Osteoinduction of porous bioactive titanium metal.

This is the first report of bone induction in a non-osseous site by titanium metal, which has long been recognized as a non-bioactive material. After undergoing specific chemical and thermal treatments, porous bioactive titanium induced bone formation without the need of additional osteogenic cells or osteoinductive agents. Four types of titanium implants were implanted in the dorsal muscles of mature beagle dogs, and were examined histologically after periods of 3 and 12 months. Chemically and thermally treated titanium, as well as pure titanium, was implanted either as porous blocks or as fibre mesh cylinders. Bone formation was found only in the chemically and thermally treated porous block implants removed after 12 months. The present study shows that even a non-soluble metal that contains no calcium or phosphorus can be an osteoinductive material when treated to form an appropriate macrostructure and microstructure. This finding may elucidate the nature of osteoinduction, and lead to the advent of epochal osteoinductive biomaterials for tissue regeneration.