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

Abstract

<p>Objective</p><p>To determine whether the effect of dentin moisture on the etch-and-rinse bonding may be minimized by dry-bonding protocols utilizing aqueous or ethanolic dimethyl sulfoxide (DMSO) pretreatments.<br></p><p>Methods</p><p>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 mm2) were tested under tension until fracture (0.5 mm/min) after 24 h and two years of storage in artificial saliva at 37 °C.</p><p>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 (α = 0.05).<br></p><p>Results</p><p>Dry bonding to untreated collagen produced inferior immediate and long-term bond strengths than wet bonding (<em>p</em> < 0.05). Regardless of initial hydration and moisture control, DMSO-dry bonding produced initially higher and stable bond strengths after aging (<em>p</em> < 0.05). DMSO-pretreated groups presented improved collagen wettability with lower silver uptake (<em>p</em> < 0.05).<br></p><p>Significance</p><p>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.</p>