Zirconia ceramic material for dental restoration and method for preparing the same

Abstract

The application discloses a kind of zirconia ceramic materials for dental restoration and preparation method thereof, it is related to dental restoration material technical field, including raw material processing system, forming system and sintering system, the raw material processing system includes ball mill, spray drying tower and cyclone separator, the forming system includes isostatic press and mould group, the sintering system includes atmosphere protection furnace and temperature control module, also includes S1, raw material weighing and mixing, S2, ball milling refinement, S3, spray drying granulation, S4, mould filling, S isostatic pressing forming and green body initial inspection, S6, pre-sintering and grain boundary control, S7, final sintering and densification strengthening, S8, precision machining and performance comprehensive evaluation.The application is prepared by S1-S8 steps, the effect that the spherical granulation powder with uniform composition, suitable granularity and good fluidity is prepared, the bending strength of zirconia ceramic material is improved simultaneously, and the light transmittance is improved, and the material color degree is closer to natural dentin by passing hydrogen sintering.

Description

Technical Field

[0001] This invention relates to the field of dental restorative materials technology, and in particular to a zirconia ceramic material for dental restoration and its preparation method. Background Technology

[0002] Dental restorative materials have evolved from metal alloys and resin composites to all-ceramic materials. Zirconia ceramics, due to their excellent mechanical properties (such as high flexural strength and fracture toughness) and good biocompatibility, have become the mainstream choice for dental restorations. In recent years, with the increasing aesthetic demands of patients, the research and development of transparent zirconia ceramics has become a hot topic. However, problems such as abnormal grain growth and phase transformation instability are prone to occur during its preparation, resulting in low yield and high cost. Furthermore, the long-term fatigue performance and edge adaptability of traditional zirconia materials still need further optimization.

[0003] Current mainstream solutions include: 1. Using 3Y-TZP (3mol% yttrium oxide-stabilized tetragonal zirconium oxide) powder to prepare the material through dry pressing and sintering. Its advantages are high strength (>1000MPa), but poor light transmittance; 2. Improving sintering performance by adding additives such as alumina or cerium oxide, but this will reduce the fracture toughness of the material; 3. Using a two-step sintering method to control grain growth, which can improve light transmittance, but the process is complex and energy-intensive; 4. Using CAD / CAM to cut pre-sintered blocks, which has high precision but material utilization is less than 40%.

[0004] In existing technologies, it is difficult to achieve both high strength and high light transmittance. The sintering process window is narrow, and precise temperature control of 1450-1550℃ is usually required. At the same time, the uneven particle size distribution in traditional powder preparation leads to insufficient density of the sintered body, and microcracks generated by cutting and machining affect the life of the restoration. Therefore, it is necessary to design a zirconia ceramic material for dental restoration and its preparation method to solve the above-mentioned problems. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by proposing a zirconia ceramic material for dental restoration and its preparation method, thereby solving the problems in the above-mentioned technical solutions.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a zirconia ceramic material for dental restoration, comprising a raw material processing system, a molding system and a sintering system, wherein the raw material processing system comprises a ball mill, a spray drying tower and a cyclone separator, the molding system comprises an isostatic press and a mold assembly, and the sintering system comprises an atmosphere protection furnace and a temperature control module; The ball mill is equipped with a mixing chamber for zirconium oxide powder and stabilizer. The spray drying tower is connected to the cyclone separator via a hot air duct. The mold assembly is composed of detachable graphite molds. The furnace chamber of the atmosphere protection furnace is equipped with a multi-layer alumina crucible rack.

[0007] Furthermore, the ball mill uses an alumina grinding jar with tungsten carbide grinding balls, the diameter of which is 5-10 mm; the nozzle orifice diameter of the spray drying tower is 0.5 mm; the working pressure of the isostatic press is 200 MPa; and the atmosphere protection furnace is equipped with a molybdenum wire heating element. The fog drying tower can be replaced by a freeze dryer; the detachable graphite mold can be replaced by a detachable silicon nitride mold.

[0008] A method for preparing a zirconia ceramic material for dental restoration, applicable to the aforementioned zirconia ceramic material for dental restoration, includes the following preparation steps: S1. Raw material weighing and mixing: Using an analytical balance with an accuracy of ±0.1mg, weigh high-purity zirconium oxide powder with a purity ≥99.9% and a D50 of 0.5μm and Y2O3 powder with a purity ≥99.99% according to the molar ratio of ZrO2:Y2O3=97:3. At the same time, weigh 0.5wt% of nano-Al2O3 powder with a purity ≥99.9% and a particle size of 50nm as an additive. Place the weighed powder in a clean stirring container and perform preliminary stirring and mixing to make it into a uniformly distributed ZrO2 powder containing 3mol%Y2O3. S2. Ball Milling Refinement: ZrO2 powder containing 3 mol% Y2O3 is placed in a ball mill equipped with an alumina grinding jar of suitable volume. Tungsten carbide grinding balls with a diameter of 5-10 mm are added at a ball-to-powder ratio of 5:1. Dry milling is performed at 300 rpm for 4 hours. Then, anhydrous ethanol is added, controlling the slurry solid content to 30 vol%, and wet milling continues for 3 hours to further refine the powder, ensuring that the 50 nm nano-Al2O3 powder additive is uniformly dispersed in the zirconia matrix. Nitrogen gas is used for protection during the grinding process, and high-purity anhydrous ethanol should be selected. The operating status of the ball mill jar is observed regularly during the ball milling process to ensure stable equipment operation. Samples are taken every 20 minutes, and the powder particle size is measured using a laser particle size analyzer to monitor particle size changes. S3. Spray Drying Granulation: The ball-milled slurry is pumped into a centrifugal spray drying tower at a rate of 20 mL / min using a peristaltic pump. The inlet temperature of the drying tower is set to 180±2℃, the outlet temperature to 80±2℃, and the atomization pressure to 0.3 MPa. Under the action of high-speed centrifugal force and hot air, the slurry is rapidly dried into spherical granules. The granules are then collected from the outlet of the cyclone separator and screened through a vibrating sieve with an 80-120 mesh screen to obtain spherical granules with good flowability and D50=80μm. At the same time, its flowability index is tested. S4. Mold Filling: Select a detachable graphite mold and check the mold cavity dimensional tolerance, controlling it within ±0.05mm. After cleaning and drying the mold, slowly fill the granulated powder with the screened powder. During the filling process, gently tap the mold continuously to initially compact the powder. After filling, place the mold on a three-dimensional vibration table at a frequency of 50Hz and an amplitude of 2mm for 10 minutes to ensure a filling density ≥1.8g / cm³. Then, place the filled powder into a flexible rubber bag, use a vacuum pump to evacuate to -0.1MPa, and then heat seal it. S5. Isostatic pressing and initial inspection of the green body: The sealed mold is placed in the isostatic press and pressurized to 150 MPa at a rate of 10 MPa / min, and held for 40 minutes to compact the granulated powder under uniform pressure in all directions. Then, the pressure is slowly released at a rate of 5 MPa / min. The green body after demolding is first visually inspected to check for obvious defects, deformation, etc. Then, an X-ray flaw detector with a resolution of ≤50 μm is used to detect whether there are cracks, holes, or other defects inside the green body. At the same time, a density testing device is used to test the density of the green body, and green bodies with uneven density and a deviation of ≥5% are rejected. S6. Pre-sintering and grain boundary control: The pre-inspected and qualified billet is placed on a multi-layer alumina crucible rack in an atmosphere-protected furnace. The heating rate is set to 5℃ / min, and the temperature is raised to 1350℃. At the same time, argon gas is introduced as a protective atmosphere, and the argon gas flow rate is controlled at 10L / min. The temperature is held for 2 hours. After the pre-sintering is completed, the billet is cooled to room temperature. The density of the billet is detected by Archimedes method, and the monoclinic phase content of zirconium oxide in the billet is detected by XRD semi-quantitative Rietveld method. S7. Final Sintering and Densification Strengthening: The pre-sintered green body is placed back into the atmosphere-protected furnace. First, a vacuum of 10⁻² Pa is drawn to remove air and other impurities from the furnace. Then, high-purity hydrogen (99.999% purity) is introduced to atmospheric pressure, and the temperature is raised to 1500℃ at a rate of 3℃ / min. The temperature is held for 4 hours for hydrogen sintering. After sintering, the microstructure of the material is observed using a scanning electron microscope to ensure that the grain size is controlled within 0.3-0.5μm. The relative density of the material is then measured again using the Archimedes method. S8. Precision Machining and Comprehensive Performance Evaluation: Based on the actual needs of dental restoration, high-precision machining equipment is used to cut, grind, and polish the sintered zirconia ceramic material to achieve the required shape and dimensional accuracy. The surface roughness is controlled within Ra≤0.05μm. Appropriate cooling and lubricating fluids are used during processing to prevent overheating, cracking, or damage to surface properties. Simultaneously, three-point bending strength, light transmittance, and XRD showing tetragonal phase content are tested. The hardness and fracture toughness of the material are tested using a Vickers hardness tester. The biocompatibility of the material is also evaluated through biological evaluation methods such as cytotoxicity tests, hemolysis tests, and sensitization tests to ensure that the material meets the biosafety requirements for dental implants.

[0009] Furthermore, in the S1 raw material weighing and mixing step, the powder can also be prepared by co-precipitation method. Y(NO3)3 and Al(NO3)3 are added to ZrOCl2 solution, and the precursor is obtained by ammonia titration. After calcination, the nanocomposite powder is obtained. The concentration of the ZrOCl2 solution needs to be controlled between 0.5-1.5 mol / L. The amount of Y(NO3)3 and Al(NO3)3 added should be accurately calculated based on the molar ratio of ZrO2:Y2O3=97:3 and the content of 0.5wt% Al2O3 in the final product. During the ammonia titration, ammonia should be slowly added to the mixed solution while continuously stirring, and the titration rate should be controlled at 2-5 mL / min. At the same time, the pH value of the solution should be monitored in real time using a pH meter and controlled within the range of 8-10 to ensure the uniform generation of the precursor. After the precursor is generated, it needs to be washed with water and alcohol multiple times to remove impurity ions. The number of washing times should not be less than 3. Then, it should be dried in an oven at 80-120℃ for 12-24 hours, and finally calcined in a muffle furnace at 600-800℃ for 2-4 hours to obtain nanocomposite powder.

[0010] Furthermore, in the S2 ball milling refinement step, the concentricity deviation of the grinding jar should not exceed 0.05mm during ball mill operation. Sampling and testing should be carried out during the ball milling process. If D50 exceeds 0.8μm, the ball milling time should be appropriately extended or the ball milling parameters should be adjusted. When the ball milling equipment runs continuously for more than 2 hours, the bearings, transmission components, etc. of the equipment need to be inspected and lubricated.

[0011] Furthermore, in the S5 cold isostatic pressing and pre-inspection step, the pressure sensor accuracy of the isostatic press should reach ±0.5MPa, and the pressure fluctuation range during the holding pressure process should be controlled within ±2MPa. During the demolding process, a special demolding tool should be used to avoid mechanical damage to the formed blank. For blanks found to have minor defects by X-ray flaw detection, a hot isostatic pressing repair process can be used, which involves treating the blank at 100-150MPa pressure and 1200-1300℃ temperature for 1-2 hours. After repair, flaw detection should be performed again, and only after passing the inspection can the next process be carried out.

[0012] Furthermore, in the S8 precision machining and performance comprehensive evaluation step, the machining debris and waste generated during precision machining are classified, collected, and recycled, with a recovery rate of not less than 80%. During the performance comprehensive evaluation, in addition to conducting routine mechanical property and biocompatibility tests, the corrosion resistance of the material in a simulated oral environment must also be tested. The material is immersed in simulated oral fluid at a constant temperature of 37°C for 7-14 days. The corrosion resistance is evaluated by detecting changes in the material's mass, surface microstructure, and ion concentration in the solution before and after immersion. At the same time, batch sampling inspections are conducted on the products, with a sampling rate of not less than 5%, to ensure the stability and consistency of the quality of each batch of products.

[0013] In summary, this invention provides a zirconia ceramic material for dental restoration and its preparation method, which has the following beneficial effects: 1. Through the steps of raw material weighing and mixing (S1), ball milling and refining (S2), and spray drying and granulation (S3), spherical granulated powder with uniform composition, suitable particle size and good flowability is prepared, providing high-quality raw materials for subsequent green body preparation and molding. At the same time, it improves the flexural strength of zirconia ceramic materials and increases light transmittance.

[0014] 2. Through the steps of S5 isostatic pressing and initial inspection of the blank, S6 pre-sintering and grain boundary control, and S7 final sintering and densification strengthening, the blank achieves uniform density, optimized microstructure, and significantly enhanced mechanical properties, meeting the high-performance requirements of dental restoration materials. It also enables the grain size to be controlled within the range of 0.4-0.6μm, avoiding strength reduction caused by abnormal growth. In addition, the introduction of hydrogen gas during the S7 final sintering and densification strengthening step makes the material's color closer to that of natural dentin.

[0015] 3. By controlling the concentricity of the grinding jar in the S2 ball milling refinement step, and ensuring pressure control accuracy and equipment maintenance in the S5 cold isostatic pressing and billet initial inspection steps, the stable operation of the equipment and the service life of the equipment are ensured, thereby ensuring the efficient and stable operation of the production process, reducing the sintering temperature and saving energy.

[0016] 4. Through waste recycling, simulated oral environment corrosion resistance testing, and batch sampling in the S8 precision machining and performance comprehensive evaluation steps, we have achieved the effects of reducing resource waste and production costs, ensuring the stability of material performance in actual use, and guaranteeing the consistency of product quality for each batch. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process of a zirconia ceramic material for dental restoration and its preparation method according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0019] Please see Figure 1 The present invention provides a technical solution: a zirconia ceramic material for dental restoration, comprising a raw material processing system, a molding system and a sintering system. The raw material processing system includes a ball mill, a spray drying tower and a cyclone separator. The molding system includes an isostatic press and a mold assembly. The sintering system includes an atmosphere protection furnace and a temperature control module. The ball mill is equipped with a mixing chamber for zirconium oxide powder and stabilizer. The spray drying tower is connected to the cyclone separator via a hot air duct. The mold assembly consists of detachable graphite molds. The furnace chamber of the atmosphere protection furnace is equipped with a multi-layer alumina crucible rack.

[0020] The ball mill uses an alumina grinding jar with tungsten carbide grinding balls, the diameter of which is 5-10 mm. The nozzle orifice of the spray drying tower is 0.5 mm. The working pressure of the isostatic press is 200 MPa. The atmosphere protection furnace is equipped with a molybdenum wire heating element. The fog drying tower can be replaced by a freeze dryer; the detachable graphite mold can be replaced by a detachable silicon nitride mold.

[0021] A method for preparing a zirconia ceramic material for dental restoration, applicable to the aforementioned zirconia ceramic material for dental restoration, includes the following preparation steps: S1. Raw Material Weighing and Mixing: Using an analytical balance with an accuracy of ±0.1 mg, high-purity zirconium oxide powder with a purity ≥99.9% and a D50 of 0.5 μm and Y2O3 powder with a purity ≥99.99% were weighed according to a ZrO2:Y2O3 molar ratio of 97:3. Simultaneously, 0.5 wt% of nano-Al2O3 powder with a purity ≥99.9% and a particle size of 50 nm was weighed as an additive. The weighed powders were placed in a clean stirring container and initially stirred to form a uniformly distributed ZrO2 powder containing 3 mol% Y2O3. Precise weighing and mixing ensured accurate proportions of each component. The addition of Al2O3 powder as an additive enhanced the toughness and stability of the material. S2. Ball Milling Refining: The ZrO2 powder containing 3 mol% Y2O3 is placed in a ball mill equipped with an alumina grinding jar of suitable volume. Tungsten carbide grinding balls with a diameter of 5-10 mm are added at a ball-to-powder ratio of 5:1. Dry milling is performed at 300 rpm for 4 hours. The ball milling refining process effectively reduces the powder particle size, allowing the nano-Al2O3 powder additive to be uniformly dispersed in the zirconium oxide matrix, significantly improving the material uniformity. Then, anhydrous ethanol is added, controlling the slurry solid content to 30 vol%, and wet milling continues for 3 hours to further refine the powder. The powder is uniformly dispersed in a zirconia matrix using nano-Al2O3 powder additives with a particle size of 50nm. Nitrogen gas is introduced during the grinding process for protection, preventing powder oxidation. High-purity anhydrous ethanol is used. The operating status of the ball mill jar is regularly monitored during ball milling to ensure stable operation. Samples are taken every 20 minutes, and a laser particle size analyzer is used to detect powder particle size changes, ensuring consistency in material performance improvement during the ball milling process and increasing product yield. S3. Spray Drying Granulation: The ball-milled slurry is pumped into a centrifugal spray drying tower at a rate of 20 mL / min using a peristaltic pump. The inlet temperature of the drying tower is set to 180±2℃, the outlet temperature to 80±2℃, and the atomization pressure to 0.3MPa. Under the action of high-speed centrifugal force and hot air, the slurry is rapidly dried into spherical granules, efficiently converting the slurry into spherical granules with good flowability, which facilitates subsequent mold filling and molding. At the same time, precise control of temperature and pressure parameters can ensure the quality and performance stability of the granulated powder. Then, the granulated powder is collected from the outlet of the cyclone separator and screened through a vibrating sieve with an 80-120 mesh screen to obtain spherical granules with good flowability and D50=80μm. At the same time, its flowability index is tested. The granulated powder with suitable particle size selected can improve the density and uniformity of the molded green body, which is beneficial to improving the quality of the final product. S4. Mold Filling: A detachable graphite mold is selected, and the mold cavity dimensional tolerance is checked and controlled within ±0.05mm. After cleaning and drying the mold, the screened granulated powder is slowly filled into the detachable graphite mold. Strict control of mold tolerance and filling process ensures the forming accuracy of the green body. During the filling process, the mold is tapped lightly to make the granulated powder initially compacted. After filling, the mold is placed on a three-dimensional vibration table at a frequency of 50Hz and an amplitude of 2mm for 10 minutes to ensure that the filling density is ≥1.8g / cm³. Vibration table compaction increases the filling density, making the internal structure of the green body more compact and reducing internal defects. Then, the granulated powder after filling the mold is placed in a flexible rubber bag, and a vacuum pump is used to evacuate to -0.1MPa before heat sealing. Vacuum heat sealing can prevent the green body from being contaminated by the outside before subsequent processing and ensure the stability of the green body quality. S5. Isostatic Pressing and Initial Inspection of Green Body: The sealed mold is placed in an isostatic press and pressurized to 150 MPa at a rate of 10 MPa / min, and held for 40 minutes to compact the granulated powder under uniform pressure in all directions. Then, the pressure is slowly released at a rate of 5 MPa / min. The demolded green body is first visually inspected to check for obvious defects, deformation, etc. Cold isostatic pressing ensures that the granulated powder is uniformly compressed, resulting in a green body with high density and uniform structure. Then, an X-ray flaw detector with a resolution of ≤50μm is used to detect whether there are cracks, holes, or other defects inside the green body. At the same time, a density testing device is used to test the density of the green body, and green bodies with uneven density and a deviation of ≥5% are rejected. The strict initial inspection process can promptly detect and reject unqualified green bodies, ensuring product quality. Green bodies with minor defects are rejected, improving the quality of the finished material. S6. Pre-sintering and grain boundary control: The pre-inspected and qualified billet is placed on a multi-layer alumina crucible rack in an atmosphere-protected furnace. The heating rate is set to 5℃ / min, and the temperature is raised to 1350℃. At the same time, argon gas is introduced as a protective atmosphere, and the argon gas flow rate is controlled at 10L / min. The temperature is held for 2 hours. The pre-sintering process can initially remove impurities and pores in the billet, and the argon gas protection prevents the billet from oxidizing. After the pre-sintering is completed, the billet is cooled to room temperature. The density of the billet is detected by Archimedes method, and the monoclinic phase content of zirconium oxide in the billet is detected by XRD semi-quantitative Rietveld method. The heating rate and holding time are precisely controlled to effectively regulate the grain boundaries, optimize the microstructure of the material, and improve the stability and mechanical properties of the material. S7. Final Sintering and Densification Strengthening: The pre-sintered green body is placed back into the atmosphere-protected furnace. First, a vacuum of 10⁻² Pa is applied to remove air and other impurities. Then, high-purity hydrogen (99.999% purity) is introduced to atmospheric pressure, and the temperature is raised to 1500℃ at a rate of 3℃ / min. Hydrogen sintering is then performed for 4 hours. After sintering, the microstructure of the material is observed using a scanning electron microscope to ensure the grain size is controlled within 0.3-0.5μm. The relative density of the material is then measured again using the Archimedes method. Hydrogen sintering further eliminates impurities, improves material density, and precisely controls the grain size within a suitable range, significantly enhancing the material's mechanical properties, hardness, strength, and fracture toughness, thus meeting the high-performance requirements of dental restoration materials. S8. Precision Machining and Comprehensive Performance Evaluation: Based on the actual needs of dental restoration, high-precision machining equipment is used to cut, grind, and polish the sintered zirconia ceramic material to achieve the required shape and dimensional accuracy. The surface roughness is controlled within Ra≤0.05μm. Appropriate cooling and lubricating fluids are used during processing to prevent overheating, cracking, or damage to surface properties. Simultaneously, three-point flexural strength, light transmittance, and XRD analysis revealing tetragonal phase content are measured. A Vickers hardness tester is used to test the material's hardness and fracture toughness. Biocompatibility is also assessed through biological evaluation methods such as cytotoxicity testing, hemolysis testing, and sensitization testing to ensure the material meets the biosafety requirements for dental implants. Precision machining ensures the material meets the shape and dimensional accuracy requirements for dental restoration, and cooling and lubricating fluids prevent material damage. Comprehensive performance evaluation ensures the material meets usage standards in terms of mechanics, biocompatibility, and corrosion resistance.

[0022] In the S1 raw material weighing and mixing step, the co-precipitation method can also be used to prepare powder. Y(NO3)3 and Al(NO3)3 are added to ZrOCl2 solution, and the precursor is obtained by ammonia titration. After calcination, nanocomposite powder is obtained. The co-precipitation method can achieve uniform mixing of each component at the atomic level. Compared with the traditional mixing method, the final material has more uniform and stable performance. The concentration of the ZrOCl2 solution needs to be controlled between 0.5-1.5 mol / L. The amounts of Y(NO3)3 and Al(NO3)3 added should be precisely calculated based on the molar ratio of ZrO2:Y2O3 = 97:3 and the content of 0.5 wt% Al2O3 in the final product. During the ammonia titration, ammonia should be slowly added dropwise to the mixed solution while continuously stirring, controlling the titration rate at 2-5 mL / min. Simultaneously, the pH value of the solution should be monitored in real time using a pH meter and controlled within the range of 8-10 to ensure uniform precursor formation. After the precursor is formed, it needs to be washed with water and alcohol multiple times to remove impurity ions, with at least three washing cycles. Then, it should be dried in an oven at 80-120℃ for 12-24 hours, and finally calcined in a muffle furnace at 600-800℃ for 2-4 hours to obtain the nanocomposite powder. Strict control of solution concentration, titration rate, and pH is essential. Parameters such as the value are used to ensure the quality of precursor generation. Subsequent washing, drying and calcination steps further purify and optimize the powder properties, providing high-quality raw materials for the preparation of high-performance dental restorative materials.

[0023] During the S2 ball milling refining process, the concentricity deviation of the grinding jar should not exceed 0.05mm during ball mill operation. Sampling and testing should be conducted during the ball milling process. If D50 exceeds 0.8μm, the ball milling time should be appropriately extended or the ball milling parameters adjusted. When the ball mill equipment runs continuously for more than 2 hours, the bearings and transmission components of the equipment need to be inspected and lubricated. Strict control of the concentricity of the grinding jar can prevent eccentric wear during ball milling and ensure uniform grinding effect of the grinding balls on the powder. Real-time monitoring of powder particle size and flexible adjustment of ball milling parameters are necessary to ensure that the powder refinement reaches the expected level. Regular inspection and lubrication of the equipment can extend its service life, reduce the impact of equipment failure on production, and ensure the stable and efficient operation of the ball milling process.

[0024] In the S5 cold isostatic pressing and pre-inspection process, the pressure sensor accuracy of the isostatic press should reach ±0.5MPa, and the pressure fluctuation range during the holding pressure process should be controlled within ±2MPa. During demolding, a dedicated demolding tool should be used to avoid mechanical damage to the formed blank. For blanks found to have minor defects through X-ray flaw detection, a hot isostatic pressing repair process can be used. This involves treating the blank at 100-150MPa pressure and 1200-1300℃ for 1-2 hours, followed by another flaw detection test. Only blanks that pass the test can proceed to the next step. High-precision pressure sensors and stable pressure control ensure accurate pressure application during cold isostatic pressing, resulting in uniform blank density. Dedicated demolding tools prevent damage to the blank. The hot isostatic pressing repair process effectively salvages blanks with minor defects, improves material utilization, reduces scrap rates, lowers production costs, and ensures high product quality standards.

[0025] In the S8 precision machining and comprehensive performance evaluation process, machining debris and waste generated during precision machining are collected and recycled with a recovery rate of no less than 80%. During the comprehensive performance evaluation, in addition to routine mechanical property and biocompatibility testing, the corrosion resistance of the material in a simulated oral environment is also tested. The material is immersed in simulated oral fluid at a constant temperature of 37°C for 7-14 days. The corrosion resistance is evaluated by detecting changes in the material's mass, surface microstructure, and ion concentration in the solution before and after immersion. Simultaneously, batch sampling inspections are conducted, with a sampling rate of no less than 5%, to ensure the stability and consistency of each batch's quality. Waste recycling reduces resource waste and production costs. The corrosion resistance test in a simulated oral environment more realistically evaluates the material's performance in actual use, ensuring long-term stability in the complex oral environment. Batch sampling inspections effectively monitor product quality fluctuations, promptly identify and resolve problems in the production process, and ensure that each batch of products meets the stringent requirements of dental restoration.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A zirconia ceramic material for dental restoration, comprising a raw material processing system, a molding system, and a sintering system, characterized in that: The raw material processing system includes a ball mill, a spray drying tower and a cyclone separator; the molding system includes an isostatic press and a mold assembly; and the sintering system includes an atmosphere protection furnace and a temperature control module. The ball mill is equipped with a mixing chamber for zirconium oxide powder and stabilizer. The spray drying tower is connected to the cyclone separator via a hot air duct. The mold assembly is composed of detachable graphite molds. The furnace chamber of the atmosphere protection furnace is equipped with a multi-layer alumina crucible rack.

2. The zirconia ceramic material for dental restoration according to claim 1, characterized in that: The ball mill uses an alumina grinding jar with tungsten carbide grinding balls, the diameter of which is 5-10 mm. The nozzle orifice diameter of the spray drying tower is 0.5 mm. The working pressure of the isostatic press is 200 MPa. The atmosphere protection furnace is equipped with a molybdenum wire heating element. The fog drying tower can be replaced by a freeze dryer; the detachable graphite mold can be replaced by a detachable silicon nitride mold.

3. A method for preparing a zirconia ceramic material for dental restoration, applied to the zirconia ceramic material for dental restoration described in any one of claims 1-2 above, characterized in that: The preparation steps include the following: S1. Raw material weighing and mixing: Using an analytical balance with an accuracy of ±0.1mg, weigh high-purity zirconium oxide powder with a purity ≥99.9% and a D50 of 0.5μm and Y2O3 powder with a purity ≥99.99% according to the molar ratio of ZrO2:Y2O3=97:

3. At the same time, weigh 0.5wt% of nano-Al2O3 powder with a purity ≥99.9% and a particle size of 50nm as an additive. Place the weighed powder in a clean stirring container and perform preliminary stirring and mixing to make it into a uniformly distributed ZrO2 powder containing 3mol%Y2O3. S2. Ball Milling Refinement: ZrO2 powder containing 3 mol% Y2O3 is placed in a ball mill equipped with an alumina grinding jar of suitable volume. Tungsten carbide grinding balls with a diameter of 5-10 mm are added at a ball-to-powder ratio of 5:

1. Dry milling is performed at 300 rpm for 4 hours. Then, anhydrous ethanol is added, controlling the slurry solid content to 30 vol%, and wet milling continues for 3 hours to further refine the powder, ensuring that the 50 nm nano-Al2O3 powder additive is uniformly dispersed in the zirconia matrix. Nitrogen gas is used for protection during the grinding process, and high-purity anhydrous ethanol should be selected. The operating status of the ball mill jar is observed regularly during the ball milling process to ensure stable equipment operation. Samples are taken every 20 minutes, and the powder particle size is measured using a laser particle size analyzer to monitor particle size changes. S3. Spray Drying Granulation: The ball-milled slurry is pumped into a centrifugal spray drying tower at a rate of 20 mL / min using a peristaltic pump. The inlet temperature of the drying tower is set to 180±2℃, the outlet temperature to 80±2℃, and the atomization pressure to 0.3 MPa. Under the action of high-speed centrifugal force and hot air, the slurry is rapidly dried into spherical granules. The granules are then collected from the outlet of the cyclone separator and screened through a vibrating sieve with an 80-120 mesh screen to obtain spherical granules with good flowability and D50=80μm. At the same time, its flowability index is tested. S4. Mold Filling: Select a detachable graphite mold and check the mold cavity dimensional tolerance, controlling it within ±0.05mm. After cleaning and drying the mold, slowly fill the granulated powder with the screened powder. During the filling process, gently tap the mold continuously to initially compact the powder. After filling, place the mold on a three-dimensional vibration table at a frequency of 50Hz and an amplitude of 2mm for 10 minutes to ensure a filling density ≥1.8g / cm³. Then, place the filled powder into a flexible rubber bag, use a vacuum pump to evacuate to -0.1MPa, and then heat seal it. S5. Isostatic pressing and initial inspection of the green body: The sealed mold is placed in the isostatic press and pressurized to 150 MPa at a rate of 10 MPa / min, and held for 40 minutes to compact the granulated powder under uniform pressure in all directions. Then, the pressure is slowly released at a rate of 5 MPa / min. The green body after demolding is first visually inspected to check for obvious defects, deformation, etc. Then, an X-ray flaw detector with a resolution of ≤50 μm is used to detect whether there are cracks, holes, or other defects inside the green body. At the same time, a density testing device is used to test the density of the green body, and green bodies with uneven density and a deviation of ≥5% are rejected. S6. Pre-sintering and grain boundary control: The pre-inspected and qualified billet is placed on a multi-layer alumina crucible rack in an atmosphere-protected furnace. The heating rate is set to 5℃ / min, and the temperature is raised to 1350℃. At the same time, argon gas is introduced as a protective atmosphere, and the argon gas flow rate is controlled at 10L / min. The temperature is held for 2 hours. After the pre-sintering is completed, the billet is cooled to room temperature. The density of the billet is detected by Archimedes method, and the monoclinic phase content of zirconium oxide in the billet is detected by XRD semi-quantitative Rietveld method. S7. Final sintering and densification strengthening: The pre-sintered green body is placed back into the atmosphere protection furnace. First, the vacuum is evacuated to 10⁻²Pa to remove air and other impurities from the furnace. Then, high-purity hydrogen with a purity of 99.999% is introduced to atmospheric pressure. The temperature is raised to 1500℃ at a heating rate of 3℃ / min and held for 4 hours for hydrogen sintering. After sintering, the microstructure of the material is observed using a scanning electron microscope to ensure that the grain size is controlled within 0.3-0.5μm. The relative density of the material was determined again using the Archimedes method. S8. Precision Machining and Comprehensive Performance Evaluation: Based on the actual needs of dental restoration, high-precision machining equipment is used to cut, grind, and polish the sintered zirconia ceramic material to achieve the required shape and dimensional accuracy. The surface roughness is controlled within Ra≤0.05μm. Appropriate cooling and lubricating fluids are used during processing to prevent overheating, cracking, or damage to surface properties. Simultaneously, three-point bending strength, light transmittance, and XRD showing tetragonal phase content are tested. The hardness and fracture toughness of the material are tested using a Vickers hardness tester. The biocompatibility of the material is also evaluated through biological evaluation methods such as cytotoxicity tests, hemolysis tests, and sensitization tests to ensure that the material meets the biosafety requirements for dental implants.

4. The method for preparing a zirconia ceramic material for dental restoration according to claim 3, characterized in that: In the S1 raw material weighing and mixing step, the powder can also be prepared by co-precipitation method. Y(NO3)3 and Al(NO3)3 are added to ZrOCl2 solution, and the precursor is obtained by ammonia titration. After calcination, the nanocomposite powder is obtained. The concentration of ZrOCl2 solution needs to be controlled between 0.5-1.5 mol / L. The amount of Y(NO3)3 and Al(NO3)3 added should be accurately calculated based on the molar ratio of ZrO2:Y2O3=97:3 and the content of 0.5wt% Al2O3 in the final product. During the ammonia titration, ammonia should be slowly added to the mixed solution while continuously stirring. The titration rate should be controlled at 2-5 mL / min. At the same time, the pH value of the solution should be monitored in real time using a pH meter and controlled within the range of 8-10 to ensure the uniform generation of the precursor. After the precursor is generated, it needs to be washed with water and alcohol multiple times to remove impurity ions. The washing number should be no less than 3 times. Then, it is dried in an oven at 80-120℃ for 12-24 hours, and finally calcined in a muffle furnace at 600-800℃ for 2-4 hours to obtain nanocomposite powder.

5. The method for preparing a zirconia ceramic material for dental restoration according to claim 3, characterized in that: During the S2 ball milling refinement process, the concentricity deviation of the grinding jar should not exceed 0.05 mm during ball mill operation. Sampling and testing should be performed during the ball milling process. If D50 exceeds 0.8 μm, the ball milling time should be extended or the ball milling parameters should be adjusted appropriately. When the ball milling equipment runs continuously for more than 2 hours, the bearings, transmission components, etc. of the equipment need to be inspected and lubricated.

6. The method for preparing a zirconia ceramic material for dental restoration according to claim 3, characterized in that: In the S5 cold isostatic pressing and pre-inspection steps, the pressure sensor of the isostatic press should have an accuracy of ±0.5MPa, and the pressure fluctuation range during the holding pressure process should be controlled within ±2MPa. During the demolding process, a special demolding tool should be used to avoid mechanical damage to the formed blank. For blanks with minor defects found by X-ray flaw detection, a hot isostatic pressing repair process can be used, which involves treating the blank at 100-150MPa pressure and 1200-1300℃ temperature for 1-2 hours. After repair, flaw detection should be performed again, and only blanks that pass the inspection can proceed to the next step.

7. The method for preparing a zirconia ceramic material for dental restoration according to claim 3, characterized in that: In the S8 precision machining and performance comprehensive evaluation step, machining debris and waste generated during precision machining are classified, collected, and recycled, with a recovery rate of no less than 80%. During the performance comprehensive evaluation, in addition to routine mechanical property and biocompatibility testing, the corrosion resistance of the material in a simulated oral environment is also tested. The material is immersed in simulated oral fluid at a constant temperature of 37°C for 7-14 days. Its corrosion resistance is evaluated by detecting changes in the material's mass, surface microstructure, and ion concentration in the solution before and after immersion. Simultaneously, batch sampling inspections are conducted on the products, with a sampling rate of no less than 5%, to ensure the stability and consistency of the quality of each batch.

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