CURRENT CONCEPTS IN ROOT CANAL IRRIGATION: A NARRATIVE REVIEW OF SODIUM HYPOCHLORITE, EDTA, ULTRASONIC, SONIC, AND NEGATIVE PRESSURE IRRIGATION PROTOCOLS

Abstract

Successful endodontic treatment depends on effective cleaning and disinfection of the root canal system, as mechanical instrumentation alone cannot adequately eliminate microorganisms, organic tissue remnants, and the smear layer from the complex anatomy of root canals. Irrigation protocols have therefore become an essential component of modern endodontic therapy, combining chemical irrigants with various activation techniques to improve antimicrobial efficacy and debris removal. Sodium hypochlorite (NaOCl) remains the gold standard irrigant because of its unique ability to dissolve organic tissues and eliminate a broad spectrum of microorganisms, while ethylenediaminetetraacetic acid (EDTA) is routinely used to remove the inorganic component of the smear layer and facilitate dentinal tubule penetration. Recent technological developments have introduced irrigation activation systems, including passive ultrasonic irrigation (PUI), sonic activation devices, and apical negative pressure irrigation, which have demonstrated improved irrigant distribution and enhanced cleaning efficiency compared with conventional syringe irrigation.

This narrative review aims to summarize current evidence regarding the effectiveness of contemporary root canal irrigation protocols and to compare their antimicrobial activity, smear layer removal, debris elimination, irrigant penetration, and clinical safety. A comprehensive literature search was performed using major biomedical databases, with emphasis on systematic reviews, meta-analyses, randomized clinical trials, and influential review articles published between 2006 and 2025.

Current evidence indicates that irrigation activation significantly improves canal cleanliness and irrigant penetration compared with conventional needle irrigation. Passive ultrasonic irrigation consistently demonstrates superior performance in smear layer and debris removal, whereas sonic activation offers effective disinfection with greater simplicity and lower equipment requirements. Negative pressure irrigation systems reduce the risk of apical irrigant extrusion while maintaining adequate irrigation of the apical third. Although no single protocol is universally superior in every clinical scenario, combining sodium hypochlorite and EDTA with an appropriate activation technique appears to provide the most predictable clinical outcomes. Future research should focus on protocol standardization and high-quality clinical trials to establish evidence-based recommendations for routine endodontic practice.