The Effect of Organic Solvents on One-Bottle Adhesives' Bond Strength to Enamel and Dentin

This study evaluated the microtensile bond strength (μTBS) of ethanol/water- and acetone-based, one-bottle adhesive systems to enamel (E) and dentin (D) in the presence (P) or absence (A) of their respective solvents. Thirty-two freshly extracted third molars were flattened with 600-grit SiC paper and restored with Single Bond (SB) or Prime&Bond 2.1 (PB) according to the manufacturers' instructions and after full solvent elimination. The molars were divided into eight test groups (n=4): G1-SB-E-P, G2-SB-E-A, G3-PB-E-P, G4-PB-E-A, G5-SB-D-P, G6-SB-D-A, G7-PB-D-P and G8-PB-D-A. After applying the adhesive resins, composite crowns of approximately 8 mm were built up with TPH Spectrum composite. After 24-hour water storage, the specimens were serially sectioned bucco-lingually to obtain 0.8-mm slabs that were trimmed to an hourglass shape, approximately 0.8 mm² at the bonded interface. The specimens were tested in tension using a universal testing machine (0.5 mm/minute). The results were statistically analyzed by ANOVA and Tukey test. The frequency of fracture mode was compared using the Kruskal-Wallis test. There were no statistically significant differences in mean bond strength among the groups restored with or without solvent for enamel. However, the results were significantly different for the dentin groups (MPa): G5-26.2 ± 8.6^a; G7-23.6 ± 11.3^ab; G6-12.8 ± 2.1 ^bc; G8-6.2 ±3.1^c. SEM examination indicated that the dentin group failure modes were significantly different from the enamel groups. The results suggest that the presence of organic solvents does not influence μTBS to enamel. However, μTBS to dentin was significantly affected by the absence of solvents in the adhesive system.