Depth of cure and surface microhardness of experimental short fiber-reinforced composite

Abstract

Objectives. The aim of this study was to analyze the depth of cure of a short fiber-reinforced composite (FRC) assessed by microhardness at different curing times and storage conditions. Material and methods. Experimental composite resin (FC) was prepared by high-speed mixing 22.5 wt% short E-glass fibers (3 mm in length) and 22.5 wt% resin matrix and gradually adding 55 wt% silane-treated silica filler. Half-split cylindrical test specimens were produced from both the FC and from the conventional particulate composite resin (control, Z250, 3M-ESPE). The test specimens (n=3/group) were polymerized at different exposure times (20, 40, 60 s) and then water-stored at 37°C for 24 h and 30 days before testing. A universal testing machine was used for testing Vickers microhardness. All results were statistically analyzed with analysis of variance (ANOVA). Results. ANOVA revealed that curing time had a significant effect (p<0.05) on the microhardness of both composite resins. Depth of cure of conventional composite resin (control) was significantly greater than that of FC (p<0.05). Microhardness after water storage decreased as curing time increased. Conclusions. The use of short fiber fillers in interpenetrating polymer network matrix (IPN) achieved the acceptable depth of cure and microhardness values recommended for clinical use, although lower than for commercial composite resin.