Hydroxy acids for adhesion to enamel and dentin: Long-term bonding performance and effect on dentin biostability.

Abstract Objectives To test the demineralization potential, bonding performance, and dentin biostability when using hydroxy acids for etching enamel and dentin. Methods Surface microhardness, roughness and depth of demineralization were investigated after etching enamel and dentin with 35% glycolic acid (Gly), tartaric acid (Ta), gluconic acid (Glu), gluconolactone (Gln), or phosphoric acid (Pa) (n = 5/group). Dentin microtensile bond strength (µTBS) after 24 h or 1 year of bonding (n = 8 teeth/group) and enamel shear bond strength (SBS) after 24 h (n = 10 teeth/group) were obtained. In dentin, failure mode was classified as adhesive, cohesive in dentin/resin, or mixed. Dentin biostability was assessed by loss of dry weight and collagen degradation after 30-day incubation (n = 10 beams/group). Statistical analysis consisted of ANOVA with post-hoc Tukey’s HSD, Tukey-Kramer test, Bonferroni correction, and Fisher’s exact tests (α = .05). Results Gly showed better or similar results than Pa for enamel microhardness and dentin roughness, while no significant differences were observed among Ta, Glu, and Gln (p > .05). Hydroxy acids produced significantly shallower demineralization than Pa (p  Conclusions Gly, Glu and Ta resulted in adequate bonding performance and reduced dentin degradation and are potential alternative etchants to improve long-term stability of adhesive restorations. Clinical significance This study supports the potential use of hydroxy acids as alternative etchants when bonding to enamel and dentin and demonstrates that specific acids are more suitable to be used in adhesion since they result in appropriate bond strength and less dentin degradation.