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At least 919 records · Page 51Linked to original sources
PubMed1989

Habitual mastication in dysfunction: a computer-based analysis.

To study the different parameters of habitual mastication in stomatognathic dysfunction, mandibular movements and electromyographic activity of the elevator muscles were recorded during three chewing sequences in 86 dysfunctional subjects. The Dysfunction Index system was used to treat two subgroups, patients with severe temporomandibular joint impairment and patients with severe muscle dysfunction. Data on the different parameters of mastication from the single patients, the whole group, and the two subgroups were statistically assessed and compared with those from 12 normal individuals. The following conclusions were drawn. (1) In dysfunctional patients the normal symmetrical and balanced distribution of the chewing cycles is lost and movements are more restricted. (2) The electromyographic data show marked alterations with a tendency to reduce or suppress the isometric phase of contraction during closing in the temporomandibular joint patients. This can be viewed as a defensive mechanism of the impaired system. (3) The data at hand are helpful in explaining some of the mechanisms that lead to muscle pain in dysfunctional patients.

Electromyography↗
PubMed1993

Kinesiographic and electromyographic assessment of the effects of occlusal adjustment therapy on craniomandibular disorders by a double-blind method.

Fifty-one patients with craniomandibular disorders were divided into two groups. One group underwent mock occlusal adjustment, the other was treated with adjustments to remove significant slides and nonworking-side interferences. Both groups received identical counseling. Kinesiographic and electromyographic assessment showed no significant difference between the two groups.

Adolescent↗
PubMed1991

Temporomandibular joint ankylosis: an Indian experience.

Seventy-five condylectomy and coronoidectomy specimens of temporomandibular joint ankylosis in 61 patients were studied. Fourteen patients had bilateral ankylosis, six of whom had fibrous ankylosis on one side. There were two types of ankyloses: intra-articular and juxta-articular. Intra-articular ankylosis was seen only in reankylosis or in postinfective cases. Sixty-six cases were posttraumatic juxta-articular ankylosis. A rudimentary temporomandibular joint with an atrophic condylar articular surface was found in all juxta-articular ankyloses. The size of new bone in the specimens varied from 0.5 to 3 cm. Fusion of the extra-articular bone mass with tympanic plate was also observed. Contracture of temporalis muscle was noted in all the cases, which made excision of the coronoid processes mandatory in all the arthroplasties. Arthroplasty early in childhood did not hamper growth; instead, facial remodeling was enhanced.

Ankylosis↗
PubMed2004

Functional influence of masticatory muscles on the fibre characteristics and capillary distribution in growing ferrets (Mustela putonusfuro)--a histochemical analysis.

OBJECTIVE: Changes in the masticatory function of ferrets have been shown to cause alterations in their craniofacial morphology. The aim of the present study was to investigate how the functional changes influence the histochemical characteristics of fibres of the masticatory muscles of the animal. DESIGN: Forty five-week old male ferrets were divided into two groups: one group was fed a diet of hard pellets (HD group), and one group was fed the same diet but softened with water (SD group). After 6 months, specimens of temporalis, masseter and digastricus were taken from each ferret and prepared for enzyme histochemical analysis RESULTS: Type I muscle fibres constituted the majority of the temporalis and the masseter, while the digastricus mainly comprised type II muscle fibres. The fibre-type composition did not differ significantly between the two groups. The mean cross-sectional area of type I and type II fibres in the temporalis and the masseter, and type II fibres in the digastricus was significantly greater in the HD group than the SD group. Furthermore, the HD group had a significantly greater number of capillaries per fibre, but not per surface unit (mm2). CONCLUSIONS: The results suggest that the muscle fibre size and the number of capillaries per fibre of the masticatory muscles are readily adaptesd to the altered masticatory muscle functions.

Animals↗
PubMed1996

Coupling electrical and mechanical outputs of human jaw muscles undertaking multidirectional bite-force tasks.

Previous studies have identified both linear and curvilinear relations between increasing bite-force magnitude and the integrated electromyogram (EMG) of jaw-closing muscles. In an attempt to explain the discrepancy, bite forces of incrementally increasing magnitude were produced on the right-hand side in five specified directions by eight humans. Linear regression lines were fitted to normalized EMG activities of the left and right masseter and temporalis muscles against increasing bite-force magnitude in each direction. The grand mean of linear correlation coefficients was 0.79 (+/- 0.11 SD), suggesting an overall linear relation. Each set of individual data was fitted with polynomial lines up to the third order. The best fit was selected by statistical significance of coefficients and the least-square analysis of the sum of residues for each fitted line; 62% of individual data-sets were best fitted with linear regression lines, 31% with quadratic lines and the remaining 7% with cubic lines. Repeated analysis of residue variance of the pooled data showed that either a linear or quadratic line fitted every data set except one, for which a cubic line had the best fit. Working-side muscles had significantly larger linear correlation coefficients than corresponding balancing-side muscles for most bite-force directions. Analysis of variance of linear correlation coefficients revealed that the degree of linearity often depended upon the roles played by a muscle in producing forces in different directions. It appears that linearity or non-linearity of the EMG force relation is a determinant, among other variables, of the direction of the resultant force.

Adult↗
PubMed1991

An evaluation of temporomandibular joints and jaw muscles after orthodontic treatment involving premolar extractions.

Experimental subjects (n = 29) were patients who had undergone orthodontic treatment in combination with extraction of maxillary or mandibular premolar teeth, or both. Control subjects (n = 29) were healthy dental students with no orthodontic or extraction experience. Sagittal (corrected axis) tomograms of the TMJs were used to determine the narrowest linear distances between the anterior and posterior outlines of the TMJ condyle and the TMJ fossa, expressed as the joint space ratio. There were no significant (p greater than 0.05) differences between the control and experimental ratios. Bipolar surface electromyograms of the masseter and anterior temporalis muscles were used to determine the isometric contraction velocities of these muscles until 50% and 100% voluntary isometric contraction effort (teeth clenching) was achieved. There were no significant (p greater than 0.05) differences between the control and experimental subjects. Electromyograms were also used to determine the relative contribution of the masseter and anterior temporalis muscles to the bite force developed during brief maximum voluntary tooth clenching, expressed as the activity index. There were no significant (p greater than 0.05) differences between the control and experimental subjects.

Adolescent↗
PubMed1981

Muscle activity for jaw closing during speech.

The incidence and timing of activity in the jaw-closing muscles was investigated during speech. Electromyographic activity was analyzed from the masseter, anterior temporalis, medial pterygoid, and lateral pterygoid muscles in four normal adults. Jaw movement was transduced with a strain-gauge system as the subjects read the Rainbow Passage, 11 different syllables, and trains of the same syllables at four rates. Medial pterygoid was active for all jaw-closing movements. Masseter and temporalis were often active. The incidence of lateral peak electromyographic activity were noted between muscles; however, the duration of activity in medial pterygoid was longer than in masseter and temporalis. A large amount of variability in the relative degree of activity between muscles was observed for repetitions of the same syllable with similar parameters of jaw movements. These data are discussed in relation to series of muscle coordination.

Adult↗
PubMed2000

Functional subdivision of the human masseter and temporalis muscles as shown by the condylar movement response to electrical muscle stimulation.

In previous studies from our laboratory, a functional subdivision of the human temporalis and masseter muscles was demonstrated by means of opto-electronic recordings of the lower incisal point movement responses to electrical muscle stimulation. In the present study, it was examined whether this subdivision was also reflected in different movement responses of the mandibular condyle. To that end, the condylar movement responses to unilateral stimulation of four masseter muscle parts and three temporalis muscle parts were studied in four different jaw positions. The kinematic centre was used for condylar reference point. For both the amplitude and the direction of the movement responses, the effects of stimulation location and jaw position were studied using multivariate ANOVA and contrast analyses. It was found that for both outcome variables, the functional subdivision of the masseter and temporalis muscles was also reflected in some, but not all, of the movement responses of the mandibular condyles. The deep masseter muscle part and the (anterior) temporalis muscle part responded similarly to electrical stimulation.

Adult↗
PubMed2002

Variation in masticatory muscle activity during subsequent, submaximal clenching efforts.

In previous studies to the relative contribution of the jaw closing muscles to the maintenance of submaximal clenching levels, a considerable variation in the electromyography (EMG) activities of these muscles during subsequent efforts was found. In this study, it was examined to what extent this variation could be explained by coincidental variations in mandibular positioning. From seven healthy individuals, a total of 90 EMG sweeps was recorded: three conditions (intercuspal position and two types of stabilization appliances) x three clenching levels (10, 30 and 50% of maximum voluntary contraction level) x 10 repetitions. Mandibular position was monitored with a six degrees of freedom opto-electronic jaw movement recording system. Variations in mandibular positioning during subsequent, submaximal clenching efforts explained up to 25% of the variance in the indices that quantify the relative contribution of the jaw closing muscles to the total clenching effort (P=0.000; ANOVA). Only a weak dependency of positioning upon clenching condition was found whereas during higher clenching levels, the positioning effect tended to be smaller than during lower levels. In conclusion small, coincidental variations in mandibular positioning during subsequent clenching efforts partly explain the variance in EMG activity of jaw closing muscles, especially at lower clenching levels.

Adult↗
PubMed2002

An unexpected difficult laryngoscopy.

A case of unexpected difficult laryngoscopy in a patient with gross hydrocephalus and generalized hypertonus is described. The 30-month-old girl had no antecedent history of such difficulty, having had two recent uneventful anaesthetics. We suggest that the reason for our inability to open the patient's mouth was a result of contracture of the temporalis muscle. The patient was managed using a laryngeal mask airway with controlled ventilation.

Anesthesia↗