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PubMed1976

The influence of percussion, occlusion and mastication on the occurrence of silent periods in masseter muscle activity.

The occurrence of silent periods in masseter muscle activity was investigated during percussion of the bony structures of the head and neck, during occlusion of the teeth on surfaces of varying hardness, and during chewing of different food-stuffs. Silent periods were demonstrated on percussion during isometric and isotonic contraction of the masseter muscles and the occurrence of silent periods was influenced by the force of occlusion and by the nature of the surface contacted. Mandibular velocity was investigated during tapping and chewing sequences by ultra-high-speed cinematography, but it was not found possible to identify a critical change in mandibular velocity associated with the occurrence of silent periods. More silent periods were observed during the chewing of hard foods than of soft foods and there were more silent periods near the beginning of chewing sequences than towards the end. Differences in latency and duration of silent periods were observed in relation to artificial changes in the occlusion.

Dental Occlusion↗
PubMed1983

Denture mobility and bolus position during mastication in patients wearing conventional and pelotte-retained full upper dentures: a cineradiographic study.

With cineradiographic technique an assessment was made of the denture mobility of conventional and pelotte dentures in the upper jaw and of the position of the bolus during chewing of meat and bread. Five randomly selected edentulous patients with moderate alveolar ridge resorption rehabilitated with dentures of conventional design, and another five with dentures furnished with subnasal retentive pelottes, were incorporated in the study. Cineradiographic registrations were made in lateral and frontal projections with a picture frame speed of 38/s. Analysis of the cineradiographic films revealed only small differences for the denture mobility for the two patient groups. This indicated in the patients with severe ridge resorption, an obvious reduction of denture displacement through the use of the nasal pelotte or prong. The displacement was of similar magnitude as for those dentures where an alveolar ridge creates effective retention and limitation of horizontal movements. The analyses of the bolus position during chewing gave the information that in all individuals wearing pelotte dentures, the bolus was positioned more distally, than for patients with conventional dentures. Presumably this was in order to reduce discomfort in the frontal region, i.e. the region of the pelottes. Patients with conventional dentures showed a more even distribution of the bolus to all regions.

Aged↗
PubMed1985

Demonstration of chewing motor disorder by recording peripheral correlates of mastication.

Chewing motor performance was examined in twenty-one patients. Twelve patients had TMJ dysfunction syndrome, eight had occlusal trauma, and one had CNS impairment. Surface electromyography and three-dimensional jaw movement was recorded. Discomfort was recorded by the patient during chewing of beefstick. Specific changes in mandibular movement were related to the presence of pain, discomfort and other symptoms of the TMJ dysfunction syndrome.

Adult↗
PubMed1985

Lateral preference in mastication: relation to pain.

Ten subjects performed deliberate right and left-sided chewing of gum, each exercise with a duration of 60 s, followed by maximum voluntary teeth clenching (MVC) until onset of pains in the masseter muscles (pain threshold). Contractile activities of the right and left masseter muscles were assessed by integrated and cumulative surface electromyography (EMG). When the right and left muscles functioned as chewing side muscles only, they generated practically identical levels of chewing force; the same applied when they functioned as non-chewing side muscles only. During identical functions, EMGs suggested identical motor unit recruitment and firing patterns in the two paired muscles; i.e., units producing relatively high tensions for chewing side activity, and other units producing relatively low tensions for non-chewing side activity. During isometric MVC activity, until onset of pains, the right and left muscles generated practically identical levels of bite force, but right and left motor unit activity patterns seemed to differ. Right and left motor units might have fired at different rates or begun to drop out at different times. In the latter case, rapidly before slowly fatigued units. There was a tendency for a low pain threshold with high chewing side activity in both masseter muscles. Motor units producing high levels of tension, but easily fatigued, might have caused early onset of muscle pains. No relationships could be established between preferred chewing side and side of initial muscle pains, nor between MVC activity and side of pain onset and preferred chewing side.

Adult↗
PubMed1988

The subjective experience of mastication in subjects with shortened dental arches.

In this study the perception of chewing is investigated in forty-three subjects with a shortened dental arch (SDA) by means of an interview. A group of fifty-four subjects with a complete dentition was used as a control group. The aim was: (i) do subjects with a SDA have a higher risk of chewing problems, and (ii) do they have different food perception and food selection leading to change in their diet? The results show that for subjects with a SDA the chewing function, food perception, food selection and actual food consumption are hindered within an acceptable degree.

Adult↗
PubMed1994

A computer-controlled experimental set-up enabling the quantification of motor performance in man, applied to mastication.

This paper describes a computer-controlled experimental set-up, which enables the simulation and manipulation of the resistance of food, the bolus size and reflex evoking events during chewing in man. Food resistance was simulated by an external downward directed force on the mandible during the closing phase. The force was supplied by a magnet-coil system. A coil, rigidly attached to the subject's mandible, was located in a permanent magnetic field. By varying the current through the coil, the force on the coil and thus on the mandible could be adjusted. The current was on line computed as a function of the jaw gape. Food resistance and bolus size could be simulated and manipulated by varying the amplitude of the force and the jaw gape at which the force started, respectively. The possibility of varying these parameters could be used simultaneously and independently. Reflex evoking events were simulated by an additional loading or unloading force pulse, superimposed on the food-simulating force. The set-up has been tested during experiments in which food resistance, bolus size and reflex evoking events were simulated. Examples of these experiments are presented in this paper.

Bite Force↗
PubMed2004

Time series analysis of jaw muscle contraction and tissue deformation during mastication in miniature pigs.

Masticatory muscle contraction causes both jaw movement and tissue deformation during function. Natural chewing data from 25 adult miniature pigs were studied by means of time series analysis. The data set included simultaneous recordings of electromyography (EMG) from bilateral masseter (MA), zygomaticomandibularis (ZM) and lateral pterygoid muscles, bone surface strains from the left squamosal bone (SQ), condylar neck (CD) and mandibular corpus (MD), and linear deformation of the capsule of the jaw joint measured bilaterally using differential variable reluctance transducers. Pairwise comparisons were examined by calculating the cross-correlation functions. Jaw-adductor muscle activity of MA and ZM was found to be highly cross-correlated with CD and SQ strains and weakly with MD strain. No muscle's activity was strongly linked to capsular deformation of the jaw joint, nor were bone strains and capsular deformation tightly linked. Homologous muscle pairs showed the greatest synchronization of signals, but the signals themselves were not significantly more correlated than those of non-homologous muscle pairs. These results suggested that bone strains and capsular deformation are driven by different mechanical regimes. Muscle contraction and ensuing reaction forces are probably responsible for bone strains, whereas capsular deformation is more likely a product of movement.

Animals↗
PubMed1980

Aging and mastication: changes in performance and in the swallowing threshold with natural dentition.

Few comprehensive studies of oral function have been conducted on adult populations. A "Longitudinal and Cross-Sectional Study of Oral Health in Healthy Veterans" was activated at the VA Outpatient Clinic in Boston in 1969; it included general oral and dental examinations as well as tests of masticatory performance and the swallowing threshold. The current investigation involved 863 subjects from the "Dental Study" who had either their natural teeth or a fixed replacement for missing teeth. Masticatory performance as measured by the subject's ability to reduce a test portion of cut carrot by a mandatory number of chewing stroked remained constant for persons with complete or partially compromised natural dentition. Swallowing threshold performance as measured by the particle size acceptable for swallowing remained constant for persons with complete dentition. Tooth loss significantly decreased the swallowing threshold performance and increased the particle size which the subject was willing to swallow. Older subjects increased the number of chewing strokes and the time required for this test, an observation not related to performance as measured by final particle size. Only with compromised dentition, however, did this increased effort result in increased performance.

Adult↗
PubMed1986

Aspects of mastication with bridges on osseointegrated implants.

Sixteen edentulous patients were examined before and 2 months after rehabilitation with fixed bridges supported by fixtures in the mandible. Data were collected regarding bite force, chewing efficiency, chewing movements and self-estimated chewing ability. The results after rehabilitation indicated that patients with an obvious improvement of chewing efficiency showed a greater increase of the mean bite force parameters than patients with unchanged chewing efficiency. However, it was not possible to find any definite pattern of differences between the groups of patients, based on the chewing efficiency index after rehabilitation. Furthermore, after rehabilitation the test group revealed a positive correlation between the duration of the occlusion phase and bite force values, negative correlations between bite force "as when chewing" and closing velocity and between duration of the occlusion phase and opening mandibular velocity and displacement, respectively.

Adult↗
PubMed1998

Non-adrenergic, non-cholinergic reflex secretion of parotid saliva in rats elicited by mastication and acid applied on the tongue.

Chewing and acid on the tongue evoked a flow of saliva from the duct-cannulated parotid gland of the conscious rat despite pretreatment with atropine and adrenoceptor antagonists. This non-adrenergic, non-cholinergic (NANC) response depended on an intact parasympathetic innervation and was abolished by a tachykinin antagonist. The present findings are consistent with a physiological role for the secretory NANC mechanisms of the salivary glands.

Adrenergic Antagonists↗
PubMed1985

The possible relation between mastication and parotid secretion in the rabbit.

Salivary flow has been recorded from conscious rabbits during 1 min periods whilst continuously chewing standard laboratory dry pellets or pieces of carrot and, in some animals, a mash of pellets with water. Flow was measured using contact drop recorders or a continuous flow recorder via Polythene tubes permanently inserted into one or both parotid ducts. Large variations in flow were obtained with unilateral recordings particularly during dry pellet chewing. Bilateral recordings showed that the flow was always greater on one side than on the other and that dominant secretion alternated from side to side in an apparently random manner. Rabbits chew unilaterally. Videotaped recordings of chewing movements showed that the greater secretion was always produced on the chewing side. To test the possibility that drying of the oral mucosa, or the prolonged hardness of the pellets may result in higher flow rates in animals with cannulated ducts than would normally be seen in intact animals, water was injected downstream into the mouth through a third cannula. This was inserted in an anterograde direction in the parotid duct on one side. Significant reductions in flow were recorded during dry pellet eating, but not during carrot eating. When animals were fed a soft pellet mash, salivary flow was significantly lower than with dry pellets. Recordings have been made from strain gauges attached to the ascending ramus of the mandible. Previous findings that dry pellets produce greater strain than carrots have been confirmed. It has also been shown that less strain is produced with soft pellet mash. The strain gauge data suggested that a relation exists between masticatory force and parotid salivary flow. The results are compatible with the hypothesis that intra-oral mechanoreceptors may be involved in a masticatory-salivary reflex.

Animals↗
PubMed1984

Mastication and acid secretion.

The gastric acid response and the buffer capacity of the stomach were measured in 30 control subjects and 22 duodenal ulcer patients in response to a masticatory (solid) and a non-masticatory (homogenized) meal having the same chemical composition. The peak acid output values were equal after a masticatory and after a non-masticatory diet in control subjects (masticatory 18.1 +/- 1.2, non-masticatory 15.7 +/- 1.3 mmol/hr) as well as in duodenal ulcer patients (masticatory 35.7 +/- 1.5, non-masticatory 33.7 +/- 1.1 mmol/hr). The buffer capacity of the stomach contents 1 hr after the meal was significantly greater after a masticatory diet than a non-masticatory diet in both controls (14.6 +/- 1.4 and 9.0 +/- 1.9 mmol) and in duodenal ulcer patients (9.5 +/- 1.5 and 7.5 +/- 1.2 mmol). Duodenal ulcer patients had a significantly lower buffer capacity compared with controls. Masticatory diets may play a part in protecting individuals from developing duodenal ulcer.

Adult↗
PubMed1994

Neuropharmacological mechanisms underlying rhythmical discharge in trigeminal interneurons during fictive mastication.

1. We have examined the effects of iontophoretic application of antagonists to excitatory amino acid (EAA) receptors, as well as glycine and gamma-aminobutyric acid (GABA), on rhythmically active (RA) brain stem neurons during cortically induced masticatory activity (RMA) in the anesthetized guinea pig. Ten of these neurons were antidromically activated at latencies of 0.3-0.9 ms by stimulation of the trigeminal motor nucleus (MoV). 2. RA neurons were divided into closer and opener type according to the phase of activation during RMA. Iontophoretic application of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a specific non-N-methyl-D-aspartate (NMDA) receptor antagonist, suppressed discharge of both closer and opener type RA neurons during RMA. In contrast, iontophoretic application of 3-((1)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), a specific NMDA receptor antagonist, was not effective in suppressing discharge of most opener type RA neurons but did reduce activity of closer type RA neurons. 3. Spike discharge of most RA neurons was time locked to each cortical stimulus during RMA. Some of the RA neurons were activated at a short latency to short pulse train stimulation of the cortex in the absence of RMA. In most cases CNQX reduced such time-locked responses during RMA and greatly reduced discharge evoked by short pulse stimulation of the cortex in all cases. In contrast, CPP was not as effective in suppressing either the time-locked responses during RMA or the discharge evoked by short pulse train stimulation of the cortex. 4. D,L-Homocysteic acid (HCA) application produced low level maintained discharge in RA neurons before RMA induction. When RMA was evoked in combination with HCA, rhythmical burst discharges with distinct interburst periods during the opening phase of RMA were observed in most closer type RA neurons. In contrast, during RMA in combination with HCA application, opener type RA neurons showed burst discharges that were modulated during the RMA cycle but lacked distinct interburst periods during the closer phase of the cycle. 5. During application of strychnine (STR), a glycine antagonist, discharge of closer type RA neurons increased in the opener phase of RMA during continuous HCA application. In contrast, bicuculline methiodide (BIC), a GABA antagonist, did not increase unit discharge of closer type RA neurons in the opener phase of RMA. 6. It is concluded that closer type RA neurons receive, alternatively, EAA-mediated excitatory and glycine-mediated inhibitory masticatory synaptic drive signals during RMA.(ABSTRACT TRUNCATED AT 400 WORDS)

6-Cyano-7-nitroquinoxaline-2,3-dione↗