Effect of Solvent Removal on Adhesive Properties of Simplified Etch-and-rinse Systems and on Bond Strengths to Dry and Wet Dentin

Purpose: This study evaluated the resin-dentin microtensile bond strength (µTBS) of ethanol/water- (Single Bond, [SB] 3M ESPE), ethanol- (Optibond Solo Plus, [OP] Kerr) and acetone-based (One-Step, [OS] Bisco) two-step etch-and-rinse adhesives in the presence or absence of their respective solvents to dry and wet dentin. The ultimate tensile strength (UTS) and the degree of conversion (DC) of the materials were also evaluated. Materials and Methods: Solvent-based and solvent-free adhesives were vigorously applied to occlusal dentin surfaces after phosphoric acid etching. Composite crowns were built up incrementally. After 24-h water storage, the specimens were sectioned in x and y directions to obtain bonded sticks (1.0 mm2) which were immediately tested in tension (0.5 mm/min). The data were analyzed by three-way ANOVA and Tukey's test (α = 0.05). For the UTS measurement, hourglass-shaped specimens of adhesives were prepared and tested in tension. FTIR analysis was used to verify the DC of adhesives. The data from UTS and FTIR was analyzed by two-way ANOVA and Tukey's test (α = 0.05). Results: High µTBS values were obtained for SB and OS, regardless of the presence or absence of solvents or the moisture condition of dentin. A lower µTBS mean was observed for the solvent-free OP compared to its solvent-based version. Significantly higher UTS values were obtained for all adhesives after removal of solvents. The DC of OS in the solvent-based condition was lower than SB and OP. After removal of solvents, only OS showed a significant increase in the DC. Conclusion: The presence of solvents was not essential for SB and OS to achieve high bond strength values to both dry and wet dentin when applied under vigorous application. Keywords: adhesive systems, moisture degree, microtensile bond strength, solvents