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Masseter
Terms modified by Masseter Selected AbstractsEating and rumination behaviour in Brahman grade cattle and crossbred water buffalo fed on high roughage dietANIMAL SCIENCE JOURNAL, Issue 5 2010Renato S. A. VEGA ABSTRACT The purpose of this study is to compare feeding and other behavior and nutrient digestibility of tropical grade Brahman (body weight (BW) = 231 kg ± 12.4; n = 3) and crossbred water buffalo (BW = 300 kg ± 13.9; n = 3). This experiment on digestibility and measures of muscles of mastication utilized one-way, and animal behavior two-way, analysis of variance, respectively. Two video camcorders were installed in each pair of buffalo and Brahman for 24 h period programmed on the 107th, 109th and 111th days of the digestion trials. Frequency and duration of feeding, meal intake, rumination, bolus, chews, drinking, defecating, standing and lying were recorded daily. Muscle diameter of Digastricus, Masseter and Pterygoid and different regions of the tongue were sampled and measured under light microscope using a standard micrometer. Buffalo obtained significantly higher intake of dry matter, roughage, crude protein, total digestible nutrient and metabolized energy than Brahman. This was supported by longer meal duration (P , 0.05), and shorter meal breaks (P , 0.05) of buffalo than Brahman. The diameter of the muscles for mastication was bigger (P , 0.05) in buffalo than in Brahman, which is indicative of stronger chewing ability. Briefly, lesser and slower chewing action; higher intake of roughage and crude protein; and longer resting behavior of crossbred water buffalo than Brahman are all indicative of better digestive and metabolic performance of the buffalo under high roughage feeding conditions. [source] Daily jaw muscle activity in freely moving rats measured with radio-telemetryEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2007Nobuhiko Kawai The jaw muscle activity of rats has been investigated for specific tasks. However, the daily jaw muscle use remains unclear. The purpose of the present study was to examine daily jaw muscle activity, and its variability over time, in the rat (n = 12) by the use of radio-telemetry. A telemetric device was implanted for the continuous recording of masseter muscle and digastric muscle activity. Daily muscle use was characterized by calculating the total time that each muscle was active (duty time), the number of bursts, and the average length of bursts. All parameters were estimated for activities exceeding various levels (5,90%) of the day's peak activity. Daily muscle use remained constant for 4 wk. At the low-activity level, the duty time and burst number of the digastric muscle were significantly (P < 0.01) higher than those of the masseter muscle, whereas the opposite was true at the high-activity level (P < 0.05). No significant intermuscular correlation was observed between the number of bursts of the masseter and digastric muscles, but the interindividual variation of both muscles changed, depending on the level of activation. These findings suggest that the masseter muscle and the digastric muscle show a differential active pattern, depending on the activity level. [source] No effect of experimental occlusal interferences on pressure pain thresholds of the masseter and temporalis muscles in healthy womenEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2006A. Michelotti It has been suggested that occlusal interferences may lead to pain and tenderness of the masticatory muscles. Tender jaw muscles are more sensitive to pressure pain, as assessed by means of pressure algometry. We tested the effects of occlusal interferences on the pressure pain threshold of the jaw muscles by means of a double-blind randomized crossover experiment carried out on 11 young healthy females. Golden strips were glued either to an occlusal contact area (active interference) or to the vestibular surface of the same tooth (dummy interference) and left for 8 d each. Pressure pain thresholds of the masseter and anterior temporalis muscles were assessed under interference-free, dummy-interference and active-interference conditions. The results indicated that the application of an active occlusal interference, as used in this study, did not influence significantly the pressure pain thresholds of these muscles in healthy individuals. [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] Effects of prolonged gum chewing on pain and fatigue in human jaw musclesEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2001Mauro Farella Gum chewing has been accepted as an adjunct to oral hygiene, as salivary stimulant and vehicle for various agents, as well as for jaw muscle training. The aim of this study was to investigate the effects of prolonged gum chewing on pain, fatigue and pressure tenderness of the masticatory muscles. Fifteen women without temporomandibular disorders (TMD) were requested to perform one of the following chewing tasks in three separate sessions: chewing a very hard gum, chewing a soft gum, and empty-chewing with no bolus. Unilateral chewing of gum or empty chewing was performed for 40 min at a constant rate of 80 cycles/min. In each session, perceived muscle pain and masticatory fatigue were rated on visual analog scales (VAS) before, throughout, and after the chewing task. Pressure pain thresholds (PPTs) of masseter and anterior temporalis muscles were assessed before and immediately after the chewing tasks, and again after 24 h. The VAS scores for pain and fatigue significantly increased only during the hard gum chewing, and after 10 min of recovery VAS scores had decreased again, almost to their baseline values. No significant changes were found for PPTs either after hard or soft gum chewing. The findings indicate that the jaw muscles recover quickly from prolonged chewing activity in subjects without TMD. [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] Adaptation of normal and hypofunctional masseter muscle after bite-raising in growing ratsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2000Andrea Bresin The aim of this study was to analyze the effects of prolonged muscular elongation induced by bite-raising on the length of the muscle belly, sarcomeres and aponeurosis of the anterior deep masseter in the growing rat. Another aim was to determine the role of different functional conditions of this muscle in the adaptation process. Ninety-six young male rats were split into two groups: one was fed a hard diet and the other a soft diet to develop different functional capacities in the masticatory muscles. After 2 wk, half of the rats in both groups were fitted with an appliance that raised the bite by 2 mm. The measurements on the muscles were performed in situ. The insertion of the appliance stretched the anterior masseter muscle. After 4 wk, the vertical dentoskeletal dimension, the muscle belly, and the sarcomeres showed no difference in length among the groups. However, the aponeurosis was longer in the rats wearing the appliance compared to the controls, and among the bite block groups it was longer in the rats fed a hard diet. Length adaptation occurred in the aponeurosis. Clinically this may imply a need for reactivation of functional appliances to increase their efficiency, at a rate possibly depending on masseter muscles functional condition. [source] Masticatory muscle architecture in the Laotian rock rat Laonastes aenigmamus (Mammalia, Rodentia): new insights into the evolution of hystricognathyJOURNAL OF ANATOMY, Issue 4 2009Lionel Hautier Abstract We present the first descriptive comparison of the skull, mandible and jaw muscles of the recently recovered Laotian rock rat Laonastes aenigmamus. The gross anatomy of five specimens captured in Laos and internal architecture of the jaw musculature were studied using dissections. The following muscles are described: temporal, masseter, pterygoids, digastric, mylohyoid, geniohyoid and transverse mandibular. The description of the masticatory apparatus of L. aenigmamus offers a rare opportunity to assess the order of establishment of the morphological characters during the evolution of Ctenohystrica. Striking convergences have occurred during the evolution of Diatomyidae and L. aenigmamus presents a unique combination of myological features that corresponds to a mixture of sciurognathous and hystricognathous characters. If L. aenigmamus is a sciurognathous rodent, we have to assume that it independently acquired a pars reflexa of the superficial masseter. We show for the first time that the development of this pars reflexa has occurred several times during the evolution of Ctenohystrica and can no longer be considered a synapomorphic feature of ,Hystricognathi'. These results bring new insights into the evolution of hystricognathy and have profound implications for the interpretation of the fossil record of early hystricognath rodents. [source] Regenerative potential of human skeletal muscle during agingAGING CELL, Issue 2 2002Valérie Renault Summary In this study, we have investigated the consequences of aging on the regenerative capacity of human skeletal muscle by evaluating two parameters: (i) variation in telomere length which was used to evaluate the in vivo turn-over and (ii) the proportion of satellite cells calculated as compared to the total number of nuclei in a muscle fibre. Two skeletal muscles which have different types of innervation were analysed: the biceps brachii, a limb muscle, and the masseter, a masticatory muscle. The biopsies were obtained from two groups: young adults (23 ± 1.15 years old) and aged adults (74 ± 4.25 years old). Our results showed that during adult life, minimum telomere lengths and mean telomere lengths remained stable in the two muscles. The mean number of myonuclei per fibre was lower in the biceps brachii than in the masseter but no significant change was observed in either muscle with increasing age. However, the number of satellite cells, expressed as a proportion of myonuclei, decreased with age in both muscles. Therefore, normal aging of skeletal muscle in vivo is reflected by the number of satellite cells available for regeneration, but not by the mean number of myonuclei per fibre or by telomere lengths. We conclude that a decrease in regenerative capacity with age may be partially explained by a reduced availability of satellite cells. [source] Comparative analysis of masseter fiber architecture in tree-gouging (Callithrix jacchus) and nongouging (Saguinus oedipus) callitrichidsJOURNAL OF MORPHOLOGY, Issue 3 2004Andrea B. Taylor Abstract Common marmosets (Callithrix jacchus) and cotton-top tamarins (Saguinus oedipus) (Callitrichidae, Primates) share a broadly similar diet of fruits, insects, and tree exudates. Common marmosets, however, differ from tamarins by actively gouging trees with their anterior teeth to elicit tree exudate flow. During tree gouging, marmosets produce relatively large jaw gapes, but do not necessarily produce relatively large bite forces at the anterior teeth. We compared the fiber architecture of the masseter muscle in tree-gouging Callithrix jacchus (n = 10) to nongouging Saguinus oedipus (n = 8) to determine whether the marmoset masseter facilitates producing these large gapes during tree gouging. We predict that the marmoset masseter has relatively longer fibers and, hence, greater potential muscle excursion (i.e., a greater range of motion through increased muscle stretch). Conversely, because of the expected trade-off between excursion and force production in muscle architecture, we predict that the cotton-top tamarin masseter has more pinnate fibers and increased physiological cross-sectional area (PCSA) as compared to common marmosets. Likewise, the S. oedipus masseter is predicted to have a greater proportion of tendon relative to muscle fiber as compared to the common marmoset masseter. Common marmosets have absolutely and relatively longer masseter fibers than cotton-top tamarins. Given that fiber length is directly proportional to muscle excursion and by extension contraction velocity, this result suggests that marmosets have masseters designed for relatively greater stretching and, hence, larger gapes. Conversely, the cotton-top tamarin masseter has a greater angle of pinnation (but not significantly so), larger PCSA, and higher proportion of tendon. The significantly larger PCSA in the tamarin masseter suggests that their masseter has relatively greater force production capabilities as compared to marmosets. Collectively, these results suggest that the fiber architecture of the common marmoset masseter is part of a suite of features of the masticatory apparatus that facilitates the production of relatively large gapes during tree gouging. J. Morphol. 261:276,285, 2004. © 2004 Wiley-Liss, Inc. [source] Neuromuscular function in healthy occlusionJOURNAL OF ORAL REHABILITATION, Issue 9 2010S. E. FORRESTER Summary, This study aimed to measure neuromuscular function for the masticatory muscles under a range of occlusal conditions in healthy, dentate adults. Forty-one subjects conducted maximum voluntary clenches under nine different occlusal loading conditions encompassing bilateral posterior teeth contacts with the mandible in different positions, anterior teeth contacts and unilateral posterior teeth contacts. Surface electromyography was recorded bilaterally from the anterior temporalis, superficial masseter, sternocleidomastoid, anterior digastric and trapezius muscles. Clench condition had a significant effect on muscle function (P = 0·0000) with the maximum function obtained for occlusions with bilateral posterior contacts and the mandible in a stable centric position. The remaining contact points and moving the mandible to a protruded position, whilst keeping posterior contacts, resulted in significantly lower muscle activities. Clench condition also had a significant effect on the per cent overlap, anterior,posterior and torque coefficients (P = 0·0000,0·0024), which describe the degree of symmetry in these muscle activities. Bilateral posterior contact conditions had significantly greater symmetry in muscle activities than anterior contact conditions. Activity in the sternocleidomastoid, anterior digastric and trapezius was consistently low for all clench conditions, i.e. <20% of the maximum voluntary contraction level. In conclusion, during maximum voluntary clenches in a healthy population, maximum masticatory muscle activity requires bilateral posterior contacts and the mandible to be in a stable centric position, whilst with anterior teeth contacts, both the muscle activity and the degree of symmetry in muscle activity are significantly reduced. [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] 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] Influence of playing wind instruments on activity of masticatory musclesJOURNAL OF ORAL REHABILITATION, Issue 9 2007A. GOTOUDA Summary, The aim of this study was to elucidate the influence of change in sound tone of playing wind instruments on activity of jaw-closing muscles and the effect of sustained playing for a long time on fatigue of jaw-closing muscles. Electromyograms (EMG) of 19 brass instrument players and 14 woodwind instrument players were measured while playing instruments in tuning tone and high tone and under other conditions. Nine brass instrument players and nine woodwind instrument players played instruments for 90 min. Before and after the exercise, power spectral analyses of EMG from masseter muscles at 50% of maximum voluntary clenching level were performed and mean power frequency (MPF) were calculated. Root mean square (RMS) of EMG in masseter and temporal muscles while playing were slightly larger than those at rest but extremely small in comparison with those during maximum clenching. Root mean square in orbicularis oris and digastric muscles were relatively large when playing instruments. In the brass instrument group, RMS in high tone was significantly higher than that in tuning tone in all muscles examined. In the woodwind instrument group, RMS in high tone was not significantly higher than that in tuning tone in those muscles. Mean power frequency was not decreased after sustained playing in both instrument groups. These findings indicate that contractive load to jaw-closing muscles when playing a wind instrument in both medium and high tone is very small and playing an instrument for a long time does not obviously induce fatigue of jaw-closing muscles. [source] Relation between cervical posture on lateral skull radiographs and electromyographic activity of masticatory muscles in caucasian adult women: a cross-sectional studyJOURNAL OF ORAL REHABILITATION, Issue 9 2007S. TECCO Summary, The aim of this study was to evaluate the association between cervical posture on lateral skull radiographs and surface electromyographic recordings (sEMG) of head and neck muscles. The sample comprised 40 Caucasian adult females, average age 26·8 (20,48); lateral skull radiographs were obtained in natural head position (mirror position). sEMG activity was bilaterally investigated for the following muscles: masseter, anterior temporalis, digastric, posterior cervical, sternocleidomastoid and upper and lower trapezius. All muscles were monitored at rest and during maximal voluntary clenching (MVC). A Pearson's correlation coefficient revealed significant correlations (P < 0·01) between cranio-cervical angulations and sEMG activity of masseter, digastric, lower trapezius, during MVC and anterior temporalis at rest. Significant correlations (P < 0·01) were also found between cervical lordosis angle and sEMG activity of masseter (during MVC) and lower trapezius (at rest). In view of transversal method, no conclusion was possible about the mechanism concerning these results. Future longitudinal studies should be directed to understand the extent of environmental and genotype influences by masticatory muscle activity on cervical posture. [source] Electromyographic activity of masticatory, neck and trunk muscles of subjects with different skeletal facial morphology , a cross-sectional evaluationJOURNAL OF ORAL REHABILITATION, Issue 7 2007S. TECCO summary, The electromyographic pattern activity of masticatory, neck and trunk muscles was assessed using surface electromyography (sEMG) in 60 Caucasian adult females (20 subjects in skeletal class I, 20 subjects in skeletal class II and 20 subjects in skeletal class III), classified on the base of their skeletal class (ANB angle), corrected on the base of maxillary and mandibular rotations. The sEMG activity was recorded at mandibular rest position and during maximal voluntary clenching. At mandibular rest position, the sEMG activities of masseter and anterior temporal muscles were significantly higher in class III subjects than in class I and class II subjects, that showed no significant difference between them. Then, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups. During maximal voluntary clenching, no significant difference was observed in the sEMG activity of masticatory muscles among the three considered groups. However, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups, which showed no significant difference between them. In conclusion, the skeletal class seems to affect the sEMG pattern activity of masticatory, neck and trunk muscles. [source] Changes in jaw muscle EMG activity and pain after third molar surgeryJOURNAL OF ORAL REHABILITATION, Issue 1 2007M. ERNBERG summary, Limited jaw-opening capacity is frequently encountered following third molar surgery and may impair function. The aim of this study was to investigate the electromyographic (EMG) activity in jaw muscles after third molar surgery to obtain more insight into the mechanisms of restrictions in jaw opening. Twenty subjects were examined before, 24 h and 1 week after surgery. Ten healthy controls were subjected to the same examination at two different occasions for intersession variability. The EMG activity of the masseter and anterior digastricus muscles was recorded at different jaw positions and during maximum voluntary clenching. Pain intensity was assessed at rest and during movements. The EMG activity in the jaw muscles increased with opening level (P < 0·01), but did not change after surgery. In contrast, the EMG activity during clenching was decreased in all muscles after surgery (P < 0·05). The pain intensity after surgery increased with jaw opening level (P < 0·001), but was in general not correlated to EMG level. Pain intensity during clenching was increased after surgery (P < 0·001), but not correlated to EMG level. The EMG activity did not change between visits in the control group. In conclusion, the results indicate that third molar surgery does not influence the EMG activity in the masseter and anterior digastricus muscles during various levels of static jaw opening, but decreases the EMG activity during clenching. However, these changes are not influenced by pain intensity. The results have implications for the understanding of the phenomenon of trismus. [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] The influence of age and dental status on elevator and depressor muscle activityJOURNAL OF ORAL REHABILITATION, Issue 2 2006I. Z. ALAJBEG summary, The objective of this study was to determine whether the muscle activity at various mandibular positions is affected by age and dental status. Thirty edentulous subjects (E), 20 young dentate individuals (G1) and 20 older dentate individuals (G2) participated in this study. Surface electromyographic (EMG) recordings were obtained from the anterior temporal (T), masseter (M) and depressor muscles (D). Muscle activity was recorded during maximal voluntary contraction (MVC), maximal opening (Omax) and in six different mandibular positions. One way anova and the Bonferroni tests were used to determine the differences between groups. Significant differences between the three tested groups were found at MVC and Omax for all examined muscles (P < 0·001). The differences in muscle activity in dentate subjects of different age were found in protrusion for depressor muscles (P < 0·05) and in lateral excursive positions for the working side temporal (P < 0·05) and non-working side masseter and depressor muscle (P < 0·05). There was a significant effect regarding the presence of natural teeth or complete dentures in protrusion and maximal protrusion for all muscles (P < 0·05) and in lateral excursive positions for non-working side temporal (P < 0·05) and working side masseter muscle (P < 0·05). Muscle activity at various mandibular positions depends greatly on the presence of the prosthetic appliance, as edentulous subjects had to use higher muscle activity levels (percentages of maximal EMG value) than age matched dentate subjects in order to perform same mandibular movement. Different elevator muscles were preferentially activated in the edentulous subjects when compared with dentate group in lateral excursive positions of the mandible. The pattern of relative muscle activity was not changed because of ageing. [source] Surface EMG of jaw-elevator muscles and chewing pattern in complete denture wearersJOURNAL OF ORAL REHABILITATION, Issue 12 2005M. G. PIANCINO summary, The aim of this study was to investigate the adaptation process of masticatory patterns to a new complete denture in edentulous subjects. For this purpose, muscle activity and kinematic parameters of the chewing pattern were simultaneously assessed in seven patients with complete maxillary and mandibular denture. The patients were analysed (i) with the old denture, (ii) with the new denture at the delivery, (iii) after 1 month and (iv) after 3 months from the delivery of the new denture. Surface electromyographic (EMG) signals were recorded from the masseter and temporalis anterior muscles of both sides and jaw movements were tracked measuring the motion of a tiny magnet attached at the lower inter-incisor point. The subjects were asked to chew a bolus on the right and left side. At the delivery of the new denture, peak EMG amplitude of the masseter of the side of the bolus was lower than with the old denture and the masseters of the two sides showed the same intensity of EMG activity, contrary to the case with the old denture. EMG amplitude and asymmetry of the two masseter activities returned as with the old denture in 3 months. The EMG activity in the temporalis anterior was larger with the old denture than in the other conditions. The chewing cycle width and lateral excursion decreased at the delivery of the new denture and recovered after 3 months. [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] Non-invasive assessment of motor unit anatomy in jaw-elevator musclesJOURNAL OF ORAL REHABILITATION, Issue 10 2005T. CASTROFLORIO summary The estimation of fibre length in jaw-elevator muscles is important for modelling studies and clinical applications. The objective of this study was to identify, from multi-channel surface EMG recordings, the main innervation zone(s) of the superficial masseter and anterior temporalis muscles, and to estimate the fibre length of these muscles. Surface EMG signals were collected from 13 subjects with a 16-electrode linear array. The innervation zones of the masseter and anterior temporalis were identified and their variability intra- and inter-subject outlined. More than one main innervation zone location was identified in the masseter of all subjects and in the temporalis anterior of 12 subjects. Average estimated fibre lengths, for the right (left) side, were (mean ± SD) 27·3 ± 2·4 mm (27·0 ± 1·7 mm) and 25·9 ± 2·3 mm (26·6 ± 1·6 mm), for the superficial masseter and temporalis anterior muscle, respectively. The range of innervation zone locations was up to approximately 50% of the fibre length, both within and between subjects. Fibre length estimates well matched with published data on cadavers. It was concluded that multi-channel surface EMG provides important and reliable information on the anatomy of single motor units in jaw-elevator muscles. [source] The influence of altered occlusal guidance on condylar displacement during submaximal clenchingJOURNAL OF ORAL REHABILITATION, Issue 10 2005N. OKANO summary As cited in literatures, canine protected occlusion has a potential to reduce clenching induced temporomandibular joint loadings. However, these previous studies did not perform a control of the clenching level which differed with the depending occlusal conditions. This result may be due largely to an associated reduced jaw closing muscle activity. The present study has investigated clenching induced condylar displacements with controlled clenching level. Twenty healthy human subjects (15 males and five females with an average age of 26·5 years) volunteered to participate in this study. Metallic occlusal overlays were fabricated for the lower working side canine and overlaid to the second molar and the non-working side second molar in order to simulate a canine protected occlusion, group function occlusion and bilateral balanced occlusion. Electromyographic (EMG) activity from the bilateral masseter, anterior temporalis, and posterior temporalis was recorded. These signals were rectified, summarized, and presented to each subject using an oscilloscope screen. Using this visual feedback, subjects were asked to perform clenching tasks at a 50% level of maximal voluntary contraction exerted with simulated group function occlusion and three-dimensional condylar displacements were recorded. An experimental occlusal pattern that shows statistically significant affects on condylar displacements (anova: P < 0·001) was found. When compared with the simulated canine protected occlusion, the simulated group function occlusion caused smaller working side condylar displacement and the simulated bilateral balanced occlusion caused significantly smaller non-working side and working side condylar displacements. These results suggest that the increased working side tooth contacts have a potential to reduce working side joint loadings, and a balancing side contact has a potential to reduce non-working side joint loadings, under the laboratory condition where the clenching level is controlled. [source] Effects of a functional appliance on masticatory muscles of young adults suffering from muscle-related temporomandibular disordersJOURNAL OF ORAL REHABILITATION, Issue 6 2004T. Castroflorio summary, The aim of this study was to investigate the effects of an original orthodontic functional appliance [function generating bite for deep bite correction (FGB-D)] on masticatory muscle activity in subjects suffering from muscle-related temporomandibular disorders (TMD). Electromyographic (EMG) analysis was performed on 33 young adults (nine men, 24 women) to evaluate the contractile symmetry of the right and left masseter and anterior temporalis muscles. The subjects were divided into three groups: a muscle-related TMD group requiring orthodontic treatment for deep bite correction (three men, eight women) and treated with FGB-D; a muscle-related TMD group not requiring orthodontic treatment (three men, eight women) and treated with a Michigan occlusal splint; and a TMD-free group (three men, eight women) as a control group. Records were made by surface EMG of maximum voluntary teeth clenching, with and without the functional appliance or occlusal splint in place, before and after 12 months of therapy. A torque index was derived from the surface EMG recordings to estimate lateral displacement of the mandible. The results show that the FGB-D corrects the torque index and thus the lateral displacement of the mandible. [source] Time series analysis of jaw muscle contraction and tissue deformation during mastication in miniature pigsJOURNAL OF ORAL REHABILITATION, Issue 1 2004Z. J. Liu summary, Masticatory muscle contraction causes both jaw movement and tissue deformation during function. Natural chewing data from 25 adult miniature pigs were studied by means of time series analysis. The data set included simultaneous recordings of electromyography (EMG) from bilateral masseter (MA), zygomaticomandibularis (ZM) and lateral pterygoid muscles, bone surface strains from the left squamosal bone (SQ), condylar neck (CD) and mandibular corpus (MD), and linear deformation of the capsule of the jaw joint measured bilaterally using differential variable reluctance transducers. Pairwise comparisons were examined by calculating the cross-correlation functions. Jaw-adductor muscle activity of MA and ZM was found to be highly cross-correlated with CD and SQ strains and weakly with MD strain. No muscle's activity was strongly linked to capsular deformation of the jaw joint, nor were bone strains and capsular deformation tightly linked. Homologous muscle pairs showed the greatest synchronization of signals, but the signals themselves were not significantly more correlated than those of non-homologous muscle pairs. These results suggested that bone strains and capsular deformation are driven by different mechanical regimes. Muscle contraction and ensuing reaction forces are probably responsible for bone strains, whereas capsular deformation is more likely a product of movement. [source] Effects of interocclusal appliances on EMG activity during parafunctional tooth contactJOURNAL OF ORAL REHABILITATION, Issue 6 2003A. L. Roark summary, To test the hypothesis that a flat plane interocclusal appliance affects the electromyographic (EMG) activity of the temporalis and masseter muscles in pain-free individuals, maxillary splints were fabricated for 20 individuals who reported no history, signs or symptoms of myofascial pain or arthralgia as determined by two trained, independent examiners. Subjects were instructed to establish light tooth contact, maximum clenching, and moderate clenching with/without the splint in place (as determined by random assignment) while EMG data from the left and right temporalis and masseter muscles were recorded. A 5-min biofeedback training session to relax the masticatory muscles was followed by a repetition of the tooth contact/clenching tasks with/without the splint in place. With the splint in place, the activity of the temporalis muscles decreased for all tasks, significantly for the left and right temporalis under maximal clenching and for the right temporalis under moderate clenching. In contrast, the activity of the masseter muscles increased under light and moderate clenching (significantly for the left masseter under moderate clenching) and decreased slightly under maximal clenching. The effectiveness of interocclusal appliances may be due to mechanisms other than redistribution of adverse loading. [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] Differences in the fatigue of masticatory and neck muscles between male and femaleJOURNAL OF ORAL REHABILITATION, Issue 6 2002H. M. Ueda The purpose of this study was to investigate the nature of fatigue and recovery of masticatory and neck muscles and the differences between sexes in normal subjects during experimentally induced loading. Subjects consisted of eight males (mean age: 27·6 years) and eight females (mean age: 24·2 years) selected from the volunteers in the Faculty of Dentistry, Hiroshima University. The inclusion criteria for the subjects were as follows: (1) good general health, (2) normal horizontal and vertical skeletal relationships, (3) no severe malocclusions and (4) no complaints of temporomandibular disorders. Each subject was requested to bite an occlusal-force meter with 98, 196 and 294 N forces on the first molar region per side for 45 s. Activities of the masseter and sternocleidomastoid (SCM) muscles were recorded during these performances. Fatigue and recovery ratios were calculated with mean power frequency of power spectrum using a fast Fourier transform algorithm. Significant differences in the fatigue ratios between both sexes were found for the masseter muscle with 98, 196 and 294 N bite forces. Meanwhile, the SCM presented a significant difference between both sexes only at 98 N biting. Significant differences in the recovery ratios between both sexes were more prominent in the masseter muscle than in the SCM. These results suggest that the differences in muscle endurance between sexes may have some association with higher susceptibility of craniomandibular disorders in females than in males. [source] Comparison of phosphocreatine concentration in the human masseter and medial pterygoid muscles by 31P-CSIJOURNAL OF ORAL REHABILITATION, Issue 11 2001T. Kanayama The aim of this study is to compare phosphocreatine (PCr) concentrations of human masseter and medial pterygoid muscles by a recently developed localized magnetic resonance spectroscopy (MRS) method, chemical shift imaging (CSI). The characteristic spectra of phosphorous metabolites including PCr and ,-ATP from the superficial part of the masseter (SM) and the deep part of the masseter (DM) and the medial pterygoid muscles (MPt) from 11 volunteers, 20,27-year-old were obtained. The study clearly demonstrated higher PCr/,-ATP in the SM and MPt than in the DM both in mean values (P < 0·01) and in individual subjects. The results indicate that SM and MPt are power producers. There were no significant differences in the mean values of the PCr/,-ATP ratios in SM and MPt, however, the PCr/,-ATP ratios varied individually and the subjects could be divided into three distinct groups: values of MPt higher than SM (group A, 4 subjects); values of MPt almost equal to SM (group B, 3 subjects); and values of MPt lower than SM (group C, 4 subjects). There appears to be a close relationship between the PCr content as determined in the groups here and occlusal guidance. [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] | |||||||||||||