Effects of fluoride-modified titanium surfaces with the similar roughness on RUNX2 gene expression of osteoblast-like MG63 cells

Chemical modification of titanium surfaces by hydrofluoric acid (HF) is an effective method to improve bone responses on titanium implant surfaces. In this study, titanium disks were sandblasted with titanium oxide grits and modified with 0.2% and 0.4% of diluted HF under different exposure times of 40 and 60 s. Surface characteristics, such as surface chemical composition, surface topography, and surface wettability, were investigated. To examine MG63 osteoblast-like cell responses to fluoride-modified titanium surfaces with roughness similar to that of nonmodified surfaces, a cell proliferation assay was performed and gene expression levels of Runx2 were evaluated using real-time PCR. Fluoride-modified titanium surfaces revealed no significant roughness difference but with hydrophilic properties than control group SB. Moreover, the relative atomic concentration percentages of fluoride were 0.7, 1.5, and 2.8. As fluoride concentrations increased, surface wettability increased and cell proliferation began earlier. However, the gene expression levels of Runx2 increased earlier on surfaces with 1.5% fluoride, with significantly high surface skewness. There seems to be an optimal fluoride concentration percentage when gene expression levels of Runx2 were taken into consideration. In addition, surface parameters, such as surface wettability and surface skewness, seem to be important factors in the enhancement of osteoblast differentiation by HF.