Moist vs over-dried etched dentin: FE-SEM/TEM and bond strength evaluation of resin-dentin interfaces produced by universal adhesives.

Objective: To evaluate the influence of the degree of dentin moisture on interfacial ultramorphology and bond strength (μTBS) of universal adhesives.

Materials And Methods: Futurabond U (FBU), Scotchbond Universal (SBU), Adhese Universal (ADU), and Prime&Bond active (PBA) were used. After acid-etching, moist or over-dried dentin surfaces were tested. Teeth were restored for scanning and transmission electron microscopy (n = 3) and μTBS evaluation (n = 5). μTBS results were analyzed by two-way ANOVA and Tukey.

Results: For moist dentin, a well-formed hybrid layer (HL) was observed. However, when applied to over-dried dentin, remarkable differences were observed. Defects, gaps, and reduced HL thickness were observed mainly for ADU and FBU. When applied to wet dentin, μTBS values were similar for all adhesives, except for FBU, which was significantly lower. When applied to over-dried dentin, PBA presented the highest μTBS values, followed by SBU, ADU, and FBU. ADU presented significantly lower μTBS when applied to over-dried dentin.

Conclusion: PBA, SBU, and FBU μTBS values were not sensitive to the degree of moisture. Even though application to over-dried dentin revealed defects, gaps and reduced HL thickness for SBU, ADU, and FBU, μTBS analysis only revealed a significant reduction for ADU.

Clinical Significance: Universal adhesives can be applied in either self-etching or etch-and-rinse mode. However, clinicians are not aware which universal adhesives should be strictly applied on a moist dentin for bonding in the etch-and-rinse mode.