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At least 307 records · Page 17Linked to original sources
PubMed1991

The effect of increased mastication by daily gum-chewing on salivary gland output and dental plaque acidogenicity.

The effect of increased mastication on plaque metabolism and salivary gland function was determined in 11 human subjects who chewed a sugarless gum for ten minutes of each waking hour for two weeks. Prior to and at the conclusion of the gum-chewing regimen, unstimulated whole saliva and 2% citric-acid-stimulated parotid saliva were collected. Flow rates, pH, and buffer capacity were determined on all saliva samples. In addition, parotid saliva was analyzed for protein concentration and the proteins further studied by SDS-PAGE. The plaque pH response to a 10% sucrose rinse was also measured before and after the regimen. Significant increases were observed in the pH and buffer capacity of unstimulated whole saliva as were similar increases in the flow rate, pH, and buffer capacity of stimulated parotid saliva. Protein concentrations and profiles remained unaffected. In addition, the resting plaque pH and minimum plaque pH reached after a sucrose challenge were both raised significantly, with a significant reduction in the cH area. The results of this study indicate that increased masticatory effort by frequent consumption of sugar-free chewing gum over a prolonged time period resulted in a functional increase in the output of stimulated parotid saliva, as well as in increases in pH and buffer capacity of whole and parotid saliva, which may help to reduce plaque acidogenicity.

Acids↗
PubMed1992

A computer simulation of the influence of selection and breakage of food on the chewing efficiency of human mastication.

The reduction of food particle sizes during mastication is considered to be the composite result of a selection and breakage process. The chance of a food particle being selected between the teeth was assumed to increase as a power function of the particle's size, whereas the breakage of food particles was described by a cumulative distribution function. The selection and breakage functions were combined with matrix algebra, resulting in a matrix model. By use of this model, particle-size distributions could be calculated after various numbers of chewing cycles. From these distributions, the decrease of the median particle size was determined as a function of the number of chewing cycles. The calculations were performed for various sets of physiologically relevant selection and breakage variables. The number of chewing cycles, N1/2, needed for the initial particle size to be halved was taken as an indication of chewing efficiency. This number varied approximately inversely with both the selection coefficient and the breakage variable. The initial particle size appeared to have the largest influence on N1/2. The theoretical results from the simulation study were also compared with data obtained from experiments on human chewing efficiency.

Computer Simulation↗
PubMed1998

Food properties that influence neuromuscular activity during human mastication.

The rate of breakdown of food in mastication depends on the ratio of two mechanical properties of the food--the toughness and modulus of elasticity (Agrawal et al., 1997)--a result which can be predicted by an analysis of the energetics of fracture. The work input to produce food fragmentation is provided by the masticatory muscles, the activity levels of which depend on sensory feedback from the mouth. Here, we test the hypothesis that the activity of a representative of this musculature is modulated by the above combination of food properties. The surface electrical activity (EMG) of the anterior temporalis muscles of ten human subjects was recorded while subjects chewed standardized volumes of 15 food types. The integrated EMG in these muscles was highly significantly related to the square root of the ratio of the above two food properties. Significant correlations were found between this food property index and integrated EMG, both when data for all chews and all subjects were lumped together (r = -0.86; p < 0.0001) and when correlation coefficients between the index and EMG were plotted for each chew made by each subject. Except for two subjects in the first chew, these coefficients reached and maintained highly significant levels throughout the masticatory sequence. Thus, a clear relationship between the electrical activity of a jaw-closing muscle and the mechanical properties of food has been found for the first time.

Adult↗
PubMed1991

Mastication and its control by the brain stem.

This review describes the patterns of mandibular movements that make up the whole sequence from ingestion to swallowing food, including the basic types of cycles and their phases. The roles of epithelial, periodontal, articular, and muscular receptors in the control of the movements are discussed. This is followed by a summary of our knowledge of the brain stem neurons that generate the basic pattern of mastication. It is suggested that the production of the rhythm, and of the opener and closer motoneuron bursts, are independent processes that are carried out by different groups of cells. After commenting on the relevant properties of the trigeminal and hypoglossal motoneurons, and of internuerons on the cortico-bulbar and reflex pathways, the way in which the pattern generating neurons modify sensory feedback is discussed.

Animals↗
PubMed1990

[Effect of coronal gingival contour on contact between food bolus and cervical tooth surface during mastication].

At the coronal cervix, the so-called uncleaned area, the path of the food bolus and its rubbing effect are said to be regulated by the coronal and gingival contours. However, it has not been ascertained whether such regulation really exists. So, the force which was generated by a food bolus rubbing on the buccal surface was measured at the height of the cervical third of the lower first molar with a load cell inserted into the denture. The results obtained were as follows: 1. Cervixward forces were observed in the closing phase and cuspward forces, in the opening phase during mastication. The intensity of cervixward forces was stronger than that of the cuspward ones. And the occurrence of the former was more frequent than that of the latter. 2. The intensity and frequency of cervixward forces differed according to the kind of food. 3. Cervixward force under the degree of convexity of 0 mm was stronger in intensity and more frequent than that under the degree of convexity of 0.5 mm. 4. Cervixward force under the marginal gingiva thickness of 1 mm was stronger in intensity and more frequent than that under the marginal gingiva thickness of 2 mm.

Bite Force↗
PubMed1981

Efficiency of mastication in relation to hay intake by cattle.

Four dry Holstein cows and four hay levels (50, 75, 100 and 125% of NRC-recommended dry matter intake) were used to study the efficiency of mastication and rumination in relation to hay intake. The experimental design was a 4 x 4 Latin square with 7-day periods. Increased hay levels resulted in increased rumination time, eating time, number of rechewings and boluses. When corrected for cell wall constituents (CWC) intake, rumination time decreased as level of hay intake increased, while eating time increased. Consequently, total chewing time per kilogram CWC intake did not differ (P less than .05) with hay level. Results indicate that ingested roughages required a constant amount of trituration either by eating or by rumination. The amount of each fecal particle size fraction retained by four different sieve sizes, and the total of these larger particles (above .3 mm), did not differ (P greater than .05) among hay levels. Results suggest that acceptability of indigestible particles by the reticulo-omasal orifice was not affected by the amount of hay intake.

Animal Feed↗
PubMed1983

Masticatory efficiency. A new method for determination of the breakdown of masticated test material.

One of the purposes of mastication is to break down the food and enlarge the area of food particles. A method is described by which the masticatory efficiency is estimated by calculating the area of a chewed test material, gelatin-hardened by formalin. When test pieces, after being chewed, are placed in a water-soluble dye, the dye will diffuse into the particles, and consequently the dye concentration in the surrounding solution will decrease. The concentration of the dye solution is read from a photometer. A close correlation was found between the gelatin particle area and the reduction of the dye solution concentration. The method will be applied in clinical studies.

Coloring Agents↗
PubMed1996

The expression of types X and VI collagen and fibrillin in rat mandibular condylar cartilage. Response to mastication forces.

Types X and VI collagen and fibrillin were localized by in situ hybridization and immunohistochemical methods in the mandibular condyles of rats, and the response of these molecules to post-weaning diets of soft food, ordinary pellets, or hardened pellets was studied. Type X collagen was synthesized, particularly in conditions of soft food consistency, by cells in the perichondrium-periosteum and in the bone and by cells at the erosion front between cartilage and bone. Type X collagen synthesis diminished under higher compression forces due to mastication and with increasing age. Type VI collagen and fibrillin were synthesized by cells in the perichondrium-periosteum and by chondrocytes and by stromal osteoblasts and were not modified by higher mechanical forces. In contrast to previous findings in the growth plate of long bones, type X collagen in the mandibular condyle was not synthesized by hypertrophic chondrocytes but was associated with cells of the osteoblastic rather than the chondroblastic phenotype.

Animals↗
PubMed1988

Influence of feed intake, forage physical form, and forage fiber content on particle size of masticated forage, ruminal digesta, and feces of dairy cows.

Two trials were conducted to determine particle size of masticates, ruminal digesta, and feces of dairy cows. In Trial 1, three Holstein cows with ruminal cannulae were fed prebloom alfalfa hay in long, chopped, or pelleted form in a Latin square design (21-d periods) conducted in early lactation (wk 3 to 11) and again during the dry period to attain high (3.75) and low (1.95% of BW) feed consumption. In trial 2, prebloom, midbloom, and full bloom alfalfa hay, mature bromegrass hay, and corn silage were fed to early lactation (wk 5 to 15) Holsteins in a 5 X 5 Latin square design (15-d periods). All diets (Trials 1 and 2) were formulated to 17% CP and contained forage:grain in a 60:40 ratio (DM basis). Similar particle distributions of digesta from long and chopped hay diets suggest little influence of chopping forage on particle size reduction when high quality forage is fed. The large proportion of DM in the small particle (less than .6 mm) pool in the rumen in both trials suggests that rate of escape of small particles from the rumen is an important factor influencing ruminal retention time. Increased proportion of coarse (greater than or equal to 2.36-mm screen) fecal particles at high intake and with fine grinding appears related to a reduction in chewing per unit feed consumed. Soluble DM and particulate matter passing a .063-mm screen made up a significant portion (30 to 50%) of the total DM sieved from all sampling sites in both trials.

Animal Feed↗
PubMed2000

Mastication in the oral myofunctional disorders.

The aim of this article is to show two ways of clinical work with mastication in Oral Myofunctional Disorders. Consideration is given to limitations that make direct treatment impossible: symptoms/signs of temporo-mandibular joint, occlusions alterations, types of orthodontics or orthopedics appliances and loosing teeth. The procedures suggested are named procedures WITH and WITHOUT LIMITATIONS.

Adult↗
PubMed2002

Influence of mastication on gastric emptying.

The role of mastication on digestion efficiency remains to be demonstrated. This study investigates whether masticatory function influences gastric emptying rate. Twelve normal volunteers were studied on two occasions after ingestion of the same test meal containing ham cubes, crackers, and egg (mixed with 13C-octanoic acid), chewed, in random order, either with 50 masticatory cycles or with 25 cycles, swallowing ham cubes whole. Lag phase (Tlag) and gastric half-emptying time (T1/2) were measured by means of the 13C-octanoic acid breath test. Trituration performance was assessed by the sieve test, and was expressed as the percentage of ham particles < or = 1 mm after 50 masticatory cycles. Tlag and T1/2 were significantly shorter when the meal was chewed with 50 cycles than with 25 cycles (Tlag 25.9+/-3.8 vs. 36.4+/-4.1 min, p=0.017; T1/2 49.1+/-5.7 vs. 62.5+/-6 min, p=0.009). Trituration performance was inversely related to both Tlag (r=0.621, p=0.031) and T1/2 (r=0.699, p=0.012). Comminution of food influences significantly gastric emptying rates.

Adult↗
PubMedDate not supplied

Modulation of mastication during experimental loosening of complete dentures.

PURPOSE: Suction is achieved when complete dentures are first fitted, but it fades during the months following insertion, when it is increasingly complemented by muscular denture control. The aim of this study was therefore to investigate the extent to which patterns of mastication are altered by experimental failure of physical retention. MATERIALS AND METHODS: Seven edentulous volunteers had maxillary replica dentures made, with fine tubes incorporated so that alternating positive and negative air pressure could be generated under the fitting surface. Mandibular movements, EMG, and pressure under the denture base were recorded during unilateral chewing. RESULTS: The change of physical retention passed undetected by all subjects; they continued chewing apparently undisturbed. However, during air injection, the mandibular excursions were slightly slower (nonsignificant) and demonstrated a reduced variance (P < or = .05). The muscle activity showed significantly longer bursts (P < or = .05), and peak activity occurred later in the cycle (nonsignificant). CONCLUSION: Sudden failure of denture retention seems to initiate an immediate and effective modulation of centrally generated muscular activity patterns.

Aged↗
PubMed2002

[Ptosis and mastication disorders revealing concurrent myasthenia gravis and chronic polyradiculoneuritis].

Although myasthenia gravis (MG) has frequently been associated with other autoimmune disorders, it has only rarely been reported in conjunction with diseases of the nervous system. A 74-year-old patient with hypertension suddenly presented left unilateral ptosis and mastication disorders. Clinical examination showed a concomitant loss of strength distally and reduced deep tendon reflex. Electrophysiologic data indicated a diagnosis of MG and chronic inflammatory demyelinating polyneuropathy; acetylcholine receptor antibody was elevated at 4.1 nmol/L (normal < 2 nmol/L). Improvement was rapid after initiation of pyridostigmine in association with corticosteroid (1 mg/kg/day). One month later, the cranial nerve deficit disappeared and strength was normal. It is likely that a basic abnormality of immune regulation was responsible for the emergence of diseases with different clinical presentations, but similar immunopathogenesis. Corticosteroid seemed to be the most effective treatment.

Adrenal Cortex Hormones↗
PubMedDate not supplied

A review: neural control of mastication in humans as influenced by food texture.

This review summerizes recent approaches to the physiology of the masticatory system in humans that aim to understand how the process is influenced by the material properties of foods. The centerpiece is a group of experiments that show that the rate of breakdown of food in human mastification depends principally on the combination of two mechanical properties of foods: toughness(R) and modulus of elasticity (E). Two mechanical indices are constructed from these properties: the square root of their product, (ER)0.5, is predicted to explain the resistance to an incisal bite, while the square root of their ratio, (R/E)0.5 is predicted to control the rate of fragmentation during a postcanie bite. Evidence for the latter is reviewed, which also appears to modulate the activity of jaw closing muscles and the extent of lateral mandibular movement during mastication. These studies provide a quantified link between the food stimulus and the physiological response of the mastiatory system for which we know of no parallel. Attempts to extend this analysis have been made by psychophysical investigations of food texture. These support some sensitivity to the mechanical index that we have identified, but are not conclusive. Finally, we provide a chart summarizing physiological responses to food texture that could interest dentists, food scientists and also those interested in the analysis of dentition and diet in mammals.

Biomechanical Phenomena↗
PubMed1992

[The action on bacterial plaque of the mastication of a sorbitol chewing gum].

The authors made a clinical evaluation of mastication of sorbitol chewing gum and its interference on plaque accumulation on teeth in 14 volunteers, 10 men and 4 women with an age average of 27 y.o., who joined both control and gum groups for 1 or 2 or 3 days. Both groups, after perfectly cleaning their teeth, were requested to avoid any measure of oral hygiene for the whole time of the study and the gum group was advised to chew one sorbitol chewing gum immediately after every assumption of solid food for unless than 30' minutes with a minimum of 4 pieces a day (after breakfast, after lunch, during the afternoon, after dinner). They were supplied with one of two most diffused sorbitol chewing gums in Italy: Vivident in 8 and Happydent in 6 cases. The choice of sorbitol was made because it can be considered a non-cariogenic sweetener and because in our country it is the most used in the so called "senza zucchero" gums and sweets. Plaque extension was evaluated by Quigley-Hein plaque index with the same procedure of the original work and taken as a parametric value in order to apply parametric tests as media, normal distribution, standard deviation, variance, Student's tests, etc. These evaluations were made on Ramfjord's teeth: 1.6, 2.1, 2.4, 3.6, 4.1, 4.4 each one divided in two half. Results, so processed, showed a significant reduction (-0.96%; p < 0.01) of plaque index for 1 day with best effect on vestibular half of frontal teeth (p between < 0.01 and < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Induction of apoptosis in human colon cancer HCT116 cells treated with an extract of the plant product, Chios mastic gum.

A hexane extract of the plant product Chios mastic gum (He-CMG) is demonstrated to kill human colon cancer cells in vitro via the process of anoikis. Specifically, the sequence of events includes He-CMG-induced GI-arrest of the cells, detachment of the cells from the substrate and subsequent apoptosis. Anoikis is dependent on the concentration and duration of treatment with He-CMG. Presence of the pan-caspase inhibitor, Z-VAD-fmk, did not prevent cell detachment, but it did prevent apoptosis of the detached cells indicating that the process of cell detachment, but not apoptosis, is independent of caspase activation. He-CMG-induced apoptosis is associated with activation of the initiator caspases-8, and -9 and the effector caspase-3. Caspases are activated in cells at a relatively long time after detachment, and caspase-3 activation may require caspase-8 or caspase-9 activation, as determined by using HCT116 isogenic clones impaired in apoptosis mechanisms that involve these two caspases. Finally, electron microscopy observations indicated a time-dependent appearance of morphological features both typical and non-typical of apoptosis in cells treated with He-CMG for various periods of time. Taken together, the results demonstrated that He-CMG induces apoptosis in HCT116 cells and, therefore, further in vivo and in vitro studies of the anticancer activities of this plant product are warranted.

Anoikis↗
PubMed1991

A computer-aided analyzing system to examine the masticatory muscle EMG during mastication.

We developed a computerized analyzing system for masticatory muscle electromyograms (EMGs), parameters of which were burst-duration time, muscle activity and electromyographic power-spectrum density during mastication. The system was tested with healthy subjects to evaluate the fatiguing process and found to work satisfactorily. It may find applications in other neuromuscular systems where control mechanisms and/or coordination is of interest.

Adult↗