Effect of double-application or the application of a hydrophobic layer for improved efficacy of one-step self-etch systems in enamel and dentin

Objectives: To evaluate the use of two alternative modes of application (double-application and placement of a hydrophobic resin coat) compared with the manufacturers' directions on the microtensile bond strength (mu TBS) of one-step, self-etch systems to enamel and dentin. Materials and Methods: Resin composite buildups were bonded to the buccal and lingual ground enamel surfaces and occlusal dentin of third molars using the following adhesives: Xeno III (XE), GBond (GB), Adper Prompt L-Pop (AD) and Clearfil SE Bond (CSE) as the control. The adhesive systems were applied: 1) following the manufacturer's directions (MD), 2) with double-application (DA) or with 3) additional placement of a hydrophobic resin layer (HR) after following the manufacturer's directions. After storage in water (24 hours/37 degrees C), the bonded specimens were sectioned into sticks (0.8 mm(2)) that were tested until failure at a crosshead speed of 0.5 mm/minute. Data from each substrate were subjected to two-way ANOVA and Tukey's test (alpha=0.05). Results: The interaction Adhesive vs Application mode was statistically significant (p<0.05) for both substrates. In dentin, XE and GB achieved high mu TBS in the HR group (p<0.05). For AD, the highest pTBS were observed in the DA group (p<0.05). For enamel, similar pTBS was observed for XE and GB among the three modes of application, while the highest pTBS of AD was observed in the HR group. Conclusion: The effects of using the double-application and placement of a hydrophobic resin coat on microtensile dentin-bond strength values seem to be effective; however, these techniques in enamel were adhesive-dependent.