Confronting Controversial Issues in Dental ... - dentalCEtoday.com

Continuing Education Course Number: 164

Confronting Controversial Issues in Dental Implant Therapy, Part 1 Authored by Gary Greenstein, DDS, MS; John Cavallaro, DDS; and Dennis Tarnow, DDS Upon successful completion of this CE activity 2 CE credit hours may be awarded

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Continuing Education

Confronting Controversial Issues in Dental Implant Therapy, Part 1 Effective Date: 8/1/2013

Dr. Tarnow is director of dental implant education and a clinical professor, Department of Periodontology, College of Dental Medicine, Columbia University, New York City. He maintains a private practice in New York City. He can be reached at [email protected].

Expiration Date: 8/1/2016

Disclosure: Dr. Tarnow reports no disclosures.

LEARNING OBJECTIVES INTRODUCTION

After participating in this CE activity, the individual will learn: • That there are abundant data to indicate that despite increased stress associated with certain types of prosthetic constructs, the survivability, technical issues and biological responses are not deterrents for employing cantilevers and increasing crown to implant ratios within certain limitations. • Recommendations for enhancing success with these types of prostheses.

Confronting controversies in implant dentistry is necessary in order to develop clarity with respect to choices clinicians have when treatment planning dental prostheses. As new information appears in the literature which conflicts with ingrained ideas, therapists may be left in a quandary concerning which facts should be applied to patient management. Therefore, it is essential to assess current data from multiple studies to determine the status of therapeutic options. In this 2-part article, 5 subjects related to implant dentistry are addressed to help clarify certain controversial issues. Part 1 discusses the topics of cantilevers off of dental implant-supported prostheses, and increased crownto-implant ratios (CIRs). Part 2 will discuss the topics of angulated abutments, connecting teeth to implants, and bone adaptation to stress. Each subject was previously reviewed by the authors.1-5 This 2-part series summarizes the critical salient facts and provides clinical guidelines to enhance patient outcomes. First, background information is provided to help understand bone tolerance levels with respect to stresses applied to dental prostheses.

ABOUT THE AUTHORS Dr. Greenstein is clinical professor, Department of Periodontology, College of Dental Medicine, Columbia University, New York, NY. He maintains a private practice in Surgical Implantology and Periodontics in Freehold, NJ. He can be reached via e-mail at the address [email protected]. Disclosure: Dr. Greenstein reports no disclosures. Dr. Cavallaro is director of the implant fellowship program and associate clinical professor of prosthodontics, College of Dental Medicine, Columbia University, New York, NY. He maintains a private practice in surgical implantology and prosthodontics in Brooklyn, NY. He can be reached at [email protected].

FORCES ACTING ON PROSTHESES Cantilevered prostheses, increased crown-to-implant ratios, angulated abutments, and connecting teeth to implants are prosthetic constructs that experience increased stresses and strains.6-9 Stress is the force acting on a prosthesis, and the biologic response is referred to as strain (deformation or elongation of bone).10 Forces beyond biomaterial tolerances

Disclosure: Dr. Cavallaro reports no disclosures.

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Confronting Controversial Issues in Dental Implant Therapy, Part 1 cantilever.26,27 The increased stress is mainly located at the bone crest adjacent to the surface of the implant facing the cantilever,28 and as the cantilever becomes longer the stress increases on the prosthesis and bone.

can cause technical problems (eg, screw loosening or breakage, implant fracture, and disruption of cement retention) and biological problems (eg, bone loss). Bone deformation is expressed in microstrains (ue), where 1,000 ue in compression shortens bone by 0.1%. The fracture strength of lamellar bone is 25,000 ue or 2.5% deformity.10 According to Frost,11 a certain amount of stress/strain is needed to maintain bone homeostasis. Too little stimulation results in bone atrophy, and too much causes microfractures and bone loss. The suggested relationship between bone microstrain and physiological responses are listed: 0 to 50 ue—atrophy, 50 to 1,500 ue—normal bone modeling, 1,500 to 3,000 ue— overload, > 3,000 ue—destructive. Forces exceeding the physiological bone tolerance around an implant can result in bone resorption and deosseointegration at the bone-implant interface.12-14 However, it is not possible to identify a precise force threshold that initiates bone loss around an implant because there are many confounding variables: loading conditions, prosthesis type (unsplinted or splinted), abutment angulation, bone type, duration of destructive overload, etc. With these concepts in mind, various types of prosthetic constructs that experience increased stress during function are examined with respect to several perspectives: long-term survivability, biological, and technical issues.

Potential Benefits Associated With Implant-Supported Cantilevered Fixed Dental Prostheses The primary benefit provided by an ICFPD is denoted by its ability to expand therapeutic options, which could simplify prosthetic restorations. Its employment may allow placing a cantilevered pontic over a site that had a lack of bone (eg, sinus, mental foramen), thus circumventing the necessity to restore bone to support an implant. This would avoid additional cost, decrease treatment time, and reduce morbidity related to surgical endeavors. Potential Shortcomings Linked to Implant-Supported Cantilevered Fixed Dental Prostheses Increased torque may potentially induce biological problems (bone-implant interface deterioration, bone resorption) and mechanical issues (screw loosening, implant and prosthesis fracture, porcelain fracture).29 Clinical Trials Evaluating Bone Resorption Around Implant-Supported Cantilevered Fixed Dental Prostheses Concerning bone loss, 2 prospective controlled investigations found no statistically significant difference with respect to bone resorption around prostheses with or without a cantilever (0.49 mm versus 0.38 mm,17 0.23 mm versus 0.09 mm18). Human Clinical Trials: Survival Rates of ICFDP— Investigations that assessed the utility of ICFDPs (one pontic cantilevered off 2 implants) demonstrated a high survival rate (Table 1).17-24 Five studies17-21 that spanned 5 years were included in a systematic review.25 The survival rate for ICFDPs at 5 years was 94.3% (95% CI: 84.1 to 98%) and after 10 years, it was 88.9% (95% CI: 70.8 to 96.1%). Three other investigations, not included in the systematic review because they did not meet all the inclusion criteria, exhibited survival rates of 98%22 to 100%23,24 (Table 1).

UNILATERAL SHORT SPAN CANTILEVERS OFF DENTAL IMPLANTS An implant-supported cantilevered fixed dental prosthesis (ICFDP) consists of one or more abutments at one end of the prosthesis and one or more unattached pontics at the other end. Concerns were expressed regarding potential biological and technical problems associated with cantilevers, because they experience increased bending moments.15,16 However, emerging data indicate that uniltateral implant-supported fixed dental prostheses with a cantilever have a high survivability rate (Table 1).17-25 Forces on a Cantilevered Prosthesis The stress on implants supporting an ICFDP is 2 to 3 times greater than found on single implants that do not support a

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Confronting Controversial Issues in Dental Implant Therapy, Part 1 Table 1. Studies Addressing Survival of Fixed Dental Prostheses With Cantilevers (ICFDP)a STUDY

IMPLANT TYPE

NO. OF PATIENTS

NO. OF ICFDPS

LOCATION OF ICFDPS

YEARS OF FOLLOW UP

NO. OF FAILED IMPLANTS

NO. OF FAILED ICFDPS

ICFDP ESTIMATED 5-YEAR SURVIVAL RATE

Wennström et al17

Astra Tech

28

24

16 maxillas 8 mandibles

5

2

2

92.6b

Hälg et al18

Straumann

27

27


5

2

3

89.5b

Eliasson et al19

Brånemark

–

61

c

10.5

2

0

100b

Kreissl et al20

3I Osseotite

20

23

maxillas and mandibles

5

1

1

95.7b

Brägger et al21

Straumann

14

18


9.4

1

3

91.5b

Becker et al22

Straumann

35

60

6 mandibles 54 maxillas

10

0

0

100

Romeo et al23

Brånemark Straumann

38

8 41


1 to 7

3

1

98

Johansson and Ekfeldt24

Brånemark

83

65

–

4.1

–

0

100

aICFDP—Implant supported fixed partial denture with a cantilever, studies listed with earliest publication date going first. bSurvival rate computed by Algietta et al.25 cNot reported, there was one lost implant in the study, but it was not indicated if it occurred in the control or the cantilever group.

Duplicated with permission of Journal of the American Dental Association.1

Systematic Reviews: Comparison of Survivability of Implant-Supported Cantilevered Fixed Dental Prostheses to Other Types of Fixed Prostheses The 10-year data indicate that the survivability of ICFDPs with a cantilever of limited mesiodistal dimension (one premolar sized tooth) is 88.9%,25 which is comparable to fixed dental prostheses retained by teeth (89.1%)30 or implants without cantilevers (86.7%).29

these complications do not jeopardize the survivability of ICFDPs, but they do underscore that maintenance is required. In a systematic review by Zurdo et al,31 based on 3 studies4,5,7 used in the Aglietta et al paper,25 they reported that the occurrence of minor technical problems happened more often with ICFDPs (weighted mean 20%, range 13% to 26%) than implant supported prostheses without a cantilever (weighted mean of 9.7%, range 0% to 12%).

Technical Problems Associated With ImplantSupported Cantilevered Fixed Dental Prostheses Complications can be divided into 3 different categories: major (implant fracture and loss of superstructures), medium (abutment, veneer or framework fracture), and minor (abutment or screw loosening, loss of retention, veneer chipping).29 The prevalence of technical complications related to ICFDPs are within the range for implant supported prostheses.29 In general,

Conclusions and Recommendations The data indicate that short span ICFDPs are a predictable technique to restore partially edentate areas of the mouth. This finding is in accord with the European Association for Osseointegration.32 The suggestions in Table 2 are provided to reduce stresses on ICFDPs, which should decrease biological and technical complications and increase their survivability.1,9,18,33-39

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Confronting Controversial Issues in Dental Implant Therapy, Part 1 Table 2. Clinical Recommendations for Restoring Teeth With Cantilevers1 1. Number of Implants—Fixed dental prostheses utilizing 2 to 3 implants to support a cantilever are successful. 2. Spacing of Implants—A span of at least 8 mm between the centers of implants seems proper.33 Stress on the prosthesis increases when interimplant spacing decreases or cantilever length increases.9 3. Width of Implants—Increased diameter avoids implant fracture that was reported with 3.3-mm implants.18 4. Mesiodistal Length of the Cantilever—Keeping the size of the cantilever to the mesio-distal dimension of a premolar.34 5. Dimensions of Connector—To calculate the rigidity of a beam for occlusal loading, the following formula can be used: I (rigidity) = WH3/12.35 This formula shows that doubling the buccolingual width (W) of the metal connection doubles the strength, but doubling the occlusogingival height (H) increases the strength 8 times. Therefore, the thickness in height and width of connectors should be increased. Furthermore, the metal connector next to the cantilevered pontic should be unit-cast and be constructed for maximum strength. 6. Preloading—Abutment screws should be retightened several minutes after the initial torque application.36 7. Technological Improvements to Implant Components and Design—Textured dental implants should be used because they provide increased retention to bone and provide greater surface area to transmit stresses to the bone.37 8. Occlusion and Occlusal Prosthesis Material—Place the cantilever in infraocclusion (0.1 to 0.2 mm).38 In addition, a nightguard can be worn to buffer forces applied while sleeping. 9. Retention of Abutment Crowns—Abutment preparations should have maximum axial wall length with minimal taper (convergence angle) to increase the retention and resistance form.39 10. Crown-to-Root Ratio—If the crown-to-implant ratio is extreme, thought should be given either to using wider implants to resist bending moments or employing additional implants for strength.

INCREASED CROWN-TO-IMPLANT RATIOS

Prosthesis Survivability and Bone Loss Around Implants Prosthetic constructs with increased CIRs from one to 2 have a high survivability rate (Table 3).42-51 Pertinently, studies that included restorations with CIRs of 2 also demonstrated high survivability (Table 3).42,44,45,48-51 Three additional studies which evaluated cantilevered prostheses reported mean CIRs of 1.6,16 1.84,21 and 1.65;18 their retention rates (≥ 5 years) respectively were 97%, 98.4%, and 95.7%. Likewise, short implants that support prostheses that have increased CIRs have high survival rates.32,52-55 The clinical height of a crown that cannot be surpassed to avoid deosseointegration or implant fracture is undefined and will be affected by many factors (eg, splinting of implants, implant diameter, and magnitude of occlusal forces). Investigators also noted that

Patients with reduced alveolar bone often present for implant supported restorations, and the final prostheses may demonstrate increased CIRs. Consequently, vertical cantilevers are created and will increase stress, which can affect clinical outcomes.40,41 Therefore, the literature was evaluated to determine if increased CIRs have a deleterious effect on prostheses. Vertical Cantilevers Bidez and Misch40 calculated that when a crown’s height is increased from 10 to 20 mm, there is 100% more force on an implant. However, the central question concerning this theoretical calculation relates to how this affects clinical outcomes.

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Confronting Controversial Issues in Dental Implant Therapy, Part 1 Table 3. Crown-to-Implant Ratios (CIRs) STUDY

SINGLE UNITS VS SPLINTING

NO. OF IMPLANTS

DURATION (MONTHS)

TYPE OF IMPLANTS

MEAN CIR

PERCENT SURVIVAL

CIR > 2

PERCENT SURVIVAL

Schulte et al42

Single units

889

27

Bicon

1.3

98.2

32/33

97

Rossi et al43

Single units

40

24

Straumann

1.5

95

a

Urdaneta et al44

Single units

326

79

Bicon

1.6

96

40/40

95

Birdi et al45

Single units

309

23

Bicon

2

100

139

100

Schneider et al46

Single units

100

60

Straumann

1.48

95.8

a

Nedir et al47

Mixed; 32% singe unitb

528

84

Straumann

1.55/ 1.97+

100

a

100

Rokni et al48

Mixed; 38% single unitsb

199

44

Endopore

1.5

98.2

20/20

100

Tawil et al49

Mixed (could not decipher)b

234

53

Brånemark

a

99

8/8

100

Blanes et al50

Mixed; 18.7% single unitsb

192

120

Straumann

1.77

99

48/51

94.1

Sohn et al51

Mixed; 17% single unitsb

122

55.8

Endopore

1 to 2

> 95

9/9

100

aNot reported. bMixed means single crowns and splinted crowns average together.

prostheses with increased CIRs did not manifest additional bone loss compared to constructs that did not have elevated CIRs.17,18,44-46,48-50

strated technical complications. The percentage of implants manifesting problems are listed (N = 100 implants): loss of retention (5%), occlusal screw loosening (4%), abutment screw loosening (4%), and chipping of veneer material (4%). These results are within the range of technical issues associated with implant supported single crowns56 and fixed dental prostheses. 29

Technical Problems There is a dearth of information addressing how often technical complications occur with various prosthetic designs (single tooth, straight-line splint, or fixed restorations that have cross arch stabilization) when there are increased CIRs. Several studies assessed the occurrence of technical problems.44,46,49 For example, Tawil and Youn 49 reported the incidence of screw loosening (7.8%) and porcelain fractures (5.2%) among teeth with increased CIRs. Similarly, Schneider et al 46 found no statistically significant increase of technical problems among prostheses with increased CIRs. They reported that 13 out of 76 patients (18.6%) demon-

Conclusions and Recommendations The data (Table 3) indicate that constructs with increased CIRs up to 2 have a high survival rate and do not cause further peri-implant bone loss. It can be concluded that implants with elevated CIRs can be used to support single teeth and fixed restorations. These remarks are in accord with the European Association for Osseointegration.32 However, since increased CIRs can

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Confronting Controversial Issues in Dental Implant Therapy, Part 1 Table 4. Clinical Recommendations for Restoring Teeth With Increased Crown-toImplant Ratios (CIRs)2 1. Restore posterior regions so that incisal or canine guidance discludes the posterior teeth and reduces lateral contact in mandibular excursions.57 2. Add additional implants to increase the surface area where occlusal forces are conveyed. 3. Wider implants will provide additional bone implant contact area. 4. Centric contacts are centered over the implants52 and decrease the occlusal width of posterior teeth. 5. In bruxers, overengineer the case or avoid elevated CIRs. 6. To decrease nocturnal stresses on the prosthetic constructs, patients can use a nightguard. 7. To maximize prosthesis support, short implants ought to be splinted together and furnish cross arch stabilization if feasible.41,58 8. A greater bone implant contact will be achieved with textured surfaced implants. 9. Flatten cuspal inclines.52 10. Use implants with reduced thread pitch (space between the threads), which increases the number of threads per unit length and surface area.57

7. Sadrimanesh R, Siadat H, Sadr-Eshkevari P, et al. Alveolar bone stress around implants with different abutment angulation: an FE-analysis of anterior maxilla. Implant Dent. 2012;21:196-201. 8. Rubo JH, Souza EA. Finite element analysis of stress in bone adjacent to dental implants. J Oral Implantol. 2008;34:248-255. 9. Brunski J. Biomechanics. In: Worthington P, Lang BR, Rubenstein JE, eds. Osseointegration in Dentistry: An Overview. 2nd ed. Hanover Park, IL: Quintessence Publishing; 2003:49-84. 10. Hollinger JO. Bone dynamics: morphogenesis, growth modeling, and remodeling. In: Lieberman JR, Friedlaender GE, eds. Bone Regeneration and Repair: Biology and Clinical Applications. Totowa, NJ: Humana Press; 2005:15. 11. Frost HM. A 2003 update of bone physiology and Wolff’s Law for clinicians. Angle Orthod. 2004;74:3-15. 12. Isidor F. Influence of forces on peri-implant bone. Clin Oral Implants Res. 2006;17(suppl 2):8-18. 13. Chambrone L, Chambrone LA, Lima LA. Effects of occlusal overload on peri-implant tissue health: a systematic review of animal-model studies. J Periodontol. 2010;81:1367-1378. 14. Vidyasagar L, Apse P. Biological response to dental implant loading/overloading. Implant overloading: empiricism or science? Stomatologija. 2003;5:83-89.

cause increased occlusal forces, techniques to reduce stresses on prostheses are listed in Table 4.2,41,52,57,58 Part 2 of this article will be published in the next issue of Dentistry Today.

REFERENCES 1. Greenstein G, Cavallaro J Jr. Cantilevers extending from unilateral implant-supported fixed prostheses: a review of the literature and presentation of practical guidelines. J Am Dent Assoc. 2010;141:1221-1230. 2. Greenstein G, Cavallaro JS Jr. Importance of crown to root and crown to implant ratios. Dent Today. 2011;30:61-66. 3. Cavallaro J Jr, Greenstein G. Angled implant abutments: a practical application of available knowledge. J Am Dent Assoc. 2011;142:150-158. 4. Greenstein G, Cavallaro J, Smith R, et al. Connecting teeth to implants: a critical review of the literature and presentation of practical guidelines. Compend Contin Educ Dent. 2009;30:440-453. 5. Greenstein G, Cavallaro J, Tarnow D. Assessing bone’s adaptive capacity around dental implants: a literature review. J Am Dent Assoc. 2013;144:362-368. 6. Rubo JH, Capello Souza EA. Finite-element analysis of stress on dental implant prosthesis. Clin Implant Dent Relat Res. 2010;12:105-113. 6


Confronting Controversial Issues in Dental Implant Therapy, Part 1 15. Rangert B, Krogh PH, Langer B, et al. Bending overload and implant fracture: a retrospective clinical analysis. Int J Oral Maxillofac Implants. 1995;10:326-334. 16. Nedir R, Bischof M, Szmukler-Moncler S, et al. Prosthetic complications with dental implants: from an up-to-8-year experience in private practice. Int J Oral Maxillofac Implants. 2006;21:919-928. 17. Wennström J, Zurdo J, Karlsson S, et al. Bone level change at implant-supported fixed partial dentures with and without cantilever extension after 5 years in function. J Clin Periodontol. 2004;31:1077-1083. 18. Hälg GA, Schmid J, Hämmerle CH. Bone level changes at implants supporting crowns or fixed partial dentures with or without cantilevers. Clin Oral Implants Res. 2008;19:983-990. 19. Eliasson A, Eriksson T, Johansson A, et al. Fixed partial prostheses supported by 2 or 3 implants: a retrospective study up to 18 years. Int J Oral Maxillofac Implants. 2006;21:567-574. 20. Kreissl ME, Gerds T, Muche R, et al. Technical complications of implant-supported fixed partial dentures in partially edentulous cases after an average observation period of 5 years. Clin Oral Implants Res. 2007;18:720-726. 21. Brägger U, Karoussis I, Persson R, et al. Technical and biological complications/failures with single crowns and fixed partial dentures on implants: a 10year prospective cohort study. Clin Oral Implants Res. 2005;16:326-334. 22. Becker CM. Cantilever fixed prostheses utilizing dental implants: a 10-year retrospective analysis. Quintessence Int. 2004;35:437-441. 23. Romeo E, Lops D, Margutti E, et al. Implant-supported fixed cantilever prostheses in partially edentulous arches. A seven-year prospective study. Clin Oral Implants Res. 2003;14:303-311. 24. Johansson LA, Ekfeldt A. Implant-supported fixed partial prostheses: a retrospective study. Int J Prosthodont. 2003;16:172-176. 25. Aglietta M, Siciliano VI, Zwahlen M, et al. A systematic review of the survival and complication rates of implant supported fixed dental prostheses with cantilever extensions after an observation period of at least 5 years. Clin Oral Implants Res. 2009;20:441-451. 26. McAlarney ME, Stavropoulos DN. Determination of cantilever length-anterior-posterior spread ratio assuming failure criteria to be the compromise of the prosthesis retaining screw-prosthesis joint. Int J Oral Maxillofac Implants. 1996;11:331-339. 27. Osier JF. Biomechanical load analysis of cantilevered

implant systems. J Oral Implantol. 1991;17:40-47. 28. Akça K, Iplikçio lu H. Finite element stress analysis of the effect of short implant usage in place of cantilever extensions in mandibular posterior edentulism. J Oral Rehabil. 2002;29:350-356. 29. Pjetursson BE, Thoma D, Jung R, et al. A systematic review of the survival and complication rates of implant-supported fixed dental prostheses (FDPs) after a mean observation period of at least 5 years. Clin Oral Implants Res. 2012;23(suppl 6):22-38. 30. Tan K, Pjetursson BE, Lang NP, et al. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. III. Conventional FPDs. Clin Oral Implants Res. 2004;15:654-666. 31. Zurdo J, Romão C, Wennström JL. Survival and complication rates of implant-supported fixed partial dentures with cantilevers: a systematic review. Clin Oral Implants Res. 2009;20(suppl 4):59-66. 32. Sanz M, Naert I; Working Group 2. Biomechanics/risk management (Working Group 2). Clin Oral Implants Res. 2009;20(suppl 4):107-111. 33. Misch CE. Natural teeth adjacent to multiple implant sites: effect on diagnosis and treatment plan. In: Misch CE, ed. Dental Implant Prosthetics. St. Louis, MO: Mosby Elsevier; 2005:184. 34. Eraslan O, Sevimay M, Usumez A, et al. Effects of cantilever design and material on stress distribution in fixed partial dentures—a finite element analysis. J Oral Rehabil. 2005;32:273-278. 35. English CE. Biomechanical concerns with fixed partial dentures involving implants. Implant Dent. 1993;2:221-242. 36. Siamos G, Winkler S, Boberick KG. Relationship between implant preload and screw loosening on implant-supported prostheses. J Oral Implantol. 2002;28:67-73. 37. Buser D, Nydegger T, Hirt HP, et al. Removal torque values of titanium implants in the maxilla of miniature pigs. Int J Oral Maxillofac Implants. 1998;13:611-619. 38. Carlsson GE. Dental occlusion: modern concepts and their application in implant prosthodontics. Odontology. 2009;97:8-17. 39. Goodacre CJ, Campagni WV, Aquilino SA. Tooth preparations for complete crowns: an art form based on scientific principles. J Prosthet Dent. 2001;85:363-376. 40. Bidez MW, Misch CE. Clinical biomechanics in implant dentistry. In: Misch CE, ed. Contemporary Implant Dentistry. 3rd ed. St. Louis, MO: Mosby Elsevier; 2008:543-556. 7


Confronting Controversial Issues in Dental Implant Therapy, Part 1 41. Bidez MW, Misch CE. Force transfer in implant dentistry: basic concepts and principles. J Oral Implantol. 1992;18:264-274. 42. Schulte J, Flores AM, Weed M. Crown-to-implant ratios of single tooth implant-supported restorations. J Prosthet Dent. 2007;98:1-5. 43. Rossi F, Ricci E, Marchetti C, et al. Early loading of single crowns supported by 6-mm-long implants with a moderately rough surface: a prospective 2-year follow-up cohort study. Clin Oral Implants Res. 2010;21:937-943. 44. Urdaneta RA, Rodriguez S, McNeil DC, et al. The effect of increased crown-to-implant ratio on singletooth locking-taper implants. Int J Oral Maxillofac Implants. 2010;25:729-743. 45. Birdi H, Schulte J, Kovacs A, et al. Crown-to-implant ratios of short-length implants. J Oral Implantol. 2010;36:425-433. 46. Schneider D, Witt L, Hämmerle CH. Influence of the crown-to-implant length ratio on the clinical performance of implants supporting single crown restorations: a crosssectional retrospective 5-year investigation. Clin Oral Implants Res. 2012;23:169-174. 47. Nedir R, Bischof M, Briaux JM, et al. A 7-year life table analysis from a prospective study on ITI implants with special emphasis on the use of short implants. Results from a private practice. Clin Oral Implants Res. 2004;15:150-157. 48. Rokni S, Todescan R, Watson P, et al. An assessment of crown-to-root ratios with short sintered poroussurfaced implants supporting prostheses in partially edentulous patients. Int J Oral Maxillofac Implants. 2005;20:69-76. 49. Tawil G, Younan R. Clinical evaluation of short, machined-surface implants followed for 12 to 92 months. Int J Oral Maxillofac Implants. 2003;18:894-901.

50. Blanes RJ, Bernard JP, Blanes ZM, et al. A 10-year prospective study of ITI dental implants placed in the posterior region. II: Influence of the crown-to-implant ratio and different prosthetic treatment modalities on crestal bone loss. Clin Oral Implants Res. 2007;18:707-714. 51. Sohn DS, Kim WS, Lee WH, et al. A retrospective study of sintered porous-surfaced dental implants in restoring the edentulous posterior mandible: up to 9 years of functioning. Implant Dent. 2010;19:409-418. 52. Morand M, Irinakis T. The challenge of implant therapy in the posterior maxilla: providing a rationale for the use of short implants. J Oral Implantol. 2007;33:257-266. 53. Renouard F, Nisand D. Impact of implant length and diameter on survival rates. Clin Oral Implants Res. 2006;17(suppl 2):35-51. 54. Fugazzotto PA. Shorter implants in clinical practice: rationale and treatment results. Int J Oral Maxillofac Implants. 2008;23:487-496. 55. Misch CE. Short dental implants: a literature review and rationale for use. Dent Today. 2005;24:64-68. 56. Jung RE, Zembic A, Pjetursson BE, et al. Systematic review of the survival rate and the incidence of biological, technical, and aesthetic complications of single crowns on implants reported in longitudinal studies with a mean follow-up of 5 years. Clin Oral Implants Res. 2012;23 (suppl 6):2-21. 57. Misch CE, Steignga J, Barboza E, et al. Short dental implants in posterior partial edentulism: a multicenter retrospective 6-year case series study. J Periodontol. 2006;77:1340-1347. 58. Guichet DL, Yoshinobu D, Caputo AA. Effect of splinting and interproximal contact tightness on load transfer by implant restorations. J Prosthet Dent. 2002;87:528-535.

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Confronting Controversial Issues in Dental Implant Therapy, Part 1 POST EXAMINATION INFORMATION

POST EXAMINATION QUESTIONS

To receive continuing education credit for participation in this educational activity you must complete the program post examination and receive a score of 70% or better.

1. In terms of the relationship between bone microstrain and physiological responses, which relationship is CORRECT? a. b. c. d.

Traditional Completion Option: You may fax or mail your answers with payment to Dentistry Today (see Traditional Completion Information on following page). All information requested must be provided in order to process the program for credit. Be sure to complete your “Payment,” “Personal Certification Information,” “Answers,” and “Evaluation” forms. Your exam will be graded within 72 hours of receipt. Upon successful completion of the postexam (70% or higher), a letter of completion will be mailed to the address provided.

50 to 1,500 ue—atrophy. 1,500 to 3,000 ue—normal bone modeling. > 3,000 ue—overload. None of the above.

2. The stress on implants supporting an implantsupported cantilevered fixed dental prosthesis (ICFDP) is __________greater than found on single implants not supporting a cantilever. a. b. c. d.

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1.5 times. 2 to 3 times. 4 times. 5 times.

3. Which statement about cantilevered prostheses off of 2 implants is FALSE? a. They have a reduced survival rate compared to implant-supported prostheses without cantilevers. b. There is no increased bone loss around the terminal abutment. c. There is increased torque on abutment teeth. d. Their utilization broadens treatment options. 4. Which recommendation for construction of cantilevers is FALSE? a. It is beneficial if the interimplant distance between 2 implants is 8 mm. b. It is beneficial if the pontic on a cantilevered prosthesis is around 8 mm. c. If a cantilevered bridge is constructed in a bruxer, the case should be overengineered. d. Cantilevered prostheses should be limited to the anterior section of the dentition.

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5. Fixed dental prostheses utilizing 2 to 3 implants to support a cantilever are successful. A span of at least 12 mm between the centers of implants seems proper. a. b. c. d.

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The first statement is true, the second is false. The first statement is false, the second is true. Both statements are true. Both statements are false.


Confronting Controversial Issues in Dental Implant Therapy, Part 1 6. Data indicate that short-span ICFDPs are a predictable technique for restoring partially edentate areas. However, this finding is not in accord with the European Association for Osseointegration. a. b. c. d.

9. When restoring teeth with increased CIRs, use implants with reduced thread pitch. Reduced thread pitch increases the number of threads per unit length and surface area.

The first statement is true, the second is false. The first statement is false, the second if true. Both statements are true. Both statements are false.

a. b. c. d.

7. The prevalence of technical complications related to ICFDPs are within the range for implant-supported prostheses. In general, these complications do not jeopardize the survivability of ICFDPs. a. b. c. d.

The first statement is true, the second is false. The first statement is false, the second is true. Both statements are true. Both statements are false.

10. Strategies to consider when fabricating fixed dental prostheses with increased CIRs include the following: a. Minimize lateral excursions on posterior prostheses and increase the number of supporting implants. b. Increase clinical crown height. c. Employ textured surfaced implants. d. Both a and c.

The first statement is true, the second is false. The first statement is false, the second is true. Both statements are false. Both statements are true.

8. When restoring teeth with increased crown-toimplant ratios (CIRs), the following is/are recommended: a. Add additional implants to increase surface area where occlusal forces are conveyed. b. Use wider implants to provide additional bone-toimplant contact. c. Flatten cuspal inclines. d. All of the above.

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Confronting Controversial Issues in Dental Implant Therapy, Part 1 PROGRAM COMPLETION INFORMATION

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