Normal teeth are located in the alveolar sockets on the alveolar bone. The alveolar bone is covered with gums and there are a large number of neurovascular vessels distributed in the alveolar bone with gums. The pain after tooth extraction is caused by the trauma to the gum and alveolar bone, which usually disappears one day after tooth extraction, while the persistent pain appears after one day or every two days, mostly because of the wound infection. Wound infection after tooth extraction is mostly chronic, mainly caused by foreign bodies such as broken tooth fragments, broken bone fragments, residual roots, dental calculus and inflammatory granulation tissue in the alveolar sockets that are not removed in time. The most serious infection after tooth extraction is dry socket, which has been described separately. The above-mentioned cases should be treated promptly at the hospital. It is important to emphasize here how to prevent such cases. First of all, the mouth should be cleaned in time before tooth extraction, and if there is calculus, it can be removed to make the mouth cleaner to reduce the causative factors. Then, anti-inflammatory drugs can be taken prophylactically before tooth extraction to reduce the chance of infection. It is also necessary to spit out the gauze roll after tooth extraction for about half an hour as instructed by the doctor, and it is strictly forbidden to rinse the mouth to prevent the clot from dissolving and falling off to cause infection. If the pain is more obvious after tooth extraction and other causes have been ruled out, painkillers such as painkillers and fen-phen etc. can be taken appropriately. It is better to take painkillers only on the day of tooth extraction and not for more than one consecutive day to avoid covering up the real condition.