1, the final alteration of the facial muscular balance has not yet been completed During the formation of malocclusion, many tissues of the muscular system produce a muscular dynamic balance that is compatible with the malformation. The completion of malformation morphology correction often precedes the transformation of function and power, and the new morphology may also be affected by the old power balance and be in an unstable state leading to relapse. 2, periapical muscle fiber tension is not restored to balance After orthodontic treatment of malocclusion, widening of the periodontal space and periodontal fiber twisting is normal, before they have established a new balance, the tooth is unstable in its new position, especially the twisted tooth, the tension of the gingival connective tissue and periodontal membrane fibers must be maintained until a new balance is established. 3, bad oral habits are not broken Bad habits can lead to abnormal muscle power balance, which is an important causative factor for malocclusion. If the original bad oral habits still exist after correction, it may cause recurrence. 4, upper and lower teeth occlusion has not been balanced The occlusal relationship of teeth is the most powerful factor for the stability of teeth in the new position. The new occlusal state needs to go through continuous tooth wear or manual adjustment to achieve a good contact relationship between the cusp bevels. During its self-adjustment process, the malocclusion has a tendency to recur. 5, the eruption of wisdom teeth Wisdom teeth (third molar) anterior inclination and horizontal obstruction have the force of forward pushing, which can lead to the recurrence of malformation. 6, the impact of growth type Different individuals have their own specific growth trend, this trend is the growth type. Patients who undergo orthodontic treatment in the early stages of permanent dentition are still in the growth phase when the treatment ends, and the jaws still grow in the original way.