Unilateral scissors bite treated by posterior segmental maxillary osteotomy and corticotomy-assisted mandibular expansion

Unilateral scissor bite is one of the rare forms of malocclusion that is accompanied by deep bite and collapsed arch. This report describes the treatment of unilateral scissors bite improved by maxillary and mandibular posterior segmental osteotomy with orthodontic treatment. The patient was a 16-year-old woman with unilateral collapsed maxillary and mandibular arch and a scissor bite of the right buccal segment, and without facial asymmetry. At first, intrusion of right maxillary molars with implant miniscrew was planned, but failure to move. To improve, posterior segmental subapical maxillary osteotomy and mandibular corticotomy were applied without changing facial appearance. Following the surgery, the expansion of the collapsed right mandibular segment bucally using an appliance during comprehensive orthodontic treatment was planned. There was no sensory or motor paralysis. After post-surgical orthodontic treatment, her occlusion improved without alteration of facial appearance and disorder of her speech. Transverse widths at the maxillary premolars and first molars were nearly stable over the 4 years postoperative interval in our patient, and her overall long-term stability showed excellent results. To our knowledge, this case was the first case to combinate two segmental subapical osteotomies without Le Fort I and sagittal split ramous osteotomy. The results indicate that this technique is useful for unilateral expansion of distorted mandibular alveolar process and maxillary and mandibular subapical osteotomy with subsequent orthodontic treatment can be used to successfully treat unilateral scissor bite.