Proliferation and differentiation parameters of human osteoblasts on titanium and steel surfaces

Commercially pure titanium (cpTi), titanium alloys, and steel are often used for dental and orthopedic implants. In these applications titanium is considered the "gold standard." However, tissue reactions around titanium implants and the changing trend to leave orthopedic devices in the body have led to a new examination of the preferred material. This in vitro study tested the behavior of osteoblasts on cpTi, Ti-6Al-7Nb, and stainless steel with surface designs similar to clinical implants. After surface characterization by scanning electron microscopy and profilometry, cell proliferation and the differentiation parameters of alkaline phosphatase (ALP) activity and osteocalcin were measured. For all materials tested, the growth curves showed a similar kinetic. On Ti-6Al-7Nb, ALP activity was significantly lower when compared with steel, and cpTi and did not change over the time. ALP activity increased moderately on steel and cpTi. Osteocalcin levels were higher on both titanium materials than on steel. Based on undisturbed cell growth and the relatively high alkaline phosphatase and osteocalcin levels, we suggest that cpTi provides the best biocompatibility with regard to proliferation, in addition to more reliable early and late differentiation markers of human osteoblasts in vitro.