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PubMed2002

Effects of reversible bilateral inactivation of face primary motor cortex on mastication and swallowing.

The effects of reversible cold block-induced bilateral inactivation of the face primary motor cortex (face MI) on mastication and swallowing were studied in awake monkeys. A warm or cold alcohol-water solution was pumped through thermodes placed bilaterally on the dura overlying the intracortical microstimulation-defined face MI while the monkey chewed and swallowed food during pre-cool (thermode temperature 37 degrees C), cold block (4 degrees C), and post-cool (37 degrees C) sessions. Vertical and horizontal jaw movements and electromyographic (EMG) activity of several muscles were monitored. Each masticatory sequence was divided into three masticatory phases (i.e. food preparatory, rhythmic chewing, preswallow). The cold block markedly affected the ability of the monkey to carry out mastication although it did not prevent mastication from occurring. The masticatory deficit was characterized by a significant elongation of the total masticatory time, including in particular elongation of the food preparatory phase. The coordination of the jaw- and tongue-muscle activities was severely disrupted during the food preparatory phase. Face MI cold block also significantly affected the duration of some masticatory-related EMG activities and had some limited effects on the temporal relationships of the EMG activities during mastication. Although cold block significantly affected the duration and some EMG parameters of the preswallow phase, it had no significant effect on swallow duration or the EMG parameters during swallowing. These findings provide further evidence that the primate face MI plays a critical role in the regulation of mastication and that it plays a role in the preparation for swallowing.

Animals↗
PubMed2001

Neuronal activity in the putamen and the globus pallidus of rabbit during mastication.

The pattern of jaw movements is changed during a masticatory sequence from ingestion of food to its deglutition. The masticatory sequence is divided into three distinct stages in the rabbit. However, the neural mechanism involved in the alteration of the masticatory stages is still unknown. This study was designed to determine whether neuronal activity in the putamen and globus pallidus is related to the alteration of the masticatory stages. Fifty-three percent of the recorded neurons showed significant alterations of activity during mastication. Of these neurons, 16% changed their firing frequency throughout the masticatory sequence (sequence-related neurons) and 84% changed their firing frequency with the transition of the masticatory stages (stage-related neurons). The stage-related neurons were classified into two groups based on their neuronal activity patterns observed during mastication, i.e. simple type and complex type. The former are the neurons that were either facilitated or inhibited once during mastication, and the latter are those showing the facilitation or inhibition twice or more during mastication. Complex-type neurons were observed more frequently in the globus pallidus than in the putamen. These results suggest that the basal ganglia is involved in mastication and may related to the transition between the masticatory stages.

Animals↗
PubMed1997

Mastication and swallowing in patients with postirradiation xerostomia.

PURPOSE: Very little objective data has been reported on mastication and swallowing in xerostomic patients, which would substantiate presumed causal relationships between xerostomia and patient complaints. The purpose was to elucidate which components of mastication and swallowing were abnormal, and most directly related to xerostomia, and which appeared unaffected. METHODS AND MATERIALS: A retrospective analysis of timing events in mastication and swallowing was done using videofluoroscopic data for 15 cancer patients with xerostomia, and 20 normal controls. Scintigraphy was also used to determine oropharyngeal residue after a water swallow. Cancer treatment modalities included radiation therapy or chemoradiation therapy. RESULTS: For barium liquid and paste substances, timing measures were equivalent for controls and patients. Xerostomic patients took 46% longer to masticate a shortbread cookie, and timing for the initiation of swallowing was shorter, but duration of swallowing appeared unaffected. Oral and pharyngeal residues following the swallow were greater in the patient group. CONCLUSIONS: Xerostomia primarily affected mastication and oral manipulation of a dry, absorbent food material. Increased oral and pharyngeal residues after a water swallow are ambiguously related to xerostomia. The initiation and duration of the pharyngeal swallow was not abnormal.

Aged↗
PubMed2003

Mastic gum has no effect on Helicobacter pylori load in vivo.

OBJECTIVE: To determine whether mastic gum suppresses or eradicates Helicobacter pylori infection in humans. PATIENTS AND METHODS: Nine patients with H. pylori infection, and without gastroduodenal ulceration, were recruited from day-case endoscopy lists and treated with mastic 1 g four times daily for 14 days. [13C]Urea breath tests (UBTs) were carried out immediately before, on day 15 and 5 weeks after treatment with mastic. RESULTS: Mastic had no effect on H. pylori status in any of the eight completed patients; all remained H. pylori positive by UBT with no change in delta scores [pre-treatment mean +/- s.e.m. 19.1 +/- 3.7, day 15 (post-treatment) 18.7 +/- 3.8, P = 0.8, paired t-test]. CONCLUSION: Despite reported anti-H. pylori action in vitro, this preliminary study shows that mastic has no effect on H. pylori in humans.

Breath Tests↗
PubMedDate not supplied

A double-blind controlled clinical trial of mastic and placebo in the treatment of duodenal ulcer.

A double-blind clinical trial was carried out on thirty-eight patients with symptomatic and endoscopically proven duodenal ulcer to compare the therapeutic responses to mastic (1 g daily, twenty patients) and placebo (lactose, 1 g daily, eighteen patients) given orally over a period of 2 weeks. Symptomatic relief was obtained in sixteen (80%) patients on mastic and in nine (50%) patients on placebo, while endoscopically proven healing occurred in fourteen (70%) patients on mastic and four (22%) patients on placebo. The differences between treatments were highly significant (P less than 0.01). Mastic was well tolerated and did not produce side effects. It is concluded that mastic has an ulcer healing effect, but further studies are needed to establish its role in treating peptic ulcer.

Adult↗
PubMed1990

Modulation of activity of spindle afferents recorded in trigeminal mesencephalic nucleus of rabbit during fictive mastication.

1. These experiments were based on the findings that antidromic firing is observed in first-order sensory afferents during fictive locomotion and were designed to test the hypothesis that a similar central modulation of afferent discharge occurs during mastication. To do this, spindle afferents were recorded in the trigeminal mesencephalic nucleus (Mes V) of anesthetized and paralyzed rabbits during fictive mastication. The cortical masticatory area was stimulated to induce mastication, and activity of the XIIth or the Vth nerves were recorded to monitor the masticatory motor rhythm. 2. Although we could find little evidence that antidromic discharges invade the somatic region of this class of sensory afferents, we did discover a previously unrecognized type of modulation of afferent firing. 3. Of 83 slowly adapting muscle spindle afferents, 33 were modulated during fictive mastication. In 28 cases, the modulation consisted of a phasic inhibition, whereas for the remaining units it could be either a phasic excitation (n = 2) or an excitation alternating with an inhibition (n = 3). 4. Rapidly adapting units were also tested when encountered. Tonic or phasic excitation was never observed. The presence of inhibition could not be verified for this population because tonic activity could not be maintained by passive stretch. 5. The main electroneurogram (ENG) burst of the XIIth and Vth cranial nerves occurred during the opening phase of the masticatory cycle, and in all cases where the records were clear (22 out of 33), phasic inhibition of the afferents coincided with the ENG burst. 6. There was no difference in the distributions of the modulated and of the unmodulated units along the length of the Mes V nucleus. 7. Approximately 40% of trigeminal spindle afferent cell bodies have dendrites, and we suggest that these are the ones rhythmically modulated during fictive mastication. The possible role of this modulation is discussed.

Animals↗
PubMed1993

An investigation of the coupling between respiration, mastication, and swallowing in the awake rabbit.

1. The interrelationships between respiration, mastication, and swallowing were studied in awake rabbits previously prepared for the chronic recording of jaw movements and the electromyographic activity of jaw and throat muscles. These signals were recorded before, during, and after the mastication of rabbit chow, together with respiratory movements. 2. The onset of activity in the thyrohyoid muscle was used as a marker for swallowing. Measurements were made of cycle duration, and the phase relationship between the masticatory and respiratory rhythms was calculated. Deviations in masticatory and respiratory movements during swallowing were detected; the phases of the masticatory and respiratory cycles in which the deviations occurred were determined, and the intervals between the deviations and the swallowing marker were calculated. 3. Two characteristic swallowing patterns were observed that were called Interposed and Terminal swallows. Interposed swallows occurred within a masticatory sequence, while Terminal swallows ended the sequence. 4. In most rabbits, respiratory rate slowed during mastication. This brought the average frequency of the two movements closer together, and there was a weak but significant correlation between the masticatory and respiratory rates. However, respiration and mastication were not linked on a cycle-by-cycle basis, and the change in respiratory rate was found to be unrelated to masticatory rate. Further, there was no tendency for the masticatory and respiratory rhythms to adopt any particular phase relationship as swallowing was approached. Some weak and transient phase coupling of the two systems occurred after swallowing. 5. During swallowing, respiration was most often inhibited soon after the start of the inspiratory phase. Swallows within a masticatory sequence occurred most frequently during the early opening phase of the masticatory cycle, and swallows after the end of a sequence occurred with the jaw in the resting position. There was a strong tendency for the durations of the masticatory and respiratory cycles containing deviations to be longer than preceding control cycles, and the effect on respiration lasted several cycles. 6. For both Interposed and Terminal swallows, a tight temporal relationship was observed between deviations in respiration and the swallowing marker: most deviations tended to occur before swallowing. In contrast, the time of deviations in mastication relative to the swallowing marker depended on swallow type and was more variable. Finally, there was no link between the start of the pauses in the two rhythms. 7. We conclude that respiratory and masticatory processes are not strongly coupled.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1997

[Anterior occlusal contact of complete denture during mastication].

The purpose of this study was to measure the actual anterior occlusal contacts in complete denture during mastication and discuss the relation between anterior occlusal contacts and masticatory movements. The actual anterior occlusal contacts were measured electrically with metal occlusal surfaces in five edentulous patients. These metal occlusal surfaces could be removed and changed into two types of occlusion. The masticatory movements were measured by Sirognathograph for seven edentulous patients. The types of anterior and posterior occlusions were changed, and the masticatory movements were analyzed for each of the four types of occlusion. The results were as follows: 1. Anterior occlusal contacts were found during mastication, but not during tapping, in bilateral balanced occlusion. 2. The frequency of anterior occlusal contacts during mastication was increased in non-balanced occlusion. 3. The frequency of occlusal contacts at the canine on the chewing side was increased by continuing of mastication, but was not increased at the canine on non-chewing side. 4. The stability of the denture tended to be lost by eliminating the anterior occlusal contact, judging from the rhythm of masticatory movements. This study suggested that anterior occlusal contacts are necessary for the functional harmony of complete denture during mastication.

Aged↗
PubMedDate not supplied

[Specifics of mastication with complete dentures].

INTRODUCTION: Mastication is a process characterized by alternating phases of physiological inactivity, food intake, initial food crumbling, mouthful formation and deglutition. Although there is a so called human type of mastication, this process is individual for variety of reasons. Mastication is not an innate characteristic and it must be learned, but once it is learned, it gets a reflexive function, demanding maximal involvement of the highest nervous system centers. DISCUSSION: Specificities of mastication in complete denture wearers are caused by specificities connected to changes of the oral cavity due to teeth loss, technical features of complete dentures and quality of their manufacture. Loss of teeth causes loss of periodontal receptors consequently damaging the source of information which, as long as teeth are present, travels from the oral cavity towards the central nervous system and regulates the masticatory muscles activity. As one of the consequences of periodontal receptors' loss, interocclusal perception decreases, because the number of receptors within the masticatory mucosa is negligible. Another problem is that loss of teeth causes loss of the occlusal surface. Occlusal surface is considered to be the only reference coordinate of the zero intermaxillary separation with precise spatial representation within the someostatic field cortex. Permanent loss of antagonistic contact causes disappearance of the memory pattern of the occlusal surface. Therefore completely edentulous mouths are characterized by disintegration of the free interocclusal space. Masticatory forces' value directly depends on the: size of muscles creating the forces, their position in the mandibula, shape of the edentulous alveolar ridge, type of chewing, the relationship between the height of the branch, length of the mandibular body, gonial angle, mandibular angle in relation to the anterior cranial base and posterior facial height and the degree of intermaxillary separation. Bite forces in complete denture wearers are significantly decreased in relation to persons with natural teeth. There is a fundamental difference in the distribution of the functional energy in complete denture wearers and subjects with intact teeth. Persons with natural teeth tend to generate energy through bolus, whereas in complete denture wearers most of the chewing energy is distributed outside bolus, directly through the denture base on the supporting tissues. RESULTS: As the result of this specific dynamics stress of supporting tissues often occurs with consequential mucosal inflammation and rapid alveolar bone resorption. Reduction of masticatory efficacy in denture wearers may be caused by irregular activity of masticatory musculature or is the consequence of irregular flow of energy during mastication. In comparison with young examinees with healthy teeth, authors have registered that complete denture wearers need about seven times more masticatory movements to achieve equal number of sample parts. CONCLUSION: It has been documented by experience and also scientifically proved, that the satisfaction of complete denture wearers is not often proportional with objective functional denture values. Comparison of subjective parameters with objective test results reveals that the percentage of complete denture wearers who consider their dentures to be good, although they objectively are not such, is significantly higher than the percentage of those who complain about their dentures, although they are functionally proper. Our study comprised patients (average age of 69) who wore complete dentures longer than five years.

Denture, Complete↗
PubMed1996

[Self-assessed quality of mastication in relation to remaining teeth and self-assessed health status in elderly persons].

To explore factors related to quality of mastication, information about teeth status and self-assessed health status were obtained by a self-administered questionnaire from participants in a dental screening program. Invitation letters for participation in the program were distributed by members of the neighborhood association to 1.275 residents of a town in Gifu prefecture aged 65 years or older. Participation rate in the dental screening program was 40.5%. A total of 513 participants (245 males and 268 females) completed the program and the questionnaire. The results were as follows. 1. Overall, 32% had 20 teeth or more and 88.4% had bridge(s) and/or denture(s). 2. The mean number of remaining teeth were 12.9 for males and 12.5 for females. There was no statistical difference in the number of remaining teeth between males and females. The mean numbers of remaining teeth among those aged 65-69 years was 15.7 and two thirds of them had lost the Lower First Molar. 3. Those who reported to be satisfied with their present mastication were 83.3% of men and 86.3% of women. The proportions were not influenced by age or sex. 4. Quality of mastication was related to self-reported "good physical condition' and "not easily tired'. 5. The proportion of those satisfied with their mastication was large in the groups with remaining teeth index 0-8 and > or = 17, and small in the group with remaining teeth index 9-16, showing a U-shaped curve for satisfaction rate against remaining teeth index. These results suggest a relationship of quality of mastication on health status. The importance of primary dental care for the elderly persons is underlined.

Aged↗
PubMed1985

Infection and tumor of the masticator space: CT evaluation.

The masticator space is a distinct deep facial space, bounded by the superficial layer of deep cervical fascia and containing the four muscles of mastication and the ramus and posterior body of the mandible. Trismus often complicates evaluation of masticator space disease. However, computed tomography (CT) clearly delineates the normal and pathologic anatomy of this region. The CT appearance of the masticator space was demonstrated in a retrospective review of 32 patients with either infection or tumor involving this space. Masticator space infections were found to have characteristic CT appearances and patterns of spread. CT was especially useful in differentiating inflammation from frank abscess, detecting mandibular osteomyelitis, and directing surgical drainage to the precise deep-tissue space involved. In cases of tumor, the primary utility of CT was in defining tumor extent accurately and in helping to assess resectability and determine radiation therapy ports.

Abscess↗
PubMed1987

Separation of the masticator space from the parapharyngeal space.

The separation of the masticator and parapharyngeal spaces is somewhat ambiguous. Anatomic specimens were dissected to define better the fascial layer representing the medial wall of the masticator space. A fascial layer was found extending from the medial pterygoid muscle to the skull base separating the masticator from the parapharyngeal space. The third branch of the trigeminal nerve was lateral to this fascial layer and thus passed through the masticator space. Clinical cases were reviewed. Tumors could be confidently assigned to the masticator, prestyloid, or poststyloid parapharyngeal spaces. Benign salivary gland tumors were found in the prestyloid parapharyngeal space only.

Face↗
PubMed2002

Functional morphology of the mastication muscles in the lesser and greater mouse deer.

The mastication muscles were examined in the lesser (Tragulus javanicus) and greater mouse deer (Tragulus napu) to clarify the form of the mastication muscles in these primitive artiodactyls. The M. masseter was well-developed in both species, however the attachment area of its origin was not confirmed in the rostral facial part. The masseter bundles were not observed on the lateral side of the maxilla bone, and their origin was restricted to the zygomatic arch area. This suggests that the M. masseter may not act as a motor raising the mandible rostro-dorsally, but pull the insertion vertically unlike the highly derived grazer of Bovidae. The Crista temporalis was weak and the M. temporalis was thin in the mouse deer, and this indicates that the M. temporalis may not be important in the mastication in the primitive artiodactyls. These findings suggest that the browser such as mouse deer has been adapted for the feeding on soft leaves, and functional-morphologically different in mastication strategy from the grazer such as developed Bovidae species. The architecture of the mastication muscles was not different between the two species. However, in the muscle weight ratios per body weight, the M. temporalis and the M. digastricus were significantly smaller in greater mouse deer than in lesser mouse deer.

Animals↗
PubMed1981

Mandibular movement and muscle activity during mastication in the guinea pig (Cavia porcellus).

Optoelectronic analysis of mandibular movement and electromyography (EMG) of masticatory muscles in Cavia porcellus indicate bilateral, unilateral, and gnawing cycles. During bilateral and unilateral cycles, the mandibular tip moves forward, lateral, and down during the lingual phase of the power stroke to bring the teeth into occlusion. EMG activity is generally asymmetric, with the exception of activity of the temporalis muscle during bilateral cycles. During gnawing cycles, the mandible moves in an anteroposterior direction that is opposite that during bilateral and unilateral chew cycles. Bilateral and unilateral cycles of pellets were significantly longer than carrot. With the exception of the width of bilateral cycles, the magnitude of cycle width, length, and height during the mastication of carrots was greater than that during the mastication of pellets. Significant differences exist between EMG durations during mastication of pellets and carrots. The lateral pterygoid displays continuous activity during gnawing cycles. Significant differences also exist in the duration of EMG activity between the working and balancing side during all three cycle types. High level of activity of balancing side temporalis and anterior belly of digastric (ABD) during bilateral cycles occurs during rotation and depression of the mandible during the power stroke. The temporalis apparently provides a "braking" or compensatory role during closing and power strokes. Differences between Cavia masticatory patterns and those shown by Rattus and Mesocricetus are apparently due to differences in dental morphology, occlusal relationships, and, possibly, the poorly developed temporalis in Cavia. The large number and wide diversity of rodent groups afford students of mammalian mastication an opportunity to investigate and compare different masticatory specializations.

Animals↗
PubMed1983

Computer simulation of the breakdown of carrot particles during human mastication.

There are two separable aspects of the mastication of food particles. One aspect describes the probability of the selection of particles for fracture (selection); the other describes the manner of fragmentation of the particles (breakage). Definitions of these concepts were used to produce an approximate equation for food breakdown, which can be solved by iteration in a computer. Values for the selection and breakage functions, obtained from 10 human subjects using carrot as a test food, were used in a computer program which modelled mastication. The model assumed (1) that selection depended only on particle size (2) that fragmentation (range of fractions or sub-particles produced) was similar for all particles, whatever their size. Good agreement was found between the actual particle-size distributions produced by mastication and those distributions generated by the computer. Simulations predicted that the initial particle size of the carrot before mastication could be varied substantially, so producing similar particle-size distributions after 15 chews.

Computers↗
PubMed1990

Mastication and its influence on human salivary flow and alpha-amylase secretion.

Unilateral parotid saliva was collected from ten subjects following oral stimulation with water, chewing on parafilm, mastication of celery and bread, and holding of bread in the mouth. Salivary flow induction was independent of chewing rate. Mastication of bread and celery resulted in higher flow rates than did chewing on parafilm. Although limited to two foods at two weights, the results suggest a possible dependence of flow rate on both the type and weight/size of the stimulus. Mastication increased the secretion rate but not the concentration of protein and alpha-amylase. The rate of alpha-amylase secretion was influenced by mastication in accord with digestive function, in that more secretion was induced by food than by nonfood stimuli, more by bread than by celery, and more by larger than smaller pieces of bread. However, these increases might be related more to the physical characteristics than the composition of the stimuli, e.g., force of chewing, dryness, and surface area.

Adult↗
PubMed1986

Evaluation of mastic, a crude drug obtained from Pistacia lentiscus for gastric and duodenal anti-ulcer activity.

The effect of mastic, a concrete resinous exudate obtained from the stem of the tree Pistacia lentiscus, has been studied on experimentally-induced gastric and duodenal ulcers in rats. Mastic at an oral dose of 500 mg/kg produced a significant reduction in the intensity of gastric mucosal damage induced by pyloric ligation, aspirin, phenylbutazone, reserpine and restraint + cold stress. It produced a significant decrease of free acidity in 6-h pylorus-ligated rats and a marked cytoprotective effect against 50% ethanol in rats which could be reversed by prior treatment with indomethacin. The protective effect was not seen when it was given intraperitoneally in phenylbutazone and restraint + cold stress models. The reduction in the intensity of ulceration in cysteamine-induced duodenal ulcers was not found to be statistically significant in mastic-pretreated rats. The results suggest that mild antisecretory and a localized adaptive cytoprotectant action may be responsible for its anti-ulcer activity. These observations support the results of an earlier study on the clinical effectiveness of mastic in the therapy of duodenal ulcer.

Animals↗
PubMed1998

Intermittency in mastication and apomorphine-induced gnawing.

Rhythmic behaviors like mastication, gnawing, and locomotion, are characterized by temporal segmentation or intermittency. That is, they frequently occur as a series of short bursts interrupted by pauses rather than as one long uninterrupted burst. The function of intermittency as well as the mechanisms that produce it are unknown. Biogenic amine systems may play a role in producing intermittency; however, experimental work to confirm this is only in its infancy. The current study evaluates the structure of intermittency associated with mastication and apomorphine-induced gnawing in the guinea pig. Thirteen free-roaming animals were videotaped while masticating or gnawing. Eight animals were given 0.5 mg/kg i.m. apomorphine and videotaped while gnawing. The remaining five animals received no apomorphine injections, but were taped while feeding on alfalfa pellets. Custom software was used to score instances of maximum jaw closures in videotaped mastication and gnawing sequences. The time between successive maximum jaw closures, called the interocclude interval (IOI), was calculated for all scored sequences. A cutoff IOI value of 0.26 s differentiated pauses (IOI values equal or greater than 0.26 s) from chews or gnaws (IOI values less than 0.26 s). Two or more successive chews or gnaws, without intervening pauses, defined behavior bursts. Chew, gnaw, and burst durations were quantified and compared. Chew and gnaw durations were similar. However, chewing bursts were significantly longer than gnawing bursts. The significance of these results is presented in light of previous neurophysiological work on rhythmic jaw movements and intermittency.

Animals↗