Biological Safety Evaluation and Surface Modification of Biocompatible Ti–15Zr–4Nb Alloy

Abstract

We performed biological safety evaluation tests of three Ti–Zr alloys under accelerated extraction condition. We also conducted histopathological analysis of long-term implantation of pure V, Al, Ni, Zr, Nb, and Ta metals as well as Ni–Ti and high-V-containing Ti–15V–3Al–3Sn alloys in rats. The effect of the dental implant (screw) shape on morphometrical parameters was investigated using rabbits. Moreover, we examined the maximum pullout properties of grit-blasted Ti–Zr alloys after their implantation in rabbits. The biological safety evaluation tests of three Ti–Zr alloys (Ti–15Zr–4Nb, Ti–15Zr–4Nb–1Ta, and Ti–15Zr–4Nb–4Ta) showed no adverse (negative) effects of either normal or accelerated extraction. No bone was formed around the pure V and Ni implants. The Al, Zr, Nb, and Ni–Ti implants were surrounded by new bone. The new bone formed around Ti–Ni and high-V-containing Ti alloys tended to be thinner than that formed around Ti–Zr and Ti–6Al–4V alloys. The rate of bone formation on the threaded portion in the Ti–15Zr–4Nb–4Ta dental implant was the same as that on a smooth surface. The maximum pullout loads of the grit- and shot-blasted Ti–Zr alloys increased linearly with implantation period in rabbits. The pullout load of grit-blasted Ti–Zr alloy rods was higher than that of shot-blasted ones. The surface roughness (Ra) and area ratio of residual Al2O3 particles of the Ti–15Zr–4Nb alloy surface grit-blasted with Al2O3 particles were the same as those of the grit-blasted Alloclassic stem surface. It was clarified that the grit-blasted Ti–15Zr–4Nb alloy could be used for artificial hip joint stems.

Development of Orthopedic Implants with Highly Biocompatible Ti Alloys

“…Biological safety evaluation tests of two Ti-Zr alloys are performed under the normal extraction condition in accordance with the ISO 10993 series and under the accelerated extraction condition [12]. Ta-free Ti-15Zr-4Nb (Ti-15-4) and Ti-15Zr-4Nb-1Ta (Ti-15-4-1) alloys are used for various biological safety evaluation tests.…”

“…Cell culture medium containing serum is used for extraction in cytotoxicity test, because it supports cellular growth as well as enables the extraction of both nonpolar and polar substances. For normal extraction in main biological safety tests except for cytotoxicity test, plate specimens are extracted in the 0.9%NaCl solution at 121°C for 1 h. On the other hand, the accelerated extraction (0.9%NaCl+HCl) solution adjusted to pH 2 can be prepared in accordance with ISO 16428 as follows [12]. 1 mol/L hydrochloric acid is added to 0.9%NaCl (physiological saline) solution, and the mixed (0.9%NaCl+HCl) solution is adjusted to pH 2.…”

Zinc-Based Biodegradable Materials for Orthopaedic Internal Fixation

“…The reported mechanical criteria for degradable metals (e.g., Mg-based) are UTS 300 MPa and ε 20% [ 22 ]. On the other hand, the current gold standard for medical metal materials, such as Ti and its alloys, has a tensile strength of over 600 MPa [ 13 ]. To certain extent, these criteria could provide guides of mechanical properties for development of Zn-based degradable materials.…”

“…Traditional fixation materials are generally nondegradable, including inert stainless steel (SS), titanium (Ti) and its alloys, and cobalt-chromium (Co-Cr) alloys [ 10 ]. They possess satisfactory biocompatibility, high wear resistance, and adequate mechanical strength ( Table 1 ) [ 11 , 12 , 13 ]. However, they have notable shortcomings when being applied in fracture fixation.…”

Tailoring a Low Young Modulus for a Beta Titanium Alloy by Combining Severe Plastic Deformation with Solution Treatment

“…The next demanding condition for the β-Ti alloy design refers to obtaining the minimum possible elastic modulus to avoid the so-named "stress shielding effect". The differences in elastic modulus between the bone and the metallic implant may lead to revision surgery [1][2][3][4][5]13,14]; thus, most research efforts have been centered on reducing the elastic modulus of the implant alloy. There have been some progress in this direction: while conventionally/commonly used αor (α + β)-Ti alloys (including consecrated Ti-6Al-4V) exhibit a modulus of about 100-110 GPa, β-Ti alloys exhibit moduli of around 55-70 GPa [15][16][17][18][19][20], which is much closer to the elastic modulus of cortical bone (approximately 30 GPa) [21].…”