Background/Purpose: Successful endodontic therapy depends on effective chemo mechanical debridement and elimination of the smear layer, which may hinder sealer penetration and compromise long-term sealing. This study aimed to compare the smear layer removal efficacy of sodium hypochlorite (NaOCl) with etidronic acid (HEBP), 17% EDTA, and silver nanoparticles (AgNPs) using scanning electron microscopy (SEM).

Materials and Methods: Eighty extracted mandibular premolars were decoronated to 12 ± 1 mm and instrumented with rotary NiTi files. Samples were divided into four groups (n = 20) according to the final irrigant: Group 1 – saline (control), Group 2 – NaOCl + HEBP, Group 3 – 17% EDTA, and Group 4 – AgNPs. Roots were longitudinally split, gold sputter-coated, and examined under SEM (×1000). Smear layer removal was scored using the Torabinejad criteria. Statistical analysis was performed using one-way ANOVA and Tukey’s post hoc test (p < 0.05).

Results: All irrigants were significantly more effective than saline (p < 0.05). AgNPs exhibited the lowest mean smear layer score [1.43 ± 0.08], indicating superior overall efficacy, particularly in the coronal third (mean = 1.00). EDTA showed the greatest smear layer removal in the apical third [0.55 ± 0.129]. NaOCl + HEBP improved cleanliness compared with saline but was less effective than EDTA or AgNPs in removing inorganic debris.