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PubMed1983

Normal variation in skin surface temperature over the temporomandibular joint and masseter muscle.

The range of the temperature at the skin surface overlying the temporomandibular joint (TMJ) and the origin of the superficial belly of the masseter muscle was investigated in 35 individuals with normal TM joints and 29 individuals with normal masseter muscles. The temperature was measured by a thermistor in contact with the skin. The temperature over the TMJ varied between 32.1 degrees C and 35.5 degrees C (average 34.3 degrees C). The difference in temperature between right and left sides was to an average 0.3 degrees C. The temperature over the masseter muscle ranged from 30.9 degrees C to 35.7 degrees C (average 33.2 degrees C). The difference in temperature between right and left sides was an average 0.4 degrees C. It was concluded that there is a fairly wide range of skin temperature over the normal TMJ and origin of the masseter muscle under the experimental conditions prevailing in this study but that the differences between right and left sides are fairly small. It therefore seems possible to use this thermometric method to assess inflammatory processes and/or changed metabolic activity in the TMJ and masticatory muscles.

Adolescent↗
PubMed2000

Genioglossus muscle activity during rhythmic open-close jaw movements.

The purpose of this study was to examine genioglossus muscle activity during rhythmic open-close jaw movements. The electromyographic activity of the genioglossus muscle was recorded with a bipolar fine-wire electrode in six healthy males. The electromyographic activities of the ipsilateral masseter and digastric muscles were simultaneously recorded with bipolar surface electrodes. The subjects were instructed to perform rhythmic open-close jaw movements in time with a metronome set at 23, 27, 33, 42 and 50 beats/min. In all of the subjects, rhythmic electromyographic activity of the genioglossus muscle was recorded in both the jaw-opening and jaw-closing phases. The activity of the genioglossus muscle was predominantly recorded in the jaw-opening phase in two subjects, and in the jaw-closing phase in two subjects. The burst duration of the electromyographic activity of the genioglossus muscle changed linearly in accordance with the cycle duration. However, the latency from the onset of the electromyographic activity of the masseter or digastric muscle to that of the genioglossus muscle was almost constant, independent of the cycle duration. Based on these findings, we conclude that the activity of the human genioglossus muscle is closely linked to that of masticatory muscles under the control of a closely related central pattern generator.

Adult↗
PubMedDate not supplied

[The prevalence of craniomandibular disorders in the military population of the Republic of Serbia].

INTRODUCTION: The aim of this study was to determine the prevalence of craniomandibular dysfunction (CMD) in the military personnel of the Republic of Serbia, as well as the distribution of sings and symptoms of CMD in this population group. MATERIAL AND METHODS: The epidemiological investigation included 284 male persons between 18 - 25 years of age. The sample consisted of Military Academy students, and soldiers from different regions of the Republic of Serbia. A questionnaire was designed using Helkimo's clinical dysfunction index and sings and symptoms of CMD were evaluated, namely the anamnestic index (Ai) and the dysfunction index (Di). RESULTS: According to the anamnestic dysfunction index (Ai), 85% of persons among the examined group presented without any symptoms of CMD (Ai = 0), 14% had mild symptoms (Ai =1) and 1% had severe symptoms of CMD (Ai = 5). Functional analysis of the orofacial system in the examined group (evaluation of dysfunction index - Di) revealed, however, that 70% of solders had at least one sign of CMD, precisely a dysfunction index Di > 0. The analysis of signs and symptoms of CMD revealed that disturbances in mandibular kinematics were the most prevalent sign of CMD in this population group, which was confirmed in 56% of examined persons. Disturbed functions of temporomandibular (TM) joints (click, and reciprocal click, deviation and deflection during mandibular opening) were established in 31% of examined persons, and sensitivity of TM joints and masticatory muscles during palpation in 4% of examined persons. Pain during mandibular movements was established only in 1% of examined persons. CONCLUSION: The results of this investigation point to significant prevalence of craniomandibular disorders in the examined population group. The incidence of TMJ and masticatory muscle pain in 4% of examined persons and of pain during mandibular movements only in 1% of examined persons, points to presence of mild or initial types of CMD in this population group.

Adolescent↗
PubMed2000

Maximal bite force and surface EMG in patients with myasthenia gravis.

Masticatory muscle strength was quantified in patients with bulbar myasthenia gravis and compared with that of patients with ocular myasthenia gravis, patients in clinical remission (whether or not pharmacological) who previously suffered from bulbar myasthenia gravis, and healthy subjects. Maximal bite force and maximal activity of the masseter and temporalis muscles and of the submental muscle complex were measured. Bite force was decreased in the patients with bulbar myasthenia gravis, but was normal in the patients in the clinical remission group and in the ocular group. These findings were consistent with the results of electromyographic data. Although subjective reports of masticatory muscle weakness provide valuable information, quantitative measurements provide more information about the degree of muscle weakness of individual muscles. This is especially important for longitudinal evaluation of therapy in individual patients and for pharmacotherapeutic research.

Adult↗
PubMed2004

Time series analysis of jaw muscle contraction and tissue deformation during mastication in miniature pigs.

Masticatory muscle contraction causes both jaw movement and tissue deformation during function. Natural chewing data from 25 adult miniature pigs were studied by means of time series analysis. The data set included simultaneous recordings of electromyography (EMG) from bilateral masseter (MA), zygomaticomandibularis (ZM) and lateral pterygoid muscles, bone surface strains from the left squamosal bone (SQ), condylar neck (CD) and mandibular corpus (MD), and linear deformation of the capsule of the jaw joint measured bilaterally using differential variable reluctance transducers. Pairwise comparisons were examined by calculating the cross-correlation functions. Jaw-adductor muscle activity of MA and ZM was found to be highly cross-correlated with CD and SQ strains and weakly with MD strain. No muscle's activity was strongly linked to capsular deformation of the jaw joint, nor were bone strains and capsular deformation tightly linked. Homologous muscle pairs showed the greatest synchronization of signals, but the signals themselves were not significantly more correlated than those of non-homologous muscle pairs. These results suggested that bone strains and capsular deformation are driven by different mechanical regimes. Muscle contraction and ensuing reaction forces are probably responsible for bone strains, whereas capsular deformation is more likely a product of movement.

Animals↗
PubMed1988

Isometric muscle tension generated by masseter stimulation after prolonged alteration of the consistency of the diet fed to growing rats.

The forces developed by the masseter muscle and the diet-related changes were studied in situ. The active tetanic tension was measured indirectly by recording the forces applied to the mandible in four different predetermined interincisal distances. The highest tension developed in all the experimental groups was with an interincisal distance of 11 mm. The tetanic tension was significantly lower in rats fed a soft diet than in those fed a normal diet. This difference might be due to the smaller muscle fibres in rats with decreased functional demand. The changes in the masticatory muscles may influence the tension applied to the facial skeleton and cause the alteration in the craniofacial growth previously found in rats fed a soft diet.

Animals↗
PubMed1984

Identification and assessment of factors contributing to variability of the jaw jerk.

Unlike limb monosynaptic reflexes, the jaw jerk reflex ( JJR ) is extremely variable. We studied 35 healthy adults to determine the relative contributions of extrinsic and intrinsic factors underlying this variability. Each subject sat in a dental chair with his head and chin securely stabilized. Chin taps, delivered by a solenoid-driven plunger, were quantified with a piezo -transducer. The reflex response was recorded from surface electrodes over the right masseter muscle. A nasal thermistor signalled phases of respiration. Five of the 35 subjects had no reflex when relaxed, but during 15 degrees neck extension or voluntary contraction of the platysma muscle, a JJR appeared. The amplitude of the reflex varied considerably from trial to trial in all but one subject. A small component of this variability was due to minute changes in tap force despite head and chin stabilization and stimulus uniformity. Mean amplitudes of the reflex tended to increase with increases in tap force, but variability was large indicating intrinsic fluctuations in motoneuron excitability. Voluntary contraction of the platysma muscle and 15 degrees neck extension reliably enhanced the reflex. The JJR showed negligible respiratory modulation during quiet breathing. The reflex's variability in and among subjects precludes the use of the JJR as an index of masseteric motoneuron excitability. Our findings suggest that branchial motoneurons innervating the masticatory muscles receive far more diverse and fluctuating inputs than do somatic motoneurons innervating limb muscles.

Adolescent↗
PubMed2004

Features and treatment of skeletal class III malocclusion with severe lateral mandibular shift and asymmetric vertical dimension.

AIM: To highlight the effectiveness of orthodontic treatment and bilateral equalization of the vertical occlusal dimension, along with the correction of asymmetric cervical and masticatory muscle activities in patients with Class III malocclusion with lateral deviation of the mandible and severely asymmetric condyle and ramus. METHODS: Two normally growing and one nongrowing Japanese patients with severe lateral deviation of the mandible, asymmetric vertical occlusal dimension, and severely asymmetric temporomandibular joints are discussed. In addition to orthodontic treatment, all patients received physiotherapy of the cervical muscles and gum-chewing training for elimination of the masticatory muscular imbalance. Patients also had postural training during treatment. All patients were treated with a bite plate to equalize the bilateral posterior vertical dimension, followed by full multi-bracketed treatment to establish a stable form of occlusion and to improve facial esthetics. RESULTS: This interdisciplinary treatment approach resulted in normalization of stomatognathic function, elimination of temporomandibular joint dysfunction symptoms, and improvement of facial appearance and posture. In growing patients, the significant response of the fossa, condyle, and ramus on the affected side during and after occlusal correction contributed to the improvement of cervical muscle activity. In contrast, less improvement was observed in the growing patient who did not receive physiotherapy of the neck muscles, postural training, or masticatory habit training during the posttreatment period. The nongrowing patient showed little morphologic improvement of the cervical spine, condyle, and fossa during treatment and after retention, even with physiotherapy of the neck muscles and attention to posture and masticatory habits. CONCLUSION: Based on these results, early occlusal improvement, combined with physiotherapy to achieve muscular balance of the neck and masticatory muscles, was found to be effective. It is important to assess the morphology and function of the neck muscles and cervical spine prior to occlusal therapy in patients with an asymmetric vertical dimension, lateral deviation of the mandible, and asymmetric temporomandibular joint structures. Therapy should correlate orthopedic and surgical patient management as needed.

Adult↗
PubMed1993

[Correlation between inner ear disorders and temporomandibular joint diseases].

Acute and chronic inner ear diseases involve many etiological factors, some as yet unknown. ENT-specific, orthopedic, hemorrheological, immunological and neurological disorders can affect the cochleovestibular system and induce hearing loss, vertigo and/ortinnitus. We performed a prospective study to analyze factors of the dentognathological system and of the temporomandibular joint that can influence acute and chronic inner ear dysfunctions. A total of 138 patients (49.3% female, 50.9% male) receiving clinical treatment for inner ear dysfunctions (12.3% chronic sensorineural hearing loss, 15.2% Ménière's disease, 52.2% sudden hearing loss, 13.8% isolated tinnitus, 6.5% recurrent hearing loss) underwent a prospective dental and gnathological examination. In particular, the patient's dental status and a functional investigation of the masticatory muscles and the temporomandibular joint were analyzed. In 20.3% patients the examination showed no pathology of the dentognathological system. In contrast, there were pathological findings in 110 patients (79.7%): in 43.5% a temporomandibular joint syndrome was diagnosed, in 29% parafunction of the occlusion, and in 35% a myopathy of the masticatory muscles. Additionally 32.6% patients showed dental disorders that required treatment; 11.65% had problems with dentures and 20.3% malpositioned wisdom teeth. In 16 patients the recommended dental treatment was followed up and improvement of otological symptoms was found in 56.6%. The present investigation shows that many patients with inner ear dysfunction suffer from dentognathological disorders. For a subgroup of patients there exists the possibility of improving otological symptoms by dental treatment. Therefore we recommend a dentognathological examination in patients with inner ear dysfunctions of unknown etiology.

Adult↗
PubMed1992

[The effect of muscle relaxants on masseter tone. An experimental study in an MH-susceptible swine model].

Malignant hyperthermia (MH) may occur, when a genetically predisposed individual or pig (MHS) is exposed to triggering agents. The increase in free, ionized sarcoplasmic calcium inducing the vicious circle of MH is believed to result from calcium-induced release with volatile anaesthetics, and from depolarization-induced calcium release with succinylcholine (SCH). The administration of SCH to susceptible humans or pigs frequently produces an increase in masticatory muscle tone. This hitherto ill-defined phenomenon is referred to as "masseter spasm" (MS). We have attempted to elucidate the pathophysiology of MS in a porcine model. METHODS. After the protocol had been approved by the state authorities, 6 MHS pigs were investigated. The pigs were mixed breeds (German Landrace and Dutch Pietrain) and were 9 +/- 1 weeks old with an average body weight of 25.5 kg. Premedication consisted of intramuscular injection of azaperone, 7.5 mg.kg-1. Anaesthesia was induced with piritramide, 1.2 mg.kg-1, administered via a cannulated ear vein. Subsequent to laryngoscopic endotracheal intubation, neuromuscular blockade was achieved with 4 mg pancuronium. Ventilation was set at 12 breaths per minute and adjusted to maintain an end-tidal CO2 concentration of 4.7% by adapting the tidal volume (PhysioFlex). Anaesthesia was maintained with piritramide, 2.25 mg.kg-1.h-1, pancuronium, 0.4 mg.kg-1.h-1, and N2O (60% in O2). Instrumentation included an arterial line, a central venous line, and a fiberoptic pulmonary artery catheter (Oximetrix). Masticatory muscle tone (MMT) was assessed with an intermolar balloon, connected to a pressure transducer and calibrated to zero prior to SCH administration. As a reference variable for effects produced by SCH, intraocular pressure (IOP) was measured manometrically in the anterior chamber. After stabilization of haemodynamic variables, the neuromuscular blockade was allowed to wear off. After recovery of the evoked masseter electromyogram, a paralyzing dose of pancuronium was administered (0.5 mg.kg-1). When paralysis was complete, SCH was administered (1.5 mg.kg-1), followed a few minutes later by dantrolene infusion (5 mg.kg-1 over 10 min). RESULTS. The administration of SCH was followed by clinically unequivocal MH episodes in all pigs, indicated by an increase in oxygen uptake (VO2; PhysioFlex; Fig. 1) and end-tidal CO2 concentration and a decrease in oxygen saturation of mixed venous blood (svO2; Fig. 2). Despite complete neuromuscular blockade (monitored with EMG), SCH produced an increase in MMT in all pigs which was reversed by dantrolene (Fig. 3). The time course of MMT paralleled that of IOP, suggesting a similar underlying mechanism. DISCUSSION. Succinylcholine is a trigger of MH in susceptible individuals; onset of the syndrome may be associated with "masseter spasm". SCH increases extraocular muscle tone, probably by means of stimulating multiply innervated fibers; the resulting IOP increase is not prevented by competitive neuromuscular blockade. The existence of multiple innervated fibers has also been shown in muscle spindles in the deep layers of the masseter, with their stimulation resulting in elevation of the jaw. We speculate that the increases in MMT and IOP observed in this study reflect the same process, i.e. a motor response, initiated by SCH-induced stimulation of the intramyocellular contractile system of multiply innervated muscle fibers, that is independent of neuromuscular transmission. Triggering of MH with SCH despite complete neuromuscular blockage suggests a mechanism other than depolarization-induced calcium increase. And, for the semantics, according to neurological terminology MS should be referred to as contracture not as spasm.

Anesthesia, Inhalation↗
PubMed1997

Management of temporomandibular disorders in a restorative practice.

Various disorders related to the masticatory muscles or to the temporomandibular joints may be encountered in a restorative dental practice. Most of them can be managed by the restorative dentist whose primary interest may not lie in the area of temporomandibular disorders. The term temporomandibular disorders is used in this discussion to denote the group of diseases of the masticatory system that involves primarily the temporomandibular joints, the masticatory muscles, and the occlusion of the teeth. The learning objective of this article is to describe temporomandibular disorders encountered in general practice. Managing these disorders in the general practice of restorative dentistry is not difficult and adds to the comfort of the patient and possibly to the success of the restorations.

Diagnosis, Differential↗
PubMed2006

Distribution of NADPH diaphorase-exhibiting primary afferent neurons in the trigeminal ganglion and mesencephalic trigeminal nucleus of the rabbit.

1. Nitric oxide (NO) is highly reactive gaseous molecule to which many physiological and pathological functions have been attributed in the central (CNS) and peripheral (PNS) nervous system. The present investigation was undertaken to map the distribution pattern of the enzyme responsible for the synthesis of NO, nitric oxide synthase (NOS), and especially its neuronal isoform (nNOS) in the population of primary afferent neurons of the trigeminal ganglion (TG) and mesencephalic trigeminal nucleus (MTN) of the rabbit. 2. In order to identify neuronal structures expressing nNOS we applied histochemistry to its specific histochemical marker nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd). 3. We found noticeable amount of NADPHd-exhibiting primary afferent neurons in TG of the rabbit under physiological conditions. The intensity of the histochemical reaction was highly variable reaching the maximum in the subpopulation of small-to-medium-sized neurons. The large-sized neurons were only weakly stained or actually did not posses any NADPHd-activity. In addition, NADPHd-positive nerve fibers were detected between clusters of the ganglionic cells and in the peripheral branches of the trigeminal nerve (TN). NADPHd-exhibiting MTN neurons were noticed in the whole rostrocaudal extent of the nucleus even though some differences were found concerning the ratio of NADPHd-positive versus NADPHd-negative cell bodies. Similarly, we observed striking diversity in the intensity of NADPHd histochemical reaction in the subpopulations of small-, medium-, and large-sized MTN neurons. 4. The predominant localization of NADPHd in the subpopulation of small-to-medium-sized TG neurons which are generally considered to be nociceptive suggests that NO probably takes part in the modulation of nociceptive inputs from the head and face. Furthermore, we tentatively assume that NADPHd-exhibiting MTN neurons probably participate in transmission and modulation of the proprioceptive impulses from muscle spindles of the masticatory muscles and mechanoreceptors of the periodontal ligaments and thus provide sensory feedback of the masticatory reflex arc.

Animals↗
PubMedDate not supplied

[The masticatory efficiency test in evaluation of the functional value of Rehm rebased newly made total dental prostheses].

The aim of the study was to determine the functional value of unrebased, rebased by Rehm and new complete dentures and compare the time of initial functional adaptation of patients to rebased and new complete dentures. The study included 72 subjects. The functional value of complete dentures was estimated by the test of masticatory muscles bioelectrical activity, by the test of masticatory efficiency and by the test of maximal physiological load. On the basis of the study it was concluded that the complete dentures rebased by Rehm were worthier in function than the unrebased ones, and the period of initial functional adaptation was missing. In the subjects with a pair of newly made complete dentures, functional tests revealed the reduction of the initial values after the new dentures were delivered. During the examination interval progressive dynamics with the tendency of establishing the optimal functional value and the initial functional adaptation was observed after 21 days.

Aged↗
PubMed1980

Activity of the temporal and masseter muscles in class II, division 1 malocclusions. An electromyographic investigation.

A quantitative analysis of EMG activity in the masticatory muscles was performed in homogeneous groups of boys with Class II, Division 1 malocclusion and normal occlusion. Integrated EMG recordings from the temporal and masseter muscles were analyzed during maximal biting in the intercuspal position (centric occlusion) and during the chewing of peanuts. The results of the investigation revealed the following: (1) During maximal biting in intercuspal position the boys with Class II malocclusion exhibited less EMG activity in the masseter and temporal muscles than the boys with normal occlusion. In the Class II boys the reduction in EMG activity was most apparent for the masseter muscle. (2) During chewing the Class II subjects showed less EMG activity in the masseter muscle than the normal occlusion subjects. For the temporal muscle, no differences were found between the two occlusion groups. (3) High positive correlations were found between the EMG activity during maximal biting and chewing for both muscles in the two occlusion groups. The impaired muscle activity found in the Class II cases may be attributed to a diverging dentofacial morphology and unstable occlusal contact conditions.

Child↗
PubMedDate not supplied

Relief of tension-type headache symptoms in subjects with temporomandibular disorders treated with botulinum toxin-A.

BACKGROUND: Temporomandibular disorder (TMD) and chronic tension headaches clinically coexist in many individuals. Generally considered as separate pathological entities, they have been clinically treated by different means. OBJECTIVE: To determine the utility of treatment with botulinum toxin for patients with coexisting TMD and chronic tension type headache. METHODS: In this open-label study of 60 subjects with chronic TMD, 46 subjects also met the diagnostic criteria for chronic tension headache. All 60 subjects were treated with 150 units of botulinum toxin-A injected into the masticatory muscles, specifically 50 units into each masseter and 25 units into each temporalis muscle. RESULTS: Thirty-eight of 60 subjects (63%) reported a 50% improvement in their facial pain during the follow-up period. The subset of 46 subjects with chronic tension headache and TMD symptoms reported a 50% or greater improvement in headache pain as well. The number of headache free days also improved postinjection. CONCLUSION: These results suggest that the masticatory muscles, specifically the temporalis, may be involved in the pathogenesis of this form of chronic tension headache found in association with TMD.

Adolescent↗
PubMed1985

Comparative electromyographic study of bite plates and stabilization splints.

The object was to study any influence on the integrated electromyographic activity in the masseter and temporal muscles of two types of occlusal appliances. Seventeen healthy subjects wore a bite plate with a frontal plateau and a full coverage stabilization splint at night, each for 1 wk. The EMG activity was recorded without appliances in situ, in the rest position, and during gentle and maximum biting before and after the use of the different appliances. After use of the bite plate, the EMG activity was not significantly different at any tested level. After use of the splint, the activity in the rest position was significantly lower in the anterior and posterior parts of the temporal muscles. The EMG activity was significantly lower in the rest position in both parts of the temporal muscle after use of the splint than after use of the bite plate. In a control group of eight subjects in whom no appliances were used, the EMG activity did not change significantly between the initial and 1- or 5-wk recordings. Thus, the occlusal design of the appliances seems to be of importance for the influence on the EMG activity in the masticatory muscles, at least in healthy subjects.

Adult↗
PubMed1991

Microscopic study of the rabbit mandibular periosteum and attached structures.

The structure of the mandibular periosteum in rabbits of different ages has been studied by different histological staining techniques and polarization microscopy. The periosteum consisted of two layers. From the inner, cellular layer the functional state could be determined. A reproducible pattern of resorptive and depository areas was found on the bony surface. In the outer, fibrous periosteal layer, collagenous and elastin fibers were running in distinct directions. The masticatory muscles appeared to be attached directly endomysially or indirectly endomysially, via the perimysium or tendinous attachment. From the periosteal structures and the characteristics of muscular fiber attachments to the bone and periosteum, especially in the ramal and condylar areas, it could be concluded that a mechanical influence of the periosteum on condylar growth is very well possible, which will probably vary during life. The masticatory muscles seemed to be only of minor influence in condylar activity.

Age Factors↗
PubMed1992

[Psychometric and psychofunctional studies of a group of patients with craniomandibular disorders].

The base myoelectric of masticatory muscles, and their response to stressor, was studied in a group of patients affected with craniomandibular disorders (CMD) and in a control group. Patients suffering from craniomandibular disorders were affected by at least two of these three groups of symptoms: 1) articular and/or muscular pain; 2) articular noise; 3) alteration of mandibular mobility. The psychofunctional investigation was as follows: in order to measure the base myoelectric activity of the masticatory muscles and their response to stress, the Myotron 222 two-channel electromyographs were used, so as to record the activity of four muscles contemporaneously. The research was conducted on the masseter and anterior fascia of the temporal muscles, which are the most readily accessible of the elevator muscles. A non-specific stressor (shot pistol) was administered to the subjects after the base myoelectric level had been established. These factors were evaluated on the electromyograms: base activity before the stressor; the shape of the response to the stressor; the recovery time after the stressor. The minimum activity before the stressor was usually measured as the minimum activity the subject was able to maintain for roughly one minute. The psychometric investigation used "Minnesota Multiphasic Personality Inventory" (MMPI); this is a nonprojective personality test widely used in clinical psychology. The base level of myoelectric activity was higher in patients affected with craniomandibular disorders than in healthy patients, who generally had low initial values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗