Sensory innervation of temporomandibular joint disk.

PURPOSE: To investigate the nerve endings of the adult temporomandibular joint disk, in particular the presence and configuration of the sensory nerve endings by silver staining and electron microscopy. METHODS: 20 cadaveric temporomandibular joints impregnated with silver stain were studied using an optical microscope; 2 other joints were studied using a transmission electron microscope. RESULTS: Free nerve endings were found in the disk parenchyma of all joints. Golgi-Mazzoni corpuscles, Ruffini corpuscles, and articular corpuscles were also observed as sensory nerve end organs. Myelinated and nonmyelinated nerve fibres were visualised in the disk parenchyma using the transmission electron microscope. CONCLUSION: Free nerve endings and sensory nerve end organs are present in the disk parenchyma of the human temporomandibular joint and are associated with sensation and proprioception, just as they are in the acetabular labrum, glenoid labrum, triangular fibrocartilage complex, and meniscus.

Cellular S-100 protein immunostaining in human dysfunctional temporomandibular joint discs.

S-100 protein was detected immunohistochemically in diseased human temporomandibular joint discs with different degrees of pathology, and the findings compared with those of normal discs. In normal discs, large nerve trunks in the posterior ligament were strongly stained by anti-S-100 antiserum; the very few chondrocyte-like cells sometimes showed faint staining, while no staining was observed in any fibrochondrocyte-like or fibroblast-like cell. In dysfunctional discs, S-100 protein immunostaining seemed to correlate with structural pathological findings. The discs showing an abnormal collagen arrangement or fragmentation of collagen fibres presented overall the same immunolabelling pattern as normal discs. In discs with fibrocartilaginous metaplasia and dystrophic cartilage formation, fibrochondrocyte cells showed a very strong immunoreaction for S-100 protein and fibroblast-like cells in some instances were also positive. These findings suggest that S-100 upregulation in disc cells can be considered an attempt at tissue repair by chondroid metaplasia following an injury in that it enables fibroblast-like cells and fibrochondrocytes to acquire a chondrogenic phenotype.

Postnatal development of substance P-, calcitonin gene-related peptide- and neuropeptide Y-like immunoreactive nerve fibres in the synovial membrane of the rat temporomandibular joint.

The postnatal (0-24 days) development of substance P (SP)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y(NPY)-like immunoreactive (LI) nerves in the rat temporomandibular joint (TMJ) was investigated immunohistochemically. Immediately after birth, SP- or CGRP-LI nerves were observed in most disc attachments. A few NPY-LI nerves were observed around the large blood vessels in the joint capsule. From days 3 to 6, the SP- or CGRP-LI nerves were first found close to the anterior, lateral, medial (third day) or posterior (sixth day) peripheral portion of the disc. The synovial cells (type A and B) first appeared at the anterior peripheral portion of the disc (sixth day), and then at the posterior, lateral and medial portions (seventh day). NPY-LI nerves were found around the blood vessels at the disc attachment on the sixth day, and then entered into the peripheral portion of the disc from days 10 to 14. At 14 days a few NPY-LI nerves were first found close to the blood vessels in the sublining layer of the synovial membrane. From days 18 to 24, a few NPY-LI nerves were located in the superficial layer of the synovial membrane. The central portion of the disc did not contain any nerves from days 0 to 24. Thus SP- or CGRP-LI sensory nerves are shown to innervate the rat TMJ at an earlier age than NPY-LI sympathetic nerves, which may modulate the regulation of blood flow in the joint capsule, disc and synovial membrane. However, it is considered that the disc itself does not contribute to the transportation of the afferent sensory information. Furthermore, from the fact that SP- or CGRP-LI nerves were found earlier than the appearance of the synovial cells, it is suggested that these nerves may be associated with the growth and proliferation of synovial cells.

Neural structures within the sheep temporomandibular joint.

To better understand pathologic processes associated with arthritis of the temporomandibular joint (TMJ), detailed information on the innervation of TMJ tissues in normal as well as arthritic joints is needed. The aim of this study was to describe the normal innervation of the sheep TMJ in preparation for using this animal as a model for the study of the effects of arthritis on joint innervation. The macroscopic and microscopic appearance plus the distribution of neural structures within the TMJ were examined using fluorescence histochemistry (glyoxylic acid), immunohistochemistry (calcitonin gene-related peptide), silver, and gold chloride techniques. Joints from 10 mature merino sheep were studied. Calcitonin gene-related peptide-immunoreactive nerve fibers were found in the capsule and the synovial membrane, but not in the disc. Nerve bundles and single nerve fibers in the capsule, synovial membrane, and the peripheral 2 to 3 mm of the disc were stained by glyoxylic acid. Ruffini, paciniform-type, and Golgi organ nerve endings plus free nerve endings were located in the capsule, with the highest density of nerve endings occurring at the site of attachment of the disc to the capsule. The highest density of neural structures (using gold chloride) was in the posterior part of the joint. The highest density of autonomic fibers (using glyoxylic acid) was in the anterior capsule. The highest density of sensory fibers (using calcitonin gene-related peptide) was in the synovial and subsynovial tissues of the anterior capsule. These results confirm the existence of autonomic and sensory nerves in the capsule, synovial membrane, and peripheral disc in healthy adult sheep.

The influence of experimentally induced osteoarthrosis on articular nerve fibers of the sheep temporomandibular joint.

AIMS: To study the effect of experimentally induced osteoarthrosis, or non-inflammatory degenerative changes, on the innervation of the sheep temporomandibular joint (TMJ) through the use of indirect immunohistochemistry and image analysis quantification. METHODS: Bilateral condylar scarification was performed in 8 sheep, which were killed at 16 weeks post-operation; 3 unoperated sheep served as controls. Tissues from 8 osteoarthrotic joints and 4 control joints were processed for the immunostaining with antisera for protein gene product 9.5 (PGP 9.5), substance P (SP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), and tyrosine hydroxylase (TH). An additional 10 joints were decalcified to study the morphologic changes induced by the condylar abrasion. RESULTS: Osteoarthrotic changes were commonly seen in the anterior and lateral regions of the joint and included fibrosis, peripheral osteophyte formation, cysts, and erosion of articular surfaces. In the osteoarthrotic joints, the distribution of PGP 9.5-, CGRP-, and SP-immunoreactive (IR) nerve fibers was similar to that observed for control joints in the capsule, synovium, and capsule/disc junction. There were statistically detectable decreases in the percent surface area of IR nerve fibers in the capsule for both PGP 9.5 and CGRP in arthrotic joints compared with control joints. The lateral and anterior regions of the capsule had greater density of PGP 9.5- and CGRP-IR nerve fibers than other parts of the capsule in both control and arthrotic joints, and the medial capsule was poorly innervated in all joints. Immunostaining for substance P was always weaker. CONCLUSION: This study suggests that while inflammatory arthritis has a marked influence on the density of sensory and autonomic nerve fibers in synovium in a variety of joints in different species, experimentally induced non-inflammatory osteoarthrosis in the sheep TMJ also leads to a depletion of the density of nerve fibers in the capsule, especially in the lateral part of the joint. Further work is required to determine whether other parts of the joint, such as synovium and marrow, respond differently to experimentally induced osteoarthrosis.

The distribution of the auriculotemporal nerve around the temporomandibular joint.

OBJECTIVE: The purpose of this cadaver dissection was to study the position of the auriculotemporal nerve in relation to the mandibular condyle, capsular tissues, articular fossa, and lateral pterygoid muscle and to evaluate the anatomic possibility of nerve impingement or irritation by the surrounding structures. STUDY DESIGN: Eight cadaveric heads (16 sides) were dissected. The auriculotemporal nerve was identified by following its course around the middle meningeal artery. The course of the nerve trunk was dissected from the middle meningeal artery to the terminal branches within the temporomandibular disk. The horizontal distance between the auriculotemporal nerve and the medial portion of the condyle/condylar neck was measured. The vertical distance from the most superior portion of the articular condyle to the superior border of the auriculotemporal nerve was measured. RESULTS: The auriculotemporal nerve was identified on each side, and a single trunk was evident along the medial aspect of the condylar neck. At the posterior border of the lateral pterygoid muscle, the nerve trunk was in direct contact with the condylar neck in every specimen. The average vertical distance between the superior condyle and the nerve was 7.06 mm (+/- 3.21 mm); the range was 0 to 13 mm. The vertical distance between the nerve and the superior condyle on one side of the specimen did not correlate with the distance on the contralateral side. CONCLUSION: The auriculotemporal nerve trunk has a close anatomic relationship with the condyle and the temporomandibular joint capsular region, and there is evidence of a possible mechanism for sensory disturbances in the temporomandibular joint region. In all cases, the nerve was in direct contact with the medial aspect of the capsule or condylar neck. Because there is no correlation between the positions of the nerves on the right and left sides, only one side may be affected. The nerve was also observed to course in direct apposition to the lateral pterygoid muscle. The findings support the hypothesis that the anatomic and clinical relationship of the auriculotemporal nerve to the condyle, articular fossa, and lateral pterygoid muscle may be causally related to compression or irritation of the nerve, producing numbness or pain, or both, in the temporomandibular joint region.

Percentage of lateral pterygoid muscle inserted in the disc of human temporomandibular joint / Porcentaje del músculo pterigoideo lateral inserto en el disco de la articulación temporomandibular humana

Insertion of the upper head of the lateral pterygoid (UHLP) in the temporomandibular joint disc (TMJ) has been linked to anterior displacement of the disc and temporomandibular disfunction. The aim of this study was to determine in human adults, the percentage of muscle fiber in the upper head of the lateral pterygoid muscle inserted in the articular disc. A systematic review of the literature was designed beginning with articles published in Medline, Lilacs and Scielo data bases between the years 1990 and 2010. Key words "Lateral Pterygoid Muscle" and Pterygoid Lateral Muscle" were used, and the term MeSH "Pterygoid Muscle" with Boolean OR "Lateral Ptrerygoid Muscle" AND "Insertion" and the free terms "Pterygoid Lateral Muscle Disc Articular" and "Pterygoid lateral Muscle Meniscus". Of the 156 articles obtained and analyzed, 18 articles meeting eligibility criteria were selected. Based on those articles the percentage of insertion of the CSPL in the TMJ disc was evaluated, each one was subsequently assigned a level of evidence according to OCEBM Oxford Centre Evidence Based Medicine. Only four articles answered the research inquiry, three studies were histological and one used imaging techniques with cross section slices with an adequate evidence level (1B). However, results differed with insertion percentages from 2 percent to 69.8 percent being reported in the superior head of the lateral pterygoid muscle in the articular disc.

La actividad de la inserción de la cabeza superior del pterigoideo lateral (CSPL) en el disco de la articulación temporomandibular (ATM) ha sido vinculada al desplazamiento anterior del disco y disfunción temporomandibular. El propósito de este estudio fue determinar el porcentaje de fibras musculares de la cabeza superior del músculo pterigoideo lateral que se insertan en el disco articular, en humanos adultos. Se diseñó una revisión sistemática de la literatura a partir de artículos primarios publicados en las bases de datos Medline, Lilacs y Scielo entre los años 1990 y 2010. Se utilizaron las palabras clave "Músculo Pterigoideo Lateral" y "Pterygoid Lateral Muscle", el Término MeSH: "Pterygoid Muscle" con los boleanos OR "Lateral Pterygoid Muscle" AND "Insertion" y los Términos Libres: "Pterygoid Lateral Muscle Disc Articular" y "Pterygoid lateral Muscle Meniscus". Se obtuvieron 156 artículos, los cuales fueron analizados y se seleccionaron 18 que cumplieron con los criterios de elegibilidad. En base a estos artículos se evaluó el porcentaje de inserción de la CSPL en el disco de la ATM, posteriormente a cada uno se les otorgó un nivel de evidencia de acuerdo a la clasificación de Oxford Centre Evidence Based Medicine (OCEBM). Solo 4 artículos respondieron a la pregunta de investigación, 3 estudios fueron histológicos y 1 imagenológico, todos con diseños de cortes transversales con buen nivel de evidencia (1b). Sin embargo los resultados fueron disímiles, reportándose porcentajes de inserción del 2 al 69,8 por ciento de la cabeza superior del pterigoideo lateral en el disco articular.

[Distribution of calcitonin gene-related peptide-like immunoreactive fibres in the temporomandibular joint of rat].

OBJECTIVE: To observe the distribution of calcitonin gene-related peptide-like immunoreactive (CGRP-LI) nerve fibres in rat's temporomandibular joint (TMJ). METHODS: The avidin-biotin-peroxidase complex method and image analysis were employed to detect CGRP-LI nerve fibres in frozen sections of TMJs in eight rats. RESULTS: CGRP-LI nerve fibres were plentifully distributed in TMJs except the central disc band and bone, mainly in the periphery of blood vessels, especially arteries. Density: anterior disc attachment and capsule, (454.6 +/- 72.8) mm(2); posterior portion, (302.7 +/- 43.4) mm(2); lateral portion, (240.2 +/- 23.6) mm(2); medial portion, (229.6 +/- 25.0)mm(2); and peripheral portion of disc, (202.4 +/- 35.2) mm(2). CONCLUSION: CGRP-LI nerve fibres were widely distributed in rat TMJ and were a part of trigeminal sensory nerve. Density was highest in anterior disc attachment and capsule.

Immunohistochemical demonstration of neuropeptides in the articular disk of the human temporomandibular joint.

The distribution of calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) was examined in the human temporomandibular articular disk using an indirect immunofluorescent method. All examined neuropeptides were observed in nerve fibers in the disk. These fibers were mostly located in the loose fibrous tissue of the posterior part (posterior attachment) and in the lateral region of the anterior part (anterolateral loose fibrous tissue) of the disk. The posterior attachment and anterolateral loose fibrous tissue occasionally contained isolated nerve fibers which usually showed immunoreactivity (IR) for CGRP or SP. In this tissue, perivascular fibers contained VIP or NPY, whereas isolated fibers and free nerve endings showed the IR for CGRP or SP. These neuropeptides may be involved in the regulation of blood flow and/or pain sensation in the human articular disk of the temporomandibular joint.

Postnatal development of protein gene product 9.5 and calcitonin gene-related peptide immunoreactive nerve fibres in rat temporomandibular joint disc.

Protein gene product 9.5 (PGP 9.5), an immunohistochemical marker of whole nerve fibres, and calcitonin gene-related peptide (CGRP), a marker of thin nerve fibres, were used to elucidate the postnatal development of nerve fibres in rat temporomandibular joint (TMJ) disc. At birth, PGP 9.5-immunoreactive nerve fibres exhibited running towards the central area of the disc, invading by approximately 95 m from the disc attachment. The nerve fibres existing inside the disc became longer during postnatal development. The number of nerve fibres in the disc increased in a progressive manner up to 40 days after birth. CGRP-immunoreactive nerve fibres also presented changes essentially similar to those of PGP 9.5-immunoreactive nerve fibres. However, the proportion of CGRP-immunoreactive nerve fibres to PGP 9.5-immunoreactive ones was approximately 80%, and remained constant up to 40 days after birth. In conclusion, the distribution and the number of nerve fibres are variable during postnatal development, although the ratio of thin nerve fibres remains invariable. It is emphasized that these changes of innervation in the TMJ are associated with the development of masticatory function.

Postnatal development of protein gene product 9.5- and calcitonin gene-related peptide-like immunoreactive nerve fibers in the rat temporomandibular joint.

BACKGROUND: The aim of this study was to investigate the little-known postnatal development of innervation in the temporomandibular joint (TMJ). METHODS: We therefore investigated the protein gene product 9.5-like immunoreactive (PGP-LI) and calcitonin gene-related peptide-like immunoreactive (CGRP-LI) nerves in the rat TMJ from days 0-24 in wholemount preparations and frozen sections by immunohistochemistry using the avidin-biotin-peroxidase complex method. RESULTS: At birth, PGP-LI and CGRP-LI nerves were observed only in the disk attachment but not in the peripheral portion of the disk. From days 3-6, the peptidergic nerves associated with the development of synovial cells were first found in the anterior (3rd day) or posterior (6th day) peripheral portion of the disk in which synovial cells later appear. From days 7-10, incisal occlusion started and simultaneously the distinct networks of the nerves were formed in four peripheral portions of the disk. On the 14th day, the PGP-LI nerves were first more numerous than the CGRP-LI nerves only in the anterior disk attachment. From days 18-24, the occlusion between the first molars started. Simultaneously, the distribution and number of the nerves were comparable to those of adult rats. However, from days 0-24, the central portion of the disk (actual disk) did not contain any nerves. CONCLUSIONS: These findings suggest that functional stimuli such as sucking and mastication might be associated with the development of nerves in the TMJ during the early and late postnatal days, whereas the actual disk except for both disk attachment and peripheral portion of the disk is not innervated and does not contribute to the afferent sensory information from the TMJ. The presence of peptidergic nerves prior to the appearance of synovial lining cells furthermore suggests that the neuropeptide released from these nerves may affect on the differenciation and maturation of synovial cells.

Distribution of substance P-like immunoreactive fibers in feline temporomandibular joint.

OBJECTIVE: To study the distribution of substance P-like immunoreactive fibers in feline temporomandibular joint. METHODS: The immunohistochemical PAP method was used for the investigation of the distribution of substance P-like immunoreactive fibers in feline temporomandibular joint. RESULTS: The TMJ capsule and the anterior and posterior disc attachments all contained SP-immunoreactive nerve fibers, but the medium fibers in diameter were mainly observed. The density of the distribution of SP-positive nerve fibers was the highest in the subsynovium of the TMJ capsule. The density of distribution was similar in the anterior and posterior disc attachments, but lower than in the subsynovium and the lateral joint capsule. Such fibers in the synovial membrane were sparser, and a part of the fibers were seen around the thin blood vessels in all the foregoing tissues. CONCLUSION: These results provide the morphological data for exploring the neurobiological mechanisms of temporomandibular joint disorder and its pain.

Expresión de neuropéptidos en la articulación temporomandibular, 1: GGRP y articulación temporomandibular / Neuropeptides expression in the temporomandibular joint, 1: CGRP and temporomandibular joint

Antecedentes: neuropéptidos como el péptido relacionado con el gen de la calcitonina (CGRP), sustancia P (SP) y neurokinina A (NKA) se relacionan con desarrollo y progresión de enfermedad degenerativa articular. Estudios previos mostraron su rol en respueta vascular y nociceptiva en artritis y su papel modulardor en hiperalgesia y dolor de tipo artrítico, comprobando su presencia en líquido sinovial de articulación temporomandibular. Propósito: evaluar presencia y contenido de neuropéptidos en tejidos retrodiscal hiperplásico de la articulación temporomandibular en pacientes con enfermedad degenerativa articular mediante radioinmunoensayo. Métodos: ocho pacientes de sexo femenino (15 articulaciones), premenopáusicas, no embarazadas ni lactando por un año, fueron diagnosticadas con enfermedad articular degenerativa (osteoartrosis). Se registraron niveles de dolor en escala visual análoga, donde 0 es ausencia de dolor y 16 dolor agudo; se clasificó la degeneración ósea entre leve, moderada y severa, de acuerdo con hallazgos de resonanacia nuclear magnética. Las pacientes fueron sometidas a cirugía abierta de ATM donde se tomaron las muestras. Los especímenes se colocaron en bloques plásticos con medio congelante y se almacenaron a -700C hasta la extracción de los neuropéptidos por radioinmunoensayo con el estuche específico para cada uno. Resultados: se estableció una relacion directamente proporcional entre grado de degeneración ósea y expresión de CGRP, y entre clasificación de osteoartrosis con escala visual análoga. Los hallazgos mostraron correlación definitiva entre niveles de dolor y expresión del péptido relacionado con el gen de la calcitonina. Conclusiones: CGRP, SP y NKA, si se expresan en tejido retrodiscal de ATM en humanos con enfermedad degenerativa articular, relacionándose CGRP directamente con niveles de osteoartrosis y dolor