Effects of Concentrations and Exposure Times of Sodium Hypochlorite on Dentin Deproteination: Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Study

Introduction: The purpose of this study was to quantitatively analyze the effects of different concentrations and exposure times of sodium hypochlorite (NaOCl) on dentin deproteination and to determine the suitable concentrations and exposure times to minimize the effects of deproteination on dentin. Methods: Intact human dentin slabs were treated with 0.5%, 1%, or 2.25% NaOCl for 1, 5, or 10 minutes. A 0.9% NaCl solution served as the control. To investigate the effect of NaOCl on the surface chemical changes to human dentin, the attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy technique was used to analyze the amide:phosphate ratio and carbonate:phosphate ratio. Results: The amide:phosphate ratio decreased significantly after NaOCl treatment as compared with the control group (p < 0.05). In the 0.5% NaOCl treatment group, the amide:phosphate ratio was significantly higher than that in the 1% and the 2.25% NaOCl treatment groups (p < 0.05). The different exposure times (1, 5, or 10 minutes) of NaOCl within the same concentration did not influence the amide:phosphate ratio (p > 0.05). NaOCl treatment did not affect the carbonate:phosphate ratio (p > 0.05). Conclusions: NaOCl, 0.5%, is recommended as the predominant concentration for routine use during root canal therapy to minimize any NaOCl-induced dentin deproteination. It is suggested that a prolonged exposure to low concentrations of NaOCl is less damaging to dentin in attempting to achieve antisepsis during instrumentation of root canal therapy. (J Endod 2010;36: 2008-2011)