Magnetic resonance tomography of temporomandibular joint

The paper shows the place of magnetic resonance imaging among other radiation diagnostic techniques in detecting abnormal changes in the temporomandibular joint. The authors' own data were based on the results of 315 examinations. The paper describes the technical features of examination of the joint and shows it possible to visualize different anatomic structures on T1-, T2- and Pd-weighted images. It also indicates the diagnostic potentialities of magnetic resonance imaging in identifying abnormal changes in the joint in its diseases and lesions. This has allowed the authors to show what is indicated for magnetic resonance imaging of the temporomandibular joint and that it is necessary to develop an algorithm of radiation diagnosis for patients with different clinical forms of joint diseases.     

Tensile properties of the porcine temporomandibular joint disc

Despite the significant morbidity associated with the temporomandibular joint (TMJ), little is known about the pathophysiology of this complex joint. TMJ disc degeneration plays a central role in the progression of TMJ disorders, and therefore disc regeneration would be a crucial treatment modality. Unfortunately, scarce information about the structural and functional characteristics of the TMJ disc is available. The current study aims to provide a standard for the biomechanical behavior of the TMJ disc for future tissue engineering studies. The disc was loaded under uniaxial tension in two directions, mediolateral and anteroposterior, and in three locations per direction. In the mediolateral direction, the posterior band was 2.5 times stiffer, 2.4 times tougher (energy to maximum stress), and 2.2 times stronger than the anterior band, which was in turn 16 times stiffer and 5.7 times stronger than the intermediate zone. In the anteroposterior direction, the central and medial regions were 74% and 35% stiffer and 56% and 59% stronger than the lateral region, respectively, although similar to each other in strength and stiffness. There was no significant difference in toughness between regions in the anteroposterior direction. These results correlated qualitatively with collagen fiber orientation and fiber size obtained using polarized light microscopy.     

Size and location of the human temporomandibular joint

The literature abounds with conflicting data on various morphometric aspects of the temporomandibular joint (TMJ). The purpose of this study was to observe the effects of sex, ethnic group, and edentulism on TMJ osseous morphology and to define possible factors which might influence variation in this structure. TMJs and related craniofacial structures were measured directly on 229 dry skulls and matching mandibles. Analysis of variance, principal component analysis, and cluster analysis were performed. Our results indicate that 1) the anteroposterior-related TMJ dimensions are independent of sex, ethnic group, and edentulism; 2) the transverse TMJ dimension is related to cranial breadth measures; and 3) the projected distance, along a midsagittal plane, between the TMJ and foramen magnum is independent of sex, ethnicity, and edentulism. It is our assertion that the TMJ must not be considered as a single morphological structure but rather viewed as a functional unit with component parts which are subordinate to completely different sets of influences. © 1996 Wiley-Liss, Inc.     

Sensory innervation of the temporomandibular joint in the mouse

The sensory innervation of the temporomandibular joints (TMJs) of 8 STR/IN mice was investigated by means of light and electron microscopy. Through the cutting of complete semithin sections in series it was possible to investigate the joints thoroughly. Additionally, one joint with its nerve supply was reconstructed three-dimensionally with a computerized three-dimensional programme. The reconstruction was based on one complete semithin section series. The joint's nerve supply originates from the nervus auriculotemporalis and additionally from motor branches of the n. mandibularis: n. massetericus, n. pterygoideus lateralis and the nn. temporales posteriores. The greatest number of nerve fibres and endings is located in the dorsolateral part of the joint capsule. They lie only in the stratum fibrosum and subsynovially. Neither the stratum synoviale nor the discus articularis contain any nerve fibres or endings, whereas the peri-articular loose connective tissue is richly innervated. The only type of nerve ending observed within the joint was the free nerve ending, which is assumed to serve not only as a nociceptor but also as a polymodal mechanoreceptor. Merely within the insertion of the musculus pterygoideus lateralis at the collum mandibulae single stretch receptors of the Ruffini type were observed. Ultrastructurally, they correspond to those described in the cat's knee joint. Neither lamellated nor nerve endings of the Golgi or Pacini type were observed in the joint or in the peri-articular connective tissue. The unexpected paucity of nerve fibres and endings in the TMJ itself of the mouse suggests that the afferent information from the joint is less important for position sense and movement than the afferent information from muscles, tendons and periodontal ligaments.     

Capsaicin receptor expression in the rat temporomandibular joint

Experimentally, temporomandibular joint (TMJ) nerve units respond to capsaicin, which is used clinically to treat TMJ pain. However, the existence of capsaicin receptors in the TMJ has not previously been clearly demonstrated. Immunohistochemical analysis has revealed the presence of transient receptor potential vanilloid subtype 1 (TRPV1) expression in the nerves and synovial lining cells of the TMJ. TRPV1-immunoreactive nerves are distributed in the synovial membrane of the joint capsule and provide branches to the joint compartment. The disc periphery is supplied by TRPV1 nerves that are mostly associated with small arterioles, and occasional nerves penetrate to the synovial lining layer. Double immunofluorescence has shown that many TRPV1-immunoreactive nerves are labeled with neuropeptide calcitonin gene-related peptide, whereas few are labeled with IB4-lectin. The results provide evidence for the presence of TRPV1 in both nerves and synovial lining cells, which might thus be involved in the mechanism of nociception and inflammation in the TMJ. This study was supported by a grant-in-aid for Scientific Research (C), no. 15591938, from the Japanese Ministry of Education, Science, Sports, Culture, and Technology (to M.A.K.).     

Multiaxial movements at the minke whale temporomandibular joint

Mandibular mobility accompanying gape change in Northern and Antarctic minke whales was investigated by manipulating jaws of carcasses, recording jaw movements via digital instruments (inclinometers, accelerometers, and goniometers), and examining osteological and soft tissue movements via computed tomography (CT)-scans. We investigated longitudinal (α) rotation of the mandible and mediolateral displacement at the symphysis (Ω₁) and temporomandibular joint (Ω₂) as the mouth opened (Δ). Results indicated three phases of jaw opening. In the first phase, as gape increased from zero to 8°, there was slight (<1°) α and Ω rotation. As gape increased between 20 and 30°, the mandibles rotated slightly laterally (Mean 3°), the posterior condyles were slightly medially displaced (Mean 4°), and the anterior ends at the symphysis were laterally displaced (Mean 3°). In the third phase of jaw opening, from 30° to full (≥90°) gape, these motions reversed: mandibles rotated medially (Mean 29°), condyles were laterally displaced (Mean 14°), and symphyseal ends were medially displaced (Mean 1°). Movements were observed during jaw manipulation and analyzed with CT-images that confirmed quantitative inclinometer/accelerometer data, including the unstable intermediate (Phase 2) position. Together these shifting movements maintain a constant distance for adductor muscles stretched between the skull's temporal fossa and mandible's coronoid process. Mandibular rotation enlarges the buccal cavity's volume as much as 36%, likely to improve prey capture in rorqual lunge feeding; it may strengthen and stabilize jaw opening or closure, perhaps via a simple locking or unlocking mechanism. Rotated lips may brace baleen racks during filtration. Mandibular movements may serve a proprioceptive mechanosensory function, perhaps via the symphyseal organ, to guide prey engulfment and water expulsion for filtration.     

Mandibular distraction in temporomandibular joint ankylosis

Condylar damage during childhood can produce ankylosis and alteration of the mandibular growth. In case of unilateral ankylosis occurring in early childhood, a mandibular hypoplasia of the affected side may develop. The patients have limitation of mouth opening, facial asymmetry, and chin deviation toward the affected side. The aims of this study are to show the use of distraction osteogenesis in mandibular hypoplasia associated with ankylosis and to present our experience with a new therapeutic option for the treatment of mandibular hypoplasia with unilateral ankylosis in the childhood consisting of the association of arthroplasty to treat the ankylosis and mandibular distraction to correct the facial asymmetry, both accomplished in the same surgical procedure. From November of 1996 to November of 1997, three male patients aged 2, 7, and 13 years with mandibular hypoplasia and ankylosis were treated by distraction osteogenesis. An arthroplasty consisting of the resection of the ankylotic block and interposition of a temporalis muscle flap, plus coronoidectomy was done in two of them and mandibular distraction was done in all three patients. Articular functional rehabilitation began on the first postoperative day. Mandibular distraction began on the fifth postoperative day with a rate of 1 mm per day, ending when the facial symmetry was achieved. From the first postoperative day, an increase in the mouth opening was achieved; this increase continued until ending the distraction. The average duration of distraction was 22 days. Average duration of consolidation was 6 weeks. Oral opening increased from 10 mm to 35 mm in the 7-year-old patient, from 9 mm to 27 mm in the 2-year-old patient, and from 14 mm to 38 mm in the 13-year-old patient. To date, oral opening and facial symmetry persist. Osseous mandibular distraction together with arthroplasty offers an excellent new alternative for treatment of patients with mandibular hypoplasia and associated ankylosis, with minimal morbidity and complications.     

Development of the temporomandibular joint in miniature pig embryos

The temporomandibular joint (TMJ) is a synovial joint involved in sliding and hinge movements of lower jaw in mammals. Studies on TMJ development in embryos have been mainly performed using rodents. However, the TMJ structure in rodents differs in several aspects from that in humans. There are few studies on the embryonic development of TMJ in large mammals. In the present study, we investigated the embryonic developmental characteristics of the TMJ in pigs histologically. Embryonic day 35 (E35), E45, E55, E75, E90, and postnatal day 1(P1) embryos/fetuses from the pigs were used for the study. The results showed condensation of mesenchymal cells on E35. The inferior articular cavity was formed on E45, together with a narrow crack in the superior articular cavity region. The superior and inferior articular cavities and articular disc of the TMJ were completely formed on E55. On E75, the condyle showed an obvious conical shape and the superior and inferior joint cavities were enlarged. Furthermore, the mandibular ramus and mandibular body under the neck of the condyle were ossified from E75 to P1 day. The chondrocyte layer of the condyle was significantly thinner from E75 to P1. It is speculated that the spatiotemporal development of the TMJ in miniature pig embryos is similar to that in humans. Embryonic development of the pig TMJ is an important bridge for translating the results of rodent research to medical applications.     

A three-dimensional investigation of temporomandibular joint loading

A mathematical model of the muscle groups applied to the human mandible is developed to study the forces developed on the condyles during maximum unilateral occlusion. The results show that the reaction forces are in approximately a 2:1 ratio with the balancing side condyle carrying the greater load. Furthermore, the direction in which these condylar reactions occur is presented.