Effect of Nd:YAG Laser Irradiation on the Survival Rate of Human Gingival Fibroblasts in vitro

Objectives: Studies have shown the coordinated effect of Nd:YAG laser with scaling and root planning. But some other studies indicated that laser may damage the root surface and collateral periodontal tissue when certain energy levels are exceeded. The present study was to evaluate the effect of the Nd:YAG laser irradiation on the survival rate of human gingival fibroblasts(HGF) at different power settings and irradiation times. Methods: HGF were obtained from a human gingival connective tissue explant and cultured on 96-well tissue culture plates. 80 multi well cell cultures were laser irradiated and the rest wells were used as control. The variable parameters were power output(0.5-2.5W) and irradiation time(10-60seconds per well). After laser treatment, the cultures were incubated for 24 hours. Photographs were taken before and after irradiation. The survival rate of HGF was determined by counting the dead cell numbers and total cell numbers under a light microscope by means of trypanblau staining. Results: The result showed that with the increase of the power output and irradiation time setting, the laser caused significant (P<0.05, t-test) reductions of survival rate of cell. Irradiation time was more relevant to this reduction than the power output. Conclusions: It indicate that when Nd:YAG laser used for periodontal pocket decontamination, if the power output and the irradiation time are not appropriate, the laser beam may cause damage to collateral periodontal tissues.