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.
