Root canal disinfection strategies in persistent endodontic infection

Abstract

Persistent endodontic infections remain a significant challenge in root canal treatment, primarily due to the survival of microorganisms within complex anatomical structures and their ability to form resistant biofilms. Despite improvements in endodontic instruments, irrigation systems, and antimicrobial agents, complete elimination of microbial communities from infected root canals remains difficult. Biofilm-associated microorganisms exhibit increased tolerance to antimicrobial substances and unfavorable environmental conditions, allowing them to persist within dentinal tubules, lateral canals, isthmuses, and apical ramifications. Enterococcus faecalis has been frequently associated with persistent infections because of its ability to penetrate dentinal structures, withstand nutrient deprivation, and tolerate alkaline environments. Effective root canal disinfection involves mechanical instrumentation, chemical irrigation, and intracanal medication to reduce microbial populations and prevent reinfection. Sodium hypochlorite remains the most widely used irrigant because of its broad antimicrobial activity and tissue-dissolving properties, while chlorhexidine, ethylenediaminetetraacetic acid, and calcium hydroxide contribute to different stages of disinfection. However, conventional irrigation methods may provide insufficient antimicrobial penetration in anatomically inaccessible regions. Advanced techniques, including passive ultrasonic irrigation, sonic activation, laser-assisted irrigation, and antimicrobial photodynamic therapy, have demonstrated potential for improving irrigant distribution, disrupting biofilms, and enhancing microbial reduction. Disinfection efficacy is influenced by several factors, including root canal morphology, irrigant concentration, contact time, microbial composition, and the presence of organic debris. Clinical outcomes are closely associated with the extent of microbial elimination, preoperative periapical conditions, treatment quality, and the prevention of coronal leakage. Persistent microbial contamination may contribute to delayed periapical healing and unfavorable treatment outcomes, even following technically adequate procedures. Integrating effective chemical disinfection with appropriate mechanical preparation and irrigant activation may improve microbial control and support long-term treatment success. Further clinical investigations are necessary to establish standardized disinfection protocols and determine the long-term effectiveness of emerging antimicrobial technologies in persistent endodontic infections.