The best time for wisdom tooth extraction is for girls aged 17-18 and boys aged 19-20. At this stage, the crowns of wisdom teeth are fully erupted and exposed in the mouth, and the X-rays show that the roots of the teeth have not yet formed, so there is no need to make a large incision when extracting them, and the trauma after extraction is small and will not cause swelling and pain. If the wisdom tooth has been developed, it should be extracted when deep cavity is not formed. When the crown of wisdom tooth is missing in a large area, it is impossible to place the dental forceps, which makes it difficult to extract the tooth. In case of repeated pulpitis or periapical inflammation, adhesion between the root and the alveolar bone and necrosis of the pulp will make the tooth tissue brittle, so that the whole tooth cannot be extracted completely when the tooth is extracted, causing a big trauma.