<scp> <i>Enterococcus faecalis</i> </scp> and Endodontic Treatment Failure: A Qualitative Systematic Review of Its Role and Elimination Strategies

The aim of this study was to synthesize evidence on the influence of Enterococcus faecalis on endodontic treatment failure and strategies for its elimination. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered in PROSPERO (CRD420251022741). PubMed and SciELO were searched using PICO terms, and 76 studies (1997 and 2025) met the inclusion criteria. Reported E. faecalis prevalence ranged from approximately 4%-78%, depending on detection methods and sampling strategies. Canal isolates frequently expressed virulence factors, formed biofilms, and survived alkaline pH and nutrient limitation, with multidrug resistance reported. Chemo-mechanical preparation with sodium hypochlorite and EDTA, often combined with ultrasonic activation, reduced intraradicular bacterial load but achieved complete sterilization. In retreatment, two-visit protocols with intracanal medication improved microbiological outcomes, although calcium hydroxide efficacy depended on vehicle and duration. Adjunctive approaches showed mainly in vitro promise. Optimised disinfection and sealing remain essential.