The influence of sulfinate agents applied as a dentin pretreatment or a mixture with multi-mode one-step self-etch adhesives (1-SEAs) on the degree of conversion (DC) and micro-tensile bond strength (μTBS) of light-cured 1-SEAs was investigated. 1-SEAs Clearfil Universal Bond Quick (UBQ) or Scotchbond Universal Adhesive (SBU) were applied to dentin in etch&rinse or self-etch mode using various application strategies: 1) no pretreatment, 2) pretreatment with 90 wt% ethanol, 3) pretreatment with a sulfinate agent Clearfil DC Activator (UDC) or Scotchbond Universal DCA (SDC), or 4) a mixture of UBQ+UDC or SBU+SDC. μTBS was measured after 24 h. Additionally, DC was measured using attenuated total reflectance Fourier-transform infrared spectroscopy. Pretreatment with sulfinate agents resulted in the highest μTBS and DC, significantly improving them especially in etch&rinse mode. The mixture of sulfinate agents with 1-SEAs was less effective. Pretreatment with ethanol significantly improved μTBS in etch&rinse mode but compromised μTBS in self-etch mode.

The effects of deproteinization using sodium hypochlorite (NaOCl) and the subsequent application of an antioxidant (sodium p-toluenesulfinate, STS) onto the bonding durability of universal adhesives on eroded dentin were investigated. Untreated sound dentin served as the control, whereas eroded dentin, which had been prepared by pH-cycling in 1% citric acid and a remineralization solution, was either untreated, deproteinized with a 10% NaOCl gel or deproteinized with the 10% NaOCl gel and subsequently treated with an STS-containing agent. The dentin surfaces were bonded using a universal adhesive (Clearfil Universal Bond Quick, Scotchbond Universal or G-Premio Bond), and the micro-tensile bond strength (µTBS) test was performed after 24 h or 10,000 thermal cycles. The µTBS data were statistically analyzed using a three-way ANOVA and Tukey’s HSD post hoc tests. The lowest µTBS was measured on untreated eroded dentin (p < 0.001). Deproteinization of eroded dentin resulted in µTBS similar to untreated sound dentin (p > 0.05), but the highest µTBS was obtained if deproteinization was followed by the application of STS. Thermocycling significantly decreased µTBS in all groups (p < 0.001), except for STS-treated deproteinized eroded dentin (p > 0.05). This indicated that deproteinization, followed by the application of STS, could enhance the bonding durability of universal adhesives on eroded dentin.