Surface electromyography and magnetic resonance imaging of the masticatory muscles in patients with arthrogenous temporomandibular disorders

Systematic Review and Meta-Analysis of Electromyography Potential to Discriminate Muscular or Articular Temporomandibular Disorders and Healthy Patients

Background/Objectives: New devices such as surface electromyography (sEMG) have been proposed to support traditional gnathological examination and diagnostic protocols. The aim of this study is to investigate whether sEMG can be considered a diagnostic instrument to discriminate between healthy subjects and patients with temporomandibular disorders (TMDs) of an articular or muscular nature. Methods: A systematic review was conducted according to PRISMA guidelines using literature searches of MEDLINE (via PubMed), Scopus, and Web of Science. Inclusion criteria: recent clinical studies (≤10 years) in English or Italian, involving electromyography in TMD diagnosis, with a control group of healthy patients. Data considered to be homogenous were subjected to meta-analysis (95% confidence interval [CI]; α = 0.05). Hedge g was calculated because all variables were continuous. Articles meeting the inclusion criteria were checked for further consideration, and relevant data were collected into two tables. In total, 18 studies were included after full-text reading. Meta-analyses were carried out for the static impact index (IMP), percentage overlapping coefficient (POC), and torque coefficient, and dynamic Symmetrical Mastication Index (SMI). Results: Patients with TMD had lower values in all parameters except IMP. sEMG registered a reduction in masseter activity, lower chewing efficiency, and an increase in fatigue during contractions in TMD patients. Conclusions: sEMG is not reliable to distinguish healthy from TMD patients, but despite the limitations related to the high variability in the studies (type of electromyography, static or dynamic tests, and population characteristics), the sEMG results are reliable considering the POC and SMI parameters, encouraging more in-depth studies for a predictable clinical practice. Patients with TMD had lower values in the dynamic index SMI and in static indexes POC and torque coefficient, except IMP. EMG might performs better if employed in muscle forms.

Baseline masticatory muscles' performance may predict pain relief in temporomandibular disorders

OBJECTIVES

To compare masticatory muscles' recruitment in patients with temporomandibular disorders and asymptomatic control subjects. To evaluate if the masticatory muscles' recruitment pattern may predict symptoms' improvement after temporomandibular disorders treatment.

MATERIALS AND METHODS

Standardized surface electromyography of anterior temporalis and superficial masseters muscles were recorded and compared at baseline in 26 patients with arthrogenous temporomandibular disorders (study group) and 26 asymptomatic subjects (control group). The study group was treated pharmacologically and by means of five arthrocentesis sessions. Pre-, during-, and post-treatment pain and mandibular function were assessed and compared among timepoints. Clinical improvement in terms of pain and mandibular function was correlated with pre-treatment standardized surface electromyography values.

RESULTS

Temporomandibular disorders patients showed improved maximum mouth opening and pain during and after treatment with arthrocentesis compared to baseline (T-test p < 0.01). Standardized surface electromyography values were significantly different in temporomandibular disorders subjects compared to controls (T-test p < 0.05). Improvement in pain at rest after treatment was inversely correlated with pre-treatment masseters standardized surface electromyography symmetry (R-coefficient 0.3936; p < 0.05).

CONCLUSIONS

Temporomandibular disorders patients showed a different muscular recruitment pattern compared to controls. The lesser the pre-treatment masseters symmetry, the greater the improvement of pain at rest after treatment.

Myofunctional orofacial examination tests: a literature review

INTRODUCTION

Myofunctional orofacial examination (MOE) is an important tool for the assessment of the stomatognathic system and orofacial functions, and the early diagnosis of orofacial myofunctional disorders. Therefore, the purpose of the study is to scan the literature and determine the most preferred test for myofunctional orofacial examination.

MATERIALS AND METHODS

A literature review was conducted to collect information. Pubmed and ScienceDirect database was explored by using keywords gained by MeSH (Medical Subject Headings).

RESULTS

Fifty-six studies were retrived from the search and all of the studies were screened and evaluated regarding the subject, aim, conclusions and the orofacial myofunctional examination test they used. It has been observed that traditional evaluation and inspection methods have been replaced by newer and methodological approaches in recent years.

CONCLUSIONS

Although the few tests used differ, 'Orofacial Examination Test With Scores' (OMES) was found to be the most preferred myofunctional orofacial evaluation method from ENT to cardiology.

Alterations in Surface Electromyography Are Associated with Subjective Masticatory Muscle Pain

Background

Tenderness of masseters and temporalis can be considered a relevant tool for diagnosis of myo-type craniofacial pain disorders, but a limit of pain score systems is that they are based on subjective pain perception. Surface electromyography (sEMG) is a noninvasive and reliable tool for recording muscle activity. Therefore, we investigated whether a correlation exists between tenderness on masseters and temporalis, assessed by subjective pain scale, and muscles activity, evaluated by sEMG, in patients with painful temporomandibular disorder (TMD) and concurrent tension-type headache (TTH).

Methods

A cross-sectional study on fifty adult volunteer patients with TMD and TTH, who underwent tenderness protocol according to Diagnostic Criteria for TMD (DC/TMD) guidelines, was conducted followed by sEMG recording of temporalis and masseters. Pearson's correlation was performed to investigate the correlation between muscular activity and subjective pain scores.

Results

An overall moderate correlation between muscle tenderness and sEMG values (y = 1 + 1.2 · x; r² = 0.62; p < 0.0001), particularly in the temporalis, was observed. Segregation of data occurred according to tenderness and sEMG values. At the highest pain score, the mean sEMG absolute value was higher at the temporalis than the masseters.

Conclusions

Our study provides evidence that subjective pain perception can be objectively quantified at a magnitude proportional to pain severity. At greater tenderness scores, higher sEMG activity at the level of temporalis could help discriminate clinically prevalent TTH versus prevalent TMD. sEMG confirms to be an accurate tool to reliably objectify the subjective perception of pain. When combined with clinical evaluation and patients' symptoms, sEMG increases diagnostic sensitivity in the field of myo-type craniofacial pain disorders. This trial is registered with NCT02789085.