Method: Sixty-six flat bovine dentin samples were randomly divided into six groups (n=11): ED: eroded dentin; SD: sound dentin – no further treatment; EDL1: eroded dentin treated with Er,Cr:YSGG laser 1.5 W; EDL2: eroded dentin treated with Er,Cr:YSGG laser 2.0 W; EDL3: eroded dentin treated with Er,Cr:YSGG laser 2.5 W and EDB: eroded dentin treated with diamond bur. The erosive cycling was performed by immersion of the samples in 0.05 M citric acid (pH 2.3, 10 min, 6x/day) and in supersaturated solution (pH 7.0, 1h, between acid attacks), for 5 days. Dentin samples were bonded with a 2-step etch-and-rinse adhesive (Adper Single Bond, 3M ESPE) and three cylinders of a flowable composite resin (0.5 mm high and 0.8 mm in diameter) were applied to the bonded dentin surface using a tygon tube (n=33). The samples were stored in distilled water at 37oC for 24h and the microshear bond strength test was performed at a cross-head speed of 1.0 mm/min. Data were statistically analyzed by one-way ANOVA and Tukey’s test (5%).
Result: The SD group (19.89±7.59) presented the highest shear bond strength values followed by the EDB group (12.17±3.85), which had no statistically significant difference between the other groups. The lowest mean value was found for group EDL2 (7.07±1.55) which did not result in significant differences compared to ED (7.49±1.84), EDL1 (8.45±1.83) and EDL3 (8.62±3.17) groups. In all experimental groups, the failure mode was predominantly adhesive (between adhesive and dentin) but in laser treated groups (2.0 and 2.5 W) cohesive failures were observed.
Conclusion: The results of the present in vitro study indicate that all treatments had no positive effect on microshear bond strength to eroded dentin.