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(1/335) Activation of peripheral GABAA receptors inhibits temporomandibular joint-evoked jaw muscle activity.

We have previously shown that injection of mustard oil or glutamate into rat temporomandibular joint (TMJ) tissues, an experimental model of acute TMJ injury, can reflexly induce a prolonged increase in the activity of both digastric (jaw-opener) and masseter (jaw-closer) muscles. In this study, GABA was applied to the TMJ region by itself or in combination with glutamate, and the magnitude of evoked jaw muscle electromyographic (EMG) activity was measured. Application of GABA alone to the TMJ region did not evoke significant jaw muscle EMG activity when compared with normal saline controls. In contrast, co-application of GABA and glutamate into the TMJ region decreased the magnitude of glutamate-evoked EMG activity. This GABA-mediated inhibition of glutamate-evoked EMG activity followed an inverse dose-response relationship with an estimated median inhibitory dose (ID50) of 0.17 +/- 0.05 (SE) micromol and 0.031 +/- 0.006 micromol for the digastric and masseter muscles, respectively. Co-administration of the GABAA receptor antagonist bicuculline (0.05 micromol) but not the GABAB receptor antagonist phaclofen (0.05 or 0. 15 micromol) reversed the suppressive actions of GABA, indicating that this action of GABA may be mediated by peripheral GABAA receptors located within the TMJ region. Our results suggest that activation of peripheral GABAA receptors located within the TMJ region could act to decrease the transmission of nociceptive information.  (+info)

(2/335) Development of the human temporomandibular joint.

A great deal of research has been published on the development of the human temporomandibularjoint (TMJ). However, there is some discordance about its morphological timing. The most controversial aspects concern the moment of the initial organization of the condyle and the squamous part of the temporal bone, the articular disc and capsule and also the cavitation and onset of condylar chondrogenesis. Serial sections of 70 human specimens between weeks 7 and 17 of development were studied by optical microscopy (25 embryos and 45 fetuses). All specimens were obtained from collections of the Institute of Embryology of the Complutense University of Madrid and the Department of Morphological Sciences of the University of Granada. Three phases in the development of the TMJ were identified. The first is the blastematic stage (weeks 7-8 of development), which corresponds with the onset of the organization of the condyle and the articular disc and capsule. During week 8 intramembranous ossification of the temporal squamous bone begins. The second stage is the cavitation stage (weeks 9-11 of development), corresponding to the initial formation of the inferior joint cavity (week 9) and the start condylar chondrogenesis. Week 11 marks the initiation of organization of the superior joint cavity. And the third stage is the maturation stage (after week 12 of development). This work establishes three phases in TMJ development: 1) the blastematic stage (weeks 7-8 of development); 2) the cavitation stage (weeks 9-11 of development); and 3) the maturation stage (after week 12 of development). This study identifies the critical period of TMJ morphogenesis as occurring between weeks 7 and 11 of development.  (+info)

(3/335) Temporomandibular joint ankylosis: the Egyptian experience.

This is a review of 204 patients with temporomandibular joint (TMJ) ankylosis treated according to a definitive protocol in the Cranio-Maxillo-Facial Department of the Alexandria University Hospital during the period 1990-1996 with a follow-up varying from 1.5 to 7 years. A history of trauma was confirmed in 98% of cases. Patients were grouped into: (1) Those with ankylosis not associated with facial deformities. The management involves release of the ankylosed joint(s) and reconstruction of the condyle ramus unit(s) (CRUs) using costochondral graft(s) (CCGs). (2) Those with mandibular ankylosis complicated by facial bone deformities, either asymmetric or bird face. The treatment consists of release of the ankylosis, reconstruction of the CRUs, and correction of jaw deformities--all performed simultaneously. Respiratory embarrassment was an important presenting symptom in the second group, all of whom complained of night snoring, eight of whom had obstructive sleep apnoea (OSA). In this latter group, respiratory obstruction improved dramatically after surgical intervention. The degree of mouth opening, monitored as the interincisal distance (IID) improved from a range of 0-12 mm to over 30 mm in 62% of patients and to 20-30 mm in 29% of patients. However, reankylosis was still around 8% and was attributed to lack of patient compliance in 75% and to iatrogenic factors in 25% of patients. CCGs resorption, whether partial or complete, occurred in 27% of patients, resulting in retarded growth, relapse of deformities and night snoring.  (+info)

(4/335) The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study.

Changes in the functional shift of the mandibular midline and the condyles were studied during treatment of unilateral posterior crossbite in six children, aged 7-11 years. An expansion plate with covered occlusal surfaces was used as a reflex-releasing stabilizing splint during an initial diagnostic phase (I) in order to determine the structural (i.e. non-guided) position of the mandible. The same plate was used for expansion and retention (phase II), followed by a post-retention phase (III) without the appliance. Before and after each phase, the functional shift was determined kinesiographically and on transcranial radiographs by concurrent recordings with and without the splint. Transverse mandibular position was also recorded on cephalometric radiographs. Prior to phase I, the mandibular midline deviated more than 2 mm and, in occlusion (ICP), the condyles showed normally centred positions in the sagittal plane. With the splint, the condyle on the crossbite side was displaced 2.4 mm (P < 0.05) forwards compared with the ICP, while the position of the condyle on the non-crossbite side was unaltered. After phase III, the deviation of the midline had been eliminated. Sagittal condylar positions in the ICP still did not deviate from the normal, and the splint position was now obtained by symmetrical forward movement of both condyles (1.3 and 1.4 mm). These findings suggest that the TMJs adapted to displacements of the mandible by condylar growth or surface modelling of the fossa. The rest position remained directly caudal to the ICP during treatment. Thus, the splint position, rather than the rest position should be used to determine the therapeutic position of the mandible.  (+info)

(5/335) Temporomandibular joint pantomography using charge-coupled device, photostimulable phosphor, and film receptors: a comparison.

Our objective was to compare the accuracy and practicality in use of three available imaging receptors for temporomandibular joint (TMJ) imaging; namely, two computer-assisted and one traditional analog x-ray film system. A standardized tissue-equivalent encased human skull specimen was imaged using lateral and posteroanterior (PA) pantomographic projections with the Orthopantomograph OP 100 (Instrumentarium Imaging, Tuusula, Finland) and three different receptor modalities: (1) Ektavision film with Ektavision screens (Eastman Kodak, Rochester, NY); (2) DenOptix photostimulable phosphor screens (Dentsply/Gendex, Chicago, IL); and (3) the charge-coupled device (CCD) receptor, DigiPan (TREX/Trophy Radiology, Marne-la-Vallee, France). The effective focal trough was found for each receptor using lead resolution grids placed at fractional millimeter distances along empirically determined beam projection angulations. The time to acquire and process images was also established. We found that the CCD system permitted real-time display, whereas the use of traditional film took 2 minutes to load the cassette in a darkroom and perform the exposure, and then a further 2 minutes to unload and process. The storage phosphor took 3 minutes to unload the cassette and process the image and a further 20 seconds to clear the plate following laser scanning. Film produced the greatest maximum resolution followed by the storage phosphor and the CCD. In conclusion, CCD-based TMJ pantomography provided an instant image. The photostimulable phosphor system used was the least satisfactory in terms of the time expended to obtain an image, but provided better spatial resolution than the CCD. Ektavision film/screens provided the best spatial resolution in this investigation.  (+info)

(6/335) Medullary dorsal horn neuronal activity in rats with persistent temporomandibular joint and perioral inflammation.

Studies at spinal levels indicate that peripheral tissue or nerve injury induces a state of hyperexcitability of spinal dorsal horn neurons that participates in the development of persistent pain and hyperalgesia. It has not been demonstrated that persistent injury in the orofacial region leads to a similar state of central hyperexcitability in the trigeminal system. The purpose of the present study was to conduct a parametric analysis of the response properties of nociceptive and nonnociceptive neurons in trigeminal nucleus caudalis (medullary dorsal horn, MDH) in a rat model of persistent orofacial inflammation. Neurons were recorded extracellularly and classified as low-threshold mechanoreceptive (LTM, n = 49), wide dynamic range (WDR, n = 82), and nociceptive-specific (NS, n = 11) neurons according to their response properties to mechanical stimuli applied to their cutaneous receptive fields (RFs). The inflammation was induced 24 h before the recordings by injecting complete Freund's adjuvant (CFA) into the temporomandibular joint (TMJ) capsule or the perioral (PO) skin. The mean areas of the high-threshold RFs of WDR neurons in TMJ (8.66 +/- 0.61 cm(2), n = 25) and PO (5.61 +/- 2.07 cm(2), n = 25) inflamed rats were significantly larger than those in naive rats (1.10 +/- 0. 16 cm(2), n = 32). The mean RF size in TMJ-inflamed rats also was significantly larger than that in PO-inflamed rats (P < 0.01). Furthermore the mean area of the RFs of NS neurons (3.74 +/- 1.44 cm(2), n = 5) was significantly larger in TMJ inflamed rats as compared with naive rats (0.4 +/- 0.09 cm(2), n = 3) (P < 0.05). The background activity in the TMJ- and PO-inflamed rats was generally greater in WDR and NS neurons, but less in LTM neurons, when compared with naive rats. The responses of WDR neurons to noxious mechanical stimuli were increased significantly in TMJ-inflamed rats (P < 0.05) as compared with naive rats. WDR neuronal responses to mechanical stimulation also were increased in PO-inflamed rats but to a lesser extent than in TMJ-inflamed rats. The injection of CFA into the TMJ or PO skin resulted in reduced responses of LTM neurons to mechanical stimuli. The responses of MDH nociceptive neurons to 48-55 degrees C heating were greater in inflamed rats as compared with naive rats. A subpopulation of WDR neurons recorded from TMJ (n = 4 of 10)- or PO (n = 3 of 13)-injected rats responded to cooling in addition to heating of the RFs but did not grade their responses with changes in stimulus intensity. These results indicate that persistent orofacial inflammation produced hyperexcitability of MDH nociceptive neurons. TMJ inflammation resulted in more robust changes in MDH nociceptive neurons as compared with PO inflammation, consistent with previous studies of increased inflammation, increased MDH Fos-protein expression, and increased MDH preprodynorphin mRNA expression in this deep tissue orofacial model of pain and hyperalgesia. The inflammation-induced MDH hyperexcitability may contribute to mechanisms of persistent pain associated with orofacial deep tissue painful conditions.  (+info)

(7/335) Airway injury during anesthesia: a closed claims analysis.

BACKGROUND: Airway injury during general anesthesia is a significant source of morbidity for patients and a source of liability for anesthesiologists. To identify recurrent patterns of injury, the authors analyzed claims for airway injury in the American Society of Anesthesiologists (ASA) Closed Claims Project database. METHODS: The ASA Closed Claims database is a standardized collection of case summaries derived from professional liability insurance companies closed claims files. All claims for airway injury were reviewed in depth and were compared to other claims during general anesthesia. RESULTS: Approximately 6% (266) of 4,460 claims in the database were for airway injury. The most frequent sites of injury were the larynx (33%), pharynx (19%), and esophagus (18%). Injuries to the esophagus and trachea were more frequently associated with difficult intubation. Injuries to temporomandibular joint and the larynx were more frequently associated with nondifficult intubation. Injuries to the esophagus were more severe and resulted in a higher payment to the plaintiff than claims for other sites of airway injury. Difficult intubation (odds ratio = 4.53, 95% confidence interval [CI] = 2.36, 8.71), age older than 60 yr (odds ratio = 2.97, 95% CI = 1.51, 5.87), and female gender (odds ratio = 2.43, 95% CI = 1.09, 5.42) were associated with claims for pharyngoesophageal perforation. Early signs of perforation, e.g., pneumothorax and subcutaneous emphysema, were present in only 51% of perforation claims, whereas late sequelae, e.g., retropharyngeal abscess and mediastinitis, occurred in 65%. CONCLUSION: Patients in whom tracheal intubation has been difficult should be observed for and told to watch for the development of symptoms and signs of retropharyngeal abscess, mediastinitis, or both.  (+info)

(8/335) Immunocytochemical demonstration of heat shock protein 25 in the rat temporomandibular joint.

The expression of heat shock protein 25 (Hsp 25) was investigated in the rat temporomandibular joint by immunocytochemistry combined with confocal and electron microscopy. Immunostaining with an antibody to Hsp25 was able to demonstrate various cellular elements in the synovial membrane of the joint. Intense immunoreaction for Hsp25 was recognized in certain cells comprising the synovial lining layer. Confocal microscopic observation revealed two characteristic profiles of the Hsp25-positive cells with cytoplasmic processes: one extended thick and long processes towards the articular cavity, and the other prejected horizontally slender processes which covered the synovial membrane. Under the electron microscope, the immunoreactive synovial lining cells were characterized by a well-developed rough endoplasmic reticulum and secretory granules, suggesting that they can be categorized as fibroblastic type B cells. The covering by the cytoplasmic extensions was confirmed by immuno-electron microscopic observations. This cytoplasmic covering presumably performs a barrier function and expedites the effective secretion/resorption of synovial fluids. Since it has been proposed that Hsp 25 is associated with an estrogen receptor, the immunopositive synovial lining cells were considered estrogen-target cells. Immunoreactivity for Hsp25 was also observed in the chondrocytes of the maturative and hypertrophic cell layers as well as in the cells of the articular disk. A suggestion was made that Hsp25 might be involved in the inhibition of apoptosis of those cells.  (+info)