ZTA ceramic intervertebral fusion cage and preparation method and application thereof

Abstract

The application discloses a ZTA ceramic intervertebral fusion cage and a preparation method and application thereof. The ZTA ceramic intervertebral fusion cage is composed of a dense outer wall and a porous inner part, wherein the porous inner part has a gradient porous three-period minimal surface structure; the material of the ZTA ceramic intervertebral fusion cage is a calcium-magnesium silicate mineral / ZTA composite ceramic material, and the preparation process comprises the following steps: ceramic powder and photosensitive raw materials are prepared according to a design proportion, ceramic slurry is obtained by mixing, the ceramic slurry is added into a photocuring printing device, photocuring printing is carried out according to a ZTA ceramic intervertebral fusion cage model to obtain a ceramic green body, and the ZTA ceramic intervertebral fusion cage is obtained by performing degreasing and sintering on the ceramic green body. The gradient biomimetic structure intervertebral fusion cage provided by the application has the properties of matching the mechanical property of autologous bone, adjustable performance, good biocompatibility, good bone inductive performance and the like.

Description

Technical Field

[0001] This invention relates to a ZTA ceramic interbody fusion device, its preparation method and application, belonging to the field of load-bearing orthopedic implant preparation technology. Background Technology

[0002] The current prevalence of cervical spondylosis in my country ranges from 3.8% to 17.6%, and is increasing year by year. Among these, neck and shoulder pain has become the second most common type of pain, accounting for 28.39%. For this severe degenerative cervical disc disease accompanied by radiculopathy or myelopathy, anterior cervical discectomy and fusion (ACDF) is the preferred surgical treatment. This surgery aims to stabilize the decompression segment and promote bone growth through the implantation of an interbody fusion cage to achieve bone fusion. Therefore, from a biomechanical perspective, the interbody fusion cage used in ACDF should provide lasting stability for intervertebral bone integration, restore the normal physiological curvature of the vertebral body, and minimize the impact on the biomechanics of adjacent segments.

[0003] Cervical spine characteristics vary across races and regions, and current interbody fusion devices are generally mass-produced using molds, which do not fully conform to the individual cervical spine anatomy. This leads to frequent cases of interbody fusion device mismatch, and can even have adverse effects on the outcome of the fusion surgery. Furthermore, long-term follow-ups of ACDF (acute cervical disc fusion) surgeries have documented various clinical complications such as prosthesis displacement, heterotopic ossification, and subsidence due to mismatches in interbody fusion device design, size, and biomechanics. Against this backdrop, developing an artificial cervical disc fusion device that meets biomechanical requirements and cervical endplate anatomical characteristics is an urgent and important task.

[0004] Currently, interbody fusion cage materials include metallic, polymeric, and ceramic materials. However, the functional requirements of interbody fusion cages impose demands on the properties of these materials, such as biocompatibility, mechanical properties, and osteoinductive properties. Metallic materials, due to their mismatch in elastic modulus with human bone, can cause stress shielding and product collapse. Polymer scaffolds, on the other hand, lack sufficient mechanical properties to match those of human bone. Furthermore, increasing evidence suggests that polymer and metal wear debris has the potential to dissolve bone in intervertebral discs and other artificial joints, and specific cases of osteolysis associated with disc replacement surgery are now emerging. Bioceramic bone repair materials, after implantation, can form a hydroxyapatite-like layer on their surface that resembles bone tissue composition and chemically bonds with bone tissue, thereby inducing ectopic osteoogenesis. However, ceramic materials such as hydroxyapatite (HA) and tricalcium phosphate (β-TCP) have uncontrollable degradation rates and their mechanical properties differ somewhat from living bone; they are typically used for non-load-bearing bone and are not suitable as interbody fusion cage materials. ZTA ceramics, due to their excellent mechanical properties and biocompatibility, have become one of the most competitive materials for preparing orthopedic implants for load-bearing sites. To improve the osteogenic properties of ZTA, active materials such as bioglass are usually added; however, the softening temperature of bioglass is more than 600°C lower than the sintering temperature of ZTA ceramics, and complex reactions or crystallization occur during the sintering process, resulting in a significant reduction in the mechanical properties of the final ceramic implant. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a ZTA ceramic interbody fusion device. The interbody fusion device provided by this invention has advantages such as a human bone-like structure, high porosity, high strength, good bioactivity, and good osteoinductive properties, and its mechanical properties can be adjusted according to the patient's needs.

[0006] The second objective of this invention is to provide a method for preparing a ZTA ceramic interbody fusion device.

[0007] The third objective of this invention is to provide an application of the ZTA ceramic interbody fusion device.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a ZTA ceramic interbody fusion device, which consists of a dense outer wall and a porous interior, wherein the porous interior has a gradient porous three-period minimal curved surface structure; the material of the ZTA ceramic interbody fusion device is calcium magnesium silicate mineral / ZTA composite ceramic material.

[0010] The ZTA ceramic intervertebral fusion cage provided by this invention has a porous interior core structure resembling an artificial intervertebral disc, combined with a dense outer wall to form a complete biomimetic structure of the artificial intervertebral disc. The intervertebral fusion cage provided by this invention is made of calcium magnesium silicate mineral / ZTA composite ceramic material, wherein the ZrO2-toughened Al2O3 composite ceramic (ZTA) exhibits excellent wear resistance, compressive strength, and biocompatibility. The calcium magnesium silicate mineral bioceramic material can act as a bioactive additive to enhance the bioactivity of ZTA and promote osteogenic induction. Simultaneously, the melting point of the calcium magnesium silicate mineral is lower than the sintering temperature range of ZTA (1550-1650℃), therefore it can act as a crystal sintering aid to improve the sintering performance of ZTA, lower the sintering temperature, and increase the sintering density. The calcium magnesium silicate mineral / ZTA composite ceramic material enables the intervertebral fusion cage to meet good mechanical properties and biocompatibility while possessing good bioactivity to promote osteogenic formation.

[0011] In a preferred embodiment, the thickness of the dense outer wall of the ZTA ceramic interbody fusion device is 0.25–0.5 mm.

[0012] The inventors discovered that when the wall thickness is 0.25 to 0.5 mm, the overall structural stress distribution is the most uniform, and the ZTA ceramic interbody fusion device has the best performance. If the wall thickness is too large, the mechanical properties are too high and not within the range of human bone mechanical properties. If the wall thickness is too small, the mechanical properties are low and do not meet the mechanical properties of human bone.

[0013] The diameter and height of the ZTA ceramic interbody fusion device can be designed according to specific needs, such as a cylindrical structure with a diameter of 10mm and a height of 5mm.

[0014] In a preferred embodiment, the average porosity inside the porous structure is 20% to 80%.

[0015] For interbody fusion devices, although the elastic modulus and compressive strength of the gradient porous biomimetic structure gradually decrease with increasing total porosity, the mechanical properties can be controlled through gradient porosity design and regulation of the magnesium feldspar content. Therefore, the porosity of ZTA ceramic interbody fusion devices can reach 80%, meeting application requirements. Of course, if the porosity is too low, an ideal gradient distribution structure cannot be obtained; if the porosity is too high, the mechanical properties decrease, and during the forming process, the exposure area is small, release is difficult, and forming failure is easily caused.

[0016] In a further preferred embodiment, the porosity of the porous interior increases gradually from the central axis to the circumferential surface, wherein the porosity (P1) at the central axis is 30%-70%, the porosity (P2) at the circumferential surface is 50%-80%, and the average porosity is 50%-70%.

[0017] The inventors discovered that when the radial internal and external porosities converge, the mechanical properties of the gradient porous biomimetic structure also tend to resemble those of a homogeneous porous structure. However, natural bone is composed of low-porosity cortical bone and high-porosity cancellous bone, exhibiting a non-uniform gradient porous structure. Moreover, by varying the porosity of the homogeneous structure, multiple gradient porous structures are obtained, which exhibit better mechanical properties than the homogeneous porous structure. In particular, when the porosity P1 at the central axis of the radial gradient porous structure is controlled at 30%-70%, and the porosity P2 at the circumferential surface of the radial gradient porous structure is 50%-80%, and the porosity gradually increases from P1 to P2 from the inside out, while controlling the average porosity at 50%-70%, a biomimetic structure with a pore gradient distribution similar to that of natural bone can be obtained, simultaneously achieving mechanical and biological properties similar to those of natural bone.

[0018] In a preferred embodiment, the internal structure of the porous structure is obtained by first forming a plane from the basic functional equation of the D-type minimal surface, and then thickening the plane. The basic functional equation of the D-type minimal surface is:

[0019] F(x,y,z)=sin(x)*sin(y)*sin(z)+sin(x)*cos(y)*cos(z)+cos(x)*siny)*cos(z)+cos(x)*cos(y)*sin(z)+C(x,y), where C(x,y)=k(x 2 +y 2 )+b, k is -0.0381 to 0, b is 0.0238 to 0.7381.

[0020] The interbody fusion device provided by this invention can control the pore size by changing the values ​​of k and b in equation C(x,y). The inventors discovered that when k is -0.0381 to 0 and b is 0.0238 to 0.7381, the porosity inside the pores exhibits the aforementioned gradient porous structure, controlling the average porosity to 50% to 70%. Therefore, the values ​​of k and b need to be effectively controlled. When the values ​​of k and b are controlled within the above range, a biomimetic structure with a pore gradient distribution similar to natural bone can be obtained, while simultaneously achieving mechanical and biological properties similar to natural bone.

[0021] In a preferred embodiment, the mass fraction of calcium magnesium silicate mineral in the ZTA ceramic intervertebral fusion device is 2.5-30%, preferably 5-20%.

[0022] The inventors discovered that controlling the mass fraction of calcium magnesium silicate minerals within the above-mentioned range yields the best final results. If the amount added is too large, it will affect the stability of the slurry. At the same time, during sintering, due to the increase in the amount of high-temperature liquid phase of calcium magnesium silicate minerals, the liquid phase is fully sintered, which causes the Al2O3 grains to grow abnormally, resulting in many micropores and a decrease in the mechanical properties of the scaffold.

[0023] In a preferred embodiment, the calcium magnesium silicate mineral is selected from magnesium feldspar (Ca2MgSi2O7), diopside (CaMgSi2O6), siliceous calcium magnesium (Ca3MgSi2O8), and wollastonite (Ca... 2+ Mg 2+ At least one of (SiO3), preferably magnesium feldspar (Ca2MgSi2O7). The inventors discovered that magnesium feldspar ceramic (Ca2MgSi2O7) has a melting point 150℃-250℃ lower than the sintering temperature of ZTA ceramic, which can better serve as a crystal sintering aid to promote the densification of ZTA, and at the same time, as a bioactive factor, it can induce osteoblast differentiation and promote bone tissue repair.

[0024] This invention also provides a method for preparing a ZTA ceramic intervertebral fusion device. The method involves mixing ceramic powder and photosensitive raw materials according to a designed ratio to obtain a ceramic slurry. The ceramic slurry is then added to a photocurable printing device, and a ceramic blank is obtained by photocurable printing based on a ZTA ceramic intervertebral fusion device model. The ceramic blank is then degreased and sintered to obtain the ZTA ceramic intervertebral fusion device. The ceramic powder is composed of ZrO2 powder, Al2O3 powder, and calcium magnesium silicate minerals.

[0025] In a preferred embodiment, the particle size of the ZrO2 powder, Al2O3 powder, and calcium magnesium silicate minerals are all in the submicron range.

[0026] The inventors discovered that when ZrO2 powder, Al2O3 powder, and calcium magnesium silicate minerals all have submicron particle sizes, the resulting composite material exhibits the best performance. However, if the particle size is too small, agglomeration will occur, which is not conducive to dispersion in ceramic slurry.

[0027] In a preferred embodiment, the mass ratio of ZrO2 powder to Al2O3 powder in the ceramic powder is 1:3 to 6, preferably 1:3, and the mass fraction of calcium magnesium silicate mineral is 2.5% to 30%, preferably 5% to 20%.

[0028] In a preferred embodiment, the photosensitive raw material, by mass percentage, comprises the following components: Solsperse 41000 1-5%, Sago-8810 0.1-3%, Rad 2500 0.1-3%, TEGO foamex N 0.1-3%, polyethylene glycol (PEG200) 0.1-3%, 1-hydroxycyclohexylphenyl ketone (184) 20-40%, trimethylolpropane triacrylate (TMPTA) 20-40%, hexanediol diacrylate (HDDA) 10-50%, and 2-hydroxyethyl acrylate (HEA) 10-30%.

[0029] The ceramic slurry of this invention is a colloidal system composed of ceramic powder and photosensitive resin. Its rheological properties are mainly determined by the combined effects of interparticle interactions (van der Waals forces, electrostatic repulsion, and steric hindrance) and Brownian motion. The inventors discovered that Al2O3 and ZrO2 powders have a large number of hydrophilic hydroxyl groups on their surfaces. Without the addition of a dispersant, the free energy of the powder surface is too high, making the powder prone to agglomeration. Simultaneously, since the HDDA+TMPTA+HEA resin system is an oily molecule, its wettability to Al2O3 and ZrO2 powders is poor, further exacerbating the agglomeration phenomenon. Given that the UV-curable resin is an organic system, the powder surface is insufficient to generate a Zeta potential. Therefore, the main stabilization mechanism of the ceramic slurry is steric hindrance stabilization. Thus, this invention adds Solsperse 41000 as a dispersant to the ceramic slurry, changing the hydrophilicity of the submicron Al2O3 and ZrO2 powder surface to hydrophobicity, and utilizing the steric hindrance effect to obtain a stable ceramic slurry. Adding Sago-8810X as an anti-settling agent imparts good thixotropic properties to the slurry, allowing weak cross-linking to be restored between slurries after the shearing action is removed. The viscosity recovers with appropriate hysteresis, giving it good leveling and anti-sagging properties. Finally, the slurry returns to its original thixotropic state. With the synergy of the above components, a ceramic slurry with good dispersibility, good flowability, and high solids content can be obtained. At the same time, with the combination of photosensitive resins in this invention, 1-hydroxycyclohexylphenyl ketone (184) serves as a photoinitiator, and a high-precision and high-performance photocurable preform can be prepared under low-energy-density ultraviolet light irradiation.

[0030] In addition, to improve the quality of the printed preform, this invention also incorporates Rad2500 as a release agent, which forms an isolation film on the mold and platform surfaces, facilitating the separation of the printed model from the platform. TEGO foamex N is used as an antifoaming agent, which can spread rapidly on the foam surface and penetrate quickly, causing the foam to burst and release gas from the slurry, thus eliminating air bubbles. Polyethylene glycol (PEG 200) is used as a plasticizer. When the plasticizer is mixed with the resin, the small molecules of the plasticizer insert into the polymer molecular chains, weakening the attraction between the polymer molecular chains and increasing the distance between them. As a result, the possibility of polymer molecular chain movement is increased, the entanglement between polymer molecular chains is reduced, plasticity is increased, and the mechanical properties of the scaffold are enhanced.

[0031] In a preferred embodiment, the mixing is carried out under vacuum conditions, and the mixing process is as follows: first mixing at 800–1200 rpm for 30 s–2 min, then mixing at 1200–2000 rpm for 3–5 min, and finally mixing at 800–1200 rpm for 30 s–2 min. The inventors have found that the slurry obtained under the above conditions has optimal dispersibility.

[0032] In this invention, a high-solids content (50-55 vol%) ceramic slurry is prepared using a vacuum high-speed stirring process.

[0033] In a preferred embodiment, the solid content in the ceramic slurry is 50-55 vol%. In this invention, the solid content of the ceramic slurry refers to the total volume percentage of ceramic powder in the ceramic slurry.

[0034] In a preferred embodiment, the process of obtaining the ZTA ceramic interbody fusion cage model is as follows: first, a planar model is formed using the basic function equations of a D-shaped minimal surface; then, the planar model is thickened to obtain a porous interior; and finally, a dense outer wall is formed on the porous interior surface to obtain the ZTA ceramic interbody fusion cage model. The basic function equations are...

[0035] F(x,y,z)=sin(x)*sin(y)*sin(z)+sin(x)*cos(y)*cos(z)+cos(x)*sin(y)*cos(z)+cos(x)*cos(y)*sin(z)+C(x,y), where C(x,y)=k(x 2 +y 2 )+b, k is -0.0381 to 0, b is 0.0238 to 0.7381.

[0036] In a preferred embodiment, the parameters for the photopolymerization printing are: exposure energy density of 0.125–0.711 J / cm². 2 The slice thickness is 30–60 μm.

[0037] In this invention, precisely controlling the process parameters within the aforementioned range ensures the controllable acquisition of high-precision ceramic blanks with consistent pore sizes as designed in the model. It can be observed that the process window of this invention is relatively small. This is because the inventors discovered that the scattering of ultraviolet light by powder particles in the ceramic slurry significantly reduces the forming accuracy of the pore size, leading to a significant deviation of the processed pore structure from the model design. When the exposure energy is too high, the pore size is smaller than the design value, even causing pore blockage; when the exposure energy is too low, the interlayer bonding strength is low, even leading to lamination manufacturing failure. This invention utilizes single-layer curing thickness experiments to establish the relationship between photocuring forming parameters (surface exposure energy density) and curing thickness, determining forming parameters that are 1.5 to 2 times thicker than the layer thickness, and initially determining the process window. Based on this, using precision model testing experiments, the relationship between surface exposure energy density, exposure time, layer thickness, and additional scattering width is established. The minimum energy density parameter that can process a precision model is selected as the optimal process parameter, resulting in a precision model with minimal manufacturing error and the highest precision.

[0038] In a preferred embodiment, the degreasing is carried out in a vacuum environment, the degreasing temperature is 400-600℃, and the degreasing time is 2500-3000 min.

[0039] In a preferred embodiment, the sintering temperature is 100-300°C lower than the ZTA sintering temperature, the sintering temperature is 0-200°C lower than the melting point of calcium magnesium silicate minerals, and the sintering time is 1-3 hours.

[0040] The inventors made an unexpected discovery: by adding calcium magnesium silicate minerals and controlling the sintering temperature to be 0–200°C below the melting point of the calcium magnesium silicate minerals (100–300°C below the ZTA sintering temperature), the calcium magnesium silicate minerals could act as a crystal sintering aid, thus promoting the densification of ZTA ceramics at this temperature. Of course, by controlling the temperature within this range, the calcium magnesium silicate minerals do not melt and can act as bioactive factors that induce osteoblast differentiation, promote bone tissue repair, and enhance the bioactivity of ZTA ceramics.

[0041] Therefore, the temperature of this invention also needs to be effectively controlled. If the temperature is too low, it cannot be sintered and densified; if the temperature is too high, it will reduce the bone-inducing properties of ZTA ceramics.

[0042] Further preferred, the sintering temperature is 1300–1400℃, and the sintering time is 1–3 hours. The inventors discovered that when the added calcium magnesium silicate mineral is Ca2MgSi2O7 (melting point 1400℃), which is 150–250℃ lower than the ZTA sintering temperature, the ZTA ceramic exhibits the highest degree of densification and the best biological activity when the sintering temperature is 0–150℃ lower than the melting point of Ca2MgSi2O7.

[0043] In a further preferred embodiment, the sintering process is as follows: first, the temperature is raised to 400-500°C at a heating rate of 0.5-1°C / min and held for 2-6 hours; then, the temperature is raised to 1300-1400°C at a heating rate of 5-10°C / min and held for 1-3 hours, followed by furnace cooling to room temperature.

[0044] The present invention also provides an application of the ZTA ceramic intervertebral fusion device, which is used as a biomimetic implant for artificial intervertebral discs.

[0045] Principles and advantages

[0046] ① Structural design of interbody fusion device

[0047] This invention designs a biomimetic interbody fusion device with high porosity, high permeability, and good mechanical properties by controlling the structural parameters of a D-shaped minimal curved surface. The model utilizes the controlled structural parameters to adjust porosity, allowing for the design and fabrication of an interbody fusion device with regulated mechanical properties. The high porosity provides pathways for bone and blood vessel growth.

[0048] ② Selection of support materials

[0049] The intervertebral fusion cage provided by this invention is made of calcium magnesium silicate mineral / ZTA composite ceramic material. In existing technologies, intervertebral fusion cages used in disc replacement surgery are made of titanium alloy. The difference in elastic modulus between titanium and the vertebral body can easily cause stress shielding, resulting in a failure of the intervertebral fusion cage to bond tightly with the vertebral body. Furthermore, titanium alloys do not possess osteogenic induction properties, and the abrasive particles generated by wear can cause inflammation at the lesion site. In addition, while bioceramic materials are currently the mainstream bone repair materials, common materials such as HA and β-TCP are only suitable for non-load-bearing bones in the human body and have low mechanical strength, which greatly limits the application range of the stent. The ZrO2-toughened Al2O3 composite ceramic (ZTA) used in this stent is a highly promising bioceramic material for orthopedic implants in load-bearing areas. This ZTA bioceramic exhibits excellent mechanical properties and bioactivity, with a relative density, Vickers hardness, and fracture toughness as high as 99.09%, 16.66 GPa, and 6.88 MPa·m, respectively. 1 / 2 Furthermore, bone marrow mesenchymal stem cells exhibit strong adhesion and proliferation capabilities on the ZTA ceramic surface, making it well-suited for various bone repair applications. Calcium magnesium silicate minerals, with melting points 150℃~250℃ lower than the ZTA ceramic sintering temperature, act as crystal sintering aids to promote ZTA densification. Simultaneously, as bioactive factors, they can induce osteoblast differentiation, promote bone tissue repair, and allow for the regulation of mechanical properties through the control of calcium magnesium silicate mineral content.

[0050] ③ Selection of preparation method

[0051] Common methods for fabricating interbody fusion cages include casting or injection molding, which cannot achieve personalized customization. 3D printing technology, however, can fabricate any complex structure, making it suitable for disc replacement surgery. However, high-melting-point bioceramics are prone to cracking under rapid cooling / heating conditions, making them unsuitable for processing using laser selective melting techniques commonly used for titanium alloys. This project innovatively employs photopolymerization 3D printing technology based on ceramic slurry to form a gradient structure interbody fusion cage, which is then sintered at high temperatures to obtain a personalized biomimetic interbody fusion cage.

[0052] Through the synergistic effect of the aforementioned structure, materials, and processes, the interbody fusion device provided by this invention has a dense outer layer of 0.25-0.5 mm, an inner layer with gradient porosity of 50%-70% average porosity, a pore gradient interpolation of 20-50%, a compressive strength of 134.31-197.54 MPa, and an elastic modulus of 5.407-6.842 GPa, meeting the requirements of human bone biomechanics (elastic modulus of 5.4-15.6 GPa, compressive strength of 130-163 MPa). Attached Figure Description

[0053] Figure 1 By controlling the values ​​of k and b, structural models of porous structures with different porosities can be obtained.

[0054] Figure 2 Schematic diagram of preparation method

[0055] Figure 3 Physical images of structures with different porosities

[0056] Figure 4 Gradient multi-porous interbody fusion device Detailed Implementation

[0057] The printing equipment used in the following examples is the CeraBuilder 60S industrial-grade high-performance ceramic 3D printer from Wuhan Intal Laser Technology Co., Ltd.

[0058] Example 1

[0059] Design of the interbody fusion cage model:

[0060] First, a planar model is formed using the fundamental functional equations of the D-type minimal surface. Then, the planar model is thickened, and a dense outer layer is added to form a gradient porous structure with a diameter of 10 mm and a height of 5 mm. The fundamental functional equations are as follows:

[0061] F(x,y,z)=sin(ax)*sin(ay)*sin(az)+sin(ax)*cos(ay)*cos(az)+cos(ax)*sin(ay)*cos(a

[0062] z)+cos(ax)*cos(ay)*sin(az)+C(x,y), where C(x,y)=k(x 2 +y 2 )+b, where k=-0.01896,

[0063] A gradient porous structure model with b = 0.238, a porosity of 40% at the central axis (P1) of the radial gradient porous structure, a porosity of 60% at the circumferential surface (P2), an average porosity of 50%, and a wall thickness of 0.5 mm.

[0064] Composition of ceramic slurry:

[0065] The photosensitizing raw materials were prepared as follows (by weight percentage): Solsperse 41000 10.24%, Sago-8810 1.46%, Rad 2550 1.46%, TEGO foamex N 1.46%, polyethylene glycol (PEG 200) 4.14%, trimethylolpropane triacrylate (TMPTA) 24.86%, hexanediol diacrylate (HDDA) 33.15%, 2-hydroxyethyl acrylate (HEA) 20.72%, and 1-hydroxycyclohexylphenyl ketone (184) 2.49%.

[0066] 100g of ceramic powder, the mass ratio of ZrO2 powder to Al2O3 powder is 1:3, and the mass fraction of Ca2MgSi2O7 powder in the ceramic powder is 5%.

[0067] The solid content of the ceramic slurry is 50 vol%.

[0068] Preparation of ceramic slurry:

[0069] Ceramic powder and photosensitive raw materials were prepared and mixed under vacuum conditions. The mixing process consisted of mixing at 800 rpm for 30 seconds, then at 1800 rpm for 3 minutes, and finally at 800 rpm for 30 seconds, resulting in a ceramic slurry with a solid content of 45 vol%. The ceramic slurry was then poured into a material tank. After the model was imported into the printer, it was processed at 0.286 J / cm². 2 Photopolymerization was performed under conditions of exposure power density and 50μm slice thickness.

[0070] The material was placed in a vacuum muffle furnace for degreasing, and the temperature was gradually increased from 0℃ to 600℃. The sintering process involved raising the temperature to 200℃ at a rate of 1℃ / min, and then raising it to 1350℃ at a rate of 5℃ / min. The temperature was held for 1 hour, and then cooled to room temperature with the furnace to obtain the artificial intervertebral disc scaffold.

[0071] The scaffold had a porosity of 50%, and its compressive strength and elastic modulus were 171.43 MPa and 4.39 GPa, respectively. CCK8 results indicated that the ceramic had good cell compatibility, and RT-PCR experiments showed that it had better gene expression.

[0072] Example 2

[0073] Design of the interbody fusion cage model:

[0074] First, a planar model is formed using the basic functional equations of the D-type minimal surface. Then, the plane is thickened, and a dense layer is added to the outer wall to obtain the artificial intervertebral disc stent model. The basic functional equations are F(x,y,z)=sin(ax)*sin(ay)*sin(az)+sin(ax)*cos(ay)*cos(az)+cos(ax)*sin(ay)*cos(az)+cos(ax)*cos(ay)*sin(az)+C(x,y), where C(x,y)=k(x 2 +y 2 The model of a gradient porous structure with a radial gradient porous structure has a porosity of 50% at the central axis (P1) and 70% at the circumferential surface (P2), an average porosity of 60%, and a wall thickness of 0.25mm.

[0075] Composition of ceramic slurry:

[0076] The photosensitizing raw materials were prepared according to the following percentages by mass: Solsperse 41000 10.24%, Sago-8810 1.46%, Rad 2550 1.46%, TEGO foamex N 1.46%, polyethylene glycol (PEG 200) 4.14%, trimethylolpropane triacrylate (TMPTA) 24.86%, hexanediol diacrylate (HDDA) 33.15%, 2-hydroxyethyl acrylate (HEA) 20.72%, and 1-hydroxycyclohexylphenyl ketone (184) 2.49%.

[0077] 100g of ceramic powder, the mass ratio of ZrO2 powder to Al2O3 powder is 1:3, and the mass fraction of Ca2MgSi2O7 powder in the ceramic powder is 10%.

[0078] The solid content of the ceramic slurry is 50 vol%.

[0079] Preparation of ceramic slurry:

[0080] Ceramic powder and photosensitive raw materials were prepared and mixed under vacuum conditions. The mixing process consisted of mixing at 800 rpm for 30 seconds, then at 1800 rpm for 3 minutes, and finally at 800 rpm for 30 seconds, resulting in a ceramic slurry with a solid content of 45 vol%. The ceramic slurry was then poured into a material tank. After the model was imported into the printer, it was processed at 0.286 J / cm². 2 Photopolymerization was performed under conditions of exposure power density and 50μm slice thickness.

[0081] The material was placed in a vacuum muffle furnace for degreasing, and the temperature was gradually increased from 0℃ to 600℃. The sintering process involved raising the temperature to 200℃ at a rate of 1℃ / min, and then raising it to 1400℃ at a rate of 5℃ / min. The temperature was held for 1 hour, and then cooled to room temperature with the furnace to obtain the artificial intervertebral disc scaffold.

[0082] The scaffold had a porosity of 60%, and its compressive strength and elastic modulus were 140.57 MPa and 4.5 GPa, respectively. CCK8 results indicated that the ceramic had good cell compatibility, and RT-PCR experiments showed that it had better gene expression.

[0083] Example 3

[0084] Design of an artificial intervertebral disc support model:

[0085] First, a planar model is formed using the basic functional equations of the D-type minimal surface. Then, the plane is thickened, and a dense layer is added to the outer wall to obtain the artificial intervertebral disc stent model. The basic functional equations are F(x,y,z)=sin(ax)*sin(ay)*sin(az)+sin(ax)*cos(ay)*cos(az)+cos(ax)*sin(ay)*cos(az)+cos(ax)*cos(ay)*sin(az)+C(x,y), where C(x,y)=k(x 2 +y 2 )+b, where k=-0.01912, b=0.74, the porosity (P1) at the central axis of the radial gradient porous structure is 60%, the porosity (P2) at the circumferential surface is 80%, the average porosity is 70%, and the wall thickness is 0.5mm.

[0086] Composition of ceramic slurry:

[0087] The photosensitizing raw materials were prepared as follows (by weight percentage): Solsperse 41000 10.24%, Sago-8810 1.46%, Rad 2550 1.46%, TEGO foamex N 1.46%, polyethylene glycol (PEG 200) 4.14%, trimethylolpropane triacrylate (TMPTA) 24.86%, hexanediol diacrylate (HDDA) 33.15%, 2-hydroxyethyl acrylate (HEA) 20.72%, and 1-hydroxycyclohexylphenyl ketone (184) 2.49%.

[0088] 100g of ceramic powder, with a ZrO2 powder to Al2O3 powder mass ratio of 1:3, and Ca2MgSi2O7 powder in the ceramic powder mass fraction of 20%.

[0089] The solid content of the ceramic slurry is 50 vol%.

[0090] Preparation of ceramic slurry:

[0091] Ceramic powder and photosensitive raw materials were prepared and mixed under vacuum conditions. The mixing process consisted of mixing at 800 rpm for 30 seconds, then at 1800 rpm for 3 minutes, and finally at 800 rpm for 30 seconds, resulting in a ceramic slurry with a solid content of 45 vol%. The ceramic slurry was then poured into a material tank. After the model was imported into the printer, it was processed at 0.286 J / cm². 2 Photopolymerization was performed under conditions of exposure power density and 50μm slice thickness.

[0092] The material was placed in a vacuum muffle furnace for degreasing, and the temperature was gradually increased from 0℃ to 600℃. The sintering process involved raising the temperature to 200℃ at a rate of 1℃ / min, and then raising it to 1400℃ at a rate of 5℃ / min. The temperature was held for 1 hour, and then cooled to room temperature with the furnace to obtain the artificial intervertebral disc scaffold.

[0093] The scaffold had a porosity of 70%, and its compressive strength and elastic modulus were 135.33 MPa and 3.54 GPa, respectively. CCK8 results indicated that the ceramic had good cell compatibility, and RT-PCR experiments showed that it had a significant effect on bone formation.

[0094] Comparative Example 1:

[0095] Other conditions were the same as in Example 1, except that the value of k in the basic function equation was set to -0.0571 and the value of b was set to 0.7381, resulting in a homogeneous structural model with a porosity of 20% at the central axis and 80% at the circumferential surface of the radial gradient pore structure. The average porosity remained at 50%. The resulting ZTA ceramic interbody fusion device achieved a compressive strength of 218.23 MPa, which is significantly different from the mechanical properties of human bone.

[0096] Comparative Example 2

[0097] Other conditions were the same as in Example 1, except that the wall thickness was 0.75 mm. The resulting ZTA ceramic interbody fusion device had a compressive strength of 248.67 MPa, which is significantly different from the mechanical properties of human bone.

[0098] Comparative Example 3

[0099] All other conditions were the same as in Example 1, except that the exposure energy density was set to 0.891 J / cm². 2 This leads to excessive internal stress in the ceramic during the printing process, causing cracks in the model during degreasing and sintering.

[0100] Comparative Example 4

[0101] Other conditions were the same as in Example 1, except that the sintering temperature was set to 1500℃. The resulting ZTA ceramic intervertebral fusion device showed poor bone induction performance in the RT-PCR experiment.

[0102] Comparative Example 5

[0103] The other conditions were the same as in Example 1, except that the mass fraction of Ca2MgSiO7 in the ceramic powder was 1.25%. The resulting ZTA ceramic intervertebral fusion device showed poor bone induction performance in the RT-PCR experiment.

Claims

1. A method for preparing a ZTA ceramic interbody fusion device, characterized in that: Ceramic powder and photosensitive raw materials are mixed according to the design ratio to obtain a ceramic slurry. The ceramic slurry is added to a photocuring printing device, and a ceramic blank is obtained by photocuring printing according to the ZTA ceramic intervertebral fusion device model. The ceramic blank is degreased and sintered to obtain the ZTA ceramic intervertebral fusion device. The ceramic powder is composed of ZrO2 powder, Al2O3 powder, and calcium magnesium silicate minerals. The sintering temperature is 100-300℃ lower than the ZTA sintering temperature and lower than the melting point of calcium magnesium silicate minerals. The difference between the sintering temperature and the melting point of calcium magnesium silicate minerals is <200℃. The sintering time is 1-3 hours. The ZTA ceramic interbody fusion device consists of a dense outer wall and a porous interior, wherein the porous interior has a gradient porous three-period minimal curved surface structure; the material of the ZTA ceramic interbody fusion device is calcium magnesium silicate mineral / ZTA composite ceramic material; Within the porous structure, the porosity gradually increases from the central axis to the circumferential surface, with the porosity at the central axis being 30%-70%, the porosity at the circumferential surface being 50%-80%, and the average porosity being 50%~70%. The internal structure of the porous structure is obtained by first forming a plane from the basic functional equation of the D-type minimal surface, and then thickening this plane. The basic functional equation of the D-type minimal surface is: ； The mass fraction of the calcium magnesium silicate mineral is 2.5% to 30%; The calcium magnesium silicate mineral is selected from magnesium yellow feldspar.

2. The method for preparing a ZTA ceramic interbody fusion device according to claim 1, characterized in that: The particle sizes of the ZrO2 powder, Al2O3 powder, and calcium magnesium silicate minerals are all in the submicron range; In the ceramic powder, the mass ratio of ZrO2 powder to Al2O3 powder is 1:3~6.

3. The method for preparing a ZTA ceramic interbody fusion device according to claim 1, characterized in that: The mixing is carried out under vacuum conditions. The mixing process is as follows: first, mix at 800~1200 rpm for 30s~2min, then mix at 1200~2000 rpm for 3~5min, and finally mix at 800~1200 rpm for 30s~2min. The solid content in the ceramic slurry is 50-55 vol.

4. The method for preparing a ZTA ceramic interbody fusion device according to claim 1, characterized in that: The process of obtaining the ZTA ceramic interbody fusion device model is as follows: first, a planar model is formed by the basic function equation of the D-shaped minimal surface; then, the planar model is thickened to obtain a porous interior; and then a dense outer wall is set on the surface of the porous interior to obtain the ZTA ceramic interbody fusion device model.

5. The method for preparing a ZTA ceramic interbody fusion device according to claim 1, characterized in that: The parameters for the photopolymerization printing are: exposure energy density of 0.125~0.711 J / cm³. 2 The slice thickness is 30~60μm; The degreasing is carried out in a vacuum environment at a temperature of 400-600℃ for a time of 2500-3000 minutes.

6. The method for preparing a ZTA ceramic interbody fusion device according to claim 1, characterized in that: The thickness of the dense outer wall of the ZTA ceramic interbody fusion device is 0.25~0.5 mm.

Images