Introduction: Dental caries is the most prevalent disease in humans and its incidence is particularly high during childhood. The use of medicinal plants is a common practice in Brazil. Objective: To evaluate the optimal antimicrobial concentration of Copaifera langsdorffii (copaiba) oil-resin, in the form of dental varnish, against Streptococcus mutans (S. mutans) in children. Methods: Twenty-four children, car...