Preparation method and medical application of porous tantalum with extremely small curved surface structure

Abstract

The invention relates to a preparation method and medical application of a porous tantalum material based on an extremely small curved surface structure. The porous tantalum material is particularly applied to medical implants such as an interbody fusion cage, an artificial vertebral body, a hip joint acetabular cup, a joint filling block and a dental implant. The material is pure tantalum or tantalum-containing alloy (such as tantalum-titanium, tantalum-niobium, tantalum-zirconium, tantalum-titanium-niobium-zirconium, and the tantalum content is greater than 1%), the material is constructed by adopting an additive manufacturing technology, the porosity is 30-90%, compared with a truss pore channel structure (such as a rhombic dodecahedron), no obvious stress concentration point exists, the strength, the modulus, the anti-fatigue performance and the like are remarkably improved, and the application prospect is wide. The method is particularly suitable for structural and functional reconstruction of large-area and load-bearing bone defects.

Description

Technical Field

[0001] The present invention relates to the field of biomedical materials, and more particularly, to a method for preparing a porous tantalum with a minimal surface structure and its medical applications. Background Art

[0002] With the development of the orthopedic and dental medical fields, the demand for biomedical implants is increasing day by day, especially implants for bone defect repair, such as intervertebral fusion cages, artificial vertebral bodies, acetabular cups, joint filling blocks, and dental implants. These implants need to have high strength, low modulus, good fatigue performance, and excellent biocompatibility simultaneously to adapt to the complex biomechanical environment and bone integration requirements. However, traditional implant materials and designs still face many challenges in practical applications.

[0003] Titanium and its alloys (such as Ti-6Al-4V, abbreviated as TC4) are currently one of the most commonly used medical implant materials because of their good mechanical properties, corrosion resistance, and biocompatibility. However, due to the relatively high modulus of titanium alloys (about 110 GPa), which is much higher than that of human bone, the "stress shielding effect" occurs between the implant and bone tissue. This effect will inhibit bone growth and ultimately lead to the failure of the implant. In addition, traditional titanium alloy implants may undergo fatigue failure under long-term loading and are difficult to meet the requirements of bone repair in high-load parts.

[0004] To solve the stress shielding problem, porous metal materials have been widely studied in recent years. The porous structure can not only adjust the modulus of the material to match that of human bone but also provide a scaffold for the adhesion, proliferation, and vascularization of bone cells through the pores. However, although the common regular porous structures currently have a certain balance between porosity and strength, their mechanical properties are limited, especially prone to local stress concentration and fatigue failure problems under high porosity conditions. In addition, these traditional porous structures also have certain limitations in terms of biomechanics and manufacturing complexity.

[0005] Tantalum has become one of the ideal candidate materials for orthopedic implants due to its excellent biocompatibility and corrosion resistance, and its natural oxide film on the surface helps to promote the adhesion and bone ingrowth of bone cells. However, traditional tantalum materials usually exist in a solid form, with a relatively large density (about 16.6 g / cm³), which limits its application in lightweight medical implants. In addition, the manufacturing process of traditional tantalum implants is complex and costly, especially facing great technical difficulties in preparing complex porous structures.

[0006] The present invention successfully solves the above problems by introducing the TPMS-Gyroid structure design and combining with the laser melting additive manufacturing technology. The prepared porous tantalum material not only has excellent strength, modulus and fatigue resistance, but also can significantly improve biocompatibility and bone ingrowth performance, providing a new solution for orthopedic and dental implants. Summary of the Invention

[0007] The present invention relates to a porous tantalum material based on the Triply Periodic Minimal Surface (TPMS) structure, its preparation method and application in the medical field. The material is made of tantalum or tantalum alloy, wherein the content of tantalum is greater than 1%, and the tantalum alloy may include but is not limited to tantalum-titanium (Ta-Ti), tantalum-niobium (Ta-Nb), tantalum-zirconium (Ta-Zr) and tantalum-titanium-niobium-zirconium (Ta-Ti-Nb-Zr). By optimizing the material composition and structure design, the present invention realizes high strength, high toughness, high fatigue performance and excellent biocompatibility of the material.

[0008] The present invention adopts the TPMS-Gyroid structure, which belongs to the periodic three-dimensional minimal surface, has isotropic mechanical properties, high porosity and good biocompatibility. The TPMS-Gyroid structure is realized by digital design and powder bed additive manufacturing technology to meet the requirements of different medical implants.

[0009] The wall thickness of the TPMS-Gyroid porous structure is 0.1-10 mm, and the pore diameter is 0.2-20 mm.

[0010] The porosity of the TPMS-Gyroid porous structure design is highly controllable. In the medical application range involved in the present invention, the porosity is 30-90%.

[0011] The medical applications are designed for orthopedics and dentistry, specifically including intervertebral fusion cages, artificial vertebral bodies, acetabular cups, joint filling blocks and dental implants, etc.

[0012] The medical application design can be composed of a fully porous structure or a partially porous structure, and can be combined with functional dense structures with different designs according to actual needs to meet different load-bearing and functional requirements.

[0013] The technical advantages of the present invention are reflected in that: compared with the traditional regular pore structure (such as the rhombic dodecahedron structure), the TPMS-Gyroid structure shows significant advantages in mechanical properties, stress distribution and biological properties. Experimental data shows that the bending strength of this structure exceeds 50 MPa, which is 68% higher than that of the rhombic dodecahedron porous structure with the same porosity; the tensile yield strength exceeds 30 MPa, which is 69% higher than that of the rhombic dodecahedron structure with the same porosity; the compressive yield strength exceeds 30 MPa, which is 35% higher than that of the rhombic dodecahedron structure with the same porosity. In terms of fatigue performance, the fatigue limit load of the TPMS-Gyroid structure specimen with 70% porosity is 5238 N, which is twice as high as 2604 N of the rhombic dodecahedron porous structure with the same porosity, showing excellent fatigue performance. The TPMS-Gyroid structure shows obvious plastic deformation characteristics in static mechanical tests, with excellent toughness, effectively avoiding the risks of stress concentration and brittle fracture. In addition, the elastic modulus of the TPMS-Gyroid porous structure is 3-11 GPa, which is between cancellous bone and cortical bone, and can effectively avoid the stress shielding effect.

[0014] Due to the continuous and smooth surface characteristics of the TPMS (periodic minimal surface) porous structure, it can not only provide excellent mechanical properties, but also effectively improve the specific strength and achieve lightweight. Research shows that the TPMS structure with 80% porosity has a specific strength close to that of the dodecahedron structure with 70% porosity while maintaining sufficient mechanical strength, indicating that the TPMS structure still has good load-bearing capacity and stability under high porosity conditions. This design helps to reduce the weight of the implant, while providing a suitable bone ingrowth environment and improving the biocompatibility and clinical applicability of the implant.

[0015] The changes in the microcrystalline structure of the TPMS-Gyroid and rhombic dodecahedron porous tantalum scaffolds before and after static compression were analyzed. The inverse pole figure (IPF) was used to characterize the grain orientation distribution, and the geometrically necessary dislocation (GND) density was evaluated by the kernel average misorientation (KAM). As shown in Figure 8, the grain color gradient of the tantalum scaffold increases after compression, indicating an increase in the orientation difference within the grains and an intensification of plastic deformation. The average KAM value of the TPMS-Gyroid porous tantalum increases from 0.4° to 1°, and that of the rhombic dodecahedron porous tantalum increases from 0.7° to 1.2°. The higher KAM value reflects an enhanced dislocation accumulation. In addition, the KAM value in the deformed and fractured regions increases significantly, indicating a higher dislocation density than in the unaffected regions. The grain boundary map shows that the number of low-angle grain boundaries (2°-15°, green solid line) increases after compression, further confirming that the material has undergone significant plastic deformation.

[0016] The medical application not only needs to withstand complex mechanical loads, but also needs to form good integration with human bone tissue. Through the TPMS-Gyroid structure design, the present invention effectively improves the stress distribution of the material, and enhances the load-bearing capacity and long-term stability. Finite element simulation analysis shows that, compared with the rhombic dodecahedron structure, the stress of the TPMS-Gyroid structure is evenly distributed on the pore walls of each layer, while the stress of the rhombic dodecahedron structure is concentrated at the connection of the pore ribs. The stress distribution of the TPMS-Gyroid structure is more uniform, the maximum stress is reduced by about 20%-30%, the deformation is smaller, and the structural reliability is higher.

[0017] The preparation method of the present invention is based on powder bed additive manufacturing technology, and mainly includes the following steps: First, design a three-dimensional model according to the TPMS-Gyroid structure, and use tantalum or tantalum alloy powder materials to form by additive manufacturing technology. Optimize parameters such as input power, scanning speed, and powder spreading thickness to ensure the forming quality; Second, perform the removal treatment of the support structure, and wire cutting technology can be used; Finally, remove the residual powder by ultrasonic cleaning and gas medium spraying, and perform annealing treatment in a vacuum environment to eliminate internal stress, improve the toughness and fatigue performance of the material.

[0018] The powder bed additive manufacturing technology is powder bed laser melting additive manufacturing technology or powder bed electron beam melting additive manufacturing technology.

[0019] The particle size of the tantalum or tantalum alloy powder is 10~100μm, and further preferably 15~53μm.

[0020] The tantalum alloy is pre-alloyed powder or mixed powder composed of corresponding pure metal powders in a certain proportion. Description of the Drawings

[0021] Figure 1 Schematic diagram and physical photo of the minimal surface structure porous tantalum three-dimensional structure of the present invention Figure 2 SEM micrograph of the minimal surface porous tantalum specimen of the present invention Figure 3 Summary of the static mechanical properties of the minimal surface porous tantalum specimen of the present invention Figure 4 Comparison of the static mechanical properties between the minimal surface porous tantalum specimen and the rhombic dodecahedron porous structure specimen of the present invention Figure 5 Comparison of the dynamic mechanical properties between the minimal surface porous tantalum specimen and the rhombic dodecahedron porous structure specimen of the present invention Figure 6 Photos of the minimal surface porous tantalum specimen after compression deformation corresponding to different strains of the present invention Figure 7Finite element simulation stress distribution diagrams of the minimal surface porous tantalum specimen and the rhombic dodecahedron porous structure specimen of the present invention Figure 8 EBSD grain analysis diagrams of the plastic deformation fracture failure regions of the minimal surface porous tantalum specimen and the rhombic dodecahedron porous structure specimen of the present invention Figure 9 Schematic diagram of the minimal surface porous tantalum acetabular cup structure in Example 1 Figure 10 Schematic diagram of the minimal surface porous tantalum lumbar interbody fusion cage structure in Example 2 Figure 11 Schematic diagram of the minimal surface porous tantalum cervical interbody fusion cage structure in Example 3 Figure 12 Schematic diagram of the minimal surface porous tantalum artificial vertebral body structure in Example 4 Figure 13 Schematic diagram of the minimal surface porous tantalum dental implant structure in Example 5

[0022] Example 1 Example 1 is a minimal surface porous tantalum hip acetabular cup. The main body adopts a TPMS-Gyroid minimal surface porous structure with a porosity of 75% and a porous structure wall thickness of 0.3 mm, which optimizes the mechanical properties of the material, avoids stress concentration problems, and at the same time maintains high strength and low stiffness, contributing to good fusion between bone tissue and the implant. The material is pure tantalum, which has excellent biocompatibility and chemical stability, can effectively avoid the release of metal ions, and reduce immune reactions. Seven evenly distributed screw holes are provided on the surface of the acetabular cup. The aperture and position are optimized, and the wall thickness of the screw holes is 1 mm, adopting a dense tantalum structure to ensure the stable fixation of the implant. A dense structure is designed on the inner side of the cup mouth, and ten circular card slots are evenly distributed for snap-fit cooperation with the liner. The TPMS-Gyroid minimal surface texture design on the outer surface not only increases the friction with bone tissue, improves the initial stability, but also provides space for the ingrowth of bone tissue, promoting bone healing. This design provides excellent mechanical properties, stability and biocompatibility, meeting the requirements of hip replacement surgery.

[0023] Example 2 Example 2 is a minimal surface porous tantalum lumbar interbody fusion device, which adopts a TPMS-Gyroid minimal surface porous structure main body with a porosity of 70% and a porous structure wall thickness of 0.3 mm. It optimizes the mechanical properties, reduces stress concentration, and enhances the fusion with bone tissue. It is prepared from pure tantalum powder by powder bed laser melting technology. The double bullet head shape design is convenient for implantation, can smoothly pass through the intervertebral space, and ensures less damage to the surrounding tissues during implantation. The endplate contact surface is designed in an arc shape, which matches the shape of the human endplate, can provide a better contact area and stability, and promotes bone fusion. The fusion device is provided with a through bone graft window, which is convenient for artificial bone grafting, helps to accelerate the bone fusion process, and improves the fusion efficiency. At the same time, the hole design on both sides of the fusion device enhances the integration of internal and external bone tissues, thereby improving the implantation stability. The endplate contact surface is also designed with anti-slip teeth, which work together with the concave-convex texture of the minimal surface to further improve the implantation stability of the fusion device and ensure that it can be stably maintained in the correct position for a long time after surgery.

[0024] Example 3 Example 3 is a minimal surface porous tantalum cervical interbody fusion device, which adopts an overall TPMS-Gyroid minimal surface porous structure with a porosity of 70% and a porous structure wall thickness of 0.25 mm. The material is tantalum-zirconium alloy with a tantalum content of 80%, and it is prepared from preformed alloy powder by powder bed laser melting additive manufacturing technology. The cervical interbody fusion device is designed as a wedge-shaped block, which can better meet the biomechanical requirements of the cervical vertebra. The anterior inclination angle of the endplate is designed to be 7°, which helps to match the natural curve of the cervical vertebra and improve the stability after implantation. The fusion device is provided with a through bone graft window, which is convenient for artificial bone grafting and accelerates the bone fusion process. The rear side is designed with an instrument hole, which is convenient for the operation and implantation of the fusion device during surgery. Like the lumbar interbody fusion device, the endplate contact surface of the cervical interbody fusion device is provided with anti-slip teeth to enhance the implantation stability and ensure that the fusion device maintains a stable position for a long time after implantation.

[0025] Example 4 Example 4 is a minimal surface porous tantalum artificial vertebral body, designed as a wedge-shaped block, with an overall TPMS-Gyroid minimal surface porous structure, a porosity of 65%, a porous structure wall thickness of 0.3 mm, a material of tantalum-titanium alloy, and a tantalum content of 60%. This artificial vertebral body is prepared by powder bed laser melting additive manufacturing technology using preformed alloy powder, ensuring high precision and stability. Since the artificial vertebral body is usually relatively large in size in the height direction (i.e., the main load-bearing direction), a dense strengthening structure is designed at its side edges to increase its mechanical reliability, improve the load-bearing capacity and reduce the risk of deformation. The fusion device is designed with a through-bone grafting window to facilitate artificial bone grafting, accelerate the bone fusion process, and enhance the fusion effect. An instrument hole is also designed on the rear side to facilitate the operation and fixation of the artificial vertebral body during the operation. Anti-slip teeth are provided on the end plate contact surface to enhance the contact with bone tissue, ensure the long-term stability of the artificial vertebral body after implantation, and prevent displacement after implantation. This design effectively improves the mechanical properties, stability and biocompatibility of the artificial vertebral body and is suitable for vertebral replacement surgery.

[0026] Example 5 Example 5 is a minimal surface porous tantalum dental implant, designed with a columnar shape, a material of tantalum-titanium alloy, and a tantalum content of 90%. This dental implant is prepared by powder bed laser melting additive manufacturing technology using preformed alloy powder. The implant consists of a dense functional area and a TPMS-Gyroid minimal surface porous structure. The porosity of the porous part is 60% and the wall thickness is 0.2 mm, which helps to promote the growth of bone tissue and provide stronger osseointegration. The porous structure is mainly located in the middle of the dental implant, optimizing the contact and fusion effect with the surrounding bone tissue. A self-tapping groove is provided in the dense area at the lower part to provide self-tapping property of the implant and facilitate implantation. An internal connection groove is provided in the upper dense area, which can be precisely matched with the dental restoration system to achieve a stable restoration installation. External threads are provided in both the upper and lower dense areas for initial fixation and long-term stability during implantation, ensuring the stability and reliability of the implant. This design effectively enhances the stability, osseointegration and long-term durability of the dental implant and is suitable for long-term dental restoration treatment.

Claims

1. A method for preparing porous tantalum with minimal surface structure and its medical application, characterized in that: The porous tantalum is prepared from pure tantalum or tantalum alloy by additive manufacturing technology, wherein the tantalum alloy is any one of tantalum titanium, tantalum niobium, tantalum zirconium, tantalum titanium niobium zirconium or a combination thereof.

2. A method for preparing porous tantalum with a minimal curved surface structure and its medical application, characterized in that: The porous tantalum is prepared from pure tantalum or tantalum alloy by additive manufacturing technology, wherein the tantalum alloy is any one of tantalum titanium, tantalum niobium, tantalum zirconium, tantalum titanium niobium zirconium or a combination thereof.

3. The method for preparing porous tantalum with minimal surface structure according to claim 1, characterized in that: The additive manufacturing technology is a powder bed laser melting molding technology or a powder bed electron beam melting molding technology.

4. The method for preparing porous tantalum with minimal surface structure according to claim 1, characterized in that: The minimal curved surface structure is a TPMS-Gyroid structure.

5. The method for preparing porous tantalum with minimal surface structure according to claim 1, characterized in that: The wall thickness of the minimal curved surface porous structure is 0.1-10 mm, the pore diameter is 0.2-20 mm, and the porosity is 30-90%.

6. The method for preparing porous tantalum with minimal surface structure according to claim 1, characterized in that: The minimal curved surface porous structure can be designed into a uniform structure or an isotropic gradient according to different application requirements.

7. The medical application of the porous tantalum with minimal curved surface structure according to claim 1, characterized in that: The porous tantalum is applied to medical implants, including but not limited to intervertebral fusion cages, artificial vertebral bodies, acetabular cups, joint filling blocks and dental implants.

8. The medical application of the porous tantalum with minimal curved surface structure according to claim 7, characterized in that: The medical implant is composed of a fully porous structure or a partially porous structure, wherein the porous structure mainly serves to fill bone defects, provide mechanical support, and provide space for tissue and blood vessel growth, and the dense structure serves to assist in mechanical support or as a functional structure.

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