Body Position and Jaw Posture Effects on Supra- and Infrahyoid Electromyographic Activity in Humans

Abstract

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.

Occlusion, orthodontics and posture: are there evidences? The example of scoliosis

“…Maximal biting force is greater when the head is extended than it is when the head is held in a natural position [41]; * a splint that places the mandible in a position determined by kinesiological tests would be likely to augment muscular force [1,32,33]. These results contradict those of another published article that avers that there is no correlation between biting force and cephalic posture [81]; * Kovero et al also did not find any significant statistical correlation between maximal biting force and cervical posture [46]; systematic topical review * the neuromuscular activity of neck and face muscles seems to influence corporal or bodily posture according to many studies [25,58,59,75], but, according to another one, do not [84]; * bruxism could be associated with a head posture that is inclined excessively downward and forward [86]; * a recent systematic review of the literature [40] surveys in 266 publications reporting on a relationship between the masticatory apparatus and disturbances of the spinal column. There is an inter-relation between the masticatory apparatus and head posture according to 216 articles, and an association between pelvic tilting and the oral cavity according to 53 studies.…”

Estudo eletromiográfico da deglutição na musculatura supra-hióidea em sujeitos Classe Ie III de Angle

“…O maior RMS obtido nos sujeitos Classe III, demonstra a necessidade de um maior esforço muscular decorrentes provavelmente da desproporção maxilo-mandibular e do tipo de encaixe das chaves de oclusão 36 . A protrusão mandibular isolada sem alteração oclusal, no entanto, não é suficiente para ocasionar uma atividade eletromiográfica diferenciada 19 . A conjugação de fatores morfológicos distintos, como maxila, mandíbula e oclusão, é necessária a fim de que a musculatura atue com outro padrão, como se pôde constatar no presente estudo.…”

“…Estudos relatam sua importância desde a fase de crescimento crânio-facial, por exercerem influência significativa na conformação óssea [4][5][6] . 17,18 , do abaixamento e estabilização mandibular 19 , elevação e anteriorização do osso hioide 13,14,17,18 e possui inserções conjuntas à musculatura da língua , a qual é intensamente recrutada nos sujeitos prognatas 20 . Como uma das preconizações fonoaudiológicas é a interveção mioterápica, a compreensão do comportamento muscular é de suma importância para a avaliação, diagnóstico 21 planejamento terapêutico, desenvolvimento de técnicas 22 , prognóstico e compreensão de recidivas do tratamento 23,24 .…”

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“…A unilateral cross-bite will exhibit, during clench, a cross pattern of the total muscle output when muscle groups are compared [13][14][15]. Various other signs of malocclusion and alteration of head posture can relate to unbalanced muscle SEMG [13,16,17]. The sequence of activation during initial tooth contact is another factor studied in SEMG.…”