A child's first set of teeth, called primary teeth, usually begin erupting at about 6 months of age, although teething can begin as early as 3 months of age. Some babies do not get their first tooth until after 12 months of age. In rare cases, the first tooth erupts as late as 16 months of age. It is extremely rare for a baby to have congenitally missing teeth, which is when primary teeth fail to develop at all.

Sometimes a baby will have a tooth at birth. This tooth usually does not have a root system and may fall out by itself. If the tooth doesn't fall out, the doctor will check to see if it needs to come out or not.

A baby can sometimes develop an extra primary tooth, most often an extra third bicuspid or fourth molar. An extra tooth may interfere with eruption of the permanent one underneath and should be removed.