and topical antimicrobial therapies. Open flap debridement, defect decontamination, and repair as well as pocket elimination have all become the mainstay of those treating this condition. So is there a crisis? The problem is that there is no clear consensus on the prevalence of the disease since this will vary according to the cut off values for the clinical parameters measured26 and to date there appears to have been little consensus of these cut off values. For example, what is the appropriate cut-off value for pocket depth that should signify disease? Is it as with the periodontium, that a >4mm pocket represents the onset of such disease? Does spot bleeding on probing represent disease? Or are these indices not relevant to the peri-implant environment? There is much to be debated. As such, estimates of prevalence of the disease appear to vary from 28% to 56% of subjects and 12% to 43% of implant sites27. Furthermore there is an ongoing controversy about the initiating process of peri-implant disease since it is potentially considered a primary infection of periodontopathic origin by some28 while others hold that it is a secondary opportunistic infection subsequent to bone loss caused by other aetiological factors28,29 such as a provoked foreign body reaction or iatrogenic dehiscence of the bone, exogenous irritants such as dental cement, bone loss through occlusal overload etc. If the latter is true then controlling the disease is theoretically made simpler by controlling the conditions for the implant, such as ensuring adequate buccal bone thickness, avoiding or controlling more carefully the use of dental cement, and paying closer attention to the occlusion. In an effort to gauge the rate of mucositis and peri-implantitis requiring surgical intervention, the author audited his patient pool in the year 2014. Out of a total of 191 patient reviews constituting 795 implants only 15 patients (7.9%) required triple

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therapy at 20 implants (2.5%) for mucositis while 10 patients (5.2%) required surgical decontamination at 10 implants (1.3%). As can be seen these are well below the figures proposed for prevalence in the article by Zitzmann & Berglundh (2005)15. This may of course reflect a more liberal approach to cut off values for parameters such as pocket depth and bleeding on probing as proposed Klinge in 2012 26. Nonetheless after over 25 years running a practice dedicated to implant dentistry the authorâ&#x20AC;&#x2122;s own audited failure rates indicate that less than 0.5% of implants present as late failures, due to peri-implantitis or fixture fracture as a result of bone loss. This would corroborate the findings by Jemt et al. in which a cohort of patients already diagnosed with peri-implant bone loss showed a slow rate of additional progressive bone loss over a 9-year follow-up with an implant failure rate of less than 3%29. In all likelihood peri-implantitis will only become an epidemic crisis if we continue to allow bad implant dentistry to persist where there is a lack of control of the initiating factors as described above. The author believes, that for the majority, it is more rather than less likely that peri-implant inflammation is the result of a secondary opportunistic infection rather than a direct susceptibility to primary infection of periodontopathic origin. However there will clearly be some patients with a high genetic susceptibility with other predisposing factors such as the presence of untreated periodontal disease, smoking and diabetes who may well succumb as a result of primary infection. Furthermore there remains a clear need to better define the different types of aetiology predisposing peri-implant disease as highlighted in a recent article by Sarmiento et al.30, since different aetiologies of the disease may result in a pathology that responds differently to different therapies applied. For example, in cement-induced peri-implantitis, removal of the cement excess is all that may be required to ensure a successful resolution of the disease, but clearly this does not apply for screw-retained structures that present with a similar pathology but different aetiology. Finally, there is an urgent need to establish a consensus as to the cut off values for the different parameters used to evaluate the disease so that future figures for incidence and prevalence are comparable.

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Dr. Michael R. Norton BDS FDS RCS(Ed) graduated from the University of Wales in 1988. He is a specialist in Oral Surgery and Fellow of the Royal College of Surgeons, Edinburgh. Michael is Adjunct Clinical Professor at the University of Pennsylvania Dental School. Michael is President & Fellow of the Academy of Osseointegration (AO) and is Past President (1999-2001) and Honorary Life Member of the Association of Dental Implantology (ADI), UK. He is past editor of Dental Implant Summaries and the AO’s Academy News and is Associate Editor of the International Journal of Oral & Maxillofacial Implants (JOMI). Michael maintains a worldwide reputation for his lectures and courses and is widely published in the literature.

References 1.

Kalykakis GK, Mojon P, Nisengard R, Spiekermann H, Zafiropoulis G-G. Clinical

and microbial findings on osseointegrated implants – Comparisons between

partially dentate and edentulous subjects. Eur J Prosthodontics and Rest Dent

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Karoussis I, Müller S, Salvi G, Heitz-Mayfield L, Brägger U, Lang N. Association

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Gatti C, Gatti F, Chiapasco M, Esposito M. Outcome of dental implants in

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10. Mombelli A, Feloutzis A, Brägger U, Lang N. Treatment of peri-implantitis by local

delivery of tetracycline – Clinical, microbiological and radiological results. Clin

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11. Romanos G, Nentwig G. Regenerative therapy of deep peri-implant infrabony

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12. Suketa N, Sawase T, Kitaura H, Naito M, Baba K, Nakayama K, Wennerberg A,

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photocatalytic bactericidal effect. Clin Impl Dent Rel Res 2005; 7: 105-111.

13. Koldsland OC, Scheie AA, Aass AM. The association between selected

risk indicators and severity of peri-implantitis using mixed model analysis. J Clin

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14. Carcuac O, Jansson L. Peri-implantitis in a specialist clinic of Periodontology.

Clinical features and risk indicators. Swed Dent J 2010; 34: 53-61

Zitzmann NU, Berglundh T. Definition and prevalence of peri-implant disease. J Clin Periodontol 2008; 35(8 suppl): 286-291. 15. Albouy JP, Abrahamsson I, Persson LG, Berglundh T. Spontaneous progression of

peri-implantitis at different types of implants. An experimental study in dogs. I:

Clinical and radiographic observations. Clin Oral Implants Res 2008;

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16. Albouy JP, Abrahamsson I, Persson LG, Berglundh T. Implant surface

characteristics influence the outcome of treatment of peri-implantitis: an

experimental study in dogs. J Clin Periodontol 2011; 38: 58-64.

17. Gosau M, Hahnel S, Schwarz F, Gerlach T, Resichert TE, Bürgers R. Effect of six

different peri-implantitis disinfection methods on in vivo human oral biofilm. Clin

Oral Impl Res 2010; 21:866-872.

18. Deppe H, Greim H, Brill T, Wagenpfeil S. Titanium deposition after peri-implant

care with carbon dioxide laser. Int J Oral & Maxillofac Implants 2002; 17:

707-714. 20

19. Walsh LJ. The current status of laser applications in dentistry. Aust Dent J 2003;

48: 146-155.

20. Bach G, Neckel C, Mall C, Krekeler G. Conventional versus laser-assisted

therapy of peri-implantitis – A five-year comparative study. Implant Dent 2000;

9: 236-246.

21. Kotsakis GA, Konstantinidis I, Karoussis I, Ma X, Chu H. A systematic review and

meta-analysis of the effect of wavelengths in the treatment of peri-implantitis. J

Periodontol 2014; 85: 1203-1213.

23. Norton MR. A One-Year Prospective Closed Cohort Study on the Efficacy of

ErYag Laser in the Decontamination of Peri-implant Disease. Int J Periodont &

Rest Dent 2017; 37: 781-788.

24. Yamamoto A, Tanabe T. Treatment of peri-implantitis around TiUnite-surface

implants using ErYAG laser microexplosions. Int J Periodontics Restorative Dent

2013; 33: 21-30.

25. Nevins M, Nevins ML, Yamamoto A, Yoshino T, Wang C-W, Kim D. Use of Er:YAG

laser to decontaminate infected dental implant surface in preparation for re-

establishment of bone-to-implant contact. Int J Periodontics Restorative Dent

2014; 34: 461-466.

26. Klinge B. Peri-implant marginal bone loss: An academic controversy or a clinical

challenge. Eur J Oral Implantol 2012; (5 Suppl): 13-19.

27. Romeo E, Ghisolfi M, Carmagnola D. Peri-implant diseases. A systematic review

of the literature. Minerva Stomatol 2001; 53: 215-230.

28. Albrektsson T, Dahlin C, Jemt T, Sennerby L, Turri A, Wennerberg A. Is marginal

bone loss around oral implants the result of a provoked foreign body reaction?

Clin Implant Dent Rel Res 2014; 16: 155-165.

29. Jemt T, Sundén Pikner S, Gröndahl K. Changes of Marginal Bone Level in Patients

with “Progressive Bone Loss” at Brånemark System® Implants: A Radiographic

Follow-Up Study over an Average of 9 Years. Clin Implant Dent Rel Res 2015; 17:

619-628. 30. Sarmiento H, Norton M, Fiorellini, J. Development of a Classification System for

Periimplant Diseases and Conditions. Int J Periodont & Rest Dent 2016; 36:

699-705.

Chapter 2

Guidelines crowns, fixed bridges and dental implants (An extract from the document by The British Society for Restorative Dentistry, 2017 with acknowledgment).

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Introduction Standards in healthcare are of fundamental importance. Evidence-based dentistry, audit and peer review are essential components of effective clinical practice. To assist with these processes, the British Society for Restorative Dentistry (BSRD) perceives a need for guidelines on acceptable levels of care in restorative dentistry. Some guidance is already available from sister organisations, the British Endodontic Society, the British Society of Periodontology and The British Society of Prosthodontics, within their spheres of interest. This document is intended to act as a stimulus to members of the Society and to the profession to seek attainable targets for quality in fixed prosthodontics. It is hoped that this document from the Society will assist in the pursuit and maintenance of high standards of clinical practice. These guidelines should not be considered prescriptive or didactic. Obviously, there will be circumstances, encountered during patient management, when the ‘ideal’ treatment may not be possible nor the outcome optimal. In addition, new techniques and materials will become available which will bring about change. However, it is the Society’s belief that these standards can and should be the goal during management of the majority of clinical cases.

Indications The decision to provide a crown or fixed bridge whether tooth or implant - supported depends on many factors, including: •

The motivation and aspirations of the patient

•

The oral and general health of the patient

•

The condition of the remaining teeth and tooth tissues, the periodontal

condition and oral

Hygiene maintenance â&#x20AC;˘

Analysis of the benefits, disadvantages and long-term consequences of

providing a crown or fixed prosthesis

â&#x20AC;˘

Complications which limit the likelihood of clinical success

â&#x20AC;˘

The skill and experience of the clinician.

In all situations, the clinical advantages and long-term benefits of crowns and fixed bridges should justify such treatment and outweigh their disadvantages. They should only be undertaken in those situations in which such advanced restorative care will clearly contribute to the oral health and welfare of the patient. The replacement of failed crowns and bridges and the teeth or implants which support them should be conditional on an understanding of the aetiology and successful preventive management of the cause(s) of failure.

Alternatives to crowns and fixed prostheses Modern dentistry offers many opportunities to provide direct and indirect restorations which satisfy aesthetic and functional requirements of patients without the need for significant, if any, tooth preparation. Vital bleaching, composite resins, ceramic inlays and onlays and resin-retained bridges frequently have major roles in any treatment plan. Where teeth are minimally or moderately restored at the time of presentation, adhesive restorations are generally most appropriate. For example, in the management of the worn dentition, particularly those damaged by erosive substances, the use of full coverage crowns has little to commend it as the first option for treatment. Dental implants may frequently be the treatment of choice when missing teeth are to be replaced. The biological cost to the patient is low when sufficient bone is available to house them. Aspects of the provision of implantbased restorative dentistry are similar to those for teeth whilst others require different considerations and skills. These guidelines will refer to implant-supported crowns and fixed prostheses as necessary. The development of adhesive techniques and the predictability of dental implants reduce the need for the removal of sound tissue as part of restorative treatment.

The rationale for the use of crowns •

To restore the form, function and appearance of teeth which are badly

broken down, worn or fractured to the extent that simpler forms of restorations

are contraindicated or have been found to fail in clinical service

•

To improve the form and appearance of unsightly teeth which cannot be

managed by more conservative cosmetic procedures

•

To reduce the risk of fractures occurring in extensively restored teeth including

endodontically treated posterior teeth

•

More rarely, to alter significantly the shape, size and inclination of teeth for

cosmetic and functional purposes

•

To restore a dental implant.

Definition of a fixed bridge Any dental prosthesis that is luted, screwed or mechanically attached or otherwise securely retained to natural teeth, tooth roots, and/or dental implant abutments that furnish the primary support for the dental prosthesis1.

Fixed bridges •

To replace one or more teeth of functional or cosmetic importance to

the patient

•

More rarely, to prevent tooth movement and improve occlusal stability.

Tooth-supported bridges require the availability of sufficient abutments of appropriate quality and prognosis. Either in the absence of adjacent suitable teeth or when they would not benefit from restoration, implant-supported prostheses should be considered. Dental implants offer the benefit of being able to facilitate tooth replacement without the need to involve teeth adjacent to the edentulous area. Where implant placement and restoration are complicated and the use of tooth-supported fixed bridgework is contra-indicated the use of removable partial prostheses will require evaluation by both the dentist and the patient.

Aims •

To determine the patient’s requirements and expectations and to gain an

informed opinion of the patient’s suitability for treatment involving the use of

crowns or fixed prostheses

•

To obtain a history, which includes details of all previous conditions and

experiences of relevance including information pertaining to any adverse

reactions to treatment, the administration of drugs and the use of materials

•

A medical history is mandatory for all patients. Treatment involving the provision

of dental implants should additionally include questioning regarding the

following recognised risk factors: osteoporosis, bisphosphonate therapy,

uncontrolled diabetes, smoking, radiotherapy.

Patients with medical conditions may still be treated with implants following advice from their physician •

To complete a comprehensive clinical examination which will include a review

of the clinical performance and mode of failure of any existing restorations. This

will require a diagnosis of existing disease and an assessment of the processes

that have resulted in the need to provide restorations and prostheses

•

To analyse the effectiveness of the patient’s control of their own dental disease.

The clinical examination may be supported by special tests, which may include: •

Sensibility testing of teeth

•

Radiographic examinations

•

Analyses of study casts mounted in a semi-adjustable articulator in an

appropriate jaw relationship

•

Assessments of the patient’s response to initial instruction in oral

hygiene procedures.

Other forms of special test may include: •

Dietary analyses

•

The use of diagnostic and provisional appliances

•

Direct observations of occlusal and masticatory function

•

Long-term monitoring against base-line study casts.

Diagnoses may take time to establish and require the use of additional special tests including dental investigations to stabilise or determine a prognosis for one or more teeth. Any case considered to be beyond a clinician’s capabilities and experience should be referred for further assessment, advice and possibly treatment. Many clinical situations benefit from the involvement of additional dental specialists or those with particular skills. Such involvement should take place prior to the establishment of a treatment plan and may increase the options available to the patient. Implant-based treatment may be provided either by a single competent operator or by a team lead by a prosthodontist and including a surgeon. The need for interdisciplinary provision and restoration of implants is based on the complexity of the case and the skill and wishes of the dentist providing the restorative care. It is important that the whole dental team is knowledgeable about dental implants. Training of dental nurses, technicians and reception staff is mandatory.

Assessment Space requirements for dental implants •

There should be adequate inter-dental and inter-occlusal space for an

implant restoration •

There should be sufficient space for the implant to be placed in the bone

without compromising adjacent structures

•

Where implants are placed between teeth or adjacent to each other there

should be sufficient space to allow normal soft tissue contours around them.

Implants should be fully covered by the bone. Where there is insufficient bone,

augmentation procedures should be considered.

•

Anatomical structures may prevent the simple placement of dental implants in

the posterior maxilla and posterior mandible

•

Bone concavities or thin ridges may compromise implant placement

•

The effects of gross resorption following tooth extraction and the presence of

flabby ridges make implant placement more difficult

•

Care must also be taken with implant placement if there is a large incisive

canal or submandibular fossa.

The number and position of implants The number and position of implants is influenced by the type of prosthesis provided, the quantity and quality of bone and the occlusal loads expected. For edentulous patients the following may be a guide:

Fixed bridge Maxilla – 6 implants Mandible – 4 implants

Overdenture Maxilla – 4 implants Mandible – 2 implants •

The implants should be placed at regular intervals and correspond to the

correct tooth positions

•

It is not necessary to use an implant for every missing tooth if long and stable

implants can be placed.

Surgical protocols for implant placement •

The placement of dental implants is under constant development. The main

aim of these developments is to reduce treatment times and improve patient

care. It is important for the clinician to follow protocols produced by

companies, or experienced teachers in the field of implantology

•

Drilling procedures should follow standard protocols. Initial stability is important

for osseointegration to occur

•

A surgical guide (template or stent) is necessary for planning, surgical

placement and the prosthodontic stages to help with design of the

superstructure. The guide helps with the positioning, spacing and angulation of

single or multiple implants in the surgical field

•

The surgical flap will be influenced by the extent of surgery, the anatomical

structures and the experience of the operator. Larger flaps will be needed to

identify the mental or inferior dental nerve and during sinus lift procedures

•

‘Flapless’ surgery involves perforation of the mucosa at the implant site only,

followed by the bone osteotomy and subsequent implant placement. The

morbidity is low and surgical time reduced. For this technique to be successful

good bone volume needs to be present or careful placement carried out with

a CAD-CAM produced surgical drilling guide based on a CT scan

•

Preservation of the gingivae or attached mucosa is important for the final

functional and aesthetic result. Soft tissue surgery, possibly involving free or

pedicle grafts, may facilitate the prosthodontic stages.

Dental implants single versus two-stage surgery There is no evidence of improved outcomes between single and two stage surgical treatments. Single stage surgery is convenient for patients and reduces treatment times. A two-stage procedure, whereby the implant is buried and subsequently uncovered after an appropriate healing time should be considered under the following circumstances: •

Where the temporary prosthesis is a denture

•

Where bone augmentation has been carried out

•

Where there is poor initial stability of the dental implant.

Immediate placement In this type of treatment the dental implant is placed immediately into the tooth socket following dental extraction. •

The bone should be healthy with no evidence of peri-radicular infection

or pathology

•

It is helpful if there is at least 5mm of apical bone to the tooth socket to allow for

good (primary) implant stability on placement

•

This technique is more difficult for multi-rooted teeth.

Immediate loading •

The temporary crown or prosthesis is attached to the implant immediately after

surgical placement of the implant

•

It can be employed for a single tooth, multiple tooth spans or a full arch

•

It is important that good primary stability of the dental implant stability

is achieved

•

Occlusal loading must be controlled

•

This treatment can be successful in the anterior mandible

•

Longer spans or full arch restorations require multiple stable implants.

Healing times Healing times refer to the time that the implant needs to osseointegrate in the jawbone. •

With developments in implant design and surface configuration these are

under constant review

•

A safe healing time in the mandible would be two to three months and three to

four months in the maxilla

•

If there are complications with implant treatment it is recommended that

the healing times should be lengthened to allow a better chance

of osseointegration.

Cemented or screw-retained restorations The decision on whether to provide a restoration that is cemented or screw-retained depends on the following factors: •

Appearance

•

Security of fixation

•

Serviceability or future maintenance

•

Space.

A screw-retained prosthesis may have a visible screw access hole but it provides the most secure retention and simplifies any future maintenance. The angulation of the implant may prevent the use of screw-retention of the restoration. Shade determination should involve consideration of the hue, chroma and value for the body, cervical and incisal portions of the proposed crown and bridge. This should involve: •

Use of a neutral colour environment

•

A shade guide familiar to the technician and appropriate for the tooth-

coloured materials to be used

•

Assessments under different lighting conditions

•

An initial rapid scan of the guide against the teeth to be restored, followed by

short duration (<5s) assessments of the suitability of possible shades

•

Time (l5-30s) spent between assessments looking at a blue background colour

to minimise the influence of negative after-images.

Shade determination is best completed pre-operatively to minimise errors related to eye fatigue, dehydration of teeth and apparent shifts in shade following the removal of tooth tissues. Details of features such as areas of opacity and translucency, cracks and any special staining effects required should be recorded as part of the shade determination. A written and diagrammatic prescription will facilitate the transfer of information between the dentist and the technician. Where appropriate, the patient and, whenever possible, the technician who will construct the restorations should participate in the completion of the prescription of colour and form. Clinical photographs may be of value in assisting a technician who is unable to examine the patient in person. Electronic colour determination using scanning devices may be helpful but an appreciation of their limitations is required. Where teeth are to be replaced, the use of a diagnostic wax-up is beneficial and may be used to construct a provisional prosthesis to facilitate patient and dentist understanding of the final form of the restoration prior to beginning definitive prosthodontic treatment. In the case of implant-supported restorations and some tooth supported fixed prostheses, the contours of the provisional restoration may be used to develop soft tissue form adjacent to the crown or fixed prosthesis. Principal considerations: •

Conservation of tooth tissue

•

Control of the path of insertion

•

Optimal retention and resistance form

•

Appropriate clearance in occlusion and articulation

•

The removal of adequate tooth tissue to allow the manufacture of restorations

with appropriate contours and aesthetics

•

The retention of basic occlusal and axio-occlusal form

•

The need for well-defined margins of appropriate design, wherever possible on

supragingival, sound tooth tissue

•

Damage limitation through the use of atraumatic techniques.

All preparations should be planned taking account of access and with reference to radiographs and study casts. The equipment for tooth preparation should be well maintained and include an appropriate range of instrumentation. Decisions regarding the form and dimension of preparations should take account of: •

Tooth morphology and anatomy

•

The quantity and location of remaining tooth tissue responsible for the retention

of existing restorations including cores

•

Occlusal relationships and function

•

The need for realignment

•

Relationships with adjacent teeth and soft tissues

•

The material(s) to be used

•

Considerations of long-term sequelae

•

Aesthetic requirements.

If pulp vitality/integrity of the tooth is likely to be put in jeopardy by the extent of the preparation required, then additional preparatory treatment involving orthodontic realignment or elective root canal therapy may be indicated. Specific consent must be sought prior to elective root canal therapy. When it is intended to remove a finite amount of tooth tissue a guide or preoperative index is a valuable aid to avoid excessive preparation.

Reference 1. The Glossary of Prosthodontic Terms. J Prosthet Dent 2005; 94: 10-92.

Chapter 3

Treatment planning for implants in the aesthetic zone Funmi Oluwajana BDS (Hons)(Dist) MFDS RCSEd Specialty Registrar in Restorative Dentistry

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Introduction Success with dental implants can largely be achieved by appropriate case selection and thorough treatment planning. There are very few absolute contraindications to implant placement but evaluation of each individual patient creates a unique picture of personal risk factors affecting implant success1.

Systemic Factors Age Whilst there is no evidence for a minimum age for the placement of implants, they are stationary in the bone and act similarly to ankylosed teeth. They have no eruptive potential and therefore cannot compensate for the skeletal changes that occur during growth. Placement of implants too early in life may result in submergence of the implant, or interference with normal development of the alveolus. It is therefore recommended that implant placement be delayed until growth has stopped; complete eruption of the permanent dentition and skeletal maturation are better guidelines than chronological age. At the other end of the spectrum, there is no evidence-based contraindication for the placement of implants in patients of increasing age. Age does not seem to have an effect on osseointegration although theoretically older patients may have longer healing times and a potentially reduced ability to deal with surgery2,3.

Diabetes mellitus Diabetic patients show delayed wound healing, increased periodontal disease, increased alveolar bone loss and increased inflammatory tissue destruction due to deleterious effects on the microvascular anatomy and cellular responses to trauma. However similar success rates of dental implants in patients with controlled

diabetes have been found. Impaired osseointegration is associated, however, with poorly controlled diabetes, consistent with our knowledge of the effects of a hyperglycaemic state on healing4. Patients whose diabetic control is poor should demonstrate consistently good control prior to undergoing such an elective procedure1,5.

Head and neck cancer patients Head and neck cancer patients are some of the most difficult patients to rehabilitate but could benefit the most from dental implants. Radiotherapy to the head and neck region has a number of deleterious side effects such as xerostomia, mucositis, fibrosis, hypovascularity, hypoxia and osteoradionecrosis, which are not absolute contraindications but can result in reduced success rates of dental implants1-3.

Metabolic bone diseases Osteoporosis is the most prevalent metabolic bone disease, characterised by the progressive loss of bone mass and density throughout the body, including the jaws, leading to fragility and pathologic fracture. It is most common in post-menopausal women1-3. The assumption is that reduced bone density of the jaws would have an effect on osseointegration but no link has been established between systemic osteoporosis and implant failure2,6. Of greater concern are the systemic antirepsorptive agents used to treat osteoporosis, mainly bisphosphonates. The risk of medication-related osteonecrosis of the jaws (MRONJ) is well established, particularly in patients receiving intravenous bisphosphonates, but the evidence for this complication when dealing with dental implants is less well recognised.

Corticosteroids Long term use of systemic corticosteroids leads to loss of bone mass, delayed wound healing and immunosuppression7. Nevertheless, outcomes do not appear to be poorer in these patients. What is more important to consider is the condition for which corticosteroids are prescribed and the patientâ&#x20AC;&#x2122;s ability to cope with surgical procedures2.

Smoking Tobacco products contain over 4,000 potentially toxic products that have effects on the systemic and local environments. Smokers experience more problems and have poorer outcomes with implants. In general, maxillary implants tend to be more greatly affected than mandibular implants, potentially due to reduced bone density in this region8. Following successful osseointegration, smokers experience more periimplantitis and faster rates of peri-implant bone loss compared with non-smokers9,10.

Psycho-social wellbeing When selecting patients for implant treatment in the aesthetic zone, the assessment of personality characteristics might be useful in predicting patient behaviour and satisfaction, and may have an effect on the provision of treatment11,12. Some patients will not be satisfied with their treatment despite a perfect result whilst others will be satisfied with an average result due to high levels of psychogenic tolerance13. When presented with a patient who is highly critical, demanding and often responds negatively, it is prudent to be cautious in providing expensive and prolonged treatment with dental implants that may be rejected on the grounds of dissatisfaction.

Local factors Oral hygiene While implants are not susceptible to caries, they are susceptible to peri-implant mucositis and peri-implantitis and assessment of a patientâ&#x20AC;&#x2122;s oral hygiene with their teeth serves as an indicator of the patientsâ&#x20AC;&#x2122; motivation and ability to maintain implant hygiene. Implant treatment in periodontitis-susceptible patients is not contraindicated, but the high incidence of peri-implantitis may reduce long term prognosis14.

Occlusion and parafunction The absence of a periodontal ligament attaching implants to alveolar bone as it does with natural teeth creates differences in the way dental implants and teeth function in occlusion. Occlusal overload or parafunctional habits such as clenching or bruxism have been identified as one of the primary causes of late-stage implant failure and can be implicated in fracture of the superstructure and peri-implant

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bone loss2. Although not a contraindication for implant placement, unidentified or uncontrolled bruxism can lead to a number of difficult to remedy biomechanical complications. Soft tissue assessment Smile line and lip line The smile line can be assessed readily from the first contact with the patient and will provide clues as to how difficult achieving good soft tissue aesthetics will be. Smile lines can be classified as low, average or high. A patient with an average smile line will show 75-100% of their maxillary central incisors and the interdental papillae when smiling. In a high smile line additional gingival tissue above the teeth is exposed, whereas in a low smile line less than 75% of the incisors are exposed15. Naturally, a patient with a high smile line poses more of an aesthetic challenge because the restoration-soft tissue interface will be completely displayed (Figures 1-3).

Fig 1: High smile line.

Fig 2: Average smile line.

Fig 3: Low smile line.

Gingival biotype Two types of gingival biotype have been described; thick and thin. Each biotype responds to the inflammation of surgery differently16; thin biotype reacts by receding labially and interproximally, hence thick tissue is inherently more favourable. The soft tissue biotype will somewhat dictate placement of the implant. A thin gingival biotype requires the implant to be placed more palatal/lingual to prevent titanium â&#x20AC;&#x2DC;show throughâ&#x20AC;&#x2122; and slightly deeper to achieve a good emergence profile17 (Figures 4, 5).

Fig 4: Thin gingival biotype; note the highly-scalloped tissues.

Fig 5: Thick gingival biotype.

Keratinised tissue The significance of keratinised tissue around dental implants is controversial. Several long-term studies show no difference between the survival of implants with and without a width of keratinised tissue. However, preservation and/or reconstruction of keratinised mucosa is advocated to facilitate good plaque control, improve aesthetics and facilitate restorative procedures18. Position of the existing tooth If a tooth of hopeless prognosis, to be extracted, is still present, evaluation of its 3D position and the effect extraction will have on future implant positioning can be evaluated. An aesthetically pleasing result will be achieved if the mesio-distal crown width is symmetrical with the contra-lateral tooth. Discrepancies in size can be corrected with restorations, enameloplasty or orthodontics17. Teeth positioned too labially often have a very thin or non-existent buccal plate. Following extraction there is significant labial and vertical bone loss, resulting in collapse of the gingival architecture. In this situation recontouring of the bony anatomy with bone grafting, prior to implant placement would be ideal. A tooth positioned more lingually/palatally is a more favourable situation as the buccal plate is thicker and less prone to post-extraction resorption19. Following extraction, the apico-coronal position of the tooth has an impact on the apical migration of the crestal bone gingival margin. The gingival margin of a tooth that was positioned ideally or apically will experience apical migration. A compromised aesthetic outcome due to a long clinical crown or visible metal margins may result. Pre-extraction orthodontic extrusion will help to migrate the crestal bone and gingival margin more coronally, so the apical bone and tissue loss following extraction is negated17. Periapical radiographs taken during assessment stages will allow assessment of the proximity of the roots of the adjacent teeth. Roots that are too close in proximity or converge towards one another need to be repositioned by orthodontics if possible to create space for implant placement19,20.

3D Spacing requirements Radiographs, clinical sounding techniques or CBCT scans can assist in assessing the dimensions of bone available. As a general rule the following guidelines should be followed when evaluating the mesio-distal space requirements and deciding what implant diameter to use:

â&#x20AC;˘

The implant should be at least 1.5mm away from adjacent teeth

â&#x20AC;˘

The implant should be at least 3mm away from an adjacent implant

â&#x20AC;˘

Wider diameter implants should be used for molar teeth due to higher

occlusal loads. These spacing requirements prevent excessive loss of bone around implants and thus contribute to healthy and aesthetic soft tissue development. They also enable proper contacts and contours of the final restoration to be developed21 (Figure 6, 7).

Fig 7: Sufficient mesio-distal space to place a dental implant to replace a missing central incisor. Note the spacing in the anterior segment; a discussion needs to be had with the patient during the planning stages as to whether they want to keep or close the spaces.

Fig 6: Sufficient mesio-distal space to place a dental implant to replace a missing canine tooth and achieve an aesthetic restoration; note the concavity in the buccal plate that will require augmentation.

In the bucco-lingual plane, a minimum of 1mm bone should be present on either side of the implant for soft tissue stability. Deficiencies in the alveolar crest width may require augmentation. Implants are often placed too bucally resulting in the loss of the buccal bone and recession of the gingival margin. The resulting restoration will therefore appear long in comparison to the adjacent teeth17 (Figure 8). Fig 8: Sufficient mesio-distal and bucco-lingual space to place a dental implant. The implant should be placed slightly more palatal to allow for the correct emergence of the final restoration. The small deficiency in the buccal bone may or may not need augmentation at the time of implant placement.

The vertical dimension is the most challenging as deficiencies in this plane are difficult to remedy. The use of a diagnostic wax up will highlight the ideal or proposed position of the gingival margin and the extent of any vertical defect. 38

Improper positioning of the implant in the vertical plane has various aesthetic and biomechanical complications. If placed too coronally, it will impede on the space required for the restorative components. Placing the implant too deep will result in excessive bone loss circumferentially and make accessing the head of the fixture difficult for restorative procedures17,22 (Figure 9). Fig 9: Trauma and post-extraction changes of UL2 led to deficiency in the vertical plane. The gingival margin of the final restoration was much more apically positioned in comparison to the adjacent teeth. However, the patient had a very low smile line so the undesirable aesthetics of the long clinical crown were hidden.

3D osseous-gingival relationship The distance between the interproximal bone height of the implant and adjacent natural teeth, and the contact point between the prosthetic tooth and natural tooth, determines whether spontaneous regeneration of the interdental papilla will occur. If the distance is greater than 5mm, complete papillary infill will be compromised; for every 1mm greater than 5mm, the chance of complete infill is reduced by 50%23,24. This is only true for implants adjacent to natural teeth and not adjacent implants as they lack the interproximal osseous peak that natural teeth have25. Furthermore, the degree of papillary infill is also dependent on the periodontal biotype. A thick periodontal biotype encourages infill, whilst with a thinner tissue type, unaesthetic black triangles are a greater risk26.

Diagnostic imaging and further investigations Periapical radiographs, panoramic images and, increasingly, three-dimensional scanning with CBCT are used to evaluate sites for implant placement with respect to the bone volume, bone density, proximity to vital structures and for the production of surgical stents to facilitate ideal implant positioning. Good quality clinical photographs showing all standard views and site-specific views, along with two sets of study models, one for planning and one as a reference, are also invaluable.

A diagnostic wax up of the ideal position of the tooth/teeth to be replaced will enable the clinician to evaluate the outcome of treatment during the planning stages and thus identify where challenges in achieving an optimal outcome might arise. Stents can be made based on this tooth set up with incorporated radiopaque markers that will show up on a CT scan. Various computer software programs exist to allow a realistic 3D plan of the position of the implant and the restorative components to be visualised27.

Conclusion Treatment planning for dental implants should be restoratively-driven and carefully considered, working backwards from the desired end-point. It may become apparent that during the planning phase an alternative method of tooth replacement is more desirable; a successful treatment plan will correctly identify which cases are and arenâ&#x20AC;&#x2122;t suitable for dental implants. All of the above factors should studied and reflected upon as they each play an important role in the decision-making process.

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based treatment planning for dental implants: report of the Committee on

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Sugerman PB, Barber MT. Patient selection for endosseous dental implants: oral

and systemic considerations. Int J Oral Maxillofac Implants 2002; 17: 191-201.

Javed F, Romanos GE. Impact of diabetes mellitus and glycemic control on the

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Beikler T, Flemmig TF. Implants in the medically compromised patient. Crit Rev

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Becker W, Hujoel PP, Becker BE, Willingham H. Osteoporosis and implant failure:

an exploratory case-control study. J Periodontol 2000; 71: 625-631.

Scully C. Medical problems in dentistry. 6th ed: Churchill Livingstone; 2010.

De Bruyn H, Collaert B. The effect of smoking on early implant failure. Clin Oral

Implants Res 1994; 5: 260-264.

Manz MC. Factors associated with radiographic vertical bone loss around

implants placed in a clinical study. Ann Periodontol 2000; 5: 137-151.

10. Strietzel FP, Reichart PA, Kale A, Kulkarni M, Wegner B, Kuchler I. Smoking

interferes with the prognosis of dental implant treatment: a systematic review

and meta-analysis. J Clin Periodontol 2007; 34: 523-544.

11. Guckes AD, Smith DE, Swoope CC. Counseling and related factors influencing

satisfaction with dentures. J Prosthet Dent 1978; 39: 259-267.

12. Reeve P, Stafford GD, Watson C, Hopkins R. The use of Cattellâ&#x20AC;&#x2122;s personality

profile in patients who have had preprosthetic surgery. J Dent 1982; 10: 121-130.

13. Branchi R, Boddi V, Corti D, Hardoy MJ. Can a prosthesis cause psychological

disturbances? J Oral Rehabil 2001; 28: 1133-1138.

14. Schou S. Implant treatment in periodontitis-susceptible patients: a systematic

review. J Oral Rehabil 2008; 35 Suppl 1: 9-22.

15. Tjan AH, Miller GD, The JG. Some esthetic factors in a smile. J Prosthet Dent

1984;51: 24-28.

16. Kan JY, Morimoto T, Rungcharassaeng K, Roe P, Smith DH. Gingival biotype

assessment in the esthetic zone: visual versus direct measurement. Int J

Periodontics Restorative Dent 2010; 30: 237-243.

17. Jivraj S, Chee W. Treatment planning of implants in the aesthetic zone. Br Dent J

2006; 201: 77-89.

18. Cairo F, Pagliaro U, Nieri M. Soft tissue management at implant sites. J Clin

Periodontol 2008; 35(8 Suppl): 163-167.

19. Kois JC. Predictable single-tooth peri-implant esthetics: five diagnostic keys.

Compend Contin Educ Dent 2004; 25: 895-896, 8, 900 passim; quiz 6-7.

20. Salama H, Salama M, Kelly J. The orthodontic-periodontal connection in implant

site development. Pract Periodontics Aesthet Dent 1996; 8: 923-932; quiz 934.

21. Shah KC, Lum MG. Treatment planning for the single-tooth implant restoration--

general considerations and the pretreatment evaluation. J Calif Dent Assoc

2008; 36: 827-834.

22. Buser D, Martin W, Belser UC. Optimizing esthetics for implant restorations in the

anterior maxilla: anatomic and surgical considerations. Int J Oral Maxillofac

Implants 2004; 19 suppl: 43-61.

23. Tarnow DP, Magner AW, Fletcher P. The effect of the distance from the contact

point to the crest of bone on the presence or absence of the interproximal

dental papilla. J Periodontol 1992; 63: 995-996.

24. Choquet V, Hermans M, Adriaenssens P, Daelemans P, Tarnow DP, Malevez

C.Clinical and radiographic evaluation of the papilla level adjacent to single-

tooth dental implants. A retrospective study in the maxillary anterior region. J

Periodontol 2001; 72: 1364-1371.

25. Tarnow DP, Cho SC, Wallace SS. The effect of inter-implant distance on the

height of inter-implant bone crest. J Periodontol 2000; 71: 546-549.

26. Jemt T. Regeneration of gingival papillae after single-implant treatment. Int J

Periodontics Restorative Dent 1997; 17: 326-333.

27. Implantology AoD. A dentist’s guide to implantology. 2012.

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Chapter 4

Recent implant research

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One of the difficulties of assessing new techniques is that it takes some time for research studies to report their results, meaning that clinicians have little evidence on which to decide whether or not to undertake such treatments. Dental implants using titanium have now been in existence and use for several decades and the range of research is not only wide but the number of studies vast. Here we look at six recent research papers which report on various aspects of this important clinical subject.

How important is the choice of surgeon? A study by Chrcanovic and co-authors1 aimed to assess the influence of several factors on the prevalence of dental implant failure, with special consideration of the placement of implants by different dental surgeons. This retrospective study was based on 2,670 patients who received 10,096 implants at one specialist clinic. Only the data of patients and implants treated by surgeons who had inserted a minimum of 200 implants at the clinic were included. Various statistical tests were applied to the data to allow comparisons between surgeons and the outcome of the implants they placed. The factors of bone quantity, bone quality, implant location, implant surface, and implant system were analysed with descriptive statistics separately for each individual surgeon. A total of 10 surgeons were eligible and the differences between the survival curves of each individual were statistically significant. The analysis showed the following variables to be statistically significant: surgeon, bruxism, intake of antidepressants, location of implant, implant length, and implant system. The surgeon with the highest absolute number of failures was also the one who inserted the most implants in sites of poor bone and used turned implants in most cases, whereas the surgeon with the lowest absolute number of failures used mainly modern implants. Separate survival analyses of turned and modern implants stratified for the individual surgeon showed statistically significant differences in cumulative survival.

Consequently, the study concluded that different levels of failure incidence could be observed between the surgeons, occasionally reaching significant levels. Although a direct causal relationship could not be ascertained, the results suggest that the surgeonsâ&#x20AC;&#x2122; techniques, skills, and/or judgment may negatively influence implant survival rates.

3D printing tested The aim of a study by Osman et al.2 was to evaluate the dimensional accuracy and surface topography of a custom designed, 3D-printed zirconia dental implant and the mechanical properties of printed zirconia discs. The implant was 3D-printed using a digital light processing technique (DLP) and the dimensional accuracy was assessed using the digital-subtraction technique. The mechanical properties were evaluated using biaxial flexure strength test. Three different build angles were adopted to print the specimens for the mechanical test; 0 degree (Vertical), 45 degree (Oblique) and 90 degree (Horizontal) angles. The surface topography, crystallographic phase structure and surface roughness were evaluated using scanning electron microscopy analysis (SEM), X-ray diffractometer and confocal microscopy respectively. The printed implant was dimensionally accurate and analysis revealed a statistically significant higher characteristic strength of 0 degree printed specimens compared to the other two groups and no significant difference between 45 degree and 90 degree build angles. SEM analysis revealed cracks, micro-porosities and interconnected pores ranging in size from 196nm to 3.3 micro m. These results lead the researchers to conclude that DLP is efficient for printing customised zirconia dental implants with sufficient dimensional accuracy and that the mechanical properties showed flexure strength close to those of conventionally produced ceramics. However, optimisation of the 3D-printing process parameters is still needed to improve the microstructure of the printed objects.

Narrow diameter implants tested The intention of research carried out in Shanghai3 was to evaluate the long-term survival, complications, peri-implant conditions, marginal bone loss, and patient satisfaction of fixed dental prostheses supported by narrow diameter implants (NDIs) in the posterior jaws. A retrospective cohort study with a mean follow-up time of 10.1 years (SD: 2.5 years), it involved reviewing patients who had received NDIs for implant survival, hardware complications, modified plaque index (mPI), peri-implant probing depth (PPD), percentage of bleeding on probing (BOP%), marginal bone loss (MBL) and patient satisfaction. 45

Sixty-seven patients with 98 NDIs (Premolar site: 81, Molar site: 17, Single crowns: 33, Splinted restorations: 65) were included. The overall implant survival rates were 96.9% at implant level and 97.0% at patient level. Veneer chipping was the most common hardware complication, the rates being 19.4% at patient level and 18.4% at implant level. All patients showed acceptable oral hygiene. Thus, the average MBL was 1.19 mm at implant level and 1.15 mm at patient level. Eight implants (8.5%) and six patients (9.2%) were diagnosed with peri-implantitis. Fifty-eight patients (89.2%) were satisfied with the aesthetics of the restorations, while 55 patients (84.6%) were satisfied with the function. Narrow diameter implants could be a predictable treatment option in the long term. High survival rates, high patient satisfaction, acceptable complication rates and marginal bone loss were found to have been achieved.

Does chronic infection affect placement? The aim of this study was to assess whether immediate implant placement into post-extraction sites presenting a chronic infection poses a greater risk of implant failure than immediate placement in non-infected sites4. Records of patients who underwent extraction and immediate implant placement into both infected and non-infected sites from January 1998 to September 2014 at five different dental centres were considered for inclusion. Included records were subjected to statistical analysis of survival rates, along with a number of other patient-, implant-, surgery-, and prosthesis-related variables. The inclusion criteria were met by 369 patients who received a total of 527 implants. The follow-up averaged 53.2 months (range 0.9 - 158.3) for implants placed into non-infected sockets (N=334) and 50.1 months (range 1.6 - 146.1) for those placed into infected sites (N=193). Seven implants failed in non-infected sites and three in infected sites. All failures occurred within one year of placement. Cumulative implant survival rate for non-infected and infected sites was, respectively, 97.9% +/- 0.8% and 98.4% +/- 0.9%, being not significantly different (P=.66). None of the investigated variables affected the outcome. The conclusion was that the placement of implants into periodontally or endodontically infected sites immediately after tooth extraction is a safe option, even when the implants are loaded immediately or early.

Quality of life assessment A review of the current literature relating to the impact of dental implants on oral health-related quality of life (OHRQoL) in edentulous or partially dentate patients was competed by Reissmann and co-authors. Systematic literature searches were performed in the PubMed, EMBASE, and Cochrane Library databases, using high level MeSH terms. The searches were limited to studies published in English from 1960 to June 11, 2017, reporting OHRQoL outcomes using validated instruments, and having enrolled at least 50 patients. After removal of duplicates, a total of 2,827 unique hits were identified. After title, abstract, and full text screening, 63 articles were included in the review presenting findings of 55 individual studies. The provision of implant-supported dentures was associated with a significant increase in OHRQoL in partially dentate and in edentulous patients, with the magnitude of achieved improvement typically being greater for implant-supported dentures than with conventional ones. Furthermore, OHRQoL impairment prior to treatment was strongly associated with OHRQoL improvement. For partially dentate patients, there is not enough evidence that implant-supported dentures are superior in terms of OHRQoL than conventional ones, but moderate evidence suggests that the former perform better than the latter. In edentulous patients, evidence suggests that only if OHRQoL at baseline is highly impaired and patients request implant treatment, are implant-supported dentures superior in terms of treatment-induced OHRQoL improvement. Patients can be informed that implant treatment is usually related to a significant improvement in OHRQoL. However, improvement is not necessarily higher than for conventional prosthodontic treatments but depends on patientâ&#x20AC;&#x2122;s clinical and psychosocial characteristics

Implants and periodontal health A study in Milan evaluated the strength of the association between three widely used clinical indexes considered as behavioural indicators of attitude-related oral status and secondary implant failure due to peri-implantitis5. These were an index of oral hygiene, the plaque index [PI] and two periodontal indexes (the presence of bleeding on probing [BOP] and of pocket probing depth [PPD]) in patients rehabilitated with cemented prosthesis. Patients who underwent implant-prosthetic rehabilitation and had joined the programme of maintenance of the same hospital were included. Implant failures, number of months between implant insertion and implant loading, and patientsâ&#x20AC;&#x2122; 47

surgical protocol were monitored and recorded. Further, PI, BOP and PPD-all attituderelated indicators of oral hygiene and periodontal inflammation-were recorded and related, in terms of odds ratios and corresponding risk factors, to secondary implant failures. A total of 1,427 patients with 2,673 implants were enrolled. The follow-up ranged from 1.5 to 9 years (mean 5.3 years+/-1.3). The cumulative survival rate was 98.01%. Thirtytwo patients (36 implants, 1.36% of all implants) had implant failure. A statistically significant association between PI, BOP, PPD and secondary failures due to periimplantitis was observed so that, within the limitations of this study, all three of these behavioural indicators proved to be significant risk indicators for secondary implant failure, both from a clinical and from a socio-psychological attitude-related perspective.

Surface coatings One of the most common causes of implant failure is peri-implantitis, which is caused by bacterial biofilm formation on the surfaces of dental implants. Modification of the surface nanotopography has been suggested to affect bacterial adherence to implants. Silver nanoparticles are also known for their antibacterial properties. In this study, titanium alloy implants were surface modified following silver plating, anodisation and sintering techniques to create a combination of silver, titanium dioxide and hydroxyapatite (HA) nanocoatings. Their antibacterial performance was quantitatively assessed by measuring the growth of Streptococcus sanguinis, proportion of live/dead cells and lactate production by the microbes over 24h. Application of a dual layered silver-HA nanocoating to the surface of implants successfully inhibited bacterial growth in the surrounding media (100% mortality), whereas the formation of bacterial biofilm on the implant surfaces was reduced by 97.5%. Uncoated controls and titanium dioxide nanocoatings showed no antibacterial effect. Both silver and HA nanocoatings were found to be very stable in biological fluids with material loss, as a result of dissolution, to be less than 0.07% for the silver nanocoatings after 24h in a modified Krebs-Ringer bicarbonate buffer. No dissolution was detected for the HA nanocoatings. Thus, application of a dual layered silver-HA nanocoating to titanium alloy implants creates a surface with antibiofilm properties without compromising the HA biocompatibility required for successful osseointegration and accelerated bone healing.

References 1.

Chrcanovic BR; Kisch J; Albrektsson T; Wennerberg A. Impact of different

surgeons on dental implant failure. Int J Prosthodontics 2017; 30: 445-454.

Osman RB; van der Veen AJ; Huiberts D; Wismeijer D; Alharbi N. 3D-printing

zirconia implants; a dream or a reality? An in-vitro study evaluating the

dimensional accuracy, surface topography and mechanical properties of

printed zirconia implant and discs. J Mechanical Behavior of Biomedical

Materials 2017; 75: 521-528.

Shi JY; Xu FY; Zhuang LF; Gu YX; Qiao SC; Lai HC. Long-term outcomes of narrow

diameter implants in posterior jaws: A retrospective study with at least 8-year

follow-up. Clin Oral Implants Res 2017; Aug 28.

Zuffetti F; Capelli M; Galli F; Del Fabbro M; Testori T. Post-extraction implant

placement into infected versus non-infected sites: A multicenter retrospective

clinical study. Clin Oral Implants Res 2017; Jul 26.

Reissmann DR; Dard M; Lamprecht R; Struppek J; Heydecke G. Oral health-

related quality of life in subjects with implant-supported prostheses: A systematic

review. J Dent 2017; Aug 05.

6. Tecco S; Grusovin MG; Sciara S; Bova F; Pantaleo G; Cappare P. The association

between three attitude-related indexes of oral hygiene and secondary implant

failures: A retrospective longitudinal study. Int J Dent Hygiene 2017; Jul 11.

Besinis A; Hadi SD; Le HR; Tredwin C; Handy RD. Antibacterial activity and biofilm

inhibition by surface modified titanium alloy medical implants following

application of silver, titanium dioxide and hydroxyapatite nanocoatings.

Nanotoxicol 2017; 11: 327-338.

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Chapter 5

Diagnostic factors and treatment planning in posterior implants

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Differences in anatomy and biomechanics make treatment of posterior quadrants with dental implants substantially different to that of anterior areas. Other than with the use of implants, when posterior teeth are lost treatment options include a long-span fixed bridge or a removable partial denture, especially when no terminal abutment is available. Implants increase the options and also allow the preservation of unrestored teeth. When teeth are missing, implant supported restorations can be considered the treatment of choice from the perspective of occlusal support, preservation of adjacent teeth and avoidance of a removable partial denture. Decisions to salvage questionable teeth can be weighed against the predictability of implant therapy and the efficacy of long-term outcomes. Due to advances in bone augmentation techniques, sinus floor elevation and distraction osteogenesis virtually no limits exist to the placement of implants. Implant retained restorations provide considerable advantages over removable partial dentures including improved support, a more stable occlusion, preservation of bone and simplification of the prosthesis. Additionally, long-term oral health is often improved because less invasive restorative procedures are required for the remaining dentition. The predictability of the outcome of an implant restoration posteriorly is dependent on many variables including:

•

Available space

•

Implant number and position

•

Occlusal considerations

•

Type of prosthesis

•

Overall treatment plan.

Treatment planning considerations Available space Mesiodistal Though aesthetics is secondary in restoring the posterior quadrants, care should still be taken with implant position to allow restorations that will be functional as close to the natural dentition as possible, to allow proper development of occlusion and embrasure forms for patient comfort. Mesiodistal space is evaluated in two dimensions as adequate prosthetic space must exist to provide the patient with a restoration that mimics natural tooth contours (Figure 1). If inadequate prosthetic space exists, it must be created through enameloplasty of adjacent teeth or orthodontic repositioning. The mesiodistal space required essentially depends on the tooth type being replaced (molar or premolar), and the number of teeth being replaced. The natural maxillary first and second premolar, and first molar have an average mesiodistal size of 7.1, 6.6 and 10.4 mm respectively and their dimensions at the cemento-enamel junction (CEJ) are 4.8, 4.7 and 7.9 mm. At a distance 2 mm from the CEJ the teeth measure 4.2 mm, 4.1 mm and 7.0 mm.

Figure 1 Radiograph showing implants placed too close together

Decisions need to be made with regards to implant size and the following guidelines can be used: â&#x20AC;˘

The implant should be at least 1.5 mm away from the adjacent teeth

â&#x20AC;˘

The implant should be at least 3 mm away from an adjacent implant

â&#x20AC;˘

A wider diameter implant should be selected for molar teeth.

Based on the above for two 4 mm diameter implants a space of 14 mm is required. This amount of space would suffice to replace two premolars. If two premolars and a molar are required an additional space is necessary. This situation can be resolved by placement of two implants and fabrication of a fixed partial denture or placement of three implants. In either case a wider diameter implant is required in the molar region (5 mm). If three implants are planned a total space of 23 mm is required. Similar guidelines should be followed when treatment planning implants in the posterior mandible. The size of the prosthetic tooth must be considered when

placing implants; the implant must be placed sufficiently away from the adjacent tooth to allow the restorative dentist to develop appropriate contours. If an implant placed for a premolar restoration is placed too close to the adjacent tooth, compromised contours and unnecessary loss of hard and soft tissue adjacent to the implant result. Placing the restoration too far from the adjacent tooth also results in unfavourable contours and development of cantilever type forces on the implant. Treatment planning a premolar restoration requires the surgeon to place the implant 1.5 mm away from the adjacent root. Molar teeth are wider mesiodistally and for molar implant restorations the implant needs to be placed 2.5 mm away from the adjacent tooth to allow development of appropriate restorative contours (Figure 2). Placing an implant for a molar tooth too close or too far from the adjacent tooth will also result in compromised restorative contours (Figure 3).

Figure 2

Figure 3

Treatment planning for molar teeth needs to take into account appropriate dimensions of a molar. The implant needs to be placed at least 2.5 mm away from the adjacent root to allow optimum emergence

Final restorations illustrating compromised aesthetics and contours

Buccolingual At least 6 mm of bone buccolingually is required for placement of a 4 mm diameter implant and 7 mm for a wider diameter 5 mm implant. The implants should be placed so that the projection of the fixture is contained within the anticipated crown form. The screw access should be positioned towards the centre of the occlusal surface. Posterior mandibular fixtures should be placed so that the exit angle of the screw access should point towards the inner incline of the palatal cusp. Posterior maxillary implants should be placed so that the exit angle of the screw access points towards the inner incline of the buccal cusp. Correct angulation is always achieved

if the surgeon is diligent and makes use of a surgical guide to place implants in the correct position. Placing implants in off angle positions always complicates the process for the restorative dentist who then has to use a host of restorative components to achieve an acceptable end result.

Occlusogingival This parameter also needs to be considered in two dimensions: â&#x20AC;˘

Adequate space for restoration

â&#x20AC;˘

Adequate osseous volume for placement of the implant.

Sufficient space must exist to allow the restorative dentist to fabricate restorations which are harmonious aesthetically with the adjacent teeth. On examination the space between the residual ridge and the opposing occlusal plane should be evaluated. Replacing premolar and molar teeth requires 10 mm of space between the residual ridge and the opposing occlusion; 7 mm would be considered the bare minimum. Often, when teeth are missing for prolonged periods of time, opposing teeth over-erupt and compromise the restorative space. If this is minimal, enameloplasy or minimal restorative therapy may be required to create space. On occasion molar teeth over-erupt to the extent that they contact the opposing residual ridge (Figure 4). Orthodontic intrusion of these teeth is a technique-sensitive procedure which requires diligence from both the surgeon and orthodontist. Options include both elective endodontics, crown lengthening and preparation of the tooth for a full coverage restoration. In instances where the root trunk is short, consideration must be given to extraction and implant replacement as an alternative so that sufficient space can be created. Often when space is limited towards the posterior quadrant the patient must be informed that it may not be possible to fabricate restorations to replace all of their missing teeth.

Figure 4 Inadequate space in posterior mandibular area for fabrication of a tooth shaped restoration

In considering adequate osseous volume for placement of the implant the clinician is often confronted with single tooth gaps that present all of the pre-requisites for successful implant therapy, with the exception of sufficient vertical bone height. The question arises: what is the minimal height of the implant required to support a posterior restoration? Clinicians have anecdotally used the longest implant possible, being concerned with the ratio between the implant and suprastructure length, the thought process being that an unfavourable implant: suprastructure ratio will cause crestal bone resorption. There are data from prospective multicentre studies to show that shorter implants of 6-8 mm did not show increased crestal bone loss in comparison to longer implants (10-12 mm) and the unfavourable ratio between the implant and the suprastructure did not lead to more pronounced crestal bone resorption. For a standard protocol 7.5 mm of bone height is required for a 6 mm long fixture and 8.5 mm is required for a 7 mm fixture. Prior to fixture placement the maxillary sinus, inferior alveolar canal and mental foramina must be evaluated by means of a CT scan. There should be at least 2 mm of bone between the apical end of the implant and neurovascular structures. Advances in onlay grafting, distraction osteogenesis and maxillary sinus augmentation allow the surgeon to place implants in sites that were previously contraindicated. Sinus augmentation provides adequate bone volume to place implants but does not correct for vertical space deficiencies. The patient must be aware that prosthetically, long teeth with root form or pink porcelain will be required. The diameter of the implant also plays a role in occluso-gingival placement. Originally, wider diameter implants were created as a rescue implant for conditions in which the standard 3.75 mm implant could not be stabilised. For the restorative dentist the wide diameter implant has been a welcome addition. The improved stability, greater surface area and improved force distribution are particular benefits in the posterior part of the mouth where forces are greater. The success with wide diameter implants replacing molar teeth has been documented in clinical studies and they certainly come closer to replicating the emergence profile of the molar tooth. With regards to placement, use of a standard 4 mm diameter implant for a molar tooth requires the implant to be placed slightly deeper so that an appropriate emergence profile can be developed. The limiting factor in placement may be vital structures, in which case the prosthesis design will require the con-tours to extend horizontally from the implant. Maintaining hygiene becomes very difficult and some patients may even complain of food entrapment. Use of wider diameter implants allows shallower placement of the implant since the transition in emergence profile from the wider diameter is not as pronounced. Clinicians have also advocated placement of two implants in molar 54

positions to compensate for poor bone quality. Double implants more closely mimic the anatomy of the roots being replaced and double the anchorage surface area. Other advantages include eliminations of antero-posterior cantilever, reduction of rotational forces exerted and reduction of screw loosening. However, daily oral hygiene may be more difficult and a major limitation in placing two implants is insufficient mesiodistal space.

Implant number and position There is insufficient scientific evidence to guide the practitioner as to how many implants are required to rehabilitate the patient when multiple teeth are missing in posterior quadrants. Most recommendations are derived from traditional prosthodontic experience and are based on clinician experience which is anecdotal. When three posterior teeth are missing, two or three implants may be required dependent on bone quantity and quality. Often in the maxilla where less dense bone is found, surgeons favour placing three implants, one for each tooth. The rationale for this is primarily restorative. Should one implant of the three fail, the restorative dentist may still continue with the anticipated prosthesis. If anterior or posterior implants were to fail the prosthesis design would include an anterior or posterior cantilever. Cantilever type prostheses have been associated with higher rates of failure in traditional prosthodontics. These types of prosthesis failed due to mechanical complications of the abutment teeth, although these can be controlled with an implant supported prosthesis. Abutments can be optimised for length and taper and connector size can be improved for maximum strength. On occasion, where bone volume is inadequate, the clinician has to decide if a bone augmentation procedure is justified or whether a more simple approach of cantilevering would suffice. When cantilevering, the occlusal surface of the cantilever should be minimised and occlusal contact should be controlled so that the majority of the load is distributed along the long axis of the implants. As with traditional prosthodontic protocols, cantilevering forward is much more favourable than cantilevering posterior to the implants. Distal cantilevers have been reported to be unfavourable from a biomechanical point of view and have increased the number of complications for implant supported prostheses. The choice between using two or three implants is also related to the biomechanics of the prosthesis and how load is distributed. With three implants it is possible to offset the implants and position them for a tripod effect. This has been claimed to give a more optimal bone support than a linear arrangement. From a practical perspective 55

it is very difficult to place three implants in an absolute linear arrangement and tripoding, to a certain degree, is always likely to occur. If only two implants are placed, use of a wider diameter implant will often provide an equivalent benefit to the non-linear configuration. When insufficient osseous volume exists in the posterior maxilla and the patient does not want to undergo a sinus augmentation procedure, consideration must also be given to implant placement in the tuberosity area.

Occlusal considerations Masticatory forces developed by a patient restored with implant supported restorations are equivalent to those of a natural dentition. When treatment planning patients for implant supported restorations, a general assessment of the likely load to be placed on the implants should be made. If the patient is a bruxer the clinician may plan additional implants to allow for more favourable load distribution. Complications with dental implants are most often the result of inadequate treatment planning. Consideration of bone density and volume, anticipated loads and planned restorative design are all important to review before number, length and diameter of implants are determined. Implants, unlike natural teeth, are ankylosed to the surrounding bone without an intervening periodontal ligament. The mean values of axial displacement of teeth in the socket vary between 25-100 microns. The range of motion of osseointegrated implants has been reported to be approximately 3-5 microns. Displacement of a tooth begins with an initial phase of periodontal compliance that is non-linear and complex, followed by a secondary movement phase occurring with the engagement of the alveolar bone. In contrast, an implant deflects in a linear and elastic pattern and movement of the implant under load is dependent on elastic deformation of the bone. There are studies supporting the finding that implants are more susceptible to occlusal overloading than natural teeth. The types and basic principles of implant occlusion have been derived from occlusal principles of traditional tooth borne restorations. Techniques should be used to minimise excessive loading on implant supported restorations. The occlusion should be evaluated and organised so that there is anterior guidance and disclusion of posterior teeth on lateral excursion. There should be no contact of posterior teeth on both working and non working sides. If the canine is compromised, group function is acceptable. Initial occlusal contact should occur on the natural dentition. The centric contacts are adjusted with light occlusal contact on the implants; the

rationale for this is that the opposing natural dentition is often compressed on firm closure. Implants have added options to successful prosthodontic rehabilitations formerly unavailable. Implants must be a consideration for every treatment plan. Implant retained restorations provide considerable advantages over removable partial dentures. Improved support, a more stable occlusion, preservation of bone and simplification of the prosthesis are a few reasons why implants are the treatment of choice for missing posterior teeth. Additionally, long term oral health is often improved because less invasive restorative procedures are required for the remaining dentition. The practitioner must carefully evaluate the parameters outlined to ensure predictability and longevity of restoration.

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Chapter 6

Peri-implantitis aetiology and prevention

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While it may be possible to feel smug in the knowledge that peri-implantitis only occurs in the presence of implants, the comfortable feeling wears off very quickly when one asks the questions, why does it happen and how can we prevent it?

Peri-implant mucositis and peri-implantitis Peri-implant mucositis (Figure 1) has similar characteristics to gingivitis and has been defined as a reversible inflammatory lesion affecting the soft tissue in the area immediately around implants but not affecting the surrounding bone. Peri-implantitis has been defined as an inflammatory lesion causing crestal bone loss and soft tissue inflammation which can present with bleeding on probing and suppuration and was first described by comparison of the microbiological features of implants considered to be successful and those that were â&#x20AC;&#x2DC;failingâ&#x20AC;&#x2122; resulting in bone loss (Figure 2). This gave the clue to how poor oral hygiene and uncleansable suprastructures increased the likelihood of a pathogenic biofilm.

Figure 1

Figure 2

Peri-implant mucositis around the upper left central and lateral incisor

Radiograph of three implants showing bone loss through peri-implantitis

Diagnostic features of peri-implantitis Peri-implant lesions are often asymptomatic in their early stages and can present as a chance finding at recall. In such cases the peri-implant soft tissues are usually inflamed, presenting with bleeding on probing, consistent with a diagnosis of peri-

implant mucositis1. Inflammation of the gingival cuff may not, however, always be present but gingival enlargement can develop if implants are located in an area of non-keratinised mucosa or if the restoration is removable. Recession may also be present as may exposed implant threads and where the gingiva is thin, a blue hue may be present due to shine-through of the underlying metal of the implant.

Probing Probing is important for both diagnosing peri-implantitis and monitoring disease progression. Similarly to probing teeth, a 0.25 Ncm force has been recommended and the epithelium around implants after probing has been shown to heal within five days. Performed this determines the location of the base of a pocket relative to a known and documented fixed landmark on the implant or its suprastructure. Probe penetration varies with the condition of the peri-implant tissues as in health and mucositis, the presence of a soft tissue collar prevents the probe from reaching the alveolar crest. In contrast, probe penetration has been shown to reach the alveolar bone level in peri-implantitis. Probing error has been shown to be greater around implants with peri-implantitis than those with mucositis or in health and consequently, standardisation of probing around implants is important for accuracy and the detection of any inflammatory changes. Measures such as reducing probing force to 0.25 Ncm and the recording of probing points and angulations in relation to the restoration might improve repeatability and accuracy. Probing around implants often tends to be more difficult than around teeth due to the need to navigate around the implant suprastructure. Where the restoration is bulky, reproducible probing depths may only be possible if the restoration is removed to assist direct visual examination. One suggestion has been to use plastic probes (TPS or WHO 621) due to their superior flexibility and ability to navigate around the implant suprastructure. The clinical process of identifying the base of the pocket with certainty can also be difficult. If the apex of the probe engages a thread this may be mistaken for the bottom of the defect. Although the use of a plastic probe has advantages, metal probes are still the first choice for probing. Interpretation of probing depths requires caution. Deeply located implants may have probing depths of 5 mm or greater but remain clinically healthy. Pathologic probing profiles around implants are usually consistent circumferentially around the fixtures.

Bleeding on probing Bleeding on probing represents the inflammatory response of tissues to the presence of a biofilm. Bleeding on probing around implants has been shown to be a significant predictor for disease presence and is a better predictor of peri-implant disease than analogous periodontal disease. As such, detection of bleeding on probing or peri-implant mucositis should be a prompt for the increased reinforcement of selfdirected oral hygiene measures as well as supportive periodontal treatment. This increased self and professionally directed maintenance is likely to be crucial in the preventing progression to peri-implantitis.

Suppuration Suppuration indicates active peri-implantitis and is likely to be associated with bone loss and future implant failure if no active preventive treatment is instigated.

Percussion Tenderness to percussion can be detected in peri-implantitis and also the rarer presentation of retrograde peri-implantitis. Implants should be percussed in lateral and apical directions to aid diagnosis. The percussion tone can also be noted since where significant bone loss has occurred the tone can often be duller than the normal high pitch associated with implants in health. However, this finding must be treated with caution due to the lack of robust evidence to support this association.

Mobility Mobility is a poor indicator for peri-implantitis progression and is only really relevant where the disease has progressed to the extent that implant removal is indicated. Where extensive reconstructions are supported by a number of implants there may be a need to deconstruct the bridgework, or bar, to fully assess the presence of mobility of individual units. Even in cases of advanced bone loss implants may remain immobile despite marked tissue loss due to partial loss of integration. Delineation between true mobility of the implant and that of its supra structure is also required. For example, detection of mobility of an implant retained crown can be performed by applying rotational movement to the crown between forefinger and thumb as opposed to a bucco-palatal direction. This is due to the orientation of the threads making rotational movement more discernible.

Radiographic features Good quality radiographic examination is valuable in the diagnosis and monitoring of peri-implantitis. Radiographs taken once the restorations are definitively placed should be adequate to provide a baseline for future reference and help to confirm optimal restoration seating. Marginal bone changes during the first year of restoration may be related to physiological bone remodelling and establishment of biologic width, and should not be confused with peri-implant disease. The baseline radiograph may be repeated after the first year in function to assess the stability of bone support, or in cases where any clinical signs may indicate incipient pathology. Any further radiographic exposures should be done on the basis of need and should be based on significant changes in the clinical picture and not just performed to follow any arbitrary protocol. Optimal beam angulation will allow threads to be recorded and provide additional information on disease progression. Indeed parallel angulation will result in thread sharpness on both sides of the implant.

Aetiology There is still debate about the aetiology of peri-implantitis even to the extent of speculation that it is a secondary manifestation of an exaggerated foreign body reaction to the implant itself or due to corrosion. While further research into aetiological factors other than biofilm development seems to be required, the development of a biofilm is considered by many to be the key factor in the development of peri-implantitis. Biofilm development may become more likely once any marginal bone loss occurs whether this be pathological or physiological. As such it can be debated that biofilm development is a secondary, as opposed to a primary, aetiological factor for peri-implant bone loss. Teeth and implants are anatomically different and as such so is the process of biofilm development. Teeth have transeptal or dentogingival fibres (Sharpeyâ&#x20AC;&#x2122;s fibres) that insert into cementum and tend to form a seal against bacteria in health. These are absent in implants and the fibres that exist are largely circumferential in nature. Once an abutment is connected to the implant the microflora that establishes in the periimplant sulcus is nearly identical to that found on adjacent teeth. Progression to bacterial population of the implant surface may result from epithelial ulceration with disruption of peri-implant connective tissue adhesion leading to biofilm establishment there.

Factors that are likely to influence the nature of the biofilm and its establishment include surface roughness, composition, and the thread profile. Implants with rougher surfaces and more aggressive thread pitches are likely to develop a biofilm that is more robust and difficult to remove. Unfortunately, these features are designed to improve osseointegration but perversely also seem to promote biofilm formation. Once a biofilm becomes adequately established inflammation of the circumferential soft tissue can result in peri-implant mucositis. Detecting progression from biofilm development to peri-implant mucositis is crucial as mucositis is readily treatable with oral hygiene measures and biofilm disruption. If this microbial colonisation is prolonged, an inflammatory infiltrate forms in response, which results in the establishment of a peri-implantitis lesion. However the progression from mucositis to peri-implantitis is not automatic and as such patients may present with erythematous tissues without associated bone loss. In cases where progression does occur the local host response mediates bone resorption in a similar way to periodontitis, resulting in decreased bone implant contact over time. There have been suggestions that peri-implantitis progresses at a greater rate than periodontitis due a variety of histological factors. Where periodontal and periimplantitis lesions are compared a protective tissue capsule, which serves to selflimit the lesion, is present in periodontitis but absent in peri-implantitis. As a result the apical extent of the lesion is more pronounced in peri-implantitis than periodontitis. Peri-implantitis lesions have been shown to exhibit signs of acute inflammation with proportionally greater amounts of inflammatory mediators and resorbing osteoclasts lining the crestal bone. It seems that the pathology associated with peri-implantitis is more aggressive and rapid and so can develop unchecked due to these characteristics. This is reflected in studies examining surface roughness and the progression of peri-implantitis; those implant surfaces with smoother surfaces exhibited less progression of peri-implantitis than those with greater surface area and geometries. As such surface area and geometry of fixtures plays a significant role in the osseointegration process but conversely appears to result in faster progression of peri-implantitis if and once the disease process has been initiated.

Differential diagnosis Bone loss around implants may occur due to reasons other than biofilm development. Once an implant is restored a period of bone remodelling is likely to occur which may result in the appearance of bone loss without infection. This establishment of the implant biologic width happens over the course of the first year after restoration after which the bone level stabilises, although the rate varies between different implant systems. 62

Implant positioning can also effect the bone remodelling, If implants are placed too close together then the risk of physiological bone loss may increase. A similar situation may arise with implants placed too deeply resulting in bone loss from bone adjacent to the submucosal component of the restoration. Gingival biotype can also influence physiological bone remodelling around implants. Thick biotypes have a lesser propensity to loose marginal bone than thinner types.

Operative factors Soft tissue manipulation techniques designed to contour restorations to preferentially mould gingival tissue can also result in bone remodelling in a similar way. Indeed some authors argue that the role of the prosthodontist in helping to prevent periimplantitis has been underestimated. Dawood et al.2 argue that the effect of prosthodontic stages of treatment on the postoperatively established state has not been adequately investigated. It is the contention of these authors that the manner in which the implant is restored contributes significantly to prognosis and peri-implant disease experience, and that the role of prosthodontic aspects of treatment in the causation of peri-implantitis may be seriously underestimated. The prosthodontist has a clear role and responsibility in the avoidance of future peri-implant problems by ensuring that implants are restored in an entirely biologically and biomechanically sound manner. The authors consider these factors under a number of different categories.

Abutment connection There is evidence that avoiding the repeated connection and disconnection of components at fixture head level will reduce bony remodelling; this would seem intuitive as every time a titanium or zirconia component is removed from the fixture head, a hemidesmosomal connection is severed and needs to be re-established. The use of an abutment is particularly important when the implant is deeply placed. While careful and purposeful repeat activity at the fixture head may be avoided, this interface must be treated with respect and unnecessary insult to the tissues or contamination of components avoided. Each treatment stage and the components and materials needed should be planned in advance, aiming to minimise the number of procedures.

Impressions and temporary restorations Whether restoration of the implant begins at the time of surgery (if immediate loading is carried out) or following a conventional healing period, making an impression with a dental impression material or using resins, composites or adhesive bonding agents will all put potentially contaminating dental materials in proximity to the implant platform or definitive abutment. Contamination of the implant or abutment surface, particularly of a high energy, rough surface with a low-viscosity dental material may have the potential to preclude uniform osseo- or tissue integration, and so their use must be carefully constrained. Clearly, if such materials are used at the time of surgery there is more scope for contamination, particularly if the rough surface of an implant is exposed, or if retraction cords are used and tissue is retracted beyond the implant platform, or if material remnants are left behind.

Laboratory phase Parameters such as material choice, abutment selection, the use of prefabricated or custom components, and the use of potentially less precise (in-house computer aided design â&#x20AC;&#x201C; computer aided manufacturing [CAD-CAM]) technologies, or cast or machined non-implant grade materials all have biological and clinical ramifications which are harder to appreciate when an impression sits on the laboratory bench. The restoration must be made to the clinicianâ&#x20AC;&#x2122;s prescription as some technical decisions which may have important biological consequences may be absolutely contrary to convenience or ideal aesthetics, for example, the subgingival extension of porcelain or resin materials.

Planning for screw or cement-retention Screw retention of implant crown and bridgework facilitates retrievability and completely eliminates the risk of subgingival cement extrusion. However, lack of precision can result in poorly fitting bridge substructures, or tight contacts between adjacent implant restorations, generating high-level standing loads with the potential to hasten component fracture and possibly contribute to crestal bone loss.

Where cement retention is unavoidable, placing the restoration/abutment margin supra-gingivally will reduce the potential for cement extrusion into the tissues (Figure 3). Even in aesthetic zones this may still be practical, by using zirconia abutments and appropriate cements/adhesives, and/or designing the contour such that only

the most visible part of the interface is designed to be at or just below the gingival margin. Repeated trauma to the tissues caused by frequent debonding of a cement retained restoration may be harmful, and also makes it more likely that cement will be extruded subgingivally. Placing restorative margins subgingivally in an attempt to improve retention will exacerbate this issue, however placing restorative margins supragingivally may reduce the height of an abutment making retention less reliable.

Figure 3 A CAD CAM zirconia abutment designed to have supragingival margins palatally, with the buccal margin just beneath the buccal gingival margin so as to minimise the potential for cement extrusion

Designing for maintenance Excellent hygiene maintenance has been shown to improve long-term outcome. Designing for maintenance begins with the correct planning and management of the surgical phase of treatment to ensure that the implant is in the correct position to support a well-designed prosthesis. Although patients may well prefer to have prostheses that tightly conform to the tissues beneath, it is important to make sure in the laboratory that there is easy access for oral hygiene procedures suited to the patientâ&#x20AC;&#x2122;s physical capacity. Ridge-laps are to be avoided, and the under surface of fixed bridgework should be easily accessed â&#x20AC;&#x201C; ideally convex along its entire length. Preferably the under surface of the bridgework would fit against the tissues with a polished titanium or zirconia surface. Fixed bridges may be provided with grooves which guide the introduction of floss or interdental brushes â&#x20AC;&#x201C; it may be useful for the technician to try these aids in the laboratory before fitting a prosthesis.

Decontamination Upon completion of laboratory work, abutments that have been open and manipulated in the laboratory should be de-contaminated and sterilised.

Removing fine debris such as porcelain or abrasive particles or metal swarf will improve seating. The presence of debris in a screw joint will increase friction and reduce dependability, making screw-loosening more likely. Similarly, single tooth restorations fitting at fixture level such as one-piece zirconia-bonded crowns require careful decontamination.

Fitting screw-retained restorations Seating screw-retained restorations should be straightforward. For fixed bridgework, each screw should rotate freely as it is tightened into place, with no build-up in tension at all until the last quarter rotation â&#x20AC;&#x201C; ideally less â&#x20AC;&#x201C; indicating that the framework fits passively (ideally onto an abutment rather than directly to the implant), the screws simply serving to hold the prosthesis in place. The clinician would be unwise to accept a poorly fitting framework; apart from possible contributions to the development of peri-implantitis later on, component failure is more likely. The abutment screw access should be adequately sealed to prevent it from acting as a channel and reservoir of microbial species. The use of polytetrafluoroethylene tape and composite resin minimises microbial leakage.

Fitting cement-retained restorations There is a view that a cement-retained prosthesis will have a better tolerance for slight misfit, however, a poor fit and subgingival open margin may cause inflammation, as it would in a con-ventional prosthesis, which may lead to plaque accumulation and the initiation of peri-implant inflammation. Cement extrusion is one of the most conspicuous and widely recognised causes of peri-implantitis and may sometimes be resolved after removal of the excess cement. The risk of cement extrusion may be minimised by planning for supragingival abutment margins, and by using just sufficient cement for the purpose; various means to achieve this have been proposed.

References 1.

Alani A, Kelleher M, Bishop. Peri-implantitis. Part 1: Scope of the problem.

Br Dent J 2014; 214: 281-287

Dawood A. Marti Marti B, Tanner S. Peri-implantitis and the prosthodontist.

Br Dent J 2017; 223: 325-332.

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