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At least 415 records · Page 23Linked to original sources
PubMed1987

Silent myocardial ischemia during mastication.

Ambulatory outpatient monitoring of patients with angina suggests a different view of myocardial ischemia than is conventionally obtained from in-hospital tests. Multiple episodes of ST segment depression occur, and the majority of these disturbances are not associated with symptoms. Recently, studies of regional myocardial perfusion using the technique of positron emission tomography with rubidium 82 have confirmed the ischemic nature of these silent ST changes. Furthermore, activities of everyday life such as mental stress or cold exposure seem to provoke both symptomatic and asymptomatic ischemia, as judged by ST depression and reduced cation uptake. This report presents an unusual case of silent myocardial ischemia observed during the chewing of food.

Aged↗
PubMed1983

An electromyographic study of mastication in the freely-moving rat.

The EMG patterns of temporalis, masseter and digastric muscles of twenty Wistar white rats were studied as they ate large and small standard food pellets, bread and pudding. Bipolar EMG electrodes were placed in the muscles and led subcutaneously to a connector pedestal on the rat's head. Integrated records of the EMG patterns were used for analysis. The open-close chewing cycle was initiated by digastric activity to open the mouth; temporalis began the closing phase, followed soon thereafter by activity in masseter. A second burst of activity from digastric occurred during this closing phase analogous to the human lateral pterygoid muscle in stabilizing the structures of the mandibular joint.

Animals↗
PubMed1984

Optimum mouthful for food comminution in human mastication.

The effect of varying the portion of food offered for chewing (termed the mouthful) on aspects of the oral comminution of salted peanuts was investigated on six human subjects. Particle-size distributions, assessed from a sieving analysis, were similar for different mouthfuls, and could be characterized by a sieve size that would pass 80 per cent of the particles by volume in a distribution. As the food weight was increased, (a) the rate of particle-size reduction of the food declined exponentially, (b) the rate of food surface area production increased, (c) the number of chews to swallow the food increased, (d) the number of chews per unit gram to swallow the food decreased, (e) the food-particle sizes that were swallowed increased. It is hypothesized that the volume of food between the teeth at any chewing stroke depends more on food-particle size than on the weight of food in the mouth. The swallowing of small mouthfuls of peanuts may have depended more on the time to wet particles with saliva than particle size.

Arachis↗
PubMed1984

Distribution of particle sizes in food comminuted by human mastication.

The masticatory performance of an individual may be quantified by describing the size distribution of particles of a comminuted test food as a function of the number of chewing strokes. A standardized sieving method and a standardized artificial test food (Optosil) were used to obtain reproducible results. Some measurements were performed using peanuts. The distribution of particle sizes of the comminuted food was adequately described by a Rosin-Rammler distribution function for the seven participating individuals which characterizes the size distribution by the median particle size (x50) and the broadness of the distribution (b). The broadness variable b hardly depends on the number of chewing strokes, and the differences in b between the individuals are small. Considerable differences in the median particle sizes at a given number of chewing strokes were observed between the subjects, reflecting differences in efficiency of comminution of a test food. For all subjects, the median particle size decreased as a function of the number of chewing strokes N according to the relation, x50 = c X N-d. Variables c and d characterized the efficiency of comminution by the subjects.

Arachis↗
PubMed1987

A mathematical description of the comminution of food during mastication in man.

Chewing performance was quantified by determining the particle-size distribution of comminuted food as a function of the number of chewing strokes. The rate of food breakdown was taken to be the result of a combined selection and breakage process; this was quantified in a mathematical model. A linear operation on the particle-size distribution described the changes in this distribution that resulted from an additional chewing stroke. Detailed information was obtained from eight subjects on the selection and breakdown of food particles of different sizes. There were considerable inter-individual differences in the selection chances for small particles. The mathematical method facilitates study of the influence of dental morphology and muscle-related factors on the comminution of food particles.

Adult↗
PubMed1993

Influence of mastication on saliva, plaque pH and masseter muscle activity in man.

An earlier study showed that frequent gum chewing may enhance parotid gland function and reduce the acidogenicity of dental plaque. The aim now was to determine whether these effects would be observed after a 2-week period of diet altered to increase masticatory effort, and secondarily to assess the effects of chewing gum on masseter muscle activity. Ten subjects took part in the first experiment. Saliva was collected before and after the diet change and the plaque pH response to a sucrose challenge was measured. Subjects completed 3-day diet histories and wore electromyographic (EMG) devices to record masseter activity. In the second experiment, 10 subjects wore EMG devices for 3 days to record masseter activity on three daily regimens: baseline (no gum chewing), hourly gum chewing (sugar-free gum chewed for 10 min every hour) and chewing five sticks of gum each for 20 min during the day. Data were analysed by paired t test or repeated-measures analysis of variance. For the first experiment, EMG data indicated significant increases in chewing activity (p < 0.05), although there were no changes in salivary flow rates or the plaque pH response to sucrose. The second experiment showed that total EMG activity increased significantly on both gum-chewing regimens (p < 0.01), the magnitude of the increase being greater for hourly chewing. Overall, masseter EMG activity was increased 41% by diet alteration, compared to increases of 96 and 152% on the five-stick and hourly gum-chewing regimens, respectively.

Adult↗
PubMed1993

A comparison between sieving and optical scanning for the determination of particle size distributions obtained by mastication in man.

Mixtures of particles of different sizes, as obtained after chewing, were analysed. Coarse, medium and fine mixtures of particles of an artificial (Optosil) test food were used. Mixtures of Optosil particles of known form and size (half-cubes) were used to validate the analytical methods. The results of both methods were described by particle size distributions based on the volume of the particles. Complete agreement between methods was found for the mixtures of half-cubes. In order to determine the median particle size by volume from the results of optical scanning an assumption on the form of the chewed particles had to be made. Using the assumption that, on average, the particles resemble spheres a slight overestimate of the median particle size was obtained for scanning as compared to sieving. It can be concluded that, although different aspects of the fragmented particles are measured, sieving and optical scanning are both adequate methods for quantifying mixtures of chewed food particles and yield similar results for the degree of particle size reduction.

Calibration↗