The timing of orthodontic treatment is important. Early intervention can reduce the severity of misalignment, whistling teeth, and ingrown teeth; early treatment can shorten treatment time and reduce treatment discomfort. You will get twice the result with half the effort! I. Teething stage (4~5 years old) Early treatment is beneficial to the development of the maxillary bone, prevention of permanent teeth recession and exposure to occlusal trauma. During this period, if children have bad oral habits, they need to be corrected to prevent the occurrence and aggravation of malocclusion. Second, the replacement phase (during tooth replacement, girls 8~10 years old, boys 9~12 years old). For early patients with functional malocclusion and bony malocclusion caused by bad oral habits, tongue interference and other factors, which should be corrected in time if found. This period is the pre-puberty and peak period of growth and development of children, which should create good conditions for the growth and development of jaws. Third, the early stage of permanent teeth (after tooth replacement, girls 10~14 years old, boys 12~16 years old). Common malocclusion can be well treated at this stage. Most of the permanent teeth have erupted, the arch development is basically completed, the misalignment has been basically set, and the jawbone is still in the growth and development period at this stage, the teeth move easily and the reconstruction of dental tissue is more easily completed, and the patient feels comfortable.