Treatment of maxillofacial asymmetry during growth is generally considered to be challenging. There are several theories as to the cause of maxillofacial asymmetry. These causes may be divided into congenital problems and acquired problems. As congenital causes, vascular abnormalities and hemorrhage in the craniofacial area, damage to Meckel's cartilages, and hemifacial microsomia, thought to be the result of abnormal development of cranial neural crest cells (1) . There have also been molec-ularlevel research findings indicating that genetic mutations including NFATC1, SOX5, NBAS, TCF7L1, ENPP1, and ESR1 are involved in leftright facial asymmetry (2, 3) . As acquired causes, early intervention following tooth eruption (4) , early tooth loss (5) , and the effects of sustained external force (6) have been suggested. Mandible morphology also changes depending on the hardness of food (7) , and functional problems such as onesided chewing are also considered to be potential causes (8) . Leftright differences in temporomandibular joint growth also induce facial asymmetry, which are caused by ailments such as tumors and by other unknown factors.