Effects of Nd : YAG laser irradiation on cultured human gingival fibroblasts

Background and Objective: The Nd:YAG laser has been proposed to apply in mi nor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG lase r on gingival fibroblasts, which play an important role in the early healin g processes of periodontal repair. Study Design/Materials and Methods: Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from health y human gingiva by an explant method. The size of laser diode was 400 mum i n diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of ir radiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vita lity was also examined with the help of MTT staining. Results: The area of laser damage on cell culture was circular in shape, wi th diameter beyond the size of laser diode. By scanning electron microscopy , we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased powe r settings. The cytomorphologic changes ranged from disappearance of cellul ar boundary, loss of identifiable cellular nucleus, and finally cell contra ction and vacuolization. Significant decrease in cellular vitality (14% sim ilar to 44%) after laser treatment with irradiation distance of nearly cont act was noted. However, 2 mm defocusing irradiation with the same power set tings did not significantly decrease cellular vitality. Conclusion: Our study demonstrated the cell damaging effects of Nd:YAG lase r, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to u nderstand the potential hazard of laser application in periodontal treatmen t. If the energy output is enough for the clinical purposes, Nd:YAG laser w ith lower pulse energy and corresponding pulse rate should be selected to m inimize the damage on adjacent soft tissue. Lasers Surg. Med. 27:471-478, 2 000. (C) 2000 Wiley Liss, Inc.