Crown size asymmetry in males with fra (X) or Martin-Bell syndrome.

We measured the mesio-distal and bucco-lingual crown diameters of 13 males with the fra(X) or Martin-Bell syndrome. Fluctuating crown-size asymmetry was calculated and compared with values obtained in normal Caucasian children and also with a sample of 19 males with Down syndrome. A statistically significant increased asymmetry was found in the fra(X) males when compared to normal control individuals. In the maxilla, Down syndrome males showed a significantly higher tooth crown asymmetry than fra(X) males. (less than 0.02); in the mandible, no significant differences were found between the 2 groups. It is suggested that crown size asymmetry be included in the evaluation of fra(X) males.