Comparison of the efficacy of maleic acid, ethylenediaminetetraacetic acid (EDTA) and phosphoric acid in removing the smear layer from the root canal: A scanning electron microscopic study

Introduction: The aim of this in vitro study was to compare the efficacy of 17% EDTA, 5% maleic acid and 6% phosphoric acid in removing the smear layer using scanning electron microcopy. Materials and Methods: In this in vitro study, eighty human single-rooted teeth were selected and divided into three experimental groups (n = 25) for the application of 17% EDTA, 5% maleic acid and 6% phosphoric acid in order to remove the smear layer and one negative control group (n = 5). The canals of all the teeth were prepared using the step-back technique up to #40 in the apical area and up to #80 in the coronal area. Then final irrigation was carried out using 5 mL of one of the experimental solutions with a 30-gauge needle for 1 minute in each group. The teeth were then cut longitudinally and split into two halves by wedging action and the canal surfaces were viewed under SEM in the coronal, middle and apical areas. The photomicrographs were scored by two observers according to the extent of the smear layer removal. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests to compare the groups and Friedman and Wilcoxson tests to compare different areas (α = 0.05). Results: No significant differences were observed between the three solutions (p value = 0.642). The cleanest area was the coronal followed by the middle and apical areas (p value = 0.001). Conclusion: All the three solutions were similarly effective in removing the smear layer from the root canal walls.   Key words: Maleic acid, Phosphoric acid, Scanning electron microscopy, Smear layer