Evaluación de la asimetría mandibular según la clase esquelética y patrón facial de pacientes simétricos sobre mandíbulas segmentadas

Abstract

Introduction: the purpose of this study was to establish if there is a relationship between the presence of mandibular asymmetries and the skeletal malocclusion or facial pattern of the patient. Material and methods: a comparative retrospective study was carried out. We analyzed images of Cone Beam Computed Tomography (CBCT) of 60 subjects from the Department of Orthodontics of the University of Valencia (34 women, 26 men, average age, 32.7 ± 11.6 years). The CBCT scans were divided into 3 groups (skeletal Class I, Class II and Class III, using tha Wits analysis) and the facial pattern of each patient was determined with FMA angle, where angles between 22º -28º are consider as normal growth. Using two computer programs (ITK-SNAP and 3DSlicer), we perform the segmentation of each patient, constructing 3D surface virtual models. The mirror image of these models was generated over the sagittal plane to flip the left and right sides of each image and to make the automatic superimposition on the cranial base to compare them. The asymmetry was defined as the discrepancy between each hemimandible. Results: there were no statistically significant differences for the evaluation of mandibular asymmetry based on the right and left reflex. According to the patient’s malocclusion, the mean of the signed distance was 0.13 mm in Class I, 0.09 mm in Class II and 0.13 mm in Class III. Considering the facial pattern, the mean of the signed distance was 0.17 mm in mesofacial, 0.06 mm in brachifacial and 0.15 mm in dolichofacial patients. Conclusions: mandibular asymmetries do not depend on skeletal malocclusion or facial pattern.