Penetration of AH plus sealer into dentinal tubules following diode laser and ultrasonic activation of N-acetylcysteine irrigant: A confocal microscopy evaluation

Introduction: Effective sealer penetration into dentinal tubules is essential for the long-term success of root canal treatment. N-acetylcysteine (NAC), a mucolytic agent with chelating properties, has demonstrated potential in smear layer removal and improving dentin permeability. This study aimed to evaluate and compare the penetration of AH Plus sealer into dentinal tubules following NAC activation using syringe irrigation, diode laser, and passive ultrasonic irrigation (PUI). Materials and Methods: Thirty-nine extracted single-rooted mandibular premolars were decoronated to 14 mm, and canals were instrumented. Samples were divided into three groups ( n = 13): Group I – conventional syringe-activated NAC, Group II – diode laser-activated NAC, and Group III – PUI-activated NAC. AH Plus sealer mixed with 0.1% rhodamine B was placed inside the root canals using a #25 Lentulo spiral, followed by gutta-percha cone placement. Samples were stored at 37°C with 100% humidity for 7 days. Roots were sectioned at 2 mm, 5 mm, and 8 mm levels, and sealer penetration was assessed under confocal laser scanning microscopy. Depth was measured using ImageJ. Statistical Analysis: Data were analyzed using repeated measures ANOVA and one-way ANOVA with Tukey’s post hoc test ( P ≤ 0.05). Results: PUI activation showed the highest sealer penetration, followed by diode laser and syringe irrigation, with significant differences noted, especially in the middle ( P < 0.0001) and apical thirds ( P = 0.0066). The coronal third also showed a significant difference among groups ( P = 0.011). Conclusion: NAC enhances sealer penetration, with PUI being the most effective activation method.