Oral diseases not only affect the function of oral organs, but also often affect the health of the whole body, leading to a decrease in the quality of life. The following are the two most common diseases of oral cavity, namely caries and periodontitis, as examples to illustrate the adverse effects of oral diseases on the whole body health and life quality. First, caries is the main cause of tooth loss. The loss of teeth inevitably leads to low chewing function, affects the digestion and absorption of food, and leads to malnutrition. For example, children with more caries often have a thin body, and serious cases affect the development. If caries is not treated in time, it can develop into chronic periapical abscess, fistula of gum, and repeatedly flowing pus, and then it can become a foci. The so-called “lesion” refers to a limited tissue with pathogenic microorganism infection. This limited foci of infection may spread to nearby tissues or organs and may cause diseases in distant organs and tissues, for example, infection of the tooth may cause arthritis, endocarditis, nephritis, etc. Oral operations such as tooth extraction and periodontal scaling can cause temporary bacteremia, but generally do not leave sequelae. In patients with organic lesions of the heart valves, bacterial endocarditis can be caused, the most predominant bacteria being Streptococcus straw green. Blood flow carries these bacteria to settle within the damaged or abnormal heart valves, causing bacterial endocarditis or endarteritis at the endocardium. Therefore, precautions such as mouth rinses with chlorhexidine solution or oral antibiotics should be taken when performing oral operations on those who may cause bacteremia, and prophylactic antibiotics should be administered before and after the operation for patients at high or moderate risk. Oral lesions can cause various kinds of arthritis, especially infectious arthritis, which may be related to the sensitivity of certain tissues of the organism, such as synovium, due to the action of streptococci. Some studies have reported that after removal of dental lesions, a variety of eye diseases were cured, such as iritis, iridocyclitis, retrobulbar optic neuritis, and retinitis. Sometimes, the symptoms of skin diseases such as erythema multiforme, herpes, urticaria, and eczema are alleviated after the healing of oral disease. It is possible that chronic glomerulonephritis can be caused as a result of the continuous action of toxins within the lesion. After removal of the lesions, continued damage to the kidneys can be prevented. The relationship between some other diseases, such as neuritis, respiratory and gastrointestinal diseases and oral lesions, has also been reported. Second, periodontitis Periodontitis is another important cause of tooth loss, mostly seen in middle-aged and elderly people. However, some periodontitis occurs in young people in their 20s, and even in those who start as early as adolescence, and it often develops rapidly and is less effective in treatment. Periodontitis is very harmful to the body, affecting the chewing function due to a group of teeth or the loosening or even loss of all teeth, increasing the functional burden on the gastrointestinal tract, coupled with the frequent swallowing of pus, causing indigestion or ulcer disease, many patients with periodontitis suffer from gastrointestinal disorders in clinical practice. The results of several studies have shown that chronic gastritis, gastroduodenal ulcers, and gastric cancer are often caused by H. pylori. The oral cavity is a reservoir for H. pylori, and the detection rate of H. pylori in saliva and dental plaque is high, even higher than that of H. pylori in the stomach. The presence of large amounts of dental plaque in periodontitis may be an important reason why patients with periodontitis are often accompanied by gastric ulcers. Elimination of this dental plaque has the potential to prevent gastric ulcers or promote healing of gastric ulcers. Prolonged septic inflammation is a drain on the organism. Bacteria and tissue breakdown products constantly enter the bloodstream and can cause bacteremia. Periodontitis can also become a focal point for lesions of distant organs, such as arthritis, iridocyclitis, and nephritis. Prolonged periodontitis with pus overflow and bad breath can have a serious impact on the patient’s work and social activities. The destructive inflammatory process of periodontitis is closely related to diabetes, and non-insulin-dependent diabetics are three times more likely to develop periodontitis than normal, and periodontal infections are more severe and can occur at a young age. A history of chronic periodontitis significantly affects the control of diabetes, probably because periodontitis increases susceptibility to infection, impairs host responsiveness, and produces excess collagenase, all of which have a detrimental effect on diabetes control. In contrast, periodontal treatment reduces serum levels of TNF-α, improves insulin sensitivity, and helps to reduce blood glucose and glycated hemoglobin levels. Periodontitis and coronary heart disease are also closely related. Some findings show that periodontal bacteria produce enzymes that promote the formation of blood clots in the body, leading to the development of cardiovascular disease. The presence of periodontal bacteria was found in the atheromatous plaques that cause coronary artery stenosis, and induction of periodontal disease in rabbits can cause deposition of coronary plaque. The risk of coronary heart disease is two times higher in patients with periodontitis than in healthy individuals, and the risk of heart disease is up to 30% or more in patients with periodontitis who have alveolar bone tissue loss. Periodontal interventions have the potential to be one of the most effective measures to reduce the risk of coronary heart disease. Periodontitis is also strongly associated with preterm low birth weight infants. One study reported that pregnant women with severe periodontitis had a 7-fold increased risk of preterm low birth weight infants compared to healthy individuals. Animal studies have shown that mothers with periodontitis produce mice that weigh 25% less than healthy mice. When toxins produced by oral bacteria were administered intravenously to rats, 15% of rats aborted at low doses; at high doses, 100% of rats aborted. The mechanism by which periodontitis leads to premature low birth weight infants may be that oral infection drives accelerated production of inflammatory mediators, such as prostaglandin E2 and tumor necrosis factor (TNF-α), which are delivered early when critical levels are reached during gestation. Bacteria associated with periodontitis produce endotoxins, inflammatory mediators that threaten the health of the placenta. Bacillus nucleatum, normally found in the oral cavity, can be isolated and cultured in the amniotic fluid of preterm pregnant women, which may be transmitted to the amniotic fluid through bacteremia. Since oral disease and systemic health are closely related, two aspects should be noted in the diagnosis: whether the oral disease seen, on the one hand, is a simple oral disease, or whether it is related to a systemic disease, or a manifestation of a systemic disease in the oral cavity, because the two are treated very differently. If it is a simple oral disease, only local treatment may be done. If it is a manifestation of a systemic disease, it often needs to be combined with systemic treatment, or even systemic treatment. For example, periodontitis in combination with diabetes must be combined with treatment of diabetes for periodontitis to be effective. Cancerous tumors of the breast, kidney, and prostate can metastasize to the gums or jaws through the bloodstream, and treatment of the primary focus should be considered first. On the other hand, it is important to consider the disease of the oral cavity and how it will affect the whole body. For example, whether distant metastases have occurred from carcinomas of the oral and maxillofacial region. Severe oral and maxillofacial interstitial infections can lead to sepsis, sepsis, cavernous sinus thrombophlebitis, etc. At this time, not only local treatment but also systemic treatment should be focused. In the course of treatment, special attention should be paid to the relationship between local and systemic. Sometimes, treatment may seem simple in terms of local lesions, such as smaller tumors in the oral cavity, which are relatively easy to remove. However, the patient may have severe cardiovascular disease that cannot withstand the blow of surgery. Relevant medical treatment is needed first to create conditions for surgery, and changes in cardiovascular lesions should be closely observed during or after surgery. There are some lesions that become oral lesions and can be eliminated or reduced systemically with timely and appropriate treatment.