This study describes the course of interdisciplinary treatment for mandibular prognathism in an adult patient with a severe Class III malocclusion and a reverse overjet of 9 mm that involved an orthodontic and surgical orthognathic treatment. The orthodontic treatment involved attaching a fixed appliance to the upper and lower dental arches to prepare the patient for the mandibular surgery. Following the orthodontic treatment, there was performed a bilateral sagittal split ramus osteotomy (BSSRO) in order to reduce the length of the mandible and to reposition the mandibular anterior segment posteriorly. The treatment turned out to be successful. The mandible was shortened and the profile was corrected. The orthognathic surgery was followed by the second step of the the orthodontic treatment of the mandible and maxilla. Now, following three years of treatment and observation, the patient shows a good face profile and occlusion as well as the acceptance of the facial aesthetics.

Key words: orthodontics, osteotomy, malocclusion.