Int J Oral Maxillofac Implants 28 (2013), No. 2 15. Mar. 2013
Purpose: The aim of this study was to compare the influence of abutment screw preload on the marginal bone stress around a conventional external-hex implant system and one with a new implant/abutment joint design.
Materials and Methods: Two implant/bone models, each consisting of three parts and fabricated of titanium and bone (cortical), were built and arranged with computer-aided design software. The first model represented an external-hex implant system, while the second had a tapered extension over the external hex, 1.5 mm high, so that the apical extension of the abutment screw in the assembly did not go beyond the lower level of the implant shoulder. Meshing and generation of boundary conditions, loads, and interactions were performed for the two models. All parts were meshed independent of each other. The sole load applied on the model was a torque of 32 Ncm on the abutment screw about its axis of rotation.
Results: The first model showed deformation of the implant collar, and the resulting von Mises stress was 60 MPa in the marginal bone. In contrast, no deformation was observed in the second model.
Conclusions: The new implant/abutment joint eliminated the deformation at the implant collar area caused by the application of tightening torque and thus eliminated the resulting stresses in the marginal bone.