The relationship between lateral displacement of the mandible and scoliosis

Objectives

Idiopathic scoliosis is an orthopaedic disease of childhood, with onset and progress occurring until adolescence. Here, the relationship between lateral displacement of the mandible and scoliosis was analysed quantitatively.

Methods

Seventy-nine non-syndromic Japanese patients (18 men, 61 women), who were diagnosed with jaw deformities and underwent surgical orthognathic treatment at Kyushu University Hospital from January 2011 to August 2014, were enrolled. Their mean age at the time of radiography was 25.3 ± 8.7 years. Postero-anterior cephalometric radiographs and chest radiographs were examined. In postero-anterior cephalometric radiographs, a horizontal baseline (X-axis) was drawn as a straight line that intersects both the zygomatic bases, and a vertical line (Y-axis) was marked perpendicular to the X-axis, with an intersection at the anterior nasal spine (ANS). Point A was defined as the intersection of the X- and Y-axes, and line A was defined as the line connecting point A to the menton. The angle made by the X-axis and line A (i.e., lateral displacement of the mandible) was measured. We designated an absolute value even if the mandibular menton was located on the right or left side. In chest radiographs, Cobb’s method was used to measure scoliosis curves; the direction of the curve was designated similarly.

Results

Nine (11.4%) individuals had a Cobb angle >10°. There was a positive correlation between the Cobb angle and the degree of mandibular deviation (p < 0.05).

Conclusion

Lateral displacement of the mandible and scoliosis are related.

     

Dorsal nasal reconstruction using bone harvested from the mandible.

PURPOSE: This article describes a technique for reconstructing nasal deformities resulting from trauma. Bone harvested from the lateral ramus/body of the mandible is used to provide nasal support for major nasal deformities. PATIENTS AND METHODS: Ten patients underwent repair of their nasal deformities with an autogenous bone graft harvested from the mandible. Primary bone grafting was used to repair a nasal deformity associated with a naso-orbito-ethmoidal fracture in 8 patients. Secondarily, 2 patients underwent placement of a graft for correction of a saddle nose deformity. RESULTS: All patients achieved aesthetic results. There was maintenance of nasal projection and symmetry without displacement of the graft. None of the patients complained of an unnatural hardness of the nasal tip or dorsum. All grafts healed without evidence of infection, dehiscence, or necrosis. CONCLUSION: The lateral ramus/body of the mandible provide an excellent donor site alternative for nasal reconstruction.     

正颌外科患者术前的颞下颌关节功能评价

目的　了解正颌患者颞下颌关节 (TMJ)的功能状况 ,探讨牙颌面畸形与颞下颌关节之间的关系。方法正颌外科发育性牙颌面畸形 12 3例患者 ,平均年龄 2 3.8岁 ,男性 45例 ,女性 78例。颞下颌关节功能的检查方法采取问诊与检查相结合 ,颞下颌关节功能记分采取 Helkim o指数记分方法。结果　 (1)牙颌面畸形患者颞下颌关节紊乱病 (TMD)各种症状发生率明显高于对照组人群。(2 )男性患者弹响症状发生率高于女性 ,而女性患者关节触诊疼发生率高。(3) 16～ 2 5岁患者张口受限发生率较高 ,但大多数为轻度张口受限。(4 )不对称畸形 (下颌前突偏斜 )者弹响症状发生率较高 ,而且相应偏斜侧最大侧向移动度小。而下颌后缩组开口度明显小于其他各组 ,提示其关节功能受损较严重。结论　牙颌面畸形患者的颞下颌关节功能不同于正常人 ,部分下颌偏斜与后缩患者关节功能受损     

Simplified stress analysis on the temporomandibular joint in Class III patients with and without mandibular asymmetry using a rigid body spring model

Authors – Ueki K, Takeuchi N, Nakagawa K, Yamamoto E Objective – Aim of this study was to investigate the differences in stress on the temporomandibular joint (TMJ) between Class III patients with and without mandibular asymmetry using a rigid body spring model (RBSM). Design – Menton (Me), the centre point of occlusal force on the line that connected the bilateral buccal cusps of the second molars and the most lateral, superior and medial points of the condyle were plotted on frontal cephalograms, and stress on the condyles was calculated with the 2‐dimensional RBSM program of fortran . Setting and Sample Population – Eighty Japanese patients with diagnosed mandibular prognathism were divided into two groups, a symmetry group and asymmetry group on the basis of the Mx‐Md midline position. Outcome measure – The degree (force partition) of the resultant force, the direction (angulation) and displacement (X, Y) of each condyle were calculated. The horizontal displacement vector (u), the vertical displacement vector (v) and rotation angle (θ) of the mandibular body at Menton were also calculated. Results – There were significant differences between the deviated and non‐deviated sides of both groups regarding resultant force (symmetry group: p = 0.0372, asymmetry group: p = 0.0054), X (symmetry group: p < 0.0001, asymmetry group: p = 0.0001) and Y (symmetry group: p = 0.0354, asymmetry group: p = 0.0043). For angulation, there was a significant difference between the deviated and non‐deviated sides in the asymmetry group (p = 0.0095). Conclusion – The results of this study suggest that difference in stress angulation on the condyles could be associated with asymmetry in mandibular prognathism.     

Tooth axis and skeletal structures in mandibular molar vertical sections in jaw deformity with facial asymmetry using MPR images

The objective of the present study was to investigate frontal morphological asymmetry in the mandibular molar region in terms of tooth axis and skeletal structures using vertical MPR sections in jaw deformity accompanied by facial asymmetry. Subjects consisted of 15 patients with jaw deformity accompanied by facial asymmetry aged 17.4 years to 37.8 years. There were four men and eleven women. Based on X-ray computed tomography (CT) scans, DICOM viewer software was used to prepare multiplanar reconstruction (MPR) sections. The mandible was then positioned on a reference plane based on the menton and left and right gonions, and a vertical MPR section passing through the mesial root of the first mandibular molar was prepared. The following measurements were made on both the shifted and non-shifted sides: maximum buccolingual width of the mandibular body; height of the mandibular body; inclination angle of the mandibular body; degree of buccal protrusion of the mandibular body; and inclination angle of the buccolingual tooth axis of the first molar. Furthermore, degree of median deviation in the menton was measured using frontal cephalograms. Differences in morphological parameters between the shifted and non-shifted sides were assessed. Furthermore, the relationship between median deviation and asymmetry were statistically analyzed. There was no significant asymmetry in the maximum buccolingual width of the mandibular body, the height of the mandibular body or the degree of buccal protrusion of the mandibular body. However, when compared to the shifted side, the inclination angle of the buccolingual tooth axis of the first molar for the non-shifted side was significantly greater. There was a relatively strong correlation between median deviation and inclination angle of the mandibular body. The above findings clarified that, in orthognathic surgery for jaw deformity accompanied by facial asymmetry, actively improving asymmetry in the buccolingual inclination of the tooth axis of the molar region during presurgical orthodontic treatment is important in achieving favorable post-treatment occlusal stability and facial symmetry.     

偏颌畸形下颌开闭口运动特征的研究

目的 研究发育性偏颌畸形患者下领开闭口运动的特点，探讨偏颌畸形对下颌运动功能的影响。方法 采用下颌运动轨迹描记仪(Sirognathograph,SGG)采集28例偏颌畸形者及41例咬合正常者最大开闭口运动的三维方向时间—位移信号，比较两组受试者下颌运动轨迹的形态、开闭口运动的位移及速度等参数的差异。结果 偏颌畸形患者开闭口运动轨迹在冠状面内主要分布在患侧，下颌向患侧移动的幅度明显大于向健侧移动的幅度，开口运动中下颌偏离中轴的程度较闭口运动时明显。偏颌者下颌开闭口运动三维空间内的位移、速度比正常咬合者大。结论 偏颌患者下颌运动处于能量消耗较高的状态，下颌运动功能的异常可能影响口颌系统的功能。     

Implant-supported mandibular splinting affects temporomandibular joint biomechanics

Objectives: Mandibular functional movements lead to complex deformations of bony structures. The aim of this study was to test whether mandibular splinting influences condylar kinematics and temporomandibular joint (TMJ) loading patterns. Materials and methods: Six subjects were analyzed by means of dynamic stereometry during jaw opening–closing with mandibles unconstrained as well as splinted transversally by a cast metal bar fixed bilaterally to two implant pairs in the (pre)molar region. Statistical analysis was performed by means of ANOVAs for repeated measurements (significance level α=0.05). Results: Transversal splinting reduced mandibular deformation during jaw opening–closing as measured between two implants in the (pre)molar region on each side of the mandible significantly by 54%. Furthermore, splinting significantly reduced the distance between lateral condylar poles (average displacement vector magnitude of each pole: 0.84±0.36 mm; average mediolateral displacement component: 45±28% of the magnitude) and led to a medial displacement of their trajectories as well as a mediolateral displacement of stress‐field paths. Conclusions: During jaw opening–closing, splinting of the mandible leads to a significant reduction of mandibular deformation and intercondylar distance and to altered stress‐field paths, resulting in changed loading patterns of the TMJ structures. To cite this article:
Zaugg B, Hämmerle CHF, Palla S, Gallo LM. Implant‐supported mandibular splinting affects temporomandibular joint biomechanics.
Clin. Oral Impl. Res. 23 , 2012; 897–901
doi: 10.1111/j.1600‐0501.2011.02241.x     

Three-dimensional analysis of facial morphology before and after orthognathic surgery

A method for three-dimensional analysis of the facial hard- and soft-tissue morphologies is described. The soft-tissue analysis consisted of calculating three-dimensional values of reference points on the face by perspective transformation of their values in two pairs of photographs, taken simultaneously, from the right and left sides of the face. The shape of the mandible was analyzed three-dimensionally by the simultaneously taken frontal and lateral cephalograms. The hard- and soft-tissue changes were analyzed with the method in 28 patients in whom mandibular prognathism had been corrected by orthognathic surgery. The magnitude of the surgically-produced soft tissue volumetric changes in the anterior mandibular region was proportional to the posterior movement of the mandible. Asymmetry of the face also improved in response to correction of lateral deviation of the mandible and a close correlation between the directional indices of asymmetry of the hard and soft tissues was observed. Thus, the method was found to be quite useful for the analysis of facial morphology in jaw deformity.     

颜面部不对称畸形患者头颅结构的三维测量和聚类分析

目的    尝试采用聚类分析方法对颜面部不对称畸形患者进行分类。方法    对2008年7月至2013年7月到中国医科大学口腔医学院口腔颌面外科就诊的44例颜面部不对称畸形患者的头颅三维CT数据测量值进行统计学研究,通过聚类分析方法将这些患者进行分类。结果    44例患者根据颌骨及牙齿的测量指标值聚类分析,可分成三大类。第一类16例,占36.4%,为上颌骨基本对称,下颌骨体部水平方向平移,双侧下颌升支与正中矢状面成角对称;第二类25例,占38.6%,为下颌骨双侧升支及下颌骨体部发育不对称,上颌骨未随之发生明显的旋转;第三类11例,占25%,为上下颌骨均整体旋转移动。结论    可以依据下颌骨体部、下颌骨升支是否对称,上颌骨是否随之发生明显的旋转把颜面部不对称畸形分成三类,便于颜面部不对称畸形的分类诊断、手术设计,有利于对此类疾病的进一步研究和学者间的交流。     

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??Objective    To classify the patients with facial asymmetry deformities by cluster analysis. Methods    Totally 44 patients with facial asymmetry deformity were selected from July 2008 to July 2013 in School and Hospital of Stomatology?? China Medical University?? the measuring data of three-dimensional craniofacial CT scan were used for statistical analysis?? and patients with asymmetry deformities were divided into several categories by cluster analysis. Results    The 44 patients were divided into three categories according to the measurement value of jaws and teeth by clustering analysis. The first category included 16 patients?? whose deformities showed that maxilla was in symmetry but the mandibular body translated horizontally??the second category included 17 patients??whose deformities showed that the bilateral ramus were asymmetrical and the maxilla didn’t rotate accordingly?? the third category included 11 patients?? whose maxilla and mandible showed overall rotational movement. This category deformity showed serious asymmetry and was familiar with hemifacial atrophy. Conclusion    Facial asymmetry can be divided into 3 categories based on the symmetry of body of the mandible and mandibular ramus and whether the maxilla has rotation. It is important for diagnosis and classification of facial asymmetry?? preoperative designing and communication among doctors.     

Fibula flap reconstruction of the condyle in disarticulation resections of the mandible: a case report and review of the technique

Segmental resection of the mandible with disarticulation of the temporomandibular joint is occasionally required in the management of extensive tumors. The reconstruction of these deformities is complex, frequently involves staged procedures, and may result in significant deformity and loss of function for patients. The fibula free flap has become a standard treatment option for primary restoration of segmental mandibular deformities. However, little is published about its role in reconstructing the mandibular condyle. This paper describes a simplified technique for primary reconstruction of mandibular defects, including the mandibular condyle, in disarticulation resections of the mandible utilizing the fibula free flap.     

The mandible in mandibulofacial dysostosis: a cephalometric study

The lower border of the mandible in mandibulofacial dysostosis is characteristic of the syndrome. Evaluation of the cephalograms by means of the medial axis analysis and inflectional tangents captures the shape deformity. Morphometric data from lateral cephalograms on seven patients, ages 3 through 20 years, are reported: a total of 22 observations on three males and four females. These forms were compared to normal mandibular forms from the University of Michigan University School Study. The curvature of the gonial angle in the study population is not distinguishable from the normal curvature. Relative to this apparently normal region, there is a marked downward displacement of the symphysis that results in the curvature typical of the lower mandibular border in this syndrome. These findings are not consistent with earlier reports.     

Helical axis errors affect computer-generated occlusal contacts

A helical axis describing mandibular motion can be calculated from two distinct positions of the mandible; however, as these positions come closer together, calculation errors increase. This study investigated the effects of errors in the calculated helical axis on simulated mandibular motion by the measurement of changes in occlusal contacts. A standard helical axis was calculated from a simulated lateral movement. A series of digital interocclusal records from centric to a 5 degree mandibular rotation about the standard helical axis was created. Digital dental cast models were aligned to the interocclusal records. Helical axis parameters and occlusal contacts calculated with the use of the aligned digital models were compared with those of the standard. Helical axes calculated from mandibular positions separated by 1.5 degrees to 5.0 degrees yielded equivalent occlusal contacts. Qualitatively, contacts for helical axes calculated from jaw rotations of 0.7 degrees or larger were nearly identical to those of the standard.     

The change of stress distribution on the condyle after mandibular setback surgery

The rigid-body spring model (RBSM) theory was incorporated into a model as a discrete method for analysing problems of limit, such as the stress distribution on the condyle. The purpose of this study was to evaluate the two-dimensional RBSM for determining stress on the temporomandibular joint (TMJ) in patients after orthognathic surgery. Thirty-two patients (five males and 27 females, mean age 21.4 +/- 4.9 years) with mandibular prognathism underwent bilateral sagittal split ramus osteotomy (SSRO) and setback; 48 subjects were recruited as controls. Anatomical landmarks were traced from pre- and post-operative lateral cephalograms and the information was processed using the Fortran analysis program. The force vector on the condyle, its degree, its direction, and the displacement co-ordinates (x, y) and rotation (theta) at the gonial angle were calculated. When muscular power was assumed to be 1, the post-operative degree of the force vector was higher than the pre-operative value (P < 0.05). The X co-ordinate, x, and rotation, theta, of the displacement vector in the pre-operative patients with mandibular prognathism were significantly higher than those in the control subjects (P < 0.05). There were still significant differences between the displacement values post-operatively between the patients and controls (P < 0.05). The results suggest that the degree and direction of the force vector and the resulting displacement co-ordinates can be used as parameters in a surgical model. The RBSM may also be useful in evaluating the pre- and post-operative skeletal morphology of jaw deformities.     

偏颌与颜面不对称畸形的诊断、分类及临床意义

依据临床特征、病理机制及颌骨结构,偏颌与颜面不对称畸形可分为单纯颌位性、关节源性与颌骨发育性3大类.单纯颌位性偏颌包括咬合阻碍、咬合代偿及咬合习惯亚型,关节源性偏颌包括髁突不对称吸收与不对称增生亚型,颌骨发育性偏颌包括上颌源与下颌源亚型.正畸治疗偏颌与颜面不对称畸形的重要原则是最大限度地纠正形成下颌偏斜的功能性颌位因素...     

The influence of the closing and opening muscle groups of jaw condyle biomechanics after mandible bilateral sagittal split ramus osteotomy

ObjectiveTo investigate the influence of the closing and opening muscle groups of the jaw on mandibular stability after mandibular bilateral sagittal split ramus osteotomy (BSSRO).Materials and methodsTo establish finite element models of four conditions (the normal mandible, preoperative mandibular prognathism, postoperative (BSSRO) mandibular prognathism, and mandibular prognathism following virtual BSSRO), we imported Digital Imaging and Communications in Medicine (DICOM) data into three-dimensional reconstruction software. Finite element analysis software and statistical software were used for analysis of the condylar stress distribution as a function of condylar position during the actions of jaw closing and jaw opening muscle groups.ResultsThe stress distribution of the normal mandibular bilateral condyle was statistically different from the normal mandibular condyle, indicating that bilateral structures are asymmetrical. There was a significant difference in stress distributions with condyle position between healthy control patients and patients prior to mandibular prognathism surgery (P < 0.05). There was no significant difference in stress distributions between the normal mandible and the mandible following virtual surgery or real mandibular prognathism surgery. Additionally, there was no significant difference at 6 months after mandibular prognathism surgery (P > 0.05).ConclusionsBilateral structures of the normal mandible were asymmetrical. After mandibular bilateral sagittal split ramus osteotomy, variation of the force arms of closing and opening muscle groups of the jaw was one of the major factors influencing mandibular stability. Virtual surgery is a promising strategy for preoperative planning to improve surgical success and reduce complications.     

Vector control in lower jaw distraction osteogenesis using an extra-oral multidirectional device.

PURPOSE: This cephalometric study describes structural changes in facial features and occlusion during distraction of the mandible. PATIENTS: Seven patients aged 7-16 years with severely retrognathic lower jaws were treated by bilateral extra-oral distraction. The direction of the distraction was changed during the distraction period (mean 30 days) using the adjustable hinge in the distractor. Cephalometric follow-up documents were analysed for changes in facial and occlusal structures. The distraction therapy proceeded in two phases. First, horizontal distraction was undertaken to achieve a good incisor relationship. After this, the direction was changed to a more vertical plane with the use of a hinge axis, and the tips of the lower incisors were used as the axis of rotation. RESULTS: The most remarkable changes were in the more anterior position of the lower jaw, the increase in ramus height and good dental overjet. The mandibular occlusal plane became more horizontal, creating a posterior open bite. By guiding the vector of distraction, no anterior open bite or lateral crossbite appeared. CONCLUSION: This study points out the advantages of using extra-oral multidimensional distractors. Severe lower jaw deficiency requires not only a long working length of the device but also precise control of the vector during the active phase of distraction.     

Unbalanced lateral mandibular deviation associated with TMJ sound as a sign in TMJ disc dysfunction diagnosis

The aim was to study the characteristics of lateral mandibular horizontal deviations during opening–closing movements and their association with TMJ sounds of the clicking type. Subjects were 28 healthy volunteers and 38 patients diagnosed with MRI imaging as having TMJ disc dysfunction, 22 with disc displacement without (DD) and 16 as having disc displacement with reduction (DDR). TMJ sounds were recorded with miniature microphones placed in the ear canals, and jaw movements were documented with a kinesiograph. A sign, unbalanced lateral deviation (ubd) was defined as a rapid, short duration, change in jaw movement direction from, and back to, a smooth deviation path in the horizontal plane. The hypotheses were that degrees of maximal deviations, proportions of unbalanced deviation (ubd) and such deviation associated with TMJ sounds (ubdS), differ between healthy subjects and patients with DD or DDR. Comparisons between groups were made using one‐way anova and chi‐square analysis, as appropriate. No differences were found between groups regarding degree of lateral deviation per se. The proportions of ubd and ubdS were significantly higher in patients with DDR than in healthy subjects and than in patients with DD (P < 0·001), but no such differences were found between healthy subjects and patients with DD. For prediction of DDR, the sensitivity and specificity of the sign ubdS were found to be 68·8% and 89·3%, respectively. For the sign ubd, they were 100·0% and 64·3%. This indicates that the sign ubdS has diagnostic value in screening for DDR.     

Changes in mandibular position and upper airway dimension by wearing cervical headgear during sleep.

We previously reported that the wearing of cervical headgear induced forward displacement of the mandible in awake subjects. However, it was unclear whether such mandibular displacement also occurred during sleep. The purpose of this study was to examine changes in mandibular position and oropharyngeal structures that were induced by the wearing of cervical headgear during sleep. Ten healthy adults (7 male and 3 female) who gave their informed consent were included in this study. A pair of lateral cephalograms was taken with the patient in the supine position with and without cervical headgear at end-expiration during stage 1 to 2 non-rapid-eye-movement sleep. The Wilcoxon signed-rank test was used for a statistical analysis. The amount of jaw opening was significantly decreased by the wearing of the cervical headgear (P <.05), although no significant anteroposterior mandibular displacement was induced. The sagittal dimension of the upper airway was significantly reduced (P <.05); however, no significant changes were observed in the vertical length of the upper airway. Although the hyoid bone and the third cervical vertebra moved significantly forward by the wearing of the cervical headgear (P <.05), the relationship among the mandibular symphysis, the hyoid bone, and the third cervical vertebra did not change. These results suggest that cervical headgear significantly reduced the sagittal dimension of the upper airway during sleep, although there was no significant anteroposterior displacement of the mandible.