Once a child is diagnosed with dental caries (tooth decay), he/she should seek treatment as soon as possible to prevent further deterioration, causing pulp infection and pain, and even affecting the development of the inherited permanent tooth germ. Some parents think that the baby teeth will be replaced and ignore the treatment is a very wrong and outdated idea, which will cause a series of health hazards, including local and systemic hazards. Localized damage refers to the painful inflammation of the tooth. Once a tooth reaches the middle layer of the dentin, it will be prone to painful symptoms, starting with pain when eating, and if left untreated, spontaneous pain will develop, gradually leading to acute pulpitis. If the infection worsens, facial swelling and pain may occur, and the infection may inherit the permanent tooth germ and affect the development of the permanent tooth germ, which may lead to poor enamel development and the root of the tooth may be affected, including root curvature and enamel underdevelopment. In addition, premature loss of milk teeth may also cause malocclusion of permanent teeth. In addition, chronic focal infection may also cause systemic diseases (e.g. nephritis, allergic purpura, rheumatic fever, etc.); again, dental caries may affect the child’s pronunciation and appearance, Thus, it may cause children’s low self-esteem and affect their physical and mental development. For the question of whether it is necessary for children to do fossa closure, I believe that many parents are also ignorant about this issue, and do not know the cause and effect very well. What exactly is a fossa closure? Why do children need to have their teeth closed? The occlusal surface of the milk molar is not flat, but uneven, with many grooves. Once the strong caries-causing bacteria invade and multiply, metabolize and produce a lot of acid, it can gradually corrode and damage the whole tooth, especially children who have the habit of sleeping at night are more likely to have serious sulcus caries of molar teeth. The “sulcus closure” is to coat the teeth with a layer of adhesive resin to protect the enamel from the erosion of bacteria and metabolic products. The incidence of molar sulcus caries is high in children aged 2-3 years old, and the children’s cooperation in tooth cleaning is not high, so the sulcus sealing can prevent molar sulcus caries. Therefore, it is recommended that parents should visit a specialist pediatric dentist for the first time at least after the eruption of the upper front teeth (about 12 months) to assess the caries risk of their children, and if the caries risk is high or if the milk molar teeth already have signs of decay, it is necessary to carry out sulcus closure of the milk molar teeth at the early age of 2-3 years to minimize the caries risk. In addition, early childhood caries also includes adjacent surface caries, and children between 3 and 5 years old have a high incidence of adjacent surface caries, so they need to floss daily to prevent the occurrence of adjacent surface caries. In addition to the closure of the sulcus of milk molars, the closure of the sulcus of “six-age teeth” is a must, and in recent years, it has been listed as a project designated by the state to be carried out free of charge. It is understood that from the end of March 2015, Guangzhou elementary school (including private schools) second grade students (about 8 years old) will carry out free closure of the sixth age teeth. However, since a group of four teeth of the sixth age is the key to the occlusion of the whole mouth, parents who are in a position to do so are advised to consult the clinic as soon as possible after the eruption of the sixth age teeth (generally around 6 years old) to carry out the free program of fossa closure without waiting for the second half of the second grade, in order to reduce the risk of caries in this important group of teeth of the sixth age. In addition, for parents who are more demanding, the 8 permanent premolars and 4 second permanent molars can be closed at the age of 10-12 years according to the eruption of the permanent teeth. Vulval closure can bring the maximum protection to the milk molar or permanent molar, and can minimize the occurrence of vulval closure caries, but vulval closure does not mean 100% protection, there are still some precautions after closure. After the closure, there are some precautions as follows: 1.After the closure, it is necessary to continue to strengthen the daily dental cleaning, it is recommended to use electric toothbrush and fluoride toothpaste. 2, need to be reviewed every six months, if the sealant is found to be severely worn out and partially fallen off, need to be done in a timely manner. 3.Socket sealant can only prevent the sulcus caries on the occlusal surface, but not the adjacent surface caries between teeth. Therefore, even if we have done the gutter closure, we still need to strengthen the use of dental floss to clean the interdental space every day to prevent the occurrence of adjacent surface caries. It is a preventive non-invasive treatment, which does not need to drill and grind the teeth, but can be completed after cleaning the acid-etching tooth surface and applying the sealant light curing, for the children with high risk of caries, it is recommended to consider the early molar sulcus closure at 2-3 years old to minimize the risk of caries. Prevention is better than treatment, so that the child can avoid the pain and swelling in case of serious caries, and avoid the medical measures such as drilling, anesthetic injection, nerve killing, tooth extraction and even treatment under general anesthesia.