title: Effects of different exposure times and concentrations of sodium hypochlorite/ethylenediaminetetraacetic acid on the structural integrity of mineralized dentin.
abstract: 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.
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Young Kyung
authors.initials: YK
authors.lastname: Kim
authors.forename: Milena
authors.initials: M
authors.lastname: Cadenaro
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Bryan
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Sidow
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Loushine
authors.forename: Jun-qi
authors.initials: JQ
authors.lastname: Ling
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
mesh_terms: 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
chemical_list: D001031:Apatites; D012388:Root Canal Irrigants; D003094:Collagen; D004492:Edetic Acid; D012973:Sodium Hypochlorite