Efeito dos materiais de cimentação, presença de preparo dental e carregamento funcional na distribuição de tensões em laminados cerâmicos: análise por elementos finitos

Abstract

The purpose of this study was to evaluate the effect of the polymerization shrinkage, functional loading and mechanical properties of luting materials on the shrinkage stress and residual occlusal stress of ultrathin 0.3-mm ceramic laminate veneers (CLVs) with and without tooth preparation. Three resin cements: RelyX Veneer (RV, 3M ESPE), Allcem Veneer APS (AV, FGM), Variolink Esthetic LC (VE, Ivoclar Vivadent), and one flowable resin composite: Tetric N-Flow (TF, Ivoclar Vivadent) were tested. Post-gel shrinkage (Shr), Knoop hardness (KHN), elastic modulus (E), compressive strength (CS) and diametral tensile strength (DTS) were performed. Finite element analysis was performed using modified von Mises criterion (mvm). IPS e.max CAD discs 0.3-mm thick were made for simulating the effects of light attenuation. Eight two-dimensional finite element models (Marc-Mentat, MSC Software) of a maxillary central incisor were generated to evaluate the shrinkage stress during the light-activation of luting materials and the residual stress during functional loading. Data of Shr, KHN and E were submitted to 2-way ANOVA and Tukey test (α=.05). TF had lower Shr when interposing ceramic disc (0.31%). TF and RV showed the highest and VE the lowest KHN and E values (P>.05). Veneers with or without preparation showed similar shrinkage stress and functional residual stress. Stress concentration was observed on the incisal edge and also on cervical region. Models with RV presented the highest and VE the lowest stresses values (MPa). Flowable composite had similar mechanical properties than resin cements. The shrinkage and functional residual stresses were similar for veneer with or without tooth preparation.