Objective: The aim of this study was to compare two methods of induction of periapical lesion. Methods: It were used 58 pre-molars from dogxs teeth. They were divided into 4 groups: I and II – root canals exposition to the bucal environment for 180 days; groups III and IV - root canals exposition to the bucal environment for 7 days, followed by crown sealing for 53 days. In the groups I and III the apical perforation was realized, and in the groups II e IV the apical perforation wasn't realized. After experimental time, the animals were killed and the histological sections was colored by Hematoxiline and eosine or Brown & Breen. Results: The histopathological evaluation of periapical inflammatory lesion and apical and periapical resorption showed less intensity of the parameters to group II (p<0,05). The histomicrobiological evaluation showed microorganisms presence in all root canal system in all groups. More presence of microorganisms were observed in root canal walls, apical ramifications and dentinal tubules, followed by cemental spaces, periapical region and cemental resorption. Conclusion: Both methods induced chronic peariapical reactions and microorganisms were observed in all root canal system and apical cement.