Characteristics of Grouped Discharge Waveforms Observed in Long-term Masseter Muscle Electromyographic Recording: A Preliminary Study

We investigated the characteristics of grouped discharge (GD) waveforms obtained from long-term masseter electromyogram (EMG) recording in 6 female temporomandibular disorder (TMD) patients with myofascial pain and 6 healthy females. The EMG measurement was performed from the morning of the experiment day until the subject woke up the next day. We observed a significantly larger number of GD waveforms in the TMD group compared to the control group (p=0.002). Our results indicate that the existence of GD waveforms in masseter EMGs might be a predictor of future TMD with myofascial pain

Mechanomyographic activity in the human lateral pterygoid muscle during mandibular movement

The activity of the lateral pterygoid muscle has been regarded to be related to the pathological condition of the temporomandibular joint (TMJ) in the craniomandibular disorders. Because the lateral pterygoid muscle is a deep muscle, a needle electrode is necessary for EMG recordings. The purpose of this study was to establish a non-invasive method for the evaluation of muscle activity of the lateral pterygoid muscle using mechanomyogram (MMG). In three male subjects, surface electromyogram (EMG) in the left masseter muscle, left anterior and posterior belly of the temporal muscle, left anterior belly of the digastric muscle and needle EMG of the inferior head of the lateral pterygoid were recorded during mandibular movement tasks simultaneously with the MMG derived from a condenser microphone in the external ear canal. There were significant positive correlations between the needle EMG signal of the lateral pterygoid muscle and the MMG signal for the tasks of static jaw opened position of 30 mm of interincisal distance (p = 0.000, R(2)=0.725), static jaw opened position of 40 mm of interincisal distance (p = 0.000, R(2) = 0.753), 5 mm protruded mandibular position (p = 0.000, R(2) = 0.653), the most protruded mandibular position (p = 0.000, R(2) = 0803). On the contrary, for the task of maximal clenching, there was no significant correlation between the EMG signal of the lateral pterygoid muscle and the MMG signal. These results suggest that the activity of the lateral pterygoid muscle could be evaluated by the MMG signals recorded in the external ear canal, unless jaw closing major muscles show active contraction

ウシ ト ソノ キンエンシュ ノ キョウツウ セッケッキュウ コウゲン

ウシとその近縁家畜に共通する赤血球抗原を特定するために,アジア在来牛,バリウシ,ガヤール,ヤク,スイギュウ,ベゾアー,ヤギおよびヒツジの計1,000頭以上について,32種類のウシ血液型判定用モノクローナル抗体を用いた試験を行なった。これらの家畜はウシと34.4～87.5%の赤血球抗原を共有していた。共通抗原の数から推定すると,ウシ亜属(Bos)とガウア亜属(Bibos)間は,ウシ亜属(Bos)とヤク亜属(Poehagus)間より近縁であった。A2抗原は調べた8種全てに分布する抗原だった。Fc抗原の存在はウシ亜科とヤギ亜科の動物を区別した。すなわちウシ,バリウシ,ガヤール,ヤク,スイギュウのすべての個体がFc抗原を持つのに対し,ヤギやヒツジでFcをもつ個体は認められなかった。To detect common erythrocyte antigens among cattle and their close relatives, extensive tests on red blood cells from more than 1,000 animals including several indigenous cattle from various Asian countries, Bali cattle, Gayal, Yaks, Water buffaloes, Bezoar and some breeds of goats and sheep were screened with thirty-two bovine red blood group monoclonal antibodies. The five species except cattle, Bezoar and Gayal shared 34.4-87.5% of erythrocyte antigens with cattle. Based on the number of common erythrocyte antigens in each species, the relationships between subgenera Bos and Bibos was closer than that between subgenera Bos and Poephagus. The A2 antigen was distributed among all the eight species screened. The presence of the Fc antigen could be used to distinguish subfamily Bovinae from subfamily Caprinae ; that is all individuals of cattle, Bali cattle, Gayal, Yaks and Water buffaloes had the Fc antigen but not goats nor sheep

Specific diurnal EMG activity pattern observed in occlusal collapse patients: relationship between diurnal bruxism and tooth loss progression.

AIM:The role of parafunctional masticatory muscle activity in tooth loss has not been fully clarified. This study aimed to reveal the characteristic activity of masseter muscles in bite collapse patients while awake and asleep. MATERIALS AND METHODS:Six progressive bite collapse patients (PBC group), six age- and gender-matched control subjects (MC group), and six young control subjects (YC group) were enrolled. Electromyograms (EMG) of the masseter muscles were continuously recorded with an ambulatory EMG recorder while patients were awake and asleep. Diurnal and nocturnal parafunctional EMG activity was classified as phasic, tonic, or mixed using an EMG threshold of 20% maximal voluntary clenching. RESULTS:Highly extended diurnal phasic activity was observed only in the PBC group. The three groups had significantly different mean diurnal phasic episodes per hour, with 13.29±7.18 per hour in the PBC group, 0.95±0.97 per hour in the MC group, and 0.87±0.98 per hour in the YC group (p<0.01). ROC curve analysis suggested that the number of diurnal phasic episodes might be used to predict bite collapsing tooth loss. CONCLUSION:Extensive bite loss might be related to diurnal masticatory muscle parafunction but not to parafunction during sleep. CLINICAL RELEVANCE SCIENTIFIC RATIONALE FOR STUDY:Although mandibular parafunction has been implicated in stomatognathic system breakdown, a causal relationship has not been established because scientific modalities to evaluate parafunctional activity have been lacking. PRINCIPAL FINDINGS:This study used a newly developed EMG recording system that evaluates masseter muscle activity throughout the day. Our results challenge the stereotypical idea of nocturnal bruxism as a strong destructive force. We found that diurnal phasic masticatory muscle activity was most characteristic in patients with progressive bite collapse. PRACTICAL IMPLICATIONS:The incidence of diurnal phasic contractions could be used for the prognostic evaluation of stomatognathic system stability

Mean number of episodes per hour.

<p>Mean number (S.D.).</p>#<p><i>p</i><0.05, vs Phasic and Mixed,</p>§<p><i>p</i><0.05, vs MC and YC.</p><p>(Bonferroni multiple comparison test).</p

ROC curve for phasic, tonic, and mixed episodes (threshold: >20% MVC).

<p>a. ROC curve for episodes during waking hours, b. ROC curve for episodes during sleep.</p

Mean duration and mean burst strength of phasic episodes between PBC, MC and YC groups while awake and asleep.

<p>Mean number (S.D.).</p>§<p><i>p</i><0.05, vs MC and YC.</p><p>(Student’s <i>t</i>-test).</p

Typical panorama x-ray view of Eichner Index B4 patient.

<p>Note the absence of posterior occlusal support with highly resorbed alveolar bone (white arrow).</p