Effect of vertical bone loss on stress distribution at the bone-implant interface around implants of varying diameters–an in silico 3D finite element analysis

Abstract

Peri-implantitis results in loss of supporting bone around an implant. An implant thus compromised, must distribute and dissipate the stresses hence generated, in an attempt to survive. A three- dimensional Finite Element Analysis helps the clinician simulate such critical clinical situations in an attempt to predict the best way ahead. The aim of this study was to determine the distribution of stresses around an implant once Peri-implantitis associated vertical bone loss enters the picture. An attempt was also made to analyse the effect of varying the implant diameter on stresses generated. A 3-D Finite Element Analysis was carried out for implants replacing lost mandibular first molars. Threaded implants of different diameters (3.75 mm, 4.3 mm, 5.0 mm) with varying levels of Peri-implantitis induced vertical bone loss were modelled and load of 118.2 N applied to the occlusal surface at an angle of 75°. Vertical stress maps presented as a ring like configuration around the implant with highest values being recorded mesially and distally. Stresses in the cortical bone were found to decrease as more bone was lost and vice versa for trabecular bone. With the bone being lost circumferentially, models beyond 10% angular bone resorption had no cortical bone in vicinity, and hence the loads were borne primarily by the cancellous bone. Cancellous bone was able to distribute stresses over a much wider area than cortical bone. Implant diameter profoundly affected the stresses generated in cortical bone, with 4.3 mm diameter being the most optimum biomechanically in majority of the bone loss situations.