The dental evidence for prenatal and early postnatal growth insults in Down syndrome

Down Syndrome (DS) (Trisomy 21) is a relatively common anomaly occurring in one in every 600-700 live births and characterized by impaired growth and development and early senescence. Signs of abnormal development have been observed on ultrasound as early as the first trimester. They include abnormal flow velocity patterns in the ductus venosus and hypoplasia of the nasal bone in addition to increased fetal nuchal translucency. By the second trimester additional signs are evident on ultrasound, affecting skeletal growth as well as other organ systems. Dental anomalies include reduced tooth size and number, thin enamel and abnormal crown form as well as taurodont roots and a high frequency of missing teeth. The severity of the dental defects varies along the tooth row with later developing teeth most severely affected. Recent studies carried out on exfoliated (shed) deciduous teeth using a combination of serial microCT scans and SEM have enabled us to reconstruct the chronology and extent of intrauterine and infant growth insults in DS infants, expressed in growth and differentiation of the developing teeth. Our results for the deciduous teeth show that in DS, there is accelerated dental development in the first trimester followed by progressive growth retardation associated with impaired differentiation of the dental tissues. These changes appear to primarily affect cells derived from ectoderm and affect cell division and differentiation. This results in a smaller modified tooth germ with impaired enamel matrix formation and bio-mineralization. The resulting enamel is thin and hypomineralized and this may contribute to the severe abrasion seen in the teeth of DS children despite the associated lack of muscle tone.