title: Antimicrobial Efficacy and Cytocompatibility of Calcium Hypochlorite Solution as a Root Canal Irrigant: An in Vitro Investigation.
abstract: BACKGROUND
  The purpose of this study was to compare the antimicrobial efficacy of sodium hypochlorite (SH) and calcium hypochlorite (CH) against Enterococcus faecalis (E. faecalis) using quantitative real-time polymerase chain reaction (qPCR) analysis and also to compare their cytocompatibility on L929 murine fibroblasts using Mossman's tetrazolium toxicity (MTT) assay.
  
  
  METHODS
  A broth micro-dilution susceptibility test was used to determine the minimum inhibitory concentration (MIC) of each irrigant against E. faecalis. Then, the root canals of 50 mature extracted human mandibular premolars were contaminated with E. faecalis and were randomly divided into three groups according to the irrigant used (n=20). Canals were irrigated with SH in group I (n=20) and CH in group II (n=20) at their obtained MIC. In group III (n=10), sterile saline was used. Microbial sampling was performed before and after biomechanical preparation. Quantitative PCR was used to quantify E. faecalis in the root canal samples. For cytocompatibility assessment, L929 murine fibroblasts were exposed to various concentrations of the irrigants.
  
  
  RESULTS
  Irrigation with test materials resulted in significant reduction in colony forming units (CFU) in post-instrumentation samples (with the MIC values of SH and CH against E. faecalis being 0.5% and 5%, respectively). However, the reduction in the normal saline group was not significant (P=0.203). In addition, 5% CH was more effective than 0.5% SH (P=0.006) in eliminating E. faecalis. Among the different concentrations of tested irrigants, 0.5% CH and 5% SH showed the least and the most cytotoxicity, respectively (P<0.001). The cytotoxicity of 5% CH and 0.5% SH was similar (P=0.99), and lower than 2.5% SH (P<0.001).
  
  
  CONCLUSIONS
  CH at an MIC of 5% was effective in eliminating E. faecalis in planktonic state and also its biofilm and exhibited comparable cytocompatibility to that of 0.5% SH.
authors.affiliation: Department of Endodontics, Dental School, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Mahdi
authors.initials: M
authors.lastname: Sedigh-Shams
authors.affiliation: Pharmaceutical Sciences Research Center and Department of Pharmaceutical Biotechnology, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Ahmad
authors.initials: A
authors.lastname: Gholami
authors.affiliation: Department of Endodontics, Dental School, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Abbas
authors.initials: A
authors.lastname: Abbaszadegan
authors.affiliation: Students' Research Committee, Dental School, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Roohollah
authors.initials: R
authors.lastname: Yazdanparast
authors.affiliation: Students' Research Committee, Dental School, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Milad
authors.initials: M
authors.lastname: Saberi Nejad
authors.affiliation: Pharmaceutical Sciences Research Center and Department of Pharmaceutical Biotechnology, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Azam
authors.initials: A
authors.lastname: Safari
authors.affiliation: Department of Endodontics, Dental School, Shiraz University of Medical Sciences, Shiraz, Iran; ; Prevention of Oral and Dental Diseases Research Center, Dental School, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mohammadreza
authors.initials: M
authors.lastname: Nabavizadeh
authors.affiliation: Pharmaceutical Sciences Research Center and Department of Pharmaceutical Biotechnology, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Younes
authors.initials: Y
authors.lastname: Ghasemi
keywords: Calcium Hypochlorite; Enterococcus faecalis; Polymerase Chain Reaction; Root Canal Irrigant; Sodium Hypochlorite