3D Cephalometric Analysis,the Changes In Condylar Position Pre And Post Orthognathic Surgery In Skeletal Class Ⅲ Malocclusion

OBJECTIVE: 1.To evaluate the treatment outcome and to compare the changes of the hard tissue before and 6 months after the orthognathic surgery in patient with severe skeletal Class Ⅲ malocclusion using the three dimensional approach.2.To evaluate the changes in the condylar axis angle(axial,coronal and sagittal)and the changes in the anteroposterior position of the mandibular condyle related to the glenoid fossa before and 6 months after the orthognathic surgery in patient with severe skeletal Class Ⅲ malocclusion using the three dimensional approach with the help of the computed tomography(CT)images.Material and methods: The study included 21 adult patients diagnosed with skeletal Class Ⅲ malocclusion who underwent orthognathic surgery and had CT images records up to 6 months after the surgery.The CT images were obtained before surgery(T0)and 6 months after surgery(T1).All the CT images were analyzed three dimensionally using the Proplan CMF 3.0 software.Different skeletal and dental parameters were used in analyzing the cephalometric analysis of the patients.The cephalometric analyses used were Condyle Points,Downs,Frankfurt,Steiner and Tweed.Moreover,the cephalometric value that were used in the comparison of the surgical changes were SNA,SNB,ANB,Left Y Axis,Right Y axis and the Mandibular plane angle.In order to evaluate the change in the condylar axis angle,the condylar position were evaluated on three planes: axial,coronal and sagittal.In addition to the condylar axis angle the post-surgical changes of the anteroposterior position of the condyle in relation to the glenoid fossa were evaluated in the sagittal plane.Paired t test were used to test the statistical significance and compare the means.The statistical analyses were performed on IBM SPSS version 23 for Windows.Results: Result 1: After the orthognathic surgery,significant changes were observed in the skeletal analysis.∠SNB,∠ANB,∠Left Y Axis,∠ Right Y axis were statistically significant(P<0.01)suggesting these values improved significantly close to the normal.∠Mandibular Plane angle was also found statistically significant(P<0.05).However,there was no significant changes made in ∠SNA.Result 2: After the careful evaluation of the condylar axis on the three planes there was significant differences between the pre and the post-surgical group on the sagittal plane(P<0.05) whereas no significant differences were noted on the axial and the coronal plane.Result 3: In the anteroposterior condylar position related to the glenoid fossa the condyle exhibited different displacement on different condyles.The right condyle exhibited more of the posterior displacement whereas the left condyle exhibited more of an anterior displacement of the condyle in relation to the glenoid fossa.Conclusion: The results of this study suggest that with increasing in the advancement of the imaging technology 3D analysis helps the surgeon in visualizing the hard and the soft tissues way better than the traditional approach.This study shows that there is a remarkable improvement in the facial profile of skeletal Class Ⅲ malocclusion.This study also suggest that the condyle tend to move in a certain direction and this can influence the treatment outcome of the patient on a long run.However,care should be taken not to change the axis of rotation of the mandibular condyle in order to prevent from the treatment relapse and to avoid different temporo mandibular disorders.