1, no important organic diseases, such as heart disease, hepatitis, nephritis, pneumonia and other diseases. 2. There is no source of oral infection, such as periodontitis and oral ulcer. 3. Routine blood and urine examinations were performed before operation, and routine health examinations such as chest X-ray and electrocardiogram were performed. 4. Check the "curved section of mandible" and lateral X-ray film of mandible.