| [Objective]Patients with facial asymmetry often have distinctive changes in condylar morphology and abnormal movements in mandibular function. This study employs three-dimensional spiral CT and eight guide contact electricity meter to record related quantitative data of temporomandibular joint (TMJ) and head and neck muscle electromyography before and after orthodontic treatments on patients with facial asymmetry in mixed dentition and permanent dentition stages, which analyse the morphology and functional characteristics on temporomandibular joint of patients with facial asymmetry and changes before and after orthodontic treatments. That will offer valuable clinical suggestions to orthodontic treatments on patients with facial asymmetry.[Methods]20children with Class III malocclusion and facial asymmetry were selected aged from8to16years, who all first visited in stomatological hospital of Shandong University.(10children are in mixed dentition stage and10children are in permanent dentition stage) The average age is11.7years old.To patients with facial asymmetry in growth and development period, if they have constricted maxillary arch, we carried on maxillary expansion for them using maxillary screw expansion appliance with maxillary occlusal pad. To patients with facial asymmetry in permanent dentition stage, all patients were treated with edgewise or straight wire technique to align and level the dentition. Finally the occlusion was adjusted in detail with fixed appliance. All process took18months. The lateral cephalograms, three-dimensional spiral CT and three-dimensional reconstruction, then Dentascan software was used to quantitative measurement analysis. There are12measurement items, which will study changes of temporomandibular joint pre-and post-treatment. At the same time, when the mandible is in the condition of postural jaw position (PP), intercuspal position (ICP), open the mouth maximumly, chewing in left and right ride, myoelectric activities of anterior Temporalis (TA), masseter muscle (MM), anterior digastrics (DA) and sternoclleidomastoid muscle (SCM) are recorded. Then we compared four pairs of muscles from two groups of subjects with EMG amplitude, the asymmetry of muscle activity index (including same muscles and ipsilateral muscles) pre-and post-treatment and carried on correlation analysis between the severity of facial asymmetry and the asymmetry of muscle index pre-treatment. All the results were analyzed with SPSS software.[Results]①Before the orthodontic treatment, both sides of the condylar shape, size are basically symmetrical in patients with facial asymmetry in mixed dentition stage (8-11years old). The difference is that the length of anterior inclined plane and the front inclination angle in deviated side are smaller than the non-deviated side (P<0.05), which shows anterior joint space reduces while upper joint space and posterior joint space significantly increases in non-deviated side, the condylar position is relatively anterior. After the orthodontic treatment, there are no statistical differences in both sides, but there are changes in the non-deviated side, which reveals that orthodontic treatment drives the condyle in non-deviated side from anterior and inferior position to posterior and upper position until the center of articular pan. Meanwhile, the position of deviated side is essentially unchanged, both sides are tend to be symmetrical.②Before the orthodontic treatment, both sides of the condylar shape, size are significantly unsymmetric in patients with facial asymmetry in permanent dentition stage (11-16years old). The height of condyle, medial-lateral diameter of condyle and the height of mandibular ramus in deviated side are smaller than the non-deviated side, but the length of posterior inclined plane and the posterior inclination angle in deviated side are larger than the non-deviated side (P<0.05), which shows height of condyle reduces while the position of condyle in articular pan retroposed; the height of condyle increases and the position of condyle in articular pan shift to anterior and inferior in non-deviated side. After the orthodontic treatment, there are no statistical differences in both sides, which reveals that orthodontic treatment drives the condyle in non-deviated side to posterior, upper and outside position until the center of articular pan. That lets anterior joint space and posterior joint space tend to be equal; but there are changes in the non-deviated side, which was maybe caused by the center of rotation of mandible from deviated side to non-deviated side closes to deviated side of condyle and mandibular rami in the treatment of facial asymmetry.③After the orthodontic treatment, in mixed dentition stage, EMG amplitude in four pairs of muscles all increased. In the condition of postural jaw position (PP), EMG amplitude in MM of deviated side, DA of non-deviated side, TA and SCM had no statistical significance, EMG amplitude in every muscle in other functional sites had statistical significance.(P<0.05)After the orthodontic treatment, in permanent dentition stage, EMG amplitude in four pairs of muscles all increased, especially that in TA and MM had significant statistical significance.(P<0.05)④After the orthodontic treatment, in mixed dentition stage, the asymmetry of muscle indexes all decreased. In the condition of postural jaw position (PP), MM/DA asymmetry of muscle indexes had statistical significance. the asymmetry of muscle indexes in four pairs of muscles all decreased in other four functional sites and had statistical significance. When chew in left and right sides, the asymmetry of muscle indexes had significant statistical significance.(P<0.05)After the orthodontic treatment, in permanent dentition stage, the asymmetry of muscle indexes are higher than those in mixed dentition stage. The asymmetry of muscle indexes in four pairs of muscles all decreased in varying degrees in every functional site and had statistical significance.(P<0.05)⑤After the orthodontic treatment, in mixed dentition stage, the asymmetry of muscle indexes in left and right sides all decreased and had statistical significance, especially in the condition of ICP. The asymmetry of muscle indexes had significant statistical significance in chewing activity.(P<0.05)After the orthodontic treatment, in permanent dentition stage, the asymmetry of muscle indexes in left and right sides all decreased and had statistical significance. The asymmetry of muscle indexes in right side (affected side, non-deviated side) decreased and had significant statistical significance when the mandible is in the condition of opening the mouth maximumly and chewing activity.(P<0.05)⑥In the condition of ICP, chin deviates facial midline in3-6mm, the severity of facial asymmetry significantly related to the asymmetry of muscle index pre-treatment.[Conclusion]①There are osseous asymmetric in patients with facial asymmetry to some extent.②In patients with facial asymmetry in mixed dentition stage, orthodontic treatment drives e both sides of the condyl to be symmetrical.③After orthodontic treatment, in patients with facial asymmetry in mixed and permanent dentition stages, EMG amplitude in four pairs of muscles from two groups of subjects increased, the asymmetry of muscle activity index (including same muscles and ipsilateral muscles) decreased. After orthodontic treatment, better occluding relation could improve the asymmetry of muscle functional activity in head and neck areas.④Early orthodontic treatment, to patients with facial asymmetry, improves facial symmetry and aesthetics and is beneficial to relief of temporomandibular disorders. |
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