Effects of Warm Air Drying on Water Sorption, Solubility, and Adhesive Strength of Simplified Etch-and-Rinse Adhesives

Purpose: To evaluate the effects of the temperature of air used for solvent evaporation on water sorption, solubility, and ultimate tensile strength (UTS) of simplified etch-and-rinse adhesives. Materials and Methods: Four commercial simplified etch-and-rinse adhesives (Adper Single Bond 2 [SB]; Te Econom [TE]; XP Bond [XP] and Ambar [AM]) were selected. Disk-shaped specimens were prepared by dispensing the uncured resin into a mold (5.8 mm x 0.8 mm). Solvent evaporation was performed using a warm (60°C) or cold (20°C) air stream for 40 s. After desiccation, the cured specimens were weighed and then stored in distilled water for evaluation of the water diffusion kinetics over a 28-day period. For the UTS measurement, hourglass-shaped specimens of adhesives were prepared and tested in tension. The data from each test were evaluated with two-way ANOVA and Tukey's test at a confidence level of 95%. Results: Water sorption and solubility varied significantly between materials, but no significant difference was observed between warm and cold conditions (p > 0.05). TE and AM showed the lowest water sorption and solubility (p 0.05). For SB, TE, and XP, the use of a warm air stream resulted in higher ultimate tensile strength (p 0.05) in both experimental conditions. Conclusions: The water sorption and solubility of the materials seem to be more influenced by their composition than by the temperature used for solvent evaporation. For some adhesives, the use of a warm air stream can yield higher ultimate tensile strength. Keywords: adhesives systems, water sorption, solubility, adhesive strength, warm air