Materials and methods. Sixty cylindrical composite resin specimens (Filtek Silorane) were fabricated and randomly divided into four groups according to surface treatment: group 1 (control group) without any mechanical surface treatment, groups 2‒4 were treated with air abrasion, Er,Cr:YSGG laser, and diamond bur, respectively. In addition, a positive control group was assigned in order to measure the cohesive strength. Silorane bonding agent was used in groups 1‒4 before adding the new composite resin. Then, the specimens were subjected to a shear bond strength test and data was analyzed using one-way ANOVA and post hoc Tukey tests at a significance level of P < 0.05. The topographical effects of surface treatments were characterized under a scanning electron microscope.

Results. There were statistically significant differences in the repair bond strength values between groups 1 and 2 and groups 3 and 4 (P < 0.001). There were no significant differences between groups 1 and 2 (P = 0.98) and groups 3 and 4 (P = 0.97). 

Conclusion. Surface treatment using Er,Cr:YSGG laser and diamond bur were effective in silorane-based composite resin repair.