不同方法预备根管对根管治疗后牙齿冠渗漏的影响

目的采用3种不同方法预备根管，评价其对根管治疗后牙齿冠渗漏的影响。方法48颗单根管离体牙随机分为4组，使用不同的根管预备方法去除根管壁的玷污层。A组为对照组，采用生理盐水和过氧化氢溶液冲洗根管；B组采用乙二胺四乙酸（EDTA）凝胶和5.25%次氯酸钠溶液冲洗；C组采用Odontoson-M型超声波治疗仪荡洗；D组采用脉冲Nd: YAG激光照射。每组取2颗牙，于扫描电子显微镜（SEM）下观察冠部玷污层的去除情况；其余10颗牙采用Obtura Ⅱ高温注射式热牙胶垂直加压法充填根管，氧化锌丁香油黏固剂封闭根管口，浸于质量浓度20 g·L-1亚甲基蓝溶液中染色7 d，脱水脱钙制作透明牙标本，体视显微镜下测量染料渗入的深度。结果SEM观察：A组
整个根管内壁被覆玷污层及大量碎屑，牙本质小管被堵塞；B组与C组根管内壁清洁，玷污层消失，牙本质小管开放；D组根管内壁牙本质小管封闭或半封闭，玷污层熔融消失。A、B、C、D组染料渗入深度分别为（2.15±0.38）、（1.75±0.28）、（2.04±0.40）、（1.73±0.36）mm。A组的渗入深度明显高于B、D组，其差异有统计学意义（P<0.05）。结论使用不同的方法预备根管去除玷污层，可以减少根管治疗后牙齿的冠渗漏。

Effect of different techniques in root canal preparation on coronal microleakage of endodontically treated teeth

Objective To compare the effect of three techniques in root canal preparation on coronal microleakage of endodontically treated teeth. Methods Forty-eight human single-rooted teeth were divided into 4 groups randomly and subjected to different techniques on removal of smear layer. Group A, the control group, irrigation with
hydrogen peroxide（H2O2 ） and normal saline（NS）; group B, smear cleared with 5.25% sodium hypochlorite（NaClO） and ethylenediamine tetraacetis（EDTA） gel; group C, irrigation with Odontoson-M ultrasonics; group D, smear layer removed with Nd: YAG laser irradiation . Two specimens of every group were split longitudinally into equal segments and canal walls at coronal portion were examined under scanning electron microscope（SEM）. Then ten teeth of every group were filled with warm vertical condensation by Obtura Ⅱ thermoplasticized gutta-perch injection technique and sealed with zinc oxide eugenol（ZOE）. The teeth were immersed in 20 g·L-1 methylene blue for 7 days, then were demineralized, dehydrated and cleared. Linear dye penetration was determined under a steremicroscope. The data were statistically analyzed. Results In group A, there were smear layer and debris remained and dentinal tubules were covered. In
group B and group C, the smear layer of root canals were removed and dentinal tubules were open. In group D, the root canal dentinal tubules were sealed or semi-sealed and the smear layer were melted and ablated. The mean length of coronal microleakage for group A, B, C, D were （2.15±0.38）, （1.75±0.28）, （2.04±0.40）, （1.73±0.36）mm. The analysis showed that the linear in group A was longer than that in group B and group D clearly（P<0.05）. Conclusion
The coronal microleakage following root canal treatment could be reduced by removing smear layer with different techniques in root canal preparation.