RESUMO
AIM: To determine whether cells pre-stressed by known cytotoxic or inflammatory agents are more susceptible to the deleterious effects of a calcium hydroxide formulation used in pulp capping. METHODOLOGY: Adult human dermal fibroblasts were treated for 48 h with 0.001% chlorhexidine, 0.2% ethanol, 5 µg mL(-1) Escherichia coli lipopolysaccharide (LPS) or 0.05 mmol L(-1) nicotine. Cells were subsequently treated with the soluble materials extracted from Dycal pellets for an additional 24 h. Controls included cells cultured in medium only and cells exposed to Dycal only. Cytotoxicity was measured using colorimetric MTT, WST and secreted lactate dehydrogenase assays. In addition, mitotic activity was evaluated using a colorimetric histone H3 phosphorylation assay. Data were statistically analysed using anova with Tukey's multiple comparison post-test and significance at P ≤ 0.05. RESULTS: For all assays, measured values for cells treated with chlorhexidine, ethanol, LPS or nicotine plus the soluble materials extracted from Dycal pellets were significantly lower compared to control (P < 0.05) for all comparisons between experimental conditions. However, between treatments and for comparisons of treatments with Dycal, there were no differences observed for any assay. CONCLUSIONS: Calcium hydroxide in a formulation used in dental clinical procedures is highly cytotoxic to cultured cells, as evidenced by several cellular assays. However, other known toxic agents, including chlorhexidine, ethanol, bacterial LPS and nicotine, do not appear to function synergistically to increase the deleterious cellular effects of the calcium hydroxide in an in vitro model of cytotoxicity.