effect of an extra hydrophobic resin layer on repair shear bond strength of a silorane-based composite resin

objectives: composite repair is a minimally invasive and conservative approach. this study aimed to evaluate the effect of an additional hydrophobic resin layer on the repair shear bond strength of a silorane-based composite repaired with silorane or methacrylate-based composite. materials and methods: sixty bar-shaped composite blocks were fabricated and stored in saline for 72 hours. the surface of the samples were roughened by diamond burs and etched with phosphoric acid; then, they were randomly divided into three groups according to the repairing process: group 1: silorane composite-silorane bonding agent-silorane composite; group 2: silorane composite-silorane bonding agent- hydrophobic resin-silorane composite, and group 3: silorane composite-silorane bonding agent-hydrophobic resin methacrylate-based composite. repairing composite blocks measured 2.5×2.5×5mm. after repairing, the samples were stored in saline for 24 hours and thermocycled for 1500 cycles. the repair bond strength was measured at a strain rate of 1mm/min. twenty additional cylindrical composite blocks (diameter: 2.5mm, height: 6mm) were also fabricated for measuring the cohesive strength of silorane-based composite. the data were analyzed using one-way anova and the post hoc tukey’s test (α=0.05). results: cohesive bond strength of silorane composite was significantly higher than the repair bond strengths in other groups (p<0.001). the repair bond strength of group 3 was significantly higher than that of group 1 (p=0.001). conclusion: application of an additional hydrophobic resin layer for repair of silorane-based composite with a methacrylate-based composite enhanced the repair shear bond strength.