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 Table of Contents  
Year : 2021  |  Volume : 33  |  Issue : 3  |  Page : 321-327

Efficacy of transcutaneous electric nerve stimulation over systemic pharmacotherapy in the management of temporomandibular joint disorders – A systematic review and meta-analysis

Department of Oral Medicine and Radiology, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India

Date of Submission18-May-2021
Date of Decision13-Aug-2021
Date of Acceptance31-Aug-2021
Date of Web Publication28-Sep-2021

Correspondence Address:
Dr. Gopal Maragathavalli
Department of Oral Medicine and Radiology, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu - 600 077
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiaomr.jiaomr_131_21

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Temporomandibular disorders (TMDs) encompass numerous clinical complications that involve the temporomandibular joint (TMJ), masticatory musculature, and its associated structures, or both. Abundant research in this field has been conducted; however, there is no conclusive evidence reported in the effective management of TMD using physical therapy such as Transcutaneous Electric Nerve Stimulation (TENS). The systematic review and meta-analysis aimed to compare and evaluate the efficacy of transcutaneous electric nerve stimulation over systemic pharmacotherapies in the management of symptomatic patients with temporomandibular joint disorders. The present review has been registered with PROSPERO – An international prospective register of systematic review (CRD42021233019). An electronic search was done in PubMed, Cochrane Library, Science Direct, Google Scholar, Latin American and Caribbean Health Sciences Literature (LILACS), ClinicalTrial.gov, and sci-hub.se. Manual electronic searches were also carried out and articles were handpicked. The assessments of articles were done using selection criteria. There are a vast number of studies done in this subject of interest and hence, only prospective clinical trials like Randomized clinical trials (RCTs) and controlled clinical trials (CCTs) were included in this review. A total of three studies were included in this review, which consisted of prospective RCTs and CCTs. Two studies have been reported for meta-analysis. The included studies show TENS is proven to be effective in the management of TMD. The currently available evidence was insufficient to conclude the effectiveness of transcutaneous electric nerve stimulation and systemic pharmacotherapies in temporomandibular joint disorders. Based on the results of the meta-analysis, we can conclude that there was a significant reduction in pain encountered due to TENS.

Keywords: Medical management, meta-analysis, pain, systematic review, temporomandibular joint disorder, transcutaneous electric nerve stimulation

How to cite this article:
Gopi I, Maragathavalli G, Uma Maheshwari T N. Efficacy of transcutaneous electric nerve stimulation over systemic pharmacotherapy in the management of temporomandibular joint disorders – A systematic review and meta-analysis. J Indian Acad Oral Med Radiol 2021;33:321-7

How to cite this URL:
Gopi I, Maragathavalli G, Uma Maheshwari T N. Efficacy of transcutaneous electric nerve stimulation over systemic pharmacotherapy in the management of temporomandibular joint disorders – A systematic review and meta-analysis. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2022 Dec 7];33:321-7. Available from: http://www.jiaomr.in/text.asp?2021/33/3/321/326893

   Introduction Top

Temporomandibular joint disorders (TMD) comprehend a wide range of clinical problems, which affect the temporomandibular joint, muscles of mastication, and other structures surrounding it or both.[1] Remarkably a higher female to the male predilection of about 10:1.6 has been stated in the literature.[2] Globally, studies have reported that approximately 10 –15% of adults have pain due to TMD and 5% have an apparent need for therapy.[3],[4] It is usually unveiled by certain signs and symptoms, namely, pain during mouth opening and/or closing, clicking, or popping sounds, limitation in jaw movement, muscle, and joint tenderness.[5] Studies have shown that individuals with TMD pain were reported to be present with psychological discomfort like depression, physical inabilities, poor quality of sleep, functional disabilities, and so on, which appear to have affected their Quality of Life (QoL).[6],[7],[8],[9]

Even though TMDs have been studied abundantly, there are still plenty of unanswered questions about their aetiopathogenesis, diagnosis, and treatment plans. The etiology of TMD is proven widely to be multifactorial. It constitutes the involvement of parafunctional habits like bruxism, malocclusion, trauma, stress, psychological, genetic, impacted, and/or buccoverted third molars, and systemic conditions like arthritis, cysts in the TMJ and associated region.[10],[11]

In 2013, the International Research Diagnostic Criteria for Temporomandibular Dysfunction Consortium Network published an updated classification for TMDs and broadly divided it into two groups namely intra-articular (within the joint) or extra-articular (involving the surrounding musculature.[12],[13]

Management of TMD is an important aspect and it involves other fields of dentistry such as prosthodontics, orthodontics, or maxillofacial surgery. According to the American Academy of Craniomandibular Disorders, physical treatment for pain due to TMD is cited as an important aspect in managing them.[14] Numerous physical therapy interventions are potentially effective in managing TMD including electrophysical modalities such as ultrasound, microwave, laser, and transcutaneous electrical nerve stimulation (TENS), exercise, and manual therapy techniques.[15]

Shane and Kessler in the year 1967 were the first people to introduce TENS in the field of dentistry. However, TENS is yet to gain well-known knowledge and practice in the field.[10],[16] TENS is a safe, non-invasive physical therapy that has the potential to have no adverse effects in patients undergoing the treatment. The mechanism of how TENS works is still not known, however, it is believed to have two theories: 1. Gate control theory 2. By the release of endomorphin-like chemicals in the brain. The third way of action of TENS is related to the automatic and involuntary contraction of muscles.[17] It works by the placement of surface electrodes on the sites where the pain is predominant and application of low-voltage electrical current of varying frequency (high or low), intensity, and pulse duration for a limited period.[18]

The first line of symptomatic management for TMD pain is the administration of systemic medications such as analgesics, anti-inflammatory, or muscle relaxants. Muscle relaxants can be peripherally or centrally acting; however, centrally acting relaxants are found to be more effective.[18] Drugs like tricyclic antidepressants (Eg: Amitriptyline) have also been found to be efficient in treating TMD pain. Drugs like Cyclobenzaprine or tizanidine are centrally acting skeletal muscle relaxants being used in various conditions such as muscle spasm, tension- type headaches, and so on that have proven to improve the QoL of individuals.[19]

The rationale behind conducting this systematic review and meta-analysis is to find out how effective is the physical mode of therapy and the systemic management and it aims to compare and evaluate their efficacy in the management of pain caused due to temporomandibular joint disorder.

Structured question:

The question that needs to be assessed in this review is –

Is transcutaneous electric nerve stimulation (TENS) better than systemic pharmacotherapies in the management of temporomandibular joint disorder pain?

PICO analysis:


All subjects present with all types of temporomandibular joint and muscle pain.


Transcutaneous electric nerve stimulation (TENS)


Pharmacotherapies are given systemically


To assess the pain intensity.

   Materials and Methods Top

Search methods for identification of studies

The present review has been registered with PROSPERO – an international prospective register of systematic review (CRD42021233019). The systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines (PRISMA) [Figure 1]. Studies that did not comply with the inclusion criteria that-is-to-say did not have full text, different languages, animal studies, and other treatment modalities from treating TMDs were all removed. Two independent authors screened the initial titles and abstracts to find all the eligible studies. The full texts were retrieved according to the inclusion and exclusion criteria. All differences of opinions were discussed and resolved in consultation with another independent author.
Figure 1: PRISMA flow diagram

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Electronic searches

An electronic search was done in PubMed, Cochrane Library, Google scholar, Web of Science, Science direct, Latin American and Caribbean Health Sciences Literature (LILACS), ClinicalTrial.gov, and sci-hub.se until January 18, 2021. Manual electronic search was done and articles were handpicked. Language barriers such as English were applied. All electronic strategies had similar Title/Abstract and MeSH terms and texts. We used the complete search terms for PubMed: “Temporomandibular joint disorders” , ” Temporomandibular joint disease”, “myofascial pain dysfunction syndrome”, “TMD”, “TMJ disease”, “TMJ Disorder”, “MPDS”, “diseases, temporomandibular joint”, “disease, temporomandibular joint”, “disease, tmj”, “Transcutaneous electric nerve stimulation”, “Transcutaneous electrical nerve stimulation”, “stimulation, transcutaneous electric”, “stimulation, transcutaneous electrical”, “Pharmacotherapy”, “Pharmacological agents”, “drug therapy”, “medical management”, “placebo”, “pharmacotherapies”, ” adjuvant drug therapy”, “agents, analgesic”, “analgesics”, “analgesics, anti inflammatory”, “agents, non steroidal anti inflammatory”, “non steroidal anti inflammatory agents”, “pain”, “pain management”, “Tmd pain management”, “management of Tmd pain”, “management of myofascial pain”, “MPDS pain management”. References in full text articles were manually searched additionally.

Searching other resources

The results were screened with title and abstract screening to select what studies will be included in this review. The references used in this study were hand searched to see if there were any clinical trials included. The last date of the search was on January 18, 2021. No relevant articles were obtained from cross-references.

Data collection and analysis

The data was collected from the studies that were included based on the author's name, publication year, study design, subjects, intervention, treatment duration, method of pain intensity measured, and outcome assessed.

Selection of studies

The data of studies that assessed transcutaneous electric nerve stimulation with systemic pharmacotherapy in subjects with temporomandibular joint and muscle pain were considered. If studies had similar parameters, the relevant data was described and synthesized.

Data extraction and management

Based on the inclusion criteria [Table 1], the data was extracted [Table 2] from the studies that were included by two independent authors after assessing the titles and abstracts of potential studies identified by the search strategy. If the title and abstract screening did not provide adequate clearance for the paper, the full text of the paper was assessed. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses study flow diagram was used to document the screening process.
Table 1: Eligibility criteria used for the study selection

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Table 2: Data extraction

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Assessment of bias in included studies

Assessment of risk of bias for all the included studies was done. This study has extracted data from randomized controlled trials (RCTs) and controlled clinical trials (CCTs) and has examined them. The risk of bias for the RCTs was assessed using the risk of a randomized trial of bias tool, given study bias does not change dependent on our review purpose. Randomized trials were assessed using the Cochrane Risk of Bias (RoB 2.0) tool and Higgins JPT 2016, which involve judgment on seven headings as formulated by the Cochrane group. The risk of bias for each of the domains and overall risk of bias was made as per the recommendations of the RoB 2.0 tool. Trials were classified as low risk of bias and unclear or high risk of bias as described in the RoB 2.0 tool.

Assessment of reporting bias

The possible influence of small study/publication biases on review findings was considered and formed a part of the GRADE level of evidence. The influence of small study biases was addressed by the risk of bias criterion “study size.” Assessment of the quality of the body of evidence was done based on Oxford's CEBM table.


The meta-analysis was carried out using RevMan software. The Forest plot also known as the blobbogram is plotted for meta-analysis for clinical trials performed using TENS and pharmacotherapy, and the results analyzed are explained later in the article.

   Results Top

A total of three studies was included in this systematic review and two in the meta-analysis based on the inclusion criteria. The mentioned studies were all carried out in the Indian population. Patients reporting symptoms of TMD, particularly pain, were alone taken into the study. Each study had 40 patients in total and have been divided into the respective groups (TENS and pharmacotherapy), accordingly. The study was conducted for 1 year at least. However, the specific duration of the study conducted by Singh et al.[24] in 2014 was not mentioned. Each of these studies did have TENS is a common intervention, however, they compared TENS with different systemic medications such as muscle relaxants and NSAIDs.

The Oxford Centre for Evidence shows level 2 for RCT and level 3 for the CCT. Of them, two studies fall under level 3 of the CCT category [Table 3].
Table 3: Evidence level of studies - Oxford Centre for Evidence Based Medicine 2011

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The risk of bias [Figure 2] and [Figure 3] of the included studies show that there was no evidence of unclear risk of bias found in the studies analyzed.
Figure 2: Risk of bias for the included studies

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Figure 3: Risk of bias summary

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The GRADE level of evidence is given in [Table 4]. It shows that the quality of evidence is moderate for the three studies and all the studies showed significant differences in pain when treated with TENS.
Table 4: GRADE level of evidence

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A graphical representation of random-effects meta-analyses was done to compare the TENS and the pharmacotherapy. The forest plot of two studies at 95% Confidence Interval with an overall effect P = 0.02 indicates that it statistically favors TENS in pain reduction than pharmacotherapy. However, the heterogeneity (I2 = 87%) is too high and denotes poor reliability [Figure 4].
Figure 4: Forest plot favoring TENS than pharmacotherapy

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   Discussion Top

Results from this systematic review indicated that there is a significant difference in the pain intensity in TMD subjects treated with TENS. Regardless of the pain intensity, Visual Analog Scale (VAS) is observed to be the choice of measurement. The initial pain and the final pain intensity are measured to evaluate the difference. A study conducted by Park JW et al.[20] states that the pain intensity in high disability patients was three times higher than for the low disability group and six times higher, than the control group. However, in this systematic review, there is no study reported to include disabled subjects.

TENS may act on various mechanisms, and it is used to relieve acute and chronic pain. However, there are very few studies done using TENS for orofacial pain.[21] Treacy et al.[22] reported that in a study conducted in patients with TMD pain there was no significant difference seen even after 20 sessions of TENS. Shanavas M et al.[23] conducted the study comparing TENS with systemic medication, a combination of an analgesic and a muscle relaxant and reported that TENS had better results in relieving pain than systemic tablets. However, he also stated that it can be used as adjuvant therapy in dentistry. Shailaja et al.[18] states that TENS helped in reducing the pain intensity and the systemic medications helped in improving the mouth opening. Singh H et al.[24] states that TENS had better results with both pain intensity and maximum mouth opening than placebo therapy. As TENS works on an electric current, it is not advised to all patients. Patients with pacemakers, pregnant women, other implants placed in the body, epileptic patients, and so on are to be cautious. However, proper evidence of not using TENS in such patients is yet to be known.

Systemic medications such as muscle relaxants, analgesics, tricyclic antidepressants, anti-inflammatory agents, serotonin receptor antagonists, and few others are used as the first line of treatment for symptomatic subjects. Centrally acting muscle relaxants act at the level of the brainstem through a mechanism in which it does not interfere with the muscle function but relieves the muscle spasm.[18] Patients with a prescribed dosage of tricyclic antidepressants have been shown to have better sleeping patterns than those who were not. Clark G et al.[25] in his study stated that administration of diclofenac systemically did not reduce the muscle tenderness. The adverse effect of advising a systemic medication is that it cannot be used in the long run. Simon LS et al.[26] states that gastrointestinal problems have been found in 30% of patients taking any NSAIDs, which was found when inspected using an endoscope, but serious problems were only reported in 1–2%. Selective COX-2 inhibitors in some studies have been shown to effectively inhibit signs of inflammation of the TMJ and decrease the risk of GI problems, but eventually with other serious systemic adverse reactions. It was also concluded that inhibition of both COX isoenzymes is needed to achieve effective analgesia for TMD. But to minimize the adverse effects on the GI mucosa, an NSAID with misoprostol added could be used.[27],[28],[29]

   Conclusion Top

The currently available evidence was insufficient to form a conclusion regarding the efficacy of transcutaneous electric nerve stimulation over systemic pharmacotherapies in the management of symptomatic patients with temporomandibular joint disorders.

Based on the results of the meta-analysis, we can determine that there was a significant reduction in pain encountered due to TENS. Hence, we can conclude that TENS was comparatively effective than systemic medications in TMD patients. However, the long-term effects of the use of these have not yet been reported.

Implications for practice

After performing detailed research, it has come to our understanding that transcutaneous electric nerve stimulation provides significant results in the management of pain on the temporomandibular joint disorder and muscle related. Most of the studies confirmed that TENS showed better results in comparison to pharmacological agents. However, pharmacological agents can be used as adjuvant therapy in dentistry. Moreover, emphasis on types of TMD, etiology, predisposing factors, and diagnosis may require modification in TENS and can be an additional focus on the practical aspect.

Implications for research

Further research regarding the number of times and duration of usage of TENS in individuals should be performed for better prediction in managing the pain. Further clinical trials ensuring rigorous methodologies such as Randomization, allocation concealment, intention to treat, analysis, and blinding should be followed.


An important limitation of the included studies is that there is no definitive data on the type of temporomandibular joint disorder patients taken into consideration. Another limitation is the duration of the usage of TENS and the medications prescribed were not standardized as this could threaten the validity of the outcome of interest.

The limitation of the sample size is another factor, which limits the validity of the studies. Lack of proper demographic data and follow-up are few other drawbacks to be considered. Further research is thus suggested to evaluate the mentioned outcomes.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3], [Table 4]


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