Electromyographic activity of frontalis and sternocleidomastoid muscles in patients with temporomandibular disorders

Pain-free bite force in a healthy population: Within-session test-retest reliability in different sitting positions

BACKGROUND

Pain-free bite force (PFBF) is a promising measure to evaluate bite function in temporomandibular disorders (TMDs), yet the reliability of the measure is unknown.

OBJECTIVES

Establish the (1) within-session test-retest reliability of PFBF in a healthy population for a single and mean of three trials in supported and unsupported sitting; (2) standard error of measurement (SEM) and minimal detectable change (MDC).

METHODS

Thirty healthy participants (n = 15 female, mean [SD] age = 34.4 [11.0] years) completed two sessions (30-60 min apart) comprising three PFBF trials on each side, in both supported and unsupported sitting, to provide data for 60 (30 participants × two sides) test-retest assessments. Test-retest reliability for the first trial and mean of three trials in each position were determined using intraclass correlation coefficients (ICCs), before calculating the corresponding SEM and MDC for males (M) and females (F) respectively.

RESULTS

Within-session reliability was considered excellent for a single trial in supported sitting (ICC = 0.85; SEM M/F = 99/84 N; MDC M/F = 275/232 N) and unsupported sitting (ICC = 0.91; SEM M/F = 72/59 N, MDC M/F = 200/163 N), and for a mean of three trials in supported sitting (ICC = 0.89; SEM M/F = 66/79 N, MDC M/F = 182/220 N) and unsupported sitting (ICC = 0.92; SEM M/F = 64/59 N, MDC M/F = 177/164 N).

CONCLUSION

Single and a mean of three trials in supported and unsupported sitting appear reliable methods to measure PFBF in a healthy population. Testing PFBF using a mean of three trials in unsupported sitting appears superior over other methods though due to higher test-retest reliability, and lower SEM and MDC. Future studies should examine the reliability of PFBF in TMD populations.

The correlation between scapulocostal syndrome and masticatory myofascial pain on selected pain and functional parameters- an observational study

OBJECTIVES

Although scapulocostal syndrome (SCS) and masticatory myofascial pain (MMP) occur in different regions, the concept of myofascial linkage and neurophysiology may be proven per the connection of the two disorders. Therefore, this study aimed to investigate the correlation between SCS and MMP on selected pain and functional parameters.

METHOD

75 participants with SCS participated in the protocol. The diagnosis of SCS was considered by the presence of muscle referred pain in the medial scapular muscles. All participants were measured for pain intensity, pressure pain threshold (PPT), and craniovertebral angle (CV-angle) for pain and functional parameters related to SCS. They were measured for pain intensity, PPT, and mouth distance for the pain and functional parameters related to MMP. The diagnosis of MMP was considered by the presence of muscle tenderness of the masticatory muscle and the decreasing of mouth opening distance. The correlation between SCS and MMP was determined using Pearson's correlation coefficient and Spearman's correlation.

RESULTS

Participants exhibiting SCS were diagnosed for MMP at 74.67%. The results showed positive correlations in pain intensity and PPT between SCS and MMP (r = 0.367, r = 0.478, p < 0.01), PPT of SCS, and mouth distance amid both pain-free and maximum mouth opening conditions, respectively (r = 0.290, r = 0.282, p < 0.05).

CONCLUSION

In conclusion, SCS and MMP present an association with each other in terms of both selected pain, and functional parameters. Thus, a treatment program for SCS patients should be concerned with the masticatory muscles even if they did not report any pain at the jaw area.

Changes in the temporomandibular joint disc and temporal and masseter muscles secondary to bruxism in Turkish patients

Objectives:

To analyze the relationships between temporalis and masseter muscle hypertrophy and temporomandibular joint (TMJ) disc displacement in patients with severe bruxism using magnetic resonance imaging (MRI).

Methods:

This retrospective study included 100 patients with severe bruxism, referred to the Department of Oral and Maxillofacial Surgery, University of Marmara and Istanbul Medipol University, Istanbul, Turkey, between January 2015 and December 2016. Patients underwent TMJ MRI with a 1.5-T system in open and closed mouth positions. The masseter and temporalis muscles were measured in the axial plane when the patient’s mouth was closed.

Results:

At its thinnest, the disc averaged was 1.11±0.24 mm. At their thickest, the masseter averaged was 13.65±2.19 mm and temporalis muscles was 12.98±2.4 mm. Of the discs, 24% were positioned normally, 74% were positioned anteriorly, and 2% were positioned posteriorly. The temporalis muscle was significantly thicker in patients with normally positioned discs than in those with anteriorly positioned discs (p=0.035).

Conclusions:

The temporalis muscle was significantly thicker in patients with normally positioned discs than in those with anteriorly positioned discs (p=0.035). Additional studies should be conducted to evaluate the relationships between all masticatory and surrounding muscles and disc movements in patients with bruxism.

Cervical-scapular muscles strength and severity of temporomandibular disorder in women with mechanical neck pain

Abstract Introduction: Changes in cervical muscle function have been observed in patients with neck pain (NP) and TMD. However, the relationship between TMD severity and neck muscle strength in the presence/absence of NP is unknown. Objective: To determine the prevalence of TMD in women with and without mechanical NP and assess the cervical-scapular muscle strength and its association with TMD severity. Methods: Fifteen volunteers without neck pain (CG) and 14 women with mechanical neck pain (NPG) took part and were selected by the Neck Disability Index. The diagnosis and severity of TMD were determined by the Research Diagnostic Criteria for TMD and Temporomandibular Index (TI), respectively. The strength of the upper trapezius muscle, and cervical flexor and extensor muscles was measured by digital hand dynamometer. Results: 64.5% of women with NP and 33.3% without NP were diagnosed with TMD (p = 0.095). The NPG showed lower strength of the cervical flexor (p = 0.044) and extensor (p=0.006) muscles, and higher TI (p = 0.038) than in the CG. It was also verified moderate negative correlation between TI and the strength of dominant (p = 0.046, r = -0.547) and non-dominant (p = 0.007, r = -0.695) upper trapezius, and cervical flexors (p = 0.023, r = -0.606) in the NPG. Conclusion: There was no difference in the prevalence of TMD in women with and without NP. However, women with NP have lower cervical muscle strength - compared to those without NP - which was associated with greater severity of TMD. Thus, in women with NP associated with TMD, it is advisable to assess and address the severity of this dysfunction and identify the cervical-scapular muscles compromise.

Assessment of thickness and function of masticatory and cervical muscles in adults with and without temporomandibular disorders

OBJECTIVE

The aim of this study was to evaluate the maximal bite force (MBF), electromyographic (EMG) activity and thickness of the masseter, anterior part of the temporalis and sternocleidomastoid (SCM) muscles in a group of young adults with and without temporomandibular disorders (TMDs).

DESIGN

Nineteen individuals comprised the TMD group (6 males/13 females, aged 25.4±3.8 years), classified based on the Research Diagnostic Criteria for TMD (RDC/TMD), and 19 comprised the control group (6 males/13 females, aged 24.1±3.6 years). The MBF was determined with a transducer placed between the dental arches at the first molars level (N). The muscles were evaluated bilaterally at rest and during maximal voluntary clenching (MVC) by assessing EMG activity and performing ultrasonography (USG). The mean values of these measures for both sides of the mouth were used. The normality of the distributions was assessed by the Shapiro-Wilks test. Variables between groups and genders were compared using two-way factorial ANOVA test and correlated using the Spearman coefficient (α=0.05). Unpaired t test was used to compare variables between TMD subgroups. Logistic regression analysis was used to identify the variables associated with the presence of TMD.

RESULTS

MBF, EMG and USG data were similar among clinical groups and among TMD subgroups. The thickness of masseter and SCM muscles in the relaxed and clenching states were significantly higher in males than females. On the other hand, the EMG of the temporalis muscle in the rest state was significantly higher in females than males. Additionally, the MBF was positively correlated with the USG characteristics of masseter and SCM muscles, as well as with the EMG activity of masseter and temporalis muscles in the TMD group. In this group, there was also a positive correlation between the thickness of the masseter muscle and its activity. On the other hand, the thickness of the SCM muscle was negatively correlated with its activity. A lower MBF was independently associated with the presence of TMD.

CONCLUSIONS

Subjects with TMD exhibited similar values of MBF, thickness and electrical activity of masticatory and cervical muscles when compared with controls; positive correlations observed between these variables may suggest a muscular alteration in TMD patients and a co-activation of masticatory and cervical muscles during mandibular movement. This fact may also be confirmed by the negative association between bite forces and presence of TMD.

Influence of different upper cervical positions on electromyography activity of the masticatory muscles

OBJECTIVE

The aim of this study was to determine the activity of the masseter and anterior temporalis muscles in relation to different positions of the upper cervical spine during maximal voluntary isometric clenching by surface electromyography (EMG).

METHODS

This was a cross-sectional study with a repeated-measures design performed using 25 asymptomatic subjects (13 female and 12 male; mean age, 31 years; SD, 8.51). The EMG activity of the masseter and anterior temporalis muscles was recorded bilaterally during maximal clenching at neutral position and during extension, flexion, ipsilateral lateral flexion, contralateral lateral flexion, and ipsilateral and contralateral rotations in maximal flexion. In addition, the upper cervical range of motion and mandibular excursions were assessed. The EMG activity data were analyzed using a 3-way analysis of variance in which the factors considered were upper cervical position, sex (male and female), and side (right and left), and the hypothesis of importance was the interaction side x position.

RESULTS

The 3-way analysis of variance detected statistically significant differences between the several upper cervical positions (F = 13.724; P < .001) but found no significant differences for sex (F = 0.202; P = .658) or side (F = 0.86; P = .53) regarding EMG activity of the masseter muscle. Significant differences were likewise observed for interaction side x position for the masseter muscle (F = 12.726; P < .001). The analysis of the EMG activity of anterior temporalis muscle did not produce statistically significant differences (P > .05).

CONCLUSION

This preliminary study suggests that the upper cervical movements influence the surface EMG activity of the masseter muscle. These findings support a model in which there are interaction between the craniocervical and the craniomandibular system.

Myosin heavy chain composition of the human sternocleidomastoid muscle

The sternocleidomastoid (SCM) muscle is one of the neck muscles responsible for head posture and control of head movement. It functions in rotation, inclination, protraction, extension and flexion of the head, whilst chewing and in exerting increased respiratory efforts. This study is the first one describing the myosin heavy chain (MyHC) isoform composition of the SCM muscle of presumably healthy young males for the purpose of better understanding the contractile properties of the muscle as well as to help in evaluation of pathologically altered structure of the muscle. Autopsy samples were processed immunohistochemically to reveal the MyHC isoform composition. The muscle fibres expressed MyHC-1 (31.5%), -2a (29.7%) and -2x (4.3%) or co-expressed MyHC-2a with MyHC-2x (26.8%), MyHC-1 with MyHC-2a (4.1%) and/or MyHC-1, -2a with -2x (1.1%). In addition to the MyHC isoforms, characteristic of adult limb muscles, a very low percentage of muscle fibres (0.2-2.7%) expressed MyHC-neo, which is normally not found in adult limb muscles. Only two samples exhibited MyHC-neo at a rather higher percentage (6.3% and 7.5%) of muscle fibres. The high share of hybrid fibres and the presence of MyHC-neo in the SCM muscle differ from that of adult limb muscles where hybrid fibres are rare and the expression of immature MyHC isoforms occurs only in pathological or experimental conditions. Since the SCM muscle shares the same embryogenic potential as limb muscles, its distinct MyHC expression appears to be associated with twin innervation and with the intrinsic specialisation to perform multiple functions.

Atividade elétrica dos músculos cervicais e amplitude de movimento da coluna cervical em indivíduos com e sem DTM

O objetivo da pesquisa foi avaliar a atividade elétrica e a dor à palpação dos músculos cervicais, a amplitude de movimento (ADM) da coluna cervical e a relação entre atividade elétrica e ADM cervical em indivíduos com e sem desordem temporomandibular (DTM). Participaram do estudo 53 voluntários, sendo 24 com DTM e 29 sem, de ambos os gêneros, com 18 a 32 anos de idade. A DTM foi diagnosticada pelo critério de diagnóstico em pesquisa para DTM (Research Diagnostic Criteria for Temporomandibular Disorders). A eletromiografia dos músculos esternocleidomastoídeo (ECOM) e trapézio superior foi realizada bilateralmente, na situação de repouso, com frequência de 2 KHz e filtro passa-faixa de 10-1000 Hz. As medidas de ADM de flexão, extensão, lateroflexão e rotação foram realizadas com um flexímetro e a comparação entre os grupos contou com o teste de Mann Whitney. O teste de Spearman foi aplicado para a correlação entre as variáveis, com nível de significância de 5%. Não foi verificada nenhuma diferença na ADM cervical entre os grupos. A atividade elétrica demonstrou-se significativamente maior nos músculos ECOM direito (p=0,0130), trapézio superior direito (p=0,0334) e esquerdo (p=0,0335) no grupo DTM em relação ao grupo controle. Não houve correlação significante entre atividade elétrica e ADM cervical. A dor nos músculos cervicais apresentou-se significativamente maior apenas no músculo ECOM direito (p=0,0055). Conclui-se que os grupos estudados registraram diferença na atividade elétrica dos músculos cervicais, sendo esta maior em indivíduos com DTM.

Postural and dynamic masseter and anterior temporalis muscle EMG repeatability in serial assessments

Electromyographic (EMG) assessment has been used as a non-invasive tool to objectively assess muscle function, although with controversial research and clinical potential. The aim of this study was to assess within-, inter-subject and between-day repeatability of serial EMG recordings. The study sample included 10 asymptomatic subjects with no history of temporomandibular disorders or muscle parafunctions. Bilateral masseter and anterior temporalis muscle EMG parameters were assessed in two standardized serial recordings (day 1 to day 2) using a portable EMG equipment (ME 6000 recorder, Mega Electronics, Kuopio, Finland). The functional tasks included postural/resting activities as pre- and post-recording series of 30 s each and jaw opening/closing, intercuspal and maximal voluntary clenching activities of 5 s, repeated three times. The assessed EMG parameters included the mean amplitude, s.d. and error. In addition, the power spectrum EMG parameter assessment included the median power frequencies and the averaged EMG spectrum data values. The results of the intraclass correlation coefficient analysis indicated reliability for nearly all of the intercuspal and all clenching EMG amplitude and power spectrum parameters. This was complemented by the repeated measures anova and post hoc analyses that indicated non-significant differences between day 1 and 2 in task- and muscle-related analyses. Most variability was noted in postural and some in opening/closing tasks. In conclusion this study assessed the reliability, repeatability and limitations of postural and various dynamic masseter and temporalis EMG recordings for serial assessment.

Review of clinical EMG studies related to muscle and occlusal factors in healthy and TMD subjects

Several electronic instruments have been developed as adjuncts to objectively record the dysfunctional features of temporomandibular disorders and to study the effectiveness of various treatment interventions. The aim of this review was to assess the value and contribution of clinical electromyographic research in the understanding of asymptomatic and dysfunctional muscle function and the therapeutic effects of interocclusal appliances. For this purpose MedLine and PubMed searches were conducted with the following main keywords alone and in various combinations: electromyography, muscles of mastication, masseter, temporalis, temporomandibular, TMD, utility, validity, repeatability, rest, postural, vertical dimension, occlusal, splint, treatment. The review includes critical evaluation, discussion and conclusions regarding electromyographic studies in asymptomatic and dysfunctional muscles, rest position, occlusal parameters and interocclusal appliances, as well as a critical summary and proposals for further research. Much of earlier critique of many electromyographic studies still applies regarding comparative sample selections, research designs, analyses and conclusions. The areas not well-understood include normal biological variation, capacity for adaptation, fluctuations regarding the clinical course and multidimensional features of temporomandibular disorders and long-term follow-up data, especially in studies that evaluate the effectiveness of therapeutic measures. Considering the required improvements in technical and research designs features and critical appraisal electromyographic research could have value as an adjunct research tool to study features of craniofacial muscle-related dysfunction. Until electromyographic measures are correlated with other multidimensional, especially subjective and pain-related methods, the clinical use of this method for diagnostic purposes of temporomandibular disorders remains in doubt, and is not at present recommended.