title: Evaluation of orange-brown precipitate formed in root canals after irrigation with chlorhexidine and QMix and spectroscopic analysis of precipitates produced by a mixture of chlorhexidine/NaOCl and QMix/NaOCl.
abstract: OBJECTIVE
  (i) To compare chlorhexidine and QMix(TM) in terms of orange-brown precipitate generation in root canals and (ii) to analyse the precipitate produced by mixing chlorhexidine and QMix(™) with NaOCl to determine whether para-chloroaniline was produced.
  
  
  METHODS
  The root canals of 57 single-rooted anterior teeth were prepared using ProTaper Universal rotary instruments up to size F4. Two millilitres of 2.5% NaOCl was used between each instrument change. The specimens were then divided randomly into three groups (n = 19) and irrigated as follows: group 1, 5 mL of distilled water (control group) for 60 s; group 2, 5 mL of 2% chlorhexidine for 60 s; and group 3, 5 mL of QMix for 60 s. The roots were split longitudinally, and one of the halves was photographed using a stereomicroscope. The amount of orange-brown precipitate was evaluated using a four-grade scoring system. The data were analysed statistically using the Kruskal-Wallis and Mann-Whitney U-tests (P = 0.05). To evaluate whether the precipitates included para-chloroaniline, 5 mL of 2% chlorhexidine and 5 mL QMix were separately mixed with 5 mL of 2.5% NaOCl in two flasks. After centrifugation, precipitates were obtained and analysed using (1) H NMR spectra. The data were subjected to statistical analysis using the Kruskal-Wallis and Mann-Whitney tests at a 95% confidence level (P = 0.05).
  
  
  RESULTS
  Chlorhexidine had significantly higher scores than QMix(™) in terms of orange-brown precipitate formed in the root canals (P < 0.001). According to the 1H NMR spectra, para-chloroaniline was present in the mixture of chlorhexidine and NaOCl. However, the mixture of QMix(™) and NaOCl did not result in para-chloroaniline formation.
  
  
  CONCLUSIONS
  QMix(™) does not form para-chloroaniline when associated with NaOCl.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Ataturk University, Erzurum, Turkey.
authors.forename: H
authors.initials: H
authors.lastname: Arslan
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Ataturk University, Erzurum, Turkey.
authors.forename: A D
authors.initials: AD
authors.lastname: Uygun
authors.affiliation: Department of Chemistry, Faculty of Science, Ataturk University, Erzurum, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Keskin
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Ataturk University, Erzurum, Turkey.
authors.forename: E
authors.identifier: http://orcid.org/0000-0002-8145-8763
authors.initials: E
authors.lastname: Karatas
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Ataturk University, Erzurum, Turkey.
authors.forename: F
authors.initials: F
authors.lastname: Seçkin
authors.affiliation: Department of Chemistry, Faculty of Science, Ataturk University, Erzurum, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Yıldırım
mesh_terms: D000814:Aniline Compounds / Q000032:analysis*; D001645:Biguanides / Q000737:chemistry*; D011232:Chemical Precipitation; D002710:Chlorhexidine / Q000737:chemistry*; D003786:Dental Pulp Cavity; D006801:Humans; D066298:In Vitro Techniques; D011108:Polymers / Q000737:chemistry*; D012388:Root Canal Irrigants / Q000737:chemistry*; D012973:Sodium Hypochlorite / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D001645:Biguanides; D011108:Polymers; C557698:QMix root canal irrigant; D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite; D002710:Chlorhexidine; C004658:4-chloroaniline
keywords: QMix; chlorhexidine; orange-brown precipitate; para-chloroaniline; sodium hypochlorite