I. Mandibular incisor position Due to the inherent stability of the mandibular incisors, the expected sagittal position of the lower incisors should be pointed out at the beginning, and whether the patient can accept the designed program. The occlusal relationship is mainly based on the incisal relationship, and clinically it is not possible to overly anterior or inwardly retract the incisors; incisal crowding can be relieved by distal-medial movement, but of course the cuspids must be moved distally first. If the degree of overcrowding is serious, the maxillary incisors cover the mandibular incisors more than 2/3, the mandibular incisors should be considered to be depressed, which is of obvious significance for the special design of the orthodontic appliance.Seep’s curve is too steep and will occupy more space, therefore, flattening the dental arch needs to provide extra space, if the teeth are aligned and overcrowded jaws are satisfied, there is no need to move the mandibular incisors. II. Position of mandibular cuspids The amount of mandibular cuspids to be moved depends on the size of the gap needed to align the mandibular incisors. Distal-medial movement of the cuspids means that the posterior teeth must provide the required space. If the mandibular incisors and cuspids are aligned and the cuspids are aligned, the cuspids do not need to be moved far center. Third, mandibular first molar A mandibular first molar with a proximo-central inclination can be straightened, but this method is rarely used clinically. If more space is needed to align the incisors and cusps, the first bicuspid is usually extracted to provide the space. The first molar is rarely moved. If less clearance is needed, the second cuspid may be extracted. If there is more remaining space and the incisors are lined up, it is often necessary to move the molar teeth forward using a fixed orthodontic appliance to relate the extraction gap and prevent the molar teeth from tilting to the side of the gap. The higher number of teeth in front of the extraction gap increases the anterior tooth support and the molar can easily be moved forward to close the extraction gap without disturbing the alignment of the anterior teeth. When crowding is moderate, the second or third molar can be extracted to relieve crowding. However, the possibility that crowding will not worsen with growth must be considered with this method. IV. maxillary incisor position Relieving anterior crowding requires clearance, which can be provided by disto-central movement of the cuspids, and by reduction of coverage, which can be provided by extraction of the first bicuspids, and by extraction of the second bicuspids when less than half a cuspidium is required. Anterior tilting of incisors in Class III malocclusion can provide additional clearance. Clearance must be provided when the occlusion is open in order to minimize coverage. In some cases, depression of the maxillary incisors is required. V. Maxillary Cusp Position The maxillary cusp position is in Class I relationship with the mandibular incisors after allowing them to align neatly. VI.Maxillary First Molar The maxillary first molar position must be adjusted in most cases to allow a Class I molar relationship with the mandibular first molar. Illustrates the adjustment of the molar relationship. It is illustrated that when the molar relationship is cuspid-to-cuspid, a Class I molar relationship can be established by pushing the molar distally using, for example, headcaps, functional orthodontic appliances, and enlarging screws. When the beginning molar relationship is completely distal-medium, extract the maxillary first bicuspid, maintain the original molar relationship, extract the maxillary and mandibular first bicuspid, maintain the maxillary molar position, and move the mandibular molar proximally to establish a Class I molar relationship; when the beginning molar relationship is completely distal-medium, extract the maxillary first bicuspid, and move the maxillary molar distal-medium, and move the mandibular molar proximally to establish a Class I molar system.