title: Toxicity of calcium hydroxide nanoparticles on murine fibroblast cell line.
abstract: BACKGROUND
  One of the major contributing factors, which may cause failure of endodontic treatment, is the presence of residual microorganisms in the root canal system. For years, most dentists have been using calcium hydroxide (CH) as the intracanal medicament between treatment sessions to eliminate remnant microorganisms. Reducing the size of CH particles into nanoparticles enhances the penetration of this medicament into dentinal tubules and increases their antimicrobial efficacy. This in vitro study aimed to compare the cytotoxicity of CH nanoparticles and conventional CH on fibroblast cell line using the Mosmann's Tetrazolium Toxicity (MTT) assay.
  
  
  METHODS
  This study was conducted on L929 murine fibroblast cell line by cell culture and evaluation of the direct effect of materials on the cultured cells. Materials were evaluated in two groups of 10 samples each at 24, 48 and 72 h. At each time point, 10 samples along with 5 positive and 5 negative controls were evaluated. The samples were transferred into tubes and exposed to fibroblast cells. The viability of cells was then evaluated. The Two-way ANOVA was used for statistical analysis and the level of significance was set at 0.05.
  
  
  RESULTS
  Cytotoxicity of both materials decreased over time and for conventional CH was lower than that of nanoparticles. However, this difference was not statistically significant (P>0.05).
  
  
  CONCLUSIONS
  The cytotoxicity of CH nanoparticles was similar to that of conventional CH.
authors.affiliation: Iranian Center for Endodontic Research, Department of Endodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran;
authors.forename: Omid
authors.initials: O
authors.lastname: Dianat
authors.affiliation: Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sina
authors.initials: S
authors.lastname: Azadnia
authors.affiliation: Iranian Center for Endodontic Research, Department of Endodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran;
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Mozayeni
keywords: Calcium Hydroxide; Cytotoxicity; Murine Fibroblast; Nanoparticles