title: An evaluation of the accuracy of labeling of percent sodium hypochlorite on various commercial and professional sources: is sodium hypochlorite from these sources equally suitable for endodontic irrigation?
abstract: BACKGROUND
  The shelf life of sodium hypochlorite (NaOCl) is limited, and a previous article showed that there can be a discrepancy between the expected concentration of free available chlorine (FAC) and the actual FAC concentration in NaOCl solutions intended for endodontic irrigation. The current study investigates the FAC content of domestic and professional NaOCls and evaluates the influences of dilution and storage on FAC concentration.
  
  
  METHODS
  First, domestic and professional NaOCls not obtained from manufacturers were iodometrically titrated. Then, NaOCls were diluted with demineralized water or tap water and stored at 4°C or 18°C and analyzed at baseline and 2 and 22 weeks. Statistical analyses included paired samples, independent samples t tests and repeated multivariate analysis of variance. Correlations were calculated with the Pearson or Spearman rank correlation test. A P < .05 was considered significant.
  
  
  RESULTS
  Label specifications of domestic NaOCl were very imprecise (ie, <5% NaOCl). Domestic NaOCl contained 1.8%-3.5% NaOCl (w/v). Professional NaOCl varied from 14.3% relative less FAC than specified on the label to 23.5% relative more FAC than specified. After 22 weeks, the relative average loss of FAC in all conditions was 5.4% FAC (P = .002). Dilution, diluents, or storage temperature had no effect on the decline of FAC caused by aging.
  
  
  CONCLUSIONS
  There is a great variation in NaOCl concentrations, with domestic NaOCl being the least accurate. NaOCl can be stored up to 5 months. The FAC concentration of domestic NaOCl is unpredictable, and, therefore, it appears less suitable for clinical application as root canal irrigant.
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands; Department of Cariology, Endodontology and Pedodontology, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands. Electronic address: s.vd.waal@acta.nl.
authors.forename: Suzette V
authors.initials: SV
authors.lastname: van der Waal
authors.affiliation: Department of Cariology, Endodontology and Pedodontology, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands.
authors.forename: Nilai E
authors.initials: NE
authors.lastname: van Dusseldorp
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands.
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: de Soet
mesh_terms: D002626:Chemistry, Pharmaceutical; D002713:Chlorine / Q000032:analysis; D004348:Drug Labeling / Q000592:standards*; D004355:Drug Stability; D004356:Drug Storage; D006801:Humans; D008422:Materials Testing; D012388:Root Canal Irrigants / Q000032:analysis / Q000592:standards*; D012973:Sodium Hypochlorite / Q000032:analysis / Q000592:standards*; D013696:Temperature; D013997:Time Factors; D017186:Titrimetry / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D012388:Root Canal Irrigants; D014867:Water; D002713:Chlorine; D012973:Sodium Hypochlorite
keywords: Concentration; endodontic; free available chlorine; irrigation; shelf life; sodium hypochlorite