I. What is the “sulcus” of teeth? More than 90% of tooth decay (commonly known as worm teeth or tooth decay) in teenagers occurs on the biting surface of molar teeth (posterior teeth) chewing food, and there are many uneven fissures on this tooth surface, which is formed by the bad calcification during the development of teeth, and we call it “sulcus”. It is complicated in form and different in depth, and the bacteria and food residue in the sulcus cannot be removed by brushing and rinsing, so it is the part where caries occurs most easily. What is the gutter closure? Vulval closure is one of the effective methods to prevent the caries in the sulcus. It is the caries prevention method recommended by WHO. It is a synthetic organic polymer resin material (harmless to human body), which is applied in the deep sulcus of the teeth, and after the material hardens, it can be retained in the sulcus for a long time, just like forming a protective barrier, isolating the corrosion of the teeth by bacteria and acid, so as to prevent the occurrence of sulcus caries. Why do we need to do sulcus closure? The newly grown permanent molars of children are uneven and there are many sulcus points on them, which cause bacteria and food residues of caries to accumulate in these parts easily and cannot be removed by brushing. After a long time, the sulcus part is easy to occur caries, called “sulcus caries”. If the sulcus caries is not treated in time, the caries will gradually progress and serious symptoms such as toothache will appear, and the teeth with larger lesions even need to be extracted, which seriously affects the health and growth and development of children. According to the statistics, more than 90% of the permanent teeth caries of children in China are sulcus caries. Therefore, the prevention of sulcus caries will greatly reduce the prevalence of permanent tooth caries in children. In addition, because children are young, generally like to eat sweet food, soft food, sticky food, these foods are easy to stick on the teeth, plus the newly erupted teeth are not completely calcified, more easy to bacterial erosion and bad. For these reasons, when the permanent molar is fully erupted, it should be done in time to close the sulcus. 4. What is the best age to do sulcus closure? Usually, the permanent molars are fully erupted before the routine sulcus closure can be done. The first permanent molars (i.e., sixth-aged teeth) begin to erupt around the age of 6, and the second permanent molars begin to erupt around the age of 12. The timing of tooth eruption varies among children, and most children can have their first permanent molar sulcus closed at age 7-9 and their second permanent molar sulcus closed at age 12-14. It is recommended that parents take their children for oral examination regularly, and after the permanent molars are found to be fully erupted, the sulcus closure should be done in time. V. Is it painful to do the closure? There is no pain in doing the closure, the operation steps are: use a small brush to thoroughly clean the tooth surface to remove the retained food residue and bacteria; then acid etching of the tooth, so that the surface of the sulcus is tiny pores, which is conducive to the penetration of the sealant; blow dry thoroughly to remove the water retained in the sulcus; apply the sulcus sealant and irradiate with a light curing lamp for 20 seconds to make the material harden. It usually takes less than 5 minutes to do a tooth’s gutter closure without grinding the tooth tissue, so there is no pain, all the child needs to do is to open his mouth to cooperate with the doctor. 6. Do I need to review after the closure? Vulcanization can prevent the occurrence of caries in permanent molars to the maximum extent, but because the rate of loss of vulcanization is about 5-10%, it will affect the effect of caries prevention. The main reason for the loss of sealant is that some children have a lot of saliva during the operation, which makes the sealant not strong and easy to fall off. Therefore, it is recommended that after the closure, the child should go to the hospital for review every six months, and if the sealant is found to fall off, the child should be re-sealed in time. If the child has already had caries, it should be treated in time, because the earlier the dental disease is treated, the less painful, the less costly and the better the curative effect.