Applications of laser light of low power density. Experimental and clinical investigations

Laser Acupuncture for Migraine and Muscle Tension Headache: A Double-Blind Controlled Trial

Twelve patients with chronic migraine recruited from a neurology clinic or a self-help group were randomly allocated to receive either 6 weeks active laser acupuncture or 6 weeks dummy laser acupuncture. Patients completed headache diaries for the 6 weeks prior to treatment and for 6 weeks following. They were then crossed over to receive the alternative treatment for a further 6 weeks. Neither patients nor operator knew which unit was the active one. There was a reduction in mean total headache score (combining duration and severity) of 18% in the active group and 43% in the control group following the first treatment period. This difference was not significant. Following the second treatment period, mean scores increased by 50% in the active group and 5% in the control group but again this difference was not significant due to inconsistent responses by some patients. When active and placebo treatments were computed for all patients, there were still no significant differences. It is concluded that laser acupuncture does not have an important clinical effect in migraine over and above the expected placebo response.

Clinical effect of CO(2) laser in reducing pain in orthodontics

OBJECTIVE

To test the hypothesis that there is no difference in the pain associated with orthodontic force application after the application of local CO(2) laser irradiation to the teeth involved.

MATERIALS AND METHODS

Separation modules were placed at the distal contacts of the maxillary first molars in 90 patients in this single-blinded study. In 60 of these patients (42 females and 18 males; mean age = 19.22 years) this was immediately followed by laser therapy. The other 30 patients (18 females and 12 males; mean age = 18.8 years) did not receive active laser irradiation. Patients were then instructed to rate their levels of pain on a visual analog scale over time, and the amount of tooth movement was analyzed.

RESULTS

Significant pain reductions were observed with laser treatment from immediately after insertion of separators through day 4, but no differences from the nonirradiated control side were noted thereafter. No significant difference was noted in the amount of tooth movement between the irradiated and nonirradiated group.

CONCLUSIONS

The hypothesis was rejected. The results suggest that local CO(2) laser irradiation will reduce pain associated with orthodontic force application without interfering with the tooth movement.

Evaluation of Facial Thermographic Changes Before and After Low-Level Laser Irradiation

OBJECTIVE

The aim of the present study was to evaluate the facial thermographic changes before and after low-level laser irradiation applied to the temporomandibular joint in normal subjects.

BACKGROUND DATA

Although this therapy has been reported to be effective in the pain management of patients with rheumatoid arthritis and degenerative joint disease, several researchers have stated that this therapy has no effect on pain of myogeneous origin.

MATERIALS AND METHODS

Nine healthy subjects underwent irradiation using the continuous wave setting of a CO2 laser with a power output of 1.0 W. The laser tip was positioned 10 cm above the skin over the right TMJ area for 10 min. The actual fluence on the facial surface was 7.64 J/cm2. Variation of the facial temperature was evaluated by using thermography.

RESULTS

The facial temperature 10 min after stopping irradiation was higher than that after 10 min of irradiation applied to the opposite side. The warmer area was found not only over the TMJ area but also over the temporal area, forehead area, and eyelid area on both sides.

CONCLUSION

These results suggested that low-level laser irradiation had a long-lasting effect on facial cutaneous tissues.

The Comparison of Effects between Pulsed and CW Lasers on Wound Healing

OBJECTIVE

In order to evaluate the effects of pulsed continuous wave (CW) laser and detect the role of wound healing in rats using both pulsed and CW 635-nm low-level laser therapy (LLLT), a pilot study was undertaken.

BACKGROUND DATA

Some acceleration effects of wound healing on animals were found after treatment using various lasers with CW. There are other reports, however, using pulsed CW laser to evaluate the effects of wound healing in rats.

MATERIALS AND METHODS

An elliptic wound was created aseptically with a scalpel on the shaved back of the rats after anesthesia. The rats treated were restrained in a Plexiglas cage without anesthesia during the laser irradiation period. An Erchonia pulse laser (635 nm) was used in the experiment. The laser beam was delivered through an expander. The percentage of relative wound healing was calculated.

RESULTS

The percentage of relative wound healing was 4.32 in 100 Hz, 3.21 in 200 Hz, 3.83 in 300 Hz, 2.22 in 400 Hz, 1.73 in 500 Hz and 4.81 in CW.

CONCLUSION

LLLT using pulsed, CW laser at the appropriate dosimetry and frequency can provide acceleration in wound healing in rats. The 100-Hz frequency had a better effect than other pulse frequencies used in the study. The effects of treatment using CW laser was higher than pulse frequency. The frequency of pulsed CW laser was not found to increase wound healing in rats compared with normal CW laser, as reported in our previous studies.

Effects of low-power laser exposure on masseter muscle pain and microcirculation

One possible cause of the reported positive treatment effect by low-power laser exposure in muscle pain conditions could be that it increases the local microcirculation. The aim of this study was therefore to investigate the immediate effects on masseter muscle blood flow by low-power laser exposure in patients with chronic orofacial pain of muscular origin in comparison to healthy individuals. Twelve patients with myofascial pain of orofacial muscles and 12 age and gender matched healthy individuals participated in the study. Before laser exposure the subjects were examined clinically and the patients scored their current pain intensity from the most tender masseter muscle. Intramuscular laser-Doppler flowmetry was performed unilaterally in the most tender point (patients) or in a standardized point (healthy subjects) of the masseter muscle. The muscle was first exposed with a Gallium-Aluminum-Arsenide laser (active laser) or placebo laser for 2 min in a randomized and double-blind manner. After another 8 min the muscle was treated with the other laser for 2 min and the LDF recording continued for 8 min. Finally, the patients again assessed the pain intensity. Data were analyzed blindly by one of the authors not participating in data collection. The pain intensity was not affected by laser exposure. The blood flow did not change significantly in the patients, but increased after active laser exposure and decreased after placebo exposure in the healthy individuals. The difference between active laser and placebo was significant. In conclusion, the results of this study do not support an effect of low-power laser exposure on masseter muscle microcirculation in patients with chronic orofacial pain of muscular origin.

Low-intensity laser therapy/combined phototherapy in the management of chronic venous ulceration: a placebo-controlled study

OBJECTIVE

The current placebo-controlled study was undertaken to investigate the efficacy of combined phototherapy and low-intensity laser therapy (LILT) in the management of chronic venous ulceration when used in conjunction with standardized nursing intervention.

MATERIALS AND METHODS

Approval was granted by Research Ethical Committees at the University of Ulster and Altnagelvin Hospitals Health and Social Services Trust. Patients (n = 15; 10 female/5 male; age +/- SD = 69.9 +/- 13.8 years) were recruited from an outpatient "leg ulcer clinic," where they attended once per week for irradiation/sham treatments for 4 weeks. Treatment was withheld for a total of 8 weeks, and patients were reviewed during this time (weeks 8 and 12) for ulcer and pain assessment only. A multisource diode array (660-950 nm) was used for irradiation; parameters were kept constant for the duration of the study (532 mW; 5 kHz; 12 J/cm(2)). Wound and pain assessment were carried out by an independent investigator. Digitizing was used to quantify surface areas from wound tracings.

RESULTS

Although there was no statistically significant difference between Treatment and Placebo groups, an apparent clinical difference in wound healing rate was noted; at postirradiation, a continued reduction in wound size was evident for the treatment group. These effects were believed to be due to an apparent delayed effect. There was no statistically significant difference between groups for pain.

CONCLUSION

These findings provide only limited evidence for the use of this modality as an adjunctive therapy with current nursing intervention. Further group studies are indicated to investigate the apparent delayed effect reported here for various etiologies of ulceration.

Helium-neon laser irradiation at fluences of 1, 2, and 4 J/cm2 failed to accelerate wound healing as assessed by both wound contracture rate and tensile strength

BACKGROUND AND OBJECTIVE

Reports in the literature indicate that low energy laser irradiation has a biostimulatory effect on wound healing; however, no mechanism of this effect has been elucidated.

STUDY DESIGN/MATERIALS AND METHODS

We attempted to establish a model from which to study the mechanism of biostimulation. The effects of low energy helium-neon irradiation on wound healing were observed in two rat models. In the first model, 1.5 cm diameter full thickness excisional skin defects were created in the dorsal midline of rats (n = 32). All animals were anesthetized and all eschars were debrided daily. Wound area was determined by caliper measurements for 2 weeks postoperatively. Rats that received a treatment of 1 J/cm2 had two defects in the dorsal skin. One wound was treated and the second was used as its own control. These measurements were not blinded. Rats that received 2 J/cm2, 4 J/cm2, or anesthesia alone had one defect on the dorsal skin. Caliper measurements of these wounds were blinded. We were unable to demonstrate any difference in the rate of wound contracture in rats that received a daily dose of 1 J/cm2, 2 J/cm2, 4 J/cm2, or anesthesia alone (P > 0.8 by student's t-test). In the second model, a single 2 cm longitudinal full thickness skin incision was created in the dorsal midline of each rat (n = 24). No difference was found between rats that received anesthesia alone and those treated daily with 2 J/cm2 as assessed by tensile strength measurements on postoperative days 7 and 14 (P > 0.8 by student's t-test between groups at both time points). These determinations were blinded.

RESULTS

Despite our intentions of studying the mechanism of low energy HeNe biostimulation, we were unable to demonstrate a beneficial effect.

CONCLUSION

In this study, helium-neon laser irradiation produced no measurable benefit on wound healing.

The use of low energy photon therapy (LEPT) in venous leg ulcers: a double-blind, placebo-controlled study

BACKGROUND

Venous ulcers are estimated to be present in 0.2 to 0.4% of the population. Although new therapies have significant promise, nonhealing ulcers still represent a significant problem.

OBJECTIVE

To evaluate the efficacy of low energy photon therapy (LEPT) in the treatment of venous leg ulcers.

METHODS

A placebo-controlled, double-blind study using low energy photon therapy was performed in nine patients with 12 venous ulcers. Treatment was given three times a week for 10 weeks, using two monochromatic optical sources. One source provided a wavelength (lambda) of 660 nm (red) while the second source delivered a wavelength of 880 nm (infrared). Two optical probes were used, one consisted of an array of 22 monochromatic sources, operating at a wavelength of 660 nm and covering an area 6 x 10 cm2. The second probe had seven infrared sources, operating at a wavelength of 880 nm and covering an area of 4 cm2. The above configuration of optical probes was selected to cover the majority of the ulcer area being treated. The patients who were randomized to placebo treatment received sham therapy from an identical-appearing light source from the same delivery system.

RESULTS

Nine patients with 12 venous ulcers were randomized to receive LEPT or placebo therapy. At the conclusion of the study, the percentage of the initial ulcer area remaining unhealed in the LEPT and placebo groups was 24.4% and 84.7%, respectively (P = 0.0008). The decrease in ulcer area (compared to baseline) observed in the LEPT and placebo groups was 193.0 mm2 and 14.7 mm2, respectively (P = 0.0002). One patient dropped out of the study, complaining of lack of treatment efficacy; he was found to be randomized to the placebo group. There were no adverse effects.

CONCLUSION

In this placebo-controlled, double-blind study LEPT was an effective modality for the treatment of venous leg ulcers.

Comparison of wound healing process using Argon and Krypton lasers

OBJECTIVE

We compared the wound healing process on Sprague-Dawley rats between Argon Laser and Krypton Laser, and calculated the laser actual doses after correction on wound healing on rats and estimated the clinical doses on wound healing for human skin.

SUMMARY BACKGROUND DATA

Laboratory work provided some support for the use of low-intensity laser radiation in wound healing. Some studies found that laser irradiation may either enhance, inhibit, or has no effect on the function of a variety of microorganisms and cells. Animal studies also offered some basis for treatment. Improvements, particularly in the earliest phases of wound healing, have been reported following laser irradiation.

METHODS

We used Argon Laser (488-514 nm) and Krypton Laser (670 nm) in the study. The laser beam was delivered through a system of fiber optic in Argon Laser and reflector in Krypton Laser. The rats treated were restrained in a Plexiglas cage without anesthesia during the laser irradiation period. The percentage of the wound healing acceleration in days and size, actual doses, and estimated clinical doses were calculated as follows: AccD = (1-TD/CD) x 100%, AccS = (1-TA/CA) x 100%, AD = D(in) - D(gl) - D(SR) and ECD = AD = D(sr), respectively.

RESULTS

The acceleration effects of wound healing in days (AccD) were 22.93% and 14.54%, size reductions (AccS) were 41.93% and 30.41% at the optimal stimulative incident dose of 20 J/cm2. Zero bioactivation shown at the incident doses of 80 J/cm2 and 100 J/cm2. The inhibitory effects of wound healing in days were -7.72% and -3.37%, in size reduction were -13.35% and -12.88% at the maximal inhibitory incident dose of 140 J/cm2 for Argon and Krypton Lasers, respectively. The actual doses were 5.21 J/cm2 and 4.03 J/cm2, the estimated clinical doses were 5.50 J/cm2 and 4.25 J/cm2 at optimal stimulative incident dose 20 J/cm2 for Argon and Krypton Lasers, respectively.

CONCLUSIONS

Low power laser therapy at the appropriate dosimetric parameters can provide the acceleration effects of wound healing on rats. The effects were dependent with the doses and laser wavelengths used. In this experiment, the optimum stimulative dose was 20 J/cm2 and the Argon Laser with 488 nm was more effective than the Krypton Laser with 670 nm. The zero bioactivation and inhibition effect of wound healing on rats occurred in Argon Laser and Krypton Laser.

Low level laser therapy in the treatment of temporomandibular disorders (TMD): a double-blind pilot study

The aim of this paper was to evaluate the efficacy of a Low-Level Laser therapy in patients with Temporomandibular Disorders (TMD) using a double-blind design. A sample of 20 patients with a chief complaint of pain was divided into myogenous and arthrogenous groups. The sample was also divided on the basis of the treatment rendered: real versus placebo treatment. An 830 nm Ga-Al-As Laser device with a energy power of 4 joules was used (OMNILASE, LASERDYNE PTY LTD.) in three treatment sessions. To evaluate the effectiveness of laser treatment, a Visual Analogue Scale (VAS) was used for pain and active range of motion (AROM) was used to measure changes in mandibular function. Using real laser treatment, the author found that there was a reported improvement in pain only for the myogenous pain patients (p < or = 0.02). For the arthrogenous pain patients, real laser treatment resulted in an improvement in Total Vertical Opening (TVO) (p < 0.05), Protrusive excursion (PROT) (p < 0.02) and Left lateral excursion (LATLEF) (p < 0.02). The placebo control group showed improvement in TVO and PROT for those patients having myogenous pain and LATLEF for those patients having arthrogenous pain. A repeated measurement one-way ANOVA demonstrated no significant differences between real and placebo groups. Considering the non-invasive and harmless characteristics of this modality, more research is recommended, using higher power and increased frequency of laser applications.

Effect of low-power He-Ne laser on fracture healing in rats

BACKGROUND AND OBJECTIVE

Helium-Neon (He-Ne) laser radiation has been found to accelerate fracture healing in laboratory animal models as well as in cultures of cells involved in this process. We investigated the radiological, biomechanical, and histological effects of He-Ne radiation on fracture healing in a rat model.

STUDY DESIGN/MATERIALS AND METHODS

Sixty-two rats underwent bilateral open osteotomies of the tibiae followed by internal fixation with intramedullary wires. The right leg received He-Ne laser radiation of 0, 2, or 4 Joules every other day for 2 to 6 weeks while the left leg served as a control.

RESULTS

Radiological and histological examinations of the osteotomy sites failed to show any enhancing effect of He-Ne laser radiation on the bone healing process. Biomechanically, the irradiated bones of two of the six test groups were significantly weaker than the controls.

CONCLUSION

These results fail to support the previously reported enhancing effect of He-Ne laser radiation on fracture healing.

The effects of low level laser treatment on recovery of nerve conduction and motor function after compression injury in the rat sciatic nerve

An animal study is presented examining the effect of low level laser (LLL) treatment on nerve regeneration following axonotmesis. Twenty animals received a standardised injury to the right sciatic nerve using a time, load and length sequence (10 min, 150 N, 5 mm) known to cause extensive axonal degeneration of the rat sciatic nerve. The LLL treatment was administered using a hand-held laser probe in light contact with the skin on the dorsal aspect of the hind leg overlying the site of the axonotmesis injury to the sciatic nerve. A group of 10 animals were treated with 6J of LLL (GaAlAs 830 nm) daily for a period of 28 d. Ten more animals were treated daily with a sham exposure setting and served as controls. Nerve function was assessed by a recognised method of walking tract print analysis; the "Sciatic Functional Index" (SFI), and nerve regeneration was assessed by recording the evoked compound action potentials (cAP) in the common peroneal nerve. At 21 d post-injury, the laser-treated group had a significantly lower median SFI than the sham laser-treated group, indicating that the real laser treatment had improved functional recovery in the nerve. However, no differences were found between the evoked cAP parameters that were measured in the laser-treated and sham laser-treated groups. Histological examination reiterated the lack of difference between the two groups. Consequently, the effects of LLL on recovery must have occurred more peripherally to the point measured.

Inhibition of prostaglandin E2 and interleukin 1-beta production by low-power laser irradiation in stretched human periodontal ligament cells

It is well-known that orthodontic treatment usually causes some discomfort and pain to the patients. Recently, it has been reported that low-power laser irradiation is effective in reducing the pain accompanying tooth movement. However, the mechanism of such pain relief cannot be elucidated. Since high levels of prostaglandin (PG) E2 and interleukin (IL)-1 beta are found in the periodontal ligament (PDL) during tooth movement, and both factors are involved in the induction of pain, the effects of low-power laser irradiation on PGE2 and IL-1 beta production in stretched human PDL cells were studied in vitro. The PDL cells, derived from healthy premolars extracted for orthodontic treatment, were utilized for experiments. Cells were seeded in flexible-bottomed culture plates, and the bottom of each plate was elongated (18% increase) under vacuum at 6 cycles per min for 1, 3, or 5 days. The stretched cells were irradiated with a Ga-Al-As low-power diode laser (60 mW) once a day for 3, 6, or 10 min (from 10.8 to 36.0 J) for 1, 3, or 5 days. PGE2 and IL-1 beta levels in the medium were measured by radioimmunoassay. In response to mechanical stretching, human PDL cells showed a marked elevation in PGE2 production in a time-dependent manner. IL-1 beta production was also elevated, but this remained constant. The increase in PGE2 production was significantly inhibited by laser irradiation in a dose-dependent manner. The increase in IL-1 beta production was also significantly inhibited by laser irradiation, although the inhibition was only partial.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of 830 nm continuous wave laser diode irradiation on median nerve function in normal subjects

The presence, magnitude, and nature of the effect that low intensity laser irradiation has on nerve function, growth, and repair constitute a contentious area of research. We have addressed one aspect of this controversy by systematically examining the influence of 830 nm laser radiation on median nerve function. In particular, we investigated median nerve motor and sensory distal latencies, action potential amplitudes, action potential areas, and conduction velocities as well as dorsal hand skin temperatures in 33 normal subjects in a double-blinded, randomized controlled study. All subjects received identical treatment: 30 seconds of "irradiation" at 10 points over the course of the right median nerve (five sites on the forearm and five sites distal to the wrist crease) with either an active (1.2 J/point) or inactive (0 J/point) 40 mW 830 nm continuous wave IR laser diode. Latencies, conduction velocities, amplitudes, areas, and skin temperatures were collected bilaterally at a baseline immediately prior to irradiation and at intervals of 1, 5, 10, 15, 20, and 30 minutes following treatment. Analysis of the results reveals that motor and sensory distal latencies were decreased in the treated limbs of the laser-treated group relative to the control group by 3-4% (P < .016 and .046, respectively, rank sum test). No significant differences in these quantities were found between the limbs within either group. Similarly, no alterations of action potential amplitudes, action potential areas, forearm conduction velocities, or skin temperatures were detected within or between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesic effect of Ga-Al-As diode laser irradiation on hyperalgesia in carrageenin-induced inflammation

This study concerned the effect of Ga-Al-As diode laser irradiation (780 nm, continuous wave, 31.8 J/s/cm2, spot size od 0.2 mm, 3 minutes/dose) on hyperalgesia induced in the hind paw of rats by injecting carrageenin. The pressure-pain thresholds of hind paws were measured by the Randall-Selitto test for evaluation of hyperalgesia. Two doses of laser irradiation, given to the inflamed region immediately before and after the injection of carrageenin, partially (approximately 50%) inhibited the occurrence of hyperalgesia accompanied with a progression of inflammation. This analgesic effect was equal to that of indomethacin (4 mg/kg, i.o.). In another group, the hyperalgesia was removed almost completely for at least 24 hours by one dose of laser irradiation, which was given 3 hours after the carrageenin injection, whereas the edema was not inhibited. This analgesic effect, however, was partially (approximately 50%) antagonized with a dose of 10 mg/kg (i.p.) of naloxone and totally inhibited with 30 mg/kg. These results suggest that low-power laser irradiation on inflamed regions of carrageenin-treated rats has a marked analgesic effect and that certain mechanisms that are not related to endogenous opioids are involved in a part of the mechanisms of the analgesic effects.

Low power laser biostimulation of chronic oro-facial pain. A double-blind placebo controlled cross-over study in 40 patients

The efficacy of low power laser stimulation in the treatment of chronic oro-facial pain conditions was investigated in a double-blind placebo controlled modified cross-over study in 40 patients. The laser was an invisible infrared (IR) diode laser with an emission at 904 nanometer (nm). Treatment effect was evaluated by means of VAS-scales and global assessment of pain. Outcome of treatment was correlated to changes in urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA). The clinical impression was that placebo was superior to laser stimulation. No statistically significant difference between the analgesic effect of the laser and placebo irradiation was found on VAS-scales. A significant (P = 0.05) increase in 5-HIAA excretion was found in the placebo group. It is concluded that the possibility of a substantial placebo response should be taken into consideration using 904 nm (IR) lasers for pain treatment in patients with this type of chronic oro-facial pain.

Helium-neon laser irradiation inhibits the growth of kidney epithelial cells in culture

We have investigated the in vitro action of helium-neon (He-Ne) laser light on the cell cycle and the growth of rat kidney epithelial cell cultures. Dose-response studies showed that repeated He-Ne irradiation (dose rate 40 mW/cm2) once a day in a dose range between 11.9 and 142 J/cm2 significantly inhibited cell growth, while daily irradiation with 4.7 J/cm2 had no effect. Microscopic examination of nuclear spreads revealed an increased number of cells in mitosis after a single irradiation with 142 J/cm2. These results support previous observations suggesting that laser light of low thermal energy interferes with cell cycling and may inhibit cell growth when irradiation is performed at doses of 11.9 J/cm2 or more.

The soft laser: therapeutic tool or popular placebo?

Because of the alleged effectiveness of soft laser therapy in the treatment of a wide range of medical and dental conditions, it is becoming increasingly popular with both patients and practitioners. It was the purpose of this study to assess soft laser treatment of hypersensitive dentin, gingivitis, pulp-capped teeth, herpes labialis, and nausea. Clinical trails demonstrated no advantage in augmenting or replacing conventional treatment of these conditions with soft laser therapy, despite its positive effect on patient attitude toward treatment.

Irradiation effect of low-energy laser on alveolar bone after tooth extraction. Experimental study in rats

A histopathological study of the initial healing of extraction wounds following low-energy laser irradiation, using a gallium-arsenide semi-conductor laser, was carried out in rats. The results suggest that this mode of treatment has a beneficial effect on initial bony wound healing. It was found that proliferation of fibroblasts was more prominent in the irradiated group, and so was the formation of trabecular osteoid tissue. The deposition of lead in the newly formed bone suggests a more rapid ossification in the irradiated group.

Irradiation effect of low-energy laser on rat submandibular salivary gland

Histopathological studies of rat submandibular salivary glands following low-energy laser irradiation using gallium-arsenide semi-conductor laser were conducted. The mitoses of duct epithelial cells without atypia increased between 1 and 24 h after irradiation, reaching a maximum of greater than 5 times control values by 24 h. Mitoses of duct epithelial cells had a tendency to be more frequent in granular ducts, less in striated ducts, and still less in intercalated ducts. Qualitative differences in the effect of low-energy lasers on salivary gland epithelia were also noted. This is the first experimental study of the effect of low-energy laser on salivary glands.