Electromyographic Study for Swallowing Muscles in Normal and TMD Patients

Faisal Taiyebali Zardi, V. Nagalaxmi, Brajesh Gupta, Ayesha Sadathullah*, Rishika Reddy and Mohammed Haris Iqbal
Sri Sai College of Dental Surgery, Hyderabad, India
*Corresponding author: Ayesha Sadathullah, Sri Sai College of Dental Surgery, Hyderabad, India.
Citation: Zardi FT, Nagalaxmi V, Gupta B, Sadathullah A, Reddy R, Iqbal MH. Electromyographic study for swallowing muscles in normal and TMD patients. J Oral Med and Dent Res. 6(1):1-13.
Received: September 25, 2024 | Published: January 02, 2025
Copyright© 2025 genesis pub by Zardi FT. CC BY-NC-ND 4.0 DEED. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License. This allows others distribute, remix, tweak, and build upon the work, even commercially, as long as they credit the authors for the original creation.
DOI: https://doi.org/10.52793/JOMDR.2025.6(1)-80
Abstract
Background: Temporomandibular disorder (TMD) is a multifactorial disease often linked to parafunctional habits such as clenching and grinding. These habits are known to influence the activity of facial muscles, potentially leading to conditions like obstructive sleep apnea (OSA) and its variant, dysphagic OSA.
Methods: This study evaluated the activity of four facial muscles (temporalis, masseter, digastric, and sternocleidomastoid) in 30 TMD patients and 12 healthy individuals using a 4-channel surface electromyography (sEMG) with Biopak software. Muscle activities were measured during rest, clenching, and swallowing. Data were analyzed statistically using the Mann-Whitney U test with a significance level set at p ≤ 0.05. Results:The study found hyperactivation of all four muscles in TMD patients compared to healthy controls.
The temporalis muscle showed significant hyperactivation on both sides during rest (p=0.001 and p=0.000), clenching (p=0.000 and p=0.001), and swallowing (p=0.001 and p=0.000). Similar significant results were observed for the masseter, digastric, and sternocleidomastoid muscles. These findings suggest an increased masticatory muscle activity in TMD patients, potentially contributing to parafunctional habits and dysphagic OSA. Conclusions:This study underscores the importance of early detection and multidisciplinary management of TMD to address parafunctional habits and prevent associated conditions like dysphagic OSA. The use of 4-channel sEMG provides valuable insights into the neuromuscular aspects of TMD, guiding clinicians towards improved diagnostic and therapeutic strategies.
Keywords
Temporomandibular Joint; Temporomandibular Joint Disorders; Obstructive Sleep Apnea; Dysphagic Obstructive Sleep Apnea; Facial Muscles; Surface EMG; Rest; Clenching; Swallowing.
Clinical Relevance Statement
The present study highlights the increased activity of facial muscles (temporalis, masseter, digastric, and sternocleidomastoid) in TMD patients during rest, clenching, and swallowing which was measured using a 4-channel surface electromyography. This hyperactivity is linked to parafunctional habits and may contribute to conditions like dysphagic OSA. Understanding these neuromuscular dynamics advances our knowledge of TMD and OSA pathogenesis and underscores the need for multidisciplinary approaches in diagnosis and treatment, aiming to improve clinical outcomes and quality of life for TMD sleep disorder patients. Clinicians are encouraged to consider these findings for early intervention and comprehensive management strategies.
Introduction
Temporomandibular disorder (TMD) is a multifactorial disease which is associated with multiple perpetuating, predisposing, and initiating factors [1-2]. It is most commonly encountered disorder among woman when compared to men [3]. This is probably correlated to increased level of production of estrogen hormone during the 2nd to 4th decades of life which ultimately declines during the phase of menopause [4-5]. One of the early sign of temporomandibular joint abnormality is presence of sounds during function [6]. The prevalence of TMD is commonly observed between the age group of 20 to 40 years [7].
Temporomandibular disease is a range of conditions which is commonly characterized by heterogeneous signs and symptoms and has been reported to be the 2nd most common musculoskeletal or neuromuscular disorders and is often associated to headache [8,10].
TMDs are considered as the primary cause of non-odontogenic pain in the orofacial region. The temporomandibular joint (TMJ) may be affected by inflammatory, traumatic, infectious, congenital, developmental, and neoplastic disease as seen in other joints [11]. Temporomandibular disease generates pain that is often unilateral in nature and referred to the ears, temporal and periorbital regions, the angle of mandible and to the posterior aspect of the neck [12,14].
Several authors hypothesized that TMD is often associated with obstructive sleep apnea (OSA [15-16]. The presence of OSA may aggravate oral parafunctional habits during sleep [17]. Studies further suggest an association between TMD and oral parafunctional habits. Clenching or grinding are often correlated to TMD [18]. The parafunctional habits are correlated to TMD pathogenesis [19].
The most common parafunctional habit evaluated is clenching [20]. Few studies have evaluated the correlation of TMD with an important and perpetuating function that occurs in daytime and during sleep i.e., swallowing. It is well known fact that the swallowing pattern differs among the population and that an alteration in positioning the tongue generates difference in both of maxillary growth and displacement of teeth [21,23]. Swallowing takes less than a second [24,26]. during which the activation of muscles induces contact between the teeth and controls stability of jaw, hyoid bone and TMJ [27].
Stomatognathic system activities, especially speaking, breathing, eating, and swallowing, are often negatively impacted by impairments of the temporomandibular joint and masticatory muscles [28]. Diagnostic tests for TMD include Jaw tracker, Joint vibration analysis, T-scan system, and electromyography.
The study of electrical activity of muscle is called electromyography (EMG). The instrument that was used to measure the electrical activity of muscles is called an electromyogram. An electromyograph is a pattern of muscular electrical activity that has been recorded. The first studies of dental applications of electromyography were published in the 1952 [29]. EMG was as used as diagnostic tool in 1996 by Okeson for evaluation of muscles [30].
EMG has three types of electrodes available. Surface electrodes are the ones which record the signals that are been generated on the surface of the skin, but these electrodes cannot detect deep potential signals occurring within the cell. Needle electrodes are the one that are inserted deep into the tissue, which records the action potential from the muscles and microelectrodes are the one which records the action potential the nerves [29].
Surface Electromyography (sEMG) is a technique in which electrodes are placed on the skin overlying a muscle to detect the electrical activity of the muscle. It’s a non-invasive and safe procedure which is indicated to study the muscle activity, relative change in timing of the muscle, assess motor control and coordination, evaluate mastication and post-surgical muscle function [29].
The aim of the present study is to evaluate oro-facial facial muscles during rest, clenching and swallowing in TMD patients using 4 channel surface EMG with Biopak software.
Methodology
Patient selection
30 TMD patients and 12 normal patients between the age range of 20 to 30 years, with a mean age of 27.4 years (Table:1) were selected from X college of dental surgery, INDIA.
Table 1: Demographic data of age and gender among cases and controls
Patients’ selection criteria were as follows: Angle’s Class I Molar relation (i.e., normal intermaxillary dental relationship), good symmetry of dental arches, and no refractive errors. Individuals with dental braces, congenital oral cavity deformities, systemic or oral diseases, missing teeth, prosthetic rehabilitation, piercings, neurological conditions, a history of mental health issues, physiotherapy, subjects taking drugs other than nonsteroid inflammatory drugs, paracetamol, or minor opioid analgesics were excluded.
TMD patients were enrolled in the study. Examination was performed using a standardized form in which included history and duration of the diseases, palpation at rest, in maximal voluntary contraction i.e., clenching and during mandibular motions of the masticatory and neck muscles, palpation of TMJ, assessment of spontaneous and triggered pain using a visual analog scale, as suggested by Okeson [30].
Before the evaluation, all the males were well-shaved. To place the electrodes, the subjects were asked to sit in an upright position with occlusal plane parallel to the floor. Skin was disinfected using spirit and cotton. To position the electrodes, subjects were requested to close their mouths and clench where the bulging of the muscle served as a templet in placement of the electrode. Ground electrodes were placed on the right and left trapezius muscle bilaterally which aids in conduction of signals. Bilateral sEMG electrodes were placed on temporalis muscles, masseteric muscles, digastric muscles, and sternocleidomastoid muscles (Figure 1a and 1b).
Figure 1a and 1b: Bilateral sEMG electrodes were placed on temporalis muscles, masseteric muscles, digastric muscles, and sternocleidomastoid muscles.
The instrument used was directly interfaced with a computer, which presented the data graphically. The signals were averaging over 25 milliseconds, with muscle activity of the 4 tested muscles expressed in microvolts. The sEMG test was performed on each patient while at rest, clenching and swallowing (Figure 2).