Are There Mandibular Morphological Differences in the Various Facial Asymmetry Etiologies? A Tomographic Three-Dimensional Reconstruction Study

Abstract

Facial asymmetries (FAs) have been classified according to the mandibular morphological differences to obtain better diagnostic and treatment decisions. The purpose of the present study was to establish diagnostic differentiation among FAs using computed tomography (CT) and 3-dimensional (3D) reconstruction. We performed a cross-sectional study of patients with a diagnosis of FA, who had been evaluated by CT and 3D reconstruction in the same clinical center from 2015 to 2018. The following mandibular anatomic characteristics were compared between the 2 sides (deviated side vs contralateral side) and type of FA: condylar length, mandibular ramus length and width, mandibular body length, and symphysis deviation. The 53 patients included 23 men and 30 women (age range, 16 to 25years). Six categories of FA were identified: hemimandibular elongation (n=25), hemimandibular hyperplasia (n=2), hybrid hyperplasia (n=3), asymmetric mandibular prognathism (n=14), asymmetry of the glenoid fossa (n=2), and functional laterognathism (n=7). The condylar length and mandibular ramus width were greater in the displaced side than in the contralateral side, with differences of -2.0±2.8mm(P<.001) and -0.5±1.7mm(P=.009), respectively. The mandibular body length was greater on the contralateral side (mean difference, 2.1±3.5mm; P<.001). The symphysis deviation was 5.0±3.4mm, and those with a hybrid form presented with a greater deviation, with values greater than 10mm, followed by those with hemimandibular elongation. The evaluation of the CT images and 3D reconstructions in patients with FA provided detailed information of the mandibular structure that is useful to compare the differences between sides and to classify the entities associated with FA.