The Biomechanical Effect of Platform Switching on External- and Internal-Connection Implants

Purpose: To evaluate the biomechanical effects of platform switching on external- and internal-connection implants with regard to strain around the implants under loading. Materials and Methods: Implant analogs (5.0 × 12 mm) with external (EX) and internal (IN) connections were embedded into an acrylic resin block that simulated an edentulous ridge. Abutments with diameters of 5.0, 4.2, and 3.7 mm were attached to EX and IN analogs. A 100-N lateral load was applied to each abutment at an angle of 30 degrees, and the experiments were repeated 10 times. Strain gauges were attached to the implant surface at 1 mm (neck area) and 8 mm (apex area) below the platform to measure the strain around the implant under loading. Statistical analyses were performed by one-way analysis of variance and Steel-Dwass test. P .05 was considered statistically significant. Results: Significantly higher strain values were found around the neck area in both analogs (EX, -682.8 µε; IN,-582.1 µε) with conventional matching 5-mm-diameter abutments, followed by the analogs with 4.2-mm-diameter (EX, -184.1 µε; IN, -229.1 µε) and 3.7-mm-diameter (EX, -150.5 µε; IN, -129.7 µε) platform-switched abutments; this was statistically significant for EX (P .05). In the apex area, a mild increase in strain was found with a decrease in abutment diameter, but no significant difference was found between 4.2- and 3.7-mm-diameter abutments for IN (P > .05). Conclusion: Within the limitations of this study, platform switching reduced strain surrounding the implant neck area in both EX and IN during loading. However, the decreases in strain values were greater with EX than with IN. Keywords: external-connection implant, internal-connection implant, platform switching, strain