Orthodontic treatment is divided into three periods: early orthodontic treatment during the period of milk teeth and replacement teeth, early comprehensive orthodontic treatment of permanent teeth and adult orthodontic treatment. I. Early orthodontic treatment during the period of milk teeth and replacement teeth 1. Interruption of orthodontic treatment during the period of milk teeth (1) Breaking of bad habits Due to the different behavioral forms and function parts of bad habits in the oral cavity, the misaligned jaws caused by them are also different. For example, finger-sucking habit can cause localized opening and closing, tongue habit can cause a larger range of opening and closing and face height increase, and mouth-breathing patients can cause maxillary protrusion and upper arch narrowing. Most oral habits occur in early childhood, but a few patients develop them at an older age. Most bad habits are unconscious behaviors and only a few are conscious behaviors. In terms of treatment conscious habits are easier to correct and unconscious habits are more difficult to treat. It is worth noting that where bad oral habits are caused by disease or anatomical factors, it is necessary for a specialist to cure the disease or anatomical disorder in question before the bad oral habits can be corrected. Tongue Habits: The tongue plays an important role in maintaining the functional balance of the muscles in the oral environment. Abnormalities in the movement and posture of the tongue due to various reasons during the growth and development period of children can affect the morphology of the teeth and jaws. For example, in patients with oversized tongue, short tongue tie, enlarged tonsils or congenital stupidity, there are also some local factors such as tooth replacement or dental caries. In addition, tongue habits can be secondary to other oral malpractices such as finger sucking and mouth breathing. Abnormal tongue movements include tongue extension, tongue spitting, and tongue licking. Finger-sucking: Almost all children suck their fingers during infancy (thumb-sucking is more common), but it usually does not last very long. If the thumb-sucking habit continues beyond the age of three and adversely affects the development of the teeth and jaws, leading to the development of malocclusion, it is considered a bad oral habit and needs to be treated. Lip habits: Unhealthy lip habits include biting the lower lip, sucking the lower lip, sucking the upper lip, etc. The more common habit is sucking the lower lip. Mouth breathing habits: (2) the dental arch relationship is not in tune with the corrective treatment of the dental arch is not in tune with the main include: the front teeth anti-maxillary “Baotian” back teeth anti-maxillary and mandibular skewed on the front teeth protruding anterior teeth open jaw, the front teeth deep overjet. The above children’s bad habits and oral teeth arch relationship is not adjusted need to be blocked early treatment, prevention and treatment of the impact of maxillofacial development. (2) Early treatment during the replacement period (3) Dental replacement disorder Early loss of milk teeth The early loss of milk teeth is often due to the tilting of the neighboring teeth or the excessive length of the teeth of the opposite jaw, resulting in the formation of dental malocclusion. Studies have shown that the gap decreases the most in the first 6 months after the loss of milk teeth. Maintenance of the gap should be performed for those who: neighboring teeth are significantly shifted toward the gap, posterior teeth do not have good cusp-socket relationships, missing teeth cause secondary poor oral habits, missing teeth exacerbate existing malocclusion, and all secondary permanent embryos are present. Premature Loss of Permanent Teeth Clinically long fabricated eruption arrestors delay the eruption of permanent teeth. Late or blocked eruption of permanent teeth Ectopic eruption of permanent teeth (4) Sequential extraction Sequential extraction is an early treatment for tooth and arch size discrepancies. By removing a series of teeth in sequence to facilitate the smooth eruption of permanent teeth, this treatment usually results in the removal of four bicuspids, but it cannot be ruled out that orthodontic appliances are still needed after the series of teeth. Early permanent teeth comprehensive orthodontic treatment Early permanent teeth refers to a period of time when the child’s milk teeth have just been replaced, generally speaking, girls at the age of 10-12 years old, boys at the age of 11-13 years old. At this stage, before or during the rapid growth period of adolescent teeth, the malocclusion is more fully manifested, such as crowding, antimandibular (periosteum), open jaw, maxillary protrusion, etc., which can be aligned by expanding the arch, pushing the molars backward, extra-oral traction, intermandibular traction, etc., to restore the normal maxillary coverage and improve the facial aesthetics. Third, adult orthodontic treatment Characteristics of adult orthodontic treatment In the last decade or so, more and more adult patients require orthodontic treatment. In the United States, about 25% of orthodontic patients for adults, in our country is also showing a rising trend. 1.Growth potential: the biggest characteristic of adult patients is that the growth period has been basically completed. Therefore, with children and adolescents is obviously different from the potential for their own growth and development of growth and deformation treatment is difficult to be effective, the choice of treatment methods are also correspondingly reduced, so the development of the treatment plan, the implementation of the treatment program and the results of the treatment of the maintenance of all the technical requirements. 2, dental disease and other systemic diseases: with the growth of age, patients may have other diseases of the teeth, such as periodontal disease, dental caries, missing teeth, etc., some patients even suffer from systemic diseases. Therefore, for adult orthodontic patients, not only need orthodontist’s careful treatment, but also need the close cooperation of other oral specialists, patients with systemic diseases still need the cooperation of internal medicine doctor’s treatment. 3, treatment requirements: adult patients are autonomous request for treatment of patients, but the individual situation varies from person to person. Different patients can only be given different treatment plans and use different treatment methods. 4, high aesthetic requirements 5, psychosocial factors General principles of adult orthodontic treatment: the goal of adult orthodontic treatment is the same as the early comprehensive orthodontic treatment of permanent teeth, some patients due to the limitations of their own factors or the existence of disease, it is difficult to achieve the ideal goal, only according to the actual situation, to be special treatment. Ceramic bracket orthodontic technology can be chosen, which is beautiful and undetectable, more beautiful and comfortable to use with transparent ligature ring, not affecting normal work and life, and suitable for patients with high demands for aesthetics. Self-ligating brackets can also be chosen, the application of self-ligating brackets without ligation, can shorten the course of treatment, the follow-up cycle can be lengthened, up to 8 weeks before follow-up.