A Titanium Surface-Modified with Nano-Sized Hydroxyapatite and Simvastatin Enhances Bone Formation and Osseointegration

The aim of the present study was to evaluate whether coating pristine titanium (Ti) with nano- sized hydroxyapatite (HAp) and simvastatin could enhance bone formation and osseointegration in vitro and in vivo because both HAp and simvastatin have the characteristic of osteogenetic induction. Pristine Ti was sequentially surface-treated with NaOH, 1,1-carbonyldiimidazole (CDI), beta-cyclodextrin-immobilized HAp powders (ss-CD/HAp), and simvastatin before analysis using scanning electron microscopy (SEM), X- ray photoelectron microscopy (XPS), and static contact angle measurement. This revealed that simvastatin was released continually for up 28 days. Modification of the Ti surface with nano- sized HAp and simvastatin (Ti/ss-CD/HAp/Sim) discs enhanced the osteogenic differentiation of MC3T3-E1 cells in vitro. Furthermore, Ti/ss-CD/HAp/Sim of screw type enhanced bone formation between the screw and the host bone when the screw implanted to the proximal tibia and femoral head of rabbits. These results suggest that surface modification of nano- sized HAp and simvastatin are effective tools for developing attractive dental implants.