Aim: Curved root canals present anatomical challenges that impede effective cleaning and shaping. Irrigation strategies optimized for these anatomies are critical to enhance debris removal. This systematic review synthesized comparative evidence on active versus passive irrigation for hard-tissue debris removal in curved root canal systems. Methods: Comprehensive searches were performed in PubMed, Scopus, EBSCOhost, Google Scholar, Medline, Lilac, Epistemonikos and gray literature till July 31, 2025. Eligible in vitro and ex vivo studies which directly compared active irrigation modalities with passive needle irrigation in curved canals and reported hard-tissue debris removal outcomes were included for the review. Risk of bias was assessed with the Risk-of-Bias tool for Pre-Clinical Dental Material Research tool. Direct acyclic graph and heat map were generated for the identification of confounders. Owing to heterogeneity in outcome measures and experimental conditions, findings were narratively synthesized without meta-analysis. Results: Fourteen studies (2000–2024) met the inclusion criteria. Most comparisons demonstrated superior debris removal with active irrigation relative to passive irrigation in curved canals, whereas two studies reported no significant difference. Substantial methodological variability precluded quantitative pooling. Conclusion: Within the limitations of in vitro and ex vivo evidence, active irrigation techniques generally achieve greater hard-tissue debris removal than passive irrigation in curved root canals. Standardized outcomes, harmonized activation protocols, and well-designed studies in extracted human teeth and clinical trials are needed to enable meta-analysis and inform practice recommendations.
Singhal et al. (Wed,) studied this question.