Aler Fuentes

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

Abstract 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.

The Effect of Tooth Clenching and Grinding on Anterior Temporalis Electromyographic Activity in Healthy Subjects

Abstract 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.

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

Abstract 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.

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

Abstract 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.

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

Abstract 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.

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.

Anterior Temporalis and Suprahyoid EMG Activity During Jaw Clenching and Tooth Grinding

Abstract 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.

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

Abstract 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.

Assessment of electromyographic activity in patients with temporomandibular disorders and natural mediotrusive occlusal contact during chewing and tooth grinding

Objectives: The aim of this study was to investigate whether the presence of a natural mediotrusive contact influences electromyographic (EMG) pattern activity in patients with temporomandibular disorders (TMDs). Method: Bilateral surface EMG activity of the anterior temporalis (AT), masseter (MM), and sternocleidomastoid (SCM) muscles was recorded in 43 subjects during unilateral chewing and tooth grinding. Thirteen patients had TMD and a natural mediotrusive contact (Group 1), 15 had TMD without a natural mediotrusive contact (Group 2), and 15 were healthy subjects without mediotrusive contacts (Group 3). All subjects were examined according to the Research Diagnostic Criteria for TMD (RDC/TMD). All EMG values were standardized as the percentage of EMG activity recorded during maximum isometric contraction on cotton rolls. Results: EMG activity from all muscles measured showed no significant differences between groups during chewing and grinding. Overall, in all groups, the EMG activity during chewing was higher in the working side than the non-working side in AT and MM muscles. During grinding, these differences were only found in masseter muscles (mainly in eccentric grinding). SCM EMG activity did not show significant differences during chewing and grinding tasks. Symmetry, muscular balance, and absence of lateral jaw displacement were common findings in all groups. Discussion: EMG results suggest that the contribution of a natural mediotrusive occlusal contact to EMG patterns in TMD patients is minor. Therefore, the elimination of this occlusal feature for therapeutic purposes could be not indicated.

Effect of natural mediotrusive contact on electromyographic activity of jaw and cervical muscles during chewing

Abstract Objective. This study evaluated the effect of a natural mediotrusive contact on the electromyographic (EMG) activity of the anterior temporalis and sternocleidomastoid muscles during chewing in healthy subjects. Materials and methods. The study sample included two groups of 15 subjects each (Group 1: with natural mediotrusive contact; Group 2: without natural mediotrusive contact). Bilateral surface EMG activity was recorded on anterior temporalis and sternocleidomastoid muscles during unilateral chewing of a half cookie and unilateral chewing of a piece of apple. Anterior temporalis and sternocleidomastoid muscle activity was normalized against activity recorded during maximal voluntary clenching in intercuspal position and maximal intentional isometric head–neck rotation to each side, respectively. The partial and total asymmetry indexes were also calculated. Data were analyzed using Mann-Whitney, Wilcoxon and unpaired t-test. Results. EMG activity of anterior temporalis and sternocleidomastoid muscles showed no significant difference between the groups. EMG activity of anterior temporalis was similar between working and non-working sides during chewing in both groups. EMG activity of sternocleidomastoid muscle was higher in the working side than in the non-working side in Group 2 subjects. Asymmetry indexes were not significantly different between groups. Conclusions. The similar EMG pattern and asymmetry indexes observed suggest the predominance of central nervous control over peripheral inputs on anterior temporalis and sternocleidomastoid motor neuron pools.