If a patient presents with asymmetry of the bones on both sides of the face, there is often an associated deformity of the facial skull or surrounding soft tissues. There are several possible reasons for this condition: 1. Congenital developmental causes. Some patients do develop bilateral facial asymmetry during the process of development, and this condition often has a corresponding family history, that is, many people in the family have this condition. 2, may be due to the wrong sleeping posture and caused. Many patients are accustomed to lying on one side for a long time, and when lying on the side more forceful, or have excessive turning, which causes a side of the skull to be overly squeezed, and then produce deformity. 3, may be due to improper occlusion and caused. Many patients are used to using one side to chew, and also like to eat harder food, which will cause one side of the bite muscle is too inflated, while the other side of the bite muscle has produced atrophy. This may also lead to bone deformities in the maxilla and mandible. 4, may be caused by trauma. Some patients have facial trauma, resulting in local fractures or dislocations, followed by this asymmetric situation.