Repair bond strength of bulk fill composites after different adhesion protocols

BACKGROUND: Repairs in composite resin restorations are common procedures in clinical practice. Many surface treatment options have been proposed to improve the adhesion between the old and new composite. The objective of this study was to evaluate the microtensile bond strength of repairs performed on aged bulk fill and conventional composites after different adhesion protocols. MATERIAL AND METHODS: First, 84 specimens (8x8x4 mm3) of a microhybrid composite and a high-viscosity bulk fill composite were prepared and aged. Afterward, they received a mechanical surface treatment by means of abrasion with a diamond bur, followed by division into six groups according to the adhesion protocol employed: PSA - etching with 35% phosphoric acid + silane + etch-and-rinse adhesive; SA - silane + etch-and-rinse adhesive; PA - etching with 35% phosphoric acid + etch-and-rinse adhesive; A - etch-and-rinse adhesive; PU - 35% phosphoric acid + universal adhesive; and U - universal adhesive. The repairs were performed with a microhybrid composite. Repaired resin blocks were cut into sticks (8x1x1 mm3) and submitted to a microtensile test. Fractured specimens were evaluated to determine the failure pattern (adhesive or cohesive). Data were analyzed by two-way ANOVA. RESULTS: No statistically significant differences were found in bond strength values among different adhesion protocols and composite types. CONCLUSIONS: The repair bond strength of a bulk fill composite was similar to that found in a conventional composite, with no distinction among adhesion protocols. Key words:Dental restoration repair, composite resins, adhesiveness.