Effect of low-level laser on controlling temporomandibular disorders

Efecto del láser de bajo nivel en el control de los trastornos temporomandibulares

Mohammad Ali Ketabi

Department of Endodontic, Dental School, Aja University of Medical Sciences, Tehran, Iran., Irán

Mojtaba Sabzijat sabzijatem@yahoo.com

Department of Endodontic, Dental School, Aja University of Medical Sciences, Tehran, Iran., Irán

This work is licensed under Creative Commons Attribution-NoDerivs 4.0 International.

According to International Association for the Study of Pain, the standard definition of temporomandibular joint disease is associated with headache or facial pains due to painful complaints developed in the temporomandibular joint, ears, masticatory muscles, as well as both or one side of the jaw pain when biting down. Also, this disorder might induce some sounds in the joint, limited mouth opening, or mandibular deviation. The muscle pain is a common related symptom of the mentioned conditions. The main etiological factors of TMD can be involved with trauma, chronic Repetitive microtraumas, non-habitual use of the mandible, and finally stress among other significant factors for the TMD.

Given that nearly 20% of people are affected by the temporomandibular disorders, and only 10-20% of patients seek the appropriate therapeutic solution, dentists and physiotherapists can consider a phototherapeutic alternative method, like the low-level laser, as an effective source for stimulating the anti-pain signals in the tissues due to their low-level waves and energies.

The low-level lasers might cause the increased beta-endorphin content, decreased both bradykinin and histamine levels, and increased lymphatic flow¹². Generally, LLLT can result in the decreased inflammatory factors and the decreased pain-related factors. The literature review revealed this alternative therapeutic option has been studied with different wavelengths, but there was not found any study to employ LLLT at 810-nm for the treatment of TMD disorders. Moreover, no follow-up studies to date have examined long term efficacy of LLLT for TMD disorders.

The sensitivity of work environment, responsibilities, and work tasks level to be completed, all together determine the stress level imposed on the work. The military settings with unique conditions, provide the chronic stressful involvement even in peace time, and are associated with a range of health-related complaints in employees. In the armed forces, the stress level is remarkably recorded higher than the average level in the society due to heavy duties and sensitive tasks^1-2.

The situations of stress might result in the increased physiological activities of the body, activated sympathetic system, and especially increased heart rate. Generally, those people being under such a condition, are reported more frequently affected by TMD^3-4. Also, the psychological stress can result in some structural changes in the condylar cartilage (TMJ), associated with the increased levels of IL-1β, or TNF-α. If the stress condition continues, the involved process induces TMJ disorders⁵.

Some studies suggested that TMD, as a psychophysical disorder, can develop associated with the changes made in the central nervous system when controlling feelings, psychological aspects and neuro-endocrines secreted by psychophysical stimuli^6-7. The prevalence of post-traumatic stress disorder was reported to range from 20 percent in normal people to 61 percent in the armed force in the war according to different studies^8,9. Therefore, one of the important tasks in State Health Department is related to the surveillance of psychophysical situations in the armed forces of any country.

The present study aims to evaluate the efficacy of 810-nm laser therapy on pain and muscular activity (the masseter and temporal muscles), and the joint movement in patients with temporomandibular disorders.

The present study evaluated the efficacy of low-level laser therapy at 810-nm on the temporomandibular disorders in a controlled trial. Based on the previous studies, 40 patients (21 males, 19 female) were selected with an age range of 19-47 years old (mean age=28.55 years). The sample recruitment was performed based on the protocol for evaluation tools of temporomandibular disorders. All subjects received the detailed explanation and signed the written. Consents all patients were exposed to LLLT for 6 sessions. LLLT was radiated to the determined tender points (λ=810 nm, power output: 0.6 watt, application time: 60 s, dose: 4 J/cm2).

Some parameters were determined, including pain intensity, the number of tender points, joint sound, maximal pain-free, and the maximum mouth opening, and right and left lateral movement, before and immediately after each therapy session, and after 1 week, 2 weeks, 1 month, 3, and 6 months of the first session.

Pain intensity was recorded in millimetres on a 100 mm Visual Analogue Scale (VAS). Number of tender points were assessed by palpation of the following 10 points on both facial sides: preauricular lymph nodes, masseter, temporalis, medial and lateral pterygoid, sternocleidomastoid, trapezius and back of the neck.

Joint sounds were determined by auscultation of TMJ during mouth opening and closing, listening for the presence of opening and closing clicks as well as fine and coarse crepitation. The total number of sounds on both sides was recorded.

The maximal pain-free and maximum mouth opening were recorded. The vertical interincisal distance between the midpoints of upper and lower central incisors was measured by a ruler and recorded in mm. The obtained data were analyzed using SPSS, version 12. The descriptive statistics, t-test, and ANOVA test were performed in order to assess the study data. Any p value <0.05 was considered significant.

The descriptive statistics of the study variables were represented in the Table 1 before and immediately after each therapy session, and after1 week, 2 weeks and 3 and 6 months of the first session.

Table 1-
Descriptive values of the study variables (Mean±STD)

Pain intensity before and after therapy session

The highest pain intensity was recorded before the first session (mean=66.23), and it decreased after the first session, and continued to decrease along time, as after 6 months of LLLT the related parameter decreased to 3.22 (Figure 1). The significant reduction was observed in the pain intensity after1 week, 2 weeks, and one month of the first session (P<0.05), but in the third and sixth months, no significant differences were reported (p>0.05).

Figure 1
The measured pain intensity before and after therapy session

Number of tender points before and after therapy session

The highest number of tender points was recorded before the first session (mean=9.55), but it decreased significantly after the first session (p<0.05) and continued to decrease along time, as after 6 months of LLLT decreased to 1.05 (Figure 2). The significant reduction was observed in the number of tender points after 1 week, 2 weeks, and one month of the first session (P<0.05), but in the third and sixth months, no significant differences were reported (p>0.05).

Figure 2.
The number of tender points before and after therapy session

Maximum mouth opening before and after therapy session

Before the first session, the maximum mouth opening and maximal pain-free showed the least levels, but after the first session, statistically significant results were achieved in the mentioned study parameters as the related values increased and continued to be raised, and finally, after 6 months of the first session, they approached to the maximal limits (Figure 3). The raised levels for the mentioned parameters were significant statistically immediately after 1 week, 2 weeks, and 1 month of the first session (p<0.05), but after three and six months, no significant differences were reported for these parameters (p<0.05).

Figure 3
The maximum mouth opening before and after therapy session

Joint sound before and after therapy session

The joint sound reached to the maximum value (mean value= 2.48) before the first therapy session, and it decreased significantly after the first session and continued the decreasing trend to one month (p<0.05). In third and sixth months, a little non-significant decrease was reported (p>0.05), as the value approached to 1.03 after 6 months of the first session (Figure 4).

Figure 4
The joint sound before and after therapy session

Figure 4. The joint sound before and after therapy session

Right and left lateral movements before and after therapy session

The mean values of right and left lateral movements were at the least limit before the first therapy session, but after that, the mentioned levels significantly decreased (p<0.05) and continued to increase non-significantly during sessions (Figure 5).

Figure 5.
The right and left lateral movements before and after therapy session

Temporomandibular disorders (TMD) is a collective term that is recognized with the pains of the temporomandibular joint, masticatory muscles, the limited and deviated mandibular movements, with or without clicking sound when the temporomandibular joint functions^10-11. Today, interest in TMD increased widely due to the raised affected patients in dentistry researches¹⁰. Although several assumptions have been proposed regarding to the temporomandibular disorders, the real etiological factors still remain unknown. Given the etiology of TMD, different therapeutic modalities have been presented. But in some cases, these disorders have not responded to the conventional treatment techniques, and the surgical operation may be the last step in the therapeutic process. Therefore, many investigators aim to propose an effective technique with less side effects and aggressive intervention.

The obtained results in our study showed that pain intensity decreased after the first session and continue to decrease significantly during each session, as it reached to 5.3 after one month. After that, we observed little changes until six months. In a study by Posten et al, the pain level achieved to a significant decrease after the completed treatment compared to the values recorded before LLLT¹². But there was a difference in the number of sessions (12 sessions) and unknown intervals between sessions. Also, Magri¹³, Kulekcioglu¹⁴, Shukla¹⁵, and Khalighi¹⁶ obtained the similar results. Moreover, in our study, the number of tender points were averaged as 9.55 before the treatment, and decreased after the first session, and during the one next month, it continued to be recorded after each therapy session reached at 1.4. Also, after that in third and sixth months of therapy, a little decrease was recorded, as it was not reported significantly. In addition, Sayed, et al.¹⁷ proved that LLLT might cause a decrease in the number of tender points. But there was a difference between the results of Sayed's study and our findings, and the observed decrease was reported significantly after the 6-month therapy. However, the present work could observe a significant difference until one month, and after that, there was no significant decrease until six months. These observed different results across studies may be attributed to race and age differences of the evaluated samples.

The maximum mouth opening showed the significant increase in the studied subjects after the first LLLT session. After one and two weeks, and one month, the increased values continued to be recorded significantly. But when measured in third and sixth months, no difference was observed in the mentioned parameter. Regarding to the maximal pain-free, the similar situation was observed. Cetiner, et al.¹⁸ evaluated LLLT on the TMD, indicated that the maximum mouth opening improved after one month of treatment. In his study with similar findings to the present study, the measurement was performed before, after, and one month of the first session. In addition, according to the study by Khoshnevis¹², the maximum mouth opening increased significantly. It should be mentioned that the duration and number of sessions were different from the present work. Ahrari, et al.¹⁹ showed that LLLT might cause the increased maximum mouth opening, and the decreased pain intensity in TMD patients. Madani²⁰ and Khalighi (160 studies achieved the similar mentioned results, too.

It was noticed that in the TMD-affected patients there was a significant decrease in joint sounds after the first session of LLLT, and till one month in the next sessions, it continued to show significant decrease, but after that, there was no reported significant decrease in this parameter. A study designed by Sayed indicated that LLLT resulted in a decreased joint sound¹⁷. In the mentioned study, the parameters were recorded during 6 months with significant changes, but in our work, there was a significant decrease only to one month of the first session. The difference observed in these two studies can be attributed to the race and age differences in the statistical samples evaluated in both works.

In addition, the study results indicated that the right and left lateral movement increased significantly after the first session, and continued to rise to one month of the first session. But after that, there was a non-significant decrease. Also, a systematic review study by Petrucci²¹ about the efficacy of LLLT on the temporomandibular disorders confirmed the increased value of right and left lateral movement during the therapy.

Chen reviewed data gathered about the efficacy of low-level laser (LLLT) on 545 patients during 1990 to 2012. This study concluded that LLLT can improve the situation of the mouth and maxilla with reduced pain^22,24. One of the evaluated components was right and left lateral excursion with a significant increase after treatment and is consistent with the findings obtained in this study. The treatment duration was not the same for each patient in this review study.

Finally, according to the results of the evaluation of the test data, it can be said that low-level laser during 1 month improves the pain relief, the number of painful parts, joint sound, maximal oral opening, maximum pain opening, left lateral movement to the right and therefore the result is that LLLT is a useful method in the proper control of temporomandibular disorders within a month of the first session.