Contraindications to dental implants: I: Conventional contraindications to surgery, such as serious heart disease, uncontrolled hypertension, coagulation disorders, serious diseases of the liver, lungs, kidneys and other important organs. II: Patients with severe smoking. III: Uncontrolled diabetes mellitus. IV: Unexplained facial pain. V: Patients with psychological disorders and mental illness. Six: local diseases of the oral cavity: tumors, acute inflammation, etc.