In-vitro cytotoxicity of three fluoride desensitizing agents

Objective: To compare the cytotoxicity of three fluoride desensitizing agents on different cell types. Methods: Three fluoride desensitizing agents: Duraphat^® (Colgate), Isodan (Septodont) and Shellac-F, a natural resin based varnish enriched with 5% NaF, were separately immersed in cell culture medium (0.1g/ml), for 24 hours at 37°C. The test media were then collected, diluted (1:1, 1:2, 1:10, 1:100, 1:1000 and 1:10,000) and used to culture three different cell types (human gingival fibroblast, human pulpal fibroblast and mouse fibroblast L929), plated at 40,000cells/cm² in nine 96-well dishes (each dish for one cell type and one agent at six different dilutions) and incubated for 24 hours at 37°C in 5% CO₂, 95% air and 100% relative humidity. A succinyl dehydrogenase (MTT) assay was performed and the absorbance of each 96-well dish was determined using an automatic microplate spectrophotometer at 550nm. The absorbance of the wells containing the same medium at the same dilution was averaged as a single measurement and calculated against the control medium to determine the percentage of cell mortality. The experiment was done in triplicate. One-way ANOVA was applied to evaluate the influence of desensitizing agents, medium dilutions and cells types on the cytotoxicity testing results. Two-way ANOVA and Scheffe test were used to compare the cytotoxicity of the three desensitizing agents at different dilutions. Results: The sensitivity of the three cell types to the three desensitizing agents showed no significant difference (p=0.9). Duraphat® and Shellac-F were non-toxic at the dilution of 1:10 (average cell viability: 91.1±11.8% and 88.7±10.8%) and Isodan at 1:100 (96.8±4.4%). Conclusions: Among the three desensitizing agents, Duraphat^® showed the lowest cell toxicity, followed by Shellac-F then Isodan.