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目的比较5种不同方法预备根管后对根尖1／3根管壁的清洁能力。方法将2007年12月至2008年3月在大连市口腔医院颌面外科门诊拔除的60颗离体牙随机分为6组，每组10颗。各组的牙齿先使用Protaper进行根管预备，然后使用不同的方法处理根管壁，分别为：A组H2O2和生理盐水（对照组）、B组EDTA凝胶和5．25％的NACLO，C组超声波荡洗根管、D组Nd：YAG激光、E组超声波（蒸馏水）＋EDTA、F组：超声波（5．25％NAcL0）＋EDTA。完成之后将样本纵向剖开，扫描电镜观察根管壁的界面，比较根尖1／3根管壁的清洁程度和牙本质小管的状态。结果对照组（A组）牙齿根尖部被玷污层全部覆盖，未见开放的牙本质小管；各实验组（B、C、D、E、F组）牙齿根尖部根管壁玷污层不同程度被去除。B、C、D、E、F组根尖1／3玷污层的评分与A组比较，差异有统计学意义（P〈0．05）；5个实验组间根尖1／3玷污层的评分比较，D组与E组差异无统计学意义（P〉0．05），其余各组间差异均有统计学意义（P〈0．05）。结论5种不同的方法在一定程度上可去除根尖部的玷污层，以超声波（5．25％NACLO）＋EDTA处理根管壁的效果最佳。

Effect of cleanness at the root tip by using five different techniques in root canal preparation

Objective To compare the ability of five techniques on cleanness at the apical third of root. Methods Sixty extracted single-rooted human teech ,randomly distributed into 6 groups ,were prepared by using Protaper rotary instru- ments and subjected to different techniques on removal of smear layer; hydrogen peroxide and normal saline（ group A） ; 5.25%sodium hypochlorite （NAOCL） and ethylenediamine tetraacetis （EDTA） gel （group B）, irrigation with ultrasonics （group C） ; with Nd： YAG laser（ group D）, EDTA gel and ultrasonics with normal saline irrigation （group E） ;EDTA gel and ultrasonics with 5.25% NAOCL irrigation （ group F）. Samples were examined under the scanning electron micro- scope （SEM） and scored for cleanness at the apical third of root and the condition of dentin tubule. Results In group A the apical root and dentine tubules were covered by smear layer. The smear layer of the other 5 groups were cleared part- ly.There were significant difference bwteen group A and other groups（P 〈 0.05）. There were no significant difference be- tween the group D and group E（P 〉 0.05）. There were significant difference among the other tested groups（P 〈 0.05）. Conclusion the smear layer at the root tip can be removed effectively by using chemical , ultrasonics and Nd：YAG la- ser. EDTA gel combined with ultrasonics and 5.25% NAOCL irrigation （group F） was best.