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At least 955 records · Page 53Linked to original sources
PubMed1987

Interrelationships among voluntary intake, eating and ruminating behavior and ruminal motility of heifers fed corn silage.

Six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) with ruminal, duodenal and ileal cannulae given ad libitum access to corn silage with or without 100 mg monensin X head-1 were used to determine interrelationships among behavior, ruminal motility and intake. Voluntary intake was positively related (P less than .001) to eating time, duration of the main morning meal and daily mastication time. Intake was negatively related to unitary times [min X g dry matter-1 X (kg body weight X 75)-1] of eating (P less than .05), rumination (P less than .001), mastication (P less than .001), unitary number of rumination boli (P less than .001), and latency time between termination of morning meal and onset of rumination (P less than .05). Both daily and unitary eating and ruminating time were positively related (P less than .001) to daily and unitary mastication time and unitary number of strong cranio-dorsal ruminal contractions. Positive relationships (P less than .01) were found between mean duration of daily meals, main evening meal and unitary eating time, and between mean duration of rumination periods and unitary ruminating time. Daily and unitary number of rumination boli and mean duration of one bolus were positively related (P less than .01) to unitary ruminating time. Interrelationships between intake, eating and ruminating activities and associated cranio-dorsal ruminal motility were all influenced (P less than .01) by individual heifer, which indicates potential in identifying individuals with better than average mastication behavior and ruminal motility.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Fragmentation and flow of grazed coastal Bermudagrass through the digestive tract of cattle.

Samples of forage fragments were obtained from the upper (RUS) and lower (RLS) strata of the reticulorumen and feces (F) of four Brahman X Jersey steers grazing Coastal bermudagrass (CB) of two maturities with dry matter digestibilities (DMD) of 54.8 and 64.3%. Forage fragments were separated by particle size and evaluated histochemically for tissue type and fragmentation pattern. Fragmentation pattern was similar to that previously observed due to ingestive mastication. There was longitudinal separation of vascular bundles (VB) and severing at VB ends. Microscopically, similar size fragments from RUS were indistinguishable from those of RLS. The major difference between RUS and RLS was the distribution of different size particles. Larger particles were associated with the RUS in cattle consuming immature and mature CB. More large particles were associated with mature compared with the immature CB in the RUS and RLS. The distribution of different size particles in the F was similar for both maturities, suggesting that similar particle size reduction was required regardless of maturity. Smaller particles in the rumen and F appeared to contain more lignin (determined histochemically) and were composed of indigestible fragments of cuticle and lignified vascular tissue. Cattle grazing mature CB had higher ruminal fills (2.40 vs 2.02 kg dry matter/100 kg body weight), reduced rates of passage and lower voluntary intake (2.50 vs 3.14 kg DM/100 kg body weight). Lower intake of mature CB may have resulted from a reduced rate of particle size reduction. Similarities in fragmentation patterns due to ingestive and ruminative mastication were interpreted to indicate that mastication was responsible for most of the particle size reduction of CB and that mastication facilitated digestion of potentially digestible tissues.

Animal Feed↗
PubMed2002

Deep extension from carcinoma arising from the gingiva: CT and MR imaging features.

BACKGROUND AND PURPOSE: CT and MR imaging are useful for evaluating the extension of carcinomas in the face and neck. We evaluated the involvement by carcinoma arising from the gingiva (ie, gingival cancer) by using CT and MR imaging. METHODS: We retrospectively examined 122 patients with squamous cell carcinoma (SCCA) in the lower (88 patients) and upper (34 patients) gingiva. Extension of SCCA into the spaces of the face and neck was evaluated with CT and MR imaging, and findings were surgically confirmed. RESULTS: Spread into the face and neck spaces occurred in 58% of patients. The buccal space was the most common site of spread, occurring in 42% of the lower and of 47% of the upper gingival cancers. Spread into the masticator space occurred from the lower gingival cancers in the molar region (20%) but not from the anterior region. Masticator space involvement from the upper gingiva was rare (4%). The retromolar triangle and buccal space immediately anterior to the ramus served as a corridor for cancer extension from the lower gingiva into the masticator space. The sublingual space (11%) was a less common site of spread from the lower gingiva. CONCLUSION: Gingival cancers spread into the masticator, buccal, and sublingual spaces depending on the primary sites in the oral cavity. An understanding of the face and neck-space anatomy is important in diagnosing cancer extension in the oral cavity gingiva and in treating patients with such disease.

Aged↗
PubMed2003

Comparison of functional and quality-of-life outcomes in patients with and without palatomaxillary reconstruction: a preliminary report.

BACKGROUND: Orodental rehabilitation of hemipalatomaxillectomy defects can be accomplished by using a prosthetic obturator or a vascularized bone-containing free flap. Whereas prosthetic obturation offers several advantages, including the opportunity for immediate dental restoration without the need for further surgery, vascularized bone grafts provide permanent closure of the oronasal communication and bone sufficient for the placement of osseointegrated implants. OBJECTIVE: To compare the functional and quality-of-life (QOL) outcomes in patients rehabilitated with a prosthetic obturator with defect-matched patients who underwent reconstruction with a vascularized bone-containing free flap. METHODS: Four hemipalatomaxillectomy patients rehabilitated with a tissue-borne prosthetic obturator were compared with 4 defect-matched hemipalatomaxillectomy patients who underwent reconstruction with a vascularized bone-containing free flap. All of the patients were objectively assessed for speech, mastication, and QOL. Functional status was assessed by mastication testing, voice analysis, and nasorhinometry. Swallowing-related QOL was assessed using a patient-reported, validated swallowing QOL questionnaire, and donor site morbidity was assessed using upper extremity and lower extremity questionnaires. RESULTS: Patients who underwent reconstruction with a vascularized bone-containing free flap achieved higher mastication and speech assessment scores with less oronasal reflux than defect-matched patients rehabilitated with a prosthetic obturator. Swallowing QOL and donor site assessments demonstrated that compared with their prosthetic counterparts, reconstruction patients enjoyed a better QOL without incurring significant donor site morbidity. CONCLUSIONS: Although palatomaxillary reconstruction with vascularized bone-containing free flaps requires a second operative site, this method of orodental rehabilitation of the hemipalatomaxillectomy defect can achieve superior functional and QOL outcomes relative to defect-matched patients rehabilitated with a prosthetic obturator.

Humans↗
PubMed2000

Strain in the galago facial skull.

Little experimental work has been directed at understanding the distribution of stresses along the facial skull during routine masticatory behaviors. Such information is important for understanding the functional significance of the mammalian circumorbital region. In this study, bone strain was recorded along the dorsal interorbit, postorbital bar, and mandibular corpus in Otolemur garnettii and O. crassicaudatus (greater galagos) during molar chewing and biting. We determined principal-strain magnitudes and directions, compared peak shear-strain magnitudes between various regions of the face, and compared galago strain patterns with similar experimental data for anthropoids. This suite of analyses were used to test the facial torsion model (Greaves [1985] J Zool (Lond) 207:125-136; [1991] Zool J Linn Soc 101:121-129; [1995] Functional morphology in vertebrate paleontology. Cambridge: Cambridge University Press, p 99-115). A comparison of galago circumorbital and mandibular peak strains during powerful mastication indicates that circumorbital strains are very low in magnitude. This demonstrates that, as in anthropoids, the strepsirhine circumorbital region is highly overbuilt for countering routine masticatory loads. The fact that circumorbital peak-strain magnitudes are uniformly low in both primate suborders undermines any model that emphasizes the importance of masticatory stresses as a determinant of circumorbital form, function, and evolution. Preliminary data also suggest that the difference between mandibular and circumorbital strains is greater in larger-bodied primates. This pattern is interpreted to mean that sufficient cortical bone must exist in the circumorbital region to prevent structural failure due to nonmasticatory traumatic forces. During unilateral mastication, the direction of epsilon(1) at the galago dorsal interorbit indicates the presence of facial torsion combined with bending in the frontal plane. Postorbital bar principal-strain directions during mastication are oriented, on average, very close to 45 degrees relative to the skull's long axis, much as predicted by the facial torsion model. When chewing shifts from one side of the face to the other, there is a characteristic reversal or flip-flop in principal-strain directions for both the interorbit and postorbital bar. Although anthropoids also exhibit an interorbital reversal pattern, peak-strain directions for this clade are opposite those for galagos. The presence of such variation may be due to suborder differences in relative balancing-side jaw-muscle force recruitment. Most importantly, although the strain-direction data for the galago circumorbital region offer support for the occurrence of facial torsion, the low magnitude of these strains suggests that this loading pattern may not be an important determinant of circumorbital morphology.

Animals↗
PubMed1979

Experimental analysis of temporomandibular joint reaction force in macaques.

Mandibular bone strain in the region immediately below the temporomandibular ligament was analyzed in adult and sub-adult Macaca fascicularis and Macaca mulatta. Following recovery from the general anesthetic, the monkeys were presented food objects, a wooden rod, or a specially designed bite-force transducer. Bone strain was recorded during incisal biting and mastication of food, and also during isometric biting of the rod and/or the transducer. The bone strain data suggest the following: The macaque TMJ is loaded by a compressive reaction force during the power stroke of mastication and incision of food, and during isometric molar and incisor biting. TMJ reaction forces are larger on the contralateral side during both mastication and isometric molar biting. Patterns of ipsilateral TMJ reaction force in macaques during isometric biting vary markedly in response to the position of the bite point. During biting along the premolars or first two molars a compressive reaction force acts about the ipsilateral TMJ; however, when the bite point is positioned along the M3, the ipsilateral TMJ has either very little compressive stress, no stress, or it is loaded in tension.

Animals↗
PubMed1994

EMG of the digastric muscle in gibbon and orangutan: functional consequences of the loss of the anterior digastric in orangutans.

Unlike all other primates, the digastric muscle of the orangutan lacks an anterior belly; the posterior belly, while present, inserts directly onto the mandible. To understand the functional consequences of this morphologic novelty, the EMG activity patterns of the digastric muscle and other potential mandibular depressors were studied in a gibbon and an orangutan. The results suggest a significant degree of functional differentiation between the two digastric bellies. In the gibbon, the recruitment pattern of the posterior digastric during mastication is typically biphasic. It is an important mandibular depressor, active in this role during mastication and wide opening. It also acts with the anterior suprahyoid muscles to move the hyoid prior to jaw opening during mastication. The recruitment patterns of the anterior digastric suggest that it is functionally allied to the geniohyoid and mylohyoid. For example, although it transmits the force of the posterior digastric during mandibular depression, it functions independent of the posterior digastric during swallowing. Of the muscles studied, the posterior digastric was the only muscle to exhibit major differences in recruitment pattern between the two species. The posterior digastric retains its function as a mandibular depressor in orangutans, but is never recruited biphasically, and is not active prior to opening. The unique anatomy of the digastric muscle in orangutans results in decoupling of the mechanisms for hyoid movement and mandibular depression, and during unilateral activity it potentially contributes to substantial transverse movements of the mandible. Hypotheses to explain the loss of the anterior digastric should incorporate these functional conclusions.

Animals↗
PubMed1977

Integrated actions of masticatory muscles: simultaneous EMG from eight intramuscular electrodes.

In 29 normal persons with complete dental arches, the muscular activity of the temporalis, masseter, medical pterygoid, anterior belly of the digastric, mylohyoid and geniohyoid muscles was studied electromyographically with bipolar fine wire electrodes during various mandibular movements--both resisted and unresisted. Action potentials were recorded on FM magnetic tape and each experiment was also videotaped. Temporalis muscle was active during centric closing of the jaw with either contact of the teeth, or against resistance; during free lateral movements to the ipsilateral side, either against resistance or occlusal contact; during incisor gum chewing, molar gum chewing on ipsilateral or contralateral sides, during normal mastication; and during forceful centric occlusion. Activity occurred in the masseter and medial pterygoid muscles during the following movements; closing the jaw slowly either without occlusal contact or with occlusal contact and against resistance; free lateral movement to contralateral side, either against resistance or with occlusal contact; protraction of the jaw either without occlusal contact or with occlusal contact; swallowing either saliva or water; incisor gum chewing with either the ipsilateral or contralateral molars; normal mastication; and during forceful centric occlusion. Activity occurred in the digastric, mylohyoid and geniohyoid muscles during the following movements; opening of the jaw either slowly or maximally against resistance; closing the jaw against resistance; free lateral movement to ipsilateral and contralateral sides, either against resistance or with occlusal contact; protraction against resistance of the jaw either without or with occlusal contact; swallowing saliva and water; and protraction of the tongue. They work in antagonism (reciprocally) during gum chewing and normal mastication.

Action Potentials↗
PubMed1975

Mandibular movements of the albino rat during feeding.

Jaw movements of albino rats during biting and mastication of relatively hard food were recorded by means of conventional and X-ray cinematography. Mandibular kinetics have been analysed in the context of passive mechanical limits imposed by jaw morphology, particularly of the joints, and by the food itself. Movements have been described in terms of degrees of gape, condylar translation and horizontal rotation of the rami about the symphysis. During biting the condyle remains in the anterior two-thirds of the fossa, moves forward as the jaw opens and the converse. The rami usually spread well apart; the lower incisors are usually approximated. Incised food particles are transported toward the molars by means of coordinated jaw and tongue movements. The prominent palatal rugae of the diastemal region abet this process. In the power stroke of mastication, the mandible shifts forward as the lower toothrows move a little inward; the condyles occupy the posterior two-thirds of the fossa. All movements seen were bilaterally symmetrical. Simultaneous chewing occurred on both sides. It is suggested that the lingual components in the primarily anterior power stroke enhance grinding efficiency. A movable symphysis appears to be of critical importance in facilitating this type of mastication.

Animals↗
PubMed1983

Aspects of masticatory form and function in common tree shrews, Tupaia glis.

Tree shrews have relatively primitive tribosphenic molars that are apparently similar to those of basal eutherians; thus, these animals have been used as a model to describe mastication in early mammals. In this study the gross morphology of the bony skull, joints, dentition, and muscles of mastication are related to potential jaw movements and cuspal relationships. Potential for complex mandibular movements is indicated by a mobile mandibular symphysis, shallow mandibular fossa that is large compared to its resident condyle, and relatively loose temporomandibular joint ligaments. Abrasive tooth wear is noticeable, and is most marked at the first molars and buccal aspects of the upper cheek teeth distal to P2. Muscle morphology is basically similar to that previously described for Tupaia minor and Ptilocercus lowii. However, in T. glis, an intraorbital part of deep temporalis has the potential for inducing lingual translation of its dentary, and the large medial pterygoid has extended its origin anteriorly to the floor of the orbit, which would enhance protrusion. The importance of the tongue and hyoid muscles during mastication is suggested by broadly expanded anterior bellies of digastrics, which may assist mylohyoids in tensing the floor of the mouth during forceful tongue actions, and by preliminary electromyography, which suggests that masticatory muscles alone cannot fully account for jaw movements in this species.

Animals↗
PubMed1991

In vivo strain in cranial sutures: the zygomatic arch.

Although cranial sutures presumably play a role in absorbing and/or transmitting loads applied to the skull, loading patterns on facial sutures are poorly understood. The zygomatic arch provides a comparatively isolated mechanical part of the skull containing a single suture, the zygomatico-squamosal. In pigs the zygomatico-squamosal suture has a short vertical segment located within the postorbital process and a longer horizontal segment which extends posteriorly. In anesthetized pigs single-element high-elongation strain gages were bonded over both segments of the suture. Strain was recorded during stimulation of the masseter muscles and while the lightly anesthetized animals masticated food pellets. The predominant strain patterns differed in the two segments of the suture. During mastication compressive strains predominated in the vertical segment, but tensile strains predominated in the horizontal segment. The same patterns were also produced by stimulation of the ipsilateral masseter muscle. Contraction of the contralateral masseter reversed the strain pattern, but strain levels were low and during mastication such reversals occurred only transiently. The two segments of the suture have contrasting morphologies. The vertical segment has broad, interdigitating contacts with fibers arranged in a compression-resisting orientation. The horizontal segment has a simple tongue and groove structure with fibers arranged to resist tension. Thus, the structure of the suture reflects the predominant strain pattern.

Animals↗
PubMed2004

Different corticostriatal projections from two parts of the cortical masticatory area in the rabbit.

The cortical masticatory area (CMA) elicits rhythmic jaw movements in response to repetitive stimulation and is involved in the control of mastication. Based on jaw movement patterns, the CMA is divided into two parts. One is the part of the CMA in which a T-pattern similar to jaw movements during food transport in natural mastication is evoked by electrical stimulation. The other is more dorsomedially located, and during chewing a C-pattern similar to jaw movements can be induced. However, it is still not known which region of the putamen receives projections from the CMA and whether projections originate from both parts of the CMA. In this study, electrophysiological and histological experiments were undertaken in rabbits to investigate projections from the CMA to the putamen. Both experiments showed that the ventral region of the putamen received projections from the CMA. The density of the projections from the CMA area inducing the T-pattern seemed to be higher than that from the area inducing the C-pattern. Furthermore, the peak latency of the evoked potentials from stimulation of the CMA area inducing the T-pattern was shorter than that from stimulation of the area inducing the C-pattern. The data obtained from the present study indicate the functional role of the ventral region of the putamen in the regulation of mastication, and further suggest that the corticostriatal pathway is involved in the transition between behavioral jaw movement patterns.

Animals↗
PubMed2006

Generation of the central masticatory pattern and its modification by sensory feedback.

Mammalian mastication results from the interaction of an intrinsic rhythmical neural pattern and sensory feedback generated by the interaction of the effecter system (muscles, bones, joints, teeth, soft tissues) with food. The main variables that explain variation in the pattern of human mastication are the subjects themselves, their age, the type of food being eaten, and time during a sequence of movements. The intrinsic pattern of mastication is generated by a central pattern generator (CPG) located in the pons and medulla. The output of the CPG is modified by inputs that descend from higher centers of the brain and by feedback from sensory receptors. Intraoral touch receptors, muscle spindles in the jaw-closing muscles, and specialized mechanoreceptors in the periodontal ligament have especially powerful effects on movement parameters.

Animals↗
PubMed1990

Patterns of mandibular movements in subjects with craniomandibular disorders.

Mandibular movements were evaluated for border and functional movements in 24 adult normal subjects and 26 adult patients with muscle pain associated with a craniomandibular disorder. The mandibular incisor position was tracked with an electromagnetic system in three planes by use of either a Myotronic Kinesiograph or a Siemens Sirognathograph instrument while the subject sat in an upright position. In the normal subjects, the maximum movements of the mandible in lateral, protrusive, and vertical directions were compared with the envelope of movement during speech and mastication. The range of the rest position was 1 to 5 mm in relation to the intercuspal position; the range of maximum excursion during speech was 30% to 36% of maximum opening; the vertical extent of excursion during mastication was 18% to 90% of the maximum vertical opening dependent on the bolus. Protrusive movements were straight forward, dividing the angle evenly between left and right laterotrusion. Laterotrusive movements were of equal length and similar to the length of protrusion. Twenty-six patients with muscle pain, in many instances, demonstrated asymmetry in the length of laterotrusive movements. Different pathways for moving the mandible away from the intercuspal position and returning to this position could be seen during laterotrusion. Unequal laterotrusive excursions and asymmetrical, nonparallel movement patterns for mandibular protrusion and retrusion were often observed. In contrast, the extent of the speech envelope and the envelope of mastication were similar to that of the controls.

Adolescent↗
PubMed2006

Mechanical behavior of an osteotomized mandible with distraction orthodontic devices.

This work analyzes the mechanical behavior of a human mandible when distraction orthodontic devices are used for correcting problems of dental overcrowding and/or arch shrinkage. The mandible 3D model is reconstructed from CT scan data and meshed into finite elements. The distractor is also modeled. FEM analysis included geometric non-linearity. Displacement field of healthy and osteotomized mandibles are compared. Progressive expansion of the distractor and effects of mastication are also analyzed. Finally, we compare two distraction protocols PROT1 and PROT2 where device is, respectively, expanded by 0.6 or 1.2mm/day. The global displacement is 6mm according to clinical recommendations. It came out that mastication forces generate displacements compatible with bone remodeling. However, parasitic rotations of the mandible arms due to mastication may counteract arch expansion induced by the device. Stress concentrations occurred where the device is fixed: stress peaks stay however below yield limit. Finally, PROT2 reduced by about 10% stresses in mandible and reproduces better than PROT1 the displacement field imposed by the device.

Biomechanical Phenomena↗
PubMed2005

Do homoiologies impede phylogenetic analyses of the fossil hominids? An assessment based on extant papionin craniodental morphology.

Homoiologies are phylogenetically misleading resemblances among taxa that can be attributed to phenotypic plasticity. Recently, it has been claimed that homoiologies are widespread in the hominid skull, especially in those regions affected by mastication-related strain, and that their prevalence is a major reason why researchers have so far been unable to obtain a reliable estimate of hominid phylogeny. To evaluate this "homoiology hypothesis", we carried out analyses of a group of extant primates for which a robust molecular phylogeny is available-the papionins. We compiled a craniometric dataset from measurements that differ in their susceptibility to mastication-related strain according to developmental considerations and experimental evidence. We used the coefficient of variation and analysis of variance with post hoc least significant difference comparisons in order to evaluate the variability of the measurements. The prediction from the homoiology hypothesis was that dental measurements, which do not remodel in response to strain, should be less variable than low-to-moderate-strain measurements, and that the latter should be less variable than high-strain measurements. We then performed phylogenetic analyses using characters derived from the measurements and compared the resulting phylogenetic hypotheses to the group's consensus molecular phylogeny. The prediction was that, if the homoiology hypothesis is correct, the agreement between the craniometric and molecular phylogenies would be best in the analyses of dental characters, intermediate in the analyses of low-to-moderate-strain characters, and least in the analyses of high-strain characters. The results of this study support the suggestion that mastication-related mechanical loading can result in variation in hominid cranial characters. However, they do not support the hypothesis that homoiology is a major reason why phylogenetic analyses of hominid crania have so far yielded conflicting and weakly supported hypotheses of relationship. These findings are consistent with a recent test of the homoiology hypothesis using craniodental data from extant hominoids, and cast doubt on the validity of the homoiology hypothesis, as originally formulated.

Animals↗
PubMed2003

Neuromuscular objectives of the human masticatory apparatus during static biting.

OBJECTIVE: The central nervous system controls the muscles of mastication and may dictate muscle outputs according to a biologically important objective. This study tested the hypotheses that (a) the effective sagittal TMJ eminence morphology, and (b) the outputs of the masticatory muscles during static biting, are consistent with minimisation of joint loads or minimisation of muscle effort. DESIGN: Numerical modelling predicted effective eminence morphology (from sagittal plane directions of TMJ force for centred loading over a range from molar to incisor biting) and TMJ and muscle forces during static unilateral biting in seven subjects. In vivo effective eminence morphology was measured from jaw tracking recorded from each subject. Muscle activities during biting tasks on first molar and incisor teeth were measured by electromyography using surface or indwelling electrodes. RESULTS: Subject-specific predicted effective eminence morphology correlated with in vivo data (0.85< or =R2< or =0.99). Mixed and random coefficient analysis of covariance indicated good agreement between predicted and measured muscle outputs for all muscles of mastication investigated. Individual linear regression analysis showed that modelled muscle outputs accurately predicted EMG data, with average errors of 8% for molar and 15% for incisor biting. CONCLUSIONS: Effective sagittal eminence morphology was consistent with minimisation of joint loads for all subjects. Masticatory muscle outputs during unilateral biting were consistent with minimisation of joint loads or minimisation of muscle effort, or both, depending on the subject. These results are believed to be the first to test model predictions of muscle output during biting for all muscles of mastication.

Adult↗
PubMed1999

Effects of dietary consistency and water content on parotid amylase secretion and gastric starch digestion in rats.

The aim was to estimate the significance of oral sensation and mastication in inducing amylase secretion from the parotid gland and subsequent starch digestion in the stomach. Rats were fed three diets of similar chemical composition but different physical presentations. Two were solid, either pellets or powder, and one was liquid. Oral sensory activity would be greatest with the pellets and least with the liquid. Only the pellets would require significant mastication. Three criteria were used to estimate amylase secretion, amylase activity in the stomach, the depletion of glandular amylase activity and plasma amylase concentrations. Gastric starch digestion was estimated by measuring the concentration of reducing-sugars in the stomach contents. Parotid amylase secretion and gastric starch digestion were similar whether rats were fed pelleted or powdered solid food but much lower in rats fed a liquid diet. These findings support the view that it is the contact of dry food with the oral mucosa rather than the jaw movements involved in mastication that stimulates parotid amylase secretion.

Amylases↗