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PubMed2000

Treating severe bruxism with botulinum toxin.

BACKGROUND: Locally administered botulinum toxin, or BTX, is an effective treatment for various movement disorders. Its usefulness in treating bruxism, however, has not been systematically evaluated. SUBJECTS AND METHODS: The authors studied 18 subjects with severe bruxism and whose mean duration of symptoms was 14.8 +/- 10.0 years (range three-40 years). These subjects audibly ground their teeth and experienced tooth wear and difficulty speaking, swallowing or chewing. Medical or dental procedures had failed to alleviate their symptoms. The authors administered a total of 241 injections of BTX type A, or BTX A, in the subjects' masseter muscles during 123 treatment visits. The mean dose of the BTX A was 61.7 +/- 11.1 mouse units, or MU (range 25-100 MU), per side for the masseter muscles. RESULTS: The mean total duration of response was 19.1 +/- 17.0 weeks (range six-78 weeks), and the mean peak effect on a scale of 0 to 4, in which 4 is equal to total abolishment of grinding, was 3.4 +/- 0.9. Only one subject (5.6 percent) reported having experienced dysphagia with BTX A. CONCLUSION: The results of this study suggest that BTX administered by skilled practitioners is a safe and effective treatment for people with severe bruxism, particularly those with associated movement disorders. It should be considered only for those patients refractory to conventional therapy. Future placebo-controlled studies may be useful in further evaluating the potential of BTX in the treatment of bruxism.

Adolescent↗
PubMed1995

Experimental occlusal interferences. Part III. Mandibular rotations induced by a rigid interference.

A rigid intercuspal interference (minimum mean height of 0.24 mm) was placed on either the right or left mandibular second premolar and first molar of 12 subjects. During brisk and forceful biting on the interference, rotational electrognathography measured maximum torque of the right and left mandibular condyles in the frontal and horizontal planes of orientation. All subjects showed frontal plan upward rotation (mean of 0.7 degrees) of the mandibular condyle contralateral to the interference. In 33% of the subjects there was no horizontal plane backward rotation. In 58% of the subjects there was horizontal plane backward rotation (mean of 0.5 degrees) of the mandibular condyle ipsilateral to the interference, and in one subject (8%) there was backward horizontal plane rotation (0.1 degree) of the mandibular condyle contralateral to the interference. It was inferred that the masseter muscle, ipsilateral to the interference, generated negative work in order to decelerate frontal plane 'unseating' of the mandibular condyle ipsilateral to the interference. It was inferred that the masseter muscle, contralateral to the interference, produced positive work in order to accelerate frontal plane 'seating' of the mandibular condyle contralateral to the interference. Finally, it was speculated that the impact forces of frontal plane 'seating' of the mandibular condyle, contralateral to the interference, might lead to 'vacuum sticking' of the temporomandibular joint disc because of the formation of negative hydrostatic pressures.

Adult↗
PubMed1993

Rabies RNA synthesis, detected with cDNA probes, as a marker for virus transport in the rat nervous system.

The kinetics of viral RNA synthesis in different parts of the rat brain, infected with fixed or street rabies virus strains, is correlated with their anatomical neuronal connections with the masseter muscles, using hybridization with rabies cDNA probes. Viral RNA synthesis is first detected in the brain-stem and in the pons where the direct anatomical projection of the masseter muscle nervous arborization into the sensory and motor nuclei is located, through the trigeminus nerve. Rabies RNA detection is delayed in the other regions of the rat brain depending on the time course of virus transport from the trigeminal nuclei through multiple nervous connections.

Afferent Pathways↗
PubMed2000

Changes in jaw-jerk on different levels of jaw closure and teeth-clenching in humans.

We investigated how the jaw-jerk in the human masseter muscle is modulated in relation to the level of jaw closure (JC) and teeth clenching. Electromyographic (EMG) activity was recorded with surface electrodes. Background EMG activity of the masseter muscle was kept at three low teeth clenching levels with visual feedback. The level of JC was changed in six steps along the habitual path of closure relative to the mean maximal jaw opening during gum chewing by inserting a bite block between the upper and lower molars. The jaw-jerk was evoked by applying mechanical stimulation of about 20 N with a hammer to the bite-fork placed on the lower molars on one side in each condition of combination of a level of JC with a level of teeth-clenching. At the resting condition the excitability of the jaw-jerk increased with JC, while at weak voluntary teeth clenching it then decreased and increased again as the jaw was progressively closed. It is suggested that the excitability of the jaw-jerk would increase toward the occlusal position, which in turn would contribute to smooth masticatory movements. In addition, the mode of modulation of the jaw-jerk was studied in a subject with skeletal malocclusion.

Adult↗
PubMed1987

Temporomandibular joint involvement in rheumatoid arthritis. A clinical study.

The aims of this thesis were to investigate individuals with rheumatoid arthritis (RA) with respect to the frequency and character of temporomandibular joint (TMJ) disorder, the relationship between TMJ involvement and general joint disease, the possibility to detect pathologic conditions in the TMJ region with skin surface temperature, and treatment effect of physical training on TMJ disorder. TMJ disorder was more frequent and more severe in RA than among normal subjects. The TMJ symptoms started frequently in the early phase of RA and were correlated to the extension of the general joint symptoms. Anterior open bite occurs in a small subgroup of RA individuals and was associated with severe TMJ disorder and high values of ESR. High concentration of serum acute-phase reactants and high values of rheumatologic indices were associated with severe TMJ involvement in RA. Skin surface temperature over the TMJ and the masseter muscle was generally low in individuals with RA compared with normal subjects. TMJ disorder was related to the overlying skin surface temperature. The low temperature over the TMJ and the masseter muscle is probably caused by disuse atrophy and an ensuing decrease in muscular blood flow. Short-term results of physical training for the stomatognathic system improved the mandibular mobility and reduced the clinical dysfunction in RA.

Adult↗
PubMed2001

Controlled study of EMG activity of the jaw closers and openers during mastication in patients with myasthenia gravis.

Mastication was evaluated in patients with bulbar myasthenia gravis and compared with that of patients with ocular myasthenia gravis, patients in remission who previously suffered from bulbar symptoms, and healthy controls. Bulbar myasthenia gravis may impair mastication due to weakness of the masticatory muscles. The aim of the study was to objectively evaluate the influence of myasthenia gravis on mastication. The subjects chewed a piece of breakfast cake and chewed 1 min on a piece of chewing gum. Surface EMG of the masseter muscle, temporalis muscle and jaw opener muscles was recorded. Statistical analysis revealed that bulbar patients produced significantly less EMG activity in the closing phase of a chewing cycle in both experiments. The EMG of the masseter muscle expressed as percentage of the maximum EMG during maximal clenching showed significantly higher values in the bulbar group than in the other groups. This was not found for the temporalis muscle. It was suggested that bulbar patients use a strategy of limited effort to produce a bolus that can be swallowed. The ocular patients and the patients in remission showed no subclinical impairments in muscle function during chewing.

Adult↗
PubMed2000

Infectivity, predilection sites, and freeze tolerance of Trichinella spp. in experimentally infected sheep.

A total of 36 sheep in groups of 4 were inoculated with 9 isolates of Trichinella and euthanized after 10 weeks. Thereafter, numbers of muscle larvae were determined in 13 different muscles/muscle groups. Muscle larvae were found in high numbers in all four sheep inoculated with T. spiralis, in lower numbers in two sheep inoculated with T. pseudospiralis (USA isolate), and in very low numbers in one sheep inoculated with T. pseudospiralis (USSR isolate) and one inoculated with T. britovi. In infections of high and moderate larval intensity, predilection sites of T. spiralis were the masseter muscles, the tongue, and the diaphragm and those of T. pseudospiralis were the masseter muscle and the neck. In low-intensity infections, muscle larvae were detected only in the diaphragm or in pooled muscle samples. For evaluation of the freeze tolerance of the different Trichinella species in sheep-muscle tissue, samples taken from the filet were stored at +5 degrees, -5 degrees, and -18 degrees C, respectively. After exposure for 1 and 4 weeks the tissue was digested and the released larvae were inoculated into mice for determination of the reproductive capacity index (RCI). Larvae of both T. spiralis and T. pseudospiralis survived freezing at -5 degrees and -18 degrees C for 4 weeks.

Animals↗
PubMed2000

Asymmetry of masticatory muscle activity during the closing phase of mastication.

The purpose of this study was to investigate the asymmetry of masticatory muscle activity between working and nonworking sides in the closing phase during mastication. Fifty adult subjects displaying normal oral function and occlusion participated in this study. Electromyographic (EMG) activity of the anterior temporalis and the superficial masseter muscle were recorded during mastication, simultaneously with motion data of the mandible. EMG activities of elevator muscles and their Asymmetry Index (AI) were analyzed depending on the vertical deviation of the lower incisal point with a two mm gap from the intercuspal position (ICP). EMG activities of both the anterior temporalis and the masseter on the working side were significantly greater than those on the nonworking side. Masseter muscles tended to show greater AI than the anterior temporalis muscles. Thus, asymmetry of the elevator muscles during mastication was a common finding in normal subjects. The normal range of variability of EMG activity and AI was confirmed in each section.

Adult↗
PubMed1989

[Silent period and initial occlusal sliding time in patients with premature contacts].

This study was designed to examine the relationship between frequency of silent period and initial occlusal sliding time. The subjects consisted of three volunteers with normal occlusal contacts and three patients with premature contacts. Electromyograms of the bilateral masseter muscles, initial occlusal contacts and jaw movements during the habitual tapping (20-25) were synchronously recorded and replayed using Takamatsu's technique. Results were as follows: 1. The frequency of silent period in the bilateral masseter muscles was 95-100% in subjects with normal occlusal contacts and 34-53% in patients with premature contacts. 2. The silent period latency in three normal subjects was 8.9 +/- 1.3 msec in the left masseter and 13.9 +/- 2.2 msec in the right masseter. The silent period latency in three patients with premature contacts was 12.4 +/- 2.6 msec in the left masseter and 13.9 +/- 8.2 msec in the right masseter. 3. The duration of silent period in three normal subjects was 12.4 +/- 2.6 msec in the left masseter and 11.1 +/- 3.7 msec in the right masseter. The duration of silent period in three patients with premature contacts was 9.1 +/- 1.7 msec in the left masseter and 11.1 +/- 5.6 msec in the right masseter. 4. Initial occlusal sliding time in three subjects with normal occlusal contacts was less than 30 msec, and 98% of all slidings lasted for less than 15 msec. Initial occlusal sliding times in patients with premature contacts were distributed between 6 and 80 msec (40%: 6 to 15 msec, 60%: greater than 15 to 80 msec).(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Occlusion, Traumatic↗
PubMed2004

Central representation of muscle pain and mechanical hyperesthesia in the orofacial region: a positron emission tomography study.

Functional neuroimaging studies of the human brain have revealed a network of brain regions involved in the processing of nociceptive information. However, little is known of the cerebral processing of pain originating from muscles. The aim of this study was to investigate the cerebral activation pattern evoked by experimental jaw-muscle pain and its interference by simultaneous mechanical stimuli, which has been shown to evoke hyperesthesia. Ten healthy subjects participated in a PET study and jaw-muscle pain was induced by bolus injections of 5% hypertonic saline into the right masseter muscle. Repeated von Frey hair stimulation (0.5 Hz) of the skin above the masseter muscle was used as the mechanical stimulus. Hypertonic saline injections caused strong muscle pain spreading to adjacent areas. von Frey stimulation was rated as non-painful but produced hyperesthesia during jaw-muscle pain. Jaw-muscle pain was associated with significant increases in regional cerebral blood flow (rCBF) in the dorsal-posterior insula (bilaterally), anterior cingulate and prefrontal cortices, right posterior parietal cortex, brainstem, cavernous sinus and cerebellum. No rCBF changes occurred in primary or secondary somatosensory cortices. In contrast, von Frey stimulation produced a significant rCBF increase in the contralateral SI face representation. Mechanical hyperesthesia was associated with significant rCBF increases in the subgenual cingulate and the ventroposteromedial and dorsomedial thalamus. These results suggest that the cerebral processing of jaw-muscle pain may differ from the processing of cutaneous pain and that mechanical hyperesthesia, which often is encountered in clinical cases, has a unique representation in the brain.

Adult↗
PubMed1989

[Investigation of an electromyogram and a mandibular movement in prognathia of mixed dentition compared with normal occlusion].

A quantitative analysis of EMG activity in temporal and masseter muscle and of mandibular movement was performed in prognathia (n = 20) and normal (n = 30) occlusion. EMG recordings were analyzed during rest position, maximal clenching and maximal clenching with a cotton-roll. Mandibular movement was examined for path of closure, amount of freeway, maximal velocity of jaw opening and closing, condylar test and amount of maximal vertical jaw opening. The results of the investigation revealed the following. Normal occlusion and prognathia were classified into two groups by path of closure. One group was going toward the upper front and another toward the upper back. The former was indicated in 77% of normal occlusion and 65% of prognathia cases examined. Amount of freeway space was the same in both groups. Maximal velocity of jaw was significantly (p less than 0.05) faster for prognethia than for normal occlusion. Condylar test was significantly (p less than 0.05) greater for prognathia than for normal occlusion. Temporal muscle activity was greater for normal occlusion than for prognathia. During maximal clenching, temporal muscle activity was greater than masseter activity in the normal occlusion. A tendency toward negative correlation was found between temporal muscle activity during maximal clenching and the mandibular plane angle, facial height and gonial angle. The same tendency was found between masseter muscle activity and the mandibular plane angle, facial height, ramus-height and gonial angle. These results prove that it is important to examine muscle activity and mandibular movement to make treatment planning.

Dental Occlusion↗
PubMed2000

Prolonged mandibular hypomobility patient with a "square mandible" configuration with coronoid process and angle hyperplasia.

The objective of this study was the surgical management of chronic severe mandibular hypomobility patients associated with square mandible morphology with coronoid process and angle hyperplasia, and one-year follow-up data is reported. Ten patients were studied. All patients were female and had a history of gradual severe jaw hypomobility. Clinical findings were similar to those of a "closed lock" patient. However, the facial appearance in these patients showed a characteristic square mandible facial configuration. Coronoid process thickening and overgrowth of the mandibular angle was evident in the radiographic findings. Diagnostic imaging scarcely depicted any disk derangement, but a severely limited jaw opening was noted in spite of acceptable excursive jaw movements. Bilateral coronoidotomy or coronoidectomy was done initially, and then masseter muscle stripping via the intraoral approach. After successful reduction of jaw hypomobility, a selective mandibular anglectomy was completed. Physical therapy began within three to five days after the surgery. Postoperatively, all patients were questioned about their jaw function and their subjective assessment of the treatment. Interincisal jaw opening was recorded with a ruler marked in millimeters. Bilateral coronoidotomy or coronoidectomy and masseter muscle stripping were done for all patients; the mandibular anglectomy was performed in seven of the cases at 13 sites. Simultaneous TMJ surgery was done on three joints for three patients. Most patients reported improvement of jaw function, and the patients' subjective assessment revealed an average satisfaction rate of 74.6%. A preoperative mean jaw opening distance of 25.6 mm increased to 36.6 mm postoperatively at a one-year follow-up (p < 0.05). The conclusion was that surgical intervention is indicated when nonsurgical treatment is unsuccessful. Etiology is unknown, but masseter and temporal muscle contracture associated with mandibular coronoid and angle hyperplasia may be a strong component of the pathophysiology.

Adolescent↗
PubMed1993

Note on the comparison of calpains I, II and calpastatin activity in two different types of porcine skeletal muscles.

1. Activities of calpains I and II and calpastatin in two different types of porcine skeletal muscles were compared. 2. Semimembranosus muscle was composed of mixed fiber types with mainly glycolytic fibers (65%), while masseter muscle was composed exclusively of oxidative fibers. 3. Calpain I activity was lower and calpain II activity was higher in masseter muscle as compared to semimembranosus muscle. Calpastatin activities were similar in both muscles.

Animals↗
PubMed1994

Jaw relaxation after a halothane/succinylcholine sequence in children.

BACKGROUND: Lack of complete jaw relaxation after a halothane-succinylcholine sequence has been described in the literature. To date, however, most existing studies are retrospective, and lack agreement on the magnitude and incidence of this phenomenon. This prospective study examined the incidence and degree of incomplete jaw relaxation in 500 children who were given intravenous succinylcholine during halothane anesthesia. METHODS: Five hundred consecutive unmedicated children received a minimum dose of 2 mg/kg intravenous succinylcholine after induction of anesthesia with halothane. The degree of jaw relaxation was assessed 45-60 s later by the same observer using a standardized clinical scale. The degree of relaxation was correlated with the type of surgical procedure, and the presence and intensity of fasciculations. RESULTS: Complete relaxation (mouth opened easily and fully) occurred in 95.4% of study patients. Incomplete relaxation (firm manual separation required to open the mouth fully) was seen in 4.4% of the patients. One child (0.2%) had masseter muscle rigidity (mouth could not be fully opened but intubation possible). There were no incidents of trismus (teeth clamped shut and intubation via direct visualization impossible). The incidence of incomplete relaxation and masseter muscle rigidity did not correlate with the presence or degree of fasciculations or the type of surgical procedure. There were no clinical signs of a hypermetabolic state or myoglobinuria in any patient. CONCLUSIONS: Incomplete jaw relaxation after a halothane-succinylcholine sequence is not uncommon in children, and is considered a normal response.

Anesthesia↗
PubMed2000

Hypertrophic branchial myopathy with uniform predominance of type 1 fibres. Case report.

A 17-year-old Japanese girl presented with left masseteric hypertrophy. She had a habit of chewing only on the affected side. Histochemical study of the masseter muscle showed myopathic changes characterised by uniform type 1 fibres with gross hypertrophy, increases of internal nuclei and split fibres, and endomysial fibrous tissue. This condition could be compatible with hypertrophic branchial myopathy, because it was confined to the masseter muscle and so cannot be classified into any known type of systemic myopathy.

Adolescent↗
PubMed2004

Comparison of algometry and palpation in the recognition of temporomandibular disorder pain complaints.

AIMS: To determine the construct validity of algometry and to compare it with that of palpation, and to compare tenderness of masticatory muscle sites and the temporomandibular joint (TMJ) on palpation and on algometry. METHODS: Two hundred fifty subjects, 148 with temporomandibular disorder (TMD) pain complaints, underwent a standardized blinded physical examination that included pain-intensity measures on palpation and pressure pain threshold measures on algometry of masseter muscle sites, temporalis muscle sites, and the TMJ. RESULTS: Logistic regression analysis indicated that the recognition of TMD pain complaints based on pressure algometry was comparable to that of palpation (R2 = 0.22 and R2 = 0.21, respectively). The masseter muscles were most tender to palpation and algometry, followed by the TMJs and the temporalis muscles. CONCLUSION: Construct validity of algometry in the recognition of TMD pain complaints is comparable to that of palpation, and differences in tenderness on palpation and on algometry are found between masticatory muscle sites and the TMJ.

Adult↗
PubMed1998

Masseteric nerve: a possible donor for facial nerve anastomosis?

In the medical treatment of facial nerve paralysis a large number of different techniques have been developed to restore the function of the facial nerve. These include (a) the ipsilateral nerve grafting (e.g., partial hypoglossal-facial, spinal accessory-facial, partial glossopharyngeal-facial), (b) crossfacial nerve grafting and (c) temporal muscle flaps or even free muscle transfers. None of these techniques uses the masseteric nerve as a graft for reconstruction of the facial nerve. This preliminary report deals with the anatomical basis, which could lead to a new technique. The masseteric nerve leaves the infratemporal fossa through the mandibular notch, accompanied by the masseteric artery. At this level the nerve consists in nine of 36 cases studied of only one branch (25.0%), in 17 cases of two branches (47.0%), in nine cases of three (25.0%), and in the remaining case of four branches (2.8%). There are three main reasons for considering the masseteric nerve as a possible donor for at least the orbicular branch of the facial nerve: (1) The approach to the mandibular notch is quite simple; (2) since the nerve consists of two or more branches in 75.0% of the cases, severe dysfunction of the masseter muscle should not occur; (3) if there is complete denervation of the masseter muscle, its function may be taken over by the temporalis muscle.

Anastomosis, Surgical↗
PubMed1989

[A case of unilateral masticatory spasm without hemifacial atrophy].

Masticatory spasm is a rare clinical feature and mostly associated with disorders of general movement. Usually it occurs bilaterally. Unilateral masticatory spasm is mostly associated with facial hemiatrophy. So, unilateral masticatory spasm without facial hemiatrophy is extremely rare. As far as we have investigated, only one case has been reported in the literature. We will report one more case herein, with some discussion on its pathogenesis. Case report A 44-year-old man presented with a 8 month history of slowly progressive recurrent spasm of the left masseter muscle. The spasm was exaggerated by tension and lasted for up to 10 seconds. Several drugs could not reduce the frequency of spasm, but only clonazepam could decrease it slightly. On admission, the spasm lasted usually for 1 or 2 seconds. Except for masticatory spasm, neurological examination comprising trigeminal nerve function, was normal and facial atrophy was not observed. On the contrary, hypertrophy of the left masseter muscle was noted. Needle electromyography (EMG) study revealed synchronized spasm discharges of the ipsilateral masseter, lateral and medial pterygoid muscles. All of other investigations, including CSF analysis, electroencephalography, somatosensory evoked potential, visual evoked potential, CT scan and vertebral angiography, showed normal findings. After all, we could not find any apparent organic lesions which cause masticatory spasm, so surgical treatments were not carried out. He was discharged and now, continues to take clonazepam daily.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗