title: Interactions between irrigants commonly used in endodontic practice: a chemical analysis.
abstract: BACKGROUND
  The aim of this work was to characterize the by-products formed in the associations between the most commonly used irrigants in endodontic practice through electrospray ionization quadrupole time-of-flight mass spectrometry analyses.
  
  
  METHODS
  Sodium hypochlorite (NaOCl) (0.16%, 1%, 2.5%, and 5.25%) was associated with 2% chlorhexidine (CHX) solution and gel, 17% EDTA, 10% citric acid, 37% phosphoric acid, saline solution, ethanol, and distilled water. CHX solution and gel were also associated with all above mentioned irrigants. The solutions were mixed in a 1:1 ratio, and electrospray ionization quadrupole time-of-flight mass spectrometry was used to characterize the precipitates when formed.
  
  
  RESULTS
  CHX produced an orange-brown precipitate when associated with NaOCl from 1%-5.25% and an orange-white precipitate when associated with 0.16% NaOCl. When associated with EDTA, CHX produced a white milky precipitate, and when associated with saline solution and ethanol, a salt precipitation was produced. No precipitation was observed when CHX was associated with citric acid, phosphoric acid, or distilled water. In the NaOCl associations, precipitation occurred only when CHX was present.
  
  
  CONCLUSIONS
  The orange-brown precipitate observed in the association between CHX and NaOCl occurs because of the presence of NaOCl, an oxidizing agent causing chlorination of the guanidino nitrogens of the CHX. The precipitates formed in the reaction of CHX with EDTA, saline solution, and ethanol were associated with acid-base reactions, salting-out process, and lower solubility, respectively. NaOCl associated with EDTA, citric acid, and phosphoric acid leads mainly to chlorine gas formation. Intermediate flushes with distilled water seem to be appropriate to prevent or at least reduce formation of by-products.
authors.affiliation: Department of Restorative Dentistry, Endodontics Division, State University of Campinas-UNICAMP, Piracicaba, São Paulo, Brazil.
authors.forename: Maíra
authors.initials: M
authors.lastname: Prado
authors.forename: Helvécio M
authors.initials: HM
authors.lastname: Santos Júnior
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Rezende
authors.forename: Angelo C
authors.initials: AC
authors.lastname: Pinto
authors.forename: Roberto B
authors.initials: RB
authors.lastname: Faria
authors.forename: Renata A
authors.initials: RA
authors.lastname: Simão
authors.forename: Brenda P F A
authors.initials: BP
authors.lastname: Gomes
mesh_terms: D011232:Chemical Precipitation; D002710:Chlorhexidine / Q000737:chemistry; D004347:Drug Interactions; D004492:Edetic Acid / Q000737:chemistry; D012388:Root Canal Irrigants / Q000737:chemistry*; D012973:Sodium Hypochlorite / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D012388:Root Canal Irrigants; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D002710:Chlorhexidine