Adult orthodontic treatment is very different from that of adolescents, because the growth and development of adults have been completed, the jaw and facial bones have become bony fusion, plasticity is very low, and the metabolic rate of adults has slowed down, biological responsiveness is reduced, which increases the difficulty of orthodontic treatment. Compared with adolescents, adult orthodontics is more complicated, and adult malocclusion is often accompanied by other oral diseases, such as caries, periodontal disease, missing teeth, tooth wear, residual crowns, and residual roots. Before starting orthodontic treatment, comprehensive control of periodontal disease and removal of intra-oral prostheses are required, otherwise the wear of aligners and movement of teeth will be affected. The adult dental system has a special physiological state, does not have the unique growth and development advantages of children and adolescents and easy to induce the favorable conditions of tissue remodeling, and adult periodontal disease patients have a high sensitivity to alveolar bone resorption, so that orthodontic treatment is subject to certain restrictions. Most adults suffer from varying degrees of periodontitis, with alveolar bone resorption, gum recession, and even tooth misalignment, such as tooth elongation, anterior tilt, gap or loss of teeth. Moving misaligned teeth in the presence of periodontitis will accelerate the resorption of alveolar bone. Therefore, before orthodontic treatment, it is necessary to receive the necessary periodontal treatment, such as scaling, subgingival scaling, flap scaling, etc. When periodontal inflammation is controlled before orthodontic treatment can begin. Periodontal treatment is also done regularly during the whole orthodontic treatment process according to the situation. Periodontal disease can help improve the health of periodontal tissue and reduce the further deterioration of periodontal disease after combined orthodontic and periodontal treatment. 2.Potential or stationary pulpal and periodontal diseases or unpredicted problems that cannot be fully detected by the examination before the implementation of orthodontic treatment may cause active lesions in the course of orthodontic treatment. Orthodontic treatment must be temporarily interrupted when symptoms such as pain, overflowing pus, or loosening of teeth occur, and orthodontic treatment can only be continued after the diseased teeth have received endodontic and periodontal treatment. Sometimes even have to terminate the orthodontic treatment, with the restoration method to solve the remaining problems, such as the use of dentures to solve the remaining gap after the extraction of teeth, the patient should be able to understand. 3, most teenagers do not produce alveolar bone resorption when the teeth move, so teenagers can easily close the gap between extracted or missing teeth; while adults are prone to alveolar bone resorption, in order to avoid such a situation, adults sometimes need to close the gap between extracted teeth with the help of dental implants and other restorative methods. 4. Because the temporomandibular joint of adolescents has a high degree of adaptability, joint symptoms rarely appear. Adults are poorly adapted to alterations and those with underlying joint disease are prone to joint dysfunction symptoms during orthodontic treatment. When there is painful joint popping, the doctor should be informed promptly for treatment. If you have symptoms of temporomandibular joint dysfunction before orthodontics, you should consult an orthopedist first. Due to its complex pathogenesis, orthodontics is only one of the treatment means, and it must be treated in cooperation with an orthopedist. 5, certain problems that cannot be fully confirmed before orthodontic treatment, such as whether the roots of the teeth are adherent to the alveolar bone? Is it a marginal case to be orthodontically treated by tooth extraction? Is the lower jaw in a functional receding or forward position? Orthodontic treatment can be performed based on the initial diagnosis, and then the final orthodontic plan can be determined through the observation of the orthodontic response to clarify the diagnosis. Therefore, please understand that it is entirely possible to modify the orthodontic treatment plan during the orthodontic treatment. 6. Since adults have no more growth potential, for deformities caused by mild to moderate skeletal disorders in the craniofacial area, only orthodontic means to move the teeth can be used to conceal some of the deformities in order to improve the facial appearance. For those who have serious jaw development deformity or require thorough improvement of facial shape, orthognathic surgery must be used to change the morphology and position of the jaws. 7, teeth clenching and grinding syndrome (including night grinding), is not conducive to periodontal tissue health, will aggravate periodontal inflammation. Such symptoms should be promptly told to the doctor, to be diagnosed and treated. 8, diabetes Bo blood disease and other systemic diseases, or long-term use of steroids or pregnancy, will affect the periodontal health, should not receive orthodontic treatment.