Hamadan University of Medical Sciences Avicenna Journal of Dental Research 2423-7582 18 1 2026 03 29 Enterococcus faecalis in Untreated Root Canal Teeth: A Microbiological Study 1 5 10.34172/ajdr.2147 EN Hadi Hossainpour https://orcid.org/0000-0002-3784-2645 Zahra Nazari Parnia Moradi Naser Vahedian Amirhooshang Alvandi Saber Khazaei Hassan Mahmoudi https://orcid.org/0000-0002-3962-4668 Journal Article 10.34172/ajdr.2147 2024 11 19 2025 02 13 Introduction: Some missteps during procedures, such as insufficient disinfectant use for root canal disinfection or instrumentation, can fail the endodontic treatment. Enterococcus faecalis can adhere to endodontic cements and root canal walls, forming a resistant biofilm. Thus, it is often isolated from root canals in secondary/persistent infection. This study focused on detecting the presence of E. faecalis in teeth with untreated root canals using molecular assay. Methods: In this study, 32 samples of untreated root canals were collected from the Dentistry Clinic of the School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Iran. The existence of E. faecalis in these samples was detected using multiple methods, such as a polymerase chain reaction (PCR) assay based on the 16SrRNA gene and traditional culture. A disk diffusion test (Kirby-Bauer susceptibility test) was used to determine the antimicrobial susceptibility of isolated strains. Results: E. faecalis was detected in six samples (18.75%) using the culture method, but four (66.67%) were confirmed by the PCR method. All E. faecalis isolates were sensitive to vancomycin and showed the highest resistance to ampicillin (100%) and chloramphenicol (83%), respectively. Conclusion: Further research is needed to develop more efficient antimicrobial agents for endodontic treatment. In addition to finding more effective root drugs, more research is necessary to design more efficient three-dimensional filling systems.