It is better to apply fluoride to teeth. The commonly used fluoride containing drugs include sodium fluoride, stannous fluoride, fluoride containing gel and fluoride containing paint. Fluoride is not corrosive to soft tissue, will not discolor teeth, and can be used for both front and back teeth, as follows: 1.Enhance enamel anti-acid: after rubbing fluoride containing drug on tooth surface, fluorine ion can directly enter into enamel, combine with hydroxyapatite to form fluorapatite, enhance enamel anti-acid. 2.Stop caries progress: after increasing fluorine concentration on tooth surface, it can prompt remineralization of early caries, block enamel 3.Preventing caries: Young children can regularly apply fluorine treatment to milk teeth and newborn permanent teeth to prevent the occurrence of caries. The position where superficial defect has been formed can be filled without filling to avoid abrasion of tooth tissue.