Blue Light from Dental Resin Curing Unit Causes Light-Induced Vasocon- striction in Isolated Rat Aorta

Aims: Currently, the blue light of resin curing unit is frequently used in dental treatment. However, the influence of the blue light irradiation on oral tissue is not clear. The aim of this study was to elucidate the effect of dental blue light irradiation on vascular smooth muscle. Methods: Isolated rat descending aorta was suspended in a superfusion chamber and superfused continuously with Krebs-Ringer solution. The changes in isometric force of blue light irradiation were assessed using vessel strips superfused with the Krebs-Ringer solution alone or the Krebs-Ringer solutions containing 10 μM phentolamine, 100 mM dimethyl sulfoxide, 10 unit/mL superoxide dismutase, or 5 mM L-histidine. The reactive oxygen species (ROS) scavenging activity of antioxidants was examined using the electron spin resonance technique respectively. Results: We first demonstrated that the vasoconstriction was induced by irradiated of blue light using dental resin curing unit. The vasoconstriction was inhibited by including in the Krebs-Ringer solution an α-receptor blocker that inhibits the neurotransmitter. This phenomenon was controlled with the addition of ROS scavengers. Conclusions: Blue light irradiation of multiple times in dental treatment might have the potential to accelerate aging of pulpal blood vessel from ischemia through dental pulp vasoconstriction via ROS generation. In addition, prolonged and/or repeated blue light irradiation could cause ROS-induced oxidative stress such as ischemia-reperfusion injury on pulpal blood vessel. Therefore, preintake of antioxidants is suggested to avoid effects such as aging of dental pulp due to blue light irradiation-induced ROS in dental clinic treatments.