A babys first tooth is a milestone for parents. The buds for all of your babys teeth are formed before birth, and usually begin to erupt by 7-8 months, although it can happen earlier. The rate and order of tooth eruption differs from one child to the next. Normally the lower middle incisors are the first to emerge, followed by the upper middle incisors. By the time a child is three, he or she will have most of their 20 baby teeth. The permanent teeth begin to erupt at around age 6, beginning with the molars and incisors. Teeth continue to erupt from this time until about age 21, when the third molars(wisdom teeth) have emerged. This gives adults a total of 32 teeth.