Microbiological and Cytotoxic Profile of Secondary/Persistent Endodontic Infection

Objectives: Secondary/persistent endodontic infections (SEIs) are the primary cause of endodontic failure. Endodontic retreatment (ER) is the main therapeutic option for resolving chronic apical periodontitis (CAP) in endodontically treated teeth. Given the complex microbiota associated with SEIs, this study aimed to profile the microbial (bacteria and fungi) and cytotoxic (LPS and LTA) aspects of root canals (RCs) recommended for ER due to the presence of CAP and correlate the microbial profile and cytotoxic load with clinical and radiographic aspects.
Methods: Microbial samples were obtained from 40 teeth recommended for ER due to endodontic failure. Microbiological and cytotoxic content collection from RCs was performed after obturation removal. The presence of 17 bacterial and 4 fungal species was evaluated using Nested-PCR. LPS assessment was conducted using the LAL test. LTA concentration was determined through ELISA assay. Statistical tests were applied, including Fischer's Exact, Shapiro-Wilk, and Mann-Whitney.
Results: Bacteria and fungi were identified in 100% of cases. The most prevalent species were Enterococcus faecalis, Porphyromonas gingivalis, and Candida albicans. LPS and LTA were found in 100% of cases. Associations with clinical signs and symptoms were observed (p<0.05). The concentration of LPS and LTA present in RCs was linked to clinical signs and symptoms (p<0.05).
Conclusions: In conclusion, the microbiota of RCs with SEIs is diverse and heterogeneous, composed of both fungal and bacterial species. The cytotoxic load associated with RCs is correlated with clinical features, signs and symptoms.