Comparative Evaluation of Depth of Irrigant Penetration Using Different Irrigation Systems: An In Vivo Study

Introduction: Effective irrigation is essential for successful root canal treatment because mechanical instrumentation alone cannot adequately clean the complex anatomy of the root canal system. Various irrigant activation techniques have been developed to enhance irrigant penetration into the apical third and anatomically inaccessible regions; however, clinical evidence comparing their penetration efficiency remains limited. The aim of our study was to compare the depth of irrigant penetration achieved using conventional manual irrigation, passive ultrasonic irrigation, sonic irrigation, air-sonic irrigation, and diode laser-assisted irrigation in the mesial canals of mandibular first molars. Materials and methods: This in vivo study included 50 mandibular first molars requiring primary root canal treatment. Following standardized biomechanical preparation, the teeth were managed using one of five irrigation activation techniques: conventional manual irrigation, passive ultrasonic irrigation, sonic irrigation, air-sonic irrigation (PATS Vario; Innovations Endo, Nashik, India), or diode laser-assisted irrigation (n = 10 per group). Iohexol contrast medium was used to evaluate irrigant penetration, and standardized digital radiographs were obtained. The linear distance between the working length and the maximum extent of dye penetration was measured using dedicated imaging software. Data were analyzed using one-way analysis of variance followed by Tukey's post hoc test, with the level of statistical significance set at p < 0.05. Results: Irrigant penetration differed significantly among the five irrigation activation techniques (p < 0.001, η² = 0.55). Diode laser-assisted irrigation showed the greatest apical penetration (0.33 ± 0.26 mm), followed by sonic irrigation (0.72 ± 0.42 mm), PATS air-sonic irrigation (0.87 ± 0.59 mm), passive ultrasonic irrigation (1.23 ± 0.78 mm), and conventional manual irrigation (2.27 ± 0.88 mm). Pairwise analysis demonstrated significantly better penetration with diode laser-assisted, sonic, PATS air-sonic, and passive ultrasonic irrigation than with conventional manual irrigation (all p < 0.05). Diode laser-assisted irrigation also outperformed passive ultrasonic irrigation (p = 0.028), whereas no significant differences were observed between diode laser-assisted irrigation and sonic or PATS air-sonic irrigation, or among the sonic, PATS air-sonic, and passive ultrasonic irrigation groups (all p > 0.05). Conclusion: Irrigant activation significantly improved apical irrigant penetration compared with conventional manual irrigation. Among the evaluated techniques, diode laser-assisted irrigation demonstrated the greatest penetration efficiency, suggesting its potential to enhance canal disinfection in clinical endodontic practice. Sonic and PATS air-sonic irrigation also provided favorable penetration and may serve as effective alternatives when laser systems are unavailable.