Haruji Watanabe

Histopathological changes in dental pulp irradiated by Er:YAG laser : a preliminary report on laser pulpotomy

OBJECTIVE The effects of Er:YAG laser irradiation on the pulp tissue during a pulpotomy procedure were evaluated histopathologically. BACKGROUND DATA The effects on pulp tissue during laser pulpotomy using Er:YAG laser irradiation are not clear. MATERIALS AND METHODS Sixty mesial root canals of mandibular first molars in rats were divided into four groups. In three of these groups, root canals were irradiated using an Er:YAG laser at 2 Hz and 34, 68, and 102 mJ/pulse for 15 sec. Non-irradiated canals served as controls. The effects of laser irradiation on the remaining pulp tissue and periodontal tissues were evaluated at 0 days, 2 days, and 1 week after irradiation under light microscopy. RESULTS At 1 week after treatment, no inflammation or resorption was observed in any cases in the control or 34 mJ/pulse-irradiated groups. However, moderate to severe inflammation was observed in 9 of 10 cases (90%) in the 68 and 102 mJ/pulse-irradiated groups. CONCLUSION These results suggest that effects on pulp tissues during a pulpotomy procedure by Er:YAG laser irradiation are minimal, if appropriate parameters are selected, and this is a potential therapy for pulpotomy of human teeth.

Histopathological study of the effects of Er:YAG laser irradiation on root canals in rats

The thermal effects of Er:YAG laser irradiation on the periodontal region during root canal preparation were evaluated using rats histopathologically. One hundred mesial root canals of mandibular first molars in rats were divided into four groups. In three of these groups, root canals were irradiated using an Er:YAG laser at 2 Hz and 34, 68, and 102 mJ/pulse for 30 s. Nonirradiated canals served as controls. The effects of laser irradiation on the periodontal tissues along the root surface and apical area were evaluated at 0, 2 days, 1, 2, and 4 weeks after irradiation under light microscopy. At 4 weeks after treatment, no inflammation or resorption was observed in any case in the control or 34 mJ/pulse-irradiated groups. However, moderate to severe inflammation with resorption of root surface was observed in four of five cases (80%) in the 102 mJ/pulse-irradiated group, which was significantly different from the control (P<0.01). These results suggest that thermal effects on periodontal tissues during root canal preparation by Er:YAG laser irradiation after pulpectomy are minimal, if appropriate parameters are selected.