3-D Comparison of the shape and position of the condyle before and after Class II correction

Abstract

Introduction: The aims of this study were to assess the changes in the shape and position of the condyle in the fossa as well as its position relative to the cranial base before and after Class II correction with the Herbst appliance (HA) or headgear (HG), and to also compare any changes to matched Class I cases. Methods: Patients were divided into four groups, Class II treated with HA and their matched Class I cases, as well as Class II cases treated with HG and their matched Class I cases. CBCTs were obtained before and after treatment in all cases. A total of 122 condyles (left and right) from 61 patients were assessed. 242 landmarks were identified on the condyle and fossa, from which 3-D surface meshes were created. 7 relatively stable landmarks were recorded on the skull to assess the position of the condyle relative to cranial base. Length of the mandible was measured on laterals cephalograms rendered from CBCTs. Principal component, generalized Procrustes, and discriminant function analyses were used to assess shape and position changes. Results: There were no significant changes in the position of the condyle relative to the cranial base before and after treatment. No significant differences were reported in the anteroposterior or vertical position of the condyle relative to the fossa (P=0.71 and P=079 respectively). There were significant changes in the shape of the condyles when Class II untreated cases were compared to controls. Untreated Class II cases had more internal rotation of the mediolateral long axis of the condyles when compared to Class I cases. There were no significant differences in changes in the length of the mandible between Class II and control cases. Conclusion: The condyles of all untreated patients, whether they were Class I or Class II initially, did not change their position (within the fossa or relative to stable cranial base structures) when assessed at the end of orthodontic treatment.