Effect of Different Surface Barrier Agents on the Microhardness of a Light-Cured Composite Resin

This study aims to evaluate the effect of the oxygen inhibition layer formed during the polymerization of composite resins on microhardness and to examine the changes in microhardness values after removing this layer using different finishing techniques. Disc-shaped specimens (10 mm in diameter and 2 mm in thickness) were prepared using Valux Plus Composite (3M ESPE, USA) and divided into four groups (n=12) to evaluate the effects of different surface barriers. The control group was polymerized without any surface barrier. In the other groups, Glycerin gel, Mylar Strip, or BisCover LV were applied to the surface of the composite before light-curing. After polymerization, they were wet-finished and polished using 1200-grit SiO2 sandpaper. The specimens were stored in distilled water at 37 °C for 24 h. Microhardness tests were performed at five different points on each specimen using a 300 g force. The data were analysed using one-way ANOVA followed by post hoc tests (α=0.05). It was observed that different finishing techniques used for the removal of the oxygen inhibition layer resulted in significant differences in the microhardness values of the composite material. The control group showed significantly lower microhardness values (99.28±6.50) compared to the other groups (p<0.05). Among all groups, the Mylar Strip group demonstrated the highest microhardness values (117.43±4.24), which were statistically significant. Different finishing procedures had significantly different effects on the surface microhardness of composite resins. Although the Mylar Strip demonstrated the most favourable results, all application procedures showed significantly better outcomes compared to the control group.