In the long evolutionary history of human beings, due to the change of natural environment, primitive human beings gradually changed from crawling to walking upright, and the center of gravity of the head changed, while the brain capacity increased due to evolution, so that the human head form gradually evolved from the original large jaw and small skull to small jaw and large skull. At the same time, due to the use of fire, ancient humans changed from raw food to cooked food, and the food became coarse and hard to soft, and the weakening of chewing function made the chewing organ gradually degenerate. The degradation rate of the tissues of the same figure is not balanced, muscle degradation is the fastest, followed by bone, teeth is the hardest organ of the body, its degradation rate is the slowest. Originally, the wide jaws of ancient humans could accommodate all the teeth, so that they were neatly arranged on the alveolar bone. However, as humans evolved, the jawbone receded significantly, forming a contradiction where the amount of teeth was relatively larger than the amount of bone, resulting in teeth not being able to have enough space and thus crowding, and even some teeth not erupting smoothly due to insufficient clearance. This is the background of the racial evolution of dental crowding in modern people. Some people can also have crowded teeth because of excessive tooth size or extra extra teeth erupting. In children, premature loss of milk teeth due to lack of timely treatment of milk tooth caries, resulting in shortening of the arch length and insufficient space for the eruption of permanent teeth, resulting in ambulatory blockage or misaligned eruption, which is another cause of tooth crowding. According to statistics, about 70% of patients with malocclusion have varying degrees of dental crowding, and some of them also form other malocclusions due to the presence of crowding. The teeth cannot be properly aligned in the dental arch due to crowding, resulting in in and out, uneven or tilted and twisted, which will inevitably affect a person’s aesthetic appearance. Crowding also makes some teeth erupt in the wrong place due to insufficient space, the most common case is that the cusp teeth erupt from the lip, protruding beyond the teeth, forming the so-called “tiger teeth”, which is very unattractive. Crowded teeth also make the food residue easy to stay in the space between the teeth, so that the teeth are not easy to clean, causing the accumulation of dental bacteria and thus inducing the formation of dental caries. Because of crowded teeth is not conducive to the maintenance of oral hygiene, but also detrimental to the health of periodontal tissues, gingivitis may arise in the light, and over time may also form periodontal disease that is difficult to heal. Thus, it can be seen that the harm of crowded teeth is multifaceted, not only affects the aesthetics and oral health, but also has a negative impact on the health of the whole body and mind. For some patients with crowded teeth or neatly aligned teeth but with protruding arches, tooth extraction is often used for orthodontic treatment. This is because in order to achieve straighter teeth or to reduce the protrusion of the dental arch, adequate clearance is required. The most direct and effective way to obtain clearance is to implement the so-called “decremental orthodontics”, i.e., to extract certain teeth in the arch that have little impact on function and arch morphology, and to use the clearance provided after extraction so that the other teeth in the arch can be gradually aligned during the orthodontic process, or to use the clearance to make the protruding anterior teeth move inward to achieve correction of anterior protrusion The purpose of orthodontic treatment is to correct protrusion. The orthodontist will make a comprehensive diagnosis and analysis of each case, and will measure the x-ray box dental model to make an orthodontic design including the extraction of teeth.