When you go to the doctor with tooth pain and cavities, the doctor usually tries to treat the tooth as much as possible and does not easily extract the tooth, even if most of the crown is decayed, if the root of the tooth is not a problem, it is also treated through the system to do crown restoration to preserve the tooth. Orthodontists, on the other hand, often need to remove 4 bicuspids for orthodontic reasons, or sometimes need to remove wisdom teeth that have not yet grown out. Sometimes in addition to the 4 bicuspids, in order to treat the need, but also will grow out or even not yet grown out, not much use of wisdom teeth extraction, so a total of 8 teeth extraction. This is incomprehensible to patients and parents, who feel that it is a pity to remove so many healthy and intact teeth, and some parents ask what to do with such a large gap after extraction, and whether they still need to set teeth. Some of the old people in the family hear that they have to extract so many teeth, but they are even more distressed and determined not to let it happen, saying that their teeth will be loose in the future and will fall out early, and therefore they refuse to be corrected, resulting in many malocclusions missing the optimal age for correction. Due to the patient’s or parent’s hesitation to extract the teeth, often interfering with the doctor to determine the corrective program, some cases even if the reluctance to use non-extraction orthodontic treatment, but the final result is very unsatisfactory, and some cases can not even be extracted without treatment. In fact, extraction orthodontic treatment in orthodontics is very common, about 65% of the patients need to be extracted orthodontic, and even if the teeth are not corrected, the majority of people wisdom teeth in a bad position to affect the periodontal and anterior teeth health also need to be extracted. Extraction orthodontic treatment has withstood the test of clinical practice in the history of orthodontics development. Some diseases, such as severe crowding of teeth, anterior protrusion must be corrected by extraction. If the teeth are not extracted, not only the deformity can not be corrected, some of the crowded teeth will soon recur back to the original deformity. Some cases of anterior protrusion, retrusion, and open jaws cannot be corrected. After the extraction of teeth there is a gap, these gaps usually do not need to be set, the doctor used to move the teeth to achieve the purpose of correction, correction is completed, most of the gaps will be completely closed. Therefore, the space provided by the extraction of teeth is used to 1, orthodontic crowding 2, correction of facial protrusion 3, correction of occlusal relationship: some patients have very straight teeth, but some open jaw, anti-mandibular, no occlusal relationship, this case of extraction of teeth is also more common.