Dental removable restoration and method for manufacturing same, and cobalt-chromium-molybdenum alloy powder

Abstract

The application relates to the field of biomedical materials, and particularly discloses a dental movable restoration, a preparation method thereof, and a cobalt-chromium-molybdenum alloy powder. The dental movable restoration is formed by laser selective melting technology and takes cobalt-chromium-molybdenum alloy as raw material. The cobalt-chromium-molybdenum alloy is composed of the following elements in percentage by weight: Cr 26-30%, Mo 4-7%, Si 0.5-1.5%, B 0.01%-0.05%, and the balance of Co and inevitable impurities. The cobalt-chromium-molybdenum alloy does not contain W and Ta, and the total amount of inevitable impurities is less than 0.5%. The preparation method comprises alloy smelting, atomization powder preparation, screening and drying, laser selective melting (SLM) forming, and stress relief annealing. The core of the application is that by adding trace boron elements and optimizing the alloy components, the dental movable restoration (such as a bracket and a clasp) formed by 3D printing can obtain high plasticity and high strength combination with an elongation at break not less than 20% and a tensile strength not less than 1000 MPa after conventional stress relief annealing at 950-1000 DEG C.

Description

Technical Field

[0001] This application relates to the field of biomedical materials, and more specifically, to a dental removable prosthesis and its preparation method, as well as cobalt-chromium-molybdenum alloy powder. Background Technology

[0002] With the rapid development of digital oral healthcare technology, 3D printing technologies such as Selective Laser Melting (SLM) have been widely used in the field of dental restoration due to their ability to quickly and accurately fabricate personalized, complex restorations. Among them, cobalt-chromium (Co-Cr) alloys, with their excellent biocompatibility, corrosion resistance, and high specific strength, have become important materials for both fixed dental restorations (such as crowns and bridges) and removable restorations (such as removable partial denture frameworks, clasps, and denture bases).

[0003] For removable prostheses, their clinical applications place more stringent and unique demands on the mechanical properties of materials. For example, denture clasps must withstand alternating stress during repeated insertion and removal, thus requiring materials with sufficiently high strength to prevent breakage. Simultaneously, to enable clinicians to precisely adjust the clasps within the patient's mouth for optimal positioning and retention, the material must possess good plasticity (i.e., high elongation after fracture) to prevent brittle fracture during adjustments. Therefore, achieving both high strength and high plasticity in 3D-printed cobalt-chromium alloys is crucial for their successful application in the field of removable prostheses.

[0004] Currently, due to the characteristics of the SLM (Surface Mount Technology) process, significant residual stress exists within the printed cobalt-chromium alloy parts. It is well known in the art that stress-relief annealing is necessary to eliminate residual stress generated during SLM forming and ensure dimensional stability. In existing technologies, the conventional and widely used stress-relief annealing temperature range for dental 3D printing cobalt-chromium alloys is 800°C to 950°C. However, a long-standing technical problem is that after annealing within this conventional temperature range, the elongation at fracture of the alloy is typically low (generally below 8%), making it difficult to meet the high plasticity requirements of removable prostheses for clinical adjustments.

[0005] To address the aforementioned issue of insufficient plasticity, existing technologies have resorted to a compromise: significantly increasing the annealing temperature to 1150℃ or even above 1200℃. While this high-temperature treatment can improve the material's plasticity to some extent, it introduces two serious drawbacks: First, severe surface oxidation: the extremely high heat treatment temperature significantly exacerbates the oxidation tendency of alloying elements. Even under a protective atmosphere, it is difficult to completely avoid the formation of a thick oxide layer on the repair surface (at high temperatures, chromium becomes very reactive and readily combines with oxygen to form chromium oxide, resulting in a green oxide layer on the part's surface, which can turn black in severe cases). This not only affects aesthetics but also damages the material's surface integrity, biocompatibility, and subsequent polishing and bonding performance. Second, the risk of deterioration in core properties: prolonged holding at excessively high temperatures can easily lead to abnormally coarse grains, impairing key mechanical properties such as toughness and fatigue strength, and affecting the material's long-term dimensional stability and reliability. Furthermore, it increases heat treatment energy consumption and places higher demands on high-temperature heat treatment furnaces.

[0006] Therefore, there is a pressing technical dilemma in the preparation of dental 3D printed cobalt-chromium alloys: if conventional and mature annealing at 800-950℃ is used, the plasticity will not meet the requirements and cannot meet the clinical adjustment needs of removable restorations; if high-temperature annealing above 1150℃ is used to improve plasticity, it will cause serious risks of oxidation and performance degradation, which is not worth the effort. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a dental removable prosthesis, a method for preparing the same, and a cobalt-chromium-molybdenum alloy powder.

[0008] The technical solution adopted in this application is as follows:

[0009] In a first aspect, this application provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis, which is formed by laser selective melting technology using cobalt-chromium-molybdenum alloy as raw material;

[0010] The cobalt-chromium-molybdenum alloy is composed of the following elements by weight percentage: Cr 26~30%, Mo 4~7%, Si 0.5~1.5%, B 0.01%~0.05%, with the balance being Co and unavoidable impurities; wherein the cobalt-chromium-molybdenum alloy does not contain W and Ta, and the total amount of unavoidable impurities is less than 0.5%;

[0011] The dental removable restoration undergoes stress-relieving annealing at a temperature range of 950℃ to 1000℃, and the elongation after fracture of the dental removable restoration after annealing is not less than 20%.

[0012] Furthermore, after the above annealing treatment, the tensile strength of the dental removable prosthesis is not less than 1000 MPa and the yield strength is not less than 740 MPa.

[0013] Furthermore, the above annealing process is carried out in a protective atmosphere or vacuum environment, and the holding time is 60~90 minutes.

[0014] Furthermore, the aforementioned dental removable prostheses are frameworks, clasps, or bases for removable partial dentures.

[0015] Secondly, this application provides a cobalt-chromium-molybdenum alloy powder for preparing the above-mentioned dental removable prosthesis. The cobalt-chromium-molybdenum alloy powder has the following composition by weight percentage: Cr 26%~30%, Mo 4%~8%, Si 0.5%~1.5%, B 0.01%~0.05%, with the balance being Co and unavoidable impurities; wherein the cobalt-chromium-molybdenum alloy powder does not contain W and Ta, and the total amount of unavoidable impurities is less than 0.5%.

[0016] Thirdly, this application provides a method for preparing the above-mentioned removable dental prosthesis, comprising:

[0017] Provides cobalt-chromium-molybdenum alloy powder;

[0018] Under an inert atmosphere, the cobalt-chromium-molybdenum alloy powder is printed layer by layer into a repair blank using laser selective melting technology;

[0019] The repair blank is subjected to stress-relief annealing under a protective atmosphere or vacuum: the temperature is raised to 900℃~1000℃, held for 60~90 minutes, and then cooled.

[0020] Furthermore, the process parameters for the laser selective melting are as follows: laser power 120~180W, scanning speed 900~1400 mm / s, scanning spacing 60~80 μm, layer thickness 20~40 μm, spot diameter 50~65 μm, using a checkerboard scanning strategy, rotating layer by layer by 45~80°.

[0021] Furthermore, the above-mentioned cobalt-chromium-molybdenum alloy powder is prepared by the following method:

[0022] Prepare raw materials by weight percentage of Cr 26%~30%, Mo 4%~8%, Si 0.5%~1.5%, with the balance being Co, and then perform vacuum melting to obtain an alloy melt.

[0023] A boron-containing additive is added to the alloy melt to achieve a boron content of 0.01% to 0.05% in the alloy.

[0024] The alloy melt with added boron is kept at a constant temperature in an tundish and then flows out through a guide pipe. It is then atomized with high-pressure inert gas to obtain alloy powder.

[0025] The alloy powder obtained by atomization is sieved, and powder within the target particle size range is collected and vacuum dried.

[0026] Furthermore, the insulation temperature of the aforementioned intermediate ladle is 1500~1650℃.

[0027] Furthermore, when sieving the alloy powder obtained by atomization, the target particle size range of the alloy powder is 270-900 mesh, and the drying temperature of the alloy powder is 100-130℃ and the drying time is 1-3h.

[0028] In summary, this application has the following beneficial effects:

[0029] The inventors discovered that traditional 3D-printed cobalt-chromium alloys, after being treated in the necessary stress-relief annealing temperature range (around 950°C), generally undergo a phase transformation from face-centered cubic (FCC) to hexagonal close-packed (HCP) and the precipitation of a large amount of brittle second phase. This results in a reduction of slip systems and obstruction of dislocation movement, manifesting as low elongation after fracture (usually below 8%), which cannot meet the clinical adjustment needs of active prostheses.

[0030] This invention utilizes boron (B) as a key additive, strictly controlling its content within the range of 0.01% to 0.05%, leveraging its unique role as an interstitial element: boron atoms dissolve in the matrix or form fine, dispersed compounds, effectively pinning dislocations and significantly increasing the stacking fault energy of the alloy. This strongly suppresses the stacking fault slip required for the transformation from the FCC phase to the HCP phase, thereby inhibiting the martensitic transformation (reducing the slip system); furthermore, the reduction in the phase transformation interface lowers the driving force for second-phase nucleation, significantly suppressing the precipitation behavior of harmful second-phase enriched at the phase interface. Through this mechanism, this invention successfully increases the elongation after fracture to no less than 20% after conventional stress-relief annealing at 900–1000°C, while maintaining a tensile strength above 1000 MPa, perfectly balancing the dual requirements of high plasticity (easy to adjust) and high strength (preventing fracture) for removable restorations.

[0031] This application enables 3D-printed cobalt-chromium alloys to achieve previously unattainable superior plasticity after undergoing standardized low-temperature heat treatment. This greatly expands the application potential of this material in dental removable prostheses with complex structures, thin walls, and high elasticity requirements (such as removable partial denture frameworks, clasps, and denture bases), improving the wearing comfort, adjustment convenience, and long-term service reliability of the prostheses, and has significant clinical significance and market application prospects. Attached Figure Description

[0032] Figure 1 XRD patterns of the gold dental removable prosthesis provided in this application: (a) Example 1; (b) Example 2; (c) Example 3; (d) Comparative Example 1; (e) Comparative Example 4;

[0033] Figure 2 Microscopic images of the cobalt-chromium-molybdenum alloy dental removable prosthesis provided in this application: (a) Example 1; (b) Example 2; (c) Example 3; (d) Comparative Example 1; (e) Comparative Example 4. Detailed Implementation

[0034] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0035] The technical solution of this invention is as follows:

[0036] This embodiment provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis, which is formed by selective laser melting technology;

[0037] The cobalt-chromium-molybdenum alloy is composed of the following elements by weight percentage: Cr 26~30%, Mo 4~7%, Si 0.5~1.5%, B 0.01%~0.05%, with the balance being Co and unavoidable impurities; wherein, the cobalt-chromium-molybdenum alloy does not contain W and Ta, and the total amount of unavoidable impurities is less than 0.5%;

[0038] The dental removable prosthesis undergoes stress-relieving annealing at a temperature range of 900℃ to 1000℃, and the elongation after fracture of the dental removable prosthesis after annealing is not less than 20%.

[0039] Regarding the adjustment of elemental composition in the cobalt-chromium-molybdenum alloy of this application:

[0040] (1) Add 0.01%~0.05% of B:

[0041] This invention adds trace amounts of boron as an interstitial element, strictly limiting its mass percentage to the range of 0.01% to 0.05%. At this content, boron can dissolve in the matrix or form fine interstitial compounds, effectively hindering the stacking fault slip required for the transformation from face-centered cubic (FCC) to hexagonal close-packed (HCP) phases during heat treatment by pinning dislocations and significantly increasing stacking fault energy, thereby suppressing the martensitic phase transformation (reducing slip systems). Furthermore, due to the reduction in phase transformation interfaces, the driving force provided by the interfacial energy for second phase nucleation is reduced, which effectively suppresses the precipitation behavior of the second phase enriched at the phase interface. Finally, by reducing the number and size of brittle precipitates, crack initiation caused by stress concentration at the interface is avoided, resulting in a significant improvement in the plasticity of the cobalt-chromium alloy prepared by 3D printing.

[0042] (2) Reduce the content of Mo by 4-7%.

[0043] In existing dental 3D printing cobalt-chromium-molybdenum alloy powders, the Mo content is above 8%. This application reduces the addition of Mo. On the one hand, by reducing the enrichment content of the second-phase precipitation element, the precipitation of the second phase is reduced, thereby enhancing plasticity and further improving the adjustability for clinical applications. Reducing the Mo content reduces the tendency for thermal cracking during the printing process and improves the flowability of the molten pool, thereby increasing the printing success rate and the density of the formed part; on the other hand, retaining some Mo is sufficient to synergistically form a more corrosion-resistant surface protective film with chromium, ensuring the safety of the restoration for long-term use in the oral environment.

[0044] (3) Remove the W element

[0045] The primary purpose of removing titanium dioxide (W) is to optimize the stability and microstructure of the 3D printing process. As a high-melting-point, high-density element, W tends to increase the molten pool and cause uneven flow during rapid laser solidification. It may also promote the segregation of coarse, brittle phases (such as carbides) during rapid solidification, thereby increasing internal residual stress, the risk of thermal cracking, and microstructure inhomogeneity in the printed part. Removing W results in a more stable molten pool and a more uniform solidification structure, directly improving printing success rate and part density. In terms of biocompatibility, removing W simplifies the alloy phase composition, reduces the risk of microgalvanic corrosion caused by multiphase structures, and makes the ion release behavior of the alloy in the oral environment more stable and predictable.

[0046] (4) Remove Ta elements

[0047] Tantalum (Ta) is not added in this invention, a targeted choice based on the core objective of this application—to address the insufficient plasticity of movable restorations after conventional low-temperature annealing. In existing technologies, tantalum is primarily added to adjust the coefficient of thermal expansion to improve the bond between metal and porcelain. This addresses the technical needs of fixed restorations (such as porcelain crowns and bridges), and is unrelated to the goal of this invention to improve the plasticity of movable restorations. Introducing elements like tantalum, which have high melting points and readily form intermetallic compounds, not only fails to improve plasticity but may also increase the complexity of the molten pool and promote the precipitation of brittle phases, thereby interfering with the core regulatory role of boron (B) in phase transformation and precipitation behavior.

[0048] In summary, the fundamental significance of reducing Mo content and removing W and Ta elements lies in ensuring that the alloy composition design is highly compatible with the characteristics of the SLM process. This collaboratively inhibits the formation of harmful structures from the printing source to the heat treatment process, thereby maximizing the alloy's plasticity potential while ensuring corrosion resistance. Simultaneously, this design eliminates expensive elements irrelevant to the core objective, achieving an optimal balance between performance, process, and cost.

[0049] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0050] Example 1

[0051] This embodiment provides a 3D printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 27%, Mo 6%, Si 1%, B 0.01%, with the balance being Co and unavoidable impurities (content less than 0.5%).

[0052] The method for preparing this removable dental prosthesis is as follows:

[0053] (1) Master alloy smelting: The elements other than B are batched according to the chemical composition, and the batched raw materials are added to a vacuum induction furnace to smelt into a master alloy ingot. The vacuum degree in the furnace during the refining period should be higher than 1.0 × 10⁻⁶. -2 Pa.

[0054] (2) Secondary melting and atomization powder making: The master alloy ingot is placed in a vacuum induction gas atomization powder making equipment, deoxidized carbon is added for refining, and NiB20 is added after refining. After being kept at 1550℃ in the intermediate ladle, it flows out through the guide pipe and is atomized under the pressure impact of argon gas flow.

[0055] (3) Sieving and drying: The cobalt-chromium alloy powder was sieved using an ultrasonic vibrating sieve, and the powder with a mesh size of 270~900 was collected and vacuum dried at 100℃ for 2 hours.

[0056] (4) 3D printing: 3D printing is performed on a substrate by layer-by-layer powder deposition and laser sintering. Oxygen is removed by purging with argon gas to maintain an oxygen content below 3000 ppm; deoxygenation begins when the content exceeds 2000 ppm and stops when it falls below 1000 ppm. A checkerboard scanning strategy is used, rotating 60° layer by layer. Printing parameters include 170W power, 1100mm / s scanning speed, 70μm scanning spacing, 30μm layer thickness, and 65μm spot diameter.

[0057] (5) Stress relief annealing: Stress relief annealing is carried out under argon atmosphere protection: the temperature is raised to 950℃ at a heating rate of 20℃ / min, held for 60min, cooled to below 400℃ in the furnace, and then air-cooled to room temperature.

[0058] Example 2

[0059] This embodiment provides a 3D printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 30%, Mo 7%, Si 1%, B 0.03%, with the balance being Co and unavoidable impurities (content less than 0.5%).

[0060] The method for preparing this removable dental prosthesis is as follows:

[0061] (1) Melting and atomizing powder making: The elements other than B are batched according to the chemical composition. The batched raw materials are added to the vacuum induction gas atomizing powder making equipment to add deoxidized carbon for refining. After refining, NiB2O is added. After being kept at 1600℃ in the intermediate ladle, it flows out through the guide pipe and is atomized under the pressure impact of argon gas flow.

[0062] (2) Sieving and drying: The cobalt-chromium alloy powder was sieved using an ultrasonic vibrating sieve, and the powder with a mesh size of 270~900 was collected and vacuum dried at 115℃ for 2 hours.

[0063] (3) 3D printing: 3D printing is performed on a substrate by layer-by-layer powder deposition and laser sintering. Oxygen is removed by evacuating and purging with argon gas to maintain an oxygen content below 3000 ppm. Deoxygenation begins when the content exceeds 2000 ppm and stops when it falls below 1000 ppm. A checkerboard scanning strategy is used, rotating 60° layer by layer. Printing parameters include 170W power, 1100mm / s scanning speed, 70μm scanning spacing, 30μm layer thickness, and 65μm spot diameter.

[0064] (4) Stress relief annealing: Stress relief annealing is carried out under argon atmosphere protection: the temperature is raised to 970℃ at a heating rate of 20℃ / min, held for 90min, cooled to below 400℃ with the furnace, and then air-cooled to room temperature.

[0065] Example 3

[0066] This embodiment provides a 3D printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 26%, Mo 5%, Si 1%, B 0.05%, with the balance being Co and unavoidable impurities (content less than 0.5%).

[0067] The method for preparing this removable dental prosthesis is as follows:

[0068] (1) Master alloy smelting: The elements other than B are batched according to the chemical composition, and the batched raw materials are added to a vacuum induction furnace to smelt into a master alloy ingot. The vacuum degree in the furnace during the refining period should be higher than 1.0 × 10⁻⁶. -2 Pa.

[0069] (2) Secondary melting and atomization powder making: The master alloy ingot is placed in a vacuum induction gas atomization powder making equipment, deoxidized carbon is added for refining, and NiB20 is added after refining. After being kept at 1650℃ in the intermediate ladle, it flows out through the guide pipe and is atomized under the pressure impact of argon gas flow.

[0070] (3) Sieving and drying: The cobalt-chromium alloy powder was sieved using an ultrasonic vibrating sieve, and the powder with a mesh size of 270~900 was collected and vacuum dried at 130℃ for 2 hours.

[0071] (4) 3D printing: 3D printing is performed on a substrate by layer-by-layer powder deposition and laser sintering. Oxygen is removed by purging with argon gas to maintain an oxygen content below 3000 ppm; deoxygenation begins when the content exceeds 2000 ppm and stops when it falls below 1000 ppm. A checkerboard scanning strategy is used, rotating 60° layer by layer. Printing parameters include 170W power, 1100mm / s scanning speed, 70μm scanning spacing, 30μm layer thickness, and 65μm spot diameter.

[0072] (5) Stress relief annealing: Stress relief annealing is carried out under argon atmosphere protection: the temperature is raised to 1000℃ at a heating rate of 20℃ / min, held for 60min, cooled to below 400℃ in the furnace, and then air-cooled to room temperature.

[0073] Example 4

[0074] This embodiment provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 27%, Mo 5%, Si 0.5%, B 0.03%, with the balance being Co and unavoidable impurities (content less than 0.5%).

[0075] The method for preparing this removable dental prosthesis is the same as in Example 3.

[0076] Example 5

[0077] This embodiment provides a 3D printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 27%, Mo 4%, Si 1.5%, B 0.02%, with the balance being Co and unavoidable impurities (content less than 0.5%).

[0078] The method for preparing this removable dental prosthesis is the same as in Example 3.

[0079] Example 6

[0080] This embodiment provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder is the same as that in Embodiment 3, but the following steps are different:

[0081] (6) Stress relief annealing: Stress relief annealing is carried out under argon atmosphere protection: the temperature is raised to 900℃ at a heating rate of 20℃ / min, held for 60min, cooled to below 400℃ in the furnace, and then air-cooled to room temperature.

[0082] Example 7

[0083] This embodiment provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder is the same as that in Embodiment 3, but the following steps are different:

[0084] (4) 3D printing: 3D printing is performed on a substrate by layer-by-layer powder deposition and laser sintering. Oxygen is removed by evacuating and purging with argon gas to maintain an oxygen content below 3000 ppm. Deoxygenation begins when the content exceeds 2000 ppm and stops when it falls below 1000 ppm. A checkerboard scanning strategy is used, rotating 45° layer by layer. Printing parameters include 120W power, 900mm / s scanning speed, 60μm scanning spacing, 20μm layer thickness, and 65μm spot diameter.

[0085] Example 8

[0086] This embodiment provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder is the same as that in Embodiment 3, but the following steps are different:

[0087] (4) 3D printing: 3D printing is performed on a substrate by layer-by-layer powder deposition and laser sintering. Oxygen is removed by evacuating and purging with argon gas to maintain an oxygen content below 3000 ppm. Deoxygenation begins when the oxygen content exceeds 2000 ppm and stops when it falls below 1000 ppm. A checkerboard scanning strategy is used, rotating 80° layer by layer. Printing parameters include 180W power, 1400mm / s scanning speed, 80μm scanning spacing, 40μm layer thickness, and 50μm spot diameter.

[0088] Comparative Example 1

[0089] This comparative example provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 26.5%, Mo 4.8%, W 5.5%, Si 1.1%, with the balance being Co and unavoidable impurities (content less than 0.5%). It does not contain element B.

[0090] The method for preparing this removable dental prosthesis is the same as in Example 3.

[0091] Comparative Example 2

[0092] This comparative example provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 26%, Mo 5%, Si 1%, with the balance being Co and unavoidable impurities (content less than 0.5%), and it does not contain element B.

[0093] Comparative Example 3

[0094] This comparative example provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 26%, Mo 5%, Si 1%, B 0.1% (B in excess), with the balance being Co and unavoidable impurities (content less than 0.5%).

[0095] The method for preparing this removable dental prosthesis is the same as in Example 3.

[0096] Comparative Example 4

[0097] This comparative example provides a 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis. The elemental composition of the cobalt-chromium-molybdenum alloy powder, by weight percentage, is Cr 26%, Mo 5%, Si 1%, with the balance being Co and unavoidable impurities (content less than 0.5%), and it does not contain element B.

[0098] The preparation method of this dental removable prosthesis is the same as that in Example 3, except that the stress-relief annealing is as follows: the temperature is raised to 1200°C at a heating rate of 20°C / min, held for 60 min, cooled to below 400°C in the furnace, and then air-cooled to room temperature.

[0099] Performance testing

[0100] I. Mechanical property testing

[0101] 1. Testing method:

[0102] Mechanical properties (including tensile strength, yield strength, and elongation after fracture) were tested in accordance with the industry standard "YY1702-2020 Laser Selective Melting Metal Materials for Additive Manufacturing of Dental Fixed and Removable Prostheses".

[0103] 2. Test Results:

[0104] As shown in Table 1.

[0105] Table 1.

[0106]

[0107] As can be seen from Example 3 and Comparative Example 1, the test pieces prepared using conventional components exhibit significantly lower plasticity than those of the present invention under the same heat treatment conditions.

[0108] As can be seen from Example 3, Comparative Example 1 and Comparative Example 2, removing the addition of element W can enhance plasticity to a certain extent, but without the addition of element B, the effect of improving plasticity is limited.

[0109] As can be seen from Example 3 and Comparative Example 3, excessive addition of element B will lead to grain boundary embrittlement, which will reduce the elongation after fracture of the material.

[0110] As can be seen from Example 3 and Comparative Example 4, the elongation after fracture of the alloy without element B can be close to the level of Example 3 after using a high-temperature heat treatment process.

[0111] II. Microscopic organizational characterization:

[0112] The microstructure of cobalt-chromium-molybdenum alloy dental removable restorations was characterized using XRD, such as... Figure 1-2 As shown.

[0113] Figure 1 XRD patterns of the gold dental removable prosthesis provided in this application: (a) Example 1; (b) Example 2; (c) Example 3; (d) Comparative Example 1; (e) Comparative Example 4.

[0114] Depend on Figure 1 It can be seen that no obvious diffraction peaks were produced at the diffraction angles of the 101 crystal plane unique to ℇ-Co (hcp phase) in Examples 1 to 3, indicating that Examples 1 to 3 effectively suppressed the transformation from α-Co (fcc phase) to ℇ-Co (hcp phase).

[0115] Depend on Figure 1 -d and Figure 1 -(a~c) It can be observed that the diffraction angle of the 101 crystal plane, unique to the ℇ-Co (hcp phase), in Comparative Example 1 shows obvious diffraction peaks, indicating that the phase composition of Comparative Example 1 is dominated by the ℇ-Co (hcp phase). Since hcp has fewer slip systems than the fcc phase, the increased number of phase transition interfaces during the fcc-hcp phase transition leads to an increase in the precipitation of the second phase enriched at the phase interfaces. The precipitated second phase hinders dislocation movement. Therefore, the plasticity of Comparative Example 1 is significantly reduced. (Comparison) Figure 1 -e and Figure 1 As can be seen from -d, the diffraction angle of the 101 crystal plane, which is unique to ℇ-Co (hcp phase) in Comparative Example 4, shows a low diffraction peak, indicating that Comparative Example 4 is dominated by α-Co (fcc phase) and contains a small amount of ℇ-Co (hcp phase).

[0116] Figure 2 Microscopic images of the cobalt-chromium-molybdenum alloy dental removable prosthesis provided in this application: (a) Example 1; (b) Example 2; (c) Example 3; (d) Comparative Example 1; (e) Comparative Example 4.

[0117] Depend on Figure 2 visible, Figure 2 - (a~c) As the heat treatment temperature increases, the amount of the second phase precipitated gradually decreases, while the corresponding elongation after fracture gradually increases, and the second phase precipitation is mainly concentrated on the grain boundaries.

[0118] contrast Figure 2 -d and Figure 2 - (a~c) It can be found that Comparative Example 1 not only has large-sized second phase precipitates at the grain boundaries, but also has densely packed second phase precipitates in a diffuse manner throughout the entire structure. Correspondingly, the elongation after fracture of Comparative Example 1 is only 4.2%. The large amount of second phase precipitates significantly reduces the plasticity of the repair (3D printed part).

[0119] contrast Figure 2 -e and Figure 2 -d It can be seen that, due to the increase of the heat treatment temperature to 1200℃, the large amount of the second term precipitate generated during the heat treatment process in Comparative Example 4 has been dissolved in the matrix, so Comparative Example 4 also has high plasticity.

[0120] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A 3D-printed cobalt-chromium-molybdenum alloy dental removable prosthesis, characterized in that, The dental removable prosthesis is made of cobalt-chromium-molybdenum alloy and formed by selective laser melting technology; The cobalt-chromium-molybdenum alloy is composed of the following elements by weight percentage: Cr 26~30%, Mo 4~7%, Si 0.5~1.5%, B 0.01%~0.05%, with the balance being Co and unavoidable impurities; wherein the cobalt-chromium-molybdenum alloy does not contain W and Ta, and the total amount of unavoidable impurities is less than 0.5%; The dental removable prosthesis undergoes stress-relieving annealing at a temperature range of 950℃ to 1000℃, and the elongation after fracture of the dental removable prosthesis after annealing is not less than 20%.

2. The 3D printed cobalt-chromium-molybdenum dental mobile restoration according to claim 1, characterized in that After annealing, the tensile strength of the dental removable prosthesis is not less than 1000 MPa and the yield strength is not less than 740 MPa.

3. The 3D printed cobalt-chromium-molybdenum dental mobile restoration according to claim 1, characterized in that The annealing process is carried out in a protective atmosphere or vacuum environment, and the holding time is 60~90 minutes.

4. The 3D printed cobalt-chromium-molybdenum dental mobile restoration according to claim 1, characterized in that The dental removable prosthesis is a framework, clasp, or base of a removable partial denture.

5. Cobalt-chromium-molybdenum alloy powder for the production of a dental mobile restoration according to any one of claims 1 to 4, characterized in that The cobalt-chromium-molybdenum alloy powder has the following composition by weight percentage: Cr 26%~30%, Mo 4%~8%, Si 0.5%~1.5%, B 0.01%~0.05%, with the balance being Co and unavoidable impurities; wherein the cobalt-chromium-molybdenum alloy powder does not contain W and Ta, and the total amount of unavoidable impurities is less than 0.5%.

6. A method of producing a dental mobile restoration according to any one of claims 1 to 4, characterized in that It includes: Provide the cobalt-chromium-molybdenum alloy powder as described in claim 5; Under an inert atmosphere, the cobalt-chromium-molybdenum alloy powder is printed layer by layer into a repair blank using laser selective melting technology; The repair blank is subjected to stress-relief annealing under a protective atmosphere or vacuum: the temperature is raised to 900℃~1000℃, held for 60~90 minutes, and then cooled.

7. The method of making a dental veneer according to claim 6, wherein, The process parameters for laser selective melting are as follows: laser power 120~180W, scanning speed 900~1400 mm / s, scanning spacing 60~80 μm, layer thickness 20~40 μm, spot diameter 50~65 μm, and a checkerboard scanning strategy is adopted, rotating 45~80° layer by layer.

8. The method of claim 6, wherein the dental restoration is a dental veneer. The cobalt-chromium-molybdenum alloy powder is prepared by the following method: Prepare raw materials by weight percentage of Cr 26%~30%, Mo 4%~8%, Si 0.5%~1.5%, with the balance being Co, and then perform vacuum melting to obtain an alloy melt. A boron-containing additive is added to the alloy melt to achieve a boron content of 0.01% to 0.05% in the alloy. The alloy melt with added boron is kept at a constant temperature in an tundish and then flows out through a guide pipe. It is then atomized with high-pressure inert gas to obtain alloy powder. The alloy powder obtained by atomization is sieved, and powder within the target particle size range is collected and vacuum dried.

9. The method of claim 8, wherein the dental restoration is a dental veneer. 5 The temperature for heat preservation in the tundish is 1500~1650℃.

10. The method of claim 8, wherein the dental restoration is a dental veneer. When sieving the alloy powder obtained by atomization, the target particle size range of the alloy powder is 270-900 mesh, and the drying temperature of the alloy powder is 100-130℃ and the drying time is 1-3h.

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