Chewing on one side for a long period of time is known as deviated chewing. If it occurs during the growth period, the crookedness of the mouth may be caused by the developmental disorder of the mandible, and if it occurs in adulthood, the crookedness of the mouth may be caused by the joint disease, and it can be improved to different degrees through corresponding treatments. 1. Mandibular development disorder: Chewing on one side of the jaw can lead to asymmetrical development of the length of the mandible and the angle of the mandible, and insufficient development of the height of the condyle, which leads to the symptom of a crooked mouth, and orthognathic surgery is needed to correct the shape of the mandible, which can alleviate the symptom of a crooked mouth. 2. Joint disease: chewing on one side for a long time will cause one side of the temporomandibular joints to be used too often, and the long time overload will cause temporomandibular joints to become diseased, and then medical intervention is needed, such as physiotherapy, treatment of joint diseases, and adjustment of the symptoms of crooked mouth. There may be other reasons for the crookedness of chewing on one side of the mouth, so it is recommended to go to the hospital in time for targeted treatment.