According to the results of the third national oral health epidemiological survey, the caries rate of 5-year-old children’s milk teeth in China is 66%, which is at a higher level in the world, and the untreated rate is as high as 97.1%. Children are in the period of human growth and development, oral diseases will have a negative impact on their health and growth. The main risk factors are eating sugary food before bedtime, brushing time and parents’ oral cleaning care for children. According to the survey, 72% of 5-year-old children eat sugary food every day; 11% of children often eat sugary food before going to bed; only 13% of children start to brush their teeth before the age of 3, only 22% brush their teeth twice a day, and 20% of 5-year-old children do not brush their teeth; only 9% of parents can help their children brush their teeth every day; only 22% of children have regular oral check-ups, and most of them seek medical treatment only when they have toothache and other problems. It is a misconception that decay is the main manifestation of children’s dental disease and the main culprit of tooth loss. The uneven depression on the biting surface of the back teeth is called sulcus, which is a defect formed by the obstruction of tooth cusp fusion during the development of teeth. The sulcus of each tooth varies in shape and depth, and is a suitable place for bacteria to grow and multiply. In this calm and hidden environment, the bacteria use the sugar (carbohydrate) in the food to reproduce and grow, and produce acid in the process of metabolism to corrode the teeth and form cavities, therefore, the risk of caries is higher in the deep sulcus. At the same time, the bottom of the sulcus is close to the boundary of enamel dentin or located in the dentin, once the caries occurs, the damage can develop rapidly to the deep, forming the cavity which is small in appearance but deep and big in reality, and this kind of caries is called sulcus caries in medical science. The caries can also spread to the pulp (dental nerve) and lead to pulp inflammation or apical inflammation, which will lead to tooth loss if not treated in time. The back teeth are responsible for the main chewing function, once lost, the chewing function will be greatly reduced, affecting the nutritional intake and growth and development. Many parents think: the first set of teeth of children – “milk teeth” will be replaced sooner or later, and the permanent teeth after replacement will be used for life and need to be well protected. This is a misunderstanding, the decayed milk teeth not only can cause severe pain, but also have to be pulled out if the damage is irreparable, and also affect the eruption of permanent teeth. The prevention of tooth decay should start from the baby teeth. After the baby’s milk teeth erupt, the mother should start to clean the baby’s teeth. The method is to use sterilized gauze wrapped on the second finger, dipped in saline or distilled water to scrub each tooth surface, twice a day, once in the morning and once in the evening; when the baby is 1~2 years old, he/she should learn to brush his/her teeth slowly and develop good oral hygiene habits. Regular oral health check-ups to prevent caries as early as possible. Conduct oral health examination once every six months, find out the problem at any time and deal with it in time, so as to facilitate the healthy growth of infants and toddlers. 3~4 years old can go to the dental hospital to coat the occlusal surface of upper and lower milk molar with sulcus sealant, so as to achieve the purpose of caries prevention.