Correcting teeth can change the face shape to a certain extent, such as the phenomenon of tiger teeth caused by crowded dentition. The common tiger teeth of ordinary people are mainly two maxillary canines impacted in a low position, and the teeth protrude out of the dentition and to the lips, so that the corners of the mouth and lips protrude laterally. After correction, the canine teeth can be returned to the correct position, that is, back to the dentition, so that the face shape can be changed. If the degree of maxillary protrusion or mandibular protrusion is not too serious, the problem of protrusion can be solved by correcting the teeth, that is, changing the axial direction of the teeth. However, if it is a very serious maxillofacial deformity or serious exostosis, or maxillary protrusion or mandibular protrusion, it is impossible to solve the fundamental problem simply by correcting teeth, and orthognathic surgery is needed. It is generally suggested that patients should undergo orthognathic surgery after 18 years old, but before orthognathic surgery, preoperative orthodontic treatment should be carried out according to the requirements of orthognathic surgery.