When we open our mouth, we can see that the biting surface of the last big tooth (the side of chewing food) is uneven, and the sunken part is called sulcus. If the development is not good, these sulci are very deep, food and bacteria embedded in it, easily occurring caries (worm teeth), medically called this caries as sulcus caries. According to the oral epidemiological survey, more than 90% of the caries (worm teeth) of our teenagers occur in the sulcus area. 2.What is the gutter closure? Closure is an effective method recommended by the World Health Organization to prevent caries on the occlusal surface of teeth. It is an artificial anti-caries material applied to the sulcus and cured by light. It is like putting a protective coat on the teeth to protect them from the erosion of bacteria and enhance their anti-caries ability, which is an effective method to prevent the occurrence of caries. 3.Why do we need to do the vulgarization for children? (1) The mouth and teeth are the starting point of the digestive system and the first step of digestion. Bad teeth will affect the child’s digestion and absorption of nutrition. Six-year-old teeth are the most important teeth that bear the function of chewing, erupting early and prone to caries (worm teeth). (2) The gutter sealant forms a protective barrier, and at the same time, the original bacteria in the sulcus gradually die because of being cut off from nutrition, thus preventing the occurrence of sulcus caries, and also stopping the development of early caries. 4.Does the gutter sealant cause any harm to the teeth? Vulval closure is a painless treatment method, which has been used for more than 50 years in the international arena. Even if the sealing material is swallowed, it will not have any adverse effect on human health. 5, the best time to treat the first permanent molar 6-7 years old, the second permanent molar 11-13 years old.