Hemifacial microsomia (HM) and Russell–Silver Syndrome are a congenital craniofacialmalformation caused by hypoplasia of anatomical structures deriving from the first and second branchial arches. HM involves absence or insufficiency of facial skeleton, soft tissues,ear, and cranial nerves1）.Under these conditions, orthodontic treatment in combination with surgery has been performed in HM patients after growth. However, in case of congenital facial asymmetry, asymptomatic facial expression becomes severe as a result of only the follow–up observation until the end of the growing period. Recently, the therapeutic approach has included the use of an asymmetrical FKO (hybrid FKO) tostimulate the growth of the affected side and consequently to improve symmetry of the mandible deficiency. This study reports on patients of HM treated with a nonsurgical approach using a hybrid FKO and effectiveness of the treatment
