Retroconjugation: When your child is still a small set of baby teeth, if they are retroconjugated, treatment can begin as soon as they are able to cooperate and wear the aligners as required by the doctor. It can begin at about three years of age. The upper front teeth that backbite on the inside are usually pushed out in about 3 months with a movable aligner during this period. The movement of the baby teeth is likely to move the permanent tooth germs on the root side along with them, so some patients with retrognathia can be completely cured without recurrence after treatment during the baby teeth period. After tooth replacement, if there is an anticlinal presence, it should also be corrected in time. Severe deep overjet, especially the upper anterior teeth inwardly inclined type of deep overjet, the lower teeth bite into the upper jaw gums. The upper jaw is significantly protruding or the lower jaw is significantly retracting. This is often a precursor of bony deformity and should be treated as early as possible. Bad oral habits: e.g. sucking the lower lip, nail biting, thumb eating, tongue spitting, mouth breathing, etc. As children develop rapidly at this time, these bad habits can easily change the developmental trend of the jaw and stereotype the poor jaw development. If they are not corrected in time, they will not only affect the development of the jaw and face, but also greatly increase the difficulty of orthodontic treatment in the future. Once the bad habits are found, some methods are taken in time, including wearing orthodontic appliances to block the bad habits, which can largely reduce the difficulty of correction in the future, and some of the teeth irregularities that have been formed may be returned to normal soon. Multiple teeth: Multiple teeth that have no significance for retention should be extracted as early as possible, with orthodontic treatment if necessary. Abnormal labial tie: The upper labial tie is attached too low, and it is difficult to close the gap between incisors.