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PubMed2006

Coordination of tongue pressure and jaw movement in mastication.

The tongue plays an important role in mastication and swallowing by its contact with the hard palate. Using an experimental palatal plate with 7 pressure sensors, and recording jaw movement using mandibular kinesiography, we assessed, in healthy subjects, the coordination of tongue and jaw movements during the entire masticatory sequence of solids, by measuring tongue pressure against the hard palate. Tongue pressure appeared during the occlusal phase, reached a peak near the start of opening, and disappeared during opening. Specific patterns in order, duration, and magnitude of tongue pressure were seen at the 7 pressure sensors in each chewing stroke. Magnitude and duration were significantly larger in the late stage of chewing (8 strokes before initial swallowing) than in the early stage (until 8 strokes after starting mastication). The normal pattern of tongue contact against the hard palate, control of tongue activity, and coordination with jaw movement during mastication is described.

Adult↗
PubMed2001

Bactericidal activity of Pistacia lentiscus mastic gum against Helicobacter pylori.

In this study we evaluated the antibacterial activity of mastic gum, a resin obtained from the Pistacia lentiscus tree, against clinical isolates of Helicobacter pylori. The minimal bactericidal concentrations (MBCs) were obtained by a microdilution assay. Mastic gum killed 50% of the strains tested at a concentration of 125 microg/ml and 90% at a concentration of 500 microg/ml. The influence of sub-MBCs of mastic gum on the morphologies of H. pylori was evaluated by transmission electron microscopy. The lentiscus resin induced blebbing, morphological abnormalities and cellular fragmentation in H. pylori cells.

Anti-Bacterial Agents↗
PubMed2002

Stresses in mandibular cortical bone during mastication: biomechanical considerations using a three-dimensional finite element method.

This study investigated biomechanical aspects of the action of the biting force during mastication upon the mandibular bone in the lower first molar area. A three-dimensional (3D) finite element model (FEM) consisting of the tooth, periodontal ligament (PDL), alveolar bone, and cortical bone corresponding to the lower first molar area based on computed tomogram (CT) images was constructed. The model was then analyzed while applying a biting force during mastication, which was transmitted from the tooth to the cortical bone, through the PDL and cancellous bone. A compressive stress of 0.3-7.9 MPa acted on the cortical bone during mastication. In the model, the stress in the cortical bone was distributed from the linguo-superior margin to the basal area, and was also observed in the bucco-medial area. These areas completely agreed with the areas that were significantly thicker in the morphological study described by Masumoto et al. (10). It is suggested that there may be a relationship between masticatory force and cortical bone hypertrophy. Further study of the effects of various factors is required.

Alveolar Process↗
PubMed1991

Effects of grass species on grazing steers: I. Diet composition and ingestive mastication.

In traditional grazing trials, per animal and per hectare productivity are determined, but pasture and animal measurements are generally inadequate to address reasons for different treatment responses. This 2-yr study examined the diet and diet characteristics of steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.) pastures. A randomized complete block design was used with two agronomic replicates. In vitro DM disappearance (IVDMD) of masticates from tall fescue (TF), switchgrass (SG), and flaccidgrass (FG) generally were similar; all exceeded 70% (70.3 to 79.9%), except for bermudagrass (BG), which was lowest (63.5 to 65.0%). Sieving the masticate DM showed BG to contain the highest proportion (20 to 29%) of particles passing a .5-mm sieve and the lowest proportion (6 to 8%) of particles retained on a 2.8-mm sieve. This resulted in BG having the smallest mean (1.29 mm) and median (1.08 mm) particle sizes in yr 1 and a mean (1.10 mm) and median (.91 mm) particle size smaller than SG in yr 2. Except for BG, the IVDMD of the masticate DM was lowest for small particles. Canopies showed BG and SG to have the highest proportion of stem (47 and 52%, respectively); the BG canopy was composed of fractions that were consistently lowest in IVDMD. In general, BG offered the grazing animal a canopy inferior in IVDMD concentration and had canopy characteristics that limited the animals' selection of a diet with quality as high as that of TF, SG, or FG.

Animal Feed↗
PubMed1997

Changes in forage quality, ingestive mastication, and digesta kinetics resulting from switchgrass maturity.

Five maturities of switchgrass hay harvested at 14-d intervals (vegetative through 20% heading) were fed to Hereford steers (297 kg) in a 5 x 5 Latin square. Relationships with switchgrass maturity were negative and quadratic (P < .05) for DMI and cubic (P < .05) for digestible DMI. Declines in apparent digestibilities of DM, ADF, and cellulose were cubic (P < .05), whereas these were quadratic (P < .05) for NDF, hemicellulose, and CP. Whole masticates from the least, mid, and most mature hays showed linear (P < .05) declines in DM concentration and IVDMD with increasing maturity, whereas NDF concentrations increased linearly (P < .05). Mean retention time of gastrointestinal DM increased linearly (P < .01) from 64 to 94 h from the least to the most mature hay, and the associated rate of passage declined linearly (P < .01) from 3.3 to 2.1%/h. Sieving of masticate DM showed a reduced proportion of large particles (> or = 2.8 mm) and an increased proportion of small particles (< or = .5 mm) with advancing forage maturity. More than 94% of the sieved fecal DM passed a 1.0-mm sieve, but particle sizes showed the same relationship with forage maturity as noted for masticate DM. This occurred despite the comminution from the rumination and digestive processes.

Animal Feed↗
PubMed1998

Performance, digestion, and mastication efficiency of Holstein steers fed whole or processed corn in limit- or full-fed growing-finishing systems.

We conducted two trials to examine the effects of restricted vs full feeding and of grain processing method on feedlot performance, digestion, and mastication efficiency by Holstein steers in different growing-finishing systems. In Trial 1, 272 Holstein steers (177 +/- 9.98 kg) were blocked by weight and assigned to growing phase diets based on corn silage (SIL), steam-flaked corn that was either limit-fed (SFLF) or full-fed (SFFF), or whole corn that was limit-fed (WCLF) or full-fed (WCFF). Limit-fed steers were fed at levels predicted to allow daily gain of 1 kg/d. On d 112, all steers were switched to WCFF or SFFF diets until the mean BW of each treatment group was 545 kg. Overall, steers fed WCLF and SFLF during the growing phase and finished on SF were 8.1 and 6.6% more efficient at converting dietary ME to gain (P = .02 and .04, respectively) than steers in the SFFF group. In Trial 2, three ruminally and duodenally cannulated Holstein steers were fed whole (WC) and rolled corn (RC) diets at FF and LF intake in an incomplete replicated 2 x 2 switchback design. Ad libitum access to feed resulted in higher (P = .02) ruminal starch digestibility than did limit-feeding, and calves had higher total tract DM (P = .05) and starch (P = .03) digestion at the heavier BW. Limit-feeding whole corn resulted in increased particle size of masticate (P = .06) compared with full-feeding whole corn. Because of apparent differences in mastication efficiency between limit-fed and full-fed calves, grain processing method during periods of restriction and compensatory growth may be important considerations for managing growth in systems that incorporate limit-feeding.

Animal Feed↗
PubMed1989

Effects of ingestive mastication on particle dimensions and weight distribution of coastal bermudagrass hay fed to steers at four levels.

Coastal bermudagrass (Cynodon dactylon [L.] Pers.) hay was fed in the long form to four ruminally cannulated steers to evaluate the effects of intake level on the physical reduction of feed particles during ingestive mastication. 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 and fed at 12-h intervals. Boli of ingested, masticated hay were collected at the cardia and separated by wet-sieving into fragments retained on sieves of .0027 to 4.0 mm (mesh aperture). In addition, particles retained on the 4.0-mm and 2.0-mm sieves were scanned by image analysis. Ingestive mastication resulted in a linear decrease (P less than .05) in the proportion of boli particles retained on the top (4.0-mm) sieve and linear increases on the 2.0- (P less than .02), 1.0- (P less than .06) and .25-mm (P less than .06) sieves with increasing level of intake. Sixteen to 21% of the ingested hay particles passed through a 1.0-mm sieve. Mean particle size, as determined by sieving data, decreased linearly (P less than .05) as feeding level increased. Image analysis showed no differences in length (L) or width (W) of particles retained on the 4.0- and 2.0-mm sieves as feeding level increased, but L/W decreased linearly (P less than .05) on both sieves. The frequency of jaw movements following feeding was very similar across feeding levels and averaged 71.3 chews/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMedDate not supplied

[Possibility of functional exploration of mastication from acoustic signals].

The chewing abnormalities are frequently evoked during odontological and medical examinations. Unfortunately, few means of investigation are available to appreciate the functional disorders. The aim of this paper was to assess masticatory parameters from observation and audiosignals of mastication with a simple analysis of records. In a first time, sixty five students (mean age = 20) applied the sugar test for the salivary capacity (dissolution time = 2 to 3 minutes). Then the chewing movements were analysed with three types (I, II, III) of salt or sweet cookies. The total duration of activity was 29.8 and 28.2 seconds respectively for the tests I and II, only 18.2 seconds for the test III. The number of cycles were 32.5, 28.1 and 19.2 mastications for respectively I, II and III tests. The later type (III) had a softer consistency than the formers. The duration Dc of masticatory cycles was constant for the same type of aliment. The values were between 0.70 for the test II and 0.90 second for the I and II ones. Signal analysis showed an important and rapid decrease of amplitude AS with an exponential-like pattern. The time constant appeared in relation with the softness. Thus, our method allows to characterize the pattern of mastication and could be used for appreciation of degrees in salivary and/or cranio-mandibular functional abnormalities.

Adult↗
PubMed1989

[A method for evaluation of compressive ability in mastication by chewing gum containing polycarbonate microcapsules].

Evaluating masticatory ability is a fundamental subject in dentistry. However there is no sufficient clinical method for it. The purpose of this study was to evaluate compressive ability in mastication from compressive energy in mastication. To measure compressive energy from compressive transformation of a material before crushing, a new artificial material, CHEWING GUM CONTAINING POLYCARBONATE MICROCAPSULES, was originated. And by the material, a method for evaluation of compressive ability was made. The method was tested on 11 persons in the twenties (6 males, 5 females). The results were as follows: 1) The coefficient of variations of values that were measured 5 times on one male subject was 4.24%. 2) The distribution of values that were measured on 11 subjects ranged widely. The ratio of the minimum value to the maximum value on 9 adults of normal occlusion was 1 : 3.0. Compressive energy and occlusal contact area in mastication were calculated from these values. The results show that the method for evaluation of compressive ability is one of the new clinical methods for evaluation of masticatory function.

Adult↗
PubMed1997

[A follow-up study on changes in mastication after insertion of mandibular bilateral free end saddle denture by EMG].

The purpose of this study was to investigate changes in the mandibular shortened arch, whose occlusal deficit had been reconstructed by removable partial denture, during mastication by using the EMG analyzing system. A total of 5 shortened dental arch patients was provided with RPDs, and observed by a sophisticated masticatory analyzing system using EMG, before and one day, about 2 weeks, 3 months, after denture insertion. The conclusions were as follows: i) The elements of the shortened arch during mastication, that is, the duration, interval, and cycletime, were prolonged at the time of insertion of RPD, but 3 months after denture insertion, they were shortened to almost the same state as before treatment. ii) Prosthetic treatment for shortened dental arch improved revitalization of functional musculatures, and their rhythmicity of functional procedure. iii) The functional tongue room for optimal bolus position in mastication was provided by insertion of mandibular bilateral free end saddle removable partial denture.

Adult↗
PubMed1999

[Evaluation of masticatory comminute function using multiple variables--Part. I: Observation of mastication using inter-jaw positional EMG].

When masticatory efficiency is measured in the normal manner, it is necessary to collect samples. The purpose of this study was to devise a possible method of measuring masticatory efficiency, obviating the necessity for collection of the sample. Peanuts mastication by subjects whose degree of comminution was already known was observed by using an "Inter-jaw positional EMG" in which an element of the jaw positions is combined with EMG. Observation of the Inter-jaw positional EMG enables understanding the appearances of each 1-cycle chewing comminution. Moreover, changes in muscle activity and jaw movement caused by the progress of mastication can be observed by arranging the Inter-jaw positional EMG to record the chewing cycle, several times. In addition, three phases in peanut mastication was observed, and it was found that analysis of the first two phases when the changes appear is very effective because the changes move similarly with the changes of particle size. In addition, the Inter-jaw positional EMG and distribution of particle size were analyzed, and both changes caused by the progress of the cycle were similar. Thus, it is possible to estimate of the masticatory efficiency using the Inter-jaw positional EMG.

Adult↗
PubMed1989

[Effects of mastication on the growth and development of salivary glands in male mice].

Mastication has attracted considerable attention in recent years for its effects on the postnatal growth and development of the mandible, brain, salivary glands and other organs in children. In this study, the relationship between mastication and growth and development of the salivary glands was examined, because the salivary glands are rich in growth factors and many kinds of biological polypeptides, and have endocrine and exocrine actions and effects, on the growth and metabolic rates in developing animals. The experiment utilized two groups of male mice, a control group fed a solid diet, and an experimental group receiving the paste diet ad lib. In the experimental group fed the paste diet, the increase of the tissue weights and the contents of DNA and RNA in the parotid and submandibular glands were lower than those of the control group. Also the rise of amylase activity in the parotid glands was depressed. Next, the polyamine metabolism in the parotid and submandibular glands was examined. The activities of the late limiting enzymes in polyamine syntheses, ornithine decarboxylase and S-adenosylmethionine decarboxylase and the lev- putrescine and spermidine in both parotid and submandibular glands were in the experimental group. These results suggest that mastication plays an important roles in the growth development of the parotid and submandibular glands in mice.

Animals↗
PubMed1989

[Effects of mastication and submandibular gland ectomy on the growth ability of isoproterenol-stimulated parotid gland and other tissues in male mice].

In a previous article we reported that mastication played an important role in the development of submandibular glands in male mice. Submandibular glands contain epidermal growth factor (EGF) which stimulates the proliferation of various cells in developing animals. In this study, the effects of the hypotrophy of submandibular glands caused by reduction of mastication and the removal of the glands on the growth ability of isoproterenol (IPR)-stimulated parotid glands and other tissues were investigated. The animals in the experiment were male mice and they divided into three groups, a control group fed a solid diet, a group fed a paste diet and a group with removed submandibular glands fed a solid diet. In comparison with the group fed a solid diet, in the group fed a paste diet a small decrease was found, and in the group with the ectomized submandibular gland a significant decrease in the rise of ornithine decarboxylase (ODC) activity, S-adenosylmethionine decarboxylase (SAMDC) activity and DNA synthesis of parotid glands caused by IPR stimulation were found. The DNA synthesis of the heart tissue of mice with ectomized submandibular glands was lower than that of the control group, but in liver, lung, stomach and testis tissue no decrease of DNA synthesis was found. These results suggest that mastication and the submandibular glands have an effect of the growth of the tissues in male mice.

Animals↗
PubMed1988

[Electromyographic study of mastication as a function of the denture in humans].

A study of mastication was conducted using global electromyography of the masseter and anterior temporal muscles. Thirty subjects were studied and distributed between two groups. A control group of 5 patients had a complete natural dentition. A group of 25 patients presented important bimaxillary tooth-loss and wore dentures. They performed masticatory cycles with and without their dentures. The masticatory efficiency of the edentulous patients was very low when compared to the control group. The use of the dentures moderately improved function. The durations of activity of the temporal muscles were slightly lengthened (but not significantly) in the edentulous patients and the denture wearers compared to control patients. The cyclic pattern of the mastication tracings persisted. On the contrary, the durations of activity of the masseters muscles were strikingly lengthened until total disappearance of the resting phases. The cyclic pattern of the mastication tracings in controls disappeared in edentulous patients and denture wearers. In the latter, the tracings were less irregular than in the edentulous patients. In conclusion, the electrical activity of temporal muscles were slightly affected by the absence and replacement of teeth, whereas the electrical activity of the masseter muscles was markedly altered.

Adult↗
PubMed1988

Development of artificial mastication system. Construction of one degree of freedom antagonistic muscle model WJ-O.

The authors have determined that there are 2 levels of control systems in mastication; the muscle control system as the lower level system and the mastication control system as the upper level system. And the authors made an experiment of the muscle control system as the first step of an artificial mastication system. The purpose of this paper is to propose the artificial muscle model which uses as DC motor under the control of position, velocity and force feedback.

Humans↗
PubMed1996

The function of mastication: a key determinant of dental occlusion.

To explain the static and dynamic relationship between the dental arches, models of functions, based on the observation of protrusion and lateral movements of the mandible, are generally presented. In clinical practice, the patients are frequently asked to complete such artificial test movements in order to assess occlusion. However, these movements are in contradiction with the knowledge acquired through examination of the kinetics of incision, mastication, and the posterior dental contacts. The learning objective of this article is to present the required integration of physiology and the kinetics of mastication with any occlusodontic procedure. Interpretation of muscular action during mastication, incision, trituration, and intradental functional guidance are discussed and illustrated.

Dental Occlusion↗
PubMed2003

Comparative morphology of the muscles of mastication in the giant panda and the Asiatic black bear.

The morphological differences in the muscles of mastication between the giant panda (Ailuropoda melanoleuca) and the Asiatic black bear (Ursus thibetanus) were sought to confirm the adaptational strategy of these muscles in the giant panda. We measured some skull characteristics and weighed the muscles of mastication, and macroscopically observed the muscles of mastication in the two species. The noticeable differences between the two species are classified as follows: (1) The size ratio of the zygomatic width was much larger in the giant panda than in the Asiatic black bear. (2) The weight ratio of the two pterygoid muscles was also much larger in the giant panda than in the Asiatic black bear. (3) The lateral slips of the temporal muscles are thicker and stronger in the Asiatic black bear than in the giant panda. (4) The deep layer of the masseter muscle was rostrocaudally divided, and a complicated running of tendons is observed in the giant panda. (5) The two pterygoid muscles were much larger and well-developed in the giant panda than in the Asiatic black bear. The points (1) and (4) may be related to the generation of the force necessary to chew the bamboo in the giant panda. We thought that the large mass of the masseter and temporal muscles are needed in this species. In the points of (2) and (5), the two pterygoid muscles were obviously different in form and weight ratio between the two species. We suggest that the two pterygoid muscles may act as an additional force generator to dorsoventrally press and crush bamboo stems.

Animals↗
PubMed2004

Occupational exposure to airborne asbestos from coatings, mastics, and adhesives.

Over the past few years, a question has arisen about the degree of exposure to airborne asbestos associated with the application, cleanup, and tear-out of glues and mastics used between 1940 and the present. These liquid products were used either to adhere insulation to pipes and boilers or to cover the insulation so as to protect it. In this study, four asbestos-containing products, a coating, two mastics, and an adhesive, which were representative of the various classes of products that have been used historically, were tested to determine the airborne concentration of asbestos fibers released during five different activities (application, spill cleanup, sanding, removal, and sweep cleaning). Each activity was performed for 30 min (often in triplicate). Personal (n=172) and area (n=280) air samples were collected during the tests, and each was analyzed for total fiber concentrations using phase contrast microscopy (PCM), and for asbestos fiber count using transmission electron microscopy (TEM). A measurable concentration of asbestos fibers was detected in six of the 452 samples collected (0.0017-0.0184 fibers/ml). The observed asbestos fibers counts for each product were similar to background. Only one asbestos fiber was detected in an indoor background sample; no asbestos fibers were identified in any of the outdoor background samples. The (raw) PCM-total fiber concentrations were adjusted based on TEM analyses that reported fraction of asbestos fibers (to derive a PCM-asbestos concentration) and by the fraction of the 8-h workday that a worker spends performing the activity (to derive a calculated TWA). For the coatings, mastics, and adhesives evaluated in the present study, the calculated TWAs using hypothetical work scenarios were well below the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 0.1 fibers/ml. The calculated TWAs ranged from 0.03 to 0.009 fibers/ml. The actual concentration of airborne asbestos due to these products is almost certainly much less than the TWAs, and may be so low as to not be measurable. These results support the historical view that these products, over the past 50 years, did not pose an occupational health hazard under foreseeable uses.

Adhesives↗