Upper incisors did not fall out lower lateral incisors fell out is a normal situation during children’s tooth replacement period, parents do not need to worry too much. Human beings have two sets of teeth, milk teeth and permanent teeth, so there is a replacement process of human teeth in childhood. There is a certain natural order of tooth replacement in children. Generally, after the fifth tooth in each quadrant of the mouth, the first permanent tooth will erupt around the age of 6, i.e., the first permanent molar, which is also known as the six-age tooth. At the same time or a little later, the other milk teeth begin to be replaced. The order is that the front teeth are replaced first, followed by the lateral teeth, and generally the lower jaw teeth are replaced earlier than the upper jaw teeth. After all the milk teeth are replaced with permanent teeth, a new tooth, the second permanent molar, grows after the first permanent molar. During the tooth replacement period, parents should encourage their children to eat fiber-rich, rough foods that can be used to increase the strength of chewing, thus facilitating the development of the jaws. If too soft food is often eaten, the development of the face and jaws may be affected. Parents should pay attention to children’s oral hygiene in general, because children’s mouths may be poorly cleaned due to discomfort during tooth replacement. If the children’s milk teeth are retained and other abnormalities, parents should bring the children to the hospital in time, the doctor will be based on the specific situation of the children, targeted treatment.