Effects of low-level laser therapy (685 nm) at different doses in osteogenic cell cultures

The present in vitro study evaluated parameters of osteogenesis under the influence of low-level laser therapy (LLLT) at different doses. Osteogenic cells originated from rat calvaria were cultivated in polystyrene plates and exposed to a laser irradiation using an indium-gallium-aluminum phosphide therapeutic laser (InGaAIP), at wavelength of 685 nm, power of 35 mW, 600-mu m-diameter optical fiber, and continuous wave. In the attempt of observing the existence of a dose response and its effects, laser irradiation was performed at 25, 77, and 130 J/cm(2) (7, 22, and 37 s, respectively). The following parameters were assessed: growth curve (4, 7, and 11 days), cell viability (24 h), and nodular formation of mineralized matrix (14 days). The results did not show significant differences related to the growth curve (4, 7, and 11 days) and cell viability (24 h). Within 14 days, osteogenic cultures showed nodular areas with well-defined calcified matrix. The total area stained with Alizarin Red did not show any differences between doses of 25 and 130 J/cm(2). However, the percentage of stained area was significantly higher in the 25 J/cm(2) group when compared to the group of 77 J/cm(2) (Kruskal-Wallis test, p < 0.05). It was possible to conclude that the 685-nm laser irradiation (at 25, 77, and 130 J/cm(2)) did not influence cell growth and proliferation, although the extracellular mineralization process may have its pattern altered by the LLLT on osteogenic cell cultures.