A lithium disilicate glass-ceramic preform, its preparation method and application

Abstract

This invention provides a lithium disilicate glass-ceramic preform, its preparation method, and its application. The lithium disilicate glass-ceramic preform comprises a lithium disilicate main crystalline phase, wherein the crystal size of the preform is between 50 and 400 nm, and the area of ​​grains longer than 350 nm accounts for less than 30% of the total area. By controlling the internal crystal size of the lithium disilicate glass-ceramic preform to below 400 nm, this invention allows for direct machining without damaging processing equipment. Furthermore, it combines advantages such as high strength, machinability, and direct color development, reducing patient waiting time for dentures and solving the problem of patients not knowing the color of all-ceramic prostheses before fabrication. This breakthrough overcomes the bottleneck of all-ceramic prosthesis materials that affect patients' ability to wear dentures on the same day, and is of great significance for achieving preoperative color matching and rapid restoration in clinical practice.

Description

Technical Field

[0001] This invention relates to the field of dental prosthesis technology, and more particularly to a lithium disilicate glass-ceramic preform, its preparation method, and its application. Background Technology

[0002] With the development of CAD / CAM (Computer-Aided Design / Computer-Aided Manufacturing) technology in recent years, the shape data of the processed dental prosthesis can be sent to a processing device for processing, enabling the rapid production of the prosthesis.

[0003] Lithium disilicate glass ceramics are a good CAD / CAM restoration material with excellent mechanical properties, translucency, and chemical stability. Its unique cross-linked and interlocked microstructure is of great significance to its mechanical properties. However, while this microstructure ensures its high strength, it also makes lithium disilicate glass ceramics unmachinable. Processing with CAD / CAM technology will cause damage to the processing tools, and the prepared restorations will have severe chipping.

[0004] US8162664B2 discloses a method for processing dental restorations using lithium disilicate "intermediate" lithium metasilicate, which makes up for the shortcomings of lithium disilicate processing. However, the dental restorations after cutting have low strength and the original color does not match the tooth color. Further heat treatment is required to convert them into lithium disilicate and then into tooth color. This increases the time cycle for restoration production, and also adds the equipment required for restoration production, thus increasing the cost.

[0005] CN113677310B discloses a processable lithium disilicate material obtained by controlling a heat treatment process. The material is characterized by the following feature: when observed under magnification within a field of view of 5 μm width and 5 μm depth, the ratio of the total area of ​​crystals with a length of 0.5 μm or more within the field of view to the area of ​​the field of view is less than 1%. However, the internal grain size distribution range of this material is 0-0.5 μm, which is relatively wide, resulting in uneven grain size and low strength performance of the lithium disilicate blank.

[0006] Therefore, it is necessary to develop a processable lithium disilicate dental prosthesis material with excellent strength. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a lithium disilicate glass-ceramic preform, its preparation method, and its applications. This invention controls the crystal size of the lithium disilicate glass-ceramic to be between 50 and 400 nm, resulting in a narrow grain size distribution and thus providing machinability. Simultaneously, it controls the proportion of grains longer than 350 nm to less than 30% of the total area, effectively avoiding the problem of poor machinability caused by large grains. Furthermore, the main crystalline phase is the lithium disilicate phase, which directly develops color, and it also possesses high strength, making it a promising candidate for application in dental restorations.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a lithium disilicate glass-ceramic preform, the lithium disilicate glass-ceramic preform comprising a lithium disilicate main crystalline phase, wherein the crystal size of the lithium disilicate glass-ceramic preform is between 50 and 400 nm, and the area of ​​grains with a length greater than 350 nm accounts for less than 30% of the total area.

[0010] The "main crystalline phase" of lithium disilicate glass-ceramic preform refers to the crystalline phase with the highest crystal precipitation rate observed by X-ray diffraction.

[0011] The crystal size is between 50 and 400 nm, for example, it can be 50 nm, 89 nm, 128 nm, 167 nm, 206 nm, 245 nm, 284 nm, 323 nm, 362 nm or 400 nm, but is not limited to the listed values. Other unlisted values ​​in this range are also applicable. Preferably, it is 100 to 390 nm, then more preferably 150 to 380 nm, and most preferably 150 to 360 nm.

[0012] The area of ​​grains with a length greater than 350 nm accounts for less than 30% of the total area. For example, it can be 29%, 28%, 27%, 26%, 25%, 22%, 20%, 19%, 18%, 17%, 15%, 12%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 2%, 1%, 0.5%, 0.2%, 0.1%, or 0%, etc., preferably less than 20%, more preferably less than 10%, even more preferably less than 5%, and even more preferably less than 1%.

[0013] In this invention, the ratio of the area of ​​grains with a length greater than 350nm to the total area is data obtained by observation within a magnified field of view of 10μm×10μm, but it is not limited to observation only using this field of view. The entire surface of the lithium disilicate glass ceramic preform exhibits this pattern.

[0014] It is worth noting that in this invention, the crystal size is controlled between 50 and 400 nm. When the crystal size is too small, the sample strength is too low and the transparency is too high, which is not conducive to color development. When the crystal size is too large, the sample cannot be cut and processed. Furthermore, the proportion of the area of ​​crystals with a length greater than 350 nm to the total area is controlled to be less than 30%. When the area of ​​crystals with this size is too large, there is a problem of reduced cutting performance and severe edge defects of the repair.

[0015] Preferably, the flexural strength of the lithium disilicate glass-ceramic preform is greater than 300 MPa, for example, it can be 301 MPa, 335 MPa, 368 MPa, 401 MPa, 434 MPa, 468 MPa, 501 MPa, 534 MPa, 567 MPa or 600 MPa, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0016] Preferably, the lithium disilicate main crystal phase has at least two crystal morphologies.

[0017] Preferably, the crystal morphology includes at least a first crystal morphology in which the ratio of any two of the length, width, and height is in the range of 0.6 to 1, such as 0.6, 0.7, 0.8, 0.85, 0.9, 0.95, or 1, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. It also includes a second crystal morphology in which at least one of the length, width, and height has a ratio of 3:1 or higher, such as 3:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, or 20:1, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] In this invention, the lithium disilicate glass-ceramic preform has two overlapping crystal morphologies, which gives it high bending strength.

[0019] Preferably, the first crystal morphology includes any one or a combination of at least two of the following: granular, ellipsoidal, rhomboid, or clustered. Typical but non-limiting combinations include the combination of granular and ellipsoidal, granular and rhomboid, rhomboid and ellipsoidal, clustered and ellipsoidal, and granular and clustered.

[0020] Preferably, the second crystal morphology includes any one or a combination of at least two of the following: spindle-shaped, plate-shaped, layer-shaped, network-shaped, rod-shaped, or needle-shaped. Typical but non-limiting combinations include the combination of spindle-shaped and plate-shaped, layer-shaped and plate-shaped, spindle-shaped and layer-shaped, network-shaped and plate-shaped, spindle-shaped and network-shaped, rod-shaped and network-shaped, and spindle-shaped and needle-shaped.

[0021] Preferably, the composition content of the lithium disilicate glass-ceramic preform, based on mass percentage, is as follows:

[0022]

[0023] In this invention, SiO2 is 62% to 75%, for example, it can be 62%, 64%, 65%, 67%, 68%, 70%, 71%, 73%, 74% or 75%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, more preferably 63% to 74%, and most preferably 64% to 73.5%.

[0024] Li2O: 8% to 18%, for example, it can be 8%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17% or 18%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. More preferably, it is 10% to 18%, and most preferably, it is 11% to 17%.

[0025] Al2O3: 0.5% to 5%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, more preferably 0.5% to 4.5%, and most preferably 0.5% to 4%.

[0026] The present invention further preferably controls the Al2O3 content to 0.5%–5%, which, in combination with the content of phosphorus pentoxide and other components, results in the final sample having lithium disilicate as the main crystalline phase. This allows for better control of crystal size uniformity and ensures that the crystal size remains within a suitable range, addressing both size uniformity and absolute size control. Ultimately, this further improves flexural strength and machinability, and further reduces the proportion of edge chipping after machining.

[0027] P2O5: 2-10%, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, more preferably 2%-9%, and most preferably 2.5%-8%.

[0028] In this invention, the P2O5 content is preferably controlled between 2% and 10%, which can simultaneously ensure the crystal size and the crystal content in the product, avoid the situation of excessive glass phase, and ultimately further improve the flexural strength and machinability.

[0029] Me(Ⅰ)2O: 1 to 10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, more preferably 1.5% to 9%, and most preferably 1.5% to 8%.

[0030] Me(II)O: 0.1% to 5%, for example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, more preferably 0.1% to 2%, and most preferably 0.1% to 1.5%.

[0031] In this invention, Me(II)O has two functions. One is to mix with Me(I)2O to achieve a mixed alkali effect, which ultimately reduces the melting temperature and thus reduces energy consumption in the subsequent melting process. The other important function is that Me(II)O can promote the precipitation of lithium disilicate with a second crystal morphology in the lithium disilicate glass ceramic preform, which then mixes with the first crystal morphology originally present in the lithium disilicate glass ceramic preform. The two have a similar effect to the combination of "steel bars and cement", which significantly improves the flexural strength of the lithium disilicate glass ceramic preform.

[0032] Colorant: 0.1% to 10%, for example, it can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the mass ratio of SiO2 to Li2O is (3.5 to 7):1, for example, it can be 3.5:1, 4.1:1, 4.4:1, 4.7:1, 6.08:1, 6.74:1 or 7:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the mass ratio of the sum of Al2O3 and P2O5 to Li2O is (0.2 to 1):1, for example, it can be 0.2:1, 0.33:1, 0.52:1, 0.63:1, 0.72:1, 0.91:1 or 1:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] In this invention, Al2O3 works together with P2O5 to regulate the grain size of lithium disilicate. Therefore, the sum of the contents of the two and the mass ratio of Li2O need to be controlled within a specific range, which is more conducive to obtaining a product with a final grain size within the target range. On the other hand, the amount of Al2O3 introduced should not be too high to avoid the situation where the crystals grow further during the subsequent glazing process, resulting in a decrease in performance.

[0036] To better obtain products with the target grain size, this invention uses a high P2O5 content and a low Al2O3 content, which can form more nuclei and thus reduce the final grain size. Aluminum oxide can reduce phase separation in the silicon-lithium system and increase the thermal stability of the system. At the same time, it can significantly reduce the crystal growth rate in the system, which is beneficial to improving the controllability of crystallization in the system.

[0037] Preferably, the Me(Ⅰ)2O comprises K2O and / or Na2O.

[0038] Preferably, the Me(Ⅱ)O comprises any one or a combination of at least two of MgO, CaO, ZnO, BaO or SrO, wherein typical but non-limiting combinations are combinations of MgO and CaO, combinations of ZnO and CaO, combinations of MgO and ZnO, combinations of BaO and CaO, combinations of MgO and BaO, combinations of SrO and BaO, and preferably at least ZnO.

[0039] In this invention, it is further preferred that Me(II)O contains ZnO, and the ZnO content is 0.05% to 5%, for example, it can be 0.05%, 0.06%, 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4%, 4.5%, or 5%, etc., preferably 0.05% to 3.0%. The final main crystalline phase is lithium disilicate, which can simultaneously obtain two crystal morphologies, and the crystal size and ratio of the two morphologies are within a suitable range, which can better improve the cutting performance and strength.

[0040] Preferably, the colorant comprises CeO2, V2O5, Er2O3, and Pr6O. 11 Combinations of at least two of Nd₂O₃, Fe₂O₃, Tb₄O₇, or TiO₂, wherein typical but non-limiting combinations are combinations of CeO₂ and V₂O₅, combinations of Er₂O₃ and V₂O₅, combinations of CeO₂ and Er₂O₃, and Pr₆O₃. 11 Combinations with V₂O₅, CeO₂ and Pr₆O 11 Combinations of Nd2O3 and Fe2O3, combinations of Nd2O3 and Fe2O3, combinations of Fe2O3 and V2O5, combinations of Tb4O7 and V2O5, and combinations of Fe2O3 and TiO2.

[0041] The present invention does not impose any restrictions on the shape of the lithium disilicate glass ceramic preform, and can adopt shapes well known to those skilled in the art, such as block, column, disc or plate, for cutting, grinding or milling by CAD / CAM equipment, preferably block or disc, more preferably block.

[0042] Generally, the dimensions of the block-shaped billet are between 11mm and 44mm in length, between 10mm and 18mm in width, and between 10mm and 18mm in height. Preferred block-shaped billet dimensions are 18mm×13mm×15mm, 40mm×15mm×14mm, 32mm×15mm×14mm, and 12mm×13mm×15mm.

[0043] The smallest surface of the block blank is bonded to a metal handle using organic adhesive. The metal handle is matched with the corresponding CAD / CAM cutting equipment. The block blank is fixed to the cutting equipment by the metal handle and then cut to obtain a denture of a specific shape.

[0044] In a second aspect, the present invention provides a method for preparing the lithium disilicate glass-ceramic preform as described in the first aspect, the method comprising: subjecting a glass preform to a first heat treatment to obtain a lithium disilicate glass-ceramic preform; wherein the heat treatment curve of the first heat treatment includes at least two plateau temperatures.

[0045] Preferably, the heating rate of the heat treatment curve is 1 to 10 °C / min, for example, it can be 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min or 10 °C / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 3 to 8 °C / min.

[0046] Preferably, the first plateau temperature in the heat treatment curve is 550℃ to 670℃, for example, it can be 550℃, 564℃, 577℃, 590℃, 604℃, 617℃, 630℃, 644℃, 657℃ or 670℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The second plateau temperature is 730℃ to 850℃, for example, it can be 730℃, 744℃, 757℃, 770℃, 784℃, 797℃, 810℃, 824℃, 837℃ or 850℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] This process includes at least two plateau temperatures. The first plateau temperature is preferably above 500°C and below 660°C, with a holding time preferably between 10 and 300 minutes, forming the nucleus for crystal growth. The second plateau temperature is higher than the first, preferably between 700°C and 850°C, with a holding time preferably between 10 and 100 minutes, completing crystal growth. The heating rate in this process needs to be controlled between 1°C / min and 10°C / min, more preferably between 3°C / min and 8°C / min, and even more preferably between 4°C / min and 6°C / min, to ensure the formation of uniform and fine crystals within the blank, with crystal sizes between 50 and 400 nm, making it suitable for processing.

[0048] Preferably, the preparation of the glass preform includes: ball milling, melting, casting and cooling of the raw material powder to obtain the glass preform.

[0049] The present invention does not impose any restrictions on the process flow, parameters and equipment of the ball milling, melting, casting and cooling steps, and any process flow, parameters and equipment known to those skilled in the art for the preparation of glass preforms can be used.

[0050] In the ball milling process, the raw materials are mixed evenly using ball milling equipment. The ball milling time is preferably 1 hour to ensure that the raw materials are mixed evenly.

[0051] In the melting process, the uniformly mixed powder is placed in a high-temperature furnace. The preferred melting temperature is 1200℃ to 1580℃, thereby obtaining molten glass, such as 1350℃, 1450℃, 1500℃ or 1580℃. The preferred melting time is more than 2 hours but less than 6 hours to obtain sufficiently uniform glass liquid, such as 3 hours, 4 hours or 5 hours. The glass can also be repeatedly melted to ensure that the glass liquid is sufficiently uniform.

[0052] In the casting preparation process, the molten glass from the melting process is poured into a mold, placed in an annealing furnace, and annealed at a temperature between 350°C and 450°C for 1-3 hours. Then it is cooled to room temperature to obtain the glass blank.

[0053] Thirdly, the present invention provides an application of the lithium disilicate glass-ceramic preform described in the first aspect in machining.

[0054] The processing method for the machinable high-strength lithium disilicate glass-ceramic preform provided by this invention is typically carried out using CAD / CAM equipment, enabling the manufacture of dentures required by dental patients in a short time. Generally, the fabrication of a single veneer involves processes such as design, cutting, sintering, grinding, and glazing / polishing. This material eliminates one sintering time step, reducing the time from 80 minutes to 55 minutes, significantly improving efficiency.

[0055] Preferably, the percentage of defective area in the lithium disilicate glass-ceramic preform after machining is less than 8%, for example, it can be 7.9%, 7.8%, 7.7%, 7.6%, 7.5%, 7.4%, 7.0%, 6.5%, 6.4%, 6.2%, 6.0%, 5.5%, 5.2%, 5.0%, 4.8%, 4.5%, 4.0%, 3.9%, 3.8%, 3.7%, 3.5%, 3.0%, 2.9%, 2.8%, 2.5%, 2.0%, 1.9%, 1.8%, 1.5%, 1.0%, 0.5%, or 0%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0056] Preferably, the machining includes CAD / CAM machining.

[0057] Preferably, the machining is used to form a dental restorative block.

[0058] In the processing steps, the lithium disilicate blank from the nucleation and crystallization process is cooled to room temperature to obtain a machinable dental restoration. The dental restoration is then machined into a denture shape using machining methods, which are not particularly limited and include cutting, grinding, etc., thus obtaining a denture.

[0059] Compared with the prior art, the present invention has at least the following beneficial effects:

[0060] (1) The lithium disilicate glass-ceramic preform provided by the present invention uses lithium disilicate as the main crystalline phase, and further optimizes the crystal size to be between 50-400nm, so that it can be directly machined and prepared into the shape of a repair body with complete and continuous edges. The introduction of ZnO and the like promotes the formation of two types of lithium disilicate nanoscale crystals after the nucleation and crystallization process inside the preform. The two types of nanoscale crystals are closely attached and interlocked, which gives it excellent processing performance and excellent mechanical strength. Under preferred conditions, its flexural strength is above 300MPa, with excellent performance and a defect area ratio of ≤8%; at the same time, it has good machinability.

[0061] (2) The preparation method of lithium disilicate glass ceramic blank provided by the present invention has a simple manufacturing process and is easy to industrialize.

[0062] (3) The lithium disilicate glass ceramic preform provided by the present invention has the advantages of high strength, machinability and direct color development. It can reduce the waiting time for patients to wear teeth and can be applied to veneers, inlays, single crowns and 3-unit bridge restorations without molars. It solves the problem of patients not knowing the color of all-ceramic dentures before tooth fabrication and breaks through the bottleneck of all-ceramic denture restoration materials that affect patients wearing teeth on the same day. It is of great significance for achieving preoperative color matching and rapid restoration in clinical practice. Attached Figure Description

[0063] Figures 1-2 This is a SEM image of the machinable lithium disilicate glass-ceramic preform prepared in Example 1.

[0064] Figure 3 This is the XRD pattern of the machinable lithium disilicate glass-ceramic preform prepared in Example 1.

[0065] Figure 4 This is the XRD pattern of the machinable lithium disilicate glass-ceramic preform prepared in Example 2.

[0066] Figure 5 This is a SEM image of the lithium disilicate glass-ceramic preform prepared in Comparative Example 2. Detailed Implementation

[0067] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0068] It should be understood that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0069] Example 1

[0070] This embodiment provides a method for preparing a lithium disilicate glass-ceramic preform, the method comprising the following steps:

[0071] According to the mass percentage of the basic glass components, weigh out the analytically pure SiO2, Li2CO3, K2CO3, Al2O3, ZnO, (NH4)2HPO4, and TiO2. 2、 The mass percentages of the oxides corresponding to each component in CeO2 and Er2O3 are 72:15.7:3.5:1:0.15:0.2:4.55:0.5:1.8:0.6.

[0072] After weighing the raw material powder, place it in a ball mill jar and use a ball mill at a speed of 500 r / min for 1 hour to ensure uniform mixing. Place the mixed raw material in a crucible and put it in a high-temperature resistance furnace. Heat the material to 1000℃ at a rate of 10℃ / min and hold for 100 min. Then heat the material to 1500℃ at a rate of 10℃ / min and hold for 3 hours. Remove the material and cast it into a graphite mold preheated to 450℃ for 60 min. Place the mold in an annealing furnace and anneal at 400℃ for 1 hour. Then cool the mold to room temperature to obtain the glass blank.

[0073] The glass preform is placed in a crystallization furnace and heated to 630°C at a rate of 5°C / min, held for 180 min, then heated to 800°C at a rate of 5°C / min, held for 30 min, and cooled to room temperature to obtain the lithium disilicate glass-ceramic preform (i.e., a machinable lithium disilicate dental prosthesis).

[0074] The microstructure and XRD images of the lithium disilicate dental prosthesis prepared in this embodiment are as follows: Figures 1-2 as well as Figure 3 As shown, its crystal content is 84%, the spindle-shaped lithium disilicate grain size is 320nm, the granular type is 230nm, and the flexural strength is 360MPa.

[0075] Example 2

[0076] This embodiment provides a method for preparing a lithium disilicate glass-ceramic preform, the method comprising the following steps:

[0077] According to the mass percentage of the basic glass components, weigh out the analytically pure SiO2, Li2CO3, K2CO3, Al2O3, ZnO, (NH4)2HPO4, and TiO2. 2、 The mass percentages of the oxides corresponding to each component in CeO2 and Er2O3 are 70:14.7:4:1:0.15:2.2:5.05:0.5:1.8:0.6.

[0078] After weighing the raw material powder, place it in a ball mill jar and use a ball mill at a speed of 600 r / min for 40 min to ensure uniform mixing. Place the mixed raw material in a crucible and put it in a high-temperature resistance furnace. Heat the material to 1100℃ at a rate of 15℃ / min and hold for 90 min. Then heat the material to 1560℃ at a rate of 5℃ / min and hold for 2.5 h. Remove the material and cast it into a graphite mold preheated to 500℃ for 50 min. Place the mold in an annealing furnace and anneal at 450℃ for 0.5 h. Then cool the mold to room temperature to obtain the glass preform.

[0079] The glass preform is placed in a crystallization furnace and heated to 670°C at a rate of 10°C / min, held for 120 min, then heated to 810°C at a rate of 2°C / min, held for 10 min, and cooled to room temperature to obtain the lithium disilicate glass-ceramic preform (i.e., a machinable lithium disilicate dental prosthesis).

[0080] The XRD pattern of the machinable lithium disilicate dental prosthesis prepared in this embodiment is shown in the figure below. Figure 4 As shown, from Figure 4 It can be seen that the quartz phase increases, while the lithium disilicate crystal content decreases to 77%.

[0081] Example 3

[0082] This embodiment provides a method for preparing a lithium disilicate glass-ceramic preform, the method comprising the following steps:

[0083] According to the mass percentage of the basic glass components, weigh out the analytically pure SiO2, Li2CO3, K2CO3, Al2O3, ZnO, (NH4)2HPO4, and TiO2. 2、 The mass percentages of the oxides corresponding to each component in CeO2 and Er2O3 are 71.5:15.7:4:1:0.15:1.2:3.55:0.5:1.8:0.6.

[0084] After weighing the raw material powder, place it in a ball mill jar and use a ball mill at a speed of 500 r / min for 1.5 h to ensure uniform mixing. Place the mixed raw material in a crucible and put it in a high-temperature resistance furnace. Heat the material to 950℃ at a rate of 5℃ / min and hold for 200 min. Then heat the material to 1400℃ at a rate of 12℃ / min and hold for 6 h. Remove the material and cast it into a graphite mold preheated to 400℃ for 120 min. Place the mold in an annealing furnace and anneal at 350℃ for 1.5 h. Then cool the mold to room temperature to obtain the glass blank.

[0085] The glass preform is placed in a crystallization furnace and heated to 550°C at a rate of 2°C / min, held for 240 min, then heated to 730°C at a rate of 10°C / min, held for 120 min, and cooled to room temperature to obtain the lithium disilicate glass-ceramic preform (i.e., a machinable lithium disilicate dental prosthesis).

[0086] Example 4

[0087] This embodiment provides a method for preparing a lithium disilicate glass-ceramic preform, the method comprising the following steps:

[0088] According to the mass percentage of the basic glass components, weigh out the analytically pure SiO2, Li2CO3, K2CO3, Al2O3, ZnO, (NH4)2HPO4, and TiO2. 2、 The mass percentages of the oxides corresponding to each component in CeO2 and Er2O3 are 69:15.7:4:1:0.55:2.3:4.65:0.5:1.7:0.6. After weighing the raw material powder, place it in a ball mill jar and use a ball mill at a speed of 500 r / min for a preferred milling time of 1 hour to ensure uniform mixing. Place the mixed raw material in a crucible and put it in a high-temperature resistance furnace. Heat the material to 1000℃ at a rate of 10℃ / min and hold for 100 min. Then heat the material to 1500℃ at a rate of 10℃ / min and hold for 3 hours. Remove the material and cast it into a graphite mold preheated to 450℃ for 60 min. Place the mold in an annealing furnace and anneal at 400℃ for 1 hour. Then cool the mold to room temperature to obtain the glass preform.

[0089] The glass preform is placed in a crystallization furnace and heated to 630°C at a rate of 5°C / min, held for 180 min, then heated to 800°C at a rate of 5°C / min, held for 30 min, and cooled to room temperature to obtain the lithium disilicate glass-ceramic preform (i.e., a machinable lithium disilicate dental prosthesis).

[0090] Example 5

[0091] This embodiment provides a method for preparing a lithium disilicate glass-ceramic preform, the method comprising the following steps:

[0092] According to the mass percentage of the basic glass components, weigh out the analytically pure SiO2, Li2CO3, K2CO3, Al2O3, ZnO, (NH4)2HPO4, and TiO2. 2、The mass percentages of the oxides corresponding to each component in CeO2 and Er2O3 are 70.4:15.7:3:2:0.15:1.1:4.65:0.5:2.0:0.5. After weighing the raw material powder, place it in a ball mill jar and use a ball mill at a speed of 500 r / min for a preferred milling time of 1 hour to ensure uniform mixing. Place the mixed raw material in a crucible and put it in a high-temperature resistance furnace. Heat the material to 1000℃ at a rate of 10℃ / min and hold for 100 min. Then heat the material to 1500℃ at a rate of 10℃ / min and hold for 3 hours. Remove the material and cast it into a graphite mold preheated to 450℃ for 60 min. Place the mold in an annealing furnace and anneal at 400℃ for 1 hour. Then cool the mold to room temperature to obtain the glass blank.

[0093] The glass preform is placed in a crystallization furnace and heated to 630°C at a rate of 5°C / min, held for 180 min, then heated to 800°C at a rate of 5°C / min, held for 30 min, and cooled to room temperature to obtain the lithium disilicate glass-ceramic preform (i.e., a machinable lithium disilicate dental prosthesis).

[0094] Example 6

[0095] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Example 1 except that the P2O5 content is only 1% and the remaining 3.55% is adapted to be SiO2.

[0096] Example 7

[0097] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Example 1 except that the P2O5 content is 12% and the SiO2 content is reduced by 7.45%.

[0098] Example 8

[0099] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Example 1 except that the Al2O3 content is 0.1% and the remaining 0.9% is adapted to be SiO2.

[0100] Example 9

[0101] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Example 1 except that the Al2O3 content is 8% and the SiO2 content is reduced by 7%.

[0102] Example 10

[0103] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Example 1 except that the ZnO content is 0.05% and the remaining 0.1% is adapted to be SiO2.

[0104] Example 11

[0105] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Example 1 except that the ZnO content is 6% and the SiO2 content is reduced by 5.85%.

[0106] Example 12

[0107] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Embodiment 1 except that ZnO is replaced with BaO.

[0108] Example 13

[0109] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Embodiment 1 except that the glass preform is placed in a crystallization furnace and heated to 700°C at a heating rate of 5°C / min.

[0110] Example 14

[0111] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Embodiment 1 except that the glass preform is placed in a crystallization furnace and heated to 500°C at a rate of 5°C / min.

[0112] Example 15

[0113] This embodiment provides a lithium disilicate glass-ceramic preform. Except for the second plateau temperature of 900°C in the heat treatment curve, which is raised to 900°C at a heating rate of 5°C / min, the lithium disilicate glass-ceramic preform is the same as that in Embodiment 1.

[0114] Example 16

[0115] This embodiment provides a lithium disilicate glass-ceramic preform, which is the same as in Embodiment 1 except that the second plateau temperature in the heat treatment curve is 700℃, i.e., it is heated to 700℃ at a heating rate of 5℃ / min.

[0116] Example 17

[0117] This embodiment provides a lithium disilicate glass-ceramic preform. Except for the second plateau temperature of 850°C and holding for 5 minutes in the heat treatment curve, which is to raise the temperature to 850°C at a rate of 5°C / min and hold for 5 minutes, the rest of the lithium disilicate glass-ceramic preform is the same as in Embodiment 1.

[0118] Comparative Example 1

[0119] This comparative example provides a lithium disilicate glass-ceramic preform, which is identical to that in Example 1 except that the ratio of SiO2:Li2O:K2O:Al2O3:ZnO:MgO:P2O5:TiO2:CeO2:Er2O3 is 68:15.2:4:2:3.5:2.2:3.2:0.4:1.0:0.5.

[0120] The SEM image of the lithium disilicate dental restoration prepared in this comparative example is shown below. Figure 5 As shown, from Figure 5 It can be seen that it only yields one type of crystal phase with poor machinability.

[0121] Test methods: The crystal content and main crystalline phase of the lithium disilicate glass-ceramic green body were tested using the X-ray crystal three-point bending test. The flexural strength of the lithium disilicate glass-ceramic green body was tested using the three-point bending test method of GB30367-2013 / ISO6872:2008. The crystal morphology types of the lithium disilicate glass-ceramic green body were tested using X-ray diffraction. The crystal morphology and grain size of the lithium disilicate glass-ceramic green body were observed and tested using scanning electron microscopy. The machinability of the lithium disilicate glass-ceramic green body was tested using CAD / CAM cutting equipment (CMW-400 cutting machine) (based on the number of facets that can be cut by one set of cutting tools). The percentage of defect area after cutting the lithium disilicate glass-ceramic green body was tested using a high-definition microscope.

[0122] The test results of the above embodiments and comparative examples are shown in Table 1.

[0123] Table 1

[0124]

[0125]

[0126] The following points can be observed from Table 1:

[0127] (1) As can be seen from Examples 1-5, the lithium disilicate glass-ceramic preform provided by the present invention uses lithium disilicate as the sole or main crystalline phase. Traditional lithium disilicate dental restorations have a cross-linked, interlocking long rod-shaped microstructure. The lithium disilicate glass-ceramic preform provided by the present invention has two crystal morphologies. The two nanoscale crystal morphologies are closely bonded and cross-interlocked, giving it excellent processing performance and excellent mechanical strength, making it suitable for use as a dental restoration. Moreover, its flexural strength is above 300 MPa, exhibiting excellent performance, with a defect area ratio of ≤8%. It also has good machinability. In other words, the lithium disilicate dental restoration provided by the present invention combines the advantages of high crystal content, high strength, and good machinability. It can be applied to veneers, inlays, single crowns, and 3-unit bridge restorations without molars, which is of great significance for improving the service life and aesthetic restoration effect of dental restoration materials.

[0128] (2) As can be seen from the combined examples 1 and 6 to 12, the selection and content of each component in the lithium disilicate glass-ceramic green body provided by the present invention have a significant impact on the flexural strength and machinability of the final lithium disilicate glass-ceramic green body. The P2O5 content is preferably controlled between 2% and 10%, the final main crystalline phase of the sample is lithium disilicate, and the crystal size can be controlled within a suitable range. The final sample has high flexural strength and a small proportion of edge chipping after cutting. Similarly, by controlling the Al2O3 content to 0.5% to 5% and the ZnO content to cooperate with other components, the flexural strength of the sample can be further improved and the proportion of edge chipping after cutting can be reduced, which has broad application prospects.

[0129] (3) As can be seen from the combined examples 1 and 13-17, the present invention preferably uses a heat treatment curve with two plateau temperatures and the temperature is controlled within a reasonable range, which can better control the size and morphology of crystal growth, and finally obtain a lithium disilicate glass ceramic blank with excellent flexural strength and cutting performance.

[0130] (4) As can be seen from the combined results of Example 1 and Comparative Example 1, the Me(II)O content in Comparative Example 1 is significantly too high, resulting in only one morphology of crystal phase and poor machinability. This indicates that the present invention can improve flexural strength and machinability by introducing two morphologies of crystal into the lithium disilicate glass-ceramic preform.

[0131] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A lithium disilicate glass-ceramic preform, characterized in that, The lithium disilicate glass-ceramic preform includes a lithium disilicate main crystalline phase, wherein the crystal size of the lithium disilicate glass-ceramic preform is between 50 and 400 nm, and the area of ​​grains with a length greater than 350 nm accounts for less than 30% of the total area; The lithium disilicate main crystalline phase has at least two crystal morphologies; The crystal morphology includes at least a first crystal morphology in which the ratio of any two of the length, width and height is in the range of 0.6 to 1, and a second crystal morphology in which at least one of the two of the length, width and height has a ratio of 3:1 or higher. The mass ratio of SiO2 to Li2O in the lithium disilicate glass-ceramic preform is (3.5~7):

1.

2. The lithium disilicate glass-ceramic preform according to claim 1, characterized in that, The flexural strength of the lithium disilicate glass-ceramic preform is greater than 300 MPa.

3. The lithium disilicate glass-ceramic preform according to claim 1 or 2, characterized in that, The first crystal morphology includes any one or a combination of at least two of the following: granular, ellipsoidal, rhomboid, or clustered.

4. The lithium disilicate glass-ceramic preform according to claim 1, characterized in that, The second crystal morphology includes any one or a combination of at least two of the following: spindle-shaped, plate-shaped, layer-shaped, network-shaped, rod-shaped, or needle-shaped.

5. The lithium disilicate glass-ceramic preform according to claim 1, characterized in that, The composition of the lithium disilicate glass-ceramic preform, based on mass percentage, is as follows: SiO2 62%~75%; Li2O 8%~18%; Al2O3 0.5%~5%; P2O5 2%~5.05%; Me(Ⅰ)2O 1%~10%; Me(II)O 0.1%~5%; Colorant: 0.1-10%.

6. The lithium disilicate glass-ceramic preform according to claim 5, characterized in that, The mass ratio of the sum of Al2O3 and P2O5 to Li2O is (0.2~1):

1.

7. The lithium disilicate glass-ceramic preform according to claim 5, characterized in that, The Me(Ⅰ)2O contains K2O and / or Na2O.

8. The lithium disilicate glass-ceramic preform according to claim 5, characterized in that, The Me(Ⅱ)O contains any one or a combination of at least two of MgO, CaO, ZnO, BaO, or SrO.

9. The lithium disilicate glass-ceramic preform according to claim 8, characterized in that, The Me(Ⅱ)O contains ZnO.

10. The lithium disilicate glass-ceramic preform according to claim 5, characterized in that, The colorant comprises CeO2, V2O5, Er2O3, and Pr6O. 11 A combination of at least two of Nd2O3, Fe2O3, Tb4O7 or TiO2.

11. A method for preparing a lithium disilicate glass-ceramic preform according to any one of claims 1 to 10, characterized in that, The preparation method includes: subjecting a glass preform to a first heat treatment to obtain a lithium disilicate glass-ceramic preform; the heat treatment curve of the first heat treatment includes at least two plateau temperatures.

12. The preparation method according to claim 11, characterized in that, The heating rate of the heat treatment curve is 1~10℃ / min.

13. The preparation method according to claim 11, characterized in that, The heating rate of the heat treatment curve is 3~8℃ / min.

14. The preparation method according to claim 11, characterized in that, The first plateau temperature in the heat treatment curve is 550℃~670℃, and the second plateau temperature is 730℃~850℃.

15. The application of the lithium disilicate glass-ceramic preform according to any one of claims 1 to 10 in machining.

16. The application according to claim 15, characterized in that, The defect area of ​​the lithium disilicate glass-ceramic preform after machining is less than 8%.

17. The application according to claim 15, characterized in that, The machining process includes CAD / CAM machining.

18. The application according to claim 15, characterized in that, The machining process is used to form dental restorative blocks.

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