RESUMEN
Abstract: Endodontic infections are considered to be caused by the presence of various microorganisms within the root canal system. Recognition of this microbiota contributes to the successful treatment of infected root canals. This study investigated the microorganisms associated with primary and secondary endodontic infections via culture methods, biochemical tests, and molecular approaches in an Iranian population. Microbial specimens were collected from 36 patients with primary endodontic infection and 14 patients with a history of root canal therapy. Advanced microbiological culture techniques were used to isolate microbiota; subsequently, biochemical tests and 16S ribosomal RNA gene sequencing were performed to identify the microorganisms. Within the total 218 cultivable isolates, Veillonella parvula (20.6%) was found to occur with the highest frequency in primary endodontic infection, followed by Porphyromonas gingivalis (14.1%), and Aggregatibacter actinomycetemcomitans (9.2%). Enterococcus faecalis (36.6%) was the most predominant microorganism in secondary endodontic infections, followed by Candida albicans, Propionibacterium acnes, and V. parvula with frequencies of 20%, 2%, and 2%, respectively. It was concluded that V. parvula and E. faecalis was most frequently found in primary and secondary endodontic infections, respectively.