Surface microhardness of a self-adhesive composite in comparison with conventional composite resins

Abstract

Background. The surface microhardness of dental composites greatly affects the durability of restorations. Objectives. The aim of this study was to compare the surface microhardness of a self-adhesive composite with that of other conventional composites. The effect aging has on surface microhardness was also evalu-ated. Material and methods. In this in vitro experimental study, the composite resins were poured into molds measuring 3 mm × 3 mm × 6 mm and cured for 40 s. The samples were then immersed in distilled water at 37°C for 24 h. After polishing, the surface microhardness of the samples was measured using the Vickers hardness tester. For this purpose, a 100-gram load was applied to 3 points on the surface of each composite sample for 20 s, and the mean value of surface microhardness was used as the Vickers hardness number. The samples were then subjected to 30,000 thermal cycles at 5–55°C in order to age them; after that, their surface microhardness was measured again. The one-way analysis of variance (ANOVA) was used for the statistical analysis. Results. The maximum hardness value before and after aging belonged to Filtek® Z250, followed by Premise™ Flow and Vertise™ Flow, with significant differences between them (p < 0.001). After aging, the surface microhardness of all composites decreased significantly (p < 0.001). The effect of aging on surface microhardness was the same in all groups (p > 0.05). Conclusions. The surface microhardness of composites was significantly different before and after aging. All composites experienced a reduction in their surface microhardness after aging.