There are congenital and acquired reasons for misalignment of teeth: 1. The most important congenital reason is genetic, and there is also the influence of the mother during pregnancy, such as rays, nutrition, disease, such as viral infection can lead to abnormal fetal development. The most typical one is cleft lip and palate, which is partly caused by genetic factors; another part is caused by maternal radiation or viral infection during pregnancy, which leads to cleft lip and palate, There are some systemic reasons, and some local reasons, such as tooth decay leading to early loss of teeth, resulting in abnormal tooth eruption, tooth displacement leading to tooth misalignment; for example, large area of tooth decay, leading to local chewing is affected, jaw bone development is affected, underdevelopment will also lead to teeth misalignment, human evolution process of jaw face is Nowadays, people eat more and more fine food, so the stimulation of jaw and face is less and less, but the number of teeth is still so much, and the local factors of tooth decay and oral cavity cause the jaw bone development to be affected, resulting in the lack of space and teeth misalignment.