The Effect of Smear Layer on Root Canal Microleakage

Objectives: To compare the effect of smear layer on the coronal microleakage of root canals sealed with AH Plus sealer. Methods: Forty five extracted premolar teeth with fully developed apices were selected. The crowns were removed 1-2 mm coronal to the cemento-enamel junction. The root canals were instrumented using the step-back technique up to a size 50. Forty four canals were irrigated with 3% sodium hypochlorite solution (NaOCl). One tooth was prepared without irrigation and served as a control for the SEM examination. The teeth were randomly divided into two groups with 22 teeth in each. Group 1 was then irrigated with 18% Ethylene diamine tetra-acetic acid (EDTA) and 3% NaOCl and Group 2 was irrigated with 3% NaOCl only. The canals were dried and obturated with AH Plus sealer using the single cone gutta-percha technique. After immersion in 2% methylene blue dye, the roots were sectioned at the coronal, middle and apical thirds. The dye penetration was measured using a light microscope at 100x magnification. Two roots from each group were split vertically and examined under scanning electron microscope. Results: Both groups showed coronal microleakage. However, no statistically significant differences were found in the levels of coronal leakage between the two experimental groups (Fisher's exact test, p< 0.05). The use of EDTA+NaOCl in Group 1 resulted in better cleaning as compared to NaOCl in Group 2. Both groups showed poor cleaning in the apical third of root canals. Conclusions: The use of EDTA and NaOCl removed the smear layer and caused clear opening of the dentinal tubules in the coronal and middle thirds, but less so in the apical third of the root canals. There was no statistically significant difference in coronal leakage when using AH Plus sealer in the presence or absence of the smear layer.