Preparation of calcium phosphate coatings on titanium implant materials by simple chemistry

A two-step chemical treatment has been developed in our group to prepare commercially pure titanium (cpTi) surfaces that will allow calcium phosphate (Ca-P) precipitation during immersion in a supersaturated calcification solution (SCS) with ion concentrations of [Ca2+] = 3.10 mM and [HPO4(2-)] = 1.86 mM. It was observed that a precalcification (Pre-Ca) procedure prior to immersion could significantly accelerate the Ca-P deposition process. In this work, the bioactivity of chemically treated cpTi and Ti6Al4V was further verified by applying commercially available Hanks' balanced salt solution (HBSS), an SCS with very low ion concentrations of [Ca2+] = 1.26 mM and [HPO4(2-)] = 0.779 mM, as the immersion solution. It was found that a uniform and very dense apatite coating magnesium impurities was formed if the Pre-Ca procedure was performed before immersion, as compared with the loose Ca-P layer obtained from the abovementioned high concentration of SCS. The formation of a microporous titanium dioxide thin surface layer on cpTi or Ti6Al4V by the two-step chemical treatment could be the main reason for the induction of apatite nucleation and growth from HBSS. Variations of pH values, Ca and P concentrations, and immersion time in HBSS were investigated to reveal the detailed process of Ca-P deposition. The described treatments provide a simple chemical method to prepare Ca-P coatings on both cpTi and Ti6Al4V.