Endodontic infections are polymicrobial and predominantly caused by anaerobic bacteria and some facultative bacteria. The list of microorganisms involved in endodontic infections keeps expanding and has the potential to become increasingly more accurate during the next few years. Copaiba oil is an important Amazonian herbal medicine commercialized worldwide. In this study, we evaluated the antimicrobial activity and minimum inhibitory concentration (MIC) of copaiba oil and substances used in the treatment of endodontic infections against anaerobic microorganisms such as Prevotella melaninogenica; Prevotella intermedia; and Clostridium acetobutylicum. The MIC was determined by thioglycollate broth dilution. The data were statistically analyzed by Tukey's parametric and non-parametric methods of Cochran and Kruskal-Wallis test with a confidence level of 99%. The analysis of the antimicrobial activity showed that the samples of Copaiba oil, Sodium Hypochlorite, Otosporin, Tricresol formalin, Chlorhexidine and PMCC showed high antimicrobial activity (p
