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Smear layer deproteinization with HOCl solution could improve dentin bonding performance of self-etch adhesive by preventing the formation of the hybridized smear layer. However, the oxidizing residuals of HOCl solution negatively affect the polymerization of the adhesive leading to impairment of bonding durability. Subsequent application of sulfinate agent is required because it can reduce the oxidizing effect and increase degree of polymerization. We hypothesized that the addition of strontium chloride to HOCl solution might resolve this problem by enhancing the degree of conversion. This study aimed to evaluate the effect of strontium chloride to degree of conversion and bonding durability of one-step self-etch adhesive to HOCl-smear layer deproteinized dentin. Human dentin surfaces were deproteinized with HOCl solution for 15 s with and without subsequent application of sulfinate agent (Clearfil DC Activator), or deproteinized with 0.4 mM strontium chloride containing HOCl solution for 15 s. After deproteinization, the specimens were washed with water for 5 s. The treated dentin surfaces were air-dried and bonded with one-step self-etch adhesive (Bond Force II). No pretreated dentin surfaces were used as control. Degree of conversion (DC) of the adhesive was evaluated by using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Microtensile bond strength (uTBS) was tested immediately after bonding for 24 h and 10,000 thermocycles. Moreover, surface morphology and deproteinizing on the pretreated dentin surface were evaluated by SEM and ATR-FTIR. Data were statistically analyzed with one-way ANOVA, Tukey's post hoc, and t-test at significance level 0.05. The addition of strontium chloride significantly increased the DC and immediate uTBS (p0.05). While pretreatment with pure HOCl did not significantly affect the DC and immediate uTBS (p>0.05), it could not stabilize the bond strength after thermocycles (p0.05). The addition of strontium chloride improved the polymerization and bonding durability of one-step self-etch adhesive to HOCl-smear layer deproteinized dentin. [ABSTRACT FROM AUTHOR]