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Bite Force (bite + force)
Kinds of Bite Force Selected AbstractsEFFECT OF SAMPLE THICKNESS ON THE BITE FORCE FOR APPLESJOURNAL OF TEXTURE STUDIES, Issue 3 2003HARUKA DAN The thickness of a piece of food and its mechanical properties affected the bite force. A multiple-point sheet sensor was used to measure the bite force applied to apple specimens of various thicknesses during the first bite with incisors. The results of wedge penetration tests on the same samples were compared with results of the bite measurements. The maximum bite force increased with the sample thickness for two apple varieties, though the maximum load measured by the wedge penetration test did not change. Therefore, it is important to consider that not only the mechanical properties but also the thickness of the sample affects the required bite force. [source] A simple morphological predictor of bite force in rodentsJOURNAL OF ZOOLOGY, Issue 4 2008P. W. Freeman Abstract Bite force was quantified for 13 species of North American rodents using a piezo-resistive sensor. Most of the species measured (11) formed a tight relationship between body mass and bite force (log 10(bite force)=0.43(log 10(body mass))+0.416; R2>0.98). This high correlation exists despite the ecological (omnivores, grazers and more carnivorous) and taxonomic (Cricetidae, Heteromyidae, Sciuridae and Zapodidae) diversity of species. Two additional species, Geomys bursarius (Geomyidae) and a Sciurus niger (Sciuridae), bit much harder for their size. We found a simple index of strength based on two measurements of the incisor at the level of the alveolus (Zi=((anterior-posterior length)2× (medial-lateral width))/6) that is highly predictive of bite force in these rodents (R2>0.96). Zi may be useful for prediction of bite force (log10 (Bite Force)=0.566log10 (Zi)+1.432) when direct measurements are not available. [source] Sexual dimorphism, body size, bite force and male mating success in tuataraBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010ANTHONY HERREL Sexual dimorphisms in body size and head size are common among lizards and are often related to sexual selection on male fighting capacity (organismal performance) and territory defence. However, whether this is generally true or restricted to lizards remains untested. Here we provide data on body and head size, bite performance and indicators of mating success in the tuatara (Sphenodon punctatus), the closest living relative to squamates, to explore the generality of these patterns. First, we test whether male and female tuatara are dimorphic in head dimensions and bite force, independent of body size. Next, we explore which traits best predict bite force capacity in males and females. Finally, we test whether male bite force is correlated with male mating success in a free-ranging population of tuatara (Sphenodon punctatus). Our data confirm that tuatara are indeed dimorphic in head shape, with males having bigger heads and higher bite forces than females. Across all individuals, head length and the jaw closing in-lever are the best predictors of bite force. In addition, our data show that males that are mated have higher absolute but not relative bite forces. Bite force was also significantly correlated to condition in males but not females. Whereas these data suggest that bite force may be under sexual selection in tuatara, they also indicate that body size may be the key trait under selection in contrast to what is observed in squamates that defend territories or resources by biting. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 287,292. [source] Task-related electromyographic spectral changes in the human jaw musclesJOURNAL OF ORAL REHABILITATION, Issue 9 2002M. FARELLA The masticatory muscles differ in their fibre type composition. It can therefore be expected that their electromyographic (EMG) power spectra will differ during the performance of different bite force tasks. In the present study surface EMG activity was picked up from the masseter, and anterior and posterior temporalis muscles of nine adult subjects. Direction and magnitude of bite force were recorded using a three-component force transducer. Bite forces were exerted in five different directions: vertical, forward, backward, to the right and to the left of the subject. Non-vertical forces were kept at an angle of 15° from the vertical. Force levels of 25, 50, 100 and 200 N were exerted in each of the investigated directions. Data collected were analysed by means of a regression model for repeated measurements. It appeared that the mean power frequency (MPF) values of the posterior temporalis were significantly lower (P < 0·01) than those of the masseter and anterior temporalis. The MPF values of the masseter muscles decreased with an increase of bite force magnitude (P < 0·001) whereas the MPF values of the anterior and posterior temporalis did not change significantly (P > 0·05). The MPF values were significantly influenced by the direction of bite force (P < 0·01). The observed changes of MPF are possibly related to the recruitment of different fibre types and support the concept that the masticatory muscles behave heterogeneously. [source] Bite forces, canine strength and skull allometry in carnivores (Mammalia, Carnivora)JOURNAL OF ZOOLOGY, Issue 2 2005Per Christiansen Abstract Skull variables were analysed for allometry patterns in 56 species of extant carnivores. As previously reported, many skull variables scale near isometrically with either skull length or lower jaw length. The maximal gape angle scales insignificantly (P<0.05) with skull size, but the clearance between the canines shows a significant relationship with skull size and scales near isometrically. Maximal bite forces were estimated from geometrical cross-sectional areas of dried skulls, and the bending strength of the canines was computed by modelling the canines as a cantilevered beam of solid, homogeneous material with an elliptical cross section. Previous hypotheses of large taxon differences in canine bending strengths, so that felids have stronger canines than canids, are corroborated when actual bite forces at the upper canine are ignored. Incorporation of bite force values, however, nullifies the differences in canine bending strength among felids and canids, and ursids seem to have stronger canines than felids. This is probably because of the significantly longer canines of felids compared to canids and ursids, and the generally high bite forces of felids. [source] Human jaw muscle strength and size in relation to limb muscle strength and sizeEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2004M. C. Raadsheer The aim of the present study was to investigate to what extent general factors (e.g. genotype, hormones) and factors at the craniofacial level (e.g. craniofacial size, jaw muscle architecture) contribute to the size and strength of the jaw muscles. A strong relationship of jaw muscle size and strength with that of other muscles would argue for general influences, whereas a weak relationship would argue for craniofacial influences. In 121 adult individuals, moments of maximal bite force, arm flexion force and leg extension force were measured. In addition, thicknesses of jaw muscles, arm flexor muscles and leg extensor muscles were measured using ultrasound. Relationships were assessed by using a principal component analysis. In females, one component was found in which all force moments were represented. Bite force moment, however, loaded very low. In males, two components were found. One component loaded for arm flexion and leg extension moments, the other loaded for bite force moments. In both females and males, only one component was found for the muscle thicknesses in which all muscle groups loaded similarly. It was concluded that the size of the jaw muscles was significantly related to the size of the limb muscles, suggesting that they were both subject to the same general influences. Maximal voluntary bite force moments were not significantly related to the moments of the arm flexion and leg extension forces, suggesting that besides the general influence on the muscle size, variation in bite force moment was also influenced by local variables, such as craniofacial morphology. [source] Task-related electromyographic spectral changes in the human masseter and temporalis musclesEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2002Mauro Farella The masticatory muscles differ in their fiber type composition. It can therefore be expected that their electromyographic (EMG) power spectra will differ during the performance of different bite force tasks. In the present study, surface EMG activity was picked up from the masseter and from the anterior and posterior temporalis muscles of nine adult subjects. At a bite force level as low as 25 N, the mean power frequency (MPF) values of the posterior temporalis were significantly lower than those of the masseter and anterior temporalis. The MPF values of the masseter muscles decreased with an increase of bite force magnitude, whereas the MPF values of the anterior and posterior temporalis did not change significantly. The MPF values were significantly influenced by the direction of bite force. The observed changes of MPF are possibly related to the recruitment of different fiber types, and support the concept that the masticatory muscles behave heterogeneously. [source] EVOLUTION ON A LOCAL SCALE: DEVELOPMENTAL, FUNCTIONAL, AND GENETIC BASES OF DIVERGENCE IN BILL FORM AND ASSOCIATED CHANGES IN SONG STRUCTURE BETWEEN ADJACENT HABITATSEVOLUTION, Issue 8 2008Alexander V. Badyaev Divergent selection on traits involved in both local adaptation and the production of mating signals can strongly facilitate population differentiation. Because of its links to foraging morphologies and cultural inheritance song of birds can contribute particularly strongly to maintenance of local adaptations. In two adjacent habitats,native Sonoran desert and urban areas,house finches (Carpodacus mexicanus) forage on seeds that are highly distinct in size and shell hardness and require different bite forces and bill morphologies. Here, we first document strong and habitat-specific natural selection on bill traits linked to bite force and find adaptive modifications of bite force and bill morphology and associated divergence in courtship song between the two habitats. Second, we investigate the developmental basis of this divergence and find that early ontogenetic tissue transformation in bill, but not skeletal traits, is accelerated in the urban population and that the mandibular primordia of the large-beaked urban finches express bone morphogenetic proteins (BMP) earlier and at higher level than those of the desert finches. Further, we show that despite being geographically adjacent, urban and desert populations are nevertheless genetically distinct corroborating findings of early developmental divergence between them. Taken together, these results suggest that divergent selection on function and development of traits involved in production of mating signals, in combination with localized learning of such signals, can be very effective at maintaining local adaptations, even at small spatial scales and in highly mobile animals. [source] CONVERGENCE AND REMARKABLY CONSISTENT CONSTRAINT IN THE EVOLUTION OF CARNIVORE SKULL SHAPEEVOLUTION, Issue 5 2007Stephen Wroe Phenotypic similarities between distantly related marsupials and placentals are commonly presented as examples of convergence and support for the role of adaptive evolution in shaping morphological and ecological diversity. Here we compare skull shape in a wide range of carnivoran placentals (Carnivora) and nonherbivorous marsupials using a three-dimensional (3-D) geometric morphometric approach. Morphological and ecological diversity among extant carnivorans is considerably greater than is evident in the marsupial order Dasyuromorphia with which they have most commonly been compared. To examine convergence across a wider, but broadly comparable range of feeding ecologies, a dataset inclusive of nondasyuromorphian marsupials and extinct taxa representing morphotypes no longer present was assembled. We found support for the adaptive paradigm, with correlations between morphology, feeding behavior, and bite force, although skull shape better predicted feeding ecology in the phylogenetically diverse marsupial sample than in carnivorans. However, we also show that remarkably consistent but differing constraints have influenced the evolution of cranial shape in both groups. These differences between carnivorans and marsupials, which correlate with brain size and bite force, are maintained across the full gamut of morphologies and feeding categories, from small insectivores and omnivores to large meat-specialists. [source] The reproductive role hypothesis explains trophic morphology dimorphism in the northern map turtleFUNCTIONAL ECOLOGY, Issue 5 2008G. Bulté Summary 1Sexually dimorphic traits often reflect factors limiting the reproductive success of animals. Thus, most sexually dimorphic traits can be directly linked to the reproductive role of each sex. Sexual dimorphism in trophic structures (e.g. beak, jaws, teeth), however, often lacks a direct link to reproduction. 2Trophic structures can be linked indirectly to reproductive allocation via energy acquisition. The reproductive role hypothesis (also known as the dimorphic niche hypothesis) posits such an indirect link, but has received heretofore little direct empirical support. We tested this hypothesis in a molluscivorous turtle exhibiting marked female-biased trophic morphology dimorphism. 3Bite force analysis showed that females have stronger jaws than males and dietary analysis revealed that females ingest snails closer to their maximum biting capacity than males. Body condition of both sexes and reproductive output of females increased with relative head width, indicating that fitness is tightly linked to head size and bite force. 4Our study provides strong evidence that reproductive role contributes to sexual dimorphism in trophic morphology. Our findings should apply to any animal in which energy intake is limited by trophic morphology. [source] Relationships between head size, bite force, prey handling efficiency and diet in two sympatric lacertid lizardsFUNCTIONAL ECOLOGY, Issue 6 2002D. Verwaijen Summary 1Relationships between morphology, bite force capacity, prey handling efficiency and trophic niche were explored in two sympatric species of lacertid lizards, Podarcis melisellensis (Braun 1877) and Lacerta oxycephala Duméril & Bibron 1839. 2Head shape showed little variation, but head size (absolute and relative to snout,vent length, SVL) differed between species and sexes. Males have larger heads than females, both absolute and relative to their SVL. In absolute terms, male P. melisellensis have larger heads than male L. oxycephala, but the reverse case was true for the females. Relative to SVL, L. oxycephala have larger heads than P. melisellensis. 3Bite force capacity was estimated by having the lizards bite on two metal plates, connected to a piezoelectric force transducer. Differences in maximal bite force between species and sexes paralleled differences in absolute head size. Differences in body size and head size explain the higher bite force of males (compared with females), but not the higher bite force of P. melisellensis (compared with L. oxycephala). Among individual lizards, bite force correlated with body size and head size. 4Prey handling efficiency, estimated by the time and number of bites needed to subdue a cricket in experimental conditions, also showed intersexual and interspecific variation. This variation corresponded to the differences in maximal bite capacity, suggesting that bite force is a determining factor in prey handling. Among individual lizards, both estimates of handling efficiency correlated with maximal bite force capacity. 5Faecal pellet analyses suggested that in field conditions, males of both sexes select larger and harder prey than females. There was no difference between the species. The proportion of hard-bodied and large-sized prey items found in a lizard's faeces correlated positively with its bite force capacity. 6It is concluded that differences in head and body size, through their effect on bite force capacity, may affect prey selection, either directly, or via handling efficiency. [source] Ultrasound parameters of bone health and related physical measurement indicators for the community-dwelling elderly in JapanGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 2 2007Wei Sun Deteriorated bone strength, which approaches osteoporosis, increases the likelihood that an elderly person will not able to live independently. However, few data are available pertaining to bone health and various physical objective indicators. The aim of the present study was to objectively assess bone health by quantitative ultrasound (QUS) and identify related physical measurement indicators among the elderly to aid the health promotion strategies in Japan. A cross-sectional study was performed at five welfare centers for the aged in the suburban area of Takatsuki city, Japan. Subjects comprised community-dwelling persons (134 men, 240 women) aged ,60 years and registered at welfare centers. QUS of the right-heel was conducted and recorded as stiffness index (SI). Physical factors including body components (fat and muscle mass), handgrip strength, daily physical activity, daily walking steps, maximum and usual walking speed and maximum bite force were examined objectively during the period May,June 2005. SI in women was lower than that in men (P < 0.01) and decreased significantly with age (P < 0.01). The SI correlated with six physical items in men and with all items in women. Multiple linear regression analysis showed that muscle mass, usual walking speed and maximum bite force were the strongest physical indicators of male SI; and muscle mass, maximum walking speed and maximum bite force were the strongest indicators of female SI. Muscle training, daily walking exercise and oral health care should be included in health promotion programs for the bone health of elderly women and men in Japan. [source] Phylogenetically structured variance in felid bite force: the role of phylogeny in the evolution of biting performanceJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2010M. SAKAMOTO Abstract A key question in evolution is the degree to which morphofunctional complexes are constrained by phylogeny. We investigated the role of phylogeny in the evolution of biting performance, quantified as bite forces, using phylogenetic eigenvector regression. Results indicate that there are strong phylogenetic signals in both absolute and size-adjusted bite forces, although it is weaker in the latter. This indicates that elimination of size influences reduces the level of phylogenetic inertia and that the majority of the phylogenetic constraint is a result of size. Tracing the evolution of bite force through phylogeny by character optimization also supports this notion, in that relative bite force is randomly distributed across phylogeny whereas absolute bite force diverges according to clade. The nonphylogenetically structured variance in bite force could not be sufficiently explained by species-unique morphology or by ecology. This study demonstrates the difficulties in identifying causes of nonphylogenetically structured variance in morphofunctional character complexes. [source] Connecting behaviour and performance: the evolution of biting behaviour and bite performance in batsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 11 2009S. E. SANTANA Abstract Variation in behaviour, performance and ecology are traditionally associated with variation in morphology. A neglected part of this ecomorphological paradigm is the interaction between behaviour and performance, the ability to carry out tasks that impact fitness. Here we investigate the relationship between biting behaviour and performance (bite force) among 20 species of ecologically diverse bats. We studied the patterns of evolution of plasticity in biting behaviour and bite force, and reconstructed ancestral states for behaviour and its plasticity. Both behavioural and performance plasticity exhibited accelerating evolution over time, and periods of rapid evolution coincided with major dietary shifts from insect-feeding to plant-feeding. We found a significant, positive correlation between behavioural plasticity and bite force. Bats modulated their performance by changing their biting behaviour to maximize bite force when feeding on hard foods. The ancestor of phyllostomids was likely a generalist characterized by high behavioural plasticity, a condition that also evolved in specialized frugivores and potentially contributed to their diversification. [source] Evolution of bite performance in turtlesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2002A. Herrel Abstract Among vertebrates, there is often a tight correlation between variation in cranial morphology and diet. Yet, the relationships between morphological characteristics and feeding performance are usually only inferred from biomechanical models. Here, we empirically test whether differences in body dimensions are correlated with bite performance and trophic ecology for a large number of turtle species. A comparative phylogenetic analysis indicates that turtles with carnivorous and durophagous diets are capable of biting harder than species with other diets. This pattern is consistent with the hypothesis that an evolutionary increase in bite performance has allowed certain turtles to consume harder or larger prey. Changes in carapace length tend to be associated with proportional changes in linear head dimensions (no shape change). However, maximum bite force tends to change in proportion to length cubed, rather than length squared, implying that changes in body size are associated with changes in the design of the jaw apparatus. After the effect of body size is accounted for in the analysis, only changes in head height are significantly correlated with changes in bite force. Additionally, our data suggest that the ability to bite hard might trade off with the ability to feed on fast agile prey. Rather than being the direct result of conflicting biomechanical or physiological demands for force and speed, this trade-off may be mediated through the constraints imposed by the need to retract the head into the shell for defensive purposes. [source] Musculoskeletal underpinnings to differences in killing behavior between North American accipiters (Falconiformes: Accipitridae) and falcons (Falconidae)JOURNAL OF MORPHOLOGY, Issue 3 2008Diego Sustaita Abstract Accipiters (Accipiter spp.) and falcons (Falco spp.) both use their feet to seize prey, but falcons kill primarily with their beaks, whereas accipiters kill with their feet. This study examines the mechanistic basis to differences in their modes of dispatching prey, by focusing on the myology and biomechanics of the jaws, digits, and distal hindlimb. Bite, grip, and distal hindlimb flexion forces were estimated from measurements of physiological cross-sectional area (PCSA) and indices of mechanical advantage (MA) for the major jaw adductors, and digit and tarsometatarsal flexors. Estimated bite force, total jaw adductor PCSA, and jaw MA (averaged over adductors) tended to be relatively and absolutely greater in falcons, reflecting their emphasis on biting for dispatching their prey. Differences between genera in estimated grip force, total digit flexor PCSA, and digit MA (averaged over inter-phalangeal joints and digits) were not as clear-cut; each of these parameters scaled positively allometric in accipiters, which may reflect the scaling of both prey size, and the proportion of mammalian prey consumed by this lineage with increasing body size. Estimated tarsometatarsal force was greater in falcons than in accipiters, due to their greater MA, which may reflect selection for incurring greater forces during prey strikes. Conversely, the comparatively lower tarsometatarsal MA in accipiters reflects their capacity for greater foot speed potentially necessary for grasping elusive prey. Thus, this study elucidates how differences in jaw and hindlimb musculoskeletal morphology of accipiters and falcons are reflected in differences in their killing modes, and through differences in their force-generating capacities. J. Morphol., 2008. © 2007 Wiley-Liss, Inc. [source] Subjective food intake ability in relation to maximal bite force among Korean adultsJOURNAL OF ORAL REHABILITATION, Issue 3 2009B. I. KIM Summary, This study examined the relationship between the subjective food intake of 30 food types and their objective bite force to identify the key food items within the 30 food types to achieve a greater depth of masticatory function in Korean adults. A sample of 308 (112 males and 196 females) adults over the age of 20 (average age, 48·6) was selected among patients who visited four dental hospitals in Seoul, Korea. The subjective masticatory ability was evaluated through an interview with food intake ability questionnaires consisting of 30 food types ranging from hard to soft using a five-step Likert scale. The objective maximal bite force was measured using pressure-sensitive films. The relationship between the food intake ability and bite force was analysed and stratified according to age, gender, number of post-canine teeth lost and several clinical oral health indicators. The key foods were selected using correlation and factor analysis. The subjective food intake ability between the 30 foods and key foods were tested by cluster and one-way anova analysis. The Pearson's correlation coefficient between food intake ability and bite force was 0·45 (P < 0·01). The five key food items selected were dried cuttlefish, raw carrot, dried peanut, cubed white radish kimchi and caramel. The correlation coefficient between the food intake ability and bite force of these items was 0·51 (P < 0·01). These results suggest that the subjective food intake ability using the 30 and five key foods can be used to evaluate the masticatory function in Korean adults. [source] Motor control of jaw muscles in chewing and in isometric biting with graded narrowing of jaw gapeJOURNAL OF ORAL REHABILITATION, Issue 10 2008P. A. PRÖSCHEL Summary, When a certain bite force is applied during unilateral chewing, the combination of jaw elevator muscle activities is different than when a comparable force is applied in unilateral isometric biting, e.g. on a force transducer. Masticatory peak force is generated in a nearly isometric phase of the chewing cycle, with a jaw gape of about 1 mm. In contrast, peak force in isometric biting on force measuring equipment usually induces jaw gapes of 6 mm or even more. Therefore, we tested the hypothesis that the jaw gape influences relative activation of elevator muscles in unilateral isometric biting. We further examined whether such influence could explain the different activity combinations of chewing and isometric biting. In thirty asymptomatic males, masseter and temporalis activities were recorded during intermittent isometric biting with jaw gapes of 6, 5, 3, 2 and 1 mm and during unilateral chewing. Activity combinations were described by working/balancing ratios and by temporalis/masseter ratios. With decreasing jaw gape the working/balancing ratio of the posterior temporalis decreased (P < 0·002) while that of the masseter increased (P < 0·001). Likewise, the temporalis/masseter ratio on the balancing side increased (P < 0·001). With decreasing jaw gape, activity ratios of isometric biting approached ratios of chewing. We conclude that: (i) relative jaw muscle activation in isometric biting depends on the jaw gape, (ii) relative muscle activation in chewing resembles relative activation of isometric biting with a small ,chewing-like' gape. This suggests that characteristic activity combinations in chewing are mainly a result of the approximately isometric contraction during the slow closing phase of the chewing cycle. [source] Functional status of masticatory system, executive function and episodic memory in older personsJOURNAL OF ORAL REHABILITATION, Issue 5 2008E. SCHERDER Summary, Findings from human experimental studies suggest that mastication positively influences cognitive function. The participants in those studies were relatively young. The goal of this study was to examine the relationship between the functional status of the masticatory system, episodic memory, and executive functions in elderly people. The participants, elderly people living independently at home, were divided into two groups. One group had a full complement of natural teeth (n = 19) and the other group had full dentures (n = 19). The functional status of the masticatory system was assessed by measuring mandibular excursions (i.e. the distances over which the mandible can move in the open, lateral, and forward directions), bite force, number of occluding pairs and complaints of the masticatory system (facial pain, headaches/migraine). Executive functions and episodic memory were assessed by neuropsychological tests. Backward regression analysis showed that only in the group of elderly people with full dentures, 22% of executive functions were predicted by complaints of the masticatory system and 19·4% of episodic memory was predicted by masticatory performance (composed of mandibular excursions and bite force). The conclusion of this study is that only in older persons with full dentures the relationship between mastication, episodic memory, and executive function becomes evident when the functional status of the masticatory system decreases. [source] Functional properties and regional differences of human masseter motor units related to three-dimensional bite forceJOURNAL OF ORAL REHABILITATION, Issue 10 2006T. OGAWA summary, The aim of this study was to estimate numerically the properties of masseter motor units (MUs) in relation to bite force magnitude and direction three-dimensionally and to confirm the hypothesis that the properties differ between different parts of the muscle by means of simultaneous recording of MU activity along with the MU location and three-dimensional (3D) bite force. The MU activity of the right masseter of four healthy men was recorded using a monopolar needle electrode in combination with a surface reference electrode. The location of the needle electrode was estimated stereotactically with the aid of magnetic resonance images and a reference plate. The magnitude and direction of the bite force was recorded with a custom-made 3D bite force transducer. The recorded bite force was displayed on a signal processor, which enabled the participant to adjust the direction and magnitude of the force. The activities of 65 masseter MUs were recorded. Each MU had specific ranges of bite force magnitude and direction (firing range: FR) and an optimum direction for recruitment (minimum firing threshold: MFT). There was a significant negative correlation between MFT and FR width. There were functional differences in MU properties between the superficial and deep masseter and between the superficial layer and deep layer in the superficial masseter. These results indicate that the contribution of human masseter motor units to bite force production is heterogeneous within the muscle. [source] Evaluation of maximal bite force in temporomandibular disorders patientsJOURNAL OF ORAL REHABILITATION, Issue 8 2006E. M. KOGAWA summary, The aim of this study was to evaluate the maximum bite force in temporomandibular disorders (TMD) patients. Two hundred women were equally divided into four groups: myogenic TMD, articular TMD, mixed TMD and control. The maximum bite force was measured in the first molar area, on both sides, in two sessions, using an IDDK (Kratos) Model digital dynamometer, adapted to oral conditions. Three-way anova, Tukey and Pearson correlation tests were used for the statistical analysis. The level of statistical significance was given when P , 0·05. The maximal bite force values were significantly higher in the control group than in the experimental ones (P = 0·00), with no significant differences between sides. Higher values were obtained in the second session (P = 0·001). Indeed, moderate negative correlation was found between age and bite force, when articular, mixed groups and all groups together were evaluated. A moderate negative correlation was also detected between TMD severity and the maximal bite force values for myogenic, mixed and all groups together. Authors concluded that the presence of masticatory muscle pain and/or TMJ inflammation can play a role in maximum bite force. The mechanisms involved in this process, however, are not well understood and deserve further investigation. [source] Biofeedback experiments with a submaximal jaw closing forceJOURNAL OF ORAL REHABILITATION, Issue 9 2002H. A. JAKSTAT Temporomandibular disorders are often accompanied with pain in the elevator muscles such as Mm. Masseterici and Mm. Temporales. In most experiments measurement of the closing force of these muscles was conducted with maximum bite force using EMG-devices. The experiments presented here were conducted using visual or audible biofeedback using force transducers. Visual feedback was presented on a computer screen using geometrical graphics. Audible feedback used two different signals, the frequency of these audio signals was modulated. The force was chosen between 5 and 30 N, which is near the forces actually used for chewing, but far less than maximum clenching force. The persons chosen for the experiments were divided into two groups: A group of younger persons did not wear any removable dentures, a group of older persons was wearing a total prosthesis of the upper and lower jaw. The results were processed statistically and graphically. The goal for the persons conducting the experiments was to select a closing force as near as possible to the given force which was shown using the biofeedback. The actual force used by the person was also shown. There were no statistically significant differences in the results using 5, 10 or 30 N as given force. Results showed that older edentulous patients can modulate the chewing force not as exactly as younger persons. Especially when using low closing forces (5 N) the edentulous persons showed less exactness in reaching the given closing force. The results of the experiments may be used to develop a test to determine the capability of older patients to perform exact closing (and chewing) movements. [source] Task-related electromyographic spectral changes in the human jaw musclesJOURNAL OF ORAL REHABILITATION, Issue 9 2002M. FARELLA The masticatory muscles differ in their fibre type composition. It can therefore be expected that their electromyographic (EMG) power spectra will differ during the performance of different bite force tasks. In the present study surface EMG activity was picked up from the masseter, and anterior and posterior temporalis muscles of nine adult subjects. Direction and magnitude of bite force were recorded using a three-component force transducer. Bite forces were exerted in five different directions: vertical, forward, backward, to the right and to the left of the subject. Non-vertical forces were kept at an angle of 15° from the vertical. Force levels of 25, 50, 100 and 200 N were exerted in each of the investigated directions. Data collected were analysed by means of a regression model for repeated measurements. It appeared that the mean power frequency (MPF) values of the posterior temporalis were significantly lower (P < 0·01) than those of the masseter and anterior temporalis. The MPF values of the masseter muscles decreased with an increase of bite force magnitude (P < 0·001) whereas the MPF values of the anterior and posterior temporalis did not change significantly (P > 0·05). The MPF values were significantly influenced by the direction of bite force (P < 0·01). The observed changes of MPF are possibly related to the recruitment of different fibre types and support the concept that the masticatory muscles behave heterogeneously. [source] Maximum bite force after the replacement of complete denturesJOURNAL OF ORAL REHABILITATION, Issue 9 2002F. MÜLLER In complete denture wearers the maximum bite force (MBF) is known to be considerably lower than in dentate people. Low MBF might therefore be an indication of poor denture fit but there is limited evidence on this. Therefore, the aim of the present study was to investigate whether MBF can be improved by the replacement of complete dentures for elderly people. Nine edentulous volunteers, average age 74·2 ± 5·5 years and average denture experience 19·4 ± 19·5 years (1,50 years), had replacement dentures made. Functional impressions were taken after border moulding using zinc oxide eugenol paste. After a rehearsal session, MBF was recorded with the old dentures, and with the new dentures immediately at insertion, at 3, 8 days, 2,3 weeks, 1, 2, 3 and 6,10 months post-insertion (p.i.). The MBF was recorded with the central bearing point method using a full-bridge strain gauge with a confirmed linearity from 1 to 1000 N and an accuracy of ±1 N. Data were analysed off-line using the mean of two peak readings per patient per session. The results indicate that MBF tended to be impaired when replacement dentures were first fitted (n.s.). However, this trend reversed during the first month p.i. for patients with a ,moderate' lower ridge resorption of Atwood (1963) grade 3 or 4 (n=5). Patients with more severe lower ridge resorption (Atwood grade 5 or 6; n=4) showed a significantly lower MBF over the entire observation period (P=0·05) and took longer to regain bite strength. Only patients with moderate bone resorption exceeded their pre-insertion level of MBF within the observation period of 6,10 months p.i. In contrast to one report of immediate improvement of MBF at insertion of a new or relined denture (Leyka et al., 2000), the present study suggests that, at least for elderly patients with severe bone resorption, delayed improvement of MBF should be expected. [source] The effects of isometric exercise on maximum voluntary bite forces and jaw muscle strength and enduranceJOURNAL OF ORAL REHABILITATION, Issue 10 2001D. J. Thompson The effects of training and exercise on the strength and endurance of limb muscles has been investigated extensively, but the response of the jaw muscles to exercise remains poorly known. The purpose of this study was to determine whether short-term isometric training increases strength and endurance of the superficial masseter and anterior temporalis muscles. Maximum and submaximum voluntary bite forces and corresponding electromyographic (EMG) activity were measured in 28 young adults, randomly divided into exercise and non-exercise (control) groups. Subjects in the exercise group performed isometric clenches against a soft maxillary splint for five 1-min sessions per day over a 6-week period. After exercise, subjects increased their maximum bite forces by 37%, but control subjects' bite forces also increased by 25%. After exercise, EMG levels per unit of bite force generally decreased, but similar decreases were also seen in the non-exercised controls. Masseter muscle activity levels during standardized 10-kg bites decreased after 6 weeks of exercise. Fatigue resistance increased significantly with exercise but did not differ significantly from control values after 6 weeks of exercise. The results of this study indicate that increases in maximum bite force can be easily produced with training, but that actual strengthening of the jaw muscles is more difficult to achieve. [source] Comparison of maximum bite force and dentate status between healthy and frail elderly personsJOURNAL OF ORAL REHABILITATION, Issue 6 2001H. Miura The purpose of the present study was to (1) determine the standard value of maximum bite force and to (2) compare the maximum bite force of the elderly between healthy and frail subjects. Subjects included 349 healthy elderly individuals (149 males, 200 females) and 24 frail elderly individuals (seven males, 17 females) ranging from 65 to 74 years of age. Maximum bite force was evaluated using a Dental Prescale systemÔ. The maximum bite force of the healthy subjects was significantly higher than that of the frail subjects in both males (P=0·020) and females (P=0·015). However, no significant difference was observed in the number of present teeth between the healthy and frail subjects. Median of maximum bite force in healthy males was 408,0 N, and that of the healthy females was 243,5 N. These results suggest that the frail elderly have latent bite force problems. [source] Quantitative study of bite force during sleep associated bruxismJOURNAL OF ORAL REHABILITATION, Issue 5 2001K. Nishigawa Nocturnal bite force during sleep associated bruxism was measured in 10 subjects. Hard acrylic dental appliances were fabricated for the upper and lower dentitions of each subject. Miniature strain-gauge transducers were mounted to the upper dental appliance at the right and left first molar regions. In addition, thin metal plates that contact the strain-gauge transducers were attached to the lower dental appliance. After a 1-week familiarization with the appliances, nocturnal bite force was measured for three nights at the home of each subject. From the 30 recordings, 499 bruxism events that met the definition criteria were selected. The above described system was also used to measure the maximum voluntary bite forces during the daytime. The mean amplitude of detected bruxism events was 22·5 kgf (s.d. 13·0 kgf) and the mean duration was 7·1 s (s.d. 5·3 s). The highest amplitude of nocturnal bite force in individual subjects was 42·3 kgf (15·6,81·2 kgf). Maximum voluntary bite force during the daytime was 79·0 kgf (51·8,99·7 kgf) and the mean ratio of nocturnal/daytime maximum bite force was 53·1% (17·3,111·6%). These data indicate that nocturnal bite force during bruxism can exceed the amplitude of maximum voluntary bite force during the daytime. [source] EFFECTS OF TEXTURAL CHANGES IN COOKED APPLES ON THE HUMAN BITE, AND INSTRUMENTAL TESTSJOURNAL OF TEXTURE STUDIES, Issue 5-6 2003HARUKA DAN A multiple-point sheet sensor was used to measure the bite force applied to raw and cooked apple specimens during the first bite with incisors. Wedge penetration tests were compared with human bite measurements on the same samples. The shape of the force-time curves during biting of cooked apples clearly differed from that for raw apples. The first curve of cooked apple biting became jagged, and the maximum force was reduced. The second curve emerged following the first curve in most subjects as a characteristic feature of cooked apple biting, whereas it was not seen in the bite curve of a raw specimen or the wedge penetration curve of a cooked specimen. The maximum force for tissue fracture decreased for cooked apples, but the duration of biting increased. No adequate counterparts for the impulse of biting could be obtained from the load-displacement curves of the wedge penetration tests. The existence of parameters only measurable by bite tests and not by mechanical tests suggests the necessity of directly measuring the human bite. [source] EFFECT OF SAMPLE THICKNESS ON THE BITE FORCE FOR APPLESJOURNAL OF TEXTURE STUDIES, Issue 3 2003HARUKA DAN The thickness of a piece of food and its mechanical properties affected the bite force. A multiple-point sheet sensor was used to measure the bite force applied to apple specimens of various thicknesses during the first bite with incisors. The results of wedge penetration tests on the same samples were compared with results of the bite measurements. The maximum bite force increased with the sample thickness for two apple varieties, though the maximum load measured by the wedge penetration test did not change. Therefore, it is important to consider that not only the mechanical properties but also the thickness of the sample affects the required bite force. [source] Implications of predatory specialization for cranial form and function in canidsJOURNAL OF ZOOLOGY, Issue 3 2009G. J. Slater Abstract The shape of the cranium varies widely among members of the order Carnivora, but the factors that drive the evolution of differences in shape remain unclear. Selection for increased bite force, bite speed or skull strength may all affect cranial morphology. We investigated the relationship between cranial form and function in the trophically diverse dog family, Canidae, using linear morphometrics and finite element (FE) analyses that simulated the internal and external forces that act on the skull during the act of prey capture and killing. In contrast to previous FE-based studies, we compared models using a newly developed method that removes the effects of size and highlights the relationship between shape and performance. Cranial shape varies among canids based on diet, and different selective forces presumably drove evolution of these phenotypes. The long, narrow jaws of small prey specialists appear to reflect selection for fast jaw closure at the expense of bite force. Generalists have intermediate jaw dimensions and produce moderate bite forces, but their crania are comparable in strength to those of small prey specialists. Canids that take large prey have short, broad jaws, produce the largest bite forces and possess very strong crania. Our FE simulations suggest that the remarkable strength of skulls of large prey specialists reflect the additional ability to resist extrinsic loads that may be encountered while struggling with large prey items. [source] | ||||||||||||||||