Stress Distribution in the Mandible Influenced by Nobel Biocare, 3i and Neoss Implant Thread Designs

Abstract

The complicated failure mechanisms at the interface between the mandible bone and dental implant, as influenced by the implant design, are investigated in this study. Using the Finite Element Method (FEM), three implant thread designs, namely, Nobel Biocare, 3i and Neoss, are evaluated for their role in the stress distribution within the mandible. The aim of this article is to help advance the use of an innovative engineering approach in dental practices, especially in the understanding of implant failures. The FEM is used to replicate the complex geometric and material properties of the bone and implant. In addition to the various implant thread design, the abutment screw preload as a result of the applied torque is also considered as a variable. The characteristics of von Mises stresses in the cancellous bone are examined for all variables. The assumptions made in the modelling and simulation process include: - a two-dimensional representation of the bone and implant is used because this is considered to be equally accurate and more efficient in terms of computation time, as compared to a three-dimensional approach; - temperature sensitive elements are used to replicate the preload within the abutment screw. This study has demonstrated that the Neoss thread design yields more favourable stress profile within the cancellous bone than the Nobel Biocare and 3i designs. Compared to the Neoss' more smoothed-out thread profile, both the Nobel Biocare and 3i designs have more abrupt changes in geometry, which results in higher stress. This is particularly true for the Nobel Biocare design where a notch is present. Although the existence of the notch helps to promote osseointegration, it on the other hand produces undesirable stresses.