The process of lubrication impairment and its involvement in temporomandibular joint disc displacement: a theoretical concept

Reliability and diagnostic validity of a joint vibration analysis device

Background

This observational study was designed to evaluate the reliability and diagnostic validity of Joint Vibration Analysis (JVA) in subjects with bilateral disc displacement with reduction and in subjects with bilateral normal disc position.

Methods

The reliability of selecting the traces was assessed by reading the same traces at an interval of 30 days. The reliability of the vibrations provided by the subjects was assessed by obtaining two tracings from each individual at an interval of 30 min. The validity compared the Joint Vibration Analysis parameters against magnetic resonance imaging as the reference standard. The data were analyzed with exploratory factor analysis.

Results

The short- term reliability of the Joint Vibration Analysis outcome variables showed excellent results. Implementing factor analysis and a receiver operating characteristic as analytical methods showed that six items of the Joint Vibration Analysis outcome variables could be scaled and normalized to a composite score which presented acceptable levels of sensitivity and specificity with a receiver operating characteristic of 0.8.

Conclusion

This study demonstrated that the composite score generated from the Joint Vibration Analysis variables could discriminate between subjects with bilateral normal versus bilateral displaced discs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-017-0346-9) contains supplementary material, which is available to authorized users.

Effects of Compressive Loading on Human Synovium-derived Cells

Compressive stress may be involved in temporomandibular joint (TMJ) synovitis, but its mechanism has not been fully elucidated. We hypothesized that mechanical stress to the synovial cells of the TMJ potentially causes degenerative changes in temporomandibular joint disease. We examined the effect of cyclic compressive loading on three-dimensionally engineered constructs using human TMJ synovium-derived cells in vitro. Human TMJ synovium-derived cells were cultured onto collagen scaffolds, resulting in three-dimensional constructs. Cyclic compression loading was applied to the constructs by means of a custom-designed apparatus. DNA amount, apoptotic cells, and mRNA levels for inflammatory cytokines were analyzed. The protein expression and activity of MMPs were examined. DNA amount or apoptotic cell number was unchanged by loading. MMP-2, -3, and IL-8 mRNA expression was up-regulated by the compression, and both MMP-1 and -3 protein expression and MMP-2 activity were detected. Thus, compression of human TMJ synovium-derived cells appears to modulate inflammatory cytokines.

The Frictional Coefficient of the Temporomandibular Joint and Its Dependency on the Magnitude and Duration of Joint Loading

In synovial joints, friction between articular surfaces leads to shear stress within the cartilaginous tissue, which might result in tissue rupture and failure. Joint friction depends on synovial lubrication of the articular surfaces, which can be altered due to compressive loading. Therefore, we hypothesized that the frictional coefficient of the temporomandibular joint (TMJ) is affected by the magnitude and duration of loading. We tested this by measuring the frictional coefficient in 20 intact porcine TMJs using a pendulum-type friction tester. The mean frictional coefficient was 0.0145 (SD 0.0027) after a constant loading of 50 N during 5 sec. The frictional coefficient increased with the length of the preceding loading duration and exceeded 0.0220 (SD 0.0014) after 1 hr. Application of larger loading (80 N) resulted in significantly larger frictional coefficients. In conclusion, the frictional coefficient in the TMJ was proportional to the magnitude and duration of joint loading.

Lubricin in synovial fluid of mild and severe temporomandibular joint internal derangements

BACKGROUND

To understand the molecular basis of temporomandibular joint (TMJ) pathologies, we aimed to investigate the lubricin levels in the TMJ synovial fluid (SF) of patients with mild to severe internal derangements (IDs).

MATERIAL AND METHODS

A total, 34 joints were the study group. Only patients, with a Wilkes stage of III, IV and V were included, in this sample. Control group consisted of SF from eight joints, from patients undergoing to orthognatic surgery. Concentrations of lubricin in the SF from both samples were measured using ELISA system.

RESULTS

The mean lubricin concentration was 7.029 ± 0.21 µg/mL in stage III patients; 5.64 ± 0.10 µg/mL in stage IV patients, and 4.78 ± 0.11 µg/mL in stage V patients. The lubricin levels from stage IV and stage V patients differed significantly (P ≤ 0.001) from those of control subjects. Lubricin levels were inversely correlated with age and to VAS score.

CONCLUSIONS

The results of this cross-sectional study highlight the relationship between disease severity and the levels of lubricin in TMJ SF. Our findings suggest that novel biotherapeutic approaches, including the administration of recombinant lubricin in the joint cavity, for the treatment of TMJ diseases can be developed.

Effects of enzymatic degradation after loading in temporomandibular joint

Synovial fluid of the joint decreases friction between the cartilage surfaces and reduces cartilage wear during articulation. Characteristic changes of synovial fluid have been shown in patients with osteoarthritis (OA) in the temporomandibular joint (TMJ). OA is generally considered to be induced by excessive mechanical stress. However, whether the changes in synovial fluid precede the mechanical overloading or vice versa remains unclear. In the present study, our purpose was to examine if the breakdown of joint lubrication affects the frictional properties of mandibular condylar cartilage and leads to subsequent degenerative changes in TMJ. We measured the frictional coefficient in porcine TMJ by a pendulum device after digestion with hyaluronidase (HAase) or trypsin. Gene expressions of interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), matrix metalloproteinases (MMPs), type II collagen, and histology were examined after prolonged cyclic loading by an active pendulum system. The results showed that the frictional coefficient increased significantly after HAase (35%) or trypsin (74%) treatment. Gene expression of IL-1β, COX-2, and MMPs-1, -3, and -9 increased significantly in enzyme-treated TMJs after cyclic loading. The increase in the trypsin-treated group was greater than that in the HAase-treated group. Type II collagen expression was reduced in both enzyme-treated groups. Histology revealed surface fibrillation and increased MMP-1 in the trypsin-treated group, as well as increased IL-1β in both enzyme-treated groups after cyclic loading. The findings demonstrated that the compromised lubrication in TMJ is associated with altered frictional properties and surface wear of condylar cartilage, accompanied by release of pro-inflammatory and matrix degradation mediators under mechanical loading.

Antioxidant capacity of synovial fluid in the temporomandibular joint correlated with radiological morphology of temporomandibular disorders

We investigated the correlation between the antioxidant capacity of synovial fluid and radiological findings of intra-articular structures in patients with disorders of the temporomandibular joint (TMJ). We recruited 21 patients (9 men and 12 women, aged 18-84 years of age) with such disorders, excluding myofascial pain and dysfunction syndrome, or other muscular disorders. The clinical variables recorded included age, sex, interincisal distance, and visual analogue pain scores (VAS). Radiological findings were obtained from diagnostic arthrogram and cone-beam computed tomography (CT). The antioxidant capacity of the synovial fluid was measured by chemiluminescence. Eleven patients were radiologically diagnosed with closed lock, and the remaining 10 with no closed lock. An anchored intra-articular disc was most often seen on cone-beam CT (n=19) followed by perforated disc (n=7), osteoarthrosis (n=7), and anterior disc displacement without reduction (n=5). Although there were no significant differences between antioxidant capacity and age, sex, VAS, or any findings on cone-beam CT, antioxidant capacity was significantly decreased in the patients with closed lock compared with those who did not have closed lock (p=0.02). The results suggest an association between the oxidative stress of the synovial fluid and closed-lock in disorders of the TMJ.

Fracture of the articular disc in the temporomandibular joint: two case reports

Disc fracture of the temporomandibular joint (TMJ) is a little-known pathological condition owing to its extreme rarity. We report two cases of elderly patients who were diagnosed with disc fracture of the TMJ based on MRI, and we review related reports. On physical examination, an incomplete bite and mild joint pain were observed on the affected side in both patients. An MRI showed a complete fracture in the intermediate zone of the articular disc in the TMJ; the posterior fragment was displaced posteriorly, causing occlusal change in the closed position of the condyle and an incomplete bite. Conservative treatment including manual manipulation, physical therapy and oral appliance had no effect on the occlusal abnormality. Although the inciting cause of the disc fracture remained unclear, the degenerative changes in the joint may have been a factor by increasing the brittleness and reducing the elasticity of the disc.

Role of interstitial fluid pressurization in TMJ lubrication

In temporomandibular joints (TMJs), the disc and condylar cartilage function as load-bearing, shock-absorbing, and friction-reducing materials. The ultrastructure of the TMJ disc and cartilage is different from that of hyaline cartilage in other diarthrodial joints, and little is known about their lubrication mechanisms. In this study, we performed micro-tribometry testing on the TMJ disc and condylar cartilage to obtain their region- and direction-dependent friction properties. Frictional tests with a migrating contact area were performed on 8 adult porcine TMJs at 5 different regions (anterior, posterior, central, medial, and lateral) in 2 orthogonal directions (anterior-posterior and medial-lateral). Some significant regional differences were detected, and the lateral-medial direction showed higher friction than the anterior-posterior direction on both tissues. The mean friction coefficient of condylar cartilage against steel was 0.027, but the disc, at 0.074, displayed a significantly higher friction coefficient. The 2 tissues also exhibited different frictional dependencies on sliding speed and normal loading force. Whereas the friction of condylar cartilage decreased with increased sliding speed and was independent of the magnitude of normal force, friction of the disc showed no dependence on sliding speed but decreased as normal force increased. Further analysis of the Péclet number and frictional coefficients suggested that condylar cartilage relies on interstitial fluid pressurization to a greater extent than the corresponding contact area of the TMJ disc.

Temporomandibular disorders: a review of etiology, clinical management, and tissue engineering strategies

Temporomandibular disorders (TMD) are a class of degenerative musculoskeletal conditions associated with morphologic and functional deformities that affect up to 25% of the population, but their etiology and progression are poorly understood and, as a result, treatment options are limited. In up to 70% of cases, TMD are accompanied by malpositioning of the temporomandibular joint (TMJ) disc, termed "internal derangement." Although the onset is not well characterized, correlations between internal derangement and osteoarthritic change have been identified. Because of the complex and unique nature of each TMD case, diagnosis requires patient-specific analysis accompanied by various diagnostic modalities. Likewise, treatment requires customized plans to address the specific characteristics of each patient's disease. In the mechanically demanding and biochemically active environment of the TMJ, therapeutic approaches that can restore joint functionality while responding to changes in the joint have become a necessity. One such approach, tissue engineering, which may be capable of integration and adaptation in the TMJ, carries significant potential for the development of repair and replacement tissues. The following review presents a synopsis of etiology, current treatment methods, and the future of tissue engineering for repairing and/or replacing diseased joint components, specifically the mandibular condyle and TMJ disc. An analysis of native tissue characterization to assist clinicians in identifying tissue engineering objectives and validation metrics for restoring healthy and functional structures of the TMJ is followed by a discussion of current trends in tissue engineering.

Improvement of asymmetric stomatognathic functions, unilateral crossbite, and facial esthetics in a patient with skeletal Class III malocclusion and mandibular asymmetry, treated with orthognathic surgery

Patients with a dentofacial skeletal deformity have not only esthetic and morphologic problems related to facial proportions and dentition, but also problems of stomatognathic functions. Therefore, in addition to morphologic analysis, functional analysis is important for the diagnosis and evaluation of treatment in these patients. However, no reports have described longitudinal simultaneous evaluations of stomatognathic functions, and the comprehensive effects of surgical orthodontics on the stomatognathic functions are unclear. A patient was diagnosed as having a skeletal Class III jaw-base relationship, mandibular asymmetry, unilateral crossbite, asymmetric stomatognathic functions, and a temporomandibular disorder. She was treated with a combination of surgery and orthodontic therapy. As a result, facial proportions and occlusion improved; in particular, asymmetric stomatognathic functions, including masticatory muscle activity, condylar movement, and occlusal force, became symmetric between the left and right sides. Moreover, after 2 years of retention, the activity of the masticatory muscles and the values of occlusal force and occlusal contact area exceeded those at pretreatment. These results suggest that improvement of asymmetric stomatognathic functions can be achieved by correction of dentofacial morphology by surgical orthodontic treatment in patients with mandibular asymmetry.

The evaluation of lateral pterygoid muscle pathologic changes and insertion patterns in temporomandibular joints with or without disc displacement using magnetic resonance imaging

Temporomandibular joint (TMJ) disc displacement is a common disorder in patients with internal derangement. Certain anatomic features of TMJ may make the patient prone to this condition, namely lateral pterygoid muscle (LPM) insertion variations. The aim of this study was to investigate LPM attachments and their relationships with disc displacement and subsequent pathologic changes. A total of 26 patients with clinical temporomandibular disorders (TMDs) and a control group of 14 unaffected individuals were studied. Magnetic resonance images (MRIs) were taken to evaluate LPM insertion patterns, superior LPM head pathologic changes, and relative disc to condyle position. Data registration and analysis were done using SPSS v. 16.0. The most common variation (type I) was shown to be the superior head with two bundles, one attached to the disc and another to the condyle. No significant relationship between LPM insertion type and disc displacement or pathologic changes of the muscle was found. However, a link between disc displacement and muscle pathologic changes was established (P=0.001).

Temporomandibular disorders: the habitual chewing side syndrome

BACKGROUND

Temporomandibular disorders are the most common cause of chronic orofacial pain, but, except where they occur subsequent to trauma, their cause remains unknown. This cross-sectional study assessed chewing function (habitual chewing side) and the differences of the chewing side and condylar path and lateral anterior guidance angles in participants with chronic unilateral temporomandibular disorder. This is the preliminary report of a randomized trial that aimed to test the effect of a new occlusal adjustment therapy.

METHODS

The masticatory function of 21 randomly selected completely dentate participants with chronic temporomandibular disorders (all but one with unilateral symptoms) was assessed by observing them eat almonds, inspecting the lateral horizontal movement of the jaw, with kinesiography, and by means of interview. The condylar path in the sagittal plane and the lateral anterior guidance angles with respect to the Frankfort horizontal plane in the frontal plane were measured on both sides in each individual.

RESULTS

Sixteen of 20 participants with unilateral symptoms chewed on the affected side; the concordance (Fisher's exact test, P = .003) and the concordance-symmetry level (Kappa coefficient κ = 0.689; 95% confidence interval [CI], 0.38 to 0.99; P = .002) were significant. The mean condylar path angle was steeper (53.47(10.88) degrees versus 46.16(7.25) degrees; P = .001), and the mean lateral anterior guidance angle was flatter (41.63(13.35) degrees versus 48.32(9.53) degrees P = .036) on the symptomatic side.

DISCUSSION

The results of this study support the use of a new term based on etiology, "habitual chewing side syndrome", instead of the nonspecific symptom-based "temporomandibular joint disorders"; this denomination is characterized in adults by a steeper condylar path, flatter lateral anterior guidance, and habitual chewing on the symptomatic side.

Management of acquired open bite associated with temporomandibular joint osteoarthritis using miniscrew anchorage

This article reports the orthodontic treatment of a patient with skeletal mandibular retrusion and an anterior open bite due to temporomandibular joint osteoarthritis (TMJ-OA) using miniscrew anchorage. A 46-year-old woman had a Class II malocclusion with a retropositioned mandible. Her overjet and overbite were 7.0 mm and -1.6 mm, respectively. She had limited mouth opening, TMJ sounds, and pain. Condylar resorption was observed in both TMJs. Her TMJ pain was reduced by splint therapy, and then orthodontic treatment was initiated. Titanium miniscrews were placed at the posterior maxilla to intrude the molars. After 2 years and 7 months of orthodontic treatment, an acceptable occlusion was achieved without any recurrence of TMJ symptoms. The retropositioned mandible was considerably improved, and the lips showed less tension upon lip closure. The maxillary molars were intruded by 1.5 mm, and the mandible was subsequently rotated counterclockwise. Magnetic resonance imaging of both condyles after treatment showed avascular necrosis-like structures. During a 2-year retention period, an acceptable occlusion was maintained without recurrence of the open bite. In conclusion, correction of open bite and clockwise-rotated mandible through molar intrusion using titanium miniscrews is effective for the management of TMJ-OA with jaw deformity.

Interventions for the management of temporomandibular joint osteoarthritis

BACKGROUND

Osteoarthritis (OA) is the most common form of arthritis of the temporomandibular joint (TMJ), and can often lead to severe pain in the orofacial region. Management options for TMJ OA include reassurance, occlusal appliances, physical therapy, medication in addition to several surgical modalities.

OBJECTIVES

To investigate the effects of different surgical and non-surgical therapeutic options for the management of TMJ OA in adult patients.

SEARCH METHODS

We searched the following databases: the Cochrane Oral Health Group Trials Register (to 26 September 2011); CENTRAL (The Cochrane Library 2011, Issue 3); MEDLINE via OVID (1950 to 26 September 2011); EMBASE via OVID (1980 to 26 September 2011); and PEDro (1929 to 26 September 2011). There were no language restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing any form of non-surgical or surgical therapy for TMJ OA in adults over the age of 18 with clinical and/or radiological diagnosis of TMJ OA according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) guideline or compatible criteria.Primary outcomes considered were pain/tenderness/discomfort in the TMJs or jaw muscles, self assessed range of mandibular movement and TMJ sounds. Secondary outcomes included the measurement of quality of life or patient satisfaction evaluated with a validated questionnaire, morphological changes of the TMJs assessed by imaging, TMJ sounds assessed by auscultation and any adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors screened and extracted information and data from, and independently assessed the risk of bias in the included trials.

MAIN RESULTS

Although three RCTs were included in this review, pooling of data in a meta-analysis was not possible due to wide clinical diversity between the studies. The reports indicate a not dissimilar degree of effectiveness with intra-articular injections consisting of either sodium hyaluronate or corticosteroid preparations, and an equivalent pain reduction with diclofenac sodium as compared with occlusal splints. Glucosamine appeared to be just as effective as ibuprofen for the management of TMJ OA.

AUTHORS' CONCLUSIONS

In view of the paucity of high level evidence for the effectiveness of interventions for the management of TMJ OA, small parallel group RCTs which include participants with a clear diagnosis of TMJ OA should be encouraged and especially studies evaluating some of the possible surgical interventions.

Expression of lumican and fibromodulin following interleukin-1 beta stimulation of disc cells of the human temporomandibular joint

Small leucine-rich repeat proteoglycans (SLRP) are present in the extracellular matrix of the temporomandibular joint (TMJ) disc. Lumican and fibromodulin, classified as class 2 SLRPs, play important roles in TMJ assembly, proliferation and inflammation. Degenerative change in the TMJ disc gives rise to the process of internal derangement (ID). In this study, we immunohistochemically examined the expression of lumican and fibromodulin in nine human TMJ specimens and examined the gene expression of both proteoglycans in cultured human TMJ disc cells under interleukin-1 beta (IL-1 β)-stimulated conditions. An articular disc cell line was established by collagenase treatment of a TMJ disc. The subcultured cells were then incubated for 1, 3, 6, 12, 24 or 48 h under both normal and IL-1 β (1 ng/mL) conditions. The gene expression of lumican and fibromodulin was examined using the reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR. We demonstrated that the expression of lumican significantly differs from that of fibromodulin in the deformed disc and that IL-1 β induces a significant increase in lumican mRNA, but not in fibromodulin mRNA, after 24∼48 h culture compared to cells cultured in the absence of IL-1 β (P<0.05). These results indicate that lumican and fibromodulin display different behaviors and that lumican may promote regeneration of the TMJ after degeneration and deformation induced by IL-1 β.

Combination of intermittent hydrostatic pressure linking TGF-β1, TNF-α on modulation of proteoglycan 4 metabolism in rat temporomandibular synovial fibroblasts

OBJECTIVE

This study was designed to evaluate the combined effects of intermittent hydrostatic pressure (IHP) and TGF-β1 or TNF-α on proteoglycan4 (PRG4) expression in rat temporomandibular synovial fibroblasts (SFs).

STUDY DESIGN

Rat SFs were isolated and expanded in monolayer cultures and subjected to IHP in the presence of TGF-β1 or TNF-α. Quantitative real-time RT-PCR was applied to analyze the PRG4 expression levels. Enzyme-linked immunosorbent assay was also used for the quantification of PRG4 accumulation in the culture medium while immunofluorescence staining was used to detect intracellular PRG4 protein expression.

RESULTS

The combination of IHP and TGF-β1 induced greater PRG4 expression than either stimulus alone. In contrast, TNF-α inhibited PRG4 expression, and this was partially alleviated by IHP.

CONCLUSIONS

Our study demonstrates a beneficial role of IHP, which can be used successfully in combination with TGF-β1 to enhance PRG4 production, and can partially counteract TNF-α-induced PRG4 inhibition in isolated rat SFs.

Effect of functional shift of the mandible on lubrication of the temporomandibular joint

Lubrication of synovial joints reduces the coefficient of friction of the articular cartilage surface. To investigate the effect of malocclusion on the lubrication of the temporomandibular joint (TMJ), we evaluated lubricin expression in the rat TMJ immunohistochemically, under conditions of functional lateral shift of the mandible, during period of growth. Thirty 5-week-old male Wistar rats were divided into experimental, recovery, and control groups. Each rt in the experimental and recovery groups was fitted with an acrylic-plate guiding appliance. The rats in the experimental and control groups were killed at 14 and 28 days after the appliance was attached. Each rat in the recovery group was detached from the appliance at 14 days, and was killed 14 days after the appliance was removed. In the experimental group, the expression of lubricin staining in TMJ cartilage was significantly decreased during the experimental period. In the recovery group, the expression of lubricin staining in TMJ cartilage was significantly greater than in the experimental group, and there was no significant difference at 28 days between the control and recovery groups. Analysis of these data suggests that a functional lateral shift of the mandible during the growth period influences lubrication of the TMJ.

Biomechanical analysis of the influence of friction in jaw joint disorders

OBJECTIVE

Increased friction due to impaired lubrication in the jaw joint has been considered as one of the possible causes for internal joint disorders. A very common internal disorder in the jaw joint is an anteriorly dislocated articular disc. This is generally considered to contribute to the onset of arthritic injuries. Increase of friction as caused by impairment of lubrication is suspected to be a possible cause for such a disorder.

METHOD

The influence of friction was addressed by analysis of its effects on tensions and deformations of the cartilaginous structures in the jaw joint using computational biomechanical analysis. Jaw open-close movements were simulated while in one or two compartments of the right joint friction was applied in the articular contact. The left joint was treated as the healthy control.

RESULTS

The simulations predicted that friction primarily causes increased shear stress in the articular cartilage layers, but hardly in the articular disc.

CONCLUSIONS

This suggests that impaired lubrication may facilitate deterioration of the cartilage-subchondral bone unit of the articular surfaces. The results further suggest that increased friction is not a plausible cause for turning a normally functioning articular disc into an anteriorly dislocated one.

Interleukin-1 beta affects cyclooxygenase-2 expression and cartilage metabolism in mandibular condyle

Extracellular matrix degradation in mandibular condylar cartilage is mediated by various cytokines in the temporomandibular joint (TMJ). Interleukin-1 beta (IL-1β) is detected in joint structures with pathologic status, and participates in catabolic action in the extracellular matrix. The purpose of this study was to investigate the effects of IL-1β on cyclooxygenase-2 (COX-2) expression and cartilage metabolism using cultured chondrocytes from mandibular condyle. Articular chondrocytes from the porcine mandibular condylar cartilage around the surface were cultured and treated with 0-10 ng/ml IL-1β or 0-1000 ng/ml prostaglandin (PGE(2)) for 0-24h. The mRNA levels of COX-2, MMP-1, -3, and -13 were evaluated by real-time PCR analysis. The protein levels of PGE(2) and MMPs were examined by ELISA and Western blot analysis, respectively. The expression levels of COX-2 and PGE(2) were enhanced by exogenous IL-1β in chondrocytes. The mRNA levels of MMP-1, -3, and -13 were up-regulated by PGE(2) treatment dose-dependently. It is shown that the expression of COX-2/PGE(2) was enhanced by IL-1β in articular chondrocytes from mandibular condyle, and that MMP-1, -3, and -13 were induced by PGE(2), suggesting that IL-1β-induced COX-2/PGE(2) play a crucial role in catabolic processes of mandibular condylar cartilage under inflammatory conditions.

Apoptosis in displaced temporomandibular joint disc with and without reduction: an immunohistochemical study

Internal derangement (ID) of the temporomandibular joint (TMJ) is due to an abnormal relationship of the articular disc to the mandibular condyle, glenoid fossa and articular eminence. The two most common types of internal derangement are anterior disc displacement with (ADDwR) and without reduction (ADDwoR). Disc displacement is associated with degenerative tissue changes. The histological features of discs from patients with TMJ ID reflect a general remodelling caused by abnormal loading. A correlation has been demonstrated between TMJ ID and apoptosis. Few investigations have addressed the role of apoptosis or caspase activity in TMJ ID. The apoptosis activation process was studied in different areas of discs from 18 patients with ID (both ADDwR and ADDwoR) and four cadavers (controls), with emphasis on the expression of caspase 3, whose activation makes the death process irreversible. The results showed a greater proportion of caspase 3-positive cells in ADDwR and ADDwoR than in control discs. Immunopositivity also varied between disc areas; in particular, in ADDwoR sections labelled cells were significantly more numerous (P < 0.01) in the posterior disc attachment than in the anterior and intermediate bands. In addition, a significantly greater proportion of labelled cells was seen in the anterior (+) and intermediate (++) band of ADDwR compared with ADDwoR discs both bands (P < 0.05). These data suggest the importance of programmed cell death in the progression of TMJ ID.

Lubricin immunohistochemical expression in human temporomandibular joint disc with internal derangement

Lubricin is a chondroprotective, mucinous glycoprotein which contribute to joint lubrication, especially to boundary lubrication and maintains joint integrity. The present investigation aimed to study the immunolocalization of lubricin in TMJ discs from patients affected by anterior disc displacement with reduction (ADDwR) ADDwoR. Eighteen TMJ displaced disc affected by ADDwoR were processed immunohistochemically, with a polyclonal anti-lubricin antibody, used at 1:50 working dilution. The percentage of lubricin immunopositive cells (extent score = ES) and the extent of lubricin staining of the disc extracellular matrix (ECM), were evaluated. Each sample was scored for histopathological changes. Percentage of immunostained surface disc cells was the same (ES = 4) in both control and ADDwOR cells, being this data not statistically significant (P < 0.05). In pathological specimens the percentages of lubricin-stained cells was very high with an ES of 4 respect to control specimen, and this difference was statistically significant different (P > 0.05). The extracellular matrix (ECM) of discs at the disc surfaces of both pathological and normal specimens was very heavily stained (++++). Both the ES and ECM staining were not statistically correlated to the TMJ degeneration score according to the Spearman's rank correlation coefficient. According to our findings, a longstanding TMJ disc injury, affects lubricin expression in the TMJ disc tissue and not its surfaces, moreover, lubricin immunostaining is not correlated to TMJ disc histopathological changes.

Nomenclature and classification of temporomandibular joint disorders

Currently, there are basically two approaches to classification, one based on structural and one on positional changes occurring within the joint. Despite the increase in knowledge of pathologic changes occurring within the temporomandibular joint (TMJ), the disc still seems to be a central issue in nomenclature and classifications of TMJ disorders. Basic pathologies of the TMJ involve inflammation and degeneration in arthritic disorders (irrespective of the presence or position of the disc) and structural aberrations in growth disorders. Some internal derangements may occur independent of underlying pathology, e.g. because of a traumatic event. In this position paper, a classification of TMJ disorders is proposed based on basic structural changes occurring in the joint.

Preliminary evaluation of histological changes found in a mechanical arthropatic temporomandibular joint (TMJ) exposed to an intra-articular Hyaluronic acid (HA) injection, in a rat model

OBJECTIVE

This study investigates the histological effects of Hyaluronic acid injections in the treatment of induced temporomandibular joint (TMJ) osteoarthritis in rats.

STUDY DESIGN

Twenty-four male Wister rats were subjected to induced mechanical osteoarthritis by manual hypermobility for 10 successive days. Animals were then divided into two groups; group I (control) and group II (experimental). Ten days after the induction of hypermobility, the right TMJ of the experimental animals was injected with a dose of 0.12 mg HA intra-articularly and 0.12 mg saline was injected into the left joint; while animals in the control group were left without any treatment. Two rats from group I were killed at one, two and six weeks; while 6 animals from group II were killed at one, two and four weeks post injection.

RESULTS

The disk of the right joints in the experimental animals was of normal thickness and there was an increase in the thickness of the fibrocartilagenous layer. In the left joint; ulcerative changes in the disk were evident where the fibres were not well oriented and scalloped areas in the temporal bone area were present denoting osteoclastic activity.

CONCLUSIONS

Repeated intra-articular TMJ injection of Hyaluronic acid appears to be a safe and effective way of inhibiting the progression of osteoarthritic changes in the joint through development of articular cartilage and reducing fibrous tissue proliferation.

Breathing and temporomandibular joint disease

Temporomandibular joint disease (TMD) refers to a collection of pain related conditions in the masticatory muscles and temporomandibular joint. Occlusal factors have been implicated in TMD pathogenesis, yet despite decades of research no causal relationship between occlusion and TMD has been found. The significance of psychosocial factors in both the assessment and the long-term management of patients with TMD is receiving increased recognition. The teaching of relaxation skills and coping strategies are effective, proven TMD therapies. The role of breathing re-education in temporomandibular joint (TMJ) disorders is rarely mentioned. A focus on breathing patterns and their disorders potentially explains how biomechanical factors associated with psychosocial influences might lead to pathophysiological changes within the TMJ as well as in the associated muscles. Attention to factors such as breathing and postural rehabilitation provides health professionals valuable, additional tools to help care for patients with TMD.

Possíveis fatores etiológicos para desordens temporomandibulares de origem articular com implicações para diagnóstico e tratamento

Os fatores envolvidos na etiologia, diagnóstico e tratamento das desordens temporomandibulares (DTM) de origem articular foram revisados. Critérios específicos de inclusão e exclusão para o diagnóstico de DTM são essenciais, mas apresentam utilidade limitada. Atualmente, os Critérios Diagnósticos de Pesquisa para Desordem Temporomandibular (RDC/TMD) oferecem a melhor classificação baseada em evidências para os subgrupos mais comuns de DTM. O RDC/TMD inclui não apenas métodos para a classificação diagnóstica física, presentes em seu Eixo I, mas ao mesmo tempo métodos para avaliar a intensidade e a severidade da dor crônica e os níveis de sintomas depressivos e físicos não-específicos, presentes em seu Eixo II. Embora historicamente as más oclusões tenham sido consideradas como fatores de risco para o desenvolvimento das DTM, incluindo as predominantemente articulares, em muitos casos a associação estabelecida entre essas variáveis parece ter tomado direção oposta. No que diz respeito aos desarranjos internos da ATM, os resultados de estudos prévios sobre a redução induzida do ramo mandibular, secundária ao deslocamento anterior do disco articular, indicam que o reposicionamento do disco deslocado em crianças ou adolescentes jovens pode fazer mais sentido do que previamente imaginado. O uso terapêutico de suplementos alimentares, como o sulfato de glicosamina, parece uma alternativa segura ao uso dos medicamentos anti-inflamatórios normalmente utilizados para controlar a dor relacionada à osteoartrite da articulação temporomandibular (ATM), embora a evidência em torno de sua eficácia para a maioria dos pacientes de DTM não tenha sido completamente estabelecida.

Quantification of disc displacement in internal derangement of the temporomandibular joint using magnetic resonance imaging

Many measures have been developed to determine the extent of disc displacement in internal derangements of the temporomandibular joint (TMJ) using magnetic resonance imaging. The purpose of this study was to develop a quantitative method of analyzing disc position and to evaluate the positions of the disc in internal derangements of the TMJ (group 1, with reduction; group 2, without reduction). Magnetic resonance images of 150 TMJs in 20 healthy volunteers and 55 patients with internal derangements were evaluated. The anatomical points of interest of the TMJ, including the anterior (DA) and posterior (DP) points of the disc, were marked on parasagittal magnetic resonance images of the TMJ disc taken in both the closed- and the open-mouth positions. All points were recorded using an x-y coordinate system, with reference to a referral line. In the closed-mouth position, the DP in patients in group 1 was situated in a more-anterior direction than the DP in volunteers. The DP in group 2 was located further anterior and inferior than the DP in group 1. However, the position of the DA did not differ between group 1 and group 2. In the open-mouth position, the DP was displaced anteroinferiorly to a greater extent in group 2 than in group 1 (one-way ANOVA, followed by Scheffe's test; P < 0.0001). The distance between the disc points in the closed- and open-mouth positions was also evaluated. Comparison of the disc point position in the closed- and open-mouth positions in symptomatic and asymptomatic displaced TMJ discs revealed no significant difference. In conclusion, most of our results quantitatively support previously reported findings in imaging, surgical, and histopathological studies of TMJ internal derangement. We suggest that our measure of disc position of the TMJ would be useful to assess the status and response to treatment of internal derangements of the TMJ.

A biomechanical basis for primary arthroplasty of the temporomandibular joint

Biomechanical principles of temporomandibular joint (TMJ) loading are unique, particularly in an orthopedic system that exhibits curvilinear general plane motion. Certain type-specific derangements can be surgically challenging and may primarily require open arthrotomy techniques rather than arthroscopy. This article discusses the basic biomechanical principles in normal and pathologic function. Three-dimensional preoperative imaging of TMJs is necessary for appropriate assessment of all patients and when open techniques are necessary as the initial surgical procedure.

Biomechanical and biochemical characteristics of the mandibular condylar cartilage

The human masticatory system consists of a mandible which is able to move with respect to the skull at its bilateral temporomandibular joint (TMJ) through contractions of the masticatory muscles. Like other synovial joints, the TMJ is loaded mechanically during function. The articular surface of the mandibular condyle is covered with cartilage that is composed mainly of collagen fibers and proteoglycans. This construction results in a viscoelastic response to loading and enables the cartilage to play an important role as a stress absorber during function. To understand its mechanical functions properly, and to assess its limitations, detailed information about the viscoelastic behavior of the mandibular condylar cartilage is required. The purpose of this paper is to review the fundamental concepts of the biomechanical behavior of the mandibular condylar cartilage. This review consists of four parts. Part 1 is a brief introduction of the structure and function of the mandibular condylar cartilage. In Part 2, the biochemical composition of the mandibular condylar cartilage is summarized. Part 3 explores the biomechanical properties of the mandibular condylar cartilage. Finally, Part 4 relates this behavior to the breakdown mechanism of the mandibular condylar cartilage which is associated with the progression of osteoarthritis in the TMJ.

Three-dimensional temporomandibular joint modeling and animation

The three-dimensional (3D) temporomandibular joint (TMJ) model derives from a study of the cranium by 3D virtual reality and mandibular function animation. The starting point of the project is high-fidelity digital acquisition of a human dry skull. The cooperation between the maxillofacial surgeon and the cartoonist enables the reconstruction of the fibroconnective components of the TMJ that are the keystone for comprehension of the anatomic and functional features of the mandible. The skeletal model is customized with the apposition of the temporomandibular ligament, the articular disk, the retrodiskal tissue, and the medial and the lateral ligament of the disk. The simulation of TMJ movement is the result of the integration of up-to-date data on the biomechanical restrictions. The 3D TMJ model is an easy-to-use application that may be run on a personal computer for the study of the TMJ and its biomechanics.