A method for preparing a 3D printed titanium alloy-based ceramic crown by micro-arc oxidation and a product thereof

Abstract

The present application relates to a kind of 3D printing titanium alloy-based ceramic crown micro-arc oxidation preparation method and product, belong to dental restoration preparation.The present application discloses a kind of 3D printing titanium alloy-based ceramic crown micro-arc oxidation preparation method and the 3D printing titanium alloy-based ceramic crown prepared, aims to solve the technical problems such as the ceramic layer of existing composite crown easy to fall off, performance is uneven, biological compatibility is insufficient, preparation process is complicated, etc., by 3D printing accurate preparation titanium alloy dental crown matrix, in situ generation even, dense, ceramic film layer with strong binding force on the surface of matrix, form the composite structure of " internal titanium alloy, external ceramic", give consideration to the high strength, toughness and biological compatibility of titanium alloy, and the aesthetic, wear resistance and corrosion resistance of ceramic, simplify preparation procedure, improve the adaptability and service life of dental crown, meet the dental clinical repair needs.

Description

Technical Field

[0001] This invention belongs to the field of dental prosthesis preparation technology, and relates to a micro-arc oxidation preparation method and product for 3D printed titanium alloy-based ceramic crowns. Background Technology

[0002] Dental crown restoration is a common method used in dental clinics to treat tooth defects, tooth discoloration, and tooth malformation. Its core requirements are biocompatibility, mechanical strength, wear resistance, and aesthetics, while also adapting to the complex physiological environment of the oral cavity (such as saliva corrosion, chewing force, temperature changes, etc.). Currently, the commonly used dental crown materials in clinical practice are mainly divided into three categories: metal crowns, ceramic crowns, and metal-ceramic composite crowns. Each type of material has obvious limitations: (1) Metal crowns (such as titanium alloys and cobalt-chromium alloys): have high mechanical strength, good toughness, excellent biocompatibility, and relatively moderate price. However, their surface gloss is very different from that of natural teeth, and their aesthetics are poor. Long-term use is prone to metal ion precipitation, which may cause oral mucosal irritation. At the same time, the surface is easily worn, affecting chewing comfort; (2) All-ceramic crowns (such as zirconia and alumina ceramics): have excellent aesthetics and can simulate the color and transparency of natural teeth. Wear-resistant and corrosion-resistant, with no risk of metal ion precipitation, but lacking mechanical toughness and impact resistance, it is prone to cracking when chewing hard objects. Moreover, the preparation process is complex and costly, and the accuracy is difficult to guarantee when adapting to complex tooth morphology. (3) Traditional metal-ceramic composite crown: It adopts a combination of metal base and ceramic surface sintering, which takes into account the strength of metal and the aesthetics of ceramic. However, the thermal expansion coefficients of metal and ceramic are quite different. During the sintering process, the ceramic layer is prone to fall off and crack. The edge of the metal base is easily exposed, affecting the aesthetics. At the same time, the preparation process requires multiple grinding and sintering, which is complicated and inefficient.

[0003] With the development of 3D printing technology, the precision and efficiency of titanium alloy crown fabrication have been significantly improved. 3D printing can accurately replicate the morphology of a patient's teeth, producing highly fitting and personalized titanium alloy crown substrates. However, simply 3D printing titanium alloy crowns still suffers from poor aesthetics and insufficient surface wear resistance. Micro-arc oxidation technology is a surface modification technique that generates a ceramic film in situ on the metal surface. Through an electrochemical reaction, a dense and strongly bonded ceramic film can be formed on the titanium alloy surface. This film combines the wear resistance, corrosion resistance, and aesthetics of ceramics, and is metallurgically bonded to the metal substrate, making it less prone to detachment. This provides an effective way to solve the aesthetic and wear resistance problems of titanium alloy crowns.

[0004] The existing surface modification methods and composite crown preparation technologies for 3D printed titanium alloy crowns still have the following shortcomings: (1) Weak bonding between ceramic layer and titanium alloy matrix: Traditional metal-ceramic composite crowns are sintered, which can easily cause the ceramic layer to fall off due to mismatch in thermal expansion coefficients. When the existing micro-arc oxidation process is used for crowns, the micro-arc oxidation ceramic film layer is not tightly bonded to the matrix due to the presence of pores and residual powder on the surface of 3D printed titanium alloy. After long-term chewing stress, it is easy to crack and fall off; (2) Uneven performance of ceramic film layer: 3D printed titanium alloy crowns have problems of uneven surface roughness and uneven microstructure. The existing micro-arc oxidation process uses a single parameter, which can easily lead to uneven thickness and color of ceramic film layer. (2) The existing composite crowns cannot meet the aesthetic requirements of the crowns, and the hardness and wear resistance of the film layer are insufficient, making it difficult to adapt to the long-term chewing needs of the oral cavity; (3) Biocompatibility needs to be improved: The oral environment is complex, and the electrolytes and bacteria in saliva can easily corrode the surface of the crown. The existing micro-arc oxidation ceramic film layer has insufficient bioactivity and cannot inhibit bacterial growth. In addition, some processes use toxic and harmful electrolytes, which may cause oral mucosal irritation; (4) The preparation process is complicated and the precision is insufficient: The existing composite crowns are mostly prepared by first 3D printing a metal base, then surface polishing, degreasing, and micro-arc oxidation. Some also require subsequent ceramic sintering. The process is complicated and can easily lead to a decrease in the precision of the crown shape, making it impossible to accurately adapt to the patient's tooth body and affecting the restoration effect.

[0005] Therefore, developing a 3D-printed titanium alloy-based ceramic crown with a simple and high-precision manufacturing process, a tight bond between the ceramic film and the titanium alloy matrix, uniform performance, and high strength, aesthetics, biocompatibility, and wear resistance, as well as its manufacturing method, has become an urgent technical problem to be solved in the field of dental restoration. Summary of the Invention

[0006] In view of this, one objective of the present invention is to provide a micro-arc oxidation preparation method for 3D printed titanium alloy-based ceramic dental crowns; another objective of the present invention is to provide a 3D printed titanium alloy-based ceramic dental crown prepared by the micro-arc oxidation preparation method for 3D printed titanium alloy-based ceramic dental crowns. The present invention aims to solve the technical problems of existing composite dental crowns, such as easy detachment of the ceramic layer, uneven performance, insufficient biocompatibility, and cumbersome preparation processes. By precisely preparing a titanium alloy dental crown substrate through 3D printing, combined with a graded micro-arc oxidation process, a uniform, dense, and strongly bonded ceramic film layer is generated in situ on the substrate surface, forming a composite structure of "inner titanium alloy, outer ceramic," which takes into account the high strength, toughness, and biocompatibility of titanium alloy, as well as the aesthetics, wear resistance, and corrosion resistance of ceramic. This simplifies the preparation process, improves the adaptability and service life of the dental crown, and meets the needs of dental clinical restoration.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing 3D-printed titanium alloy-based ceramic dental crowns using micro-arc oxidation, the method comprising the following steps: S1, Preparation of titanium alloy dental crown matrix: (1) Scanning and modeling: Obtain the three-dimensional data of the patient's target tooth through an oral scanning device, design the crown shape using dental design software, and generate a three-dimensional model of the crown; (2) 3D printing parameter adjustment: Select medical pure titanium or Ti6Al4V titanium alloy powder as printing material, and use the laser powder bed melting (LPBF) method to 3D print according to the three-dimensional model of the crown to obtain the 3D printed matrix; (3) Post-processing of matrix: Remove the support structure on the surface of the 3D printed matrix, polish it step by step with sandpaper, and then perform vacuum annealing treatment and cool it to room temperature in the furnace to obtain the titanium alloy dental crown matrix; S2, Pretreatment of titanium alloy crown matrix: The titanium alloy crown matrix is ​​sequentially subjected to degreasing, acid washing and activation, water washing and drying to obtain a pretreated titanium alloy crown matrix; S3, graded micro-arc oxidation treatment: The pretreated titanium alloy crown substrate is used as the anode and the graphite electrode is used as the cathode. It is placed in a biocompatible composite electrolyte and fixed with a detachable special clamp to ensure good conductivity and no oxidation dead corners. After graded micro-arc oxidation treatment, the titanium alloy crown substrate with micro-arc oxidation treatment can be obtained. S4, Post-treatment of crowns: The titanium alloy crown substrate that has undergone micro-arc oxidation treatment is rinsed with deionized water, then subjected to low-temperature curing treatment, and finally finely ground and polished. S5, Quality Inspection: Inspect the performance, morphology, and fit of the ceramic film layer of the post-processed crown in S4. If the preset requirements are not met, return to steps S3 and S4 to re-oxidize until the preset requirements are met to obtain the 3D printed titanium alloy-based ceramic crown.

[0008] Preferably, in step (1) of S1, the purity of the medical pure titanium or Ti6Al4V titanium alloy powder is ≥99.9%, the sphericity is ≥90%, and the particle size is 15~53μm; In step (2) of S1, the specific parameters of the 3D printing are: laser power 180-220W, scanning speed 800-1200mm / s, layer thickness 20-40μm, scanning spacing 80-120μm, printing atmosphere is argon protection, argon flow rate 0.8-1.2L / min; In step (3) of S1, the annealing temperature is 600-700℃ and the holding time is 30-60min. The surface roughness (Ra) of the titanium alloy crown matrix prepared after vacuum annealing is ≤0.8μm and the density is ≥99%.

[0009] Preferably, in S2, the degreasing and oil removal uses an environmentally friendly alkaline degreasing agent, wherein the alkaline degreasing agent consists of sodium hydroxide at a concentration of 40-60 g / L, sodium carbonate at a concentration of 20-40 g / L, and a nonionic surfactant at a concentration of 1-3 g / L. The degreasing and oil removal process uses ultrasonic cleaning at 40-60 kHz, and the degreasing and oil removal temperature is 40-50°C and the degreasing time is 10-15 min. In S2, the pickling activation uses a mixed acid solution of hydrofluoric acid and nitric acid, wherein the concentration of hydrofluoric acid is 5-10 vol% and the concentration of nitric acid is 15-25 vol%, and the pickling activation temperature is 20-25°C and the pickling time is 0.5-1.5 min. In S2, the surface roughness of the acid-washed and activated titanium alloy crown matrix is ​​Ra = 0.3-0.5 μm; In S2, the water washing and drying is carried out using vacuum drying, with a drying temperature of 60-80℃, a drying time of 10-15 min, and a vacuum degree of 0.05-0.08 MPa.

[0010] Preferably, in S3, the biocompatible composite electrolyte comprises the following components: sodium dihydrogen phosphate at a concentration of 8–15 g / L, silicic acid at a concentration of 5–10 g / L, sodium fluoride at a concentration of 0.5–2 g / L, zirconium oxide powder at a concentration of 1–3 g / L, medical-grade zinc oxide at a concentration of 0.3–0.8 g / L, and deionized water. The pH of the biocompatible composite electrolyte is 6.5–7.5, and the particle size of the zirconium oxide powder is 50–100 nm. The biocompatible composite electrolyte also includes 0.1–0.3 g / L of medical-grade cerium oxide; The pH value of the biocompatible composite electrolyte is adjusted by citric acid or sodium hydroxide.

[0011] Preferably, in step S3, the graded micro-arc oxidation includes a film-forming stage, a densification stage, and an aesthetic modification stage. The specific parameters for the hierarchical micro-arc oxidation are as follows: (1) Film formation stage: voltage 80-120V, current density 5-10A / dm 2 The oxidation time is 10–15 min, and the electrolyte temperature is 25–30 °C. (2) Densification stage: voltage 150-180V, current density 10-15A / dm 2 The oxidation time is 15–20 min, and the electrolyte temperature is 30–35 °C. (3) Aesthetic finishing stage: voltage 120-150V, current density 8-12A / dm 2The oxidation time is 5-10 min and the electrolyte temperature is 28-32℃.

[0012] Preferably, in S3, during the micro-arc oxidation process, the biocompatible composite electrolyte is continuously stirred and monitored in real time by a stirring device. The stirring speed is 150-250 r / min. When the real-time monitoring detects that the temperature exceeds 35°C, the cooling device is activated to reduce the temperature. In S3, argon gas with a flow rate of 0.5 to 0.8 L / min is used for protection during the micro-arc oxidation process, and the detachable special fixture used in the micro-arc oxidation process is made of titanium alloy with surface insulation treatment.

[0013] Preferably, in S4, the temperature of the low-temperature curing treatment is 300-400°C and the holding time is 20-30 minutes, and inert gas protection is used during the low-temperature curing treatment. The fine polishing is done using 3000#-5000# sandpaper; The polishing process uses diamond polishing paste. The surface roughness Ra of the titanium alloy dental crown substrate obtained after the fine grinding and polishing is ≤0.2μm.

[0014] Preferably, in S5, the preset standard is as follows: the ceramic film thickness is 8-20 μm, the thickness uniformity error is ≤ ±1 μm, the film bonding strength is ≥30 MPa, there is no peeling in the cross-cut test, the ceramic film hardness is ≥800 HV, the friction coefficient is ≤0.3, the cytotoxicity is ≤1 and there is no sensitization, and the crown fitting gap is ≤0.05 mm.

[0015] The present invention also provides a 3D printed titanium alloy-based ceramic dental crown prepared according to the above preparation method.

[0016] Preferably, the 3D-printed titanium alloy-based ceramic crown is a composite structure of "inner titanium alloy and outer ceramic", including a titanium alloy matrix and a micro-arc oxidation ceramic film layer; The titanium alloy matrix is ​​prepared by 3D printing and is made of medical pure titanium or Ti6Al4V titanium alloy. The micro-arc oxidation ceramic film is generated in situ on the surface of the titanium alloy substrate and is metallurgically bonded to the titanium alloy substrate. The main components of the film are TiO2, ZrO2 and SiO2. The thickness of the micro-arc oxidation ceramic film is 8-20 μm and the surface is smooth and the color is uniform. The surface of the micro-arc oxidation ceramic film is distributed with nanoscale micropores of 50-200 nm, and the film contains zinc oxide and / or cerium oxide with antibacterial properties.

[0017] The beneficial effects of the present invention are as follows: The present invention discloses a micro-arc oxidation preparation method for 3D printed titanium alloy-based ceramic crowns and the 3D printed titanium alloy-based ceramic crowns prepared therefrom. Compared with the prior art, it has the following beneficial effects: (1) The composite structure has significant advantages and takes into account multiple performance aspects: The composite structure of “internal titanium alloy and external ceramic” is adopted. The titanium alloy matrix provides excellent mechanical strength, toughness and biocompatibility. It can withstand long-term chewing force in the oral cavity, avoid crown cracking, and has no risk of metal ion precipitation. The micro-arc oxidation ceramic film is generated in situ and metallurgically combined with the matrix. The bonding force is strong and it is not easy to fall off. At the same time, it has the aesthetics, wear resistance and corrosion resistance of ceramics. The color is similar to that of natural teeth, which solves the problems of poor aesthetics of traditional metal crowns, insufficient toughness of ceramic crowns and easy fall off of traditional composite crowns. (2) High precision and good adaptability: The laser powder bed fusion 3D printing process can accurately replicate the three-dimensional data of the patient's teeth to prepare a highly fitting and personalized titanium alloy crown matrix with a fit gap of ≤0.05mm. No need for extensive subsequent polishing, avoiding a decrease in the precision of the crown shape. At the same time, the synergistic optimization of 3D printing parameters and micro-arc oxidation parameters can ensure that the ceramic film layer has uniform thickness and consistent color, adapting to the tooth shape and aesthetic needs of different patients. (3) Excellent performance and long service life of ceramic film layer: The graded micro-arc oxidation process combined with a special composite electrolyte makes the ceramic film layer dense and uniform, with a hardness of ≥800HV, wear-resistant and corrosion-resistant, and a friction coefficient of ≤0.3, which can withstand long-term chewing wear in the oral cavity. The zinc oxide and cerium oxide components added to the film layer give the crown good antibacterial properties, inhibit bacterial growth, and reduce the risk of oral infection. The low-temperature curing treatment further improves the density and bonding of the film layer, extending the service life of the crown. The expected service life can reach more than 10 years. (4) Excellent biocompatibility and suitability for the oral environment: The titanium alloy matrix is ​​made of medical-grade pure titanium or Ti6Al4V titanium alloy with a purity of ≥99.9%, exhibiting excellent biocompatibility and being non-allergenic and non-cytotoxic; the micro-arc oxidation electrolyte uses environmentally friendly components and does not contain toxic or harmful ingredients; the biocompatibility of the ceramic membrane meets the standards for medical dental materials, and it can be well compatible with oral mucosal tissue, avoiding oral irritation and suitable for long-term oral implantation. (5) Simple preparation process, high efficiency and low cost: The integration of 3D printing, graded micro-arc oxidation and simple post-processing steps eliminates the need for multiple sintering and polishing of traditional composite crowns, simplifying the preparation process and shortening the production cycle; the electrolyte can be recycled, reducing processing costs; 3D printing enables personalized mass production, improving preparation efficiency and meeting the personalized restoration needs of dental clinics.

[0018] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the fabrication process of the 3D-printed titanium alloy-based ceramic dental crown of the present invention; Figure 2 This is a schematic diagram of the structure of the 3D-printed titanium alloy-based ceramic dental crown of the present invention. Detailed Implementation

[0020] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0021] Example 1 For the restoration of damaged anterior teeth, a 3D-printed pure titanium-based ceramic crown was prepared. The specific steps of the preparation method are as follows: S1. Design of dental crown model and 3D printing preparation of titanium alloy matrix (1) Scanning and modeling: Three-dimensional data of the anterior tooth defect site of the patient is obtained by oral CBCT scanning equipment. The crown shape is designed using Exocad dental design software, the occlusal surface and crown margin are optimized to ensure fit, and a three-dimensional model of the crown is generated. (2) 3D printing parameter adjustment: Medical pure titanium powder with a purity of 99.95% was selected, with a powder particle size of 15-53μm and a sphericity of 92%. Laser powder bed fusion (LPBF) process was used for printing. The parameters are as follows: laser power 200W, scanning speed 1000mm / s, layer thickness 30μm, scanning spacing 100μm, argon flow rate 1.0L / min, and room temperature printing. (3) Substrate post-treatment: Remove the support structure, and polish with 800#, 1200# and 2000# sandpaper in stages to remove burrs and residual powder; vacuum annealing treatment, temperature 650℃, heat for 45min, and furnace cooling. After annealing, the surface roughness of the substrate Ra=0.6μm and the density is 99.2%.

[0022] S2, Matrix Pretreatment (1) Degreasing and oil removal: Prepare an alkaline degreasing agent (50g / L sodium hydroxide, 30g / L sodium carbonate, 2g / L polyethylene glycol octylphenyl ether, and the remainder is deionized water), place it into the crown matrix, and clean it with ultrasonic waves at 45kHz for 12 minutes at 45℃; rinse twice with deionized water. (2) Pickling and activation: Mixed acid solution (8 vol% hydrofluoric acid, 20 vol% nitric acid, the remainder is deionized water), temperature 23℃, pickling for 1 min; rinsed 4 times with deionized water; (3) Water washing and drying: vacuum drying oven, temperature 70℃, vacuum degree 0.06MPa, drying for 12min, the surface roughness of the substrate after acid washing Ra=0.4μm.

[0023] S3, Preparation of Micro-arc Oxidation Electrolyte Sodium dihydrogen phosphate 12g / L, sodium silicate 8g / L, sodium fluoride 1.2g / L, zirconium oxide powder 2g / L (particle size 80nm), medical grade zinc oxide 0.5g / L, medical grade cerium oxide 0.2g / L, the remainder being deionized water; stir well, adjust the pH to 7.0, and let stand for 1.5h for later use.

[0024] S4, graded micro-arc oxidation treatment The titanium alloy crown serves as the anode, graphite as the cathode, and is fixed in place by a special titanium alloy clamp with a contact resistance of 0.08Ω; the argon flow rate is 0.6L / min, the stirring speed is 200r / min, and the cooling device provides real-time temperature control. (1) Film formation stage: voltage 100V, current density 8A / dm 2 Time: 12 min; Electrolyte temperature: 28℃; (2) Densification stage: voltage 160V, current density 12A / dm 2 Time: 18 min; Electrolyte temperature: 32℃; (3) Aesthetic finishing stage: Voltage 130V, current density 10A / dm 2 The time was 8 minutes and the electrolyte temperature was 30℃.

[0025] S5, Post-coronation treatment Rinse with deionized water to remove residual electrolyte, under nitrogen protection (flow rate 0.8 L / min), low-temperature curing temperature 350℃, hold for 25 min, and cool with the furnace; polish with 3000# and 5000# sandpaper, polish with diamond polishing paste, correct the interlocking surface, and achieve a surface roughness Ra=0.15μm.

[0026] S6, Quality Inspection The test results are as follows: the ceramic coating thickness is 14μm, the thickness uniformity error is ±0.8μm, the color is milky white, matching the natural anterior teeth; the coating bonding strength is 35MPa, and there is no detachment in the cross-cut test; the surface hardness is 850HV, the coefficient of friction is 0.25, and the wear is 0.008mm. 3 / (N·m); Cytotoxicity grade 1, non-sensitizing; Crown occlusion gap 0.04mm, good occlusion, meeting the needs of anterior tooth restoration.

[0027] Example 2 For the restoration of posterior tooth defects, a 3D-printed Ti6Al4V titanium alloy-based ceramic crown was prepared. The specific steps of the preparation method are as follows: S1. Design of dental crown model and 3D printing preparation of titanium alloy matrix (1) Scanning and modeling: Oral scans are used to obtain three-dimensional data of posterior teeth. Dental design software is used to design crowns, optimize the load-bearing structure of the occlusal surface, and generate three-dimensional models. (2) 3D printing parameter adjustment: Ti6Al4V titanium alloy powder, purity 99.9%, particle size 15-53μm, sphericity 90%, LPBF process printing: laser power 210W, scanning speed 900mm / s, layer thickness 35μm, scanning spacing 110μm, argon flow rate 1.1L / min; (3) Substrate post-treatment: Remove the support, polish with 800#-2000# sandpaper, vacuum anneal at 680℃, hold for 50min, after annealing the surface roughness Ra=0.7μm and the density 99.1%.

[0028] S2, Matrix Pretreatment Alkaline degreasing agent (sodium hydroxide 55g / L, sodium carbonate 35g / L, polyethylene glycol octylphenyl ether 2.5g / L), ultrasonic cleaning at 50kHz, temperature 48℃, time 14min; mixed acid solution (hydrofluoric acid 9vol%, nitric acid 22vol%), acid washing for 1.2min; vacuum drying at 75℃, 0.07MPa, drying for 13min, after acid washing Ra=0.45μm.

[0029] S3, Preparation of Micro-arc Oxidation Electrolyte Sodium dihydrogen phosphate 14g / L, sodium silicate 9g / L, sodium fluoride 1.5g / L, zirconium oxide powder 2.5g / L (particle size 90nm), medical grade zinc oxide 0.6g / L, cerium oxide 0.25g / L, deionized water to make up the difference; pH value 7.2, let stand for 2 hours before use.

[0030] S4, graded micro-arc oxidation treatment Anode: dental crown; cathode: graphite; contact resistance: 0.07Ω; argon flow rate: 0.7L / min; stirring speed: 220r / min. (1) Film formation stage: voltage 110V, current density 9A / dm 2 Time: 14 minutes; Temperature: 29℃; (2) Densification stage: voltage 170V, current density 13A / dm 2 Time: 19 minutes; Temperature: 33℃; (3) Aesthetic finishing stage: Voltage 140V, current density 11A / dm 2 Time: 9 minutes, Temperature: 31℃

[0031] S5, Post-coronation treatment Rinse with deionized water, protect with argon gas (flow rate 0.9L / min), cure at low temperature 380℃, hold for 28min; polish with 3000#-5000# sandpaper, surface Ra=0.18μm.

[0032] S6, Quality Inspection The ceramic film is 17μm thick with a uniformity error of ±0.9μm. It is light yellow in color, matching the natural color of posterior teeth. The bonding strength is 38MPa, the surface hardness is 880HV, the coefficient of friction is 0.27, and the wear is 0.009mm³ / (N·m). It meets biocompatibility standards, has a bonding gap of 0.03mm, and provides good occlusal load-bearing capacity, meeting the chewing force requirements of posterior teeth.

[0033] A schematic diagram of the fabrication process of the 3D-printed titanium alloy-based ceramic dental crown of this invention is shown below. Figure 1As shown. The preparation method of the present invention has the following advantages: In step S1, the purity of medical pure titanium or Ti6Al4V titanium alloy powder is ≥99.9%, and the sphericity of the powder is ≥90%, which can improve the 3D printing accuracy and the density of the titanium alloy matrix, reduce surface porosity, and lay the foundation for the uniform growth of the subsequent micro-arc oxidation ceramic film; after vacuum annealing, the surface roughness Ra of the titanium alloy matrix is ​​≤0.8μm, ensuring surface flatness; in step S2, the surface roughness Ra of the acid-washed and activated titanium alloy crown matrix is ​​0.3-0.5μm, which avoids the surface being too smooth, affecting the bonding force of the ceramic film, and also prevents the surface being too rough, leading to… Uneven film thickness is caused by the use of polyethylene glycol octylphenyl ether as a nonionic surfactant, which is environmentally friendly and non-irritating, improving the degreasing effect and preventing residue from affecting subsequent micro-arc oxidation. In step S3, 0.1-0.3 g / L of medical-grade cerium oxide can be added to the electrolyte to enhance the antibacterial properties of the ceramic film, inhibit the growth of bacteria in the oral cavity, and improve the corrosion resistance of the film. The pH value of the electrolyte is adjusted by citric acid or sodium hydroxide to ensure the stability of the electrolyte system and prevent decomposition. In step S4, the detachable special clamp is made of titanium alloy with an insulating surface to prevent the clamp from reacting with the electrolyte and to ensure the safety of the tooth crown base. All parts of the crown can be evenly contacted with the electrolyte, especially for complex areas such as the occlusal surface and margins of the crown. The clamp angle can be adjusted to avoid oxidation dead zones. Simultaneously, during the micro-arc oxidation process in step S4, the argon gas flow rate in the argon protective atmosphere is 0.5-0.8 L / min to prevent oxidation damage to the titanium alloy substrate and ceramic film, thus improving the chemical stability of the film. In step S5, fine grinding is performed using 3000#-5000# sandpaper, and polishing is done with diamond polishing paste to ensure that the surface roughness Ra of the crown is ≤0.2μm, resulting in a smooth surface that reduces food residue and bacterial adhesion, while also improving aesthetics. Low-temperature curing is then performed. The process is protected by inert gas, and the inert gas is nitrogen or argon with a flow rate of 0.6-1.0 L / min. In step S6, the specific indicators for quality inspection are as follows: (1) Ceramic film: thickness is 8-20 μm, thickness uniformity error is ≤ ±1 μm, surface color is uniform, and there are no cracks, pinholes, or peeling. (2) Film bonding strength: cross-cut test is adopted, and there is no peeling or flaking after cross-cut test, and the bonding strength is ≥30 MPa. (3) Surface hardness: ceramic film hardness is ≥800 HV, and titanium alloy substrate hardness is ≥300 HV. (4) Wear resistance: friction coefficient is ≤0.3, and wear amount is ≤0.01 mm. 3 / (N·m); (5) Biocompatibility: Cytotoxicity ≤ Grade 1, no sensitization, meets the biocompatibility standard for medical dental materials; (6) Crown fit: The fit gap with the patient's three-dimensional tooth model is ≤ 0.05 mm, the occlusal surface fits well, and there is no warping.

[0034] Figure 2This is a schematic diagram of the structure of the 3D-printed titanium alloy-based ceramic dental crown prepared in Example 1 of the present invention.

[0035] The 3D-printed titanium alloy-based ceramic crown prepared by the method of this invention is a composite structure of "inner titanium alloy and outer ceramic". It includes a titanium alloy matrix (prepared by 3D printing, made of medical pure titanium or Ti6Al4V titanium alloy, whose shape is precisely adapted to the patient's target tooth, and whose surface is annealed and polished to achieve a density of ≥99%) and a micro-arc oxidation ceramic film (generated in situ on the surface of the titanium alloy matrix, and is metallurgically bonded to the matrix. The main components of the film are TiO2, ZrO2 and SiO2, with a thickness of 8-20μm, a smooth surface, and a uniform color, presenting a milky white or light yellow color similar to natural teeth). In addition, the surface of the micro-arc oxidation ceramic film has nano-sized micropores with a diameter of 50-200nm, which can enhance the bioactivity of the crown, promote the biocompatibility of oral mucosa tissue, and reduce food residue and bacterial adhesion. The ceramic film also contains zinc oxide and cerium oxide, which have good antibacterial properties and can inhibit the growth of common bacteria such as Escherichia coli and Staphylococcus aureus in the oral cavity.

[0036] Performance testing The performance of the 3D-printed titanium alloy-based ceramic dental crown prepared in Example 1 was tested, and the results are shown below: 1. Bonding strength test (scratch test / tensile test): (1) Critical load: ≥40N (scratch test), far exceeding conventional porcelain coating (≈20N); (2) Tensile bond strength: ≥30MPa, the fracture occurred in the matrix rather than the interface, proving that the bond strength is higher than that of the titanium alloy itself.

[0037] 2. The hardness of the film layer is close to that of zirconium oxide, which is much higher than that of natural teeth and titanium alloy substrates, and the wear resistance life is increased by 5 to 10 times. The hardness of the 3D printed titanium alloy-based ceramic crown prepared by this invention is shown in Table 1 below: Table 1 Hardness of different materials

[0038] 3. Wear resistance (coefficient of friction / wear rate): The coefficient of friction of the micro-arc oxidation ceramic film layer is 0.3~0.4 (dry friction), lower than that of titanium alloy (0.6~0.8); the wear rate is ≤1×10 -6 mm 3 / (N·m), which is more than 80% lower than that of titanium alloys.

[0039] 4. Mechanical properties of titanium alloy matrix prepared by 3D printing: tensile strength ≥900MPa, yield strength ≥800MPa, meeting the strength requirements for dental restoration (ISO22674); dimensional accuracy: ±0.02mm, with better adaptability than traditional casting (±0.1mm).

[0040] 5. Corrosion resistance salt spray test (5% NaCl, 35℃): Ceramic film prepared by graded micro-arc oxidation: ≥1000h no rust or peeling; Titanium alloy substrate prepared by 3D printing: <200h pitting corrosion.

[0041] 6. Long-term stability of the oral environment: Clinical simulated immersion (artificial saliva, 37℃, 6 months): The membrane showed no discoloration, dissolution, or peeling, and the surface morphology remained intact.

[0042] 7. Biocompatibility test (human gingival fibroblasts / MC3T3-E1 osteoblasts): Cell adhesion: The adhesion rate of the micro-arc oxidation ceramic film surface is ≥90% after 24 hours, which is higher than that of titanium alloy (≈70%), and the cells spread well.

[0043] Proliferation activity: After 7 days of culture, the cell viability of the MAO group was 20-30% higher than that of the titanium alloy group.

[0044] Osteogenic differentiation: Alkaline phosphatase (ALP) activity and osteocalcin (OCN) gene expression were significantly upregulated, and calcium and phosphorus deposition was close to that of human bone (Ca / P≈1.53).

[0045] 8. Clinical life expectancy prediction Based on accelerated aging tests (5000 cycles of hot and cold, 5℃~55℃): the ceramic film prepared by graded micro-arc oxidation showed no cracking or detachment, maintained a bonding strength of ≥85%, and had a predicted clinical service life of ≥15 years, which is higher than that of ordinary porcelain crowns (5~8 years).

[0046] 9. Comparison of crown preparation precision and clinical performance: The comparison results are shown in Table 2: Table 2 Comparison of crown preparation accuracy and clinical performance

[0047] Similarly, the performance of the 3D printed titanium alloy substrate and the graded micro-arc oxidation ceramic film prepared in Example 2 was tested. The results were basically consistent with those in Example 1. It can be seen that the 3D printed titanium alloy substrate and the graded micro-arc oxidation ceramic film prepared by the present invention have good bonding force, high surface hardness, wear resistance, and corrosion resistance. It takes into account mechanical, aesthetic and biocompatibility, simplifies the manufacturing process, makes precise adaptation, has biomimetic color and extended life, and meets the needs of high-end dental restoration.

[0048] In summary, this invention discloses a micro-arc oxidation preparation method for 3D printed titanium alloy-based ceramic crowns and the prepared 3D printed titanium alloy-based ceramic crowns. Compared with the prior art, it has the following beneficial effects: (1) The composite structure has significant advantages and takes into account multiple performance aspects: The composite structure of "internal titanium alloy and external ceramic" is adopted. The titanium alloy matrix provides excellent mechanical strength, toughness and biocompatibility, which can withstand long-term chewing force in the oral cavity, avoid crown cracking, and has no risk of metal ion precipitation; the micro-arc oxidation ceramic film is generated in situ and metallurgically bonded to the matrix. The bonding force is strong and it is not easy to fall off. At the same time, it has the aesthetics, wear resistance and corrosion resistance of ceramics. The color is similar to that of natural teeth, which solves the problems of poor aesthetics of traditional metal crowns, insufficient toughness of ceramic crowns and easy fall off of traditional composite crowns. (2) High precision and good adaptability: The laser powder bed fusion 3D printing process can accurately replicate the three-dimensional data of the patient's teeth to prepare a highly fitting and personalized titanium alloy crown matrix with a fit gap of ≤0.05mm. No need for extensive subsequent polishing, avoiding a decrease in the precision of the crown shape. At the same time, the synergistic optimization of 3D printing parameters and micro-arc oxidation parameters can ensure that the ceramic film layer has uniform thickness and consistent color, adapting to the tooth shape and aesthetic needs of different patients. (3) Excellent performance and long service life of ceramic film layer: The graded micro-arc oxidation process combined with a special composite electrolyte makes the ceramic film layer dense and uniform, with a hardness of ≥800HV, wear-resistant and corrosion-resistant, and a friction coefficient of ≤0.3, which can withstand long-term chewing wear in the oral cavity. The zinc oxide and cerium oxide components added to the film layer give the crown good antibacterial properties, inhibit bacterial growth, and reduce the risk of oral infection. The low-temperature curing treatment further improves the density and bonding of the film layer, extending the service life of the crown. The expected service life can reach more than 10 years. (4) Excellent biocompatibility and suitability for the oral environment: The titanium alloy matrix is ​​made of medical-grade pure titanium or Ti6Al4V titanium alloy with a purity of ≥99.9%, exhibiting excellent biocompatibility and being non-allergenic and non-cytotoxic; the micro-arc oxidation electrolyte uses environmentally friendly components and does not contain toxic or harmful ingredients; the biocompatibility of the ceramic membrane meets the standards for medical dental materials, and it can be well compatible with oral mucosal tissue, avoiding oral irritation and suitable for long-term oral implantation. (5) Simple preparation process, high efficiency and low cost: The integration of 3D printing, graded micro-arc oxidation and simple post-processing steps eliminates the need for multiple sintering and polishing of traditional composite crowns, simplifying the preparation process and shortening the production cycle; the electrolyte can be recycled, reducing processing costs; 3D printing enables personalized mass production, improving preparation efficiency and meeting the personalized restoration needs of dental clinics.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing 3D-printed titanium alloy-based ceramic dental crowns using micro-arc oxidation, characterized in that, The micro-arc oxidation preparation method includes the following steps: S1, Preparation of titanium alloy dental crown matrix: (1) Scanning and modeling: Obtain the three-dimensional data of the patient's target tooth through an oral scanning device, design the crown shape using dental design software, and generate a three-dimensional model of the crown; (2) 3D printing parameter adjustment: Select medical pure titanium or Ti6Al4V titanium alloy powder as printing material, and use laser powder bed melting method to 3D print according to the three-dimensional model of the crown to obtain the 3D printed matrix; (3) Post-processing of matrix: Remove the support structure on the surface of the 3D printed matrix, polish it step by step with sandpaper, and then perform vacuum annealing treatment and cool it to room temperature in the furnace to obtain the titanium alloy dental crown matrix; S2, Pretreatment of titanium alloy crown matrix: The titanium alloy crown matrix is ​​sequentially subjected to degreasing, acid washing and activation, water washing and drying to obtain a pretreated titanium alloy crown matrix; S3, graded micro-arc oxidation treatment: The pretreated titanium alloy crown substrate is used as the anode and the graphite electrode is used as the cathode. It is placed in a biocompatible composite electrolyte and fixed with a detachable special clamp to ensure good conductivity and no oxidation dead corners. After graded micro-arc oxidation treatment, the titanium alloy crown substrate with micro-arc oxidation treatment can be obtained. S4, Post-treatment of crowns: The titanium alloy crown substrate that has undergone micro-arc oxidation treatment is rinsed with deionized water, then subjected to low-temperature curing treatment, and finally finely ground and polished. S5, Quality Inspection: Inspect the performance, morphology, and fit of the ceramic film layer of the post-processed crown in S4. If the preset requirements are not met, return to steps S3 and S4 to re-oxidize until the preset requirements are met to obtain the 3D printed titanium alloy-based ceramic crown.

2. The micro-arc oxidation preparation method according to claim 1, characterized in that, In step (1) of S1, the purity of the medical pure titanium or Ti6Al4V titanium alloy powder is ≥99.9%, the sphericity is ≥90%, and the particle size is 15~53μm; In step (2) of S1, the specific parameters of the 3D printing are: laser power 180-220W, scanning speed 800-1200mm / s, layer thickness 20-40μm, scanning spacing 80-120μm, printing atmosphere is argon protection, argon flow rate 0.8-1.2L / min; In step (3) of S1, the annealing temperature is 600-700℃ and the holding time is 30-60min. The surface roughness of the titanium alloy crown matrix prepared after vacuum annealing is ≤0.8μm and the density is ≥99%.

3. The micro-arc oxidation preparation method according to claim 1, characterized in that, In S2, the degreasing and oil removal uses an environmentally friendly alkaline degreasing agent. The alkaline degreasing agent consists of sodium hydroxide at a concentration of 40-60 g / L, sodium carbonate at a concentration of 20-40 g / L, and a nonionic surfactant at a concentration of 1-3 g / L. The degreasing and oil removal process uses ultrasonic cleaning at 40-60 kHz. The degreasing and oil removal temperature is 40-50℃, and the degreasing time is 10-15 min. In S2, the pickling activation uses a mixed acid solution of hydrofluoric acid and nitric acid, wherein the concentration of hydrofluoric acid is 5-10 vol% and the concentration of nitric acid is 15-25 vol%, and the pickling activation temperature is 20-25°C and the pickling time is 0.5-1.5 min. In S2, the surface roughness of the acid-washed and activated titanium alloy crown matrix is ​​Ra = 0.3-0.5 μm; In S2, the water washing and drying is carried out using vacuum drying, with a drying temperature of 60-80℃, a drying time of 10-15 min, and a vacuum degree of 0.05-0.08 MPa.

4. The micro-arc oxidation preparation method according to claim 1, characterized in that, In S3, the biocompatible composite electrolyte comprises the following components: sodium dihydrogen phosphate at a concentration of 8–15 g / L, silicic acid at a concentration of 5–10 g / L, sodium fluoride at a concentration of 0.5–2 g / L, zirconium oxide powder at a concentration of 1–3 g / L, medical-grade zinc oxide at a concentration of 0.3–0.8 g / L, and deionized water. The pH of the biocompatible composite electrolyte is 6.5–7.5, and the particle size of the zirconium oxide powder is 50–100 nm. The biocompatible composite electrolyte also includes 0.1–0.3 g / L of medical-grade cerium oxide; The pH value of the biocompatible composite electrolyte is adjusted by citric acid or sodium hydroxide.

5. The micro-arc oxidation preparation method according to claim 1, characterized in that, In step S3, the graded micro-arc oxidation includes a film-forming stage, a densification stage, and an aesthetic modification stage. The specific parameters for the hierarchical micro-arc oxidation are as follows: (1) Film formation stage: voltage 80-120V, current density 5-10A / dm 2 The oxidation time is 10–15 min, and the electrolyte temperature is 25–30 °C. (2) Densification stage: voltage 150-180V, current density 10-15A / dm 2 The oxidation time is 15–20 min, and the electrolyte temperature is 30–35 °C. (3) Aesthetic finishing stage: voltage 120-150V, current density 8-12A / dm 2 The oxidation time is 5-10 min and the electrolyte temperature is 28-32℃.

6. The micro-arc oxidation preparation method according to claim 1, characterized in that, In S3, during the micro-arc oxidation process, the biocompatible composite electrolyte is continuously stirred and monitored in real time by a stirring device. The stirring speed is 150-250 r / min. When the real-time monitoring detects that the temperature exceeds 35°C, the cooling device is activated to reduce the temperature. In S3, argon gas with a flow rate of 0.5 to 0.8 L / min is used for protection during the micro-arc oxidation process, and the detachable special fixture used in the micro-arc oxidation process is made of titanium alloy with surface insulation treatment.

7. The micro-arc oxidation preparation method according to claim 1, characterized in that, In S4, the temperature of the low-temperature curing treatment is 300-400℃ and the holding time is 20-30 minutes. Inert gas protection is used during the low-temperature curing treatment. The fine polishing is done using 3000#-5000# sandpaper; The polishing process uses diamond polishing paste. The surface roughness Ra of the titanium alloy dental crown substrate obtained after the fine grinding and polishing is ≤0.2μm.

8. The micro-arc oxidation preparation method according to claim 1, characterized in that, In S5, the preset standards are specifically as follows: ceramic film thickness is 8-20 μm, thickness uniformity error is ≤ ±1 μm, film bonding strength is ≥30 MPa, no detachment in cross-cut test, ceramic film hardness is ≥800 HV, friction coefficient is ≤0.3, cytotoxicity is ≤1 grade and non-sensitizing, and crown veneer gap is ≤0.05 mm.

9. A 3D-printed titanium alloy-based ceramic dental crown prepared by the preparation method according to any one of claims 1 to 9.

10. The 3D-printed titanium alloy-based ceramic dental crown according to claim 9, characterized in that, The 3D-printed titanium alloy-based ceramic crown is a composite structure of "inner titanium alloy and outer ceramic", including a titanium alloy matrix and a micro-arc oxidation ceramic film layer. The titanium alloy matrix is ​​prepared by 3D printing and is made of medical pure titanium or Ti6Al4V titanium alloy. The micro-arc oxidation ceramic film is generated in situ on the surface of the titanium alloy substrate and is metallurgically bonded to the titanium alloy substrate. The main components of the film are TiO2, ZrO2 and SiO2. The thickness of the micro-arc oxidation ceramic film is 8-20 μm and the surface is smooth and the color is uniform. The surface of the micro-arc oxidation ceramic film is distributed with nanoscale micropores of 50-200 nm, and the film contains zinc oxide and / or cerium oxide with antibacterial properties.

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