Dry bonding to dentin: Broadening the moisture spectrum and increasing wettability of etch-and-rinse adhesives

Objective. To determine whether the effect of dentin moisture on the etch-and-rinse bond -ing may be minimized by dry-bonding protocols utilizing aqueous or ethanolic dimethyl sulfoxide (DMSO) pretreatments. Methods. H3PO4-etched mid-coronal dentin surfaces from human molars were randomly blot-or air-dried for 30 s and pretreated with DMSO/H2O or DMSO/EtOH solutions. Untreated samples served as control. Moisture control was performed by either blot-or air-drying. Samples were bonded with a multistep etch-and-rinse adhesive. Restored crown segments (n = 8/group) were stored in distilled water for 24 h and sectioned for microtensile bond strength testing. Resin-dentin beams (0.8 mm(2)) were tested under tension until fracture (0.5 mm/min) after 24 h and two years of storage in artificial saliva at 37 degrees C. SEM nanoleakage evaluation was performed on aged samples. Collagen wettability was also measured by sessile drops of the hydrophilic and hydrophobic bonding resins (n = 8/group). Data were examined by factorial ANOVA followed by the Tukey test (alpha = 0.05). Results. Dry bonding to untreated collagen produced inferior immediate and long-term bond strengths than wet bonding (p < 0.05). Regardless of initial hydration and moisture control, DMSO-dry bonding produced initially higher and stable bond strengths after aging (p < 0.05). DMSO-pretreated groups presented improved collagen wettability with lower silver uptake (p < 0.05). Significance. Despite the common belief that etch-and-rinse adhesives must be applied onto moist collagen, DMSO-dry bonding protocols not only improved bonding performance and hybrid layer integrity, but also brought more versatility to collagen hybridization by reducing overdrying-related issues. (C) 2021 The Authors. Published by Elsevier Inc. on behalf of The Academy of Dental Materials.