effect of intermediate agents and preheated composites on repair bond strength of silorane-based composites

objectives: repairing composite restorations is a challenging procedure especially when two different types of composites are used. this study aimed to compare the repair strength of silorane-based composite (sc) (filtek p90) with that of preheated sc, methacrylate composite (mc)(z250), flowable mc (filtek supreme plus) and different adhesive/composite combinations. materials and methods : eighty-four sc specimens were fabricated and randomly divided into seven groups (g). in the control group (g7), sc was bonded immediately to sc. the other specimens were water-aged for two months and were then roughened, etched and repaired with the following materials: g1) silorane adhesive bond (sab)/sc; g2) preheated sc; g3) sab/mc; g4) adper single bond (sb)/mc; g5) flowable mc/mc; g6) preheated mc. after water storage and thermocycling, the repaired specimens were subjected to shear bond strength testing. the data were analyzed using anova and tukey’s test. results : preheated sc and mc, flowable mc and sab/sc resulted in bond strength comparable to that of the control group. preheated sc showed significantly higher bond strength when compared to sab/mc ( p=0.04) and sb/mc ( p<0.001). bond strength of sb/mc was significantly lower than that of the other groups (p<0.05), except for sab/sc and sab/mc. conclusion : all repairing materials except for sb/mc resulted in bond strength values comparable to that of the control group. repair with preheated sc yielded the highest bond strength.