Purpose: Several long-term clinical studies have shown a mean marginal bone loss around dental implants of 1.5 to 2 mm in the first year after prosthetic restoration. Currently, concepts to avoid bone remodeling around dental implants have been developed. The use of prosthetic abutments with reduced width in relation to the implant diameter (platform switching) seems to have the greatest potential to limit the crestal resorption. The purpose of this clinical trial was to show that crestal bone height around dental implants could be influenced using a platform switch protocol and that the bone level would remain stable within 1 year after final prosthetic reconstruction.
Materials and methods: Fifteen patients were treated with fixed implant retained prosthesis; 14 wide-diameter implants were supplied with platform-switched abutments and served as the test group. Eight implants with regular diameter were reconstructed with traditional abutments and served as the control group. Standardized digital radiographs were obtained for evaluation of the peri-implant bone levels at the time of installation of the final restoration and at 1-year follow-up. Marginal peri-implant bone levels were measured at the mesial and distal surfaces of each implant using digital image analysis.
Results: The mean values of crestal bone height at baseline were -0.09 mm +/- 0.65 mm for the platform-switched implants and -1.73 mm +/- 0.46 mm for the nonplatform-switched implants. One year after final restoration, the mean value of crestal bone height was -0.22 mm +/- 0.53 mm for the test group and -2.02 mm +/- 0.49 mm for the control group. When tested with statistical means, the differences were significant for baseline and for follow-up (P </= .0001). Mean bone level change from baseline to 1-year follow-up was -0.12 mm +/- 0.40 mm for the test group and -0.29 mm +/- 0.34 mm, respectively, for the control group. On analysis using ANCOVA, this difference was shown to be significant (P </= .0132).
Conclusion: The concept of platform switching appears to limit crestal resorption and seems to preserve peri-implant bone levels. A certain amount of bone remodeling 1 year after final reconstruction occurs, but significant differences concerning the peri-implant bone height compared with the nonplatform-switched abutments are still evident 1 year after final restoration. The reduction of the abutment of 0.45 mm on each side (5 mm implant/4.1 mm abutment) seems sufficient to avoid peri-implant bone loss.