Shear Bond Strength of Repaired Composites Using Surface Treatments and Repair Materials: An In vitro Study

BACKGROUND: Enhancement of bond strength between new and old composite usually requires increased surface roughness of old composite to promote mechanical interlocking and subsequent coating with bonding agents to improve surface wetting and chemical bonding. So this study was carried out to evaluate and compare the effects of different surface treatments and repair materials on the shear bond strength (SBS) of composite repairs The mode of failure of repaired composites whether cohesive or adhesive was also evaluated. MATERIALS AND METHODS: The substrates for 60 composite specimens were fabricated and aged with water treatment and subjected to various surface treatments. The surface treatment regimens used in the study were: No surface treatment, abraded with diamond bur, air abraded (sandblasted) with 50 µ aluminum oxide particles. Specimens were then repaired with fresh composite using either Clearfil(™) repair or all-bond two adhesive systems. Specimens were water stored, thermocycled and tested for SBS using universal testing machine. Fractured specimens were then examined under stereomicroscope to determine the mode of failure. RESULTS: It was clearly showed that surface roughening of the aged composite substrate with air abrasion, followed by the application of Clearfil(™) repair adhesive system (Group IIIa) yielded the highest repair bond strength (32.3 ± 2.2 MPa). CONCLUSION: Surface treatment with air abrasion followed by bonding with Clearfil(™) repair adhesive system can be attempted clinically for the repair of composite restorations.