Abstract: PURPOSE: To investigate the effects of different surface treatments and adhesive self-etch functional monomers on the immediate repair bond strength and integrity of the repaired resin composite interface. METHODS: Ninety-eight resin composite blocks made of a nanohybrid resin composite were randomly divided into seven groups, each with 14 blocks, including positive control group: non-conditioned surface, Group A1: Gluma Comfort Bond, Group A2: Gluma Comfort Bond and sandblasting, Group B1: Tokuyama Bond Force II^TM adhesive system, Group B2: Tokuyama Bond Force II^TM adhesive system and sandblasting, Group C: polishing, and Group D: sandblasting. Resin composite identical to the substrate was applied and the repaired specimens were subjected to shear bond strength (SBS) testing. Representative samples from all groups received scanning electron microscopy and surface profilometry to determine their mode of failure. The data were processed with SPSS 20.0 software package. RESULTS: SBS of Group D was significantly higher than that of positive control group (P<0.05). SBS of Group A1, A2, B1 and B2 was significantly higher than that of Group C and D (P<0.05). Comparison of SBS among Group B1, D and A1 showed no significant difference(P>0.05). SBS between Group B2 and positive control group had no significant difference(P>0.05). Except specimens with sandblasting and the use of TBF II system, SBS of positive control group was significantly higher than that of Group A1 and C(P<0.05). The polished specimens had significantly more adhesive failures than those with sandblasted surfaces (P<0.05). Specimens treated with polishing and Gluma Comfort Bond showed significantly more adhesive failures than those treated with polishing and TBF II system (P<0.05). The sandblasted surfaces conditioned with TBF II showed significantly more cohesive failures than those treated with polishing and TBF II (P<0.05). The sandblasted specimens provided significantly more irregular and rougher surface finish than the polishing technique (P<0.05). CONCLUSIONS: Sandblasting of the composite substrate and the use of TBF II adhesive system shows the highest repair bond strength, higher adhesive interfacial failures and fewer cohesive failures; however, it is noteworthy that the composite substrate types yield statistically higher food residue rate, which results in poor oral hygiene maintenance. Therefore, the application of this repair protocol should match up with correct oral health behaviors.

Key words: Surface treatments, Self etching functional monomer of binder, Resin composite interface, Immediate repair bond strength, Integrity