title: Qualitative analysis of precipitate formation on the surface and in the tubules of dentin irrigated with sodium hypochlorite and a final rinse of chlorhexidine or QMiX.
abstract: BACKGROUND
  Interaction of sodium hypochlorite (NaOCl) mixed with chlorhexidine (CHX) produces a brown precipitate containing para-chloroaniline (PCA). When QMiX is mixed with NaOCl, no precipitate forms, but color change occurs. The aim of this study was to qualitatively assess the formation of precipitate and PCA on the surface and in the tubules of dentin irrigated with NaOCl, followed either by EDTA, NaOCl, and CHX or by saline and QMiX by using time-of-flight secondary ion mass spectrometry (TOF-SIMS).
  
  
  METHODS
  Dentin blocks were obtained from human maxillary molars, embedded in resin, and cross-sectioned to expose dentin. Specimens in group 1 were immersed in 2.5% NaOCl, followed by 17% EDTA, 2.5% NaOCl, and 2% CHX. Specimens in group 2 were immersed in 2.5% NaOCl, followed by saline and QMiX. The dentin surfaces were subjected to TOF-SIMS spectra analysis. Longitudinal sections of dentin blocks were then exposed and subjected to TOF-SIMS analysis. All samples and analysis were performed in triplicate for confirmation.
  
  
  RESULTS
  TOF-SIMS analysis of group 1 revealed an irregular precipitate, containing PCA and CHX breakdown products, on the dentin surfaces, occluding and extending into the tubules. In TOF-SIMS analysis of group 2, no precipitates, including PCA, were detected on the dentin surface or in the tubules.
  
  
  CONCLUSIONS
  Within the limitations of this study, precipitate containing PCA was formed in the tubules of dentin irrigated with NaOCl followed by CHX. No precipitates or PCA were detected in the tubules of dentin irrigated with NaOCl followed by saline and QMiX.
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, Canada.
authors.forename: Kamil P
authors.initials: KP
authors.lastname: Kolosowski
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Canada.
authors.forename: Rana N S
authors.initials: RN
authors.lastname: Sodhi
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, Canada.
authors.forename: Anil
authors.initials: A
authors.lastname: Kishen
authors.affiliation: Discipline of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, Canada. Electronic address: Bettina.basrani@dentistry.utoronto.ca.
authors.forename: Bettina R
authors.initials: BR
authors.lastname: Basrani
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry / Q000494:pharmacology; D001645:Biguanides / Q000737:chemistry / Q000494:pharmacology*; D011232:Chemical Precipitation; D002710:Chlorhexidine / Q000737:chemistry / Q000494:pharmacology*; D003116:Color; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D004492:Edetic Acid / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry / Q000494:pharmacology*; D012388:Root Canal Irrigants / Q000737:chemistry / Q000494:pharmacology*; D012965:Sodium Chloride; D012973:Sodium Hypochlorite / Q000737:chemistry / Q000494:pharmacology*; D018629:Spectrometry, Mass, Secondary Ion
chemical_list: D000814:Aniline Compounds; D001645:Biguanides; D011108:Polymers; C557698:QMix root canal irrigant; D012388:Root Canal Irrigants; D012965:Sodium Chloride; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D002710:Chlorhexidine; C004658:4-chloroaniline
keywords: Chlorhexidine; TOF-SIMS; hypochlorite; parachloroaniline; tubules