January 2015

Purpose: To analyze and compare the stress distribution around tapered and cylindrical implants and investigate how different abutment diameters influence crestal bone stress levels. Materials and Methods: Six finite element models of an abutment (5 mm, 4.3 mm, and 3.5 mm in diameter) and supporting implants (tapered and cylindrical) were designed. A vertical force of 100 N and a 15-degree oblique force of 100 N were applied separately on the occlusal surface, and von Misses stresses were evaluated in the cortical and cancellous bone. Results: Higher stress was observed under oblique loading than under vertical loading of both tapered and cylindrical implants. Tapered implants demonstrated more stress under both vertical and oblique loading. Platform switching reduced peri-implant crestal bone stress in all models under vertical and oblique forces. The peri-implant crestal bone around tapered implants experienced 4.8% more stress under vertical loading and 35% more stress under oblique loading in comparison to bone around cylindrical implants (2.62 MPa with vertical loading, 8.11 MPa under oblique loading). Oblique loads resulted in much higher stress concentrations in the peri-implant crestal bone than vertical loads (238% in cylindrical and 308% in tapered implants). When the abutment diameter decreased, both models showed reductions of stress in the crestal bone under both types of loading. Conclusion: In this finite element analysis, tapered implants increased crestal bone stress upon loading, and platform switching minimized the stress transmitted to the crestal bone in both tapered and parallel wall implants.