Dry socket is a type of acute infection of the extraction wound, which is more common in the posterior mandibular teeth. Under normal circumstances, the wound gradually heals and the pain gradually disappears after 2-3 days; in patients with dry socket, the pain continues to radiate to the ear and neck and usually cannot be relieved by using painkillers, the specific differences include: 1. Normal cavity: 15 min after tooth extraction, a blood clot can be formed to fill the socket, while the gingival margin around the socket shrinks and involutes to reduce the wound. After 24 hours, the clot gradually disappears; 3-4 days later, the gingival margin around the socket proliferates toward the center of the socket; 7 days later, the trauma can be completely covered; 2. Dry socket cavity: the socket is empty, or there is a gray-white decayed and degenerated blood clot. The necrotic material covering the walls of the alveolar sockets may have a foul odor, thus causing the patient to have bad breath. Examination using a probe may result in sharp pain with direct palpation of the bone surface, no significant swelling of the cheek, no significant restriction of mouth opening, and histopathological examination showing superficial osteitis of the alveolar fossa bone wall or a mild limited type of osteomyelitis. If dry socket has occurred, active medical treatment is required. Treatment of dry socket requires complete removal of decaying material under anesthesia and placement of iodoform gauze with clove oil and rehabilitation solution, which is removed after 8-10 days to promote healing of the socket. Dry socket is related to surgical trauma and bacterial infection, and antibiotics are given as prescribed by the doctor if necessary. Some people will call dental caries as cavity, which usually appears as lusterless white plaque or appears yellowish-brown on the surface of teeth at the beginning and forms cavity at the later stage and is more sensitive to external stimulation. When the caries has reached the deep layer of dentin, there will be obvious pain when touched with objects, so treatment should be carried out in time when the symptoms are found.