Home About us Contact
|
Home About us Contact | ||
|
|
||
Mastication
Terms modified by Mastication Selected AbstractsRHEOLOGY, FOOD TEXTURE AND MASTICATIONJOURNAL OF TEXTURE STUDIES, Issue 2 2004KATSUYOSHI NISHINARI ABSTRACT i [source] MULTIVARIATE ANALYSIS OF ELECTROMYOGRAPHIC (EMG) FREQUENCY SPECTRA TO CHARACTERISE MASTICATIONJOURNAL OF TEXTURE STUDIES, Issue 1 2002E.K. KEMSLEY ABSTRACT On five separate occasions, eight volunteers were asked to consume five edible gels with known texture and flavour properties. The electrical activity of their temporal and masseter muscles was recorded using electromyography (EMG). The electrode voltages were sampled at a rate of 1 kHz, starting when each volunteer began to masticate, and terminating when the volunteer indicated that the gel's flavour could no longer be perceived. Data from the mastication phase (first 20 s) were Fourier transformed to give a power spectrum in the frequency domain. Upon visual examination, the low frequency (< 10 Hz) region was found to contain spectral features that differ between volunteers, and the differences were generally consistent between sessions. Principal component analysis (PCA) supported this finding, by showing some clustering of the scores from different volunteers. However, when PCA was applied to the whole of the frequency range, the clustering became much more pronounced, indicating that higher frequencies also contribute to the distinction between volunteers. Clusters of readings from each volunteer were almost entirely separated using internally cross-validated canonical variate analysis (CVA), showing that each individual demonstrated characteristic and consistent mastication behaviour. Finally, a statistically significant association was found between the integrated power spectrum and the concentration of flavour compound in the gels; however, a similar relationship was discovered to exist between the flavour and the texture, as determined by cutting and compression. Hence, it was not possible to determine conclusively whether flavour alone has an effect on mastication characteristics. [source] Impaired mastication modifies the dynamics of bolus formationEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2006Claude Yven Mastication is a complex sensory-motor activity whereby a food product is transformed into a bolus. Consumers mainly perceive the sensory properties of the food during the intra-oral manipulation of the product. Consequently, the quality of the chewing process could have consequences on the perception of sensory properties and food choice. By focusing on meat products, this study aimed to analyze the influence of dental status on (i) dynamic adaptation of the chewing behavior (evaluated by electromyography) to the changes in texture during bolus formation and (ii) bolus properties (mechanical resistance and saliva incorporation) obtained from meat of different initial textures. Two groups of subjects (dentate subjects and denture wearers), known to present highly different chewing efficiency, were compared. For both groups, salivary flow rates were evaluated at rest and after stimulation by chewing (paraffin and meat). The salivary flow rates, assessed during chewing of a nonedible matrix (paraffin), were a good predictor of salivary flow rates induced by meat chewing for both groups of subjects. Salivary flow rates were not affected by the dental status. In contrast, the chewing behavior varied between groups. For denture wearers, the chewing pattern was strongly impaired and not adapted to the changes in meat structure during bolus formation. Denture wearers swallowed less fragmented boli than dentate subjects, but boli had a similar level of moisture for both groups of subjects. [source] Role of mastication and swallowing in the control of autonomic nervous activity for heart rate in different posturesJOURNAL OF ORAL REHABILITATION, Issue 12 2003E. Nitta summary, Mastication and swallowing increase the heart rate, and posture change and respiration also modulate the heart rate. To clarify the role of mastication and swallowing in the modulation of the autonomic nervous activity, we investigated how they interact with modulation of the heart rate by changing body positions and respiration in young healthy subjects. R,R intervals of electrocardiogram at rest were significantly changed with different body positions, compared with supine and standing. A net shortening by mastication of a chewing gum base was similar in various postures. Respiration induced a periodic change in the R,R intervals, depending on the body postures, but mastication did not markedly change them in each posture. Dry swallowing at rest and spontaneous swallowing during the mastication in the sitting position induced a similar transient shortening and suppressed the respiration-induced changes after the swallowing. The net transient shortening by dry swallowing at rest was similar in the different postures. These results suggest that signals from mastication and swallowing are summated with those from body positions and respiration for shortening the R,R intervals and that signals from swallowing suppress the respiration-induced periodic changes. [source] INFLUENCE OF MEASUREMENT TECHNIQUE, TEST FOOD, TEETH AND MUSCLE FORCE INTERACTIONS IN MASTICATORY PERFORMANCEJOURNAL OF TEXTURE STUDIES, Issue 1 2007FLÁVIA RIQUETO GAMBARELI ABSTRACT The role of texture and flavors in mastication is evident, but it is difficult to understand the interactions among food properties, oral physiology and perception. Mastication results from rhythmic mandibular movements. The teeth and masticatory muscles together form the mechanism whereby the food particles are fragmented. Masticatory performance and efficiency are defined as the capacity to reduce natural or artificial test materials during mastication, or by counting the number of strokes required to reduce food, respectively. Foods eaten for nourishment are very different from the industrial test materials used to quantify masticatory performance, thus, divergences could arise if the chewable material can or cannot be swallowed. This study presents a synopsis of masticatory performance methods, which is also related to muscle force, number of teeth and test chewing substance diversity. PRACTICAL APPLICATIONS The attributes of food, such as appearance, flavor and texture, as well as its interaction with saliva, number of teeth and conditions of the biomechanical system, influence the chewing process. In addition, reflex control and cognition can influence food perception and breakdown in the mouth. Food acceptability and choice depend on sensory properties of the food, which are perceived during chewing and swallowing. Masticatory performance and maximal occlusal force measurement may provide essential information that could lead to an appropriate diagnosis as regards masticatory function. Masticatory efficiency and performance can be measured to determine the individual's capacity to comminute a natural or a chewable test material. A material with uniform properties that can be reliably reproduced is essential to provide an ideal test bolus for the scientific study of masticatory effectiveness. [source] The Muscles of Mastication in the Caspian Seal (Phoca caspica)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2002H. Endo Summary The muscles of mastication and their related skull characters in the Caspian seal (Phoca caspica) were anatomically examined and compared with those of the Baikal (Phoca sibirica) and ringed (Phoca hispida) seals. A well-developed masseter muscle was observed in the Caspian seal, whereas the temporal muscle consisted of thin bundles. The skull of the Caspian seal possessed the same thin frontal bone and the dorso-ventrally developed zygomatic arch found in the Baikal seal that are required to install the enlarged eyeball into the orbit. The temporal bone was not robust, and the digastric muscle was well-developed in the ventral space of the auditory bulla. The present results suggest that the skull form of the Caspian seal has changed morphologically from its ringed seal-like ancestors, and suggest that the evolutionary strategy of the muscles of mastication in the Caspian seal is principally consistent with that of the Baikal seal. [source] Understory vegetation response to mechanical mastication and other fuels treatments in a ponderosa pine forestAPPLIED VEGETATION SCIENCE, Issue 2 2010Jeffrey M. Kane Abstract Questions: What influence does mechanical mastication and other fuel treatments have on: (1) canopy and forest floor response variables that influence understory plant development; (2) initial understory vegetation cover, diversity, and composition; and (3) shrub and non-native species density in a second-growth ponderosa pine forest. Location: Challenge Experimental Forest, northern Sierra Nevada, California, USA. Methods: We compared the effects of mastication only, mastication with supplemental treatments (tilling and prescribed fire), hand removal, and a control on initial understory vegetation response using a randomized complete block experimental design. Each block (n=4) contained all five treatments and understory vegetation was surveyed within 0.04-ha plots for each treatment. Results: While mastication alone and hand removal dramatically reduced the midstory vegetation, these treatments had little effect on understory richness compared with control. Prescribed fire after mastication increased native species richness by 150% (+6.0 species m2) compared with control. However, this also increased non-native species richness (+0.8 species m2) and shrub seedling density (+24.7 stems m2). Mastication followed by tilling resulted in increased non-native forb density (+0.7 stems m2). Conclusions: Mechanical mastication and hand removal treatments aided in reducing midstory fuels but did not increase understory plant diversity. The subsequent treatment of prescribed burning not only further reduced fire hazard, but also exposed mineral soil, which likely promoted native plant diversity. Some potential drawbacks to this treatment include an increase of non-native species and stimulation of shrub seed germination, which could alter ecosystem functions and compromise fire hazard reduction in the long-term. [source] Relationship of cranial robusticity to cranial form, geography and climate in Homo sapiensAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Karen L. Baab Abstract Variation in cranial robusticity among modern human populations is widely acknowledged but not well-understood. While the use of "robust" cranial traits in hominin systematics and phylogeny suggests that these characters are strongly heritable, this hypothesis has not been tested. Alternatively, cranial robusticity may be a response to differences in diet/mastication or it may be an adaptation to cold, harsh environments. This study quantifies the distribution of cranial robusticity in 14 geographically widespread human populations, and correlates this variation with climatic variables, neutral genetic distances, cranial size, and cranial shape. With the exception of the occipital torus region, all traits were positively correlated with each other, suggesting that they should not be treated as individual characters. While males are more robust than females within each of the populations, among the independent variables (cranial shape, size, climate, and neutral genetic distances), only shape is significantly correlated with inter-population differences in robusticity. Two-block partial least-squares analysis was used to explore the relationship between cranial shape (captured by three-dimensional landmark data) and robusticity across individuals. Weak support was found for the hypothesis that robusticity was related to mastication as the shape associated with greater robusticity was similar to that described for groups that ate harder-to-process diets. Specifically, crania with more prognathic faces, expanded glabellar and occipital regions, and (slightly) longer skulls were more robust than those with rounder vaults and more orthognathic faces. However, groups with more mechanically demanding diets (hunter-gatherers) were not always more robust than groups practicing some form of agriculture. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] The nitric oxide/cyclic guanosine monophosphate pathway modulates the inspiratory-related activity of hypoglossal motoneurons in the adult ratEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2008Fernando Montero Abstract Motoneurons integrate interneuronal activity into commands for skeletal muscle contraction and relaxation to perform motor actions. Hypoglossal motoneurons (HMNs) are involved in essential motor functions such as breathing, mastication, swallowing and phonation. We have investigated the role of the gaseous molecule nitric oxide (NO) in the regulation of the inspiratory-related activity of HMNs in order to further understand how neural activity is transformed into motor activity. In adult rats, we observed nitrergic fibers and bouton-like structures in close proximity to motoneurons, which normally lack the molecular machinery to synthesize NO. In addition, immunohistochemistry studies demonstrated that perfusion of animals with a NO donor resulted in an increase in the levels of cyclic guanosine monophosphate (cGMP) in motoneurons, which express the soluble guanylyl cyclase (sGC) in the hypoglossal nucleus. Modulators of the NO/cGMP pathway were micro-iontophoretically applied while performing single-unit extracellular recordings in the adult decerebrated rat. Application of a NO synthase inhibitor or a sGC inhibitor induced a statistically significant reduction in the inspiratory-related activity of HMNs. However, excitatory effects were observed by ejection of a NO donor or a cell-permeable analogue of cGMP. In slice preparations, application to the bath of a NO donor evoked membrane depolarization and a decrease in rheobase, which were prevented by co-addition to the bath of a sGC inhibitor. These effects were not prevented by reduction of the spontaneous synaptic activity. We conclude that NO from afferent fibers anterogradely modulates the inspiratory-related activity of HMNs by a cGMP-dependent mechanism in physiological conditions. [source] Discharge patterns of neurons in the medial pontobulbar reticular formation during fictive mastication in the rabbitEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2001K.-G. Westberg Abstract In this study, we describe functional characteristics of neurons forming networks generating oral ingestive motor behaviours. Neurons in medial reticular nuclei on the right side of the brainstem between the trigeminal and hypoglossal motor nuclei were recorded in anaesthetized and paralysed rabbits during two types of masticatory-like motor patterns induced by electrical stimulation of the left (contralateral) or right (ipsilateral) cortical masticatory areas. Sixty-seven neurons in nucleus reticularis pontis caudalis (nPontc), nucleus reticularis parvocellularis (nParv), and nucleus reticularis gigantocellularis (Rgc) were studied. These were classified as phasic or tonic depending on their firing pattern during the fictive jaw movement cycle. Phasic neurons located in the dorsal part of nPontc were active during the jaw opening phase, whilst those in dorsal nParv tended to fire during the closing phase. In most neurons, burst duration and firing frequency changed between the two motor patterns, but there was little change in phase of firing. Tonic units were mainly recorded in the ventral half of nPontc, and at the junction between Rgc and caudal nParv. Cortical inputs with short latency from the contralateral masticatory area were more frequent in phasic (82%) than tonic (44%) neurons, whilst inputs from the ipsilateral cortex were equal in the two subgroups (57% and 56%). Phasic neurons had significantly shorter mean contralateral than ipsilateral cortical latencies, whilst there was no difference among tonic neurons. Intra- and perioral primary afferent inputs activated both types of neurons at oligo-synaptic latencies. Our results show that subpopulations of neurons in medial reticular nuclei extending from the caudal part of the trigeminal motor nucleus to the rostral third of the hypoglossal motor nucleus are active during the fictive masticatory motor behaviour. Unlike masticatory neurons in the lateral tegmentum, the medial subpopulations are spatially organized according to discharge pattern. [source] Evidence for functional compartmentalization of trigeminal muscle spindle afferents during fictive mastication in the rabbitEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2000K. -G. Abstract Primary afferent neurons innervating muscle spindles in jaw-closing muscles have cell bodies in the trigeminal mesencephalic nucleus (NVmes) that are electrically coupled and receive synapses. Each stem axon gives rise to a peripheral branch and a descending central branch. It was previously shown that some spikes generated by constant muscle stretch fail to enter the soma during fictive mastication. The present study examines whether the central axon is similarly controlled. These axons were functionally identified in anaesthetized and paralysed rabbits, and tonic afferent firing was elicited by muscle stretch. For the purpose of comparison, responses were recorded extracellularly both from the somatic region and from the central axon in the lateral brainstem. Two types of fictive masticatory movement patterns were induced by repetitive stimulation of the masticatory cortex and monitored from the trigeminal motor nucleus. Field potentials generated by spike-triggered averaging of action potentials from the spindle afferents were employed to determine their postsynaptic effects on jaw-closing motoneurons. Tonic firing of 32% NVmes units was inhibited during the jaw-opening phase, but spike frequency during closing was almost equal to the control rate during both types of fictive mastication. A similar inhibition occurred during opening in 83% of the units recorded along the central branch. However, firing frequency in these was significantly increased during closing in 94%, probably because of the addition of antidromic action potentials generated by presynaptic depolarization of terminals of the central branch. These additional spikes do not reach the soma, but do appear to excite motoneurons. The data also show that the duration and/or frequency of firing during the bursts varied from one pattern of fictive mastication to another. We conclude that the central axons of trigeminal muscle spindle afferents are functionally decoupled from their stem axons during the jaw-closing phase of mastication. During this phase, it appears that antidromic impulses in the central axons provide one of the inputs from the masticatory central pattern generator (CPG) to trigeminal motoneurons. [source] Impaired mastication modifies the dynamics of bolus formationEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2006Claude Yven Mastication is a complex sensory-motor activity whereby a food product is transformed into a bolus. Consumers mainly perceive the sensory properties of the food during the intra-oral manipulation of the product. Consequently, the quality of the chewing process could have consequences on the perception of sensory properties and food choice. By focusing on meat products, this study aimed to analyze the influence of dental status on (i) dynamic adaptation of the chewing behavior (evaluated by electromyography) to the changes in texture during bolus formation and (ii) bolus properties (mechanical resistance and saliva incorporation) obtained from meat of different initial textures. Two groups of subjects (dentate subjects and denture wearers), known to present highly different chewing efficiency, were compared. For both groups, salivary flow rates were evaluated at rest and after stimulation by chewing (paraffin and meat). The salivary flow rates, assessed during chewing of a nonedible matrix (paraffin), were a good predictor of salivary flow rates induced by meat chewing for both groups of subjects. Salivary flow rates were not affected by the dental status. In contrast, the chewing behavior varied between groups. For denture wearers, the chewing pattern was strongly impaired and not adapted to the changes in meat structure during bolus formation. Denture wearers swallowed less fragmented boli than dentate subjects, but boli had a similar level of moisture for both groups of subjects. [source] Effects of masticatory muscle function on craniofacial morphology in growing ferrets (Mustela putorius furo)EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2003Tailun He Studying the effects of masticatory muscle function on craniofacial morphology in animal models with different masticatory systems is important for further understanding of related issues in humans. Forty 5-wk-old male ferrets were equally divided into two groups. One group was fed a diet of hard pellets (HDG) and the other group was fed the same diet but softened with water (SDG). Lateral and dorsoventral cephalograms were taken on each group after 6 months. Cephalometric measurements were performed by digital procedures. For SDG ferrets, the hard palate plane was more distant from the cranial base plane, and canines were more proclined compared with HDG ferrets. The SDG ferrets were also found to have smaller interfrontal and interparietal widths, and a slenderer zygomatic arch than the HDG ferrets. In the mandible, the coronoid process was generally shorter and narrower for the SDG ferrets. The effects of the altered masticatory muscle function on craniofacial morphology in growing ferrets seemed to differ from those previously reported in other animal models studied under similar experimental conditions. Such differences in the effects are presumably related to the differences in the mode of mastication, craniofacial anatomy and growth pattern in different animal models. [source] Variability of the masticatory process during chewing of elastic model foodsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2000Claire Lassauzay Many studies show a consistent individual chewing pattern; chewing being governed by a pattern generator and regulated by sensory feedback. The aim of this study was to determine the variation in chewing between sessions, replicates and subjects using elastic model foods. Fifteen young male subjects were selected to chew four food products differing in hardness. Four sessions were performed at 1-wk intervals for each subject and, within each session, the four model foods were presented 3 times each. Jaw movement was recorded simultaneously with masseter and anterior temporalis electromyographic activities. Several chewing characteristics increased progressively from one session to the next; the largest increase occurred from the 1st to the 2nd session, with little difference between the last two sessions. No differences were observed between the samples of the same food product within a session. As mastication progressed, the amplitude and speed of the cycles and the muscular work decreased progressively. The first cycle appeared to be very different from the subsequent for all parameters except for occlusal duration. Thus, under our experimental conditions, the origin and amount of variation in chewing patterns were identified and provide information to improve the accuracy and comparability of results in studies of mastication. [source] Modularity of the rodent mandible: Integrating bones, muscles, and teethEVOLUTION AND DEVELOPMENT, Issue 6 2008Miriam Leah Zelditch Summary Several models explain how a complex integrated system like the rodent mandible can arise from multiple developmental modules. The models propose various integrating mechanisms, including epigenetic effects of muscles on bones. We test five for their ability to predict correlations found in the individual (symmetric) and fluctuating asymmetric (FA) components of shape variation. We also use exploratory methods to discern patterns unanticipated by any model. Two models fit observed correlation matrices from both components: (1) parts originating in same mesenchymal condensation are integrated, (2) parts developmentally dependent on the same muscle form an integrated complex as do those dependent on teeth. Another fits the correlations observed in FA: each muscle insertion site is an integrated unit. However, no model fits well, and none predicts the complex structure found in the exploratory analyses, best described as a reticulated network. Furthermore, no model predicts the correlation between proximal parts of the condyloid and coronoid, which can exceed the correlations between proximal and distal parts of the same process. Additionally, no model predicts the correlation between molar alveolus and ramus and/or angular process, one of the highest correlations found in the FA component. That correlation contradicts the basic premise of all five developmental models, yet it should be anticipated from the epigenetic effects of mastication, possibly the primary morphogenetic process integrating the jaw coupling forces generated by muscle contraction with those experienced at teeth. [source] Release of cell contents and comminution of particles of perennial ryegrass herbage during ingestion by dairy cows fed indoors or grazingGRASS & FORAGE SCIENCE, Issue 3 2006A. Boudon Abstract The effect of feeding indoors fresh perennial ryegrass vs. grazing on ingestive behaviour, release of cell contents and comminution of particles during ingestion, as well as on gas production of ingested boli fermented in vitro, was studied. Indoor feeding and grazing were compared using four dairy cows according to a triple reversal design with six periods. Chemical and morphological composition of the ingested herbage was similar for both indoor feeding and grazing treatments. The intake rate was markedly higher indoors compared with grazing [52·1 vs. 22·9 g dry matter (DM) min,1] with heavier boli and less saliva added per gram of DM intake. The proportions of intracellular nitrogen and chlorophyll released during mastication after ingestion of herbage fed indoors were lower, and the median size of the particles in the boli was larger (5·97 vs. 4·44 mm) compared with grazing. As a result, the rate of gas production in vitro was also lower for herbage fed indoors compared with grazing (0·423 vs. 0·469 mL min,1 g,1 incubated DM). Indoor feeding or grazing may have limited consequences in vivo on the kinetics of availability of nutrients for micro-organisms in the rumen, because the consequences of the more extensive physical damage suffered by herbage ingested at grazing could be compensated by a lower intake rate. [source] The antioxidant capacity of salivaJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 3 2002M. Battino Abstract Background/aims: Saliva, a heterogeneous fluid comprising proteins, glycoproteins, electrolytes, small organic molecules and compounds transported from the blood, constantly bathes the teeth and oral mucosa. It acts as a cleansing solution, an ion reservoir, a lubricant and a buffer. In addition to its other host-protective properties, saliva could constitute a first line of defence against free radical-mediated oxidative stress, since the process of mastication and digestion of ingested foods promotes a variety of reactions, including lipid peroxidation. Moreover, during gingival inflammation, gingival crevicular fluid flow increases the change of saliva composition with products from the inflammatory response; this, in turn, could have some rôle in controlling and/or modulating oxidative damages in the oral cavity. This is the reason why the antioxidant capacity of saliva has led to increasing interest, and the development of techniques suitable for saliva antioxidant evaluation. Materials and Methods: Here, we review the current peer-reviewed literature concerning the nature and characteristics of free radicals, reactive oxygen species, oxidants, pro-oxidants and antioxidants in saliva, especially pro-oxidant and antioxidant features, as well as current methods for assessing the antioxidant capacity of saliva. Results and Conclusions: In the last decade, several methods have been developed for assaying the antioxidant activity of saliva, indicating an increasing interest of researchers and clinicians. Unfortunately, systematic studies of saliva are still lacking, even in healthy populations. Zusammenfassung Hintergrund/Zielsetzung: Der Speichel, eine heterogene Flüssigkeit bestehend aus Proteinen, Glykoproteinen, Elektrolyten, kleinen organischen Molekülen und Bestandteilen aus dem Blut, umspült andauernd Zähne und Mundschleimhäute. Er wirkt als Reinigungslösung, Reservoir für Ionen, als Schmiermittel und als Puffer. Zusätzlich zu seinen anderen Abwehreigenschaften könnte der Speichel eine erste Verteidigungslinie gegen durch freie Radikal verursachten oxidativen Stress sein, da der Prozess der Nahrungszerkleinerung und -verdauung eine Vielzahl von Reaktionen auslöst einschließlich der Lipidperoxidation. Darüber hinaus erhöht sich während gingivaler Entzündung der Sulkusflüssigkeitsfluss und verändert die Zusammensetzung des Speichels durch Produkte der Entzündungsreaktion. Dies könnte eine Rolle bei der Kontrolle und/oder Beeinflussung oxidativer Schäden in der Mundhöhle spielen. Dies sind die Gründe dafür, warum die antioxidative Kapazität des Speichels zu einem wachsenden Interesse und zur Entwicklung von Techniken geführt hat, die die Bestimmung der antioxidativen Kapazität des Speichels erlauben. Material und Methoden: In diesem Übersichtsartikel wird die akutelle Literatur hinsichtlich der Natur und Charakteristika freier Radikale, reaktiver Sauerstoffarten, Oxidantien, Prooxidantien und Antioxidantien im Speichel, insbesondere Eigenschaften der Pro- und Antioxidantien sowie aktuelle Methoden zur Bestimmung der antioxidative Kapazität des Speichels, dargestellt. Ergebnisse/Schlussfolgerungen: Während des vergangenen Jahrzehnts wurden mehrere Methoden für die Bestimmung der antioxidativen Kapazität des Speichels entwickelt, was für ein wachsendes wissenschaftliches und klinisches Interesse spricht. Unglücklicherweise fehlen noch systematische Studien zum Speichel selbst für gesunde Kollektive. Résumé Origine/but: La salive, fluide hétérogène constitué de protéines, de glycoprotéines, d'électrolytes, de petites molécules organiques et de composés transportés du sang, baigne constamment les dents et les muqueuses buccales. Elle agit comme une solution nettoyante, comme réservoir d'ions, comme lubrifiant et comme tampon. En plus de ces propriétés protectrices pour l'hôte, la salive pourrait constituer une première ligne de défense contre le stress oxydatif dû aux radicaux libres puisque le processus de mastication et de digestion des nourritures ingérées induit une variété de réactions, telle la peroxidation des lipides. De plus, pendant l'inflammation gingivale, le flux gingival sulculaire augmente et altère la compositon de la salive par les produits de la réponse inflammatoire. Cela, à son tour, pourrait avoir un rôle dans le contrôle ou la modulation des dommages oxydatifs dans la cavité buccale. C'est la raison pour laquelle la capacité antioxydant de la salive a connu un intérêt croissant et le développement de techniques fiables pour l'évaluation des antioxydants salivaires. Matériaux et méthodes: Ici, nous passons en revue de façon concise la littérature actuelle concernant la nature et les caractéristiques des radicaux libres, des espèces réactives à l'oxygène, des oxydants, des pro-oxydants et des antioxydants dans la salive, particulièrement les caractéristiques pro-oxydante et antioxydante et les méthodes actuelles de mise en évidence des capacités antioxydantes de la salive. Résultats et conclusions: Lors de la dernière décade, plusieurs méthodes ont été développées pour tester l'activité antioxydante de la salive, ce qui prouve un intérêt grandissant des chercheurs et des cliniciens. Malheureusement, des études systématiques sur la salive manquent même pour les populations saines. [source] Deformation of nasal septal cartilage during masticationJOURNAL OF MORPHOLOGY, Issue 10 2009Ayman A. Al Dayeh Abstract The cartilaginous nasal septum plays a major role in structural integrity and growth of the face, but its internal location has made physiologic study difficult. By surgically implanting transducers in 10 miniature pigs (Sus scrofa), we recorded in vivo strains generated in the nasal septum during mastication and masseter stimulation. The goals were (1) to determine whether the cartilage should be considered as a vertical strut supporting the nasal cavity and preventing its collapse, or as a damper of stresses generated during mastication and (2) to shed light on the overall pattern of snout deformation during mastication. Strains were recorded simultaneously at the septo-ethmoid junction and nasofrontal suture during mastication. A third location in the anterior part of the cartilage was added during masseter stimulation and manipulation. Contraction of jaw closing muscles during mastication was accompanied by anteroposterior compressive strains (around ,1,000 ,,) in the septo-ethmoid junction. Both the orientation and the magnitude of the strain suggest that the septum does not act as a vertical strut but may act in absorbing loads generated during mastication. The results from masseter stimulation and manipulation further suggest that the masticatory strain pattern arises from a combination of dorsal bending and/or shearing and anteroposterior compression of the snout. J. Morphol., 2009. © 2009 Wiley-Liss, Inc. [source] The effects of manual therapy and exercise directed at the cervical spine on pain and pressure pain sensitivity in patients with myofascial temporomandibular disordersJOURNAL OF ORAL REHABILITATION, Issue 9 2009R. LA TOUCHE Summary, No studies have investigated the effects of the treatments directed at the cervical spine in patients with temporomandibular disorders (TMD). Our aim was to investigate the effects of joint mobilization and exercise directed at the cervical spine on pain intensity and pressure pain sensitivity in the muscles of mastication in patients with TMD. Nineteen patients (14 females), aged 19,57 years, with myofascial TMD were included. All patients received a total of 10 treatment session over a 5-week period (twice per week). Treatment included manual therapy techniques and exercise directed at the cervical spine. Outcome measures included bilateral pressure pain threshold (PPT) levels over the masseter and temporalis muscles, active pain-free mouth opening (mm) and pain (Visual Analogue Scale) and were all assessed pre-intervention, 48 h after the last treatment (post-intervention) and at 12-week follow-up period. Mixed-model anovas were used to examine the effects of the intervention on each outcome measure. Within-group effect sizes were calculated in order to assess clinical effect. The 2 × 3 mixed model anova revealed significant effect for time (F = 77·8; P < 0·001) but not for side (F = 0·2; P = 0·7) for changes in PPT over the masseter muscle and over the temporalis muscle (time: F = 66·8; P < 0·001; side: F = 0·07; P = 0·8). Post hoc revealed significant differences between pre-intervention and both post-intervention and follow-up periods (P < 0·001) but not between post-intervention and follow-up period (P = 0·9) for both muscles. Within-group effect sizes were large (d > 1·0) for both follow-up periods in both muscles. The anova found a significant effect for time (F = 78·6; P < 0·001) for changes in pain intensity and active pain-free mouth opening (F = 17·1; P < 0·001). Significant differences were found between pre-intervention and both post-intervention and follow-up periods (P < 0·001) but not between the post-intervention and follow-up period (P > 0·7). Within-group effect sizes were large (d > 0·8) for both post-intervention and follow-up periods. The application of treatment directed at the cervical spine may be beneficial in decreasing pain intensity, increasing PPTs over the masticatory muscles and an increasing pain-free mouth opening in patients with myofascial TMD. [source] Distance of the contact glide in the closing masticatory stroke during mastication of three types of foodJOURNAL OF ORAL REHABILITATION, Issue 8 2009B. RILO Summary, This study was designed to characterize the distance of the contact glide in the closing masticatory stroke in healthy adult subjects, during chewing of three types of food (crustless bread, chewing gum and peanuts). Mandibular movements (masticatory movements and laterality movements with dental contact) were registered using a gnathograph (MK-6I Diagnostic System) on the right and left side during unilateral chewing of the three food types. Length of dental contact was measured in masticatory cycle, which is defined as where the terminal part of the chewing cycles could be superimposed on the pathways taken by the mandible during lateral excursions with occlusal contacts. The length of dental contact during mastication of chewing gum is 1·46 ± 1 mm, during chewing of soft bread is 1·38 ± 0·7 mm and during chewing of peanuts is 1·45 ± 0·9 mm. There is no significant difference in the lengths of dental contact during mastication of three types of foods that enable direct tooth gliding. [source] Influence of gum-chewing on the haemodynamics in female masseter muscleJOURNAL OF ORAL REHABILITATION, Issue 4 2009N. ABE Summary, Blood flow in active skeletal muscles provides energy substrate, oxygen and reduction of excessive heat and metabolic by-products. Although cyclic jaw motions such as those during mastication and speech articulation are the primitive oro-facial functions, possible effects of the cyclic muscle contractions on the intramuscular haemodynamics of the jaw muscles remains scarcely known. We investigated the masseteric haemodynamics during and after gum-chewing. Ten healthy female adults participated in the study. Electromyography, kinetics of masseter muscle oxygenation, electrocardiogram and blood pressure were recorded simultaneously. The subjects were asked to perform gum-chewing and cyclic jaw motion without gum bolus (empty-chewing task). The haemodynamics parameters were compared between the two experimental conditions. During gum-chewing task, deoxygenated haemoglobin and sympathetic nerve activity increased, while tissue blood oxygen saturation decreased. Blood pressure and parasympathetic nerve activity did not change. The overall behaviour of haemodynamic parameters during empty-chewing task was similar to that observed during gum-chewing task. However, the latency periods from the end of chewing until significant changes in the haemodynamic parameters were notably shorter (P < 0·05) in gum-chewing task as compared with those associated with empty-chewing task. The duration of the changes was shorter with empty-chewing than with gum-chewing. Fluctuations in masseter muscle haemodynamics associated with chewing jaw movement differed depending on the level of muscle contraction during movement. The differences became statistically significant immediately after the commencement of chewing and after the cessation movement. During the chewing movement, automatic nerve activities increased in response to the level of muscle contraction during movement. [source] Relationship between pattern of masticatory path and state of lateral occlusal contactJOURNAL OF ORAL REHABILITATION, Issue 4 2009H. SHIGA Summary, The purpose of this study is to clarify whether the state of occlusal contact on lateral excursion is related to the pattern of masticatory movement path. The masticatory movement during mastication of softened chewing gum and the occlusal contact on lateral sliding of the mandible by 1 mm (L1), 2 mm (L2) and 3 mm (L3) were recorded in 50 healthy subjects. The path of masticatory movement was classified into one of seven patterns. The number of teeth involved in the occlusal contact in each pattern was investigated and compared among different lateral occlusal positions. The occlusal contact was then classified into 15 types based on one or a combination of the following four regions; incisal region, canine region, premolar region and molar region. The number of occlusal contact type for each pattern was investigated and compared among patterns. The number of teeth involved in occlusal contact decreased as the degree of lateral excursion increased, and significant differences were observed among the lateral occlusal positions (P < 0·001). The occlusal contact tended to decrease in the molar region and increase in the canine or premolar regions as the degree of the lateral excursion increased. When comparing among patterns, significant differences were observed at L2 and L3 (L2; P < 0·001, L3; P = 0·030) but not at L1 (P = 0·318). The difference was remarkable at L2. It was suggested that the state of occlusal contact at L2 and L3, particularly at L2 was related to the masticatory path pattern. [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] Automatic regulation of occlusal force because of hardness-change of the bite objectJOURNAL OF ORAL REHABILITATION, Issue 1 2008A. SHIMADA Summary, It is considered that the information of chewed food, such as size and texture, is important for smooth mastication. In this study, we analysed aspects of the control of occlusal force, by experimentally reproducing situations in which the hardness of food changed unpredictably during mastication, using a device that utilized a 3-sectioned urethane rubber piece with different hardness values. Seven healthy subjects were instructed to perform repetitive jaw open,close movements paced by a metronome (1·0 Hz) and to maintain constant occlusal force throughout the trial. Using the device, the following parameters were measured during the first to fifth strokes after changing the hardness, peak value, impulse, duration and time to peak of occlusal force in the waveform of occlusal force, cycle time of open,close jaw movements, jaw gape and maximum speed in the closing phase in the waveform of the jaw movements. Each parameter value was statistically analysed by anova with Fisher's least significant difference method (P < 0·05). Peak occlusal force, impulse and jaw gape were significantly affected by the change in hardness, while an increase in hardness caused increases in the values for peak occlusal force and impulse against the instruction, after which those values remained constant while the subjects occluded the same level of hardness. Our results indicate that the level of the resulting occlusal force is regulated automatically according to the hardness of the chewed food. We concluded that occlusal force was adapted for efficient mastication when the hardness of foods changes unpredictably. [source] Validation of video versus electromyography for chewing evaluation of the elderly wearing a complete dentureJOURNAL OF ORAL REHABILITATION, Issue 8 2007E. NICOLAS summary, Chewing efficiency may affect nutritional status in the elderly. Many elderly patients are complete denture wearers, and often present cognitive problems. Those two factors make evaluation of mastication difficult with experimental methods. Analysis of video recording may be a simple way to routinely assess chewing parameters. This study aimed at validating several parameters of video evaluation versus electromyography (EMG), which is considered the ,gold standard'. The design was a prospective randomized study, carried out at the Faculty of Dentistry, University of Auvergne, Clermont-Ferrand, France. Twelve complete denture wearers chewed four model foods differing in hardness. Sessions were videotaped and EMG recordings were registered. Mastication time, number of masticatory cycles and cleaning time were recorded simultaneously by video and EMG. Two investigators independently analyzed the videos twice, in random order. Evaluation of criterion validity: a positive video/EMG correlation was found for the parameters ,chewing time' (0·89, Pearson) and ,number of masticatory cycles' (0·94, Spearman), whereas no statistical difference was found between these two EMG and video variables (t -test). Inter and intra-rater reliability gave a positive intraclass coefficient (ICC) for duration of mastication (0·86,0·98), number of masticatory cycles (0·90,0·97) and cleaning time (0·90,0·98). Discriminatory ability was studied using anova (P = 0·01): variation was significant in masticatory duration (F = 10), number of masticatory cycles (F = 10) and cleaning time (F = 4). Video may be a useful assessment tool in prosthetic rehabilitation and can be applied to help choose the type of food (solid, semi-liquid or liquid) to administer to dependent persons, particularly those suffering from dementia. [source] Masticatory problems after balloon compression for trigeminal neuralgia: a longitudinal study1JOURNAL OF ORAL REHABILITATION, Issue 2 2007S. R. D. T. DE SIQUEIRA summary, Idiopathic trigeminal neuralgia (ITN) is a chronic neuropathic pain that affects the masticatory system. The objective of this study was to identify orofacial pain and temporomandibular characteristics, including temporomandibular disorder (TMD), in a sample of 105 ITN patients treated with compression of the trigeminal ganglion. The evaluations occurred before, 7, 30 (1 month), 120 (3 months) and 210 days (7 months) after surgery. The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD), the Clinical Questionnaire (EDOF-HC) and Helkimo Indexes were used. Findings before neurosurgery were used as control for parameters. McNemar test and variance analysis for repetitive measurements were used for statistical analysis; 45·3% of the edentulous patients presented severe dental occlusion index; numbness was an important masticatory complaint in 42·6%; mastication became bilateral, but its discomfort continued during all period; headache and body pain reduced after surgery; TMD, present in 43·8% before surgery, increased but normalized after 7 months; jaw mobility compromise was still present, but daily activities improved after 7 months. We concluded that: (i) ITN relief reduced headache, body pain, depression and unspecific symptoms; and (ii) TMD before surgery and at 7 months suggests that this may be a contributory factor to patients' pain complaints. [source] Sensory-motor function of human periodontal mechanoreceptors,JOURNAL OF ORAL REHABILITATION, Issue 4 2006M. TRULSSON summary, Natural teeth are equipped with periodontal mechanoreceptors that signal information about tooth loads. In the present review, the basic force-encoding properties of human periodontal receptors will be presented along with a discussion about their likely functional role in the control of human mastication. Microneurographic recordings from single nerve fibres reveal that human periodontal receptors adapt slowly to maintained tooth loads. Most receptors are broadly tuned to the direction of force application, and about half respond to forces applied to more than one tooth. Populations of periodontal receptors, nevertheless, reliably encode information about both the teeth stimulated, and the direction of forces applied to the individual teeth. Information about the magnitude of tooth loads is made available in the mean firing rate response of periodontal receptors. Most receptors exhibit a markedly curved relationship between discharge rate and force amplitude, featuring the highest sensitivity to changes in tooth load at very low force levels (below 1 N for anterior teeth and 4 N for posterior teeth). Thus, periodontal receptors efficiently encode tooth load when subjects contact and gently manipulate food using the teeth. It is demonstrated that signals from periodontal receptors are used in the fine motor control of the jaw and it is clear from studies of various patient groups (e.g. patients with dental implants) that important sensory-motor functions are lost or impaired when these receptors are removed during the extraction of teeth. [source] Preliminary rapport on head posture and muscle activity in subjects with class I and IIJOURNAL OF ORAL REHABILITATION, Issue 11 2005I. C. GADOTTI summary, Forward head posture may cause alterations in the stomatognathic system, including changes in the muscle activity of the masticatory muscles and dental occlusion alterations. Considering the need for further understanding of the relationship between the stomatognathic system and the cervical region, the purpose of this study was to analyse the head posture and the electromyographic (EMG) activity of the anterior portion of temporal and masseter muscles bilaterally among bruxist's subjects with different dental occlusion classifications using the Angle method. The study consisted of 20 female volunteers, between the ages of 17 and 27 years. They were separated into two groups (class I and class II occlusions) according to a dentist-performed evaluation. An assessment of forward head posture was conducted using a photographic technique (angular calculus) combined with a clinical analysis. In the EMG analyses, active differential surface electrodes (Ag) were utilized and were placed bilaterally on the belly of masseter and temporal muscles, perpendicular to the muscles fibres. The EMG signal recorded during bilateral isotonic mastication, was presented using the Root Mean Square and was processed by Matlab software. The results indicated that the EMG responses of temporal and masseter muscles tend to be modified by occlusion alteration class II. Subjects with class II occlusion tended to present more occurrence of forward head posture with alterations in the muscle activity pattern between masseter and temporal muscles. [source] Condylar resorption during active orthodontic treatment and subsequent therapy: report of a special case dealing with iatrogenic TMD possibly related to orthodontic treatmentJOURNAL OF ORAL REHABILITATION, Issue 5 2005Y. H. SHEN summary, A 28-year-old female underwent orthodontic treatment for approximately 22 months. During the later stages of this treatment, the patient reported right shoulder and neck-muscle pain. In addition, temporomandibular joint disorder (TMD) with a ,clicking' sound during mastication commenced 5 months prior to treatment completion. Specific medication to deal with these symptoms was suggested by medical specialists, as were some stress-relief methods, although the pain still progressed, and subsequent clinical and radiographical examinations were undertaken by another orthodontist. Right mandibular condylar resorption was observed from both the panorex and temporomandibular joint (TMJ) radiographs. No clinical signs of rheumatic disease were observed, although bruxism was noted. Following the termination of the orthodontic treatment by the second practitioner, the patient was treated with splint therapy 1 month subsequent to which, the previous symptoms of pain in the shoulder and neck, and the clicking sound during mastication had subsided. During the 14-month period of splint therapy and follow-up, new bone growth in the right condyle was observed from radiographs. [source] Chewing side preference as a type of hemispheric lateralityJOURNAL OF ORAL REHABILITATION, Issue 5 2004J. Nissan summary, Chewing side preference is a factor that could effect prosthodontic treatment. The purpose of this study was to determine whether chewing side was another type of hemispheric lateralization comparable with footedness, handedness, eyedness and earedness. Chewing side preference was tested in 189 subjects of whom 84 were partially edentulous, 98 had a full compliment of dental units (81 included implant-supported restoration restoring the missing teeth and 17 with fully intact dentitions), and seven were fully edentulous, restored with complete dentures. Laterality tests were carried out for the first cycle of mastication, handedness, footedness, earedness and eyedness and patient questionnaire. Most patients preferred chewing on the right side (78,3%) and were right sided. Chewing side preference correlated with other tested hemispherical lateralities. Missing teeth, occlusion type, lateral guidance, gender, implant-supported restorations and complete dentures do not affect the side preference for chewing. This presents a strong argument that chewing side preference is centrally controlled and provides food for thought regarding its significance in prosthodontics. [source] | ||||||||||||||||