Maxillofacial 3-dimensional Morphological Analysis For Patients With Class Ⅲ Malocclusion And Facial Asymmetry

Objective:The purpose of this study was to use 3D computed tomography to investigate skeletal structure features of facial asymmetry in skeletal classâ…¢malocclusion patients and which skeletodental factors are related to chin point deviation.Methods:1. The first part is the analysis of the symmetry of the mandibular in skeletal classâ…¢malocclusion patients with mandibular deviation and without mandibular deviation. Forty adult female patients with Classâ…¢,who had 3D CT taken before orthodontics treatment, were assigned to group symmetry or group asymmetry according to the amount of chin point deviation from facial midline.Cranial base,midfacial and mandibular variables were measured with software. The data were analyzed with SPSS13.0 software package,using Paired-samples t test.2.The second part is the analysis of differences of skeletal structure features of skeletal classâ…¢malocclusion patients with mandibular deviation and without mandibular deviation. All statistical analyses were taken on SPSS13.0 package, paired t-tests of the same side skeletal structure features between group symmetry and group asymmetry and Pearson correlation between chin point deviation and skeletodental factors. Results:1. There were no significant differences in symmetry between deviation side and opposite side of group symmetry.In group asymmetry, the ramus and condyle of the opposite side are the predilection sites for the mandible deviation,which usually overgrow in this side and exhibits slightly undergrow in the deviation side. The vertical distance from the upper canine(U3) and first molar (U6) to the FH plane in the deviation side of group asymmetry was shorter than in the opposite side,there was no statistically significant asymmetry in mandibular body length and cranial base. 2. Comparing with the group symmetry patients, the deviation side mandibular ramal height of group asymmetry was significantly shorter, the ramus of the opposite side inclined more mesially to the sagittal plane and more forward to the coronary plane,and and differences in the vertical distance from the upper canine(U3) and first molar (U6) to the FH plane between the 2 groups were significant.There was no statistically significant asymmetry in mandibular body length and cranial base. Menton deviation was significantly correlated with mandibular ramal height of the deviation side, the difference of ramal height between two sides, condyle height of the opposite side, the transverse, vertical and sagittal position of gonion (Go). Menton deviation was also correlated with the difference of mandibular body length, ramus inclination to the sagittal plane, ramus inclination to the FH plane.Conelusions:1. Facial asymmetry in SCâ…¢patients gradually worsened from cranial base to mandibular,especially for the differences of ramus and condyle of two sides.2. The maxillary alveolar bone had compensatory alteration in mandibular asymmetry cases.3. Facial asymmetry in Classâ…¢patients occurs due to undergrowth of ramus in the deviation side, forward and mesial inclination of the opposite ramus.