1. Chewing period: Children in this age group are generally 3-6 years old. The arrangement of children's deciduous teeth is not very neat, but at this time, children's deciduous teeth are relatively stable. The course of treatment is almost six months. Early correction of children's teeth is of great benefit to children's tooth development. If not corrected in time, it may aggravate the abnormal development of teeth.

2. Mixed dentition: The child's age is about 7- 1 1 year. At this time, the child's teeth will grow rapidly, which is the high incidence period of tooth deformity. The main reason is due to bad eating habits. At this time, it is necessary to use orthoses according to different situations, and even cooperate with external plastic surgery to correct the arrangement of children's teeth.

3. Permanent tooth period: At this time, the child's age is about 12- 18 years old. At this time, all the deciduous teeth have been replaced, and the big teeth are growing rapidly. At this time, the diagnosis of tooth deformity is more clear, and the correction is faster and the effect is stable.