In the oral cavity, there are many grooves on top of the molar teeth. These grooves are uneven, like a grinding disc, which can increase the chewing area and increase the friction, and help to chew the food fully. The sulcus of molar teeth is deep and numerous, and is more obvious in the newly erupted permanent teeth. The depth and shape of the sulcus vary, with a typical molar sulcus being up to 1.5 mm deep and the diameter of the sulcus only 0.5 mm, and some porous structures can only be seen under high magnification. However, it is not negligible that these parts of the fissure are deeper, easy to accumulate caries-causing bacteria, and not easy to remove, once the bacteria invade, it can gradually damage the whole tooth, forming a cavity. Tooth decay, commonly known as tooth decay, “worm teeth”, is one of the most common oral diseases of human beings, and the World Health Organization has listed it as one of the three most prevalent diseases endangering human health together with tumor and cardiovascular disease. Although tooth decay is a common dental disease, but the harm it brings is great. Most children like to eat sweets and are not so conscious of cleaning their teeth, which greatly increases the possibility of developing dental caries. Vulcanization is a safe and effective method to prevent the occurrence of dental caries in children. It is a material (synthetic organic polymer resin which is harmless to human body and can be self-consolidated) that is coated in the small but deep sockets of teeth, and in liquid state it can penetrate into the sockets on the surface of teeth and is cured by light. It is like putting a protective coat on the teeth to prevent cariogenic bacteria and their acidic metabolites, food residues, etc. from entering the sulcus and eroding the teeth. It is a painless, non-invasive, safe and easy method to prevent children’s sulcus caries. As long as the sulcus sealant is kept on the tooth surface intact, it can effectively protect children’s teeth and prevent the occurrence of caries. Sometimes, even if the sealant falls off, the resin protrusion penetrating into the tooth enamel has a certain protective effect on the teeth. The sealing material used in the gash closure is called gash sealant, which is closely bonded to the wall of the gash after curing and has a certain anti-chewing pressure, so it is not harmful to eating, and the gash sealant is non-toxic and harmless to human body after curing. The principle of the gutter sealant is to fill the sulcus of the teeth with polymer material to make the tooth surface smooth and easy to clean. After the sulcus is closed, the original bacteria in the sulcus are cut off from the source of nutrition and gradually die; in addition, the cariogenic bacteria outside cannot enter again, thus achieving the purpose of preventing sulcus caries. For different age groups, different teeth can be sealed, for children from 3 to 4 years old, the milk molar is sealed; for children from 6 to 9 years old, the first permanent molar is sealed; for children from 12 to 15 years old, the second permanent molar is sealed. Usually, the teeth are closed within 4 years after eruption. If the teeth of children have good self-cleaning effect, there is no caries in the mouth, or the sulcus is superficial, the sulcus can not be closed. Some of the young people with deep sockets can also have their sockets closed to prevent caries. Sixth-aged teeth (the first permanent molar erupted around 6 years old) are the most prone to caries, mainly because: 1. The newly erupted teeth are not yet fully developed, the surface calcification is insufficient and the acid resistance is poor, so it is easy to occur caries, and it is easy to develop to the deep layer, which can lead to pulpitis and periapical disease in a short time. 2.The occlusal surface of six-year-old teeth has many deep sockets and grooves compared with other permanent teeth, plaque and food debris are hidden in these sockets, which are difficult to be removed by brushing, especially for children. 3, children’s diet has a large proportion of sugar food, these foods can promote the growth and reproduction of caries-causing bacteria. Therefore, it is especially important to perform the closure of sockets for six-year-old teeth in time. Avoid biting hard and sticky food, such as chewing gum, with the newly closed teeth. After the closure, the chance of tooth decay will be greatly reduced, but it does not mean that the teeth will be in the “safe” from now on. Therefore, we suggest parents to take their children for oral examination every 3-6 months, and check the closed teeth to see if the sealant falls off. If the sealant is found to have fallen off, the sealant can be re-applied.