Since ancient times, the Chinese have traditionally used tea and tea water as a mouth rinse to prevent cavities. Su Shi once created a method of strengthening teeth with strong tea: brew ordinary tea very strong and use it to rinse the mouth after meals. This removes greasy residue without harming the spleen and stomach. Leftover meat scraps in the teeth will "fall off unconsciously," eliminating the need to pick teeth, and "the teeth will gradually become firm and dense, and cavities will heal naturally." This tooth-protecting method has been recognized by modern Chinese medicine: tea contains caffeine and theophylline, which are alkaline. Rinsing the mouth with tea water after meals neutralizes acidity, cleans the mouth, and eliminates residual sour, sweet, or spicy flavors, helping to restore the sensitivity of taste nerves.

(1) Tea prevents cavities. Research has proven that the main components in tea that prevent tooth decay are fluoride and catechins. Fluoride ions can convert hydroxyapatite in tooth enamel into fluorapatite, improving the structure of enamel and enhancing its acid resistance. Catechins can inhibit the proliferation of Streptococcus mutans (cavity-causing bacteria) in the mouth. A survey found that among children aged 8 to 9, rinsing the mouth with tea water every morning reduced cavities by 70% after two semesters.

(2) Modern research indicates that tea contains alkaline substances, which are far more effective at removing dirt, fishy smells, and greasiness than ordinary water. Regularly rinsing the mouth with tea water after meals can remove dirt, kill bacteria, reduce inflammation, and strengthen teeth and body. In many European and American countries, drinking tea after meals has become a measure to combat halitosis caused by diets rich in cheese and meat.

(3) In recent years, Japanese scientists have also discovered that food residues left between teeth, if not cleaned promptly, can be decomposed or fermented by bacteria and biological enzymes in the mouth, producing ammonia-containing toxins and carcinogens like nitrites. Tannic acid in tea contains an active component that animal experiments have shown to have anti-cancer effects. Therefore, regularly rinsing the mouth with tea water can also help combat potential carcinogens in the mouth.