JOMI Thematic Abstract Review: Nov/Dec 2019

Are Strong Occlusal Forces Detrimental to Osseointegration?

Technical or mechanical implant-related complications such as fracture of veneering material or abutment screw loosening have a significant force-related etiology. Bone is capable of a long-term adaptive response over a broad range of loading values, but significant forces can cause a pathologic response (Stanford and Brand, 1999).¹ This leads to a natural question: Are biologic implant-related complications, such as implant failure or bone loss, also force-mediated? If strong forces are detrimental to osseointegration, research would be expected to demonstrate that bruxers have higher rates of biologic implant complications in comparison to patients who are not bruxers and that patients with force magnifiers such as cantilevers and high crown-to-implant ratios have higher rates of biologic implant complications in comparison to patients without such force magnifiers. Similarly, if strong forces are detrimental to osseointegration, research would be expected to support the concept of “implant-protected occlusion,” which typically consists of recommendations for eliminating cantilevers, narrowing occlusal tables, and decreasing cusp steepness of implant-supported restorations.

Bruxism is a “repetitive jaw muscle activity characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible” (Lobbezoo et al, 2013).² Etiology of bruxism is multifactorial and consists of a combination of psychologic factors (eg, stress and anxiety), physiologic factors (eg, genetics), and exogenous factors (eg, alcohol and psychotropic medications). Bruxism can be associated with wakefulness or with sleep and is found in up to 30% of the population (Manfredini et al, 2013).³ A formal diagnosis of nighttime parafunction can be made through polysomnography; however, it is impractical for daily clinical use. In clinical practice and in many clinical studies, diagnosis of bruxism is made based on patients’ self-reporting, which may not reflect true presence. Bruxism has been demonstrated to have a negative impact on prosthodontic technical complications, including implant fracture. By contrast, bruxism has not been found to be associated with periodontal tissue destruction (Manfredini et al, 2015).⁴

The findings of systematic reviews are largely consistent on the topic of association of bruxism and implant biologic complications. Systematic reviews focusing on animal data found no association between overload and peri-implant bone loss in the absence of inflammation (Naert et al, 2012; Chambrone et al, 2010).^5,6 Systematic reviews focusing on human data concluded that bruxism is unlikely to be a risk factor for biologic problems around implants (Manfredini et al, 2014; Chrcanovic et al, 2015).^7,8 All systematic reviews highlighted the low quality of the underlying clinical studies focusing on this topic, including reliance on self-reporting to diagnose bruxism, inconsistent definitions of implant failure, and poor control for all confounding variables.

A similar conclusion regarding a lack of significant impact of forces on biologic implant outcomes was reached by studies examining high crown-to-implant ratios (Garaicoa-Pazmiño et al, 2014; Ravidà et al, 2019),^9,10 poor prosthesis fit (Katsoulis et al, 2017; Slauch et al, 2019),^11,12 and the presence of cantilevers.^13–15 A review looking at evidence for the use of occlusal splints in bruxers after implant therapy was unable to identify a single clinical trial addressing this topic (Mesko et al, 2014).¹⁶ A systematic review on splinting of adjacent implants provided contradictory evidence (de Souza Batista et al, 2019)¹⁷; it appears that splinting has no impact on bone levels but is beneficial in increasing implant survival.

Two recent studies (Chrcanovic et al, 2016; Chrcanovic et al, 2017)^18,19 came to a different conclusion with respect to the association of bruxism and biologic implant complications. Chrcanovic et al (2016)¹⁸ undertook multilevel mixed effects parametric survival analysis to test the association between bruxism and risk of implant failure while adjusting for potential confounders in a group of 2,670 patients who received 10,096 implants. In an important improvement from previous research efforts, formal criteria were used to define and diagnose bruxism. This retrospective study found that implant failure rates were 13.0% for bruxers and 4.6% for nonbruxers (P < .001). The authors’ statistical model showed that bruxism was a statistically significant risk factor for implant failure (HR: 3.4; 95% CI: 1.3 to 8.8; P = .012). Chrcanovic et al (2017)¹⁹ used the same population to conduct a case-control matching study to match the bruxers with a group of nonbruxers. Ninety-eight of 2,670 patients were identified as bruxers. The odds ratio of implant failure in bruxers in relation to nonbruxers was found to be 2.7 (95% CI: 1.3 to 5.9).

Little is known about private practice clinicians’ opinions regarding the influence of bruxism and implant treatment outcomes. A recent study (Thymi et al, 2018)²⁰ conducted semi-structured interviews with dentists who were practicing in nonacademic clinical settings and who had significant experience in implant therapy. The authors observed that provision of implant treatments in bruxing patients was generally a well-accepted practice. Complications were often expected, with most being of minor impact. Contradicting attitudes emerged on the topic of bruxism being an etiologic factor for peri-implant bone loss and loss of osseointegration.

Overall, the topic of forces and biologic implant complications is a complex one with incomplete agreement. On balance, existing evidence points to the implant-bone interface being robust and likely stronger than currently appreciated. This is indirectly evidenced by a gradual shift toward the use of smaller implants and prostheses with larger pontic-to-abutment ratios. Little evidence exists to support the concept of “implant-protected occlusion.”

David Chvartszaid, DDS, MSc
University of Toronto
Toronto, Canada

Thematic Abstract Review Section Editor
Clark M. Stanford, DDS, PhD
The University of Illinois at Chicago
Chicago, Illinois, USA

Abstracts referenced:

Ravidà A, Barootchi S, Alkanderi A, Tavelli L, Suárez-López Del Amo F. The effect of crown-to-implant ratio on the clinical outcomes of dental implants: A systematic review. Int J Oral Maxillofac Implants 2019;34:1121–1131.

Romeo E, Storelli S. Systematic review of the survival rate and the biological, technical, and aesthetic complications of fixed dental prostheses with cantilevers on implants reported in longitudinal studies with a mean of 5 years follow‐up. Clin Oral Implants Res 2012;23(suppl 6):s39–s49.

de Souza Batista VE, Verri FR, Lemos CAA, et al. Should the restoration of adjacent implants be splinted or nonsplinted? A systematic review and meta-analysis. J Prosthet Dent 2019;121:41–51.

Slauch RW, Bidra AS, Wolfinger GJ, Kuo CL. Relationship between radiographic misfit and clinical outcomes in immediately loaded complete‐arch fixed implant‐supported prostheses in edentulous patients. J Prosthodont 2019;28:861–867.

Chrcanovic BR, Kisch J, Albrektsson T, Wennerberg A. Bruxism and dental implant failures: A multilevel mixed effects parametric survival analysis approach. J Oral Rehabil 2016;43:813–823.

Thymi M, Rollman A, Visscher CM, Wismeijer D, Lobbezoo F. Experience with bruxism in the everyday oral implantology practice in the Netherlands: A qualitative study. BDJ Open 2018;4:17040.

All references:

1. Stanford CM, Brand RA. Toward an understanding of implant occlusion and strain adaptive bone modeling and remodeling. J Prosthet Dent 1999;81:553–561.
2. Lobbezoo F, Ahlberg J, Glaros AG, et al. Bruxism defined and graded: An international consensus. J Oral Rehabil 2013;40:2–4.
3. Manfredini D, Winocur E, Guarda-Nardini L, Paesani D, Lobbezoo F. Epidemiology of bruxism in adults: A systematic review of the literature. J Orofac Pain 2013;27:99–110.
4. Manfredini D, Ahlberg J, Mura R, Lobbezoo F. Bruxism is unlikely to cause damage to the periodontium: Findings from a systematic literature assessment. J Periodontol 2015;86:546–555.
5. Naert I, Duyck J, Vandamme K. Occlusal overload and bone/implant loss. Clin Oral Implants Res 2012;23(suppl 6):s95–s107.
6. 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.
7. Manfredini D, Poggio CE, Lobbezoo F. Is bruxism a risk factor for dental implants? A systematic review of the literature. Clin Implant Dent Relat Res 2014;16:460–469.
8. Chrcanovic BR, Albrektsson T, Wennerberg A. Bruxism and dental implants: A meta-analysis. Implant Dent 2015;24:505–516.
9. Garaicoa-Pazmiño C, Suárez-López del Amo F, Monje A, et al. Influence of crown/implant ratio on marginal bone loss: A systematic review. J Periodontol 2014;85:1214–1221.
10. Ravidà A, Barootchi S, Alkanderi A, Tavelli L, Suárez-López del Amo F. The effect of crown-to-implant ratio on the clinical outcomes of dental implants: A systematic review. Int J Oral Maxillofac Implants 2019;34:1121–1131.
11. Katsoulis J, Takeichi T, Sol Gavira A, Peter L, Katsoulis K. Misfit of implant prostheses and its impact on clinical outcomes. Definition, assessment and a systematic review of the literature. Eur J Oral Implantol 2017;10(suppl 1):s121–s138.
12. Slauch RW, Bidra AS, Wolfinger GJ, Kuo C. Relationship between radiographic misfit and clinical outcomes in immediately loaded complete-arch fixed implant-supported prostheses in edentulous patients. J Prosthodont 2019;28:861–867.
13. 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.
14. Zurdo J, Romao C, Wennström JL. Survival and complication rates of implant-supported fixed partial dentures with cantilevers: A systematic review. Clin Oral Implants Res 2009;20:59–66.
15. Romeo E, Storelli S. Systematic review of the survival rate and the biological, technical, and aesthetic complications of fixed dental prostheses with cantilevers on implants reported in longitudinal studies with a mean of 5 years follow-up. Clin Oral Implants Res 2012;23:39–49.
16. Mesko ME, Almeida RC, Porto JA, Koller CD, da Rosa WL, Boscato N. Should occlusal splints be a routine prescription for diagnosed bruxers undergoing implant therapy? Int J Prosthodont 2014;27:201–203.
17. de Souza Batista VE, Verri FR, Lemos CAA, et al. Should the restoration of adjacent implants be splinted or nonsplinted? A systematic review and meta-analysis. J Prosthet Dent 2019;121:41–51.
18. Chrcanovic BR, Kisch J, Albrektsson T, Wennerberg A. Bruxism and dental implant failures: A multilevel mixed effects parametric survival analysis approach. J Oral Rehabil 2016;43:
    813–823.
19. Chrcanovic BR, Kisch J, Albrektsson T, Wennerberg A. Bruxism and dental implant treatment complications: A retrospective comparative study of 98 bruxer patients and a matched group. Clin Oral Implants Res 2017;28:e1–e9.
20. Thymi M, Rollman A, Visscher CM, Wismeijer D, Lobbezoo F. Experience with bruxism in the everyday oral implantology practice in the Netherlands: A qualitative study. BDJ Open 2018;4:17040.

This article was originally published in the November/December 2019 edition (Vol 34, issue 6) of The International Journal of Oral & Maxillofacial Implants.

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