Root canal microbiota of dogs’ teeth with periapical lesions induced by two different methods Flaviana Bombarda de Andrade Ferreira, BDS, MSc, a Helena Rosa Campos Rabang, BDS, MSc, b Ericka Tavares Pinheiro, BDS, MSc, c Cícero Romão Gadê-Neto, BDS, MSc, d Alexandre Augusto Zaia, BDS, MSc, PhD, e Caio Cezar Randi Ferraz, BDS, MSc, PhD, f Francisco José de Souza-Filho, BDS, MSc, PhD, g and Brenda Paula Figueiredo de Almeida Gomes, BDS, MSc, PhD, h Bauru, Londrina, Piracicaba, Rio de Janeiro, and Natal, Brazil UNIVERSITY OF SÃO PAULO, STATE UNIVERSITY OF CAMPINAS, NORTH PARANÁ DENTAL SCHOOL, NAVAL DENTAL CLINIC, AND POTIGUAR UNIVERSITY Objective. The microbial composition was investigated in root canals of dogs’ teeth with periapical lesions induced by 2 different methods: open versus sealed canals. Study design. Teeth from Group I (n = 16) were left open for a week, then sealed with composite resin for 120 days. The teeth from Group II (n = 16) were left open for the same period. Microbiological samples from the root canals were collected and processed by the anaerobic technique for identification and counting of microorganisms after establishment of periapical reactions. Results. Seventy-four cultivable isolates were recovered in sealed canals (Group I). Strict anaerobes accounted for 64.9% of all species isolated, and gram-negative microorganisms accounted for 55.4%. Microbial genera most frequently isolated were Prevotella, Fusobacterium, Peptostreptococcus, Streptococcus, Enterococcus, Clostridium, and Porphyromonas. Statistical analysis by Pearson chi-square or Fisher’s test revealed positive association between sealed teeth and strict anaerobes (P  .05). In open canals (Group II), from a total of 58 cultivable isolates, 19% were strict anaerobes and 81% facultative anaerobes, with predominance of gram-positive species (75.8%). Genera most frequently isolated were Streptococcus, Propionibacterium, Staphylococcus, Neisseria, and Prevotella. Conclusion. Strict anaerobes were most frequently found in sealed teeth rather than in the teeth with canals left exposed to the oral cavity for 4 months. Therefore, the method that induced periapical inflammatory lesions by intentional oral exposure, followed by tooth sealing, produced root canal microbiota similar to the same found in humans. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:564-70) Bacteria invading the root canal system may interact with host tissues and cause periradicular endodontic disease. 1 A number of animal models were used to study the pathogenesis of periapical lesions, 2 the dy- namics of root canal infections, 3 and also the response of periapical tissues after endodontic therapy. 4 In the animal experimental model, certain desirable attributes must be met for the results to represent the human situation. 2 The dog is a suitable animal for endodontic research, 5,6 mainly because of the close similarity in the healing processes of periapical tissues found in humans and dogs. 4 Moreover, as a model in endodontic research, information on the composition This work was supported by the Brazilian agencies FAPESP (2000/ 13689-7), CNPq, and CAPES. a Postgraduate Student, Department of Restorative Dentistry, Endodontic Area, Bauru Dental School, University of São Paulo, São Paulo. b Postgraduate Student, Department of Restorative Dentistry, End- odontic Area, Piracicaba Dental School–State University of Campi- nas—UNICAMP & Affiliated to the Naval Dental Clinic, Brazilian Navy, Rio de Janeiro. c Postgraduate Student, Department of Restorative Dentistry, End- odontic Area, Piracicaba Dental School–State University of Campi- nas—UNICAMP. d Postgraduate Student, Department of Restorative Dentistry, End- odontic Area, Piracicaba Dental School–State University of Campi- nas—UNICAMP. e Associate Professor, Department of Restorative Dentistry, Endodon- tic Area, Piracicaba Dental School–State University of Campinas— UNICAMP. f Associate Professor, Department of Restorative Dentistry, Endodon- tic Area, Piracicaba Dental School–State University of Campinas— UNICAMP. g Associate Professor, Department of Restorative Dentistry, Endodon- tic Area, Piracicaba Dental School–State University of Campinas— UNICAMP. h Associate Professor, Department of Restorative Dentistry, Endodon- tic Area, Piracicaba Dental School–State University of Campinas— UNICAMP. Received for publication July 6, 2004; returned for revision July 14, 2005; accepted for publication Sept 13, 2005. 1079-2104/$ - see front matter © 2006 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2005.08.041 564