Preparation method of dental restoration lithium disilicate microcrystalline glass

Abstract

The application provides a dental repair lithium disilicate glass ceramic and a preparation method thereof. In the formula composition, the strength of the glass ceramic is increased by adjusting the silicon-lithium ratio SiO2 / Li2O (2.0-2.9). Meanwhile, a small amount of Rb2O and Cs2O is doped to replace K2O ((Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O))=0-1. After the batching is completed, the mixture is firstly pre-burned at 300-600 DEG C for 3-5 hours. Then, the wet ball milling is carried out to reduce the particle size, so that the melting temperature is reduced, and the energy consumption is saved. In the process of melting and preparing the base glass, the platinum gold crucible continuous melting technology is introduced, and the processes such as bubbling, clarifying and stirring are added, so that the glass ceramic material with better uniformity and more compact structure can be prepared. Finally, the 3-stage nucleation and crystallization heat treatment process system is carried out after the base glass is prepared, so that the glass ceramic has ideal crystal phase composition and structure performance.

Description

Technical Field

[0001] This invention relates to a method for preparing lithium disilicate glass-ceramics for dental restoration, belonging to the field of glass-ceramic preparation. Background Technology

[0002] Lithium disilicate glass-ceramics, also known as glass-ceramics, is a polycrystalline material obtained from a matrix glass through nucleation and crystallization. It possesses the high strength and hardness of ceramics while retaining the translucent optical properties of glass. Compared to traditional dental restorative materials, it exhibits excellent biocompatibility, superior corrosion resistance, and high wear resistance, along with unique aesthetic properties. It can effectively mimic the luster and translucency of natural teeth. Therefore, it has become the preferred material for anterior dental restorations.

[0003] Currently, dental lithium disilicate glass-ceramic materials are limited in variety and entirely dependent on imports, resulting in high costs and restricting their widespread clinical application. Therefore, developing lithium disilicate glass-ceramic products with independent intellectual property rights is of significant theoretical and practical importance for breaking through technological monopolies, promoting the application of all-ceramic restorations, and reducing restoration costs.

[0004] Although many research institutes and enterprises are currently conducting related research, the structural stability, uniformity, and strength of this material still lag behind those of foreign materials.

[0005] CN113501668A proposes a method for preparing high-strength and high-transparency lithium disilicate glass ceramics. This method simply increases the crystal size (≥700nm and ≤1200nm) through nucleation and crystallization treatments to achieve the purpose of strengthening. The basic glass melt preparation process is too simple, and the material has poor structural stability and uniformity, which is not conducive to subsequent processing.

[0006] CN106277800A proposes using ZrO2 and P2O5 as mixed nucleating agents. The former mainly induces the formation of β-quartz solid solution as the main crystalline phase in the glass system, while the latter mainly promotes the dissolution of ZrO2 in the glass and increases the nucleation rate. The two promote each other, thus obtaining microcrystalline glass with finer grains. This preparation method can produce relatively uniform microcrystalline materials, but its strength is too low and the grain size is small. It is only suitable for the fabrication of multi-unit bridges for anterior teeth or dental veneers and is not suitable for posterior teeth used for chewing.

[0007] CN107698167A proposes a chemical tempering method (ion exchange method) in which the prepared matrix glass is placed in rubidium salt powder and heat-treated at 400-600℃ for 1-8 hours. Although this method can effectively improve the strength of microcrystalline glass, it adds unnecessary steps and is time-consuming and labor-intensive.

[0008] A review of relevant literature reveals that most authors enhance the strength of the material by nucleation, crystallization, ion exchange, or spraying high-strength material coatings after preparing the matrix glass. However, the preparation process of the matrix glass, including formulation design and melting, rarely incorporates techniques for achieving high strength, high uniformity, and high stability. This invention addresses this technological gap by proposing a method for preparing lithium disilicate microcrystalline glass for dental restorations. Summary of the Invention

[0009] To address the existing problems of lithium disilicate microcrystalline glass, this invention proposes a dental restorative lithium disilicate microcrystalline glass and its preparation method. In terms of formulation composition, the strength is increased by adjusting the silicon-to-lithium ratio (SiO2 / Li2O) to 2.0-2.9. Simultaneously, doping with trace amounts of Rb2O and Cs2O to replace K2O ((Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O)) = 0-1; or even eliminating K2O from the formulation, can effectively increase the structural stability of the material. This is because excessive K2O intake in the formulation can inhibit the formation of lithium disilicate crystals later, while also exacerbating phase separation in the glass matrix, which is detrimental to the stability of the microcrystalline glass. After batching, the batch is first pre-fired at 300℃-600℃ for 3-5 hours. Then, wet ball milling is performed to reduce the particle size, thereby lowering the melting temperature and saving energy. By introducing continuous melting technology using platinum crucibles into the substrate glass melting process, and adding processes such as bubbling, clarification, and stirring, microcrystalline glass materials with better uniformity and denser structure can be prepared. Finally, after the substrate glass is prepared, a three-stage nucleation and crystallization heat treatment process is carried out to give it ideal crystal phase composition and structural properties.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A type of dental restorative lithium disilicate microcrystalline glass comprises the following components: SiO2: 50-75%, Li2O: 10-30%, K2O: 4-10%, Al2O3: 1-3%, P2O5: 3-5%, TiO2: 0.1-1.5%, CeO2: 0.1-2.0%, ZnO: 1.0-3.0%, MgO: 0.1-1.5%, B2O3: 1.0-2.0%, ZrO2: 1.0-4.0%, Cs2O: 0-1.0%, Rb2O: 0-1.0%.

[0012] The SiO2 / Li2O ratio is 2.0 to 2.9, and (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O)) = 0 to 1, and is not 0.

[0013] The SiO2 / Li2O ratio is preferably 2.140 to 2.896.

[0014] A method for preparing lithium disilicate microcrystalline glass for dental restoration specifically includes the following steps:

[0015] Step 1: Design and calculation of the formula. The formula composition is as follows:

[0016] SiO2: 50~75%, Li2O: 10~30%, K2O: 4~10%, Al2O3: 1~3%, P2O5: 3~5%, TiO2: 0.1~1.5%, CeO2: 0.1~2. 0%, ZnO: 1.0~3.0%, MgO: 0.1~1.5%, B2O3: 1.0~2.0%, ZrO2: 1.0~4.0%, Cs2O: 0~1.0%, Rb2O: 0~1.0%.

[0017] The SiO2 / Li2O ratio is 2.0 to 2.9, and (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O)) = 0 to 1, and is not 0.

[0018] The SiO2 / Li2O ratio is preferably 2.140 to 2.896.

[0019] Step 2: Ingredient Preparation

[0020] Weigh the designed formulation components as needed into a V-type mixer and mix evenly for 20-30 minutes. The chemical raw materials are of industrial grade 1 purity. Specifically, SiO2 is introduced as high-purity quartz sand, Li2O and K2O are introduced as lithium carbonate and potassium carbonate, Al2O3 as aluminum hydroxide, P2O5 as ammonium dihydrogen phosphate, MgO as basic magnesium carbonate, B2O3 as boric acid, Cs2O and Rb2O as cesium carbonate (cesium nitrate) and rubidium carbonate (rubidium nitrate), respectively, and the remaining chemical raw materials are introduced in oxide form.

[0021] Step 3: Preheating

[0022] The mixed batch from step two is loaded into a muffle furnace and preheated at 300℃~600℃ for 3~5 hours.

[0023] Step 4: Ball milling

[0024] The pre-calcined batch material from step three is then placed into a ball mill for further ball milling to reduce the particle size and thus lower the melting temperature.

[0025] Step 5: High-temperature melting

[0026] The batch material ground in step four is added in batches to the platinum pot, which has been preheated to 1400℃~1500℃, until the liquid level reaches 4 / 5 of the pot. Then, the feeding is stopped, and the pot is kept warm for 1~2 hours. High-purity nitrogen gas is then introduced for bubbling for 40~50 minutes at a flow rate of 1.0L / min. This ensures that the glass melt is further mixed evenly under the action of the bubbling gas, making the melting more complete.

[0027] Step Six: Clarification and Homogenization + Stirring

[0028] The homogeneous glass melt obtained in step 5 is further heated to 1600℃~1650℃ for clarification and homogenization to eliminate internal bubbles. After cooling down to 10℃~20℃ above the upper limit of crystallization temperature, the stirrer is turned on and stirred. The stirrer motor frequency is 42Hz~45Hz and the speed is 36~38r / min until the internal streaks are completely eliminated.

[0029] Step 7: Material Discharge and Molding

[0030] The highly uniform molten glass obtained in step six is ​​discharged from the discharge pipe at the bottom of the platinum pot and formed into a graphite mold that has been preheated to 400℃~700℃.

[0031] Step 8: Annealing

[0032] The glass block formed in step seven, along with the graphite mold, is placed in a muffle furnace that has been preheated to 400℃~700℃ for annealing. After holding at this temperature for 1~2 hours, the power is turned off and the glass block is cooled to room temperature along with the furnace to obtain a transparent matrix glass block.

[0033] Step Nine: Nucleation and Crystallization Heat Treatment

[0034] The transparent matrix glass block obtained in step eight is placed in a muffle furnace preheated to 500℃~550℃ for a first nucleation heat treatment of 30min~60min, a second crystallization heat treatment of 600℃~750℃ for 90min~120min, and a third crystallization heat treatment of 780℃~890℃ for 150min~240min. The furnace is then cooled after the power is turned off to obtain the microcrystalline glass material.

[0035] The beneficial effects achieved by this invention are as follows:

[0036] 1. The strength of lithium disilicate glass can be enhanced by adjusting the SiO2 / Li2O ratio in the formulation. A SiO2 / Li2O ratio that is too low results in a mixture of lithium phosphate and lithium metasilicate as the main crystalline phases, with a hexagonal granular structure. This results in excessively low strength (microscopic strength less than 300 MPa) and flexural strength less than 130 MPa), failing to meet the strength requirements for dental restorative materials. Conversely, a SiO2 / Li2O ratio that is too high results in a mixed crystalline phase of lithium disilicate and quartz crystals, which is unfavorable for subsequent processing into dental restorative materials, making processing more difficult. Furthermore, it lacks translucency and has poor aesthetic performance. This is because the reaction equation for the formation of lithium disilicate is:

[0037] (1) P2O5 (glass) + 3Li2O (glass) = 2Li3PO4 (crystalline phase)

[0038] (2) Li2O (glass) + SiO2 (glass) = Li2SiO3 (crystalline phase)

[0039] (3) Li2SiO3 (crystalline phase) + SiO2 (glass) = Li2Si2O5 (crystalline phase)

[0040] As described in the above reaction equations, in order to obtain the ideal crystal phase composition, the above three chemical equations must be satisfied. A lower silicon-lithium ratio can only carry out the first step reaction and a small amount of the second step reaction. Only an appropriate SiO2 / Li2O ratio can yield a dental restorative material with lithium disilicate as the main crystal phase, lithium metasilicate as the secondary crystal phase, and excellent optical properties. Therefore, this invention has a limitation on the SiO2 / Li2O ratio.

[0041] 2. To further enhance the strength and structural stability of the glass-ceramic, a certain amount of nucleating agent and flux is introduced into the formulation. This invention introduces P2O5 and ZrO2 as a mixed nucleating agent and K2O as a flux. K2O not only lowers the melting and softening temperatures of the glass, but also reduces its viscosity, facilitating gas release during sintering and resulting in higher density, thereby improving the flexural strength of the glass-ceramic. However, excessive K2O can inhibit the formation of the lithium silicate phase. To further consolidate the structural stability of the glass-ceramic, this invention introduces a certain amount of Cs. The K2O content in the formulation is replaced by Cs2O and Rb2O, which ensure that it can play a role in fluxing, reducing viscosity, and improving flexural strength, without inhibiting further crystallization. Cs2O and Rb2O, which are alkali metal elements of the same group, are used to replace K2O. The ionic radii of Cs and Rb are larger than those of K, and their outermost electrons are more easily lost. The lower the electric field strength, the easier it is to reduce the glass melting temperature. At the same time, the replacement of K with Cs and Rb with larger particle radii in the entire glass network results in a denser glass network structure, higher strength, and better stability, which is also a major innovation of this invention.

[0042] 3. A continuous platinum crucible melting technology was proposed. In the preparation of matrix glass, after pre-firing and secondary ball milling to obtain a more uniform particle size, the batch is fed in batches into a platinum crucible preheated to 1400℃~1500℃. Due to the smaller particle size, the melting temperature is lower than that of traditional preparation methods, further saving energy. At the same time, a high-purity nitrogen bubbling process is added, which makes the glass melt melt more completely under the continuous turbulence of the bubbling gas. A high-temperature clarification process is further added, clarifying and homogenizing at 1600℃~1650℃ to eliminate internal small bubbles. A platinum agitator has been added to the glass melt. After being cooled by the cooling pipe, the glass melt flows into the discharge pool equipped with the agitator. The agitator rotates continuously to eliminate the internal streaks in the glass melt. The glass melt is then discharged through the platinum discharge pipe at the bottom, resulting in a uniform and stable matrix glass melt. Compared with traditional manual casting, this method can better avoid the scouring streaks or even phase separation caused by secondary scouring of the mold inner wall during the casting process. Moreover, using mechanical equipment instead of manual operation not only saves time and labor but also makes it more reproducible and more conducive to obtaining highly uniform glass blocks.

[0043] 4. This invention employs a three-stage nucleation and crystallization heat treatment process. The first stage involves nucleation at 500℃ to 550℃ for 30 to 60 minutes, inducing nucleation to obtain Li3PO4 (crystalline phase). The second stage involves crystallization at 600℃ to 750℃ for 90 to 120 minutes, yielding Li2SiO3 (crystalline phase) with a uniform hexagonal granular microstructure. The third stage involves crystallization at 780℃ to 890℃ for 150 to 240 minutes, yielding Li2Si2O5 (main crystalline phase) with a rod-shaped interlocking crystal structure, resulting in a significant increase in its fracture strength.

[0044] This invention achieves superior structural stability and uniformity by addressing three aspects: formulation, smelting process, and heat treatment process. The main crystalline phase is lithium disilicate, and the secondary crystalline phases are lithium metasilicate and lithium phosphate. The microstructure consists of a rod-shaped interlocking structure and a hexagonal granular crystalline structure intertwined and interlocked grains, resulting in high fracture strength. The coexistence of the glassy phase formed by excess SiO2 and the crystalline phase provides semi-transparency and aesthetic appeal. Attached Figure Description

[0045] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0046] Figure 1 The XRD diffraction pattern of the sample obtained in Example 4, whose main crystalline phase is lithium disilicate;

[0047] Figure 2 is a scanning electron microscope image of the sample obtained in Example 4, whose main crystalline phase is lithium disilicate;

[0048] Figure 3 shows images of teeth after nucleation and crystallization treatment of the sample obtained in Example 4;

[0049] Figure 4 shows the platinum device structure designed in this invention; Detailed Implementation

[0050] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0051] The present invention will be further illustrated below with reference to specific embodiments. These embodiments should be understood as illustrative only and not as limiting the scope of protection of the present invention. After reading the description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

[0052] The tests described in the following embodiments are performed according to the following test methods:

[0053] (1) X-ray diffraction analysis (XRD)

[0054] A smooth surface of the sample was selected, and the X-ray diffractometer (D / max3B) manufactured by Rigaku Corporation, Japan, was used for testing. The test conditions were: tube voltage 40 kV, tube current 30 mA, scanning range 10°~70°, scanning speed 5° / min, and sampling interval 0.02°.

[0055] (2) Scanning electron microscopy (SEM)

[0056] A cross-section of the glass sample was selected, and the cross-section was sputtered with gold. The microstructure of the glass-ceramic was then observed using a JSM-7800F scanning electron microscope.

[0057] (3) Mechanical performance testing

[0058] The test sample was prepared into a strip shape of 2mm × 5mm × 30mm using low-speed cutting and grinding equipment. The glass sample was then polished with polishing powder. The fracture strength of the sample was tested using a universal strength tester employing the three-point bending test method. The instrument loading speed was 1mm / min, and the span was 20mm, which allows for the determination of the maximum load when the glass breaks. The fracture strength of the sample can be calculated using the following formula.

[0059] As shown in the formula:

[0060]

[0061] Where M is the three-point bending strength (MPa), W is the maximum load (N), l is the span (mm), b is the sample width (mm), and d is the sample thickness (mm), the fracture strength of the sample can be obtained through calculation.

[0062] Comparative Example 1

[0063] The formula was designed and calculated, and its composition is as follows:

[0064] SiO2:58%, Li2O:27%, K2O:5%, Al2O3:1%, P2O5:1.4%, TiO2:0.4%, CeO2:0.1%, ZnO:1.3%, MgO:0.2%, B2O3:2.0%, ZrO2:3.6%

[0065] Where SiO2 / Li2O=2.148, (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O))=0.

[0066] Example 1

[0067] The formula was designed and calculated, and its composition is as follows:

[0068] SiO2:58%, Li2O:27%, K2O:4%, Al2O3:1%, P2O5:1.4%, TiO2:0.4%, CeO2:0.1%, ZnO:1.3%, MgO:0.2%, B2O3:2.0%, ZrO2:3.6%, Cs2O:1.0%

[0069] Where SiO2 / Li2O=2.148, (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O))=0.33.

[0070] Example 2

[0071] The formula was designed and calculated, and its composition is as follows:

[0072] SiO2:58%, Li2O:27%, K2O:4%, Al2O3:1%, P2O5:1.4%, TiO2:0.4%, CeO2:0.1%, ZnO:1.3%, MgO:0.2%, B2O3:2.0%, ZrO2:3.6%, Rb2O:1.0%

[0073] Where SiO2 / Li2O=2.148, (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O))=0.33.

[0074] Example 3

[0075] The formula was designed and calculated, and its composition is as follows:

[0076] SiO2:58%, Li2O:27%, K2O:3.4%, Al2O3:1%, P2O5:1.4%, TiO2:0.4%, CeO2: 0.1%, ZnO: 1.3%, MgO: 0.2%, B2O3: 2.0%, ZrO2: 3.6%, Cs2O: 0.8%, Rb2O: 0.8%

[0077] Where SiO2 / Li2O=2.148, (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O))=0.89.

[0078] Example 4

[0079] The formula was designed and calculated, and its composition is as follows:

[0080] SiO2: 62%, Li2O: 23%, K2O: 3.4%, Al2O3: 1%, P2O5: 1.4%, TiO2: 0.4%, CeO2: 0.1%, ZnO: 1.3%, MgO: 0.2%, B2O3: 2.0%, ZrO2: 3.6%, Cs2O: 0.8%, Rb2O: 0.8%

[0081] Where SiO2 / Li2O=2.696, (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O))=0.89.

[0082] In Examples 1, 2, and 3, 1.0% Cs2O, 1.0% Rb2O, and (Cs2O:0.8% + Rb2O:0.8%) respectively replaced an equal amount of K2O in the formulation, and SiO2 / Li2O = 2.148. In Example 4, SiO2 / Li2O was adjusted to 2.696 based on Example 3.

[0083] The above method for preparing microcrystalline glass includes the following steps:

[0084] Step 2: Ingredient Preparation

[0085] Weigh the designed formulation components as needed into a V-type mixer and mix evenly for 25 minutes. The chemical raw materials are of industrial grade 1 purity. Specifically, SiO2 is introduced in the form of high-purity quartz sand, Li2O and K2O are introduced in the form of lithium carbonate and potassium carbonate, Al2O3 is introduced in the form of aluminum hydroxide, P2O5 is introduced in the form of ammonium dihydrogen phosphate, MgO is introduced in the form of basic magnesium carbonate, B2O3 is introduced in the form of boric acid, Cs2O and Rb2O are introduced in the forms of cesium carbonate and rubidium carbonate, respectively, and the remaining raw materials are introduced in the form of oxides.

[0086] Step 3: Preheating

[0087] The mixed batch from step two is loaded into a muffle furnace and pre-fired at 500°C for 5 hours.

[0088] Step 4: Ball milling

[0089] The pre-calcined batch material from step three is then placed into a ball mill for further ball milling to reduce the particle size and thus lower the melting temperature.

[0090] Step 5: High-temperature melting

[0091] The batch material ground in step four is added in batches to the platinum pot that has been preheated to 1450℃ until the liquid level reaches 4 / 5 of the entire pot. Then, the feeding is stopped, and the pot is kept at this temperature for 2 hours. High-purity nitrogen gas is then introduced for bubbling for 40 minutes at a flow rate of 1.0 L / min to ensure that the glass melt is further mixed evenly under the action of the bubbling gas, so that the melting is more complete.

[0092] Step Six: Clarification and Homogenization + Stirring

[0093] The homogeneous glass melt obtained in step 5 is further heated to 1600℃ for clarification and homogenization to eliminate internal bubbles. After cooling down to above the upper limit temperature for crystallization (20℃), the stirrer is turned on and stirred at a motor frequency of 42Hz and a rotation speed of 36r / min until the internal streaks are completely eliminated.

[0094] Step 7: Material Discharge and Molding

[0095] The highly uniform molten glass obtained in step six is ​​discharged from the discharge pipe at the bottom of the platinum pot and formed into a graphite mold that has been preheated to 580°C.

[0096] Step 8: Annealing

[0097] The glass block formed in step seven, along with the graphite mold, is placed in a muffle furnace that has been preheated to 580°C for annealing. After holding at that temperature for 2 hours, the power is turned off and the glass block is cooled to room temperature along with the furnace to obtain a transparent matrix glass block.

[0098] Step Nine: Nucleation and Crystallization Heat Treatment

[0099] The transparent matrix glass block obtained in step eight is placed in a muffle furnace preheated to 580°C for a first nucleation heat treatment of 60 min, a second crystallization heat treatment of 650°C for 120 min, and a third crystallization heat treatment of 800°C for 180 min. The furnace is then cooled after the power is turned off to obtain the microcrystalline glass material.

[0100] Comparative Example 2

[0101] The formula was designed and calculated, and its composition is as follows:

[0102] SiO2:56%, Li2O:29%, K2O:4%, Al2O3:1%, P2O5:1.4%, TiO2:0.4%, CeO2:0.1%, ZnO:1.3%, MgO:0.2%, B2O3:2.0%, ZrO2:3.6%, Cs2O:1.0%

[0103] Where SiO2 / Li2O=1.931 (≤SiO2 / Li2O=2.148, which is not within the scope of this application)

[0104] (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O))=0.33.

[0105] Microcrystalline glass material samples were prepared using the preparation methods in steps two through nine.

[0106] Comparative Example 3

[0107] Steps three, four, and six are omitted; the rest are the same as in Example 1.

[0108] Table 1. Test results of mechanical properties of glass-ceramics

[0109]

[0110] The results show that:

[0111] Examples 1, 2, and 3, which used appropriate amounts of Cs₂O and Rb₂O, or a mixture thereof, to replace a small amount of K₂O in the formulation, yielded microcrystalline glass with a 17% increase in microhardness before crystallization and a 14% increase in microhardness after crystallization compared to Comparative Example 1 (which did not use other elements for substitution). Example 4, based on Example 3, adjusted the SiO₂ / Li₂O ratio to 2.696, resulting in a 19% increase in microhardness and a 49% increase in fracture strength compared to Examples 1, 2, and 3. Comparative Example 2 (SiO₂ / Li₂O = 1.931), using a SiO₂ / Li₂O ratio not covered in this application, employed the same preparation method to characterize mechanical properties. Compared to Comparative Example 1, the microhardness decreased by 15% and the fracture strength decreased by 19% before and after crystallization. This is because the excessively low SiO₂ / Li₂O ratio resulted in insufficient SiO₂ to further react during matrix glass formation, producing a crystalline mixture with lithium phosphate and a small amount of lithium metasilicate as the main crystalline phase. This mixture had lower strength but better uniformity. Comparative Example 3 has the same formulation as Example 1, but was prepared using a traditional matrix glass melt preparation method. Compared to Example 1, the microhardness decreased by 28% and the fracture strength increased by 4.6% before and after crystallization. This is because the traditional glass melt preparation method results in poor uniformity and glass consistency, with local phase divisions, streaks, and bubbles within the glass, leading to inconsistent strength. Therefore, the microhardness decreased while the flexural strength increased slightly. Obviously, the formulation and preparation method of this invention can significantly improve the pre-preparation of microcrystalline glass materials with high microhardness, fracture strength, and better uniformity.

[0112] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A type of dental restorative lithium disilicate microcrystalline glass, characterized in that: It comprises the following components: SiO2: 50–75%, Li2O: 10–30%, K2O: 4–10%, Al2O3: 1–3%, P2O5: 3–5%, TiO2: 0.1–1.5%, CeO2: 0.1–2.0%, ZnO: 1.0–3.0%, MgO: 0.1–1.5%, B2O3: 1.0–2.0%, ZrO2: 1.0–4.0%, Cs2O: 0–1.0%, Rb2O: 0–1.0%. The SiO2 / Li2O ratio is 2.0 to 2.9, and (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O)) = 0 to 1, and is not 0.

2. The dental restorative lithium disilicate microcrystalline glass according to claim 1, wherein the SiO2 / Li2O ratio is 2.140 to 2.

896.

3. A method for preparing lithium disilicate microcrystalline glass for dental restoration, specifically including the following steps: Step 1: Design and calculation of the formula. The formula composition is as follows: SiO2: 50~75%, Li2O: 10~30%, K2O: 4~10%, Al2O3: 1~3%, P2O5: 3~5%, TiO2: 0.1~1.5%, CeO2: 0.1~2. 0%, ZnO: 1.0~3.0%, MgO: 0.1~1.5%, B2O3: 1.0~2.0%, ZrO2: 1.0~4.0%, Cs2O: 0~1.0%, Rb2O: 0~1.0%; The ratio of SiO2 / Li2O is 2.0 to 2.9, and (Cs2O+Rb2O) / (K2O-(Cs2O+Rb2O)) = 0 to 1, and is not 0. Step 2: Ingredient Preparation Weigh the raw materials according to the above-designed formula components and mix them evenly in a V-type mixer for 20-30 minutes. Step 3: Preheating The mixed batch from step two is loaded into a muffle furnace and pre-fired at 300℃~600℃ for 3~5 hours; Step 4: Ball milling The pre-calcined batch material from step three is put into a ball mill for further ball milling to reduce the particle size and thus reduce the melting temperature. Step 5: High-temperature melting The batch material ground in step four is added in batches to the platinum pot that has been preheated to 1400℃~1500℃ until the liquid level is 4 / 5 full. Then, stop adding material and keep it at the temperature for 1~2 hours. Then, start bubbling with high-purity nitrogen gas to ensure that the glass melt is further mixed evenly under the action of the bubbling gas, so that it melts more completely. Step Six: Clarification and Homogenization + Stirring The uniform glass melt obtained in step 5 is further heated to 1600℃~1650℃ to clarify and homogenize, eliminating internal bubbles. After cooling to 10℃~20℃ above the upper limit temperature for crystallization, the stirrer is turned on to stir until the internal streaks are completely eliminated. Step 7: Material Discharge and Molding The highly uniform molten glass obtained in step six is ​​discharged from the discharge pipe at the bottom of the platinum pot and formed into a graphite mold that has been preheated to 400℃~700℃. Step 8: Annealing The glass block formed in step seven, together with the graphite mold, is placed in a muffle furnace that has been preheated to 400℃~700℃ for annealing. After holding at the temperature for 1~2 hours, the power is turned off and the glass block is cooled to room temperature with the furnace to obtain a transparent matrix glass block. Step Nine: Nucleation and Crystallization Heat Treatment The transparent matrix glass block obtained in step eight is placed in a muffle furnace preheated to 500℃~550℃ for a first nucleation heat treatment of 30min~60min, a second crystallization heat treatment of 600℃~750℃ for 90min~120min, and a third crystallization heat treatment of 780℃~890℃ for 150min~240min. The furnace is then cooled after the power is turned off to obtain the microcrystalline glass material.

4. The method for preparing a dental restorative lithium disilicate microcrystalline glass according to claim 3, wherein SiO2 is introduced in the form of high-purity quartz sand, Li2O and K2O are introduced in the form of lithium carbonate and potassium carbonate, Al2O3 is introduced in the form of aluminum hydroxide, P2O5 is introduced in the form of ammonium dihydrogen phosphate, MgO is introduced in the form of basic magnesium carbonate, B2O3 is introduced in the form of boric acid, Cs2O is introduced in the form of cesium carbonate or cesium nitrate, Rb2O is introduced in the form of rubidium carbonate or rubidium nitrate, and the remaining raw materials are introduced in the form of oxides.

5. In the method for preparing a dental restorative lithium disilicate microcrystalline glass according to claim 3, the bubbling time in step five is 40-50 min, and the bubbling flow rate is 1.0 L / min.

6. In the method for preparing a dental restorative lithium disilicate microcrystalline glass according to claim 3, the stirrer motor frequency in step six is ​​42Hz~45Hz, and the rotation speed is 36~38r / min.

7. The method for preparing a dental restorative lithium disilicate microcrystalline glass according to claim 3, wherein the SiO2 / Li2O ratio in the ingredients is 2.140 to 2.896.

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