Cavity dimension effect on MOD dental restoration filled with resin composite - A finite element interface stress evaluation

Resin composite has been one of the widely used materials in dental restorations. The polymerization shrinkage of this material is one of the critical defects provoking failures for the restoration. The biomechanical responses resulted from the interface stress between the resin and tooth (generated by the polymerization shrinkage) would be an important issue in determining the success of restoration. The aim of this study was to evaluate the biomechanical effects of cavity dimension in Class II MOD (mesial-occlusal-distal) restoration using finite element analysis. Solid model of a plastic synthetic second premolar was established by the transverse section slices of the plastic tooth. The model was then revised to create a sub-volume in the crown region to represent the resin filled cavity with various cavity dimensions. Resin material properties were applied in the elements within the cavity and shrinkage of these elements was simulated by a negative thermal expansion. The interface normal stress between the resin and tooth structure induced by this resin shrinkage was evaluated. The results shown that a larger cavity dimension is not always generated a greater interface stress. Since a larger cavity could increase the degree of contraction that leads to the interface stress, it also weakens the remaining tooth structure thus reduce the interface stress.