Analysis of Degree of Asymmetry between Right and Left halves of the Mandible in A sample of Egyptian Individuals

Mandibular reconstruction is mandatory for patients with mandibular defect. Computer assisted surgery (CAS), enables the surgeon to obtain stereolithographic (STL) model by mirroring the normal side on the affected one for adaptation of reconstruction plate. However, accuracy of adaptation may be influenced by the natural asymmetry of human skull. So this study was conducted to determine the degree of asymmetry between right and left halves of the mandible. The sample consists of 21 facial CT scans of intact mandible for reconstruction of virtual 3D model .For 3D linear and angular measurements; eight points were marked on each half of the mandible. Another nine points were marked on the whole mandible at its bottom view. For 2D measurements, points used for measurements of buccolingual thickness of the mandible were first marked at 3D model, and then measured at the 2D axial cut. These points were taken at three levels, the alveolar bone (Tha), above mental foramen (Thb), and the inferior border (Thc). At each level, three points were taken on each side. Using paired Student’s t test to analyze the difference between right and left halves of the mandible we found that there was a non-significant difference between right and left halves at 2D and 3D measurements, except for Thb1 (p=0,006) and Thc1 (p=0.008). Therefore we concluded that the mirroring tool is a reliable method in virtual reconstruction of the mandible in cases of unilateral mandibular defect with subsequent printing STL model for preoperative adaptation of the reconstruction plate.