Effect of laser therapy on attachment, proliferation and differentiation of human osteoblast-like cells cultured on titanium implant material

The aim of this in vitro study was to investigate the effect of low-level laser therapy (LLLT) on the attachment, proliferation, differentiation and production of transforming growth factor-ß1 (TGF-β1) by human osteoblast-like cells (HOB). Cells derived from human mandibular bone were exposed to GaAlAs diode laser at dosages of 1.5 or 3 J/cm2 and then seeded onto titanium discs. Non-irradiated cultures served as controls. After 1, 3 and 24 h, cells were stained and the attached cells were counted under a light microscope. In order to investigate the effect of LLLT on cell proliferation after 48, 72 and 96 h, cells were cultured on titanium specimens for 24 h and then exposed to laser irradiation for three consecutive days. Specific alkaline phosphatase activity and the ability of the cells to synthesize osteocalcin after 10 days were investigated using p-nitrophenylphosphate as a substrate and the ELSA-OST-NAT immunoradiometric kit, respectively. Cellular production of TGF-β1 was measured by an enzyme-linked immunosorbent assay (ELISA), using commercially available kits. LLLT significantly enhanced cellular attachment (P<0.05P<0.05). Greater cell proliferation in the irradiated groups was observed first after 96 h. Osteocalcin synthesis and TGF-β1 production were significantly greater (P<0.05P<0.05) on the samples exposed to 3 J/cm2. However, alkaline phosphatase activity did not differ significantly among the three groups. These results showed that in response to LLLT, HOB cultured on titanium implant material had a tendency towards increased cellular attachment, proliferation, differentiation and production of TGF-β1, indicating that in vitro LLLT can modulate the activity of cells and tissues surrounding implant material.