China is the first country in the world to cultivate and drink tea. Since ancient times, we have been drinking tea and gargling with tea water as a method of caries prevention. Preventing caries by tea Our country has a large population and the tradition of drinking tea, so it has the positive significance and convenient condition to promote caries prevention by tea. According to the domestic research, the main component of tea that can prevent caries is fluorine and catechol. Fluorine ion can change the hydroxyapatite in tooth enamel into fluorapatite, which improves the structure of tooth enamel and enhances its anti-acid effect; catechol and other substances can inhibit the proliferation of Streptococcus pyogenes (i.e. caries-causing bacteria) in the mouth. Wang Wanxiang et al. (1980) conducted a survey in Huoshan Tea Factory in Anhui Province on the workers and family members aged 7 to 50 who had the habit of drinking tea, and found that the caries rate was very low, only 21.1%. Gao Quanfu et al. (1978) conducted a survey on children aged 8 to 9 years old, rinsed their mouth with tea once every morning, and after two semesters, the caries rate was reduced by 70%. Thus, if we can insist on drinking tea, rinsing mouth with tea water and brushing teeth with tea water every day, we will definitely get better effect for protecting teeth and preventing caries. Modern research points out that tea contains alkaline substances, and its effect of removing dirt and fishy, eliminating greasy is much stronger than general water. It is often used to gargle tea after daily meals, which can remove stains, sterilize, anti-inflammatory, and achieve the effect of healthy teeth and strong body. At present, in many countries in Europe and the United States, has been drinking tea after meals, as one of the measures to solve the problem of bad breath due to the diet cheese, meat and more. Some people in China also after eating garlic, immediately chew a little tea, it is said to have the effect of removing bad odor. In recent years, Japanese scientists have also found that the daily diet attached to the food residue in the gap between the teeth, such as not timely washing, brush clean, easy to be decomposed by the bacteria in the mouth, biological enzymes or fermentation, resulting in carcinogenic substances such as ammonia toxins and nitrites. Because the tannic acid in tea contains an active ingredient, animal experiments have proved that it has anti-cancer effects, so commonly used tea gargle, but also conducive to the fight against possible carcinogenic substances in the mouth.