Background. The growth and proliferation of? gingival fibroblasts are important in the process of? oral wound healing, and photobiomodulation (PBM) might be able to modify this process. Objectives. The aim of?the current study was to evaluate the biomodulatory effect of?a?single session of?laser PBM by means of?810?nm and 940?nm diode lasers alone and their combined application with different fluencies on human gingival fibroblasts (HGFs). Material and methods. Cells were provided by the Pasteur Institute, the National Cell Bank of? Iran (NCBI) (C-165). Laser irradiation was carried out using 810?nm, 940?nm and 810?nm 940?nm in the continuous wave (CW) mode, 100?mW, and energy densities of?0.5, 1.5 and 2.5?J/cm2 . Cell viability was evaluated at 24?h with the MTT assay. Trypan blue staining was used to evaluate proliferation 24, 48 and 72?h after laser therapy. Propidium iodine was used to stain DNA and the cell nucleus. Results. Laser irradiation (810?nm, 0.5?J/cm2 ) increased the viability of?gingival fibroblasts, while this dose had an?inhibitory effect with 940?nm. No positive effect on cell viability was found with other settings at 24?h. The viability results were not statistically different from those of?the control in the dual wavelength group. At all single-laser irradiation doses, the cell proliferation results were lower as compared to the control at 48 and 72?h. The dual wavelength group results were significantly better than those of?the control for the 1.5?J/cm2 and 2.5?J/cm2 energy densities (p??0.001). Propidium iodine staining showed no negative effect of?laser irradiation on the cell nucleus in any of?the groups. Conclusions. Although a?single irradiation dose of?810?nm, 0.5?J/cm2 , resulted in a?positive effect on cell viability at 24?h, no statistically significant stimulatory effect on viability and proliferation was observed for the other single wavelength group. When a?combination of?the 2 wavelengths was used, better results were observed as compared to the control, which needs to be further investigated in future studies.
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