Hossain M, Nakamura Y, Kimura Y, Yamada Y, Kawanaka T, Matsumoto K
Department of Endodontics, Showa University School of Dentistry, Tokyo, Japan.
J Clin Laser Med Surg. 2001 Apr;19(2):105-8. doi: 10.1089/104454701750285421.
The purpose of this study was to investigate the effect of Nd:YAG laser irradiation on the acid demineralization of enamel and dentin by spectrophotometry. A mechanism of acquired acid resistance is also proposed.
The ability of Nd:YAG laser irradiation to the enhanced resistance to artificial caries formation is still controversial.
A pulsed Nd:YAG laser at 1.064-micron wavelength was used to irradiate the human enamel and dentin samples from 20 extracted human molars at the parameters of 1, 2, and 3 W and 20 pps for a total of 9 sec after painting with black ink. Samples were then subjected to 2 microliters of 0.1 M lactic acid solution (pH 4.8) for 24 h at 36 degrees C. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometry and the morphological changes were also investigated by scanning electron microscopy (SEM).
The lowest mean Ca2+ ppm was recorded in the samples irradiated at 3 W, in those by irradiated at 2 W and 1 W. The unlased samples showed the highest Ca2+ ppm. SEM observation showed that in the lased areas, the smear layer was partially melted and the underlying primary enamel or dentin seemed to be thermally degenerated.
The results of this study suggested that melted smear layer and underlying enamel or dentin degenerated thermally by the heat treatment of Nd:YAG laser might play a major role to enhance resistance to artificial caries-like formation.
本研究旨在通过分光光度法研究钕钇铝石榴石（Nd:YAG）激光照射对牙釉质和牙本质酸脱矿的影响。同时还提出了一种获得性抗酸性的机制。
Nd:YAG激光照射增强人工龋形成抗性的能力仍存在争议。
使用波长为1.064微米的脉冲Nd:YAG激光，以1、2和3瓦以及20脉冲每秒的参数，对20颗拔除的人类磨牙的牙釉质和牙本质样本进行照射，照射前先用黑色墨水涂抹，共照射9秒。然后将样本置于2微升0.1M乳酸溶液（pH 4.8）中，在36摄氏度下放置24小时。通过原子吸收分光光度法测定每种溶液中溶解的钙离子（Ca2+）的百万分率（ppm），并通过扫描电子显微镜（SEM）研究形态变化。
在3瓦照射的样本中记录到的平均Ca2+ ppm最低，其次是2瓦和1瓦照射的样本。未照射的样本显示出最高的Ca2+ ppm。SEM观察表明，在照射区域，玷污层部分熔化，其下方的原始牙釉质或牙本质似乎发生了热变性。
本研究结果表明，Nd:YAG激光热处理使玷污层和下方的牙釉质或牙本质发生热变性，可能在增强对人工龋样形成的抗性中起主要作用。
