Abstract
Root canal system variations can occur in each tooth group and significantly influence the outcome of the endodontic treatment. Upper first molars often present with some variations, mostly due to the presence of a second mesio-buccal root canal. Other types of atypical root canal system anatomy in upper first molars have also been reported but with a significantly smaller frequency. The aim of this article is to describe a clinical case of a C-shaped root canal configuration in a maxillary first molar - the diagnosis, preparation, irrigation, and final definitive obturation of the root canal system.