目的 建立近场微波检测系统,并评价其测量含水量的准确性,观察不同方法干燥根管的效果。方法 构建近场微波反射检测系统,检测Eppendorf管中、离体牙根管内已知定量的蒸馏水并记录微波反射系数,评价近场微波系统测量含水量的准确性。将12颗牙根发育完全、根管弯曲度小于10°的单根管下颌前磨牙截冠后保留14 mm牙根,机械预备至F3后烘干,向根管内注入10 μL蒸馏水,按照不同干燥方法分为4组(n=12),采用近场微波系统检测烘干后和干燥完成后含水量的变化,评价其干燥效果:(1)阴性对照组,根管内注入10 μL蒸馏水,不采用任何干燥方法;(2)纸尖干燥实验组,用4根 #60纸尖依次插入根管中上1/3至有阻力,再用#40纸尖插入根管内至工作长度,重复至立体显微镜下纸尖尖端无水痕视为干燥完成;(3)95%(体积分数)乙醇干燥实验组,使用纸尖干燥根管(干燥方法同纸尖实验组)后,向根管内注入10 μL 95%乙醇,静置10 s后,再用纸尖干燥;(4)70%(体积分数)异丙醇干燥实验组,使用纸尖干燥根管(干燥方法同纸尖实验组)后,向根管内注入10 μL 70%异丙醇,静置10 s后,再用纸尖干燥。采用线性回归分析比较近场微波法和物理测量法检测含水量的相关性,计算Pearson相关系数。采用卡方检验比较不同方法干燥根管的差异,并进行两两比较。结果 Eppendorf管及离体根管内含水量的近场微波反射系数和含水量的物理测量值呈线性关系,R ²分别为0.991和0.970。不同干燥方法的实验组之间的微波反射系数差异具有统计学意义(P<0.05)。纸尖干燥后根管内残余的含水量最多,微波反射系数最大,为 0.023。70%异丙醇进行根管干燥,残余的含水量最少,微波反射系数为0.006,干燥效果最佳。结论 近场微波系统可以用来检测根管内含水量的变化,70%异丙醇干燥根管的效果优于95%乙醇和纸尖干燥法。

Objective: To set up near-field microwave detection system, to evaluate the accuracy of measuring water and to compare the effects of different methods on drying root canal.Methods: Known and quantitative distilled water in Eppendorf tube and root canal was detected by near-field microwave detection system which was set up first. The microwave reflection coefficient was recorded so as to evaluate the accuracy of the measuring water. 12 single-rooted mandibular premolar teeth with apical matureness and a curvature less than 10° were decoronated, leaving roots 14 mm in length. After instrumentation to F3, the root canals were air-dried and injected with 10 μL distilled water each. Then all the root canals were assigned to 4 groups (n=12) according to different methods on root canal drying. Near-field microwave detection system was used to detect the change of water after air-drying and root canal drying so as to evaluate the effects of different root canal drying methods: (1) negative control group, the canals were injected with 10 μL distilled water and no root canal drying method was performed; (2) paper points drying experimental group, four #60 paper points were used to blot-dry the middle and upper part of the canal, followed by #40 paper points blot-drying the apical area. The above step was repeated with the tip of paper point that appeared with no water under microscope as finished; (3) 95% (volume fraction) ethanol drying experimental group, after the distilled water was removed with paper points (similar to paper points experimental group), 10 μL 95% ethanol was injected into the canal and was left in place for 10 s, then paper points were used to dry the canal; (4) 70% (volume fraction) isopropyl alcohol drying experimental group, after the distilled water was removed with paper points (similar to paper points experimental group), 10 μL 70% isopropyl alcohol was injected into the canal and was left in place for 10 s, then paper points were used to dry the canal. The linear correlation analysis was used to test the accuracy of the measuring water by near-field microwave detection method and physical measurement. The Pearson correlation coefficient was calculated based on the data. The effects of different methods on drying root canal were analyzed by Chi square test.Results: The R ² for the microwave reflection coefficient and the physical measurement of the water in Eppendorf tube and root canal were 0.991 and 0.970. The microwave reflection coefficient in all the experimental groups showed significant difference (P<0.05). After drying with paper points, the residual water was the most, and the microwave reflection coefficient was the highest: 0.023. While after 70% isopropyl alcohol drying root canal, the residual water was the least with the microwave reflection coefficient 0.006, showing that the effect of drying was the best.Conclusion: Near-field microwave detection system could detect the change of water in root canal. The effect of root canal drying by 70% isopropyl alcohol was superior to 95% ethanol and paper points.