title: Evaluation and prevention of the precipitate formed on interaction between sodium hypochlorite and chlorhexidine.
abstract: BACKGROUND
  The purpose of this study was (1) to evaluate maximum thickness the and chemical composition of the precipitate formed between sodium hypochlorite (NaOCl) and chlorhexidine (CHX) and (2) to evaluate effectiveness of absolute alcohol to remove residual NaOCl and thereby prevent the formation of the precipitate.
  
  
  METHODS
  Forty extracted single-rooted human teeth were decoronated, and the canals were instrumented. In the test group (Ts group), canals were irrigated with 17% EDTA and 2.5% NaOCl followed by 2% CHX. In the absolute alcohol (Aba), saline (Sa), and distilled water (Dw) groups, intermediate flushes of absolute alcohol, saline, and distilled water were used between the last two irrigants. Teeth were sectioned longitudinally and subjected to stereomicroscopic examination.
  
  
  RESULTS
  The Ts group samples showed orange-brown precipitate, concentrated more in the coronal and middle thirds, whereas the Aba group showed no evidence of precipitate. The Sal and Dw groups showed minimal precipitate in the coronal and middle thirds. The thickness of the precipitate was measured using the ProgRes computer software (Olympus, Hamburg, Germany). The chemical composition of the precipitate was confirmed by Beilstein and HCl tests, and the nuclear magnetic resonance imaging technique confirmed chlorine in the para position of the benzene ring.
  
  
  CONCLUSIONS
  The interaction between NaOCl and CHX resulted in an insoluble neutral salt as a precipitate that can be prevented using absolute alcohol and minimized using saline and distilled water as intermediate flushes.
authors.affiliation: Department of Conservative Dentistry and Endodontics, RV College of Dentistry, Rajiv Gandhi University of Health Sciences, Bangalore, Karnataka, India. shashbang2007@rediffmail.com
authors.forename: Shashikala
authors.initials: S
authors.lastname: Krishnamurthy
authors.forename: Sunu
authors.initials: S
authors.lastname: Sudhakaran
mesh_terms: D000814:Aniline Compounds / Q000032:analysis; D002614:Chelating Agents / Q000737:chemistry; D011232:Chemical Precipitation; D002710:Chlorhexidine / Q000737:chemistry*; D003116:Color; D003786:Dental Pulp Cavity / Q000473:pathology; D004492:Edetic Acid / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D012388:Root Canal Irrigants / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods; D012965:Sodium Chloride / Q000737:chemistry; D012973:Sodium Hypochlorite / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D000814:Aniline Compounds; D002614:Chelating Agents; D012388:Root Canal Irrigants; D014867:Water; D000431:Ethanol; D012965:Sodium Chloride; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D002710:Chlorhexidine; C004658:4-chloroaniline