Hydroxy acids as etchants tied to appropriate bond strength and less dentin degradation: Study

Cristina de Mattos Pimenta Vidal and colleagues from the Department of Operative Dentistry, College of Dentistry and Dental Clinics, University of Iowa, Iowa City, IA, United States conducted the present study with the main objective to test the demineralization potential, bonding performance, and dentin biostability when using hydroxy acids for etching enamel and dentin.

The authors investigated the surface microhardness, roughness and depth of demineralization 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 micro-tensile 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 = 0.05).

The following results were noted-

1. 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).
2. Hydroxy acids produced significantly shallower demineralization than Pa (p < .05).
3. Gln resulted in the lowest SBS and μTBS, while Gly, Glu, Ta, and Pa showed no significant difference.
4. There was no significant difference in μTBS between 24 h and 1 year of storage.
5. The association between failure mode and etchant was statistically significant after 24 h only (p < .001).
6. Hydroxy acids resulted in higher dentin biostability than Pa (p < .05).