First, the deciduous teeth stage: malocclusion or malocclusion (partial occlusion) of deciduous teeth should be corrected as soon as possible. The treatment age is about 3 ~ 6 years old. At this time, the child's permanent teeth have not erupted, and the roots of deciduous teeth have not been absorbed and are relatively stable. It can be corrected by wearing oral appliance for about 6 months. If it is not corrected in time, it may aggravate the deformity in this rapid growth period. Therefore, the first best period of orthodontics is 3-6 years old.

The second is mixed dentition: about 7 ~ 1 1 year. At this time, new permanent teeth began to erupt, teeth grew rapidly, and occlusion was unstable, which was the frequent period of tooth deformity. The main reason is that deciduous teeth fall off prematurely, which leads to the reduction of dental arch length, which in turn leads to the inability to arrange teeth. Such children should be regarded as gap holders. The deciduous teeth fall off prematurely and close the gap, which leads to insufficient eruption space of permanent teeth and tooth deformity. The gap should be repaired with orthodontic appliances. Tooth deformity caused by bad oral habits or hobbies can be corrected by removable or fixed appliances or even external plastic force according to different situations while overcoming and changing bad habits. This stage is the best time for orthodontics the next day.

Third, the permanent tooth period: It can be said that the permanent tooth period is the best period for orthodontics, because all the deciduous teeth have been replaced at this stage, and the second and third big teeth are in another rapid growth period, generally around 12 ~ 18 years old. At this time, the diagnosis of tooth deformity is clear, and the correction speed is fast and the correction effect is stable in this rapid growth period.