Vulval sealant is an effective caries prevention method that protects tooth enamel from bacterial and metabolic product erosion and enhances tooth caries resistance without removing tooth tissue on the occlusal surface and coating a layer of adhesive resin on it. The sealant forms a protective barrier to prevent bacteria and food residues from entering the sulcus, and at the same time, the existing bacteria in the sulcus gradually die because they are deprived of nutrition, thus preventing the occurrence of sulcus caries and stopping the development of early caries. Who needs to do the closure? When is it suitable for fossa closure? 1.In general, deep sulcus, especially those that can be stuck to the probe (including suspicious caries); 2.Patients with other teeth, especially those with caries on the opposite side or those with caries tendency should have sulcus closure; 3.Children’s teeth are suitable for sulcus closure when they reach the occlusal plane after eruption, usually within six months to one year after eruption. 4.The best time for closure is: the milk molar is 3-4 years old, the first permanent molar is 6-8 years old, and the second permanent molar is 11-13 years old. The method of socket closure is very simple and can be completed by cleaning the teeth, acid etching, rinsing and drying, applying sealant and curing in several steps. After curing, the material is tightly bonded to the wall of the sulcus and has a certain resistance to chewing pressure, which is not a hindrance to eating. Moreover, the material is non-toxic and harmless to human body after curing. However, it is important to emphasize that fossa closure needs to be performed by a professional and requires the necessary instruments and equipment. The sign of successful closure is that the sealant is intact, suspicious of wear and tear but cannot fall off, so it needs to be checked regularly and re-sealed if the material falls off.