Page 9 - MSAM-3-1

Materials Science in Additive Manufacturing Preparation and modification of porous Ti

are introduced (Section 3). Subsequently, the current specific surface area) will cause changes in permeability,
surface modification methods of medical porous titanium fluid shear force, cushioning energy absorption, and other
alloys are reviewed (Section 4), and finally, the future properties, thus affecting cell adhesion, migration, and
development direction is summarized (Section 5). tissue growth. In addition, pore characteristics also affect
23
the transport of nutrients, the exchange of oxygen, and the
2. Performance requirements and removal of metabolites within the cell tissue. Therefore,
24
influencing factors of porous titanium alloy the bionic porous design of porous titanium alloys is also
Compared with the external environment, the physical and one of the requirements.
chemical environments of various tissues and organs in the In addition to the internal structure, surface
human body are vastly different from each other and in a morphology and roughness have a significant effect on cell
complex and dynamic state. To ensure durable functionality, adhesion and bone mineralization. Studies have shown
16
human bones must be able to withstand pressure, tension, that the roughness range of 1 – 10 μm can promote the
and other load changes encountered in daily life. After being mineralization reaction and mineralization of bone tissue
implanted in the human body, more stable metal materials in the implant and improve protein adsorption, osteoblast
25
are also prone to corrosion, wear, fatigue fracture, and other adhesion, and the healing rate of the peripheral area
failures. Therefore, higher requirements are put forward for outside the implant. Therefore, it is important to explore
porous titanium alloys in clinical practice, and ideal titanium the suitable surface morphology to enhance the bonding of
implants should have mechanical properties, morphology, the implant with the tissue to improve the biocompatibility
structure, and physical and chemical properties similar to of porous implants.
those of the human body. 17
2.3. Factors affecting the properties of porous
2.1. Performance requirements of porous titanium titanium alloys
alloys
The composition and type of titanium alloy are the primary
Porous titanium alloys must fulfill the necessary functions factors affecting its performance. Pure titanium is the
or specific requirements in tissue engineering. In these earliest form of material used in making titanium alloy, but
standards, mechanical properties such as strength, elastic its modulus can reach as high as 110 GPa; TC4 is the second
modulus, and flexibility are the basic requirements most widely used material after pure titanium due to its
18
for maintaining structural function and durability. low cost, but it can precipitate Al/V elements in the human
Considering the influence of different parts and age factors, body for a long time, jeopardizing the human nervous
the strength of human bone ranges from 33 to 193 MPa, system. Therefore, β titanium alloys with lower modulus
26
and its modulus is between 0.3 and 30 GPa. To qualify as and less toxicity are gradually emerging, and β phases with
19
a medical metal material, its properties should fall within lower modulus are formed inside titanium alloys by adding
the above-mentioned ranges. biological elements such as Nb, Ta, and Zr. At present,
27
Biocompatibility is also an essential variable guaranteeing the modulus of TiNbTaZr, TiNbZr, and other materials has
the function of porous titanium. Porous titanium alloy’s been reduced to 50 GPa, with high strength and, low mode
20
28
biological properties are mainly reflected in two aspects: (i) characteristics and good biocompatibility. Developing
The material is non-toxic and will not cause local or systemic new materials can improve the performance of implants
immune reactions and (ii) it can promote intracellular protein from the source. Still, the development and application
expression and accelerate tissue recovery and growth. 21 of new materials are restricted by their high development
cost, long cycle, and minor performance adjustment range.
Wear and corrosion resistance play a decisive role
in the lifespan of joint implants. Low wear resistance Compared with the research and development of new
22
will produce extremely severe wear, causing loosening of materials, optimizing the preparation process and structural
the fit. In addition, metal particles generated by wear or design of existing materials is a more efficient pathway to
metal ions generated by corrosion will also lead to adverse material enhancement. Especially when coinciding with the
reactions in the cellular organization. Therefore, titanium rise of the additive manufacturing process, the mechanical
alloy materials must have excellent wear resistance. properties of materials can be significantly adjusted to our
favor, and an optimized structural design can help realize
2.2. Structural characteristics of porous titanium the precise regulation of porous titanium alloys. These
alloys procedures could constitute a systematic structural design
Human bones, teeth, and other tissues and organs are graded method. The strength, modulus, and other properties of
porous structures. Changes in pore characteristics (porosity, porous titanium can be directly adjusted by changing the

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