Low-Level Laser Therapy in Acute Pain: A Systematic Review of Possible Mechanisms of Action and Clinical Effects in Randomized Placebo-Controlled Trials (original) (raw)
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Analgesic effect of He-Ne (632.8 nm) low-level laser therapy on acute inflammatory pain
… and Laser Surgery, 2005
Objective: The aim of this study was to evaluate the analgesic effect of the low level laser therapy (LLLT) with a He-Ne laser on acute inflammatory pain, verifying the contribution of the peripheral opioid receptors and the action of LLLT on the hyperalgesia produced by the release of hyperalgesic mediators of inflammation. Background data: All analgesic drugs have undesired effects. Because of that, other therapies are being investigated for treatment of the inflammatory pain. Among those, LLLT seems to be very promising. Material and methods: Male Wistar rats were used. Three complementary experiments were done. (1) The inflammatory reaction was induced by the injection of carrageenin into one of the hind paws. Pain threshold and volume increase of the edema were measured by a pressure gauge and plethysmography, respectively. (2) The involvement of peripheral opioid receptors on the analgesic effect of the laser was evaluated by simultaneous injection of carrageenin and naloxone into one hind paw. (3) Hyperalgesia was induced by injecting PGE 2 for the study of the effect of the laser on the sensitization increase of nociceptors. A He-Ne laser (632.8 nm) of 2.5 J/cm 2 was used for irradiation. Results: We found that He-Ne stimulation increased the pain threshold by a factor between 68% and 95% depending on the injected drug. We also observed a 54% reduction on the volume increase of the edema when it was irradiated. Conclusion: He-Ne LLLT inhibits the sensitization increase of nociceptors on the inflammatory process. The analgesic effect seems to involve hyperalgesic mediators instead of peripheral opioid receptors.
Lasers in Medical Science, 2013
Synovial membrane inflammation plays an important role in osteoarthritis (OA) pathophysiology. The synovial tissue of patients with initial OA is characterized by mononuclear cell infiltration and the production of proinflammatory cytokines and other mediators of joint injury. The study aims to evaluate the effect of low-level laser therapy (LLLT) at doses of 2 and 4 J on joint inflammation in rats induced by papain through histopathological analysis, differential counts of inflammatory cells; gene expression of IL-1β, IL-6, and IL-10; and TNF-α protein expression. Male Wistar rats (20) were randomly divided (5 animals each) into a negative control group, an inflammation injury positive control group, a 2-J LLLT group subjected to injury and treated with 2 J of LLLT, and a 4-J LLLT group subjected to injury and treated with 4 J of LLLT. The animals were subjected to joint inflammation (4 % papain solution) and treated with LLLT. On the day of euthanasia, articular lavage was collected and centrifuged. The supernatant was analyzed for TNF-α protein expression by ELISA and IL-1β, IL-6, and IL-10 mRNA by RT-PCR. The joint tissue was also examined histologically. ANOVA with Tukey's post hoc test was used for comparisons. All data were expressed as means ± S.D. (p <0.05). Both laser modalities were efficient in reducing cellular inflammation and decreasing the expression of IL-1β and IL-6. However, the 2-J treatment led to more reduction in TNF-α than the 4-J treatment. A single application of LLLT with 2 J was more efficient in modulating inflammatory mediators and inflammatory cells.
Lasers in surgery and medicine, 2017
Low-level laser therapy (LLLT) is the direct application of light to stimulate cell responses (photobiomodulation) to promote tissue healing, reduce inflammation, and induce analgesia; the molecular basis for these effects of LLLT remains unclear. The objective of this study was to evaluate the analgesic effect of LLLT in the rat plantar incision model of postoperative pain as well as to investigate some of the possible mechanisms involved in this effect. Wistar rats were submitted to plantar incision and treated with LLLT (830 nm, continuous-mode, 30 mW/cm(2) , 1-12 J/cm(2) ). Postoperative thermal and mechanical hypersensitivity were monitored for 24 hours post-incision. In addition, the animals were pretreated with saline, naloxone (a nonselective opioid receptor antagonist; 20 µg/5 µl) or methysergide (5-HT2C , 5-HT2A , 5-HT7 , 5-HT5a , 5-HT6, and 5-HT1F receptors antagonist; 30 µg/5 µl). Moreover, 24 hours after incision and treatment, the TNF-α and IL-1β levels in serum were e...
Photomedicine and Laser Surgery, 2007
Objective: This study evaluated the action of low-level laser therapy (LLLT) on the modulation of inflammatory reactions during wound healing in comparison with meloxicam. Background Data: LLLT has been recommended for the postoperative period because of its ability to speed healing of wounds. However, data in the literature are in disagreement about its anti-inflammatory action. Methods: Standardized circular wounds were made on the backs of 64 Wistar rats. The animals were divided into four groups according to the selected postoperative therapy: group A-control; group B-administration of meloxicam; and groups C and D-irradiation with red (؍ 685 nm) and infrared (؍ 830 nm) laser energy, respectively. The animals were killed at 12, 36, and 72 h and 7 days after the procedure. Results: Microscopic analysis revealed significant vascular activation of irradiated sites in the first 36 h. Only group B showed decreases in the intensity of polymorphonuclear infiltrates and edema. Group D showed a higher degree of organization and maturation of collagen fibers than the other groups at 72 h. The animals in group C showed the best healing pattern at 7 days. The anti-inflammatory action of meloxicam was confirmed by the results obtained in this research. The quantification of interleukin-1 (IL-1) mRNA by real-time polymerase chain reaction (PCR) did not show any reduction in the inflammatory process in the irradiated groups when compared to the other groups. Conclusions: LLLT improves the quality of histologic repair and is useful during wound healing. However, with the methods used in this study the laser energy did not minimize tissue inflammatory reactions.
Study the beneficial activity of low level laser in experimentally induced pain in mice
Iraqi Journal of Veterinary Sciences, 2021
Low-level laser therapy (LLLT) was applied to alleviate pain with minimal adverse effects. This study was conducted to evaluate the analgesic effects of low-level laser therapy for pain control to help in surgical and emergency cases. The present study has demonstrated these effects experimentally on forty-five male albino mice weighing 45±5 grams. Creation of pain in animals was done by injection of 50µl of 5% formalin into the left posterior paw. Lifting of the paw was considered as an indicator of the pain. All animals were divided into 3 groups 15 mice in each group. In group A the LLLT 820nm.200mw, 48J/cm2 was focused on the affected paw for 1 min. In group B a diode laser with same dose in group A and different time used to irradiate the injected paw continuously for 30 seconds. The group C (control group); the laser probe was placed over the affected paw for concurrent but the apparatus was switched off. The results demonstrated that there were significant differences between group A and B when compared with group C during the 5 minutes as well as in 10 minutes and 15 minutes. Group A also registered a superior analgesic effect when compared with group B. Groups of LLLT were better than those found for control one and the irradiation continuous for one minute was better than 30 seconds at 5,10 and 15 minutes after the creation of pain.
Journal of Physical Therapy Science, 2015
This study aimed to evaluate the anti-inflammatory and analgesic effects of intraoral application of low-level laser therapy (660 nm) to control pain, swelling and interincisal opening following the extraction of mandibular third molars. [Subjects and Methods] Ten patients underwent removal of lower third molars using the same surgical protocol and pharmacological approach. In the postoperative period, all patients received four consecutive daily sessions of low-level laser therapy, beginning 24 hours after the surgery. Intraoral applications using the diode laser with 660 nm wavelength in the continuous scan mode were performed covering the entire surgical area, which was divided into four quadrants, each of 1 cm 2 area at a distance of 1 cm. The energy applied at each point was 5 J/cm 2 during 8 seconds. [Results] The swelling and interincisal opening returned to normal 24 hours after the first low-level laser therapy application (Friedman test). Moreover, the pain intensity was reduced on the third postoperative day, according to the Friedman test. [Conclusion] Low-level laser therapy (660 nm), at the dosimetry used in this study, was effective in reducing postoperative pain and swelling following oral surgery.
Infrared (810-nm) low-level laser therapy on rat experimental knee inflammation
Lasers in Medical Science, 2012
Arthritis of the knee is the most common type of joint inflammatory disorder and it is associated with pain and inflammation of the joint capsule. Few studies address the effects of the 810-nm laser in such conditions. Here we investigated the effects of low-level laser therapy (LLLT; infrared, 810-nm) in experimentally induced rat knee inflammation. Thirty male Wistar rats (230-250 g) were anesthetized and injected with carrageenan by an intraarticular route. After 6 and 12 h, all animals were killed by CO 2 inhalation and the articular cavity was washed for cellular and biochemical analysis. Articular tissue was carefully removed for real-time PCR analysis in order to evaluate COX-1 and COX-2 expression. LLLT was able to significantly inhibit the total number of leukocytes, as well as the myeloperoxidase activity with 1, 3, and 6 J (Joules) of energy. This result was corroborated by cell counting showing the reduction of polymorphonuclear cells at the inflammatory site. Vascular extravasation was significantly inhibited at the higher dose of energy of 10 J. Both COX-1 and 2 gene expression were significantly enhanced by laser irradiation while PGE 2 production was inhibited. Low-level laser therapy operating at 810 nm markedly reduced inflammatory signs of inflammation but increased COX-1 and 2 gene expression. Further studies are necessary to investigate the possible production of antiinflammatory mediators by COX enzymes induced by laser irradiation in knee inflammation.