The main purpose of the sulcus closure of teeth is to prevent the occurrence of sulcus caries. Some newly erupted permanent teeth, mainly the sixth-aged teeth, its occlusal surface will become the site of caries easily because of the deep sulcus formed during the development process, and after eruption, bacteria and food residues will easily accumulate in this location. It is possible to close the sulcus by using the fossa sealant, so that the bacteria and food residues in the mouth can not enter and prevent the occurrence of sulcus caries. The fluoride ion is also contained in the sealant, which has the function of preventing caries. Therefore, it is an effective method to prevent the caries of the sulcus, and it is generally implemented to seal the sulcus of the teeth before the occurrence of caries.