(a) Local contraindications to oral implantation: 1, poor intermaxillary relationship: need to be corrected before implantation, such as orthodontic, orthognathic or prosthetic. 2, the presence of occlusion and dysfunction: after the treatment of dysfunction, implant restoration can be considered. 3, the presence of lesions in the jaw bone: jaw bone tumor, inflammation, etc., need to be treated first, after healing can be considered implant restoration Hu Xiulian, Department of Oral Implantology, Peking University Stomatological Hospital. 4, dry mouth syndrome: such patients have a higher risk of implantation, prone to peri-implant tissue inflammation and implant dislodgement. 5, megalingual disease: to do too much force on the implant, if you want to perform implant treatment, you need to correct the megalingual surgery first. 6.Untreated caries and periodontal disease, poor oral hygiene: the implant can only be planted after treatment and if the patient can develop good oral hygiene habits. (B) Oral implant systemic contraindications: 1. Temporary systemic contraindications: (1) Uncontrolled acute inflammation (2) Pregnancy (3) Short-term use of anticoagulants or immunosuppressants (4) Short-term physical and psychological stress overload 2. Absolute contraindications to implantation: (1) Psychosomatic abnormalities (2) Patients with poor compliance (3) Alcohol and drug use (4) Neurosis, neuropathy (5) Patients with problems, such as emotional (3) Relative absolute contraindications to implantation: (1) Very poor general nutritional status, if it can be improved and reach normal, implantation can be considered. (2) Long-term use of corticosteroids, immunosuppressants, antibiotics, assessment of the patient’s systemic condition, and the need to consult the appropriate internal medicine doctor. (3) Metabolic disorders, such as uncontrolled hyperthyroidism or diabetes mellitus, may be considered for implantation after the disease is controlled or healed and the patient’s general condition is evaluated. (4) Hematologic disorders, such as anemia, leukopenia, bleeding disorders, etc., require treatment and consultation with an internist for suitability for implantation. (5) Cardiovascular system diseases, such as hypertension and coronary heart disease, need to control the disease and be considered according to the patient’s general condition. (6) Abnormal bone metabolism, such as chondromalacia, deformed osteitis, osteogenesis imperfecta, requires consultation with the appropriate internist to assess the patient’s systemic condition and then determine the suitability of implantation. (7) Collagen diseases, such as scleroderma, Sjögren’s syndrome, rheumatoid arthritis, require consultation with the appropriate physician to assess the patient’s systemic condition and then determine the suitability of implantation.