Role of calcium ions in defining the bioactivity of surface modified Ti metal.

Nano-structured hydrogen titanate and sodium hydrogen titanate layers were formed when Ti metal was treated with H2O2 and NaOH solutions, respectively. The chemically treated Ti metals upon subsequent treatment with Ca(NO3)2 and CaCl2 solutions, resulted in incorporation of Ca2+ ions into the nano-structured titanate layer. Thus formed nano-structured titanate layers containing Ca2+ ions when subjected to heat treatment, forms anatase and calcium titanate-rutile phases, respectively. In vitro apatite-forming ability in simulated body fluid (SBF) was positive for H2O2-Ca and heat-treated Ti metal in contrast to NaOH-Ca and heat treatment. Formation of anatase phase together with Ca2+ ion release into SBF was found to be the key driving force for such a high bioactivity of Ca2+ containing H2O2 treated Ti metal on contrary to NaOH and heat treatment. This study provides a new insight into the factors accelerating the bioactivity of Ti metals during various chemical and thermal treatments, which further aid and abet to design dental and orthopaedic implants with high bone-bonding ability.