Extraction orthodontics is a more clinically applied method, but specifically for each patient the need to use extraction orthodontics, how many teeth are extracted, and which teeth are extracted, the physician will conduct a comprehensive and in-depth diagnostic analysis of each case, and finally make an orthodontic plan including the relevant extractions by measuring the x-rays and dental and jaw models. The main reasons for malocclusion are as follows: 1. When there is severe crowding or close to severe crowding (severe crowding means crowding of more than 8 mm), the teeth should be extracted as needed to align the teeth, achieve aesthetic requirements, and at the same time to ensure the stability of the orthodontic effect. If the teeth are not extracted and the teeth are barely aligned, the orthodontic effect is not stable, and it is easy to relapse into the original crowded jaw; 2, the teeth are neatly aligned without crowding, but dental maxillary protrusion, bimaxillary protrusion, in order to correct the protrusion deformity, it is also necessary to extract the teeth orthodontically, that is, the position after extraction, by the inward intake of the front teeth to occupy; 3, the permanent teeth with severe decay For most cases that must be extracted orthodontically, the most commonly extracted The first bicuspid is the preferred tooth. This tooth is located after the cuspid, at the junction of the anterior and posterior teeth, and the gap after extraction can be easily used by the crowded or anteriorly protruding anterior teeth, while its morphology is similar to the second bicuspid, and the cuspid and the second bicuspid can have a better adjacent relationship after the gap is closed. Generally speaking, the removal of bicuspids has little effect on the morphology and function of the dental arch. In order to maintain the symmetry of the left and right tooth alignment after orthodontic treatment, the teeth are usually extracted simultaneously on the left and right sides. Similarly, in order to establish a good occlusal relationship between the upper and lower teeth after orthodontic treatment, the upper and lower arches are usually extracted simultaneously. In this way, the most commonly used orthodontic solution is the extraction of the first bicuspid from the upper and lower left and right sides. Of course, some patients may have other extraction options, which are determined by a specific diagnostic analysis of the individual case.