Power density and exposure time of He‐Ne laser irradiation are more important than total energy dose in photo‐biomodulation of human fibroblasts in vitro

Abstract

The absorption spectrum of human fibroblast monolayers showed several absorption peaks, among them one at a wave-length of 630 nm. Cultures of these fibroblasts were subjected to He-Ne laser (632.8 nm) irradiation of various energy doses by varying power density and exposure time. On three consecutive days the cell monolayers were irradiated for periods between 0.5 and 10 min. Laser power varied from 0.55 to 5.98 mW. Both cell number and collagen type I production were determined for each irradiation condition within one experiment. Results show that laser power below 2.91 mW could enhance cell proliferation (as determined by cell counting), whereas higher laser power (5.98 mW) had no effect. Stimulatory effects were most pronounced at irradiation times between 0.5 and 2 min. Collagen type I production (as determined by an ELISA) was affected in the opposite direction to cell proliferation: when the cell proliferation was increased, collagen type I production was decreased. From these experiments it is clear that exposure time and power density determine the effects of laser irradiation. Both stimulation and inhibition of the observed cell properties can be obtained with the same laser on the same cells.

Effect of 810 nm Diode Laser Therapy on the Rate of Extraction Space Closure

“…Power calculation was done for separate arches as well, for maxilla, it was 99.56% and, for mandibular arch, it was 97.83%. 23 noted that the power density is more important than the total dose in initiating biomodu lation. The most commonly available soft tissue lasers in the dental office have a wave-length of 810, 910 or 940 nm.…”

Polarized Light (400–2000 nm) and Non-ablative Laser (685 nm): A Description of the Wound Healing Process Using Immunohistochemical Analysis

“…2 Controversies regarding doses continue, though previous reports have pointed out that low doses result in positive effects on living organisms. 3,4 On the other hand, higher doses have not been shown to have positive effects on stimulating living tissues.3,5-7 Wavelength is also important, as visible laser light seems to be more effective in inducing cell proliferation than infrared light. 8 Laser light is monochromatic, possesses high intensity, and is coherent-unlike visible light.…”

Los diferentes tipos de láser y sus aplicaciones en podología

“…También el vocablo se ha usado para nombrar el método de laserterapia sobre puntos de acupuntura, tanto con criterios de la medicina occidental, como de la medicina oriental 17 . En los últimos años diversos estudios publicados sobre el efecto del láser de baja potencia demuestran que con su aplicación se consigue un aumento de trifosfato de adenosina 18 , una influencia positiva en los fibroblastos 19 y la sín-tesis de colágeno 20 a nivel celular molecular. Existen protocolos clínicos para el uso y manejo del láser de baja potencia para su aplicación en patologías dolorosas y afecciones como la artritis reumatoide, osteoartritis, dolor a nivel cervical, tendinopatías y en dolores crónicos en las articulaciones.…”