Polymerization Shrinkage Stresses of Low Shrink Versus Conventional Micro-Hybrid Composites MOD Restorations: A 3-D Finite Element Analysis Study

Using 3-D finite element analysis (FEA), this study aimed to test the hypothesis that dimethacrylate-based composites (Filtek Z250) with greater polymerization shrinkage will show higher stress generation, within the restorative material system and the supporting structures, than low shrink silorane-based composites (Filtek P90), particularly in large cavities (MOD). A tooth model for maxillary first molar with a MOD cavity was constructed using Solid works Premium 2012 software. The ANSYS 13.0 software was used to assign the materials and tissues properties. A 3D structural static finite element analysis was then conducted. Data analysis revealed that the resulting Von Mises Equivalent Stresses (MES) generated within the enamel, dentin and composite were higher with Filtek Z250. MES increased monotonically as the polymerization process progressed. The highest MES existed at the axio-gingival line angle and cervical cavo-surface margin of enamel, dentin and adhesives. Within the composite material, the highest MES existed at the restoration occluso-axial surface. As a clinical consequence, the composite material system with higher polymerization shrinkage stresses is more susceptible to microcracking and accordingly earlier failure than low shrink system.