In vitro apatite formation on chemically treated (P/M) Ti–13Nb–13Zr

Objectives Titanium alloys are considered the material of choice when used as endosteal part of implants. However, they are not able to bond directly to bone. The objective of this study was to suggest a chemical surface treatment for Ti–13Nb–13Zr to initiate the formation of hydroxy carbonated apatite (HCA) during in vitro bioactivity tests in simulated body fluid (SBF). Methods Titanium, niobium, and zirconium hydride powders were blended, compacted and sintered. Sintered Ti–13Nb–13Zr samples were etched in HCl, H3PO4, and in a mixture of HF + HNO3, respectively, and subsequently pretreated in NaOH. The influence of acid etching conditions on the microstructure of the Ti–13Nb–13Zr alloys as well as on the rate of HCA formation was evaluated using SEM-EDS, FTIR, and gravimetric analyses. Results Sintered Ti–13Nb–13Zr alloys consist of a Widmannstätten (α + β) microstructure. Exposure of chemically etched and NaOH activated samples to SBF for 1 week leads to the formation of a HCA layer on the surface of HCl as well as H3PO4 treated samples. No HCA formation was found on HNO3 treated samples. After 2 weeks in SBF the mass increase, that can be correlated to the HCA formation rate, was the highest for HCl pretreated samples (2.4 mg/cm2) followed by H3PO4 (0.8 mg/cm2) and HNO3 pretreated ones (0.2 mg/cm2). Significance Since the in vitro HCA formation from SBF is generally accepted as a typical feature for bioactive materials, it is supposed that HCl etching with subsequent NaOH treatment might enhance the in vivo bone-bonding ability of Ti–13Nb–13Zr.