Effects of Er:YAG and Er,Cr:YSGG laser irradiation on the adhesion to eroded dentin

Limited information is available regarding the adhesion to eroded dentin. This study aims to evaluate the effect of different surface treatments on eroded dentin morphology and on microtensile bond strength (μTBS) of adhesive systems to this substrate. Ninety-six extracted third molars were randomly divided into eight groups (n = 12) according to the type of surface treatment and the adhesive system: G1 = Control + Clearfil SE Bond [SE], G2 = Diamond bur [DB] + SE, G3 = Er:YAG laser (60 mJ, 2 Hz, 0.12 W, 19.3 J/ cm2) + SE, G4 = Er,Cr:YSGG laser (50 mJ, 30 Hz, 1.5 W, 4.5 J/ cm2) + SE, G5 = Control + Single Bond [SB], G6 = DB + SB, G7 = Er:YAG + SB, G8 = Er,Cr:YSGG + SB. The erosive cycling was performed by immersion in 0.05 M citric acid (pH 2.3, 10 min, 6x/day) and in supersaturated solution (pH 7.0, 1 h, between acid attacks), during 5 days. Blocks of composite were bonded to the samples according to the manufacturers' instructions. After 24 h-storage in distilled/deionized water (37 °C), stick-shaped samples were obtained and submitted to μTBS test. Each surface treatment was analyzed under scanning electron microscopy (n = 4) and the bond strength values (megapascal) were analyzed by two-way ANOVA and Tukey tests (α = 0.05). All surface treatments lead to changes on eroded dentin. G4 showed the highest bond strength mean (28.3 ± 9.2 MPa), which was statistically significant higher than all the other groups (p < 0.05). The surface treatment with Er,Cr:YSGG laser irradiation (4.5 J/cm2/50 mJ/30 Hz/140 μs) prior to bonding with a self-etching adhesive system significantly increases adhesion to eroded dentin, as compared to conventional treatment.