Microtensile bond strength of resin composite to dentin treated with Er:YAG laser of bleached teeth

The objective of this study was to evaluate the influence of Er:YAG laser (ƒة=2.94 ƒتm) on microtensile bond strength (ƒتTBS) and superficial morphology of bovine dentin bleached with 16% carbamide peroxide. Forty bovine teeth blocks (7 پ~ 3 پ~ 3 mm3) were randomly assigned to four groups: G1- bleaching and Er:YAG irradiation with energy density of 25.56 J/cm2 (focused mode); G2 - bleaching; G3 - no-bleaching and Er:YAG irradiation (25.56 J/cm2); G4 - control, non-treated. G1 and G2 were bleached with 16% carbamide peroxide for 6 h during 21 days. Afterwards, all blocks were abraded with 320 to 600-grit abrasive papers to obtain flat standardized dentin surfaces. G1 and G3 were Er:YAG irradiated. Blocks were immediately restored with 4-mm-high composite resin (Adper Single Bond 2, Z-250-3 M/ESPE). After 24 h, the restored blocks (n=9) were serially sectioned and trimmed to an hour-glass shape of approximately 1 mm2 at the bonded interface area, and tested in tension in a universal testing machine (1 mm/ min). Failure mode was determined at a magnification of 100پ~ using a stereomicroscope. One block of each group was selected for scanning electron microscope (SEM) analysis. ƒتTBS data was analyzed by two-way ANOVA and Tukey test (ƒ؟=0.05). Mean bond strengths (SD) in MPa were: G1- 32.7 (5.9)A; G2- 31.1 (6.3)A; G3- 25.2 (8.3)B; G4- 36.7 (9.9).A Groups with different uppercase letters were significantly different from each other (p<.05). Enamel bleaching procedure did not affect ƒتTBS values for dentin adhesion. Er:YAG laser irradiation with 25.56 J/cm2 prior to adhesive procedure of bleached teeth did not affect ƒتTBS at dentin and promoted a dentin surface with no smear layer and opened dentin tubules observed under SEM. On the other hand, Er:YAG laser irradiation prior to adhesive procedure of non-bleached surface impaired ƒتTBS compared to the control group.