text: Twenty.  Baby or primary teeth are lettered A through T.  Unless there is an unusual circumstance: example some children retain baby teeth when there is not a permanant tooth under it.  Children have twenty teeth by about age three.  The permanant molars come in behind the last teeth in the child's mouth.  Central incisors, Lateral incisors, canines, and premolars (bicuspids) come in as the baby teeth fall out.  Most children have all of their permanant teeth by age thirteen or fourteen give or take.  Except wisdom teeth which can come in between the ages of 17-21.  Note not all children have wisdom teeth, some have four, some two, and so on.  In the case of my son he is missing a permanant premolar (lower left side, second one) his baby tooth will have to suffice for as long as possible or until he stops growing, then we will have an implant placed in this missing tooth area.  Adult teeth are numbered 1-32.