Hello: The purpose of tooth extraction is to (1) align the crowded teeth with the gap between tooth extraction. Patients with crowding degree II-III are more likely to have their teeth extracted. (2) Retract the anterior teeth between tooth extraction, improve the protrusion of dental arch and improve the face shape. For example, some people have protruding lips. After tooth extraction, the protrusion of lips will become smaller and the face will become beautiful. (3) The occlusal relationship of the posterior teeth is adjusted by the extraction interval, so that the posterior teeth are staggered and the occlusal contact area is the largest, and the best chewing efficiency is achieved.