Tooth size in children and young adults with trisomy 21 (Down) syndrome.

Mean values and variances of the mesiodistal and buccolingual dimensions of all deciduous and permanent teeth, except third molars, were compared between 147 Down syndrome and 265 control subjects. Permanent tooth dimensions were significantly smaller in the Down syndrome group and also tended to show greater variability. However, for the deciduous dentition, some dimensions were significantly larger in Down syndrome and no systematic differences in variability were noted between the groups. These findings indicate that there may be an initial transitory acceleration in mitotic activity of developing enamel organs in Down syndrome followed by the characteristic generalized retardation in growth.