Effect of different implant-abutment mismatch sizes on marginal bone loss - prospective clinical trial

16180 ORAL COMMUNICATION CLINICAL RESEARCH - PERI-IMPLANT BIOLOGY

Background

The horizontally inward repositioning of the implant-abutment interface, so-called platform-switching (PS), has been suggest as capable of reducing the periimplant marginal bone loss. However, PS has been a generic term used for different implant-abutment mismatch sizes, among the studies. It is yet not well understood to which extent different mismatch size may influence the extension of marginal bone preservation for PS implants.

Aim/Hypothesis

To evaluate the effect of different implant-abutment mismatch sizes on marginal periimplant bone loss.

Material and Methods

Twelve patients received four Ø 4.5 x 13 mm external hex implants, and abutments diameters of 4.5 mm (conventional matching implant-abutment design - CMD), 4.1 mm (PS04), 3.8 mm (PS07) and 3.3 (PS12), randomly placed based on a split-mouth design. Clinical parameters were evaluated at 6 sites around the implants, at a 12-, 36-, and 60-month follow-up. The distance from the top of the implant to the first bone-to-implant contact - IT-FBIC was evaluated on standardized digital peri-apical radiographs acquired at 1-, 3-, 6-, 12-, 36-month follow-up. Comparison among multiple periods of observation was performed using repeated-measures Analysis of Variance (ANOVA), followed by a Tukey post hoc test, while two-period based comparisons were made using paired t-test. Further, 12 computer-tomographic based finite element (FE) models were accomplished and the results for the peak EQV strain in periimplant bone were interpreted by means of ANOVA.

Results

After 3-year follow-up, the variation in periimplant bone loss assessed from the radiographs was different between CMD (1.88 ± 0.41), PS07 (1.14 ± 0.94) and PS12 (0.74 ± 0.58), P < 0.05 and P < 0.01, respectively. No differences on marginal bone loss were demonstrated between CMD (1.88 ± 0.41) and PS04 (1.65 ± 0.68), nor between PS07 (1.14 ± 0.94) and PS12 (0.74 ± 0.58), P = 0.179 and P = 0.0702, respectively. All clinical parameters did not present significant differences. In FE analysis, the increase in mismatch size of platform-switching configuration results in a significant decrease of strain levels in bone for osseointegrated implants.

Conclusion and clinical implications

In general, platform-switching concept showed a positive effect on marginal bone levels, when compared with conventional matching implant-abutment design. However, the efficiency of platform-switching on the preservation of periimplant marginal bone is dependent on the implant-abutment mismatch size.