Non-specific effects and clusters of women with painful TMD responders and non-responders to LLLT: double-blind randomized clinical trial

Abstract

The aim was to analyze the non-specific effects (placebo, spontaneous remission, and regression to the mean) of the low-level laser therapy (LLLT) in women with myofascial pain (painful temporomandibular disorder (TMD)), as well as to differentiate between responders and non-responder clusters to active and placebo LLLT according to the anxiety levels, salivary cortisol, use of oral contraceptives, and premenstrual period. Sixty-four women diagnosed with myofascial pain (Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD)) were included, divided into laser (n = 20), placebo group (n = 21), and 23 controls (without treatment (WT)). The LLLT applied was 780 nm, masseter and temporal = 5 J/cm (20 mW-0.5 W/cm), and TMJ area = 7.5 J/cm (30 mW-0.8 W/cm), eight sessions, twice a week. The pain intensity (visual analogue scale (VAS)), anxiety (Beck Anxiety Inventory), salivary cortisol, and menstrual cycle's data at the baseline, T1-T8, and 30 days after LLLT (follow-up) were evaluated. The laser group showed 80% of pain reduction, placebo 85%, and WT 43% in T8. Women with severe anxiety and at the premenstrual period did not reduce pain with any LLLT. Active and placebo LLLT had similar effectiveness during the treatment period; however, women with moderate anxiety, cortisol levels above 10 ng/ml, and without contraceptive use maintain analgesia longer with active LLLT than placebo (follow-up 30 days). Women with low levels of anxiety, salivary cortisol below 10 ng/ml, and with contraceptive use showed the higher pain reduction. The analgesia promoted by LLLT in women with myofascial pain is a result of non-specific effects during the treatment period, although active LLLT is more effective in maintaining the analgesia after treatment (30 days) for the cluster of women with moderate anxiety, salivary cortisol above 10 ng/ml, and without contraceptive use.

Photobiomodulation in Temporomandibular Disorders

“…46,48 Collecting information of these heterogeneous clinical trials showed beneficial impacts of PBM on reducing pain at the shortterm follow-up (10 days to 4 weeks) both in the visual analog scale 36 and in the anxiety questionnaire. 46,47,[55][56][57] Among these studies, GaAlAs diode at 780 nm wavelength and 50 mW power showed the most frequent nonsignificant effects. 58,59 Functionality of TMJ was assessed in terms of maximum opening, electromyography, geometric mean diameter, colorimetric capsule method, and craniomandibular index, indicating that the total effect favored PBM in comparison with placebo.…”

Acupuncture for pain, mandibular function and oral health‐related quality of life in patients with masticatory myofascial pain: A randomised controlled trial

“…Moreover, the absence of a significant difference between groups leads to the assumption that non‐specific factors may have influenced treatment outcomes. Among these, the placebo effect has been considered very important, mainly in acupuncture clinical trials because of individual psychosocial factors that modify biochemistry and neural circuits 45,46 . Hence, the placebo effect as well as other unspecific factors such as natural history and regression to the mean could not be ruled out in this study.…”

Absorption Capability of a 645-nm Diode Laser on Swine Soft Tissue Samples: a Preliminary Study in an Ex-Vivo Model Tissue Samples: a Preliminary Study in an Ex-Vivo Mo

“…The post-extraction sockets 18,19 (even if a first intention closure is performed), periodontal surgery and implantology 20 , orthodontics 21,22 , temporomandibular joints disorders, and neurological conditions may all benefit from superficial irradiation in which part of the laser beam penetrates a deeper level 23,24 .…”