Multilayered zirconia with different yttria contents

Abstract

To provide a dental zirconia blank highly transparent and reproducible of natural tooth-like hue, and having a strength to withstand the use in the mouth, and also to provide a dental zirconia blank having further strength that enables fabrication of a prosthetic device with 4 or more units.SOLUTION: The present invention relates to a dental zirconia blank having a plurality of layers, the dental zirconia blank comprising: a first layer composed of a high-transparent ceramics including 91.6-96.5 mol% of zirconium oxide and 3.5-8.4 mol% of yttrium oxide; and a second layer composed of a low-transparent ceramics including 95.6-98.5 mol% of zirconium oxide and 1.5-4.4 mol% of yttrium oxide. The percentage content of yttrium oxide in the low-transparent ceramics is 0.5-5.4 mol% less than the percentage content of yttrium oxide in the high-transparent ceramics. The first layer is located at one end in the lamination direction of the plurality of layers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dental zirconia blank used in cutting for CAD / CAM in the dental field. [Background technology]

[0002] Traditionally, dental treatment for crown defects has generally involved prosthetic restoration using cast crowns and bridges or dentures. Specifically, clinical applications of porcelain-fused-to-a-bridge crowns and bridges, which combine functionality and aesthetics by replicating the shape of a tooth crown by fusing porcelain to the surface of a metal frame made from a casting alloy for porcelain fusion, include:

[0003] Furthermore, from the viewpoint of the risk of developing metal allergies, rising prices due to fluctuations in the market price of precious metals, and aesthetics that can mimic the color tone of natural teeth, attention has been drawn to prosthetic devices made by techniques such as the dipping method using alumina, aluminosilicate glass, lithium disilicate glass, etc., or the pressing method using ceramic ingots, known as all-ceramics, and prosthetic restorations using such devices are also on the rise.

[0004] In recent years, the technology of fabricating prosthetic devices by machining using dental CAD / CAM systems has rapidly become widespread. This has made it possible to easily fabricate prosthetic devices by machining blanks such as blocks and disks made of zirconia, alumina, aluminosilicate glass, and lithium disilicate glass. Zirconia is also widely used in clinical settings as a high-strength ceramic. To improve the machinability of zirconia blanks, pre-sintered zirconia blanks are generally used, which are pre-sintered at low firing temperatures without being fully sintered to achieve strength and hardness suitable for machining.

[0005] Among zirconia blanks, those containing 3 mol% yttrium oxide have been put to practical use because they have the bending strength required for bridge frames with four or more units. A small amount of alumina is added to these zirconia blanks to improve sinterability and suppress low-temperature degradation.

[0006] However, it was difficult to reproduce the transparency of tooth enamel with zirconia blanks containing 3-4 mol% yttrium oxide. Therefore, it was necessary to build up a glass called porcelain on the enamel. However, this process was very complicated and required the technician's skill.

[0007] In recent years, zirconia blanks made from zirconia powder with an extremely low alumina content have been used clinically to increase the light transmittance suitable for full crowns on molars. Also, zirconia blanks designed to be highly light transmittant by increasing the content of yttrium oxide added as a stabilizer to 5-6 mol% have been used so that they can be used for full crowns on anterior teeth, where greater aesthetics are required.

[0008] Patent Document 1 describes that a zirconia sintered body containing more than 4.0 mol% and not more than 6.5 mol% yttrium oxide has a total light transmittance of 37% or more and less than 40%, and has translucency and strength particularly suitable for use in anterior teeth. The translucency is high, and the bending strength is said to be 500 MPa or more. However, while a bending strength of 500 MPa can be said to be sufficient for a single crown, 500 MPa is not sufficient strength for a multi-unit prosthetic device such as a bridge. In particular, the connecting parts are subjected to large forces due to occlusion, so they are required to have a higher bending strength. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2015-143178 Summary of the Invention [Problem to be solved by the invention]

[0010] The use of conventional zirconia powder has improved light transmission and aesthetics, but at the cost of reduced strength. This reduced strength limits the number of cases in which it can be used and raises the risk of the prosthetic device cracking inside the mouth. An object of the present invention is to provide a dental zirconia blank that has high transmittance, can reproduce a color tone close to that of natural teeth, and has strength that can withstand the oral cavity.Furthermore, an object of the present invention is to provide a dental zirconia blank that has high strength and can be used to fabricate prosthetic devices with four or more units. [Means for solving the problem]

[0011] The present invention provides a dental zirconia blank having multiple layers, comprising: a first layer made of a high-permeability ceramic containing 91.6-96.5 mol% zirconium oxide and 3.5-8.4 mol% yttrium oxide; and a second layer made of a low-permeability ceramic containing 95.6-98.5 mol% zirconium oxide and 1.5-4.4 mol% yttrium oxide, wherein the yttrium oxide content of the low-permeability ceramic is 0.5-5.4 mol% less than the yttrium oxide content of the high-permeability ceramic, and the first layer is located at one end of the stacking direction of the multiple layers.

[0012] In the present invention, the first layer is preferably composed of a plurality of highly permeable layered regions having different compositions. In the present invention, the first layer preferably has a plurality of highly permeable layered regions having different contents of zirconium oxide and / or yttrium oxide in the highly permeable ceramic. In the present invention, it is preferable that at least one highly transmissive layered region contains 0.0001 to 0.30 mol % of erbium oxide. In the present invention, the second layer is preferably composed of a plurality of low-permeability layered regions having different compositions. In the present invention, the second layer preferably has a plurality of low-permeability layered regions having different zirconium oxide contents and / or different yttrium oxide contents in the low-permeability ceramic. In the present invention, it is preferable that at least one low-permeability layered region contains 0.0001 to 0.30 mol % of erbium oxide. In the present invention, the highly permeable ceramic is preferably a calcined body of a plurality of ceramic powders having different compositions. In the present invention, the low-permeability ceramic is preferably a calcined body of a plurality of ceramic powders having different compositions. In the present invention, the first layer is preferably positioned within a range of 5 to 40% of the dimension on a perpendicular line from the center of gravity of the surface on one end side in the stacking direction of the dental zirconia blank on which the first layer is positioned to the surface on the other end side opposite the surface on the one end side. In the present invention, the ceramic powder constituting the high permeability ceramic and the ceramic powder constituting the low permeability ceramic have a difference in BET specific surface area of 2 m 2 / g and the difference in average primary particle diameter is preferably in the range of 20 nm. In the present invention, it is preferable that the transparency of at least one high-transmittance layered region is higher than the transparency of the second layer, and when the chromaticity of the first layer according to the L*a*b* color system is expressed as LE, aE, and bE, LE is 65.0 or more and 82.0 or less, aE is -4.0 or more and 2.0 or less, and bE is 0.0 or more and 20.0 or less. In the present invention, it is preferable that the transparency of the first layer is higher than that of the second layer, and that when the chromaticity of the first layer according to the L*a*b* color system is expressed as LE, aE, and bE, LE is 65.0 or more and 82.0 or less, aE is -4.0 or more and 2.0 or less, and bE is 0.0 or more and 20.0 or less. In the present invention, the first layer preferably contains 0.0001 to 0.00 mol % of erbium oxide. In the present invention, the second layer preferably contains 0.0001 to 1.00 mol % of erbium oxide.

[0013] In the present invention, the highly permeable ceramic is preferably made of zirconium oxide and yttrium oxide. In the present invention, the low permeability ceramic preferably comprises zirconium oxide and yttrium oxide. In the present invention, the first layer is preferably made of a highly permeable ceramic. In the present invention, the second layer is preferably made of low-permeability ceramics. In the present invention, the dental zirconia blank preferably comprises a first layer and a second layer.

[0014] The perpendicular line from the center of gravity in this specification is, for example, that shown in FIG. [Effects of the Invention]

[0015] According to the present invention, it is possible to machine the zirconia prosthetic device using CAD / CAM technology, and after sintering, it is possible to obtain a highly transparent and strong zirconia prosthetic device. It can be used in a variety of cases without being limited to specific cases, and the multi-colored multi-layer structure makes it possible to reproduce a color tone close to that of natural teeth. DETAILED DESCRIPTION OF THE INVENTION

[0016] The dental zirconia blank of the present invention has multiple layers, including at least a first layer and a second layer located at one end of the stacking direction of the multiple layers. The first layer and the second layer do not indicate the order. It is preferable that the first layer is an enamel layer and the second layer is a body layer.

[0017] The first layer is composed of a highly permeable ceramic containing 91.6-96.5 mol% zirconium oxide and 3.5-8.4 mol% yttrium oxide.

[0018] If the yttrium oxide content in the high-transmittance ceramic is less than 3.5 mol%, it becomes difficult to reproduce the enamel layer. Furthermore, if the yttrium oxide content in the high-transmittance ceramic exceeds 8.5 mol%, it becomes difficult to obtain sufficient bending strength. The yttrium oxide content in the high-transmittance ceramic is preferably 4.0 to 8.0 mol%, and most preferably 4.5 to 6.5 mol%. By adjusting the content in this range, it is possible to increase the permeability and achieve sufficient bending strength.

[0019] The second layer is composed of a low-permeability ceramic containing 95.6-98.5 mol% zirconium oxide and 1.5-4.4 mol% yttrium oxide.

[0020] If the yttrium oxide content in the low-permeability ceramic is less than 1.5 mol%, the sintered body will be destroyed. Furthermore, if the yttrium oxide content in the low-permeability ceramic exceeds 4.4 mol%, the background color will be reflected even if coloring is applied. The yttrium oxide content in the low-permeability ceramic is preferably 2.0 to 4.0 mol%, and most preferably 2.5 to 3.5 mol%. By setting the content in this range, the ceramic will be less affected by the background color and will achieve sufficient bending strength.

[0021] The yttrium oxide content of the low-permeability ceramic is 0.5-5.4 mol% less than the yttrium oxide content of the high-permeability ceramic. If the difference in yttrium oxide content is less than 0.4 mol%, the effect of improving aesthetics due to the multi-layer structure may not be realized. On the other hand, if it is greater than 5.4 mol%, aesthetics will be impaired. The difference in yttrium oxide content between the first layer and the second layer is preferably 0.5-4.0 mol%, most preferably 0.5-3.0 mol%. By setting the content in this range, a more natural gradation of transparency can be achieved, improving aesthetics.

[0022] The first layer may be composed of multiple highly permeable layered regions with different compositions. For example, the first layer may have multiple highly permeable layered regions with different zirconium oxide and / or yttrium oxide contents in the highly permeable ceramic. This configuration provides a gradation of color and / or transparency, enabling the fabrication of a prosthetic device that more closely resembles natural teeth.

[0023] In this case, it is preferable that at least one high-permeability layered region included in the first layer contains 0.0001 to 0.30 mol% of erbium oxide. When at least one high-permeability layered region contains erbium oxide, it is dissolved, resulting in the effect of preventing color bleeding due to firing and achieving a reddish color. If the erbium oxide content is less than 0.0001 mol%, it is difficult to achieve this effect. On the other hand, if the erbium oxide content is more than 0.30 mol%, the reddish color may become too strong and may not be suitable for dental crown color.

[0024] The second layer may be composed of multiple low-permeability layered regions with different compositions. For example, the second layer may have multiple low-permeability layered regions with different zirconium oxide and / or yttrium oxide contents in the low-permeability ceramic. This configuration provides a gradation of color and / or transparency, enabling the fabrication of a prosthetic device that more closely resembles natural teeth.

[0025] In this case, it is preferable that at least one low-permeability layered region included in the second layer contains 0.0001 to 0.30 mol% of erbium oxide. When at least one low-permeability layered region contains erbium oxide, it is dissolved in solid solution, which has the effect of suppressing color bleeding due to firing and achieving a reddish color. If the erbium oxide content is less than 0.0001 mol%, it is difficult to achieve this effect. On the other hand, if the erbium oxide content is more than 0.30 mol%, the reddish color may become too strong and may not be suitable as a tooth crown color.

[0026] Highly permeable ceramics can be calcined from multiple ceramic powders with different compositions. This configuration allows for the easy production of prosthetic devices with different colors and / or permeabilities by forming the shape of a tooth using cutting with CAD / CAM technology and then sintering. In this case, the multiple ceramic powders with different compositions may form multiple highly permeable layered regions, or a single highly permeable layered region. Using multiple highly permeable layered regions provides excellent color reproducibility, while using a single highly permeable layered region provides excellent productivity and allows for color reproducibility.

[0027] Low-permeability ceramics can be calcined from multiple ceramic powders with different compositions. This configuration allows for the easy production of prosthetic devices with different colors and / or permeabilities by forming the shape of a tooth using cutting with CAD / CAM technology and then sintering. In this case, the multiple ceramic powders with different compositions may form multiple low-permeability layered regions, or a single high-permeability layered region. Using multiple ceramic powders provides excellent color reproducibility, while using a single ceramic powder provides excellent productivity and allows for color reproducibility.

[0028] The dental zirconia blank of the present invention can be obtained by forming the first layer and the second layer in a mold and sintering them. Dental zirconia blanks are used for cutting using CAD / CAM technology. Dental zirconia blanks are provided as sintered or semi-sintered bodies. More preferably, they are provided as semi-sintered bodies. Dental zirconia blanks provided as semi-sintered bodies are re-fired after cutting using CAD / CAM technology, and used in the oral cavity as a sintered body. The shape of the dental zirconia blank may be a disk type, which is a cylinder, or a block type, which is a cube or rectangular parallelepiped.

[0029] When preparing a dental zirconia blank, a coloring material can be mixed with the ceramic powder constituting the high-permeability ceramic and the ceramic powder constituting the low-permeability ceramic. It is preferable to dissolve or contain a coloring material in the ceramic powder constituting the high-permeability ceramic or the ceramic powder constituting the low-permeability ceramic when preparing the ceramic powder. Examples of coloring materials include iron compounds, cobalt compounds, chromium compounds, praseodymium compounds, and vanadium compounds.

[0030] The ceramic powders constituting the high-transmittance ceramics and the ceramic powders constituting the low-transmittance ceramics can contain aluminum oxide as a sintering aid to improve sinterability. The aluminum oxide content is preferably 0.005 to 0.5 mol%. If the content is more than 0.5 mol%, the translucency decreases, and the aesthetics may be poor, especially when making anterior teeth.

[0031] As shown in Figure 1, the first layer can be located within a range of 5 to 40% of the dimension on a perpendicular line from the center of gravity of the surface on one end side in the lamination direction of the dental zirconia blank where the first layer (enamel layer in Figure 1) is located to the surface on the other end side opposite the surface on the one end side.

[0032] Preferably, the first layer contains 50-100% of the highly transparent layered regions having the same yttrium oxide and erbium oxide content and colorant content, and more preferably, the first layer contains 50-100% of the highly transparent layered regions along a perpendicular line from the center of gravity in Figure 1.

[0033] The second layer preferably contains 50-100% of low-transmittance layered regions having the same yttrium oxide and erbium oxide content and colorant content, and more preferably 50-100% of the second layer along a perpendicular line from the center of gravity in Figure 1.

[0034] The average primary particle size of the ceramic powders that make up the high-permeability ceramics and the ceramic powders that make up the low-permeability ceramics is 10-1000 nm, and the BET specific surface area is 5-20 m 2 / g. If the average primary particle size is smaller than 10 nm, molding is often hindered. If the average primary particle size is larger than 1000 nm, molding is often hindered. The BET specific surface area is 5m 2 If the BET specific surface area is less than 20m / g, it tends to be difficult to sinter at low temperatures. 2 If it is greater than / g, the cohesive force is significant.

[0035] The difference in BET specific surface area between the ceramic powders that make up the high-permeability ceramics and the ceramic powders that make up the low-permeability ceramics is 2m 2 / g. Furthermore, the difference in BET specific surface area is preferably in the range of 1 m 2 / g. The difference in average primary particle size between the ceramic powder constituting the high-permeability ceramic and the ceramic powder constituting the low-permeability ceramic is preferably in the range of 20 nm. Furthermore, the difference in average primary particle size is preferably in the range of 10 nm. The difference in BET specific surface area between the ceramic powders that make up the high-permeability ceramics and the ceramic powders that make up the low-permeability ceramics is 2m 2 / g and the difference in average primary particle diameter is preferably within a range of 20 nm. 2 / g and the difference in average primary particle diameter is preferably within a range of 10 nm. When ceramic powders with large differences in BET specific surface area and average primary particle size are laminated and sintered, distortion of the zirconia blank occurs. In particular, when cutting out from a semi-sintered zirconia blank, the blank itself distorts and warps, and the prosthetic device cracks during final sintering, resulting in poor fit and other problems.

[0036] The BET specific surface area and average primary particle size can be adjusted during the production of the ceramic powder constituting the high-permeability ceramic and the ceramic powder constituting the low-permeability ceramic.

[0037] The second layer of the dental zirconia blank of the present invention preferably has a bending strength of 1000 MPa or more, and more preferably 1200 MPa or more. If the second layer has a bending strength of 1000 MPa or more, it can be applied to a bridge frame of four or more units. On the other hand, the first layer preferably has a bending strength of 300 MPa or more, and more preferably 700 MPa or more. If the first layer has a bending strength of 300 MPa or more, it can withstand the occlusal force of molars. In this specification, bending strength refers to the three-point bending strength measured in accordance with ISO 6872.

[0038] Furthermore, the dental zirconia blank of the present invention is preferably composed of multiple high-permeability layered regions and / or multiple low-permeability layered regions. Preferably, the total number of high-permeability layered regions and low-permeability layered regions is 3-10, more preferably 4-6. By including multiple high-permeability layered regions and / or multiple low-permeability layered regions, aesthetics can be more easily achieved. However, if there are 11 or more layers, productivity tends to decrease. If there are 4-6 layers, a dental zirconia blank will be obtained that is well-balanced in terms of aesthetics, productivity, etc.

[0039] It is preferable that the highly permeable surface layer region has the highest transparency, as indicated by the contrast ratio, among the highly permeable layer regions contained in the dental zirconia blank.

[0040] When the chromaticity of the first layer is expressed by LE, aE, and bE in the L*a*b* color system, it is preferable that LE is 65.0 to 82.0, aE is -4.0 to 2.0, and bE is 0.0 to 20.0. It is more preferable that LE is 69.0 to 80.0, aE is -3.0 to 1.0, and bE is 2.0 to 15.0. Furthermore, when the chromaticity of at least one high-transmittance layered region is expressed by LE, aE, and bE in the L*a*b* color system, it is preferable that LE is 65.0 to 82.0, aE is -4.0 to 2.0, and bE is 0.0 to 20.0. It is more preferable that LE is 69.0 to 80.0, aE is -3.0 to 1.0, and bE is 2.0 to 15.0. Furthermore, the transparency of the first layer and / or at least one highly transparent layered region is preferably greater than the transparency of the second layer, which facilitates coloring of a prosthetic device fabricated from the zirconia blank to reproduce a color similar to that of natural teeth.

[0041] When the chromaticity of the second layer according to the L*a*b* color system is expressed as LB, aB, and bB, it is preferable that LB is 67.0 or more and 78.0 or less, aE is -2.5 or more and 1.0 or less, and bB is 5.0 or more and 15.0 or less.

[0042] The contrast ratio of the first layer of the dental zirconia blank is preferably 0.71 or less if the first layer does not contain a coloring material, as this enhances aesthetics. On the other hand, if the first layer contains a coloring material, the contrast ratio of the first layer is preferably 0.75-0.85. If the contrast ratio of the first layer containing a coloring material is less than 0.75, the transparency may be too high, resulting in a dark appearance and poor aesthetics. If the contrast ratio of the first layer containing a coloring material is greater than 0.85, the transparency may be too low, resulting in a lack of transparency similar to that of natural teeth.

[0043] The contrast ratio of the second layer of the dental zirconia blank is preferably 0.70 or higher when the second layer does not contain a coloring material, as this enhances aesthetics. On the other hand, when the second layer contains a coloring material, the contrast ratio of the second layer is preferably 0.80-0.90. If the contrast ratio of the second layer containing a coloring material is less than 0.80, the transparency may be too high and the blank may be easily affected by the color of the abutment tooth. If the contrast ratio of the second layer is greater than 0.90, the transparency may be too low, making it difficult to blend in with adjacent teeth in the oral cavity. [Example]

[0044] The present invention will be described in more detail and specifically below with reference to examples, but the present invention is not limited to these examples. (Ceramic powder blending for each layer) The average primary particle size is 40-90nm, and the BET specific surface area is 7-13m 2 Commercially available zirconia powder, yttrium oxide-containing zirconia powder, erbium oxide-containing zirconia powder, and colorant-containing zirconia powder were used. Zirconia powder, yttrium oxide-containing zirconia powder, erbium oxide-containing zirconia powder, and colorant-containing zirconia powder were mixed to obtain the ceramic powders used in the first and second layers, as shown in Table 1. The ceramic powders contain trace amounts of colorants, such as iron compounds and cobalt compounds, to achieve the desired color. (Method for molding dental zirconia blanks) The required amount of each ceramic powder was filled into a 100 mm diameter mold in the order listed in the table, starting from the first layer, and then press-molded at a pressure of 10 kN for 1 minute. The shape of the test specimen is shown in Figure 1. The top of Figure 1 is the first layer, and the bottom is the second layer. After press molding, CIP molding was performed at a pressure of 200 MPa for 1 minute. The press-molded body was debound by heating it to 500°C at a heating rate of 50°C / h, holding it for 2 hours, and then cooling it to room temperature at a heating rate of 100°C / h. After debinding, the body was heated to 1000-1200°C at a heating rate of 100°C / h, held for 2 hours, and then allowed to cool in the furnace to obtain a pre-sintered zirconia blank.

[0045] (Judgment of warpage during pre-firing) The dental zirconia blanks (semi-sintered bodies) molded using the above method were checked for warpage. When the blanks were placed with the convexly deformed side facing downwards, the distance from the placement surface to the bottom surface was measured using a digital microscope VHX-5000 (Keyence Corporation). Measurements were taken at 10 locations, and a maximum distance of 1 mm or less was evaluated as ◯, and a maximum distance of more than 1 mm was evaluated as ×.

[0046] (Judgment of warpage during final firing) A wax-up of a six-tooth bridge was made on a plaster model with six abutment teeth prepared for the front teeth, and the data for the six-tooth bridge was imported using a D2000 (3shape) scanner. The dental zirconia blank molded using the above method was then machined using a DWX-50 (Roland) processing machine to create a six-tooth bridge with the imported data. The temperature was raised to 1450°C at a rate of 5°C / min, and after two hours, the bridge was left to cool to room temperature in the furnace to form a sintered body, and its compatibility was confirmed. When the sintered six-tooth bridge was returned to the plaster model, if it fit without any rattle, it was judged as ○, and if there was rattle and it did not fit, it was judged as ×.

[0047] (3-point bending test) Test specimens were machined from 45-55% of the first and second layers of the dental zirconia blank molded using the method described above. The specimens were heated to 1450°C at a rate of 5°C / min, held for 2 hours, and then allowed to cool to room temperature in the furnace to form sintered bodies. These were then flat-polished to prepare bending specimens measuring 4 mm wide, 1.2 mm thick, and 16 mm long. The bending test was conducted in accordance with ISO 6872:7.3 Flexural strength, with a support distance of 12 mm. Clinically acceptable bending strengths of the first layer were 300 MPa or greater. Clinically acceptable bending strengths of the second layer were 1000 MPa or greater. (Color and contrast ratio measurement) Test specimens were machined from each layer of the dental zirconia blank molded by the above method, heated to 1450°C at a heating rate of 5°C / min, and then left for 2 hours. After cooling to room temperature in the furnace, the sintered bodies were obtained. Further, the surface was polished to produce round plates with a diameter of 14 mm and a thickness of 1.2 mm. The color tone was measured using a spectrophotometer (CM-5: Konica Minolta) to measure the chromaticity (L*, a*, b*) measured against a white background. Furthermore, colorimetry was performed against a white background and a black background, and the measured Y values (the Y value measured against the white background is called YW, and the Y value measured against the black background is called YB) were used to calculate the Y value. (Contrast ratio)=1-(1-YB / YW) The contrast ratio was calculated using the formula. The contrast ratio of the first layer was considered clinically acceptable if it was 0.71 or less when it contained no coloring material, and 0.75-0.85 when it contained coloring material. The contrast ratio of the second layer was considered clinically acceptable if it was 0.70 or more when it contained no coloring material, and 0.80-0.90 when it contained coloring material.

[0048] [Table 1]

[0049] [Table 2]

[0050] [Table 3]

[0051] [Table 4]

[0052] [Table 5]

[0053] [Table 6]

[0054] In Examples 1 to 20, the warpage during pre-sintering was within 1 mm, and there was no rattle during sintering, resulting in good compatibility. Furthermore, the three-point bending strength of the specimens fabricated from the intermediate layer of the zirconia blank (position 45-55% from the surface of the first layer) was 1000 MPa or more. Furthermore, the contrast ratio of the first layer was 0.71 or less, and the contrast ratio of the second layer was 0.70 or more. Furthermore, since the contrast ratio of the first layer was less than the contrast ratio of the second layer, the specimens had sufficient aesthetic appeal. In Comparative Example 1, the bending strength of the first layer was insufficient. In Comparative Example 2, the warpage during pre-firing was greater than 1 mm, and there was rattle during main sintering, so the compatibility was poor. In Comparative Example 3, the contrast ratio in the first layer was high, and sufficient aesthetics were not obtained. In Comparative Example 4, there was no difference in the contrast ratio between the first layer and the second layer, and sufficient aesthetics were not obtained. In Comparative Example 5, the contrast ratio in the second layer was low, and sufficient aesthetics were not obtained. In Comparative Example 6, the sintered body collapsed, and the test could not be carried out. [Industrial Applicability]

[0055] This invention can be machined using CAD / CAM technology, and after sintering, it is possible to obtain a zirconia prosthetic device with high transparency and high strength. It can be used in a variety of cases without limiting the applicable cases, and its multi-colored multilayer structure makes it possible to produce a zirconia prosthetic device that can reproduce the color tone close to that of natural teeth. [Brief explanation of the drawings]

[0056] [Figure 1] FIG. 1 is an image diagram of a dental zirconia blank, with auxiliary lines indicating imaginary perpendicular lines. [Explanation of symbols]

[0057] 1. First layer (enamel layer) 2. Second layer (body layer)

Claims

1. A dental zirconia blank having a plurality of layers, a first layer made of a highly permeable ceramic containing 91.6-96.5 mol% zirconium oxide and 3.5-8.4 mol% yttrium oxide; a second layer made of a low-permeability ceramic containing 96.5-97.5 mol% zirconium oxide and 2.5-3.5 mol% yttrium oxide; The yttrium oxide content of low-permeability ceramics is 0.5-5.4 mol% less than that of high-permeability ceramics. the first layer is located at one end in the stacking direction of the plurality of layers, the second layer is composed of a plurality of low-permeability layered regions each containing 96.5-97.5 mol% zirconium oxide and 2.5-3.5 mol% yttrium oxide and having different compositions; A dental zirconia blank, characterized in that the ceramic powder constituting the high-permeability ceramic and the ceramic powder constituting the low-permeability ceramic have an average primary particle size of 10-1000 nm and a BET specific surface area of 5-20 m 2 / g.

2. The dental zirconia blank according to claim 1, characterized in that the first layer is composed of a plurality of highly permeable layered regions each containing 91.6-96.5 mol% zirconium oxide and 3.5-8.4 mol% yttrium oxide and having different compositions.

3. 3. The dental zirconia blank according to claim 2, wherein the first layer has a plurality of highly permeable layered regions having different contents of zirconium oxide and / or yttrium oxide in the highly permeable ceramic.

4. 4. The dental zirconia blank according to claim 2, wherein at least one highly permeable layered region contains 0.0001 to 0.30 mol % of erbium oxide.

5. The dental zirconia blank according to any one of claims 1 to 4, characterized in that the second layer has a plurality of low-permeability layered regions in which the content of zirconium oxide and / or the content of yttrium oxide in the low-permeability ceramic differs from one another.

6. 6. The dental zirconia blank according to claim 1, wherein at least one low-permeability layered region contains 0.0001 to 0.30 mol % of erbium oxide.

7. 7. The dental zirconia blank according to claim 1, wherein the highly permeable ceramic is a calcined body of a plurality of ceramic powders having different compositions.

8. 8. The dental zirconia blank according to claim 1, wherein the low-permeability ceramic is a calcined body of a plurality of ceramic powders having different compositions.

9. 9. The dental zirconia blank according to any one of claims 1 to 8, characterized in that the first layer is located within a range of 5 to 40% of the dimension, on a perpendicular line from the center of gravity of the surface on one end side in the lamination direction of the dental zirconia blank where the first layer is located, to the surface on the other end side opposite to the surface on the one end side.

10. The difference in BET specific surface area between the ceramic powders that make up the high-permeability ceramics and the ceramic powders that make up the low-permeability ceramics is 2m 2 10. The dental zirconia blank according to any one of claims 1 to 9, wherein the average primary particle diameter is in the range of 20 nm.

11. the transparency of the at least one high-transmittance layered region is greater than the transparency of the second layer; When the chromaticity of the at least one high transmittance layered region is expressed by LE, aE, and bE in the L*a*b* color system, LE is 65.0 or more and 82.0 or less, aE is between -4.0 and 2.0, 4. The dental zirconia blank according to claim 1, wherein bE is 0.0 or more and 20.0 or less.

12. The transparency of the first layer is higher than the transparency of the second layer; When the chromaticity of the first layer in the L*a*b* color system is expressed as LE, aE, and bE, LE is 65.0 or more and 82.0 or less, aE is between -4.0 and 2.0, 12. The dental zirconia blank according to claim 1, wherein bE is 0.0 or more and 20.0 or less.

13. 13. The dental zirconia blank according to claim 1, wherein the first layer contains 0.0001 to 0.30 mol % of erbium oxide.

14. The dental zirconia blank according to any one of claims 1 to 13, characterized in that the second layer contains 0.0001 to 0.30 mol % of erbium oxide.

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