Nd : YAGレーザーの根管内照射の可能性

コア径150μmの導光ファイバーを用いた基礎的検討

抄録

In order to apply laser to endodontics, it is necessary to use a narrow fiber to irradiate the laser in the canal. Recently, a new type of optical fiber of diameter 150 micrometers has been developed. This size is comparable with the tip diameter of a #25 file. Accordingly, the fiber is supposed to reach the apical portion of a fine canal. The objective of this study was to investigate the application of 150-micrometer-diameter fiber to endodontics. Cantilever bending testing of the fiber and a stainless steel K file was performed to measure the bending load at 2.4 mm deflection in the loading process. Then, dentin plates were prepared from a bovine tooth crown. The surfaces of the plates were irradiated by a Nd: YAG laser with 5% TiO₂ solution for 5 seconds. The laser energy was 200, 300 and 350mJ with a pulse frequency of 20 pps. The fiber was moved parallel to the dentin surface at a speed of 1mm/s during lasing. Then, the irradiated surfaces were observed by digital microscopy and confocal laser microscopy. The width and depth of the laser irradiated surfaces were evaluated (n=4). Moreover, scanning electron microscopic observation was performed. Carbonization of the irradiated dentin surfaces was not observed by digital microscopy. The widths of 200, 300, and 350mJ laser-irradiated surfaces were 77, 227, and 193 micrometers, respectively. The depths of 200, 300, and 350 mJ laser-irradiated surfaces were 11, 32, and 35 micrometers, respectively. Melted dentin was observed by scanning electron microscopy. In clinical settings, this fine fiber has a possibility to enlarge the narrow apical portion of the canal. Our results suggest that the fiber tested might be useful for root canal preparation.