During the period of teething (3 to 5 years old) and the period of tooth replacement (6 to 11 years old), general malocclusion such as individual teeth misalignment does not require immediate orthodontic treatment and should continue to observe and correct bad oral habits, because during this period, the teeth and jaws are in a period of adjustment, and with the correction of bad habits, malocclusion can often partially correct itself. This is a time of rapid growth and development, and inappropriate orthodontic forces can interfere with development. However, for malocclusions that seriously impede growth and development, initial orthodontic treatment is required. For example, malocclusion can hinder the development of the upper jaw and affect the appearance of the face and should be treated early. If the child can cooperate, it can be corrected at the age of 3 to 5. Another example is severe mandibular recession, which can be treated early during the teething period (7-10 years old) to stop its development to a serious level and reduce the difficulty of subsequent orthodontic treatment. Severe torsion of the permanent incisors can also be treated during the period of dentofacialization. Most malocclusions are not corrected until the permanent period when teeth are replaced, about 12 to 14 years of age. This is because the permanent tooth roots are gradually developed and the occlusal relationship between the upper and lower teeth is adjusted, so that a clear diagnosis of the type of malocclusion can be made and the appropriate orthodontic treatment can be adopted. After the completion of orthodontic treatment, it is easy to maintain a stable effect and there will be no major changes. Theoretically, the best age for orthodontic treatment of malocclusion in children is during the growth spurt of children. Boys are between 12 and 14 years old and girls are between 11 and 13 years old. However, there are individual differences in the growth and development of each child, and no generalizations can be made. The correct way to estimate the growth spurt is through certain tests. Such as taking wrist X-rays, continuous height measurements, knowing the first menstrual period of women, and paying attention to children’s shoes, socks, clothing and hats. Correction during this period is a short course of treatment with good results. If you miss this period, such as 15 to 17 years old, still in the adolescent period, growth and development is still relatively active, although the difficulty increases slightly, but the correction effect is also better. If after the age of 18, entering adulthood, growth and development is basically completed, the orthodontic effect is not as good as in childhood and adolescence. However, for severe bony malocclusion, patients who cannot be treated with orthodontic treatment alone should wait until the age of 18 and later in adulthood to be treated with surgical procedures.