Bone platform switching: A retrospective study on the slope of reverse conical neck

Objective: Bone platform switching results in an inward bone ring in the coronal part of an implant that is in continuity with the alveolar bone crest. Bone platform switching is achieved by using a dental implant with a reverse conical neck (RCN). A retrospective study was performed to determine the impact of RCN on crestal bone remodeling (CBR). Method and Materials: A series of 191 implants with the same morphology, but three slopes of RCN, were evaluated. Lost implants and CBR around implants still in place at the end of the follow-up were considered to investigate those variables potentially associated with the clinical outcome. Radiographic examinations were performed for each implant before surgery and at the end of the follow-up to detect the degree of CBR. Time-dependent cutoff values were used to select implants with higher CBR. These implants were considered unsuccessful. The Kaplan-Meier algorithm was applied to detect those variables potentially associated with the clinical outcome (ie, lost implants or implants with higher CBR). Results: Only 5 of 191 implants were lost (survival rate 97.4%). No statistical differences were detected among the studied variables by using lost implants. Conclusions: Although no statistical differences were detected among the three types of implants, the data seem to indicate a correlation between CBR and the slope of the RCN, with a better outcome for implants with a more angulated RCN. Keywords: alveolar crest, bone, implant, Kaplan-Meier algorithm, remodeling