Laser Phototherapy at High Energy Densities Do Not Stimulate Pre-Osteoblast Growth and Differentiation

Objective: The aim of this study is to evaluate the effects of red and infrared lasers at high energy densities on pre-osteoblast MC3T3 proliferation and differentiation. Background data: The acceleration of bone regeneration by low intensity laser irradiation may hold potential benefits in clinical therapy in orthopedics and dentistry. Materials and methods: Cells were irradiated with red (660 nm) and infrared (780 nm) lasers (90 and 150 J/cm(2), 40 mW). The control group did not receive irradiation. Cell growth was assessed by a colorimetric test (MTT) (24, 48, 72, 96 h) and cell differentiation was evaluated by alkaline phosphatase (ALP) quantification after growth in osteogenic medium (72, 96 h; 7, 14 days). Results: None of the irradiation groups had an enhancement in cell growth (p < 0.05). The production of ALP was not influenced by irradiation at any period of time (p > 0.05). Conclusions: The low intensity laser stimulated neither cell growth nor the production of alkaline phosphatase.