Comparative Evaluation Of Neem Extract, Green Tea Extract, And Sodium Hypochlorite On Smear Layer Removal And Dentinal Tubule Penetration: An In Vitro Scanning Electron Microscopic And Stereomicroscopic Study

Background: Persistence of microorganisms within the smear layer and dentinal tubules is a principal cause of endodontic treatment failure. Sodium hypochlorite (NaOCl) remains the irrigant of choice, but its inability to remove the inorganic component of the smear layer, its cytotoxicity, and its adverse effect on dentin have prompted interest in biocompatible herbal alternatives such as neem (Azadirachta indica) and green tea (Camellia sinensis). Aim: To comparatively evaluate the smear layer removal efficacy and dentinal tubule penetration depth of neem extract, green tea extract, and 3% NaOCl. Materials and Methods: Sixty extracted single-rooted human mandibular premolars were decoronated to a standardized root length of 14 mm, instrumented with ProTaper Gold rotary files to size F3, and divided into three groups of twenty (n = 10 for smear layer evaluation and n = 10 for dentinal tubule penetration per group): Group 1, 3% NaOCl; Group 2, neem extract; Group 3, green tea extract. Smear layer was scored at the middle third under field emission scanning electron microscopy (FESEM, 5000×) using the Torabinejad criteria. Dentinal tubule penetration depth was assessed at the middle third with crystal violet dye under a stereomicroscope (20×). Data were analyzed with the independent samples t-test (α = 0.05). Results: Mean smear layer scores were 2.2 ± 0.4 (NaOCl), 1.3 ± 0.5 (neem), and 2.9 ± 0.3 (green tea) (p < 0.001). Neem showed significantly lower (better) scores than both NaOCl (p = 0.045) and green tea (p < 0.001); NaOCl and green tea were statistically similar (p = 0.086). Mean dentinal tubule penetration depths were 0.51 ± 0.02 mm (NaOCl), 0.59 ± 0.04 mm (neem), and 0.36 ± 0.02 mm (green tea) (p < 0.001), with all pairwise differences significant (NaOCl–neem, p = 0.044; neem–green tea, p < 0.001; green tea–NaOCl, p = 0.029). Conclusion: Within the limitations of this in vitro study, neem extract demonstrated superior smear layer removal and dentinal tubule penetration compared with 3% NaOCl and green tea extract, indicating its potential as an alternative or adjunctive endodontic irrigant. NaOCl retained moderate, reliable performance, while green tea extract was the least effective irrigant for these two parameters.