Response of crestal bone to platform – switched healing abutments

Background: Maintaining alveolar crestal bone is crucial to the success of dental implants. While numerous factors have been demonstrated to be associated with crestal bone changes adjacent to matched-abutment and platform-switched titanium implants, limited knowledge exists on the response of crestal bone to platformswitched healing abutments with different emergence profiles. Aim: To evaluate radiographic crestal bone changes around implants with platform-switched healing abutments of varying emergence profiles. Methods: Twenty-four patients who had satisfied predetermined criteria and who had received two adjacent dental implants unilaterally were consecutively enrolled in this prospective clinical study. All 48 adjacent implants were inserted so that the implant shoulder was level with the alveolar crest. Following insertion, one of the two adjacent implants was assigned a transgingival platformswitched healing abutment with a steep emergence profile (n=24)and the other implant was assigned to one of two procedures: (1) placement of a transgingival platform-switched healing abutment with a flat emergence profile (n=11) or (2) placement of a submerged platform-switched healing abutment with a flat emergence profile (n=13). Radiographs were performed and crestal bone levels were evaluated at implant placement and 3 months postoperatively, with the healing abutments in situ. Crestal bone loss below the implant shoulder reference point was regarded as undesirable, and stable crestal bone levels or bone appositionwas defined as desirable outcomes. An aggregated data analysis was performed comparing the different abutments using the Fisher’s exact test (a=0.05). Results: Radiographic analysis revealed no crestal bone loss around implants with transgingival steep emergence profiles, and slight bone apposition with submerged flat emergence profile healing abutments. There was no significant difference between these groups. However, statistically significant bone loss occurred at implants with transgingival flat emergence profile healing abutments (P<0.05). These exhibited crestal bone loss at 22 of the 26(85%) measured sites. Conclusions and clinical implications: Within the limitations of the present study, the following conclusions can be drawn: (1) the design of the healing abutment affects peri-implant crestal bone levels; (2) submerged platform-switched healing abutments with flat emergence profiles may be recommended for facilitating crestal bone apposition; and (3) transgingival platform-switched healing abutment with steep emergence profiles result in crestal bone loss around implants. Thus, it may be suggested that the use of transgingival platform-switched healing abutment with steep emergence profiles results in unfavourable crestal bone changes around implants.