The eruption of milk teeth usually starts at 6 to 8 months after birth, and most of them come out before the age of 3. The absence of milk teeth after 13 months is considered as delayed eruption. At the time of birth, milk teeth are ossified, but hidden in the jawbone and covered by the gums. 6 to 8 months after birth, milk teeth usually start to erupt, and the order of eruption is generally the lower jaw is first than the upper jaw, and the teeth erupt from the front to the back, and they usually erupt before the age of 3 years old. The eruption time of milk teeth is related to endocrine, heredity, diet and so on, and there is a big difference between individuals, the time of eruption of milk teeth may be too early or late, if there is still no eruption of milk teeth after 13 months, it is called delayed eruption of milk teeth, and it may be related to rickets, osteochondrosis and so on. Parents are advised to pay attention to dental and physical health during teething period, and should consult the doctor in time if there is premature or delayed teething, as well as low fever and irritability during teething period.