Processing, characterization, and in vitro/in vivo evaluations of powder metallurgy processed Ti-13Nb-13Zr alloys.

This article presents details of processing, characterization and in vitro as well as in vivo evaluations of powder metallurgy processed Ti-13Nb-13Zr samples with different levels of porosity. Sintered samples were characterized for density, crystalline phases (XRD), and microstructure (SEM and EDX). Samples sintered at 1000 degrees C showed the highest porosity level ( approximately 30%), featuring open and interconnected pores ranging from 50 to 100 mum in diameter but incomplete densification. In contrast, samples sintered at 1300 and 1500 degrees C demonstrated high densification with 10% porosity level distributed in a homogeneous microstructure. The different sintering conditions used in this study demonstrated a coherent trend that is increase in temperature lead to higher sample densification, even though densification represents a drawback for bone ingrowth. Cytotoxicity tests did not reveal any toxic effects of the starting and processed materials on surviving cell percentage. After an 8-week healing period in rabbit tibias, the implants were retrieved, processed for nondecalcified histological evaluation, and then assessed by backscattered electron images (BSEI-SEM) and EDX. Bone growth into the microstructure was observed only in samples sintered at 1000 degrees C. Overall, a close relation between newly formed bone and all processed samples was observed.

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, H(3)PO(4), and in a mixture of HF+HNO(3), 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 (alpha+beta) 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 H(3)PO(4) treated samples. No HCA formation was found on HNO(3) 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/cm(2)) followed by H(3)PO(4) (0.8 mg/cm(2)) and HNO(3) pretreated ones (0.2 mg/cm(2)). 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.