Osteoarthrosis of the temporomandibular joint following experimental disc perforation in Macaca fascicularis

Effects of Glucosamine in the Temporomandibular Joint Osteoarthritis: A Review

Osteoarthritis in the temporomandibular joint (TMJ) is a chronic disease characterized by irreversible damage to articular surfaces, including inflammation, loss of articular cartilage, and subchondral bone alterations, which would be radiographically evident only in later stages. Symptomatic slow-acting so-called nutraceutical drugs have been proposed as a treatment for osteoarthritis in comparison to non-steroidal anti-inflammatory drugs (NSAID) because of their appreciable safety profile even in long-term intake. Glucosamine, being one among them, proved highly efficient in knee osteoarthritis. However, its application in TMJ osteoarthritis dates back only to 2001 and is still inconclusive in its efficiency even with systematic reviews, in restoring the structural and functional aspects of damaged TMJ. Glucosamine, being a natural compound and also a contributor to building the matrix of articular cartilage, can be utilized effectively for TMJ osteoarthritis as an adjunct along with other conventional treatment modalities available till now, which also have moderate prognosis in most of the clinical scenarios. This review summarizes data relating to the mechanism of osteoarthritis and its management using glucosamine formulations. The beneficial effects of glucosamine on the pathophysiology of TMJ osteoarthritis are possibly due to its contribution to hyaluronic acid regulation and in establishing a proper balance between anabolism/catabolism in the articular tissues.

Gender and Age Differences of Temporomandibular Joint Disc Perforation: A Cross-Sectional Study in a Population of Patients With Temporomandibular Disorders

The presence or absence of disc perforation (DP) has great value for the treatment planning of temporomandibular disorders (TMDs). Epidemiologic features of DP are limited in the literature. The present study investigated the epidemiologic features of DP by retrospectively reviewing 13,556 temporomandibular joint arthrographic examinations. Pearson Chi-squared test demonstrated that the rate of male patients who received the examinations more than once was significantly lower than that of female patients and the rate of DP in males was significantly lower than that in females. The age of all patients showed a bimodal distribution, with a 1st peak around 21 years of age, and a 2nd peak around 53 years of age. Linear regression analysis showed that the rate of DP was positively correlated with ages. The DP rate was increased by 0.3% for every 1 year of age. This retrospective cross-sectional study validated some findings about the gender and age differences of temporomandibular joint DP in the literature, and more importantly uncovered the exact relationship between the DP rate and the age in a large TMD patient population.

Tissue engineering toward temporomandibular joint disc regeneration

Treatments for temporomandibular joint (TMJ) disc thinning and perforation, conditions prevalent in TMJ pathologies, are palliative but not reparative. To address this, scaffold-free tissue-engineered implants were created using allogeneic, passaged costal chondrocytes. A combination of compressive and bioactive stimulation regimens produced implants with mechanical properties akin to those of the native disc. Efficacy in repairing disc thinning was examined in minipigs. Compared to empty controls, treatment with tissue-engineered implants restored disc integrity by inducing 4.4 times more complete defect closure, formed 3.4-fold stiffer repair tissue, and promoted 3.2-fold stiffer intralaminar fusion. The osteoarthritis score (indicative of degenerative changes) of the untreated group was 3.0-fold of the implant-treated group. This tissue engineering strategy paves the way for developing tissue-engineered implants as clinical treatments for TMJ disc thinning.

Two-photon fluorescence and second harmonic generation characterization of extracellular matrix remodeling in post-injury murine temporomandibular joint osteoarthritis

End stage temporomandibular joint osteoarthritis (TMJ-OA) is characterized by fibrillations, fissures, clefts, and erosion of the mandibular condylar cartilage. The goal of this study was to define changes in pericellular and interterritorial delineations of the extracellular matrix (ECM) that occur preceding and concurrent with the development of this end stage degeneration in a murine surgical instability model. Two-photon fluorescence (TPF) and second harmonic generation (SHG) microscopy was used to evaluate TMJ-OA mediated changes in the ECM. We illustrate that TPF/SHG microscopy reconstructs the three-dimensional network of key fibrillar and micro-fibrillar collagens altered during the progression of TMJ-OA. This method not only generates spatially distinct pericellular and interterritorial delineations of the ECM but distinguishes early and end stage TMJ-OA by signal organization, orientation, and composition. Early stage TMJ-OA at 4- and 8-weeks post-injury is characterized by two structurally distinct regions containing dense, large fiber collagens and superficial, small fiber collagens rich in types I, III, and VI collagen oriented along the mesiodistal axis of the condyle. At 8-weeks post-injury, type VI collagen is locally diminished on the central and medial condyle, but the type I/III rich superficial layer is still present. Twelve- and 16-weeks post-injury mandibular cartilage is characteristic of end-stage disease, with hypocellularity and fibrillations, fissures, and clefts in the articular layer that propagate along the mediolateral axis of the MCC. We hypothesize that the localized depletion of interterritorial and pericellular type VI collagen may signify an early marker for the transition from early to end stage TMJ-OA, influence the injury response of the tissue, and underlie patterns of degeneration that follow attritional modes of failure.

Removal of the articular fibrous layers with discectomy leads to temporomandibular joint ankylosis

OBJECTIVE

The aim of this study was to investigate whether direct damage of the articular fibrous layers without condylar fracture, combined with discectomy, was enough to induce temporomandibular joint (TMJ) ankylosis.

STUDY DESIGN

Bilateral TMJ surgery was performed in 8 growing sheep. Disk removal (DR) was performed in the lateral two-thirds on the control side, and disk and articular fibrous layers removal (DFLR) was performed in the lateral two-thirds on the experimental side. Four animals were sacrificed for each side at 1 and 3 months postoperatively.

RESULTS

Fibrous ankylosis was achieved on the DFLR side in 2 of 4 sheep and fibro-osseous ankylosis in the other 2 sheep at 1 month after surgery. Fibro-osseous ankylosis developed on the DFLR side in 4 sheep at 3 months postoperatively. On the DR side, pathologic characteristics of TMJ osteoarthritis could be seen; however, no evidence of ankylosis was observed. The scores of TMJ ankylosis for the DR side were significantly lower than those for the DFLR side at different time points (P < .05).

CONCLUSIONS

This study demonstrated that removal of articular fibrous layers combined with discectomy can lead to traumatic TMJ ankylosis.

Experimentally Induced Unilateral Tooth Loss: Histochemical Studies of the Temporomandibular Joint

Occlusal abnormality may contribute to osteoarthrosis of the temporomandibular joint (TMJ). Since mechanical force may induce changes in the extracellular matrix, we tested the hypothesis that unilateral removal of teeth and the resulting unilateral mastication change the content of glycosaminoglycans (GAGs) in the TMJ condyle and disc. Lower-right-side teeth were extracted from 12 adult male rabbits, which were killed 3 or 6 weeks later. Three normal rabbits served as controls. Sections were analyzed for morphological changes and levels of sulfated GAGs in the condyle and disc. Unilateral removal of teeth led to thickening of the condylar cartilage, alterations in the morphology of chondrocyte nuclei in the condylar cartilage and disc, and increases in levels of negatively charged ions in the hypertrophic layer of condylar cartilage. Small differences were observed, after unilateral removal of teeth, between the functional and non-functional sides of the TMJ. The results suggest that in response to mechanical stress, chondrocytes alter sulfated glycosaminoglycan (GAGs) synthesis and degradation rates, resulting in an elevated level of sulfated GAGs in the condylar cartilage.

Effects of injury or removal of the articular disc on maxillomandibular growth in young rats

PURPOSE

This study analyzed the effects of injury and removal of the articular disc on maxillomandibular growth in young rats.

MATERIALS AND METHODS

Thirty 1-month-old male Wistar rats were divided into 3 groups: injury, removal, and sham operated. Unilateral injury of the articular disc, removal of the articular disc, or only surgical access was performed. The animals were sacrificed at 3 months of age. Specimens were submitted to radiographic incidences and cephalometric mensurations were performed using a computer system. Data were subjected to statistical analyses among groups and between sides in each group.

RESULTS

There were degenerative changes of the condylar process in the injury and removal groups. Significant differences between sides were observed for length of the premaxilla, height of the mandibular body, and length of the mandible. Concomitant group comparisons showed significant differences in the height of the mandibular body (P = .003) and the length of the mandible (P = .001). There were important decreases to the height of the mandibular body and mandibular length in the injury group, whereas there was an important decrease only for the length of the mandible in the removal group. Specific measurements of mandibular ramus structures exhibited differences between the injury and sham-operated groups and between the removal and sham-operated groups.

CONCLUSION

Experimental injury and removal of the articular disc during the growth period in rats had deleterious effects on ramus structures and induced asymmetry of the mandible, with worse outcomes resulting from injury to the articular disc.

Temporomandibular joint disc perforation: long-term results after operative arthroscopy

PURPOSE

Disc perforation (DP) is one of the most important pathologic signs of intracapsular temporomandibular joint (TMJ) disease; however, few clinical studies have focused on the arthroscopic management of this feature. The purpose of the present study was to assess whether operative arthroscopy with abrasion of the perforation borders is effective for the treatment of this alteration of the internal derangement of the TMJ.

PATIENTS AND METHODS

Thirty-six patients (39 joints) who underwent TMJ arthroscopy under general anesthesia and presented with DP (Wilkes stages IV and V) from 1994 through 2006 were included in this study. The age range at the time of surgery was 14 to 59 years. DPs were classified into 3 groups according to size: small (SMA), medium (MED), or large (LAR). Pain (visual analog scale, scores 0 to 100), maximal interincisal opening, and lateral and protrusive excursions were assessed at 1, 3, 6, 12, 24 and 48 months after surgery. Preoperative and postoperative scores were compared and tested for statistically significant differences by the Student t test for paired data. The level of statistical significance was set at .05. Differences in the global, SMA, MED, and LAR groups were evaluated.

RESULTS

In the global group, the mean score of preoperative pain according to the visual analog scale was 53.97 mm, which decreased to 14.33 mm at 4-year follow-up. The maximal interincisal opening improved from a mean of 28.56 mm before surgery to 34.88 mm after the final follow-up. SMA perforations were found in 11 cases (28.20%), MED in 19 cases (48.71%), and LAR in 9 cases (23.07%). A significant decrease in pain (P < .01) was observed from the first postoperative month to the end of the follow-up period in the global and SMA groups. A statistically significant increase in mouth opening was observed in the global group from 6 months postoperatively; however, no significant differences were observed in the MED and LAR groups from before surgery to the different times of follow-up. After the final follow-up, 2 patients underwent open TMJ surgery owing to unfavorable results.

CONCLUSIONS

Operative arthroscopy of the TMJ is a reliable and effective procedure for the articular dysfunction associated with DP because this procedure alleviates pain and improves mouth opening. Patients with SMA perforations are better candidates for this surgical treatment.

Synovial fluid dynamics with small disc perforation in temporomandibular joint

The articular disc plays an important role as a stress absorber in joint movement, resulting in stress reduction and redistribution in the temporomandibular joint (TMJ). The flow of synovial fluid in the TMJ may follow a regular pattern during movement of the jaw. We hypothesised that the regular pattern is disrupted when the TMJ disc is perforated. By computed tomography arthrography, we studied the upper TMJ compartment in patients with small disc perforation during jaw opening-closing at positions from 0 to 3 cm. Finite element fluid dynamic modelling was accomplished to analyse the pattern of fluid flow and pressure distribution during the movements. The results showed that the fluid flow in the upper compartment generally formed an anticlockwise circulation but with local vortexes with the jaw opening up to 2 cm. However, when the jaw opening-closing reached 3 cm, an abnormal flow field and the fluid pressure change associated with the perforation may increase the risk of perforation expansion or rupture and is unfavourable for self-repair of the perforated disc.

Usefulness of cone beam computed tomography in temporomandibular joints with soft tissue pathology

OBJECTIVE

the aim of the study was to evaluate the usefulness of cone beam CT (CBCT) in temporomandibular joints (TMJs) with soft tissue pathology.

METHODS

106 TMJs of 55 patients with temporomandibular disorder (TMD) were examined by MRI and CBCT. MR images were used for the evaluation of disc displacement, disc deformity, joint effusion and obscurity of temporal posterior attachment (TPA). CBCT images were evaluated for the presence or absence of osseous abnormalities. The chi(2) test was used to analyse the association between MRI and CBCT findings.

RESULTS

MRI of 106 TMJs revealed disc displacement, disc deformity, joint effusion and obscurity of the TPA in 68, 73, 28 and 27 joints, respectively. Of the 68 TMJs with disc displacement, anterior disc displacement without reduction (ADDWR) was seen most frequently (47/68). CBCT imaging found 65 TMJs were characterized by the presence of osseous abnormalities and were significantly associated with disc deformity and ADDWR (P < 0.05). There was no statistically significant association between the presence of joint effusion and obscurity of TPA and TMJ osseous abnormalities.

CONCLUSIONS

TMD patients with confirmed ADDWR or disc deformity on MRI are at risk of having osseous abnormalities in the TMJ and further examination with CBCT is recommended.

Experimental model of zymosan-induced arthritis in the rat temporomandibular joint: role of nitric oxide and neutrophils

AIMS

To establish a new model of zymosan-induced temporomandibular joint (TMJ) arthritis in the rat and to investigate the role of nitric oxide.

METHODS

Inflammation was induced by an intra-articular injection of zymosan into the left TMJ. Mechanical hypernociception, cell influx, vascular permeability, myeloperoxidase activity, nitrite levels, and histological changes were measured in TMJ lavages or tissues at selected time points. These parameters were also evaluated after treatment with the nitric oxide synthase (NOS) inhibitors L-NAME or 1400 W.

RESULTS

Zymosan-induced TMJ arthritis caused a time-dependent leucocyte migration, plasma extravasation, mechanical hypernociception, and neutrophil accumulation between 4 and 24 h. TMJ immunohistochemical analyses showed increased inducible NOS expression. Treatment with L-NAME or 1400 W inhibited these parameters.

CONCLUSION

Zymosan-induced TMJ arthritis is a reproducible model that may be used to assess both the mechanisms underlying TMJ inflammation and the potential tools for therapies. Nitric oxide may participate in the inflammatory temporomandibular dysfunction mechanisms.

Ultrastructural study of the temporomandibular joint after unilateral meniscectomy in Wistar rats

Meniscectomy of the temporomandibular joint (TMJ) was frequently performed until a few years ago but now is seldom employed. This procedure induces important articular modifications but the complete extent of ultrastructural changes is still unknown. Twenty-one Wistar rats were submitted to unilateral meniscectomy. Animals were randomly divided into three groups and followed for 15, 35 or 60 days. After killing both meniscectomized and contralateral TMJ specimens were sectioned sagittally and prepared for light and scanning electron microscopy studies. Normal TMJs are characterized by glenoid fossa and condylar process with distinct conjunctive layers in which regularly arranged type 1 collagen fibres predominate. Meniscectomized animals initially exhibit a different tissue covering the eroded articular surface of the condyle with the prevalence of type 3 collagen fibres but type 1 fibres predominate in the late postoperative period. Subchondral cysts are clearly visible. A complex remodelling process of the TMJ after meniscectomy is evident with important ultrastructural modifications that may correlate to unsatisfactory clinical results. The dynamic nature of this process is also observed when specimens from different postoperative periods are compared. Surgeons should always bear in mind these alterations when indicating this procedure.

Expression of receptor activator of nuclear factor-κb ligand in synovial tissue: Comparison with degradation of articular cartilage in temporomandibular joint disorders

OBJECTIVE

The present study was performed to investigate the correlations between expression of the receptor activator of nuclear factor-kappaB ligand (RANKL) in synovial tissue and the degrees of synovitis, degeneration of articular cartilage, and adhesions in patients with internal derangement (ID) of the temporomandibular joint (TMJ).

STUDY DESIGN

Expression of RANKL, detected immunohistochemically, and the severity of arthroscopic features (synovitis, degenerative changes of articular eminence, and adhesion) in 30 patients with ID of the TMJ were assessed and the correlations between them were analyzed statistically.

RESULTS

RANKL expression was detected in the cytoplasm of synovial lining cells, endothelial cells, and fibroblast cells. However, there were no correlations between RANKL expression in any cell type and the severity of arthroscopic features.

CONCLUSION

These observations indicated that the cellular source of osteoclastic differentiation exists in TMJ with ID and may provide insight into the mechanism of osteoclast differentiation.

Mechanical work during stress-field translation in the human TMJ

The pathomechanics of degenerative joint disease of the temporomandibular joint (TMJ) may involve fatigue produced by mechanical work on the articulating tissues. This study tested the hypotheses that mechanical work in the TMJ (i) varies with the type of mandibular activity, and (ii) is evenly distributed over TMJ surfaces. Ten healthy human participants were recorded with Magnetic Resonance Imaging (MRI) and jaw tracking. The data were used to reconstruct and animate TMJ activity. Aspect ratios, instantaneous velocities, and distances of stress-fields translation were used to calculate work (mJ). The results were analyzed by least-squares polynomial regression and ANOVA. Work magnitudes were related to peak velocity (R(2) = 0.92) and distance of stress-field translation (R(2) = 0.83), and were distributed over the joint surfaces (p < 0.03). During mandibular laterotrusion, average mechanical work was 1.5 times greater in the contralateral joint. Peak magnitudes of work (> 3000 mJ) were 4 times that previously reported.

Modeling of Temporomandibular Joint Function Using MRI and Jaw-Tracking Technologies – Mechanics

The study of mechanics of the temporomandibular joint (TMJ) is important because its dysfunction and breakdown could be, at least partially, of mechanical origin. The incongruity of the articular surfaces of the TMJ is compensated by a fibrocartilaginous articular disc. Its dislocation and failure seem to be closely related to the development of osteoarthritis of the TMJ. The analysis of mandibular kinematics permits the detection and assessment of irregularities of TMJ function due to internal obstacles such as a displaced articular disc. Furthermore, the measurement of the dynamic relationship between the articular surfaces of the TMJ is useful to determine the strains undergone by the disc that if too high might compromise its integrity. The development of our research in TMJ mechanics has evolved from the acquisition of the traces of single mandibular points to an accurate and compact description of mandibular motion, in which the mechanical advantage of jaw muscles, and forces and torques acting on the jaw are considered as well. The combination of three-dimensional software models of TMJ anatomies obtained from MRI and jaw tracking with six degrees of freedom permits a subject-specific dynamic analysis of the intra-articular space, providing insight into individual disc deformation during function and TMJ loading. Studies performed with this system indicate that both TMJs are loaded during chewing, the balancing more so than the working joint. In fact, during chewing, the intra-articular distance is smaller for hard than for soft food, on closing than on opening, on the balancing than on the working side. This last finding is confirmed by static biting experiments, in which the condyle-fossa distance decreases more on the side contralateral to the bite force, depending on its magnitude. Also studies on the dynamics of compression areas indicate that plowing can occur through the disc during function, especially mediolaterally, due to stress field translation. This effect might contribute to cartilage wear and fatigue also because the disc is weaker mediolaterally. Further data indicate that the lateral area of the disc is mostly exposed to a higher mechanical energy density. This will be more intensively investigated using finite element method.

Osteoclastogenesis inhibitory factor/osteoprotegerin in synovial fluid from patients with temporomandibular disorders

The goal of this study was to measure the activities of osteoclastogenesis inhibitory factor/osteoprotegerin (OCIF/OPG), interleukin-1beta (IL-1beta), and tumour necrosis factor-alpha (TNF-alpha) in synovial fluid from 24 patients with internal derangement and 26 with osteoarthritis of the temporomandibular joint (TMJ). Five asymptomatic healthy volunteers were studied as control. Concentrations of OCIF/OPG, IL-1beta, and TNF-alpha were determined by enzyme-linked immunosorbent assay. The mean OCIF/OPG concentration in the patients with osteoarthritis (71 pg/ml) was significantly lower than those in the patients with internal derangement (160 pg/ml, P< 0.05) and the healthy volunteers (196 pg/ml, P< 0.01). In contrast, the IL-1beta and TNF-alpha concentrations were similar in all three groups. These results suggest that OCIF/OPG is associated with the pathogenesis of osteoarthritis of the TMJ. Perhaps, decreased OCIF/OPG concentrations promote osteoclastic activity and induce osteoarthritis of the TMJ.

Intracapsular fractures of mandibular condyle: diagnosis, treatment, and anatomical and pathological evaluations

The aim of this study was to attempt to establish a correlation between condylar localized fracture, onset of anatomicopathological lesions of the articular structures, and determination of ankylosis so as to define appropriate diagnostic and therapeutic procedures. Clinical, arthroscopic, and histological studies were carried out in two patients with a severe temporomandibular joint disorder after a condylar localized fracture. Treatment included removal of the displaced fragments, condylar surface remodeling, suture of retrodiskal perforations, and diskal repositioning. The histological study of the condylar specimens revealed signs of osteoarthrosis of the articular surface and chondroid metaplasia of the bilaminar zone with early onset of ankylosis. Results of this study confirmed the presence of causal relations between condylar localized fracture and ankylosis with alterations in retrodiskal tissue. These relations are found in 1) tissue damage caused by bony fragments remaining in the articular cavity (underestimated and poorly treated fractures), 2) the lesion that occurs in association with mechanical trauma; and, particularly, c) the disk and retrodiskal impairments caused by catabolic and degenerative osteoarthrotic changes secondary to condylar marrow damage. Thus, timeliness and accuracy of the diagnosis of condylar localized fracture are most important, as are correct diagnosis and treatment before the onset of degenerative anatomicopathological lesions.

Alteration of the horizontal mandibular condyle size associated with temporomandibular joint internal derangement in adult females

OBJECTIVES

The purpose of this retrospective study was to analyse the relationship between horizontal size of the mandibular condyle and internal derangement (ID) of the temporomandibular joint (TMJ).

METHODS

One hundred and thirty-nine joints in 88 women aged over 18 years were included in this study. The horizontal condylar size was measured in the antero-posterior and medio-lateral (ML) dimensions using axial magnetic resonance (MR) images. Radiological findings of ID were also assessed from MR imaging.

RESULTS

The condyles in the joints with permanent disk displacement were smaller than those in joints without displacement in both dimensions (Fisher's protected least significant difference, P<0.05). There were statistically significant correlations between horizontal condylar size in the ML dimension and both disk morphology and radiological stage of ID (Spearman's correlation coefficient by rank, P<0.05).

CONCLUSIONS

The results of this study suggest a possible relationship between horizontal condylar size and disk displacement. It is also suggested that the condyle becomes smaller in the ML dimension with advancement of ID.

Changes of the collagen fibre arrangement of the rabbit temporomandibular joint following discectomy

PURPOSE

The purpose of the present study is to examine changes in arrangement of collagen fibres of the temporomandibular joint (TMJ) following discectomy.

MATERIAL AND METHODS

Twelve male Japanese white rabbits were used. The right TMJs of six rabbits were surgically exposed, and the disc removed with a scalpel. Three untreated and three sham-operated rabbits were used as controls. The TMJs were removed in three rabbits 1 month and in three other rabbits, 3 months after discectomy and processed for demonstration of collagen fibres.

RESULTS

One month after discectomy, collagen fibres in the fibrous layers of condyle and articular eminence were of various sizes and were running in various directions. Collagen fibres in the cartilaginous layers were sparser in the study TMJs than in the control TMJs. Three months after discectomy, the direction of collagen fibres in the fibrous layers of the condyle and articular eminence became organized and were similar to that in the control TMJs. However, collagen fibres in the cartilaginous layers of the condyle remained sparser 3 months after discectomy than in the control TMJs.

CONCLUSION

Experimental discectomy in the rabbit alters the distribution and density of collagen fibres in the TMJ. Thorough postoperative follow-up seems to be necessary after discectomy.

Age changes in the cells of the intra-articular disc of the temporomandibular joints of rats and marmosets

Cells in the intra-articular disc of the temporomandibular joint were studied ultrastructurally at three different ages to investigate any age changes. Rats aged 2, 15.5 months, and 2.5 years, and marmosets aged 21 months, 7 years, and between 10.5 and 14 years were studied. In the first two age groups of the rat and the first of the marmoset, the cells were generally rounded and had moderate amounts of rough endoplasmic reticulum and other organelles associated with protein synthesis and secretion. Many cells had conspicuous amounts of microfilamentous material and cell membranes were closely applied to the collagen fibrils of the extracellular matrix. Occasionally, a narrow, irregular space containing microfilamentous material lay adjacent to the cell membrane. In the 2.5-year-old rats and the two older age groups of marmosets, cells with chondrocyte-like morphology were present. These cells were surrounded by a conspicuous pericellular matrix devoid of collagen fibrils and composed of microfilamentous material embedded in an amorphous ground substance. They resembled cells described in fibrocartilage from other sites, but differed from chondrocytes in hyaline cartilage by lacking a pericellular capsule. Thus, rats and marmosets both show cellular age changes in the intra-articular disc of the mandibular joint, which can be considered as changing from fibrous to fibrocartilaginous with age, a condition similar to that reported in humans.

The role of the disk in sheep temporomandibular joint ankylosis

OBJECTIVE

The purpose of this study was to determine the role of the disk in intraarticular ankylosis of the temporomandibular joint.

STUDY DESIGN

Twelve adult sheep were divided into 2 groups. In group 1, removal of the temporal and condylar articular surfaces was performed on the right temporomandibular joint and the disk was maintained; in group 2, removal of the articular surfaces and diskectomy were performed on the right temporomandibular joint. One sheep from each group was killed just after surgery and 5 sheep from each group were killed at 3 months. The joints were examined radiologically, macroscopically, and histologically. The range of jaw movements was recorded preoperatively and at sacrifice.

RESULTS

Each of 2 sheep in group 2 had lost 4% of their body weight by 3 months; all of the other sheep maintained or increased their weight. The range of jaw motion to the right was significantly lower in group 2 than in group 1 (P<.01). In group 1, fibrous repair of the articular surface and regeneration of the condylar head was seen. In group 2, each of the joints showed a total fibrous ankylosis with some calcification. There was a statistically significant difference in radiologic score between the groups (P<.0001). Histologic scores for group 1 demonstrated significantly lower scores on the degree of ankylosis scale and degree of calcification scale (P<.0001).

CONCLUSIONS

This study showed that the presence of the disk prevented the development of fibrous intraarticular ankylosis of the temporomandibular joint.

Discectomy of the temporomandibular joint: an experimental study in monkeys

Postoperative changes have been observed in the temporomandibular joint (TMJ) after discectomies. Animal models have often shown that interventions in the TMJ may heal uneventfully. Discectomies were performed on 14 Macaca fascicularis and macroscopic and microscopic examination performed after sacrifice of the animals. Two of the animals did not show any apparent macroscopic or microscopic changes. The remaining 12 joints showed minor to major changes. The most serious changes were seen in three joints with fibrous ankylosis and five joints showed marked destruction of the articular cartilage.

Immunolocalization of gelatinase-A (matrix metalloproteinase-2) in damaged human temporomandibular joint discs

The fibrous tissue of the articular disc of the dysfunctional temporomandibular joint undergoes deep and variable structural modifications. Here the concurrence of morphological changes and the expression of matrix metalloproteinase-2 (MMP-2) in damaged discs from individuals suffering joint dysfunction was investigated. Microscopic, ultrastructural and immunocytochemical investigations were made on variously damaged articular discs and on one control sample. Disaggregation of collagen fibres, an increase in cellular components and calcification of large areas of tissue were observed in the damaged discs. These modifications were accompanied by a positive immunoreaction pattern for MMP-2. Fibroblast-, chondroblast- and osteoblast-like cells displayed a positive cytoplasmic reaction. In samples displaying evidence of synovial hyperplasia, some cells of the synovial protrusions were MMP-2 immunoreactive. No MMP-2 staining was observed in the control sample. These findings demonstrate that structural modifications of the articular disc could be specific responses to changes in the function of the temporomandibular joint. Variations in extrinsic stimuli may activate intrinsic factors, such as MMPs, that induce structural modifications in the discal tissue.

Macroscopic osseous changes in the temporomandibular joint related to dental attrition in Japanese macaque skull

The purpose of this study was to investigate the relationship between osseous changes in the temporomandibular joint (TMJ) and dental attrition in the Japanese macaque. One hundred and thirty Japanese macaque skulls (54 male and 76 female) from animals which had been bred in the same environment, were randomly sampled from a collection at the Primate Research Institute of Kyoto University. The age at death had been recorded in all cases. TMJ osseous changes were independently evaluated by three examiners, and were defined as an irregular surface or a perforated compact bone layer with a markedly irregular surface on either the temporal or condylar components. Age was a significant factor in predicting TMJ osseous changes (P < 0.001). A strong relation was observed between age and dental attrition (P < 0.001), while dental attrition was not a significant factor in predicting TMJ osseous changes (P = 0.334). The prevalence TMJ osseous changes in male animals was slightly higher than in females (P = 0.057). The results of this study suggest that osseous changes in the macaque TMJ are mainly related to age, not to dental attrition.

Morphologic changes in the elastic fibers of the temporomandibular joint after experimental disc perforation in the rabbit

PURPOSE

Elastic fibers in the attachment regions of the temporomandibular joint (TMJ) are considered important in the movements of the disc during jaw motion. This study was designed to determine whether there are change in the elastic fibers of the TMJ when the disc is perforated for a long period.

MATERIALS AND METHODS

Each TMJ of five rabbits was surgically exposed, and a mediolateral perforation was made in the center of the articulating region of the disc with a scalpel. Five untreated and three sham-operated rabbits were used as controls. The TMJs were removed after 10 months and processed for histochemical demonstration of elastic fibers.

RESULTS

Osteoarthritic changes and a significant decrease in number of the elastic fibers in the anterior-inferior attachment and posterior-inferior attachment of the TMJ disc were observed after disc perforation. Conversely, elastic fibers appeared in the fibrous tissue on the resorbed bone of the articular eminence.

CONCLUSIONS

Experimental disc perforation changes the distribution and density of the elastic fiber in the TMJ as well as causes osteoarthritis. A knowledge of these facts may improve our understanding of perforation of the disc.

Effect of postoperative diet on condylar cartilage response to discectomy

PURPOSE

Recent studies have shown that metabolic and structural changes occur in the condylar cartilage after surgical removal of the articular disc. There is some evidence that these structural changes are less pronounced in animals provisioned with a soft diet after disc removal. This study was initiated to assess whether a soft diet after discectomy in growing rats also results in alterations in the composition or metabolic activity of the matrix of the condylar cartilage.

MATERIALS AND METHODS

In two identical experiments, 28 thirty-day-old female Sprague-Dawley rats underwent unilateral surgical removal of the articular disc (discectomy) and were then provisioned with either a soft, mushy diet or a diet of normal rat pellets. When they were killed 3 weeks later, the condylar cartilages were removed, weighed, pulse-labeled in organ culture with [35S]-sulfate for 2 hours, and analyzed for sulfated glycosaminoglycan (GAG) content and [35S]-sulfate uptake.

RESULTS

As in previous studies, tissue weights and hydration were increased, and sulfated GAG content and [35S]-sulfate uptake decreased on the surgery side in animals fed a hard diet. Overall, fewer differences were present in the animals fed a soft diet, although tissue weights and hydration were still elevated on the discectomized side. Analysis of ratios of surgery/nonsurgery values in the hard diet versus the soft diet sample indicated that dietary consistency was a significant factor for tissue weights and [35S]-sulfate uptake, but not for hydration or sulfated GAG content.

CONCLUSIONS

These data suggest that discectomy exerts a more pronounced effect on growing animals fed a hard diet, although some changes also persist after discectomy in animals fed a soft diet.

Presence of calcified tissue in the human temporomandibular joint disc

Large calcified areas were observed in the articular discs of the temporomandibular joint from five patients suffering from articular dysfunctions. The calcified regions were always located inside the fibrous tissue of the discs. They had a woven bone-like morphological pattern and consisted of a compact mineralized tissue containing cells in irregular lacunae. In all the samples the calcified tissue was completely surrounded by a mineralizing border rich in cells and variously arranged collagen fibrils. Energy-dispersive spectrometry showed that mineralized regions contained large amounts of Ca and P. X-ray powder diffraction identified the crystals in these areas as hydroxyapatite.

Synovia hyperplasia and calcification in the human TMJ disk: a clinical, surgical, and histologic study

The aim of the study was to investigate the morphologic modifications occurring in the synovial tissue after severe derangement of the articular structures with dislocation or perforation of the disks. Light microscopic, ultrastructural, and immunocytochemical investigations were performed on 10 disks. Arthroscopic examinations had documented adhesions between the diskal surfaces and the glenoid eminence or the condylar head in all the selected cases. Histologic examination showed a remarkable hyperplasia of the synovial tissue with the formation of prominent protrusions. An evident increase of type B (fibroblast-like) cells and the presence of cells with the ultrastructural and immunocytochemical characteristics of myofibroblasts were observed. Foci of mineral precipitates and large deposits of calcified tissue were present in the synovial villi in three samples. Our observations suggest that functional failure and morphologic lesions of the synovia may be caused by arthropathy.

The articular disc surface in different functional conditions of the human temporo-mandibular joint

The peripheral discal tissue and the surface covering layer have been studied in normal and in variously damaged human temporo-mandibular joint discs. In the normal disc the tissue consisted of dense bundles of fibers and rare fibrocytes. The surface of the disc was covered by a regular basophilic and electron-dense layer. These morphological characteristics persisted also in some pathological discs in which fibrous derangements had already occurred in the deep parts. In very deformed and damaged discs associated with serious functional anomalies, the superficial discal tissue consisted of rare fibers dispersed in a loose ground substance and of an increased number of cells. The superficial coating was formed by an irregular dense lamina and aggregates of various materials containing cellular debris, vesicles, filaments and amorphous components. These deposits are probably due to degeneration processes of discal tissue. This investigation suggests that the superficial discal tissue and the covering layer are together involved in maintaining the functional properties of the articular surfaces. Their structural modification in severe functional anomalies leads to failure in the maintenance of nonadherence conditions and to deterioration of the functional defect.

Four-year follow-up study of temporomandibular joint arthroscopic surgery for advanced stage internal derangements

PURPOSE

This study evaluated the long-term outcome after temporomandibular joint (TMJ) arthroscopic surgery for patients with internal derangement with stage V disease.

MATERIALS AND METHODS

Fifteen female patients (24 TMJs) who underwent arthroscopic surgery were evaluated by a questionnaire preoperatively and postoperatively 3 to 5 years later (mean: 4 years, 2 months). The questionnaires consisted of a visual analog scale, pain and jaw dysfunction scores, and self-measured interincisal opening. Clinical examination and conventional radiographic evaluation were done in nine patients (13 joints). Postoperative magnetic resonance imaging was done in two patients (3 joints).

RESULTS

All post-treatment scores showed a statistically significant improvement, although joint noise remained in some patients. The radiographic examination revealed mild to moderate degenerative changes, but no abnormal resorption was detected. The surgical success rate was 93.3%.

CONCLUSION

Arthroscopic surgery is a useful, minimal invasive, surgical procedure for advanced stage internal derangement of the TMJ.

Reconstruction of the temporomandibular joint using a temporalis graft with or without simultaneous orthognathic surgery

PURPOSE

This article reports the outcome of free temporalis fascia and muscle graft (TFG) reconstruction of the temporomandibular joint (TMJ) with and without simultaneous orthognathic surgery (SOS).

MATERIALS AND METHODS

Twenty-nine patients (45 joints) were evaluated retrospectively. Group 1 consisted of 17 patients (16 women 1 man) and 30 joints. Fifteen (88%) patients had sagittal split ramus osteotomies (SSRO); 8 (53%) of these patients also had Le Fort I osteotomies, and 2 patients (12%) had only Le Fort I osteotomies with TFG. Group 2 consisted of 12 patients (15 joints) who received only TFG and no SOS.

RESULTS

Group 1 had 9 patients (53%) with an incisal opening greater than 35 mm, 11 joints (37%) with greater than 6 mm lateral excursive movement, and 11 patients (65%) were asymptomatic postoperatively. Average follow-up was 57.4 months (range, 23 to 69 months). Group 2 had eight patients (67%) with an incisal opening greater than 35 mm, six joints (40%) with greater than 6 mm lateral excursive movement, and seven patients (58%) were asymptomatic postoperatively. Average follow-up was 55.1 months (range, 48 to 64 months).

CONCLUSION

TFG with and without SOS produced similar treatment outcomes in comparing groups 1 and 2. No significant differences were observed for the number of patients with an incisal opening > 35 mm (P = .703), lateral excursion > 6 mm (P = 1.00), and successful elimination of pain (P = 1.00), even though group 2 had a significantly greater number of patients (P < 0.01) that were operated on unilaterally. Combining treatment outcomes for both groups, the number of previous joint surgeries significantly affected success (P < .01). The presence of osteoarthritic changes did-not significantly affect treatment outcome (P = .187).

A microscopic and immunocytochemical study of structural changes in dysfunctional human temporomandibular joint discs

The central part of 12 articular discs from patients with serious alterations in function of the temporomandibular joint were investigated. The control discs were removed at autopsy from individuals who did not have any such functional defects. The anomalous discs had an increased cellular component; fibrocytes, fibroblasts, numerous myofibroblasts and, less frequently, smooth muscle cells and mast cells were present. The myofibroblasts, which had numerous bundles of thin filaments in the cytoplasm, were positive to the immunocytochemical reaction with antibody to alpha-smooth muscle actin. In one disc only a large part had changed into a mostly fatty tissue. In the majority of the altered discs, the part examined, which usually is neither vascularized nor innervated, was characterized by the presence of numerous blood vessels. Besides the capillary network several larger vessels were present. In one disc, several myelinated and unmyelinated fibres, isolated or in nerve bundles, were also seen. These observations show that the disc fibrous tissue may undergo deep structural modifications that appear to indicate not only a capacity for repair but also an ability to adapt to new functional conditions.

Repair of temporomandibular joint disc perforation using a synovial membrane flap in Macaca fascicularis monkeys: light and electron microscopy studies

Previous studies have demonstrated that experimentally produced perforations in the discs of Macaca fascicularis monkeys lead to osteoarthrosis. Synovial membrane hyperplasia also was demonstrated in monkey and human joints with disc perforations. The hypothesis was advanced that a synovial flap obtained from within the affected joint would be the most appropriate tissue to repair chronic disc perforation. To test this hypothesis, four adult M fascicularis monkeys were anesthetized and 4- to 6-mm perforations were made in the posterolateral aspects of the avascular discs bilaterally. The wounds were sutured leaving the perforations open, and the animals were fed their normal diet. After 4 weeks, one joint in each monkey was reopened and a repair was performed using a double-layered flap from the synovial lining of the superior and inferior recesses. Four weeks after repair, the animals were killed and the temporomandibular joints (TMJs) were removed en bloc and decalcified. The joints were sectioned into lateral, middle, and medial sections and were photographed using a stereomicroscope and then processed for light and electron microscopy. The same processing was done to four intact joints that were used as controls. Eight weeks following perforation, the joint components showed degenerative changes consistent with osteoarthritis. Close to the perforations the disc showed loss of collagen, vacuolation of extracellular matrix, accumulation of dense proteoglycan-like material, and the appearance within the disc of type A or macrophage-like cells of the synovium. The discal tissue away from the perforation showed high cellularity and vascularity. The temporal and condylar surfaces showed denudation, fibrillation, osteophytes, and chondrocytic clustering, all characteristics of osteoarthrosis. The surgically repaired discs were intact and the articular surfaces showed no degenerative changes. Discal collagen was restored and appearance of myofibroblasts and elastogenesis were a consistent feature of the repaired disc. The vascularity of the condylar cartilage of the repaired joints appeared similar to that of embryonic cartilage. The reversibility of the degenerative alterations following discal repair in this experimental model should provide the basis for a rational and useful method for surgical repair of TMJ disc perforation using intraarticular synovial tissue.

Chondrocyte clusters in the condylar cartilage of an ankylosed temporomandibular joint

A complete condyle specimen from a female patient who had temporomandibular joint (TMJ) ankylosis and associated craniofacial deformities was obtained. Abundant chondrocyte clusters were found in the remaining cartilage of the enlarged condyle. The implications of the clusters in this patient are discussed.

Experimental temporomandibular joint disc perforation in the rabbit: a gross morphologic, biochemical, and ultrastructural analysis

This study evaluates the progression of osteoarthritis (OA) in the adult New Zealand white rabbit temporomandibular joint following unilateral disc perforation. Thirty-seven animals were divided into five groups: control (n = 8), 6-week sham (n = 5), and experimental 6-, 12-, and 24-weeks (n = 8 each). Quantitative data was examined with two-way analysis of variance, and followed by Scheffe pair-wise comparisons. Transmission electron microscopy, acid phosphatase [AcP] activity, uronic acid content, and gross morphologic analysis indicated that disc perforation induced remodeling activity and degenerative changes in the condylar cartilage and bone as early as 6 weeks postoperatively. AcP activity of homogenized cartilage samples was significantly increased in experimental joints versus the side that did not undergo surgery at 6 and 12 weeks (P < .05). Uronic acid content was significantly greater in experimental joints versus the side that did not undergo surgery at 6 weeks (P < .05). Heightened cellular activity was present in the deep zone of osteoarthritic fibrocartilage of the 6- and 12-week experimental groups. Degenerating chondrocytes appeared to contain greater proportions of intracytoplasmic filaments and lysosome-like bodies. Disc perforation provided the impetus for degenerative or remodeling changes in the condylar cartilage of experimental joints, and is consistent with secondary OA. These dynamic events were most significant in the deep zone of articular fibrocartilage.

A comparison of electromyographic activity between anterior repositioning splint therapy and a centric relation splint

The purpose of this study was to compare the electromyographic activity of masticatory muscles (temporal and masseter) with the use of an anterior repositioning splint and a centric relation superior repositioning splint. Twenty-six consecutive patients, who referred with the chief complaint of temporomandibular pain and/or headache were selected from one of the author's practices. All these subjects were diagnosed as having internal derangement of the temporomandibular joint. Ten normal subjects were used as controls. Surface electromyographic recordings were taken of each subject prior to the beginning of clinical therapy for the patients. The results show significantly less masseter and temporal muscle activity with anterior repositioning splint therapy compared to the centric relation superior repositioning splint therapy.

Treatment outcomes for temporomandibular joint reconstruction after Proplast-Teflon implant failure

A retrospective study of 107 patients (male, n = 13; female, n = 94) with 163 joints previously treated with Proplast-Teflon (PT; Vitek, Inc, Houston, TX) implants was performed. The average time in situ for the PT was 59.8 months (range, 2 to 126 months). Average length of follow-up was 84.6 months (range, 59 to 126 months). Only 12% of joints showed no significant osseous changes radiographically. Forty-five patients (42%) continue to have in situ PT implants and 36% of them experience pain that requires medication; 25% have developed an anterior open bite and malocclusion; 9% have limited vertical opening; and 40% are asymptomatic. Temporomandibular joint (TMJ) reconstruction after PT implant failure was performed with five different autologous tissues or a total joint prosthesis. Autologous tissues used to reconstruct the TMJ and the rates of success were as follows: 1) 31% free temporalis fascia and muscle graft with and 13% without sagittal split ramus osteotomy, 2) 8% dermis, 3) 25% conchal cartilage, 4) 12% costochondral grafts, and 5) 21% sternoclavicular grafts. The success rate decreased in all autologous tissue groups as the number of TMJ surgeries performed before reconstruction increased. Ankylosis was the most common cause of failure. Results of TMJ reconstruction with a total joint prosthesis were as follows: 1) 88% functional and occlusal stability of total joint prosthesis; 2) level of pain reduction was rated as 46% good, 38% fair, and 16% poor; and 3) an average interincisal opening of 27 mm at 24 months or less, and 33 mm at 25 months and beyond.(ABSTRACT TRUNCATED AT 250 WORDS)

An experimental model of osteoarthrosis in the temporomandibular joint of the rabbit

Degenerative changes in the temporomandibular joint were induced in 24 rabbits by surgical perforation of the disk. The incongruence obtained between the joint surfaces caused a gradual increase in macroscopic and microscopic changes, including gross remodeling, loss of tissue volume, and altered cell morphology within a 16-week observation period. These changes occurred concurrently with major alterations in the composition of the matrix, as demonstrated by increase in the glycosaminoglycan content of both condylar cartilage and disk and by loss of hydroxyproline in the disk. The lesions in the disk tissue were clearly discernible, whereas those in the condylar cartilage were less extensive. The described method is concluded to give alterations in the temporomandibular tissues, as seen in degenerative joint disease of an early stage.

Facial skeleton remodeling due to temporomandibular joint degeneration: an imaging study of 100 patients

One hundred patients with recently acquired, externally visible mandibular deformity and no history of previous extraarticular mandible fracture were selected for retrospective analysis. All had been investigated clinically and with radiography, tomography, and high-field surface-coil MR imaging to determine the presence or absence and extent of temporomandibular joint degeneration. Temporomandibular joint degeneration was found in either one or both joints of each patient studied. Chin deviation was always toward the smaller mandibular condyle or more diseased joint, and many patients either complained of or exhibited malocclusion, often manifested by unstable or fluctuating occlusion disturbances. Three radiologically distinct forms of degenerative vs adaptive osteocartilaginous processes--(1) osteoarthritis, (2) avascular necrosis, and (3) regressive remodeling--involving the mandibular condyle and temporal bone were identified in joints most often exhibiting meniscus derangement. Osteoarthritis and avascular necrosis of the mandibular condyle and temporal bone were generally associated with pain, mechanical joint symptoms, and occlusion disturbances. Regressive remodeling was less frequently associated with occlusion disturbances, despite remodeling of the facial skeleton, and appears to result from regional osteoporosis. Forty patients (52 joints) underwent open arthroplasty procedures, including either meniscectomy or microsurgical meniscus repair, at which time major radiologic diagnoses were confirmed. Surgical and pathologic findings included meniscus displacement, disk degeneration, synovitis, joint effusion, articular cartilage erosion, cartilage healing/fibrosis, cartilage hypertrophy, osseous sclerosis, osteophyte formation, osteochondritis dissecans, localized or extensive avascular necrosis, and decreased mandibular condyle mass and vertical dimension. We conclude that temporomandibular joint degeneration is the principal cause of both acquired facial skeleton remodeling and unstable occlusion in patients with intact dentition and without previous mandible fracture.