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Year : 2020  |  Volume : 31  |  Issue : 1  |  Page : 42-47
Comparative efficacy of low-Level laser and TENS in the symptomatic relief of temporomandibular joint disorders: A randomized clinical trial

Department of Oral Medicine and Radiology, Sree Balaji Dental College and Hospital, Chennai, Tamil Nadu, India

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Date of Submission26-Sep-2018
Date of Decision20-Nov-2018
Date of Acceptance06-Jan-2019
Date of Web Publication02-Apr-2020


Aim: Temporomandibular disorders (TMDs) comprise a number of signs and symptoms affecting the masticatory muscles, temporomandibular joint (TMJ), or both. Because of the multifactorial etiology of such problems, the treatment usually involves more than one modality. Objectives: Therefore, the aim of this study was to compare the effectiveness of transcutaneous electric nerve stimulation (TENS) and low-level laser therapy for the treatment of patients with TMD. Materials and Methods: The clinical trial was performed with 60 patients diagnosed with TMD of multiple causes. All the patients received both methods of treatment in 6 consecutive weeks. A paired t-test was applied to verify the significance of the results. Results: A significant improvement in the range of motion and pain relief for both the therapies was observed. Conclusions: Comparatively after analyzing the two methods, the values obtained after LLLT were significantly higher than those obtained after TENS therapy (P < 0.01).

Keywords: Low-level laser, physical therapy, temporomandibular joint disorders, transcutaneous electric nerve stimulation

How to cite this article:
Chellappa D, Thirupathy M. Comparative efficacy of low-Level laser and TENS in the symptomatic relief of temporomandibular joint disorders: A randomized clinical trial. Indian J Dent Res 2020;31:42-7

How to cite this URL:
Chellappa D, Thirupathy M. Comparative efficacy of low-Level laser and TENS in the symptomatic relief of temporomandibular joint disorders: A randomized clinical trial. Indian J Dent Res [serial online] 2020 [cited 2021 May 11];31:42-7. Available from:

Temporomandibular joint (TMJ), the area where the mandible articulates with the cranium, is one of the most complex joints in the body. In 1934, Costen described a group of symptoms that described the ear and TMJ.[1] The American Dental Association later adopted the term “temporomandibular disorders” in 1997.[2]

The orofacial pain classification outlined by Okeson has divided pain into two groups as physical (Axis 1) and psychological (Axis 2) conditions.[3] TMJ is often affected by inflammatory, traumatic, infectious, congenital, developmental, and neoplastic diseases, and it may also be caused by malocclusion, parafunctional habits such as bruxism, lip biting, stress, anxiety, or abnormalities of the intra-articular disc.[4],[5]

The prevalence of temporomandibular disorders (TMDs) is about 40%–75%. Solberg et al. showed that 76% of subjects between 18 and 25 years of age had one or more signs associated with TMD and 26% had at least one symptom associated with TMD. TMJ sounds and deviation on opening the jaw occur in approximately 50% of the patients, but only 5% seek treatment.[5],[6] The management of TMDs involves multidisciplinary approach together with self-care at home, counseling, physiotherapy techniques, pharmacotherapy, jaw-appliance medical aid, behavioral medicine, and surgery. Almost 85%–90% of TMDs are of articular or muscular origin.[7] They can be treated with noninvasive medical procedures, nonsurgical, and reversible interventions. For patients with intra-articular disorders that does not respond to nonsurgical intervention for more than 3–6 months, surgical intervention may be considered as the treatment of choice.[4] Nonsurgical treatments ought to be considered for every symptomatic patients with Internal Derangement/Osteoarthritis. Patients with severe pain and dysfunction may likewise be dealt with nonsurgical modalities. But if symptoms does not resolve within 2–3 weeks, surgical intervention is indicated.[5]

Among such treatments, acupuncture, muscle exercises, massages, thermal therapy, transcutaneous electric nerve stimulation (TENS), ultrasound, and low-level laser (LLL) have been used successfully. TENS is used to relax hyperactive muscles;[7],[8] it acts like a neuromuscular stimulator. TENS equipment produces a low-amplitude, low-frequency alternating stimulus that causes muscles to contract and relax. It is applied bilaterally between the TMJ and the coronoid region. This therapy is applied to reduce the muscular activity of masticatory muscles.[9],[10]

Low-level laser therapy (LLLT) seems to be in accordance with TMD's treatment philosophy, because it represents a noninvasive, reversible therapy without any known side effects. LLLT makes use of the electromagnetic radiation of a single wavelength, usually in the red or infrared regions. This provides treatment for several pathologies, including impaired wound healing, pain conditions, and inflammatory situations.[11],[12] Several reports have documented the positive effects of LLLT in TMD.[11],[12] Kulekcioglu et al.[13] showed that after 15 sessions of LLLT, TMD of both myogenic and arthrogenic causes responded to therapy with a significant reduction in pain, improvement in mouth opening and lateral motion, and a diminished number of trigger points. However, the clinical efficacy of LLLT has been questioned.[11] Given the large range of treatment parameters involved in this therapy (i.e. wavelength, fluence, intensity, exposure time, total duration of treatment), it is not difficult to understand that results differ from one study to the next.[12]


The aim of this study was to evaluate and analyze the efficacy of LLLT and TENS in patients suffering from pain associated with TMJ dysfunction.

Inclusion criteria

  • Patients with history of persistent, recurrent, or chronic TMJ pain for more than 3 months not relieved by analgesics
  • Patients falling in Research Diagnostic Criteria for TMJ disorders (RDC/TMD)
  • Patients willing to participate in this study
  • Patients in pain with the presence of reciprocal joint clicking, restricted mouth opening, and jaw deviation who have not undergone any medical or pharmacological treatment for TMD.

Exclusion criteria

  • Cases with congenital abnormality and neoplastic conditions in TMJ region
  • Patients with a recent history of acute trauma or any form of treatment within the last month
  • Patients who are not willing to participate in the study
  • Epileptic patients
  • Patients with known skin disorders (psoriasis, eczema)
  • Apprehensive patients (patients with communication handicap/mental disability)
  • Patients with cerebrovascular problems (patients with history of aneurysms, stroke, and transient ischemia) (as it stimulates peripheral blood flow which causes claudication and cramping pain due to obstruction of arteries)
  • Patients who are allergic to adhesive tape or electrodes of TENS machine
  • Patients with neurological diseases involving head and neck
  • Patients who have already been treated with TENS without any improvement in condition.

   Materials and Methods Top

Study population

This study was performed on patients who reported to the Department of Oral Medicine and Radiologyat a Dental Institution in Chennai, with orofacial pain who satisfied the RDC/TMD. Sixty subjects were selected based on clinical diagnosis and were randomly divided into two groups for the treatment, namely, LLLT group (Group A) and TENS group (Group B). All the recruited patients were asked to refrain from consuming pain killers and other forms of therapy such as palliative care, massage, and physiotherapy. All the patients were explained about the procedure in detail, and signed informed consent was obtained.

Methodology and devices used

LLLT conveyance is through a Zolar photon 3-W semi-conductive laser [Figure 1], 672-nm diode laser (Zolar Technology and Mfg. Co. Inc., Ontario, Canada), with 50 mW of output yield power and 3 Joules per site/four sites of fluence (masseter, temporalis region, condylar region, and intra-auricular portion). Treatment was done in alternative days; two sessions/week for 3 weeks. Each tender point was exposed to 120 seconds of LLLT. Patients were subjected to LLLT with “scanning movements” instead of touching skin directly over the painful area.
Figure 1: Zolar diode 3-W soft tissue laser unit

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TENS therapy was given with a two-electrode unit at 20 W with the maximum frequency of 60 Hz, adjusted according to patient's response. Patients of Group B (30 cases) were subjected to TENS therapy, two sessions/week for 3 weeks in alternative days for 15 min per sitting. A TENS unit (Digi Dual Pocket Model TENS; Bharath Medical Systems, Chennai, Tamil Nadu, India), which emits low-level electric pulses rhythmically every 1.5 s, was used [Figure 2]. Adhesive leads with electrodes were placed over the tender points and pain areas, and intensity was set by patient's tolerability (rate 2 Hz; pulse 240 μs).
Figure 2: Digitens conventional TENS unit used in this study

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The first researcher applied laser therapy and TENS and conducted physical evaluation of the patients before and after treatment sessions. The second researcher carried out the selection of patients and co-ordination of the study.

After every therapy session and before initiating the treatment to any patient, evaluation was done promptly by the methods of Numeric Pain Distress scale, by evaluating the mandibular active range of motion (maximal pain-free mouth opening) and by palpating the masticatory muscles.

The Numeric Pain Distress scale consists of a single horizontal level line measuring from 0 to 10, on which the patient marks; that particular position denotes the level of pain and agony perceived by the patient at that point of time.

Bilateral masticatory muscle palpation was done by applying delicate, constant, and firm pressure, as described by Conti et al.[14] In this way, based on the responses showed by people, the degree of pain under palpation was appraised as follows – 0: no pain; 1–3: mild pain; 4–6: moderate pain; 7–10: severe pain. The muscles assessed were masseter and the anterior portion of the temporalis muscle.

Statistical analysis

Statistical analyses were accomplished using paired t- test. A P value of <0.05 was considered to indicate a statistically significant difference between the groups.

   Results Top

This randomized clinical trial was conducted to compare the efficacy LLLT and TENS in the treatment of TMDs. Permission from the Institutional Ethical Committee of the dental insitu tion was obtained before starting the study. The results were judged by visual analog scale (VAS) scores and maximal pain-free mouth opening after each visit.

The VAS is considered an accurate and reliable scale to quantify pain. In this study, the VAS was used to measure the intensity of pain. The scores were quick and easy to use, and it is a valid technique for evaluation of subject's pain as it is related to self-selected functional activity. In this study, a statistically significant decrease in VAS scores following TENS and LLLT was evident, and a considerable reduction (74.19%) in pain was noted.

   Discussion Top

There are several methods reported for the management of TMDs; however, the use of noninvasive interventions is recommended in most cases. TENS device is often used in dentistry to control chronic pain and relax masticatory muscles. In recent years, LLLT has been used for the management of musculoskeletal pain, wound healing, and inflammation.[15],[16]

LLLT is the application of light, usually a low-power laser, to a pathology to promote tissue regeneration, reduce inflammation, and relieve pain. The light is typically of narrow spectral width in the red or near-infrared spectrum (600–1000 nm), with a power density (irradiance) between 1 mW and 5 W/cm2. It is typically applied to the injury for a minute or so, a few times a week for several weeks. Unlike other medical laser procedures, LLLT is not an ablative or thermal mechanism, but rather a photochemical effect.[17]

The mechanism of LLLT effects involves mitochondria. The effects of laser and other illumination on mitochondria increase the proton electrochemical potential, enhance ATP synthesis, increases RNA and protein synthesis, increase oxygen consumption and membrane potential, and enhance the synthesis of NADH and ATP. This photostimulatory effect in mitochondria processes enhances growth factor release leading to cell proliferation.[18]

TENS is widely used nowadays to relieve acute and chronic pain and in various conditions such as back pain, neck pain, phantom limb pain, and extremity pain, but there have been few studies on its use for the relief of orofacial pain.[19],[20] TENS therapy works on several interrelated theories. It suggests that TENS stimulates thick, myelinated, sensory fibers (A-fibers), which in turn block the impulses of thin pain-modulating fibers (C-fibers) and close the gate to pain signals at the level of their entry into the spinal cord.[13],[21]

The results of this study demonstrated a decrease in the pain report for both groups, when VAS was used. When intragroup analysis is considered, however, the laser group had a better outcome when compared with TENS group, in agreement with Bertolucci et al.[22] The whole sample has reported a significant improvement in the final assessment. The different initial mean VAS between groups certainly influenced the final difference between both modalities. When comparing the VAS reduction for both groups [Figure 3], similar results were observed (86% and 83% for LLLT and TENS, respectively).
Figure 3: Intergroup comparison of VAS scores in Groups A and B

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In this study, the initial mean maximum mouth opening of the whole sample was 33.8 mm, and the final mean after the six sessions of therapy was 42.9 mm [Figure 4]. Obviously, improvement in this feature can be understood as a secondary effect of pain reduction, as a result of laser and TENS therapy. This fact is in agreement with Anuj Mishra et al.[23]
Figure 4: Intergroup comparison of mouth opening scores in Groups A and B

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Even though LLLT and TENS have been frequently used nowadays as a treatment for soft tissue inflammation, it cannot be considered as a gold standard treatment option because the currently available research regarding its clinical efficacy remains inconclusive.[24]

The difference in VAS scores and mouth opening before and after treatment with LLLT and TENS showed a statistically significant P value of 0.00.

[Table 1] and [Figure 3] and [Figure 4] show the intergroup comparison of two groups, Group A and Group B. The results of these two groups were also statistically significant. For both the groups, the initial mean values compared with final values showed significant improvement in range of mandibular motion in all study subjects (P < 0.01).
Table 1: Intergroup comparison between Group A and Group B

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In this study, the patients with chronic symptoms for more than 3 months showed significant improvement after 1 week of LLLT and TENS therapy. This was in accordance with Bharat Khosla et al.[24] who evaluated the short-term efficacy of LLLT and TENS in TMJ disorders. The results showed marked improvements in clinical parameters with both LLLT and therapeutic TENS in patients with osteoarthritis. Hence, it requires further research to obtain a better understanding of this technique.[25]

[Figure 5] shows the mean values of VAS scores of both groups during the study period. VAS score for TMJ pain steadily decreased over the study period in both the LLLT group (P < 0.01) and the TENS group (P < 0.06). The baseline VAS pain scores before the first visit were compared with scores before the fourth visit to determine the effect of repeated treatments. A significant improvement was observed in the LLLT group (P < 0.01), but there was no significant change in the TENS group (P = 0.064). Furthermore, the decrease in VAS pain score was significantly different between the two groups (P < 0.01).
Figure 5: Mean values of VAS scores of both groups during the study period

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[Figure 6] shows that the mean values of mouth opening before LLLT were 41.2 mm. Immediately, at the end of the therapy, the mean values of mouth opening were 43.3 mm. The values after therapy were significantly higher than the initial ones (P = 0.00). Similarly, the mean values of mouth opening before TENS therapy were 38.8 mm. The amplitude of mouth opening after treatment was significantly higher (P = 0.03). In this study, LLLT was significantly more efficient in improving the mouth opening as there was a gradual increment in range of motion following visits compared with TENS group.
Figure 6: Mean values of mouth opening of both groups during the study period

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In our study, even though both the groups showed significant improvement, LLLT group seems to be a little superior than TENS group which was evident in the improvement of clinical symptoms and marked improvement in mouth opening which was also statistically significant.

A number of other variables were kept constant in this study, such as the frequency, wavelength of LLLT unit, intensity of TENS and LLLT, the mode of LLLT (continuous vs. pulsed), duration of treatment, and transmission of LLLT and TENS to get a better understanding of this technique. Hence, it requires further research to get a better understanding of this technique.

   Conclusion Top

In this study, VAS scores and the range of mandibular motion were evaluated in patients following LLLT or TENS to assess pain reduction and improvement in mouth opening immediately after therapy. Both therapies were effective in improving the amplitude of mandibular movement. These treatments should be performed before conventional dental treatment in patients with TMD. Comparing the two methods, LLLT was more effective than TENS therapy. This study results conclude that statistically there was a significant difference between LLLT and TENS groups in the symptomatic relief of TMDs.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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Ferreira AP, Costa DR, Oliveira AI, Carvalho EA, Conti PC, Costa YM,et al. Short-term transcutaneous electrical nerve stimulation reduces pain and improves the masticatory muscle activity in temporomandibulardsisorder patients: Arandomized controlled trial. J Appl Oral Sci 2017;25:112-20.  Back to cited text no. 11
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Kulekcioglu S, Sivrioglu K, Ozcan O, Parlak M. Effectiveness of low-level laser therapy in temporomandibular disorder. Scand J Rheumatol 2003;32:114-8.  Back to cited text no. 13
Conti PCR. Low level laser therapy in the treatment of temporomandibular disorders (TMD): Adouble-blind pilot study. Cranio 1997;15:144-9.  Back to cited text no. 14
Wu JH, Chang WD, Hsieh CW, Jiang JA, Fang W, Shan YC,et al. Effect of low-level laser stimulation on EEG. Evid Based Complement Alternat Med 2012;2012:951272.  Back to cited text no. 15
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da Silva MA, Botelho AL, Turim CV, da Silva AM. Low level laser therapy as an adjunctive technique in the management of temporomandibular disorders. Cranio 2012;30:264-71.  Back to cited text no. 17
Núñez SC, Garcez AS, Suzuki SS, Ribeiro MS. Management of mouth opening in patients with temporomandibular disorders through low-level laser therapy and transcutaneous electrical neural stimulation. Photomed Laser Surg 2006;24:45-9.  Back to cited text no. 18
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Lassemi E, Jafari SM, Motamedi MHK, Navi F, Lasemi R. Low-level laser therapy in the management of temporamandibularjoint disorder. J Oral Laser Appl 2008;8:83-6.  Back to cited text no. 21
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Mishra A, Sinha A, Mehrotra P, Agarwal N, Srivastava S. A comparative study on efficacy of three different treatment modalities for temporomandibular joint pain and dysfunction. Oral Health Dent Manag 2015;3:27-32.  Back to cited text no. 23
Khosla B, Singh A, Agarwal N, Mishra A. Comparative evaluation between the effects of low-intensity laser therapy and transcutaneous electric nerve stimulation on temporomandibular joint disorders. Int J Sci Study 2015;3:86-92.  Back to cited text no. 24
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Correspondence Address:
Deepika Chellappa
239/5, Kattabomman Street, Sadhanandapuram, Chennai - 63, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijdr.IJDR_735_18

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

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