An Analysis of Mandibular Characteristics According to Biological Sex Using Three-Dimensional Computed Tomography Scans in Koreans: A Retrospective and Observatoinal Study

TL;DR

This study uses 3D CT scans to identify mandibular differences between biological sexes in Koreans, aiding facial feminization surgery planning.

Contribution

Provides population-specific mandibular morphological data for Korean individuals to support gender-affirming surgical planning.

Findings

Males had significantly larger mandibular angles, lengths, and widths compared to females.

Females predominantly showed pointed chins and straight inferior mandibular borders, while males had round/square chins and rocker-shaped borders.

Sexual dimorphism in the Korean population includes angularity, transverse width, and chin morphology differences.

Abstract

Background and Objectives: With the increasing demand for gender-affirming procedures, facial feminization surgery (FFS) has become an essential component in the management of patients with gender dysphoria. In this study, ‘male’ and ‘female’ refer to biological sex as recorded in the medical record; gender identity was not assessed. The mandible is widely recognized as one of the most sexually dimorphic facial bones and plays a critical role in defining masculine and feminine facial contours. However, quantitative mandibular data directly applicable to surgical planning for FFS, particularly in Asian populations, remain limited. The purpose of this study was to analyze gender differences in mandibular morphology using three-dimensional (3D) computed tomography (CT) images and to provide clinically relevant anatomic data applicable to mandibular contouring in FFS. Materials and Methods: In this single-center retrospective study, 275 Korean patients who underwent facial CT between January 2017 and December 2019 were enrolled. Three-dimensional cephalometric analysis was performed to obtain surgically relevant mandibular measurements, including angular, linear, and transverse parameters, as well as non-metric characteristics such as chin shape and inferior mandibular border contour. Statistical comparisons were conducted to evaluate gender differences. Results: Significant gender differences were observed in mandibular angle (p < 0.001), mandible length (p < 0.001), antegonial notch distance (p < 0.001), intercondylar width (p < 0.001), and intergonial width (p < 0.001). Ramus length and chin width did not demonstrate statistically significant differences. Non-metric analysis revealed significant gender differences in chin morphology and inferior mandibular border contour (p < 0.01). Males predominantly exhibited a round or square chin (79.5%) and a rocker-shaped inferior border, whereas females commonly demonstrated a pointed chin (82.3%) and a straight inferior mandibular border (94.4%). Conclusions: The sexual dimorphism of the mandible in the Korean population is characterized by differences in angularity, transverse width, antegonial morphology, and inferior border contour. These findings provide population-specific morphological reference ranges that may support individualized preoperative assessment for mandibular contouring in facial feminization surgery.

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