Takeda F H, Harashima T, Kimura Y, Matsumoto K
Department of Endodontics, Showa University School of Dentistry, Tokyo, Japan.
J Clin Laser Med Surg. 1998 Apr;16(2):117-22. doi: 10.1089/clm.1998.16.117.
The aim of this study was to analyze the effectiveness of three types of laser, argon, Nd:YAG, and Er:YAG, to remove the smear layer from the prepared root canal walls in vitro.
After cleaning and shaping by step-back preparation, 32 human extracted maxillary molar teeth were divided randomly into four groups. Root canals in group 1 (G1) were unlased and were irrigated by 17% EDTA. In group (G2), root canals were irradiated by argon laser at the parameters of 1 W, 50 mJ, and 5 Hz. In group 3 (G3) root canals received Nd:YAG laser irradiation at 2 W, 200 mJ and 20 Hz. Teeth in group 4 (G4) were irradiated by Er:YAG laser at the following parameters: 1 W, 100 mJ and 10 Hz. Then these teeth were bisected longitudinally, observed using SEM, and evaluated.
The middle third of the teeth from G1 showed clean wall surfaces with open dentinal tubules. In G2, at the middle third, the smear layer was free and vaporized pulpal tissue remnants were observed. In G3, most of the specimens showed very clean walls with the smear layer evaporated, melted, fused, and recrystallized in both the middle and apical thirds. The walls of G4 revealed the evaporated smear layer and open dentinal tubules in the middle and apical thirds. Statistical analysis showed significant differences between G1 and G2, G1 and G3, and G1 and G4.
These results show that the argon laser and Nd:YAG laser are useful to remove the smear layer and that the Er:YAG laser irradiation is the most effective to remove the smear layer on root canal walls.
本研究旨在分析氩离子激光、钕钇铝石榴石激光和铒钇铝石榴石激光三种类型的激光在体外去除预备根管壁玷污层的有效性。
通过逐步后退法进行根管清理和成形后，将32颗拔除的人上颌磨牙随机分为四组。第1组（G1）的根管未进行激光照射，用17%乙二胺四乙酸（EDTA）冲洗。第2组（G2）的根管以1W、50mJ和5Hz的参数接受氩离子激光照射。第3组（G3）的根管以2W、200mJ和20Hz的参数接受钕钇铝石榴石激光照射。第4组（G4）的牙齿以1W、100mJ和10Hz的参数接受铒钇铝石榴石激光照射。然后将这些牙齿纵向剖开，用扫描电子显微镜观察并评估。
G1组牙齿的中1/3显示管壁表面清洁，牙本质小管开放。在G2组中，中1/3处玷污层脱落，可见汽化的牙髓组织残余物。在G3组中，大多数标本显示管壁非常清洁，中1/3和根尖1/3处的玷污层均已蒸发、熔化、融合和重结晶。G4组的管壁在中1/3和根尖1/3处显示有蒸发的玷污层和开放的牙本质小管。统计分析显示G1与G2、G1与G3以及G1与G4之间存在显著差异。
这些结果表明，氩离子激光和钕钇铝石榴石激光有助于去除玷污层，而铒钇铝石榴石激光照射去除根管壁玷污层的效果最为显著。
