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1.
Arch Oral Biol ; 122: 105021, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33348206

RESUMEN

OBJECTIVE: The aim of this study was to analyze the function of the palatal muscles in vivo by real-time wireless electromyography in rats. The effects of palatal wounding were also analyzed. METHODS: Microelectrodes were implanted six rats; in the masseter muscle (two-rats) for comparison, in the unwounded soft palate (two-rats) and the soft palate that received a surgical wound (two-rats). Two weeks after implantation, a wound was made in the soft palate using a 1 mm biopsy-punch. Electromyographic measurements and video-recordings were taken weekly to monitor train-duration and peak-amplitude during eating, grooming and drinking. RESULTS: The train-duration of the masseter muscle during eating was 0.49 ±â€¯0.11 s (rat-1) and 0.56 ±â€¯0.09 s (rat-2), which was higher than during grooming. In the unwounded soft palate the train-duration during eating was 0.63 ±â€¯0.12 s (rat-1) and 0.69 ±â€¯0.069 s (rat-2), which was higher than during grooming and drinking. The peak-amplitude for eating in the normal soft palate before surgery was 0.31 ±â€¯0.001 mV (rat-1) and 0.33 ±â€¯0.02 mV (rat-2). This decreased to 0.23 ±â€¯0.03 mV and 0.25 ±â€¯0.11 mV respectively, after surgery. For drinking the peak-amplitude was 0.30 ±â€¯0.01 mV (rat-1) and 0.39 ±â€¯0.01 mV (rat-2) before surgery, which decreased to 0.23 ±â€¯0.09 mV and 0.20 ±â€¯0.14 mV respectively, after surgery. CONCLUSION: The reduced peak-amplitude suggests impaired soft palate function after wounding. This is the first study into the in vivo function of the soft palate after surgical wounding. This model will contribute to develop strategies to improve soft palate function in patients.


Asunto(s)
Músculos Palatinos/fisiología , Paladar Blando/fisiología , Heridas y Traumatismos/fisiopatología , Animales , Electromiografía , Músculo Masetero/fisiología , Paladar Blando/lesiones , Ratas
2.
PLoS One ; 15(12): e0243495, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33320876

RESUMEN

The maintenance of postural balance can be influenced by the lifestyle of a population. This study aimed to determine the electromyographic activity of the masseter and temporalis muscles during mandibular tasks and habitual and non-habitual chewing in indigenous individuals to reveal the differences among white Brazilian individuals. Sixty Brazilians (18 and 28 years) were divided into two groups: 30 Xingu indigenous individuals and 30 white Brazilian individuals, with 20 men and 10 women in each group. The individuals were assessed using the normalized electromyographic activity of mandibular tasks (rest, protrusion, right and left laterality) and electromyographic activity of masticatory cycles in habitual (peanuts and raisins) and non-habitual (Parafilm M) chewing. Data were analyzed using Student's t-test (p < .05). Comparisons between the groups demonstrated significant differences. Indigenous individuals group presented a decrease in the normalized electromyographic activity of the masticatory muscles during mandibular rest [right masseter (p = .002) and left masseter (p = .004) muscles]. There was increase in the normalized electromyographic activity during protrusion [left temporal (p = .03) muscle]. There was increase in the electromyographic activity during chewing: peanuts [right masseter (p = .001), left masseter (p = .001) and right temporal (p = .01) muscles], raisins [right masseter (p = .001), left masseter (p = .002), right temporal (p = .008), left temporal (p = .01) muscles] and Parafilm M [left masseter muscle (p = .05)]. From the findings of this study, we concluded that in the comparison between indigenous and white individuals, positive changes were observed in the electromyographic pattern of the masticatory muscles in the mandibular postural conditions, with greater masticatory efficiency in the indigenous group.


Asunto(s)
Electromiografía , Músculo Masetero/fisiología , Músculo Temporal/fisiología , Adolescente , Adulto , Brasil , Femenino , Humanos , Pueblos Indígenas , Masculino , Masticación/fisiología , Adulto Joven
3.
Niger J Clin Pract ; 23(8): 1095-1102, 2020 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-32788487

RESUMEN

Aims: The purpose of this study is to compare the thickness and elasticity of the masseter muscle before and after orthognathic surgery in patients with class III skeletal deformity and to investigate the relationship between the sonographic changes in the masseter muscle and the amount of mandibular setback. Subjects and Methods: The study group consisted of 14 patients with skeletal class III malocclusions who had orthognathic surgery. The control group consisted of 14 patients who had dental and skeletal class I occlusion. Muscle thickness measurements were performed with B-mode and high-frequency linear scanning probe of the ultrasound device. Elastography feature and muscle hardness ratio were obtained by applying compression and decompression on muscles at rest and during maximum contraction in the transverse plane. Patients were categorized into two groups according to the mandibular setback as <5 mm and ≥5 mm. Results: The masseter muscle thickness after surgery was found statistically increased bilaterally in both at rest and during contraction for the study group (P < 0.05). No difference was found between preoperative orthognathic measurements and postoperative measurements for elasticity index ratio measurements (P > 0.05). Conclusion: We believe that in the present study important findings have been emphasized for further research aiming to investigate the possible relationship between masticatory alterations and surgical outcomes after orthognathic surgery.


Asunto(s)
Diagnóstico por Imagen de Elasticidad/métodos , Maloclusión de Angle Clase III/cirugía , Mandíbula/diagnóstico por imagen , Músculo Masetero/diagnóstico por imagen , Procedimientos Quirúrgicos Ortognáticos/efectos adversos , Adulto , Cefalometría , Femenino , Humanos , Masculino , Músculo Masetero/fisiología , Resultado del Tratamiento , Ultrasonografía
4.
Br J Radiol ; 93(1111): 20200136, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32406752

RESUMEN

OBJECTIVE: The measurement of muscle area is routinely utilised in determining sarcopaenia in clinical research. However, this simple measure fails to factor in age-related morphometric changes in muscle quality such as myosteatosis. The aims of this study were to: firstly investigate the relationship between the masseter area (quantity) and density (quality), and secondly compare the prognostic clinical relevance of each parameter. METHODS: Cross-sectional CT head scans were reviewed for patients undergoing carotid endarterectomy. The masseter was manually delineated and the total masseter area (TMA) and the total masseter density (TMD) calculated. Measurements of the TMA were standardised against the cranial circumference. Observer variability in measurements were assessed using Bland-Altman plots. The relationship between TMA and TMD were evaluated using Pearson's correlation and linear regression analyses. The prognostic value of TMA and TMD were assessed using receiver operator curves and cox-regression analyses. RESULTS: In total, 149 patients who had undergone routine CT scans prior to a carotid endarterectomy were included in this study. No significant observer variations were observed in measuring the TMA, TMD and cranium circumference. There was a significant positive correlation between standardised TMA and TMD (Pearson's correlation 0.426, p < 0.001, adjusted R-squared 17.6%). The area under the curve for standardised TMA in predicting all-cause mortality at 30 days, 1 year and 4 years were higher when compared to TMD. Standardised TMA was only predictive of post-operative overall all-cause mortality (adjusted hazard ratio 0.38, 95% confidence interval 0.15-0.97, p = 0.043). CONCLUSION: We demonstrate a strong relationship between muscle size and density. However, the utilisation of muscle area is likely to be limited in routine clinical care. ADVANCES IN KNOWLEDGE: Our study supports the utilisation of muscle area in clinical sarcopaenia research. We did not observe any additional prognostic advantage in quantifying muscle density.


Asunto(s)
Endarterectomía Carotidea , Músculo Masetero/anatomía & histología , Anciano , Amaurosis Fugax/diagnóstico por imagen , Amaurosis Fugax/mortalidad , Amaurosis Fugax/cirugía , Trastornos Cerebrovasculares/diagnóstico por imagen , Trastornos Cerebrovasculares/mortalidad , Trastornos Cerebrovasculares/cirugía , Angiografía por Tomografía Computarizada , Estudios Transversales , Femenino , Fragilidad/diagnóstico por imagen , Fragilidad/mortalidad , Fragilidad/fisiopatología , Humanos , Masculino , Músculo Masetero/diagnóstico por imagen , Músculo Masetero/fisiología , Variaciones Dependientes del Observador , Complicaciones Posoperatorias/mortalidad , Pronóstico , Estudios Prospectivos , Tomografía Computarizada por Rayos X
5.
Artículo en Inglés | MEDLINE | ID: mdl-32466588

RESUMEN

AIM: This study investigated the effect of neuromuscular electrical stimulation (NMES) on masseter muscle thickness and maximal bite force among healthy community-dwelling elderly persons older than 65 years. MATERIALS AND METHODS: A total of 40 participants were randomly assigned to the experimental and placebo groups. In the experimental group, NMES was applied to both masseter muscles, and electrical signals were gradually increased until the participants felt a grabbing sensation (range 6.0-7.5 mA) in the masseter muscle. The placebo group, in contrast, underwent NMES in the same manner and procedure as the experimental group with less electrical intensity (0.5 mA). All interventions were administered five times a week for six weeks, 20 min per day. The outcomes were masseter muscle thickness assessed using ultrasound and maximal bite force using a bite force meter. The level of significance was set as p < 0.05. RESULTS: The experimental group showed a significant increase in both masseter muscle thickness and maximal bite force as compared with the placebo group (p = 0.002 and 0.019, respectively). Moreover, the degree of change in the masseter muscle thickness and maximal bite force significantly increased in the experimental and placebo groups (p < 0.001, both). CONCLUSIONS: This study demonstrated that NMES could be an effective modality for increasing masseter muscle thickness and maximal bite force in healthy older adults.


Asunto(s)
Fuerza de la Mordida , Vida Independiente , Músculo Masetero , Anciano , Método Doble Ciego , Estimulación Eléctrica , Electromiografía , Femenino , Humanos , Masculino , Músculo Masetero/fisiología
6.
Exp Brain Res ; 238(3): 565-574, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-31993683

RESUMEN

Aging is associated with physiological changes which can manifest as age-related slowing of voluntary movements. Dual-task conditions can magnify this slowing process in older adults. The current study describes healthy adult chewing patterns and examined effects of concurrent chewing on performance of simple reaction time (RT), finger tapping, and gait. Chewing rates were measured from electromyographic (EMG) activity from the masseter muscle. Stepping rates were calculated using accelerometers mounted on the lower trunk and leg. Tapping rates were collected using accelerometers secured to a fixed surface. Simple RT was attained from a purposely designed switch. Results demonstrated that older adults walked slower, tapped slower, and had slower reaction times compared to young individuals, however chew rates were similar. This dichotomy became more pronounced when motor tasks were performed at faster speeds, with the exception being chewing. Additionally, chewing altered performance of secondary motor tasks for all individuals. Strong coupling emerged between cyclical actions (i.e., chewing-gait and chewing-tapping), reflecting entrainment between the respective neural oscillators driving the actions. In contrast, RT responses slowed appreciably when chewing was performed concurrently, indicating an interference effect. Taken together, these results illustrate the contrasting effects of chewing on a secondary motor task and highlights bidirectional effects of dual tasking on performance.


Asunto(s)
Envejecimiento/fisiología , Marcha/fisiología , Desempeño Psicomotor/fisiología , Caminata/fisiología , Anciano , Cognición/fisiología , Femenino , Humanos , Masculino , Músculo Masetero/fisiología , Persona de Mediana Edad , Tiempo de Reacción , Adulto Joven
7.
Magn Reson Med Sci ; 19(3): 268-275, 2020 Aug 03.
Artículo en Inglés | MEDLINE | ID: mdl-31548479

RESUMEN

We analyzed the correlations between the T2 shift and integrated electromyographic (iEMG) values in the masseter and temporal muscles. Six healthy adults engaged in a clenching task over two durations at various bite forces. We evaluated the mean T2 shift per voxel and assessed their correlations with iEMG using a linear mixed model. The regression coefficients were different for each muscle type, similar for the left and right sides, and decreased upon doubling duration.


Asunto(s)
Electromiografía , Imagen por Resonancia Magnética , Músculo Masetero , Relajación Muscular/fisiología , Músculo Temporal , Adulto , Fuerza de la Mordida , Humanos , Músculo Masetero/diagnóstico por imagen , Músculo Masetero/fisiología , Músculo Temporal/diagnóstico por imagen , Músculo Temporal/fisiología
9.
Arch Oral Biol ; 108: 104548, 2019 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-31491685

RESUMEN

OBJECTIVE: To investigate the effects of liquid diet on the development of masseter muscle fibers and whether the changes in the masseter muscle can be recovered by chewing of solid diet. DESIGN: Masseter muscles from 40 rabbits (solid- and liquid-diet groups, n = 30; unweaned group, n = 5; recovery group, n = 5) were histochemically examined at 4, 12, 18, and 33 weeks after birth. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were distinguished via mATPase staining. Muscle fiber diameter and fiber type composition were measured and compared between groups. RESULTS: In the liquid diet group, the diameter of types IIAB (solid group: 81.7 µm, liquid group: 60.9 µm) and IIB (solid group: 89.3 µm, liquid group: 68.8 µm) and the fiber type composition of type I (solid group: 18.4%, liquid group: 9.6%) decreased significantly at 33 weeks of age. In the recovery group, the fiber type composition of type I fibers recovered to 16.5%, while no recovery of type IIAB (56.6 µm) and IIB (64.6 µm) fiber diameter was observed. CONCLUSIONS: Liquid diet caused atrophy of muscle fibers and an increase in the proportion of fast-twitch fibers. Although the diameter and ratio of slow-twitch fibers were recovered by chewing of solid diet, recovery was not observed for fast-twitch fibers. Our findings are relevant for dental medicine as it explored the possibility of masticatory muscle function recovery by hard food.


Asunto(s)
Dieta , Músculo Masetero , Masticación , Músculos Masticadores , Animales , Músculo Masetero/fisiología , Músculos Masticadores/fisiología , Fibras Musculares de Contracción Rápida , Fibras Musculares Esqueléticas , Conejos
10.
J Morphol ; 280(11): 1706-1713, 2019 11.
Artículo en Inglés | MEDLINE | ID: mdl-31513299

RESUMEN

Bite force is a measure of feeding performance used to elucidate links between animal morphology, ecology, and fitness. Obtaining live individuals for in vivo bite-force measurements or freshly deceased specimens for bite force modeling is challenging for many species. Thomason's dry skull method for mammals relies solely on osteological specimens and, therefore, presents an advantageous approach that enables researchers to estimate and compare bite forces across extant and even extinct species. However, how accurately the dry skull method estimates physiological cross-sectional area (PCSA) of the jaw adductor muscles and theoretical bite force has rarely been tested. Here, we use an ontogenetic series of southern sea otters (Enhydra lutris nereis) to test the hypothesis that skeletomuscular traits estimated from the dry skull method accurately predicts test traits derived from dissection-based biomechanical modeling. Although variables from these two methods exhibited strong positive relationships across ontogeny, we found that the dry skull method overestimates PCSA of the masseter and underestimates PCSA of the temporalis. Jaw adductor in-levers for both jaw muscles and overall bite force are overestimated. Surprisingly, we reveal that sexual dimorphism in craniomandibular shape affects temporalis PCSA estimations; the dry skull method predicted female temporalis PCSA well but underestimates male temporalis PCSA across ontogeny. These results highlight the importance of accounting for sexual dimorphism and other intraspecific variation when using the dry skull method. Together, we found the dry skull method provides an underestimation of bite force over ontogeny and that the underlying anatomical components driving bite force may be misrepresented.


Asunto(s)
Fuerza de la Mordida , Maxilares/anatomía & histología , Músculos Masticadores/anatomía & histología , Nutrias/anatomía & histología , Caracteres Sexuales , Animales , Fenómenos Biomecánicos , Femenino , Maxilares/fisiología , Masculino , Músculo Masetero/anatomía & histología , Músculo Masetero/fisiología , Músculos Masticadores/fisiología , Modelos Biológicos , Nutrias/fisiología , Cráneo/anatomía & histología , Cráneo/fisiología , Músculo Temporal/anatomía & histología , Músculo Temporal/fisiología
11.
Sensors (Basel) ; 19(15)2019 Aug 06.
Artículo en Inglés | MEDLINE | ID: mdl-31390830

RESUMEN

We intend to develop earphone-type wearable devices to measure occlusal force by measuring ear canal movement using an ear sensor that we developed. The proposed device can measure occlusal force during eating. In this work, we simultaneously measured the ear canal movement (ear sensor value), the surface electromyography (EMG) of the masseter muscle and the occlusal force six times from five subjects as a basic study toward occlusal force meter development. Using the results, we investigated the correlation coefficient between the ear sensor value and the occlusal force, and the partial correlation coefficient between ear sensor values. Additionally, we investigated the average of the partial correlation coefficient and the absolute value of the average for each subject. The absolute value results indicated strong correlation, with correlation coefficients exceeding 0.9514 for all subjects. The subjects showed a lowest partial correlation coefficient of 0.6161 and a highest value of 0.8286. This was also indicative of correlation. We then estimated the occlusal force via a single regression analysis for each subject. Evaluation of the proposed method via the cross-validation method indicated that the root-mean-square error when comparing actual values with estimates for the five subjects ranged from 0.0338 to 0.0969.


Asunto(s)
Conducto Auditivo Externo/fisiología , Electromiografía/métodos , Potenciales de Acción , Adulto , Fuerza de la Mordida , Femenino , Humanos , Masculino , Músculo Masetero/fisiología , Movimiento , Dispositivos Electrónicos Vestibles , Adulto Joven
12.
Acta Med Okayama ; 73(4): 357-360, 2019 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-31439959

RESUMEN

We investigated the characteristics of grouped discharge (GD) waveforms obtained from long-term masseter electromyogram (EMG) recording in 6 female temporomandibular disorder (TMD) patients with myofascial pain and 6 healthy females. The EMG measurement was performed from the morning of the experiment day until the subject woke up the next day. We observed a significantly larger number of GD waveforms in the TMD group compared to the control group (p=0.002). Our results indicate that the existence of GD waveforms in masseter EMGs might be a predictor of future TMD with myofascial pain.


Asunto(s)
Electromiografía/métodos , Músculo Masetero/fisiología , Trastornos de la Articulación Temporomandibular/fisiopatología , Anciano , Dolor Facial , Femenino , Humanos , Persona de Mediana Edad
13.
Exp Brain Res ; 237(10): 2559-2571, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31346648

RESUMEN

Since humans in daily life perform multiple motor behaviors that often involve the simultaneous activation of both jaw and tongue muscles, it is essential to understand the effects of combined orofacial sensorimotor tasks on plasticity in corticomotor pathways. Moreover, to establish novel rehabilitation programs for patients, it is important to clarify the possible interrelationships in corticomotor excitability between jaw and tongue motor control. The aim of this study was to examine the effect of a combination of a repetitive tooth bite task (TBT) and a repetitive tongue lift task (TLT) on corticomotor excitability of the tongue and jaw muscles as assessed by transcranial magnetic stimulation (TMS). Sixteen healthy individuals participated in three kinds of training tasks consisting of 41-min TBT, 41-min TLT, and 82-min TBT + TLT. Motor-evoked potentials (MEPs) from the tongue muscle, masseter muscle, and first dorsal interosseous muscle were measured before and after the training tasks. The amplitude of tongue MEPs after training with TLT and TLT + TBT, and masseter MEPs after training with TBT and TLT + TBT, were significantly higher than before training (P < 0.05). Tongue MEPs and masseter MEPs were significantly higher after TLT + TBT than after TBT or TLT (P < 0.05). The present results suggest that a task combining both jaw and tongue movement training is associated with a greater degree of neuroplasticity in the corticomotor control of jaw and tongue muscles than either task alone.


Asunto(s)
Potenciales Evocados Motores/fisiología , Músculos Faciales/fisiología , Corteza Motora/fisiología , Plasticidad Neuronal/fisiología , Adulto , Electromiografía/métodos , Femenino , Humanos , Masculino , Músculo Masetero/fisiología , Lengua/fisiología , Estimulación Magnética Transcraneal/métodos
14.
Clin Neurophysiol ; 130(9): 1511-1519, 2019 09.
Artículo en Inglés | MEDLINE | ID: mdl-31295720

RESUMEN

OBJECTIVE: To provide normative data for the Vestibulo-Masseteric Reflex (VMR) and Acoustic-Masseteric Reflex (AMR) in healthy subjects, stratified for age and gender. METHODS: A total of 82 healthy subjects (M:F 43:39, mean age 39.3 ±â€¯18.4 years, range 13-79 years) underwent recording of click-evoked VMR and AMR (0.1 ms duration, 5 Hz frequency) from active masseter muscles. Masseter responses to uni- and bilateral stimulation were recorded in a zygomatic and a mandibular configuration, according to the position of the reference electrode. Stimulation intensity curves were recorded for each reflex in ten subjects (mean age 20.7 ±â€¯8.1 years). Gender effect was investigated in 62 subjects and age effect was analyzed in six 10-subject groups aged from <25 to >65 years. Onset and peak latencies, interpeak intervals, raw and corrected amplitudes, latency and amplitude asymmetries were analyzed. RESULTS: VMR had a higher elicitation rate than AMR. For both reflexes, rates of elicitation, and corrected amplitudes were higher in the zygomatic configuration, and bilateral stimulation elicited larger responses. Best acoustic ranges of elicitation were 98-113 dB for AMR and 128-138 dB for VMR. Reflex latencies were shorter in females than males. Frequency and amplitude of VMR and AMR decreased substantially over 55 year olds. CONCLUSIONS: VMR and AMR can be easily performed in any clinical neurophysiology laboratory. SIGNIFICANCE: These reflexes can find application in the investigation of brainstem function in central neurological disorders.


Asunto(s)
Factores de Edad , Músculo Masetero/fisiología , Reflejo Acústico/fisiología , Factores Sexuales , Potenciales Vestibulares Miogénicos Evocados/fisiología , Adolescente , Adulto , Anciano , Tronco Encefálico/fisiología , Electrodos Implantados , Electromiografía/métodos , Femenino , Humanos , Masculino , Mandíbula , Persona de Mediana Edad , Adulto Joven , Cigoma
16.
Eur J Pain ; 23(9): 1619-1630, 2019 10.
Artículo en Inglés | MEDLINE | ID: mdl-31192515

RESUMEN

BACKGROUND: Quantification of motor-evoked potentials (MEPs) can contribute to better elucidate the central modulation of motor pathways in response to nociceptive inputs. The primary aim of this study was to assess the modulatory effects of nerve growth factor (NGF) injection on masseter corticomotor excitability. METHODS: The healthy participants of this randomized, double blind placebo-controlled experiment were assigned to have injected into the right masseter muscle either NGF (n = 25) or isotonic saline (IS, n = 17). The following variables were assessed at baseline and 48 hr after the injection: right masseter MEP amplitude and corticomotor mapping and clinical assessment of jaw pain intensity and function. Repeated Measures ANOVA was applied to the data. RESULTS: NGF caused jaw pain and increased jaw functional disability after the injection (p < 0.050). Also, the participants in the NGF group decreased the MEP amplitude (p < 0.001) but the IS group did not present any significant modulation after the injection (p > 0.050). Likewise, the participants in the NGF group reduced corticomotor map area and volume (p < 0.001), but the IS group did not show any significant corticomotor mapping changes after the injection (p > 0.050). Finally, there was a significant correlation between the magnitude of decreased corticomotor excitability and jaw pain intensity on chewing 48 hr after the NGF injection (r = -0.51, p = 0.009). CONCLUSION: NGF-induced masseter muscle soreness can significantly reduce jaw muscle corticomotor excitability, which in turn is associated with lower jaw pain intensity and substantiates the occurrence of central changes that most likely aim to protect the musculoskeletal orofacial structures. SIGNIFICANCE: Intramuscular administration of nerve growth factor into masseter muscle causes inhibitory corticomotor plasticity, which likely occurs to prevent further damage and seems associated with lower pain intensity on function.


Asunto(s)
Potenciales Evocados Motores/fisiología , Músculo Masetero/efectos de los fármacos , Músculo Masetero/fisiología , Factor de Crecimiento Nervioso/farmacología , Adulto , Método Doble Ciego , Electromiografía , Dolor Facial , Femenino , Humanos , Masculino , Mialgia
17.
Arch Oral Biol ; 105: 35-45, 2019 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-31254839

RESUMEN

OBJECTIVE: Determine sarcomere length (Ls) operating ranges of the superficial masseter and temporalis in vitro in a macaque model and examine the impact of position-dependent variation on Ls and architectural estimates of muscle function (i.e., fiber length, PCSA) before and after Ls-normalization. DESIGN: Heads of adult Macaca fascicularis (n = 4) and M. mulatta (n = 3) were bisected postmortem. One side of the jaw was fixed in occlusion, the other in maximum gape. Ls was measured bilaterally using laser diffraction and these measurements were used to estimate sarcomere-length operating ranges. Differences in fiber length and PCSA between sides were tested for significance prior to and following Ls-normalization. RESULTS: Sarcomere-length operating ranges were widest for the anterior superficial masseter and narrowest for the posterior temporalis. Compared with other mammals, macaque operating ranges were wider and shifted to the right of the descending limb of a representative length-tension curve. Fibers were significantly stretched by as much as 100%, and PCSAs reduced by as much as 43%, on the maximally gaped compared with occluded sides. Ls-normalization substantially reduced position-dependent variance. CONCLUSIONS: The superficial masseter ranges between 87-143% and the temporalis between 88-130% of optimal Ls from maximum gape to occlusion, indicating maximum relative Ls for these macaque muscles exceeds the upper end range previously reported for the jaw muscles of smaller mammals. The wider macaque operating ranges may be functionally linked to the propensity for facially prognathic primates to engage in agonistic canine display behaviors that require jaw-muscle stretch to facilitate production of wide jaw gapes.


Asunto(s)
Maxilares , Músculo Masetero/fisiología , Sarcómeros/fisiología , Animales , Conducta Animal , Rayos Láser , Macaca fascicularis , Macaca mulatta
18.
Eur J Oral Sci ; 127(3): 222-231, 2019 06.
Artículo en Inglés | MEDLINE | ID: mdl-30945364

RESUMEN

Occlusal support may influence muscular function during complex motor tasks. This study evaluated the duration and sequence of muscular activation of masticatory (temporal, masseter), postural head/neck (sternocleidomastoid, trapezius), postural trunk (rectus abdominis, paravertebrals), and low extremity strength (rectus femoris, gastrocnemius) muscles during simulation of activities of daily living (ADL) in edentulous women wearing complete dentures (n = 10) and in dentate women (n = 10). Electromyographic activity was recorded during tests of stand-up/sit down in the Chair, sit up/lie down in the Bed and lift/lower Bags. Occlusal support (dentures) had a significant effect on duration of muscular activation in the Chair Test: the masseter muscle activated longer with dentures during the standing movement. The masseter and sternocleidomastoid muscles showed significant alteration in their order of activation in non-denture-wearing women. For the Bed Test, dentures had significant effect for the gastrocnemius during the sitting-up phase and for the rectus abdominis during the lying-down movement. For the Bag Test, head/neck muscles were activated in a different order as a function of occlusal support. Anticipation of activation of the paravertebral muscles, rectus abdominis, and gastrocnemius was observed in dentate women compared with denture wearers. These findings suggest that occlusal support influences electromyographic activity of some muscles during simulation of ADL.


Asunto(s)
Actividades Cotidianas , Dentadura Completa , Músculo Masetero/fisiología , Músculos Masticadores/fisiología , Boca Edéntula , Adulto , Anciano , Estudios Transversales , Electromiografía , Femenino , Humanos , Masticación , Persona de Mediana Edad , Adulto Joven
19.
J Appl Physiol (1985) ; 127(1): 11-21, 2019 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-31018744

RESUMEN

The extrinsic tongue muscles are activated in coordination with pharyngeal muscles to dilate the airways as needed during breathing. The genioglossus (GG) activity is known to be modulated by several reflexes evoked via the mechanoreceptors of the upper airways. The primary objective of this paper was to investigate the effectiveness of activating these reflex pathways using mechanical stimulation of the mandible or the submandibular muscles. In eight healthy subjects, 3-s long, 5-mm vertical mechanical vibrations were delivered at 8 and 12 Hz to the lower jaw in a seated position, while the GG EMG was recorded using a custom-made sublingual electrode, along with the activity of the masseter (MS) and mylohyoid (MH). All three muscle activities were significantly higher during stimulation compared with the baseline (P < 0.02), and the increase was larger at 12 Hz versus 8 Hz (P < 0.02). All three muscle responses had components that synchronized with the mechanical stimuli, but those of MS were much more strongly phase-locked to the vibrational cycle. In 10 healthy subjects, we also applied mechanical vibrations to the submandibular muscles at three different stimulation intensities, while subjects were lying in a supine position. The GG activity increased significantly above the baseline (P = 0.026) in 9 out of 10 subjects, and the elevated activity persisted after termination of the stimulus for a few seconds. The results demonstrate that GG muscle responses can be evoked with mechanical vibrations applied to the lower jaw or the submandibular muscles in healthy subjects during wakefulness. NEW & NOTEWORTHY The evoked responses observed in the genioglossus (GG) activity during mechanical vibrations of the lower jaw or the submandibular muscles may lead to therapeutic applications for improving the patency of airways during sleep. The presence of these GG reflexes may also explain a mechanism by which the vibrations produced during snoring can help the airways stay open in individuals who may otherwise have obstructed airways in sleep.


Asunto(s)
Músculos Faciales/fisiología , Mandíbula/fisiología , Músculo Masetero/fisiología , Adulto , Músculos Faciales/metabolismo , Femenino , Humanos , Masculino , Mandíbula/metabolismo , Músculo Masetero/metabolismo , Mecanorreceptores/metabolismo , Persona de Mediana Edad , Músculos del Cuello/metabolismo , Músculos del Cuello/fisiología , Músculos Faríngeos/metabolismo , Músculos Faríngeos/fisiología , Reflejo/fisiología , Lengua/metabolismo , Lengua/fisiología , Vibración
20.
Physiol Behav ; 204: 129-139, 2019 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-30797813

RESUMEN

INTRODUCTION: Pain-related behavior secondary to masticatory function can be assessed with the rodent bite force model. A reduction of the bite force has been shown to be related to pain associated with the masseter muscle and jaw activity, while an increase in bite force suggests improvement of muscle function and less pain. To evaluate the usefulness of the bite force measure in studying long-lasting orofacial pain we analyzed biting parameters during prolonged myofascial pain induced by ligation injury of the masseter muscle tendon (TL) in mice. METHODS: C57Bl/6 mice were habituated to bite at a pair of aluminum plates attached to a force displacement transducer. The transduced voltage signals were amplified and converted to force through calibration with a standard weight set. Voluntary biting behavior was recorded for 100 s/session and those with bite forces ≥980 mN were analyzed. Nociception was also verified with von Frey, conditioned place avoidance (CPA) tests and mouse grimace scale. Persistent orofacial pain was induced with unilateral ligation of one tendon of the masseter muscle (TL). RESULTS: To reduce interference of random bites of smaller forces, the top 5 or 15 bite forces (BF5/15) were chosen as a measure of masticatory function and related to pain behavior. Both male and female mice exhibited similar BF5/15. For the first nascent test of all mice, mean bite force was significantly and positively correlated with the body weight. However, this correlation was less clear in the latter tests (2-8 w). TL induced a reduction of BF5/15 that peaked at 1 w and returned to the baseline within 3 w. The von Frey and CPA tests indicated that mechanical allodynia/hyperalgesia persisted at the time when the BF had returned to the pre-injury level. Infusion of pain-relieving bone marrow stromal cells improved biting behavior in both male and female mice as shown by significantly increased BF5/15, compared to vehicle-treated mice. CONCLUSIONS: Mouse voluntary biting behavior can be reliably measured and quantified with a simplified setup. The bite force showed an inverse relationship with the level of pain after TL and was improved by pain-relieving manipulations. However, the injury-induced reduction of bite force peaked early and did not parallel with other measures of nociception in the later phase of hyperalgesia. The results suggest that multiple factors such as the level of habituation, cognitive motive, physical status, and feeding drive may affect random voluntary biting and confound the biting parameters related to maintained hyperalgesia.


Asunto(s)
Fuerza de la Mordida , Dolor Facial/psicología , Animales , Reacción de Prevención , Fenómenos Biomecánicos , Peso Corporal , Electromiografía , Expresión Facial , Femenino , Hiperalgesia/psicología , Masculino , Músculo Masetero/fisiología , Músculos Masticadores/fisiología , Ratones , Ratones Endogámicos C57BL , Dimensión del Dolor , Tendones/fisiología
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