Soft tissue facial growth and development as assessed by the three-dimensional computerized mesh diagram analysis.

Abstract

The normal growth and development of facial soft tissues from 6 years to adulthood has been studied by the 3D computerized mesh diagram analysis. The analysis allows independent quantifications of size and shape modifications both between different age groups, and between males and females. Normal age-related and sex-related references are provided. The three-dimensional facial morphometry method has been used for the collection of the x, y, z coordinates of 22 soft tissue landmarks in 2023 examinations performed on 1157 healthy white children and adolescents between 6 and 17 years of age and 191 young adults. The method detects the three-dimensional coordinates of retroreflective, wireless markers positioned on selected facial landmarks using two charge-coupled device cameras working in the infrared field. For each sex and age class, mean values were computed, and a standardized mesh of equidistant horizontal, vertical, and anteroposterior lines was consequently constructed. Within each age group, male meshes were superimposed on female meshes. Moreover, within each sex, the adult reference mesh was superimposed on the reference mesh of each age group. The global (size plus shape) difference was then evaluated by the calculation of the relevant displacement vectors for each soft tissue landmark. A global difference factor was calculated as the sum of the modules of all the displacement vectors. Consequently, a size normalization was performed, and the shape difference (size standardized) was then evaluated by the calculation of new relevant displacement vectors for each landmark, as well as a shape-global difference factor. When compared to the young adult situation, the largest child discrepancies were found in the soft tissue profile. After size standardization, shape differences were found in the forehead, nose, and chin. The soft tissue facial dimensions of boys and girls grow with similar characteristics and at the same rate between 6 and 11 years of age, but showed different patterns after this age. Within each age class, most of the sex-related differences were dimensional discrepancies that were corrected after size standardization. Nevertheless, before adolescence even these size differences were limited. On average, male faces had a larger forehead, longer and more vertical nose, more inferior and posterior gonia, more inferior and prominent lips, and a larger mouth than female faces of corresponding age.