Three-Dimensional Geometric Morphometric Characterization of Facial Sexual Dimorphism in Juveniles

Background: The characterization of facial sexual dimorphic patterns in healthy popu-lations serves as valuable normative data to tailor functionally effective surgical treat-ments and predict their aesthetic outcomes and to identify dysmorphic facial traits re-lated to hormonal disorders and genetic syndromes. Although the analysis of facial sexual differences in juveniles of different ages has already been investigated, few studies have approached this topic with three-dimensional (3D) geometric morpho-metric (GMM) analysis, whose interpretation may add important clinical insight to the current understanding. This study aims to investigate the location and extent of facial sexual variations in juveniles through a spatially dense GMM analysis. Methods: We investigated 3D stereophotogrammetric facial scans of 304 healthy Italians aged 3 to 18 years old (149 males, 155 females) and categorized into four different age groups: early childhood (3–6 years), late childhood (7–12 years), puberty (13–15 years), and adoles-cence (16–18 years). Geometric morphometric analyses of facial shape (allometry, gen-eral Procrustes analysis, Principal Component Analysis, Procrustes distance, and Partial Least Square Regression) were conducted to detail sexually dimorphic traits in each age group. Results: The findings confirmed that males have larger faces than females of the same age, and significant differences in facial shape between the two sexes exist in all age groups. Juveniles start to express sexual dimorphism from 3 years, even though biolog-ical sex becomes a predictor of facial soft tissue morphology from the 7th year of life, with males displaying more protrusive medial facial features and females showing more outwardly placed cheeks and eyes. Conclusions: We provided a detailed characteriza-tion of facial change trajectories in the two sexes along four age classes, and the provided data can be valuable for several clinical disciplines dealing with the craniofacial region. Our results may serve as comparative data in the early diagnosis of craniofacial abnor-malities and alterations, as a reference in the planning of personalized surgical and or-thodontic treatments and their outcomes evaluation, as well as in several forensic ap-plications such as the prediction of the face of missing juveniles.