There are two sets of teeth in a person’s life, the milk teeth and the permanent teeth, and there are big differences between them. The number of permanent teeth is usually 28-32; 3. Color: Since the outermost layer of teeth is enamel, the yellow color of tooth essence comes through as the enamel layer of permanent teeth is better mineralized. The mineralization of milk teeth is poorer and covers the color of dentin. Therefore, milk teeth are generally milky white, permanent teeth are generally yellowish, and the glossiness of permanent teeth is better than milk teeth; 4, emergence time: all milk teeth erupt at about 3 years old, and begin to fall out at the age of 5-7 years old, and completely fall out at about 12 years old. Permanent teeth start to erupt at the age of 5-7, so teeth that erupt after the age of 5 are usually not milk teeth, and permanent teeth will not be replaced after they have fully erupted. If parents cannot distinguish them with the naked eye, they can go to the hospital or dental clinic to take x-rays for an accurate identification.