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At least 289 records · Page 16Linked to original sources
PubMed1997

Mastication-related neurons in the orofacial first somatosensory cortex of awake cats.

In the orofacial area of the first somatosensory cortex (SI), we recorded single unit activity from 699 neurons in 11 awake cats. Fifty-two percent (362/699) were mastication-related neurons (MRNs) showing activity related to some aspects of masticatory movements. MRNs were divided into three types by their activity patterns: (1) the rhythmical type, showing rhythmical bursts in pace with the masticatory rhythm; (2) the sustained type, showing a sustained firing during the period of taking food and (3) the transient (biting) type, showing intense discharges in coincidence with biting hard food. MRNs had mechanoreceptive fields in the perioral, tongue, periodontal and mandibular regions. The activities of perioral rhythmical-MRNs, mandibular transient-MRNs, tongue rhythmical-MRNs and periodontal transient-MRNs were correlated with food texture, while perioral rhythmical-MRNs, perioral sustained-MRNs and tongue sustained-MRMs were not. Both facial and intraoral MRNs were scattered throughout the facial and intraoral projection areas in SI. These findings provide evidence that the orofacial SI monitors masticatory movements for food ingestion.

Afferent Pathways↗
PubMed2002

Measurement of surface area, gel weight and saliva weight in a gelatin-based gel over the course of mastication.

The aim was to devise a method for the measurement of total surface area and weight, as well as saliva weight, for a gelatin-based confectionery gel over the course of human mastication for input into separate modelling of flavour release. The method is based on an alcohol rinse to remove saliva, followed by immersion in amaranth dye to give a thin surface dye layer coating the gel fragments. Total surface area is then found by measurement of quantity of absorbed dye. The resulting time profiles for the six panellists showed that surface area reached a maximum of 3000 mm2 with the 4.28 g gel weight being consumed over 41 to 64 sec with differing numbers of swallows (4-6) and chews (52-103). Calculated total relative saliva weights, 498-993 g kg-1, and flow rates, 2.8-5.6 g min-1, were towards the upper range of those reported in the literature.

Amaranth Dye↗
PubMed2005

Mastication influences the survival of newly generated cells in mouse dentate gyrus.

We examined the effects of soft food and tooth loss on neurogenesis in the adult dentate gyrus. Four-week-old mice were subjected to a powder diet for 10 weeks with or without removal of molars. They received a daily injection of bromodeoxyuridine (BrdU) at 14 weeks of age for 12 consecutive days. The number of BrdU-positive cells in the dentate gyrus of these mice did not differ from that of control at 1 day after the last BrdU injection. However, the BrdU-positive cells in these mice showed a larger reduction in number than in control at 5 weeks after the BrdU injection and the ratio of neurons to BrdU-positive cells decreased in the molarless mice. These results suggest that mastication influences the survival of newly generated cells in the adult dentate gyrus.

Age Factors↗
PubMed1983

Tooth contact patterns and contractile activity of the elevator jaw muscles during mastication of two different types of food.

The pattern of molar and canine contacts and the contractile activity of the masseter and anterior temporal muscle were studied, through integrated electromyography, during right-sided mastication of banana and apple in ten healthy male subjects. Tooth contacts occurred on both the chewing and the non-chewing side. This study does not support the clinical concept that non-chewing side contacts are necessarily detrimental to the jaw muscles and the temporomandibular joints. The activity of the elevator jaw muscles and the tooth contact patterns suggest that the mandible tilted around a sagittal axis, and rotated around a vertical axis, during the phase of elevation of a masticatory cycle.

Adult↗
PubMed1985

Lateral preference in mastication: a feasibility study.

To study lateral bolus placement during mastication, referred to as masticatory lateral preference, fifteen males and ten females chewed sugarless gum for 15, 20 and 25 s, and visual inspections were done of either right or left side bolus placements. In each of three series of observations, there were no significant differences between right or left side bolus placements. Three consecutive spot checks, in single subjects, showed that lateral preference occurred at random. However, information on a favoured chewing side predicted fairly reliably the side of observed masticatory lateral preference. Observed lateral preference could not be predicted from hand laterality. Consistent and predominant right or left lateral preference was, presumably, an expression of mainly motivational chewing behaviour.

Adult↗
PubMed1985

Lateral preference in mastication: an electromyographic study.

To study concurrence of specific electromyographic chewing patterns and the side of mastication, twelve subjects chewed gum for 15, 20 and 25 s. Gum bolus placement on the right or left side of the dentition was estimated by three series of visual inspections. Contraction patterns of the chewing and non-chewing side masseter muscles were appraised by integrated and cumulative surface electromyography. Consistent and predominant gum bolus placement on the right side of the dentition could be predicted fairly reliably from comparative electromyographic observations. This was also the case in instances of consistent left-sided gum bolus placement, but not in predominant left-sided bolus placement. The latter phenomenon was explained by deviant observations made in two subjects only. Agreement between a presumed chewing side and a predictive contractility pattern was established in 78% of observations (P less than 0.001).

Adult↗
PubMed1987

The coefficient of swallowable composition of masticated hard-baked soya beans.

In addition to the graphical representation of swallowable composition (SC) of masticated food, an index--the coefficient of swallowable composition (CSC)--has been proposed in this study. This index was tested using hard-baked soya beans on various types of dentitions. The value of CSC ranged from +24 to -14 in full dentition and full denture wearers respectively.

Dentition↗
PubMed1990

Comparison of food particle distribution masticated by subjects wearing complete dentures and with natural teeth.

The sizes of soya particles masticated by 12 complete denture wearers and 10 subjects with natural dentition were directly measured by means of a graphic digitizer and computer, following a varied number of chewing strokes. It was found that the chewed particle size frequency distributions of the two groups tended to a state of normal logarithm distribution. Compared with the dentate subjects, the mean, 20th, 50th and 80th percentile of the particle sizes chewed by complete denture wearers were increased, whilst the distribution shapes were nearly identical. The results suggest that there are no qualitative differences in the manner in which the two groups break up food. Selection and breakage functions of complete denture wearers are decreased, and this could be related to the denture conditions and the change of oral state in such individuals.

Adult↗
PubMedDate not supplied

Coordinated electromyographic activity of the human masseter and temporalis anterior muscles during mastication.

The present report aimed at evaluating the within- and between-subject electromyographic coordination between the masseter (M) and temporalis anterior (T) muscles during the performance of a standardized chewing task. Electromyographic activity of M and T muscles was recorded in 60 young healthy adults (30 men, 30 women) during two 15-s unilateral mastications of gum. Left-right differential potentials (delta M = MR-ML, delta T = TR-TL) were computed and the square root of (delta M2 + delta T2) moduli were calculated. The maximum modulus relative to each masticatory cycle was located, and each modulus and differential potential were expressed as a % of the maximum modulus for each subject and chewing trial. For each subject and chewing side, the masticatory frequency was computed, and statistics of the moduli as %s of the maximum were determined by means of bivariate analysis. Within-subject repeatability of the unilateral chewing patterns was good. Mean population values for the modulus position (bivariate analysis), chewing frequency, and maximum modulus of the differential potentials (univariate statistics) were computed. A significant gender difference was found for the masticatory frequency, with larger values in men than in women. Conversely, no gender or side differences were found for the mean values of the maximum modulus or for the mean position of the percentage moduli. The chewing test applied allowed the evaluation of the neuromuscular coordination during the performance of a standardized physiologic activity. In particular, it quantified the within-subject and chewing side repeatability of the muscular pattern.

Adult↗
PubMed2006

Impaired mastication modifies the dynamics of bolus formation.

Mastication is a complex sensory-motor activity whereby a food product is transformed into a bolus. Consumers mainly perceive the sensory properties of the food during the intra-oral manipulation of the product. Consequently, the quality of the chewing process could have consequences on the perception of sensory properties and food choice. By focusing on meat products, this study aimed to analyze the influence of dental status on (i) dynamic adaptation of the chewing behavior (evaluated by electromyography) to the changes in texture during bolus formation and (ii) bolus properties (mechanical resistance and saliva incorporation) obtained from meat of different initial textures. Two groups of subjects (dentate subjects and denture wearers), known to present highly different chewing efficiency, were compared. For both groups, salivary flow rates were evaluated at rest and after stimulation by chewing (paraffin and meat). The salivary flow rates, assessed during chewing of a nonedible matrix (paraffin), were a good predictor of salivary flow rates induced by meat chewing for both groups of subjects. Salivary flow rates were not affected by the dental status. In contrast, the chewing behavior varied between groups. For denture wearers, the chewing pattern was strongly impaired and not adapted to the changes in meat structure during bolus formation. Denture wearers swallowed less fragmented boli than dentate subjects, but boli had a similar level of moisture for both groups of subjects.

Adaptation, Physiological↗
PubMed2006

Occlusal interference during mastication can cause pathological tooth mobility.

BACKGROUND AND OBJECTIVE: Despite little evidence regarding the relationship between tooth mobility and nonworking contact, the evaluation of occlusion is performed mainly by the detection of premature and/or nonworking contacts during tapping movements and lateral excursion. The hypothesis of this study is that occlusal contact during mastication is potentially traumatic to periodontal tissue. It clarifies the relationship between chewing patterns and the status of periodontal tissue. MATERIAL AND METHODS: Subjects included 73 adults, 20-29 years of age (39 men and 34 women), with complete sets of teeth and no history of orthodontic treatment or periodontal disease. The closing chewing patterns of each subject were classified into three groups by the Masticatory Deviation Index, which depicts the deviation from the normal chewing patterns within 5 mm from the intercuspal position. Periotest was used to diagnose teeth mobility and the values were compared among the three groups. RESULTS: The present study indicates that the chewing movements which deviated from the normal chewing movements increased the mobility of specific types of teeth. CONCLUSION: The results of this study imply a relationship between chewing movements and tooth mobility and indicate that functional evaluation of occlusion is necessary for the examination of periodontal tissue. Occlusal evaluation with border and tapping movements might be insufficient, and functional occlusal evaluation during chewing movements can be clinically useful for using to evaluate periodontal tissue.

Adult↗
PubMed2000

Results of simulated mastication suggest existence of a periodontogastric motility reflex.

Various reflexes inhibit gastric motor activity. Might a contrary one permit the oral region to increase gastric motility? Ten fasted rats were allowed to feed for 15 min. Following anesthesia and cannula insertion, antral pressure was recorded during three consecutive 5-min intervals: the baseline, procedure, and postprocedure periods. The procedure involved manually lowering and raising the mandible about once per second, causing repetitive molar occlusion. Doing this when food is in the stomach resembles conditions as the latter part of a meal is consumed. Gastric motor events increased from 1.10 +/- 1.67 (mean +/- SD) to 5.50 +/- 4.12 per 5 min during the procedure (p < 0.05) and 5.80 +/- 3.97 in the ensuing period (p < 0.05). The findings suggest an excitatory reflex following stimulation of mechanoreceptors in one or more sites related to mastication: the periodontium, temporomandibular joints, or masticatory muscles. Because rubbing the maxillary molars while the mouth remained constantly open also increased motor events, the periodontium is the most likely location of the receptors. They and associated trigeminal neurons would comprise the reflex's afferent arm. The vagi, perhaps with intermediaries, are its likely efferent arm. In these recently fed rats this reflex acts despite receptive relaxation and enterogastric reflexes to increase distal gastric motor activity.

Animals↗
PubMed2004

Influence of age on adaptability of human mastication.

The objective of this work was to study the influence of age on the ability of subjects to adapt mastication to changes in the hardness of foods. The study was carried out on 67 volunteers aged from 25 to 75 yr (29 males, 38 females) who had complete healthy dentitions. Surface electromyograms of the left and right masseter and temporalis muscles were recorded simultaneously with jaw movements using an electromagnetic transducer. Each volunteer was asked to chew and swallow four visco-elastic model foods of different hardness, each presented three times in random order. The number of masticatory cycles, their frequency, and the sum of all electromyographic (EMG) activity in all four muscles were calculated for each masticatory sequence. Multiple linear regression analyses were used to assess the effects of hardness, age, and gender. Hardness was associated to an increase in the mean number of cycles and mean summed EMG activity per sequence. It also increased mean vertical amplitude. Mean vertical amplitude and mean summed EMG activity per sequence were higher in males. These adaptations were present at all ages. Age was associated with an increase of 0.3 cycles per sequence per year of life and with a progressive increase in mean summed EMG activity per sequence. Cycle and opening duration early in the sequence also fell with age. We concluded that although the number of cycles needed to chew a standard piece of food increases progressively with age, the capacity to adapt to changes in the hardness of food is maintained.

Adaptation, Physiological↗
PubMed2000

Effect of food size on the movement of the mandibular first molars and condyles during deliberate unilateral mastication in humans.

To date, the effect of food size on the movement of the mandibular first molars and condyles during chewing has not been fully examined due to methodological problems. The purpose of the present study was to examine the previously unknown effect of food size on masticatory jaw movement. Using a face bow, light-emitting diodes, and optical cameras, we recorded, in 16 young adults with good occlusion, mandibular movement for the first 10 strokes during the unilateral chewing of similarly shaped hard gummy jellies weighing 5 g and 10 g, respectively. The chewing cycle time for the 10-g jelly was significantly longer than that for the 5-g jelly. The jaw-closing and -opening maximum velocities, gapes at the maximum velocities, and maximum gape were significantly faster and larger when 10-g gummy jellies were chewed, compared with results with 5-g jellies, at the mandibular first molar on the chewing side and the condyle on the non-chewing side. With the exception of the velocity, similar tendencies were observed at the molar on the non-chewing side. However, such significant differences were not detected at the condyle on the chewing side. The mandibular first molar on the chewing side was that most affected by food size, and the mean value of the maximum gape coincided approximately with the height of each jelly. These results suggest that humans chew hard coherent food such that the mandibular teeth that come into contact with the food open to a height equivalent to that of the food bolus, and that the changes in movement of the other parts of the mandible are minimized, ensuring efficient mastication.

Adult↗
PubMed1977

Mastication and maturity: a longitudinal study in pigs.

The electromyography of mastication was studied longitudinally in miniature pigs, and the effects of age and food type were assessed. Within-individual variation was large relative to between-individual variation. Duration of chewing strokes increased with age and with more resistant foods. The results are compared with data on human beings and other animals.

Age Factors↗
PubMed1983

The effect of mastication on marginal adaptation of composite restorations in vivo.

The marginal adaptation of composite restorations placed in vivo in acid-etched cavities in teeth with and without antagonists was compared. The results showed that functional mastication has a major influence on the marginal adaptation of composite restorations in the oral environment and must therefore be considered in the planning of future leakage experiments.

Acid Etching, Dental↗
PubMed1986

Relationship between jaw movement and food breakdown in human mastication.

Different quantities and sizes of peanuts were offered to six human subjects for mastication at two or three experimental sessions during which jaw movements and chewing cycle duration were measured. The amplitude of vertical movement and cycle duration depended on the position of a chew in a sequence of chews (masticatory sequence). Cycle duration also depended on the position of a given masticatory sequence during the first experimental session, the earlier sequences tending to be longer. Lateral jaw movements fluctuated about a reasonably constant value during a sequence and were unaffected by different food inputs. The amplitude of vertical movements increased markedly with an increase in food weight but was unaffected by change in the initial food particle size. These results were analyzed in the light of previous reports on the comminution of peanuts. It is hypothesized that observed jaw movements were unrelated to food particle size but that the amplitude of each vertical movement depended on the volume of food that was broken by the teeth during the next closing stroke. This food volume was provided and selected by bulk movements of the tongue during the preceding jaw opening.

Adult↗
PubMed1990

Textural properties of food used in studies of mastication.

Foods are known to influence jaw elevator muscle activity in chewing. With the long-range goal of gaining insight into force control and modeling muscle recruitment, these initial experiments were performed to determine the textural properties of commonly used test food. Experiments were carried out by means of a standard Instron instrument, equipped with a compression cell. A stylus with 45-degree cuspal angulation and an opposing copper-plated lower arch was used for approximation of the natural situation. The breakage force characteristics of a single peanut, a carrot cube, beefstick, and monkey chow were determined. The peanut demonstrated the steepest and beefstick the least steep force build-up, with breaking forces of 104 N (Newtons) for monkey chow, 66 N for the carrot, and 52 N for the peanut. No clear breakage point was found with beefstick; the force build-up showed an initial plateau at 25 N, which was followed by a significantly steeper force increase to peak. We conclude that each of the test foods commonly used in studies of mastication had particular breakage characteristics in terms of its force-time curve.

Analysis of Variance↗