Bond strength of resin composite to light activated bleached enamel

Objectives: This study evaluated the microtensile bond strength (μTBS) of a resin composite bonded to bleached enamel as a function of bleaching conditions. Materials and Methods: The whiteness hydrogen peroxide (HP) bleaching agent containing 35% HP was applied to the central incisors’ facial enamel surface and irradiated as follows: No treatment (G1; control); no light (G2); light‑emitting diode, the 40s (G3); diode laser, the 20s (G4); and neodymium:yttrium aluminum garnet laser, 20s (G5). A Variolink II resin composite structure was then built up incrementally on the surface. The teeth were sectioned into three 1.2 mm × 1.2 mm wide “I”‑shaped sections. The specimens were then subjected to microtensile testing at a crosshead speed of 1 mm/min. Data were analyzed using one‑way ANOVA ( α =0.05) followed by the Tukey Honestly Significant Difference post‑hoc test. The fractured surfaces were observed with a stereomicroscope at × 100 magnification. Results: One‑way ANOVA revealed no statistical differences among the groups ( P > 0.05). No differences appeared between the groups bonded 14 days after bleaching ( P > 0.05). Mean μTBS values (MPa) were as follows: 22.05 ± 5.01 (G1); 19.6 ± 5.6 (G2); 19.3 ± 5.4 (G3); 20.08 ± 2.08 (G4); and 18.1 ± 4.8 (G5). Many adhesive failures occurred at the bleached and irradiated enamel surfaces. Conclusion: The various irradiation treatments following the application of the whiteness HP bleaching agent to enamel did not significantly reduce the μTBS within a 14‑day period. Keywords: Bleaching agents, lasers, lasers neodymium: yttrium aluminum garnet, resin bonding, tooth bleaching