title: Effect of the combination of sodium hypochlorite and chlorhexidine on dentinal permeability and scanning electron microscopy precipitate observation.
abstract: BACKGROUND
  This study compared the combined use of sodium hypochlorite (NaOCl) and chlorhexidine (CXH) with citric acid and CXH on dentinal permeability and precipitate formation.
  
  
  METHODS
  Thirty-four upper anterior teeth were prepared by rotary instrumentation and NaOCl. The root canal surfaces were conditioned for smear layer removal using 15% citric acid solution under ultrasonic activation and a final wash with distilled water. All teeth were dried, and 30 specimens were randomly divided into three equal groups as follows: positive control group (PC), no irrigation; 15% citric acid + 2% CHX group (CA + CHX); and 1% NaOCl + 2% CHX group (NaOCl + CHX). All roots were immersed in a 0.2% Rhodamine B solution for 24 hours. One-millimeter-thick slices from the cementum-enamel junction were scanned at 400 dpi and analyzed using the software ImageLab (LIDO-USP, Sao Paulo, Brazil) for the assessment of leakage in percentage. For scanning electron microscopy analysis, four teeth, irrigated for NaOCl + CHX samples, were split in half, and each third was evaluated at 1,000x and 5,000x (at the precipitate).
  
  
  RESULTS
  Using the analysis of variance test followed by the Bonferroni comparison method, no statistical differences between groups were found when analyzed at the cervical and medium thirds. At the apical third, differences between the PC and NaOCl + CHX (p < 0.05) and CA + CHX and NaOCl + CHX could be seen (p < 0.05).
  
  
  CONCLUSIONS
  The combination of 1% NaOCl and 2% CHX solutions results in the formation of a flocculate precipitate that acts as a chemical smear layer reducing the dentinal permeability in the apical third.
authors.affiliation: Post-Graduate Program in Endodontics, University of São Paulo, São Paulo/SP, Brazil.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Akisue
authors.forename: Viviane S
authors.initials: VS
authors.lastname: Tomita
authors.forename: Giulio
authors.initials: G
authors.lastname: Gavini
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Poli de Figueiredo
mesh_terms: D000704:Analysis of Variance; D002710:Chlorhexidine / Q000494:pharmacology; D019343:Citric Acid / Q000494:pharmacology; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D003806:Dentin Permeability / Q000187:drug effects*; D004338:Drug Combinations; D006801:Humans; D008855:Microscopy, Electron, Scanning; D012388:Root Canal Irrigants / Q000494:pharmacology*; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000494:pharmacology; D018709:Statistics, Nonparametric
chemical_list: D004338:Drug Combinations; D012388:Root Canal Irrigants; D019343:Citric Acid; D012973:Sodium Hypochlorite; D002710:Chlorhexidine