title: Combined and independent cytotoxicity of sodium hypochlorite, ethylenediaminetetraacetic acid and chlorhexidine.
abstract: OBJECTIVE
  To evaluate the capacity of commonly used root canal irrigants to induce cytotoxic effects, when applied singly or in combination. The hypothesis tested was that the irrigants were less cytotoxic when applied in combination than independently.
  
  
  METHODS
  MRC5 cells were grown as monolayer cultures at 37 °C in an atmosphere containing 5% CO2 in air and 100% relative humidity. Cells were exposed to sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA), chlorhexidine (CHX) and their combinations (NaOCl/EDTA, NaOCl/CHX, EDTA/CHX) in serial dilutions. Growth medium was Dulbecco's modified Eagle's medium supplemented with 10% foetal bovine serum and antibiotics and was used as control. The effect on cell survival was estimated after 6 and 24 h of exposure by means of the sulforhodamine B assay, in reference to controls. Dose-response curves were plotted, and 50% inhibitory doses (IC50 ) were subjected to statistical analysis (anova and post hoc comparison test; P < 0.05). Analysis of cell survival and interaction of the irrigants was performed using CalcuSyn dose effect analyzer software to calculate a combination index (CI).
  
  
  RESULTS
  The tested irrigants were cytotoxic in dose- and time-dependent manner. CHX was the most cytotoxic irrigant tested, followed by NaOCl, whilst EDTA was the least cytotoxic irrigant tested. The difference between CHX and NaOCl was significant (P < 0.05) as well as between NaOCl and EDTA (P < 0.05). Based on CalcuSyn modelling, a mainly antagonistic effect was recorded with NaOCl/CHX and NaOCl/EDTA combinations. The combination EDTA/CHX had an additive to antagonistic effect.
  
  
  CONCLUSIONS
  CHX was significantly more cytotoxic than NaOCl and EDTA. NaOCl was significantly more cytotoxic than EDTA. The combined action of irrigants did not produce a significant increase in their cytotoxicity.
authors.affiliation: Department of Endodontology and Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: T
authors.initials: T
authors.lastname: Vouzara
authors.affiliation: Department of Endodontology and Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Koulaouzidou
authors.affiliation: Department of Endodontology and Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: F
authors.initials: F
authors.lastname: Ziouti
authors.affiliation: Department of Endodontology and Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: N
authors.initials: N
authors.lastname: Economides
mesh_terms: D000704:Analysis of Variance; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D002460:Cell Line; D002710:Chlorhexidine / Q000494:pharmacology*; D004492:Edetic Acid / Q000494:pharmacology*; D006801:Humans; D012388:Root Canal Irrigants / Q000494:pharmacology*; D012973:Sodium Hypochlorite / Q000494:pharmacology*; D018675:Toxicity Tests
chemical_list: D000891:Anti-Infective Agents, Local; D012388:Root Canal Irrigants; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D002710:Chlorhexidine
keywords: chlorhexidine; cytotoxicity; ethylenediaminetetraacetic acid; irrigant combinations; sodium hypochlorite