There are many sockets and gaps on the biting surface of children’s molar teeth, which can easily retain food and bacteria and lead to dental caries, and if the caries is not treated in time, it will lead to pulpal periapical infection and other diseases. The sulcus closure is to apply a protective film on the tooth surface to close the open sulcus gap and prevent the bacteria from entering, so as to prevent the caries effectively. However, for the formed caries, filling treatment should be carried out. The best time to seal the sulcus is: the milk molar is 3-4 years old, the first permanent molar (“six-age tooth”) is 6-8 years old, and the second permanent molar is 12-14 years old. Maintenance of treatment: Check every six months to prevent the loss of the fossa sealant and the occurrence of new caries.