Effect of laterotrusive occlusal scheme on chewing duration, external intercostal muscular activity, heart rate, and oxygen saturation.

Objective: To evaluate the effect of the laterotrusive occlusal scheme on chewing duration, external intercostal (EIC) electromyographic (EMG) activity, heart rate (HR), and oxygen saturation (OS) during different tasks in the upright seated position.Methods: Fifty young participants, 25 with canine guidance and 25 with group function, were included. Chewing duration, bilateral EIC EMG activity, HR, and OS were recorded during the following tasks: 1) chewing until swallowing threshold; 2) laterotrusive teeth grinding.Results: Chewing duration, bilateral EIC EMG activity, HR, and OS showed no significant differences between the two laterotrusive occlusal schemes during the tasks studied.Conclusion: These results suggest that chewing duration, EIC muscle activity, HR, and OS were not significantly influenced by the laterotrusive occlusal scheme. Therefore, when a modification of the laterotrusive occlusal scheme is needed during oral rehabilitation or orthodontic treatment, canine guidance or group function should not significantly change EMG activity of EIC muscles.

Awake teeth grinding in participants with canine guidance or group function: Effect on diaphragm EMG activity, heart rate, and oxygen saturation.

Objective: To compare the effect of canine guidance or group function on diaphragm activity, heart rate, and oxygen saturation during awake teeth grinding at different body positions. Methods: Fifty healthy participants, 25 with canine guidance and 25 with group function, were included. Bilateral electromyographic (EMG) recordings of the diaphragm (DIA) during awake teeth grinding were performed in standing, seated upright, and right lateral decubitus positions. Simultaneously, heart rate and oxygen saturation were measured. Results: EMG activity of the DIA muscle was similar in the working side and non-working side between participants with canine guidance and group function in the different body positions studied. The heart rate and oxygen saturation showed no significant differences between the two groups. Conclusion: EMG activity of the DIA muscle, the heart rate, and oxygen saturation during teeth grinding are not significantly influenced by the type of laterotrusive occlusal scheme.

Effect of breathing type on electromyographic activity of respiratory muscles during tooth clenching at different decubitus positions.

OBJECTIVE: To compare the effect of breathing type on electromyographic (EMG) activity of respiratory muscles during tooth clenching at different decubitus positions. METHODS: Forty young men participants were included, 11 with upper costal, 9 with mixed, and 20 with costo-diaphragmatic breathing type. EMG recordings of diaphragm (DIA), external intercostal (EIC), sternocleidomastoid (SCM), and latissimus dorsi (LAT) muscles during tooth clenching in the intercuspal position were performed in dorsal, left lateral, and ventral decubitus positions. RESULTS: DIA EMG activity was higher in subjects with upper costal or mixed than with costodiaphragmatic breathing type (p = 0.006; 0.021, respectively), whereas it was similar between upper costal and mixed breathing types. EIC, SCM, and LAT activity was similar among breathing types. CONCLUSION: Higher DIA activity would be a risk factor to exceed the adaptive capability of healthy subjects with upper costal or mixed breathing type.

Effects of breathing type on electromyographic activity of respiratory muscles at different body positions.

AIM: To compare the effect of breathing type on the activity of respiratory muscles at different body positions. METHODOLOGY: Two groups of 20 subjects each, one with upper costal and the other with costodiaphragmatic breathing, were studied. Electromyographic activity of sternocleidomastoid (SCM), diaphragm (DIA), external intercostal (EIC), and latissimus dorsi (LAT) muscles was recorded at standing and lateral decubitus positions during swallowing and maximal voluntary clenching. RESULTS: All muscles showed higher activity during standing in upper costal breathing subjects except the SCM muscle. EIC activity was higher during standing in the costodiaphragmatic breathing group. Subjects with upper costal breathing showed higher DIA activity than subjects with costodiaphragmatic breathing at both body positions and higher SCM activity at lateral decubitus position, whereas, EIC activity was only higher during swallowing. CONCLUSIONS: Subjects with upper costal breathing presented higher respiratory effort than subjects with costodiaphragmatic breathing, being most prominent at the lateral decubitus position.

Comparison of muscle activity between subjects with or without lip competence: Electromyographic activity of lips, supra- and infrahyoid muscles.

AIM: This study compares the electromyographic (EMG) activity of the muscles from the lips and hyoid bone in subjects with or without lip competence. METHODOLOGY: Two groups of 20 subjects each, with or without lip competence were studied. EMG activity of the superior orbicularis oris (SOO), inferior orbicularis oris (IOO), suprahyoid (SH) and infrahyoid (IH) muscles was recorded with the subject seated in the upright position during the following tasks: (1) at rest; (2) speaking; (3) swallowing; (4) forced deep breathing; (5) maximal voluntary clenching; and (6) chewing. RESULTS: EMG activity was significantly higher in subjects without competent lips than with competent lips in the SOO and IOO muscles during tasks 3 and 4, SOO during task 2 and IOO during task 6. EMG activity was similar in the SOO and IOO muscles during tasks 1 and 5, SOO during task 6 and IOO during task 2. Activity of the SH and IH muscles was similar in both groups for all tasks. CONCLUSIONS: Higher activity in subjects without competent lips implies a higher muscular effort due to the requirement of lip sealing during functional activities. Hyoid muscular activity was not modified by the presence or absence of lip competence.

Effect of upper costal and costo-diaphragmatic breathing types on electromyographic activity of respiratory muscles.

AIM: To compare electromyographic (EMG) activity in young-adult subjects with different breathing types. METHODOLOGY: This study included 50 healthy male subjects with complete natural dentition, and no history of orofacial pain or craniomandibular-cervical-spinal disorders. Subjects were classified into two groups: upper costal breathing type, and costo-diaphragmatic breathing. Bipolar surface electrodes were located on sternocleidomastoid, diaphragm, external intercostal, and latissimus dorsi muscles. Electromyographic activity was recorded during the following tasks: (1) normal quiet breathing; (2) speaking the word 'Mississippi'; (3) swallowing saliva; and (4) forced deep breathing. RESULTS: Sternocleidomastoid and latissimus dorsi EMG activity was not significantly different between breathing types, whereas diaphragm and external intercostal EMG activity was significantly higher in the upper costal than costo-diaphragmatic breathing type in all tasks (P<0·05; Wilcoxon signed rank-sum test). CONCLUSION: Diaphragm and external intercostal EMG activity suggests that there could be differences in motor unit recruitment strategies depending on the breathing type.

The effect of a mandibular advancement appliance on cervical lordosis in patients with TMD and cervical pain.

AIMS: A preliminary study to compare cervical lordosis by means of cervical cephalometric analysis, before and after six months of continuous mandibular advancement appliance (MAA) use, and to show how physical therapy posture re-education would improve the cervical lordosis angle. METHODOLOGY: Twenty-two female patients with temporomandibular disorders (TMD) and cervical pain with lordosis <20° were included. Patients had to have a muscle pain history for at least six months, and with an intensity ⩾6, measured by means of a visual analog scale (a horizontal 0-10 numeric rating scale with 0 labeled as 'no pain' and 10 as 'worst imaginable pain'). Patients had to present the angle formed by the posterior tangents to C2 and C7 of equal or less than 20°. Cephalometric and clinical diagnostics were performed initially (baseline) and at the end of the study period (six months). During the third month with MAA treatment, a physical therapist evaluated the postural deficit and performed a program of postural re-education. Angular and linear dimension data presented a normal distribution (P>0·05; Shapiro Wilk Test), so the paired comparison of the cephalometric measurements was made by t-test for dependent samples. RESULTS: Angle 1 (OPT/7CVT); angle 3 (CVT/EVT) and angle 4 (2CL/7CL) showed a significant increase in the cervical lordosis. Angle 2 (MGP/OP), angle 5 (HOR/CVT) and the distances C0-C2 and Pt-VER, presented no significant changes. CONCLUSIONS: The increase in cervical lordosis implies that six months of continuous MAA use, together with a program of postural re-education, promotes the homeostasis of the craniocervical system.

Electromyographic activity during awake tooth grinding tasks at different jaw posture in the sagittal plane.

OBJECTIVE: The goal of this study was to evaluate the electromyographic (EMG) activity of the anterior temporalis, suprahyoid, infrahyoid and trapezius muscles during tooth grinding at different jaw posture tasks. MATERIALS AND METHODS: Participants were 30 healthy subjects with natural dentition, bilateral molar support and incisive protrusive guidance. Bipolar surface electrodes were located on the right side of the subject. EMG recordings were performed in the following tasks: (A) Eccentric grinding from intercuspal position to protrusive edge-to-edge contact position; (B) concentric grinding from protrusive edge-to-edge contact position to intercuspal position; (C) eccentric grinding from intercuspal position to the maximum voluntary retrusive position; and (D) concentric grinding from the maximum voluntary retrusive position to intercuspal position. The results were analyzed statistically by Friedman test and Wilcoxon signed rank-sum test. RESULTS: EMG activity in the anterior temporalis and infrahyoid muscles was significantly higher during task C than the other tasks. EMG activity in the suprahyoid muscles was significantly higher during task C than task D. EMG activity in the trapezius muscle was significantly higher during task C than tasks A and B. CONCLUSIONS: The higher EMG activity recorded in task C could become important when its frequency, duration and magnitude are enough to exceed the adaptation capability of the individual.

Bilateral supra- and infrahyoid EMG activity during eccentric jaw clenching and tooth grinding tasks in subjects with canine guidance or group function.

This study compares the effect of tooth clenching and grinding on supra- and infrahyoid electromyographic (EMG) activity during different laterotrusive jaw posture tasks. The study included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance and 15 with bilateral group function. Bipolar surface electrodes were located on the left and right supra- and infrahyoid muscles. EMG activity was recorded during the following tasks: A. eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; B. clenching in right edge-to-edge lateral contact position; C. concentric grinding from right lateral edge-to-edge contact position to intercuspal position. EMG activity was not significantly different between tasks on the working side, nonworking side, or between both sides, in subjects with canine guidance or group function (Wilcoxon rank-sum test). When comparing EMG activity by occlusal scheme, no significant differences were found either on the working side or the non-working side (Mann-Whitney U test). This result suggests that supra- and infrahyoid EMG activity in its predominant stabilizing role of the hyoid bone is not significantly modified by the type of laterotrusive occlusal scheme.

Anterior temporalis and suprahyoid EMG activity during jaw clenching and tooth grinding.

The aim of this study was to evaluate the anterior temporalis and suprahyoid electromyographic (EMG) activity during jaw clenching and tooth grinding at different jaw posture tasks. The study included 30 healthy subjects with natural dentition and bilateral molar support, incisive protrusive guidance and bilateral laterotrusive canine guidance. Bipolar surface electrodes were located on the right anterior temporalis and suprahyoid muscles. Three EMG recordings in the standing position were performed in the following tasks: C. clenching in the intercuspal position (IP); P1. eccentric grinding from IP to protrusive edge-to-edge contact position; P2. clenching in protrusive edge-to-edge contact position; P3. concentric grinding from protrusive edge-to-edge contact position to IP; L1. eccentric grinding from IP to laterotrusive edge-to-edge contact position; L2. clenching in laterotrusive edge-to-edge contact position; L3. concentric grinding from laterotrusive edge-to-edge contact position to IP. EMG activity during protrusive and laterotrusive tasks was lower than intercuspal position in the anterior temporalis, whereas an opposite EMG pattern was observed in the suprahyoid muscles activity, excepting recorded activity in L2 (mixed model with unstructured covariance matrix). Anterior temporalis activity was higher during P3 than P1 and P2 tasks and during L3 than L1 and L2 tasks, whereas in the suprahyoid muscles, activity was higher during P1 than P2 tasks and during L1 than L2 and L3 tasks. These results could support the idea of a differential modulation of the motor neuron pools of anterior temporalis and suprahyoid muscles of peripheral and/or central origin.

[Olfactory sensory perception]. / Sensopercepción olfatoria: una revisión.

The five senses have had a fundamental importance for survival and socialization of human beings. From an evolutionary point of view the sense of smell is the oldest. This sense has a strong representation within the genome, allowing the existence of many types of receptors that allow us to capture multiple volatile odor producing molecules, sending electrical signals to higher centers to report the outside world. Several cortical areas are activated in the brain, which are interconnected to form an extensive and complex neural network, linking for example, areas involved with memory and emotions, thus giving this sense of perceptual richness. While the concept of flavor is largely related to the sense of taste, smell provides the necessary integration with the rest of the senses and higher functions. Fully understanding the sense of smell is relevant to health professionals. Knowing the characteristics of the receptors, the transduction processes and convergence of information in the higher centers involved, we can properly detect olfactory disorders in our patients.

Influence of jaw clenching and tooth grinding on bilateral sternocleidomastoid EMG activity.

This study compares the effect of tooth clenching and grinding on sternocleidomastoid electromyographic (EMG) activity during different laterotrusive jaw posture tasks. The study included 28 healthy subjects with natural dentition and bilateral molar support, 14 with bilateral canine guidance and 14 with bilateral group function. Bipolar surface electrodes were located on the left and right sternocleidomastoid muscles. EMG activity was recorded during the following tasks: (A) eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; (B) clenching in right edge-to-edge lateral contact position; (C) concentric grinding from right lateral edge-to-edge contact position to intercuspal position. On the working side, activity in the task C was significantly higher than in tasks A and B in subjects with canine guidance, whereas no significant differences were observed between tasks in subjects with group function. On the nonworking side, activity was significantly lower during task A than in tasks B and C, in both occlusal schemes (mixed model with unstructured covariance matrix). When comparing by side, EMG activity was significantly lower during task B on the working side than on the nonworking side. However, there were no significant differences during tasks A and C. The EMG activity was significantly lower with canine guidance than group function on the working side during tasks A, B, and C, and on the nonworking side during tasks B and C. These results could explain muscular symptoms in the sternocleidomastoid muscles if the subject is experiencing parafunctional habits while awake and/or during sleep that exceed the individual's adaptation capability.

Sensopercepción olfatoria: una revisión / Olfactory sensory perception

The five senses have had a fundamental importance for survival and socialization of human beings. From an evolutionary point of view the sense of smell is the oldest. This sense has a strong representation within the genome, allowing the existence of many types of receptors that allow us to capture multiple volatile odor producing molecules, sending electrical signals to higher centers to report the outside world. Several cortical areas are activated in the brain, which are interconnected to form an extensive and complex neural network, linking for example, areas involved with memory and emotions, thus giving this sense of perceptual richness. While the concept of fl avor is largely related to the sense of taste, smell provides the necessary integration with the rest of the senses and higher functions. Fully understanding the sense of smell is relevant to health professionals. Knowing the characteristics of the receptors, the transduction processes and convergence of information in the higher centers involved, we can properly detect olfactory disorders in our patients.

Sensopercepción gustativa: una revisión / Gustatory sensory perception: a review

Los órganos de los sentidos confieren a los seres humanos la capacidad de percibir y responder a una gran gama de estímulos que provienen del entorno, lo cual nos brinda la facultad de elaborar respuestas con el fin de adaptarnos a los cambios medioambientales, cubrir nuestras necesidades básicas y sobrevivir. Para nutrirnos, el sentido del gusto posee un rol primordial que nos permite seleccionar dentro de una amplia variedad de alimentos, las sustancias que son necesarias para nuestro metabolismo, protegiéndonos a su vez de compuestos potencialmente nocivos, debido a su toxicidad o grado de descomposición. Este sentido también es capaz de brindarnos la capacidad de seleccionar y discriminar alimentos que nos permitan sentir agrado y placer. Para los dentistas es fundamental comprender adecuadamente los complejos procesos del sentido del Gusto, identificar las estructuras involucradas tanto a nivel periférico (papilas, receptores y vías nerviosas) como a nivel central (núcleos y cortezas cerebrales); además de conocer las modalidades básicas del gusto y sus respectivos mecanismos de transducción. Este conocimiento aportará los elementos necesarios para enfrentar de manera correcta una situación en la cual un paciente presente una alteración gustativa, siendo capaz de identificar las posibles causas y adoptar medidas adecuadas para resolverla y/o tolerarla en el caso de ser provocada en forma transitoria por un procedimiento que forme parte o no de nuestro tratamiento.

The sense organs give to humans the ability to perceive and respond to a wide range of stimuli from the environment. This allows us the power to shape responses in order to adapt to environmental changes, control our basic needs and survive. The sense of taste has a key role in nurture. Enable us to select from a wide variety of foods, elements that are necessary for metabolism and also protecting from potentially harmful compounds, as of its toxicity or degree of decomposition. This sense of taste is also capable of giving us the ability to select and discriminate food that allow us to feel enjoy and pleasure. For dentists is critical to understand adequately the complex processes of taste, identify the structures involved peripheral (papillae, nerve pathways and receptors) and central (nuclei and cerebral cortices), besides knowing the basic modalities of taste and their respective transduction mechanisms. This knowledge will provide the basis to address properly a situation in which a patient has an altered taste, being able to identify possible causes and take appropriate action to resolve it and / or tolerate if temporary caused by a procedure that may be part of our dental treatment.

The effect of tooth clenching and grinding on anterior temporalis electromyographic activity in healthy subjects.

The aim of this study was to determine the effect of tooth clenching and grinding on anterior temporalis electromyographic (EMG) activity. The sample included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance and 15 with bilateral group function. An inclusion criterion was that subjects have to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left and right anterior temporalis muscles. EMG activity was recorded during the following conditions: A. eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; B. clenching in right edge-to-edge lateral contact position; and C. concentric grinding from right lateral edge-to-edge contact position to intercuspal position. On the working side, EMG activity was not significantly different between conditions in both occlusal schemes. On the nonworking side, EMG activity was significantly higher during condition C than condition B in both occlusal schemes (mixed model with unstructured covariance matrix). When comparing by side, EMG activity was significantly higher during conditions A and B on the working side than on the nonworking side. However, there was no significant difference during condition C. EMG activity was significantly lower with canine guidance than group function on the working side (in all conditions) as well as during concentric grinding on the nonworking side. These results could explain muscular symptoms in the anterior temporalis muscles if the subject is experiencing parafunctional habits either while awake and/or sleep that exceed the individual's adaptation capability.

Clenching and grinding: effect on masseter and sternocleidomastoid electromyographic activity in healthy subjects.

This study compares the effect of clenching and grinding on masseter and sternocleidomastoid electromyographic (EMG) activity during different jaw posture tasks in the sagittal plane. The study included 34 healthy subjects with natural dentition, Class I bilateral molar Angle relationship, and absence of posterior occlusal contacts during mandibular protrusion. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the right masseter and sternocleidomastoid muscles. EMG activity was recorded while the subjects were in standing position, during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge protrusive contact position; C. maximal clenching in the edge-to-edge protrusive contact position; D. grinding from edge-to-edge protrusive contact position to intercuspal position; E. grinding from retrusive contact position to intercuspal position. EMG activities in tasks B, C, D, and E were significantly lower than in task A in both muscles (mixed model with unstructured covariance matrix). EMG activity among tasks B, C, D, and E did not show significant differences in both muscles, except between tasks D and E in the masseter muscle. A higher effect was observed on the masseter than on the sternocleidomastoid muscle to avoid excessive muscular activity during clenching and grinding. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.

Influence of laterotrusive occlusal scheme on bilateral masseter EMG activity during clenching and grinding.

This study was designed to determine the effect of the occlusal scheme on masseter EMG activity at different jaw posture tasks. The sample included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance, and 15 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left and right masseter muscles. EMG activity was recorded during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge lateral contact position; C. maximal clenching in the edge-to-edge lateral contact position; D. grinding from edge-to-edge lateral contact position to intercuspal position. EMG activity in tasks B, C, and D was lower than in task A (mixed model with unstructured covariance matrix). EMG activity was not significantly different with canine guidance or group function. EMG activity recorded on the nonworking side was higher than the working side during task C, and no different between tasks B or D. On the nonworking side, EMG activity in task B was significantly lower than C and D, and similar between task C and D. On the working side, EMG activity was significantly higher in task D than C and B, and in task B significantly higher than task C. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.

Electromyographic evaluation of anterior temporal and suprahyoid muscles using habitual methods to determine clinical rest position.

The purpose of this study was to compare the electromyographic (EMG) activity of the anterior temporal and suprahyoid muscles using habitual methods to determine the clinical rest position. The sample included 26 healthy subjects with natural dentition, bilateral molar support, and bilateral molar Angle Class I occlusion. Bipolar surface electrodes were located on the right anterior temporal and suprahyoid muscles for EMG recordings. In each subject EMG activity was recorded while standing while performing the following jaw posture tasks: during light occlusal contact in the intercuspal position; during and after pronouncing the word Mississippi, during and after pronouncing the Spanish terms Sesenta y seis (English translation: sixty six); during and after pronouncing the word, business, during and after swallowing of saliva; and while maintaining their mandible in a relaxed posture. Anterior temporal EMG activity in the intercuspal position was significantly higher than all the other conditions. The same was observed in the suprahyoid muscles excepting after pronouncing the words Mississippi, and business. EMG activity recorded in the clinical rest position by means of phonetic methods, swallowing of saliva and maintaining the mandible in a relaxed posture did not show a significant difference. From an EMG point of view any of these methods could be used to determine clinical rest position.

Laterotrusive occlusal schemes and jaw posture tasks effects on supra- and infrahyoid EMG activity in the lateral decubitus position.

The purpose of this study was to determine the effect of canine guidance and group function on supra- and infrahyoid EMG activity in the lateral decubitus position at different jaw posture tasks. The sample included 40 healthy subjects with natural dentition and bilateral molar support, 20 with bilateral canine guidance and 20 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left supra- and infrahyoid muscles for EMG recordings. In the lateral decubitus position, EMG activity was recorded in subjects with canine guidance or group function, during the following jaw posture tasks: A. maximal clenching in the edge-to edge lateral contact position; B. grinding from intercuspal position to edge-to-edge lateral contact position, and C. grinding from edge-to-edge lateral contact position to intercuspal position. Supra- and infrahyoid EMG activity was not significantly different with canine guidance or group function (mixed model with unstructured covariance matrix). Overall comparison of suprahyoid or infrahyoid EMG activity among the three jaw posture tasks studied showed a significantly higher activity during jaw posture task A (clenching) than jaw posture tasks B and C (grinding). Suprahyoid EMG activity was significantly higher during jaw posture task C than B, whereas infrahyoid EMG activity did not present a significant difference between jaw posture tasks C and B. These EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding. The neurophysiological mechanisms involved are discussed.

Body position and jaw posture effects on supra- and infrahyoid electromyographic activity in humans.

The purpose of this study was to record the pattern of electromyographic (EMG) activity of supra- and infrahyoid muscles at different body positions and jaw posture tasks. The sample included 22 healthy subjects with natural dentition, bilateral molar support, and absence of posterior occlusal contacts during mandibular protrusion. Bipolar surface electrodes were located on the left supra- and infrahyoid muscles for EMG recordings. In each subject EMG activity was recorded while standing and in the lateral decubitus position, during the following jaw posture tasks: swallowing of saliva, maximal clenching in the intercuspal position, grinding from intercuspal position to protrusive edge-to-edge contact position, and grinding from retruded contact position to intercuspal position. Suprahyoid EMG activity was significantly higher in the intercuspal position than in all the other jaw positions studied (mixed model with unstructured covariance matrix). Suprahyoid EMG activity was similar in both body positions studied. Infrahyoid EMG activity in the intercuspal position was significantly higher than grinding from intercuspal position to protrusive edge-to-edge contact position, similar to swallowing of saliva, and significantly lower than grinding from the retruded contact position to intercuspal position. Infrahyoid EMG activity in the lateral decubitus position was significantly higher than in the standing position. The EMG pattern observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding. The neurophysiological mechanisms involved are discussed.