Induction of c-fos and c-jun protooncogenes expression by formaldehyde-releasing and epoxy resin-based root-canal sealers in human osteoblastic cells

An important requirement for a root-canal sealer is biologic compatibility; most evaluations have focused on general toxicological and local tissue irritating properties. There is only scant information about mutagenicity or carcinogenicity testing for root-canal sealer. It has been shown that c-fos and c-jun are induced rapidly by a variety of chemical and physical stimuli. Numerous works have extensively investigated the induction mechanisms of c-fos and c-jun protooncogenes by these agents; however, little is known about the induction of cellular signaling events and specific gene expression after cell exposure to root-canal sealers. Therefore, we used osteoblastic cell line U2-OS to examine the effect of zinc-oxide eugenol-based (N2 and Endomethasome), epoxy resin-based (AH Plus), and calcium hydroxide-based (Sealapex) root-canal sealers on the expression of c-fos and c-jun protooncogenes to understand in more detail the molecular mechanisms of root-canal sealer-induced genotoxicity. The cytotoxicity decreased in an order of N2 > Endomethasome > AH Plus > Sealapex. In addition, N2, Endomethasome, and AH Plus rapidly induced c-jun and c-fos mRNA levels in cells. However, Sealapex did not induce c-jun and c-fos mRNA expression at detectable levels all time points. Taken together, persistent induction of c-jun and c-fos protooncogenes by formaldehyde-releasing and epoxy resin-based root-canal sealers may be distributed systemically via apex to cause some unexpected adverse effects on human beings. These data should be taken into consideration when choosing a root-canal sealer.