ABSTRACT
The purpose of the present study was to determine the effect of 17% Ethylene, di-amine, tetra-acetic acid [EDTA], 6% phosphoric acid and Erbium: Yttrium, Aluminum, Garnet [Er:YAG] Laser in removing the smear layer by scanning electron microscopy. In this study, 80 single-rooted human teeth were selected. Instrumentation was done by use of hand files and step-back technique up to file #40 at apical and file #80 at coronal area. During instrumentation, 1ml of 5.25% sodium hypochlorite [NaOCl] was used as irrigation between each file. The teeth were randomly divided into four groups with different methods of smear removal.17% Ethylene, di-amine, tetra-acetic acid was used in group 1, 6% Phosphoric acid in group 2, Erbium: Yttrium, Aluminum, Garnet laser in group 3, and no intervention in group 4 [as control]. Roots were then longitudinally sectioned and prepared for scanning electron micrograph in cervical, middle and apical areas. Data were analyzed by Kruskal-Walis, Mann-Whitney, Friedman and Wilcoxson tests [P<0.05]. The results showed a significant difference in smear layer removal between three methods in favor of the EDTA [P<0.001] and Phosphoric groups [P<0.001] with no significant difference between them [P=0.49]. Although Er:YAG laser showed some limited ability to remove the smear layer, the effectiveness was not significantly different from the control group [P=0.157]. Based on the findings of this study, EDTA and Phosphoric acid were effective methods to remove smear layer from the root canal walls but Er:YAG laser showed less efficacy compared to the other experimental groups