Palatal and mandibular arch morphology in 47,XYY men and in other sex-chromosome anomalies.

Dimensions of the maxilla and mandible were studied in 47,XYY men and their first-degree male relatives, and the results compared with similar studies of other sex-chromosome anomalies. An extra Y chromosome in 47,XYY men caused an increase in palatal growth transversely and anteroposteriorly and in mandibular arch length anteroposteriorly compared to normal men. Palatal height and mandibular width were smaller with this chromosome pattern. Increase in the number of sex chromosomes is associated with changes in palatal and mandibular arch dimensions, more often an increase than a decrease. The findings support earlier observations that the palate becomes shallower with the addition of an X chromosome. It is also apparent that the influence of X and Y chromosomes differs, at least regarding the magnitude of metric changes.