This case report describes the treatment and management of occlusion for a patient with hemifacial microsomia. A girl aged 4 years and 8 months was transferred to Tokyo Dental College, Department of Orthodontics for orthodontic diagnosis, preparation of distraction osteogenesis, and for management of occlusion during and after distraction osteogenesis. The patient was diagnosed with right hemifacial microsomia (Pruzancky grade II) with facial asymmetry and occlusal cant. In preparation for distraction osteogenesis, to enable traction from the upper-right deciduous molars to the lower-left deciduous molars, a trans-palatal arch and lingual arch were delivered to the maxillary and mandibular arch, respectively. At 6 years and 4 months, mandibular distraction osteogenesis was performed. A Zurich pediatric ramus distractor was used. Latency period was five days, and the rhythm of distraction was 0.5 mm twice a day. The direction of distraction was parallel to the mandibular ramus. The total amount of lengthening was 17 mm and the consolidation period was seven months. To keep the occlusion from changing, traction by elastics was done from the upper-right (affected side) deciduous molars to the lower-left (normal side) deciduous molars. By distraction osteogenesis, facial symmetry was obtained without destruction of occlusion such as open bite or lateral cross bite. Afterwards, an activator as a functional appliance was delivered to keep an even cant of the occlusal plane and growth was observed. However, because of the different growth potential between the normal and affected condyle, facial asymmetry recurred. Therefore, at 18 years and 7 months, two-jaw surgery was performed at Tokyo Dental College Chiba Hospital, followed by post-operative orthodontic treatment. At 19 years and 8 months retention was initiated. In cases where distraction osteogenesis is performed in the growing period, it is essential to explain beforehand that there is a possibility of recurrence of facial asymmetry and secondary surgery.
