1·Methods: To observe the gaps between material and the walls of canals by scanning electron microscope, the apical sealing ability of material by dye penetration method.
方法：采用染料渗漏法和扫描电镜观察新型聚氨酯液体根充材料与根管壁之间的密合度及其对根尖孔的封闭能力。
2·Conclusions: the variation of tooth position could affect the magnitude and direction of the main apical stress, in which the symmetry of the occlusion type was also involved.
结论：牙在下颌骨上相对位置的变化会对其根尖主应力大小及方向产生一定的影响，而且其影响程度还会受到咬合对称性等因素的影响。
3·Conclusions fe Compound Enzyme was a safe and effective drug for controlling the local infection of acute apical periodontitis.
结论FE复合酶是一种安全、有效的控制急性根尖周炎的局部使用药物。
4·Patients with acute or chronic apical periodontitis were randomly selected, and their symptoms were recorded before treatment.
随机选择急慢性根尖周炎患者，记录患者用药前各项临床体征。
5·Apical positioning and root canal measurement are the key to the success of the toot canal treatment.
根尖定位和根管长度测量是根管治疗术是否能够成功的关键。