Caries is the main disease that endangers the oral health of children and adolescents. In the United States, 84% of caries in people aged 6~17 years old are sulcus caries. Since the 1960s, the technique of fossa sealant has been widely used as an effective method to prevent fossa caries in children. What is a fossa closure? Vulval sealant is to apply a layer of liquid resin substance on the tooth surface, especially in the sulcus of the tooth, without grinding the tooth tissue, so that it can penetrate into the sulcus of the tooth surface and solidify quickly on the tooth surface by light, forming a protective barrier covering the sulcus, isolating the erosion of bacteria and acid to the tooth, just like putting a protective coat on the tooth, thus preventing the occurrence of sulcus caries. Why is the sulcus point gap prone to dental caries? The sulcus is a structural defect in the development of tooth enamel, it is complex in form and different in depth, the depth of a typical molar sulcus can reach 1.5mm, the diameter of sulcus mouth is only 0.5mm, the diameter of near the bottom of sulcus can be as fine as 0.1mm, lack of self-cleaning effect. Under the action of chewing pressure, the food residue is pressed into the sulcus, and the diameter of toothbrush bristles is about 0.2 mm, so it is difficult to clean the sulcus completely by toothbrush and mouthwash, and the enamel of the inner wall of the sulcus is thin and the content of calcium and phosphorus is relatively small, so it is easy to occur caries. There are also domestic studies which prove that the caries rate of the sixth-aged teeth (the first permanent molar) in the permanent teeth is the highest, especially in the sulcus of the tooth surface, which is due to its early eruption time, the longest exposure to the caries-causing environment of the oral cavity, and the most opportunities to be attacked by bacteria. Fluoride caries prevention has a certain effect on the smooth surface caries of teeth, but the effect on the occlusal surface sulcus caries is not ideal. It is the most effective and important measure to prevent the occurrence of caries on the occlusal surface at home and abroad by using sulcus closure. Steps of fossa closure The operation of fossa closure is very simple, first clean the tooth surface with small brush, isolate the saliva with cotton ball, apply acid etching agent on the tooth surface, rinse and blow dry after 20~30 seconds. Then apply the fossa sealer directly on the tooth surface so that the sealer reaches into the fossa and has a certain thickness. After light curing, just check for air bubbles, complete closure and occlusal high points. The whole process takes about 20 minutes and does not require drilling or any pain, the child only needs to open his mouth to cooperate during the operation. The advantage of the gutter closure The use of gutter closure to prevent the occurrence of occlusal surface caries is an important part of caries prevention measures. It has been recognized that the gutter closure is a successful caries prevention measure, and even if the tooth sealant is partially lost, the caries susceptibility is smaller than that of unsealed teeth. After decades of application, many scholars at home and abroad have agreed that the implementation of the gully closure can effectively prevent caries. Some fluoride is contained in the sealant, and the sealant acts as a “fluoride reservoir” to release fluoride to the adjacent tooth tissue slowly for a long time, which can greatly reduce the caries of the enamel in the adjacent area and decrease the caries rate of the sulcus wall, and has obvious caries inhibiting effect. Timing and clinical application principle of fissure closure To obtain the success of fissure closure and good caries prevention effect, it is very important to master the timing of closure. Regarding the timing of clinical application of fossa closure, scholars hold different views. The timing of early sulcus closure is mostly at the age of 3~5 years for milk molars; within 3 years after the eruption of permanent molars of adolescents, i.e., the closure of six-year-old teeth (first permanent molars) is appropriate at the age of 6~7 years, and the closure of second permanent molars is appropriate at the age of 12~13 years. At present, most scholars believe that the caries rate of individual, teeth and tooth surfaces will change at any time during the patient’s life, so the application of the socket closure must be based on this, and the proposal of the socket closure only within two or three years after the eruption of teeth is not correct. The British Society of Paediatric Dentistry has made the following rules about the indications for the closure of sockets: For patients: 1. children with serious systemic diseases, serious physical or mental defects, and children with poor social background, all occlusal surfaces of permanent teeth should be closed with sockets if they can cooperate with the closure operation. 2. children with extensive decay of milk teeth should be closed with sockets immediately after the eruption of permanent molars. Physician: 1.In addition to the occlusal surface of permanent molar, sulcus closure can also be applied to other tooth surfaces, such as the malformed lingual fossa of upper anterior teeth; 2.Under normal circumstances, sulcus closure should be done when the tooth eruption has sufficient height to allow wet saliva isolation; 3.If the child has a certain first permanent molar with occlusal surface caries, sulcus closure should be done for the remaining normal teeth of the same name; 4.If the occlusal surface caries has involved one or more first permanent molars The sulcus closure should be done immediately after the full eruption of the second permanent molar. In a word, the following principles should be followed: the sooner the teeth are fully erupted, the better; there should be sufficient clinical examination, and the patient’s degree of cooperation, general medical history, previous caries condition and family environment should be considered. For those sockets that are prone to caries, we can do sulcus closure regardless of the time of tooth eruption. Does it mean that you won’t get caries after having the gutter closure? The gutter closure is not a permanent solution, some scholars have studied that the three-year retention rate of gutter sealant is 58.3~84.2%. A large number of clinical studies have shown that the teeth which have been sealed with a sulcus can be carious when the sealant is completely or partially lost, but the teeth with good preservation of sulcus sealant are not carious. Therefore, the teeth should be reviewed regularly after 3 months, 6 months and one year after the closure, and the integrity of the sealant should be noted during the review, and should be closed in time if it falls off. In conclusion, besides paying attention to oral hygiene and reducing the intake of sugary food, children and adolescents should go to the hospital regularly for check-ups and carry out gully closure when needed to achieve early prevention, early detection and early treatment.