Effects of Visible-Light Irradiation on Eugenol-Treated Oral Mucosa

Objectives: The visible-light (VL) irradiation system is widely used as resin-restoration system in dentistry. We previously reported that eugenol (EUG) used as a component of zinc-oxide EUG cements shows the higher cytotoxicity by VL-irradiation against human gingival fibroblast cells. The cytotoxitity is possibly due to the formation of EUG semiquinone radicals involving reactive oxygen species. In the present study, we investigated whether EUG- or isoeugenol (IsoEUG)-treated oral mucosa of rats could be damaged by VL-irradiation. Materials and Methods: Six adult mice (ICR, 8 weeks) were divided into two groups. The oral mucosa for one group were treated for 1 minute with 1 cm diameter round-shaped filter paper having 0.5 cc EUG or IsoEUG under an anesthesia. Additionally, VL was irradiated for 5 minutes for other group. Their histological changes have been investigated by H-E stain and TUNEL method. Results: In the absence of VL-irradiation, pathological changes by IsoEUG were greater than that by EUG. Also, VL-irradiated EUG significantly enhanced the damage of oral mucosa. VL-irradiated IsoEUG caused the great structural destruction of oral mucosa, i. e. a necrosis. The induction of apoptosis in addition to necrosis was found in irradiated-EUG, judged by TUNEL method. Conclusions: The damage of tissues by IsoEUG was markedly greater than EUG, and both compounds were highly enhanced by the VL-irradiation.