Abstract
Purpose: This laboratory study aimed to assess the dentin bond fatigue resistance and interfacial characteristics of a universal adhesive in etch-and-rinse and self-etch modes. Methods: The universal adhesive used was Clearfil Universal Bond Quick (Kuraray Noritake Dental, Tokyo, Japan). The dentin surfaces were treated with the universal adhesive in either etch-and-rinse or self-etch mode. Initial bond strength was measured by loading 15 specimens per test group to failure using an all-electric dynamic instrument with a chisel-shaped metal load at a crosshead speed of 1.0 mm/min. The fatigue load was applied to the specimens using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. The surface free energy characteristics of adhesive-treated dentin were determined. Scanning electron microscopy (SEM) observations of the resin-dentin interface of the adhesive were also conducted for each etching mode. Results: For the universal adhesive tested, etching mode did not affect the bond fatigue resistance. The surface free energy characteristics of the baseline showed that the γs, γsd, γsp, and γsh values for dentin in etch-and-rinse mode were significantly lower than in self-etch mode. The surface free energy values of adhesive-treated dentin in etch-and-rinse mode were not significantly decreased by adhesive application, while both γs and γsh values were decreased after adhesive application in self-etch mode. In SEM observations of adhesive interfaces, deeper penetration of adhesives into the dentinal tubules was observed in etch-and-rinse mode due to removal of the smear layer and opening of the dentinal tubules. Conclusion: The results suggest that the dentin bonding performance of the universal adhesive was not affected by etching mode.