Effect of Halogen, Led and Plasma on Human Gingival Fibroblasts

Objectives: The purpose of this study was to investigate the biologic effects of blue light curing sources on the physiology of human gingival fibroblasts (hGF). Methods: Primary cultures of hGF were exposed to halogen, LED and plasma arc irradiation for 240 s, 240 s and 120 s respectively, simulating the time frames applied in full orthodontic bondup; the halogen lamp was used on the standard mode, the LED at the highest energy level. The tip of the lamps was positioned on top of the free culture surface of 1-cm2 vials. As a control, cells were exposed to ionizing radiation (10 Gy) in a 60 Co source. Results: No double-strand DNA breaks were observed, as assessed by immunofluorescence by using an anti-gammaH2Ax antibody. In addition, there was no immediate effect on cell proliferation, tested by tritiated thymidine incorporation (p>0.05). However, exposure of cells to lights induced an inhibition of proliferation (40% relative to control; gamma radiation induced a 75% inhibition p<0.05). Further investigation of the mechanism mediating the observed effect with the use of N-acetyl-cysteine, a potent antioxidant, did not result in a reversal of the cytostatic effect; this implies that oxidative stress may not be involved in the light-induced decrease of cell proliferation. Conclusions: The effects shown, albeit mild in potency, necessitate further study to clarify the exact mechanism underlying the anti-proliferative action on human cells.