RESUMEN
OBJECTIVE: The objective of the study was to evaluate the microtensile bond strength (µTBS) of a composite resin to abraded or non-abraded bleached enamel after Er,Cr:YSGG laser irradiation and to observe the fracture patterns of the tested interfaces. MATERIALS AND METHODS: Two hundred twenty-eight bovine incisors were sectioned, resulting in 228 enamel blocks (7 × 4 × 4 mm3) that were divided into 12 groups (n = 19) according to the factors "adhesion" after bleaching (immediate adhesion; after 14 days; and a control group with adhesion on unbleached teeth); enamel "abrasion" (with or without abrasion simulating cavity preparation); and "laser" (with or without Er,Cr:YSGG laser irradiation). Bleached enamel groups were treated with 20% carbamide peroxide, 8 h/day for 21 days. Abrasion was performed with silicon carbide sandpaper. Specimens were restored with adhesive system and a composite resin (Adper Single Bond 2 and Z250; 3M ESPE). After 7 days, specimens were prepared by cutting into 1 mm beans to µTBS test performed in a universal testing machine. Fracture mode analysis was performed by using a stereoscopic loupe. The µTBS data were statistically analyzed by three-way analysis of variance with 95% confidence level and compared by running a Tukey post hoc test (α = 0.05). RESULTS: There was no statistically significant difference between triple interaction and double interactions among factors. There was no significant difference between the factors "adhesion," "abrasion," and "laser." Laser irradiation produced significantly lower bond strength values in irradiated groups compared with the non-irradiated ones. All groups had a high percentage of adhesive failures. CONCLUSIONS: Abrasion provided no benefit to bond strength of composite resins to bleached enamel. Er,Cr:YSGG (20 Hz, 0.5 W, 3.97 J/cm2) treatment reduced the bond strength of composite resins to enamel.