Three-dimensional longitudinal assessment of facial symmetry in adolescents.

Recent advances in laser scanning technology provide the opportunity to examine faces in three dimensions. The aim of this prospective clinical study was to explore facial symmetry in healthy growing individuals and determine whether asymmetric changes occur during adolescent growth. Non-invasive laser surface scanning was performed to capture facial images of 60 Caucasian Finnish adolescents (30 males and 30 females, mean 11.5 years). Facial symmetry was analysed on images obtained at the initial scanning (T₁), 2.5 (T₂), and 4.5 (T₃) years thereafter. The final sample consisted of 39 adolescents (19 males and 20 females, mean 16 years). Three-dimensional images were processed and analysed using an in-house developed subroutine for commercial software. A mirror image was generated and superimposed on the original image to create a symmetric face and establish the midsagittal plane. The surface matching of the original face and the mirror face (amount of symmetry) was measured for the whole face, upper, middle, and lower thirds at tolerance level 0.5 mm and presented with colour maps. Three angular and 14 linear measurements were made based on 21 soft tissue landmarks, which have proven to be reliable. The results of the Friedman test showed that facial symmetry parameters did not significantly differ over time (P > 0.05). Mann-Whitney U-test did not reveal statistically significant differences between genders at any time point (P > 0.05). Facial growth of healthy individuals during adolescence is symmetric, although further investigation on larger randomized sample is suggested.