During the period of tooth growth and development, the two growth lobes are connected to form the developmental sulcus, and if the enamel at that place is not completely connected or calcification is not complete, deeper point gap fissure – sulcus will be formed. Bacteria, food residue, saliva and so on remain in these deep grooves and fissures, which are difficult to be removed by conventional oral hygiene measures, and cariogenic bacteria metabolize and produce acid in them, and lead to tooth demineralization and caries (tooth decay) formation. The anatomical structure such as sulcus fissure on the tooth surface is the susceptible site and the starting site of caries, and some research shows that sulcus caries accounts for 90% of caries. At present, the main methods of caries prevention include the application of fluoride, preventive filling, sulcus closure, etc. Among them, sulcus closure is an effective method to prevent the occurrence of sulcus caries. The sulcus closure is also called point gap fissure closure, which is an effective method to prevent the occurrence of caries by applying a layer of adhesive resin to the point gap fissure on the tooth joint surface, buccal surface and lingual surface without removing the tooth tissue to protect the tooth enamel from the erosion of bacteria and its metabolites. The polymer material used in the sulcus closure is called sulcus sealant, also called anti-caries coating. When the sulcus on the tooth surface is closed, the nutrient source of the bacteria originally existing in the sulcus is cut off, 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. Vulval closure plays a very important role in providing effective and high quality caries prevention measures. Vulval sealants have been recommended for almost 40 years as an effective method of preventing sulcus caries in milk molars and young permanent molars, which has been proven in many studies and is widely accepted. For many years, dental sulcus closure was considered an appropriate caries prevention measure for children. However, recently, in the United States, the use of fissure sealants for caries prevention has been introduced in college students and the military, and it has been suggested that age is not a deciding factor for the use of fissure sealants. In recent years, some scholars have advocated that the focus of modern dentures should be on teeth and tooth surfaces with caries risk factors or a tendency to develop caries, and that the duration of dentures can be extended from 4 years after the eruption of molars to adulthood. The correctness of the concept that “the application of sealants is determined by the presence or absence of caries risk factors” has been confirmed by several studies. The resin penetrates into the porous demineralized tissue to provide local support and form a barrier against microorganisms, thus preventing further demineralization. The indications for sulcus closure: The teeth are suitable to be closed after eruption when they reach the coalescence plane, usually within 4 years after eruption. Usually the age of 3-4 years for milk molars, 6-7 years for the first permanent molars and 11-13 years for the second permanent molars is the most suitable age for closure. Deep sulcus, especially can be inserted or stuck probe (including suspected caries); other teeth of the patient, especially the opposite side of the same name teeth with caries or have the tendency to have caries; enamel development is not complete, sulcus point gap initial caries, the coaptation surface has fillings but there is not closed sulcus, can be decided according to the specific situation whether to close.