The effect of sex and age on facial asymmetry in healthy subjects : a cross-sectional study from adolescence to mid-adulthood

Purpose: The study assessed the effects of sex and age on 3-dimensional (3D) soft-tissue facial asymmetry. Patients and Methods: The 3D coordinates of selected soft-tissue facial landmarks were digitized on 314 healthy white subjects (40 male and 33 female adolescents, aged 12 to 15 years; 73 female and 89 male young adults, aged 18 to 30 years; and 41 male and 38 female adults, aged 31 to 56 years) by an electromagnetic instrument. Facial asymmetry was quantified by detecting a plane of symmetry and the centers of gravity of the right and left hemifaces and by calculating the distance between the 2 centers of gravity (distance from the symmetry [DFS]). Both absolute (millimeters) and percentage (of the nasion-center of gravity distance) DFS were obtained, as well as the maximum normal asymmetry. The asymmetry of single landmarks was also quantified. Results: No gender- or age-related differences were found for both absolute and percentage DFS (P > .05). The maximum normal asymmetry was slightly greater in females than in males of corresponding age; within each sex, the largest values were found in the adolescent group. Tragion, gonion, and zygion were the most asymmetric landmarks in all groups (about 10% to 12% of the nasion-facial center of gravity distance), whereas the least asymmetric was endocanthion (4% to 6%). Conclusions: A slight soft-tissue facial asymmetry was found in normal subjects. The maximum normal asymmetry could be useful in identifying borderline asymmetric patients.