A dental restorative material with a mechanical gradient and its preparation method and application

Abstract

The present invention discloses a dental restorative material with a mechanical gradient, a preparation method thereof, and an application thereof. The dental restorative material is prepared from micron-sized powders having a particle size of 90 μm to 100 μm and at least one particle size of 30 μm to 90 μm, and two or more glassy silicate granules having a particle size of 50 nm to 1000 nm as raw materials. The materials are stacked in descending order of particle size and from bottom to top, and pressed twice, wherein the first pressing adopts 3t to 6t ultrahigh pressure pressing, and the second pressing adopts 50 to 250 MPa cold isostatic pressing, and is pressed into a multilayer ceramic body, which is obtained by high-temperature sintering and resin infiltration curing. The dental restorative material provided by the present invention has a gradient change in its organizational structure and mechanical properties, and is close to the mechanical changes of native teeth, can be well adapted to native teeth, and can be used to repair different parts of teeth.

Description

Technical Field

[0001] The present invention belongs to the field of dental restoration, and more specifically, relates to a dental restoration material with a mechanical gradient, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of computer-aided design and computer-aided manufacturing (CAD-CAM) equipment and their system software, CAD-CAM blocks have been widely used in recent years. Currently, the commonly used CAD-CAM blocks on the market are mainly divided into two types according to the material: ceramics and composite materials. However, ceramics have a hardness and elastic modulus significantly higher than that of natural teeth, and wear and mechanical transmission mismatch of natural teeth are often seen in clinical practice. Composite materials have the advantages of both ceramics and polymers. In particular, resin-infiltrated ceramic composites have good cutting properties and do not require re-sintering in clinical use. Compared with other materials, they are gradually highlighting their advantages as CAD-CAM block materials for chairside restorations and are more suitable for permanent restorations.

[0003] Currently, representative composite materials used for permanent restorations include Lava Ultimate (3M ESPE), Enamic (Vita), Block HC (Shofu), and Brilliant Crios (Coltene). However, these composite materials have single mechanical properties and their hardness generally does not exceed 2.5 GPa. The structure and mechanical properties of different parts of native teeth are heterogeneous. The elastic modulus of enamel ranges from 32.36 to 91.36 GPa, and the Vickers hardness ranges from 1.069 to 4.515 GPa; the elastic modulus of dentin ranges from 18.05 to 29.05 GPa, and the Vickers hardness ranges from 0.640 to 1.234 GPa. Because existing dental composite materials have single mechanical properties, and the hardness and elastic modulus of the enamel and dentin regions of native teeth have certain mechanical gradient characteristics, existing dental composite materials generally have poor compatibility with native teeth, making it difficult to meet the personalized mechanical performance requirements of repairing different parts of teeth or different parts of the same tooth, and causing significant damage to the native teeth.

[0004] Therefore, researching a dental restorative material with a structural gradient and mechanical gradient close to that of native tooth tissue will help improve the compatibility of the restorative material with native teeth and reduce the damage of the dental restorative material to the native teeth. Summary of the Invention

[0005] In response to the above defects or improvement needs of the prior art, the present invention provides a dental restorative material with a mechanical gradient, a preparation method and application thereof, the purpose of which is to find a dental restorative material prepared by using micron-sized powders with a particle size of 90μm to 100μm and at least one particle size of 10μm to 90μm, and two or more nano-sized glass phase silicate granules with a particle size of 50nm-1000nm, and obtaining a multilayer ceramic green body by two pressing steps, wherein the first step is ultra-high pressure pressing and the second step is cold isostatic pressing, and the dental restorative material prepared by high-temperature sintering and resin infiltration curing can simulate the structure and mechanical properties of native tooth tissue, thereby solving the technical problems of the existing dental restorative materials having a single mechanical property and poor compatibility with native teeth.

[0006] To achieve the above object, according to one aspect of the present invention, a method for preparing a dental restorative material having a mechanical gradient is provided, comprising the following steps:

[0007] (1) screening micron-sized silicate powders with a particle size of 90 μm to 100 μm and at least one particle size of 10 μm to 90 μm, and two or more nano-sized granules with a particle size of 50 nm to 1000 nm, wherein the granules are obtained by spray granulation of silicate powders of corresponding particle sizes mixed with a binder;

[0008] (2) stacking the micron-sized silicate powder and nano-sized granules obtained in step (1) in descending order of particle size and from bottom to top, and pressing them twice to form a multilayer ceramic body;

[0009] The first pressing is performed with a pressure of 3t-6t and a holding time of 30-60s. The second pressing is performed with a cold isostatic pressing pressure of 50-250MPa and a holding time of 2-4min.

[0010] (3) The multilayer ceramic body obtained in step (2) is subjected to high-temperature sintering and resin infiltration curing to obtain a dental restorative material with a mechanical gradient.

[0011] Preferably, in the method for preparing the dental restorative material with a mechanical gradient, the at least one micron-sized silicate powder with a particle size of 10 μm to 90 μm in step (1) is screened as follows:

[0012] At least one micron-sized powder is selected from silicate powders having a particle size of 90-80 μm, 80-70 μm, 70-60 μm, 60-50 μm, 50-40 μm, 40-30 μm, 30-20 μm, and 20-10 μm;

[0013] The granules are prepared according to the following method:

[0014] Silicate powders with particle sizes of 1000nm-800nm, 800nm-600nm, 600nm-400nm, 400nm-200nm, 200-100nm and 100-50nm are mixed with a binder respectively so that the solid content in the mixed liquid is 20-40wt%, and granules with corresponding particle sizes are prepared by spray granulation.

[0015] Preferably, in the method for preparing the dental restorative material with a mechanical gradient, the layers are stacked sequentially from bottom to top in step (2), wherein the thickness ratio of the bottom layer: the middle single layers: the top layer is 1-2: 1-1.2: 1.5-2.

[0016] Preferably, in the method for preparing the dental restorative material with a mechanical gradient, the thickness ratio between the individual layers is 1:1.

[0017] Preferably, in the preparation method of the dental restorative material with a mechanical gradient, the two pressings in step (2) are as follows: the first pressing has a pressure of 5t-6t and a holding time of 30-60s; the second pressing has a cold isostatic pressing pressure of 150-250MPa and a holding time of 2-4min.

[0018] Preferably, in the preparation method of the dental restorative material with a mechanical gradient, in step (3), the multilayer ceramic body is first modified with a silane coupling agent after high-temperature sintering, and then resin infiltration curing is performed; the high-temperature sintering is performed at a temperature of 700-800°C, a holding time of 10min-3h, and a heating rate of 1-5°C / min; the resin infiltration curing adopts high-temperature and high-pressure polymerization curing, the temperature is 50°C-120°C, the pressure is 100-200MPa, and the polymerization time is 2-5h.

[0019] Preferably, in the method for preparing the dental restorative material with a mechanical gradient, the silicate powder includes but is not limited to sodium aluminosilicate powder, quartz powder, barium glass powder, silica-zirconia composite powder, silica-ytterbium oxide composite powder, nano-silica powder, and nano-zirconia powder; and the binder includes PVA and PEG.

[0020] In addition, the present invention also provides a dental restorative material with a mechanical gradient, wherein the dental restorative material has the characteristics of a native tooth tissue structure gradient and a mechanical property gradient, and is prepared according to the preparation method of the present invention.

[0021] In addition, the present invention also provides a use of the dental restorative material with a mechanical gradient as described in the present invention in dental restoration.

[0022] Preferably, the dental restorative material with a mechanical gradient is used in dental restoration to repair different parts of teeth or different parts of the same tooth.

[0023] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0024] Since micron-sized powders with a particle size of 90μm to 100μm and at least one particle size of 10μm to 90μm, as well as two or more glass phase silicate granules with a particle size of 50nm-1000nm are used as raw materials, two pressings are adopted, wherein the first pressing is an ultra-high pressure pressing of 3t-6t, and the second pressing is a cold isostatic pressing of 50MPa-250MPa, to obtain a multilayer ceramic green body. Experiments show that its organizational structure is similar to that of native teeth. The material prepared by high-temperature sintering and resin infiltration curing has a gradient change in its mechanical properties. Experiments show that the mechanical gradient change of the material is close to that of native teeth, and it has good adaptability to native teeth, and can be used to repair teeth in different parts or repair different parts of teeth. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a dental restorative material with a mechanical gradient. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0027] Existing dental ceramic restorative materials are usually made by pressing granules of the same particle size into ceramic green bodies, which are then sintered at high temperature to remove binders. The mechanical properties of the material, such as hardness and elastic modulus, are single. This is mainly due to the sensitivity of ceramics to defects such as heterogeneity, which greatly increases the difficulty of preparing restorative materials with mechanical gradient characteristics. They are often used in the repair of dentures, that is, replacing the entire tooth.

[0028] The present invention is based on the structure and mechanical property data of human native tooth tissue. Through the improvement of the preparation process of dental composite materials, it is found that by using micron-sized silicate powders with a particle size of 90μm to 100μm and at least one particle size of 10μm to 90μm, and two or more nano-sized glass phase silicate granules with a particle size of 50nm to 1000nm, the silicate powders and granules are stacked from large to small according to particle size and from bottom to top, and pressed twice, wherein the first press adopts 3t-6t ultra-high pressure pressing and the second press adopts 50-250MPa cold isostatic pressing to press into a multi-layer ceramic body, and then subjected to high-temperature sintering and resin infiltration curing, a resin-infiltrated ceramic composite material with the structural gradient and mechanical property gradient characteristics of native tooth tissue can be obtained, wherein 90μm to 100μm is the largest particle size layer, corresponding to the dentin layer of human teeth, 10μm to 90μm is the middle particle size layer, and 50nm to 1000nm is the smallest particle size layer, corresponding to the enamel layer of human teeth.

[0029] Based on this improved production process, the present invention provides a method for preparing a dental restorative material with a mechanical gradient, which comprises the following steps:

[0030] (1) obtaining silicate powders and granules of different particle sizes: screening micron-sized silicate powders with a particle size of 90 μm to 100 μm and at least one particle size of 10 μm to 90 μm, and two or more glassy silicate granules with a particle size of 50 nm to 1000 nm;

[0031] The silicate granules are obtained by spray granulating a mixture of silicate powder of corresponding particle size and a binder, for example, granules of 50-60 nm are obtained by spray granulating a mixture of silicate powder of 50-60 nm particle size and a binder;

[0032] The silicate powder includes but is not limited to sodium aluminosilicate, quartz powder, barium glass powder, silicon oxide-zirconia composite powder, silicon oxide-ytterbium oxide composite powder, nano silicon oxide powder, nano zirconium oxide powder; the binder includes PVA, PEG;

[0033] It is preferred that the particle size interval between different silicate powders is greater than 5 μm.

[0034] (2) preparing a multilayer ceramic body: stacking the micron-sized powder and nano-sized granules obtained in step (1) in descending order of particle size and from bottom to top, and pressing them twice to form a multilayer ceramic body;

[0035] The first pressing is performed with a pressure of 3t-6t and a holding time of 30-60s. The second pressing is performed with a cold isostatic pressing pressure of 50-250MPa and a holding time of 2-4min.

[0036] Preferably, the layers are stacked from bottom to top, wherein the thickness ratio of the bottom layer: the middle single layers: the outermost layer is 1-2:1-1.2:1.5-2; more preferably, the thickness ratio of the middle single layers is 1:1.

[0037] (3) Preparation of a dental restorative material with a mechanical gradient: The multilayer ceramic body obtained in step (2) is subjected to high-temperature sintering and resin infiltration curing to obtain a dental restorative material with a mechanical gradient; preferably, the multilayer ceramic body is first modified with a silane coupling agent after high-temperature sintering and then subjected to resin infiltration curing.

[0038] By stacking the above-mentioned different silicate powders and granules in order from large to small and from bottom to top according to particle size, and using two pressing and high-temperature sintering, it was found that the gradient change of the mechanical properties of native teeth can be simulated, and a composite material with a tissue structure and mechanical property gradient close to that of native teeth can be prepared, which can achieve a highly bionic effect with native teeth.

[0039] Experiments have found that under the production process conditions provided by the present invention, as the particle size of silicate powders and granules decreases, the Vickers hardness and elastic modulus of the restorative material show an overall upward trend. The Vickers hardness of the restorative material of glassy phase silicate granules with a particle size of 50nm-1000nm is above 2.5GPa, which is within the range of native tooth enamel and can even approach the average hardness of enamel. The particle size interval between different silicate powders is above 5μm, which can better simulate the tooth tissue structure. The test results show that the Vickers hardness and elastic modulus of the material show a gradient change, which is close to the gradient of the mechanical properties of native teeth. Among them, 90μm to 100μm is the largest particle size layer, corresponding to the dentin layer of human teeth, 10μm to 90μm is the intermediate particle size layer, and 50nm to 1000nm is the smallest particle size layer, corresponding to the enamel layer of human teeth.

[0040] Furthermore, in some embodiments, the at least one micron-sized powder having a particle size of 10 μm to 90 μm in step (1) is screened specifically as follows:

[0041] At least one micron-sized powder is selected from silicate powders having a particle size of 90-80 μm, 80-70 μm, 70-60 μm, 60-50 μm, 50-40 μm, 40-30 μm, 30-20 μm, and 20-10 μm.

[0042] The granules are prepared according to the following method:

[0043] Silicate powders with particle sizes of 1000nm-800nm, 800nm-600nm, 600nm-400nm, 400nm-200nm, 200-100nm and 100-50nm are mixed with a binder respectively to make the solid content of the mixed liquid 20-40wt%, and are prepared by spray granulation; the binder includes PVA and PEG.

[0044] In some embodiments, the two pressings in step (2) are preferably performed at a pressure of 5t-6t for the first pressing and a holding time of 30-60s, and a cold isostatic pressing pressure of 150-250MPa for the second pressing and a holding time of 2-4min, wherein the pressure increase rate is 100-200MPa / min;

[0045] The high-temperature sintering includes high-temperature debinding and pre-sintering, the temperature is 700-800°C, the holding time is 10min-3h, and the heating rate is 1-5°C / min.

[0046] The resin infiltration adopts the mixed liquid infiltration of resin matrix and curing agent, wherein the resin matrix includes one or more combinations of bisphenol A dimethacrylate glycidyl ester (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), and diurethane dimethacrylate (UDMA); the curing agent includes benzoyl peroxide (BPO), and the mass ratio of the curing agent to the resin matrix is ​​0.5%-1.5%.

[0047] The curing adopts high temperature and high pressure polymerization curing, wherein the temperature is 50° C.-120° C., the pressure is 100-200 MPa, and the polymerization time is 2-5 hours.

[0048] In addition, the present invention also provides a dental restorative material with a mechanical gradient, which is prepared according to the preparation method of the present invention. The dental restorative material with a mechanical gradient has a structural gradient and mechanical gradient performance close to that of native tooth tissue.

[0049] The present invention also provides a dental restorative material with a mechanical gradient for use in dental restoration, particularly for restoring different parts of teeth or different parts of the same tooth. The bonding surface of the metal handle of the material has the lowest hardness at the bottom and increases in hardness toward the top.

[0050] The following are embodiments:

[0051] The micron-sized powders and nano-sized granules used in the following examples were prepared as follows:

[0052] (1) Micron-sized silicate powder

[0053] Sodium aluminum silicate salt powder is passed through a glass melting furnace to prepare coarse glass particles, which are crushed by a Jaw crusher and further pulverized by a jet mill. The powder is then screened by a powder screening device to obtain micron-sized silicate powders with nine particle sizes: A: 100-90 μm, B: 90-80 μm, C: 80-70 μm, D: 70-60 μm, E: 60-50 μm, F: 50-40 μm, G: 40-30 μm, H: 30-20 μm, and I: 20-10 μm.

[0054] (2) Nano-granules

[0055] The sodium aluminosilicate powder is further crushed by a sand mill, and sieved by a powder screening device to obtain nano-scale powders with six particle sizes: J: 1000nm-800nm, K: 800nm-600nm, L: 600nm-400nm, M: 400nm-200nm, N: 200-100nm, and O: 100-50nm;

[0056] The six powders of particle sizes I to O are evenly mixed with an aqueous solution containing 6% PVA with a solid content of 30 wt%. The liquid mixture is passed through a spray granulation tower to prepare six granules of corresponding particle sizes, and the granules are marked as I' to O' respectively; in this embodiment, the sodium aluminosilicate powder can also be replaced by quartz powder, barium glass powder, silica-zirconia composite powder, silica-ytterbium oxide composite powder, nano-silica powder, and nano-zirconium oxide powder, and the binder PVA can also be replaced by PEG.

[0057] Example 1 Dental restorative material 1 with mechanical gradient

[0058] (1) Preparation of a multilayer ceramic body: Take the four micron-sized powders of A, C, E, and G and the two nano-sized granules of I' and K', and stack them in order from bottom to top in the order of A, C, E, G, I', and K', wherein the thickness ratio of A, C, E, G, I', and K' in the mold is 1-2:1-1.2:1-1.2:1-1.2:1-1.2:1.5-2, and the specific thickness of each layer of powder or granule can be adjusted according to the actual mold size so that the thickness of the middle layers is not much different or the same, and the thickness of the bottom layer and the surface layer is 1.5-2. The total thickness of each layer of raw material in the mold is adjusted according to the preset thickness of the ceramic body. It is not necessary to fill the mold completely, that is, the overall thickness of the ceramic body after pressing meets the preset requirements. For example, the mold size (L×W×H, mm) used in this embodiment is 18×12×14, wherein the thickness ratio of A, C, E, G, I', and K' in the mold is 1.5:1:1:1:1:2; the six layers of raw materials of different particle sizes are hydraulically formed by a hydraulic press, and the hydraulic press is set to a pressure of 6t and the pressure is maintained for 30s.

[0059] (2) Preparation of dental restorative materials with mechanical gradient: the multilayer ceramic body is placed in a protective film, sealed, and then cold isostatically pressed at a pressure increase rate of 200 MPa / min, maintained at 200 MPa for 3 minutes, and then the pressure is reduced and taken out; after high-temperature treatment of grate glue and pre-sintering, the temperature is increased at a rate of 5°C / min, maintained at 700°C for 3 hours, and then cooled with the furnace and taken out, the pre-sintered porous ceramic is modified with a silane coupling agent, and dried in a vacuum drying oven at 110°C for 2 hours; a vacuum-pressure-resin infiltration device is used to infiltrate the resin monomer mixture into the porous ceramic, and the pressure is set to 0.6 MPa. The resin monomer mixture is obtained according to the mass ratio of Bis-GMA:TEGDMA:BPO=55:45:1.

[0060] The porous ceramics fully infiltrated with resin are packaged in a high-temperature vacuum film and polymerized at high temperature and high pressure. Specifically, the packaged porous ceramics are placed in a high-pressure chamber, the hydraulic oil in the high-pressure chamber is heated to 60°C, the pressure is increased to 120MPa, and the temperature is kept at this temperature for 2 hours. The temperature is then raised to 120°C, the pressure is adjusted to 180MPa, and the temperature is kept at this temperature for 2 hours before being taken out. This is a dental restorative material with a mechanical gradient, such as Figure 1 As shown, the formed dental restoration material is finely processed and polished with animal hair or nut shells mixed with a polishing agent, and is used after polishing.

[0061] Example 2 Dental restorative material with mechanical gradient 2

[0062] (1) Preparation of multi-layer ceramic green body: take the above three kinds of powders A, D, and G and the two kinds of granules J' and M', and stack them in order from bottom to top in the order of A, C, E, G, I', and K', wherein the thickness ratio of A, C, E, G, I', and K' in the mold is 1.5:1:1:1:2, and hydraulically form a ceramic green body with multiple layers of powders of different particle sizes stacked on top of each other by a hydraulic press, set the pressure of the hydraulic press to 6t, and maintain the pressure for 30s.

[0063] (2) Preparation of dental restorative materials with mechanical gradient: the multilayer ceramic body is placed in a protective film, sealed, and then cold isostatically pressed at a pressure increase rate of 200 MPa / min, maintained at 230 MPa for 3 minutes, and then the pressure is reduced and taken out; the grate glue is treated and pre-sintered at a high temperature at a heating rate of 1°C / min, maintained at 750°C for 2.5 hours, and then cooled with the furnace and taken out, and the pre-sintered porous ceramic is modified with a silane coupling agent and dried in a vacuum drying oven at 110°C for 2 hours; a resin monomer mixture is infiltrated into the porous ceramic using a vacuum-pressure-resin infiltration device, and the pressure is set to 0.6 MPa. The resin monomer mixture is obtained according to a mass ratio of Bis-GMA:TEGDMA:BPO=60:40:1.

[0064] The porous ceramics fully infiltrated with resin are packaged in a high-temperature vacuum film and polymerized at high temperature and high pressure. Specifically, the packaged porous ceramics are placed in a high-pressure chamber, the hydraulic oil in the high-pressure chamber is heated to 65°C, the pressure is increased to 120MPa, and the temperature is kept at this temperature for 2 hours. The temperature is then increased to 120°C, the pressure is adjusted to 180MPa, and the ceramics are taken out after being kept at this temperature for 2 hours to obtain a dental restorative material with a mechanical gradient.

[0065] Example 3 Dental Restorative Material with Mechanical Gradient 3

[0066] (1) Preparation of multi-layer ceramic green body: take the above-mentioned four kinds of powders A, C, E, and G and the four kinds of granules I', K', M', and O', and stack them in order from bottom to top according to A, C, E, G, I', K', M', and O', with a thickness of 1.2:1:1:1:1:1:1:1:2, and hydraulically form a ceramic green body with multiple layers of raw materials of different particle sizes stacked on top of each other by a hydraulic press. The hydraulic press is set to a pressure of 5t and the pressure is maintained for 30s.

[0067] (2) Preparation of dental restorative materials with mechanical gradient: the multilayer ceramic body is placed in a protective film, sealed, and then cold isostatically pressed at a pressure increase rate of 200 MPa / min, maintained at 230 MPa for 3 minutes, and then removed by reducing the pressure; after high-temperature treatment of grate glue and pre-sintering, the temperature increase rate is 1°C / min, and maintained at 720°C for 140 minutes, then cooled with the furnace, removed, and the pre-sintered porous ceramic is modified with a silane coupling agent and dried in a vacuum drying oven at 110°C for 2 hours; a resin monomer mixture is infiltrated into the porous ceramic using a vacuum-pressure-resin infiltration device, and the pressure is set to 0.6 MPa. The resin monomer mixture is obtained according to the mass ratio of UDMA:TEGDMA:BPO=65:35:1.

[0068] The porous ceramics fully infiltrated with resin are packaged in a high-temperature vacuum film and polymerized at high temperature and high pressure. Specifically, the packaged porous ceramics are placed in a high-pressure chamber, the hydraulic oil in the high-pressure chamber is heated to 65°C, the pressure is increased to 120MPa, and the temperature is kept at this temperature for 2 hours. The temperature is then increased to 120°C, the pressure is adjusted to 180MPa, and the ceramics are taken out after being kept at this temperature for 2 hours to obtain a dental restorative material with a mechanical gradient.

[0069] Example 4 Dental Restorative Material with Mechanical Gradient 4

[0070] (1) Preparation of a multilayer ceramic body: Take the above-mentioned four powders A, D, F, and H and the four granules I', K', M', and O', and stack them in order from bottom to top in the order of A, D, F, H, I', K', M', and O', wherein the thickness ratio of A, D, F, H, I', K', M', and O' in the mold is 1.5:1:1:1:1:1:1:1:1.5, and hydraulically form a ceramic body with multiple layers of powders of different particle sizes stacked on top of each other by a hydraulic press, set the pressure of the hydraulic press to 6t, and maintain the pressure for 30s.

[0071] (2) Preparation of dental restorative materials with mechanical gradient: the multilayer ceramic body is placed in a protective film, sealed, and then cold isostatically pressed at a pressure increase rate of 100 MPa / min, maintained at 50 MPa for 3 minutes, and then the pressure is reduced and taken out; the grate glue is treated and pre-sintered at a high temperature at a heating rate of 1°C / min, maintained at 800°C for 10 minutes, and then cooled with the furnace and taken out, and the pre-sintered porous ceramic is modified with a silane coupling agent and dried in a vacuum drying oven at 110°C for 2 hours; a resin monomer mixture is infiltrated into the porous ceramic using a vacuum-pressure-resin infiltration device, and the pressure is set to 0.6 MPa. The resin monomer mixture is obtained according to the mass ratio of UDMA:TEGDMA:BPO=75:25:1.

[0072] The porous ceramics fully infiltrated with resin are packaged in a high-temperature vacuum membrane and polymerized at high temperature and high pressure. Specifically, the packaged porous ceramics are placed in a high-pressure chamber, the hydraulic oil in the high-pressure chamber is heated to 50°C, then raised to 80°C, the pressure is adjusted to 200MPa, and the ceramics are taken out after being kept at this temperature and pressure for 2 hours to obtain a dental restorative material with a mechanical gradient.

[0073] Example 5 Dental Restorative Material with Mechanical Gradient 5

[0074] (1) Preparation of multi-layer ceramic green body: take the above-mentioned two powders A and E and three granules I', L', O', and stack them in order of A, E, I', L', O' from bottom to top, wherein the thickness ratio of A, E, I', L', O' in the mold is 1:1:1:1:1.5, and hydraulically form a ceramic green body with multiple layers of powders of different particle sizes stacked on top of each other by a hydraulic press, set the pressure of the hydraulic press to 6t, and maintain the pressure for 30s.

[0075] (2) Preparation of dental restorative materials with mechanical gradient: the multilayer ceramic body is placed in a protective film, sealed, and then cold isostatically pressed at a pressure increase rate of 100 MPa / min, maintained at 150 MPa for 3 minutes, and then the pressure is reduced and taken out; the grate glue is treated and pre-sintered at a high temperature at a heating rate of 1°C / min, maintained at 750°C for 2 hours, and then cooled with the furnace and taken out, and the pre-sintered porous ceramic is modified with a silane coupling agent and dried in a vacuum drying oven at 110°C for 2 hours; a resin monomer mixture is infiltrated into the porous ceramic using a vacuum-pressure-resin infiltration device, and the pressure is set to 0.6 MPa. The resin monomer mixture is obtained according to a mass ratio of Bis-GMA:TEGDMA:BPO=50:50:1.

[0076] The porous ceramics fully infiltrated with resin are packaged in a high-temperature vacuum membrane and polymerized at high temperature and high pressure. Specifically, the packaged porous ceramics are placed in a high-pressure chamber, the hydraulic oil in the high-pressure chamber is heated to 55°C, and then to 90°C, the pressure is adjusted to 120MPa, and the ceramics are taken out after being kept at this temperature and pressure for 2 hours to obtain a dental restorative material with a mechanical gradient.

[0077] Example 6 Dental Restorative Material with Mechanical Gradient 6

[0078] (1) Preparation of a multilayer ceramic body: Take the above-mentioned four powders A, B, E, and F and the three granules I', M', and O', and stack them in order from bottom to top in the order of A, B, E, F, I', M', and O', wherein the thickness ratio of A, B, E, F, I', M', and O' in the mold is 2:1:1:1:1:1:1:2, and hydraulically form a ceramic body with multiple layers of raw materials of different particle sizes stacked on top of each other using a hydraulic press. The hydraulic press is set to a pressure of 3t and the pressure is maintained for 30s.

[0079] (2) Preparation of dental restorative materials with mechanical gradient: the multilayer ceramic body is placed in a protective film, sealed, and then cold isostatically pressed at a pressure increase rate of 200 MPa / min, maintained at 240 MPa for 3 minutes, and then the pressure is reduced and taken out; the grate glue is treated and pre-sintered at a high temperature at a heating rate of 1°C / min, maintained at 720°C for 80 minutes, and then cooled with the furnace and taken out, and the pre-sintered porous ceramic is modified with a silane coupling agent and dried in a vacuum drying oven at 110°C for 2 hours; a vacuum-pressure-resin infiltration device is used to infiltrate the resin monomer mixture into the porous ceramic, and the pressure is set to 0.6 MPa. The resin monomer mixture is obtained according to the mass ratio of Bis-GMA:UDMA:TEGDMA:BPO=30:30:40:1.

[0080] The porous ceramics fully infiltrated with resin are packaged in a high-temperature vacuum membrane and polymerized at high temperature and high pressure. Specifically, the packaged porous ceramics are placed in a high-pressure chamber, the hydraulic oil in the high-pressure chamber is heated to 55°C, and then to 90°C, the pressure is adjusted to 200MPa, and the ceramics are taken out after being kept at this temperature and pressure for 2 hours to obtain a dental restorative material with a mechanical gradient.

[0081] Example 7 Performance test of dental restorative materials with mechanical gradient

[0082] The dental restorative materials with mechanical gradients obtained in Example 1 and Example 2 were used as test objects, respectively, as follows:

[0083] (1) The three-point bending strength, bending modulus, fracture toughness, Vickers hardness, and elastic modulus of the six single-layer composite materials in Example 1, as well as the Vickers hardness and elastic modulus of the corresponding six regions of the dental restorative material with a mechanical gradient were tested. The results are as follows:

[0084]

[0085]

[0086] In the table, “--” means not tested, the same below; 145.26(19.02) means 145.26±19.02, and other data are the same.

[0087] (2) The three-point bending strength, bending modulus, fracture toughness, Vickers hardness, and elastic modulus of the five single-layer composite materials in Example 2, as well as the Vickers hardness and elastic modulus of the corresponding five regions of the dental restorative material with a mechanical gradient were tested. The results are as follows:

[0088]

[0089]

[0090] The elastic modulus of enamel of native teeth is 32.36~91.36GPa, and the Vickers hardness of enamel is 1.069~4.515GPa, with an average value of 3.121±1.090GPa; the elastic modulus of dentin is 18.05~29.05GPa, and the Vickers hardness of dentin is 0.640~1.234GPa.

[0091] As shown in the table above, the dental restorative material prepared according to the preparation method provided by the present invention exhibits a superior mechanical gradient. The hardness of the material's surface region, with the maximum hardness, is within the range of tooth enamel and close to the average hardness of tooth enamel (3.121 ± 1.090 GPa). Compared to typical resin-infiltrated ceramic composites, this material's maximum hardness exceeds 2.5 GPa and even approaches the average hardness of native tooth enamel (3.1 GPa). Furthermore, the elastic modulus of the material's underlying region, with the minimum elastic modulus, is within the range of dentin, demonstrating good compatibility with adjacent native teeth.

[0092] In summary, the dental restoration material provided by the present invention can simulate the mechanical properties and tissue structure gradients of the mechanical gradient of native teeth, can be used as a composite material for dental restoration, and has good compatibility with teeth.

[0093] Comparative Example 1

[0094] The four powders A, C, E, and G were mixed uniformly with a 6% PVA aqueous solution to a solid content of 30 wt%. The liquid mixture was passed through a spray granulation tower to produce granules of corresponding particle sizes. These granules were then thoroughly mixed with the I' and K' granules to prepare a mixture of the six granules. The mixture was then pressed twice into a ceramic body using the same pressing conditions and molds as in Example 1. The Vickers hardness and elastic modulus of the five regions corresponding to the material in Example 1 were tested, and the results were as follows:

[0095]

[0096]

[0097] The test results show that there is no obvious difference in the Vickers hardness and elastic modulus of the six regions of the material as a whole, and the average value is lower than the performance of the middle layer; in addition, the pressing after mixing of each layer of granulation can easily lead to inconsistent particle size of the entire ceramic body, which can easily cause the overall hardness and modulus of the material to decrease and the surface hardness to be lower than 2.0GPa.

[0098] Comparative Example 2

[0099] The six powders A, C, E, G, I, and K were stacked in sequence, with the thickness ratio of A, C, E, G, I, and K in the mold being 1.5:1:1:1:1:2. The powders were pressed twice to form a multilayer ceramic body. The pressing conditions and mold were the same as in Example 1. The Vickers hardness and elastic modulus of the five regions corresponding to the materials in Example 1 were tested. The test results are as follows:

[0100]

[0101] The test results show that the Vickers hardness and elastic modulus of the six regions of the material first decrease and then increase with the powder particle size, and there is no obvious change. The hardness of the area with the maximum hardness on the surface of the material is lower than 2.5GPa. In addition, the mechanical properties between the layers of the material are relatively small, and the overall mechanical gradient changes are quite different from those of native teeth.

[0102] Comparative Example 3

[0103] Preparation of a multilayer ceramic body: The four micron-sized powders A, C, E, and G and the two nano-sized granules I' and K' were stacked from bottom to top in the order of A, C, E, G, I', and K', wherein the thickness ratio of A, C, E, G, I', and K' in the mold was 1.5:1:1:1:1:1:2, and a ceramic body was formed by cold isostatic pressing at 200 MPa for 30 min. Other aspects were the same as in Example 1. The test results are as follows:

[0104]

[0105] The test results show that the Vickers hardness and elastic modulus of the five regions of the material increase and then decrease as the powder particle size decreases, and the hardness corresponding to the area with the maximum hardness of the material is lower than 2.5GPa, which makes it difficult to simulate the changes in the mechanical properties of native teeth.

[0106] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a dental restorative material having a mechanical gradient, characterized in that: The following steps are involved: (1) Screening micron-sized silicate powders with a particle size of 90 μm to 100 μm and at least one particle size of 10 μm to 90 μm, and two or more nano-sized granules with a particle size of 50 nm to 1000 nm; the granules are obtained by spray granulation of silicate powders of corresponding particle sizes mixed with a binder; the binder is an aqueous solution containing 6% PVA; the at least one micron-sized silicate powder with a particle size of 10 μm to 90 μm is screened specifically as follows: At least one micron-sized powder is selected from silicate powders having a particle size of 90-80 μm, 80-70 μm, 70-60 μm, 60-50 μm, 50-40 μm, 40-30 μm, 30-20 μm, and 20-10 μm; The granules are prepared according to the following method: Silicate powders with particle sizes of 1000nm to 800nm, 800nm ​​to 600nm, 600nm to 400nm, 400nm to 200nm, 200nm to 100nm, and 100nm to 50nm are mixed with a binder respectively so that the solid content in the mixed solution is 20-40wt%, and granules with corresponding particle sizes are prepared by spray granulation; (2) The micron-sized silicate powder and nano-sized granules obtained in step (1) are stacked in descending order of particle size and from bottom to top, and pressed twice to form a 5-8-layer ceramic body; The first pressing is performed at a pressure of 3t-6t and a holding time of 30-60s. The second pressing is performed by cold isostatic pressing, at a pressure of 50-250MPa and a holding time of 2-4min. (3) The multilayer ceramic body obtained in step (2) is subjected to high-temperature sintering and resin infiltration curing to obtain a dental restorative material with a mechanical gradient.

2. The method for preparing a dental restorative material having a mechanical gradient according to claim 1, wherein: In step (2), the layers are stacked from bottom to top, wherein the thickness ratio of the bottom layer: the middle single layers: the top layer is 1~2:1~1.2:1.5~2.

3. The method for preparing a dental restorative material having a mechanical gradient according to claim 2, wherein: The thickness of each single layer in the middle is consistent.

4. The method for preparing a dental restorative material having a mechanical gradient according to claim 2 or 3, wherein: In the two pressings in step (2), the first pressing is performed at a pressure of 5t-6t and a holding time of 30-60s, and the second pressing is performed at a cold isostatic pressing pressure of 150-250MPa and a holding time of 2-4min.

5. The method for preparing a dental restorative material having a mechanical gradient according to claim 4, wherein: In step (3), the multilayer ceramic body is first modified with a silane coupling agent after high-temperature sintering, and then subjected to resin infiltration curing; wherein the high-temperature sintering temperature is 700-800°C, the holding time is 10min-3h, and the heating rate is 1-5°C / min; the resin infiltration curing adopts high-temperature and high-pressure polymerization curing, the temperature is 50°C-120°C, the pressure is 100-200MPa, and the polymerization time is 2-5h.

6. The method for preparing a dental restorative material having a mechanical gradient according to claim 1, wherein: The silicate powder is sodium aluminosilicate powder.

7. The method for preparing a dental restorative material having a mechanical gradient according to claim 6, wherein: The silicate powder may also be replaced by quartz powder, barium glass powder, silicon oxide-zirconia composite powder, silicon oxide-ytterbium oxide composite powder, nano silicon oxide powder, or nano zirconium oxide powder.

8. A dental restorative material with a mechanical gradient, characterized in that: The dental restorative material has the characteristics of native tooth tissue structure gradient and mechanical property gradient, and is prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the dental restorative material with a mechanical gradient according to claim 8 in the preparation of dental restorative products.

10. The use according to claim 9, characterized in that: It is used to prepare dental restoration products for repairing teeth in different parts or different parts of the same tooth.

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