Facial Asymmetry of Italian Children: A Cross-Sectional Analysis of Three-Dimensional Stereophotogrammetric Reference Values.

Reference data on the asymmetry of facial thirds of children is still scarce, although it can offer meaningful comparative information for clinical studies. This study aims to provide reference data on the facial asymmetry of Italian children using a 3D analysis of facial thirds divided according to the trigeminal nerve distribution (upper, middle, and lower). A 3D surface-based approach was conducted on the digital models of the faces of 135 children (74 M, 61 F), acquired by stereophotogrammetry. In addition to sex, two different age classes were analyzed (4-8 years and 9-12 years). For each facial third, the asymmetry was expressed as root-mean-square distance (RMS) by calculating the point-to-point distances between the original and the reflected 3D models. A 3-way ANOVA test verified significant differences between the two sexes, the two age classes, and the three facial thirds (p-value < 0.05), and also their interaction. Significant differences were found between the sexes (females were more symmetric, p = 0.005) and the two age groups (younger were more symmetric p < 0.001). According to Tukey's HSD post-hoc test, among the thirds, the middle one proved to be significantly more symmetrical (p < 0.001). No significant interaction impacting the asymmetry was found when the main factors were considered in any combination. Reference data on the "normal" facial asymmetry of Italian children was provided for further clinical purposes. Normal children have low average RMS values (0.30-0.51 mm) and younger, in particular females, proved more symmetrical than older children, while among the facial surfaces, the middle proved most symmetrical in both sexes, although with little clinical relevance. Since there is no consensus on the amount of symmetry deemed clinically acceptable, further studies on larger randomized samples are auspicial.