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PubMed1992

Temporomandibular-related pressure thresholds: a model for establishing baselines.

The use of pressure threshold measurement to quantify tender spots and trigger points in muscles is well established. Its application to the field of temporomandibular disorders, however, has been more recent and less widely published. Pressure threshold measurement may be useful to define values for dysfunctional muscles or structures so that changes in muscle condition through a course of treatment can be quantified. Normal values for many muscles in the body have been established, but studies of this type in the masticatory system are limited and have often used a fixed, pre-determined pressure cutoff, rather than measuring thresholds across a number of patients. This pilot study seeks to determine whether normal values exist for the anterior temporalis muscles, the masseter muscles, and the lateral capsules of the temporomandibular joints. Intrarater and interrater reliability in measuring thresholds was also studied with the aim of contributing toward a methodological model for further study.

Adolescent↗
PubMed1996

Alteration in the bite force and EMG activity with changes in the vertical dimension of edentulous subjects.

The bite force and EMG activity of jaw closing muscles were studied at seven different vertical jaw positions around the occlusal vertical dimension (OVD) in 10 edentulous subjects. When the masseteric EMG activity was maintained at constant values (40% and 20% of the maximum activity at the OVD), the bite force increased in proportion to increase of the vertical dimension. On the other hand, when the bite force was maintained at constant values (4 kg and 8 kg), the EMG activities of the jaw closing muscles decreased, with an increase of the vertical dimension. These results indicate that the OVD is not the position at which the most efficient exertion of the bite force is obtained.

Adaptation, Physiological↗
PubMed2001

Excitability of the human trigeminal motoneuronal pool and interactions with other brainstem reflex pathways.

We studied the properties of motoneurones and Ia-motoneuronal connections in the human trigeminal system, and their functional interactions with other brainstem reflex pathways mediated by non-muscular (Abeta) afferents. With surface EMG recordings we tested the recovery cycles of the heteronymous H-reflex in the temporalis muscle and the homonymous silent period in the masseter muscle both elicited by stimulation of the masseteric nerve at the infratemporal fossa in nine healthy subjects. In four subjects single motor-unit responses were recorded from the temporalis muscle. In six subjects we also tested the effect of the stimulus to the mental nerve on the temporalis H-reflex and, conversely, the effect of Ia input (stimulus to the masseteric nerve) on the R1 component of the blink reflex in the orbicularis oculi muscle. The recovery cycle of the H-reflex showed a suppression peaking at the 5-20 ms interval; conversely the time course of the masseteric silent period was facilitated at comparable intervals. The inhibition of the test H-reflex was inversely related to the level of background voluntary contraction. Single motor units were unable to fire consistently in response to the test stimulus at intervals shorter than 50 ms. Mental nerve stimulation strongly depressed the H-reflex. The time course of this inhibition coincided with the EMG inhibition elicited by mental nerve stimulation during voluntary contraction. The trigeminal Ia input facilitated the R1 component of the blink reflex when the supraorbital test stimulation preceded the masseteric conditioning stimulation by 2 ms. We conclude that the time course of the recovery cycle of the heteronymous H-reflex in the temporalis muscle reflects the after-hyperpolarization potential (AHP) of trigeminal motoneurones, and that the Ia trigeminal input is integrated with other brainstem reflexes.

Adult↗
PubMed1995

Ultrastructural finding of vascular degeneration in fibrodysplasia ossificans progressiva (FOP).

The masseter and temporalis muscles were investigated ultrastructurally in 2 patients having fibrodysplasia ossificans progressiva (FOP). Results showed atrophy and necrosis of muscle fibres. Both cases contained cartilage which was calcified in the second case and was associated with degenerating chondrocytes. The blood vessels showed various changes, with haematoma formation and large fibrin deposits. Some of the fibrin deposits seen in the second case were surrounded with cartilage. This suggests that the cartilage probably forms as a reaction to an old haemorrhage. It is possible that the effect of the mutant gene found in FOP is on blood vessels rather than the normal regulatory mechanisms of the inducible osteogenic precursor cells. These degenerating blood vessels often result in haemorrhage and fibrin deposits; the fibrosis, cartilage or bone formation are probably secondary changes. Amianthoid fibres found in the tendon of the temporalis muscles of the second case, together with the other changes of fibrosis and cartilage formation, account for the severe restricted mouth opening suffered by these patients.

Adolescent↗
PubMedDate not supplied

Treatment of muscle spasticity in patients with cerebral palsy using BTX-A: a pilot study.

This study was designed to verify the safety and efficacy of botulinum toxin type A (BTX-A) used as a neuromuscular block on spastic masticatory musculature of children with cerebral palsy. Six patients who had spastic-tetraplegic cerebral-palsy, aged 5 to 20 years were selected. All patients had spasticity of the jaw muscles, bruxism, lower lip trauma, limited mouth opening, and difficulties in cleaning the oral cavity. The patients were sedated under general anesthesia, while the dentist injected the masseter and temporalis muscles bilaterally with 150 and 75 units of BTX-A each. Clinical examinations were conducted at 7, 14, 30, and 90 days after the initial appointment. We found statistically significant decreases in muscle spasticity and bruxism (p = 0.002), improved inter-incisal opening (p = 0.002), improved oral hygiene (p = 0.031), and less lower lip trauma (p = 0.060) after the neuromuscular blocking.

Adolescent↗
PubMed2001

Ascending necrotising fasciitis as a result of odontogenic infection: a report of two cases.

Necrotising fasciitis is a severe soft tissue infection which spreads rapidly through fascial planes, is characterised by soft tissue necrosis and is potentially life-threatening. It is a rare entity in the head and neck region. The management of this condition is difficult and early diagnosis and aggressive surgical and medical management are essential. This paper reports two cases of necrotising fasciitis as a result of ascending odontogenic infection involving the temporalis muscle.

Adult↗
PubMed1994

The intracellular Ca2+ transient and tension in frog skeletal muscle fibres measured with high temporal resolution.

1. The purpose of this study was to determine, with high temporal resolution, the relationship between the intracellular Ca2+ transient (ICT) and the mechanical responses of intact, single skeletal muscle fibres of frogs following stimulation by a single, brief depolarization. 2. The time course of the ICT was monitored using the Ca(2+)-sensitive fluorescent dyes mag-fura-2 (furaptra) and mag-fura-5. The mag-fura dyes have a low affinity for Ca2+ and have been shown to track the ICT with no appreciable kinetic delay. Continuous records of mag-fura fluorescence, tension and stiffness responses were obtained simultaneously at high time resolution at a sarcomere length of 2.9 microns. Experimental temperature was 3 degrees C. 3. When a delay of 0.4 ms due to the low-pass filter associated with the photodetector was included, the onset of the fluorescence response preceded the onset of latency relaxation (the small fall in tension that precedes positive tension generation) by 3.1 +/- 0.2 ms (mean +/- S.E.M., n = 8). After its onset, the mag-fura fluorescence signal continued to change rapidly (indicating increasing intracellular [Ca2+]) to an extreme level that occurred 1.5 +/- 0.5 ms (mean +/- S.E.M., n = 7) before tension had recovered to its resting level following latency relaxation. The time delay from the extreme of the fluorescence signal to the peak of the tension signal was 239 +/- 27 ms (mean +/- S.E.M., n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Electromyographic heterogeneity in the human temporalis and masseter muscles during static biting, open/close excursions, and chewing.

The human temporalis and masseter muscles are not activated homogeneously during static bite force tasks. In this study, we studied the possible existence of regional differences in these muscles under dynamic conditions. Electromyographic (EMG) activity was recorded by means of bipolar fine-wire electrodes. Six electrodes were inserted into the temporalis muscle and three into the masseter muscle. Recordings were made during maximal effort intercuspal and incisal static clenches, open/close excursions from both the intercuspal and incisal positions, and unilateral gum and licorice chewing on right and left sides. The EMG peak amplitudes and the peak occurrences were compared. During the static clenches and the open/close excursions, no differences could be demonstrated between the regions of the temporalis muscle. However, during the chewing tasks, the anterior and posterior regions behaved differently. Throughout almost all tasks, both superficial and deep parts could be distinguished in the masseter muscle. A further division of the deep masseter was task-dependent. In both the temporalis and masseter muscles, maximal activity (100%) was reached during intercuspal clenches. The average activity declined to 35% of the maximal activity in the temporalis muscle, to 47% in the deep, and to 86% in the superficial masseter during incisal clenches. During all chewing tasks, the EMG peak activity of the anterior temporalis and the superficial masseter muscles was higher in the working than in the balancing condition. The general finding was that different regions were preferentially activated, according to task. The detailed regional specialization previously observed during static bite force tasks could not be demonstrated in the present study.

Adult↗
PubMed1997

Jaw movement tremor as a predictor of chewing performance.

The purpose of this study was to investigate normal physiologic tremor in jaw movement as a factor that may influence chewing performance more directly than either muscle activity or jaw displacement. Chewing performance was defined in terms of the reduction in food particle size after 15 chewing strokes. Data on chewing particle size and electromyographic activity were available for 24 asymptomatic adults from an earlier study. Jaw movements during chewing were recorded using electrognathography, and velocity and acceleration in three planes were determined. Power spectrum for acceleration was calculated during opening and closing phases of the chewing cycle. The frequency of the peak amplitude in the power spectrum represented physiologic tremor of the jaw. Tremor frequencies during both opening and closing phases of the chewing cycle were strong predictors of chewing performance. A multivariate model composed of variables derived from acceleration, together with electromyographic and jaw movement variables, produced a multivariate model that was able to predict chewing performance with an adjusted R2 value of .78.

Adult↗
PubMedDate not supplied

Immediate effect of occlusal contact pattern in lateral jaw position on the EMG activity in jaw-elevator muscles in humans.

PURPOSE: The aim of this study was to investigate the effect of experimental alterations of nonworking-side occlusal contacts on jaw-elevator muscle activity. MATERIALS AND METHODS: Individual devices were fabricated to simulate various lateral occlusal relationships. Twelve human subjects were asked to carry out submaximal lateral clenching, and electromyographic (EMG) activity of the masseter and anterior and posterior temporalis muscles was measured. RESULTS: Clenching in a lateral mandibular position under natural conditions induced an activity pattern with a clear dominance of the anterior and posterior temporalis muscles on the working side. Working-side dominance in the anterior temporalis was reduced moderately when an experimental nonworking-side occlusal contact was added. Dominance decreased dramatically when an experimental nonworking-side interference was added. The working-side activity in the posterior temporalis was also reduced dramatically by an experimental nonworking-side interference, but not by a nonworking-side occlusal contact. None of the experimental contact patterns had a significant effect on the masseter activity. CONCLUSION: These results suggest that the nonworking-side occlusal contacts have a significant effect on clenching-induced temporalis muscle activity.

Adult↗
PubMed2001

Myoepithelioma of the palate: a case report.

Myoepithelioma is a rare malignant neoplasm, representing about the 1% of all the salivary gland's tumors. It mainly affects women, particularly in the 7th and 8th decade of life. A case of myoepithelioma of the palate in a 70-year-old woman is described. The tumor was completely excised two years ago. Nowadays, there are no signs of local recurrence and/or distant metastasis. The discrepancy between the histological diagnosis of low-grade malignancy and the clinical aggressive behavior of the tumor is discussed.

Aged↗
PubMed1998

Short-term reproducibility of pressure pain thresholds in masticatory muscles measured with a new algometer.

The purpose of this project was to test the within-day and between-days reproducibility of a new and inexpensive algometer. Twelve symptom-free men and nine women participated. Pressure pain thresholds (PPTs) of the bilateral masseter and temporalis muscles were assessed during four sessions (mornings and afternoons of days 1 and 3). During each session, each palpation point of the masticatory muscles was measured four times. There was an interval of only a few seconds between measurements 1 and 2, and between measurements 3 and 4, respectively, while at least 5 minutes of rest were allowed between measurements 2 and 3. The PPT values between the morning and afternoon sessions and between days 1 and 3 were not significantly different. When the within-session reproducibility for all muscles was considered, only the PPT values between measurements 2 and 4 were not significantly different. Analysis of variance showed that the interindividual variability of PPT was 1.4 to 6.8 times higher than the variability observed within or between sessions and days. No gender difference was found.

Adult↗
PubMed1988

The effects of muscle fatigue on the silent period of the masticatory muscles.

Thirteen healthy adults performed sustained clenching at 50% maximum clenching level judged electromyographically. Electromyograms were recorded from both anterior temporal and masseter muscles during clenching and the silent period latency and duration were measured. As the result of muscle fatigue, the silent period latency significantly decreased, whilst the duration significantly increased up to 3 min from the beginning of clenching.

Adult↗
PubMed1998

Sequential increases in capillarization and mitochondrial enzymes in low-frequency-stimulated rabbit muscle.

To investigate temporal changes in capillarization and increases in mitochondrial enzyme activity, rabbit tibialis anterior muscles underwent chronic low-frequency stimulation for up to 50 days. Capillary density (CD), capillary-to-fiber ratio (C/F), intercapillary distance (ICD), and mean capillary area (MCA), as well as several other parameters of capillarization, were examined. In addition, tissue levels of mRNA specific to vascular endothelial growth factor (VEGF) were assessed by reverse transcriptase-polymerase chain reaction. Citrate synthase (CS) activity, a marker of aerobic-oxidative metabolic potential, was measured in the same muscles. Significant increases in CD and C/F, respectively, and decreases in ICD and MCA were observed after 2 days. These changes reached stable maxima by 14 days. The increases in capillarization occurred in a fiber-type-specific manner, affecting type IId fibers before types IIda and IIa. VEGF mRNA levels increased in a bimodal time pattern with a first elevation (2.5-fold) after 1 day and a second (9-fold) after 6-8 days. Increases in CS were first noted after 8 days. Obviously, increases in capillarization as induced by enhanced contractile activity precede increases in the aerobic-oxidative potential of energy metabolism.

Aerobiosis↗
PubMed2001

Rho-dependent agonist-induced spatio-temporal change in myosin phosphorylation in smooth muscle cells.

Agonist-induced translocation of RhoA and the spatio-temporal change in myosin regulatory light chain (MLC20) phosphorylation in smooth muscle was clarified at the single cell level. We expressed green fluorescent protein-tagged RhoA in the differentiated tracheal smooth muscle cells and visualized the translocation of RhoA in a living cell with three-dimensional digital imaging analysis. The stimulation of the cells by carbachol initiated the translocation of green fluorescent protein-tagged wild type RhoA to the plasma membrane within a minute. The change in MLC20 phosphorylation level after carbachol stimulation was monitored by using phospho-Ser-19-specific antibody recognizing the phosphorylated MLC20 in single cells. Cells expressing the dominant negative form (T19N) of RhoA significantly suppressed sustained MLC20 phosphorylation during the prolonged phase (>300 s), whereas the maximum phosphorylation level (reached at 10 s after stimulation) of these cells was not significantly different from the control cells. The kinetics of RhoA translocation was consistent with that of sustained myosin phosphorylation, suggesting the involvement of a RhoA pathway. Carbachol stimulation increased myosin phosphorylation within a minute both at the cortical and the central region. On the other hand, during prolonged phase, myosin phosphorylation was sustained at the cortical region of the cells but not at the central fibers. A myosin light chain kinase-specific inhibitor, ML-9, diminished myosin phosphorylation at the central region of the cells after the stimulation but not at the cortical area. On the other hand, Y-27632, a Rho kinase-specific inhibitor, diminished myosin phosphorylation at the cortical region but not the central region. The results clearly show that the myosin light chain kinase pathway and the Rho pathway distinctly change myosin phosphorylation in smooth muscle cells in both a temporal and spatial manner.

Animals↗
PubMed2002

Masticatory performance in patients with myasthenia gravis.

Masticatory muscle electromyograms (EMGs) were recorded while patients with bulbar myasthenia gravis chewed artificial food and compared with those of patients with ocular myasthenia gravis, patients in clinical remission who had previously suffered from bulbar myasthenia gravis and healthy individuals. Masticatory performance and EMGs were significantly smaller in the bulbar group. There were no indications of subclinical masticatory muscle weakness in patients with bulbar myasthenia gravis in remission and in patients with ocular myasthenia gravis. Patients with bulbar myasthenia gravis barely compensated for muscular weakness by chewing at a higher percentage of their maximal EMG. These quantitative findings, when combined with subjective reports of masticatory muscle weakness, show that a need to support the jaw is characteristic of patients with bulbar myasthenia gravis who produce low EMG activity.

Adult↗