In orthodontics, most teeth move back and forth, so the opposite changes greatly. The most obvious is buck teeth correction. When correcting buck teeth, the lips will be easier to close because the front teeth move backward, and the front teeth are not easy to be exposed, so the face will look better from the side or from the front. Because it involves future stability, general orthodontics does not change the width of dental arch much. Even in some adolescent cases, rapid maxillary expansion may be used to correct the narrow maxillary arch, but it should not have much impact on facial width. Doctors can't control the facial changes of growing patients. The facial changes of adult patients may be caused by lifestyle changes such as inconvenient diet, pain and psychological stress during orthodontic treatment. The root cause of facial changes is still unclear, which is one of the academic difficulties in orthodontics.