A cephalometric study of mandibular asymmetry in a longitudinally followed sample of growing children.

A longitudinally followed sample derived from the Burlington serial control group was used to investigate changes in mandibular symmetry according to age and sex. Hard tissue asymmetry was recorded as the difference between right and left mandibular lengths measured from 45 degrees oblique cephalograms. Differences (right minus left) in gonial angle measurements were also compared. Asymmetries were common at all ages; the mean values are presented in tabular format to serve as diagnostic guidelines and to aid in treatment planning. A strong trend of left- to right-sided dominance in mean mandibular length exists. The right-sided dominance was expressed by the age of 12 years in girls, but not until the age of 16 years in boys; at this age, 5% to 10% of the children had asymmetries greater than 5 mm. Mean mandibular lengths were consistently larger for boys than for girls, with the exception at 12 years of age where there was no significant difference in length. Although the boys tended to be more asymmetric at younger ages, by the age of 14 years there was no significant gender difference. Relative to the age of 6 years of age, there was a near equal probability for a child's asymmetry to improve (approach the mean) by the age of 16 years. In contrast, no significant difference between left and right gonial angles was noted, and no age-related trends were apparent.