Effect of manual dynamic activation with citric acid solutions in smear layer removal: A scanning electron microscopic evaluation

BACKGROUND/PURPOSE: Chelating agents have been used for the removal of the smear layer on teeth. However, due to inadequate volume and/or penetration of the solutions during irrigation, smear layer removal is less effective in the apical third. The purpose of this study was to compare the efficacy of three chelating solutions with and without manual dynamic irrigation in smear layer removal. MATERIALS AND METHODS: Sixty-six single-root canal teeth were decoronated, instrumented, and divided into six experimental groups (n = 10) and two control groups (n = 3). The groups received a final rinse with 1 mL of 17% EDTA and 5% or 10% citric acid (CA) for 1 minute, with or without manual dynamic activation, followed by a final 3-mL rinse with 4.2% NaOCl (5 minutes). The teeth were then longitudinally split and prepared for environmental scanning electron microscopy analysis. Digital images (500×) were taken for smear layer removal evaluation at 2 mm, 6 mm, and 10 mm from the working length. RESULTS: The most effective smear layer removal occurred with 5% and 10% CA combined with manual dynamic activation (Groups 7 and 8), where significant differences were observed when compared with the EDTA groups (Groups 2 and 6; P < 0.05). We found no significant differences between manual dynamic activation with 5% and 10% CA (Groups 7 and 8) in smear layer or debris removal (P > 0.05). CONCLUSION: Manual dynamic activation of CA improves smear layer removal, and a reduction in CA concentration to 5% does not compromise smear layer removal in comparison with higher concentrations.