| Objective: To evaluate three-dimensionally how the maxillofacial hard tissues of skeletal class Ⅲ malocclusion patients with facial asymmetry were changed after surgical-orthodontic treatment and to analyze the relationships among variables by using cone-beam computerized tomography.Methods: 40 adult patients of skeletal Class Ⅲ malocclusion with facial asymmetry were strictly selected to meet the inclusion criteria,and all patients were treated with orthodontic-orthognathic therapy in our hospital from 2011 to 2017.The study group included One-Jaw Surgery group with 20 patients and Two-Jaw Surgery group with 20 ones.Cone-beam computerized tomography scans were taken before the orthognathic operation(T0),after presurgical-orthodontic treatment(T1)and after surgical-orthodontic treatment(T2).Mimics 19.0 was used to rebuild the maxillofacial hard tissues of patients three-dimensionally and 3-Matics 7.0 was to measure all skeletal and dental indices.Paired-samples T-test was performed to assess the differences of the maxillary,mandibular and temporomandibular joint(condylar)structure characteristics between T0 and T2.Pearson correlation analysis was used for analyzing the correlations among the above variables.Additionally,the changes of crown inclination of the bilateral first molars from T0 to T2 and alveolar bone morphology around them from T0 to T1 were assessed by utilizing paired-samples T-test.Results:(1)The measurements of jaws: In the two groups,the orthognathic surgery had markly improved chin point deviation and the asymmetry of bilateral mandible body length along with side-shift,horizontal and coronal rotations of the distal segment in BSSRO(P < 0.05);However,the maxilla was rotated towards the non-deviated side coronally(P < 0.05)and coronal ramus angle on the deviated side(P < 0.05)was significantly decreased to correct the asymmetry of the jaws after combined surgical-orthodontic treatment in Two-Jaw Surgery group.In addition,the 3-dimentional changes of condylar position were insignificant in either group between T0 and T2(P > 0.05);In the One-Jaw Surgery group,there were significant backward rotations of the condyle and ramus on the non-deviated side at T2(P < 0.05);But the condyle of the deviated side rotated inward and forward significantly in the Two-Jaw Surgery group after surgical-orthodontic treatment(P < 0.05).Compared with T0,the Two-Jaw Surgery group showed significantly decreases about the coronal occlusal cants of upper and lower jaw(P<0.05),although there was a significant decrease only in the occlusal cant of mandible in another group at T2 stage(P < 0.05).(2)Pearson correlation analysis: The change of the chin point deviation was significantly positively correlated with that of coronal mandibular inclination(P < 0.05)and the vertical distance of mental foramen to the sagittal plane(P < 0.01)between T0 and T2 in the two groups,and there was a significant positive correlation between the changes of coronal occlusal cant of lower jaw and coronal mandibular inclination(P < 0.01).In the Two-Jaw Surgery group,the change of occlusal cant of upper jaw was significantly positively correlated with those of maxillary inclination(P < 0.01)and occlusal cant of lower jaw on the coronal view(P < 0.05)after T2.(3)The measurements of the first molar: The two groups exhibited upright tendencies about bilateral first molars after presurgical-orthodontic treatment(P > 0.05).Compared to T0,the buccolingual angle of mandibular first molar on the deviated side was increased significantly(P < 0.05),but the decrease of that in the other side was insignificant at T2(P > 0.05)in One-Jaw Surgery group;Besides,in the Two-Jaw Surgery group,the buccolingual angles of mandibular first molar on the deviated side and maxillary first molar on the non-deviated side at T0 were significantly smaller than those at T2(P < 0.05),but the angles of maxillary first molar on the deviated side(P < 0.01)and mandibular first molar on the non-deviated side(P > 0.05)were greater than those before treatment.Nevertheless,the mesiodistal angles of all the first molars exhibited no significant changes from T0 to T2(P > 0.05).There were no significant differences in total alveolar thickness of bilateral molars at the stage of dental decompensation between T0 and T1(P > 0.05).The ratio of buccal and total bone thickness around maxillary first molar of the deviated side was decreased significantly at T1 than T0(P < 0.05),so was the mandibular first molar on the non-deviated side(P < 0.05).Conclusions:(1)Surgical-orthodontic treatment improved obviously the asymmetry on the maxillofacial hard tissues of patients with skeletal class malocclusions and facial asymmeⅢ try,and in the Two-Jaw Surgery group,the occlusal plane cant of upper jaw and the asymmetry of bilateral coronal ramus angles were markly corrected.(2)After surgical-orthodontic treatment,the condylar position remained relatively stable,but the angles of the condyle and ramus might change.(3)The buccolingual angles of first molars were corrected by combined surgical-orthodontic treatment.Since the remodeling of cortical bone of adult patients with skeletal class Ⅲmalocclusions and facial asymmetry developed slowly during pre-surgery orthodontic treatment,the reconstruction of the alveolar bone had not been consistent with the degree of tooth movement. |
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