LAUSR

Abstract Background Nowadays, most of the dental manufacturers claimed that ‘Universal’ or ‘multi-mode’ adhesives in self-etch technique can obtain good bonding results comparing to etch-and-rinse or selective etching application techniques. The rationale behind this study was that a multi-mode adhesive, when proven to be effective, would enable general practitioners to apply the adhesive using either an ‘etch-and-rinse’ or an ‘self-etch’ adhesive mode strategy, basically depending on their interpretation of what appears to be most appropriate upon examination of the actual cavity and the overall restoration conditions. Objective This study examined the effect of acid etching on microtensile bond strength (μTBS), micromorphological patterns of resin-dentin interface using scanning electron microscope (SEM) and SEM of tracer-infused water-rich zones within the hybrid layers of ultra-mild self-etch adhesives bonded to coronal dentin. Methods Sixty extracted permanent molars were assigned into six groups based on μTBS (n = 10). The groups were bonded with Adper single bond (SB) plus adhesive in etch-and-rinse mode and Adper easy one (EO) bond in self-etch mode as controls; Single Bond Universal self-etch (SUSe) and etch-and-rinse (SUEr); Adhese Universal self-etch (AUSe) and etch-and-rinse (AUEr). The bonded specimens were stored in deionized water for 24 h. Composite/dentin beams were prepared (1 mm2). μTBS testing was performed. Micromorphological evaluation of extra teeth from each study group was conducted using SEM, and nanoleakage (NL) was evaluated. μTBS data were statistically analyzed using two-way ANOVA and multiple comparison post-hoc tests. Results AUEr had the highest μTBS (p   0.05). The μTBS for SUEr was similar to the SB control adhesive (p > 0.05), while the μTBS for SUSe was higher than the EO control adhesive (p  Conclusion Application of an etching step prior to water-based adhesive improves its dentin penetration, but it does not affect its μTBS; while application of an etching step prior to ethanol-based adhesive improves its dentin penetration and its μTBS.