removal of smear layer by two endodontic irrigation solutions and erbium: yttrium, aluminum, garnet (er:yag)laser. a scanning electron microscope (sem) study

introduction: 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. methods: 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). results: 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). conclusion: 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.