effect of er:yag laser versus chlorhexidine disinfection on dentin bond strength of two adhesive systems

Objective: this study evaluated the effects of 2% chlorhexidine (chx) and er:yag laser on the shear bond strength (sbs) of resin composite to affected dentin using two adhesive systems.methods: sixty extracted third molars were randomly assigned to three disinfection groups (control, 2% chx, and er:yag laser). each disinfection group was further divided into two subgroups based on the adhesive system used (an etch-and-rinse or a universal self-etch system), yielding a total of six groups (n=10). after caries excavation, dentin surfaces were treated according to the assigned disinfection and adhesive protocols. the resin composite was then applied to the treated surface using a cylindrical mold. samples underwent 10,000 thermal cycles, followed by shear bond strength (sbs) testing and failure mode analysis. data were analyzed using two-way anova and chi-square test at the significance level of p < 0.05.results: anova revealed no significant differences in mean bond strength among the disinfection groups with either adhesive system (p > 0.05).  however, the etch-and-rinse adhesive showed significantly higher sbs compared to the universal self-etch adhesive across all disinfection groups (p < 0.05). chi-square analysis revealed no significant differences in failure modes among the groups (p = 0.71).conclusions: disinfection of affected dentin with either er:yag laser or 2% chx does not reduce the bond strength of adhesive systems. the etch-and-rinse adhesive consistently achieved higher sbs than the universal adhesive after dentin disinfection, suggesting that it may be preferred for clinical use.