Targeted detection and antimicrobial susceptibility of common pathogens of failed root canal treatments: A cross-sectional study.

BACKGROUND: Pathogens persisting in the root canals lead to endodontic treatment failure. Understanding their prevalence and antimicrobial susceptibility is essential for improving disinfection and treatment outcomes. OBJECTIVE: To estimate the prevalence of five specific pathogens in failed root canal treatment cases using both culture-based and molecular methods and to evaluate the association between pathogen detection and clinical/radiographic findings and assess the antimicrobial susceptibility of the isolates. METHODOLOGY: One hundred samples were collected using the absorbent paper point method and analyzed using culture and multiplex quantitative polymerase chain reaction (qPCR) for the detection of Enterococcus faecalis, Candida albicans, Streptococcus mutans, Fusobacterium nucleatum, and Porphyromonas gingivalis. Antimicrobial susceptibility testing was performed on culture-positive isolates (n = 34). Statistical analysis included the Chi-square test, Fisher's exact test, and logistic regression. P < 0.05 was considered statistically significant. RESULTS: Detection rates were 29% by culture and 82% by qPCR, with E. faecalis frequently identified. No statistically significant association was observed between pathogen detection and clinical/radiographic findings. Isolates were relatively more sensitive to combined antibiotic formulations than individual antibiotics and resistant to calcium hydroxide under test conditions. CONCLUSION: Failed root canal treatments demonstrated a high prevalence of persistent pathogens, which are better detected by molecular methods. Observed antimicrobial resistance (AMR), particularly to conventional intracanal medicaments, highlights the growing concern of AMR in endodontic infections and the need for better disinfection strategies.