When people reach middle and old age, due to the degenerative changes in the physiological function and anatomical morphology of the oral cavity, they are prone to the following oral diseases: 1. Periodontal diseases Periodontal diseases are the main cause of tooth loss in middle and old age, so middle and old age should raise awareness of this disease and achieve effective prevention. Prevention method: Brush and floss effectively with a health care toothbrush every morning and evening. Regular oral examinations, once every six months. Regular scaling (commonly known as scaling) to remove tartar and plaque. Pay attention to the dietary balance to maintain the bone tissue and gum health. 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. Prevention method: choose fluoride toothpaste to brush teeth, regular examination, early detection and early treatment. 3.Dentin allergy The chewing surface of teeth can be abraded because of chewing food for a long time, that is, the outermost layer of tooth enamel is worn and the dentin is exposed. At this time, local symptoms of sensitivity to cold, hot, sour, sweet, appear. Treatment: often chew raw walnuts or tea, brush your teeth with desensitizing toothpaste, and go to the hospital for desensitizing treatment. 4, wedge-shaped defect The cervical part of the tooth is the weak link of the tooth structure, low resistance to wear and tear, in this part of the lip and buccal surface is easy to form two smooth oblique surface of the defect, called wedge-shaped defect. Prevention and treatment methods: (1) Use health care toothbrush, using vertical brush or rotary brush method. (2) Eat less acidic food. (3) Treat stomach problems. (4) Go to the hospital for filling. 5, missing teeth Missing teeth are more common in the elderly. Missing teeth should be restored in time. Generally, it will be done about 3 months after the extraction. Commonly used methods are: partial or full denture, movable or fixed denture, and implant denture. Implant denture is an artificial tooth root made of metal that is implanted in the alveolar bone of the missing tooth and then the denture is placed. The implant denture is the most modern method of denture restoration because it is stable, comfortable and aesthetically pleasing, and can withstand high occlusal forces.