The Mechanistic Basis for Photobiomodulation Therapy of Neuropathic Pain by Near Infrared Laser Light

Background and Objective Various irradiances have been reported to be beneficial for the treatment of neuropathic pain with near infrared light. However, the mechanistic basis for the beneficial outcomes may vary based on the level of irradiance or fluence rate used. Using in vivo and in vitro experimentalmodels, this study determined the mechanistic basis of photobiomodulation therapy (PBMT) for the treatment of neuropathic pain using a high irradiance. Study Design/Materials and Methods ln vitro experiments: Cultured, rat DRG were randomly assigned to control or laser treatment (L T) groups with different irradiation times (2, 5, 30, 60 or 120s). The laser parameters were: output power » 960 mW, irradiance » 300mW/cm2, 808 nm wavelength and spot size » 3cm diameter/ area » 7.07cm2, with different fluences according to irradiation times. Mitochondrial metabolic activity was measured with the MTS assay. The DRG neurons were immunostained using a primary antibody to ß-Tubulin III. ln vivo experiments: spared nerve injury surgery (SNI), an animal model of persistent peripheral neuropathic pain, was used. The injured rats were randomly divided into three groups (n » 5). 1) Control: SNI without LT, 2) Short term: SNI with LT on day 7 and euthanized on day 7, 3) Long term: SNI with LT on day 7 and euthanized on day 22. An 808 nm wavelength laser was used for all treatment groups. Treatment was performed once on Day 7 post-surgery. The transcutaneous treatment parameters were: output power: 10 W, fluence rate: 270 mW/cm2, treatment time: 120s. The laser probe was moved along the course of the sciatic/sural nerve during the treatment. Within 1 hour of irradiation, behavior tests were performed to assess its immediate effect on sensory allodynia and hyperalgesia caused by SNI. Results ln vitro experiments: Mitochondrial metabolism was significantly lower compared with controls for all LT groups. Varicosities and undulations formed in neurites of DRG neurons with a cell body diameter 30µm or less. ln neurites of DRG neurons with a cell body diameter of greater than 30µm, varicosities formed only in the 120s group. ln vivo experiments: For heat hyperalgesia, there was a statistically significant reduction in sensitivity to the heat stimulus compared with the measurements done on day 7 prior to LT. A decrease in the sensitivity to the heat stimulus was found in the LT groups compared with the control group on day 15 and 21. For cold allodynia and mechanical hyperalgesia, a significant decrease in sensitivity to cold and pin prick was found within 1 hour after L T. Sensitivity to these stimuli returned to the control levels after 5 days post-L T. No significant difference was found in mechanical allodynia between control and L T groups for all time points examined. Conclusion These in vitro and in vivo studies indicate that treatment with an irradiance/fluence rate at 270 m W/cm2 or higher at the level of the nerve can rapidly block pain transmission. A combination therapy is proposed to treat neuropathic pain with initial high irradiance/fluence rates for fast pain relief, followed by low irradiance/ fluence rates for prolonged pain relief by altering chronic inflammation.

Comparison of the effects of transcutaneous electrical nerve stimulation and low-level laser therapy on drug-resistant temporomandibular disorders

Statement of the Problem: Temporomandibular disorder [TMD] is a clinical term used for clinical signs and symptoms that affect the temporomandibular joints, masticatory muscles, and associated structures. Surgical and non-surgical treatments can be used for management of TMD. Non-surgical route is the main part of the treatment, since clinicians prefer non-aggressive treatment for TMD such as pharmacological and physical therapy. Low-level laser therapy [LLLT] and transcutaneous electrical nerve stimulation [TENS] are the main procedures in physical therapy

Purpose: The aim of this study was to evaluate the effectiveness of TENS and LLLT in treatment of TMD patients who did not respond to pharmacological therapy

Materials and Method: This clinical trial was performed on 45 patients who randomly received either TENS or LLLT for 8 sessions. LLLT was applied with diode laser [Ga-Al-As, 980nm, dose 5micro/cm[2]] and TENS by using two carbon electrodes with 75 Hz frequency [0.75 msec pulse width]

Helkimo index and visual analogue scale [VAS] were measured during the treatment period and throughout the follow-up sessions

Results: Significant reduction in the VAS and Helkimo index was observed in both TENS and LLLT group. There was no significant difference between the two methods during the treatment; however, TENS was more effective in pain reduction in follow-ups

Conclusion: This study justified the use of TENS therapy as well as LLLT in drug-resistant TMD. Both were useful in relieving the pain and muscles tenderness, although, TENS was more effective than LLLT

Stimulatory effect of helium-neon laser irradiation on human umbilical vein endothelial cells

Low-level laser irradiation [LLLI] has been shown to modulate the proliferation of endothelial cells. Helium-neon [He-Ne] laser is the best type of laser for biostimulation. The aim of the present study was to investigate the direct stimulatory effect of LLLI on the proliferative potential of human umbilical vein endothelial cell line in vitro. This study included five groups: group I [zero time after seeding He-Ne laser irradiation], group II [24 h after seeding He-Ne laser irradiation], group III [48 h after seeding He-Ne laser irradiation], group IV [96 h after seeding He-Ne laser irradiation], and group V [cumulative He-Ne laser irradiation every 48 h for a period of 6 days]. Each group was subdivided into three subgroups: subgroup a [control], subgroup b [1.77 J/cm[2]He-Ne laser irradiation], and subgroup c [3.54 J/cm[2] He-Ne laser irradiation]. A continuous wave He-Ne laser, emitting a wavelength of 632.8 nm with a power output of 5 mW was used for irradiating the cells. A growth curve was constructed for each group to determine the growth parameters. The most efficient cellular response to LLLI was in subgroup Ic depending on the population doublings achieved, followed by subgroup Ib. Therefore, the early the use of He-Ne laser irradiation for the cultured cells, the more the cellular stimulation and proliferation. Meanwhile, their delayed use resulted in less cellular stimulation and proliferation. Moreover, the results showed that 1.77 and 3.54 J/cm[2] of He-Ne laser irradiation were always stimulatory for endothelial cells either significantly or insignificantly. The present study showed that 1.77 and 3.54 J/cm[2] of He-Ne laser irradiation stimulated human umbilical vein endothelial cell line proliferation

Antibacterial effectiveness of low energy diode laser irradiation on management of periodontitis in Down syndrome

With the poor oral hygiene exhibited by patients with Down syndrome, the potential for a robust flora arises causing Periodontitis. Along with periodontal disease, the patient population has other medical conditions that limit treatment. This study was conducted to evaluate the antibacterial effectiveness of an 870-nm diode laser on periodontitis in patients with Down syndrome. Thirty five patients with Down syndrome suffering from periodontitis were included in this study and divided into two groups, Group I [25 patients] laser was applied to one half of the mouth and the other half was considered as a control and Group II included [10 patients] basic periodontal treatment was applied to evaluate the systemic effect of laser. Quantification of A. actinomycetemconcomitans, P. Gingivalis and Capnocytophaga were carried out using real-time PCR technique at baseline and at 2 weeks, at 6 weeks and at 12 weeks post periodontal and laser treatment. A. Actinmycetcomitans and P. gingivalis were the most common organisms found in the studied patients and Capnocytophaga was the least common organisms. In group I the quantitative results of A. actinomycetemconcomitans, P. Gingivalis at 2 weeks were significantly lower in both sides of mouth than that of baseline level. After 6 week, it was still significantly lower than that of the baseline in the right side of the mouth, but at 12 weeks no significant difference was observed in both sides. In group II, quantitative results of A. actinomycetemconcomitans, P. Gingivalis at 2 weeks were also significantly lower than that of baseline but not at 6 and at 12 weeks. As regards, Capnocytophaga there was no significant difference at baseline, at 2 weeks, at 6 weeks and at 12 weeks post periodontal and laser treatment in both groups I and II. Scaling and root planning plus laser therapy was better than scaling and root planning alone in the chosen patients and this antibacterial effect continues to be significant up to 6 weeks after therapy. Based upon the results of the study, it was found that Laser therapy could be used for the treatment of periodontitis as a complementary therapy not to replace mechanical intervention

Terapia a laser de baixa potência e sua eficácia na cicatrização de incisões cirúrgicas na pele de ratos / Effects of low laser power laser therapy in wound healing in rats

A terapia com laser de baixa potencia se tornou algo de inúmeras pesquisas,devido a melhora do processo cicatricial.Um estudo experimental foi realizado para avaliar se há benefícios dessa terapia na cicatrização de feridas na pele de ratos com análises não pareadas e pareadas. Foram utilizados 20 ratos Wistar dividos em 4 grupos, submetidos a 4 incisões lineares na pele do dorso.No Grupo 1, usamos uma dose de laser no pós-operatório; no Grupo 2, duas doses, uma no pós-operatório e após 24 horas; no Grupo 3, três doses, no pós-operatório , 24 e 48 horas.O grupo controle foi submetido às incisões da pele.Foram testadas a força de ruptura e analisados os achados histopatológicos das incisões.Em análise não pareada, o grupo 1 apresenta o maior valor, tendo diferença (p = 0,040). A força de ruptura dos quatro grupos de ratos para as feridas não tratadas, não ocorreu. Na análise pareada as feridas tratadas com laser nos grupos 1, 2 e 3 e grupo controle, não houve diferença. Em análise não pareada, segundo a epitelização e a granulação, o grupo 3 apresentou maior freqüência para epitelização (p=0,002) e granulação (p=0,012).Nas feridas não tratadas nos quatro grupos não houve diferença entre elas em relação à epitelização e à granulação. Na análise pareada, não ocorreram diferenças dessas para os ferimentos produzidos nos grupos.É improvável existir relação entre a terapia a laser e a cicatrização, sendo a associação na análise não pareada apenas aparente, justificada pelo método de avaliação .(AU)

Low power laser therapy is recently in focus due to its properties in angiogenesis, fibroblast and colagenase activity. Based on these facts, the benefits of low laser power therapy in wound healing have been considered. In order to evaluate the benefits of low power therapy in wound healing, twenty Wistar rats were divided into four groups (n=5) which received four linear incisions in the back and then the following treatments, 1: a post-incision laser dose 2: one post-incision and 24 hours later dose 3: one post-incision, 24 and 48 hours later laser doses. 4: control group, with the four skin incisions and no laser therapy. Rupture force and histopathological analyses were performed. Unpaired analyses showed that epithelialization (p= 0.002) and granulation (p=0.012) were more frequent. But there were no differences between groups, using paired analyses. Thus, it is not likely that there is a correlation between low power laser treatment and wound healing. Our findings using unpaired analyses can be justified by the findings using unpaired analyses can be justified by the method of analyses.(AU)

Pulsed low-intensity ultrasound versus low-level laser therapy for chronic lateral epicondylitis [Tennis elbow]

Lateral epicondlitis [LE] is a chronic condition that has proven to be challenging to treat. To date, systematic reviews looking at a range of outcome measures on treatments for LE have failed to draw any firm conclusions as to what treatment is most effective in managing this condition. To evaluate the effects of Low-level Laser therapy [LLLT] and to compare these with the effects of US treatment in the management of tennis elbow. Sixty patients with LE were enrolled in this study and randomized into three groups: group A treated with US plus brace, group B treated with laser plus brace and group C [control group] used brace only. Pain, grade of tenderness, range of wrist motion and both maximal and pain-free grip strength were assessed at baseline. Patient's perception of benefit through a global improvement, and all other outcome measures were assessed at four, eight weeks of treatment and four weeks after the end of treatment. Significant reduction in pain from baseline in all studied groups with significant difference between mean VAS of pain of patients treated with either US or laser and that of patients in control group were detected in all stages of the study. Furthermore, significant difference in pain reduction between US treated group and laser treated group. Also significant improvements in all other outcome measures were detected. The current clinical study provides further evidence of the efficacy of LLLT and pulsed low US in the management of LE with better results obtained using US