Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MASTICATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources
PubMed1989

Eating and ruminating behavior of steers fed Coastal Bermudagrass hay at four levels.

Effects of feeding level on chewing behavior and physical reduction of particles during ingestive mastication and rumination were examined in four ruminally cannulated steers fed Coastal bermudagrass (Cynodon dactylon [L.] Pers.) hay in the long form. The experimental design was a 4 x 4 latin square with 18-d periods. Treatments based on previous intakes were set at 50, 70, 90 and 110% of feed consumed per animal. Steers were fed at 12-h intervals. Chewing behavior was monitored over 4 d with a computerized system. Boli of ingested, masticated hay (MH), collected at the cardia, and serial samples of digesta taken from the ruminal upper strata (RUS) were wet-sieved. Dimensions of MH particles retained on 4.0- and 2.0-mm sieves were determined by image analysis. Increasing feeding level resulted in a linear increase in the number of boli ruminated (P less than .01) and in linear increases in eating (P less than .01), ruminating (P less than .05) and total chewing time (P less than .01). Linear increases in number of eating (P less than .01), ruminating (P less than .01) and total chews (P less than .01) also were observed. Feeding level had no effect on bolus duration, number of chews/bolus, number of boli/min rumination time and number of chews/min rumination time. The extent of particle breakdown during ingestive mastication was a determinant of the number of boli ruminated daily and their associated number of chews. Number of boli ruminated daily also was related to the RUS mean particle size. Eating time did not provide a reliable indication of how well feed was chewed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1997

[Biomechanical relationship between intercusp relation and masticatory movement during final stage of occlusion--time-course efficiency of food destruction].

The purpose of this study was to investigate the relationship between intercusp relation and masticatory movement during the occlusal phase by dynamic evaluation of the efficiency of mastication. The methods and the results were as follows: 1. Study of model The efficiency of mastication of cusp-to-cusp model A and cusp-to-fossa model B relationship models was highest in the movement from mesial to distal and from buccal to lingual sides for A and B, respectively. 2. Study of clinical data 2.1 The masticatory movement of (case-A) and of (case-B) having been evaluated, case-A, compared with case-B, had a greater anteroposterior movement, and there was little difference in the efficiency. 2.2 In postorthodontic treatment, the alteration of movement from anteroposterior to lateral direction was observed. The results indicated that the efficiency of mastication is determined not only by the static contact morphology of maxillary and mandibular teeth but also by the dynamic masticatory movement, adjusting to the morphology according to the intercusp relation of teeth. The direction of the adjusted masticatory movement compensated for the position and occlusal morphology of teeth to increase the efficiency as verified by the simulation and clinical data.

Biomechanical Phenomena↗
PubMedDate not supplied

Facial skeletal growth in growing "toothless" osteopetrotic (op/op) mice: radiographic findings.

The defective bone resorption in the osteopetrotic (op/op) mouse brings about failure of tooth eruption. Furthermore, the op/op mouse has been studied as a "toothless" mouse in recent morphological and physiological investigations of the relationship between mastication and masseter muscle development. The present study was conducted to examine in detail the nasal bone and the premaxillary bone in this mutant mouse and to assess the roles of incisor growth and the mechanical stress of mastication in nasal bone and premaxillary bone growth. The forms of the nasal bone and the premaxillary bone were observed using roentgenography in both toothless op/op and normal (control) mice. In the op/op mouse, the nasal bone and the premaxillary bone show remarkable deformity. In contrast, the normal mouse appears well developed. This suggests that growth of the incisor root is important to normal upper jaw growth in the mouse. Furthermore, it is proposed that the upper facial phenotype seen in the op/op mice results from not only decreased bone resorption, but also from absence of the mechanical stress provided by normal mastication.

Age Factors↗
PubMed1992

Preweaning feeding mechanisms in the rabbit.

Muscle contraction patterns and mandibular movements of infant rabbits during suckling and chewing were compared. Oral muscle activity was recorded by fine-wire electromyography, while jaw movements and milk bottle pressure were registered. Suckling and mastication have a comparable cycle duration and share a common pattern of oral muscle activity which consists of a succession of a jaw closer burst, during which the jaw closes and undergoes a power stroke (in mastication), a suprahyoid burst with a stationary or slightly opening jaw and a digastric burst with fast jaw opening (the power stroke of suckling). Compared to suckling, mastication shows decreased jaw opener activity, increased jaw closer activity, development of jaw closing activity in the lateral pterygoid, and increased asymmetry in the masseter by development of a new differentiated motor pattern on the working side. The study shows that the suckling motor pattern enables the infant rabbits to change to chewing with just a few modifications.

Animals↗
PubMed2005

All-ceramic partial coverage premolar restorations. Cavity preparation design, reliability and fracture resistance after fatigue.

PURPOSE: To investigate the effects of different cavity preparation designs on the reliability and fracture resistance of partial coverage restorations (PCR) which were luted adhesively to natural premolars after exposure to a mastication simulator. METHODS: 80 caries-free, extracted human maxillary premolars were randomly divided into two control groups (A, B) and three test groups (C-E) consisting of 16 specimens each. Group A served as a control group with no preparation. The specimens of Groups B to E were prepared as follows: Group B: MOD inlay, Group C: PCR (palatal), Group D: PCR (palatal and buccal), Group E: complete veneer. Using pressed ceramic IPS e.max Press (VP 1989), 64 all-ceramic restorations were fabricated and luted adhesively. The 80 specimens were subjected to 1.2 million mastication (F= 49 N) and 5500 thermal cycles at 5 degrees C and 55 degrees C in a mastication simulator. Subsequently, all test specimens were loaded occlusally until fracture using a universal testing machine. The statistical analysis included the unpaired Wilcoxon rank sum test and box plots. RESULTS: All the specimens withstood the masticatory simulation. The following mean fracture strength values (N) (minimum/maximum) were recorded: Group A: 1446 (417/2404), Group B: 1351 (657/2096), Group C: 837 (346/1472), Group D: 963 (481/1691), Group E: 1361 (900/2211). The fracture strength values of Groups A, B and E were statistically significantly higher (P < 0.05) than those of Groups C and D. Inlays and complete veneers made of IPS e.max Press reached fracture strength values corresponding to those of natural premolars.

Aluminum Silicates↗
PubMed2006

Palatal coverage disturbance in masticatory function.

Oral sensorimotor function is essential for mastication. We hypothesized that palatal coverage would disturb mastication and sensorimotor function. Masticatory efficiency, which was expressed by the declination rate of particle size, and oral stereognosis ability (OSA) were measured for 20 dentate subjects. Both measurements were first performed without an experimental palatal plate. These measurements were then repeated with the plate on the day of the plate insertion, then again on the 3rd and 7th day. After 2 months, another series of measurements for the OSA test were performed without the plate with the same time-course. Masticatory efficiency significantly decreased with the plate. OSA score, which continuously increased during the experimental period, showed no difference between with and without the plate. Positive correlation between masticatory efficiency and the OSA score was found only without the plate. It was suggested that coordination between mastication and the sensorimotor function was disturbed by palatal coverage.

Adult↗
PubMedDate not supplied

[A procedure for the 3-dimensional recording of human mandibular movements].

A 3 dimensional process of recording the human mandible movements. Our system belongs to a general process made by the C.N.E.S. (Centre National d'Etudes Spatiales) in Toulouse; it records and measures the movements of body and limbs of spacemen. A test of this process is adapted for movements of mandible. The system uses a various instrumentation: two electronic cameras; infrared rays; reflectors; a multiplexor case; a magnetoscope; a dimultiplexor; a computer; two screens of control. Four reflectors are fixed on the face of subject; two others are fixed on a metallic system that is glued on the buccal face of inferior canines. These reflectors record the specific movements of mandible. Usual mastication and mastication on one side in turn are recorded in a young man with his natural teeth. Some graphs are showed for example. A data processing system measures the trajectory of mandible in the three dimensions of space, according to time and rapidity of movement. This video data processing seems to be a good method to analyze movements of mandible and mastication.

Adult↗
PubMed1990

[Study on the relation for physical properties of masticatory jelly and masticatory muscle activity].

To measure the masticatory force used for everyday foods it is desirable to base the measurements on one mouthful of food. However, one mouthful of food changes in size and hardness. The purpose of this study is to establish a formula for estimating a correlation between the amount and force of mastication, active potentials and their integrated values, and the concerned material's size and hardness no matter they are same or unified. It is possible to measure the amount of mastication for normal foods without recording electromyographically. The effective method for recording the hardness of the jelly is the application of needle plunger. The thickness divided by the hardness and multiplying the value with the volume of the material, an estimated formula is thereby established to correlate with the integrated values of mastication.

Bite Force↗
PubMed1989

[Studies on stress distribution under simulated muscles on dry skull].

In case of occlusion, the mandible is elevated by the muscles of mastication with T. M. J. as the fulcrum point, and at this time, the masticatory force concentrated mainly on the dental arch is absorbed into the jaw bone through the periodontal tissues. Therefore, it is of great significance for the study of prosthodontics to assess what distribution of mechanical strain the maxillar and mandibular bones exhibit to occlusal force at mastication. Very many studies have been made to clarify this point, but many of them were analyses of stress pattern when a tooth (a point) is under force on models prepared on the assumption that a tooth is planted on the jaw bone, but there are only very few studies which made analysis of stress pattern when the mandible is under force by elevating it mainly along the direction of the M. masseter upon positioning the bone similarly as in vivo mechanism. With the purpose of assessing the distribution of mechanical strain received when the mandible is elevated by the muscle of mastication, the author has assessed the change in the stress distribution under 2 conditions of light and hard tensile forces by setting the M. masseter form the center of the inferior border of the zygomatic bone and center of the zygomatic arch to the mandibular angles on the assumption that self memory alloy takes the places of the M. masseter (the masseter) and M. temporalis (the temporalis) on the experimental model. As a result, the following conclusions have been reached: 1. When the origin of the masseter is at the center of the inferior border of the zygomatic bone, the maximum exhibited tensile strain at all the measuring points both under light and hard tensile forces. Under light tensile force, the minimum strain showed compressive strain in the region from the lower canine to the lower first under hard tensile force, the minimum strain exhibited tensile strain at all measuring points. The amount of strain under hard tensile force exceeded the amount under light tensile force. 2. When the origin of the masseter is at the center of the zygomatic arch, the maximum strain showed tensile strain at all the measuring points both under light and hard tensile foece. The minimum strain exhibited compressive strain at all the measuring points both under light and hard tensile foece. The amount of strain under hard tensile force always exceeded the amount under light tensile force.(ABSTRACT TRUNCATED AT 400 WORDS)

Dental Stress Analysis↗
PubMed1985

Masticatory ability in patients with removable dentures. A clinical study of masticatory efficiency, subjective experience of masticatory performance and dietary intake.

One of the functions of the masticatory system is to grind the food, salivate and prepare it for swallowing. Individuals who have lost many teeth or wear removable dentures, both complete and partial, find it more difficult to grind food i.e. they suffer from impaired masticatory efficiency (ME). Some of these subjects have to avoid food-stuffs which are hard and difficult to chew. This could influence the social well-being and may eventually lead to an increased risk of malnutrition. Many different methods have been used to evaluate ME. In most of them the degree to which the masticated food or test material was broken down was measured by fractionating the particles in a sieve system. However, one of the purposes of chewing the food is to enlarge the surface area to be exposed to the digestive juices. A few authors have applied this idea and have calculated ME using the summarized area of the masticated test material. This is physiologically a more correct method. ME was investigated in 19 complete denture wearers who were fitted with new dentures. The subjects were tested twice with the old dentures and 5 times with the new ones. The last test took place about 18 months after insertion of the new dentures. The test material was gelatin hardened with formalin. The breakdown of test material was calculated by fractionating it in a sieve system. ME was also evaluated in two other groups, 43 complete denture wearers, who were in need of new dentures, and 19 subjects who were in need of RPDs in the lower jaw. In these two studies ME was evaluated in two ways. Firstly the summarized area of masticated gelatin particles was calculated and used as a measure of ME. Secondly almonds were used as test material and the breakdown was calculated by fractionating in a sieve system. The subjects were tested on three occasions, before prosthetic treatment and about one and four months after insertion of the dentures. On the first and last occasions the subjective experience of masticatory performance was assessed as well as the dietary intake. The results revealed no systematic change in ME when the 19 subjects were fitted with new complete dentures and when the breakdown of the test material was evaluated by fractionating it in a sieve system.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1997

Studies on the effects of the spillway on the occlusal table of complete dentures upon the bearing of masticatory force.

We studied the effect of spillways in the posterior artificial teeth of complete dentures in reducing masticatory pressure on the basal mucosa by making completely edentulous patients masticate food. Using two kinds of experimental dentures, one with spillways on the occlusal table and the other without, five subjects wearing complete dentures were instructed to masticate four different types of test food. The results showed that the mastication time and the number of masticatory strokes were not much affected by the existence of spillways. However, the masticatory force of artificial teeth with spillways was slightly smaller than that of artificial teeth without spillways.

Aged↗
PubMed1998

Seed handling by three prosimian primates in southeastern Madagascar: implications for seed dispersal.

In this paper, we studied three species of prosimian primate (Propithecus diadema edwardsi, Eulemur fulvus rufus, and Eulemur rubriventer) from June-July 1995 at the Ranomafana National Park to answer three questions: 1) how they handle and process seeds, 2) how the physical properties of seeds influence seed handling and seed fate, and 3) whether handling and processing patterns influence seed dispersal. Seeds from five plant species were collected from feces and examined for external damage (punctures and scrapes), weighed, measured, and checked daily for germination. P. d. edwardsi masticated seeds into two or more pieces while feeding. Seed fragments were either dropped under the parent tree or chewed and swallowed; seeds never emerged as recognizable units in feces. In contrast, both Eulemur species either dropped or swallowed seeds whole while feeding. E. rubriventer passed seeds that were longer, wider, and heavier than seeds passed by E.f. rufus. Although seeds emerged as separate units when passed by both Eulemur species, 65 Protorhus sp. seeds were scraped and/or punctured prior to being swallowed. Based on physical property tests, Protorhus seeds were more susceptible to mastication than undamaged seeds from Eugenia sp., Cissus sp., and Chrysophyllum madagascariensis. H. madagascariensis seeds also were undamaged but had physical properties comparable to Protorhus and may avoid being masticated due to their small size (2-3 mm). All damaged seeds were moldy or rotten within 6 days, and only 15% of the undamaged seeds passed by E. rubriventer germinated. None of the seeds passed by E.f. rufus germinated. Eulemur species also rested in the same tree after feeding and defecated prior to a new feeding bout or before moving, so seeds were most likely to be dispersed under the parent tree. Consequently, we concluded that these primate species do not appear to serve as effective seed dispersers for these plant species at this time of year.

Animals↗
PubMed1994

Mandibular growth and function in Archaeolemur.

Ontogenetic changes in the morphology of the mandibular symphysis are described in Archaeolemur so as to infer the functional significance of symphyseal fusion in this subfossil Malagasy lemur. The first regions of the symphysis to show a more complex morphology were the lower and anterior borders of the joint and, to a lesser extent, the lingual borders of the superior and inferior transverse tori. During growth, these regions became increasingly rugose and encroached upon a centrally located, smooth, "oval" region, which may have been a principal pathway for neurovascular structures communicating with the unfused joint. In subadults, the symphysis was completely fused except for the lingual surface of the inferior transverse torus, where a patent suture and potential space were present between dentaries. Thus, in Archaeolemur there was an age- and size-related pattern of increased symphyseal ossification or fusion that was complete by adulthood. The morphology of the interlocking bony processes and the sequence of ossification in the symphysis suggest that increased dorsoventral shear stress during mastication was the most likely determinant of symphyseal fusion in Archaeolemur. The allometric pattern of greater symphyseal fusion may be linked to the presence of relatively greater dorsoventral shear in adults due to an increased recruitment of balancing-side jaw-muscle force. There is little indication that the symphysis of juvenile Archaeolemur was buttressed to resist forces associated with "wishboning" during mastication or vertical bending during incision. Our observations, as well as those of others, suggest that symphyseal fusion in primates occurs initially as a response to increased dorsoventral shear during mastication. Therefore, wishboning stress might only become a major determinant of symphyseal form and function in those taxa that develop a fused symphysis to counter increased dorsoventral shear.

Animals↗
PubMed1995

A very-low-calorie conventional Japanese diet: its implications for prevention of obesity.

A very-low-calorie conventional Japanese diet of 370 kcal/day has been shown to be useful for weight reduction and its long-term maintenance. Sources of the diet were mainly from chicken fillet, egg white, fish white-meat, mushroom, seaweed and low- or non-calorie fiber-rich vegetable, and contained 4.4g fat, 38.1g protein, 45.2g carbohydrate and essential minerals and vitamins. However, metabolic and neural implications of a commercial very-low-calorie liquid formula diet have rarely been investigated from the view point of food intake and appetite regulation. Animal studies have demonstrated the rationale for efficacy of the very-low calorie conventional Japanese diet as follows: (1) Increased hypothalamic histamine suppressed food intake through H1-receptors in the ventromedial hypothalamus (VMH) and paraventricular nucleus, the satiety centers. (2) Low energy intake enhanced satiety and decreased food intake through histaminergic activation of VMH neurons. (3) Mastication activated afferent signal transmission from proprioceptors in the oral cavity to the mesencephalic trigeminal nucleus(Me5). Histaminergic systems in the hypothalamus were activated by mastication and low energy supply, which was accompanied by satiation through the action of histamine in the VMH. Usefulness of the very-low-calorie conventional Japanese diet derives from utilization of conventional Japanese food stuffs as a fiber rich, low energy food source, and from enhancement of satiation by increased mastication required of the diet. The properties of the diet seemed to effect a closed positive feedback loop between histaminergic activation in hypothalamic satiety centers and behavioral changes to enhance satiation and cause feeding suppression.

Diet, Reducing↗
PubMed1981

Effect of bone strain on cortical bone structure in macaques (Macaca mulatta).

It has recently been shown that the consistency of food significantly affects levels of bone strain in the mandible during mastication (Hylander, '79a). Mandibular bone histology was examined to test the effects of a diet of hard food compared to a diet of soft food in two groups of monkeys. One group of rhesus macaques (Macaca mulatta) was fed a diet of commercially prepared hard biscuits. The second group was fed a soft diet the consistency of fudge. Both diets were nutritionally adequate for normal growth and development. As a control for other factors influencing cortical bone structure, fibular morphology was also examined. At the end of the test period, mandibular and fibular tissue samples from the two groups were prepared to determine the amount of secondary Haversian bone present. Mandibular depth at M2 and fibular anteroposterior diameter were also measured and compared between the two dietary groups. The soft-diet monkeys showed low levels of remodeling in their mandibles. There were large patches of unremodeled bone and resorption spaces were common. The hard-diet monkeys exhibited more extensive evidence of secondary Haversian remodeling in their mandibles. The hard-diet monkeys also had deeper mandibles. In contrast, the fibulae from the two groups had similar mean diameters and showed comparable levels of secondary remodeling. We infer that the higher mandibular bone remodeling levels in the hard-diet monkeys represent an adaptive response to remove and replace fatigued mandibular bone due to higher stress levels associated with the ingestion and mastication of hard foods. We also infer that greater depth of the mandible at M2 found in the hard-diet group represents an adaptive response to higher stress levels associated with the ingestion and mastication of hard foods.

Animals↗
PubMed2006

Chemical study of triterpenoid resinous materials in archaeological findings by means of direct exposure electron ionisation mass spectrometry and gas chromatography/mass spectrometry.

A systematic study of standard triterpenes (alpha-amyrine, oleanolic acid, betulin, lupeol, betulinic acid and lupenone) and of raw resinous materials (frankincense resin, mastic resin and birch bark pitch) was performed using direct exposure electron ionisation mass spectrometry (DE-MS) and gas chromatography/mass spectrometry (GC/MS). DE-MS provides a mass spectral fingerprint of organic materials in a few minutes which highlights the compounds that are the main components in the sample. The application of principal component analysis (PCA) on DE-MS data in the mass ranges m/z 181-260 and m/z 331-500, corresponding to the fragmentation of triterpenoid molecules, enabled us to distinguish between different triterpenoid materials such as mastic resin, frankincense resin and birch bark pitch, and to graphically plot the resinous substances in three separate clusters, retaining 89% of the total variance. GC/MS analysis of the same materials has permitted us to elucidate in detail the molecular composition and to identify minor components and species that act as markers of the degradation undergone by the materials. The paper also reports the results for the organic residues contained in an Egyptian censer (5th-7th century AD) which was recovered in the excavation of the Necropolis of Antinoe (Egypt), and for the hafting material found on a Palaeolithic tool recovered at the site of Campitello (Arezzo, Tuscany), dating back to the Mid-Pleistocene period. Although DE-MS was found to be a fast analytical tool, it failed to give any information on the presence of less abundant compounds when applied to mixtures of different materials: only mastic resin was found in the residues from the Roman censer, whereas GC/MS analysis identified the presence of a vegetable oil from Brassicaceae seeds and Pinaceae resin. Birch bark pitch as a pure material was identified in the sample from the Palaeolithic flint flake using both procedures.

Archaeology↗
PubMed1984

The mandible, an overhanging mechanically suspended structure. Considerations on the system of attachment and servo-command of the mandible.

The mandible, owing to its form, surrounding muscles and "position" in the craniofacial unit can be assimilated to an overhanging mechanically suspended structure. The hypothesis, according to which the temporomandibular joints would be submitted to pressure during mastication should be abandoned on the basis of anatomical and clinical findings. Furthermore, this hypothesis is in disagreement with the results of simulation on a physicomathematical model of the mandible. Accordingly, it is reasonable to assume that the mandible is a suspended structure and that the elevator muscles of mastication, especially the masseter and medial pterygoid (together forming the mandibular sling), and probably also the anterior belly of the temporalis muscle play a twin role in the suspension of this bone. These muscles obviously command the movement of closure. They also constitute the suspensory apparatus of the mandible and, by mechanical computation, should display a certain degree of elasticity and undergo most of the mechanical constraints developed during mastication. One can also consider the cranio-facio-mandibulo-hyoid group as a suspended structure. The comparison of this type of system to the basic principles of servo-robotics allows to understand that such a structure is capable of extremely precise movements in all spatial planes with a minimum of effort.

Biomechanical Phenomena↗
PubMed2005

Relevance of mandibular helical axis analysis in functional and dysfunctional TMJs.

The helical axis (HA), or motion screw, yields a comprehensive description of joint motion. The perspective representation of this axis clearly visualizes the regularity of mandibular functional movements (Yatabe et al. 1997. Journal of Dentist Research 76, 714-719 and Gallo et al. 2000. Journal of Dental Research 79, 1566-1572). In this study, the sensitivity of the HA representation was investigated relative to (a) irregularities in pathologic motion of clicking temporomandibular joints (TMJs) for jaw opening/closing and (b) differences in food bolus size and consistency for unilateral mastication in subjects with normal TMJs. Mandibular motion relative to the head was acquired using a jaw tracker with six degrees-of-freedom with a sampling frequency of 70 Hz. The HA was calculated according to an eigenvalue method (Spoor and Veldpaus 1980. Journal of Biomechanics 13, 391-393) and parameters were defined describing its position and orientation relative to the anatomy. We analyzed 39 subjects with unilateral or bilateral reciprocal TMJ clicking during jaw opening/closing and seven asymptomatic subjects during unilateral mastication of five different types of soft and hard food in two different bolus sizes. The results showed a greater variability of the HA parameters in the group of clicking joints than in the asymptomatic group: in particular, the area in which the HA moved was wider in clicking joints than in normal ones and the HA in clicking TMJs had a much greater fluctuation than in normal ones. During unilateral mastication, for more consistent food or a bigger bolus the HA showed a significantly greater excursion of the orientation parameters. Furthermore a significantly greater excursion of the dorsoventral and of the craniocaudal component of the distance vector from the HA to the condyle were found. The helical axis analysis of mandibular movements was sensitive to kinematic irregularities of the mandible due to an internal joint derangement as well as to differences in food bolus size and consistency.

Adult↗