Low Pulse Energy Nd:YAG Laser Irradiation Exerts a Biostimulative Effect on Different Cells of the Oral Microenvironment: "An In Vitro Study"

Background and Objectives: Dental lasers represent a promising therapeutic tool in the treatment of periodontal and pen-implant diseases However, their clinical application remains still limited. Here, we Investigated the potential biostimulatory effect of low pulse energy neodymium:yttrium aluminum garnet (Nd.YAG) laser irradiation on different cells representative of the oral microenvironment and elucidated the underlying molecular mechanisms. Materials and Methods: Saos-2 osteoblasts, H-end endothelial cells, and NIH/3T3 fibroblasts pre-treated or not with photosensitizing dye methylene blue (MB), were irradiated with low pulse energy (20 mJ) and high repetition rate (50-70 Hz) Nd YAG laser, and evaluated for cell viability and proliferation as well as for the expression of specific differentiation markers by confocal immunofluorescence and real-time RT-PCR. Changes in intracellular Ca2+ levels after laser exposure were also evaluated in living osteoblasts. Results: Nd:YAG laser irradiation did not affect cell viability in all the tested cell types, even when combined with pre-treatment with MB, and efficiently stimulated cell growth in the non-sensitized osteoblasts Moreover, a significant induction in the expression of osteopontin. ALP, and Runx2 in osteoblasts, type I collagen in fibroblasts, and vinculin in endothelial cells could be observed in the irradiated cells Pre-treatment with MB negatively affected cell differentiation in the unstimulated and laser-stimulated cells. Notably, laser irradiation also caused an increase in the intracellular Ca2+ in osteoblasts through the activation of TRPC1 ion channels. Moreover, the pharmacologic or genetic inhibition of these channels strongly attenuated laser-induced osteopontin expression, suggesting a role for the laser-mediated Ca2+ influx in regulating osteoblast differentiation Conclusion: Low pulse energy and high repetition rate Nd.YAG laser irradiation may exert a biostimulative effect on different cells representative of the oral microenvironment, particularly osteoblasts. Pre-treatment with MB prior to irradiation hampers this effect and limits the potential clinical application of photosensitizing dyes in dental practice Lasers Surg. Med 42:527-539, 2010 (C) 2010 Wiley-Liss, Inc.