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 pull out the tooth easily, even if the crown is mostly decayed, if there is no problem with the root of the tooth, the crown restoration will be done through systematic treatment to keep the tooth. In contrast, orthodontists often have to extract 4 bicuspids for orthodontic needs, or sometimes they need to extract wisdom teeth that have not yet grown. Sometimes, in addition to the 4 bicuspids, the wisdom teeth that have grown or even not yet grown, which are not very useful, have to be extracted for the treatment, so that a total of 8 teeth are extracted. Some parents even asked what to do with the large gaps after the extractions, and whether they would need to set the teeth. Some elderly people at home are distressed to hear that so many teeth have to be extracted and are determined not to allow it, saying that the teeth will be loose and will fall out early, and therefore refuse to correct it, resulting in many malocclusions missing the best age for correction. As patients or parents hesitate to extract teeth, often interfere with the doctor’s determination of the orthodontic program, some cases even if reluctantly orthodontic treatment with no extraction, but the final result is very unsatisfactory, and some cases can not even be treated without tooth extraction. In fact, tooth extraction orthodontic treatment in orthodontics is very common, and even without orthodontic treatment, most people with poorly positioned wisdom teeth affecting periodontal and anterior tooth health should be extracted. Extraction orthodontics has withstood the test of clinical practice in the history of orthodontic development. Some diseases, such as severe crowding and protrusion, must be treated by tooth extraction. Without extraction, not only will the deformity not be corrected, but some of the teeth that have been crowded with great effort will soon relapse back to their original deformed appearance. Some cases of protrusion, retrusion, and open jaw will not be corrected. After the teeth are extracted there are gaps, which are generally not used for veneers and are used by the doctor to move the teeth for orthodontic purposes, and most of the gaps will be completely closed after the orthodontic treatment is completed. Therefore the gaps provided by tooth extraction are used for: 1. correction of crowding; 2. correction of facial protrusion; 3. correction of occlusal relationship: some patients have very flush teeth but some open jaws, anti-jaws and no occlusal relationship, and this case of tooth extraction is also more common.