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At least 1,135 records · Page 63Linked to original sources
PubMed1989

Interactions between jaw-muscle recruitment and jaw-joint forces in Canis familiaris.

Electromyographic activity from the jaw-adductor muscles was recorded during mastication and bone crushing in domestic dogs (Canis familiaris). During mastication, balancing-side temporalis electromyographic activity was much less than that of the working side while masseter muscle electromyographic activities were of similar amplitude. Despite the large bite forces that were produced during bone crushing, balancing-side masseter and temporalis electromyographic activities were always smaller than the working-side electromyographic amplitudes. Based upon geometric modelling, it is proposed that balancing-side muscle activity is reduced because of its tendency to produce mechanically disadvantageous jaw-joint forces. This hypothesis was tested by correlating bone strain adjacent to the jaw joint measured during manipulations of the mandibular condyle with bone strain recorded during the simulation and stimulation of jaw-adductor muscle activity. Working-side muscle activity produced bone strain that correlated with a compressive joint loading, while balancing-side muscle activity, with an occlusal fulcrum at the carnassial teeth, produced bone strain indicative of an anteroventral movement of the working-side mandibular condyle which eventually ruptured the joint capsule. When the temporalis and masseter muscles were stimulated bilaterally with a carnassial bite point, bone strain indicative of a ventrally directed and potentially damaging condylar movement was produced. It is proposed that working-side muscle activity exceeds balancing-side muscle activity during carnassial biting to maintain jaw-joint stability.

Animals↗
PubMed1978

[Electromyographic silent period in the masseter and temporal muscles].

For some years, many authors have studied the silent periods (S.P.) in masticatory human muscles, during voluntary clenching, biting or mastication as well as during electrical or mechanical stimulation of various parts of the mouth. This S.P. appears as a flattening in the electromyograph tracing taken from masseter and temporalis anterior muscles simultaneously. After an analysis of the methods and results of previous authors, we give and discuss our result, obtained from records on masseter and temporalis anterior muscles, on right and left sides, on healthy subjects. They tapped first their teeth, then masticated pea-nuts, pieces of apple and soft bread. We obtained 571 S.P. after recording 1 745 cycles, and in contrary to the opinion of most of the authors, we were not able to obtain simultaneous S.P. in all four muscles at every cycle, except on 26 occasions. To conclude, we discuss our observations and suggest pathways for the inhibiting reflex of masticatory muscles during functions.

Adult↗
PubMed1985

Masticatory rhythm analyzing method and clinical application.

The rhythm of mastication is one of the important factors in evaluating the masticatory function. This masticatory rhythm should be observed from both the mandibular movements and masticatory muscular activities. In addition, the changes in the rhythm from the beginning to the end of the mastication process should be reflected by the chosen parameters. In order to achieve this, a new analyzing method was devised in which the electromyographic burst duration time was divided into three divisions based upon the mandibular movement phase, and two parameters were chosen to represent the rhythm. In this paper, the new method was used on the patients with a temporomandibular joint dysfunction and patients who had a mandibular segmental resection in order to evaluate its validity and clinical applicability. By the comparison of the masticatory rhythms before and after treatment, the effectiveness of this analyzing method in evaluating the masticatory functions was shown.

Adult↗
PubMed1982

The effect of maximum biting force and bone loss upon masticatory function and dietary selection of the elderly.

Simple methods are described for measuring masticatory effectiveness--the percentage of sugar chewed out of chewing gum in 20 strokes--and the height of residual mandibular bone using callipers. Both are objective methods, they are acceptable to the elderly, appropriate for denture wearers and practicable for use in domiciliary surveys. Using these and other methods, the masticatory effectiveness of housebound pensioners is shown to relate to maximum biting force, denture quality, remaining mandibular bone and dietary selection. However, opinions on the difficulty of mastication are completely unrelated to any of these measures. The level of compensation for inadequate mastication is indicated by the percentage of difficult foods eaten by geriatric hospital inpatients: there was complete overlap of percentages in those endentulous patients using dentures and those without dentures. Presumably many of these patients had adapted to swallowing very poorly chewed food. The contrasts shown between hospital inpatients and old people still at home indicate the progressive consequences of physical and neurological deterioration.

Adult↗
PubMed1995

Constrained and unconstrained postures of the mandible--a break with tradition?

Evaluation of detailed electrognathographic recordings of various movements of the mandible (and points on it) suggested interpretations at variance with some traditional concepts. Data previously accumulated from several sources were subjected to critical analysis. An objective was to assess the manner in which two rotations of the mandible influenced its postures during trials of mastication and deliberate lateral excursions. Rotations about a vertical and an antero-posterior axis appear to facilitate a greater functional posturing potential of the mandible than has previously been reported. In most instances the influence of the rotations upon mandibular posture is considerably greater than the size of the recorded angles would suggest. Some of the resulting postures seem to challenge concepts derived strictly from cadaverine anatomy. For example, during mastication the condyle does not simply glide forward and backward relative to the eminence but may be distracted downward away from it for a part of the time. Furthermore, the ability of a subject to effect a considerable variety of mandibular postures challenges traditional reliance upon constrained mandibular movements as a means of evaluating function.

Humans↗
PubMed1995

[An evaluation of complete denture with the EMG of masseter in chewing cycle].

The aim of this investigation was to study the EMG of masseter of edentulous patients in chewing cycle. 18 subjects were examined by Disa-2000M Neuro-electromyograph. It was found that the period of chewing cycle of the patients with complete denture was distinctly longer than that of normal people, and the change of the duration prolongs the time phases. The velocity was relatively slow when trying to keep the stability of dentures. The amplitude of potential in masseter was lower in chewing cycle, but it did not affect the function of mastication. The abnormal pause after occlusal contact of denture had an influence on the function of mastication.

Adult↗
PubMed1995

Biomechanics of occlusion and the articulator.

The evaluation of the occlusion is important in prosthodontics and restorative dentistry because the occlusal surfaces of the teeth to be restored must be functional units of the patient's stomatognathic system. Specifically, the morphology of the cusps, fossae, grooves, and marginal ridges should support the mandible in the intercuspal position and where appropriate, during eccentric jaw movements and in functional activities such as mastication. Restored teeth should not interfere with mandibular function in mastication, speech, and swallowing nor should they transmit excessive force to the attachment apparatus or the temporomandibular joint either in the intercuspal or eccentric jaw positions or during movement.

Biomechanical Phenomena↗
PubMed1994

Recording mandibular movement: technical and clinical limitations of the Sirognathograph.

It is essential to know the limitations of any equipment used for research or clinical purposes. Clinical electronic equipment is commonly sold for "black box" use without specification of artifacts. This study tested the technical and clinical limitations of the Sirognathograph, which is a device used for recording mandibular movement. From a technical point of view, the Sirognathograph's slow sampling speed and sample artifacts have been shown to be the system's main limitations; however, it was possible to eliminate sampling artifacts by using a customized pulse generator and software for controlled data acquisition. Clinically, the Sirognathograph appears to have some inherent limitations in its accuracy. The effect of cranial movements during mastication can cause a baseline drift with consequent errors in the recording of mandibular position. This problem was controlled in this study by using a headband to stabilize the cranial movements during mastication. Also, the spatial relationships between the aerial and both the cranial base and the magnet were found to be critical for repeatability of the recordings.

Adolescent↗
PubMed1994

[For practical salivary flowmetry. A weighing technic].

No one method of salivary flowmetry has been found to be practical, reliable and fully significant. Consequently, the diagnosis of salivary gland failure remains uncertain and imprecise even though the diagnostic question is often raised. A simplified and effective weight measurement could be more widely used. Saliva is sampled easily with small compresses inserted into the sublingual groove and left in potion for 5 minutes without deglutition or mastication for a saliva collection and close as possible to the baseline level; then for 1 minute after mastication to collect stimulated secretion. The compresses are then weighted. The reliability of this method must be confirmed with a multicentric study.

Absorption↗
PubMed1996

Effects of anatomic site, oral stimulation, and body position on estimates of body temperature.

BACKGROUND: A prior investigation characterized the range of body temperature in healthy young adults and established the importance of diurnal variations in defining the febrile state. METHODS: Sequential rectal, oral, and tympanic membrane temperature measurements were performed on 22 healthy subjects to determine the quantitative effects of anatomic site, oral stimulation, and body position on estimates of body temperature. RESULTS: Mean rectal temperatures exceeded concurrent oral readings by 0.4 degrees C +/- 0.4 degrees C (0.8 degrees F +/- 0.7 degrees F), which, in turn, exceeded concurrent tympanic membrane readings (obtained with a digital thermometer [IVAC Corp, San Diego, Calif]) by 0.4 degrees C +/- 1.1 degrees C (0.7 degrees F +/- 2.0 degrees F). Tympanic membrane readings were significantly more variable (both intrasubject and intersubject) than rectal or oral readings, especially when cerumen was present in the external ear canal being examined (P<.05). Mastication and smoking both caused significant increases in oral temperature that persisted for greater than 20 minutes. Drinking ice water caused a significant but more transient decrease in oral temperature. Of these activities, only mastication appeared to influence tympanic membrane readings. Body position exerted a modest effect on rectal temperature readings, but did not significantly affect oral or tympanic membrane readings. CONCLUSIONS: These findings indicate that, in addition to diurnal fluctuations in body temperature, the effects of anatomic site, oral stimulation, and body position should be considered in establishing criteria for the febrile state.

Adult↗
PubMed1996

[Biological role of movement in the temporomandibular joint in sheepdogs and house cats].

The temporomandibular joints of the dog and the cat differ in morphology and movement. Characteristic differences in the teeth and the movement of the mandibula result in species-specific mastication: The dog grinds and crunches food. Moving the molars vertically, the cat cuts food to pieces. It has been postulated that the cat masticates more thoroughly than the dog. This is not true. The unilateral mincing of the cat is due to the extremely secodont teeth without possibility to grind.

Animals↗
PubMed1997

[Use of an overdenture in the prosthetic correction in a patient with cleft palate].

A fourty-year old male patient with cleft palate had been operated on four times in his childhood in order to close the defect. The shrinked dental arch and the pseudoprogenia, remaining after the operation, caused problems in the mastication and esthetic defects to the patient. With the help of an overdenture a new dental arch was created, in this way the pseudoprogenia could be eliminated, the facial harmony and the mastication could be restored.

Adult↗
PubMed1996

The histochemistry of reactive masticatory muscle hypertrophy.

There are two types of hypertrophy of the muscles of mastication in man: reactive hypertrophy, the more common form; and nonreactive enlargements-myositic, genetic, myopathic, and idiopathic. Reactive hypertrophy develops when the masticatory muscle workload is increased by local bone and dental disorders; such triggers are not powerful but act over long periods, thus demanding increased endurance. Exercise for endurance has a greater effect on the muscles of mastication than it has on the large muscles of the limbs; these react solely by stimulating the oxidative metabolism of type 1 fibers, whereas masticatory muscle reacts structurally by hypertrophy and progressive type 1 fiber predominance. Eventually enzyme instability of type 1 fibers and end stage atrophy of type 2 fibers may appear. Unexpectedly, lesions have also been found in control masticatory muscle, in particular type 2 fiber specific atrophy like that seen in long-standing acquired autoimmune myasthenia gravis. It is suggested that the adverse lesions in hypertrophied and control masticatory muscle are the consequence of post-activation fatigue.

Adult↗
PubMed2000

Ontogeny of histochemical fiber types and muscle function in the masseter muscle of miniature swine.

In this study of masticatory maturation, the ontogeny of the histochemical fiber type composition of musculus masseter is examined in the omnivorous miniature swine (Sus scrofa). Fiber type characteristics are interpreted by comparison with electromyography (EMG) recorded during feeding behavior. Similar to locomotion studies, the results suggest a correspondence between the composition and arrangement of motor units and their recruitment pattern. Serial sections of masseter muscles from 10 minipigs, ranging from 2 weeks to slightly over 1 year of age, were stained for myosin adenosine triphosphatase (mATPase) activity to distinguish slow-twitch from fast-twitch fibers, and for nicotinamide adenosine dehydrogenase-tetrazolium reductase to assess the aerobic capacity of the same fibers. Although maintaining a uniformly high aerobic capacity throughout ontogeny and in adult animals, a transition is observed in the relative proportions of fast- and slow-twitch fibers. The primarily fast-twitch neonatal pig masseter eventually comprises approximately 25-30% slow-twitch fibers in adults, with a higher predominance of slow fibers in the deep (vs. superficial) and anterior (vs. posterior) regions of the muscle. Furthermore, while individual fibers of adult masseters generally stain for either alkaline- or acid-stable mATPase activity, a substantial proportion of cells in developing animals exhibits the presence of both isozymes. EMG results indicate functional heterogeneity within the masseter of adult pigs. During chewing, when pig chow is replaced by cracked corn, EMG activity in the deep portion of the muscle either decreases or increases slightly. In the superficial portion, however, muscle amplitudes become dramatically higher for corn, surpassing levels generated for chewing the less obdurate chow. These results are consistent with a behavioral transition from neonatal suckling to sustained mastication of foods of more complex textures eaten by adult pigs. The relationship between these fiber type and EMG results for pig masseter corresponds to those pertaining to motor unit recruitment in the extensor muscles of locomotion. Implications of this work for the evolutionary morphology of mastication also are discussed.

Animals↗
PubMed1989

Food transport through the anterior oral cavity in macaques.

Intraoral transport, the movement of food or liquid through the oral cavity and oropharynx, is a major component of feeding behavior. Stage I transport, transport through the oral cavity prior to mastication, has been described for several mammals (Franks et al.: Arch. Oral Biol. 30:539, 1985; Hiiemae and Crompton: Hildebrand et al. (eds.): Functional Vertebrate Morphology, Cambridge, MA, Belknap Press, 1985). Previous work (Franks et al.: Am. J. Phys. Anthropol. 65:275, 1984) indicated that this was not a significant behavior in macaques in a laboratory setting, because food was ingested directly to the region of the cheek teeth. Although relatively infrequent in a captive situation, stage I transport does occur in long-tailed macaques through a mechanism similar to other mammals, but also subject to unique aspects of primate anatomy. Transport takes several cycles during which the food moves back and forth in an anterior/posterior direction, due to tongue movements. Because anthropoid primates lack the pronounced rugae that in other mammals prevent the anterior displacement of a bolus, stage I transport uses the rounded arch of the upper, anterior dentition to hold the food during the forward movement of the tongue. During the final cycle of transport, a pronounced twisting of the tongue, along a midline anteroposterior axis helps funnel the food item toward the postcanine teeth for subsequent mastication. This twisting, which was described in humans by Abd-El-Malek (J. Anat. 100:215, 1955) but not within the context of jaw movement, occurs prior to the closing phase of the jaw cycle.

Animals↗
PubMed1988

Quantitative electromyography of the masticatory muscles of Pteropus giganteus (Megachiroptera).

Mastication has been studied by cinematography and quantitative electromyography while flying foxes, Pteropus giganteus, were freely feeding on standardized pieces of apple, soaked raisin, and banana. The primarily orthal mandibular movements are caused by mainly bilaterally symmetrical firing of all the masticatory muscles. Asymmetric activity in the superficial and deep masseter and medial pterygoid causes slight protrusion early in opening. Slight lateral deviations at the end of opening and at the start of closing are caused by asymmetric and asynchronous activity in the pterygoids and digastrics, and by asynchronous firing of the deep temporalis and zygomaticomandibularis. Food consistency affects movement characteristics as well as characteristics of muscular activity. In this study electromyograms were digitized and the number of spikes and mean amplitude per interval (set by the filming rate) recorded. Although a significant correlation exists between descriptors, the product thereof appears to be the best predictor of certain kinematic variables (cycle length and maximum excursion of the mandible). On the other hand, the changes in magnitude of muscular activity as a function of the position of a cycle in the reduction sequence and as a function of food consistency are more translated in a variation of the mean amplitude than in a variation of the number of spikes per interval. Observed variation differs among muscles studied. It is most apparent in the superficial and deep masseter and least in the temporalis and zygomaticomandibularis. Late cycles of apple and raisin mastication are long and exhibit large gapes but almost no anterior movement. The adductor activity frequently shows a synchronized, pulsatile pattern leading to an unfused tetanus.

Animals↗
PubMed1995

Ethopharmacological analysis of naloxone-precipitated morphine withdrawal syndrome in rats: a newly-developed "etho-score".

The intensity of opiate withdrawal syndrome in rats is usually quantified on the basis of selected physical signs or global scores. However, the selection criteria of signs and scores have not been subjected to an ethological discussion, hence they appear to be somewhat arbitrary. The objectives of this study were thus: i) to analyse the rat's behaviour during the naloxone-precipitated morphine withdrawal syndrome, ii) to evaluate the validity of classic methods, and iii) to design a new "etho-score". Ten rats were implanted with morphine pellets (75 mg x 2, SC), all receiving different naloxone doses following a within-subject design (0, 0.01, 0.05, 0.1, 0.5, 1 mg/kg SC). Twenty unexperienced rats and 20 with placebo pellets were injected with either saline or naloxone. Behaviour was videotaped and later analysed by computer-based ethological techniques. The ethogram encompassed 16 patterns displayed by rats during morphine withdrawal. Frequency, duration and latency of each pattern was measured, and a cluster analysis allowed discerning the structure of behaviour. Several physical signs and the Gellert-Holtzman score were also evaluated. The data revealed that writhing responses linearly changed in a dose-related fashion, and mastication was also enhanced after naloxone. Wet-dog shakes and jumping changed following an U-shaped curve. Significant changes in weight loss were found to be dose-dependent, and highly correlated to diarrhea. Learning effects were found to reliably affect exploration, writhing responses and some physical signs. The Gellert-Holtzman score was gradually enhanced after naloxone, being affected by learning as well. Naloxone affected lying and self-care responses in placebo rats. To sum up, the data indicated that: i) classic signs are useful, although most of them are disrupted by high naloxone or affected by learning effects, ii) the Gellert-Holtzman score was validated in this study, and iii) mastication and weight loss are good indicators of naloxone-precipitated morphine withdrawal, representing the basis of an "etho-score" which is herein proposed.

Animals↗
PubMed2004

Age- and sex-stratified prevalence of physical disabilities and handicap in the general population.

BACKGROUND AND AIMS: Our aim was to provide age- and sex-stratified prevalence estimates of physical disabilities and handicap in the general Belgian population. METHODS: A cross-sectional and demographically representative health interview survey was conducted nationwide in Belgium in 1997. The 8836 persons aged 15 years and over who answered the health interview were included in this study. Seventeen items from the survey encompassing main activities of daily living (ADL) and confining were analyzed. To provide prevalence estimates as detailed as possible, neither aggregation nor dichotomization were applied. RESULTS: Women consistently reported more disability than men: mobility (p < 0.001), transfer in-out bed (p < 0.001), transfer in-out chair (p < 0.001), dressing (p = 0.004), washing hands and face (p = 0.029), getting to and using toilet (p = 0.003), continence (p < 0.001), seeing (p < 0.001) and mastication (p < 0.001). As expected, there was a marked trend for increased prevalence of disability with increasing age for both sexes. Moderate disability arose mainly from the 25-34 age group for both sexes. For both genders, severe disability appeared mainly at higher ages, particularly for the 65-74 age group. Nevertheless, the data suggest that continence problems for women, mobility and transfer issues for men, as well as mastication problems for both genders, clearly emerge earlier than age 65. Regarding handicap, observed prevalence rates were increasing, in age as was the case for disability, but no differences were found between men or women, except for confinement to house/garden, for which women presented a higher rate in general (p < 0.001) and in the 75-84 age group (p = 0.036) in particular. CONCLUSIONS: This study shows the wide range of disability types in the general population and their association with handicap. While elderly individuals consistently report higher degrees of disability and handicap, attention should also be paid to younger age groups. Disability calls for wide, coherent and relevant medical as well as social responses.

Activities of Daily Living↗