Vulval closure, also known as fissure closure, is an effective caries prevention method that does not remove the tooth tissue, and applies a layer of adhesive resin to the fissure of the facial, buccal, or lingual surfaces to protect the enamel from the erosion of bacteria and metabolic products to prevent the occurrence of caries. When the sulcus on the tooth surface is closed, the nutrient source of the bacteria originally existing in the sulcus is denied, which plays the role of preventing the occurrence of caries on the one hand, and on the other hand, the sulcus closure can also prevent the development of the existing early caries, so it is used for treatment before the early caries becomes a cavity. It can effectively prevent the development of caries with high quality. 1.The best time to close the sulcus is when the tooth is completely erupted and the caries has not yet occurred. 2.The best time to seal the sulcus is when the teeth are fully erupted and the caries has not yet occurred. 3.Milk molar is at the age of 3-4 years old. 4.The first permanent molar is at 6-7 years old. The second permanent molar is at the age of 11-13. 5.Second permanent molar is at 11-13 years old. 6, children 5-7 years old sealant is more likely to fall off, should be reviewed once in six months to a year, fall off and then closed again, after about 3 years will not fall off. 7, permanent teeth closure is generally a year to two years to review once, found to fall off again re-closure. After that in 5-10 years basically will not fall off.