Effect of passive ultrasonic irrigation and manual dynamic irrigation on smear layer removal from root canals in a closed apex in vitro model

AIM: To compare the effect of passive ultrasonic irrigation with manual dynamic irrigation on smear layer removal from root canals using a closed apex in vitro model. METHODS: The root canals of 45 freshly-extracted human single-rooted mandibular premolar teeth were prepared by the Pro-Taper rotary system to an apical preparation of F4 size. Prepared teeth were randomly divided into three groups; two experimental groups and one control group (n = 15) on the basis of the type of activation of final irrigation as follows: (a) Group A, 3% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA), no activation received; (b) Group B, 3% NaOCl and 17% EDTA, ultrasonic activation with a small file; and (c) Group C, 3% NaOCl and 17% EDTA, manual activation with a master gutta-percha point. The prepared teeth were decoronated and split into two halves longitudinally, and observed under a scanning electron microscope to assess the removal of the smear layer. RESULTS: In the apical-third region, the mean smear scores for groups B and C were significantly less than those of Group A (control group) (P < 0.05). CONCLUSION: Both activation techniques are important adjuncts in removing the smear layer, with manual dynamic activation being a simpler, safer, and more cost-effective technique.