单侧髁突骨折对下颌骨应力分布的影响

目的 探讨单侧髁突骨折对下颌骨应力分布的影响,用以分析颞下颌关节损伤引起颞下颌关节紊乱病的生物力学机制。方法 采用三维有限元应力分析方法,对模拟正中咬合状态下的健康人及右侧髁突颈部骨折、错位愈合所致颞下颌关节紊乱病患者下颌骨的应力分布特征进行对比、定量分析。结果 该患者两侧下颌骨相对应部位最大、最小主应力大小及性质均有差异。骨折侧下颌骨应力明显大于非骨折侧,呈不对称性应力分布,尤以髁突应力异常最为     

Influence of friction at articular surfaces of the temporomandibular joint on stresses in the articular disk: a theoretical approach with the finite element method

The present study was designed to assess stress and displacement of the temporomandibular joint (TMJ) disk during jaw opening with different frictional coefficients (micro) from 0.0001 to 0.5 at the TMJ disk and bony component interfaces using three-dimensional finite element (FE) models of individual TMJs based on magnetic resonance (MR) images. An asymptomatic female volunteer and a female patient with anterior disk displacement without reduction were selected, and serial sagittal and frontal slices of their MR images were used for the TMJ reconstruction procedure. The condylar movement was recorded during jaw opening by a Gnatho-hexagraph and used as the loading condition for the subsequent stress analysis of the model. In the asymptomatic subject, relatively high von Mises stresses were observed in the anterior and lateral regions of the disk during jaw opening, and the superior boundary, contacting with the glenoid fossa, exhibited lower stresses than those on the inferior boundary facing the condyle. In the symptomatic subject, although the stress value in the disk was relatively low, the posterior connective tissue exhibited high stress throughout jaw opening. Additional increments in stress values and disk displacement were observed as the coefficient of friction increased, especially in the asymptomatic subject. It is concluded that an augmentation in the friction between the disk, glenoid fossa, and condyle produces an increment in stress and displacement of the disk.     

Masticatory muscles. Part VI. Masticatory muscles and movement of the lower jaw

The movement paths of the kinematic center of the temporomandibular joint were recorded by means of a jaw movement recording system (OKAS-3D) under 3 conditions: 1. free open and close movements; 2. free opening and loaded closing movements (subjects closed against a small, manually applied, downward directed force on the chin); and 3. during chewing of chewing gum. During free jaw movements, the opening path of the kinematic center lies above the closing path. During loaded closing movements, the opening and closing paths coincide. This indicates that during opening and loaded closing, the condyle-disc complex is slightly pressed against the articular eminence. However, during free closing, there is more space between the articulating surfaces. During gum chewing, the opening and closing paths of the condyle coincide on the balancing side, on the working side they don't. Thus, the joint on the balancing side is loaded and the joint on the working side is not.     

Motion of the human mandibular condyle during mastication

It has been reported that loading to the mandible during closing movement makes the condylar path move more in the superior direction than that during the free closing movement. In this study, the hypothesis was tested that the displacement of the condyle on the chewing side is greater in the direction of the mandibular fossa than that on the non-chewing side. Using a six-degrees-of-freedom jaw movement recording system, we recorded condylar motion in 12 healthy adults without TMD, during the chewing of a large hard gummy jelly. The maximum displacements at the condyle on the chewing side from the maximum intercuspation (CO) position were significantly larger in the superior and medial directions at the initial stage and in the posterior direction at all stages (0.5 mm, 0.5 mm, and 0.6 mm, respectively) than those on the non-chewing side (0.0 mm, 0.1 mm, and 0.1 mm, respectively). This suggests that, in healthy adults, the condyles at CO are located in a position such that excessive load is not applied to the temporomandibular joint when there are the aforementioned displacements.     

Frequency of temporomandibular disorder signs in individuals with cerebral palsy

Summary  This study aimed to determine the frequency of temporomandibular disorder (TMD) signs in 68 individuals with cerebral palsy, aged between 3 and 23 years. TMD signs were evaluated according to the Research Diagnostic Criteria to assess temporomandibular joint sounds, lateral jaw deviation during opening and closing movements and limitation of maximum mouth opening (>40 mm). The frequency of TMD signs observed in the cerebral palsy group (46/68–67·6%) was higher than in the control group (17/68–25%). The clinical scenario of CP seems to make these individuals more prone to the development of TMD signs.     

(牙合)夹板对颞下颌关节紊乱病患者下颌骨应力分布的影响

目的　探讨夹板治疗颞下颌关节紊乱病 (temporomandibularjointdisorders,TMD)的生物力学机制。方法　采用三维有限元法模拟分析TMD患者夹板治疗前后下颌骨应力分布特征的变化。结果　夹板影响了TMD患者下颌骨的应力分布特征 ,使其下颌骨各部位最大、最小主应力明显降低 ,尤其是患侧髁突应力降低更为显著 ,使两侧髁突应力分布趋于一致 ,而下颌骨各部位应力对称性亦有所改善。结论　夹板通过改善颞下颌关节的应力分布状况 (应力大小、性质和对称平衡性 )减轻甚至消除对其的损伤 ,使失衡的关节内环境得到调整和恢复 ,此为夹板治疗TMD的最主要的生物力学机制之一。     

下颌角稳定型骨折坚强内固定后对髁突影响的有限元分析

目的:分析下颌角稳定型骨折坚强内固定以后对髁突应力分布的影响,探讨下颌角骨折引起颞下颌关节紊乱病的生物力学机制。方法:采用螺旋CT技术、计算机图形图像处理功能、有限元处理分析软件Ansys建立下颌骨正常有限元模型及下颌角骨折有限元模型并模拟坚强内固定,定量对比分析髁突应力分布状况。结果:患侧髁突表面应力分布发生了明显改变,尤以髁突前斜面和嵴顶部最为显著;健侧髁突表面应力分布未发生明显改变。结论:下颌角稳定型骨折在外斜线行坚强内固定后髁突表面应力分布发生了异常改变,破坏了颞下颌关节的生物力学环境,可能是下颌骨损伤后颞下颌关节紊乱病的致病原因之一。     

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.     

下颌骨矢状劈开后退术对颞下颌关节的影响

目的:评价下颌骨矢状劈开后退术对颞下颌关节(TMJ)的影响.方法:研究我院50 例术前有颞下颌关节病(TMD),且行下颌骨矢状劈开后退术的患者,从关节压痛、弹响、张口度、张口型等方面量化评估术前、术后颞下颌关节症状变化情况.结果:从关节压痛、弹响、张口度、张口型等各方面评估均显示术后颞下颌关节症状评分均显著低于术前(P<0.05).结论:对于术前有颞下颌关节病的患者,行下颌骨矢状劈开后退术可以有效改善颞下颌关节症状.     

髁突运动中心大张口轨迹与关节窝形态的关系及临床应用探讨

目的　探讨髁突运动中心大张口轨迹与关节窝形态的关系 ,对TMD患者髁突运动中心轨迹特征进行初步研究。方法　利用自行开发的髁突运动中心轨迹显示分析系统 ,分别以运动中心、终末绞链轴点作为参考点 ,观察 10名健康人和 7例临床检查怀疑盘前移位的TMD患者大张口轨迹 ,与磁共振成像得到的相应关节窝形态及关节盘位置诊断结果进行比较。结果　健康人左右侧运动中心轨迹与关节窝形态曲线重合率分别为 80 % (8/ 10 )和 90 % (9/ 10 ) ;终末绞链轴点轨迹与关节窝形态重合率均为 0 (0 / 10 )。TMD患者中 ,11侧盘前移位关节 ,除 1侧可复性盘前移位关节外 ,髁突运动中心轨迹均与正常的轨迹明显不同 ,出现各种改变 ;3侧正常盘位关节 ,髁突运动中心轨迹均与健康人的轨迹相似。结论　运动中心轨迹较终末绞链轴点个体稳定 ,可认为是较理想的研究髁突运动轨迹的参考点     

Three-dimensional finite element analysis of the mandible and temporomandibular joint during vertical ramus elongation by distraction osteogenesis

Distraction osteogenesis has been accepted as an alternative treatment modality for hypoplastic mandibles. Knowledge about the changes occurring in the temporomandibular joint region during mandibular distraction osteogenesis is, however, limited and controversial. Stress distribution in the temporomandibular joint region during unilateral vertical mandibular ramus distraction was studied using a finite element model. The finite element model was based on computed tomography scans and magnetic resonance imaging scans of a patient with unilateral hypoplasia of the right mandibular ramus caused by juvenile idiopathic arthritis. The character of stress distribution in the temporomandibular joint and mandible was analyzed quantitatively at different intervals of the vertical mandibular ramus elongation. During the distraction phase, the condyles, articular disks, and glenoid fossa regions were loaded with a differentiated stress pattern. The affected right condyle, disk, and fossa were submitted to increasing loads with increasing elongation compared with the contralateral temporomandibular joint. Loading on the unaffected left side shifted posteriorly and slightly laterally, because the left condyle was the center of rotation. The loading of the temporomandibular joint regions was low during the active distraction phase, although local areas were subjected to elevated peak stresses.     

最大闭口咬合状态下颞下颌关节的接触特征分析

目的研究颞下颌关节在最大闭口咬合状态下的接触方式和应力分布。方法用可视化人体图像数据先建立颞下颌关节的三维实体模型,在Marc中再进行有限元模型的建立,定义髁状突、关节盘、关节窝三者之间的接触关系,观察其接触特征。结果在最大闭口咬合接触下,髁状突先与关节盘后带与双板区交界处发生接触,同时,关节盘相对髁状突作向前滑动,髁突的等效应力值大于关节盘,而关节窝的应力水平最小。结论在最大闭口咬合状态下,关节盘后带与双板区的交界处以及中间带均为重要的应力缓冲区域。     

Effects of the closing and opening muscle groups on jaw condyle biomechanics after prominent mandibular angle osteotomy

ObjectivesThe aim of this study was to determine the effect of closing and opening muscle groups of the jaw on mandibular stability after prominent mandibular angle osteotomy, through three-dimensional finite element analysis (FEA).Materials and methodsSix patients with prominent mandibular angles, without malocclusion, were selected as finite element models of preoperative and postoperative prominent mandibular angle surgery. Computed tomographic (CT) scans were undertaken of the patients before and after surgery and three-dimensional images reconstructed using Simpleware software. The images were imported into an FEA software. Boundary-constrained and load conditions were applied. The solution process was run, and actions of closing and opening muscle groups were simulated and calculated.ResultsThe Von Mises stresses on the condyle position after the operation were higher than those before the operation. A significant difference was found between the stress distributions in the condyle position between prominent mandibular angle patients and mandibular angle ostectomy patients (P < 0.05).ConclusionsAfter osteotomy, the variation in force exerted by the closing and opening muscle groups of the jaw is one of the major factors affecting mandibular stability. FEA is a promising strategy in pre-surgical planning for improving surgical success and reducing complications.     

无牙颌患者垂直距离对髁状突前斜面应力分布的影响

目的探讨无牙颌患者垂直距离对髁状突前斜面应力分布的影响。方法构建无牙颌患者配戴不同垂直高度全口义齿时下颌骨及颞下颌关节三维有限元模型,分析载荷状态下髁状突前斜面的应力分布状况。结果髁状突前斜面下外侧为主要应力集中区,随垂直距离变化:由H-2位到H-4、H-6位时各区应力值呈减小趋势,在H-8位时各区应力值又呈增大趋势。结论无牙颌患者垂直距离变化对髁状突前斜面应力分布产生影响。     

一侧下颌角受力对双侧关节盘及髁突软骨的影响

目的:利用三维有限元分析法,从生物力学角度探讨一侧下颌角受力瞬间双侧颞下颌关节(TMJ)关节盘及髁突软骨的相应变化及其与临床实际的关系。方法:建立下颌骨和TMJ共5个不同开口度(闭口位及1、2、3、4cm开口位)的三维有限元数字模型;于左侧下颌角下缘向上,施以与眶耳平面垂直的1000N压力。获取受力后双侧关节盘和髁突软骨产生的平均主应力的分布及其峰值大小。结果:(1)闭口位时,双侧关节盘和髁突软骨的平均主应力(EQV应力)峰值明显较小;(2)在不同开口位,关节盘EQV应力峰值多位于后带,髁突软骨则多位于前斜面;(3)关节盘EQV应力峰值始终是左侧大于右侧,而髁突软骨在闭口位及1、4cm开口位时左侧EQV应力峰值大于右侧,2、3cm开口位时则是右侧大于左侧;(4)双侧关节盘和髁突软骨的EQV应力峰值出现的部位基本对称。结论:(1)本组模型较精确地反映了实物,并且实验结果与临床实际相接近,解决了以往实验中遇到的一些问题,为TMJ的生物力学研究提供了新的途径。(2)稳定的咬合关系可以明显减小TMJ的间接损伤。(3)关节盘后带病变及髁突器质性病变可能由下颌骨一次性暴力创伤后造成的TMJ间接损伤引起;受力侧关节盘比对侧更易受损伤,而双侧髁突软骨都有受到严重损伤的可能。     

Dynamic intra-articular space variation in clicking TMJs

During mandibular movement, the geometric relationships of the articular surfaces in the temporomandibular joint (TMJ) change, so that the disc undergoes different stress concentrations with respect to time and position. In this study, we compared the intra-articular space variations of 13 clicking and 15 asymptomatic TMJs for jaw opening/closing. Magnetic resonance imaging and jaw tracking were combined to display the motion of the whole condyle within the fossa. In clicking TMJs, the mediolateral spread s of the stress-field trajectories was 2.4 +/- 1.0 mm (s(max) = 4.9 +/- 2.1 mm) with an aspect ratio a/h of 2.5 +/- 1.6, both significantly greater than in controls (p < 0.05). The stress-field trajectories of the controls coincided during opening/closing (s = 0.9 +/- 0.2 mm, s(max) = 1.8 +/- 0.8 mm, a/h = 1.6 +/- 0.3). Clicking TMJs showed much less coincident stress-field paths and much "flatter" stress-fields than controls during jaw opening/closing.     

JOINT DISORDER: NONREDUCING DISC DISPLACEMENT WITH MOUTH OPENING LIMITATION – REPORT OF A CASE

The internal derangement of the temporomandibular joint (TMJ) represents 8% of all cases of temporomandibular disorders (TMD) posing difficulties to establish an accurate diagnosis and treatment because of its low prevalence. This article presents the case of an 18-year-old Caucasian female patient who came to our Orofacial Pain and TMD Outpatient Service with complaints of intense pain on the right TMJ and limitation of mouth opening (maximum interincisal opening of 29 mm) with deviation to right, which she had been experiencing for the past 3 years. After a detailed clinical interview, a diagnosis hypothesis of nonreducing disc displacement with mouth opening limitation was established. The proposed treatment consisted of intra-joint infiltration with anesthetic in the right TMJ followed by jaw manipulation to recapture the articular disc, which was impeding the complete translation movement of the affected TMJ. After jaw manipulation, a new evaluation was done and showed the re-establishment of jaw dynamics with mouth opening and closing without deviation to the right side, clicking, opening limitation or pain. The patient was followed up at 6 months intervals. Two years after treatment, the patient was reevaluated and her mandibular range of motion without aid increased to 54 mm with no clicking, deviation to right, trismus or pain on the TMJ, indicating success of the treatment approach without recurrence of the pathology.     

The craniocervical connection: a retrospective analysis of 300 whiplash patients with cervical and temporomandibular disorders

Because the concept of whiplash as a causative factor for temporomandibular disorders (TMD) is highly controversial, we decided to do a retrospective analysis of patients treated in our office who had sustained whiplash injuries and were treated for cervical and temporomandibular disorders. The records of 300 patients with TMD preceded by a motor vehicle accident were examined retrospectively. The most common presenting symptoms, in order, were: jaw pain, neck pain, post-traumatic headache, jaw fatigue, and severe temporomandibular joint (TMJ) clicking. The most common TMD diagnoses were: masseter trigger points, closing jaw muscle hyperactivity, TMJ synovitis, opening jaw muscle hyperactivity, and advanced TMJ disk derangement. Based primarily on the physical examination, we concluded that the TMJ and surrounding musculature should be examined similarly to other joints, with no preconceived notion that TMD pathology after whiplash is unlikely.     

Stress-field translation in the healthy human temporomandibular joint

Movement over the surface of the temporomandibular joint (TMJ) disc produces tractional forces. These forces potentially increase the magnitude of shear stresses and contribute to wear and fatigue of the disc. Theoretically, tractional forces in all synovial joints are the result of frictional forces, due to rubbing of the cartilage surfaces, and plowing forces, due to translation of the stress-field through the cartilage matrix as the joint surface congruency changes during motion. For plowing forces to occur in the TMJ, there must be mediolateral translation of the stress-field as the condyle moves dorsoventrally during jaw function. To test whether mediolateral stress-field translation occurs in the intact TMJ, we measured stress-field position and translation velocities in ten normal individuals during rhythmic jaw opening and closing. Magnetic resonance imaging and jaw tracking were combined to animate the three-dimensional position of the stress-field between the articulating surfaces. This allowed for mediolateral translation velocity measurements of the centroid of the stress-field. The results showed that during jaw opening and closing at 0.5 Hz, the average peak mediolateral translation velocity was 35 +/- 17 mm/sec. When opening and closing increased to 1.0 Hz, the average peak velocity was 40 +/- 19 mm/sec. Theoretical model estimates of the work done during such translation ranged from 6 to 709 mJ between the individual joints studied. The potential clinical importance of this measure is that long-term exposure of the TMJ disc to high work may result in fatigue failure of the TMJ disc.     

Stress analysis in the TMJ during jaw opening by use of a three-dimensional finite element model based on magnetic resonance images.

This study was designed to investigate temporomandibular joint (TMJ) stress distribution during mouth opening using a finite element (FE) model of an individual TMJ based on magnetic resonance (MR) images. A dry skull with a silicon disk was used to test the three-dimensional reconstruction procedure, and showed enough accuracy and reproducibility in linear dimensions and disk volume for the following FE modelling for stress analysis in the TMJ. From an individual FE analysis of a normal subject, relatively high stresses were observed in the anterior and posterior regions of the disk during mouth opening, and furthermore, the superior boundary contacting with the glenoid fossa exhibited lower stresses than those on the inferior boundary facing the condyle. During transmission of stress through the disk, mechanical stress may be reduced by the stress redistribution function of the disk.