Cotton balls are usually used as compression to stop bleeding after tooth extraction, and can usually be removed after 30~40 minutes, at which time the blood clot has been formed and there is no active bleeding from the extraction wound. After tooth extraction, due to the apical blood vessels and periodontal tissue tearing, bleeding in the alveolar fossa, bleeding will usually stop after 15~30 minutes, the formation of blood clot closed wound. Cotton balls promote hemostasis and protect the blood clot, so they should be removed after the bleeding has stopped and the blood clot has formed. If the cotton ball is removed earlier, it may lead to extraction wound infection, dry socket and other adverse effects. If the bleeding from the extraction wound does not stop or secondary bleeding occurs, it is recommended to visit the hospital in time to clarify the cause with the help of the doctor and then carry out targeted treatment.