The effect of a deproteinizing pretreatment on the bonding performance and acid resistance of a two-step self-etch adhesive on eroded dentin
Abstract
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 acid-base resistant zone (ABRZs) 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 min) and remineralization (buffer solution with pH=6.4; 3.5 h). 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 h or 20,000 thermal cycles (TC). The 𝜇TBS data were statistically analyzed using Welch's t-tests with Bonferroni correction. Failure mode was determined with scanning electron microscopy (SEM), which was also used for the observation of ABRZ.
Results: The highest 𝜇TBS was measured on sound dentin (p<0.001). Among experimental groups, there was no significant difference between the negative control, HOCl, and HOCl+DCA, but significantly higher 𝜇TBS was measured with NaOCl and NaOCl+DCA (p<0.001). TC decreased 𝜇TBS significantly in all groups (p<0.05) except for sound dentin and NaOCl+DCA. 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, as opposed to 50ppm HOCl.