Evaluation of Laser Phototherapy in the Inflammatory Process of the Rat's TMJ Induced by Carrageenan

Photobiostimulation conjugated with stem cells or their secretome for temporomandibular joint arthritis in a rat model

BACKGROUND

Temporomandibular joint (TMJ) arthritis is a debilitating, challenging condition and different methods have been implicated for its treatment. This study aimed to test the therapeutic potentials of low-level laser therapy (LLLT) associated with adipose derived stem cells (ADSC) or their derived secretome on a murine model induced arthritis.

METHODS

Forty eight rats were divided into four groups where group I was the sham control, the rest of animals were subjected to arthritis induction using complete Freund's adjuvant, then divided as follows: group II received phosphate buffered saline (PBS) intraarticular injection and irradiation of 0 j/cm2, group III received ADSCs derived secretome and irradiation of 38 j/cm2, and group IV received ADSCs and irradiation of 38 j/cm2 as well. One and three weeks after treatment, animals were euthanized, and paraffin blocks were processed for histological assessment by hematoxylin and eosin stain with histomorphometrical analysis. Histochemical evaluation of joint proteoglycan content was performed through toluidine blue stain, and immunohistochemical staining by the proinflammatory marker tumor necrosis factor-α (TNF-α) was performed followed by the relevant statistical tests.

RESULTS

The arthritis group showed histological signs of joint injury including cartilage atrophy, articular disc fibrosis, irregular osteochondral interface, and condylar bone resorption together with high inflammatory reaction and defective proteoglycan content. In contrast, the treated groups III and IV showed much restoration of the joint structure with normal cartilage and disc thickness. The inflammation process was significantly suppressed especially after three weeks as confirmed by the significant reduction in TNF-α positive immunostaining compared to the arthritic group, and the cartilage proteoglycan content also showed significant increase relative to the arthritic group. However, no significant difference between the results of the two treated groups was detected.

CONCLUSION

LLLT conjugated with ADSCs or ADSCs derived secretome can efficiently enhance the healing of arthritic TMJs. Stem cell secretome can be applied as a safe, potent therapy. However, further investigations are required to unravel its mechanism of action and pave its way as a safe, novel, cell free therapy.

Efficacy of Occlusal Splints and Low-Level Laser Therapy on the Mandibular Range of Motion in Subjects with Temporomandibular Joint Disc Displacement with Reduction

Aims and Objectives

The study was carried out to evaluate the efficacy of four conservative therapeutic modalities on the mandibular range of motion (MRM) in subjects with anterior disc displacement with reduction (ADDwR) of the temporomandibular joint (TMJ).

Materials and Methods

One hundred patients (64 women and 36 men) were selected, and randomly distributed into four groups. Group I: Subjects receiving behavioral therapy (BT). Group II: Subjects receiving low-level laser therapy (LLLT). Group III: Subjects receiving maxillary anterior repositioning splint (MARS). Group IV: Subjects receiving stabilization splint (SS). The MRM was evaluated for each patient before treatment and after 6 months. Paired t test and one-way analysis of variance (ANOVA) tests were used for statistical analysis followed by a post hoc Tukey test (P ≤ 0.05).

Results

All groups showed significant improvement in MRM after 6 months of treatment (P ≤ 0.05) except for BT. There was a significant improvement for SS and MARS on the different movements of MRM, more than for LLLT and BT (P ≤ 0.05).

Conclusion

The MARS and the SS are effective in increasing the MRM for patients with ADDwR.

Resistance exercise and low-level laser therapy improves grip strength and morphological aspects in the ankle joint of Wistar rats with experimental arthritis

Rheumatoid arthritis (RA) is an inflammatory disease mainly affecting synovial joints. Photobiomodulation through low-level laser therapy (LLLT) and resistance exercise may improve the inflammatory process. Therefore, we analyzed the effects of resistance exercise, LLLT, and the combination of both treatments on hind paw grip strength and ankle joint histomorphometric aspects of Wistar rats subjected to experimental RA. A total of 64 male Wistar rats were divided into eight groups: control, control LLLT, control exercise, control LLLT and exercise, arthritis, arthritis LLLT, arthritis exercise, and arthritis LLLT and exercise groups. The experimental RA was induced by a complete Freund's adjuvant injection into the knee joint cavity. Climbing exercises and LLLT (660 nm; 5 J/cm² per point) were performed as the treatment. In addition, muscle strength was evaluated using the grip strength test, and morphometric evaluations were performed on the ankle joint. Generalized mixed models and multivariate analysis of variance tests were used for statistical analysis. Statistical significance was set at a p-value of .05. Arthritis LLLT, exercise, and LLLT and exercise had positive effects on grip strength between the groups (F[7.56] = 5.8, p < .004) and within the groups (F[4.3] = 9.9, p < .002) throughout the evaluations. Morphometry revealed degenerative lesions in the ankle joint as subintima with angiogenesis, inflammatory cells, flocculated articular cartilage, chondrocyte disorganization, and pannus in the arthritis group (p < .001). The treated groups exhibited morphological characteristics similar to those of the control group. LLLT and resistance exercise restored muscle strength and morphological aspects of the ankle joint in rats with experimentally induced RA.

Promising minimally invasive treatment modalities for symptomatic temporomandibular joint disc displacement with reduction: a randomized controlled clinical trial

BACKGROUND

Pain and clicking are the primary complaints in patients suffering from temporomandibular joint disc displacement with reduction (DDwR), negatively affecting the patients' quality of life, making the treatment essential. This prospective randomized controlled trial (RCT) was conducted to evaluate the effectiveness of botulinum toxin type-A (BTX-A) and low level laser therapy (LLLT) in comparison to anterior repositioning appliance (ARA) for the treatment of DDwR.

METHODS

A total of 27 patients were randomly allocated to 3 groups; ARA (control group), BTX-A, and LLLT; with 9 patients each. All patients were evaluated before and 3 months after the treatment using a visual analogue scale (VAS) and magnetic resonance imaging (MRI).

RESULTS

At 3 months follow-up, all groups showed a significant reduction in pain assessed by VAS (P = 0.007). Measured on MRI, there was a significant improvement in disc position and joint space index (JSI) in BTX-A group (P < 0.001, P = 0.011) and LLLT group (P = 0.002, P = 0.017) in comparison to the control group (P = 0.087, P = 0.066) respectively. As for time of recovery, a statistically significant difference was observed in BTX-A group (P < 0.001) and LLLT (P < 0.001) group in comparison to ARA group, which showed the most prolonged duration for reduction of DDwR symptoms.

CONCLUSION

We concluded that BTX-A and LLLT could be considered effective alternative treatment modalities to ARA regarding reducing joint pain, clicking, and improving disc position in patients with symptomatic DDwR.

TRIAL REGISTRATION

This prospective double-blinded RCT has been registered at ClinicalTrials.gov with identification number: NCT05194488, 18/1/2022.

Pharmacological effects of a complex α-bisabolol/β-cyclodextrin in a mice arthritis model with involvement of IL-1β, IL-6 and MAPK

Inflammatory arthritis is the most prevalent chronic inflammatory disease worldwide. The pathology of the disease is characterized by increased inflammation and oxidative stress, which leads to chronic pain and functional loss in the joints. Conventional anti-arthritic drugs used to relieve pain and other arthritic symptoms often cause severe side effects. α-bisabolol (BIS) is a sesquiterpene that exhibits high anti-inflammatory potential and a significant antinociceptive effect. This study evaluates the anti-arthritic, anti-inflammatory and antihyperalgesic effects of BIS alone and in a β-cyclodextrin (βCD/BIS) inclusion complex in a CFA-induced arthritis model. Following the intra-articular administration of CFA, male mice were treated with vehicle, BIS and βCD/BIS (50 mg/kg, p.o.) or a positive control and pain-related behaviors, knee edema and inflammatory and oxidative parameters were evaluated on days 4, 11, 18 and/or 25. Ours findings shows that the oral administration of BIS and βCD/BIS significantly attenuated spontaneous pain-like behaviors, mechanical hyperalgesia, grip strength deficit and knee edema induced by repeated injections of CFA, reducing the joint pain and functional disability associated with arthritis. BIS and βCD/BIS also inhibited the generation of inflammatory and oxidative markers in the knee and blocked MAPK in the spinal cord. In addition, ours results also showed that the incorporation of BIS in cyclodextrin as a drug delivery system improved the pharmacological profile of this substance. Therefore, these results contribute to the pharmacological knowledge of BIS and demonstrated that this terpene appears to be able to mitigate deleterious symptoms of arthritis.

Photobiomodulation inhibits inflammation in the temporomandibular joint of rats

Photobiomodulation (PBM) has been applied as a non-invasive technique for treating temporomandibular joint symptoms, especially on painful condition's relief, however the anti-inflammatory mechanism underlying the effect of PBM remains uncertain. This study aims to evaluate the mechanisms of action of PBM (808 nm) in a carrageenan-induced inflammation on temporomandibular joint (TMJ) of rats. In this study male Wistar rats were pre-treated with irradiation of a low-power diode laser for 15 s on TMJ (infra-red 808 nm, 100 mW, 50 J/cm² and 1.5 J) 15 min prior an injection in the temporomandibular joint of carrageenan (100 μg/TMJ). 1 h after the TMJ treatments, the rats were terminally anesthetized for joint cavity wash and periarticular tissues collect. Samples analysis demonstrated that PBM inhibit leukocytes chemotaxis in the TMJ and significantly reduces amounts of TNF-α, IL-1β and CINC-1. In addition, Western blotting analysis demonstrated that PBM significantly decreased the protein levels of P2X3 and P2X7 receptors in the periarticular tissues. On the other hand, PBM was able to increase protein level of IL-10 (anti-inflammatory cytokine). In summary, it is possible to suggest that PBM inhibit inflammatory chemotaxis, modulation the balance of the pro- and anti-inflammatory characteristics of inflammatory cells.

Comparison of the Efficiency of High-Intensity Laser Therapy and Transcutaneous Electrical Nerve Stimulation Therapy in Patients With Symptomatic Temporomandibular Joint Disc Displacement With Reduction

PURPOSE

Many different treatment modalities have been tried in the treatment of temporomandibular joint (TMJ) disorders and different results have been reported. The aim of the study was to investigate and compare the effects of high-intensity laser therapy (HILT) and transcutaneous electrical nerve stimulation (TENS) therapy on the treatment of patients with TMJ disc displacement with reduction(DDWR).

METHODS

Researchers conducted a prospective, single-blind, controlled clinical trial on patients with TMJ disc disease at a university's oral and maxillofacial surgery clinic. One hundred two patients were randomized into 3 groups (HILT, TENS and control group). The patients were evaluated in terms of maximum mouth opening (MMO), assisted MMO, Visual Analog Scale (VAS) (pain), and VAS (function). In addition, the disability status of the patients with the Jaw Functional Limitation Scale-20 (JFLS-20) and the quality-of-life with the Oral Health Impact Profile (OHIP-14) was evaluated.

RESULTS

At the start of the trial, in terms of socio-demographic characteristics, no significant differences existed between the groups. Significant improvements were seen in pain (VAS), MMO, total JFLS-20 and total OHIP-14 scores in the HILT and TENS groups compared to the control group. At week 4, the VAS pain score decreased significantly in the HILT group compared to the TENS group (48 and 25%, respectively), while the MMO was significantly increased (24 and 10%, respectively). In addition, there was a significant improvement in both the total JFLS-20 score and the total OHIP-14 score at weeks 4 and 12 in the HILT group compared to the TENS group (P < .05).

CONCLUSION

It was observed that the healing effect of pulsed Nd: YAG laser therapy was significantly higher than TENS in patients with DDWR. Therefore, HILT should be a priority option over TENS therapy in patients with disc displacement.

Effects of arthrocentesis and low-level laser therapy on patients with osteoarthritis of the temporomandibular joint

This retrospective study examined whether arthrocentesis combined with 10 sessions of low-level laser therapy (LLLT) improved the clinical outcomes of patients with temporomandibular joint osteoarthritis (TMJ-OA) compared with arthrocentesis alone. Data from two groups of patients (total: n=36) with unilateral TMJ-OA were evaluated. The groups were established according to their treatment regimens: Group 1 (arthrocentesis alone; n=19) and Group 2 (arthrocentesis plus LLLT; n=17). All patients had been diagnosed in accordance with the Research Diagnostic Criteria for Temporomandibular Joint Disorders (RDC/TMD) (Axis I Group IIIb) protocol. They all underwent the same arthrocentesis protocol, but those in Group 2 also received 10 sessions of LLLT immediately afterwards. The outcome variables were the visual analogue scale scores (VAS 1, VAS 2) for various treatment outcomes and millimetric measurements of mandibular movements over both the short and long term. Intra-group comparisons showed significant short and long-term improvements for both groups, but outcomes were better over the long term than the short term in both. In addition, greater improvements in muscle palpation scores and mandibular movements were achieved in Group 2 than in Group 1. In conclusion, although both techniques improved joint pain and function, a combination with LLLT seemed to have an additional benefit for myofascial components.

Photobiostimulation activity of different low-level laser dosage on masticatory muscles and temporomandibular joint in an induced arthritis rat model

This study aimed to investigate the anti-inflammatory effects of different dosage of low-level laser therapy (LLLT) in an experimental model of temporomandibular joint (TMJ) arthritis. One hundred male Wistar rats were used and divided into the following groups: CG, control group; AG, animals group with left TMJ arthritis induced by intra-articular injection of Complete Freund's adjuvant - CFA; LG5, LG10 and LG20 - animals with arthritis and treated with LLLT at doses 5, 10, and 20 J/cm², respectively. Morphological analysis was performed by TMJ histological sections stained with hematoxylin-eosin (HE), picrosirius (PSR), and toluidine blue (TB), as well as histomorphometric evaluation of cartilage, articular disc, and masticatory muscles. The amount of feed consumed within 3 weeks was evaluated, and biochemical analysis of TMJ tissues included measurement of sulfated glycosaminoglycans (GAGs), matrix metalloproteinases (MMPs) 2 and 9 zymography, and ELISA for cytokines IL-6, TNF-α, and IL-1β. Only the 20 J/cm² dose promoted higher feed intake compared to AG. On the other hand, all LLLT doses promoted better organization of articular disc collagen fibers, greater number of proteoglycans in articular cartilage, increased area and diameter of left lateral pterygoid fibers, reduced latent and active MMP 9 and 2 activity, and lower IL-1β concentration compared to AG. Considering the study limitations, it was observed that LLLT treatments were effective in protecting and tissue cleansing joint structures, accelerating tissue repair, especially at lower doses.

Evaluation of the efficacy of different treatment modalities for painful temporomandibular disorders

The purpose of this study was to clinically evaluate the efficacies of three treatment methods and to compare their outcomes in patients with painful disc displacement. The study group comprised 45 patients with unilateral temporomandibular disorders who fell into Axis I group II (with limited mouth opening) of the Research Diagnostic Criteria for Temporomandibular Disorders. Magnetic resonance imaging was used for definitive diagnosis. The patients were divided randomly into three groups according to the treatment method: splint therapy, splint therapy with ultrasound-guided arthrocentesis, and splint therapy with low-level laser therapy. Patients were followed up after treatment for 6 months. The groups were compared in terms of pain and functional jaw movements (unassisted mouth opening without pain, maximum unassisted mouth opening, and contralateral movements). At the end of treatment, functional jaw movements were significantly increased while pain values were significantly decreased in all groups (P<0.05). Group 2 had a quicker improvement in terms of mouth opening scores at the end of the first month, and unassisted mouth opening without pain was found to be more than 35 millimetres in all groups at the end of 6 months. All treatment modalities showed effective results on pain and functional jaw movements in the treatment of temporomandibular disorders.

The effectiveness of photobiomodulation in the management of temporomandibular pain sensitivity in rats: behavioral and neurochemical effects

This study analyzed the effects of photobiomodulation (PBM) with low-level laser therapy on nociceptive behavior and neuronal activity in the trigeminal nucleus after experimental unilateral temporomandibular joint (TMJ) disc injury. The animals were divided into 4 groups (n = 10 each): group 1, surgical injury of the articular disc and PBM; group 2, sham-operated subjected to PBM; group 3, surgical injury of the articular disc; and group 4, control (Naïve). Ten sessions of PBM were performed using GaAs laser with a wavelength of 904 nm, power of 75 W pico, average power of 0.043 W, area of the beam of 0.13 cm², duration of the pulses of 60 nseg (in the frequency of 9500 Hz), energy density of 5.95 J/cm², energy per point of 0.7 J, and power density of 333.8 mW/cm², and the irradiation was done for 18 s per point. Neuropathic symptoms were evaluated using the von Frey test. Trigeminal ganglion samples underwent immunoblotting to examine the expression of substance P, vanilloid transient potential receptor of subtype-1 (TRPV-1), and peptide related to the calcitonin gene (CGRP). There was a total decrease in pain sensitivity after the second session of PBM in operated animals, and this decrease remains until the last session. There was a significant decrease in the expression of SP, TRPV-1, and CGRP after PBM. Photobiomodulation therapy was effective in reducing nociceptive behavior and trigeminal nucleus neuronal activity after TMJ disc injury.

Photobiomodulation Therapy for Myofascial Pain in Temporomandibular Joint Dysfunction: A Double-Blinded Randomized Clinical Trial

Aims

Temporomandibular disorder (TMD) is a complex process that affects the temporomandibular joint (TMJ). The multifactorial process is of unknown etiology and has many manifestations and thus many management options. Photobiomodulation therapy has been suggested for management of TMD, despite the lack of understanding of its exact mechanism. The aim of this study is to examine the effectiveness of photobiomodulation in the treatment of myofascial type TMD.

Methods

Patients with unilateral TMJ and masticatory muscles pain during function were recruited and divided into two groups: a control group that received a sham laser treatment every 48 h for 10 days and a test group that received the same frequency of treatment to deliver a dose of 257 J per treatment and a total dose of 1285 J for the entire treatment. Pain was assessed using the visual analog scale (VAS).

Results

There was a significant difference in VAS scores between the test and control groups with the test group scoring lower.

Conclusion

Photobiomodulation therapy proved to be an effective short-term therapeutic modality for myofascial TMD pain. It is non-invasive, easy to apply with no systemic side effects. Its long-term effect and its effect on different subtypes of TMD need further investigation.

Low-level laser therapy stimulates tissue repair and reduces the extracellular matrix degradation in rats with induced arthritis in the temporomandibular joint

The objective of this study was to characterize morphological and biochemistry action of low-level laser therapy (LLLT) on induced arthritis in the temporomandibular joint (TMJ) of rats. Twenty-four male Wistar rats were randomly divided into groups with 12 animals each: (AG) group with arthritis induced in the left TMJ and (LG) group with arthritis induced in the left TMJ and treated with LLLT (830 nm, 30 mW, 3 J/cm(2)). Right TMJs in the AG group were used as noninjected control group (CG). Arthritis was induced by intra-articular injection of 50 μl Complete Freund's Adjuvant (CFA) and LLLT began 1 week after arthritis induction. Histopathological analysis was performed using sections stained with hematoxylin-eosin, Toluidine Blue, and picrosirius. Biochemical analysis was determined by the total concentration of sulfated glycosaminoglycans (GAGs) and evaluation of matrix metalloproteinases (MMP-2 and MMP-9). Statistical analysis was performed using paired and unpaired t tests, with p < 0.05. Compared to AG, LG had minor histopathological changes in the TMJ, smaller thickness of the articular disc in the anterior (p < 0.0001), middle (p < 0.0001) and posterior regions (p < 0.0001), high birefringence of collagen fibers in the anterior (p < 0.0001), middle (p < 0.0001) and posterior regions (p < 0.0001) on the articular disc, and statistically lower activity of MMP-2 latent (p < 0.0001), MMP-2 active (P = 0.02), MMP-9 latent (p < 0.0001), and MMP-9 active (p < 0.0001). These results suggest that LLLT can increase the remodeling and enhancing tissue repair in TMJ with induced arthritis.

Assessment of different energy delivery settings in laser and LED phototherapies in the inflammatory process of rat's TMJ induced by carrageenan

Temporomandibular disorders (TMDs) are mostly inflammatory conditions widespread in the population. Previous studies have shown positive effects of either laser or light-emitting diode (LED) phototherapies on treating TMDs, but their action and mechanism in the inflammatory infiltrate of the temporomandibular joint are still poorly understood. The aim of this study was to assess, through histological analysis, the effectiveness of using laser light (λ 780 nm, 70 mW, continous wave (CW), 10 J) and LED (λ 850 ± 10 nm, 100 mW, CW, 10 J) on the inflammation of the temporomandibular joint of rats induced by carrageenan. Forty-five animals were divided into three groups with five animals each according to the experimental times of 2, 3, and 7 days: inflammation, inflammation+laser phototherapy, and inflammation+LED phototherapy. The first irradiation was performed 24 h after induction with an interval of 48 h between sessions. After animal death, specimens were processed and stained with hematoxylin-eosin (HE) and picrosirius. Then, the samples were examined histologically. Data were statistically analyzed. The inflammation group showed mild to moderate chronic inflammatory infiltrate between bone trabecules of the condyle. Over the time course of the study in the laser group, the region of the condyle presented mild chronic inflammation and intense vascularization. In the LED group, the condyle showed aspects of normality and absence of inflammation in some specimens. In all the time points, the laser-irradiated groups showed greater amount of collagen deposition in the condyle (p = 0.04) and in the disc (p = 0.03) when compared to the inflammation and LED groups, respectively. Laser- and LED-treated groups demonstrate a smaller number of layers of the synovial membrane when compared to the non-irradiated groups. It was concluded that, in general, laser and LED phototherapies resulted in a reduction of inflammatory infiltrate in the temporomandibular joint of rat.

Therapeutic effect of irradiation of magnetic infrared laser on osteoarthritis rat model

Osteoarthritis (OA) is a degenerative joint disease caused by articular cartilage loss. Many complementary and alternative medicines for OA have been reported so far, but the effectiveness is controversial. Previously, we have shown anti-inflammatory effects of low level laser therapy with static magnetic field, magnetic infrared laser (MIL), in various animal models. Therefore, the beneficial effects were examined in OA rat model. Rats were divided by six groups; no treatment controls of sham and OA model, three MIL treatment groups of OA model at 6.65, 2.66 and 1.33 J cm(-2), and Diclofenac group of OA model with 2 mg kg(-1) diclofenac sodium. The OA control exhibited typical symptoms of OA, but 4-week MIL treatment improved the functional movement of knee joint with reduced edematous changes. In addition, cartilage GAGs were detected more in all MIL treatment groups than OA control. It suggests that 4-week MIL irradiation has dose-dependent anti-inflammatory and chondroprotective effects on OA. Histopathological analyses revealed that MIL treatment inhibits the cartilage degradation and enhances chondrocyte proliferation. The fact that MIL has an additional potential for the cartilage formation and no adverse effects can be regarded as great advantages for OA treatment. These suggest that MIL can be useful for OA treatment.

Evaluation of anti-nociceptive and anti-inflammatory activity of low-level laser therapy on temporomandibular joint inflammation in rodents

The aim of this study was to investigate the analgesic and anti-inflammatory activity of low-level laser therapy (LLLT) on the nociceptive behavioral as well as histomorphological aspects induced by injection of formalin and carrageenan into the rat temporomandibular joint. The 2.5% formalin injection (FRG group) induced behavioral responses characterized by rubbing the orofacial region and flinching the head quickly, which were quantified for 45 min. The pretreatment with systemic administration of diclofenac sodium-DFN group (10 mg/kg i.p.) as well as the irradiation with LLLT infrared (LST group, 780 nm, 70 mW, 30 s, 2.1 J, 52.5 J/cm(2), GaAlAs) significantly reduced the formalin-induced nociceptive responses. The 1% carrageenan injection (CRG group) induced inflammatory responses over the time-course of the study (24 h, and 3 and 7 days) characterized by the presence of intense inflammatory infiltrate rich in neutrophils, scanty areas of liquefactive necrosis and intense interstitial edema, extensive hemorrhagic areas, and enlargement of the joint space on the region. The DFN and LST groups showed an intensity of inflammatory response that was significantly lower than in CRG group over the time-course of the study, especially in the LST group, which showed exuberant granulation tissue with intense vascularization, and deposition of newly formed collagen fibers (3 and 7 days). It was concluded that the LLLT presented an anti-nociceptive and anti-inflammatory response on the inflammation induced in the temporomandibular joint of rodents.

Evaluation of effect of low-level laser therapy on adolescents with temporomandibular disorder: study protocol for a randomized controlled trial

Background

A number of problems involving the temporomandibular joint (TMJ) and associated structures can lead to temporomandibular disorder (TMD). The aim of the proposed study is to assess the effect of low-level laser therapy on occlusal contacts, mandibular movements, electromyography activity in the muscles of mastication and pain in adolescents with TMD.

Methods/Design

A randomized, controlled, double-blind, clinical trial will be carried out involving 85 male and female adolescents between 15 and 18 years of age. The research diagnostic criteria for TMD will be used to assess all individuals who agree to participate. All participants will be submitted to a clinical examination and electromyographic analysis of the masseter muscles and anterior bundle of the temporal muscles bilaterally, to determine TMD. Based on the clinical findings, the participants will be classified as having or not having TMD. Those with TMD will be divided into four groups, three of which will receive low-level laser therapy and one of which will receive a placebo treatment. The treatments will involve the TMJ region alone, the masseter and temporal muscles alone, or both these regions together. The data will be submitted to descriptive statistical analysis. The chi-square test and Fisher’s exact test will be used to determine associations among the categorical variables. The Student’s t test and analysis of variance will be used for the comparison of mean electromyographic signals. Pearson’s correlation coefficients will be calculated for the analysis of correlations among the continuous variables.

Trial registration

The protocol for this study has been submitted to Clinical Trials – registration number (NCT01846000).