The optimal age for correction of most of the malocclusions is at the peak of growth and development of children (12-16 years old), but for some serious cases affecting the growth and development of jaws, they should be detected early and treated in time. For some bad oral habits of children, such as finger sucking, biting the lower lip, mouth breathing and tongue spitting habits, the bad habits can be corrected through orthodontic measures; for the case of anterior anti-mandibular teeth, it should be actively treated when the child is 3-5 years old; for the early stage of mild bony deformity (mandibular protrusion or retrusion), it can be in the period of replacement teeth (7-10 years old) for the growth of the improvement of orthodontic treatment, in order to prevent the generation of serious bony deformity. Many people also ask if adults can undergo orthodontic treatment. The answer is yes. There is no age limit for orthodontic treatment and adults can have orthodontic treatment as well. It can align misaligned teeth and improve incongruous craniofacial relationships. However, adult orthodontics has its own special characteristics. First of all, adult oral health is a diversity of changing trends, more missing teeth, periodontal disease, temporomandibular joint disorders, etc., which increases the difficulty of orthodontic treatment, and secondly, the growth potential of adults is limited, the metabolism of bone tissues is slow, and adaptive remodeling is slower than that of adolescents. Therefore, adult orthodontic treatment course is longer, and the retention period of orthodontic treatment is also longer.