Abstract: Objective: To compare the removal of smear layer of root canal by Qmix, EDTA and MTAD using scanning electron microscope(SEM). Methods: Forty human mandibular premolar teeth with single canal were taken and decoronated to standardize the canal length to 14mm. Tooth were prepared by S3 rotary system to an root canal preparation of file size 3S, and then randomly divided into 4 groups according to the different final irrigations: 5ml saline for 1 min (Group A; negative control), 5ml 17% EDTA for 1 min (Group B), 5ml MTAD for 1min (Group C), and 5ml Qmix for 1 min (Group D). After the completion of root canal preparation, the teeth were split into two halves longitudinally. The smear layers in the root canal of apical 1/3 (Apical 1-2mm), root 1/3 (Apical 6-7mm), and root 1/3 (Apical 10-12mm) were observed with SEM, and the data were statistically analyzed. Results: The results of group B, C, D group were statistically significant different from that of group A (control group) (P<0.001). And group D was superior to group B and C, group C was better than group B (P<0.001). The coronal thirds of each group was better than the middle thirds of root, and the middle thirds of root was superior to the apical thirds of root (P<0.05). Conclusion: Qmix can effectively remove the root canal smear layer.

Key words: Root canal irrigation, Smear layer, Scanning electron microscope, Root canal preparation, Qmix