Three-dimensional Morphological Analysis For The Adult Patients With Mandible Deviation

Mandibular deviation is defined when the mandible displays asymmetry to the middle sagittal plane. The deformity affects not only the harmony and aesthetic of the face,but also change the occolusion and spine posture. The severity of the deformity increases with the growth of individual. Without discovery and treatment in an early stage, the functional mandibular shift might develop into genuine skeletal deformity.The former study use 2-dimensional radiographs as method. However, mandible has very complex 3-dimensional structure features. Conventional Lateral cephalometric radiographs sometimes exhibiting distortion and transfiguration due to overlapping, amplification and rotation of the skeletal structure, which failed to provide sufficient and accurate information for diagnosis and treatment of mandibular deviation. Nowadays, 3-dimensional reconstruction based on CT radiographs is used in medical field widely and makes accurate diagnosis possible and becomes an important method for the study concentrating on growth and development. So far, we haven't found detailed research for the mandibular deviation by 3-dimensional analysis. In this study, our objects take spiral CT scan voluntarily. We reconstruct three-dimensional graphs on the computer and try to reveal the skeletal structure features and the difference from normal people, in doing which, we can then provide reference for the diagnosis and treatment plan making of adult mandibular deviation.In this study, patients with mandibular deviation were as sample and compare with those who exhibiting normal occlusion. 3-dimensional graphs were used to investigate the skeletal structure, the mandible posture features and the difference from those normal occlusion people, through which,we can then provide reference for the diagnosis and treatment plan making of adult mandibular deviation.The study consists of three parts:1. Mandible three-dimensional reconstruction and morphological analysis for individual normal occlusion patientsPatients with individual normal occlusion were as sample in this study. After the reconstruction of the mandible, we then form a set of landmarks for the skeleton,the mandibular developmental asymmetry was assessed by measuring the difference between both sides in coronary, sagittal and axial dimensions respectively. The result showed that: except some landmarks which are slightly difficult to locate on the X or Z axis, most landmarks exhibit highly consistency. This set of landmarks and their definition is feasible for this study. Individual normal occlusion patients exhibit excellent symmetry in coronary, sagittal and axial dimensions by both the linear and angular measurements.2. Mandible three-dimensional morphological analysis for adult patients with mandibular deviation Patients with mandibular deviation were used as samples in this study. After the reconstruction of the mandible, the mandibular developmental asymmetry was assessed by measuring the difference between both shifted side and nonshifted side in coronary, sagittal and axial dimensions respectively. The result showed that: Ramus, especially condyle, are the most likely parts responsible for the mandibular deviation , which means that the non-shafted side of the mandible has longer ramus and longer condyle and the height of ramus and condyle is bigger than the shafted side. There were significant differences between the shifted side and the nonshifted side in SSG, SGM, SGS, CLA, R-FH , R-MS and R-MP, all bigger in non-shafted side ,except SSG. In coronal view, the lateral angle of the ramus in non-shafted side is bigger, the mandible rotates in the same direction of the mental region; in middle sagittal view, the landmarks of InfSig, Scp and Go are in a lower position compare to the shafted side and the height of ramus and condyle are bigger and the ramus inclines backward in the non-shafted side; in transverse view, the Go point is in a more anterior position in the non-shafted side, the mandibular body rotates in the same direction of the mental region. These should be paid great attention to during the orthodontic and orthognathic treatment.3. Mandible 3-dimensional morphological analysis for mandibular deviation comparing with individual normal occlusion patientsPatients with mandibular deviation were as sample and compare with those who exhibiting normal occlusion. After the reconstruction of the mandible, the mandible structure was assessed by measuring the difference between two sides in coronary, sagittal and axial dimensions respectively. The result showed that: Comparing with the individual normal occlusion patients, the ramus and condyle of the non-shafted side are the predilection sites for the mandible deviation, which usually overgrow in this side and exhibits normal or slightly undergrow in the shafted side; there are no difference in the length and height of mandibular body between both sides, the same as the individual normal occlusion patients. Except the transformation due to the overgrow of the ramus and condyle in the non-shafted side, the mandible also rotates against the skeleton because of the drag of the mastication muscles. In the coronal plane, the height of the condyle and ramus are bigger in the non-shafted side, which contributes to the mandibular rotation and the direction is the same with the mental region rotation, the individual normal occlusion patients show good symmetry and no rotation; in the middle sagittal plane, the ramus inclines backward in the non-shafted side, the both sides of the individual normal occlusion patients overlap well; in horizontal plane, we can observe the mandibular rotation and the direction is the same with the mental region rotation, while the individual normal occlusion patients show good symmetry. We shall take care of the structural deformation as well as the linear coordination when we perform surgery.