Bonding of adhesives to bur-cut, Er:YAG laser-irradiated and ultrasonic-excavated dentin

Objective: The aim of this study was to investigate the effect of Er:YAG laser and ultrasonic instrument on bonding to caries-affected dentin. Method: Extracted human carious teeth were ground to expose flat dentin surfaces with carious lesions. Carious lesions were removed using Er:YAG laser, ultrasonic instrument and high-speed diamond bur as a control. After clinical caries excavation, the cavities in each experimental group were restored with three self-etching priming adhesive systems, Clearfil SE Bond (Kuraray Medical), One-up Bond F (Tokuyama Dental) and G-Bond (GC), plus composite. Hourglass-shaped samples through the bond interfaces were sectioned and microtensile bond strengths were recorded. Scanning electron microscopy (SEM) was used to observe the morphology at the resin-dentin interface. Data were analyzed by 2-way ANOVA and Scheffe's test at a significance level of 0.05. Results: For all adhesive systems Er:YAG laser-irradiated dentin showed the lowest average bond strength and the ultrasonic-excavated dentin produced the highest average bond strength. For bur-cut and Er:YAG laser-irradiated dentin the bond strength of Clearfil SE Bond was significantly higher than that of One-up Bond F (p<0.05), but there were no significant differences in bond strengths to ultrasonic-excavated dentin among three adhesive systems (p>0.05). SEM observation revealed the meshwork hybrid layer and the gathered resin-tags for Er:YAG-lased dentin group, and the uniform hybrid layer and typical resin-tags for bur-cut and ultrasonic instrument groups. Conclusion: These results indicated that the ultrasonic caries excavation was most effective for dentin bonding of self-etching priming adhesive systems, and the Er:YAG laser-irradiated dentin was unfavorable for bonding.