BACKGROUND: Cytotoxicity of root canal irrigants is important due to their close contact with host tissues. The aim of this study was to assess the cytotoxic effect of NaOCl 3%, Chx 2%, and MTAD on rat periodontal ligament fibroblasts, at 0.1 and 100 µl/mL, using WST-1 colorimetric method.

MATERIAL AND METHODS: Rat ligamental fibroblasts were exposed to the irrigants and their viability was assessed after 1, 24, 48, and 72 h. The measurements were determined using WST-1 assay, using a micro ELISA reader.

RESULTS: At 100 ml/L all 3 irrigants were strongly cytotoxic, although CHX was less so than NaOCl and MTAD. At the 0.1 ml/L concentration, NaOCl and MTAD were only moderately cytotoxic, whereas Chx was highly deleterious to cell viability at all time points. There was a significant influence of the dilution rate of the substance, because the odds ratio for cell viability being over 50% was increased 51 times between the 100 ml/L and 0.1 ml/L dilutions.

CONCLUSIONS: It seems that irrigating solutions should be used at lower concentrations to enhance cell viability.

Keywords: Cell Death - drug effects, Cell Survival - drug effects, Endodontics, Periodontal Ligament - pathology, Root Canal Irrigants - pharmacology