Treatment of unilateral posterior crossbite with facial asymmetry in a female patient with transverse discrepancy

•Consideration of hidden functional shift by compensated dentition is important.•Orthognathic surgery may not be necessary to correct Class I facial asymmetry.•Arch relationship can be normalized by decompensation of a compensated dentition.•Minimally invasive treatment can correct a unilateral posterior crossbite with a transverse discrepancy.

A unilateral posterior crossbite with facial asymmetry is difficult to correct with orthodontic treatment alone. This case report describes the orthodontic treatment and additional plasty without orthognathic surgery for a 19-year-old woman with a transverse discrepancy. The posterior crossbite was resolved by expansion of the narrow maxillary arch and space closure in the mandibular arch. This accelerated the correction of the functional shift of the mandible. After resolution of the unilateral posterior crossbite, the problems of the anteroposterior molar relationship were treated using orthodontic mini-implants. Mandibular angle reduction plasty was performed for the asymmetric mandibular border to improve the facial appearance. After treatment, the patient had a more symmetrical facial appearance, normal overjet and overbite, and midline coincidence. The treatment results remained stable 1 year after treatment. This case report demonstrates that a minimally invasive treatment can successfully correct a unilateral posterior crossbite with a transverse discrepancy.