In facial asymmetry cases, it is necessary to increase the amount of mandibular setback of the non-deflection side during surgery in order to improve mandibular deviation. We present a case of jaw deformity with facial asymmetry treated by extraction of both maxillary first premolars and the mandibular right first premolar, together with orthognathic surgery.
A male patient, 20 years and 11 months old, who was concerned about the crowding of his front teeth and mandibular deviation, visited our clinic. Intraorally, he had Angle ClassⅢmalocclusion on both the left and right sides, because the mandible showed deviation to the right, but there was no major laterality in the molar tooth relations due to mandibular right molar mesial displacement. Furthermore, there was crowding among the front mandibular teeth.
Cephalometric analysis indicated a ClassⅢskeletal pattern with SNA of 78.8°, SNB of 83.6°, and ANB of －4.8°, as well as mandibular deviation towards the right side. Labial inclination of the maxillary anterior teeth （U1 to SN） was 124.2°, and lingual inclination of the mandibular anterior teeth （L1 to mandibular） was 81.5°.
The patient was diagnosed as skeletal ClassⅢwith edge-to-edge occlusion with midline shift caused by mandibular deviation towards the right side.
We decided to extract both maxillary first premolars and the mandibular right first premolar, and to employ a multi-bracket system. Thereafter, the patient underwent mandibular setback by sagittal split ramus osteotomy. The amount of mandibular setback was approximately 13mm on the left, and approximately 5mm on the right, such that the right molar relationship was ClassⅠand the left was full-step ClassⅡ. In cephalometric results, the SNB angle decreased from 83.6° to 81.1°, and the ANB angle improved from －4.8° to －2.4°. A proper overbite （＋2.0mm） and overjet （＋2.5mm） were obtained. In short, we were able to establish facial symmetry and effectively correct the midline shift.
Asymmetric extraction in consideration of facial asymmetry improved the shift of the midline and the facial asymmetry, and was extremely effective.
