The two main categories are generally genetic and acquired factors. Genetic factors are mainly racial evolution and degeneration, and genetic factors account for about 30%. Acquired factors are the following: 1. Early loss of milk teeth: there will be insufficient space and crowding misalignment. Loss of guide eruption, misalignment and inability to erupt when permanent teeth erupt. 2, bad habits: mostly finger sucking habits, tongue habits, lip biting habits, biting habits, jaw stretching habits, bad swallowing habits, sideways chewing habits, etc., can cause a variety of misalignment. 3, multiple teeth: multiple teeth can cause the morphological and kinetic disorders of the teeth and jaw system, and multiple teeth between the central incisors can lead to the formation of the central incisors gap, etc. 4, congenitally missing teeth: mostly for developmental and embryonic reasons, and the missing third molars are mostly degenerative phenomena occurring in the germline. 5.Milk teeth retention: individual teeth are overdue for milk teeth retention, which can lead to the eruption of secondary permanent teeth is blocked and buried, or misaligned eruption. 6.Insufficient wear of milk cusp teeth: Because children eat too soft food, some milk cusp teeth do not wear as much as other teeth, so they are higher than the tooth surface of the dental arch, resulting in early contact, causing anterior or lateral movement, forming antitusks. 7, There are also many systemic factors and local disease factors, such as infectious diseases, malnutrition, endocrine factors, vitamin deficiency, cleft lip and palate, benign hypertrophy of the mandibular condyle, facial hypertrophy, etc. The clinical manifestations of dental irregularities are “geodontia”, “creeping teeth”, “double teeth” and “tiger teeth”. Many people have uneven teeth and feel that there is nothing they can do but resign themselves to their fate, but this is actually the result of ignorance. The incidence of malocclusion in the population is as high as about 70%, but in Western countries, there are very few people aged 16 to 17 years or older suffering from malocclusion. This is because foreign countries attach great importance to dental care, and children are taken to dental clinics by their parents to have their teeth straightened from an early age. In Japan, November 8 every year is designated as National Orthodontic Day. However, in China, the awareness rate of society and parents about the idea that misaligned teeth should be corrected is very low. Malocclusion (medically known as malocclusion) is a deformity in the development of teeth, jaws and face of a child due to genetics, disease, impaired tooth replacement and bad oral habits. However, by paying attention to dental care from childhood, avoiding early loss of milk teeth and overcoming bad oral habits, some people can have a set of neat and beautiful teeth after tooth replacement. The clinical symptoms are mainly toothache, bleeding gums and bad breath, which eventually cause loose teeth and tooth loss. In addition, the abnormal relationship between the upper and lower jaw arches will greatly reduce the chewing function and cause intestinal disorders such as indigestion, while the facial deformity will seriously affect the aesthetic appearance and directly lead to psychological abnormalities. These patients often show low self-esteem, in the normal social, career and spouse selection encounter frustration, and may even show introverted, withdrawn, out-of-touch personality. The traditional concept that orthodontics is only suitable for children during the growth period, due to the rapid development of orthodontics today, the scope of orthodontic treatment has been extended to adults, adults can also achieve perfect results.