Bone preservation

Abstract: Background: Platform switching for maintaining peri-implant bone levels has gained popularity among implant manufacturers over the last few years. However, the assumption that the inward shifting of the implant-abutment junction may preserve crestal bone was primarily based on serendipitous finding rather than scientific evidence. The objectives of the present study were to systematically review radiographic marginal bone-level changes and the survival of platform-switched implants compared to conventional platform-matched implants. Methods: A literature search of electronic databases (MEDLINE, EMBASE, The Cochrane Oral Health Group’s Trials Register, The Cochrane Central Register of Controlled Trials, the U.K. National Research Register, the Australian New Zealand Clinical Trials Registry, the Database of Abstracts of Reviews of Effectiveness, and Conference Proceedings Citation Index) was performed up to March 15, 2010. Hand searches included several dental journals, and authors were contacted for missing information. Controlled trials that compared marginal bone-level changes around platform-switched dental implants with those restored with platformmatched prostheses were selected. The review and meta-analysis were done according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Data were analyzed using two meta-analytic statistical packages. Mean differences (MDs) were calculated for analyzing continuous data, and risk ratios (RRs) were used for dichotomous data with 95% confidence intervals (CIs). Results: Ten studies with 1,239 implants were included. The marginal bone loss around platform-switched implants was significantly less than around platform-matched implants (MD: -0.37; 95% CI: -0.55 to -0.20; P <0.0001). No statistically significant difference was detected for implant failures between the two groups (RR: 0.93; 95% CI: 0.34 to 2.95; P = 0.89). Subgroup analyses showed that an implant-abutment diameter difference ‡0.4 was associated with a more favorable bone response. Conclusions: The review and meta-analysis show that platform switching may preserve interimplant bone height and soft tissue levels. The degree of marginal bone resorption is inversely related to the extent of the implant-abutment mismatch. Further long-term, well-conducted, randomized controlled studies are needed to confirm the validity of this concept. J Periodontol 2010;81:1350-1366.

Abstract: Prediction of human skeletal preservation at mortuary sites is important in archaeological research and in cultural resources management. In this study, correlations between osseous deterioration and soil acidity, as measured by pH, were found to be significant. Age-associated preservation biases were also evident. The use of multiple regression is suggested as a technique for estimating recovery of human osteological remains in archaeological context.

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