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At least 973 records · Page 54Linked to original sources
PubMed1997

Comparison of habitual masticatory patterns in men and women using a custom computer program.

STATEMENT OF PROBLEM: Though computer-based systems for recording three-dimensional jaw motion and muscle activity during mastication are common, few computer programs are available to analyze the resultant data. Few studies have discussed the variability over time of the many parameters of the masticatory cycle now measurable by computer systems. PURPOSE: The purposes of this study were to (1) use a custom computer program, (MAS), for analysis of long-term repeated measurements of mandibular motion and muscle activity; (2) determine sex differences for mandibular movements and activity of the muscles involved during mastication; and (3) determine the variability over time and the statistical power of these methods. MATERIALS AND METHODS: Masticatory cycles of 20 normal men and 17 normal women were examined during mastication of a constant bolus at a sampling rate of 500 fps. Measurements included duration of chewing cycle and its component phases, mandibular displacement in three dimensions, and electromyographic activity in the temporalis and masseter muscles. The MAS custom computer program was used for analysis. Two-way repeated measures analysis of variance was used to compare the men with the women over three trials at 0, 6, and 12 months. The variability over time associated with each measurement was also estimated. RESULTS: Timing of the phases of the chewing cycle were most repeatable between trials, whereas lateral excursions and muscle force magnitudes were the least repeatable measures. Durations of total cycle, its slow-open and fast-close phases, were significantly longer for the female group, and their bursts of muscle activity tended to be longer. The amount of vertical mandibular excursion tended to be greater for men. There were no gender-related differences in the amplitude of muscle activity. CONCLUSIONS: This study demonstrated that men have significantly shorter chewing cycles with faster velocities than women. Men used significantly greater chewing force than women, although their electromyographic activity levels were equivalent. The masticatory measurements made by the MAS program had differing amounts of variation over time. Total duration of the chewing cycle and amount of opening varied the least, whereas amount of lateral excursion and jaw muscle electromyographic magnitudes exhibited the greatest variation.

Adult↗
PubMed1982

Measurement of condylar loading forces by instrumented prosthesis in the baboon.

Mathematical models have been developed to predict hypothetical forces acting on the mandibular condyles during mastication, but no direct measurements of condylar forces in vivo have been reported. This preliminary study presents the technical development of an instrumented prosthesis which was implanted in the mandibular ramus of a baboon, and some preliminary data collected while measuring with this prosthesis the condylar forces exerted during simulated mastication under general anaesthesia. Simulated mastication was induced by stimulating the motor tracts of the trigeminal nerve bilaterally, and the forces in response to increasing amperage were recorded. The pathogenesis of TMJ degeneration may be more fully understood by directly measuring the direction and magnitude of forces acting on the condyles during function. In addition, the future development of a total TMJ replacement for traumatized, deranged, or degeneratively impaired joints, must be accomplished with reliably engineered prostheses based upon direct force measurements.

Animals↗
PubMed2002

Comparison of electromyographic pattern of sensory experts and untrained subjects during chewing of Mahon cheese.

Use of electromyography (EMG) to monitor mastication is a relatively new concept in assessing food physical and sensory properties. Although expert assessment of cheese characteristics is widely used, the effect of training in sensory analysis on mastication patterns, as assessed using EMG is not well known. Nine samples of the same Mahon cheese (60 days ripening) were given to 24 subjects (8 experts, 16 untrained) and EMG recorded for each chewing sequence. Three samples were tested in a single session by each subject, and three sessions carried out on different days. EMG was recorded from four masticatory muscles for each subject. From EMG records the following was extracted: number of chews, chewing time, mean and maximum voltage of EMG bursts (i.e. chews) across chewing sequence, chewing work and chewing rate. No gender bias was found for the EMG parameters considered, therefore, as regards gender, each group was considered to be homogeneous. Variability within-subjects across samples was greater for experts than untrained subjects. Significant differences in chewing time, chewing work and chewing rate were found between the expert and untrained groups. Data analysis of the three sessions showed an influence of cognitive constructs, mediating states, on the chewing process. The experts were found to be goal driven as to their mastication process. Experts showed no significant differences between sessions, untrained subjects were found to vary their EMG output in successive sessions for number of chews, chewing time, mean voltage, and chewing work.

Adult↗
PubMed1997

Chewing activity and activities of daily living in the elderly.

The present study was conducted in order to determine the statistical relationship between chewing activity and activities of daily living (ADL) in the elderly. Subjects which took part were 79 elderly individuals (37 males, 42 females) ranging in age from 65 to 74 years. Based on questionnaires regarding diet, a mastication score was determined to evaluate chewing activity in each subject. This score was scaled from 0 to 100%. ADL levels were determined using two indices: the guidelines of the Ministry of Health and Welfare of Japan and the Tokyo Metropolitan Institute of Gerontology (TMIG) index. The TMIG index is a multidimensional 13-item index of competence in which scores range from 0 to 13 points. According to the guidelines of the Ministry of Health and Welfare, the independence level of each subject was evaluated as independent, home-bound, or bedridden. These independence levels showed a significant correlation with the mastication score (P < 0.01). The mastication score also significantly correlated with the TMIG index, showing a Spearman coefficient of correlation of 0.63 in males (P < 0.01) and 0.71 in females (P < 0.01). These results suggest that chewing activity is related to ADL levels in elderly subjects.

Activities of Daily Living↗
PubMed2002

Correlation between elevator muscle activity and direction of sagittal closing pathway during unilateral chewing.

The closing pathway of masticatory movement in the vicinity of the intercuspal position (ICP) is considered as a functional movement in reconstructing the occlusal guidance. The purpose of this study was to examine a correlation between elevator muscle activity and direction of the closing pathway in the vicinity of the ICP during mastication. Fifty subjects (18 male and 32 female subjects aged from 21 to 34 years) were selected randomly from the students of the Kanagawa Dental College. The measurements of jaw movement during mastication were recorded using a Sirognathograph instrument and surface electromyography (EMG) of the anterior temporalis and masseter muscles simultaneously. The muscle activity and the direction of the closing pathway were calculated on the working and non-working sides during unilateral chewing and analysed at the sections of ICP-2 mm and 2-4 mm in sagittal view. The direction of the closing pathway was expressed by the angle to a vertical reference axis. The direction of the closing pathway correlated significantly with the activity of the anterior temporalis muscles on the non-working side and the masseter muscles on the working side at ICP-2 mm. From the results of this study, it was suggested that the elevator muscle activity may be associated with the direction of the closing pathway during mastication.

Adult↗
PubMed1996

Enhancement of salivary esophagoprotection: rationale for a physiological approach to gastroesophageal reflux disease.

BACKGROUND & AIMS: Secretion of salivary protective factors in patient s with gastroesophageal reflux disease is impaired. However, the impact of physiological stimulus mastication on salivary protective factors output remains largely unknown. The aim of this study was to measure salivary volume, pH, HCO3-, peptide growth factors, prostaglandin, mucin, protein, and viscosity during mastication. METHODS: In 31 asymptomatic volunteers and 36 patients with endoscopic reflux esophagitis, in basal and parafilm chewing-stimulated saliva, its volume, pH, bicarbonate, epidermal growth factor, transforming growth factor alpha, prostaglandin E2, mucin, protein, and viscosity were investigated. RESULTS: Masticatory stimulation in controls resulted in a significantly increased salivary volume by 205%, pH by 7.6%, bicarbonate by 335%, mucin by 137%, protein by 98%, epidermal growth factor by 123%, and prostaglandin E2 by 132%, accompanied by an increase in transforming growth factor alpha by 80% with 19% decline in viscosity vs. basal values. Mastication in reflux esophagitis significantly increased salivary volume by 215%, pH by 6.8%, bicarbonate by 257%, mucin by 135%, protein by 94%, epidermal growth factor by 207%, and prostaglandin E2 by 240%, whereas transforming growth factor alpha increased by 225% and viscosity by 64% when compared with corresponding basal values. CONCLUSIONS: A profound and significant increase in the secretion rate of inorganic and organic protective components in saliva during masticatory stimulation suggests its potential value as a therapeutic approach to the treatment of patients with gastroesophageal reflux disease.

Adult↗
PubMed2006

Influence of oral characteristics and food products on masticatory function.

Mastication is a complex process that involves activities of the facial muscles, the elevator and suprahyoidal muscles, and the tongue. These activities result in patterns of rhythmic mandibular movements, food manipulation, and the crushing of food between the teeth. Saliva facilitates mastication by moistening food particles, making a bolus, and assisting swallowing, whereas food consistency modifies masticatory forces, the mandibular jaw movements, the duration of the mastication cycle, and the number of cycles preceding the first swallow. Jaw elevator EMG activity research shows a clear relation between muscular activity and food properties. The teeth, masticatory muscles, and temporomandibular joints are also important because together they form the mechanism by which the food particles are fragmented. Hard and dry foods require more chewing cycles and a longer time in the mouth until swallowing for sufficient breakdown to take place and for enough saliva to be added to form a coherent bolus safe enough for swallowing. Product characteristics, the amount of saliva, dentition, and bite force affect the chewing performance. This study presents an update and synopsis of the effects of saliva, food, dentition, muscle force, and temporomandibular disorders on the masticatory process.

Animals↗
PubMed1983

Development of the swallowable composition of food in normal dentate subjects.

This study aimed to find out the changes which occur in the frequency distribution of the size of particles produced during mastication of a convenient mouthful of hard-baked soya beans to its swallowable composition (SC), and to identify the particles which undergo rapid pulverization. In this group the total number of masticatory strokes utilized to prepare food for the SC varied between forty and eighty masticatory strokes. All the subjects produced a similar pattern of the frequency distribution of particles produced at the end of mastication and when mastication was interrupted at a particular phase. Particles larger than 1180 micrometers were pulverized to form particles smaller than 1180 micrometers. Most rapid pulverization was seen in particles of 2400 micrometers whereas particles of average size 655 micrometers, formed rapidly.

Adult↗
PubMedDate not supplied

Chewing ability of the long-term hospitalized elderly.

We investigated the chewing ability of 260 (25 percent men) long-term hospitalized elderly patients 60 years of age and older in Laakso hospital, Helsinki, Finland, in relation to their mastication capacity, sore mouth and degree of dependence. The subjects' (mean age 83.3 years, SD = 8.1 years) mastication capacity was determined by a specialist dentist by means of: (a) number of functioning teeth and dentures; (b) modified Eichner Index; and (c) the Eichner Score, based on the index. Based on the information given by the nursing staff, an indicator of chewing ability was created. The chewing ability was poor for 55 percent, limited for 17 percent, moderate for 14 percent and excellent for 14 percent. Excellent or moderate ability to chew was related to a subject's lesser degree of dependence (OR = 1.5; p = 0.02) and higher Eichner Score (OR = 1.3; p = 0.000). More attention should be focused on mastication capacity of the hospitalized elderly.

Aged↗
PubMed1984

Analysis of rhythmical jaw movements produced by electrical stimulation of motor-sensory cortex of rabbits.

The anterolateral regions of the cerebral cortex of rabbits anesthetized with urethan were stimulated with either short trains of electrical pulses at high-frequency (3 pulses, 500 Hz) or 10-s trains of shocks at 50 Hz. The movements of the mandible and the electromyographic (EMG) activity from the muscles of mastication were recorded on magnetic tape and later analyzed by computer. Two basic types of responses are reported: twitches of the digastric muscles that followed the stimulus at short-latency (4-6.7 ms) and rhythmical masticatory movements that could only be evoked by prolonged stimulation. The cortical representations of the short-latency twitch contractions and mastication overlap. Different masticatory patterns are represented in separate areas of the cortex. The movements represented in the anteromedial half of the masticatory area are made mainly in the vertical plane, whereas stimulation of the posterolateral part produces movements in which the jaw swings to the contralateral side during closure. Increases in stimulus intensity usually increase the frequency of the movements, but other changes in the pattern depend on the site of stimulation. The rhythmical bursts of EMG activity often contain stimulus-bound short-latency responses but, since these are not always present, we conclude that they are not essential components of the masticatory pattern. We suggest that the basic patterns of mastication are elaborated by brain stem circuits that are themselves controlled by specific regions of the motor-sensory cortex.

Animals↗
PubMed1993

Coordination of cortically induced rhythmic jaw and tongue movements in the rabbit.

1. Rhythmic movements of the jaw, tongue, and hyoid that were induced by stimulation of the cortical masticatory area (CMA) were recorded cineradiographically in the anesthetized rabbit. Jaw movements were also recorded by a laser position detector. 2. The evoked jaw movements were classified into four types: small circular (type A), large circular (type B), large vertical (type C), and crescent-shaped (type D). Among these, types B and D resembled the jaw movements of the food transport cycle and those of the chewing cycle in a masticatory sequence. 3. Each type of jaw movement was associated with a particular pattern of tongue and hyoid movements. In general, the tongue protruded during jaw opening and retracted during jaw closure. The hyoid generally moved upward and forward during jaw opening but downward and backward during jaw closure. 4. Electromyograms (EMGs) were recorded from jaw muscles [masseter (Ma) and digastric (Di) muscles], extrinsic tongue muscles [styloglossus (Sg) and genioglossus (Gg) muscles], and hyoid muscles [sternohyoid (Sh) and geniohyoid (Gh) muscles] during cortically induced rhythmic jaw and tongue movements (CRJTMs). These muscles were classified into two groups: group 1 was activated mainly in the jaw opening phase, and group 2 was activated mainly in the jaw closing and power phases. The Di, Gg, and Gh were included in the former, and the Ma, Sg, and Sh were included in the latter. 5. The timings of EMG activation to a jaw movement cycle were relatively constant for the muscles of group 1, irrespective of the types of CRJTMs, whereas those for the muscles of group 2 altered considerably with the different types of CRJTMs. 6. Relationships of the integrated muscle activity between the Di and Gg and between the Di and Gh were significant, whereas those between the Ma and Sg and between the Ma and Sh were not. 7. When a small strip of polyurethane form of various degrees of hardness was inserted between the opposing molars during CRJTMs, EMG activity of the muscles of group 2 increased with the hardness of the strip. On the other hand, EMG activities of the muscles of group 1 were less affected by the same intraoral stimuli. 8. Two conclusions were reached: first, physiological properties of the CRJTMs and cortically induced rhythmic movements of the hyoid were essentially similar to those observed in natural mastication. This fictive mastication might thus be regarded as a suitable model for simulating natural mastication.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

The effect of daily gum-chewing on salivary flow rates in man.

Following reports of increased salivary gland size and increased function, induced by increased mastication in animals, the effects of long-term, frequent gum-chewing on resting and stimulated flow rates were studied in human volunteers in separate experiments in Newcastle upon Tyne and in Toronto. In both experiments, unstimulated and stimulated saliva flow rates were measured in student volunteers at intervals of one or two weeks over a baseline period. Approximately half of the subjects were then given sugarless gum to be chewed (four pieces per day) over the experimental period; controls refrained from vigorous mastication. During (and, in Newcastle, after) the experimental period, salivary flow rates were measured at intervals, as before. In Newcastle unstimulated, but not stimulated, flow rates increased in the gum-chewing group and were still elevated (compared with controls) eight weeks following the experiment. In Toronto, the mean results showed no effect of gum-chewing, but the seven gum-chewers among the 11 subjects with low baseline flow rates (less than 0.3 mL/min) showed a 43% rise in unstimulated flow rate (p approximately 0.05). The results suggest that increased mastication, in the form of gum-chewing, can increase unstimulated flow rates, especially in those with low salivary function. In addition to short-term beneficial effects of sugarless gum, these long-term effects indicate the possibility of a beneficial effect in caries prevention.

Adult↗
PubMed1989

Amalgam margin breakdown caused by creep fatigue rupture.

This study was designed to determine whether the mechanical cyclic stressing that occurs during normal mastication contributes to margin breakdown of dental amalgam restorations. The method used appears to duplicate the mechanical stresses developed in vivo during mastication, as the result of tooth flexing. We evaluated one low-copper alloy--NTD--and three high-copper alloys--Dispersalloy, Phasealloy, and Tytin. We prepared simple amalgam restorations in a cavity centrally located in an aluminum beam. Each specimen received five periods of three-point cyclical loading (1.7 hertz, 4200 cycles at 37 degrees C). The margin area was subjected to SEM examination prior to and at the completion of each period of cycling. At the beginning of each period of cycling, beam deflection was set to establish a maximum theoretical stress of 1, 2, 4, 6, or 8 MPa. For all brands, cycling resulted in margin gap formation and surface wrinkling. Wrinkling in Dispersalloy occurred as a wide band of shallow wrinkles, whereas that in NTD occurred as a narrow band of deep wrinkles. At 21,000 cycles, very little void formation and fracturing had occurred in the Dispersalloy or NTD restorations. In contrast, the Phasealloy and Tytin restorations developed extensive fracturing even after 4200 cycles. Fracture surface analyses of Phasealloy and Tytin indicated that creep fatigue rupture was the fracture mechanism responsible for margin breakdown in these amalgam restorations, when subjected to cyclic compressive loading similar to that experienced during mastication.

Copper↗
PubMed1998

Functional properties of jaw and tongue muscles in rats fed a liquid diet after being weaned.

Decreased masticatory demands due to liquid or soft diets cause a reduction in the growth of craniofacial bones and in the development of feeding musculature, but the effects on masticatory function and jaw/tongue muscle activities are unclear. The present study was undertaken to test the hypotheses that a liquid diet feeding after weaning affects the critical-period programming of mastication and the motor performances of jaw and tongue muscles. Thirty-six male Wistar rats were divided into two equals groups at weaning and fed either a solid (solid-diet group) or a liquid (liquid-diet group) diet until they reached 50 days of age. Electromyograms (EMG) of the masseter, medial pterygoid, temporalis, anterior digastric, styloglossus, and genioglossus were recorded while animals were naturally ingesting ordinary pellets, apple cubes, and a liquid diet. It was found that: (1) a more irregular chewing rhythm, a shorter chewing sequence, and a longer chewing cycle were found in the liquid-diet group, but there were no differences observed during lapping/licking between the two groups; (2) during the chewing cycles, the EMG onset of each muscle in relation to that of the masseter in the liquid-diet group was similar to that in the lapping/licking cycles in both groups; (3) the activities of jaw elevators (masseter, medial pterygoid, and temporalis) during the chewing cycles were significantly higher in the liquid-diet group; and (4) the increase in the EMG activities of jaw elevators during pellet chewing compared with apple cube chewing was significantly weaker in the liquid-diet group, whereas such an enhancement was found simultaneously in the styloglossus in the solid-diet group, and in the anterior digastric in the liquid-diet group. These findings verify that: (1) the motor output of jaw and tongue muscles may be altered in rats fed a liquid diet after being weaned; (2) the feeding of a liquid diet to rats after being weaned may obstruct the functional transition from suckling to mastication; and (3) jaw elevators that develop without motor learning of mastication are inefficiency when performing functionally.

Analysis of Variance↗
PubMed1990

The functional result of mandibular reconstruction.

A study was performed to determine if patients who underwent mandibular reconstruction were functionally rehabilitated. Five parameters were evaluated: deglutition, mastication, cosmesis, diet, and the use of dentures. Deglutition was not improved in patients who had mandibular continuity restored. Problems with deglutition were related to soft tissue resection. Mastication was poorer in the reconstructed group due to scarring, loss of the muscles of mastication, and inhibition of compensatory mandibular motion. Cosmesis was improved in patients who had immediate restoration of mandibular continuity. Cosmesis was not improved in patients with delayed mandibular reconstruction due to previous scarring. Prosthetic rehabilitation was poor in both groups of patients. Reconstructed patients had a greater number of hospitalizations due to management of, or complications from reconstructive surgical procedures. The results of this study suggests that restoration of mandibular continuity does not enhance the functional rehabilitation of the majority of patients with oral-pharyngeal malignancy.

Adult↗
PubMed2006

[Masticatory muscle activity during exertion of the back].

PURPOSE: The lower jaw is considered to be fixed during body exercise. However, its mechanism remains to be elucidated. The present study investigated masticatory muscle activity during of the back. METHODS: The subjects were 9 healthy dentulous patients. The maximum back strength of the patients was measured with a back-dynamometer. Muscle activities of the temporal, masseter and digastric muscles during exertion of the back and mastication of peanuts were measured. Muscle activities of the temporal and masseter muscle during maximum voluntary clenching and that of the digastric muscles during exertion of resistance against forced mouth opening were also measured, and maximum voluntary muscle activities were obtained. The relative percentage of each masticatory muscle against maximum voluntary activity was calculated from the data obtained, and muscle activities during exertion of the back, mastication of peanuts and maximum muscle activity were compared. RESULTS: Muscle activities of the temporal, masseter and digastric muscles during exertion of back muscles against maximum voluntary muscle activity were 32.1%, 26.4% and 97.4% respectively. Muscle activities of these muscles during mastication of peanuts against maximum voluntary muscle activity were 40.7%, 36.0% and 17.3% respectively. CONCLUSIONS: Muscle activities during exertion of the back were 30% in the temporal and masseter muscle, and approximately 100% in the digastric muscles. The result suggests that the digastric muscles play a key role in fixing the mandible in all masticatory muscles including jaw-opening and closing muscles. People exert back strength not only in sports but also in daily life. This study demonstrates the stronger involvement of the digastric muscles in fixation of the mandible during exercise than during strong clenching. The results are of interest in terms of mandibular position, occlusal contact and the load on the temporomandibular joint (TMJ) since there is no wide mouth opening.

Adult↗
PubMed1989

[Differential Lissajous EMG of masticatory muscles and its application in man].

Difference in the activity of masticatory muscles between subjects with normal teeth alignment and occlusion and patients with disorders at the oral region was investigated using a differential Lissajous EMG method. Surface EMGs were recorded from the right and left temporal and masseter muscles during peanut and chewing gum mastications. The difference of the integrated EMGs between both sides was obtained in both the temporals and masseters, then two differences were synthesized to a Lissajous figure. The figures generally showed the following: 1) In the normal subjects, the muscle behavior varied from stroke to stroke in peanut mastication, while it was constant in chewing gum mastication. 2) Activity of some muscles of the patients was quietly weak, while that of the normal subjects was totally balanced. 3) In the patients, combination of use between the temporal and masseter muscles and contraction order among the muscles tended to be reversed compared to the normal subjects.

Arachis↗
PubMed2003

Characterization of season and sampling method effects on measurement of forage quality in fescue-based pastures.

Information on seasonal changes and effects of sampling methods on the measurement of forage quality is limited for fescue-based pastures. Eight continuously grazed, 0.76-ha, fescue-based pastures were used to compare forage type, method of collection, and seasonal effects on forage quality in a repeated-measures, split-plot design. Four pastures were interseeded with red clover in March 2000. Masticate (M; from four ruminally cannulated steers) and hand--clipped (C) samples were collected every 28 d from April to October 2000. Interseeding red clover did not affect (P > 0.10) OM, CP, NDF, and ADF concentrations or CP degradability. Sampling method and season interacted (P < 0.03) for OM, CP, NDF, and ADF concentrations. Concentrations of OM averaged 5 percentage units more (P < 0.01) in C than in M in all months and were more variable with M than with C. Samples clipped between April and September averaged 5.5 percentage units greater NDF (P < 0.01), 3.0 percentage units greater ADF (P < 0.01), and 4.5 percentage units less CP (P < 0.01) than masticate samples obtained during the same time period. Fiber and CP concentrations did not differ (P > 0.10) between C and M samples obtained in October. Differences in CP degradability estimates (using Streptomyces griseus protease) between the two sample types were greater in late-season samples than in samples obtained from April to June. When S. griseus protein degradability estimates were compared with in situ estimates for masticate samples, no differences (P > 0.10) were detected early in the season (April to June). However, the S. griseus procedure overestimated in situ values (P < 0.01) by an average of 3 percentage units in samples obtained between July and October. Differences in composition of C and M samples were substantial until late season, when opportunities for selective grazing were minimal. Small differences between S. griseus and in situ estimates of CP degradability indicate that the S. griseus procedure can yield useful CP degradability estimates for fescue-based pasture samples. Although it might be possible to apply correction values to clipped samples to estimate CP and fiber concentrations of diets selected by grazing cattle, inconsistent relationships preclude this approach for estimates of CP degradability.

Animal Feed↗