Objectives: The purpose of this study was identify cultivable microorganisms from primary endodontic infections in the apical third, in vivo. Methods: The study sampled included 20 subjects who attended the Graduated Endodontics Clinic in the Faculty of Dentistry, University of San Luis Potosi, Mexico. Single-and multi-rooted teeth were selected, that had a negative response to thermal pulp tests, periapical radiolucency, sufficient tooth structure for proper rubber dam isolation, no previous history of endodontic treatment, and complete root formation. Samples were processed inside an anaerobic chamber (85% N2, 10% H2, 5%CO2 ) (Coy Laboratory Products, Grass Lake, MI, USA). Speciation was based on colony morphology, type of hemolysis, cell morphology, Gram-staining reaction, catalase and oxidase positivity, and the ability to grow in air supplemented with 10% CO2. All microorganisms were characterized using identification kit API 20A (Analytical Profile Index; Biomeriéux, France). Conventional biochemical tests were also used to supplement the commercial kits when necessary. .
Results: Sixteen species were identified, more common genus were, Bacteroides (29/60), Actinomyces (27/60), Bifidobacterium (17/60), Streptococcus (14/60). Bacteroides ovatus was the most common bacteria isolate (11/21). The range of species found per canal was 1 to 9, been mostly obligate anaerobes. 94.16% of the taxa identified by culture were obtained.
Conclusion:. The polymicrobial nature and the predominance of Gram-negative rods in primary endodontic infections has been confirmed by this study. Also, that the culture method is an useful tool to identify microorganisms of the endodontic infections.