Objective: It is unclear whether crestal bone behaviour proximal to oral implants is age- and site- specific. This study tested the hypothesis that crestal bone resorption proximal to oral implants in completely edentulous jaws cannot be predicted by age- and site-specific aspects of bone condition. Methods: An observational study was conducted over 4 to 17 years among 130 patients planned consecutively for 617 Brånemark implants and 139 complete dental prostheses. Statistical analysis (stepwise multiple linear regression using P<.05 for entry and P<.10 for removal) assessed the relationship between independent variables, for example age, jawbone condition and years of edentulism, and the mean crestal bone level at loading and mean annual vertical crestal bone loss during several periods after loading based on radiographic measurements. Results: 73 original implants failed during the study yielding a cumulative survival rate of 85.5%. The mean bone level among 123 prosthetic sites at loading was 1.3 mm apical to the implant collar. During the first year of loading, the mean crestal bone loss was 0.2 mm among prosthetic sites. Therafter the mean annual crestal bone loss was 0.04 mm per year among prosthetic sites. The bone level at loading was predicted by status of the opposing dentition, jawbone quantity and surgeon, whereas the crestal bone loss during and after the first year of loading was predicted by the years of edentulism and restorative dentist. Regression models were highly statistically significant, however could predict only 20 to 25% of the variation in crestal bone behaviour. Conclusion: The hypothesis is upheld implying that it remains difficult to predict crestal bone behaviour proximal to oral implants. Although variation in crestal bone behaviour surrounding oral implants remains difficult to predict, patients should be advised of the likelihood of ongoing but usually modest crestal bone loss associated with oral implants.

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