As people become more and more demanding about their aesthetics, many people are becoming aware that their teeth are very misaligned. So, why do misaligned teeth occur? Misaligned teeth emerged gradually during the evolution of human beings, and it has become especially serious in modern times. Archaeological findings show that ancient humans 800,000 years ago did not have misaligned teeth, 100,000 years ago had very slight misalignment, and the proportion of misaligned teeth was about 25% in humans more than 3,000 years ago, and up to 70% in modern humans. At present, it is believed that there are two main reasons for uneven teeth. 1. Genetic factors. Human beings in the evolutionary process of food from raw to cooked, from hard to soft, from coarse to fine, the stimulation of chewing organs gradually reduced, chewing organs gradually degraded. But in the process of degradation of the jawbone degradation is fast, the teeth degradation is slow, so the jawbone of modern people gradually can not arrange so many teeth, the teeth do not appear. 2. Environmental factors. In the process of development before birth, if there are some abnormalities, there will also be uneven teeth. Such as abnormal development of the number of teeth, abnormal development of tooth shape, cleft lip and palate, etc.. After birth, if the child’s development process with mouth breathing, abnormal tooth replacement, have bad oral habits, etc., will lead to the occurrence and aggravation of dental irregularities. Therefore, it is necessary to go to the dental hospital regularly for oral examination during the growth and development of the child, and to deal with the dental irregularities in time.