Fluorine is one of the nutritional elements of the human body and is present in varying concentrations in various tissues of the body. Fluorine is also widely present in nature in many forms, including drinking water, soil, atmosphere, and in plants and animals. The human body takes in fluoride in many ways. Fluorine is necessary for the normal development and mineralization of teeth and bones. Fluoride caries prevention is one of the effective caries prevention means recognized by domestic and foreign dental experts at present, with various advantages such as low cost, convenient use and good effect. There are mainly two methods of systemic and local fluoride application, and at present, the commonly used method in China is local fluoride application, including fluoride toothpaste, fluoride dental floss, fluoride solution rinse and fluoride foam, etc. The latter two methods must be operated under the guidance of dental professionals. The mechanism of fluoride anti-caries is mainly the following: 1, fluorine can directly inhibit the energy metabolism needed for the growth of bacteria in the mouth, inhibit the adhesion of bacteria to the tooth surface, inhibit the activity of various enzymes in the process of bacterial metabolism, so that bacterial growth and metabolism are disrupted or stopped. 2.Fluorine combines with hydroxyapatite in the tooth enamel structure, reducing the solubility of the enamel surface and enhancing the resistance to acid. 3.Fluorine can also promote the adhesion of calcium and phosphorus in saliva on the tooth surface, which helps the continued maturation of enamel after tooth eruption and the recovery of destroyed apatite in the caries lesion site, and promotes the remineralization of caries damage. 4.Higher concentration of fluoride has the effect of killing cariogenic bacteria and other bacteria. Our department has carried out the local use of fluoride foam for many years to prevent caries, and it is widely used in kindergartens and outpatient clinics. The product has the advantages of good taste, convenient operation and obvious effect of caries prevention, which is welcomed by parents and health practitioners of nursery schools.