A comparison between the capacity of 2D and 3D finite element models in analyzing the stress distribution in shear and microshear bond strength tests

Abstract

Numerical computational analyses by means of finite element method (FEM) have been allowing the understanding of how the test set-up configurations influence on stress distribution in the tested specimen. During such analysis, the models are simplified but, at the same time, they must allow obtaining enough data and, thus, enough knowledge for changing and standardizing the tests set-ups. This study aimed at comparing the capacity of 2D plane strain simplified finite element models, simulated in a previous study, in analyzing the shear and microshear bond strength tests set-ups, compared to 3D more refined models. Booth 2D and 3D models represented a resin-composite cylinder (with two different stiffness) adhered to a dentin flattened surface by means of an adhesive layer. The shear and microshear specimens had dimensions in a 5:1 ratio, except for the adhesive layer thickness, which remained constant in booth-sized models. It was simulated a load applied by an orthodontic wire-loop in all the cases, varying the distance from the load to the adhesive interface. The 2D models showed to be enough for analyzing the stress distribution patterns along the dentin-adhesive interface. They also allowed verifying the influence of variables such as the relative thickness of the adhesive layer and the distance between the loading and the adhesive interface on the stress distribution. However, the 2D plane strain models showed an opposite effect of the elastic modulus of the resin-composite cylinder on the stress concentration. Furthermore, they lead to a different prediction with respect to the real test set-up configurations. As the 3D models were built with more realistic geometrical refinements compared to the simplified 2D models, they should be considered as more reliable than the 2D models for analyzing the shear and microshear bond strength test set-ups.