A two-part in vivo and in vitro study is described to assess the effects of helium neon laser radiation on the mouse macrophage. In the first in vivo section 36 mice were used, divided into three groups: two helium neon (HeNe) laser irradiation groups, and the unirradiated control group. For the HeNe groups, the area over the liver or spleen of the mouse was irradiated with the HeNe laser at an energy density of 3,82 J/cm2. After irradiation, in all three groups, a Chinese calligraphic ink solution (containing a high concentration of pure carbon particles) was injected into the veins in the tail, and clearance of the carbon particles from the blood was assayed. It was demonstrated that the clearance of carbon granules increased in those animals who had HeNe LLLT. In the second section of the study, peritoneal macrophages were irradiated in vitro using the HeNe laser at a range of doses (3.1 J/cm2, 21.8 J/cm2 and 46.8J/cm2, The amount of lysozyme (48 animals in four groups: control plus three laser) and activity of acid phosphatase in the lysosomes (72 animals in four groups) were found to be statistically markedly higher in the laser-irradiated solutions than in the controls, especially at the two higher energy densities. The results indicated that the HeNe laser may exert an activating influence upon the immune response of the mononuclear macrophage system both in vivo and in vitro, and that additionally the degree of the influence is dose-related,
Low level laser therapy (LLLT) has been in clinical use in the United Kingdom for over 15 years, Recently, clinicians have expressed concern that if LLLT is used to treat a lesion adjacent to an active growth plate in a child, they may compromise the normal growth and development of that bone. The aim of this study was to examine the effect of 820 nm wavelength low level laser light on the healthy growth plate of the rat. Twenty-four female Wistar rats (aged 32 to 60 days) were used in the study. One knee joint of each animal in the experimental g.roup was irradiated three times a week at an energy density of 5 J cm-2. Animals were examined histologically after six and 12 treatments. The irradiated growth plates Were compared histomorphometrically with the untreated contralateral growth plates and also with the sham-irradiated growth plates of control animals. The results show that irradiation with low level laser light of wavelength 820 nm and energy density 5 J cm-2 had no significant effect on the healthy growth plates of the rat knee joint.
Low reactive-level laser therapy (LLLT) has been reported as having a beneficial effect in the therapy of rheumatoid arthritis. Some concerns have been expressed about the possible photothermal damage to articular tissue, for example the synovial membrane, following extended doses of LLLT such as are usually applied. The present study was designed to assess qualitatively and quantitatively the possible photothermal damage to articular membranous tissue foltowing an extended exposure (30 min) of infrared laser radiation on the rat synovial membrane, both through the capsule and with the capsule dissected away to aliow direct exposure. A third group of unirradiated anima]s acted as the control. The laser was a gallium aluminium arsenide (GaAlAs) diode laser system, delivering 60 mW, to a total spot size from three diodes of approximately 0.3 cm2, power density ≅ 0.2 W/cm2, incident energy 108 J, energy density 360 J/cm2. Evaluation of any photoinduced thermal damage was made both macroscopically and with blinded microscopic histological assessment. No damage was macroscopically visible, and no difference was found in the histology of the control, indirectly and directly-irradiated synovial membrane specimens. The authors conclude that, at the wavelength and delivery parameters given, even with extended dosage, laser therapy has no adverse photothermal effects on encapsulated or exposed synovial membrane in vivo.
The incidence of the use of the laser in laser therapy, or LLLT, rather than laser surgery, has been reported as increasing in many areas, While the applications of LLLT increase, concern has been expressed in the literature regarding the possible damage to tissue following extended doses of laser radiation having low incident power densities, such as are used in laser therapy. The present study was designed to evaluate any such adverse effects of 830 nm infrared laser energy (60 mW, continuous wave, spot size 0.3 cm2, power density ≅ 0.2 W/cm2, irradiation times of 3 and 30 min, energy densities 36 J/cm2 and 360 J/cm2, respectively) in vivo on rat skin and subcutaneous tissue, with normal and extended dosage at a low incident power density. A third group of unirradiated but identically handled animals acted as the control. Evaluation was made both macroscopically, recorded photographically, and microscopically with haematoxylin-eosin (HE) staining of histological specimens. Additional evaluation of tissue temperature rise as a function of irradiation time was recorded using digitalized thermography. Histological samples were coded, randomized and evaluated by an independent histologist. Skin temperature at the irradiated area rose by 1.1 °C over the first 4 min of irradiation, and then remained constant at that level for the remainder of the 30-min irradiation period. Macroscopically, there were no visible signs of alteration of skin colour or texture. Histology revealed no difference in the epidermal, dermal and subdermal tissue architecture in control. 3-min and 30-min irradiated specimens. The authors conclude that, for the range of parameters quoted above, laser therapy is inherently photothermally safe for in vivo irradiated tissue, bringing about no macroscopic or microscopic change in tissue architecture which could be classed as ‘damage ’.
We performed an experimental study to determine the effect of low incident levels of carbon dioxide (CO2) laser irradiation on the survival of experimental acute random skin flaps in the rat model, In the experimental group (n=11) the skin flaps were irradiated postoperatively with the defocused beam of the CO2 laser (power density 300 mW/cm2), two times a day, for 7 days. The survival length of the skin flaps was measured at the 14th postoperative day. The mean survival length of the skin flaps was 5.83 ± 1.02 cm (mean ± S.D,) in experimental group, and 3.60 ± 0.49 cm (mean ± S.D.) in the control group (n=11). The result showed a statistically significant difference between the irradiated and unirradiated groups (t=6.53, P<0.001). In a separate related controlled experiment. the morphological and metabolic changes of the irradiated and unirradiated skin flaps were studied. The effects of LLLT on enhanced survival of skin flaps in the rat model are attributed to an enhanced circulatory response, and as part of the enzymatic response, a decrease in LDH activity was found, possibly reducing total lactate content, thus helping to control acidosis at a cellular level. The authors conclude that, at the parameters used in the present study, LLLT with the CO2 laser certainly prolongs the survival of flaps at a cellular level, thus aiding swifter revascularization and thus improving the overall survival of the irradiated flaps.
This study was undertaken to determine whether the infrared (IR) beam of the gallium-arsenide (GaAs) laser at low reactive-level laser therapy (LLLT) levels has biostimulative effect on the oral flora as well as the tissue cell using spectrophotometeric assay, and to suggest an hypothesis on the mechanism of accelerated healing following low reactive-level laser therapy (LLLT) of the infected lesion according to the previously reported results that there were changes in the composition of various kinds of bacteria in addition to the decrease in the gingival inflammation. Eighty samples of Streptococcus mutans for 4 days were used and divided into four groups. (control, 1 min, 2 min, 3 min). Five samples of each group were sacrificed everyday for 4 days using a spectrophotometer to measure the optical density, and then the control and experimental groups were compared according to the time interval and irradiation time. Conclusions based on the results for this study were as follows: (l) Gallium-arsenide laser irradiation at LLLT levels stimulated the increase of bacterial growth. (2) The rate of increase of bacteria did not coincide with that of laser fluence and the biostimulative effect of LLLT on bacterial cells was most effective when the energy fluence was at 337.0 mJ at the parameters in this study.
At present there is only a little knowledge about the stimulation of nerve regeneration. Recently low level laser therapy (LLLT) has been reported as one of the best tools for nerve regeneration, We treated an intractable tarsal tunnel syndrome patient who was 39 years old and had no specific past history, The pain and gait disturbance had not responded to several conservative treatments. But 1 week's use of LLLT left the patient free from limping and pain. The effects were confirmed electrophysiologically. The authors think that LLLT could be useful for various kinds of nerve lesions.