The effect of hydrofluoric acid treatment of TiO2 grit blasted titanium implants on adherent osteoblast gene expression in vitro and in vivo.

It is widely accepted that implant surface factors affect the quality of the bone-to-implant interface. Recent additional treatments superimposed on moderately rough cpTitanium surface provide further enhancement of bone-to-implant contact. The aim of this study was to compare osteoinductive and bone-specific gene expression in cells adherent to titanium dioxide-grit blasted (TiO2) versus TiO2 grit blasted and HF treated (TiO2/HF) cpTitanium implant surfaces. MC3T3-E1 cells were grown in osteogenic supplements on the titanium disk surfaces for 1-14 days. Real-time PCR was used to measure RUNX-2, Osterix, and bone sialoprotein (BSP) mRNA levels. Implants were placed in rat tibia and, following harvesting at 1-7 days after placement, real-time PCR was used to measure RUNX-2, alkaline phosphatase (ALP), and BSP mRNA levels in implant adherent cells. In cell culture, RUNX-2 and Osterix levels were significantly increased (p<0.05) on the TiO2/HF surfaces as compared to the TiO2 and smooth surfaces through the cultural period, while BSP expression was elevated on both TiO2 and TiO2/HF surfaces when compared to a machined surface control. In cells adherent to implants retrieved from rat tibia, RUNX-2 mRNA levels were 2-fold and 8-fold greater on the TiO2/HF surfaces at 1-3 and 7 days following implantation. This was paralleled by significantly greater levels of ALP at 3 and 7 days and BSP mRNA at 7 days following implantation. As a marker of osteoinduction, the increased levels of RUNX-2 in cells adherent to the TiO2/HF surfaces suggest that the additional HF treatment of the TiO2 grit blasted surface results in surface properties that support adherent cell osteoinduction. In vivo assessments of implant adherent cell phenotypes provide further insight into the mechanisms affecting alloplast-tissue interactions.