The milk teeth stage: 4 to 5 years old, children grow their first set of teeth. This period is mainly applicable to mastoid retrusion (diastema). Early orthodontic treatment is beneficial for maxillary bone development and prevention of permanent teeth retrusion and bony malocclusion. If the child has bad habits (such as tongue sticking out, lip biting, etc.), they can also be corrected at this stage to prevent the occurrence of malocclusion. Teething stage: Girls are 8 to 10 years old and boys are 9 to 12 years old, the period when the milk teeth and permanent teeth alternate. If parents find that their children have bad habits, abnormal facial shape and abnormal tooth alignment, they should take their children to the orthodontic specialist for examination and consultation in time to determine whether the malocclusion is purely dental, functional or bony, and to determine the treatment time and treatment plan. Because this stage is the prepubertal and peak growth period of your child, if your child has functional or bony malocclusion, then treatment at this stage can make full use of the growth potential of the jawbone and achieve the treatment purpose by promoting or inhibiting the growth of the jawbone, which is more beneficial to improve the facial shape and function of your child. The permanent dentition stage: girls are 11 to 14 years old and boys are 13 to 15 years old. Generally common malocclusions can be well treated at this stage. In addition, individual serious malocclusion, such as “severe antimandibular” with family history, should undergo orthognathic surgery after the age of 18 in order to achieve the desired effect.