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PubMed1982

TMJ symptoms and referred pain patterns.

The purpose of this study was to determine the relationship between TMJ symptoms, (muscle tenderness, joint noise, deviant jaw opening and closing patterns, and limited jaw opening), and a history of referred pain patterns (earaches, headaches, neck pain, and sinus problems). A questionnaire was completed by 100 subjects regarding histories of the previously mentioned problems. The researcher then examined the subject's TMJs, and their symptoms were recorded as being present or absent. The following relationships were found to be significant: Headaches and lateral pterygoid muscle tenderness, Earache and medial pterygoid muscle tenderness, Neck pain and one or more tender muscles, Sinus problems and one or more tender muscles, Sinus problems and temporal muscle tenderness, Sinus problems and medial pterygoid muscle tenderness. However, r values for the above relationships were between 0.22 and 0.3 indicating that the relationships were not strong. It appears that some normal patients already have patterns of masticatory muscle tenderness and associated referred pain patterns prior to seeking treatment for acute TMJ symptoms.

Adult↗
PubMed2000

Adaptation of normal and hypofunctional masseter muscle after bite-raising in growing rats.

The aim of this study was to analyze the effects of prolonged muscular elongation induced by bite-raising on the length of the muscle belly, sarcomeres and aponeurosis of the anterior deep masseter in the growing rat. Another aim was to determine the role of different functional conditions of this muscle in the adaptation process. Ninety-six young male rats were split into two groups: one was fed a hard diet and the other a soft diet to develop different functional capacities in the masticatory muscles. After 2 wk, half of the rats in both groups were fitted with an appliance that raised the bite by 2 mm. The measurements on the muscles were performed in situ. The insertion of the appliance stretched the anterior masseter muscle. After 4 wk, the vertical dentoskeletal dimension, the muscle belly, and the sarcomeres showed no difference in length among the groups. However, the aponeurosis was longer in the rats wearing the appliance compared to the controls, and among the bite block groups it was longer in the rats fed a hard diet. Length adaptation occurred in the aponeurosis. Clinically this may imply a need for reactivation of functional appliances to increase their efficiency, at a rate possibly depending on masseter muscles functional condition.

Acrylic Resins↗
PubMed2001

Histopathologic features of masseter muscle in the distrophic hamster (UM-X7.1 Syrian hamster).

Dystrophic hamster has been regarded as the useful model animal for Severe childhood autosomal recessive muscular dystrophy (SCARMD). Although, many studies on Dystrophic hamster have utilized the muscular tissue of the trunk, however no study have been analyzed for the masticatory muscle. For this study, we used a Dystrophic hamster (UM-X7.1 Syrian hamster) to histochemically investigate the effect of muscular dystrophy on the masseter muscle. Large and small regenerated muscle fibers, and necrotic fibers were detected almost in all areas. Opaque fiber, hypertrophic fiber with fiber splitting structure and necrotic fiber filled up by mononuclear phagocytes were recognized. The region, in which the mononuclear phagocytic cells infiltrated, showed strong positivity to acid phosphatase, and lysosome enzyme. There were many muscle fibers with reduced levels of succinate dehydrogenase (SDH) activities in the muscle fiber. Some TUNEL-positive cells were confirmed in both necrotic and non-necrotic areas. It was suggested that a part of TUNEL-positive cells are the cells originated from the connective tissue or immunocytes. In this result, histopathologic changes of the masseter muscle of the UM-X7.1 Syrian hamster was similar to muscle of the body trunk in the past reports. As the result, it was suggested that jaw closing movements may be negatively affected caused by the decline of the masseter muscle twitch. And, the point of view by which apoptosis is the trigger for the muscle fiber collapse were not seen in the Dystrophic hamster masseter muscle. We suggest that apoptosis is a one step in the process of regeneration of muscle fibers.

Acid Phosphatase↗
PubMed2004

The association between the masseter muscle, the mandibular alveolar bone mass and thickness in dentate women.

OBJECTIVE: Since muscle strength has been demonstrated to affect the bone in the long bones and spine, the possibility exists that the bone mass and dimension of the alveolar processes could be influenced by the function of the masticatory muscles. Therefore, the purpose of this study was to investigate whether two local factors (ultrasonographic masseter thickness, and occluding teeth) plus the skeletal bone mineral density (BMD) affect the mandibular alveolar bone mass (MABM) and the bucco-lingual alveolar thickness of the alveolar process. DESIGN: The thickness of the masseter muscle was evaluated by ultrasound imaging in 62 dentate women (40-75 years) with no periodontal disease and no dental infection in the premolar region consecutively selected from the patients in a public dental clinic. MABM was evaluated using periapical radiographs. The bucco-lingual thickness of the alveolar process was measured on dental casts with a dial calliper. BMD of the forearm was determined with dual energy X-ray absorptiometry. RESULTS: Multiple regression analyses demonstrated that masseter thickness and the number of occluding mandibular teeth in the lateral segment were significant determinants of MABM and of the interdental thickness, but BMD was not. The number of years after menopause and struma/gastro-intestinal disease influenced MABM but not the alveolar thickness. CONCLUSION: The local factors played an important role in the posterior mandibular segment and their effect might partly explain the low correlation between MABM and skeletal BMD.

Adult↗
PubMed1990

Facial growth and oral function in a case of juvenile rheumatoid arthritis during an 8-year period.

The present report is a detailed analysis of facial growth and oral function in a girl with juvenile rheumatoid arthritis of the temporomandibular joints. She was followed from 9 to 17 years of age prior to and after orthognathic surgery. Facial growth was assessed by facial photographs, dental casts, and roentgencephalometry, and oral function was assessed clinically by electromyography, kinesiography, and bite force. In addition, histological and histochemical analysis was performed on biopsy material from her masseter muscle obtained at the time of surgery. The study showed a clear relationship between facial growth and oral function. Dysplastic growth of the mandible led to an increasingly unstable occlusion with poor working conditions for the masticatory muscles. The muscles became weak, and even revealed marked structural histological and histochemical changes. Based on these observations it is suggested that the conventional treatment strategy with postponement of orthodontic or orthognathic surgical treatment until cessation of growth is abandoned and that early treatment should be undertaken to maintain occlusal stability throughout the growth period.

Arthritis, Juvenile↗
PubMed2003

Masseter muscle thickness and maxillary dental arch width.

The purpose of the present investigation was to study the relationship between the ultrasonographic thickness of the masseter muscle and the width of the maxillary dental arch. The sample comprised 60 consecutive orthodontic patients (37 females, 23 males), 7-18 years of age with a Class I relationship and minor malocclusion. The thickness of the masseter muscle was measured ultrasonographically. Recordings were performed bilaterally with the muscles both in relaxation and under contraction. Maxillary intermolar width was measured with an electronic calliper as the distance between the palatal surfaces of the first permanent molars. Intermolar width showed no association with age and gender. However, masseter muscle thickness showed a direct, significant (P < 0.0001) association with these two factors together, i.e. the masseter muscle was thicker in older individuals and in males. In the female group, maxillary intermolar width showed a direct, significant association with masseter thickness both during contraction (P < 0.006) and relaxation (P < 0.013), i.e. females with thicker masseter muscles had a wider maxillary dental arch. In the male group, however, no significant relationship was found between maxillary intermolar width and masseter thickness. The findings of this study indicate that the functional capacity of the masticatory muscles may be considered as one of the factors influencing the width of the maxillary dental arch.

Adolescent↗
PubMed2005

Changes in masseter muscle blood flow during voluntary isometric contraction in humans.

The effect of jaw clenching on local blood flow in the masseter muscle was measured using the hydrogen clearance method in 13 healthy subjects. Sustained isometric masseter-muscle contraction levels of 25 and 50% of maximum voluntary contraction (MVC) were investigated. The blood flow at 25% MVC before contraction, during contraction and after contraction was 12.3 +/- 10.9, 19.2 +/- 12.1 and 78.8 +/- 63.9 mL min(-1) (100 g)(-1) (mean +/- s.d.), respectively. At 50% MVC, it was 14.2 +/- 12.9, 18.6 +/- 10.0 and 80.1 +/- 61.8, respectively. The volume of blood flow was significantly greater after contraction as compared with before contraction at both levels (P < 0.0001) and there was no significant difference between before and during contraction periods (P = 0.17: 25% MVC; P = 0.38: 50% MVC). At 50% MVC blood flow before contraction and the difference in blood flow before and during contraction showed significant negative correlation (r = -0.636, P < 0.02). When the volume of blood flow was low before contraction it tended to increase during contraction and decreased when it was high before contraction. These findings indicate that blood flow in the masseter muscle during sustained isometric contraction is affected by the condition of contraction and may be influenced by the muscle region. It was also indicated that the blood flow during high level contraction was influenced by the volume of blood flow before contraction. Clinically, our findings may help to understand pathological changes which may lead to chronic masticatory muscle pain.

Adult↗
PubMed1983

Computed tomography of the nasopharynx and related spaces. Part II: Pathology.

Malignant tumors of the nasopharynx were analyzed by region of origin and route of spread. Nasopharyngeal carcinomas produced early submucosal infiltration of the deglutitional muscle layer with enlargement of the levator palati muscle and lateral displacement of the parapharyngeal space. Serous otitis media was frequently associated, and the trigeminal nerve was occasionally involved. Intracranial extension via the foramen lacerum was frequent. Metastases to the infratemporal fossa produced early involvement of the masticatory muscle layer with medial displacement of the parapharyngeal space. Adenoid cystic carcinomas showed late but disproportionate involvement of the sphenoid sinus. Chordomas extended into the retropharyngeal soft tissues via the petro-occipital fissure. Maxillary sinus carcinomas, which were very large at the time of presentation and impinged on the nasopharynx, showed extensive destruction of the pterygoid plates.

Carcinoma, Adenoid Cystic↗
PubMed1996

Electrical stimulation of masseter muscles maintains condylar cartilage in long-term organ culture.

When condylar cartilage is maintained under nonfunctional organ culture conditions, its phenotypic expression is altered to a premature form with less expression of the type II collagen characteristic of mature chondroblasts. The aim of this study was to examine whether, by electrical stimulation of the major masticatory muscle, the masseter muscle, chondrogenic expression could be maintained under organ culture conditions in which the jaws with the craniomandibular joint were cultured in one block. Sixty BALB/c mice of both sexes were divided randomly into three groups of equal size. Two groups were decapitated at the age of 5 days. The cranial base and mandible were dissected out in one block, and the explant was placed on its cut surface on a culture dish. The masseter muscles of the explants in one group were stimulated with an electric pulsing device delivering an AC current of a frequency of 0.7 Hz and an amplitude of 5V with hourly active and silent periods. Five experimental and five control explants were fixed after culture periods of 1, 3, 7, and 14 days. The mice in the third group were used as in vivo controls. By electrical stimulation of the masseter muscle, the phenotypic characteristics of the condylar chondroblasts, such as the deposition of type II collagen and the thickness of the cartilage layers, closely resembled the situation in vivo, while the controls in a non-functional environment gradually lost their characteristic form.

Analysis of Variance↗
PubMed2003

Chemical phenotypes of muscle and cutaneous afferent neurons in the rat trigeminal ganglion.

Retrograde labeling was combined with cytochemistry to investigate phenotypic differences in primary afferent neurons relaying sensory information from deep and superficial craniofacial tissues. Calcitonin gene-related peptide (CGRP), substance P (SP), somatostatin (SOM) immunoreactivity and isolectin IB4, and cholera toxin B (ChTB) binding were examined for trigeminal masticatory muscle and cutaneous afferent neurons. Somata labeled from muscle were larger than cutaneous afferent neurons. Muscle afferent neurons exhibited positive staining as follows: 22% CGRP, 5% SP, 0% SOM; 18% ChTB, 5% IB4. The somata of CGRP- and SP-positive muscle afferent neurons were smaller than that of the overall muscle afferent population. Size differences were not detected between IB4- or ChTB-binding muscle afferent neurons and the total muscle afferent population. The following distribution was found for cutaneous afferent neurons: 26% CGRP, 7% SP, 1% SOM, 26% ChTB, 44% IB4. Cutaneous afferent neurons positive for SP were smaller, while ChTB-binding cutaneous afferents were larger than the overall cutaneous afferent population. No size differences were found between cutaneous CGRP-, SOM-, or IB4-positive neurons and the total cutaneous afferent population. Target-specific differences exist for SOM and IB4. The percentage of cutaneous afferent neurons positive for SOM and IB4 exceeds that for SOM- or IB4-positive muscle afferents. The number of retrogradely labeled neurons never differed between sexes. The percentage of retrogradely labeled muscle afferent neurons that were CGRP-positive was greater in males than females. These data indicate the presence of phenotypic, target, and sex differences in trigeminal ganglion primary afferent neurons.

Animals↗
PubMed1997

A controlled evaluation of ibuprofen and diazepam for chronic orofacial muscle pain.

The clinical efficacy, side effect liability, and hormonal effects of two prototypic pharmacologic agents were evaluated for the management of chronic myogenous facial pain in a double-blind, randomized, controlled clinical trial. Thirty-nine subjects (35 women,. 4 men) with daily or near-daily orofacial pain of at least 3 months' duration and tenderness to palpation of masticatory muscles participated. Patients were randomly allocated to one of four treatments: placebo, diazepam, ibuprofen, or the combination of diazepam and ibuprofen. Pain, mood, muscle tenderness, maximal interincisal opening, and plasma levels of beta-endorphin were measured following 2-week baseline and 4-week treatment periods. Pain, as measured by a visual analog scale, was significantly decreased in the diazepam and diazepam plus ibuprofen groups but not for the ibuprofen or placebo groups. Analysis of variance showed a significant drug effect for diazepam but not for ibuprofen, indicating that pain relief was attributable to diazepam. No significant changes were noted in muscle tenderness, interincisal opening, or plasma beta-endorphin level. This study supports the efficacy of diazepam in the short-term management of chronic orofacial muscle pain. The lack of effect following administration of an anti-inflammatory analgesic suggests that inflammation is not the basis for chronic muscle pain in the orofacial region, and that the analgesic effect of such medications is not sufficient for pain relief in this condition.

Adult↗
PubMed2001

Conditioning of heteronymous H reflex in human temporalis muscle by stimulation of perioral afferents.

A heteronymous H reflex in the temporalis muscle can be elicited by selective stimulation of the masseteric nerve. The present study aimed at defining the optimal amplitude of the H reflex to detect inhibitory changes induced by stimulation of the perioral afferents and at providing new information on the control of masticatory muscles. Sixteen healthy volunteers participated in the experiment. A conditioning stimulus (CS) to the perioral skin was applied at various delays before an ipsilateral selective masseteric nerve stimulation (test stimulus: TS) while the subject was clenching the teeth at 25% of the maximal voluntary contraction. Two intensities of CS and TS were employed, high and low. The peak-to-peak amplitude of the H reflex (TS) and the root-mean-square value of the preceding electromyography were measured and the data analyzed by three-way analysis of variance and Tukey's posthoc tests. For both intensities used the heteronymous H reflex in the temporalis muscle was significantly decreased by prior activation of perioral afferents for delays from 5 to 60 ms. With a delay of 5 and 35 ms the preceding EMG level was not changed, while it was reduced at 20 and 60 ms delay. The intensities used to elicit the heteronymous H reflex of the temporalis muscle were appropriate to detect a reduction in motoneuron excitability. The reduction in the H reflex without a change in the preceding EMG at 5 and 35 ms delays could be due to presynaptic inhibition of the masseteric afferents exerted by the ipsilateral perioral afferents.

Adult↗
PubMed2000

Surface electromyographic evaluation of the asymptomatic human masseter muscle with turns and amplitude analysis.

Electromyographic turns, or reversals of direction, per second (TS) and mean amplitude per turn (AT) are variables that have been widely used to assist and support an electrodiagnosis in neuromuscular disorders. The purpose of this study was to explore the feasibility of utilizing the TS and AT in conjunction with surface electrodes as a method for assessing masticatory muscle function. Ten normal subjects were instructed to exert brief isometric contractions at various levels, and the TS and AT were calculated from the surface electromyographic signals of the masseter muscle. Our results showed that the AT increased with contraction at all contraction levels, demonstrating a linear relationship, while the TS showed a nonlinear increase characterized by an initial steep rise followed by a plateau, which was simulated with a third polynomial function. It is considered that the TS and AT may provide valuable physiological information about the underlying mechanisms of recruitment and the firing of motor units.

Adult↗
PubMed2005

Myosin heavy chain protein and gene expression in the masseter muscle of adult patients with distal or mesial malocclusion.

The aim of this study was to determine the amount of myosin heavy chain (MyHC) proteins and MyHC mRNA in muscles of patients with different positions of the mandible. Ten adult patients for orthognathic surgery were divided into two groups: distal and mesial malocclusion. The mRNA expression of two MyHC isoforms of the anterior and posterior part of the right and left side of the human masseter muscle was analysed with a competitive RT-PCR assay. An exogenous template that includes oligonucleotide sequences specific for sarcomeric MyHC isoforms (1 and 2x) was constructed and utilized as competitor. Different isoforms of the MyHC protein were identified by Western blot analysis. In the total mRNA pool of the masseter muscle, the MyHC 1 mRNA level was 25.5 +/- 7.6% and the MyHC 2x mRNA was 2.5 +/- 1.2%. The anterior part of the masseter muscle from patients with distal occlusion contained more type 1 and 2x MyHC mRNA, as compared to patients with mesial occlusion (P < 0.05). No difference in the protein distribution was observed. The differences in mRNA expression may be caused by the enforced stress of the masticatory muscle in distal occlusion because of the disadvantageous pivot.

Adult↗
PubMed2003

Sex differences in rabbit masseter motoneuron firing behavior.

To evaluate whether sex differences in the proportions of fibers of different phenotypes in the masseter muscle might be the result of differences in the behavior of their motoneurons, we studied the firing patterns of masseter motoneurons in adult male and female rabbits. Activity in individual motoneurons was determined from high spatial resolution EMG recordings made during cortically evoked rhythmic activation of the masticatory muscles. Although some motoneurons could be said to fire according to slow-tonic or fast-phasic patterns, most did not. In both sexes a substantial range of median firing rates and median firing durations was found. In adult males, masseter motoneurons fired more rapidly than those recorded from adult females. No significant sex differences in motoneuron firing duration were found. These results are consistent with the hypothesis that androgen-induced differences in rabbit masseter muscle fiber phenotype are a reflection of differences in motoneuron firing rate. Whether this effect of androgen is directly upon the motoneurons or is the result of a response of muscle fibers to androgen remains to be investigated.

Action Potentials↗