Abstract ▼ AI-Helper

Many of dental epoxy resin components are leaching from the filling materials and some of these ingredients are cytotoxic, genotoxic and estrogenic. Recent study reports that formaldehyde leaches out of root canal sealer and setting materials and it participates in the development of periapical infl...

Many of dental epoxy resin components are leaching from the filling materials and some of these ingredients are cytotoxic, genotoxic and estrogenic. Recent study reports that formaldehyde leaches out of root canal sealer and setting materials and it participates in the development of periapical inflammation or the continuation of a pre-existing periapical lesion. Since formaldehyde is continuously leached from the dental material, public concern over the toxic effects is growing. The present study attempted to analyze mechanism of toxic effects of formaldehyde on human epithelial cells in culture. Both MTT and LDH assay were conducted to assess the cytotoxicity of formaldehyde on the human epithelial cells in culture. Cytotoxic effects of formaldehyde were shown above 5 mM. There was no significant cytotoxic effects up to 3 mM formaldehyde, which was the highest concentration used in the present study. Apoptotic effects of formaldehyde was analyzed by EISA kit, which detects DNA fragmentation with DNA-histone antibody. Formaldehyde induced dose-dependent apoptosis from 1 mM. Considering the fact that milimolar level of exposure induced apoptosis, it is suggested that formaldehyde is a weak inducer of apoptosis on the human epithelial cells. Generation of reactive oxygen species (ROS) was increased from 0.5 mM with a maximum of 2.2 fold at 3 mM. To confirm ROS generation by formaldehyde, antioxidants (trolox and vitamin C) or GSH depleting agent (BSO) was treated prior to formaldehyde exposure. Production of ROS was blocked by the treatment of antioxidants but the dramatic increase of ROS was observed after the GSH depleting agent. These results indicate that formaldehyde directly induces ROS generation on the human epithelial cells. To analyze the effects of signaling pathway following formaldehyde exposure, western blot analysis was performed to analyze the PKC isozyme-specific activity. While PKC-α showed only a marginal translocation, significant translocation of PKC-ε from cytosolic to membrane fraction was observed. These results suggest that formaldehyde plays a role in the signaling pathway thru the altered activity of a specific PKC isozyme. Formaldehyde is reported to affect the inflammation of periapical region. The present study showed that interleukin-1 and -6 may be involved in the formaldehyde-induced inflammation process. Taken together, the present study suggests that formaldehyde is a potent ROS producer and its overproduction may play a major role in formaldehyde-induced toxic process. In addition, alteration of signaling pathway, which results in aberrant phosphorylation of target molecules by the altered PKC expression, may be associated with abnormal process of apoptosis. This study provided the scientific data to evaluate the effects of formaldehyde leached from the dental materials and to improve the quality control on the manufacturing of dental materials.

Keyword