Dental asymmetry and mental retardation: a comparison of subjects with mental retardation resulting from prenatal or postnatal influences.

The development of phenotypic characteristics is believed to be stabilised within certain limits of variability by processes described as canalisation or developmental homeostasis. Dental asymmetry is thought to reflect the relative success that developmental homeostasis has in countering developmental disturbances. The present study demonstrated that dental asymmetry of the permanent dentition was generally higher in non-Down retarded subjects whose mental retardation was associated with a prenatal rather than a postnatal or birth related insult. Because variations in the size and shape of teeth are generally produced during the prenatal period, the finding of increased fluctuating dental asymmetry in the group with prenatal insult supported the contention that dental asymmetry reflects the relative success that developmental homeostasis has in countering developmental disturbances.