Orthodontics is the science of studying the etiological mechanism of malocclusion, diagnosis and analysis as well as its prevention and orthodontic treatment. Malocclusion refers to the normal development of teeth, jaws and craniofacial surface of children due to congenital genetic factors or acquired environmental factors, such as diseases, bad oral habits and abnormal tooth replacement, resulting in misalignment of teeth, abnormal dental relationship between upper and lower dental arches, abnormal size and morphological position of upper and lower jaws, etc. It is called malocclusion. The clinical manifestations of malocclusion are various, simple ones only show the misalignment of individual teeth, complex ones can show the malformation of dental arch, jaw bone and craniofacial. The pathogenesis of malocclusion is the incongruity between the amount of teeth and bone, teeth and jaws, upper and lower dental arches, upper and lower jaws, and jaws and craniofacial surface. The prevalence of malocclusion in the country is 29.33-48.87% according to the standard survey statistics of individual normal fit; while the prevalence of malocclusion is 91.20% according to the standard survey statistics of ideal normal fit. The harm of malocclusion (1) affect the development of the jaw and face: because most of the malocclusion is formed in the process of growth and development of children, some malocclusion will affect the normal development of the upper and lower dental arches or the upper and lower jaws, and the development of malocclusion becomes more and more serious. (2) Affect the oral health: when the teeth are crowded and misaligned, it is not easy to self-clean and can cause gum and periodontal inflammation, and it is good to develop dental caries. Meanwhile, the misaligned teeth can affect the health of periodontal tissues due to the abnormal occlusion. (3) Affect the health of oral and jaw system: serious misalignment can affect the normal function of the oral and jaw system, such as severe mandibular recession, open lip and exposed teeth can easily cause mouth breathing and affect the respiratory function; posterior teeth locking teeth can affect the chewing function; severe mandibular protrusion can cause abnormal swallowing; severe mandibular protrusion combined with open teeth can change the normal position of the tongue, changing the position of the tongue and teeth in the process of swallowing, and The anterior teeth opening and closing and severe mandibular protrusion will cause abnormal pronunciation; misalignment will cause abnormal position of teeth and jaws and joint interference, which will lead to impaired opening and closing of the jaws, forward extension and lateral movement, thus affecting the normal function of the temporomandibular joint and organic lesions of the temporomandibular joint. (4) Affect the appearance of appearance: various types of malocclusion can affect the appearance of appearance to varying degrees, and can present deformities such as open lips and open teeth, double jaw protrusion, too long or too short in the lower 1/3 of the face. (5) Systemic harm: misalignment will not only affect the health of the oral and jaw systems, but also cause damage to the whole body. When the misalignment is serious, the chewing function is obviously reduced, which can cause digestion and gastrointestinal diseases. In addition, facial deformities not only affect the appearance, and even affect the choice of social and professional, resulting in mental and psychological abnormalities. Orthodontic treatment of malocclusion (a) Preventive treatment: During the embryonic and acquired development of teeth, jaws and craniofacial surfaces, various preventive measures are taken to prevent the occurrence of various malocclusions, the main elements of preventive treatment. For example, the mother’s attention to nutrition during pregnancy, careful use of drugs, avoid radiation exposure, etc. (B) Interrupted orthodontic treatment: In the early stage of the occurrence of malocclusion, early orthodontic treatment through simple methods to interrupt the development of malocclusion in the direction of severity, the development of teeth, jaws and face to normal is called interrupted orthodontic treatment. (III
) General orthodontic treatment: It is the most commonly used method in orthodontic treatment. Depending on the type of malocclusion, various different types of aligners, such as removable aligners, fixed aligners, and functional aligners, are selected for correction. The general orthodontic treatment is more complex and should be carried out by an orthodontist. (IV
) Surgical orthodontics: refers to the completion of growth and development, severe bony misalignment misalignment using surgery for correction of a method, also known as orthognathic surgery or surgical orthodontics. Surgical orthodontics must be done by the oral and maxillofacial surgery and orthodontics physicians to ensure that the relationship and jaw deformity are well corrected. The standard of treatment for malocclusion should be the individual normal fit, not the ideal normal fit. The orthodontic goals for malocclusion are balance, stability and aesthetics.