Relapse after orthodontic treatment is a serious problem encountered by doctors and its related factors: (1) Relapse of orthodontic treatment is directly related to the orthodontic plan, for example, during the orthodontic treatment, move the teeth to slowly apply light force, orthodontic force is too strong or exceed the limit of correction. (2) Relapse is easily caused by the failure of coordination and balance between teeth, periodontium, jawbone and muscles. (3) The effect of orthodontic treatment will not be stable if the bad habits that caused the deformity are not completely eliminated. (4) Orthodontic treatment is usually carried out in the early stages of permanent dentition and takes about 18-30 months, mostly ending at the age of 14-15 years. However, vertical and longitudinal growth and development often continues for several years later, even into adulthood. If the patient’s jaws continue to grow and develop in the same way after orthodontic treatment, the malocclusion will reappear. (5) When the third permanent molar develops and erupts, especially in the case of anterior inclination and horizontal blocking, there is a forward pushing force that may cause relapse.