Biomedical Applications of Titanium Alloys: A Comprehensive Review

Abstract

Titanium alloys have emerged as the most successful metallic material to ever be applied in the field of biomedical engineering. This comprehensive review covers the history of titanium in medicine, the properties of titanium and its alloys, the production technologies used to produce biomedical implants, and the most common uses for titanium and its alloys, ranging from orthopedic implants to dental prosthetics and cardiovascular devices. At the core of this success lies the combination of machinability, mechanical strength, biocompatibility, and corrosion resistance. This unique combination of useful traits has positioned titanium alloys as an indispensable material for biomedical engineering applications, enabling safer, more durable, and more efficient treatments for patients affected by various kinds of pathologies. This review takes an in-depth journey into the inherent properties that define titanium alloys and which of them are advantageous for biomedical use. It explores their production techniques and the fabrication methodologies that are utilized to machine them into their final shape. The biomedical applications of titanium alloys are then categorized and described in detail, focusing on which specific advantages titanium alloys are present when compared to other materials. This review not only captures the current state of the art, but also explores the future possibilities and limitations of titanium alloys applied in the biomedical field.

Keywords: 3D printing; biocompatibility; cardiovascular devices; dental implants; orthopedics; osseointegration; titanium alloys.

Figure 1

Summary diagram of the contents of this review, with the numbers and titles of sections and sub-sections.

Figure 2

Effects of (a) alpha and (b) beta stabilizers on the microstructure of titanium alloys. The dotted black lines represent the region of metastability of α-β alloys, the red dotted lines represent the expected microstructure at room temperature, (c) an example of a typical commercially pure α-titanium microstructure, and (d) an example of a typical annealed Ti-6Al-4V α-β alloy microstructure.

Figure 2

Effects of (a) alpha and (b) beta stabilizers on the microstructure of titanium alloys. The dotted black lines represent the region of metastability of α-β alloys, the red dotted lines represent the expected microstructure at room temperature, (c) an example of a typical commercially pure α-titanium microstructure, and (d) an example of a typical annealed Ti-6Al-4V α-β alloy microstructure.

Figure 3

Relationship between ultimate strength and elastic modulus for a selection of alloys commonly applied in the biomedical field, grouped by chemical composition.

Figure 4

Relationship between the ultimate tensile strength and the qualitative corrosion resistance of titanium alloys applied in the biomedical field. The colored areas indicate the kind of alloys.

Figure 5

Implant failures divided by category, going from 0% (in the center of the triangle) to 100% (at the outermost corners) of the failures.

Figure 6

Survival rate over time for different categories of titanium biomedical devices.

Figure 7

Examples of (a) fretting damage after 5 years in vivo and (b) mechanical failure due to fretting corrosion after just 2 years in vivo for Ti-6Al-4V tapers in modular femoral stems.