Three-dimensional Condyle Changes And Remodeling In Patients With Skeletal Class Ⅲ Malocclusion Without Mandibular Deviation

Objective: In order to clarify the angle,displacement change of bilateral condyle in the three-dimensional direction and the bone reconstruction of the upper surface of the condyle,and to analyze the relationship between the degree of mandibular retraction and the postoperative changes of the condyle,and whether there is a correlation between the angle change and the displacement.18 cases of skeletal class III malocclusion without deviated were involved.We used three-dimensional reconstruction software such as Proplan CMF（2.09,Belgium）and Materialise Mimincs（21.0,Belgium）to reconstruct the skull model and perform punctuation calculations via CT data.Methods: 18 patients（17-29 years old,with an average of 20.64±3.68 years old,3 males and 15 females）were included in the study.The spiral CT data of craniofacial parts were collected before surgery（T0）,two weeks after surgery（T1）,and six months after surgery（T2）.After craniofacial reconstruction,punctuation and data acquisition using Proplan CMF（2.09,Belgium）,the Angle and displacement changes of bilateral condyles in horizontal,sagittal and coronal planes were calculated.The CT data of T0 and T2 will be introduced into Geomagic Studio2021（USA）.The upper surface of the condyle will be divided into four areas: anterometer-medial area,anterolateral area,posterometer-medial area and posterolateral area,and the bone remodeling of the condyle will be calculated within six months by using the software’s own registration function.Different bands were used to distinguish the amount of bone remodeling.The condylar head was amputated by Materialise Mimincs（21.0,Belgium）and the condylar volume of T0 and T2 was calculated.SPSS20.0 was used to conduct normal test on the Angle and displacement of the condyle,and Pearson correlation test was conducted between the degree of mandibular regression and the Angle and displacement of the condyle.SPSS20.0 was used to perform single-factor repeated measure ANOVA for 3d Angle and displacement data of condyle,and then statistical analysis was performed.Results: The left condyle showed backward and upward movement two weeks after surgery（T1）.During the postoperative recovery period（T1-T2）,the left condyle moved outwards and downward,and compared with the operation period（T0-T2）,the left condyle moved outwards,backward and downward as a whole.Immediately after surgery,the right condyle moved outward,backward,and upward.During the postoperative recovery period（T1-T2）,the condyle continued to shift downward on the coronal plane,and moved backward on the whole six months after surgery compared with that before surgery.The left condyle rotated backwards,outwardly and upward during T0-T1.The long axis of the condyle recovered in the coronal and sagittal plane during postoperative recovery（T1-T2）,and still rotated backwards,outwardly and upward six months after surgery compared with that before surgery.The right condyle rotated outwards,forwards and downwards after surgery.Postoperative recovery（T1-T2）showed a trend of recovery to the original direction in horizontal plane,sagittal plane and coronal plane,and postoperative overall（T0-T2）showed outward,backward and upward rotation.By Pearson correlation analysis of mandibular regression degree B1-B0 with 3D displacement and Angle,it can be seen that there is a very significant and strong correlation between mandibular regression degree B1-B1 and MPLZ0-2,MPRX0-1 and MPRX1-2.No statistical difference was found between B1-B0 and 3D Angle or other displacements.With the development of time,there was no statistical difference in the Angle changes of the two condyles in different periods.In the single-factor repeated measure ANOVA of displacement changes,the difference between LPRX0-1,LPRX1-2 and LPRX0-2 was statistically significant,and the number of LPRX0-1 was significantly higher than that of LPRX1-2 and LPRX0-2.The displacements in other periods showed no statistical difference with time.The volume of the left condyle at six months after surgery was 99% of the preoperative volume,and that of the right condyle was 94%.Conclusion: 1.The degree of mandibular regression B0-B1 was strongly correlated with MPLZ0-2,MPRX0-1,MPRX0-2 and MPRX1-2.2.Minor bone remodeling of condyle occurs after orthognathic surgery,which does not exceed the physiological limit of the joint.3.Postoperative bone resorption of the condyle is mainly in the anterolateral region,and osteogenesis is mainly in the posterolateral region.