Children can have their teeth straightened when their permanent teeth are complete (about 12 years old). When children appear teeth are not aligned, there are wrong deformities, if not timely correction of teeth, can cause facial appearance is not coordinated, jawbone and soft tissue growth abnormalities, affect chewing function, gums, periodontal inflammation, etc., affecting the children’s life, so often orthodontic. The time for orthodontic treatment is often chosen after the permanent teeth have grown in, about 12 years old. When children are young, their milk teeth have not been replaced by permanent teeth, and the position of their teeth has not been completely fixed, so this time is not suitable for orthodontic treatment. When the permanent teeth have grown in, the position of the teeth and the bite relationship have also been fixed, to the dentist, it is convenient for the dentist to choose the appropriate method of orthodontic, and better able to maintain the effect of orthodontic.