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Materials Science in Additive Manufacturing Preparation and modification of porous Ti

1. Introduction properties at the interface between the scaffold and the
surrounding tissue. Surface modification technology is a
Millions of people around the world suffer from incurable method to change the surface properties of materials by
injuries due to infection debridement, cardiovascular physical or chemical means, which plays an important role
and cerebrovascular diseases, degenerative orthopedic in the functional transformation of titanium alloys. 13
diseases, and oral and maxillofacial diseases every year,
posing a huge socio-economic burden on society and Medical porous titanium alloy implants have gradually
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the health-care system. Biomedical materials, which are emerged as a critical ingredient in the orthopedic,
used in fixing, supporting, and repairing damaged parts, stomatologic, cardio-cerebrovascular, and other fields.
are key players in moving medical advancements forward. Researchers have focused on improving the mechanical
As clinical product technology and quality requirements and biological properties of materials by optimizing the
continue to improve, there is a growing demand for preparation process and surface modification process. 14,15
biomedical materials that are cost-effective, of higher Despite the continuous technological advancements, there
quality, and can be processed more conveniently. is still a lack of comprehensive and in-depth summary in
the field of processing and surface modification of medical
According to the type of material, biomedical materials porous titanium alloys, especially about (i) the complexity
can be divided into metal materials, ceramic materials, of the preparation process of porous scaffolds and the
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and polymer materials. Among them, metal materials have comparison of advantages and disadvantages; (ii) the
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many excellent properties, such as high strength, good wear application scenarios and influencing factors of various
resistance, and easy processing, occupying 70 – 80% of the surface modification methods; and (iii) the synergistic
entire market share of medical materials. Commonly used effect between the preparation method of porous
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medical metal materials include titanium and titanium
alloy, stainless steel, nickel-cobalt alloy, and magnesium structure and the surface modification. This paper aims
to provide a timely, comprehensive, and critical review
alloy. Titanium and its alloys have the advantages of high of the preparation and surface modification of medical
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strength and low modulus, high fatigue performance, and porous titanium alloy scaffolds. The overall content of the
excellent biocompatibility, attributes that make them the paper is shown in Figure 1. The paper first outlines the
most widely used medical metal materials for being able to
meet most medical needs. 7 performance requirements, structural requirements, and
influencing factors of the medical titanium alloy porous
However, it is found that titanium alloy as an endoprosthesis scaffold (Section 2). Then, the preparation methods of
is prone to loosening when it has been implanted in the human porous scaffolds and their advantages and disadvantages
body for a long period of time. The loosening occurs due to
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two major factors: (i) Dense titanium and titanium alloys
have high elastic modulus compared with human bone/tissue,
which will cause a “stress shielding” effect; (ii) traditional
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titanium and titanium alloys are bioinert metal materials,
and implants cannot form a good biological fixation with the
surrounding tissues of the human body. 9
To address the above clinical problems, researchers
integrated three-dimensional (3D) porous structures into
titanium alloy implants to effectively reduce the elastic
modulus of implants, reduce the “stress shielding” effect,
and improve the bonding strength between implants and
human tissues. Therefore, porous titanium has been used
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as a promising new biomedical material for artificial joints,
spinal fusion devices, dental implants, and cardiovascular
scaffolds and in other fields. 11

However, introducing a porous structure to reduce the
modulus alone cannot alter the bioinert nature of titanium
alloy, which still lacks the capacity to promote cell adhesion,
tissue differentiation, and bacterial suppression. To
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enhance the biological performance of porous titanium Figure 1. Overview of performance requirements preparation processes,
scaffolds, it is crucial to improve the physicochemical and modification methods for medical porous titanium implants. 2

Volume 3 Issue 1 (2024) 2 https://doi.org/10.36922/msam.2753