Influence of the photoactivation mode and the distance of light-curing unit in mechanical properties of silorane and methacrylate based resins.

Abstract

This in vitro work had as aim evaluate the effect of photoactivation mode and the distance of light-curing unit (LCU) in microhardness Knoop (KHN) and the diametrical tensile strength (DTS) of methacrylate and silorane-based resins. Filtek Z250 (methacrylate-based resin) and Filtek P90 (silorane-based resin), both from 3M Espe, were selected for this work. The photoactivation were performed by one of the following modes: Valo (Ultradent) at 1000 mW/cm² X 18 s (S); 1400 mW/cm² X 12 s (HP); 3200 mW/cm² X 6 s (PE); and XL 3000 (3M Espe) at 450 mW/cm² X 40 s (XL). Resin composite were inserted in one increment into a bipartide Teflon matrix (5mm X 2mm) and photoactivated at 0mm, 3 or 6mm from the increment surface, according to the experimental groups. After the confection, the specimens (n=5) were submitted to KHN on the top (T) and on the bottom (B), and to DTS. Data were analyzed through ANOVA/Tukey tests (?=5%). It was observed that Filtek Z250 presented values of KHN equal or higher than Filtek P90. The surface T presented higher values of KHN than B. For both composite resins, the values of KHN on the surface B were lower, as higher the distance of LCU. In relation to DTS, the higher values were observed in Filtek Z250. Silorane base composite resin presented lower mechanical properties when compared to the methacrylate base resin. The distance of LCU is able to influence the microhardness of bottom surface.