Morphometric variables of the primary second molar in children with Down syndrome.

: Thirty-seven second primary molar teeth of children with DS were examined from casts of 6 girls and 8 boys aged 7-14 years, obtained from two centers for DS in Jerusalem and Haifa, Israel. One hundred and eighty-two primary second molars of normal children were examined from dental casts of 26 boys and 21 girls, which were taken for routine orthodontic evaluation. The following variables were examined on the teeth: all the inter-cuspal distances, the angle between the cusps, the area within the line connecting cusp tips, maximal buccolingual and mesiodistal dimensions, maximal perimeter of the occlusal table, maximal area of the occlusal table, maximal perimeter of the tooth crown from occlusal view, and maximal area from occlusal view. The results indicate that the second primary molars in individuals with DS are generally larger in the external dimensions (bl, md) than teeth of normal children, with larger inter-cuspal distances ('internal dimensions'). No significant change in the angles between the cusps were recorded. Thus, it seems that DS second primary molars retain the same cuspal shape of normal teeth, but with larger proportions. Sexual dimorphism was found to be more pronounced in the DS children. It is suggested that in DS, there may be a transitory acceleration in mitotic activity of developing enamel organs at about the early stage of gestation, which persists during the initial stages of mineralization of the primary teeth. The initial acceleration would then be followed by the widely recognized retardation in growth, reflected in smaller permanent teeth.