Comparative Evaluation of Smear Layer Removal Efficacy of Ethylenediaminetetraacetic Acid (EDTA) Gel Versus Solution With Sonic Activation: A Scanning Electron Microscopic Study

Introduction: During root canal instrumentation, a smear layer forms on the dentinal walls, which may hinder effective disinfection. Ethylenediaminetetraacetic acid (EDTA) is commonly used to remove this layer through calcium ion chelation. This study aims to compare the smear layer removal efficacy of EDTA gel and EDTA solution when used with sonic activation, evaluating their performance in the coronal, middle, and apical thirds of single-rooted human teeth using scanning electron microscopy (SEM). Methodology: Sixty freshly extracted single-rooted human teeth were randomly allocated into four groups (n = 15 each): Group 1 (17% EDTA gel), Group 2 (19% EDTA gel), Group 3 (17% EDTA solution), and Group 4 (18% EDTA solution). Following standardized biomechanical preparation to size #30/.04 taper using NeoEndo rotary files (Orikam Healthcare India Pvt. Ltd., Haryana, India) and 5% sodium hypochlorite (NaOCl) irrigation, each assigned irrigant (5 mL) was delivered with a 30-gauge side-vented needle and immediately activated using a sonic activator system (25/04 tip, 10,000 rpm) for one minute. Specimens were longitudinally sectioned, sputter-coated, and examined by SEM at ×1000 magnification. Smear layer presence at coronal, middle, and apical thirds was scored. Data were analyzed by one-way ANOVA and post-hoc Tukey’s test (p < 0.05). Results: Statistically significant intergroup differences in mean smear layer scores were observed (F = 24.10, p = 0.001). Group 4 (18% EDTA solution) demonstrated the lowest mean score (1.48 ± 0.30), indicating superior smear layer removal, while Group 1 (17% EDTA gel) recorded the highest mean score (2.55 ± 0.34), reflecting the poorest efficacy. Post-hoc Tukey analysis confirmed significant differences between solution and gel groups (p < 0.001). Segment-wise analysis revealed the greatest intergroup variation at the apical third (F = 31.48, p < 0.001). Intragroup analysis demonstrated statistically significant deterioration of cleaning efficacy from coronal to apical in gel groups (Group 1: p = 0.004; Group 2: p < 0.001), whereas solution groups showed uniform performance across all thirds (p > 0.05). Conclusion: Within the limitations of this in vitro study, EDTA solution formulations were significantly more effective than gel formulations in smear layer removal under sonically activated conditions. The 18% EDTA solution provided the most consistent and superior cleaning across all canal thirds, particularly at the apical level, suggesting that solution formulations should be preferred when sonic activation protocols are employed.