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At least 253 records · Page 14Linked to original sources
PubMed1986

A comparative electromyographic and kinesiographic study of deliberate and habitual mastication in man.

Twelve healthy, fully-dentate subjects participated in experiments which included the continuous recording of surface electromyography and jaw movement during habitual and deliberate right-sided or left-sided chewing of a coherent bolus. Analogue data streams were converted to digital values. Root-mean-square (r.m.s.) muscle-activity traces were computed from raw electromyographic data. The working side was defined as the side from which the mandible approached the position of occlusal stoppage when in the most cranially directed part of the chewing cycle. In any given muscle, greater mean peak r.m.s. activities were found with ipsilateral than contralateral bolus replacement (p less than 0.01, s); such differences were more pronounced for the masseter than the anterior temporal muscles. During habitual chewing, mean peak r.m.s. activities exceeded the value established by deliberate mastication with ipsilateral bolus placement in 27 of 48 muscles; this may be because of more vigorous chewing during habitual performance. No subject was strictly unilateral in their preference for bolus placement and in 6 of the 12 subjects, there was a timed side-switching of the bolus within the masticatory sequence. The results also indicated that any averaging of data based upon time-amplitude alone would be inappropriate for habitual chewing because of the call for different working sides within a particular masticatory sequence. Thus a new data format based upon numerical representation of the electromyographic activity against time was introduced.

Adult↗
PubMed1988

Three-dimensional movement analysis of lateral pterygoid electromyographic activity during mastication in the rat.

Simultaneous recordings of mandibular movement in three dimensions (frontal, horizontal and sagittal plane), and lateral pterygoid electromyographic (EMG) data during mastication of pellets and slurry, were collected from 5 rats by the opto-electronic mandibular tracking (OMT) method and computerized digital-processing of the EMG wave-forms. The microcomputer analyses allowed determination of frontal-, horizontal- and sagittal-plane movement displacements and velocities for whole chew cycles and, during lateral pterygoid activity, opening burst (OB) and closing burst (CB) latencies. There were significant (p less than or equal to 0.01) differences between duration, displacement and velocity data from slurry and pellet chew cycles. OB latencies were significantly (p less than or equal to 0.01) longer than CB, and OB displacements started significantly (p less than or equal to 0.01) farther from minimal gape than CB ones. Working-side OB activity occurred as the mandible moved inferiorly, laterally and posteriorly; working-side CB activity occurred as the mandible moved superiorly, medially and anteriorly. A secondary peak of OB activity, coinciding with anterior sagittal translation during the last third of mandibular depression, was detected; this may represent independent activity of the rat superior lateral pterygoid effecting anterior translation of the mandibular-joint disc and capsule. Rat lateral pterygoid activity has the same basic, bimodal pattern (active during both mandibular depression and elevation) as is found in humans.

Animals↗
PubMed1980

Cerebellar ablation and mastication in the guinea pig (Cavia porcellus).

The jaw movements of 3 subadult guinea pigs were recorded before and after cerebellar ablation with the aid of an optoelectronic tracking system. Despite overall ataxia of the animals' body and limbs, masticatory patterns were essentially normal. The major effects of cerebellar ablation upon Cavia mastication were a statistically significant (P < 0.01) increase in chew cycle duration and a decrease in chew duration variability.

Animals↗
PubMed1984

Patient response to variations in denture techniques. Part VI: Mastication of peanuts and carrots.

This 5-year study was designed to determine if differences in masticatory ability existed among patients for whom dentures had been prepared with two different techniques. Patients were instructed to chew a given amount of a reliable test food for a certain number of strokes on each side of the mouth. After each trial the food was collected into a No. 8 mesh screen, washed, dried, and weighed. The percentage weight of food masticated per side per patient was recorded for each year. Results were combined for each group results and analyzed statistically. Statistical analysis of the two groups revealed changes in masticatory ability over the 5-year period. However, no significant statistical differences in masticatory ability existed between the two groups.

Arachis↗
PubMed1990

Mastication in patients treated for head and neck cancer: a pilot study.

Patients with head and neck cancer will experience alteration of oral anatomy and physiology caused by the disease and the treatment required. Despite the implied effects on the dynamics of mastication, objective studies have not been conducted to evaluate masticatory function of these patients. Masticatory performance and swallowing threshold performance were evaluated with Frito corn chips as the test substance. Edentulous patients treated for cancer demonstrated deficiencies in both tests. Masticatory performance and swallowing threshold performance improved with prosthodontic rehabilitation but this improvement was less than with comparable controls. Techniques to evaluate masticatory factors such as dentition, dentures, biting force, temporomandibular joint status, range of motion, and saliva are suggested.

Aged↗
PubMed1990

Reaction of mastication to occlusal changes induced by correction of mandibular prognathism.

Incisor-point masticatory movements of 22 patients were recorded before and after correction of mandibular prognathism. Chewing patterns and movement parameters were compared between preoperative and postoperative states and to corresponding quantities of 85 persons with normal dentitions. The prognathism patients most frequently revealed "chopping-type" patterns characterized by nearly vertical closing strokes, whereas mastication in the reference group was dominated by lateral grinding-type movements. There were no significant differences in the pattern distributions and parameter values between the preoperative and postoperative states. An individual assessment, considering random fluctuations of chewing behavior, showed that only five patients had changed their chewing mode possibly because of the treatment. Only a minor part of these changes could be directly related to the altered occlusion. It is concluded that the characteristic chewing mode of persons with mandibular prognathism does not interfere with the occlusal profile, and hence does not react to alterations.

Adult↗
PubMed1990

Masticatory efficiency determined with direct measurement of food particles masticated by subjects with natural dentitions.

The size of soya particles masticated by 10 subjects with natural teeth were directly measured by means of a graphic digitizer and a computer at a varied number of masticatory strokes. The statistical parameters were calculated by computer and a test of normality was used for estimating the frequency distribution. It was found that the frequency distribution of chewed particle size was a positive skew state; its shape was asymmetric, wide, and flat. After natural logarithm transformation the distribution tended toward normal. Increasing the number of masticatory strokes decreased the mean and median of the distribution (p less than 0.01) and did not change the coefficient of variation, skewness, and kurtosis (p greater than 0.05). The results show that the distribution of chewed particle size tends toward a normal logarithmic distribution; the distribution shapes at various numbers of strokes are the same; these parameters can be used for determining masticatory efficiency. Direct measurement of the particles is more convenient and reliable than dyeing particles or fractionating the particles in a sieve system.

Adult↗
PubMed1991

A comparative study of mastication between complete denture wearers and dentate subjects.

A computer system was used for simultaneously collecting and processing mandibular movements and the myoelectric activities of the masticatory muscles of 15 dentate subjects and 11 complete denture wearers. The displacement, velocity, cycle of mandibular movements, and the muscular mean potentials were indices in observing mastication. A good complete denture should perform with physiologic characteristics, and restore masticatory function and oral health. The kinetic energy from the velocities of lateral and vertical directions can serve for the chewing and comminution of food, but lateral comminution may affect denture retention. The mean myoelectrical potentials of the mandibular elevator muscles of complete denture wearers tend to increase at the opening phase; however, the potentials decrease at the closing phase.

Adult↗
PubMed1979

The absence of proprioceptive nerve endings in the human periodontal ligament: the role of periodontal mechanoreceptors in the reflex control of mastication.

A review of the literature was conducted to determine the presence or absence of proprioceptive nerve endings in the human periodontal ligament. A histologic review of the periodontal ligament innervation concluded that nerve endings found were those mediating pain, pressure, or touch and that there is no histologic evidence of any "classic" proprioceptive nerve ending in the periodontal ligament. A summary is given concerning the precise role of nerve endings in the periodontal membrane, their afferent pathways, and the role of masticatory muscle proprioception, jaw reflexes, and the temporomandibular joint in the coordinated control of mastication and mandibular proprioception.

Afferent Pathways↗
PubMed1989

Osteoradionecrosis related to mastication and parafunction.

This article discusses mastication and parafunctional habits as possible etiologic factors in the development of osteoradionecrosis. From the three case reports presented it was noted that bone necrosis can occur after extended periods after radiation therapy, is seen most frequently in the mandible, and occurs most often at dosage levels exceeding 6500 rad. Recommendations after treatment to patients receiving 6500 rad or more should include caution regarding consistency of diet, use of existing prostheses, and the potential harmful effects of parafunctional habits.

Carcinoma, Squamous Cell↗
PubMed1994

Variation of the jaw-opening reflex during spontaneous mastication in rabbits.

To understand the modulation of periodontal mechanoreceptor activity on mastication, the jaw-opening reflex (JOR) evoked by electrical stimulation of the inferior alveolar nerve (IAN) was studied during chewing in freely behaving rabbits. Spontaneous chewing movements were intact from the IAN stimulation below two times the threshold (T) which was measured at rest. As the stimulus intensity was increased to more than 2.5 T, the amplitude of the masseter activity decreased or it was abolished; however, the chewing rhythm was still maintained up to 3.0 T. When the low-threshold primary afferents were tested while the rabbit chewed pellets rhythmically, the amplitude in the JOR was inhibited below the prior control level. The inhibitory effect on the JOR was larger in the opening phase than that in the closing phase. In conclusion, the JOR was tonically depressed during the masticatory cycle and the inhibition of the JOR was rhythmically modulated in a phase-linked manner that was larger in the opening phase than in the closing phase.

Animals↗
PubMed2003

Jaw kinematics during mastication after unilateral fractures of the mandibular condylar process.

This study compared the mandibular kinematics during mastication of patients treated for unilateral fractures of the mandibular condylar process with those of control subjects. We used a Sirognathograph (Siemens, Bensheim, Germany) to record the chewing cycles of 81 male patients with unilateral condylar process fractures while they chewed a constant bolus unilaterally on the same side as the fracture and on the opposite side. Recordings were made at 6 weeks, 6 months, 1 year, and 2 years after treatment. Similar chewing cycles were recorded for 15 male controls (Class I dental and Class I skeletal occlusion) without fractures of the condylar process. The chewing cycles of both groups were analyzed with a custom computer program, and the duration, excursive ranges, and 3-dimensional cycle shape were compared at each time interval with multilevel linear modeling statistics. Fracture patients had significantly slower chewing cycles, with significantly less maximum excursion toward the working side during the closing phase and significantly greater excursion toward the balancing side during the opening phase than the controls. The opening pathway of the incisors showed greater differences between patients and controls than the closing pathways. Differences in chewing cycle shape persisted for up to 2 years, especially when chewing was on the side opposite the fracture. Unilateral condylar process fractures produce long-lasting changes in chewing cycle duration and chewing cycle shape of adults.

Adult↗
PubMed2005

Influence of mastication and salivation on swallowing in stroke patients.

OBJECTIVE: To determine differences of the oral swallowing functions between stroke and normal subjects and to identify those factors affecting dysphagia of stroke patients. DESIGN: Case-control study. SETTING: University hospital. PARTICIPANTS: Ten stroke and 10 healthy subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Resting saliva flow rate, the total number of chews, and the duration of the oral phase until onset of pharyngeal swallow, and food viscosities both before and after the oral phase using diluted barium, pudding, thick rice gruel, and curd type yogurt. RESULTS: The viscosity of all test foods was significantly reduced after the oral phase in both groups (P<.01). Resting saliva flow rate and the viscosity of thick rice gruel after the oral phase in the stroke group were significantly lower than in the control group (P<.01). However, there were no differences in the viscosities of the other foods between both groups. And a longer oral phase and a greater number of chews prior to pharyngeal swallow were revealed in the stroke group than in the control group (P<.01). CONCLUSIONS: This study shows that the food requiring mastication demands a longer oral phase and a greater number of chews, and has more altered rheologic characteristics during the oral phase in stroke patients. These findings suggest that masticatory function is impaired in stroke patients, which may contribute to their swallowing dysfunction.

Aged↗
PubMed2004

Extrinsic tongue and suprahyoid muscle activities during mastication in freely feeding rabbits.

To evaluate the coordination of tongue and suprahyoid muscle activities during natural mastication, electromyograms (EMGs) of jaw-closer, jaw-opener, suprahyoid (mylohyoid, MH), tongue-retractor (styloglossus, SG) and tongue-protractor (genioglossus, GG) muscles were recorded as well as the jaw-movement trajectories in vertical and horizontal axes in awake rabbits. Each masticatory cycle had three components including the fast-closing (FC), slow-closing (SC) and opening (Op) phases. The duration of the SC phase was much longer during pellet chewing while the durations of the FC and Op phases were much shorter during pellet chewing than bread or banana chewing. The jaw movements during banana chewing had a small amplitude of lateral excursion and a large amplitude of gape as compared with those during pellet and bread chewing. The MH muscle exhibited double-peaked EMG bursts during the Op phase. The MH bursts in the late part of the Op phase were dominant on the non-chewing side during pellet and bread chewing. The SG muscle also exhibited double-peaked EMG bursts. During pellet and bread chewing, the SG bursts during the SC phase were significantly larger on the chewing side than the non-chewing side. These bursts were also dominant during pellet chewing as compared with banana chewing. There was little difference in the GG bursts between the chewing and non-chewing sides or among the foods. Our results suggest that patterns of the MH and SG muscle activity are affected by the peripheral inputs and/or chewing patterns while those of the GG muscle activity was less modulated regardless of the consistency of foods.

Animal Feed↗
PubMed2005

Clinical evaluation of mastication: validation of video versus electromyography.

BACKGROUNDS AND AIMS: The ability to evaluate masticatory function in people with neurological disabilities is important as this function is often compromised in these groups. However, current standard techniques are often impossible in such groups due to cognitive difficulties. This study is a validation of several variables read from standardised video recordings of mastication as indicators of masticatory function. METHODS: Fifteen healthy, fully dentate male subjects were recorded using EMG and by video simultaneously. An evaluation was undertaken of the video parameters (i) to compare their validity against the electromyographic parameters, (ii) to test intra-rater and inter-rater reliability and (iii) to test the ability to discriminate between four model foods differing in hardness. RESULTS: Masticatory time and the number of masticatory cycles counted on video were found to be valid and reliable indicators. In addition, the number of active chewing cycles performed with an open mouth and identification of the chewing side, were found to have reasonable validity and reliability. The former may allow discrimination between food types. CONCLUSION: As an alternative to the complex evaluation of masticatory function, observation of certain parameters from video recording could be an alternative for use in uncooperative patients.

Adult↗
PubMed2004

Effects of food consistency on the pattern of extrinsic tongue muscle activities during mastication in freely moving rabbits.

The effects of physical characteristics of foods on the coordination of extrinsic tongue muscle activities during natural mastication were evaluated. Electromyograms of tongue-retractor (styloglossus, SG) and tongue-protractor (genioglossus, GG) muscles as well as the jaw-movement trajectories were recorded during raw rice and chow pellet chewing in the freely moving rabbit. Each masticatory cycle included a jaw closing (Cl) phase consisting of a fast-closing (FC) and a slow-closing (SC) phase, and a jaw opening (Op) phase. The duration of the Cl and SC phases was found to be much larger while the duration of the FC phase was much smaller during rice chewing than pellet chewing. The jaw movements during rice chewing had smaller amplitudes of the gape and lateral excursion of the jaw as compared with those during pellet chewing. The SG muscle had a double-peaked burst activity in each masticatory cycle with one peak during the Op phase (the SG1 burst) and the other during the Cl phase (the SG2 burst). They were significantly larger during pellet chewing as compared with rice chewing, but the duration of the SG2 burst was significantly longer during rice chewing than pellet chewing. The offset of the SG2 burst was delayed during rice chewing as compared with that during pellet chewing. There was little difference in the activity pattern of the GG burst between the foods. Our present results suggest that the SG muscle activity could be modified by the sensory feedback possibly to adapt to environmental demands during chewing.

Animals↗
PubMed2001

Influence of parasympathetic non-adrenergic, non-cholinergic mechanisms on [3H]thymidine uptake in rat parotid salivary glands in response to mastication following upon a liquid regimen.

A role for parasympathetic non-adrenergic, non-cholinergic (NANC) mechanisms in parotid gland cell hyperplasia in response to mastication was investigated. Following a liquid regimen for 1 week, aiming at glandular inactivity, rats were offered hard chow for 2 h to throw their parotid glands into secretory activity. In response to the increasing demands, [3H]thymidine incorporation into the trichloroacetic acid-insoluble material increased by 76% in normally innervated glands, while there was no increase in glands parasympathetically denervated in advance. In innervated glands of rats pretreated with atropine and alpha- and beta-adrenoceptor blockers the increase was 46%. The results suggest a potential contribution of parasympathetic NANC mechanisms to the mitotic response of the parotid gland under natural feeding conditions.

Adrenergic Antagonists↗
PubMed2002

Movement of temporomandibular joint tissues during mastication and passive manipulation in miniature pigs.

Movement is an important aspect of the biomechanics of the temporomandibular joint (TMJ). To track the relative movements of TMJ components, radio-opaque markers were implanted in the left squamosal bone, mandible and retrodiscal tissue of miniature pigs. Medial-lateral (ML) and dorsal-ventral (DV) fluoroscopic records were made 8-10 weeks later during chewing and passive manipulation. Marker movements were digitized from the videotapes. During passive manipulation, the deformation of the lateral capsule was also measured with a differential variable-reluctance transducer. The results provide new details about porcine chewing pattern, which is distinguished by a regularly alternating chewing side. During masticatory opening, the mandible had a centre of rotation (CR) well inferior to the condyle and close to the angle. In contrast, the passive opening movement showed a higher CR location close to the condylar neck, indicating a different motion from masticatory opening. The retrodiscal tissue followed the movements of the mandibular condyle during both mastication and passive manipulation. The lateral capsule elongated during ipsilateral shifts and retrusion, implying a possible role in limiting such movements. These movement characteristics provide a useful reference for studies on the TMJ using pigs.

Animals↗