title: Calcium Hypochlorite Solutions: Evaluation of Surface Tension and Effect of Different Storage Conditions and Time Periods over pH and Available Chlorine Content.
abstract: BACKGROUND
  The aim of this study was to evaluate the pH and the available chlorine content from sodium hypochlorite (NaOCl) and calcium hypochlorite (Ca[OCl]2) solutions stored in different conditions and time periods and the surface tension of Ca(OCl)2 solutions in comparison with NaOCl.
  
  
  METHODS
  Solutions at 0.5%, 1%, 2.5%, and 5.25% concentrations were prepared. The pH level and the available chlorine content of freshly prepared solutions and solutions stored for 30, 60, and 90 days at 25°C, 4°C, or 37°C were evaluated in a digital pH meter and by titration, respectively. Surface tension was tested using a Du Nouy tensiometer (Sigma 702, Force Tensiometer; Attension, Espoo, Finland). Descriptive and inferential statistical analyses were performed.
  
  
  RESULTS
  A precipitate formed by 2.5% and 5.25% Ca(OCl)2 solutions was observed. Ca(OCl)2 showed a higher concentration of available chlorine than NaOCl. Both 2.5% and 5.25% NaOCl and Ca(OCl)2 had a decrease in the available chlorine content when compared with freshly prepared solutions; 0.5% and 1% NaOCl tend to have a lower pH compared with 0.5% and 1% Ca(OCl)2. NaOCl, 5.25%, showed higher pH compared with 5.25% Ca(OCl)2. NaOCl and Ca(OCl)2 in 0.5% and 1% concentrations tend to show a reduced pH level, whereas 2.5% and 5.25% solutions showed an increase in pH. The heat contributed to the instability of the solutions. NaOCl showed lower surface tension values than Ca(OCl)2.
  
  
  CONCLUSIONS
  Ca(OCl)2 solutions are extremely alkaline and tend to have more available chlorine content than NaOCl but have a higher surface tension than NaOCl. Regarding the available chlorine content, these solutions tend to be stable to 30 days of storage when kept at 4°C or at 25°C.
authors.affiliation: Post Graduation Program in Dentistry, Dental School, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Natália Gomes e Silva
authors.initials: NG
authors.lastname: Leonardo
authors.affiliation: Post Graduation Program in Dentistry, Dental School, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Israel Bangel
authors.initials: IB
authors.lastname: Carlotto
authors.affiliation: Department of Conservative Dentistry, Dental School, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Simone Bonato
authors.initials: SB
authors.lastname: Luisi
authors.affiliation: Department of Conservative Dentistry, Dental School, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Patrícia Maria Poli
authors.initials: PM
authors.lastname: Kopper
authors.affiliation: Department of Conservative Dentistry, Dental School, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. Electronic address: fabiana.grecca@ufrgs.br.
authors.forename: Fabiana Soares
authors.initials: FS
authors.lastname: Grecca
authors.affiliation: Department of Conservative Dentistry, Dental School, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Francisco
authors.initials: F
authors.lastname: Montagner
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D004202:Disinfectants / Q000737:chemistry; D004356:Drug Storage; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008422:Materials Testing; D012388:Root Canal Irrigants / Q000737:chemistry*; D012973:Sodium Hypochlorite / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D013500:Surface Tension
chemical_list: D017610:Calcium Compounds; D004202:Disinfectants; D012388:Root Canal Irrigants; D012996:Solutions; C004488:calcium hypochlorite; D012973:Sodium Hypochlorite
keywords: Calcium hypochlorite; chlorine content; pH; sodium hypochlorite; surface tension