A Cone Beam CT Study On Morphology And Position Of Temporomandibular Joint In Skeletal Class â…¢ Adult Patients With And Without Mandibular Deviation

Objective:The aim of this study was to explore the symmetry of temporomandibular joint morphology and position in skeletal Class Ⅲ adult patients with and without mandibular deviation by cone-beam computed tomography(CBCT), in order to have a better understanding of this craniofacial deformity and to provide a reference for clinical diagnosis and treatment designs.Methods: The study comprised class I normal occlusion(group 1) and skeletal class Ⅲ malocclusion subjects(groups 2 and 3).Twenty student-volunteers of Xiamen Medical College with normal occlusion(male 10, female 10, age 20.62±2.19) were selected as a Group 1(Normal occlusion). At the same time, twenty skeletal Class Ⅲ adult patients without mandibular deviation(male 10, female 10, age 23.71±3.57) and twenty skeletal Class Ⅲ adult patients with mandibular deviation(male 10, female 10, age 22.79±3.15) were selected as group 2(symmetric skeletal Class Ⅲ) and group 3(asymmetric skeletal Class Ⅲ) respectively from the patients who visited Department of Orthodontic at Xiamen Dental Hospital during December 2012 to December 2014. CBCT image of all the subjects were acquired. The data obtained were exported in the DICOM format into the Mimics14.0 software, and the 3D reconstructions were creat. It was the following anatomy measurement of temporomandibular joint that were made on 3D reconstruction images : the morphology of condyle, the position of condyle, the morphology and position of glenoid fossa. Statistical software SPSS19.0 was used. Kolmogorov-Smimov test was used to test the normal distribution. Paired-samples t test was used to analyse the symmetry of bilateral TMJ in each group. Then the mean and the differences in the bilateral means were compared by one-way ANOVA among 3 groups. A p-value of < 0.05 was chosen for the significance level in all tests.Results: 1. Asymmetry alteration of bilateral condylar morphology existed in skeletal Class Ⅲ patients with mandibular deviation(P ﹤ 0.05). compared with the contralateral side, the condylar perpendicular height, condylar anteroposterior diameter, condylar medialateral diameter, the distance between Co T to LP, were significantly smaller but the angle among Co A, Co T and Co P was significantly larger in deviated side. 2. Compared with bilateral condylar morphology means of normal occlusion group and skeletal Class Ⅲ without mandibular deviation group, the condylar perpendicular height, condylar anteroposterior diameter, condylar medialateral diameter, the distance between Co T to LP, and the angle among Co A, Co T and Co P were significant smaller in deviated side but the angle among Co A, Co T and Co P was significantly larger(P﹤0.05);while contralateral side were not significant(P﹥0.05). 3. Asymmetry alteration of bilateral condylar position occurred in skeletal Class Ⅲ patients with mandibular deviation(P﹤0.05). The coronal medial space, anterior joint space and superior joint space were significantly smaller in the contralateral side than the deviated side. The distance from Co T to FHP was smaller in the deviated side than the contralateral side. Compared with the contralateral side, the distance from Co C to MSP was smaller but the distance from Co C to SCP was larger in the deviated side. Asymmetry position alteration of bilateral mandibular ramus plane relative to craniofacial occurred in skeletal Class Ⅲ patients with mandibular deviation(P﹤0.05). The angle between MRP and FHP and angle between MRP and SCP were significantly larger but the angle between MRP and MSP was significantly smaller in the deviated side than the contralateral side. The angle between CCP and SCP was significantly larger but the angle between CCP and MSP was significantly smaller in the contralateral side than the deviated side. 4. The asymmetry alteration of bilateral morphology and position of glenoid fossa in skeletal Class Ⅲ patients with mandibular deviation was not significant. Only fossa volume and the distance from FR to SCP were significantly larger in the contralateral side than the deviated side(P﹤0.05).Conclusion: 1. The bilateral asymmetry of condylar morphology and position in Skeletal Class Ⅲ Patients with mandibular deviation were significant but the morphology and position ofthe glenoid fossa were not. 2. The deviated side in Skeletal Class Ⅲ patients with mandibular deviation was the abnormal side and contralateral side was normal side. 3. The bilateral asymmetric fossa-condyle relationship in Skeletal Class Ⅲ patients With mandibular deviation found in the present study was due to the effect of condylar rotation and alteration.