The Effect of EDTA and Citric Acid on Smear Layer Removal of Mesial Canals of First Mandibular Molars, A Scanning Electron Microscopic Study

Background: The purpose of this in vitro study was to determine the effect of EDTA and citric acid on smear layer removal in different regions of root canals. Methods: In this study, mesial roots of 48 freshly extracted human mature mandibular first molar teeth with curved mesial roots of about 15-45 degrees and lengths of 20-23 mm were used. Instrumentation was done using the crown down technique by hand and rotary filing. Irrigant used during instrumentation was NaOCl. The teeth were divided in three groups. The mesial canals of teeth were irrigated by 17% EDTA in group I, 7% citric acid in group II and 5.25% NaOCl in group III as the control group. Then, the mesial roots were split in to two parts and studied under scanning electron microscopy. Results: The degree of cleanliness by 17% EDTA and 7% citric acid were 96.55% and 95% respectively. Although both solutions seem to be appropriate, their difference was statistically significant (P<0.05) and EDTA proved better than citric acid especially in middle and apical thirds of canals. The smear layer removal in apical area was less than that in other areas and was maximum in the middle third. However, the removal of smear layer in apical area was acceptable in both groups. Conclusion: It seems that use of both 17% EDTA and 7% citric acid offer desired results and they can remove smear layer from narrow and curved canals especially from apical region. Keywords: EDTA, citric acid, smear layer, irrigation