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At least 199 records · Page 11Linked to original sources
PubMed1993

Effects of oral sensory afferents on mastication in the miniature pig.

The performance of mastication is presumed to be influenced by afferent stimulation, but little information is available from awake, intact animals. Thirteen experiments were carried out with four miniature pigs. Electromyographic signals from the jaw muscles were recorded simultaneously with jaw movements during natural chewing of foods of differing hardnesses. Harder foods were found to be associated with higher activity levels of jaw-closing muscles and greater lateral deviation, but reduced jaw opening. The sensory supply from one side of the oral cavity was then removed by injected local anesthetic, and the recordings repeated. In addition to decreased activity levels, the jaw-closing muscles showed reduced ability to adjust to different foods. The frequency of mastication fell slightly, and the animals preferred to chew on the uninjected side. Lateral deviation was reduced, but at the same time the jaw-opening muscles usually became more active and accordingly the jaw opened more widely. These findings provide new information on the role of oral sensory afferents in regulating natural chewing patterns. The decreased activities of the jaw-closing muscles are consistent with, although they do not demonstrate, the existence of a positive feedback from periodontal afferents.

Afferent Pathways↗
PubMed2002

Characteristics of mastication in the anodontic mouse.

Teeth and periodontal mechanoreceptors play important roles in regulating jaw movements during mastication. However, little is known concerning how jaw movements develop without tooth eruption. To answer this question, we studied masticatory behavior in the osteopetrotic mouse, where tooth eruption does not occur and periodontal mechanoreceptors are missing. A masticatory sequence of the osteopetrotic mouse was divided into two stages: incision and chewing. Incision is characterized by small amplitude and rapid (7 Hz) open-close jaw movements, while slow (5 Hz) and large amplitude open-close jaw movements characterize chewing. The frequency and properties of jaw movements were comparable with those in the normal mouse, though the osteopetrotic mouse had a higher cycle number during incision than did the normal mouse. These results indicate that conversion from sucking to mastication occurs in the anodontic mouse, and the central pattern generator producing the masticatory rhythm develops almost normally without tooth eruption.

Animals↗
PubMed2003

New animal model for studying mastication in oral motor disorders.

To identify the basic parameters of oral behavior in mice, we recorded the three-dimensional jaw movement trajectories and masseter and digastric muscle activities in freely behaving mice eating foods of various textures. Results showed that: (1) there are characteristic jaw movement patterns for food intake and mastication; (2) the pattern in a chewing cycle may be divided into opening, closing, and protruding (power) strokes; and (3) food texture affects basic patterns of jaw movement, muscle activities, and chewing rhythms. The oral motor behavior of mice appears identical to those of other experimental animals, so mice are appropriate animal models for the study of mastication.

Animals↗
PubMed2004

Particle size distribution of food boluses after mastication of six natural foods.

There is a large variability between and among individuals in the physiology of mastication, but it is not known whether this produces a similar variability in the particle sizes of food boluses at the end of the chewing process. Food boluses obtained just before swallowing were analyzed in ten subjects (aged 36.7 +/- 9.5 yrs) with normal dentition. Food samples of 3 nuts (peanut, almond, pistachio) and 3 vegetables (cauliflower, radish, and carrot) were chewed and expectorated after self-estimated complete mastication. Measurements with sieving and laser diffraction methods indicated that particles were much larger in vegetables than in nuts. Particle size distributions were similar among nuts and among vegetables. Surprisingly, no inter-individual variability was observed in the particle distributions for the 6 foods, although several sequence variables differed markedly. A need for a bolus to be prepared with a precisely determined texture before it can be swallowed may explain the inter-subject variability of the masticatory function.

Deglutition↗
PubMed2005

Influence of bitter taste on mastication pattern.

Mastication is a rhythmic activity that can be modified by peripheral information generated in the mouth. To study whether taste cognition could influence the way in which a food is broken down in the mouth, subjects masticated firm, sugar-based gelatine gels with differing concentrations of quinine, up to 1500 micromol/kg, while electromyography (EMG) of masticatory muscles was recorded. Taste intensity and composition of saliva were measured. With increasing quinine concentration, the average number of chews for nine subjects decreased from 30 to 22, and their average clearance time increased from 7 to 14 sec. Quinine concentration had no effect on chewing frequency (1.3 Hz) or on the rate of salivation (5.5 g/min). Bitterness increased, while acceptability and sweetness decreased, with increasing concentration of quinine in the gel and in saliva. Taste cognition could therefore modify food breakdown in the mouth.

Adult↗
PubMed1989

[Occlusal contacts of complete denture during mastication in telemetry system].

The purpose of this study was to develop a telemetry system and to analyze the occlusal contacts of complete denture during mastication. The telemetry system consisted of a transmitter unit and a receiver unit. The transmitter allowed 6 channels of information of the occlusal contacts to be telemetered by time division multiplex communication method within the approximate distance of 2 m. The occlusal surface of the upper complete denture was made of metal and that of the lower denture was made of metal contact plates of 0.5 mm in width with each space of 0.5 mm. Then the transmitter was embedded in the lower complete denture. Occlusal contacts of 66 aged edentulous male were investigated both on the chewing side and on the nonchewing side in the premolar, the 1st molar and the 2nd molar regions. The results were as followed: 1. The occlusal contacts in the nonchewing side preceded those in the chewing side, with higher frequency and longer duration. 2. In the nonchewing side, the occlusal contact occurred at different time; the occlusal contact was observed first in the 2nd molar, then 32-48 ms later in the 1st molar, and 2-48 ms later in the premolar regions. 3. It is suggested that the balancing contact should be considered for stabilizing the denture in mastication.

Dental Occlusion↗
PubMed2005

[A case report of treatment for complex dysfunction of occlusion and mastication due to a maxillary fracture].

PATIENT: A case report of a 39-year-old man complaining of complex dysfunction of occlusion and mastication is presented. The patient came to Iwate Medical University Hospital following urgent hospitalization and treatment at a local hospital after catching his head in a forklift. The patient consulted the Second Prosthetic Department with the purpose of occlusal examination in April, 1994 and he was diagnosed with a malunited maxillary fracture. Afterwards, surgical correction was performed, but complex dysfunction of occlusion and mastication remained. Fixed prosthesis treatment was then planned and a dental prosthesis was set in April, 2000. His prognosis has since remained favorable. DISCUSSION: At the commencement of treatment, both surgery and orthodontic treatment were considered, but the patient desired early social rehabilitation. Therefore, a dental prosthesis was used to restore facial asymmetry and mandibular function. CONCLUSIONS: Rehabilitation of occlusal function was achieved by using a dental prosthesis. This facilitated early social rehabilitation and helped improve the patient's quality of life. Since there have been few reports of cases in which a dental prosthesis was used to correct occlusal disharmony after surgical correction due to maxillary fracture, long-term follow-up will be needed for this patient in order to increase knowledge about treatment strategies for such cases.

Adult↗
PubMed1991

Image analysis and nonlinear modeling to determine dimensions of wet-sieved, masticated forage particles.

A procedure to estimate dimensions of digesta particles was developed and evaluated. After wet sieving, particles of masticated switchgrass and bermudagrass hays retained on sieves with apertures of 1.0 mm2 or larger were placed on moist white filter paper, separated manually, and photographed. Photographs were scanned with a flat-bed scanner, scaled to size, and digitized. Projected area, perimeter, length, and width of particles were determined by a microcomputer system. Variables derived for each particle included the form factor, which was defined as (4 x pi x area)/perimeter2, and each particle's length: width ratio. Ninety-three percent of data from two trials with steers had significant lack of fit (P less than .05 to P less than .0001) to normal, lognormal, Weibull, or gamma distributions. As an alternative, individual particle measurements were summed on a cumulative percentage basis for each variable and were fit to an inverted Gompertz function to estimate median, mode, and mean dimensions of scanned particles. Estimates from the equation fit the distribution well; asymptotic SE averaged 3.5 and 1.4% of parameter means for dimensions of masticated switchgrass and bermudagrass hay particles, respectively. No analytic solution exists for the mean, which must be estimated numerically, but analytic solutions are available for the median and mode. Use of this equation will prevent bias caused by lack of fit to a particular distribution and yield more accurate estimates of mean particle dimensions than arithmetic means.

Animal Feed↗
PubMed2001

[Influence of mastication on the amount of hemoglobin in human brain tissue].

The purpose of this study was to investigate the influence of mastication on the amount of hemoglobin in human brain tissue. Nine healthy volunteers (6 males and 3 females) participated in this study. They underwent two tasks: 1) at rest, 2) gum-chewing. In seven of the nine (4 males and 3 females), experimental occlusal interference was applied to the first molar of the mandibule on the habitual masticatory side. They underwent the gum-chewing task. To evaluate the amount of hemoglobin, both the hemoglobin oxygenation state and blood volume during gum-chewing were measured in the frontal region, using near-infrared spectroscopy. The amount of total-hemoglobin (blood volume) and oxyhemoglobin of subjects significantly increased during gum-chewing (p < 0.01). When the subjects finished gum-chewing, both levels returned to the original levels. When experimental occlusal interference was imposed on the subject, the amount of them significantly decreased compared with subjects without experimental occlusal interference (p < 0.05). The results suggested that increases of cerebral blood flow in the frontal region were not due to the mandibular movement, and that human brain activity caused by mastication was not only in the cortical masticatory area but also in the frontal region.

Adult↗
PubMed2000

Assessment of regional cerebral blood flow by xenon-enhanced computed tomography during mastication in humans.

It is suggested that mastication stimulates the brain and accelerates its energy-consuming metabolism. This study was designed to determine its effects on regional cerebral blood flow (rCBF) using xenon-enhanced computed tomography (Xe-CT). Seven male volunteers, aged 24-57 years, inhaled 30% xenon in a 4 minutes wash-in and 4 minutes wash-out protocol. CT was scanned every 54.5 seconds. The subjects were instructed to chew a gum continuously at a rate of 1 bite per second except at the time of CT scanning (5.5 seconds). A second CBF was done 20 minutes later. Subtraction (mastication-baseline) maps were created. CT images were taken at three levels so as to include the cortex, basal ganglia, limbic system, brainstem and cerebellum. The results demonstrated a significant rCBF increase in the fronto-temporal cortex, caudate nucleus, thalamus and minor increase in the rolandic areas, insula, cingulate and cerebellum. Further studies are needed to validate the clinical significance of these findings.

Adult↗
PubMed1999

Study of mandibular movements in mandibulectomy patients--border movements and functional movements during mastication, deglutition and speech.

In mandibulectomy patients who have not undergone surgical reconstruction, the remaining mandibular segment is unstable and often deviated. Its movements have low reproducibility during mastication, deglutition and speech. The purpose of this study was to clarify three-dimensionally the differences in mandibular movements for each of these oral functions in mandibulectomy patients with and without mandibular continuity. Four mandibulectomy subjects (Group I) without mandibular continuity and three subjects (Group II) with mandibular continuity were selected. Their mandibular movements were recorded using a jaw movement tracking device with six degrees of freedom. Each movement was assessed graphically at the virtual incisor point and the rotational angles of the mandible in the frontal, sagittal and horizontal plane were analyzed. The findings were as follows; 1. In Group I, the border movements at the virtual incisor point exhibited an irregular and asymmetric envelope deviated to the resected side in the frontal plane, whereas Group II exhibited a smooth and symmetric envelope. 2. In Group I, the rotational angles in the frontal plane during border movements and mastication, in all planes during speech, and in the frontal and horizontal plane during deglutition were significantly larger than in Group II. A comparison among border and all functional movements in mandibulectomy patients revealed characteristic movements in the rotation of the mandible in the frontal plane. It is suggested that the rotational angle of the mandible is a useful parameter for assessment of mandibular movements in mandibulectomy patients.

Aged↗
PubMedDate not supplied

[The comparative characteristics of mastication tests].

Changes in the values of Manly's [correction of Manley's], Rubinov's, and the author's mastication tests were studied in subjects with intact dentition, orthognathic occlusion; the tests were carried out 3 times each with intervals of 2-3 weeks. Correlations of the data of Dahlberg's [correction of Dalberg's], Manley's, Rubinov's and the author's tests were studied and the pattern of changes in the data of the tests in minor dentition defects analyzed. Repeated tests yielded better results; the data of various tests were found incompatible; the suggested test was found the most sensitive and accurate. The basic requirements to a mastication test are formulated.

Adolescent↗
PubMed2005

[Evaluation of mastication function after three-dimensional maxillary reconstruction].

OBJECTIVE: To evaluate the mastication function of the patient whose maxilla was reconstructed with individual titanium mesh and Chinese flap or combined with fibular flap. The superiority of this method on maxillary functional reconstruction was testified. METHODS: Since March of 2001, 10 cases of maxillary defect were reconstructed with individual titanium mesh and Chinese flap or combined with fibular flap, and routine removal partial dentures were fixed after 3 - 6 months postoperatively. Assessment of occlusal force was proceeded by T-Scan II system (Tekscan company, USA). RESULTS: The occlusal force analysis results indicated the asymmetry index of bite force and asymmetry index of occlusal contact area differed significantly between preoperation and postopertion (P < 0.05). The recovery rate of total occlusal force was between 27.05%-74.06%, and the average was 50.15%. CONCLUSION: This new three-dimensional maxillary functional reconstruction method had a satisfactory recovery in both of contour and function recently, especially restored the mastication function effectively.

Humans↗
PubMed2006

[Jaw evolution and function of mastication].

Gnathostomata improved the brachial cartilages of Agnahta into jaws. At the same time, such a jaw formation resulted not only in the development of eye, nose, and ear for searching foods but also in the development of brain which regulates the functions of these sense organs and mastication muscles. In this paper, we described about the muscles, mouth, tongue, and jaw which participate in mastication from a view point of morphology and molecular biology.

Animals↗
PubMed2006

[Chewing gum influence upon blood supply of mastication muscles].

A total of 27 volunteers 16-26 years of age participated in the study of the influence of chewing gum use in different regimens upon velocity parameters of blood supply of mastication muscles at dopplerography (MM-D-K dopplerograph made in Russia). It was established that regular and continuous (30 min) chewing the gum and also of big volume (in two) but short-term chewing (5 min) equalizes blood supply of mastication muscles on both working and non-working sides.

Adolescent↗
PubMed1991

[Mastication and the electromyographic silent period in denture wearers].

The purpose of this study is to compare the masticatory efficiency and the physiological activity of masticatory muscles among patients with removable partial dentures (R.P.D.) and patients with natural dentition. The masticatory efficiency is assessed from the duration of chewing sequences for various foods, from the first masticatory cycle to the swallowing. The physiological activity is tested by the duration of the inhibition reflex called the "silent period" (S.P.) obtained upon each muscle examined: 29 subjects are examined, 24 of them had a R.P.D.; they were divided into four groups according to the extent of their edentation; 5 control subjects have full natural dentition. The study is performed using global electromyography of the two masseter muscles and the two anterior temporal muscles. The mastication of the control subjects appears to have a regular alternance of working potential and periods of rest. The duration of the chewing sequences is determined by the nature of the food, brief for soft food, long for hard food. The mastication of patients with R.P.D. appears more irregular with a lengthening of active phases. The duration of chewing sequences is significantly longer for the control subjects. The duration of the S.P. is 19-21 milliseconds for the masseter muscles of the patients with dentures and the control patients, and 20-22 milliseconds for the temporal muscles for the same individuals. The differences of the S.P. durations between control subjects and patients with R.P.D. is never significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Characteristics of condylar movements during mastication in stomatognathic dysfunction.

In this investigation of the relationship between mastication and TMJ abnormalities, the movements of the incisal point and condyles during mastication were analyzed in two normal subjects and six patients with unilateral TMJ abnormalities. The path of the nonworking condyle was shorter than that of the working condyle when patients chewed on the side of the normal TMJ, causing the mandible to deviate to the abnormal side at the point of transition from opening to closing. Also, the mobility of the abnormal condyle influenced the convexity of the opening path, and posterior dislocation of the condyle resulted in a crossover chewing pattern.

Adult↗
PubMed1989

[Human mastication and its observation].

Human mastication is a very complicated three dimensional jaw movement. The movement is driven primarily by the chewing center or the rhythm generator located in the brain stem below the level of the mesencephalus. Recent studies have revealed that the first opening action is voluntary and food determined, while the later opening and closing movements are solely of central regulation. Variability of speed, direction, and range of vertical, horizontal, and anteroposterior deflection ect, in the chewing strokes is reflexly modulated through peripheral and central feedback. The effects of pain in teeth, oral mucosa, muscles and temporomandibular joints on the masticatory movements can be instantaneous and transient. However the altered pattern, if it lasts long, can become one's new pattern and needs time to be eliminated even when the cause is removed. Observation of the jaw movement during mastication requires a system with minimum interference and careful interpretation. Photoelectric, magnetoelectric and radio isotopes have been used although none of them is completely undistorted. The jaw movement during different types of food chewing in different situations have long been studied in detail. The results have suggested a high intraindividual and even higher interindividual difference, which made the categorization of chewing movement impractical. Conclusions drawn from the comparison of normal and abnormal patterns of chewing movement should be based on very carefully defined parameters.

Brain Stem↗