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PubMed1989

Guidelines for the examination and diagnosis of temporomandibular disorders.

These guidelines propose performance criteria for the history and examination of patients with temporomandibular (TM) disorders. Pertinent diagnostic subcategories are identified, and the comprehensive history and review of systems are described. The examination procedures include documentation of temporomandibular and craniocervical range of motion, TM joint sounds, and the recording of muscle and joint tenderness. The TM disorders addressed include muscle problems such as myalgia, protective splinting or trismus, spasm, myositis, dyskinesia, muscle contracture, hypertrophy, and bruxism. Temporomandibular joint disorders addressed include disk-condyle incoordination, restricted condyle translation, open condyle dislocation, arthralgia, osteoarthritis, polyarthritis, and traumatic joint injury. Disorders of mandibular mobility such as ankylosis, adhesions, fibrosis, skeletal obstruction, and hypermobility are also described. Finally, disorders of maxillomandibular growth, including masticatory muscle hypertrophy, atrophy, neoplasia, maxillomandibular hypoplasia, condylar agenesis, maxillomandibular hyperplasia, and condyle hypertrophy are described.

Humans↗
PubMed2003

Longitudinal outcome of temporomandibular disorders: a 5-year epidemiologic study of muscle disorders defined by research diagnostic criteria for temporomandibular disorders.

AIMS: To investigate the course of myofascial pain defined by Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) over a period of 5 years, and to identify prognostic factors from baseline data. METHODS: Subjects were 155 consecutive patients and 80 community cases identified from an age-stratified representative population sample; all met the primary selection criterion of reporting pain in the temporomandibular joint (TMJ) or masticatory muscles. The 2 groups were combined to yield a total sample of 235 subjects (50 male, 185 female; mean age = 39 years). Subjects were evaluated at baseline, 1 year, 3 years, and 5 years by trained examiners using standardized, reliable methods. Psychological and behavioral factors were assessed by self report. RESULTS: According to RDC/TMD criteria, 50 (31%) of the 165 subjects presenting with myofascial pain (MFP) at baseline continued to have their disorder over a period of 5 years; 55 (33%) remitted, and 60 (36%) were recurrent cases. Bivariate statistics and multivariate logistic regression analyses indicated that baseline pain frequency, number of painful palpation sites, and total number of body sites with pain were significant predictors of persistent vs remitted and recurrent cases. No predictors that distinguished remission vs recurrence could be identified. Thirty subjects from the 70 without a diagnosis of MFP at baseline developed a new MFP. A high baseline somatization score (without pain items) was a significant risk factor for onset of MFP. CONCLUSION: Muscle disorders classified by RDC/TMD are predominantly chronic or fluctuating pain conditions, with a modest probability (31%) of remission.

Adolescent↗
PubMed1995

Muscular and osseous anatomy of the primate anterior temporal fossa and the functions of the postorbital septum.

Many adaptive explanations for anthropoid origins incorporate hypotheses regarding the function of the postorbital septum. Two hypotheses are evaluated here: Cachel's ([1979b] Am. J. Phys. Anthropol. 50:1-18) hypothesis that the anthropoid postorbital septum evolved to augment muscle attachment area in the anterior temporal fossa and Cartmill's ([1980] in RL Ciochon and AB Chiarelli (eds.): Evolutionary Biology of the New World Monkeys and Continental Drift. New York: Plenum, pp. 243-274.) hypothesis that the septum evolved to insulate the foveate eye of haplorhines from movements in the temporal fossa during mastication. Dissections of the masticatory muscles of 55 species of primates, with emphasis on the anatomy of the anterior temporal fossa, reveal that in all anthropoids the temporal muscles take origin from the portion of the septum formed by the frontal bone. In some platyrrhines this muscle is anterior temporalis, and in others it is zygomatico-mandibularis. In tarsiers and most platyrrhines, muscle attachment to the zygomatic portion of the postorbital septum is very restricted (and of possibly varying homologies), whereas in catarrhines the zygomatico-mandibularis arises from the postorbital ridge on the zygomatic portion of the septum. This suggests that, contrary to Cachel's hypothesis, the earliest anthropoids did not have extensive areas of muscle attachment on the postorbital septum, a suggestion supported by the bony morphology of Catopithecus browni. Dissections also indicate that in all haplorhines the anteriormost temporal fibers curve around the postorbital septum between origin and insertion, implying that, were the septum not present, the anterior temporal muscles would disturb the orbital contents when contracting. This suggests that insulation may have been the septum's original function, even in the absence of a retinal fovea. In anthropoids, the rostral migration of the line of action of the anterior temporal muscles relative to the eye is attributed to their possession of extreme degrees of both orbital frontation and convergence; in tarsiers it is attributed to their possession of both massively hypertrophied eyes and moderately convergent and frontated orbits. It is argued that the postorbital septum is most likely to have evolved in a morphological context similar to that exhibited by omomyids.

Animals↗
PubMed1995

Premotor neurons for trigeminal motor nucleus neurons innervating the jaw-closing and jaw-opening muscles: differential distribution in the lower brainstem of the rat.

The distribution of premotor neurons for trigeminal motor nucleus neurons innervating the jaw-closing and jaw-opening muscles was examined in the lower brainstem of the rat by using retrograde and anterograde labeling techniques. First, Fluorogold, a fluorescent retrograde tracer, was injected into the dorsolateral or ventromedial division of the trigeminal motor nucleus, each of which contains motoneurons innervating the jaw-closing or jaw-opening muscles, respectively. Second, Phaseolus vulgaris-leucoagglutinin, an anterograde tracer, was injected into each of the lower brainstem sites, where clusters of retrogradely labeled premotor neurons had been seen in the first set of experiments. Third, after injection of the anterograde tracer into a lower brainstem site, followed by injection of the retrograde tracer cholera toxin B subunit into a masticatory muscle, termination of anterogradely labeled axons onto retrogradely labeled motoneurons was confirmed with the aid of a confocal laser-scanning microscope. It was found that the premotor neurons distributed in the mesencephalic trigeminal nucleus, medial part of the parabrachial region, supratrigeminal region, and dorsal parts of the principal sensory, oral spinal and interpolar spinal trigeminal nuclei project preferentially to the dorsolateral division of the trigeminal motor nucleus, whereas those in the lateral part of the parabrachial region, intermediate parts of the principal sensory, oral spinal and interpolar spinal trigeminal nuclei, and alpha part of the gigantocellular reticular nucleus project preferentially to the ventromedial division of the trigeminal motor nucleus. The dorsal and lateral parts of the medullary reticular formation and the medullary raphe nuclei contain premotor neurons of both types. Group k motoneurons, a cluster of trigeminal motoneurons that innervate the tensor tympani muscle, receive projection fibers predominantly from the dorsolateral part of the oral pontine reticular formation.

Animals↗
PubMed2006

Variability of centric relation position in TMD patients.

Reproducibility of the centric relation position for patients with temporomandibular disorders (TMD) is not documented in the current literature. It was the objective of this study to assess clinical variability of the centric relation position for TMD patients with a muscle-determined technique by means of an anterior deprogramming device, the leaf gauge. A sample of 60 patients with signs of TMD was selected, 8 men (Mean age 28,6, SD 5,2) and 52 women (Mean age 30,5, SD 10,1). All patients were examined with the Research Diagnostic Criteria, including pain on movement and/or function, mouth opening, joint sounds and palpation of masticatory muscles. All 60 patients were allocated to one of the following diagnostic subgroups: myofascial pain, disk displacement with reduction, disk displacement without reduction, osteoarthritis, trauma. Twelve control subjects were taken from a previous study. Three sequential centric relation records were taken; the first one was used to mount a set of casts to an articulator. Criteria of precision were formulated beforehand: 2 out of 3 centric relation records had to be identical in a split-cast procedure. Variables XL and XR represented mandibular displacement in the sagittal plane, variables YL and YR in the transversal plane, and ZL and ZR in the vertical plane, on the left and right condylar level respectively. Variables XMIN, YMIN and ZMIN represented the minimal sagittal, transversal and vertical displacement left or right respectively. Likewise, variables XMAX, YMAX and ZMAX represented the maximal sagittal, transversal and vertical displacement left or right. XDIFF, YDIFF and ZDIFF represented the difference between the minimal and maximal values of X, Y and Z. The diagnostic subgroup trauma was excluded, because there was only one patient. The null-hypothesis of no between-group differences in within-subject and total variability was tested with an analysis of variance (ANOVA). The level of significance was set at 0.05. To minimize type I errors caused by multiple testing Scheffe's test was used to maintain an overall significance of 0.05. No significant difference between patients and control subjects could be found for variables XL, XR, YL, YR, ZR and ZL. Variables XMIN, YMIN, ZMIN, XMAX, YMAX, ZMAX, XDIFF, YDIFF and ZDIFF showed no significant differences. Scheffe's testing for the variables XL, XR, YL, YR, ZL and ZR, as well as the variables XMIN, YMIN, ZMIN, XMAX, YMAX, ZMAX, XDIFF YDIFF and ZDIFF showed no significant differences. The results of this study suggest no variability in centric relation position between TMD-patients and control subjects by means of the leaf gauge.

Adult↗
PubMed1999

Involuntary movements and abnormal spontaneous EMG activity in syringomyelia and syringobulbia.

OBJECTIVE: To describe different types of involuntary movements and abnormal spontaneous electromyographic (EMG) activity in patients with syringomyelia. BACKGROUND: A comprehensive study on involuntary movements in patients with syringomyelia has not yet been undertaken, to these authors' knowledge. METHODS: One hundred adult patients with syringomyelia were examined over the last 15 years. Involuntary movements were videotaped and evaluated by two independent observers. Electromyographic recordings were made using bipolar surface electrodes. The H-reflex recovery curve was obtained after stimulation of the median nerve at the elbow and recording from the flexor carpi radialis. RESULTS: Involuntary movements or abnormal postures were observed in 22 patients. Three patients showed segmental spinal myoclonus, nine minipolymyoclonus, and four propriospinal myoclonus. Five patients had unilateral or bilateral hand postural tremor (8-10 Hz). Focal or segmental dystonia was observed in three patients. Electromyography showed spontaneous bursts of grouped action potentials synchronous in muscles innervated by the same spinal segment, synchronous firing of neurogenic motor unit potentials, or continuous motor unit activity. Increased H-reflex responses to conditioning stimuli were found in patients with spinal myoclonus. Long latency responses were obtained during peripheral nerve stimulation in four patients. Four patients had rigidity and abnormal upper limb posture. Respiratory synkinesis was observed in three patients. One patient developed inverse masticatory muscle activity. CONCLUSIONS: Patients with syringomyelia showed a wide spectrum of involuntary movements. An increased excitability of spinal motor neurons was probably the basic underlying mechanism.

Adolescent↗
PubMed2001

Nutrition and oral health.

Reduced chewing function in community-dwelling older people with adequate general health is linked to having fewer than 20 teeth present or to wearing removable dentures. By chewing for longer periods of time or swallowing larger food particles they are normally able to compensate for the impaired function. The masticatory function can be restored by adequate prosthetic therapy, which results in increased activity of the masticatory muscles during chewing and reduces the chewing time and the number of chewing strokes until swallowing. In frail or dependent elderly people undernutrition is prevalent because of health problems, reduced appetite and poor quality of life. Poor oral health and xerostomia are often associated with a reduced body mass index and serum albumin level and the avoidance of difficult-to-chew foods. Maintenance or re-establishment of masticatory function is an integral part of the medical health care of these patients, with the aim of improving their nutritional status and quality of life.

Aged↗
PubMed2002

A telemetry system to chronically record muscle activity in middle-sized animals.

Radio-telemetry enables the long-term recordings of biopotentials that may be obtained in freely moving animals without interference by the experimenter. The purpose of this study was to test a fully implantable device for: (1) its transmission range; (2) the characteristics of the transmitted signals; and (3) its actual application in long-term in vivo registration of EMG. Transmission range was tested by changing the device's position relative to the receiver. Computer simulation of the filtering characteristics provided comparison of original and transmitted signals. Implantation of the device in masticatory muscles, followed by analysis of telemetred signals and determination of activity levels allowed for examination of daily muscle use. The implant's transmission range covered the cage size for middle-sized animals with a minimum of signal dropouts. Transmitted signals were marked by (partial) loss of frequencies beyond 50 Hz, decreased amplitude and slightly delayed timing relative to original waveforms. Analysis of the transmitted EMG revealed that the device can be used for prolonged in vivo EMG registration, detection of peak activity levels, and the examination of general muscle use by the time spent at different levels of activity.

Animals↗
PubMed2000

The effect of surgical treatment of the temporomandibular joint: a survey of 70 patients.

Most patients with temporomandibular disorders (TMD) can be successfully treated by conservative methods, but approximately 10-20 percent have persistent symptoms. The aim of this study was to evaluate the signs and symptoms of TMD in patients treated with open surgery of the TMJ. Seventy-two patients (13 men, 59 women, mean age 37 years, range 14-68 years) were evaluated during an eight-year period. Altogether 45 right TMJs and 39 left TMJs were treated, including both TMJs during the same operation in eight of the cases. The patients were evaluated at follow-up in 1997. The degree of TMD at follow-up was assessed using the anamnestic and clinical dysfunction Helkimo indices. Most of the patients reported at the follow-up that they were subjectively satisfied with the surgical treatment. The main clinical findings in the post surgical patients at follow-up were TMJ sounds and deviation of the mandible during opening. The tenderness in the masticatory muscles and TMJs on palpation was reduced significantly and the ranges of mandibular movement were improved for all the patients. The mean anamnestic and clinical indices decreased with a statistical significance from the shortest follow-up group (Group I) to the longest on group (Group IV) (p = 0.000). The conclusion of this study was that after open surgical treatment of the TMJ, the patients have significantly better functioning of the masticatory system and reduced signs and symptoms of TMD in the long term.

Adolescent↗
PubMed1997

Excitability of the central masticatory pathways in patients with painful temporomandibular disorders.

Much is unclear about the pathophysiological mechanisms underlying painful temporomandibular disorders. In addition to various other theories, masticatory muscle dysfunction and pain have also been attributed to primary central nervous system hyperactivity. We assessed this possibility in a study using recent neurophysiological techniques. From among outpatients whose diagnosis of temporomandibular disorders had been obtained in stomatognathic facilities, we studied 10 patients with bilateral pain and 15 patients with unilateral pain, in whom electromyographic examination of the trigeminal reflexes disclosed normal findings except for absence or amplitude asymmetry of the jaw jerk. Transcranial magnetic stimulation yielded masseter motor evoked potentials of normal latency and amplitude, but five patients had to exert a near-maximum contraction to obtain their responses. The masseter silent periods elicited by the double-shock technique recovered normally. Because these tests measure the excitability of the masticatory system (including motor cortex, corticobulbar and corticoreticular connections, reticular interneurones and lower motoneurones), the lack of facilitation in these patients' responses excluded central hyperactivity as the primary cause of their masticatory dysfunction and pain.

Adult↗
PubMed1999

Masseter muscle volume measured using ultrasonography and its relationship with facial morphology.

The aims of this study were to measure the volume, cross-sectional area, thickness, width, and length of contracted masseter muscles in a sample of adults, four males and six females, using three-dimensional (3D) ultrasonography, and to correlate these measurements with the variations in facial morphology of the sample. The scans were carried out bilaterally using a hand-held probe carrying a magnetic positional sensor, which enabled a computer to reconstruct the images into a 3D array of slices. Measurements were made by the computer from the reconstructed images using specially written software. Cephalometric analysis initially involved seven angular, eight linear, and two proportional variables, but as these were strongly inter-dependent, the variables were reduced to four principal components prior to statistical comparison with the mean muscle variables. The values found for muscle volume, cross-sectional area, and thickness were broadly consistent with those of previous investigators. Volume showed a significant, negative correlation with mandibular inclination including gonial angle (P < or = 0.001), and a significant, positive correlation with total posterior face height and ramus height (P < or = 0.001), and lower posterior face height percentage (P < or = 0.01). Weaker correlations were found for length and thickness. While the results support existing evidence that large masticatory muscles are associated with brachycephalism and vice versa, a cautious interpretation is necessary in view of the small sample size. The 3D ultrasonography system is at an experimental stage and requires further development and evaluation.

Adolescent↗
PubMed1995

Ultrastructural basis for synaptic transmission between jaw-muscle spindle afferents and trigeminothalamic neurons in the rostral trigeminal sensory nuclei of the rat.

Trigeminothalamic neurons were retrogradely labeled by injection of horseradish peroxidase into the ventroposteromedial nucleus of the thalamus in rats. Jaw-muscle spindle afferent axons were then physiologically identified and intracellularly stained with biotinamide. The ultrastructure of labeled spindle afferent boutons was then studied in the caudolateral supratrigeminal region (Vsup) and dorsomedial trigeminal principal sensory nucleus (Vpdm). A total of 418 stained spindle afferent boutons were identified in Vsup and Vpdm; approximately 75% of these synapsed with dendrites, 10% synapsed with somata, and 15% synapsed with axons. Most jaw-muscle spindle afferent boutons were postsynaptic to unlabeled P-type boutons. Reciprocal synapses between spindle afferent boutons and unlabeled boutons were occasionally observed. A few dendrites in Vsup and Vpdm received synapses from multiple spindle afferent boutons. Conversely, some large (from 3 x 6 to 4 x 8 microns) and giant (from > 4 x 8 to 5 x 10 microns) spindle afferent boutons simultaneously contacted two to five dendrites and/or somata. Jaw-muscle spindle afferent boutons also formed synapses with retrogradely labeled trigeminothalamic neurons in Vsup and Vpdm. Numerous unlabeled S-and F-type boutons converged onto the same trigeminothalamic dendrite or soma contacted by a spindle afferent bouton. A small number of synaptic triads consisting of an unlabeled P-type bouton, a spindle afferent bouton, and either a dendrite or soma were also encountered. These data indicate that sensory feedback from the masticatory muscles is subject to presynaptic inhibition and integration prior to reaching the thalamus. This pathway is likely to be important in the relay of proprioceptive and kinesthetic information from the muscles of mastication to the thalamus.

Afferent Pathways↗
PubMed1996

The effect of propranolol on sleep bruxism: hypothetical considerations based on a case study.

The purpose of this study was to investigate the effect of the beta-adrenergic antagonist, propranolol, on the nocturnal masseter muscle activity of a heavy sleep bruxist. Three all-night polysomnographic registrations were performed with bilateral masseter muscle EMG recordings. The first night study served as the baseline night, the second night registration was performed after total sleep deprivation and the third night registration was made with propranolol. Sleep deprivation decreased the masseter contraction (MC) index by 61% and propranolol by 72% when compared to the level of the baseline night. This preliminary observation is in line with our hypothesis suggesting a link between autonomic regulation of circulation and rhythmic activation of masticatory muscles, especially when associated with body movements during sleep.

Adrenergic beta-Antagonists↗
PubMed1999

[The changes of chewing ability after orthognathic therapy: electromyographic analysis]

OBJECTIVE:The maxillo-facial skeletal deformity can only be corrected through orthognathics that consists of orthodontics and operation.There are various changes in aspect of the bite relationship between upper and lower dentition after orthognathic surgery.The change feature of the chewing efficiency of oral maxillary system can be detected through comparing studying of the contracti on force of chewing muscles before and after surgical operation.METHODS:All 6 patients in this research were diagnosed to be skeletal crossbite.Electromyogram was used to test the change of activity of superficial masseter,temporalis and digastrics.The examination was carried out 1 week before operation and 3 months after the operation. RESULTS:When mandibular is in its rest status,there is no significant difference in the change of muscular activities.when it is active,there is significant difference. CONCLUSION:The chewing ability of masticatory muscles is reduced after orthognathic surgery.The result indicated that there is a negative bite relationship between the upper and lower dentition,the occlusion relationship needs accurate adjustment for gaining stability of oral maxillary system.Therefore,orthodontics after operation is of vital importance.

Journal Article↗
PubMed2006

Impact of post-synaptic block of neuromuscular transmission, muscle unloading and mechanical ventilation on skeletal muscle protein and mRNA expression.

To analyse mechanisms of muscle wasting in intensive care unit patients, we developed an experimental model where rats were pharmacologically paralysed by post-synaptic block of neuromuscular transmission (NMB) and mechanically ventilated for 9+/-2 days. Specific interest was focused on the effects on protein and mRNA expression of sarcomeric proteins, i.e., myosin heavy chain (MyHC), actin, myosin-binding protein C (MyBP-C) and myosin-binding protein H (MyBP-H) in fast- and slow-twitch limb, respiratory and masticatory muscles. Muscle-specific differences were observed in response to NMB at both the protein and mRNA levels. At the protein level, a decreased MyHC-to-actin ratio was observed in all muscles excluding the diaphragm, whereas at the mRNA level a decreased expression of the dominating MyHC isoform(s) was observed in the hind limb and intercostal muscles, but not in the diaphragm and masseter muscles. MyBP-C mRNA expression was decreased in the limb muscles, but it otherwise remained unaffected. MyBP-H conversely increased in all muscles. Furthermore, we found myofibrillar protein and mRNA expression to be affected differently when comparing NMB animals with peripherally denervated (DEN) ambulatory rats. We report that NMB has both a larger and different impact on muscle, at the protein and mRNA levels, than DEN has.

Animals↗
PubMed1995

[The relationships between the EMG excitation pattern of the masseter muscle and the facial skeletal morphology].

The purpose of this study was to investigate the correlations between malocclusions and the electromyographic activity of the orofacial muscles as this activity reveals itself through multi-channel, simultaneous recording of surface potentials from the masseter muscle. Thirty adults with class II or class III malocclusion formed the study's patient base. Surgical correction of the anomaly was planned for all patients. Ten patients served as the control group. In addition to the standard diagnosis, EMG were recorded during various stress situations such as maximal intercuspidations, chewing, swallowing, and mandible protrusion. We obtained a so-called "myomap" by means of the simultaneous multi-channel recording of the surface potential of the right masseter. Comparison of the EMG revealed a higher activity from the masticatory muscles in the class II cases than in the class III cases. The analysis of the masseter excitation pattern brought to light interesting differences. A higher activity on the lower margin of mandible in the area of the superficial part of masseter was found in the class II cases, whereas contrary to this an increase in EMG activity was found above the deep part of masseter in class III cases. The differing distribution of excitation of the 2 parts of the muscle in class II and class III malocclusions confirms the correlation between muscle function and morphology.

Adolescent↗
PubMed1987

Effects of maternal food restriction during lactation on craniofacial growth in weanling rats.

Adult Holtzman rats were submitted during suckling period to a food restriction with or without protein or carbohydrate restoration. Twenty-one-day-old weanling pups were compared with controls of 9, 13, 17, and 21 days of age. Lateral craniofacial roentgenographies were taken. The length in midsagittal plane of each bone and its angle with respect to the vestibular line were measured in males. In females, the brain and the left masseter muscle were weighed, and the muscle/brain ratios (neuromuscular index) were calculated. Food restriction altered skull size and shape. Size changes were due to arrested lengths in all studied skull bones. Shape variation was evident by orthocephalization changes, reflected in angulation changes of bones belonging to the frontoethmofacial (frontal, nasal, and maxillary bones) and to the occipitointerparietal (interparietal bone) complexes. Partial restorations by both protein or carbohydrate supplementation were found. Nutritional stresses during lactation affected orthocephalization through an altered growth ratio between two soft tissues functionally associated to the craniofacial complex: brain and masticatory muscles.

Aging↗