Effects of Different Exposure Times and Concentrations of Sodium Hypochlorite/Ethylenediaminetetraacetic Acid on the Structural Integrity of Mineralized Dentin

Kai Zhang, Young Kyung Kim, Milena Cadenaro, Thomas E. Bryan, Stephanie J. Sidow, Robert J. Loushine, Jun qi Ling, David H. Pashley, Franklin R. Tay

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Introduction: This study tested the null hypothesis that there is no difference between the use of 1.3% NaOCl/17% ethylenediaminetetraacetic acid (EDTA) and 5.25% NaOCl/17% EDTA irrigation regimens on the collagen degradation and flexural strength reduction in mineralized dentin. Methods: Dentin powder and mineralized dentin sections were immersed in 1.3% or 5.25% NaOCl for 10-240 minutes and then rinsed with 17% EDTA as the final irrigant for 2 minutes. Untreated mineralized dentin powder/sections served as controls in the respective experiments. Dentin powders were examined by using Fourier transform infrared (FT-IR) spectroscopy to analyze their relative subsurface intact collagen content with the apatite/collagen ratio. Hydrated dentin sections were subjected to 3-point flexure under water for determining their flexural strengths. Results: Collagen degradation was significantly increased and the flexural strength of mineralized dentin was significantly reduced after the use of 5.25% NaOCl as the initial irrigant for more than 1 hour (P < .05). Conversely, changes were insignificant when 1.3% NaOCl was used as the initial irrigant for up to 4 hours (Kruskal-Wallis analysis of variance, n = 10, P < .05). Conclusions: The null hypothesis was rejected. The deleterious effects attributed to the use of NaOCl on dentin are concentration-dependent and time-dependent and are not associated with the demineralization caused by the use of EDTA as the final active irrigant.

Original languageEnglish (US)
Pages (from-to)105-109
Number of pages5
JournalJournal of endodontics
Issue number1
StatePublished - Jan 1 2010



  • Collagen
  • Fourier transform infrared spectroscopy
  • denaturation
  • ethylenediamine tetraacetic acid
  • flexural strength
  • irrigation
  • sodium hypochlorite
  • three point bending

ASJC Scopus subject areas

  • Dentistry(all)

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