Effect of surface treatments on the tensile bond strength of repaired water-aged anterior restorative micro-fine hybrid resin composite

OBJECTIVES: The purpose of this study was to characterize changes in surface topography associated with different surface treatments and their effect on tensile bond strength (TBS) of repaired water-aged anterior restorative micro-fine hybrid resin composite. METHODS: The TBS of repaired resin-based composite slabs either non-treated or exposed to different mechanical and/or chemical surface treatment procedures were measured. The cohesive tensile strength of non-repaired intact slabs was used as a control group. The topographical effects of acid etching, grinding, and grinding followed by acid etching were characterized by AFM and SEM. RESULTS: All repaired groups showed significantly lower TBS than the control group. The TBS of repaired groups was ranged from 15% to 59% of the cohesive tensile strength of the control group (18.8+/-4.5MPa). The surface roughness of the non-treated aged specimens was significantly higher than other treated specimens. Specimens treated by acid etching showed significant increase in surface area compared to the non-treated and treated specimens. CONCLUSIONS: Aging process resulted in the formation of degradable surface layer which adversely affects the repair bond strength. The use of silane primer prior to the application of the adhesive after mechanical grinding, with or without the use of 37% phosphoric acid etching; improves the repair bond strength.