Efeito da espessura de materiais restauradores CAD-CAM na transmissão de luz e na microdureza de um cimento resinoso dual

Abstract

The aim of this study was to evaluate the hardness of a dual cure conventional resin cement light-cured either through or without the indirect restoration and tested immediate or 24 h after polymerization. The light transmission was evaluated through three types (Lava Ultimate, 3M ESPE; Vita Enamic, Vita Zahnfabrik; Emax CAD, Ivoclar Vivadent e Brava Block, FGM) and four thickness (1,0/1,5/2,0 e 3,0 mm) of CAD-CAM materials with a spectrometer (MARC PS system, Bluelight Analytics, Halifax, NS, Canada). The specimens (n=5) of the luting resin cement RelyX ARC (3M ESPE/ Cor A1) were made in the cylindrical ring stainless steel mold with dimensions 8.0 mm in diameter and 0.5 mm thickness. Samples were polymerized through a mylar strip, with or without (positive control) interposition of CAD-CAM discs for 40 seconds using a LED Emitter C (Schuster), with 1200 mW/cm2. The negative control was not photoactivated. The resin cement specimens were submitted to microhardness tests (HMV-2; Shimadzu, Tokyo, Japan), with a load of 50g applied for 10 seconds, immediate after polymerization and after storage at 37ºC for 24 hours. Three indentations were made on the top surface of each specimen. The microhardness of each specimen was recorded as the average of the three readings. Data were submitted to ANOVA followed by Bonferroni and Dunnet post hoc test (α = 0.05). Statistically significant differences were found in irradiance values measured through the materials, in relation to that measured directly at the tip of the light source, and between the different thicknesses. In general, microhardness values were not affected by the material type or thickness. The hardness was negatively influenced by the interposition of an indirect restorative material. There was a significant increase in Knoop hardness after 24 hours.