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PubMed1999

Technical developments in intra-operative monitoring for the preservation of cranial motor nerves and hearing in skull base surgery.

Although EMG recordings from mimic muscles have become the standard for intra-operative facial nerve monitoring, few data are available concerning other motor cranial nerves (MCN). Auditory brainstem responses (ABR) are a proven tool for intra-operative hearing preservation, but have their limitations, suggesting the application of supplementary methods. This paper describes new developments of MCN and cochlear nerve monitoring in skull base surgery. Up to 2 x 8 EMG channels were recorded after bipolar stimulation of MCN using concentric coaxial probes. A special software enabled event-dependent registrations of all signals exceeding a definable threshold level. Selective recordings from masticatory muscles (N.V) were obtained using rectangular Teflon-insulated needle electrodes. For oculomotor (Nn.III/ VI) nerve recordings bipolar needle electrodes were precisely placed by orbital ultrasound guidance. Lower cranial nerves were monitored inserting needle electrodes into the soft palate (N.IX), tongue (N.XII) and vocal muscles (N.X) during laryngoscopy using a special applicator. For ABR recordings, click stimuli (95 dB HL) were applied monaurally through insert earphones. Electrocochleography was simultaneously recorded as a near-field potential without averaging after promontory (transtympanic) electrode placement using otomicroscopy. Regarding the ABR biosignal, a characteristic response pattern was detected following bipolar electrical stimulation of the auditory nerve possibly useful for its intra-operative identification.

Cochlear Nerve↗
PubMed1996

Ultrasonographic assessment of the swelling of the human masseter muscle after static and dynamic activity.

Work-related fatigue, pain and disorders in skeletal muscles have been related to prolonged static and dynamic activity. Such contractions have been shown to impair blood flow and increase muscle thickness and fluid. In the present study the effect of static and dynamic activity was evaluated from changes in masseter thickness as a measure of oedema, simultaneously with assessment of perceived pain/discomfort and cardiovascular responses. As static activity, fourteen young healthy women bit at 15% maximal voluntary contraction on bite-force transducers in the molar regions until exhaustion or 20 min at maximum (median endurance time 7.1 min). For dynamic activity, the same individuals chewed gum unilaterally until exhaustion or 40 min at maximum (all endured 40 min) with a cycle time of 725 ms, an average load of 9.3% of maximal electromyographic activity (maxEMG) and a peak mean voltage of 54.3% of maxEMG. Muscle thickness was measured by ultrasonography at the mid-portion of the ipsilateral masseter. Immediately after exercise, muscle thickness was significantly increased, more after static (14.0%) than dynamic (8.6%), and returned to pre-exercise values after 20-min recovery. Visual analogue scales (VAS) revealed the concomitant occurrence of pain (static 11.9 VAS%; dynamic 5.9 VAS%), and discomfort (static 8.1 VAS%; dynamic 5.9 VAS%), and both sensations decreased to pre-exercise values after 20-min recovery. Systolic blood pressure increased significantly, more during static (12.5%) than dynamic activity (4.3%), whereas heart rate rose significantly only during dynamic exercise (13.3%). Hence, activity was associated with muscular swelling and pain, and, despite the relatively small size of the masticatory muscles, also with general cardiovascular responses.

Adult↗
PubMed1986

Effect of sleep position on sleep apnea and parafunctional activity.

Parafunctional activity (toothgrinding, toothclenching and bruxism) is a common problem which may lead to masticatory muscle and temporomandibular joint pain, and may result from sleep arousal or disturbances. Sleep apnea is another common sleep disorder which results in disrupted sleep architecture and frequent arousals. Because sleep apnea leads to sleep arousals, and because sleep arousals are thought to result in increased parafunctional activity, we undertook the present study to determine the relationship between sleep apnea and parafunctional activity. We were also interested in assessing the effects of sleep posture on sleep disordered breathing and parafunctional activity. We prospectively studied 24 patients who were referred to the clinical sleep apnea laboratory for study. They underwent standard nocturnal polysomnographic examination; in addition, masticatory activity was measured with a masseter electromyogram. Patients slept in the supine and lateral decubitus positions. Nocturnal clenching was slightly higher in patients with sleep apnea than those without (12.2 vs 7.6 clenches/hr, p = 0.18), and there was a correlation between the clench index (CI) and apnea plus hypopnea index (A + HI) by linear regression (r = 0.49, p less than 0.05). There were significant falls in both the A + HI (64.4 +/- 28.8 vs 36.5 +/- 36.7, p = 0.02) and CI (12.5 +/- 12.1 vs 7.0 +/- 8.6, p = 0.04) in the lateral decubitus vs supine sleeping positions. We conclude that there is an association between obstructive sleep apnea and parafunctional activity, that sleep position affects the incidence of both sleep disordered breathing and parafunctional activity, and that analysis of apneas and hypopneas in both supine and lateral decubitus sleeping positions may be helpful.

Adolescent↗
PubMed1992

Discrimination of clenches at varied jaw positions using autoregressive model coefficients of myoelectrical activities of anterior temporal and masseter muscles.

During 10% maximum clenching at intercuspal, protruded, retruded contact and lateral positions, the surface electromyograms (EMG) of bilateral anterior temporal and masseter muscles of 20 normal subjects with intact natural dentitions were recorded. The autoregressive (AR) model of the sampled EMG was then built and the obtained coefficients of the AR model were accepted as featured parameters of the EMG. Finally Bayes' stepwise discriminant analysis was used for establishing discriminant functions of estimating low level clenches at varied jaw positions. It was found that total conformation rates of internal and external sample substitution (15 and 5 subjects) were 82.67% and 78% respectively; the discriminant effect between intercuspal and retruded contact position was not up to predicted standard. The results indicate that AR model coefficients may describe the characteristics of surface EMG of masticatory muscles and easily be used in multiple statistical analysis, from which the classification and diagnosis may be taken.

Adult↗
PubMed1992

Sleep movements in teethgrinders.

To investigate the nocturnal motor activity associated with teethgrinding, 12 patients and 12 controls were recorded during sleep with the masseter muscle electromyogram (EMG) and the static charge-sensitive bed movement sensor. The frequency of body movements per hour was 21.4 in the teethgrinders and 14.0 (P less than .05) in the control group. The movement time was 87.4 seconds per hour in the teethgrinders and 55.2 seconds per hour (P less than .01) in the controls. The differences were most obvious in the body movements with temporal association to EMG elevation during the first stage of sleep. The number of isolated EMG elevations showed great interindividual variation and did not differ between groups. The teethgrinders complained more frequently of delayed sleep onset and daytime tiredness. The data suggest that the motor disturbance of teethgrinding is not limited to masticatory muscles but is manifested also as increased general body movement activity.

Adult↗
PubMed1986

Results obtained from patients referred for the investigation of complaints related to oral galvanism.

One hundred consecutive patients, 74 women and 26 men, aged between 18 and 83 years (mean = 54.8 years), referred with complaints related to oral galvanism were investigated and treated and the treatment results were evaluated after 2-3 years. Forty of the patients reported facial pain, pain from the teeth, temporomandibular joints (TMJ) and masticatory muscles and TMJ clicking and locking and 26 reported headache. Smarting in the oral mucosa, smarting of the tongue and xerostomia were reported by 26, 21 and 24 patients, respectively, and 30 patients reported an unpleasant taste, a metallic taste or a battery taste. The same patient often reported several symptoms. The patients also reported various general symptoms, above all joint symptoms, pain in the back, neck and shoulders and general muscular pain but also tiredness, weakness, difficulty in concentrating, depression and insomnia. After clinical and radiological examination, salivary tests, determination of the maximum galvanic current at metallic contacts and screening for contact allergy to dental materials, various oral diagnoses could be established. Most of the patients exhibited functional disturbances of the masticatory system, periodontitis, smarting of the oral mucosa, xerostomia, pulpitis and pulpal necrosis and mucosal lesions. The medical illnesses the patients reported themselves to be suffering from or had been treated for included cardiovascular disorders, high and low blood pressure, asthma, rheumatic disorders, diabetes, pernicious anaemia, gastritis and peptic ulcer. Seventy-six patients took drugs regularly. In most cases there were several oral, dental and medical explanations for the symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2003

Sex differences in rabbit masseter muscle function.

The proportions of fibers of different phenotypes in the rabbit masseter muscle differ strikingly in adult males and females. Muscles from females contain similar proportions of small fibers that express both the slow/beta and cardiac alpha myosin heavy chain (MyHC) isoforms and larger fibers containing the IIa MyHC isoform. In muscles from males, nearly 80% of fibers are of the IIa phenotype. To evaluate the functional significance of these sex differences, we used finely graded intramuscular microstimulation to study the contractile properties of masseter motor units in >6-month-old male and female rabbits. Twitch forces and torques in males were significantly greater in magnitude than those of females. Greater proportions of units that produced larger forces/torques were encountered in the males. The same motor units produced force or torque more rapidly in males than in females, principally because units in which twitch rise times were >22 ms were found only in females. The forces applied to the mandible and the torques generated about the right mandibular condyle were studied during cortically evoked rhythmic activation of the masticatory muscles. The overall range of torque rise times and the magnitudes of the peak torques did not differ between sexes. The mean rise time was significantly shorter and the mean peak torque was significantly greater in males. We conclude that sex differences in fiber phenotype proportions are reflected in sex differences in motor unit properties and in the function of these motor units during rhythmic activation.

Animals↗
PubMed1981

A preliminary field trial to evaluate the use of immunisation for the control of naturally acquired Taenia saginata infection in cattle.

The efficiency of immunisation of cattle with antigens collected during 14-day in vitro cultivation of Taenia saginata or T hydatigena oncospheres for the control of naturally acquired bovine cysticercosis was tested on a farm which uses sewage effluent to irrigate pasture. A total of 260 first-calf heifers of mixed breed were divided into four groups which were either sham-vaccinated or vaccinated with T saginata antigen at 49 to 124 days or 16 to 91 days before calving or vaccinated at 49 to 124 days prepartum with T hydatigena antigen. Ten calves from each group were killed at about three months of age and all muscles, including heart, tongue and oesophagus, were examined for cysticerci. Precalving vaccination with T saginata antigen significantly reduced the number of cysticerci found. Calves from sham-vaccinated cows were either sham-vaccinated or vaccinated with T saginata antigen or T hydatigena antigen at 46 to 121 days olds. Calves from cows immunised with T saginata antigen were either sham-vaccinated or immunised with T saginata antigen. Calves from cows injected with T hydatigena antigen were either sham-vaccinated, vaccinated once with T hydatigena antigen when 46 to 121 days of age or vaccinated twice with T hydatigena antigen at median ages of 65 days and 99 days. All these calves were killed at 13 to 14 months old and their heart, diaphragm, tongue and masticatory muscles examined for cysticerci. Of the 38 surviving sham-vaccinated calves from sham-vaccinated cows, 21 animals (55 per cent) were infected. Several of the vaccination regimes reduced this rate of infection significantly but the most effective was precalving vaccination of the cow and vaccination of the calf with T saginata antigen which reduced infection by 78 per cent compared with the controls. Precalving vaccination of cows with T hydatigena antigen together with double vaccination of their calves with the same antigen preparation also significantly reduced infection in the calves by 64 per cent.

Animals↗
PubMed1995

Statistical analysis of differential lissajous EMG from normal occlusion and Class III malocclusion.

The method of differential lissajous electromyography (DL-EMG) was applied to investigate the relationship among the integrated EMG activity, timing, and coordination of the bilateral superficial anterior temporal and masseter muscle activities in normal occlusion and Class III malocclusion subjects. In both Class III malocclusion and normal occlusion subjects, the working side muscles showed a higher mean cumulative voltage (MCV) and mean maximum peak voltage (MMPV) compared with the balancing side. In addition, a higher MCV and MMPV of the working side masseter was observed in the normal occlusion group compared with that seen in the Class III group during both right and left side chewing (p < 0.01). Discriminant analysis applied to examine the distribution, the size and the shape of DL-EMG pattern further indicated a statistical difference between subject groups (p < 0.01). Finally, there was a significantly higher percentage of clockwise DL-EMG pattern-generation in the normal group compared with that seen for Class III subjects (p < 0.01). These data indicate that, compared with normal subjects, patients with a Class III malocclusion have a demonstrably abnormal masticatory muscle balance which is well characterized by the DL-EMG method.

Adolescent↗
PubMed2000

The function of tensor veli palatini muscles in patients with aural symptoms and temporomandibular disorder. An EMG study.

This preliminary study investigated Myrhaug's neuromuscular hypothesis by means of audiological and electromyographic assessment. After a clinical examination of the TMJ system, the activity of the tensor veli palatini muscles in the state of rest and during swallowing was investigated in 16 patients with the help of an EMG recording, and the tube-opening function was evaluated endoscopically. Results showed that 6.25% of the patients suffered from mild joint-dysfunction (group I), 81.25% from a moderate dysfunction (group II), and 12.5% from severe dysfunction (group III). Although five patients suffered from tinnitus and 11 from fullness in the ear, both the audio- and tympanogram performed on 15 patients displayed normal recordings. Only one patient suffered from moderate sensorineural hearing loss. In the EMG recording, 11 of the 16 subjects displayed normal EMG patterns in state of rest and during swallowing contraction. In two cases, abnormal EMG recordings were obtained due to incorrect insertion of the EMG needle. The study's results indicate that spasm in the masticatory muscles of TMJ patients neither seems to cause reflex spasm of the tensor palatini muscles nor to effect significant alterations in Eustachian tube function.

Adult↗
PubMed1994

A three-dimensional finite element model of the mandible including the TMJ and its application to stress analysis in the TMJ during clenching.

The purpose of this study was to develop a three-dimensional finite element model of the mandible including the temporomandibular joint (TMJ) and further to investigate stress distributions in the TMJ during clenching. The model consisted of 2088 nodes and 1105 elements, comprising cortical and cancellous bones, articular disc, articular cartilage layer and periodontal ligament. For loading condition, a resultant force of 500 N derived from the cross-sectional areas of the muscles was applied to the model. Compressive stresses were induced in the anterior, middle and lateral areas of the TMJ during clenching, whereas the tensile stresses were induced in the posterior and medial areas. The mean principal stresses on the surface of condyle were -1.642, -0.543, 0.664, -1.017, 0.521 MPa in the anterior, middle, posterior, lateral and medial areas, respectively. The mean stresses on the surface of glenoid fossa were approximately 1/5 to 4/5 those on the surface of condyle, although the patterns of stress distributions were almost similar. In both the articular disc and cartilage layer, the stress distributions were very approximate in qualitative and quantitative aspects. Thus, it is shown that stresses during clenching vary substantially in different structures and areas of the TMJ and that the stresses are reduced by the articular disc and cartilage layer in comparison with actual biting forces exerted by the masticatory muscles, if anatomic relation between various TMJ components is well maintained.

Biomechanical Phenomena↗
PubMed1994

Effects of the anabolic steroid nandrolone phenylpropionate on craniofacial growth in rats.

Primary testosterone and its derivatives are anabolic steroids used in the treatment of osteoporosis and Turner syndrome. They also enhance fast-twitch muscle weight in female rats. The present study examines the effect of an anabolic steroid on craniofacial growth and development in rats. Five-week-old female Sprague-Dawley rats (125) were divided into experimental and control groups. The experimental group was injected subcutaneously with 1 mg nandrolone phenylpropionate in the interscapular region on alternate days, whereas those in the control group were injected with a vehicle, arachis oil. Rats were sacrificed at 60 and 120 days of age. Cephalometric analysis of soft X-ray cephalograms showed that chronic administration of the anabolic steroid, nandrolone phenylpropionate, resulted in: (1) about a 20% increase in body weight, (2) an increase in total skull length, (3) elongation of the maxillary and mandibular incisors, (4) an increase in the depth of the antegonial notch, and (5) downward-forward growth of the viscerocranium against the neurocranium. These results suggest that nandrolone phenylpropionate may accelerate craniofacial growth and/or induce high functional activity of the masticatory muscles in female rats.

Anabolic Agents↗
PubMed1999

Relationship between anteroposterior maxillomandibular morphology and masticatory jaw movement patterns.

The causal relationships between oral function and craniomandibular morphology are poorly understood. The aim of this study was to determine whether quantifiable features of masticatory jaw movements and associated EMG activity correlated with variation in morphology as defined by the ANB angle. Thirty-six healthy subjects with no previous orthodontic treatment, asymptomatic masticatory muscles, and asymptomatic temporomandibular joints participated. While subjects chewed gum, jaw movement data and surface EMG data were digitized and then quantified into a 300 variable vector for each subject. ANB angle measurements were calculated from digitized tracings of lateral cephalographs. Step-wise linear regression and discriminant analyses were used to determine the relationship between the ANB angle and a subset of the variables defining jaw movement patterns and EMG patterns. A linear combination of seven jaw movements and EMG variables accounted for over 75% of the variation in the ANB angle (adjusted x R2 = 0.78, P <.001). A jackknifed cross-validation of the discriminant analysis, which was forced to use the same seven variables as the regression analysis, resulted in correct classification of 14 of 20 skeletal Class I, 7 of 9 skeletal Class II, and 7 of 7 skeletal Class III subjects. These results suggest that there is an association between anteroposterior skeletal morphology, as quantified by the ANB angle, and masticatory jaw movement patterns, as quantified in this study.

Adolescent↗
PubMed2004

[Efficacy of treatment with hard and soft occlusal appliance in TMD].

Temporomandibular disorders (TMD) include clinical disorders involving the masticatory muscles, the temporomandibular joints (TMJ) and the adjacent structures. TMD was recognized as a main source for pains in the orofacial area, which are not caused from dental origin, and is defined by the American Academy of Orofascial Pain (AAOP) as a sub-group within the frame of musculoskeletal disorders. The main etiology for TMD has not been found yet. The customary treatments for this disorder include treatment with occlusal splints, physiotherapy, medicaments, behavioral-cognitive treatment, hypnosis, acupuncture and surgery that should be considered only if all conservative treatments were unsuccessful. Occlusal splint is the most common and efficient treatment for TMD patients proved by many studies with a successful rate of 70-90%. The following article reviews the different opinions in the treatment of TMD with special attention to hard and soft occlusal appliances. Based upon much research, and despite the many disagreements regarding its efficacy, the hard splint is a customary application which has the most successful outcome in patients who suffer from functional disorders of the masticatory system. The stabilization splint has an important benefit for being a non-penetrating and reversible appliance. However, despite this, the dentist should evaluate the joint or muscular problem, and seriously consider the various available treatments before deciding to use the appliance as a means of treatment.

Centric Relation↗
PubMed1992

Influence of asymmetric occlusal relationships and decreased maxillary width on the growth of the facial skeleton in the guinea pig.

The purpose of this study was to evaluate the effect of muscle function and occlusal form on mandibular growth in guinea pigs. We hypothesized that restriction of maxillary width and asymmetric function of the mandible would lead to mandibular asymmetry. The hard palate of 12 animals was exposed at the age of ten days, and cyanocrylate was used to close the midpalatal suture in order to restrict transverse maxillary growth. The right incisors and right molars were ground obliquely at the time of surgery and every two weeks thereafter until the animals were sacrificed 4, 8 and 12 weeks later (four animals in each time group). Six age-matched animals served as controls. Dorsoversal x-rays were taken at sacrifice, followed by the removal of small biopsies from six different sites of the maxillomandibular skeleton for biochemical studies, which will be reported separately. Relative to controls, the treated animals exhibited a narrow maxilla and asymmetry in the height of the ramus and in the length of the mandible from the mental foramen to the angular process. The maximum width between the angular processes of the mandible was extremely narrow, as was the condylar neck especially on the right side. It was concluded that abnormal masticatory muscle function caused by occlusal deviation led to a narrowing and a slight asymmetry of the mandible in the growing guinea pig.

Aging↗
PubMed1978

Reflex activation of extrinsic tongue muscles by jaw closing muscle proprioceptors.

Depression of the mandible in the decerebrate cat induced retraction of the tongue. The mechanism of this jaw-tongue reflex was analyzed by recording electromyographic activity from the temporal and styloglossal muscles as representative masticatory and extrinsic tongue muscles, respectively. Tongue muscle activity was elicited when the mouth was opened beyond 10 degrees while the threshold for the masticatory muscle activities was around 2 degrees. Neither sectioning of the masseteric nerve nor anesthetization of the temporomandibular joint capsule affected the tongue muscle activities. In contrast, exfoliation of the temporal muscle from the temporal bone greatly reduced the effects of jaw depression. When the isolated coronoid process of the mandible was stretched downwards, activities were evoked in the tongue muscle. Repetitive electrical stimulation at a frequency of 100 Hz to the temporal nerve activated the tongue muscle, and the threshold of reflex activation was between 1.3 and 1.7 times threshold of the temporal nerve. Vibratory stimuli applied to the mandible at frequencies below 130 Hz were also effective in evoking tongue muscle activity. However, when the frequency was above 135Hz, tongue muscle activity was not induced although activity was still observed in the masticatory muscles. These results indicate that the jaw-tongue reflex is elicited mainly by proprioceptors in the temporal muscle, and that they may probably be the Golgi tendon organs and the secondary endings rather than the primary endings of the muscle spindle.

Animals↗