Effects of different exposure times and concentrations of sodium hypochlorite/ethylenediaminetetraacetic acid on the structural integrity of mineralized dentin.
BACKGROUND
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.
Zhang
Kai
K
Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China.
Kim
Young Kyung
YK
Cadenaro
Milena
M
Bryan
Thomas E
TE
Sidow
Stephanie J
SJ
Loushine
Robert J
RJ
Ling
Jun-qi
JQ
Pashley
David H
DH
Tay
Franklin R
FR
D001031:Apatites / Q000032:analysis; D003094:Collagen / Q000032:analysis / Q000737:chemistry / Q000187:drug effects; D003799:Dental Stress Analysis; D003804:Dentin / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000008:administration & dosage*; D006801:Humans; D018583:Pliability / Q000187:drug effects; D011489:Protein Denaturation; D012388:Root Canal Irrigants / Q000008:administration & dosage* / Q000009:adverse effects; D012973:Sodium Hypochlorite / Q000008:administration & dosage* / Q000009:adverse effects; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors; D017001:Tooth Demineralization
D001031:Apatites; D012388:Root Canal Irrigants; D003094:Collagen; D004492:Edetic Acid; D012973:Sodium Hypochlorite