Although these devices are currently highly touted by individual manufacturers and their paid proponents, they need to be regarded with a critical eye.
First of all, these systems operate at high energy levels and may therefore be bioinhibitory and I quote the Arndt Shultz Law which states that a small dosage of light may have no biological effect, a moderate dosage may have a biostimulatory effect, and a large dosage may have a bioinhibitory or even cytotoxic effect. Moreover, Class IV devices do not reduce the severity of the inflammatory process so essential to therapy and do not accelerate the regeneration of individual cells. Indeed in review, they have proven to slow wound healing and accordingly their advertising hype never mentions the healing of wounds. It should be observed that the healing of wounds does not differ from the healing of other tissues, notwithstanding the existing degree of pathology. The generation of the heat imposed also detracts from the effectiveness of therapy.
Wavelengths from the 900-1000 level are primarily absorbed by lipids and water and therefore have minimal effect on the cells involved in the pathological process. Once again, it should be noted that Class IV Lasers are not applied directly to the tissues because to do so would cause burns using the high powered settings recommended. The 980 nm diodes incorporated in Class IV Lasers do not increase penetration, as much of the light energy is absorbed superficially and more rapidly, leading to heat generation. This diminishes the physiological benefits so essential to cellular activity.
It should be noted that Tuner and Hode, who have a good grasp of the physics of laser light, do not recommend Class IV Lasers and state that Class IIIB devices, properly engineered, are most appropriate for cellular healing (excerpted from an article, “No Cure from LiteCure” by Jan Tuner).
However Lasers may be classified, whether Class II, III or IV, it is an extensive combination of factors that are essential to promote cellular healing and the production of optimal clinical outcomes. These include malleable parameters such as pulse frequency, duty cycle, waveform, wavelength, energy density, duration, etc. The diodes utilized must be minimally degradable and applied directly to tissue to achieve maximum benefit. The benefits derived from Class IV Lasers generally, removed some distance from the tissues and covered by either a plastic or glass protective barrier, are negatively affected by the refraction of light as it transverses the atmosphere and reflection as it strikes the epidermal surface.
While curtailing the so-called benefits of higher powered lasers, the degree of power cannot be accurately determined and effects on tissue will therefore be random, unpredictable and potentially produce serious adverse effects.