Effect of air-drying on the solvent evaporation, degree of conversion and water sorption/solubility of dental adhesive models.

This study evaluated protocols to eliminate acetone from dental adhesives and their effect on the kinetic of water sorption and percent of conversion of these adhesives. Experimental methacrylate-based adhesives with increasing hydrophilicity (R2, R3, R5) were used as reference materials. Primer-like solutions were prepared by addition of 50 wt% acetone. Acetone elimination was measured gravimetrically before and after: a spontaneous evaporation, an application of air-drying at room temperature or application of 40°C air-drying. Protocols were performed from 15 to 60 s. Specimens of adhesive/acetone mixtures were photo-activated and tested for degree of conversion, water sorption and solubility. Data were analyzed by ANOVA and Bonferroni's tests (α = 0.05). Complete acetone elimination was never achieved, but it was significantly greater after the 40°C air-drying application. Higher acetone elimination was observed for the least hydrophilic adhesive. Longer periods for acetone evaporation and heated air-stream can optimize polymerization and reduce the water sorption/solubility of adhesive system models.