The pit after tooth extraction is actually a hollow sulcus. The appearance of white substance in the sulcus is firstly considered to be a cotton debris or food residue embedded in the hemostasis, and patients are advised to rinse their mouth more or use a flosser to remove it to avoid causing infection, which is not conducive to wound recovery. In addition, there may be a pseudomembrane, or it may be caused by tissue necrosis or infection. 1. Pseudomembrane: As bleeding often occurs after tooth extraction, blood clots are mechanized and form a light-colored or white pseudomembrane, which is a manifestation of wound healing, and there is no need to remove the pseudomembrane to avoid bleeding or inducing dry socket. 2. Tissue necrosis: Local gums may be damaged during tooth extraction, resulting in mild edema and necrosis of tissues. Due to local ischemia and loss of nutrition, it may appear white. According to medical advice, good oral hygiene and disinfection can be done, and will generally disappear with the healing of the sulcus; 3, infection: if there are white objects accompanied by pain, yellow pus-smelling liquid outflow and other symptoms, consider that it may be intra-alveolar infection, it is recommended that patients go to the hospital for disinfection and antibacterial treatment. Commonly used antibacterial drugs such as metronidazole, amoxicillin, azithromycin, roxithromycin, etc. For severe pain, medications such as ibuprofen and aspirin can be taken for pain relief as prescribed by the doctor. Patients should keep their mouth clean after tooth extraction and avoid licking the wound with tongue to prevent infection caused by bacterial growth. Avoid spicy, greasy, hard and hot diet and alcohol to reduce the stimulation to the wound.