Most of the pain after tooth extraction will be to some extent, and if it is gradually relieved, there is no need to worry. However, there is a type of pain that starts only 3-4 days after tooth extraction, which is clinically known as “dry socket” and requires the attention of patients. Dry socket mainly occurs after the extraction of mandibular blocked wisdom teeth and the infection of bone trauma caused by oral bacteria. Currently, it is believed that trauma and infection and large extraction sockets are the main causes. Therefore, in order to prevent the occurrence of dry socket, trauma should be minimized during the extraction process and the extraction wound should be minimized after the extraction; antibiotics should be used before and after the extraction to prevent infection. Dry socket is another type of acute infection of extraction trauma, which is more common in mandibular posterior teeth, especially after extraction of mandibular obstructive third molar, with the following incidence in order: mandibular third molar, mandibular first molar, mandibular second molar, and less common in other teeth, with the lowest incidence in anterior teeth. Under normal circumstances, the pain of the incision will gradually disappear after 2 to 3 days, even for flap debridement extraction surgery. If severe pain occurs 2 to 3 days after extraction, with pain radiating to the auriculotemporal region, submandibular region or the top of the head, and cannot be relieved with general pain medication, dry socket may have occurred. Clinical examination of the alveolar fossa is empty, or there is a corrupt and denatured blood clot that is grayish in color. The broken dead material covering the walls of the alveolar fossa has a foul odor, and the bone surface can be directly palpated with a probe and has sharp pain. There is no obvious swelling of the maxillofacial area, no obvious restriction of mouth opening, and there may be enlarged and painful lymph nodes under the lower jaw.