It is normal for babies to grow one tooth at a time, and some children will have symmetrical eruption of two teeth at the same time, which is individualized and normal. The eruption of baby teeth has a certain pattern, generally in the baby 4~6 months, the latest not more than 10 months will erupt the lower side of the two incisors, some babies are two at the same time eruption, some babies grow one first, which is a normal phenomenon. The baby will then erupt the upper two central incisors, followed by the lower two lateral incisors and the upper two lateral incisors, followed by the first molar, the tiger tooth and the second molar. Generally speaking, the baby will have all 20 milk teeth by the age of two and a half years. If the baby still has not erupted milk teeth after the age of one year, only then will we consider that the delay in the eruption of milk teeth may be due to rickets or congenital ectodermal underdevelopment, etc. If the baby has already erupted a single tooth, there is no need to worry about these situations. If your baby has only one tooth, you can consult the dentistry and pediatrics departments of your hospital and ask your doctor to identify the cause and dispose of it.