Does breathing type influence electromyographic activity of obligatory and accessory respiratory muscles?

Craniomandibular electromyographic (EMG) studies frequently include several parameters, e.g. resting, chewing and tooth-clenching. EMG activity during these parameters has been recorded in the elevator muscles, but little is known about the respiratory muscles. The aim of this study was to compare EMG activity in obligatory and accessory respiratory muscles between subjects with different breathing types. Forty male subjects were classified according to their breathing type into two groups of 20 each: costo-diaphragmatic breathing type and upper costal breathing type. Bipolar surface electrodes were placed on the sternocleidomastoid, diaphragm, external intercostal and latissimus dorsi muscles. EMG activity was recorded during the following tasks: (i) normal quiet breathing, (ii) maximal voluntary clenching in intercuspal position, (iii) natural rate chewing until swallowing threshold, (iv) short-time chewing. Diaphragm EMG activity was significantly higher in the upper costal breathing type than in the costo-diaphragmatic breathing type in all tasks (P < 0·05). External intercostal EMG activity was significantly higher in the upper costal breathing type than in the costo-diaphragmatic breathing type in tasks 3 and 4 (P < 0·05). Sternocleidomastoid and latissimus dorsi EMG activity did not show significant differences between breathing types in the tasks studied (P > 0·05). The significantly higher EMG activity observed in subjects with upper costal breathing than in the costo-diaphragmatic breathing type suggests that there could be differences in motor unit recruitment strategies depending on the breathing type. This may be an expression of the adaptive capability of muscle chains in subjects who clinically have a different thoraco-abdominal expansion during inspiration at rest.

Laterotrusive occlusal schemes and their effect on supra- and infrahyoid electromyographic activity.

The objective of this study was to determine the effects of canine guidance and group function on supra- and infrahyoid electromyographic (EMG) activity. The sample included 40 healthy subjects, 20 with bilateral canine guidance and 20 with bilateral group function. Surface electrodes were used to record the integrated EMG (IEMG) activity of the left supra- and infrahyoid muscles during (1) grinding from intercuspal position to lateral edge-to-edge contact position (with canine guidance or group function), (2) static clenching in edge-to-edge lateral contact position with canine guidance or group function, and (3) grinding from lateral edge-to-edge contact position (with canine guidance or group function) to intercuspal position. IEMG activity in the suprahyoid or infrahyoid muscles was not significantly different with canine guidance or group function. Supra- and infrahyoid IEMG activity in condition 2 was significantly higher than in condition 3, which was significantly higher than in condition 1. Supra- and infrahyoid IEMG activity was not significantly different with canine guidance and group function. Supra- and infrahyoid IEMG activity during the static recording (clenching) was significantly higher than during the dynamic recordings (grinding). Activity during grinding from the lateral edge-to-edge contact position to the intercuspal position was higher than vice versa.

Influence of mucosal mechanoreceptors on anterior temporalis EMG activity in patients with craniomandibular dysfunction: a preliminary study.

An analysis of saliva swallowing and tonic electromyographic (EMG) activity was undertaken in 15 young adult patients with craniomandibular dysfunction with and without a palatal base inserted. Recordings were performed by placing surface electrodes on the right and left anterior temporal muscles. Saliva swallowing and tonic activity were initially recorded with and without the palatal base inserted. After one week of continuous use of the palatal base, EMG activity was recorded again. Nonsignificant differences in EMG activity were observed in the studied conditions. EMG results do not support the therapeutical use of palatal base as a conservative and reversible treatment in patients with craniomandibular dysfunction.

Influence of occlusal splints on bilateral anterior temporal EMG activity during swallowing of saliva in patients with craniomandibular dysfunction.

A full-arch maxillary stabilization occlusal splint was made for each of 10 patients with craniomandibular dysfunction. These splints were divided into three sections (one anterior and two posterior). This procedure allowed variation in the anteroposterior centric localization of occlusal contacts, thus permitting the recording of the EMG effects produced by the different occlusal splint sections. The integrated EMG activity was recorded from the right and left anterior temporal muscles during swallowing of saliva in habitual occlusion and with the different occlusal splint sections inserted. EMG activity during swallowing of saliva was significantly lower with the different occlusal splints than in habitual occlusion. This supports the rationale for diurnal wear of the occlusal splint. No differences in EMG activity were found during swallowing of saliva when different sections of the occlusal splints were used. This fact points out the possibility for therapeutic use of different occlusal splints for improving swallowing function.

Influence of stabilization occlusal splints on sternocleidomastoid and masseter electromyographic activity.

The present work was conducted in order to determine the effect of stabilization occlusal splints on electromyographic (EMG) activity of sternocleidomastoid and masseter muscles, in subjects with tenderness to palpation in these muscles. A full-arch maxillary stabilization occlusal splint was made for each of 14 subjects. Tonic EMG activity, as well as during saliva swallowing and maximal voluntary clenching, was recorded with and without a stabilization occlusal splint inserted. Similar tonic, as well as maximal voluntary clenching EMG activity, with and without the stabilization occlusal splint, was observed. During saliva swallowing, the activity in both muscles was significantly lower with the stabilization occlusal splint. This suggests that daytime use of the stabilization occlusal splint might improve tenderness to palpation in the studied muscles, since the frequency of swallowing function is higher during waking hours.

Influence of stabilization occlusal splint on craniocervical relationships. Part II: Electromyographic analysis.

The aim of this study was to determine the effect of stabilization occlusal splints on electromyographic (EMG) activity of sternocleidomastoid and trapezius muscles in subjects with spasm in the mentioned muscles. A full-arch maxillary stabilization occlusal splint was made for each of the 15 subjects. In the sternocleidomastoid muscle, tonic and saliva swallowing EMG activity decreased significantly with the splint, whereas maximal clenching activity did not change. In the trapezius muscle, no significant changes were observed with the occlusal splint. The different pattern in both muscles during tonic and swallowing EMG activity with the splint is attributed to differences in the synaptic inputs to the respective motoneuron pools, suggesting that a differential modulation of the motor neuron pools may exist of both muscles, of peripheral and/or central origin.

Effects of head and neck inclination on bilateral sternocleidomastoid EMG activity in healthy subjects and in patients with myogenic cranio-cervical-mandibular dysfunction.

This study was conducted in order to determine the effect of head and neck position on bilateral electromyographic (EMG) activity of the sternocleidomastoid muscles. The study was performed on 16 patients with myogenic cranio-cervical-mandibular dysfunction (CMD) and 16 healthy subjects. EMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the right and left sternocleidomastoid muscles. EMG activity was recorded in the left lateral decubitus position, in a darkened room and with the individual's eyes closed, under the following experimental conditions: 1. Head, neck, and body horizontally aligned; 2. Head and neck upwardly inclined with respect to the body, simulating the effect of a thick pillow, 3. Head and neck downwardly inclined with respect to the body, simulating the effect of a thin pillow. Variation of head and neck positions was determined by measuring the distance from the angle of neck and shoulder and the apex of the shoulder (SND = shoulder-neck distance) of each individual. Then, head and neck were forward or downwardly inclined with respect to the body at one-third of SND. A significantly higher contralateral EMG activity and a more asymmetric EMG activity were observed in the CMD group than in the healthy subjects (Kruskal-Wallis Test). These results suggest a different behavior of bilateral sternocleidomastoid EMG activity in CMD patients than in healthy subjects depending on the positioning of the head and neck.

Body position effects on EMG activity of sternocleidomastoid and masseter muscles in patients with myogenic cranio-cervical-mandibular dysfunction.

This study was conducted in order to determine the effects of body position on integrated electromyographic (IEMG) activity of sternocleidomastoid and masseter muscles in 17 patients with myogenic cranio-cervical-mandibular dysfunction. EMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the sternocleidomastoid and masseter muscles (contralateral to the habitual side of sleeping of each patient), in the following body positions: standing, seated, supine, and lateral decubitus position. Significant higher EMG activities were recorded in the sternocleidomastoid muscle in the lateral decubitus position and in the supine position (except during swallowing), whereas a significant higher EMG activity was recorded in the masseter muscle during maximal voluntary clenching in standing and seated positions. The EMG pattern observed suggests that the presence of parafunctional habits and body position could be closely correlated with the clinical symptomatology in the sternocleidomastoid and masseter muscles at wakening and during waking hours, respectively, in patients with myogenic cranio-cervical-mandibular dysfunction.

Influence of stabilization occlusal splint on craniocervical relationships. Part I: Cephalometric analysis.

This study was conducted in order to determine the effect of an occlusal splint on craniocervical relationships, in subjects with muscle spasms in the sternocleidomastoid and trapezius muscles. A full-arch maxillary stabilization occlusal splint was made for each of the 15 subjects. Two lateral craniocervical radiographs were taken for each subject, with and without an occlusal splint. Cephalometric analysis showed that the splint caused a significant extension of the head on the cervical spine. There was also a significant decrease in the cervical spine lordosis in the first, second and third cervical segment. These cervical changes could be a compensation mechanism caused by the extension of the cranium on the upper cervical spine. The change in the curvature implies that it is necessary to periodically evaluate the changes occurring in the craniocervical relationships after the occlusal splint has been inserted.

Influence of variation in jaw posture on sternocleidomastoid and trapezius electromyographic activity.

This study was conducted in order to determine the influence of variation in the occlusal contacts on electromyographic (EMG) cervical activity in 20 patients with myogenic cranio-cervical-mandibular dysfunction. EMG recordings during maximal voluntary clenching were performed by placing surface electrodes on the left sternocleidomastoid and upper trapezius muscles in the following conditions: intercuspal position; edge to edge left laterotrusive contacts (ipsilateral); edge to edge right laterotrusive contacts (contralateral); edge to edge protrusive contacts; and retrusive occlusal contacts. A significant higher EMG activity was recorded in both muscles during maximal voluntary clenching in retrusive occlusal contact position, whereas no significant differences in EMG activity were observed between intercuspal position, ipsilateral, contralateral and protrusive contact positions. The EMG pattern observed suggests that a more frequent intensity and duration of tooth clenching in retrusive occlusal contact position could result in more clinical symptomatology in these cervical muscles in patients with myogenic cranio-cervical-mandibular dysfunction.

Body position effects on sternocleidomastoid and masseter EMG pattern activity in patients undergoing occlusal splint therapy.

This study was conducted in order to determine the effects of body position on electromyographic (EMG) activity of sternocleidomastoid and masseter muscles, in 15 patients with myogenic cranio-cervical-mandibular dysfunction undergoing occlusal splint therapy. EMG activity was recorded by placing surface electrodes on the sternocleidomastoid and masseter muscles (contralateral to the habitual sleeping side of each patient). EMG activity at rest and during swallowing of saliva and maximal voluntary clenching was recorded in the following body positions: standing, supine and lateral decubitus. In the sternocleidomastoid muscle significant higher EMG activities at rest and during swallowing were recorded in the lateral decubitus position, whereas during maximal voluntary clenching EMG activity did not change. In the masseter muscle significant higher EMG activity during maximal voluntary clenching in a standing position was observed, whereas EMG activity at rest and during swallowing did not change. The opposite pattern of EMG activity supports the idea that there may exist a differential modulation of the motor neuron pools of the sternocleidomastoid and masseter muscles, of peripheral and/or central origin. This suggests that the presence of parafunctional habits and body position could be closely correlated with the clinical symptomatology in these muscles in patients with myogenic craniomandibular dysfunction.

Increase of the vertical occlusal dimension by means of a removable orthodontic appliance and its effect on craniocervical relationships and position of the cervical spine in children.

The aim of this study was to determine the effect of the increase in the occlusal vertical dimension by means of an orthodontic appliance on craniocervical relationships and position of the cervical spine. Thirty children presenting malocclusion were divided into two groups of 15 (a study and a control group). Those in the study group wore an orthodontic appliance to correct cross-bite. The children in the control group had no treatment during the experimental period. Two lateral craniocervical radiographs were taken for each child. The first one was taken in the intercuspal position in both groups. The second radiograph was taken of the study group after four months of wearing the appliance and also of the control group after four months. Cephalometric analysis in the study group showed a significant forward cervical spine position. There were no significant changes in the control group. The changes found in the study group suggest that when there are signs and symptoms of cervical dysfunction in children undergoing long-term orthodontic treatment, it is necessary to make an evaluation of the cervical column position after the insertion of any orthodontic appliance which increases the occlusal vertical dimension.

Body position effects on EMG activity of sternocleidomastoid and masseter muscles in healthy subjects.

This study was conducted in order to determine the effects of body position on integrated electromyographic (IEMG) activity of sternocleidomastoid and masseter muscles in 20 healthy subjects. EMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the sternocleidomastoid and masseter muscles (contralateral to the habitual side of sleeping of each subject), in the following body positions: standing, seated, supine, and lateral decubitus position. Significant higher EMG activities were recorded in the sternocleidomastoid muscle in the lateral decubitus position, whereas significant lower EMG activities were recorded in the masseter muscle in the supine position. This finding supports the idea that there may exist a differential modulation of the motor neuron pools of the sternocleidomastoid and masseter muscles of peripheral and/or central origin. Significant differences in the EMG pattern as well as in the levels of EMG activities upon variations in body positions were observed between healthy subjects and patients with myogenic craniomandibular dysfunction reported by Palazzi, et al.

Body position effects on EMG activity of the temporal and suprahyoid muscles in healthy subjects and in patients with myogenic cranio-cervical-mandibular dysfunction.

This study was conducted in order to determine the effects of body position on integrated electromyographic (IEMG) activity of anterior temporal and suprahyoid muscles. The study was performed on 15 patients with myogenic cranio-cervical-mandibular dysfunction (CMD) and 15 healthy subjects. IEMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the anterior temporal and suprahyoid muscles in the following body positions: standing, seated, supine, and lateral decubitus position. Insignificant changes in IEMG activity of both muscles were observed upon variations in the body position. Insignificant differences in IEMG activity were observed between patients with myogenic CMD and healthy subjects. A pattern of higher IEMG at rest and during swallowing of saliva was observed in the suprahyoid muscles than in the anterior temporal muscles, whereas during maximal clenching activity, an opposite pattern was observed. Results of the present study seem to suggest that for the anterior temporal and suprahyoid muscles there is no specific body position that could be relevant to initiate and/or to perpetuate a craniomandibular dysfunction.

Visual input effect on EMG activity of sternocleidomastoid and masseter muscles in healthy subjects and in patients with myogenic cranio-cervical-mandibular dysfunction.

This study was conducted in order to determine the input visual effect on electromyographic (EMG) activity of the sternocleidomastoid and masseter muscles in the supine and lateral decubitus positions. The study was performed on 22 patients with myogenic cranio-cervical-mandibular dysfunction (CMD) and 18 healthy subjects. EMG activity at rest and during swallowing of saliva and maximal voluntary clenching was recorded in the supine and lateral decubitus positions in the following conditions: 1. with eyes open; and 2. with eyes closed after 5 minutes in a dark room. A significant decrease of EMG activity at rest with closed eyes in both groups was observed in the sternocleidomastoid (lateral decubitus position) and in the masseter muscle (supine position). During swallowing of saliva a significant decrease of EMG activity with closed eyes was observed only in the sternocleidomastoid muscle (lateral decubitus position) in healthy subjects. During maximal voluntary clenching any significant differences were observed upon variation in the visual input. The significant change in EMG activity, mainly observed at rest, suggests that the visual input effect is weak. The absence of a significant change in EMG activity during maximal voluntary clenching upon variation in the visual input could be clinically relevant in patients with myogenic CMD who habitually brux.

Effects of two types of pillows on bilateral sternocleidomastoid EMG activity in healthy subjects and in patients with myogenic cranio-cervical-mandibular dysfunction.

This study was conducted in order to determine the effects of two types of pillows on bilateral electromyographic (EMG) activity of the sternocleidomastoid muscles. The study was performed on 15 patients with myogenic cranio-cervical mandibular dysfunction (CMD) and 15 healthy subjects. EMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the right and left sternocleidomastoid muscles. EMG activity was recorded in the supine position and in the lateral decubitus position (according to each individual's normal resting habit), with their eyes closed and with the head supported by means of: 1. a Sleep Easy Pillow (Interwood Marketing Groups, Concord, Ontario, Canada) and 2. a Standard Pillow (INDUVET). In the lateral decubitus position a significantly higher contralateral than ipsilateral EMG activity at rest in the sternocleidomastoid muscles was observed with both types of pillows in all the sample studied (ANOVA and Duncan's Multiple-Range Test). Asymmetrical bilateral EMG activity in the lateral decubitus position with both types of pillows in healthy subjects and in patients with myogenic CMD, suggests that if this body posture is prolonged, it could be important in the genesis of sternocleidomastoid hyperactivity.

Después de cien años de uso: ¿las férulas oclusales tienen algún efecto terapéutico? / After a century of use: do the occlusal appliances have any therapeutic effects?

Las férulas o planos oclusales han sido utilizadas desde hace más de un siglo, generando controversia acerca de su verdadero valor terapéutico. Esto motivó una revisión histórica y actualizada que permitiera evaluar sus efectos de acuerdo a la evidencia científica. Se discuten múltiples aspectos como el concepto de relación céntrica y su determinación como punto de inicio de tratamiento en la rehabilitación oral; el uso de las férulas para deprogramar; su efecto sobre la conducta motora oral que conocemos como bruxismo; su efecto en la actividad electromiográfica tónica, durante la deglución y el máximo apriete en los músculos masticatorios y cervicales; su influencia en la eficiencia muscular; su efecto en la carga articular y las evidencias experimentales del uso de distintas férulas sobre signos y síntomas especíicos como dolor y ruido articular. Se plantean desafíos para la investigación sobre cambios degenerativos en las articulaciones, en la relación craneovertebral y en la curvatura e inclinación de la columna cervical. Se concluye que es necesario utilizar una férula diseñada para el trastorno específico del paciente y que su verdadero valor terapéutico queda demostrado al mejorar algunos signos y síntomas, en músculos masticatorios y cervicales. El conocimiento parcial del mecanismo de acción de las férulas contribuye a que persista la controversia de su utilización en el tratamiento de ruidos articulares y para revertir cambios degenerativos en las articulaciones. Persiste el desafío de nuevas investigaciones, que sustenten el uso de estos dispositivos como un método eficaz para tratar a nuestros pacientes, utilizando protocolos de manejo y controles periódicos.

Occlusal appliances or splints have been used for over a century, generating controversy about their real therapeutic value. This led to an updated review to assess their effects according to scientific evidence. The concept of centric relation and its determination as a starting point of treatment; the use of splints to deprogram; their effect on the oral motor behaviour known as bruxism are discussed. Their effect on EMG activity during resting, swallowing and maximal clenching in the masticatory and neck muscles; their effect on muscular eficiency; their effect decreasing the joint overload; and experimental evidence of the use of several appliances on speciic symptoms such as pain and joint noise, are also treated. The true challenge is to generate new knowledge about joint degenerative changes, the craniocervical relationships, tilt and curvature of the cervical spine. In conclusion, it's necessary to use an occlusal appliance designed for the specific condition of the patient, and its real therapeutic value is demonstrated by the improvement of some signs and symptoms in masticatory and cervical muscles. However, the action mechanisms of occlusal appliances are not fully understood. The lack of scientiic support contributes to the persistent controversy of the use of these appliances in the treatment of temporomandibular joint sounds and reversing degenerative changes. It is still a challenge to carry out new researches supporting the use of these appliances as an effective method to treat our patients using management protocols and periodic evaluations.

Influence of mucosal mechanoreceptors on elevator muscle activity in healthy subjects.

An analysis of saliva swallowing and tonic electromyographic activity was undertaken in 15 healthy subjects with complete natural dentitions with and without a palatal base inserted. Recordings were performed by placing surface electrodes on the left anterior temporal and masseter muscles. In eight subjects tonic electromyographic patterns of activity differed for the two muscles, depending upon the presence of the palatal base, whereas during swallowing of saliva only four subjects showed different patterns. In tonic activity of elevator muscles, there is probably a differential peripheral and/or central modulation of motoneuron pools of both elevator muscles. The lower different pattern in electromyographic activity of the two muscles during saliva swallowing in the intercuspal position suggests that periodontal mechanoreceptor stimulation might have such a powerful influence on electromyographic activity of both muscles that any difference originating in other inputs could have been obscured.

Influence of the vertical dimension in the treatment of myofascial pain-dysfunction syndrome.

Occlusal splints constructed at three different vertical heights were used to study the influence of vertical dimension in the etiology of bruxism and MPD syndrome. The vertical dimension of least EMG activity was determined for each of 75 patients who were randomly divided into three groups according to the vertical dimension at which the occlusal splint was constructed. Group I occlusal splints were constructed at 1 mm from the occlusal vertical dimension, group II splints at 4.42 mm, and group III splints at 8.15 mm. Results showed a faster and more complete reduction in clinical symptoms for groups II and III than for group I. The temporary use of occlusal splints with a vertical height exceeding the physiologic rest position did not encourage a greater muscular tonus or hyperactivity of jaw muscles. It can be concluded that elongation of elevator muscles to or near the vertical dimension of least EMG activity by means of occlusal splints is more effective in producing neuromuscular relaxation.

Comparative study between children with and without cleft lip and cleft palate, part 2: electromyographic analysis.

OBJECTIVE: This study was conducted to compare electromyographic (EMG) activity of superior orbicularis oris muscle between children with repaired cleft lip and cleft palate and children without clefts. METHODS: This study included 28 children with mixed dentition. They were divided into two groups. The study group included 14 children with repaired unilateral cleft lip and cleft palate, ranging in age from 6 to 12 years, who presented clinically with a short upper lip, abnormal lip seal, and inhibition of sagittal development of the midface as assessed radiographically. The control group included 14 children without clefts ranging in age from 8 to 11 years. All had normal lip seal, nasal breathing, and a clinically normal body posture. DESIGN: Bipolar surface electrodes were used for EMG recordings of resting level activity and during swallowing of saliva, speech, and chewing and swallowing of an apple. RESULTS AND CONCLUSIONS: A significantly higher level of activity at rest and during swallowing of saliva was observed in the cleft lip and cleft palate group. Similar activity during speech and chewing and swallowing of an apple was observed in both groups. The higher level of activity at rest and during swallowing of saliva in children with cleft lip and cleft palate seems to suggest that upon higher functional demands their activity increases less than in children without clefts. From a clinical point of view, if increased EMG activity at rest and during swallowing of saliva reflects increased force on the maxilla, then our findings may corroborate Bardach's findings (1990) that surgical treatment of cleft lip has an iatrogenic effect on facial growth, although the lack of significant correlation between the cephalometric data and EMG findings in the present study.