下颌持续前导作用下髁状突软骨改建的超微结构变化

背景：以往的动物实验证明,前导下颌可以导致年轻SD大鼠的颞下颌关节组织发生改建,主要表现为髁状突组织的生长速度加快,下颌骨发生继发性生长。但其髁突软骨细胞的超微结构改建研究仍是研究的关键所在。 目的：观察生长期大鼠在下颌持续前导作用下髁状突软骨生长和改建的组织学和超微结构的变化。 方法：将4周龄SD大鼠随机分为对照组和实验组,实验组24 h佩戴下颌前导矫治器,分别在干预3,7,14,21,30 d麻醉处死动物并取材,光学显微镜和透射电镜观察大鼠髁突软骨的组织学和超微结构的变化。 结果与结论：从干预14 d开始,实验组髁突软骨厚度在观察周期中出现先增加后变薄的现象,髁状突中后部软骨厚度变化显著(P < 0.01)。从干预7 d开始髁突软骨细胞的超微结构发生改建,包括细胞内细胞核固缩,粗面内质网腔隙肿胀,脂滴变小甚至消失,核周微丝变少且不规则,细胞外基质增宽变多以及出现大片空白等。结果证实,在下颌前导作用下,大鼠髁突软骨会随着承受力的时间增厚或变薄,软骨细胞基质合成能力也会显著增强。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Modelling of mandibular movement

In this paper, the authors presented a novel method to reconstruct individual mandible movement in three dimensions by a virtual articulator system. The system provides a synchronized 3D mandibular movement that faithfully reappear one's natural occlusion movements--sagittal border, lateral, and open-close movements. Movement trajectories are approximated by cubic or high-degree curves modelling. During the whole process, X-ray exposure on human is avoided. The authors apply the optimal methodology to approach the collected samples of movements in order to generate specific occlusion curves and surfaces. The system provides a novel method of mimicking occlusion of individuals. It is a useful tool for recording dynamic movements of an individual in both pre- and post-surgery and also for predicting surgical outcomes.     

Magnetic resonance imaging findings of true bifid mandibular condyle with duplicated mandibular fossa

Bifid mandibular condyle (BMC) is a rare asymptomatic morphological alteration with no predilection for age group or gender. Its morphology varies from a shallow groove to two condylar heads with separate necks, oriented mediolaterally or anteroposteriorly. This report describes an unusual case of anteroposterior bifid condyle in a 39-year-old female patient with the main complaint of mouth-opening limitation and a deviation of the mandible to the left side. Magnetic resonance imaging (MRI) findings revealed a bifid condyle on the left side and duplicated mandibular fossa, with the articular disc over the anterior head. The MRI images in the open-mouth position revealed minimal movement of the condyle. Despite the increased number of mediolateral bifid mandibular condyle cases described in the literature, none of previously reported cases of BMC included an anteroposterior bifid condyle case with two distinct mandibular fossa.     

下颌角整形术对下颌骨应力以及颞下颌关节功能的影响

目的分析基于东方经典美丽分析面罩的下颌角整形术对人体下颌骨及颞颌关节功能的影响。方法获取病人术前和术后头部CT图像数据,通过Simpleware有限元建模软件生成计算模型,利用Abaqus软件观察手术前后模型上的应力分布及数值大小。结果获得了具有良好形态的下颌骨三维有限元模型,根据在不同部位施加不同负荷模拟模型各部分的力学改变,发现手术前后下颌骨部及关节附近的应力分布有差异。结论基于东方经典美丽分析面罩的下颌角整形术,手术前后对病人的下颌骨及颞颌关节附近的应力减小。     

Biomechanical aspects of mandibular growth

The subject of this study was to analyse how functional parameters of stomatognathic systems are influenced by growth. For this purpose, two cephalometric radiographs of 65 patients with class-II-relation treated with functional appliances were superimposed on the occlusal plane. The two patient groups consisted of 32 open bite and 33 deep bite cases. The direction of the condylar growth significantly differed for both cases. Nevertheless the hypothesis could be confirmed that the original functional structure was hardly affected by growth.     

Angiosarcoma of the mandibular gingiva

Angiosarcoma of the oral cavity is extremely rare. A 77-year-old woman consulted to our hospital because of polypoid mass of the mandibular gingival. Physical examination showed polypoid reddish mass measuring 1.5 × 1.5 × 1 cm in the mandibular gingival posterior to the front tooth. Enucleation of the tumor was performed. Grossly, the tumor was not encapsulated. Histologically, the tumor consisted of atypical spindle with hyperchromatic nuclei with nucleoli. Mitotic figures were scattered. Vasoformative channels were present in some areas. The surgical margins were positive. Immunohistochemically, the tumor cells were positive for factor VIII-related antigen, CD31, CD34, vimentin, p53 protein, but negative for pancytokeratin (AE1/3 and CAM5.2), S100 protein, α-smooth muscle antigen, and desmin. The Ki-67 labeling was 60%. A pathological diagnosis of angiosarcoma was made. Radical operation is planned now.     

Double mandibular foramen leading to the accessory canal on the mandibular ramus

Purpose

The knowledge of the variation in the mandibular foramen and canal is clinically significant in surgical procedures of the mandible. This study aims to evaluate the anatomical characteristics of double mandibular foramen leading to the accessory canal on the mandibular ramus using cone beam CT.

Methods

The sagittal, cross-sectional, and three-dimensional images of cone beam CT data from 446 patients were evaluated in the presence of double mandibular foramen and the accessory canal passing through the foramen. The accessory canals were classified into two types according to the configuration (forward and retromolar type), and the location of double mandibular foramen was recorded.

Results

The eight double mandibular foramina leading to the accessory canals were observed in six patients out of 446 patients (1.35 % of population). Regarding the configuration of the accessory canal, there were two forward types and six retromolar types. All double mandibular foramina were located above the mandibular foramina on the medial aspect of the mandibular ramus.

Conclusion

Three-dimensional images of cone beam CT data are useful in confirming the presence of double mandibular foramen leading to the accessory canal. The variation may cause failure in the routine mandibular nerve block anesthesia and it is often vulnerable during surgical procedures involving the mandibular ramus. Also, double mandibular foramen is considered as an easy route for tumor cell to spread following the radiotherapy. Therefore, the variation should be carefully investigated using reconstructed cone beam CT images in planning of dental surgery or radiotherapy in the mandible.     

下颌管与下颌后牙的位置关系及临床意义

目的: 为下颌牙种植术等临床口腔外科提供解剖学基础。方法：选取新鲜下颌骨标本10例、成人全牙下颌骨标本18例和20名全牙志愿者,分别暴露出下牙槽神经血管束、下颌管与下颌后牙牙根和CT连续扫描后进行三维重建。观察下牙槽神经、血管的排列关系,用游标卡尺和CT三维重建工作站分别测量下颌后牙牙根至下颌管上壁的距离。结果：下颌管自牙槽窝下方走行,其舌侧骨板较厚;下颌管内的下牙槽血管位于下牙槽神经上方。下颌磨牙的远中根至下颌管的距离均较近中根近。在标本及影像上的第1前磨牙、第2前磨牙、第1磨牙、第2磨牙、第3磨牙牙根至下颌管上壁的距离分别为(8.36±2.34)　mm和(8.42±2.42)mm、(7.36±2.21)mm和(7.52±2.18)mm、(3.22±1.40)mm和(3.36±1.85)mm、(2.96±1.54)mm和(2.84±1.55)mm、(3.64±1.72)mm和(3.88±1.76)mm。结论：（1）下颌后牙至下颌管的距离以第2磨牙最近,由近及远依次为第2磨牙、第1磨牙、第3磨牙、第2前磨牙和第1前磨牙。（2）对选择适宜长度的牙种植体,避免牙种植体损伤下牙槽神经等具有重要意义。     

Uncommon trajectory variations of the mandibular canal and of the mandibular incisive canal: case report

Purpose

This paper aims to report and discuss a case in which unusual anatomical variations were observed in the mandibular canal (MC) and the mandibular incisive canal (MIC) in a same patient.

Materials and methods

A 49-year-old healthy female was referred for mandibular dental implant placement. Panoramic radiography and cone beam computed tomography (CBCT) were performed. Cross-sections, axial, coronal, panoramic reconstructions and volume rendering were obtained.

Results

The panoramic radiograph did not show any evidence of abnormality. CBCT showed a bifid MC on the right side. It extended to the buccal cortex, exteriorized for 6 mm and returned to its conventional trajectory to reach the mental foramen. On the left side, the MIC initially followed its normal trajectory for 4 mm but, in the canine region, it also extended to the buccal cortex and exteriorized.

Conclusion

The advent of CBCT in Dentistry allowed a greater accuracy in the diagnosis of anatomical variations in the jaws, preventing injury to the neurovascular bundle and enabling an adequate surgical planning in the region.     

下颌骨骨折机理的解剖学研究

目的:为下颌骨骨折机理的研究提供解剖学依据。方法:10例新鲜颅面标本进行解剖,对咀嚼肌、位进行观察,把下颌骨横断截开,测量各个解剖区全厚骨质厚度。结果:下颌骨各部分骨质厚度:颏部正中(12.4±0.7)mm、颏孔区(10.6±1.1)mm、磨牙区(14.1±0.9)mm、下颌角(6.8±0.5)mm、下颌孔前区(10.1±1.0)mm、下颌孔后区(6.2±0.5)mm。下颌第3磨牙阻生时,骨质变薄。牙缺失时,骨质吸收牙槽突降低。咀嚼肌在下颌骨两侧呈镜面影像,附着于下颌骨的不同部位。牙尖交错位和下颌后退接触位时上下牙列接触,髁状突与颞骨关节面无间隙,下颌姿势位时使上下牙列及髁状突与颞骨关节面之间均有间隙。结论:(1)颏部正中、下颌体部、下颌角、髁突颈部为下颌骨解剖薄弱区域,下骨全厚骨质厚度和骨折无相关性;(2)下颌第3磨牙阻生、缺失牙、颏孔和尖牙窝使下颌骨变薄弱;(3)咀嚼肌的收缩和位的不同可以改变下颌骨骨折的发生部位;(4)下颌骨薄弱区、咀嚼肌和位共同影响下颌骨骨折的发生。     

Plate osteosynthesis of the mandibular condyle

The aim of this study is to evaluate and compare the biomechanical stability of various osteosynthesis materials for mandible condylar-process fractures. On 160 porcine mandibles, four different monocortical plating techniques (40 per group) were investigated. Condyles were fractured at a defined location from the incisure to the posterior border. After correct anatomical reduction the fractures were plated, using four different techniques. Osteosynthesis materials used were the delta plate, the trapezoid plate, the dynamic compression plate and double mini-plates. Each group was subjected to linear loading in lateral to medial, medial to lateral, anterior to posterior and posterior to anterior directions by a universal mechanical testing machine TIRAtest 2720. Yield load, yield displacement were measured for the different plates. Statistically significant differences were noted between the fixation groups in all four directions. Rigid internal fixation with double mini plates showed the best stability in all directions except posterior to anterior. In this direction, the delta-plate resisted the highest loads. In the three other directions, the delta plate was second best with data similar to double miniplates but lower in magnitude.     

下颌神经管的解剖结构

背景:在下颌后牙种植术中,由于下颌神经管走行于下颌骨体内,有时可损伤下齿槽神经,因而制约了牙种植术的应用。 因此,牙种植术的应用需详细了解下颌神经管的解剖结构。 目的：观察下颌神经管在下颌骨内的走行及管内的解剖结构。 方法：共纳入15具成人牙下颌骨标本与4具新鲜下颌骨动脉灌注标本。纳入对象均牙列完整,后牙无缺失,牙槽骨无吸收。测量15具成人牙下颌骨标本下颌管走行及其管腔各径长度,包括下颌管横径与纵径,下颌管至上下内外缘距离。观察4具新鲜下颌骨动脉灌注标本管内下颌神经管内神经、血管位置关系。 结果与结论：下颌管内缘至舌侧骨板的距离比下颌管外缘至颊侧骨板距离短(P < 0.01);下颌管上缘至牙槽嵴顶的距离较下颌管下缘至下颌骨下缘的距离大(P < 0.01)。表明下颌管在下颌骨体部走行中偏舌侧、偏下颌骨下缘。下颌神经管在下颌骨体部的部分横径小于纵径(P < 0.05),亦即下颌管截面形态为上下径略长的椭圆形。神经管横纵径于前后牙位区差异无显著性意义。实验还发现在暴露的下颌管腔中下牙槽神经及伴随血管有一层被膜包绕成神经血管束,血管位于神经上方,而且位置恒定,并发出小分支包绕神经。结果提示,下牙槽血管神经束在下颌管内走行中血管位于神经之上。     

Human mandibular prenatal growth: bivariate and multivariate growth allometry comparing different mandibular dimensions

Summary Mandibular growth was studied in 36 human fetuses (both sexes) ranging from 13 to 37 weeks of gestation by bivariate and multivariate analyses (bivariate allometry and principal components analysis, PCA). Several mandibular dimensions were measured and correlated with fetal weight. Considering the different mandibular dimensions in sequence of increasing component weights, PCA agreed with bivariate analysis. No mandibular dimension was considered to increase in isometric relationship. PCA showed the following distances with negative allometry: caput mandibulæ-gnathion (both sides), gonion-processus coronoideus (both sides), caput mandibulæ-processus coronoideus (both sides) and gonion-gnathion (right side). On the other hand, the following dimensions grew with positive allometry: goniongnathion (left side) and symphyseal height (both sides). PCA and bivariate analysis showed higher growth rates for the gonion-processus coronoideus distance and symphyseal height on the right side than on the left. All other mandibular dimensions presented more elevated growth rates on the left than on the right side. During the second and third trimesters of prenatal life the mandibular growth was allometrical; the mandibular body grew with more intensity than the ramus in both length and height. The greatest growth rate was found for the height at the symphysis. The angulus mandibulæ presented a negative and slight correlation with the other linear dimensions of the mandible during prenatal life.Abbreviations CM-Gn Caput mandibulæ-gnathion - Go-PC Gonion-processus coronoideus - Go-Gn Gonion-gnathion - CM-PC Caput mandibulæ-processus coronoideus - SH Symphyseal height - AM Angulus mandibulae     

Tissue engineering the mandibular condyle

Tissue engineering provides the revolutionary possibility for curing temporomandibular joint (TMJ) disorders. Although characterization of the mandibular condyle has been extensively studied, tissue engineering of the mandibular condyle is still in an inchoate stage. The purpose of this review is to provide a summary of advances relevant to tissue engineering of mandibular cartilage and bone, and to serve as a reference for future research in this field. A concise anatomical overview of the mandibular condyle is provided, and the structure and function of the mandibular condyle are reviewed, including the cell types, extracellular matrix (ECM) composition, and biomechanical properties. Collagens and proteoglycans are distributed heterogeneously (topographically and zonally). The complexity of collagen types (including types I, II, III, and X) and cell types (including fibroblast-like cells, mesenchymal cells, and differentiated chondrocytes) indicates that mandibular cartilage is an intermediate between fibrocartilage and hyaline cartilage. The fibrocartilaginous fibrous zone at the surface is separated from hyaline-like mature and hypertrophic zones below by a thin and highly cellular proliferative zone. Mechanically, the mandibular condylar cartilage is anisotropic under tension (stiffer anteroposteriorly) and heterogeneous under compression (anterior region stiffer than posterior). Tissue engineering of mandibular condylar cartilage and bone is reviewed, consisting of cell culture, growth factors, scaffolds, and bioreactors. Ideal engineered constructs for mandibular condyle regeneration must involve two distinct yet integrated stratified layers in a single osteochondral construct to meet the different demands for the regeneration of cartilage and bone tissues. We conclude this review with a brief discussion of tissue engineering strategies, along with future directions for tissue engineering the mandibular condyle.     

ADAMTSL1 and mandibular prognathism

Mandibular prognathism is characterized by a prognathic or prominent mandible. The objective of this study was to find the gene responsible for mandibular prognathism. Whole exome sequencing analysis of a Thai family (family 1) identified the ADAMTSL1 c.176C>A variant as the potential defect. We cross-checked our exome data of 215 people for rare variants in ADAMTSL1 and found that the c.670C>G variant was associated with mandibular prognathism in families 2 and 4. Mutation analysis of ADAMTSL1 in 79 unrelated patients revealed the c.670C>G variant was also found in family 3. We hypothesize that mutations in ADAMTSL1 cause failure to cleave aggrecan in the condylar cartilage, and that leads to overgrowth of the mandible. Adamtsl1 is strongly expressed in the condensed mesenchymal cells of the mouse condyle, but not at the cartilage of the long bones. This explains why the patients with ADAMTSL1 mutations had abnormal mandibles but normal long bones. This is the first report that mutations in ADAMTSL1 are responsible for the pathogenesis of mandibular prognathism.     

单侧下颌骨牵张成骨的数值模拟

目的针对颜面短小患者建立下颌骨及咀嚼肌模型,通过有限元方法研究牵张成骨过程中下颌骨的形变规律,并与患者实际手术效果进行对比,为类似病例的治疗过程提出改进意见。方法依据临床颜面短小患者原始数据,结合MIMICS医学影像控制系统软件,运用三维重建技术构造患者下颌骨及咀嚼肌的实体结构,最后导入ANSYS有限元软件完成单侧下颌骨延长的有限元模型,并模拟手术效果。结果所建立的术前术后有限元分析模型具有数字化、个性化特征。结论数值模拟结果与手术效果进行对比,重合度较好,可以为不同病情的病人术前提供个性化的手术指导。