Abstract
Purpose: This study aimed to investigate the effect of surface moisture on the enamel and dentin bonding performances of a universal adhesive in the etch-and-rinse mode based on shear bond strength (SBS) tests. Methods: Enamel and dentin surfaces were prepared (moist and dry conditions) using bovine mandibular incisors and treated with the universal adhesive Clearfil Universal Bond Quick (CU) using the etch-and-rinse mode. Resin composite was condensed into a plastic mold clamped to a fixture against the adherend surfaces and light-cured for 40 s. The bonded specimens (n=15) were either stored in distilled water at 37°C for 24 h or underwent 10,000 thermal cycles between 5°C and 55°C before the SBS tests. The universal adhesive interfaces in the etch-and-rinse mode were observed via scanning electron microscopy (SEM). Results: The CU’s enamel and dentin bond strengths were not influenced by the surface moisture, regardless of the storage condition. Based on the SEM observations, surface moisture did not influence the widths of the adhesive and hybrid layers in the resin-dentin interfaces. However, the lengths of the resin tags in the moist group were longer than those in the dry group. Conclusion: These findings indicated that the surface moisture content of the enamel and dentin might not significantly influence CU bonding performance regardless of the storage conditions. The presence of a new hydrophilic amide monomer in this universal adhesive might be a key factor that influences its bonding performances with enamel and dentin.