Caracterização mecânica e óptica de resinas compostas de cor única utilizadas em dentes posteriores

Abstract

OBJECTIVES: This study aimed to evaluate the optical and mechanical performance of two single-shade resin-based composites (RBCs) compared with a conventional RBC for incremental filling technique in posterior teeth. METHODS: Two single-shade , Omnichroma (Tukoyama) and Vittra Unique APS (FGM) and a conventional RBC, Filtek Z350XT shade A2 (3M Oral Care) were tested in this study. Optical performance involved analysis of shade matching checked using spectrophotometer. The Light transmission was performed using beam profiling method of the VALO Grand (Ultradent) and of the light transmitted through the 2.0mm of specimen of each RBC. The mechanical performance was expressed by calculation of the Knoop hardness (KH, N/mm2), degree of conversion (DC, %) at top and bottom using Raman spectroscopy, the flexural strength (FS, MPa) and elastic modulus (E, MPa) using 3-point bending test, diametral tensile strength (DTS, MPa), compression strength (CS, MPa) using axial compression test, post-gel shrinkage (%) using strain-gauge test, shrinkage and residual stress using finite element analysis. Scanning electronic microscopy was performed for filler characterization. Data of FS, E, DTS, CS and Shr were analyzed by 1-way ANOVA and KH and DC by 1-way ANOVA repeated measurement followed by Tukey's test (α = 0.05), and residual shrinkage was analyzed quantitatively and qualitatively by modified the von Mises criteria. FS, DTS, CS, E were analyzed using a 1-way analysis of variance and KH and DC data were analyzed using a 1-way analysis of variance for repeated measures followed by Tukey post-hoc test (α = 0.05). The modified von Mises stresses values, light transmission and the SEM imagens were analyzed qualitatively. RESULTS: KH and DC values reduced significantly from the top to the bottom of the specimens for all RBCs (P < 0.001), however the ratio values were always higher than 80%. There was significant difference among RBCs for E (P < 0.001), DTS (P = 0.008), higher values for Filtek Z350XT; CS (P <0.001) Vittra Unique APS and Filtek Z350XT had lower values than Omnichroma. The single-shade RBCs obtained similar shrinkage stress to the tooth during occlusal loading. Filtek Z350XT resulted in slightly more shrinkage stress within the 13 RBCs. There was no difference for FS (P = 0.083) and Shr (P = 0.144). Omnichroma showed less color difference than Vittra Unique APS irrespective of shade. All single-shade RBCs showed more color variation compared to the control RBC. The light transmitted through all RBCs decreased significantly. Omnichroma and Vittra Unique APS increased light transmission during the polymerization process. CONCLUSION: Omnichroma and Vittra Unique APS have similar or superior mechanical properties than Filtek Z350XT. The single-shade RBCs tend to increase light transmission during the photoactivation process. The Omnichroma showed less shade difference than Vittra Unique APS independent of tooth shades.