Radiographic evaluation of marginal bone maintenance around tissue level implant and bone level implant: a randomised controlled trial. A 1-year follow-up.

The etiologic factors associated with crestal bone loss have not been comprehensively clarified. Several theories exist as to the reason for the observed changes in crestal bone height following implant restoration. In the 1990s, the wide-diameter implants were commercially introduced. Initially, the implants were restored with standard-diameter abutments because of lack of matching prosthetic components. Long-term radiographic follow-up of these 'platform-switched' restored wide-diameter dental implants has demonstrated a smaller-than-expected vertical change in the crestal bone height around these implants that is typically observed around implants restored conventionally with prosthetic components of matching diameters. The aim of this randomised controlled study was to assess radiographically marginal bone level alterations in implants restored according to the platform-switching concept compared with traditionally restored implants. Fifty-four subjects to participate in this randomised controlled study were selected. Two groups were assigned at random: control group (56 implants were restored with standard matching-diameter abutments) and test group (58 implants were restored with medialised abutments). X-ray explorations were taken for peri-implant bone level at the minute the last cementing of the prosthesis and at 1-year follow-up. NHI Image was used to digitally process and manipulate the radiographic images and perform the measurements. Mean of bone loss with platform-switching implants was -0·01 mm, and the mean of bone loss with standard platform implant was 0·42 mm. Outcomes of this study indicated that the platform-switching design could preserve the crestal bone levels to 1-year follow-up. There was a statistically significant difference in marginal bone loss.