<P> Tooth development or odontogenesis is the complex process by which tooth form from embryonic cells , grow , and erupt into the mouth . For human teeth to have a healthy oral environment , all parts of the tooth must develop during appropriate stages of fetal development . Primary ( baby ) teeth start to form between the sixth and eighth week of prenatal development , and permanent teeth begin to form in the twentieth week . If teeth do not start to develop at or near these times , they will not develop at all , resulting in Hypodontia or Anodontia . </P>
when do the first signs of tooth development begin
between the sixth and eighth week of prenatal development