Human forearm fibroblasts were irradiated, in vitro, using a Microlaser Medical Pen Unit (Johnson and Johnson) with a wavelength of 860 nm, and an average power output of 50 mW. The irradiation distance and times were adjusted to give energy densities of 2 J/cm² and 16 J/cm² respectively. The control unit was adjusted to give a continuous waveform. Fibroblast proliferation and succinic dehydrogenase activity were assessed every 24 hrs over a five day period. The results obtained suggest a relationship between fibroblast proliferation and succinic dehydrogenase activity. At the lower energy density (2 J/cm²), succinic dehydrogenase levels rise with fibroblast proliferation. However, at an energy density of 16 J/cm², the succinic dehydrogenase levels and fibroblast proliferation appear to be inhibited. These findings agree with previously reported data.

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This study was performed to investigate the bioactivation effects of low level laser therapy (LLLT) on the fungus, Candida albicans, during its short term cell cycle. The laser used was a pulsed GaAs semiconductor laser emitting at 904 nm with a peak power of 27 W. The pulsing frequency could be selected to give a range of average output powers. Samples were divided into 6 groups, five irradiated experimental groups and one unirradiated control. The five experimental groups were each irradiated with a different pulsing frequency and average power: 500 Hz, 1 mW; 1.5 kHz, 3 mW; 3 kHz, 6 mW; 6 kHz, 14 mW; and 10 kHz, 27 mW, respectively. All samples were irradiated for 1 minute once at the beginning and then at regular two-hourly intervals during the approximate 27 hours of the cell cycle of C. albicans, and the optical density of the culture was assessed by spectrophotometry every two hours as a marker of the degree of photoactivation of cell replication. The collected data were subjected to statistical analysis. It was found that there was no statistically significant difference between the control and any of the groups irradiated at the two-hourly interval.

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Adult male BALB/C mice were used to investigate the influence of low level diode laser therapy (830 nm 30 mW C/W and 904 nm, pulsed, peak power, 30 W) on tibial fracture healing. Quantifiable and reproducible bone fractures were produced following the method of Borque et al. Evaluation of bone radiographs was performed using a laser densitometer “UltroScan XL ”. It was demonstrated that after three weeks of a daily regimen of irradiation by laser beam at a power of 4.0 J/cm² the irradiated calluses presented significantly higher optical density on radiograms than the control (non-irradiated) calluses. The effect of pulsed 904 nm irradiation was significantly higher than 830 nm C/W laser irradiation. It was concluded that near infrared LLLT using diode lasers accelerates bone fracture healing. The authors suggest that the photoacoustic generation of an ultrasonic wave by the pulsed laser in the irradiated bone may play an additional role in the mechanism of callus formation.

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Over the past year, eight patients with postherpetic neuralgia (PHN) were treated with diode low reactive-level laser therapy (LLLT) with an output power of 60 mW at 830 nm, while a further nine cases of PHN were treated with 830 nm diode LLLT at an output power of 150 mW. The data were analyzed to compare the efficacy of the two regimens. Although all the patients were successfully treated, those patients who had received LLLT at 150 mW showed a quicker overall recovery from PHN when compared to those treated with 60 mW LLLT. No clinically significant adverse effect resulting from either of the two regimens was noted. Our results in this preliminary study suggest that 150 mW LLLT was a much more effective therapy than 60 mW LLLT for the treatment of PHN within the period tested. Further controlled and double blinded studies in larger populations will be required to corroborate these preliminary findings.

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In order to investigate the efficacy of LLLT with the gallium arsenide (GaAs) semiconductor laser in the therapy of acute and chronic osteoarticular pain, the author presents an analysis of 938 irradiated patients. The GaAs laser equipment used has a wavelength of 904 nm. The laser is pulsed, pulse width of 200 nsec, pulse frequency 10,000 Hz, a peak power of 20 W and an average power of 40 mW. The patients were treated five times a week on several points with doses of 6-10 J/cm² on each point in the painful area or areas. The efficacy of the laser treatment at the end of 10 sessions was evaluated using a colour scale with a four grade estimation: excellent, good, little or no effect and poor. Laser efficacy was arrived at by combining the excellent and good responses. The overall effectiveness was 74.73%, but considering acute pain it was elevated to 88.20%, and in chronic pain it was 69.27%. In some specific locations such as acute cervical pain, acute lumbar pain and tenosynovitis the major statistical effectiveness was achieved (100%, 88.46% and 84%, respectively). In chronic knee and hip pain the response was poor (38.23% and 35.71%, respectively). These results suggest that GaAs laser therapy at the parameters as reported is an effective, easy to apply and side effect free treatment for osteoarticular pain. From the reported data, the efficacy of 904 nm GaAs LLLT is greater in acute pain therapy compared with chronic pain types, and some anatomical areas tend to respond better to GaAs diode LLLT than others.

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Experimentally-induced teat wall wounds (1 x 3 cm) in four dairy cattle were subjected to treatment with a helium-neon (HeNe) laser at 632.8 nm wavelength. The 16 teats were divided in a Latin Square design into 4 groups and subjected to different doses of low level laser: (1) Group A, 3.64 J/cm² for 15 min; (2) Group B, 2.42 J/cm² for 10 min; (3) Group C, 1.21 J/cm² for 5 min; and (4) Group D - control. Tissue samples from treatment and control groups were collected during surgery and after 13 sessions of laser therapy. Histological and histochemical examinations of posthealing specimens were condueted for evaluation of epidermal and fibroblast proliferation, production of collagen and ground substance, and neovascularization. Epithelialization and epithelial differentiation and keratinization in Groups A and B were more advanced compared with Groups C and D. Also, collagen fibres in Groups A and B were thicker, denser and more aligned than in Groups C and D. The posthealing histoarchitectural view of irradiated specimens, particularly in Groups A and B, suggests that low level laser therapy has a beneficial influence on wound healing.

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