الفهرس 
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Abstract
Title: Repair of Bulk-Fill Resin Composite: Effect of Different Surface Treatments and Repair Materials on Shear Bond Strength Purpose: To evaluate and compare the effect of different surface treatments on shear bond strength of bulk-fill repaired with flowable bulk-fill and flowable conventional resin composites. Materials and methods: Sixteen blocks were prepared from Tetric N-Ceram BFRC using a stainless-steel mold (25x4x4) mm, and aged by thermocycling then stored in artificial saliva for 6 months. The blocks were divided into 4 groups according to the surface treatment applied; group 1: roughened by coarse discs, group 2: roughened by coarse disc and silanization, group 3: roughened by air abrasion device, and group 4: roughened by air abrasion device and silanization. Then each group was subdivided into 2 subgroups according to the repair restorative system was used. Subgroup A repaired with Tetric N-Bond universal adhesive/Tetric N-Flow BFRC, and subgroup B repaired with Prime& Bond universal adhesive / Spectra ST flow CRC (n=2). The repair RC material was placed on the RC blocks using tygon tubes and cured. The specimens were then tested for SBS using a universal testing machine (0.5 mm/min). Results: The results of this study showed that different surface treatments and repair materials had significant effect on shear bond strength. The results of two-way ANOVA test showed that different surface treatments had statistically significant effect on shear bond strength (p<0.001), while a non-statistically significant effect was found for different repair materials (p=0.814). Combined effect of change in surface treatments and repair material type had statistically significant effect on shear bond strength (p<0.001). Conclusions: Based on the results of the current study, air abrasion of the aged bulk-fill resin composite material followed by silane surface treatment is the best protocol to improve repair bond strength. Bulk-fill or conventional resin composites could be used in repairing the aged bulk-fill resin composite.