Abstract: Objective　To compare the effect of different root canal wettability on root canal filling.  Methods　A total of 50 intact single-tube teeth were collected. The crown of the tooth was removed at the neck to make the distance between the root tip and the cross section being 10 mm. Root canal was prepared to 30#. After routine irrigation combined with ultrasonic washing, root canal moisture was measured by different root canal drying methods. Root canal moisture meter was used to measure root canal moisture. The measured data were divided into five groups according to measurement data of the moisture meter. A group: completely dry, display data 0;  B group: display data 0.1~5; C group：display data 5.1~10; D group：display data 10.1~15; E group：completely wet, display data＞15 (15 was the saturation value of the root canal moisture meter). The root canals were filled by the lateral compression method immediately, and X-ray film found that the root canal filling was perfect. Scanning electron microscopy was used to observe the consistency of gutta percha point and root canal side wall after transverse spiting. The filling clearance was measured by gap width measurement.　Results　Under different humidity conditions, the gutta-percha tip and the lateral wall of the root canal consistently had gaps. There was no statistical difference in gap width A and B (P＞0.05). C, D and E were statistically significant compared with A and B (P＜0.05).　Conclusions　The gap width of 0.1~5 is small, the tightness is high, and the root canal filling effect is the best.

Key words: Root canal wetness, 　Tightness, 　Root canal filling, 　Scanning electron microscope