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

Effects of sitting posture and jaw clenching on neck and trunk muscle activities during typing

Neck pain is one of the most common musculoskeletal complaints. Evidence suggests that increased activities of neck and trunk muscles are one of the mechanisms related to neck pain. Jaw clenching and sitting posture may modulate the muscle activity in neck and trunk muscles during typing. The present study aimed to assess the effects of different postural positions and clenching conditions on neck and trunk muscle activities. Thirteen healthy adults (39.8 ± 5.0 years) performed computer typing tasks in four conditions (two postural positions [upright vs slouched] and two jaw clenching conditions [clenching vs non-clenching]). Integrated surface electromyography (iEMG) was measured in sternocleidomastoid (SCM), upper trapezius (uTP) and middle trapezius (mTP) muscles and compared between conditions. The Friedman and Wilcoxon signed-rank tests with Bonferroni's corrections were used to estimate the condition-specific differences in the iEMG data. The statistical significance level was set at 5%. In both postural positions, iEMG_SCM was significantly greater under the jaw clenching than under the non-clenching condition (χ²  = 21.700, P < .01). Under both jaw clenching conditions, iEMG_uTP was significantly greater in the slouched than in the upright postural position (χ²  = 23.182, P < .01). No significant differences in iEMG_mTP were seen across conditions (χ²  = 5.018, P = .10). Sitting posture and jaw clenching appear to influence activities of different muscles.

Prediction of Ergogenic Mouthguard Effects in Volleyball: A Pilot Trial

Dental occlusion may affect static and dynamic balance. The effects of a mouthguard on pinpoint accuracy in volleyball were investigated in 28 players who completed a volleyball specific test. Also, masticatory electromyographic tests were performed. The mean pinpoint accuracy was significantly higher with a mouthguard (68.6±9.3 vs. 64.0±7.0 points from 100; p< 0.006). However, differential mouthguard effects were seen, and three subgroups were classified: Group 1 (markedly improved pinpoint accuracy), Group 2 (improved pinpoint accuracy), and Group 3 (reduced pinpoint accuracy). Group 1 had a high masseter resting tone, the masseter activity was low in MVC (maximum voluntary clench) and increased in BOC (maximum bite on cotton rolls; p< 0.04). This indicates a masseter weakness, which would be compensated by a mouthguard. In Group 2, the masseter activity in MVC was high-normal with an imbalance which was improved in BOC (p< 0.01), indicating a possible mouthguard benefit. In Group 3, MVC and BOC were in a high-normal range and showed no relevant deficits. In these subjects the mouthguard had adverse effects. Overall, subjects with masticatory deficits had a benefit from the mouthguard in pinpoint accuracy. Positive or negative mouthguard responders may be detectible from electromyographic tests.

Análise comparativa entre dois ângulos cervicais com a oclusão em crianças com e sem DTM

OBJETIVO: comparar dois ângulos cervicais com as classificações oclusais em crianças de 6 a 10 anos com e sem Disfunção Temporomandibular (DTM),identificar se há prevalência de DTM quanto ao gênero, e se há influencia da oclusão sobre os ângulos estudados. MÉTODO: realizou-se um estudo observacional transversal com 91 crianças de ambos os gêneros de uma Instituição de Ensino privado, dispostas em Grupo A (sem DTM) e Grupo B (com DTM). Todas as crianças foram avaliadas seguindo uma ficha cadastral constituída de dados referentes a sexo, idade, peso, altura e exame clínico intra-oral para classificação oclusal de Angle. O diagnóstico e a severidade da DTM, foram verificados pelo questionário proposto por Fonseca. Para avaliação dos ângulos cervicais (A1 e A2) foi utilizada a fotogrametria e o Software Alcimagem®. RESULTADOS: entre as crianças avaliadas, 52 (57,14%) apresentaram maloclusão, sendo 29 com DTM e 23 sem DTM, 39 (42,85%) apresentaram normoclusão, sendo 18 sem DTM e 21 com DTM. Quando comparados os ângulos (A1 e A2) a classe oclusal, foi encontrada diferença significante entre as crianças normoclusivas e maloclusivas com o ângulo A1 (p=0,04). CONCLUSÃO: esse estudo demonstrou que o ângulo A1 (C7, ATM e Ápice do Mento) foi estatisticamente significante quando associado com a condição oclusal. Não foi encontrado associação, na população estudada, entre ângulo cervical e DTM. Além disso, também foi possível observar que, a prevalência de crianças do gênero feminino com DTM é significantemente maior que a do gênero masculino. Esse estudo demonstrou que a maloclusão pode alterar somente o ângulo A1 e que a DTM não interfere nos ângulos cervicais estudados.

Postural evaluation of patients with temporomandibular disorders under use of occlusal splints

Objectives:

Alterations in the temporomandibular complex can reflect in adaptations of the individual's entire muscular system, intervening with the head position and scapular waist, developing postural alterations and modifying all corporal biomechanics. The aim of this study was to evaluate the head position (HP) and head postural alterations before and after installation of occlusal splints.

Material and Methods:

Twenty patients with temporomandibular disorders (TMD) underwent clinical and postural examination, before the installation of an occlusal splint, and after 1 week and 1 month of use.

Results:

There were statistically differences for HP, between the initial values and after 1 week of use of the occlusal device (p= 0.048) and also between 1 week and 1 month of evaluation (p= 0.001). Decrease of the painful symptomatology and maintenance of the rectification were also observed.

Conclusions:

The individual's postural position can suffer biomechanical alterations due to stomatognathic alterations, causing clinically visible changes in dysfunctional individuals and affecting the performance of the involved structures.

[Does dysfunctional swallowing influence posture?]

Swallowing is one of the first functions to be set up in utero for vital reasons. Physiological and psychic maturation then occur to lead from a dysfunctional to a functional state. Nevertheless, for certain individuals, maturation is incomplete, and swallowing remains dysfunctional. The clinical literature has already proven the incidence of a dental change of occlusion and the consequences of a lingual dysfunction upon posture. This work proposes to show that the posture can be affected by dysfunctional deglutition because of the lack of dental contacts during this function and because of the lingual dysfunction which characterizes it. We studied a population of 20 young adults, divided into two groups: a group of subjects presenting with a functional swallowing, and a group of subjects presenting with a dysfunctional swallowing. The experimental protocol includes four conditions: mandibular rest, cognitive task of articulation, functional swallowing, dysfunctional swallowing. Their effect on the posture is evaluated by means of a standardized stabilometric platform, and is supplemented by an electromyographic study of a manducator muscle (the masseter) and of a muscle of the cephalic posture (the sternocleidomastoid). The results show that swallowing would have the same postural effects as the cognitive task by increasing the postural oscillations and the energy spent by the postural system. Furthermore, the deglutition would have increased effects when it corresponds to a forced deglutition for the subject.

Vectored upper cervical manipulation for chronic sleep bruxism, headache, and cervical spine pain in a child

OBJECTIVE

To discuss the management of chronic sleep bruxism in a 6-year old girl. Clinical features The patient had morning headaches and cervical spine pain. Due to abnormal tooth wear, bruxism had been previously diagnosed and was verified by observation during sleep. She also had abnormal postural and palpatory findings, indicating upper cervical joint dysfunction. Intervention and outcome Bilateral rotary cervical stretching/mobilization and a vectored high-velocity, low-amplitude adjustment were performed in the upper cervical spine, using the atlas transverse process as the contact point. There was complete relief of the chronic subjective symptoms concomitant with remission of the objective signs of joint dysfunction.

CONCLUSIONS

Cervical, particularly upper cervical, spine muscle-joint dysfunction should be considered as a potential etiology in chronic childhood sleep bruxism.

Use of surface electromyography to estimate neck muscle activity

This paper reviews the literature concerning the use of surface electromyography (sEMG) for the study of the neck musculature in response to work and workplace design during light work and semi-static tasks. The paper also draws upon basic research and biomechanical modeling in order to provide methodological recommendations for the use of surface electromyography in this region of the body and to identify areas which require further investigation. The paper includes review and discussion of electrode site location, methods of normalization, data reliability, and factors that can affect sEMG signals from this region, including noise, physiologic artifact, stress, visual deficiencies, and pain. General guidance for maximum exertions with the neck musculature, for sEMG normalization or other purposes, is also included.