Research progress on the structural features, treatments, and association with temporomandibular disorder in patients with skeletal class Ⅲ malocclusion with mandibular deviation / 口腔疾病防治

@#Skeletal angle class Ⅲ malocclusion with mandibular deviation involves the rotation and translation of the cranial base, maxilla, mandible, and soft tissue. It compromises the patients’ appearance and stomatognathic function. The treatment outcome is not satisfactory, and correct evaluation is of great significance. The causal relationship between skeletal Class Ⅲ with mandibular deviation and TMD remains controversial. This review focuses on the structural alterations of hard and soft tissue, the etiology, the choice of treatment methods, and the association with TMD in patients with skeletal class Ⅲ malocclusion with mandibular deviation. The results show that mandibular deviation is a complex disease with unclear etiology. It involves morphological changes, rotation and displacement of the cranial base, maxilla and mandible, morphological changes of the soft tissue, and occlusal changes, which also compromise the temporomandibular joint and mandibular function. Skeletal Class Ⅲ malocclusion is common in patients with mandibular deviation. Early treatment is needed; however, the treatment methods vary. The correct evaluation of the morphological changes of soft and hard tissues leading to facial asymmetry is the premise of treatment. Orthodontic and orthognathic treatment (combined with soft tissue repair when necessary) is an effective method for the treatment of skeletal class Ⅲ malocclusion with mandibular deviation. In addition, there is a close relationship between mandibular deviation and TMD, which needs to be fully considered in the design of treatment.

Construction of point-based mandibular median sagittal plane / 上海交通大学学报（医学版）

Objective: To develop a new point-based mandibular median sagittal plane (MMSP) by selecting from varied mandibular planes which were formed by combining bony landmarks derived from multiple regions of the mandible. Methods: Forty adult patients were evenly divided into two groups by the degree of chin deviation: mandibular asymmetric group (MA group) and mandibular symmetric group (MS group). Three dimensional (3D) mandibular models were rebuilt by Mimics 19.0 software. In this software, 3D coordinates of 4 central landmarks and 6 pairs of lateral landmarks were collected. Then 120 candidate planes were constructed by point-based method, and compared with the reference plane formed by the iterative closest point (ICP) algorithm. All the planes were reordered and screened by geometric indices such as angle, distance and area in MS group. In addition, the clinical symmetrical indices such as point-to-plane distance, surface area difference, volume difference, and 3D deviation ratio of screened planes were compared in MA and MS groups. Results: The candidate planes co-constructed with landmarks from three mandibular regions (symphysis, mandibular angle and coronoid process) were the top 5% of all the planes. Among them, no statistical difference between B-Cor-Golat plane (constructed with supramentale, coronoid superius and gonion lateralis) and ICP plane was found (P >0.05), while there were significant differences between the rest screened planes and the reference plane (P<0.05). Conclusion: The B-Cor-Golat plane can be used as the mandibular median sagittal plane to reflect the symmetrical degree of the mandible well.

Three-dimensional study on symmetry of the first molar and its peripheric alveolar bone in skeletal class III patients with mandibular deviation / 上海交通大学学报（医学版）

Objective: To compare the difference of the first molar and alveolar morphology between the deviated side and non-deviated side in skeletal class III patients with mandibular deviation by using cone-beam computed tomography (CBCT) image combined with three-dimensional reconstruction measurement technology. Methods: Fifty-six asymmetric CBCT data were evaluated by Mimics 10.0 and 3-Matic software. Some measures were analyzed by t-test including the buccolingual angle, the mesiodistal angle, crown root ratio of first molar and the thickness of alveolar or cancellous bone. Results: The buccolingual angle and crown root ratio of mandibular first molar were significantly larger on the deviated side than on the non-deviated side (P=0.021, P=0.004). Compared with the non-deviated side, the buccal and total cancellous bone thickness of mandibular first molar were significantly smaller on the deviated side (P=0.043, P=0.048). There was no significant difference in the ratio of buccal and total cancellous bone thickness on mandibular first molar (both P=0.118). The measurements of maxillary first molar and maxillary alveolar bone morphology were not significantly different between two sides (all P>0.05). Conclusion: In skeletal class III patients with mandibular deviation, although the buccolingual compensation of first molar is found, the position of first molar in the alveolar bone is symmetrical. The asymmetry of alveolar bone morphology are mainly manifested in the reduction of the buccal and total cancellous bone thickness on the mandibular deviated side.

Three-dimensional study on symmetry of the first molar and its peripheric alveolar bone in skeletal class Ⅲ patients with mandibular deviation / 上海交通大学学报（医学版）

Objective·To compare the difference of the first molar and alveolar morphology between the deviated side and non-deviated side in skeletal class Ⅲ patients with mandibular deviation by using cone-beam computed tomography (CBCT) image combined with three-dimensional reconstruction measurement technology. Methods·Fifty-six asymmetric CBCT data were evaluated by Mimics 10.0 and 3-Matic software. Some measures were analyzed by t-test including the buccolingual angle, the mesiodistal angle, crown root ratio of first molar and the thickness of alveolar or cancellous bone. Results·The buccolingual angle and crown root ratio of mandibular first molar were significantly larger on the deviated side than on the non-deviated side (P=0.021, P=0.004). Compared with the non-deviated side, the buccal and total cancellous bone thickness of mandibular first molar were significantly smaller on the deviated side (P=0.043, P=0.048). There was no significant difference in the ratio of buccal and total cancellous bone thickness on mandibular first molar (both P=0.118). The measurements of maxillary first molar and maxillary alveolar bone morphology were not significantly different between two sides (all P>0.05). Conclusion·In skeletal class Ⅲ patients with mandibular deviation, although the buccolingual compensation of first molar is found, the position of first molar in the alveolar bone is symmetrical. The asymmetry of alveolar bone morphology are mainly manifested in the reduction of the buccal and total cancellous bone thickness on the mandibular deviated side.

Treatment of an adult patient with skeletal crossbite and mandibular deviation by distalization of the mandibu-lar molar / 实用口腔医学杂志

An adult patient with skeletal crossbite and mandibular deviation was treated by mandibular molar distalization using micro-im-plant and intermaxillary traction.After treatment,the facial contour of the patient was improved,the Class Ⅰ molar and cuspid relationship was achieved.

Postoperative positional change of condyle after bilateral sagittal split ramus osteotomy associated with mandibular asymmetry

Purpose: After the surgical correction with sagittal split ramus osteotomy, the position of the mandibular condyle in the glenoid fossa and the proximal segment of the mandible change because of bony gap between proximal and distal segment, especially in case of mandibular setback asymmetrically. In this study, positional changes in the condyle and proximal segment after BSSRO were estimated in the mandibular asymmetry patient by analyzing the in submentovertex view and P-A cephalogram for identification of ideal condylar position during surgery. Patients and Methods: The 20 patients were selected randomly who visit Dankook Dental Hospital for mandibular asymmetry. Bilateral sagittal split ramus osteotomy with rigid fixation was performed and P-A cephalogram and submentovertex view was taken at the time of preoperative, immediate postoperative, 3 month postoperative period. Results: Intercondylar length and transverse condylar angle was increased due to inward rotation of proximal segment and anteromedial rotation of lateral pole of condyle head. The condylar position had a tendency to return to the reoperative state and after 3 months return up to about half of the immediate post-operative changes, and all the results showed more changes in asymmetry patient and deviated part of the mandible. Conclusion: Based on all these results above, surgeon should make efforts to have a precise preoperative analysis and to have a ideal condylar position during rigid fixation after BSSRO.