OBJECTIVES: This study evaluated how deproteinization using sodium hypochlorite (6% NaOCl) or hypochlorous acid (50 ppm HOCl) with or without the subsequent use of an arylsulfinate salt-containing agent (Clearfil DC Activator; DCA; Kuraray Noritake Dental) affects the micro-tensile bond strength (μTBS) and formation of an acid-base resistant zone (ABRZ) of a two-step self-etch adhesive on eroded dentin. METHODS: Coronal dentin surfaces of sound human molars were exposed to 48 cycles of demineralization (1% citric acid; 5 minutes) and remineralization (buffer solution with pH=6.4; 3.5 hours). They were then assigned to experimental groups according to the pretreatment used: none (negative control), NaOCl, NaOCl+DCA, HOCl, and HOCl+DCA. Sound dentin surfaces with no pretreatment were used as a positive control. The dentin surfaces were bonded with Clearfil SE Bond 2 (Kuraray Noritake Dental), and μTBS was measured either after 24 hours or 20,000 thermal cycles (TC). The μTBS data were statistically analyzed using a mixed-model analysis of variance (ANOVA) and t-tests with Bonferroni correction. Failure mode was determined with scanning electron microscopy (SEM), which was also used for the observation of ABRZ. RESULTS: Among experimental groups, there was no significant difference between the negative control, HOCl, and HOCl+DCA after 24 hours, but the HOCl-pretreated groups exhibited significantly higher μTBS than the negative control after TC (p<0.01). Pretreatment with NaOCl and NaOCl+DCA resulted in significantly higher μTBS (p<0.001), but the highest μTBS was measured on sound dentin (p<0.001). TC decreased μTBS significantly in all groups (p<0.001) except for sound dentin and NaOCl+DCA (p>0.05). Adhesive failures prevailed in eroded groups, whereas cohesive failures were predominant on sound dentin. ABRZ was recognized in all groups but marked morphological differences were observed. CONCLUSIONS: The combined use of 6% NaOCl and the arylsulfinate salt-containing agent partially reversed the compromised bonding performance on eroded dentin, while the effect of 50 ppm HOCl was negligible.

*Go Inoue DDS PhD Department of Cariology and Operative Dentistry Graduate School of Medical and Dental Sciences Tokyo Medical and Dental University Tokyo Japan

Antonin Tichy DDS PhD Department of Cariology and Operative Dentistry Graduate School of Medical and Dental Sciences Tokyo Medical and Dental University Tokyo Japan; Institute of Dental Medicine 1st Faculty of Medicine of the Charles University and General University Hospital Prague Prague Czech Republic

Junji Tagami DDS PhD Department of Operative Dentistry Faculty of Dentistry Chulalongkorn University Bangkok Thailand

Keiichi Hosaka DDS PhD Department of Regenerative Dental Medicine Tokushima University Graduate School of Biomedical Sciences Tokushima Japan

Masaomi Ikeda DDS PhD Department of Oral Prosthetic Engineering Graduate School of Medical and Dental Sciences Tokyo Medical and Dental University Tokyo Japan

Yasushi Shimada DDS PhD Department of Cariology and Operative Dentistry Graduate School of Medical and Dental Sciences Tokyo Medical and Dental University Tokyo Japan

Yi Yang DDS PhD student Department of Cariology and Operative Dentistry Graduate School of Medical and Dental Sciences Tokyo Medical and Dental University Tokyo Japan

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