Studies on biochemical mechanisms of dental materials-elicited cellular toxicity

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The purpose of the present research is to elucidate the biochemical mechanisms of action formaldehyde, the main component of formocresol which is one of root canal disinfectants, using various biochemical parameters in JTC-12, MDCK(from kidney) and PL(from periodontal ligament)cells. Formaldehyde caused leakage of lactate dehydrogenase, and inhibited the uptake of neutral red and the reduction of MTT in a concentration-and time -dependent manner. The testing method as an index of the uptake of neutral red was sensitive in the following order : PL cells(〕SY.gtoreq.〔) MDCK cells > JTC-12 cells. The sensitive sequence of the type of cells by the testing method as an index of the reduction of MTT was PL cells>JTC-12 cells>MDCK cells. In JTC-12 cells, alkaline phosphatase(ALPase), (Na^++K^+)-ATPase and (H^++K^+)-ATPase activities were concentration -dependently inhibited by formaldehyde. In MDCK cells, alkaline phosphatase(ALPase)and(NA^++K^+)-ATPase activities were also concentration-dependently inhibited by formaldehyde, whereas(H^++K^+)-ATPase activity was potentiated by 1mM formaldehyde but inhibited in higher concentrations than 1mM.Formaldehyde had no stimulating effects on leakage of gamma -glutamyl transpeptidase within the range of concentrations examined in both cell. Lipid peroxidation and production of superoxide anion radical were increased by formaldehyde in MDCK cells. In JTC-12 cells, formaldehyde had no effects on these biochemical parameters. On the other hand, formaldehyde lowered the production of superoxide anion radical in PL cells. These results indicated that these effects of formaldehyde was varied, depending on the type of cells and duration of treatment. Furthermore, intracellular calcium ion was increased by formaldehyde in a concentration-dependent manner in JTC-12 and MDCK cells. This effect was inhibited by verapamil, a calcium channel blocker and slightly did by TMB-8, a blocker intr