The effect on somatosensory trigeminal evoked potentials (STEP) and latencies by intraoral low level laser irradiation of the maxillary nerve was evaluated. After electrical input at the left infraorbital foramen on 24 experimentally blinded pain-free subjects, He-Ne laser irradiation (1.7mW, 632.5nm, 50Hz) was performed for two minutes on 12 of these subjects, and sham irradiation on the other 12, at the left maxillary third molar apical area. Far-field STEP latencies and amplitudes were recorded: at base-line, immediately after intervention, and ten and twenty minutes after intervention. In the irradiated group, an immediate (average) STEP amplitude decrease from base-line of 60 per cent occurred, with further reduction to 65 and 72 per cent, at the ten and twenty minute intervals (p > .0001). No significant change occurred in the sham irradiation group (p > .05), and no change in latencies occurred in either group (p > .997). Low level laser treatment is commonly used in musculoskeletal and neurologic conditions, with mixed results. This experiment demonstrates that intraoral laser application to the maxillary nerve, where covered only by mucous membrane, results in significantly reduced STEP amplitudes. This findings suggests that intraoral laser therapy may be an effective pain control treatment.

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The scoring of pain attenuation in laser therapy (and other modalities) has traditionally been accomplished by using the visual analog scale (VAS), recognized as a very subjective method and thus open to possibly severe patient-specific skewing of the scoring data. An easy to use but objective method has yet to be developed. Through special symposia in their 11th and 12th meetings, (1999 and 2000), the Japan Laser Therapy Association (JaLTA) sought to improve the objectivity of the method of pain attenuation scoring while maintaining ease-of-use and minimizing expense, by comparing the results of questionnaires to participating institutes using laser therapy in pain attenuation for a specific set of four pain types; shoulder, lumbar and knee pain, and post-herpetic neuralgia (PHN). The VAS was initially used in combination with the pain relief score (PRS). Unlike the VAS, the PRS always has an initial value of 10 (maximum pain), and the patient's pain relief post-therapy is scored from 10 down to 0 (pain free). Ten sessions were set for both trials, and at the end of the tenth session, the patient's satisfaction index (SI) was recorded, in which the patients rated their satisfaction with the treatment over four grades in1999, ('Very satisfied', 'Satisfied', 'Dissatisfied' and 'Exacerbation’), which was subsequently increased to five grades in 2000, with the addition of 'Fairly satisfied' inserted before 'Dissatisfied'. In the 2000 meeting report, when the results of the five point SI were graphically compared with the overall PRS at the 10th treatment, a good statistical correlation was seen. In conclusion, it was decided that all JaLTA members should use the following assessment protocol: the VAS was to be used only at the initial consultation and the PRS exclusively hereafter, as the PRS incorporated VAS data but with the advantage of a standardized starting point and a larger movement on the scale; the SI should be assessed at the end of the 10th session, since the SI, while still subjec-tive, in combination with the averaged results of the PRS, can provide a more objective overview of the efficacy of the particular treatment regimen. Finally it was pro-posed that, after a suggested period of 3-5 yrs, these data for all pain entities should be collected in summary from JaLTA members, together with the treatment regimens, and could well be useful in the formulation of guidelines for the ideal and most satisfactory laser therapy regimen for each pain entity.

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Tissue healing is a complex process that involves local and systemic responses. The use of Low Level Laser Therapy (LLLT) for wound healing has been shown to be effective in modulating both local and systemic response. Usually the healing process of bone is slower than that of soft tissues. The effects of LLLT on bone are still controversial as previous reports show different results. This paper reports recent observations on the effect of LLLT on bone healing. The amount of newly formed bone after 830nm laser irradiation of surgical wounds created in the femur of rats was evaluated morphometricaly. Forty Wistar rats were divided into four groups: group A (12 sessions, 4.8J/cm² per session, 28 days); group C (three sessions, 4.8J/cm² per session, seven days). Groups B and D acted as non-irradiated controls. Forty eight hours after the surgery, the defects of the laser groups were irradiated transcutaneously with a CW 40mW 830nm diode laser, (f∼1mm) with a total dose of 4.8J/cm². Irradiation was performed three times a week. Computerized morphometry showed a statistically significant difference between the areas of mineralized bone in groups C and D (p=0.017). There was no significant difference between groups A and B (28 days) (p=0.383). In a second investigation, we determined the effects of LLLT on bone healing after the insertion of implants. It is known that dental implants need four and six months period for fixation on the maxillae and on the mandible before receiving loading. Ten male and female dogs were divided into two groups of five animals that received the implant. Two animals of each group acted as controls. The animals were sacrificed 45 and 60 days after surgery. The animals were irradiated three times a week for two weeks in a contact mode with a CW 40mW 830nm diode laser, (f ∼1mm) with a total dose per session of 4.8J/cm² and a dose per point of 1.2J/cm². The results of the SEM study showed better bone healing after irradiation with the 830nm diode laser. These findings suggest that, under the experimental conditions of the investigation, the use of LLLT at 830nm significantly improves bone healing at early stages. It is concluded that LLLT may increase bone repair at early stages of healing.

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During the last decade, it was discovered that low-power laser irradiation has stimulatory effects on bone cell proliferation and gene expression. The purposes of this review are to analyze the effects of low- power laser irradiation on bone cells and bone fracture repair, to examine what has been done so far, and to explore the additional works needed in this area. The studies reviewed show how laser therapy can be used to enhance bone repair at cell and tissue levels. As noted by researchers, laser properties, the combinations of wavelength and energy dose need to be carefully chosen so as to yield bone stimulation. With better study designs, the results will be more credible, allowing for greater recognition of advances in bone repair using laser therapy. Many studies on the effects of laser therapy on bone healing and fracture repair have used biochemical and histological methods. However, in order to establish the effects of laser treatment on bone, additional studies need to be performed using biomechanical tests, the ultimate evidence of bone repair. Finally, future studies are needed to demonstrate that the same bone stimulation effects occurring in animals may also be seen in humans.

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The effects of reactive oxygen species, especially as generated by photosensitizers and light, may serve as a model for light-induced effects relying on endogenous chromophores. Early events in the series of reactions initiated by these processes are reviewed and representative data on block of ionic currents, membrane permeabilization and increase in intracellular calcium concentration are presented. A general model for the effects of oxidative stress ranging from no effect with mild challenge to necrosis following severe challenge is presented. The results suggest that a ¹O₂ mechanism could be operative for some forms of low level laser therapy. Energetic considerations suggest that this mechanism is only likely for irradiation wavelengths shorter than 1270 nm.

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We studied the depth of penetration and the magnitude of attenuation of 632.8nm and 904nm light in skin, muscle, tendon, and cartilagenous tissues of live anaesthetized rabbits. Tissue specimens were dissected, prepared, and their thicknesses measured. Then, each wavelength of light was applied. Simultaneously, a power meter was used to detect and measure the amount of light transmitted through each tissue. All measurements were made in the dark to minimize interference from extraneous light sources. To determine the influence of pulse rate on beam attenuation, the 632.8nm light was used at two predetermined settings of the machine; continuous mode and 100 pulses per second (pps), at an on:off ratio of 1:1. Similarly, the 904nm infra-red light was applied using two predetermined machine settings: 292 pps and 2,336 pps. Multiple regression analysis of the data obtained showed significant positive correlations between tissue thickness and light attenuation (p < .001). Student's t-tests revealed that beam attenuation was significantly affected by wavelength. Collectively, our findings warrant the conclusions that (1) The calf muscles of the New Zealand white rabbit attenuates light in direct proportion to its thickness. In this tissue, light attenuation is not significantly affected by the overlying skin, a finding which may be applicable to other muscles. (2) The depth of penetration of a 632.8nm and 904nm light is not related to the average power of the light source. The depth of penetration is the same notwithstanding the average power of the light source. (3) Compared to the 904nm wavelength, 632.8nm light is attenuated more by muscle tissue, suggesting that is is absorbed more readily than the 904nm wavelength or conversely that the 904nm wavelength penetrates more. Thus, wavelength plays a critical role in the depth of penetration of light.

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Low Level Laser Therapy (LLLT) is controversial because of conflicting outcomes in peer reviewed literature. The possible combination and permutation of laser parameters is almost infinite. Defining what is an appropriate dose of laser energy for anyone condition remains anecdotal. A number of factors have contributed to the heterogenity of the literature and the variable outcomes. This paper examines how the confusion between laser acupuncture and non-acupuncture laser therapy has added to the dose dilemmas faced by clinicians using LLLT. Both historical and scientific perspectives on these differences are used to compare these two paradigms of laser therapy. An understanding of these differences may foster a more rational development of LLLT protocols.

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We used single photon emission computed tomography (SPECT) in brain perfusion imaging to study the changes of regional cerebral blood flow (rCBF) and cerebral function in brain infarction patients treated with intravascular low intensity laser irradiation of blood (ILIB). Seventeen of 35 patients with brain infarction were admitted to be treated by ILIB on the base of standard drug therapy, and SPECT brain perfusion imaging was performed before and after ILIB therapy with self-comparison. The results were analyzed using the brain blood flow function change rate (BFCR%) model. The effect of ILIB during the therapy process in the other 18 patients was also observed. In the 18 patients, SPECT indicated an improvement of rCBF (both in focus and in total brain) and cerebral function after a 30 min-ILIB therapy. And the 17 patients showed an enhancement of total brain rCBF and cerebral function after ILIB therapy in comparison with that before, especially for the focus side of the brain. The enhancement for the focal area itself was extremely obvious with a higher significant difference (P<0.0001). The mirror regions had no significant change (P>0.05). BFCR% of foci was prominently higher than that of mirror regions (P<0.0001). In conclusion, the ILIB therapy can improve rCBF and cerebral function and activate brain cells of patients with brain infarction. The results denote new evidence of ILIB therapy for those patients with cerebral ischemia.

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A brief review is made about the properties of the laser radiation, with particular emphasis on their importance in low level laser therapy. An important part of this section is dedicated to the properties of the laser beams emitted by the semiconductor lasers (laser diodes or diode lasers) given the broad use of such lasers in low level laser therapy. The basic elements about the laser beam interaction with the tissues are introduced in close connection with the penetration depths of the laser beams into the target tissues. A general scheme of a medical laser equipment is introduced, according to the author’s experience, insisting on the requirements which result from the need to deliver to the medical doctors friendly, easy to use laser medical equipment. The simple formula used to compute the doses for tissue exposure at laser radiation with specific comments dedicated to the low level laser therapy applications are introduced. Lasers and laser medical products classes are introduced in connection with the laser safety rules to be considered while using the products for therapy applications. The practical rules recommended for the safe use of medical laser equipment are specified based on the author’s experience and recommendations for room arrangement and instrument selection in medical praxis related to the laser medical applications are given. The laser safety practical rules for the patients and the medical personnel are specified in direct connection with the current laser medical applications.

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