Three dimensional CBCT analysis of morphology in patients with chin deviation
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Introduction: Facial symmetry is defined as the correspondence in size, form, and arrangement of the facial features on opposite sides of the median sagittal plane. Although mild facial asymmetry is the norm, significant facial asymmetry is not uncommon. Mandibular asymmetry, in which the chin position deviates from the midsagittal plane, is one of the largest contributors to facial asymmetry. Seeking a reliable measurement for evaluation of facial asymmetry with chin deviation is a difficult task. Radiographically, 2-dimensional films such as posteroanterior cephalogram, submentalvertex views and panoramic films have been used by different investigators for diagnosis of facial and mandibular asymmetry. Objective: The purpose of this study is to investigate which anatomic areas contribute to asymmetry in patients with chin deviation. Material and Methods: 31 adult patients were divided into facial symmetry (n=16) and chin deviation groups (n=15), with asymmetry being defined as at least a 2 degree deviation between Me-ANS and the midfacial plane. Patients included had no history of trauma, temporomandibular disease, or craniofacial tumors. Three-dimensional cone-beam computed tomography (CBCT) scans were used to locate surface landmarks that represented condylar, coronoid, gonial angle, body and chin units. This method has been used in a recent study. These landmarks were used to calculate the lengths and widths of each mandibular component. For each measurement, the difference between the two sides in the chin deviation group was compared to the difference between the two sides in the control group. Student's t-test was used to test the differences between the 2 groups for significance. Results: The difference in mandibular body unit length and chin unit length between the right and left sides was significantly greater in the chin deviation group (P = 0.03 and p =0.001, respectively) than in the control group. The measurements of condylar length, coronoid length, and condylar width, angular unit width, ramal heights between the chin deviation and control groups were not found to be statistically significant. Within the chin deviation group, the side from which the chin was deviated had a statistically significant longer body unit length and chin unit length. Conclusion: Asymmetry in the mandibular body unit length and chin length seem to be a consistent feature in patients with chin deviation. The heterogeneity of facial asymmetry with chin deviation may explain the lack of consistent asymmetry in other areas such as mandibular condylar length, coronoid length, ramal length, angular width, and condylar width. Comparison of unit volumes between the two groups will be investigated. A larger sample size may be needed to see other differences.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact email@example.com.Thesis (MSD) --Boston University, Henry M. Goldman School of Dental Medicine, 2013 (Department of Orthodontics and Dentofacial Orthopedics).Includes bibliographic references: leaves 33-36.
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