3D printing porous implants for bone defect treatment is a new breakthrough in the field of tissue engineering. Using 3D printing technology, precise micropore design can be performed on physical parameters such as pore size, porosity, pore shape and surface topography of the implant material. This advantage is difficult to compare with traditional bone implant scaffolds, so it can be produced Personalized implants with more ideal biocompatibility and mechanical properties can fully meet the needs of patients.
Why choose titanium alloy
Titanium and titanium alloys are a kind of metal materials that only gradually began to develop in the middle of the 20th century. It has the characteristics of low density, high specific strength, good corrosion resistance, and good biocompatibility. It is widely used in aerospace, petrochemical and medical and health fields.
The first stage
Regarding the application of titanium in medical implants, as early as 1940, scholars reported the inertia between titanium implants and mouse femurs. In 1951, some scholars further confirmed that pure titanium has better biocompatibility than other traditional implant materials. However, due to the high production cost of titanium alloys and the mature market of stainless steel in implants, the application and development of titanium alloys in the medical field has been relatively slow.
Second stage
Since the 1960s, pure titanium has been used in clinical oral research as a human implant. With the development of Ti-6Al-4V alloys with more excellent performance, titanium alloys have begun to be widely used in the medical implant market.
The problem we are facing
Although the elastic modulus of Ti-6Al-4V is only about 114GPa, which is lower than other biological materials such as stainless steel and cobalt-chromium alloy, it is still one higher than human cortical bone (15-25GPa) and cancellous bone (0.05-3GPa) Magnitude. Such a large difference will cause the so-called "stress shielding" effect to occur, which will cause bone resorption around the implant in the long term, and even cause the implant to slip off, reducing the success rate of bone implantation.
The "stress shielding" effect refers to the elastic modulus of the biological implant (>100GPa) and the elastic modulus of the receptor bone 。
At the same time, the Al, V and other elements contained in the composition have certain biological toxicity. Long-term use in the human body will cause tissue lesions around the implant and induce symptoms such as encephalopathy and anemia. It is not suitable for long-term use in the human body. .
Solution Biological toxicity
In recent years, for biological titanium alloys, researchers have developed Gum alloys containing Ti-Nb-Ta-Zr and TLM alloys containing Ti-Nb-Zr-Mo-Sn around the characteristics of non-toxicity and low elastic modulus. And Ti2448 alloy containing Ti-Nb-Zr-Sn, etc., these alloys all use Nb, Zr, Mo and other elements with good biocompatibility. Experimental results show that the biological performance of such titanium alloys such as bone promotion and sensitization are better than Ti-6Al-4V and Ti-6Al-7Nb used in traditional implants.
Stress shielding
Research data shows that the development of porous materials can effectively reduce the elastic modulus, provide physical space for bone ingrowth, and enhance bone fixation. For bone implant porous materials, some scholars have reported that the porosity should be controlled between 65% and 80%. For implant materials with excessive porosity, the porosity will significantly reduce the compressive strength and fatigue properties of the material, which can hardly meet the normal use requirements of the material; while the porous material below this value has higher density, Affect the bone tissue to grow into the material and reduce the bonding strength between the implant and the material.
Comparison of traditional method VS3D printing
In order to meet the design requirements of the porosity of the above-mentioned materials, the traditional preparation methods of porous titanium alloy materials mainly include: powder metallurgy method, slurry method and fiber sintering method.
However, the porous materials produced by such methods generally have small pore diameters, uneven pore distribution, low through-porosity, or a large number of micropores in the pore wall structure, which limits their further development in the field of biomaterials. In recent years, with the introduction of "3D printing" technology, due to its processing characteristics, the advantages of using 3D printing to make porous materials have become more apparent.
In the future, with the resolution of porous material porosity and pore size, elastic modulus, biological toxicity and other issues, as well as the integration and breakthrough of various disciplines including materials science, stem cell technology, etc., 3D printing titanium alloy substitutes will become a kind of personality The advanced and precise medical technology is widely used in orthopedics clinics to effectively solve the treatment problems of bone repair.
Raiming laser titanium alloy printing case
References:
"Tensile properties of 3D printed titanium alloy trabecular bone porous structure"
"Animal Experimental Study on the Effect of 3D Printing Porous Titanium Alloy Scaffold Pore Structure on Bone Ingrowth Effect"
"Research Progress of 3D Printing Medical Titanium Alloys"
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