Oral cancer is a general term for malignant tumors that occur in the oral cavity and can appear in any part of the oral cavity, including the lips, tongue, floor of the mouth, buccal mucosa, gums, hard palate, and posterior molar area. The exact cause of oral cancer is unknown, and it is presumed to be related to many factors; the most important risk factors are smoking, alcohol consumption and betel nut chewing. In Hunan, Guangdong, Taiwan and other places in China, betel nut chewing is prevalent. The risk of oral cancer increases significantly if people have the habit of drinking alcohol, smoking or chewing betel nut at the same time. Other risk factors for oral cancer include: family genetic factors; viral infection; excessive sunlight exposure (lip cancer); poor oral hygiene; sharp tooth edges and improperly made or broken or old denture, which cause chronic injury by stimulating the tongue, gums or buccal mucosa; long-term nutritional deficiency or imbalance, etc. If oral cancer can be diagnosed early and treated timely, not only the cure rate is very high (the cure rate can be over 95%), but also the complications of treatment are rare, the sequelae are minimal and the cost is low. Therefore, it is recommended that the general public should know the following health behavioral strategies to prevent and treat oral cancer: 1. Stay away from tobacco, do not abuse alcohol and avoid betel nut. Do not expose to strong sunlight for a long time. 2. Eat a normal diet with balanced nutrition. Less meat, more fruits and vegetables. 3.Any changes that occur in the mouth and face and neck that have not improved for more than two weeks, including changes in sensation (pain, numbness), shape (ulcers, lumps, bulges), color (white, red, black), texture (soft tissue becomes hard, hard tissue becomes soft), and function (restricted mouth opening, restricted tongue extension), must be examined by a physician and must not be presumed to be You should not think that it is “fire” or “inflammation”. The following enumerates the various clinical manifestations of oral cancer. Most of these clinical manifestations are not unique to oral cancer. The mere appearance of these symptoms or manifestations may not be oral cancer; however, oral cancer patients who delay diagnosis and treatment, miss the timing of treatment, and eventually become fatal diseases are often ignoring these symptoms or manifestations. (1) Prolonged ulcers in the mouth that do not heal for more than 10 days. The degree of pain of oral cancer ulcers varies, some of them are more obvious, some of them are only slightly painful when eating, and some of them even have no uncomfortable feeling. (2) Swellings, hard nodes and other growths. The typical oral cancer is “cauliflower-like” growths. Usually there is no pain, and it is often discovered unintentionally when the tumor grows larger. After the discovery of the lesion, the patient often ignores and delays the treatment of the disease. (3) Pain. Some oral cancers do not have ulcers and no growths can be found, but only pain. Most of the pain caused by oral cancer is different from “toothache”. The degree of “cancer pain” in oral cavity is generally mild, mostly tolerable and persistent, and may be slightly aggravated when eating, but the pain is not aggravated by cold or hot temperature change. (4) Numbness of lips and tongue. Persistent and simple numbness of lips and tongue is almost a characteristic manifestation of malignant tumor, so it is important to pay attention and seek medical consultation. (5) Loose teeth. After the dental examination, the loose teeth caused by periodontal disease and so on are excluded, especially the loose teeth of single tooth or limited range, which means the loose teeth are caused by local factors. Malignant tumor is one of the not so rare local factors. (6) Change in the color of oral mucosa. White, red or black oral mucosal plaques, whether symptomatic or not, should be treated. (7) Enlarged lymph nodes in the neck. Submandibular lymph nodes are located at the lower edge of the mandible and can often be palpated, either singly or bilaterally, with a maximum diameter of about 0.5-1.0 cm, which is a normal lymph node and not a cause for concern. In addition, if there are palpable lymph nodes in the neck, or larger lymph nodes or multiple lymph nodes, you should seek consultation and examination from a physician. (8) Restriction of mouth opening. The distance between upper and lower incisors is about 4.0cm when the mouth is opened at maximum in normal people. The restriction of mouth opening caused by malignant tumor develops gradually from mild to severe. However, inflammation caused by wisdom teeth and temporomandibular joint disorder are the most common causes of mouth opening restriction, therefore, a doctor needs to be consulted to rule out these two conditions. (9) Bleeding in the mouth, which has been ruled out as a result of gingivitis and periodontal disease. (10) Disorders of lip and tongue movement, such as difficulty in tongue extension, crookedness, difficulty in speaking or swallowing, should be seen promptly. (11) The denture worn for a long time appears to be ill-fitting. 4. Develop proper oral hygiene habits (rinsing and brushing, flossing), ask the dentist to check the oral cavity at least every six months, and have an oral cleaning once a year. Regular oral examination can not only detect and treat common oral diseases such as caries and periodontal disease early, but also expect to detect oral cancer and precancerous lesions early (see later). Many clinical early oral cancers with mild symptoms are discovered by dentists during dental treatment. For elderly patients, if they have improperly made, broken or old dentures, once they are loose and unsuitable, rubbing or damaging the surrounding tissues, they should ask the dentist to promptly adjust, grind, modify and remake them, and should not be accommodated. 5.Recognize precancerous lesions: precancerous lesions in the oral cavity include white spots, red spots, black spots, submucosal fibrosis, warty growths and chronic ulcers. Precancerous lesions are not cancerous in themselves, but may develop into cancer. For single, limited precancerous lesions, surgical excision can be considered to eliminate future problems; for multiple and/or large precancerous lesions, close monitoring is required.