In clinical work, we often see children who are more than 1 year old visit the clinic to see the front teeth, parents find that the child’s newly grown teeth have become yellow, or the teeth are peeling off piece by piece, the child dare not use the front teeth to bite things, or even serious teeth are so bad that only the roots of the teeth remain, and the gums appear red and swollen. This situation is not only distressing to parents, but also to doctors. Clinically, this disease is called “low age child caries”. Yang Yuan, Department of Pediatric Stomatology, Peking University Stomatological Hospital, Beijing, China It is very difficult to treat the teeth of children under the age of 3. The risk of treatment under general anesthesia is increased for children over one year old, and the treatment is usually done under restraint in the outpatient clinic, so it is inevitable that children cry and do not cooperate. In this case, parents and children are very painful; on the other hand, the treatment is more difficult and requires a professional pediatric dentist with many years of clinical experience. Because the child is small, he/she cannot cooperate with the treatment for a long time, and sometimes it is necessary to make several visits. So, what are the reasons for the appearance of low age child caries? In the clinical consultation, such children have a common feature that there are poor feeding habits. Whether breast-feeding or formula milk bottle-feeding, these children have the characteristics of falling asleep with a bottle and frequent feeding at night, which is also called “night milk habit”. The harm of this bad habit is that the contact between the sugary milk and teeth for a long time will cause the demineralization and dissolution of tooth enamel on the surface of teeth, resulting in tooth defects and tooth decay. Because the secretion of oral saliva decreases at night when you sleep, the PH value of the mouth cannot be buffered well, therefore, drinking milk at night is more harmful. This kind of caries is characterized by early occurrence (can appear in 8-9 months old baby), very rapid development, and great damage to the teeth, often causing extensive damage to the crown, involving multiple tooth surfaces, difficult to fill and repair, the filling material is easy to fall off after treatment, and the treatment is more difficult. Therefore, parents must cultivate good feeding habits for their children, stop the habit of falling asleep with a bottle and falling asleep with mother’s nipple, reduce night milk as much as possible, wean night milk early, and do a good job of cleaning children’s mouth and teeth every day. How to clean the mouth and prevent the occurrence of tooth decay, we will expand in the next section.