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At least 19 recordsLinked to original sources
PubMed2005

A surface-regional and freeze-thaw characterization of the porcine temporomandibular joint disc.

The temporomandibular joint (TMJ) disc is a central element in several TMJ disorders. Tissue-engineered TMJ disc replacements may alleviate discomfort associated with TMJ disorders; however, prior to developing a replacement, a thorough understanding of the native disc must be attained. Toward this end, we developed an unconfined compression, incremental stress relaxation viscoelastic model which simultaneously incorporates the strain increment magnitude and total deformation in the stress relaxation solution. This multiple strain step model was fit to stress relaxation data from (i) 80 test sites from eight porcine TMJ discs for the purposes of a surface-regional characterization and (ii) 30 test sites from five porcine TMJ discs for the purposes of a freeze-thaw characterization. The model estimated viscoelastic parameters accurately and surface-regional variations were detected throughout the TMJ disc. Regionally, the medial and anterior regions have the largest relaxation moduli, and the posterior and anterior regions have the largest instantaneous moduli. The inferior surface was found to have higher instantaneous modulus values than the superior surface. Furthermore, material properties were retained over five freeze-thaw cycles. The results of this study allow for the creation of design and validation criteria for future engineering efforts and shed light on the disc's role in TMJ function and dysfunction.

Animals↗
PubMed2003

Biomechanical behavior of the temporomandibular joint disc.

The temporomandibular joint (TMJ) disc consists mainly of collagen fibers and proteoglycans constrained in the interstices of the collagen fiber mesh. This construction results in a viscoelastic response of the disc to loading and enables the disc to play an important role as a stress absorber during function. The viscoelastic properties depend on the direction (tension, compression, and shear) and the type of the applied loading (static and dynamic). The compressive elastic modulus of the disc is smaller than its tensile one because the elasticity of the disc is more dependent on the collagen fibers than on the proteoglycans. When dynamic loading occurs, the disc is likely to behave less stiffly than under static loading because of the difference of fluid flow through and out of the disc during loading. In addition, the mechanical properties change as a result of various intrinsic and extrinsic factors in life such as aging, trauma, and pathology. Information about the viscoelastic behavior of the disc is required for its function to be understood and, for instance, for a suitable TMJ replacement device to be constructed. In this review, the biomechanical behavior of the disc in response to different loading conditions is discussed.

Adaptation, Physiological↗
PubMed2006

Effects of ascorbic acid concentration on the tissue engineering of the temporomandibular joint disc.

The temporomandibular joint (TMJ) disc is a specialized fibrocartilaginous tissue. When the disc becomes an obstacle and becomes damaged, surgeons have no choice but to perform a discectomy. Tissue engineering may provide a novel treatment modality for TMJ disorder patients who undergo discectomy. No studies have been conducted on the most favourable media for TMJ disc cells. The objective of the current study was to examine the effects on biochemical and biomechanical properties of varying ascorbic acid concentrations (0, 25, or 50 microg/ml) on TMJ disc cells seeded on non-woven PGA scaffolds. The ascorbic acid concentration of the 25 microg/ml group resulted in more effective cell seeding of the scaffolds, with 1.53 million cells per construct, by comparison with the 0 and 50 microg/ml groups which had 1.20 million and 1.32 million cells per scaffold respectively. At week 4, the 25 microg/ml group had a higher collagen content than the 0 microg/ml group, with 30.4 +/- 2.7 and 24.9 +/- 3.3 microg of collagen per construct respectively. The 25 microg/ml group had a higher aggregate modulus than the 50 microg/ml group, with values of 6.1 +/- 1.3 and 4.0 +/- 0.9 kPa respectively at week 4. The results of this study indicate that the use of 25 microg/ml of ascorbic acid in culture media is effective for the tissue engineering of the TMJ disc, significantly outperforming media without or with 50 microg/ml of ascorbic acid.

Animals↗
PubMed1997

Clinical and magnetic resonance imaging findings in temporomandibular joint disc displacement.

OBJECTIVES: To describe the clinical and MRI findings in patients with disc displacement of the temporomandibular joint. METHODS: Eighty-eight joints in 51 patients referred for suspected TMJ disc displacement were examined by MRI. Two oral radiologists assessed the images. The clinical findings were obtained by retrospective review of the patients' records. RESULTS: Clicking was the most common clinical finding, present in 47 joints. Pain was reported for only 30 joints. Anterior disc displacement with reduction was found in 39 joints, anterior disc displacement without reduction in 31 joints, compound dislocations (anterolateral or anteromedial) in 13 joints and sideways displacement in 5 joints respectively. In about one-fourth of the joints, MRI revealed abnormal configuration of both disc and condyle. The osseous changes were subtle. Only 9% of the joints exhibited an osteophyte. Joint effusion in either the upper or the lower joint compartment was found in 19 joints. Out of 14 patients with joint effusion, six patients complained of pain from the TMJ region. CONCLUSION: The most extensive soft and hard tissue changes were found in patients with anterior disc displacement without reduction. Pain was not a characteristic symptom for any type of disc displacement.

Adolescent↗
PubMed2001

A model for temporomandibular joint disc repositioning surgery.

PURPOSE: The present study establishes a model of reversible anterior disc displacement using the rabbit craniomandibular joint (CMJ) and examines the period required for successful disc repositioning surgery. MATERIALS AND METHODS: The left CMJ was exposed surgically in 27 animals and a suture positioned at the posterolateral portion of the disc was pulled in an anterior direction causing 7 mm of anterior disc displacement. The suture was then fixed to the zygomatic arch. The changes in the CMJ were observed microscopically in 3 rabbits each at 2, 3, 5, 8, and 24 weeks. Another 12 rabbits underwent secondary disc repositioning surgery either the second and third week after disc displacement, and then 3 rabbits from each group were assessed microscopically at 5 to 6 weeks and 21 to 22 weeks after the first operation. Ten rabbits had a sham operation, and 2 served as unoperated controls. Histomorphometric evaluation included changes in morphology, cartilage, and disc condition. RESULTS: Progressive osteoarthritic change was induced by disc displacement. Articular disc perforation at 5 weeks after the first operation was accompanied by subchondral bone exposure. The CMJ morphology was almost normal in rabbits that underwent secondary disc repositioning 2 weeks after disc displacement. However, osteoarthritic changes and perforated discs similar to those in rabbits that did not undergo secondary disc repositioning were seen in animals in which repositioning was done in the third week. CONCLUSION: Artificial disc displacement in the rabbit causes osteoarthritic changes are reversible when the displaced disc is restored within after 2 weeks but not at 3 weeks.

Animals↗
PubMed1999

Efficacy of a mandibular manipulation technique in reducing the permanently displaced temporomandibular joint disc.

PURPOSE: The purpose of this study was to determine whether disc reduction occurred in patients with closed lock after mandibular manipulation (MM) and to analyze the factors that influenced the result. PATIENTS AND METHODS: Two hundred fifteen patients with closed lock received MM. Of these, 74 patients (79 joints) were assessed by means of magnetic resonance imaging (MRI) for disc reduction. The results of the MRI were compared with the findings from the clinical and radiographic examinations. RESULTS: According to the MRI assessment, only 18% (14 of 79) of the joints had successful disc reduction. The unsuccessfully treated joints had severe joint pain, disc displacement, condylar bone change, and disc deformity. CONCLUSIONS: The results of this study suggest that successful reduction of the disc by MM is rare. They also suggest that MM is least effective in the advanced stages of internal derangement, when the disc becomes deformed.

Adult↗
PubMed1998

Natural course of untreated symptomatic temporomandibular joint disc displacement without reduction.

In some patients with disc displacement without reduction, the symptoms of pain and decreased range of motion have been observed to resolve spontaneously over time without treatment. The natural history of this condition, however, is not well-understood. Thus, to study the natural course of disc displacement without reduction, we followed 40 patients without treatment for a period of 2.5 years. The diagnosis was established by history and physical examination and confirmed with magnetic resonance (MR) imaging. After 2.5 years, 43% of the patients were asymptomatic, 33% had decreased symptoms, and 25% of the patients showed no improvement or had required treatment. MR evidence of osteoarthritis and advanced stages of internal derangement at the initial evaluation was associated with a poor prognosis. The result of this prospective cohort study indicated that approximately 40% of patients with symptomatic disc displacement without reduction will be free of symptoms within 2.5 years, one-third will improve, whereas one-quarter will continue to be symptomatic. This knowledge should be valuable for the treatment planning and evaluation of prognosis of patients with non-reducing symptomatic disc displacement.

Adolescent↗
PubMed1999

Differential activation by cytokines of mitogen-activated protein kinases in bovine temporomandibular-joint disc cells.

Temporomandibular disorders affect a significant proportion of the population. While their aetiology is not well defined, recent histological studies suggest that the majority are similar to the osteoarthritis seen in other joints. Inflammatory cytokines such as interleukin-1 and tumour necrosis factor-alpha appear to be important in the cascade of events leading to joint destruction in osteoarthritis. Here, cells from the disc of bovine temporomandibular joint were used to examine the response to various cytokines in vitro. Disc cells were stimulated with interleukin-1alpha, tumour necrosis factor-alpha, transforming growth factor-beta, platelet-derived growth factor, and basic fibroblast growth factor. Their effects were monitored by assessing the phosphorylation of selected signal-transduction intermediates using western blot. Mitogen-activated protein kinases (Erk 1, Erk 2) were rapidly phosphorylated by exposure to basic fibroblast growth factor, platelet-derived growth factor, and tumour necrosis factor-alpha, while interleukin-1alpha showed a weak response. Transforming growth factor-beta failed to activate these kinases. Examination of the effect of these cytokines on p38 (an intermediate in the stress-activated protein-kinase pathway) showed an increase in phosphorylated p38 when stimulated with tumour necrosis factor-alpha and interleukin-1alpha. The amounts of phosphorylated signal transducer and activator of transcription-3 did not significantly increase when the cells were exposed to any of the cytokines.

Animals↗
PubMed1999

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.

Adult↗
PubMed2001

Magnetic resonance imaging evaluation of temporomandibular joint disc deformities in relation to type of disc displacement.

PURPOSE: This study was undertaken to assess the relationship between the temporomandibular joint (TMJ) disc deformity and the type of internal derangement. PATIENTS AND METHODS: One hundred thirty-three TMJs of 72 patients (53 female and 19 male) with intracapsular dysfunction were studied using clinical and magnetic resonance imaging examinations. RESULTS: Of the 133 TMJ discs, 41.35% had no deformity, whereas 18% of the discs were folded, 19.55% were lengthened, 9.77% were round, 7.51% were biconvex, and 3.75% had thick posterior bands. The frequency of disc deformity was greater with anterior disc displacement without reduction than in cases of anterior disc displacement with reduction (P <.001). Folded and round discs were most common in cases with TMJ anterior disc displacement without reduction (P <.0001). An increase in length was seen in 56.75% of the cases with anterior disc displacement with reduction, whereas 100% of nonreducing discs were mainly folded or rounded. Crepitation was correlated with folded and round disc deformities, whereas lengthening was the feature of reducing discs associated with early and intermediate clicking. CONCLUSIONS: The results show that the degenerative changes in the TMJ disc are influenced by the degree and the type of disc displacement. The more advanced the internal derangement, the more deteriorated the disc configuration.

Adolescent↗
PubMed2002

Characterization of tissue components in the temporomandibular joint disc and posterior disc attachment region: internal derangement and control autopsy specimens compared by morphometry.

PURPOSE: Our aim was to morphologically investigate the occurrence of fibroblasts, chondrocytes, and blood vessels in the tissue of the temporomandibular joint (TMJ) disc, the intermediate zone, and the posterior disc attachment region in control autopsy specimens and to compare the results with those observed in corresponding tissues from patients with TMJ internal derangement. PATIENTS AND METHODS: First, 20 bilateral TMJ disc specimens from selected autopsy cases were analyzed by conventional morphometry. Thus, the volume density of fibroblasts, chondrocytes, and blood vessels was determined. Second, the obtained results from the right joint of the autopsy disc specimens were compared with 12 TMJ disc specimens obtained at surgery from patients with internal derangement. RESULTS: The tissue compartments of interest (disc, intermediate zone, and posterior disc attachment region) were identified unequivocally in all specimens. None of the autopsy cases showed any significant difference between the right and left joints or related to gender. The only variable that differed between autopsy and patient specimens was volume density of blood vessels, which was higher in patient specimens. CONCLUSIONS: We found that the volume density of blood vessels was significantly higher in the posterior disc attachment region in patient specimens than in autopsy controls. Whether this reflects a role for vessels in the pathogenesis of TMJ internal derangement or merely is a reaction to another type of injury remains to be settled. In both the autopsy control and patient specimens, chondrocytes and fibroblasts were characteristic for disc respective posterior disc attachment region. Thus it appears that the occurrence of these cells can be used to distinguish TMJ disc from posterior disc attachment in small biopsy specimens.

Adolescent↗
PubMedDate not supplied

Changes in the chemical composition of the bovine temporomandibular joint disc with age.

The bovine temporomandibular joint disc is a fibrocartilaginous structure composed largely of collagen and proteoglycans. Little is known about changes in its composition accompanying growth and maturation. Discs were collected from immature foetuses (3-5 months), mature foetuses (6-8 months, adolescents (18 months), young adults (2-3 yr) and mature adults (over 4 yr), dissected free of fibrous attachments, and separated into outer and inner tissues. For the outer tissues the major findings were that: (1) water content in postnatal specimens was less than in prenatal specimens: (2) collagen content (relative to tissue dry weight) increased up to adolescence with little change thereafter; (3) total glycosaminoglycan, chondroitin sulphate and hyaluronic acid contents decreased during foetal development and then remained relatively constant, and (4) dermatan sulphate (the major glycosaminoglycan at all ages) decreased at maturity while keratan sulphate increased slightly. Results for the inner tissues were similar except that: (1) total glycosaminoglycan content was much higher in postnatal animals; (2) chondroitin sulphate was the major glycosaminoglycan after birth; and (3) keratan sulphate, which was barely detectable in the foetal specimens, increased rapidly after birth. Evidence was also obtained for changes in the copolymeric nature of galactosaminoglycans in the inner tissue. These findings, especially the different pattern of age-related changes in outer (presumably non-compressed) and inner (presumably compressed) tissue, suggest that the disc has the capacity to continually modify its composition in response to the mechanical stresses placed on it.

Adaptation, Biological↗
PubMed1983

Histopathology associated with malposition of the human temporomandibular joint disc.

Anterior displacement of the temporomandibular joint disc is associated with a general remodeling of the joint's soft tissues. The anterior part of the posterior attachment becomes fibrotic. The external shape and the internal architecture of the disc change in characteristic ways. The disc appears to overlie more of the lateral pterygoid muscle than is normal. The capsule connecting the anterior band of the disc to the condyle appears to be elongated.

Adult↗
PubMed2003

Structure and function of the temporomandibular joint disc: implications for tissue engineering.

The temporomandibular joint (TMJ) disc is a little understood structure that, unfortunately, exhibits a plethora of pathologic disorders. Tissue engineering approaches may be warranted to address TMJ disc pathophysiology, but first a clear understanding of structure-function relationships needs to be developed, especially as they relate to the regenerative potential of the tissue. In this review, we correlate the biochemical content of the TMJ disc to its mechanical behavior and discuss what this correlation infers for tissue engineering studies of the TMJ disc. The disc of the TMJ exhibits a somewhat biconcave shape, being thicker in the anterior and posterior bands and thinner in the intermediate zone. The disc, which is certainly an anisotropic and nonhomogeneous tissue, consists almost entirely of type I collagen with trace amounts of type II and other types. In general, collagen fibers in the intermediate zone appear to run primarily in an anteroposterior direction and in a ringlike fashion around the periphery. Collagen orientation is reflected in higher tensile stiffness and strength in the center anteroposteriorly than mediolaterally and in the anterior and posterior bands than the intermediate zone mediolaterally. Tensile tests have shown the disc is stiffer and stronger in the direction of the collagen fibers. Elastin fibers in general appear along the collagen fibers and most likely function in restoring and retaining disc form after loading. The 2 primary glycosaminoglycans of the disc by far are chondroitin sulfate and dermatan sulfate, although their distribution is not clear. Compression studies are conflicting, but evidence suggests the disc is compressively stiffest in the center. Only a few tissue engineering studies of the TMJ disc have been performed to date. Tissue engineering studies must take advantage of existing information for experimental design and construct validation, and more research is necessary to characterize the disc to create a clearer picture of our goals in tissue engineering the TMJ disc.

Compressive Strength↗
PubMed2002

The mediolateral temporomandibular joint disc position: an in vivo quantitative study.

AIMS: Temporomandibular joint (TMJ) discs displaced simultaneously, dorsoventrally, and mediolaterally are assumed to be rotated. However, a pilot study performed with individualized oblique-axial scans on supposedly rotated discs did not show disc rotation consistently. The aim of this study was the quantitative evaluation of disc rotation on a larger sample size, assessing the mediolateral disc geometry and position by the use of a reference system determined by the condylar long axis. METHODS: Eighty-five TMJs from 50 subjects were analyzed. One series of sagittal and 1 of 14 individualized oblique-axial magnetic resonance (MR) scans were taken for each joint. The dorsoventral disc position was diagnosed by means of the sagittal scans. The mediolateral disc width and position were then measured on every oblique-axial scan. The width and midline was computed for each disc and its deviation from the perpendicular to the condylar long axis was calculated. Finally, a statistical analysis was performed to study whether the disc width and the direction of the disc midline varied between discs normally positioned and anteriorly displaced. RESULTS: The disc width varied significantly more within the anteriorly displaced discs than within the normal ones. The midline of the anteriorly displaced discs deviated more from the perpendicular to the condylar long axis than that of normally positioned discs and was mostly in a lateral direction. The disc midline also deviated more in the ventral than in the dorsal part of the disc. CONCLUSION: Most anteriorly displaced discs were laterally displaced and showed a larger width variation than normally positioned discs. This fact seems to indicate disc deformation.

Adult↗