Influence of Occlusal Forces on Stress Distribution on Preloaded Dental Implant Abutment Screws: A Finite Element Analysis Study

Purpose: The aim of the study is to determine stress distribution on preloaded implant-abutment screws in three different implant systems under simulated occlusal loads. Materials and methods: Three abutments to implant internal hex joint systems were simulated by using the 3-dimensional finite element analysis; (1) Nobel Biocare replace tapered (2) Uniti (3) Lifecare self-threaded tapered cement retained abutments. Thermal load and contact analysis were used to simulate preload resulting from the torque in implant screw joint assemblies. The simulated preload implants were then loaded with three static occlusal loads (10N horizontal; 35N vertical; 70N oblique) onto the crown into the implant complex. Results: Under preload and static occlusal forces, maximum Von-Mises stresses were concentrated at the lower portion of abutment for all systems. Maximum stresses were concentrated at lower threaded portion of abutment screw in Nobel Biocare, Uniti but in Lifecare system, stresses were concentrated at the middle threaded portion. Maximum stresses were concentrated at middle threaded portion of implant in Nobel Biocare, Uniti but at the upper threaded portion in Lifecare. Stresses increased under static occlusal forces in abutment screw in Nobel Biocare and Uniti but were more under oblique forces. In Lifecare stresses decreased under horizontal forces and increased in vertical and oblique forces. Conclusion: Although, an increase or decrease was demonstrated for the maximum calculated stress values in preloaded screws. After occlusal loads, these maximum stress values were well below the yield stress of abutment screw systems tested.