Loading patterns and jaw movements during mastication in Macaca fascicularis: a bone-strain, electromyographic, and cineradiographic analysis.
01 Mar 1987-American Journal of Physical Anthropology (Am J Phys Anthropol)-Vol. 72, Iss: 3, pp 287-314
TL;DR: The bone strain and jaw movement data indicate that during vigorous mastication the transition between fast close and the power stroke is correlated with a sharp increase in masticatory force, and they also show that in most instances the jaws of macaques are maximally loaded prior to maximum intercuspation.
Abstract: Rosette strain gage, electromyography (EMG), and cineradiographic techniques were used to analyze loading patterns and jaw movements during mastication in Macaca fascicularis. The cineradiographic data indicate that macaques generally swallow frequently throughout a chewing sequence, and these swallows are intercalated into a chewing cycle towards the end of a power stroke. The bone strain and jaw movement data indicate that during vigorous mastication the transition between fast close and the power stroke is correlated with a sharp increase in masticatory force, and they also show that in most instances the jaws of macaques are maximally loaded prior to maximum intercuspation, i.e. during phase I (buccal phase) occlusal movements. Moreover, these data indicate that loads during phase II (lingual phase) occlusal movements are ordinarily relatively small. The bone strain data also suggest that the duration of unloading of the jaw during the power stroke of mastication is largely a function of the relaxation time of the jaw adductors. This interpretation is based on the finding that the duration from 100% peak strain to 50% peak strain during unloading closely approximates the half-relaxation time of whole adductor jaw muscles of macaques. The EMG data of the masseter and medial pterygoid muscles have important implications for understanding both the biomechanics of the power stroke and the external forces responsible for the "wishboning" effect that takes place along the mandibular symphysis and corpus during the power stroke of mastication. Although both medial pterygoid muscles reach maximum EMG activity during the power stroke, the activity of the working-side medial pterygoid peaks after the balancing-side medial pterygoid. Associated with the simultaneous increase of force of the working-side medial pterygoid and the decrease of force of the balancing-side medial pterygoid is the persistently high level of EMG activity of the balancing-side deep masseter (posterior portion). This pattern is of considerable significance because the direction of force of both the working-side medial pterygoid and the balancing-side deep masseter are well aligned to aid in driving the working-side lower molars across the upper molars in the medial direction during unilateral mastication.(ABSTRACT TRUNCATED AT 400 WORDS)
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TL;DR: It is suggested that the production of the rhythm, and of the opener and closer motoneuron bursts, are independent processes that are carried out by different groups of cells.
Abstract: This review describes the patterns of mandibular movements that make up the whole sequence from ingestion to swallowing food, including the basic types of cycles and their phases. The roles of epithelial, periodontal, articular, and muscular receptors in the control of the movements are discussed. This is followed by a summary of our knowledge of the brain stem neurons that generate the basic pattern of mastication. It is suggested that the production of the rhythm, and of the opener and closer motoneuron bursts, are independent processes that are carried out by different groups of cells. After commenting on the relevent properties of the trigeminal and hypoglossal motoneurons, and of internuerons on the cortico-bulbar and reflex pathways, the way in which the pattern generating neurons modify sensory feedback is discussed.
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TL;DR: The biplanar fluoroscopy hardware and computational methods described here should make XROMM an accessible and useful addition to the available technologies for studying the form, function, and evolution of vertebrate animals.
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422 citations
Cites background from "Loading patterns and jaw movements ..."
...In agreement with traditional perspectives on mandible movement that emphasize jaw depression, elevation, protrusion, and retrusion (e.g., Hiiemae and Crompton, ’85; Hylander et al., ’87; Hiiemae, 2000; Herring, 2007), we find that mandible movement in our JCS is dominated by Rz and Tx (Fig....
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TL;DR: Alternation of jaw adductor and abductor activity during mastication provided a framework for integration of chewing, transport, and swallowing.
Abstract: The coordination of mastication, oral transport, and swallowing was examined during intake of solids and liquids in four normal subjects. Videofluorography (VFG) and electromyography (EMG) were recorded simultaneously while subjects consumed barium-impregnated foods. Intramuscular electrodes were inserted in the masseter, suprahyoid, and infrahyoid muscles. Ninety-four swallows were analyzed frame-by-frame for timing of bolus transport, swallowing, and phases of the masticatory gape cycle. Barium entered the pharynx a mean of 1.1 s (range −0.3 to 6.4 s) before swallow onset. This interval varied significantly among foods and was shortest for liquids. A bolus of food reached the valleculae prior to swallow onset in 37% of sequences, but most of the food was in the oral cavity at the onset of swallowing. Nearly all swallows started during the intercuspal (minimum gape) phase of the masticatory cycle. Selected sequences were analyzed further by computer, using an analog-to-digital convertor (for EMG) and frame grabber (for VFG). When subjects chewed solid food, there were loosely linked cycles of jaw and hyoid motion. A preswallow bolus of chewed food was transported from the oral cavity to the oropharynx by protraction (movement forward and upward) of the tongue and hyoid bone. The tongue compressed the food against the palate and squeezed a portion into the pharynx one or more cycles prior to swallowing. This protraction was produced by contraction of the geniohyoid and anterior digastric muscles, and occurred during the intercuspal (minimum gape) and opening phases of the masticatory cycle. The mechanism of preswallow transport was highly similar to the oral phase of swallowing. Alternation of jaw adductor and abductor activity during mastication provided a framework for integration of chewing, transport, and swallowing.
392 citations
Cites background from "Loading patterns and jaw movements ..."
...The animal swallows during the intercuspal phase of a gape cycle, and jaw motion continues [13, 14]....
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TL;DR: Finite element analysis has much potential in addressing questions of form-function relationships, providing appropriate questions are ask, and explicit hypothesis-testing bridges these two standpoints.
Abstract: Finite element analysis (FEA) is a technique that reconstructs stress, strain, and deformation in a digital structure. Although commonplace in engineering and orthopedic science for more than 30 years, only recently has it begun to be adopted in the zoological and paleontological sciences to address questions of organismal morphology, function, and evolution. Current research tends to focus on either deductive studies that assume a close relationship between form and function or inductive studies that aim to test this relationship, although explicit hypothesis-testing bridges these two standpoints. Validation studies have shown congruence between in vivo or in vitro strain and FE-inferred strain. Future validation work on a broad range of taxa will assist in phylogenetically bracketing our extinct animal FE-models to increase confidence in our input parameters, although currently, FEA has much potential in addressing questions of form-function relationships, providing appropriate questions are ask...
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References
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01 Jan 1978TL;DR: In this paper, elementary elasticity and fraction mechanics stress strain and the stress-strain relationships basic equations and plane-elasticity theory are discussed and an introduction to strain measurements electrical resistance strain gages strain gage circuits recording instruments strain analysis methods.
Abstract: Part 1: Elementary elasticity and fraction mechanics stress strain and the stress-strain relationships basic equations and plane-elasticity theory. Elementary fracture mechanics. Part 2: Strain-measurement methods and related instrumentation introduction to strain measurements electrical resistance strain gages strain gage circuits recording instruments strain analysis methods. Part 3: Optical methods of stress analysis basic optics moire methods theory of plasticity applied photoelasticity - two and three dimensional stress analysis optical methods for determining fracture parameters coating methods - photoelastic coatings and brittle coating statistical analysis of experimental data.
1,324 citations
TL;DR: The tension in tetanized cat soleus and lateral gastrocnemius muscles was measured during alternating lengthening and shortening movements.
Abstract: 1. The tension in tetanized cat soleus and lateral gastrocnemius muscles was measured during alternating lengthening and shortening movements. Sinusoidal movements were sometimes used; on other occasions the movement was at a constant velocity but with periodic reversal of direction.
2. With constant velocity movements of small amplitude the tension rose steeply during lengthening and fell during shortening in a relatively simple way. With longer movements the tension at first changed steeply as it had done with the smaller movement, but later in the movement the resistance of the muscles decreased so that the tension change became more gradual. The muscles resisted a small movement or the first part of a larger movement with a `short range stiffness' which did not persist as the movement continued.
3. So long as the constant velocity movement was not too slow the short range stiffness was independent of velocity though it lasted for more of a fast movement than of a slow one.
4. In small movements the muscle was never extended beyond its short range stiffness, and the over-all peak-to-peak tension change was therefore large compared with the amplitude of movement. When, with larger movements, the muscle was stretched into a range in which it became more compliant, the peak-to-peak force fluctuation did not increase by an equivalent amount, and over the whole course of the movement the force change per unit extension was smaller.
5. When the movement was confined to a short range, little work was expended in driving the muscle through a cycle of movement; its properties were essentially elastic. With larger amplitudes the muscle met the movement with a frictional resistance, the tension during lengthening then being greater than during shortening. A considerable amount of work had then to be done on the muscle to maintain the movement.
6. The short range stiffness was also apparent in the response to sinusoidal movements.
7. The short range stiffness was attributed to elastic properties of cross-bridges between thick and thin filaments in the myofibrils.
8. The effect of the short range stiffness on the mechanical properties of the limb is discussed.
542 citations
TL;DR: The most effective influence on the amount of intracortical secondary osteal remodelling was also the maximum strain rate ratio, which could only explain 43% of the variance in the total number of secondary osteons formed.
475 citations
TL;DR: The results suggest that the observed changes in the morphology of the jaw apparatus have probably occurred within the limits set by a pre-existing behavioral pattern.
Abstract: Masticatory movements and molar wear facets in species of Tupaia, Galago, Saimiri, and Ateles have been examined using cinefluorography and occlusal analysis. The molars have been compared with those of a fossil series: Palenochtha, Pelycodus and Aegyptopithecus.
The extant primates are almost identical in their feeding behaviour, the movements and timing of the masticatory cycle. Food is first puncture-crushed where the cycle is elongated, the power stroke attenuated and abrasion facets are produced on the molars. Chewing follows, the movements are more complex, the power stroke has two distinct parts and attrition facets are produced. In the primitive forms (Tupaia, Palenochtha), shearing blades, arranged in series (en echelon) were used to cut the food during the first part (Phase I) of the power stroke as the lower teeth move into centric occlusion. This mechanism has been progressively replaced by a system of blade-ringed compression chambers which cut and compartmentalise the food in Phase I. This is followed by an anteromedially and inferiorly directed movement away from centric occlusion (Phase II) in which the food is ground. In both extant and fossil series there has been a clear trend towards the elongation of Phase II with a corresponding reduction in Phase I.
These results suggest that the observed changes in the morphology of the jaw apparatus have probably occurred within the limits set by a pre-existing behavioral pattern.
407 citations
TL;DR: The data suggest that during the power stroke of mastication, the macaque symphysis is predominately sheared dorsoventrally and/or twisted about a transverse axis and bent by lateral transverse bending of the mandibular corpora.
Abstract: The primary purpose of this study was to test various hypotheses about symphyseal stress in primates. First, those patterns of symphyseal strain that would be associated with various hypothetical patterns of symphyseal stress were formulated. Then these hypothetical patterns of stress and strain were tested by comparing the formulated bone strain pattern with actual in vivo symphyseal bone strain patterns. Patterns of in vivo symphyseal bone strain were determined by bonding rosette and/or single-element strain gages to the midline of the middle and lower third of the labial aspect of the symphysis of six adult Macaca fascicularis. Following recovery from the anesthetic, bone strain was recorded during mastication, incision, and isometric biting. Symphyseal bone strain was also recorded during yawning, licking, and threat behaviors. The data suggest that during the power stroke of mastication, the macaque symphysis is predominately sheared dorsoventrally and/or twisted about a transverse axis and bent by lateral transverse bending of the mandibular corpora. During lateral transverse bending of the mandibular corpora, the labial aspect of the macaque symphysis experiences compressive bending stress, while the lingual aspect experiences tensile bending stress. During the opening stroke of mastication and during other jaw opening behaviors, the macaque symphysis is bent by medial transverse bending of the mandibular corpora. At this time the labial aspect of the symphysis experiences tensile bending stress, while its lingual aspect experiences compressive bending stress. During both the power and opening strokes of mastication, the macaque mandible is bent in the plane of its curvature, and therefore the mandible acts as a curved beam. This is important because it results in elevated levels of stress along the lingual aspect of the macaque symphysis, particularly during the power stroke of mastication. During the power stroke of incision, the local effects of the bite force are unknown; however, at this time the lower half of the macaque symphysis is both sheared dorsoventrally and bent due to twisting of the mandibular corpora about their long axes. The results of this stress analysis have implications for understanding the mechanical attributes of symphyseal structure. In order to counter dorsoventral shear, the most important symphyseal attribute is to have adequate cross-sectional area of bone in the plane of the applied stress. In contrast, both the cross-sectional area of bone and symphyseal shape is important in order to counter stress effectively during symphyseal torsion and the three symphyseal bending regimes.(ABSTRACT TRUNCATED AT 400 WORDS)
364 citations