effect of different surface treatments on the shear bond strength of nanofilled composite repairs

background. repairing aged composite resin is a challenging process. many surface treatment options have been proposed to this end. this study evaluated the effect of different surface treatments on the shear bond strength (sbs) of nanofilled composite resin repairs. methods. seventy-five cylindrical specimens of a filtek z350xt composite resin were fabricated and stored in 37°c distilled water for 24 hours. after thermocycling, the specimens were divided into 5 groups according to the following surface treatments: no treatment (group 1); air abrasion with 50-µm aluminum oxide particles (group 2); irradiation with er:yag laser beams (group 3); roughening with coarse-grit diamond bur + 35% phosphoric acid (group 4); and etching with 9% hydrofluoric acid for 120 s (group 5). another group of filtek z350xt composite resin samples (4×6 mm) was fabricated for the measurement of cohesive strength (group 6). a silane coupling agent and an adhesive system were applied after each surface treatment. the specimens were restored with the same composite resin and thermocycled again. a shearing force was applied to the interface in a universal testing machine. data were analyzed using one-way anova and post hoc tukey tests (p < 0.05). results. one-way anova indicated significant differences between the groups (p < 0.05). sbs of controls was significantly lower than the other groups; differences between groups 2, 3, 4, 5 and 6 were not significant. surface treatment with diamond bur + 35% phosphoric acid resulted in the highest bond strength. conclusion. all the surface treatments used in this study improved the shear bond strength of nanofilled composite resin used.