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Abstract
Objectives: the aim of the study was to evaluate the effect of repairing bulk-fill resin composite restoration by the same bulk-fill composite material after surface treatment either by bur, etch and resin adhesive system or both at different time intervals using micro-shear bond strength test. Methods:A total number of 180 discs of bulk fill composite resin (Xtra-fill) used in this study. Different surface treatment was done for the composite disc for repair procedure either by diamond bur or by etchant (Vococid 37% phosphoric acid etch) or by adhesive system (Solo Bond M). Five micro cylindrical composite was constructed on previously surface treated bulk fill composite disc using cylinder of plastic Tygon tube. The specimens were stored in artificial saliva at 37{u2103} till testing after 24 hours followed by 2 weeks then 1 month time intervals. Micro shear bond strength test was performed using Universal Testing Machine; then the debonded specimens were examined using digital microscope to determine the mode of failure. Two ways ANOVA was done to detect effect of each variable. One way ANOVA followed by pair-wise Tukey{u2019}s post-hoc tests were performed to detect significance between subgroups within each group. Results: Regardless of surface treatment, the 2 weeks group recorded statistically non-significant higher æ-shear bond strength mean value (27.02±3.6MPa) followed by 24 hr group mean value (26.56±5.7MPa) while 1 month group recorded the lowest æ-shear bond strength mean value (26.05±2.3MPa). The difference between all groups was statistically non-significant as indicated by two way ANOVA (P=0.6307>0.05)