Temporomandibular joint: surgically created disk displacement causes arthrosis in the rabbit.

To document a causal relationship between temporomandibular joint disk displacement and arthrosis, the disk was surgically displaced in one temporomandibular joint in each of three rabbits. The rabbits were sacrificed after 4 weeks and the mandibular condyles were studied radiographically and histologically. All three joints that underwent disk displacement had radiographic and histologic evidence of arthrosis, which included erosion of the bone, irregularity and fissure formation of the articular soft tissue cover, disruption of the subchondral layer of cartilage cells, and chondrocyte proliferation. No radiographic or histologic changes occurred in the joints that were untouched. The results suggest that surgically created disk displacement can cause arthrosis in the temporomandibular joint of the rabbit.     

Mandibular length and midline asymmetry after experimentally induced temporomandibular joint disk displacement in rabbits.

The purpose of the present investigation was to test the hypothesis that permanent disk displacement in the temporomandibular joint (TMJ) is one causal factor in the development of mandibular midline asymmetry. Unilateral, nonreducing disk displacement was therefore created in growing rabbits. The right TMJ in seven experimental animals was surgically opened, and the disk was anteriorly displaced with the posterior disk attachment kept intact above the condyle. The right TMJ in seven sham animals was surgically opened and closed without any disk manipulation. Seven additional rabbits served as reference animals. For identification of mandibular growth, tantalum implants were inserted into the mandibular body, and lateral cephalograms were exposed at the beginning and at the end of the experimental period. After the animals had been sacrificed, the mandibles were dissected and measurements were performed on the mandibular specimens. Axial radiographs of the mandibles were then exposed and measurements of mandibular length and midline shift were performed in the radiographs. The mandible in the experimental animals was consistently shorter on the disk displacement side resulting in a midline shift to the ipsilateral side. No mandibular asymmetry was observed in the sham and reference groups. The hypothesis was verified; disk displacement in the TMJ with an onset during the growth period can cause mandibular length and midline asymmetry in growing rabbits.     

Analysis of kinesiograph recordings and masticatory efficiency after treatment of non-reducing disk displacement of the temporomandibular joint

The purpose of this study was to clarify the kinesiographs of chewing movement and masticatory efficiency before and after treatment in patients with non-reducing disk displacement of the temporomandibular joint (TMJ). Twenty patients who were diagnosed with unilateral non-reducing disk displacement of the TMJ were treated with pumping of the joint with injection of sodium hyaluronate. Chewing movement patterns in these patients were evaluated, using mandibular kinesiography (MKG) at their initial visit and at mean 19-month follow-up and the results were compared. Masticatory efficiency was also measured. As controls, 23 volunteers without TMJ dysfunction were employed. Far from the results of normal volunteers, chewing movement patterns of the patients on MKG did not show deviation to the chewing side in the TMJ-unaffected-side chewing in the horizontal plane. However, such patterns of the patients became similar to those of normal volunteers after treatment. Masticatory efficiency of the patients improved after treatment, though it was impaired at initial visit. The MKG and masticatory efficiency test appeared to be a useful method of comparing masticatory function before and after treatment in patients with non-reducing disk displacement of the TMJ.     

Temporomandibular joint sounds and condyle/disk relations on magnetic resonance images.

This study compared the condyle/disk relationships on magnetic resonance images (MRIs) in a group of subjects with completely silent temporomandibular joints (TMJ) when tested clinically with those in subjects with readily discernible TMJ sounds. The sounds were recorded with an accelerometer as the transducer. Selected degrees of jaw separation were electronically determined and recorded with interocclusal wafers for use with the imaging process. Of the "silent joints" 89% were found to have sounds when tested with the accelerometer. These "subclinical" sounds tended to be of shorter duration and occurred at a greater degree of vertical opening than the clinically discernable sounds. The MRIs of the group with clinically discernable sounds tended to show a change in the relationship between the head of the condyle and the intermediate zone of the disk, at the degree of jaw separation of the sound occurrence, whereas no condyle/disk change occurred in the group with "clinically silent joints." It is likely that all joints create sound during function. The different characteristics of the subclinical sounds versus the clinical sounds may indicate differing sound origins.     

Temporomandibular joint disk fracture: a case report

A case of a patient with a fracture of the temporomandibular joint (TMJ) disk is reported. The patient presented with posterior bilateral open-bite and difficulty to chew due to lack of contact between the posterior teeth. Diagnosis of disk fracture of the right TMJ was made based on magnetic resonance imaging (MRI), with posterior displacement of the posterior fragment of the disk, causing the posterior open-bite, and anterior displacement of the anterior fragment of the disk. TMJ manipulation failed to reposition the posterior fragment of the disk, and the patient refused to undergo TMJ arthroscopy to try to remove it. After four months, the posterior open-bite was reduced, probably because of remodeling of the posterior TMJ capsule and extrusion of the molars and premolars. Contact with the patient was lost after that time.     

Changes in chewing pattern after surgically induced disc displacement in the rabbit temporomandibular joint.

PURPOSE: This study investigated whether surgically induced disc displacement (DD) in the rabbit temporomandibular joint leads to joint dysfunction. MATERIALS AND METHODS: Fourteen adult Japanese white rabbits were divided into two groups. Eight animals had surgically induced DD, and 6 were used as a sham operation group. Jaw movement trajectories during chewing were recorded preoperatively and 2 weeks after induction of DD. Postoperative recordings after administration of a nonsteroidal anti-inflammatory drug (NSAID) were also performed to eliminate any influence of joint pain on chewing. Vertical and horizontal ranges of chewing movement, duration of the opening and closing phase, and total cycle of chewing were analyzed. Thereafter, the presence of induced DD was confirmed histologically. RESULTS: In the sham group, the rhythm and pattern of chewing were almost the same as preoperatively. In the experimental group, increase in the cycle duration and decrease in the vertical and horizontal ranges of movement were observed. When the sham and experimental groups were compared, there was a decreased ratio of vertical movement in the experimental animals. There was no effect of preadministration of the NSAID in either the DD or sham group. All of the experimental animals had total anterior DD histologically. CONCLUSION: Changes in the chewing pattern of the experimental animals occurred from mechanical interference of the displaced disc. This animal model can be used as a model for human internal derangement.     

Histopathological changes in rabbit craniomandibular joint associated with experimentally induced anterior disk displacement (ADD)

Several studies have shown that anterior disk displacement (ADD) of human temporomandibular joint (TMJ) can lead to cellular and extracellular alterations in the disk proper, bilaminar zone (BZ), condyle, articular eminence and synovial membrane. Due to lack of an animal model for this disease, it is not known whether the mechanical displacement of the disk could lead to the observed histopathological changes. The purpose of this experiment was to investigate the histopathological changes that occur in the rabbit craniomandibular joint (CMJ) following surgical induction of ADD. The right CMJ was exposed surgically and the discal attachments were severed except for the BZ attachments. Then the disk was displaced anteriorly and sutured to the zygomatic arch. The left joint served as surgical control. The CMJs were removed after 24 h, 1 week, 2 weeks or 6 weeks and stained with H&E or modified Masson stain. The results showed neovascularization, cell clustering and fibrillation of the displaced disk. The BZ showed marked fibrosis. The condyle showed subchondral hemorrhage and fibrosis followed by osteoarthritic changes in the articular cartilage. The articular eminence showed chondrocytic clustering and an increase in the amount of chon-droid bone. Synovial membrane exhibited marked hyperplasia. We concluded that surgical induction of ADD in the rabbit CMJ leads to cellular and extracellular alterations in the disk proper, BZ, condyle, articular eminence and synovial membrane similar to those described previously in human ADD. It appears that the mechanical trauma resulting from ADD could lead to a cascade of reparative and degenerative changes of the affected joints similar to those described for osteoarthritis.     

Natural course of non-reducing disc displacement of the temporomandibular joint: changes in electromyographic activity during chewing movement

The purpose of this study is to examine whether electromyographic activity (EMG) during chewing movement changes towards the control level spontaneously in the subsequent course after diagnosis in patients with non-reducing disc displacement of the temporomandibular joint (TMJ) who do not receive any treatment. In 15 such patients, EMG data were examined at initial visit and at a mean follow-up of 21.7 months. As a control, 23 persons who had no TMJ dysfunction were studied. The results of EMG were compared among patients at initial visit, those at follow-up, and controls. The patients' clinical signs and symptoms were alleviated during the follow-up period. Duration of muscle contraction, cycle time and integrated EMG value (IEMG) at initial visit in patients were significantly different from those in the controls. In patients, IEMG for chewing-side masseter during chewing in the TMJ-affected side was greater at follow-up (14.2 +/- 8.01 microV s) than that at initial visit (10.5 +/- 3.69 microV s) (P < 0.05). In patients, duration of muscle contraction or cycle time at follow-up was not different from that at initial visit. Patients with non-reducing disc displacement of the TMJ showed spontaneous increasing of IEMG without any treatment in the subsequent course after diagnosis, coupled with improvement of clinical signs and symptoms. Duration of muscle contraction or cycle time did not change towards the control level. The results presented are useful as control data to understand the true effect of a particular treatment for patients with non-reducing disc displacement of the TMJ.     

MR grading of temporomandibular joint fluid: association with disk displacement categories, condyle marrow abnormalities and pain

The purpose of this study was to investigate temporomandibular joint (TMJ) effusion on magnetic resonance (MR) images, and its association with specific categories of disk displacement, bone marrow abnormalities and pain. From a series of 523 consecutive TMJ MR imaging studies of patients referred to imaging because of pain and dysfunction, those with TMJ effusion, defined as an amount of fluid that exceeded the maximum amount seen in a control group of asymptomatic volunteers, were analysed. The selected patients were reassessed and the amount of TMJ fluid was graded bilaterally according to a set of reference films. Other parameters recorded included disk displacement categories and condyle marrow abnormalities. Pain self-records were obtained from the patients immediately before MR imaging. The association between the recorded parameters and TMJ pain was analysed with t-tests and regression analysis. Of the 523 patients, 70 (13%) had TMJ effusion, which was unilateral in 61%. Only 9% of the 70 patients had effusion bilaterally, whereas bilateral disk displacement was found in 80%. In the 76 joints with effusion, 83% showed two specific categories of disk displacement at closed mouth. Condyle marrow abnormalities were found in 31% of the 70 patients, mostly on one side, and in 24% of the 76 joints. An in-patient regression analysis of the side difference in TMJ pain showed that effusion and condyle marrow abnormalities were significant pain-increasing factors. In conclusion, patients with TMJ effusion represent a subgroup with pain and dysfunction with more severe intra-articular pathology than those with disk displacement but no other joint abnormalities.     

Temporomandibular joint: diagnosis of medial and lateral disk displacement with anteroposterior arthrography. Correlation with cryosections.

The purpose of this investigation was to determine whether it is possible to diagnose medial and lateral disk displacements by single-contrast lower-compartment arthrography with an anteroposterior projection. Contrast medium was injected into the lower joint space of 29 fresh temporomandibular joint autopsy specimens. Anteroposterior arthrograms and anteroposterior arthrotomograms were obtained. Enlargement of the medial or lateral recess of the lower joint space was considered an arthrographic indication of medial or lateral displacement of the disk. After arthrography the joints were deep frozen and cryosectioned in the coronal plane. Imaging findings were correlated to observations in the cryosections in a blind fashion. The anteroposterior arthrograms were 48% accurate in determining the position of the disk in the coronal plane. The anteroposterior arthrotomograms were 59% accurate. It was concluded that anteroposterior lower joint space arthrography as well as arthrotomography is not reliable for diagnosis of medial or lateral disk displacement.     

Temporomandibular joint reconstruction with medial femoral condyle osseocartilaginous flap: a case series

Reconstruction for large-scale temporomandibular joint (TMJ) defects can be challenging. We have used the medial femoral condyle (MFC) osseocartilaginous flap for repair of TMJ defects. The aim of this paper was to describe our technique and to present the preliminary results. The MFC osseocartilaginous flap was used as a free vascularized graft for TMJ defect in four patients who had undergone resection for benign tumor of the TMJ region (n = 2) or TMJ ankylosis (n = 2). A computer-assisted technique was used in all cases. Symmetry of the mandible was objectively evaluated by postoperative computed tomography. Complications were recorded during follow-up visits. Lower extremity functional status was assessed by the Lower Extremity Functional Scale (LEFC) questionnaire. The MFC osseocartilaginous flap success rate was 100%; bony union was obtained in all four patients, and normal occlusion was achieved within 6–11 months after surgery. No flap-related complications occurred. All patients were satisfied with their postoperative facial symmetry and oral function. The LEFC score ranged from 72 to 80, indicating normal lower extremity function. Vascularized MFC osseocartilaginous flap appears to be a reliable option for reconstruction of large-scale TMJ defects.     

再定位牙合垫戴入前后颞下颌关节盘和髁突的位置改变

目的测量再定位牙合垫（ARS）戴入前后关节盘和髁突的位置改变,探讨ARS的治疗机制。方法选择22例单侧或双侧可复性颞下颌关节盘前移位患者进行研究,其中关节盘前移位的关节31侧,设为前移位组;关节盘位置正常的关节13侧,设为正常组。分别在闭口位（ARS戴入前）、对刃位和下颌最少前伸位（ARS戴入后）行磁共振成像扫描,测量不同下颌位置时的2组关节的盘突角度、关节盘和髁突位置的变化。结果1）盘突角度：闭口位时前移位组为54.23°,正常组为9.80°;对刃位和下颌最少前伸位时,前移位组的盘突角度多可回复至正常范围。2）关节盘位置：从闭口位至对刃位或下颌最少前伸位,正常组关节盘位置无明显改变,前移位组关节盘明显向后移动。3）髁突位置：从闭口位至对刃位或下颌最少前伸位,髁突在关节窝中向前下方移动,正常组与前移位组比较的差异无统计学意义（P＞0.05）。结论ARS使髁突向前下方移动,关节盘向后回复。ARS的作用可能是阻止已经向后上方移动而复位的关节盘在闭口过程中再次发生前移位,起到固定作用。     

The surface structure of the temporomandibular joint disk: a scanning electron microscopic study

The surface appearance of seven temporomandibular joint disks obtained at postmortem has been studied by scanning electron microscopy. Two of the disks had lateral perforations which corresponded, in position, to macroscopic changes in the condylar and temporal joint components. The nature of the disk surfaces has been described. The central portion of the disks consisted of tightly bound collagen bundles; the bundles of the anterior and posterior parts were more loosely bound and irregularly orientated. The implications of the findings have been discussed in terms of articular function and dysfunction and of disease processes within the joint.     

Temporomandibular joint sounds in adolescents: a longitudinal study

A 2-year longitudinal study on signs and symptoms of mandibular dysfunction was performed with 285 17-year-old adolescents living in a certain geographic area in Skellefte?, Sweden. Crepitation was neither reported nor recorded in any subject. Both reports and recordings of TMJ clicking sounds fluctuated with time. The 2-year period prevalence was 24%, and 5.8% consistently reported TMJ clicking sounds. The corresponding figures for clinically recorded clickings were 36% and 9.3%, respectively. Both reported and recorded joint sounds were significantly more frequently found in 19-year-old girls than in boys. No consistent pattern of relationships between reported and recorded clicking sounds and single factors obtained by the questionnaire or clinically recorded variables could be found. Palpation tenderness in three muscle sites was to a varying degree related to both reports and recordings of clicking. Each year, significant relationships were found between reports of TMJ sounds and symptom indices. Recorded sounds were significantly related to a clinical index in the two oldest age groups. The prevalence of TMJ clicking sounds increases with age, and girls are more prone to have them than boys. In view of the natural longitudinal fluctuations, most clickings only need to be supervised, and when there is a demand for treatment, reversible methods are advocated in adolescents.     

关节盘穿孔对兔颞下颌关节影响的扫描电镜观察

目的研究兔关节盘穿孔后对颞下颌关节（TMJ）髁状突和关节盘表面超微结构的影响。方法12只3～4月龄的新西兰白兔,随机均分为实验组和对照组。以质量分数为50mg/ml的氯胺酮溶液按1ml/kg对实验动物进行肌注麻醉,对照组于无菌条件下先后暴露左右侧关节盘,实验组并以特制的穿刺针于关节盘后外侧部制作直径为2.6mm的穿孔。分别于术后12、24和36周完整取出双侧TMJ,扫描电镜观察关节盘和髁状突的变化。结果扫描电镜下可见关节盘穿孔后关节表面凝胶状物质不完整,关节盘及髁状突表面均出现明显的退行性改变：凝胶样物质掀起、剥脱,胶原纤维疏松、暴露、断裂、排列紊乱。结论关节盘穿孔可以引起TMJ表面退性行改变。     

Transmission electron microscopic and light microscopic study of condylar and joint disk in TMJ disturbance syndrome

Temporomandibular joint disturbance syndrome (TMJDS) is a complex disease. Its etiological factors and pathologic nature are not clear still. After studying the condyles and discs of 3 normals and 14 TMJDS patients by transmission and scanning electron microscopy and light microscopy, we found: The pathologic changes of TMJDS are similar to those of osteoarthritis. These changes may be associated with the microtrauma in TMJ. There are some repair reactions after destruction of the articular cartilage. The destruction of fibrils is one of the main destruction in TMJDS. The changes of bilaminar zone may be one of the causes of treatment failure by conservative methods in some patients.     

颞下颌关节盘前移位关节区组织病理变化的实验研究

目的通过建立关节盘前移位实验动物模型的方法,来研究人类关节盘前移位病变早期阶段的发展过程和病理学改变。方法１２只新西兰大白兔左颞下颌关节经实验诱导为关节盘前移位模型,右侧为手术对照组。于术后２４ｈ、１周、２周、３周、４周、１０周各处死２只,切取关节组织,ＨＥ染色,光镜观察。结果早期：关节结节、髁突关节软骨增生明显,髁突软骨下出血,骨组织内血管网消失;后期：髁突关节软骨、骨组织及滑膜出现骨关节炎（ＯＡ）样改变。结论实验诱导关节盘前移后关节区的病理学变化与人类相似;关节盘前移位关节区的创伤可引起关节骨关节炎样改变。     

Temporomandibular joint prosthesis as treatment option for mandibular condyle fractures: a systematic review and meta-analysis

The aim of this study was to perform a systematic review of the literature on the temporomandibular joint (TMJ) prosthesis as a treatment option after mandibular condyle fracture. Three databases were searched (PubMed, Embase, Cochrane Library) and 2670 unique papers were identified. A total of 337 studies were included (121 case reports, 89 case series, and 127 cohort/clinical studies). In total 14,396 patients and 21,560 prostheses were described. Of the 127 cohort or clinical studies, 100 (79%) reported inclusion criteria, 54 (43%) reported exclusion criteria, and 96 (76%) reported the inclusion period. The base population from which patients were recruited was reported in 57 studies (45%). The reason for TMJ prosthesis implantation was reported for 4177 patients (29.0%). A history of condylar fracture was present in 83 patients (2.0%); a history of mandibular trauma was present in 580 patients (13.9%). The meta-analysis showed a pooled prevalence of condylar fracture of 1.6% (95% confidence interval 0.9–2.4%) and a pooled prevalence of trauma or condylar fracture of 11.3% (95% confidence interval 7.1–16.0%). Heterogeneity was highly significant (P < 0.001). The TMJ prosthesis appears to be reserved for patients with persistent pain, bony or fibrous ankylosis, or osteomyelitis after primary closed or open treatment of fractures of the mandibular condyle.