Biomechanical Evaluation of the Effects of Implant Neck Wall Thickness and Abutment Screw Size: A 3D Nonlinear Finite Element Analysis

In this study, we evaluate the influence of implant neck wall thickness and abutment screw size on alveolar bone and implant component biomechanical responses using nonlinear finite element (FE) analysis. Twelve internal hexagon Morse taper implant-abutment connection FE models with three different implant sizes (diameters 4, 5, and 6 mm), secured with 1.4, 1.6, and 1.8 mm abutment screws to fit with three unilateral implant neck wall thicknesses of 0.45, 0.50, and 1.00 mm, were constructed to perform simulations. Nonlinear contact elements were used to simulate realistic interface fixation within the implant system. A 200 N concentrated force was applied toward the center of a hemispherical load cap and inclined 30 degrees relative to the implant axis as the loading condition. The simulation results indicated that increasing the unilateral implant neck wall thickness from 0.45 to 1.00 mm can significantly decrease implant, abutment, and abutment screw stresses and bone strain, decreased to 58%, 48%, 54%, and 70%, respectively. Variations in abutment screw size only significantly influenced abutment screw stress, and the maximum stress dissipation rates were 10% and 29% when the diameter was increased from 1.4 to 1.6 and 1.8 mm, respectively. We conclude that the unilateral implant neck wall thickness is the major design factor for the implant system and implant neck wall thickness in effectively decreasing implant, abutment, and abutment screw stresses and bone strain.