Glass-ceramic dental crown and method for manufacturing same

Abstract

The application discloses a glass ceramic dental crown and a preparation method thereof, and relates to the technical field of glass ceramic dental crown. The preparation method adopts lithium disilicate as a base material, and is combined with rare earth doped hydroxyapatite and functional crystals. By accurately controlling the synergistic ratio of each component, the unity of mechanical properties, biological adaptability and aesthetic effect is realized. The rare earth doped hydroxyapatite is prepared by a hydrothermal precipitation method, the dispersion effect of trisodium citrate is used to inhibit particle agglomeration and promote the interface combination with human hard tissues; and the rare earth doped fluorescent powder is used to construct monodisperse light emitting centers by controlling a rare earth ion doping process, so that concentration quenching is avoided, and the fluorescent properties close to natural teeth are given to the dental crown.

Description

Technical Field

[0001] This application relates to the technical field of ceramic dental crowns, and in particular to a glass-ceramic dental crown and its preparation method. Background Technology

[0002] Tooth defects and tooth loss are common oral conditions with a large patient population, driving a continuous increase in demand for ceramic cosmetic restorations. Among dental crown restoration materials, lithium disilicate glass-ceramics have become the first choice for single crowns, fixed bridges, and other restorations due to their excellent translucency, strength, chemical stability, and machinability, playing a prominent role in improving tooth defects and restoring tooth function and aesthetics. However, existing glass-ceramic crowns have many shortcomings, limiting their clinical application and long-term use. Their mechanical properties are weak, exhibiting high brittleness and low fracture toughness, making them unable to withstand long-term chewing pressure; their biocompatibility is poor, with insufficient compatibility with human hard tissue components, and the interfacial bonding stability needs improvement; they also have weak resistance to oral acid and alkali corrosion; their function is relatively limited, lacking the fluorescent properties of natural teeth or having insufficient fluorescence intensity, easily appearing unnaturally white under certain lighting conditions, showing a significant visual difference from natural teeth, and lacking methods for detecting restoration effects, making real-time monitoring of the restoration's condition impossible. The industry also faces difficulties, with high-end dental glass-ceramic preparation technology monopolized by a few foreign companies, and domestic clinical restorations heavily reliant on imported materials. In the long-term dynamic service environment of the oral cavity, which encompasses complex conditions such as daily chewing, fluctuations in oral pH, temperature changes, and light stimulation, restorations must withstand chewing loads of varying intensities, cope with the instantaneous impact of tooth occlusion, and resist fluctuations in salivary pH and corrosion caused by food residue. They must also adapt to temperature changes in the oral environment, from cold drinking water to hot eating. For anterior tooth restorations, they must cope with different lighting scenarios, including natural light and indoor lighting, to avoid aesthetic discrepancies caused by fluorescence loss. For posterior tooth restorations, the focus should be on resisting the mechanical wear and tear caused by long-term chewing, ensuring the structural integrity of the restoration. Furthermore, under these conditions, the restoration must form a stable bond with the alveolar bone and periodontal tissues to reduce inflammatory responses caused by poor biocompatibility. It must also possess detectable fluorescent signals to enable real-time monitoring of damage such as wear and cracks, balancing mechanical reliability, biocompatibility, and aesthetics. Summary of the Invention

[0003] The purpose of this application is to provide a glass-ceramic dental crown with good mechanical and fluorescent properties, while taking into account mechanical reliability, biocompatibility and aesthetics.

[0004] Firstly, this application provides a glass-ceramic dental crown and its preparation method, which adopts the following technical solution: A glass-ceramic dental crown comprises the following raw materials in parts by weight: 70-85 parts lithium disilicate, 12-18 parts rare earth-doped hydroxyapatite, and 0.5-2 parts functional crystals; wherein the rare earth-doped hydroxyapatite comprises the following raw materials: a rare earth mixture, a calcium source, a phosphorus source, and trisodium citrate; wherein the mass ratio of the rare earth mixture, calcium source, phosphorus source, and trisodium citrate is (0.015-0.025):1:(0.7-0.75):(0.033-0.045); wherein the rare earth mixture is a mixture of europium source, dysprosium source, and holmium source.

[0005] By adopting the above technical solution, lithium disilicate is used as the matrix. This weight proportion ensures the semi-transparency and machinability of the material base, providing stable support for the crown. Rare earth-doped hydroxyapatite is prepared according to a specific mass ratio of rare earth mixture, calcium source, phosphorus source, and trisodium citrate. As a major component of natural teeth, hydroxyapatite can significantly improve biocompatibility and promote interfacial bonding with human hard tissues. The controlled proportion of trisodium citrate can effectively inhibit particle aggregation, allowing hydroxyapatite to be uniformly dispersed and enhancing the material's toughness. Introducing a ternary rare earth mixture of europium, dysprosium, and holmium sources into the glass-ceramic crown allows for the control of fluorescence and optical properties through lattice doping, enabling the crown to exhibit a blue-white fluorescence effect close to that of natural teeth, enhancing the aesthetics of the restoration. Simultaneously, utilizing the thermosensitive response of the dysprosium source and the photosensitive response of the holmium source, non-invasive monitoring of oral temperature and crown chewing stress can be achieved, providing timely feedback on the fit and potential cracks. Rare earth doping optimizes the lattice stability of hydroxyapatite, enhances biocompatibility, and balances fluorescence intensity with long-term optical durability. Dispersants create monodisperse luminescence centers, preventing concentration quenching and stabilizing fluorescence performance. This allows the crown to exhibit fluorescence similar to natural teeth under excitation, improving the problem of luminescence defects and enabling non-invasive detection. The addition of functional crystals further optimizes the material's microstructure, enhancing mechanical strength and chemical stability. Precise matching of component mass ratios ensures both the basic properties of the matrix and the synergistic effect of biocompatibility, fluorescence, and mechanical properties, avoiding a single outstanding performance at the expense of others. Ultimately, this results in glass-ceramic crowns with excellent clinical fit, aesthetics, and long-term stability, meeting the diverse needs of dental restoration.

[0006] Optionally, the rare earth-doped hydroxyapatite is prepared by the following method: S1. Dissolve the rare earth mixture in water and stir to obtain a rare earth ion mixed solution; S2. Prepare a calcium source dispersion by mixing water, calcium source, and trisodium citrate. Add the rare earth ion mixed solution prepared in step S1, add a dispersant, and sonicate to obtain a rare earth composite solution. S3. Prepare a phosphorus source solution by mixing water and phosphorus source; S4. Heat and stir the rare earth composite solution prepared in step S2, add ammonia water to adjust the pH, add the phosphorus source solution prepared in step S3, add ammonia water to maintain a constant pH, stir at a constant temperature, stir and age at room temperature, and centrifuge to obtain the first precursor. S5. Wash the first precursor prepared in step S3, vacuum dry it, and calcine it to obtain rare earth-doped hydroxyapatite.

[0007] By adopting the above technical solution, step S2 involves preparing a calcium source dispersion by combining water, calcium source, and trisodium citrate. Trisodium citrate acts as a dispersant, preventing calcium source particle agglomeration and providing a uniform ionic environment for subsequent reactions. Step S3 involves preparing a separate phosphorus source solution to ensure complete dissolution and prevent premature reaction with other components that could affect effectiveness. In step S4, heating, stirring, and precise pH adjustment and maintenance create suitable reaction conditions for the formation of hydroxyapatite, facilitating the uniform doping of rare earth ions into the crystal lattice. Constant-temperature stirring and room-temperature aging promote uniform crystal nucleus growth, improving the integrity and uniformity of the crystal structure. Centrifugation quickly yields a pure first precursor. The washing step in step S5 effectively removes impurity ions from the precursor, vacuum drying prevents particle agglomeration during drying, ensuring dispersibility, and subsequent calcination further refines the crystal lattice, enhancing the material's stability and fluorescence properties. The overall method requires no complex equipment, and the steps are logically connected. It can achieve uniform doping of rare earth ions, and ensure the crystallinity, dispersibility and performance stability of the product, which is suitable for the biocompatibility and fluorescence function requirements of glass ceramic crowns.

[0008] Optionally, the molar ratio of the europium source, dysprosium source, and holmium source is (8-12):1:(0.3-0.6).

[0009] By adopting the above technical solution, the rare earth mixture uses europium, dysprosium, and holmium sources in combination, and the molar ratio of the three is limited to this range. This is a precise design based on the aesthetic requirements, intelligent monitoring function, and material stability of glass-ceramic crowns. The europium source, as the core functional component, dominates the fluorescent aesthetic effect of the crown. This ratio range ensures that it forms sufficient and uniform luminescent centers in the hydroxyapatite lattice, allowing the crown to exhibit a blue-white fluorescence that matches natural teeth, avoiding weak fluorescence or color deviation. The dysprosium and holmium sources, as functional auxiliary components, are added in low proportions. This does not interfere with the core fluorescent performance of the europium source, while fully utilizing their respective characteristics: the thermosensitive response of the dysprosium source enables non-invasive monitoring of oral temperature, and the photosensitivity and stress response of the holmium source can provide early warning of microcracks and wear in the crown. The ratio of the two is suitable for the detection sensitivity requirements, with no functional interference. Meanwhile, this ratio is highly compatible with the crystal structure of hydroxyapatite. The three rare earth ions can be stably embedded in the crystal lattice through isomorphic substitution without causing lattice distortion, ensuring the biocompatibility and mechanical stability of the material, and avoiding concentration quenching caused by rare earth ion aggregation, while also taking into account the fluorescence effect.

[0010] Optionally, the europium source is any one or more of europium nitrate hexahydrate and europium oxide; the dysprosium source is any one or more of dysprosium nitrate hexahydrate or dysprosium oxide; and the holmium source is any one or more of holmium nitrate hexahydrate or holmium oxide.

[0011] By adopting the above technical solutions, nitrate raw materials exhibit excellent water solubility, allowing for direct ion-level homogeneous mixing with other components. This facilitates hydrothermal precipitation processes without complex pretreatment, ensuring uniform doping of rare earth ions. Oxide raw materials demonstrate strong stability, convenient storage and transportation, and are free of easily residual harmful impurities. They can be converted into ionic states through simple acid dissolution to participate in the reaction, reducing impurity residues during subsequent calcination and improving the material's biocompatibility. Both types of substances can stably provide the target rare earth ions, and their ionic radii are compatible with calcium ions in the hydroxyapatite lattice, allowing for stable embedding within the lattice without disrupting the crystal structure. This ensures stable performance of fluorescence and intelligent response functions while maintaining the material's mechanical strength and compatibility.

[0012] Optionally, the heating temperature in step S4 is 48-52℃; and the calcination temperature in step S5 is 650-695℃.

[0013] By adopting the above technical solution, the temperature range of step S4 matches the growth characteristics of hydroxyapatite crystals, which can promote the uniform formation and growth of crystal nuclei, avoid slow reaction and incomplete crystallization due to excessively low temperature, or particle agglomeration and impurity generation due to excessively high temperature, thus ensuring the crystallinity and dispersibility of the product. The calcination temperature range of step S5 can promote the full perfection of the hydroxyapatite crystal lattice, improve the stability of the crystal structure, and at the same time help rare earth ions to stably embed into the crystal lattice, ensuring the compatibility of the material with biocompatibility and mechanical properties.

[0014] Optionally, the aging time in step S4 is 12-20 hours.

[0015] By adopting the above technical solution, the aging time range of 12-20 hours in step S4 provides suitable conditions for the improvement of rare earth-doped hydroxyapatite. This time length allows the crystal nuclei in the precursor to grow fully, promoting a more complete and uniform crystal structure, improving the crystallinity and performance stability of the product, while effectively avoiding problems such as incomplete crystal development and uneven particle size distribution caused by insufficient aging. At the same time, this range can avoid the austenitic ripening of particles caused by excessively long aging, preventing the dissolution of small particles and the excessive growth of large particles, ensuring the monodispersity and particle size uniformity of the product. A reasonable aging time can also promote the full precipitation of unreacted ions in the reaction system, reducing impurity residues.

[0016] Optionally, the pH in step S4 is 9.9-10.1.

[0017] By adopting the above technical solution, the pH range in step S4 provides the optimal reaction environment for the preparation of rare-earth-doped hydroxyapatite and rare-earth-doped phosphors. This pH range can precisely control the reaction rate of calcium and phosphorus ions, promote uniform nucleation and growth of crystal nuclei, ensure the formation of a pure-phase crystal structure in the product, and avoid the formation of impurity phases due to pH deviation, which would damage the integrity of the crystal lattice. At the same time, a suitable alkaline environment is conducive to the stable doping of rare-earth ions into the lattice sites, forming uniform luminescent centers, avoiding concentration quenching, and ensuring stable fluorescence performance. In addition, this pH range can maintain the reaction stability of the system, reduce the impact of ammonia volatilization on pH fluctuations, and help to accurately control subsequent real-time pH compensation, thereby ensuring the uniformity and dispersibility of the product particle size.

[0018] Optionally, the calcium source is calcium chloride; the phosphorus source is diammonium hydrogen phosphate; and the chlorine source is ammonium chloride.

[0019] By adopting the above technical solution, calcium chloride, diammonium hydrogen phosphate, and ammonium chloride are used as the calcium source, phosphorus source, and chlorine source, respectively, to meet the preparation requirements of glass-ceramic dental crowns. These substances all possess good water solubility, allowing them to dissolve rapidly and disperse uniformly in the reaction system, ensuring sufficient ionic reaction and facilitating the formation of a uniform crystal structure. The chlorine source can assist in controlling crystal morphology and structure, improving material stability. The purity of each substance is easily controlled, with low impurity content, reducing adverse effects on the mechanical properties, biocompatibility, and fluorescence of the product, ensuring that the final dental crown material meets the diverse requirements of clinical applications.

[0020] Optionally, the functional crystal is any one or more of silicon nitride and boron nitride.

[0021] By adopting the above technical solutions, both silicon nitride and boron nitride, as functional crystals, can meet the performance optimization requirements of glass-ceramic dental crowns. Silicon nitride can form a three-dimensional network structure in the glass substrate, significantly improving the material's mechanical strength and fracture toughness, and enhancing the crown's resistance to chewing pressure; its stable interface with the matrix allows it to synergistically optimize mechanical properties with hydroxyapatite. Boron nitride, on the other hand, possesses good dispersibility and chemical stability, improving the material's resistance to oral acid and alkali corrosion, while not affecting the fluorescence properties brought about by rare earth doping, and also helping to improve the material's processability.

[0022] Secondly, the glass-ceramic dental crown and its preparation method provided in this application adopt the following technical solution: A method for preparing a glass-ceramic dental crown includes the following steps: Step 1: Mix lithium disilicate, rare earth-doped hydroxyapatite, and functional crystals, add a mixed solvent and zirconium beads, ball mill, centrifuge to obtain a precipitate, vacuum dry, grind, and obtain a composite. Step 2: Mix the composite with the binder, dry, and sieve to obtain granulated powder. Make the granulated powder into a mold blank, remove the glue, nucleate, sinter, and cool to obtain a glass-ceramic dental crown.

[0023] By adopting the above technical solution, in step one, the ball milling and mixing of various raw materials ensures the uniform dispersion of lithium disilicate, rare-earth-doped hydroxyapatite, and rare-earth-doped phosphor. The combination of the mixed solvent and zirconium beads helps the raw materials to fully integrate and reduces agglomeration. Centrifugation, vacuum drying, and grinding steps remove impurities and excess solvent, ensuring the purity and dispersibility of the composite. In step two, the composite and binder are mixed and granulated, which improves the powder forming performance and makes the preform structure dense and uniform. The subsequent glue removal, nucleation, and sintering processes are carried out step by step, which can effectively remove binder residues, promote the directional growth of crystals and form a stable interlocking structure, enhance the mechanical properties of the material, and at the same time ensure the stability of the fluorescence performance brought by rare-earth doping. The overall method is suitable for large-scale production, enabling dental crowns to have good mechanical strength, biocompatibility, and fluorescence effect, meeting the diverse needs of clinical restoration.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. Compared with existing technologies, by precisely controlling the key process parameters of rare earth-doped hydroxyapatite, the microstructure and performance of the functional components are effectively optimized. The pH control of the reaction system ensures the formation of a pure-phase crystal structure, avoids the generation of impurity phases, and promotes the uniform doping of rare earth ions into lattice sites. The appropriate reaction temperature and aging time work synergistically to ensure sufficient growth of crystal nuclei and perfect crystal form, while effectively suppressing particle agglomeration and austenitic ripening. Differentiated calcination temperatures are tailored to the lattice perfection requirements of the two materials, ensuring the crystallization stability of hydroxyapatite and the dispersion of phosphor luminescent centers, thereby significantly improving the crystal integrity and functional stability of the material. 2. Compared with existing technologies, the synergistic combination of rare-earth-doped hydroxyapatite and functional crystals endows glass-ceramic crowns with superior comprehensive performance. Hydroxyapatite, as a major component of natural teeth, significantly enhances the material's biocompatibility and promotes stable interfacial bonding with human hard tissues. Phosphors, by constructing monodisperse luminescent centers, endow the restoration with fluorescence properties close to natural teeth, effectively avoiding the "false white" phenomenon and possessing potential non-invasive monitoring capabilities. The introduction of functional crystals, by forming a reinforcing phase, significantly improves the material's mechanical strength and fracture toughness. The synergistic effect of these three elements enables the crown to possess reliable mechanical support, good biocompatibility, and a natural aesthetic effect in the complex oral cavity service environment. Detailed Implementation

[0025] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this application are commercially available products. Example 1

[0026] A method for preparing a glass-ceramic dental crown includes the following steps: The first step is to prepare rare earth-doped hydroxyapatite.

[0027] Add 0.8g europium nitrate hexahydrate, 0.1g dysprosium nitrate hexahydrate, and 0.02g holmium nitrate hexahydrate to 1L of water and stir at 500rpm for 1h to obtain a mixed solution of rare earth ions.

[0028] Mix 50 mL of water, 1 g of anhydrous calcium chloride, and 0.033 g of trisodium citrate, and sonicate at 1000 rpm for 20 min to obtain a calcium source dispersion. Let it stand for 5 min before use. Add 0.15 g of a rare earth ion mixed solution to the calcium source dispersion, and then add 0.035 g of 5 wt% polyvinylpyrrolidone K30 solution. Sonicate at 1000 rpm for 10 min to obtain a rare earth composite solution.

[0029] Add 0.7g of diammonium hydrogen phosphate to 30mL of water and stir magnetically at 400rpm for 10min to obtain a diammonium hydrogen phosphate solution. Prepare and use immediately to avoid hydrolysis.

[0030] The rare earth composite solution was magnetically stirred at 50℃ and 400 rpm. A 50 wt% dilute ammonia solution was added dropwise to the rare earth composite solution at a rate of 1 mL / min, and the pH was measured to be 10.0. Maintaining the temperature at 50℃, the stirring rate at 400 rpm, and the pH at 10.0, diammonium hydrogen phosphate solution was added dropwise at a rate of 1.0 mL / min. During the addition, the pH slowly decreased; dilute ammonia was added to maintain the pH deviation ≤0.1 until the diammonium hydrogen phosphate solution was completely added. The mixture was then kept at a constant temperature of 50℃ and magnetically stirred at 400 rpm for 2 hours to obtain the first mixture.

[0031] The first mixture was aged at 25°C and 200 rpm for 12 h with stirring to obtain a first suspension. The first suspension was placed in a high-speed refrigerated centrifuge and centrifuged at 10000 rpm and 4°C for 10 min. The supernatant was discarded to obtain the first precursor. The first precursor was added to 50 mL of water, sonicated at 1000 rpm for 5 min, and centrifuged at 10000 rpm for 10 min. The supernatant was discarded, and the first precipitate was retained. The first precipitate was added to 50 mL of anhydrous ethanol, sonicated at 1000 rpm for 5 min, and centrifuged at 9000 rpm for 8 min. The supernatant was discarded, and the second precipitate was retained. The second precipitate was dried at 60°C and 0.08 MPa under vacuum for 12 h to obtain a powder. The powder was spread to a thickness of 1 cm, heated from 25°C to 650°C at a rate of 2°C / min, held at 650°C for 2 h, and then cooled to 25°C to obtain rare earth-doped hydroxyapatite.

[0032] The second step is to prepare glass-ceramic dental crowns.

[0033] 80g of lithium disilicate, 15g of rare-earth-doped hydroxyapatite, and 1g of silicon nitride were mixed and added to a 160mL mixture of anhydrous ethanol and triethanolamine in a 1:1 volume ratio. Then, 400g of zirconium beads were added, and the mixture was ball-milled at 250rpm for 5 hours to obtain a slurry. The slurry was centrifuged at 8000rpm for 10 minutes, filtered, and the supernatant was discarded to obtain a precipitate. The precipitate was dried at 80℃ for 12 hours, ground in a mortar, and passed through a 200-mesh sieve to obtain a composite powder. The composite powder was mixed with a 10wt% polyvinyl alcohol aqueous solution (powder to polyvinyl alcohol aqueous solution mass ratio 10:1), ground, dried at 60℃ for 2 hours, and passed through an 80-mesh sieve to obtain granulated powder. The granulated powder was placed on a dry pressing machine, subjected to a pressure of 20MPa, held for 5 minutes, and demolded to obtain a green body. The green body was heated to 450℃ at a rate of 1℃ / min and held for 2 hours. The temperature is then increased from 450℃ to 750℃ at a rate of 2℃ / min and held for 3 hours. The temperature is then increased from 750℃ to 1000℃ at a rate of 3℃ / min and held for 4 hours to obtain the glass-ceramic crown. Example 2

[0034] The difference between Example 2 and Example 1 is that the 0.15g rare earth ion mixed solution, 1g anhydrous calcium chloride, 0.033g trisodium citrate, and 0.7g diammonium hydrogen phosphate in Example 1 are replaced with 0.2g rare earth ion mixed solution, 1g anhydrous calcium chloride, 0.038g trisodium citrate, and 0.72g diammonium hydrogen phosphate. Example 3

[0035] The difference between Example 3 and Example 1 is that the 0.15g rare earth ion mixed solution, 1g anhydrous calcium chloride, 0.033g trisodium citrate, and 0.7g diammonium hydrogen phosphate in Example 1 are replaced with 0.25g rare earth ion mixed solution, 1g anhydrous calcium chloride, 0.045g trisodium citrate, and 0.75g diammonium hydrogen phosphate. Example 4

[0036] The difference between Example 4 and Example 2 is that the preparation method for the rare earth ion mixed solution in Example 4 is different. Add 0.9g europium nitrate hexahydrate, 0.08g dysprosium nitrate hexahydrate, and 0.01g holmium nitrate hexahydrate to 1L of water and stir at 500rpm for 1h to obtain a mixed solution of rare earth ions. Example 5

[0037] The difference between Example 5 and Example 2 is that the preparation method for the rare earth ion mixed solution in Example 5 is different. Add 0.9g europium nitrate hexahydrate, 0.05g dysprosium nitrate hexahydrate, and 0.01g holmium nitrate hexahydrate to 1L of water and stir at 500rpm for 1h to obtain a mixed solution of rare earth ions. Example 6

[0038] The difference between Example 6 and Example 5 is that the aging time of 12h for rare earth-doped hydroxyapatite in Example 5 is replaced with 6h. Example 7

[0039] The difference between Example 7 and Example 5 is that the heating temperature of rare earth-doped hydroxyapatite in Example 5, which is 50°C, is replaced with a heating temperature of 52°C. Comparative Example 1

[0040] The difference between Comparative Example 1 and Example 1 is that the 0.15g rare earth ion mixed solution, 1g anhydrous calcium chloride, 0.033g trisodium citrate, and 0.7g diammonium hydrogen phosphate in Example 1 are replaced with 0.05g rare earth ion mixed solution, 0.5g anhydrous calcium chloride, 0.62g trisodium citrate, and 0.35g diammonium hydrogen phosphate. Comparative Example 2

[0041] The difference between Comparative Example 2 and Example 2 lies in the preparation method of the rare earth ion mixed solution in Example 4: Add 0.6g europium nitrate hexahydrate, 0.09g dysprosium nitrate hexahydrate, and 0.03g holmium nitrate hexahydrate to 1L of water and stir at 500rpm for 1h to obtain a mixed solution of rare earth ions. Comparative Example 3

[0042] The difference between Comparative Example 3 and Example 5 is that the aging time of 12h for the rare earth-doped hydroxyapatite prepared in Example 5 is replaced with 25h. Comparative Example 4

[0043] The difference between Comparative Example 4 and Example 5 is that the heating temperature of rare earth-doped hydroxyapatite in Example 5, which is 50°C, is replaced with a heating temperature of rare earth-doped hydroxyapatite of 55°C.

[0044] Test case Bending strength: The ceramic crowns prepared in Examples 1-7 and Comparative Examples 1-4 were cut using a diamond dicing cutter to produce 2.2mm × 2.2mm × 25mm specimens (n=15). The specimens were sanded with 1000, 1500, and 2000 grit sandpaper, and then polished with 0.5μm diamond suspension to obtain samples with dimensions of 2mm × 2mm × 25mm. The samples were used for bending strength testing; the test results are shown in Table 1.

[0045] Fluorescence performance: Fluorescence intensity was measured using a Hitachi High-Tech F-7000 spectrophotometer in fluorescence mode with an excitation wavelength of 365 nm. Rhodamine B was used for inter-model spectral correction of fluorescence intensity. The obtained spectra showed fluorescence wavelengths ranging from 430 nm to 600 nm, with the wavelength exhibiting the highest intensity being the maximum wavelength, and the intensity of the maximum wavelength being the maximum intensity. Transmittance and fluorescence performance results are shown in Table 1.

[0046]

[0047] A comparative analysis of Examples 1-3 and Comparative Example 1 revealed that the glass-ceramic crown prepared in Example 2 exhibited the best performance. The difference in performance may be due to variations in the mass ratios of the rare earth mixture, anhydrous calcium chloride, trisodium citrate, and diammonium hydrogen phosphate, which in turn affected the performance of the rare earth-doped hydroxyapatite. Anhydrous calcium chloride provides the calcium source, while diammonium hydrogen phosphate provides the phosphorus source. Trisodium citrate, as a dispersant, must be used in a proportion appropriate to the calcium and phosphorus content; insufficient dosage leads to particle agglomeration, while excessive dosage leaves residual impurities that hinder crystal growth. As a core component for fluorescence enhancement, the amount of rare earth mixture directly affects the fluorescence and mechanical properties of the crown. An appropriate amount of rare earth mixture ensures that rare earth ions are uniformly doped into the hydroxyapatite lattice, reducing fluorescence quenching sites and improving fluorescence emission efficiency. At the same time, rare earth ions can fill lattice defects, enhance the integrity of the crystal structure, and indirectly improve the bending strength of the crown. If the amount of rare earth mixture is insufficient, the number of fluorescence centers decreases, the fluorescence intensity decreases, and it cannot effectively fill lattice defects, resulting in limited improvement in mechanical properties. If the amount is too large, rare earth ions are prone to agglomeration, which will not only exacerbate fluorescence quenching but also destroy the regularity of the crystal structure, leading to a decrease in bending strength.

[0048] Among the differences in formulation between Examples 1-3 and Comparative Example 1, the formulation in Example 2 is closer to the optimal calcium-to-phosphorus ratio, and the amount of trisodium citrate is appropriate. This promotes the formation of complete and uniformly dispersed nanocrystals of hydroxyapatite, reducing internal porosity and defects, improving the structural stability of the ceramic crown, and thus enhancing its bending strength. Simultaneously, the appropriate formulation ensures uniform doping of rare earth elements, reducing fluorescence quenching sites and improving fluorescence emission efficiency. In Comparative Example 1, insufficient calcium and phosphorus and excessive trisodium citrate resulted in incomplete crystallization and particle agglomeration of hydroxyapatite, reducing structural strength and causing uneven distribution of rare earth elements, exacerbating fluorescence quenching, decreasing fluorescence intensity, and shifting the maximum fluorescence wavelength. Because the formulations in Examples 1 and 3 deviated from the optimal values, the crystal quality and rare earth doping effect were inferior to those in Example 2, resulting in slightly lower performance. This confirms that the mass ratio of the three components needs to be precisely controlled to ensure the performance of hydroxyapatite and thus optimize the overall performance of the crown.

[0049] A comparative analysis of Examples 4-5 and Comparative Example 2 revealed that the glass-ceramic crown prepared in Example 5 exhibited the best performance. The difference in performance may be attributed to the varying molar ratios of europium nitrate hexahydrate, dysprosium nitrate hexahydrate, and holmium nitrate hexahydrate used in the rare earth mixture preparation. Rare earth-doped hydroxyapatite, as the core functional phase of the glass-ceramic crown, directly determines the crown's bending strength and fluorescence properties through its crystal structure integrity and the synergistic effect of rare earth ions. The differences in the molar ratios of europium nitrate hexahydrate, dysprosium nitrate hexahydrate, and holmium nitrate hexahydrate essentially regulate the substitution behavior, energy transfer efficiency, and crystal defect state of rare earth ions within the hydroxyapatite lattice. Hydroxyapatite crystals are hexagonal, containing two types of unequal calcium ion sites. Rare earth ions, with ionic radii similar to calcium ions, can achieve lattice substitution, while the differences in the radii of the three rare earth ions result in varying substitution priorities and stability. An appropriate molar ratio allows the three types of ions to be uniformly dispersed in the crystal lattice, reducing lattice distortion, increasing crystal density, and thus enhancing the bending strength of the crown. If the ratio is unbalanced, an excess of ions with mismatched radii will cause lattice dislocations and an increase in defects, becoming stress concentration points and reducing mechanical properties. The difference in fluorescence performance stems from the energy level transitions of rare earth ions. Europium ions are the main luminescent centers, while dysprosium and holmium ions participate in energy transfer as auxiliary ions. Under appropriate ratios, the three can form an efficient energy transfer channel, improving fluorescence emission efficiency. An improper ratio will lead to obstructed energy transfer or the generation of too many defect centers, exacerbating fluorescence quenching. At the same time, changes in lattice symmetry will affect the fluorescence emission wavelength and intensity, ultimately resulting in significant differences in the mechanical and fluorescence properties of crowns under different molar ratios.

[0050] Comparative analysis of Example 6 and Comparative Example 3 revealed that the glass-ceramic crown prepared in Example 5 exhibited the best performance. The difference in performance may be attributed to variations in aging time during the preparation of rare-earth-doped hydroxyapatite. Aging time is a key factor affecting the crystallization quality and dispersibility of rare-earth-doped hydroxyapatite, thus determining the mechanical and fluorescent properties of the glass-ceramic crown. A suitable aging time allows for sufficient precursor crystallization, reducing lattice defects and forming particles with regular morphology and uniform size. This enhances the interfacial bonding with the lithium disilicate matrix, strengthens the crown's bending strength, and facilitates uniform dispersion of rare-earth ions, optimizing fluorescence emission. Insufficient aging time results in incomplete crystallization, poor particle dispersibility, and easy agglomeration. This reduces interfacial bonding tightness, leading to decreased mechanical properties, and also causes uneven distribution of fluorescence centers, affecting fluorescence intensity and wavelength stability. Excessive aging time leads to excessive particle growth and agglomeration, disrupting system homogeneity. This not only weakens the crown's mechanical properties but also triggers rare-earth ion concentration quenching, causing fluorescence degradation. Therefore, Example 5 exhibited the best aging time suitability and performance.

[0051] Comparative analysis of Example 7 and Comparative Example 4 revealed that the glass-ceramic crown prepared in Example 5 exhibited the best performance. The difference in performance may be attributed to the different heating temperatures of the rare-earth-doped hydroxyapatite. The preparation temperature of rare-earth-doped hydroxyapatite directly affects crystal integrity, rare-earth ion doping efficiency, and particle morphology, thus influencing the mechanical and fluorescent properties of the glass-ceramic crown. A suitable heating temperature promotes sufficient precursor crystallization, reduces lattice defects, forms uniformly sized and well-dispersed particles, enhances interfacial bonding with the lithium disilicate matrix, strengthens crown bending strength, and facilitates stable rare-earth ion doping, optimizing fluorescence emission. Temperature mismatch leads to insufficient crystallization or excessive growth, causing particle agglomeration, which reduces interfacial bonding tightness, weakens mechanical properties, and disrupts the luminescence environment of rare-earth ions, resulting in a shift in the maximum fluorescence wavelength and attenuation of fluorescence intensity. Example 5 demonstrated the best temperature compatibility between the two raw materials, achieving a synergistic improvement in crystal quality and doping efficiency, thus resulting in the best overall crown performance.

[0052] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A glass-ceramic dental crown, characterized in that, The preparation materials include the following parts by weight: 70-85 parts lithium disilicate, 12-18 parts rare earth-doped hydroxyapatite, and 0.5-2 parts functional crystals; the rare earth-doped hydroxyapatite includes the following preparation materials: rare earth mixture, calcium source, phosphorus source, and trisodium citrate; the mass ratio of the rare earth mixture, calcium source, phosphorus source, and trisodium citrate is (0.015-0.025):1:(0.7-0.75):(0.033-0.045); the rare earth mixture is a mixture of europium source, dysprosium source, and holmium source.

2. The glass-ceramic dental crown according to claim 1, characterized in that, The rare earth-doped hydroxyapatite was prepared by the following method: S1. Dissolve the rare earth mixture in water and stir to obtain a rare earth ion mixed solution; S2. Prepare a calcium source dispersion by mixing water, calcium source, and trisodium citrate. Add the rare earth ion mixed solution prepared in step S1, add a dispersant, and sonicate to obtain a rare earth composite solution. S3. Prepare a phosphorus source solution by mixing water and phosphorus source; S4. Heat and stir the rare earth composite solution prepared in step S2, add ammonia water to adjust the pH, add the phosphorus source solution prepared in step S3, add ammonia water to maintain a constant pH, stir at a constant temperature, stir and age at room temperature, and centrifuge to obtain the first precursor. S5. Wash the first precursor prepared in step S3, vacuum dry it, and calcine it to obtain rare earth-doped hydroxyapatite.

3. The glass-ceramic dental crown according to claim 1, characterized in that, The molar ratio of the europium source, dysprosium source, and holmium source is (8-12):1:(0.3-0.6).

4. The glass-ceramic dental crown according to claim 1, characterized in that, The europium source is any one or more of europium nitrate hexahydrate and europium oxide; the dysprosium source is any one or more of dysprosium nitrate hexahydrate or dysprosium oxide; the holmium source is any one or more of holmium nitrate hexahydrate or holmium oxide.

5. The glass-ceramic dental crown according to claim 2, characterized in that, The heating temperature in step S4 is 48-52℃; the calcination temperature in step S5 is 650-695℃.

6. The glass-ceramic dental crown according to claim 2, characterized in that, The aging time in step S4 is 12-20 hours.

7. The glass-ceramic dental crown according to claim 2, characterized in that, The pH value in step S4 is 9.9-10.

1.

8. The glass-ceramic dental crown according to claim 1, characterized in that, The calcium source is calcium chloride; the phosphorus source is diammonium hydrogen phosphate; and the chlorine source is ammonium chloride.

9. The glass-ceramic dental crown according to claim 1, characterized in that, The functional crystal is any one or more of silicon nitride and boron nitride.

10. A method for preparing a glass-ceramic dental crown as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Mix lithium disilicate and rare earth-doped hydroxyapatite, add a mixed solvent and zirconium beads, ball mill, centrifuge to obtain a precipitate, vacuum dry, grind, and obtain a composite. Step 2: Mix the composite with binder and functional crystals, dry, and sieve to obtain granulated powder. Make the granulated powder into a mold blank, remove the glue, nucleate, sinter, and cool to obtain a glass-ceramic dental crown.

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