Human tooth-size asymmetry in cleft lip with or without cleft palate.

Failure of corresponding teeth on the right and left sides to form as exact mirror images of each other is an expression of imprecise developmental control. Levels of tooth-size asymmetry can therefore be used to quantify developmental instability in different regions of the dentition. Mesiodistal and buccolingual diameters of deciduous and permanent teeth were measured to the nearest 0.1 mm on serial plaster models of 77 patients with cleft lip with or without a cleft of the palate, and 63 control non-cleft orthodontic patients. In the cleft group as a whole, there were abnormally high levels of tooth-size asymmetry but, although most marked in the upper lateral incisor region, these were neither restricted to the vicinity of the cleft nor to the upper jaw. Thus, in addition to major local disturbances related to the malformation itself, it appears that tooth-size asymmetry results from a generally high level of developmental instability throughout cleft lip/palate dentitions. This generalized developmental instability may be to some extent under genetic control, as cases with positive family histories showed some signs of greater asymmetry than those with negative family histories.