When people reach middle and old age, due to degenerative changes in physiological functions and anatomical forms of the oral cavity, they are prone to the following oral diseases. Periodontal disease Periodontal disease is the main cause of tooth loss in middle-aged and old people, so middle-aged and old people should raise awareness of this disease and do effective prevention. Preventive methods: Effective brushing and flossing with a healthy toothbrush every morning and evening. Regular oral checkups, once every six months. Regular scaling (commonly known as teeth cleaning) to remove tartar and plaque. Pay attention to dietary balance to maintain healthy bone tissue and gums. 2.Root surface caries After the gums recede and the roots are exposed, caries can occur on the root surface, which is called root surface caries. Preventive methods: use fluoride toothpaste to brush teeth, regular checkups, early detection and early treatment. 3, dentin allergy teeth chewing surface due to long-term chewing food, there can be abrasion, that is, the tooth’s outermost layer of enamel is worn, dentin exposed. At this time, the local appearance of cold, hot, sour, sweet, sensitive symptoms. Treatment: often chew raw walnuts or tea, brush teeth with desensitizing toothpaste, go to the hospital for desensitization treatment. 4, wedge-shaped defect The neck of the tooth is the weak link of the dental structure, low wear resistance, in this part of the lips and cheeks are prone to the formation of two smooth slopes composed of defects, known as wedge-shaped defects. Prevention and treatment methods: (1) Choose health care toothbrush, using vertical brush or rotary brush method. (2) Eat less acidic food. (3) Treat gastric diseases. (4) Go to the hospital for filling. 5, missing teeth Older people with missing teeth are more common. The missing teeth should be restored in time. Generally about 3 months after the extraction of the set back. Commonly used methods are, partial denture or full denture, movable denture or fixed denture, and implant denture. The so-called implant denture is an artificial tooth root made of metal, which is implanted into the bone of the missing tooth, and then set with a denture. Implant dentures are the most modern method of restoring teeth, as they are stable, comfortable and aesthetically pleasing, and can withstand high biting forces.