Unilateral Crossbite Malocclusion: Assessment of Asymmetry
Objectives: The aim of this study was to identify and quantify skeletal and dental asymmetries in unilateral crossbite malocclusion based on the evaluation of 3D mesh surface models.
Methods: 3D volumetric label maps were built for each subject’s original CBCT scans for 25 unilateral crossbite malocclusion subjects. Sixteen landmarks were identified in all original volumetric label maps of the skull. All original surface models then were oriented in a common coordinate system. The original scan and associated 3D volumetric label map were mirrored to generate a second scan and a second 3D volumetric label maps. Registration of original and mirrored images relative to the anterior cranial base and regional registrations (maxilla and mandible) were performed. 3D surface mesh models were generated in Slicer software. 3D differences between right and left sides, and the amount of directional differences in each plane of the 3D space between original and registered mirrored models were quantified. Statistical analysis was performed by evaluating the mean and standard deviation, paired t-test (comparison between sides).
Results: Crossbite patients showed variable degrees of dental and skeletal asymmetries. The 3D components differences using mirroring revealed that the unilateral crossbite patients had small differences in the A-P position of the fossa, significant differences in the A-P length of the mandible, mandibular yaw toward the crossbite side, lateral displacement of the mandible, and lower midline toward the crossbite side. 3D measurements of the right and left sides showed that differences between both sides were significant for mandibular length.
Conclusions: Unilateral crossbite malocclusion is more frequently related to mandibular yaw, mandibular lateral displacement and lower midline deviation toward crossbite side.