Objective To investigate the influence of sealer placement on apical sealability in root canal treatment. Methods 100 extracted single root canal teeth were selected. All canals were prepared by manual Protaper instrument in a step- back way. The samples were divided into 5 groups randomly. A group: 30 samples, sealer placement by chief gutta percha; B group: 30 samples, sealer placement by K file; C group: 30 samples, sealer placement by spreader; D group: 5 samples, a positive control; E group: 5 samples, a negative control. There were 2 subsets in each experimental group which were obturated by lateral gutta percha with or without sealer. Glucose oxidase method was used to measure the apical leakage at the 1st, 2nd, 4th, 7th, 10th, 15th, 20th, 25th, 30th day of the experiment. Results Apical sealability varied with different sealer placement methods（F=4.832, P=0.001）. Sealer placement by chief gutta percha（A group） had the best instant apical sealability. However, lateral gutta percha with or without sealer didn′t affect the apical sealibility. Conclusion Placing the same kind sealer in different ways can affect the apical sealability. There were no significant differences of the apical leakage no matter the lateral gutta percha with or without sealer. In order to get better instant apical sealability and simplify the clinic operation, placing the sealer with a chief gutta percha while the lateral gutta percha without sealer is recommended.
