RESUMO
<p><b>OBJECTIVE</b>To evaluate the effect of the pulsed Nd: YAG laser irradiation on the survival rate of human penodontal ligament fibroblast (PDLF) at different power and irradiation time settings, and to compare the morphological change of cells before and after irradiation.</p><p><b>METHODS</b>The cells were cultured and placed into the 96-well tissue culture plates. Cells were divided into groups according to the irradiation time (10 s, 20 s, 40 s, 60 s) and the output energy (0.5 W, 1.0 W, 1.5 W, 2.0 W, 2.5 W). After the irradiation, the cell number were counted and the survival rates were calculated. The correlation between the survival rate and irradiation time as well as power output was analyzed.</p><p><b>RESULTS</b>No significant reduction of survival rates were found in 10 s group, as well as in 20 s group with 0.5 W, 1.0 W setting. The increase of the power output and increase of the irradiation time caused significant reduction of cell survival rate (P <0.05). The irradiation time was more relevant to this reduction than the power output.</p><p><b>CONCLUSION</b>It indicates that the laser irradiation may cause damage to PDLF and decrease the cell survival rate. The irradiation time is more related to this effect than the power output.</p>