Introduction

Temporomandibular disorders (TMDs) are a collective term that includes disorders of the temporomandibular joint (TMJ), and of the masticatory muscles and their associated structures, characterized by pain, joint sounds, and restricted mandibular movement [1, 2]. TMD has a multifactorial etiology, including the presence of parafunctional habits, trauma stress, as well as emotional, systemic, hereditary, and occlusal factors [2]. The etiology is related to an association of predisposing factors that increase the risk of TMD, initiating factors that cause the onset of TMD, and perpetuating factors that interference with healing or enhance TMD progression [3]. TMD is considered the most common cause of pain of nondental origin in the orofacial region and contains a varied group of disorders with common symptoms of psychophysiological orofacial pain, masticatory dysfunction, or both. Signs and symptoms of this dysfunction are present in approximately 86% of the population, most frequently in women in the 30 years old age group [4]. Over the decades TMDs have been managed by non-surgical and surgical methods. Non-surgical management is always started with until the patients are refractory. Non-surgical management includes pharmacologic therapy, psychological counseling, use of occlusal splints, and heat therapies [5].

Lasers have been used extensively in the field of medicine and dentistry since its development by Maiman in 1960 [6]. Endre Mester in the late 1960s pioneered the biostimulatory effect of low-level laser, who demonstrated an increase in collagen synthesis in skin wounds [7]. Low-level lasers do not liberate heat or destruct the fibers, and they are named so because their density is lower than 0.5w/cm2. Some advantages of low-level laser therapy (LLLT) are stimulating biological system and improving cellular metabolism in the injured cells, having anti-irritant effect, improving blood circulation, increasing pain tolerance based on changes in the potential of embryonic layer, adjusting the immune system, increasing intracellular metabolism, speeding up scar recovery and indolence [8]. Due to its easy application, limited treatment time, and minimum contraindications, its analgesic, anti-inflammatory, and regenerative effects, this study has been carried out to evaluate the efficacy of LLLT in the management of TMDs.

Material and Methods

The study was a randomized controlled clinical trial with interventional design and parallel arm design. Patients reporting with pain in the TMJ region were included in the study. All these patients had history of initial treatment in the form of self-care, physiotherapy, occlusal splint therapy which had failed to obtain pain relief. All the study participants were informed about the details of the procedure and a written consent was obtained from them in the language they comprehend the best. The study was approved by the Institutional ethical committee and obtained clearance. A total of 60 patients were selected and divided into two groups of 30 each using the systematic random sampling method with table of random numbers as per Consort 2010 guidelines as shown in Table 1. Sample size was calculated based on the previous studies which performed a similar clinical trial and using the formula for one tailed hypothesis testing, for the hypothesis H0: π1- π2 = 0 against H1: π1- π2 > 0 with the following specifications; with α = 0.05% (5%) and β, Power = 80% (0.80) [9].

Table 1 Consort diagram
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Group-1: Placebo group where no laser was applied.

Group-2: Patients who received LLLT.

The inclusion and exclusion criteria were:

Inclusion Criteria

  • (1) Patients willing to participate in the study.

  • (2) The presence of TMJ pain during function, absence of a specific clinical TMJ disorder condition defined according to the Clinical Diagnostic Criteria for TMDs [10].

Exclusion Criteria

  1. (1)

    Patients with a myalgia, collagen vascular disease, or a history of trauma and previous surgery to joint.

Independent single investigator from the Dept of Physiotherapy was used to apply the laser therapy, who was not aware of the outcome of the study. The patients, research therapist as well as investigators were unaware of which type of treatment was applied during the sessions and subsequent follow-ups during the study.

Methodology

Sixty patients selected were divided into two groups of 30 each. The LASER was applied by a blind investigator.

Group-1 the placebo group received laser mimicking LLLT (It was not fired).

Group-2 the patients received LLLT.

The laser used was Helium–neon LASER available in the Dept of physiotherapy (Fig. 1). The probe was placed directly on the skin perpendicularly at the center of the upper joint space, approximately 1 cm in front of the tragus (Fig. 2). The laser beam was delivered through a handheld single laser probe. Each session, consisted of 2 min at both the closed mouth and maximum mouth opening position. Each patient received series of 20 treatments. Each series lasted 8 weeks, and patients were treated 2–3 times a week as per indication. Evaluation of TMJ pain during function was accomplished by patient self-assessment using a visual analog scale (VAS) as per Fig. 3 patients registered the mean pain perceived on chewing or eating hard foods in the preceding 7 days. Maximum interincisal mouth opening, mandibular movements in various excursions and deviation on opening or closing (figs. 4, 5, 6, 7). The data were obtained at baseline (week 0) and follow-up (weeks 2, 4, and 8 after the first laser therapy). Data obtained were analyzed statistically. All the patients who were still symptomatic were treated by conservative means that is mouth opening exercises and diet modification as well.

Fig. 1
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Helium–neon laser

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Fig. 2
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Positioning of the laser

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Fig. 3
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VAS for pain

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Fig. 4
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Recording of pre-op maximum interincisal mouth opening

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Fig. 5
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a and b Pre-op recording of lateral movements toward right and left side

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Fig. 6
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Recording of post-op maximum interincisal mouth opening

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Fig. 7
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a and b Post-op recording of lateral movements toward right and left side

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Results

Of the 60 patients included in the study, it comprised of 38 females and 22 males with age ranging from 25 to 54 with mean age of 38.4. Gender distribution was similar in both groups with no significance statistically (p value > 0.05) as shown in Table 2.

Table 2 Age and sex distribution
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The statistical analysis of various variables was carried out. Various parameters included VAS, maximum mouth opening, and lateral movements. Readings were noted at week 0, week 2, week 4, and week 8. The statistical analysis included comparative evaluation between the groups and within each group.

The comparative analysis of the degree of pain based on VAS among both groups showed that there was statistically significant improvement in the degree of pain in both the groups at week 2, week 4, and week 8 as shown by p value < 0.05, but as compared to group 1, group 2 showed better improvement in the degree of pain as indicated by higher mean values as shown in Table 3.

Table 3 Degree of pain based on VAS
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The maximum mouth opening in Group I improved from a mean of 24.03 mm at week 2 to mean of 25.73 mm at week 8, whereas Group II showed mean value of degree of mouth opening of 29.10 mm at week 2 to mean value of 35.36 at week 8. The improvement in the degree of mouth opening was statistically significant in both groups (p value < 0.05), but it was higher in Group II as shown in Table 4.

Table 4 Degree of mouth opening
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The degree of lateral movement improved from 3.73 mm to 8.86 mm in Group II over a period of 08 weeks in comparison with improvement from 3.8 mm to 4.6 mm in Group I. Group II showed a statistically significant results (p value < 0.05), as shown in Table 5.

Table 5 Degree of lateral movement
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Further the statistical analysis was carried out within each group to know the changes in each of the group. In group 1, i.e., the non-LASER group, there was improvement in the degree of pain from week 0 to week 2 and week 0 to week 4 but it was not statistically significant (p value < 0.05). However, there was statistically significant improvement in the degree of pain from week 0 to week 8. In Group 2, i.e., the LASER group, there was statistically highly significant improvement in the degree of pain from week 0 to week 2, week 0 to week 4, and week 0 to week 8 (p value < 0.0001), thus showing better results in the LASER group (Tables 6, 7, 8).

Table 6 Degree of pain
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Table 7 Degree of mouth opening
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Table 8 Degree of lateral movement
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The statistical analysis for the degree of mouth opening within group 1 as well as group 2 showed significant improvement in the values at week 0–week 2, week 0–week 4, and week 0–week 8.

The statistical analysis for the degree of lateral movement within Group 1 showed that the improvement from week 0 to week 2 was not statistically significant (p value > 0.5). But there was statistically significant improvement at week 4 and week 8 from the baseline at week 0 (p value < 0.05). In group 2 the improvement was statistically highly significant at all intervals week 0–week 2, week 0–week 4, and week 0–week 8 (p value < 0.05).

Discussion

Photobiotherapy is an old method which has been used from years for treatment. This dates back to when sunlight radiations were being used, but because normal light has the natural properties of releasing and distributing in all directions, it is unable to penetrate enough living tissues, thus limiting its role only for biologic stimulation in limited dermal treatments. Laser, on the other hand, can be easily localized due to its property of monochromaticity and directionality and the power of penetration helps to accelerate tissue growth and development via cellular stimulation without the use of any drug [11].

LLLT has gained lot of popularity as a method of management of many localized, painful, musculoskeletal conditions. LLLT makes use of the electromagnetic radiation of a single wavelength, usually in the red or infrared regions. LLLT provides treatment for several pathologies, including impaired wound healing, pain conditions, and inflammatory situations [12]. Its basic effects are biostimulative, regenerative, analgesic and anti-inflammatory. It also seems to act on the immune, circulatory, and hematological systems [3]. LLLT may promote analgesic effects via several mechanisms (e.g., increases liberation of endogenous opiates, increases urinary excretion of glucocorticoids, improves local microcirculation, increases lymphatic flow thus reducing edema, decreases permeability of the nerve cell membrane, decreases release of algesic agents in pathological sites, increases ATP production, decreases tissue asphyxia and acceleration of wound healing) [13, 14].

The importance of investigating the actual analgesic efficacy of LLLT lies on the fact that TMD symptoms have been treated by a wide array of methods separately, such as interocclusal splint, medication, physical therapy, and transcutaneous electric nerve stimulation; in most cases, however, better outcome is achieved when the therapies are associated, where lasers can be of great value [15]. In view of the above we conducted a study to evaluate the efficacy of LLLT in management of the painful TMJs.

This study used a specific type of LLLT treatment (HeNe, continuous wave, 632.8 nm, 30 mW) involving direct irradiation on painful TMJs, applied 2 to 3 times a week over 8 consecutive weeks. Participants with TMJ pain did benefit throughout the treatment period from the LLLT protocol used in this study. The variable of VAS pain during function improved significantly in both groups, and the active LLLT treatment group failed to show any tendency for greater beneficial changes compared with the placebo group. This finding is most likely related to the placebo effect. In support of our findings, better therapeutic results of LLLT compared to placebo laser treatment were also described in studies by Bradley et al., Bertolucci and Grey, Kulekcioglu et al., Beckerman et al., Cetiner et al., Sanseverino et al. and Gray et al. [13, 16,17,18,19,20,21].

Hanssen and Thoroe described no difference between active and placebo laser therapy [22]. In a meta-analysis Gam et al. [23] did not find a better therapeutic effect for active laser therapy than for placebo [23]. Similarly, significant differences between real and placebo laser treatment were not found in a study by Conti [24].

When the amount maximum mouth opening was compared among the groups, there was statistically significant increase in both groups but higher in the Group 2. This was not in agreement with the study by Camila et al. [9]. In the study conducted by them, nonsignificant increase in maximum mouth opening was found in the post-treatment evaluation of the LLLT group and a nonsignificant reduction was found in the placebo group. Their data did support the hypothesis that LLLT increases the range of motion, whereas Ahrari et al. found better results in the laser group than the placebo group regarding pretreatment and post-treatment maximum mouth opening mandibular range of motion [25].

The statistical analysis of the lateral movement showed significant improvement in both the groups with higher mean values in Group 2. Mazzetto et al. found similar results with improved pain and range of mandibular movement compared with placebo [15]. In contrast to our study, Da Cunha et al. and Emshoff found that LLLT was not effective in the treatment of temporomandibular disorders compared with placebo [26, 27].

The use of laser as a modality of TMD treatment presents several advantages, since it induces healing and allows for tissue reorganization [28, 29]. Besides, it provides fast response, is user-friendly, and may be employed for both acute and chronic pain. Kitchen and Partridge also reported that the low-level laser promotes cell alteration and proliferation, phagocytosis, and increased immune response [30]. They also stated that healing occurs by stimulation of macrophages, mast cells degranulation, activation of fibroblasts, alteration of cell membrane, angiogenesis, and photodissociation of oxyhemoglobins.

Conclusion

The present study was conducted at a single center in a comparatively small cohort. To confirm the outcome of the study, a longitudinal study with a larger sample size needs to be carried out to achieve the consistent results. Low-level therapy (LLLT) definitely has a role to play in reducing TMJ pain and improving the range of motion.

In view of the increase in the quantum of the patients with TMDs, LLLT can be made available at the maxillofacial surgical center to enable effective treatment of these patients. LLLT is not an alternative but an effective adjunct for the existing treatment modalities for treating TMDs.