Mohadeseh Shokripor
Loghman Rezaei Soufi
Banafsheh Ahmadi
Emira Najafrad
Masoud Azizian Mosleh

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 microhybrid composite resin repairs. Methods: Sixty-four cylindrical specimens of a Filtek Z۲۵۰۳M composite resin were fabricated and stored in ۳۷°C distilled water for two weeks. The specimens were divided into ۸ groups according to the following surface treatments: composite primer (group ۱); composite primer + G-premio (group ۲); composite primer + SE bond (group ۳); roughening with coarse-grit diamond bur + composite primer + G-premio (group ۴); roughening with coarse-grit diamond bur + composite primer + SE bond (group ۵); Er,Cr:YSG + G premio (group ۶) Er,Cr:YSG + Se bond (group ۷); bulk composite (positive control group). Then the same composite resins were packed on specimens into layers. After being stored in distilled water for ۲۴ hours, specimens were thermocycled. The SBS of the resin composites were tested with a universal test machine. Data was analyzed using one-way ANOVA and Tukey test (P < ۰.۰۵). Results: One-way ANOVA indicated no significant differences between groups ۲, ۳, ۴, ۵, ۷ and control group. SBS of group ۱ and ۶ was significantly lower than control group. Surface treatment with diamond bur + composite primer + SE bond resulted in the highest bond strength. Conclusions: Surface roughening with bur and using sixth generation adhesives (SE bond) and eighth generation bonding agents (G-premio) and laser with sixth generation indicated similar result to intact composite, although use of composite primer did not lead to acceptable bond strength for repairing composite. However Clearfil SE bond show highest bond strength.