Bimodal lithium disilicate glass-ceramics and restorations and methods of making

Abstract

The application discloses a kind of bimodal particle size distribution lithium disilicate glass ceramic and restoration and preparation method;Wherein the preparation method of lithium disilicate glass ceramic includes batching, melting, quenching, crushing and rotary heat treatment and the like steps, by specific setting to raw material and cooperate quenching and rotary heat treatment step, obtain the spherical lithium disilicate glass ceramic powder with bimodal particle size distribution in specific particle size range, can prepare high solid content, excellent rheological property printing slurry, by specific setting to one-step heat treatment method 3D printing restoration preparation method, on the basis of the spherical lithium disilicate glass ceramic powder with bimodal particle size distribution in specific particle size range as raw material, by setting one-step heat treatment method, the lithium disilicate glass ceramic restoration with higher aesthetic characteristics is prepared.

Description

Technical Field

[0001] This invention relates to the field of nano-ceramic materials technology, and in particular to a lithium disilicate glass ceramic with a bimodal particle size distribution, a repair body, and a preparation method thereof. Background Technology

[0002] Lithium disilicate glass-ceramics possess high optical transmittance and are primarily used for aesthetic restorations of dental crowns and veneers. Their main raw materials are Li₂O and SiO₂, with auxiliary additions of P₂O₅, ZrO₂, K₂O, and Al₂O₃. After being melted and uniformly mixed at high temperature, they are quenched and crushed to obtain amorphous glass powder, which is then heat-treated to obtain the final glass-ceramic product. Currently, lithium disilicate restorations used clinically are manufactured using hot-pressing and CAD / CAM cutting techniques. Traditional processing techniques are highly sensitive, resulting in approximately 90% material waste, while 3D printing technology can effectively overcome these drawbacks.

[0003] Current research focuses on using irregularly shaped flakes or lumps of powder with a single, concentrated particle size distribution as raw materials for molding, followed by multiple heat treatments to form the final product. This method still has the following drawbacks: First, the photocurable slurry prepared from irregularly shaped flakes or lumps of powder with a single, concentrated particle size distribution has poor fluidity, low solid content, and large sintering shrinkage. Second, current research shows that 3D-printed lithium disilicate glass ceramics suffer from low transmittance and poor aesthetic performance, lacking sufficient translucency and unsuitable for aesthetic restoration. Third, traditional techniques require multiple heat treatment steps such as degreasing, low-temperature crystallization, and high-temperature sintering, increasing post-processing time and thus extending the time required for clinical restoration.

[0004] Chinese invention patent CN118239685B discloses a method for photopolymer additive manufacturing of high-transparency lithium disilicate glass ceramics. This technical solution obtains spherical powder in a different way, by using amorphous powder granulation to obtain spherical powder. However, spray granulation requires specialized equipment, which increases costs and makes the operation more complicated.

[0005] Chinese invention patent publication CN117285255A discloses a 3D-printed lithium disilicate microcrystalline glass, its preparation method, and its application. This technical solution focuses on improving the mechanical properties of 3D-printed lithium disilicate glass ceramics, aiming to achieve high-strength, high-density, and crack-free lithium disilicate glass ceramic materials. By adjusting the solid content of the powder, the cracks in the printed green body are reduced, and the density is improved. Furthermore, the mechanical properties of the material are further improved through ion exchange. However, the semi-permeability of the material is not studied.

[0006] Chinese invention patent publication CN114835401A discloses a 3D printing method for lithium disilicate glass ceramics. This method uses direct ink writing technology to prepare 3D printed lithium disilicate glass ceramics. However, due to the inherently lower precision of direct ink writing compared to photopolymerization, it has limitations when preparing high-precision restorative materials such as dental prostheses. The samples provided by this method show that the surface of the printed samples is relatively rough. This method uses different powders, including lithium disilicate, lithium metasilicate, and silicon oxide, as well as lithium silicate glass powder. During high-temperature sintering, lithium disilicate may remain unchanged, while lithium metasilicate reacts with silicon oxide to form new lithium disilicate. However, a large amount of lithium disilicate itself affects sintering densification, and the difference in composition leads to uneven reaction. Therefore, the density and mechanical properties of this method are relatively poor, less than 100 MPa. Optical properties need improvement.

[0007] Therefore, there is an urgent need to develop a lithium disilicate glass-ceramic restoration that can shorten the heat treatment process time, solve the problems of low solid content and poor fluidity of photocurable slurry, and improve the transmittance and aesthetics of lithium disilicate glass-ceramic. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a spherical lithium disilicate glass-ceramic powder with a bimodal particle size distribution and a one-step heat treatment method for 3D printing to prepare lithium disilicate glass-ceramic restorations. This solves the problems of poor flowability, low solid content, and low optical transmittance (<15%) in the preparation of slurries from traditional single-particle-size glass powders, which result in poor aesthetic performance. At the same time, the one-step heat treatment process shortens the preparation cycle of the restoration and produces 3D-printed lithium disilicate glass-ceramic restorations with a density greater than 99.6%, linear transmittance >50%, and excellent aesthetic performance.

[0009] The technical solution of this invention is implemented as follows:

[0010] A method for preparing lithium disilicate glass ceramics with a bimodal particle size distribution includes the following steps:

[0011] (1) Ingredients: 55-75 parts by weight of SiO2, 12-20 parts by weight of Li2O, 5-7 parts by weight of P2O5, 1-5 parts by weight of ZrO2, 2-7 parts by weight of K2O, 1-3 parts by weight of Al2O3, 1-2 parts by weight of MgO, 1-2 parts by weight of CeO2, 0-2 parts by weight of Na2O and 0-1 parts by weight of La2O3.

[0012] (2) Melting: The raw materials obtained in step (1) are placed into a melting furnace and heated and melted to obtain molten material.

[0013] (3) Quenching: The molten material from step (2) is brought into contact with a copper plate and quenched using a copper plate quenching method to obtain a solid material.

[0014] (4) Crushing: The solid material obtained after quenching in step (3) is crushed to obtain glass ceramic powder.

[0015] (5) Rotary heat treatment: The glass ceramic powder obtained in step (4) is placed into a rotary heating device, an inert gas is introduced, the heating temperature is set to 500~800℃, the rotation speed of the rotary heating device is 0.1~20 rpm, and after rotary heating for 30~600 min, it is taken out to obtain lithium disilicate glass ceramic powder with bimodal particle size distribution.

[0016] Preferably, the heating and holding temperature for melting in step (2) is 1400~1600℃, and the material is held at this temperature for 90~180 minutes to obtain the molten material.

[0017] Preferably, in step (3), during the quenching process of the copper plate, deionized water is continuously introduced into the copper plate at a temperature of 5~15℃ and a flow rate of 0.5~3.5m / s.

[0018] Preferably, the crushing in step (4) specifically refers to crushing the solid material into powder with a particle size of 0.5~11µm.

[0019] Preferably, the inert gas in step (5) is one or both of nitrogen or argon.

[0020] Preferably, the inert gas flow rate in step (5) is 1~40 L / min.

[0021] A lithium disilicate glass-ceramic with a bimodal particle size distribution, wherein the lithium disilicate glass-ceramic with a bimodal particle size distribution is prepared by the above-described preparation method.

[0022] Preferably, the lithium disilicate glass ceramic with bimodal particle size distribution has a particle size range of 0.5~11µm, where D10 is 0.9~1.1µm, D50 is 2.8~3.5µm, and D90 is 6.3~7.5µm, and has two particle size peaks, which are 0.8~2µm and 5~8µm, respectively.

[0023] A method for 3D printing lithium disilicate glass-ceramic restorations using a one-step heat treatment process includes the following steps:

[0024] S1, the powdered lithium disilicate glass ceramic with a bimodal particle size distribution prepared by the above preparation method is mixed with a liquid mixture at a mass ratio of (70~80):(20~30) to obtain a photocurable ceramic slurry; the liquid mixture is a photosensitive resin, a dispersant and a photoinitiator.

[0025] S2, the photocurable slurry obtained in step S1 is molded using a 3D printer to obtain a green body for the repair.

[0026] S3. After cleaning and drying the green body obtained in step S2, perform a one-step degreasing and sintering heat treatment. The heating rate of the degreasing and sintering heat treatment is 0.1~30℃ / min, and the temperature is raised to 840~900℃. Hold at this temperature for 5~20min. Then, cool down with the furnace to 500℃ and take it out to cool naturally to obtain the 3D printed lithium disilicate glass ceramic repair body product.

[0027] Preferably, in step S1, the dispersant in the liquid mixture accounts for 0.5~2 wt.% of the powder mass, the photoinitiator is 1~3 wt.% of the photosensitive resin, and the remainder is the photosensitive resin.

[0028] Preferably, the photosensitive resin is a photosensitive resin composed of monofunctional acrylic resin, difunctional acrylic resin and polyfunctional acrylic resin mixed in a mass ratio of (1~3):(1~2):1.

[0029] Preferably, the dispersant is one or more of the following: an alkyl hydroxy ammonium salt of an acidic copolymer, a polyphosphate solution, an alkyl ammonium salt of a high molecular weight copolymer, γ-methacryloyloxypropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane.

[0030] Preferably, the photoinitiator is one or both of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0031] A lithium disilicate glass-ceramic restoration, wherein the lithium disilicate glass-ceramic restoration is prepared by the above method.

[0032] The technical effects of this invention are as follows:

[0033] 1. This invention, by specifically defining the content of raw material components, and after melting and quenching, uses a rotary heating device with specific parameters for granulation to obtain lithium disilicate glass ceramic powder with a bimodal particle size distribution of approximately 1μm and 5.5μm. Through rotary heating and specific settings for controlling the rotation and temperature of the rotary heating device, a bimodal particle size distribution structure with "coarse particles as the skeleton and fine particles filling the gaps" is formed. The particles have good sphericity and uniform size, making them suitable for subsequent 3D printing and one-step heat treatment. The proportions are not only superior to single-peak particle size distribution particles but also superior to existing bimodal particle sizes with larger particle sizes. The focus of this invention is on how to prepare high-density, high-semi-permeability lithium disilicate glass ceramics. This invention selects spheroidizing powder to increase solid content and improve the density of the green body, thus preparing a crack-free green body, and sintering to prepare ultra-high semi-permeability, high-strength lithium disilicate glass ceramics. This design improves the flowability and spreadability of the powder, ensuring uniform layup in 3D printing. Existing bimodal particle sizes with larger particle sizes have large gaps between layers, are prone to voids, and while they offer good flowability, they lack density. Existing unimodal particle sizes are prone to agglomeration, resulting in prominent layup defects and poor stability. Simultaneously, this design increases the green body density, supports uniformity in one-step heat treatment, and reduces the risk of breakage. Existing larger bimodal particle sizes have low green body density and are prone to uneven heating and cracking; while existing unimodal green bodies have extremely poor density and strength, leading to a high breakage rate. This invention uses a rotary heating device to granulate particles with a specific small bimodal particle size distribution, improving sintering activity. The coarse particles in the bimodal structure inhibit abnormal grain growth, laying the foundation for mechanical properties. Existing larger bimodal particle sizes suffer from uneven grain growth, making it difficult to consistently achieve the required flexural strength; existing unimodal particle size distributions lack coarse-fine synergy, resulting in insufficient mechanical properties and an inability to withstand oral chewing pressure. This invention achieves a bimodal particle size distribution for small particles by specifically setting the parameters of the rotary device, eliminating the need for subsequent graded mixing, thus simplifying the process and reducing costs. In contrast, existing methods require additional grading for larger bimodal particle sizes, resulting in cumbersome processes and high costs; existing single-peak particle size distributions suffer from high scrap rates and high costs, hindering large-scale production. Specifically, this invention obtains a bimodal particle size distribution powder by setting specific component contents and then using a rotary heating device with specific parameters for granulation after melting and quenching. The spherical lithium disilicate glass-ceramic powder with a bimodal particle size distribution is used to prepare a high-solids-content printing slurry with excellent rheological properties, solving the problems of low solids content and poor flowability in photocurable slurries, and significantly improving the solids content of 3D printing slurries.

[0034] 2. This invention, by obtaining ceramic powder with a bimodal particle size distribution, uses this ceramic powder as raw material and employs a relatively low-temperature one-step degreasing heat treatment, shortening the heat treatment process time and increasing manufacturing efficiency by more than 30%. It also solves the shortcomings of poor transmittance and insufficient aesthetics in 3D printing lithium disilicate glass ceramics, compensating for the technical deficiencies of 3D printing. In the process of preparing the restoration, this invention first obtains a light-curing ceramic slurry through defoaming and mixing in a vacuum defoaming machine, achieving light-curing printing, which significantly improves precision. The crowns prepared by this invention are more aesthetically pleasing. Furthermore, by selecting a single powder, the reactions occurring during sintering are more singular, resulting in a more uniform composition of the sintered sample. Therefore, this invention achieves superior mechanical (310 MPa) and aesthetic properties (light transmittance > 50%). The invention employs a one-step heat treatment method, requiring only a standard muffle furnace to heat-treat the powder to obtain spherical powder while simultaneously achieving the nucleation of lithium disilicate. This essentially places the nucleation step within the production process, simplifying post-processing time and reducing the time required for clinical preparation. In the subsequent heat treatment stage, we selected a single program to complete degreasing and sintering, eliminating the time required for cooling, transfer, and reheating, further reducing post-processing time and increasing clinical convenience. By setting specific heating rates and holding temperatures for the one-step heat treatment, it is adapted to the critical crystallization temperature of lithium disilicate (> 800℃), simultaneously completing degreasing and sintering crystallization; and the bimodal particle size of this invention allows for precise adaptation. Existing bimodal particle sizes are difficult to adapt to, while single-peaked particles are completely unsuitable and prone to degreasing and sintering defects. This design achieves thorough degreasing on the basis of bimodal particle size distribution powders, simultaneously achieving sintering crystallization and avoiding cracking and deformation of the green body. However, if larger bimodal particles are used, pores are easily generated, resulting in a high risk of cracking and deformation; existing single-peak particle size distributions result in numerous pores and an extremely high probability of cracking and deformation. The design of this invention achieves uniform heat transfer. Uniform crystallization during sintering improves mechanical properties. In contrast, crystal precipitation with existing larger bimodal particle sizes is prone to disorder and poor performance stability. Overall, the two existing steps are combined into one, shortening the cycle by more than 30%, reducing energy consumption and labor costs, and avoiding secondary heating oxidation color differences, ensuring the aesthetics and surface smoothness of the finished product.

[0035] 3. This invention combines the preparation of a bimodal particle size distribution using a rotary heating device with a one-step heat treatment process. This achieves complementary support between the bimodal powder and the one-step process, resulting in a synergistic effect superior to existing larger bimodal particle sizes and completely avoiding the undesirable consequences of a single-peak process. This synergistic approach enables the finished product to achieve a density ≥99.6%, flexural strength ≥310 MPa, suitable for oral chewing, and a molding accuracy ≤50μm and light transmittance of 40%-70% (most components are above 50%), suitable for dental clinical applications. Existing larger bimodal particle sizes fail to meet the accuracy and light transmittance standards; while existing single-peak particle size distributions are aesthetically and technically unsatisfactory. Furthermore, through the synergistic cooperation of the two, the process can be simplified, the efficiency can be increased, the scrap rate can be reduced, and the advantages of large scale can be achieved. The final product is pure, biocompatible, and meets dental standards. The technical solution of this invention (1μm+5.5μm bimodal + one-step heat treatment process) has significant advantages over the existing larger bimodal particle size, and can avoid the adverse consequences of single peak. It is an efficient, low-cost, and high-quality 3D printed dental restoration preparation solution. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a particle size distribution diagram of the powder in Example 1 of the present invention.

[0038] Figure 2 This is a SEM image of the powder from Example 1 of the present invention.

[0039] Figure 3 This is a particle size distribution diagram of the powder in Comparative Example 1.

[0040] Figure 4 This is a SEM image of the powder in Comparative Example 1.

[0041] Figure 5 This is a photograph of the repair obtained in Embodiment 2 of the present invention.

[0042] Figure 6 This is a photograph of the repair obtained in Embodiment 3 of the present invention.

[0043] Figure 7 This is a test diagram of the optical performance of the restoration obtained in Embodiment 2 of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0045] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0046] Those skilled in the art should understand that the following specific embodiments or implementation methods are a series of optimized configurations listed to further explain the specific content of the invention. These configuration methods can be combined or used in conjunction with each other, unless the invention explicitly states that some or a specific embodiment or implementation method cannot be associated with or used in conjunction with other embodiments or implementation methods. Furthermore, the following specific embodiments or implementation methods are only considered as optimized configurations and are not intended to limit the scope of protection of the invention.

[0047] The present invention will be further explained below with reference to specific embodiments.

[0048] Example 1

[0049] This embodiment illustrates a method for preparing lithium disilicate glass ceramics with a bimodal particle size distribution, comprising the following steps:

[0050] (1) Ingredients: 65 parts by weight of SiO2, 16 parts by weight of Li2O, 6 parts by weight of P2O5, 3 parts by weight of ZrO2, 4.5 parts by weight of K2O, 2 parts by weight of Al2O3, 1.5 parts by weight of MgO, 1 part by weight of CeO2, 0.5 parts by weight of Na2O and 0.5 parts by weight of La2O3.

[0051] (2) Melting: The raw materials obtained in step (1) are placed into a melting furnace for heating and melting. The heating and holding temperature is 1500℃, and the temperature is held for 120 minutes to obtain molten material.

[0052] (3) Quenching: The molten material in step (2) is brought into contact with a copper plate and quenched by copper plate quenching to obtain a solid material. During the copper plate quenching process, deionized water is continuously introduced into the copper plate at a temperature of 10°C and a flow rate of 2 m / s.

[0053] (4) Crushing: The solid material obtained after quenching in step (3) is crushed to a powder with an average particle size of 3.67 μm to obtain glass ceramic powder.

[0054] (5) Rotary heat treatment: The glass ceramic powder obtained in step (4) is placed into a rotary heating device, nitrogen gas is introduced, the gas flow rate is 2L / min, the heating temperature is set to 700℃, the rotation speed of the rotary heating device is 2rpm, and after 300min of rotary heating, it is taken out to obtain lithium disilicate glass ceramic powder with bimodal particle size distribution.

[0055] In a further preferred embodiment, the rotary heating device of the present invention is a specific modification of a conventionally known small rotary kiln. Specifically, a threaded rod is horizontally arranged inside the inner cavity of the rotary kiln, with the axis of the threaded rod coinciding with the axis of the inner cavity of the rotary kiln (i.e., the threaded rod is coaxially arranged with the horizontally arranged cylindrical inner cavity of the rotary kiln). The threaded rod and the cavity of the rotary kiln rotate relative to each other (rather than synchronously). Furthermore, preferably, the diameter at the top of the external thread of the threaded rod is 40-90% of the inner diameter of the inner cavity of the rotary kiln. The relative rotation between the threaded rod and the inner cavity of the rotary kiln allows for smoother transfer of powder from one end of the cavity to the other. This arrangement ensures uniform heating of the powder, prevents powder from sticking to the wall, and enables continuous production.

[0056] The lithium disilicate glass-ceramic powder obtained in this embodiment was subjected to particle size analysis and SEM analysis, and the results were as follows: Figure 1 and Figure 2 The results are shown. (Through) Figure 1 It can be seen that the lithium disilicate glass-ceramic powder obtained in this embodiment has a clear bimodal structure, with the first particle size peak at approximately 1 µm and the second particle size peak at approximately 5.5 µm. Furthermore, D10 is 1.03 µm, D50 is 3.24 µm, and D90 is 6.89 µm. Figure 2It can be seen that the two particle size distributions obtained in this embodiment are clustered near the peak, thus proving that the particle size distribution of the lithium disilicate glass ceramic powder obtained by the present invention has a clear bimodal structure. Moreover, the peak values ​​of the bimodal particle size distribution of the present invention are completely different from those of the prior art. This specific bimodal structure of particle size can improve the process adaptability in the subsequent fabrication of restorations using 3D printing. The coarse particles (5.5μm) play a supporting role in the skeleton, while the fine particles (1μm) fill the gaps, thereby reducing the agglomeration of fine particles, reducing powder friction, and improving fluidity and spreadability. It is compatible with mainstream dental 3D printing technologies such as photopolymerization and selective laser sintering. Furthermore, this specific bimodal distribution can further ensure molding accuracy. The coarse and fine particles clustered near the bimodal distribution in this embodiment are tightly packed, which greatly improves the green body density and reduces the green body porosity and breakage risk. Subsequent degreasing and sintering shrinkage are more uniform, reducing the probability of deformation and cracking. It can accurately replicate the design model, adapt to the patient's tooth morphology, and reduce the amount of subsequent finishing work. Furthermore, this specific bimodal particle size distribution optimizes mechanical and optical properties. Enrichment within the fine particle size range enhances sintering activity and lowers sintering temperature; coarse particles inhibit abnormal grain growth, optimize the microstructure, and achieve a sintered body density exceeding 99.6%, a flexural strength exceeding 310 MPa, and a hardness approaching that of natural tooth enamel, thus meeting oral chewing requirements. Simultaneously, it balances translucency and optical uniformity, allowing for precise matching of natural tooth color and improved aesthetics. Moreover, this specific bimodal particle size distribution enhances subsequent processability and practicality. The combination of coarse and fine particles reduces powder preparation costs, shortens printing and sintering cycles, reduces scrap rates, and facilitates large-scale production, promoting clinical adoption. In short, this bimodal particle size distribution comprehensively addresses the shortcomings of single-size powders and the drawbacks of bimodal aggregation at relatively large particle sizes, achieving high-precision, high-mechanical-performance, aesthetically pleasing, and highly practical dental restorations, meeting the core requirements of subsequent specific restoration products.

[0057] Comparative Example 1

[0058] This comparative example is used to illustrate a comparative test that does not employ the rotary heating device of the present invention. The difference from Example 1 is that this comparative example does not include step (5), while steps (1) to (4) are exactly the same as in Example 1.

[0059] Particle size analysis and SEM analysis were performed on the obtained lithium disilicate glass-ceramic powder to obtain the following results: Figure 3 and Figure 4 The results are shown. (Through) Figure 3It can be seen that the lithium disilicate glass-ceramic powder obtained in this comparative example has a single-peak structure in its particle size distribution, with a single peak size of approximately 2.47 µm, concentrated in the 2-3 µm range. Furthermore, the D10 (10% of particles < this size) is 0.98 µm, the D50 (50% of particles < this size) is 2.47 µm, and the D90 (90% of particles < this size) is 5.35 µm. And combined with… Figure 4 As can be seen, the powder prepared in this way lacks a clear particle size concentration, with various particle sizes being widely distributed. This relatively uniform particle size distribution, along with its single-peak structure, can lead to problems during subsequent restoration fabrication and 3D printing. The concentrated particles are prone to agglomeration, resulting in poor flowability, blockages, uneven layer thickness, and other defects, leading to poor printing continuity and a high scrap rate. Furthermore, the inability to fill the gaps between particles results in low green body density and susceptibility to breakage. Uneven sintering shrinkage leads to deformation, dimensional deviations, and substandard precision in the finished product. During sintering, the low sintering activity necessitates high-temperature, long-duration sintering, causing abnormal grain growth. The sintered body has low density, insufficient mechanical properties, and is prone to cracking and wear. Uneven grain size results in poor light transmittance and optical uniformity, leading to poor aesthetics; high brittleness and poor machinability; and a rough surface that easily breeds bacteria. The printing process is characterized by numerous defects, high energy consumption, low efficiency, increased costs, and weak powder versatility, making it unsuitable for large-scale production. The present invention spheroidizes a portion of the particles through a specific rotary heat treatment method, and allows a portion of the particles to grow appropriately as cores, thus forming a bimodal particle size distribution with a specific peak particle size. This proves that the present invention has the pioneering ability to obtain a ceramic powder structure with a specific bimodal structure through granulation by a specific rotary heat treatment method.

[0060] Example 2

[0061] This embodiment illustrates a method for 3D printing lithium disilicate glass-ceramic restorations using the ceramic powder prepared in Example 1 as raw material via a one-step heat treatment process, including the following steps:

[0062] S1, the lithium disilicate glass ceramic with a bimodal particle size distribution prepared by the method described in Example 1 is mixed with a liquid mixture at a mass ratio of 75:25 in a vacuum defoamer to obtain a photocurable ceramic slurry; the liquid mixture consists of a photosensitive resin, a dispersant, and a photoinitiator. The photosensitive resin is a mixture of monofunctional acrylic resin, difunctional acrylic resin, and polyfunctional acrylic resin in a mass ratio of 3:2:1. The dispersant is 3-mercaptopropyltriethoxysilane. The photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. The mass of the dispersant in the liquid mixture is 0.75 wt.% of the mass of the lithium disilicate glass ceramic powder, the photoinitiator is 1.5 wt.% of the mass of the photosensitive resin, and the remainder is the photosensitive resin.

[0063] S2, the photocurable slurry obtained in step S1 is molded using a 3D printer to obtain a green body for the repair.

[0064] S3. After cleaning and drying the green body obtained in step S2, a one-step degreasing and sintering heat treatment is performed. The heating rate of the sintering heat treatment after degreasing is 10℃ / min, and the temperature is raised to 870℃ and held at this temperature for 15min. Then the furnace is cooled down to 500℃ and the furnace is opened to obtain the 3D printed lithium disilicate glass ceramic repair body product.

[0065] The obtained lithium disilicate glass-ceramic restoration products, such as Figure 5 As shown, its optical performance was tested, and the results were as follows. Figure 7 The results are shown.

[0066] Example 3

[0067] The other settings in this embodiment are the same as in embodiment 2, except that the shape of the 3D printed green body is different from that in embodiment 2. The final 3D printed lithium disilicate glass-ceramic restoration product is as follows: Figure 6 As shown.

[0068] Analysis of Examples 2 and 3 revealed that, Figure 5 and Figure 6 The surface of the restoration is smooth and has a certain degree of light transmittance, while combined with... Figure 7 It can be seen that the light transmittance of the restoration obtained in this embodiment gradually increases with wavelength (400-800 nm visible light region), reaching more than 50% at 800 nm (while the highest light transmittance of existing technologies, such as CN118239685B, only reaches 50%). As a restoration, the light transmittance curve of Embodiment 2 of the present invention matches the spectral characteristics of natural teeth, avoiding a "dead white" or "gray" appearance and improving the aesthetics of the restoration. Figure 5 and Figure 6 The exhibited smooth surface design reduces plaque adhesion and lowers the risk of secondary caries. This demonstrates that restorations prepared using lithium disilicate glass-ceramic powder with a bimodal particle size distribution, specifically designed in this invention, via a one-step heat treatment method, possess high light transmittance and aesthetically pleasing results that closely resemble natural teeth.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for 3D printing lithium disilicate glass-ceramic restorations using a one-step heat treatment process, characterized in that, Includes the following steps: S1, a photocurable ceramic slurry is obtained by mixing and defoaming a powdered lithium disilicate glass ceramic with a liquid mixture at a mass ratio of (70~80):(20~30) in a vacuum defoaming machine; the liquid mixture consists of photosensitive resin, dispersant and photoinitiator. S2, the photocurable slurry obtained in step S1 is molded using a 3D printer to obtain a green body of the repair. S3. After cleaning and drying the green body obtained in step S2, a one-step degreasing and sintering heat treatment is performed. The heating rate of the degreasing and sintering heat treatment is 0.1~30℃ / min, and the temperature is raised to 840~900℃. The temperature is held for 5~20min. Then the furnace is cooled to 500℃ and the body is taken out and allowed to cool naturally to obtain the 3D printed lithium disilicate glass ceramic repair body product. The lithium disilicate glass-ceramic with a bimodal particle size distribution described in step S1 is prepared using the following steps: (1) Ingredients: 55-75 parts by weight of SiO2, 12-20 parts by weight of Li2O, 5-7 parts by weight of P2O5, 1-5 parts by weight of ZrO2, 2-7 parts by weight of K2O, 1-3 parts by weight of Al2O3, 1-2 parts by weight of MgO, 1-2 parts by weight of CeO2, 0-2 parts by weight of Na2O and 0-1 parts by weight of La2O3. (2) Melting: The raw materials obtained in step (1) are placed into a melting furnace and heated to melt, resulting in molten material; (3) Quenching: The molten material from step (2) is brought into contact with a copper plate and quenched using copper plate quenching to obtain a solid material; (4) Crushing: The solid material obtained after quenching in step (3) is crushed to obtain glass ceramic powder; (5) Rotary heat treatment: The glass ceramic powder obtained in step (4) is placed into a rotary heating device, an inert gas is introduced, the heating temperature is set to 500~800℃, the rotation speed of the rotary heating device is 0.1~20rpm, and after rotary heating for 30~600min, it is taken out to obtain lithium disilicate glass ceramic powder with bimodal particle size distribution. The obtained lithium disilicate glass ceramic with bimodal particle size distribution has a particle size range of 0.5~11µm, where D10 is 0.9~1.1µm, D50 is 2.8~3.5µm, and D90 is 6.3~7.5µm. It also has two particle size peaks, which are 0.8~2µm and 5~8µm, respectively.

2. The method according to claim 1, characterized in that, The melting heating and holding temperature in step (2) is 1400~1600℃, and the temperature is held for 90~180min to obtain the molten material; In step (3), during the quenching process of the copper plate, deionized water is continuously introduced into the copper plate at a temperature of 5~15℃ and a flow rate of 0.5~3.5m / s.

3. The method according to claim 1 or 2, characterized in that, The crushing mentioned in step (4) specifically refers to crushing solid materials into powder with a particle size of 0.5~11µm.

4. The method according to claim 1 or 2, characterized in that, The inert gas mentioned in step (5) is one or both of nitrogen and argon; The inert gas flow rate in step (5) is 1~40 L / min.

5. The method according to claim 1, characterized in that, In step S1, the mass of the dispersant in the liquid mixture is 0.5~2wt% of the mass of the lithium disilicate glass ceramic powder, the mass of the photoinitiator is 1~3wt% of the mass of the photosensitive resin, and the balance is the photosensitive resin.

6. The method according to claim 5, characterized in that, The photosensitive resin is a photosensitive resin composed of monofunctional acrylic resin, difunctional acrylic resin and polyfunctional acrylic resin mixed in a mass ratio of (1~3):(1~2):

1. The dispersant is one or more of the following: an alkyl hydroxy ammonium salt of an acidic copolymer, a polyphosphate solution, an alkyl ammonium salt of a high molecular weight copolymer, γ-methacryloyloxypropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane; The photoinitiator is one or both of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

Images