As the saying goes, “disease enters from the mouth”, the oral cavity is the beginning of the digestive tract, the gateway to the respiratory tract, oral diseases and systemic diseases are closely related, if not treated in time, it is easy to endanger the whole body. 1, oral lesions threaten the whole body health: oral lesions refer to dental caries, periodontitis, apical inflammation, jaw bone osteomyelitis, tooth residual root crown and apical cyst, etc. The bacteria and viruses in the lesions reach the whole body organs and tissues through blood and lymphatic fluid, which can cause many systemic diseases, such as chronic nephritis, chronic gastritis, rheumatic fever, arthritis, chronic pharyngitis, migraine, skin disease, unexplained low fever, etc. Once the local diseases or lesions in the mouth are removed, the corresponding systemic diseases mentioned above also subside. 2, dental disease prone to gastric disease: food by mechanical digestion and chemical digestion after absorption of nutrients, the first pass is in the mouth through full chewing of mechanical digestion and chemical digestion after mixing with saliva when chewing food, and then swallowed to the stomach, digestion and absorption by gastric and intestinal juices. If you have dental disease and swallow the food in one gulp, the food cannot be fully chewed and digested in the mouth, which will directly increase the burden of gastrointestinal tract and cause gastrointestinal tract diseases, and for children, it will lead to indigestion and nutrition absorption disorder and affect the development and growth. 3, caries can cause eye disease: the bacteria in caries can directly spread to the orbit and cause intraorbital infection, and further development of caries can cause acute and chronic pulpitis and apical inflammation, and its bacteria and toxin or tissue protein decomposition often enter the blood, and through the blood circulation to the eye easily cause allergic reaction. For patients with eye disease, we should pay attention to observe whether they have caries or not, if they have, they should be treated actively. 4, dental disease can endanger heart health: periodontitis is a risk factor for coronary heart disease, myocardial infarction and stroke. Bacteria and toxins in oral lesions are easily transferred to the heart through blood to cause bacterial endocarditis. Bacteremia of periodontitis predisposes to myocardial infarction and coronary heart disease. Domestic and foreign survey statistics show that the incidence of coronary heart disease in men under 50 years of age with periodontitis or without teeth is 70% higher than that in the general population. The incidence of fatal coronary heart pain and cardiac arrest in patients with severe alveolar bone resorption is two times and three times higher than that of the normal population, respectively. In some patients with a history of myocardial infarction, the dental pain before the attack indicates the aggravation of the disease and should be taken seriously. 5, dental disease can induce lung infection: research shows that geriatric pneumonia is closely related to various dental pain, because a large number of bacteria in the mouth can be inhaled into the lungs, leading to pneumonia. Therefore, good oral cleaning is important for the prevention of pneumonia in the elderly. 6, dental disease can induce diabetes: research has proved that periodontitis and diabetes have a two-way relationship, that is, periodontitis if not treated will induce or aggravate diabetes, diabetes in turn can complicate periodontitis. Insulin-dependent diabetic patients with severe periodontitis have significantly poorer glycemic control than patients without periodontal disease. If periodontal infection is effectively treated, the patient’s muscle tissue response to insulin can be restored to normal. 7, dental disease is prone to preterm birth: research has proven that the risk rate of preterm birth and low birth weight babies in pregnant women with periodontitis is 7.5 times that of normal people. Therefore, women should pay attention to the diagnosis and treatment of oral diseases before pregnancy. 8, male infertility and dental disease: medical experts observed that the male infertility patients suffering from bad pulp teeth, apical cysts, chronic jaw inflammation for oral treatment, the results of one-third of the patients happy offspring, this is because the oral inflammation of bacteria through the oral capillaries into the human blood circulation, further invasion of the reproductive system, so that the sperm motility decreased. Oral cavity is a mirror of the body, on the one hand, oral diseases can reflect systemic diseases, on the other hand, many systemic diseases are caused by oral disorders. Therefore, we should have a holistic view of oral diseases, and dental diseases should be examined and treated promptly. We recommend that every six months to a year to the regular dental clinic or dental hospital for oral examination, so that dental disease early detection, early treatment, can not take dental disease lightly, because of small diseases mistaken for big diseases.