WO2023127559A1 - 優れた機械加工性を有する歯科用酸化物セラミックス仮焼体及びその製造方法 - Google Patents

優れた機械加工性を有する歯科用酸化物セラミックス仮焼体及びその製造方法 Download PDF

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WO2023127559A1
WO2023127559A1 PCT/JP2022/046470 JP2022046470W WO2023127559A1 WO 2023127559 A1 WO2023127559 A1 WO 2023127559A1 JP 2022046470 W JP2022046470 W JP 2022046470W WO 2023127559 A1 WO2023127559 A1 WO 2023127559A1
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Prior art keywords
calcined body
oxide ceramic
dental
alumina
sintered body
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English (en)
French (fr)
Japanese (ja)
Inventor
貴理博 中野
紘之 坂本
信介 樫木
新一郎 加藤
博重 石野
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Kuraray Noritake Dental Inc
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Kuraray Noritake Dental Inc
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Priority to JP2023570864A priority Critical patent/JPWO2023127559A1/ja
Priority to KR1020247020757A priority patent/KR20240114752A/ko
Priority to US18/722,858 priority patent/US20250049547A1/en
Publication of WO2023127559A1 publication Critical patent/WO2023127559A1/ja
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K6/00—Preparations for dentistry
    • A61K6/15—Compositions characterised by their physical properties
    • A61K6/17—Particle size
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A61C13/0003—Making bridge-work, inlays, implants or the like
    • A61C13/0022—Blanks or green, unfinished dental restoration parts
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A61C13/08—Artificial teeth; Making same
    • A61C13/083—Porcelain or ceramic teeth
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C5/00—Filling or capping teeth
    • A61C5/70—Tooth crowns; Making thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K6/00—Preparations for dentistry
    • A61K6/15—Compositions characterised by their physical properties
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K6/00—Preparations for dentistry
    • A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
    • A61K6/802—Preparations for artificial teeth, for filling teeth or for capping teeth comprising ceramics
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K6/00—Preparations for dentistry
    • A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
    • A61K6/802—Preparations for artificial teeth, for filling teeth or for capping teeth comprising ceramics
    • A61K6/818—Preparations for artificial teeth, for filling teeth or for capping teeth comprising ceramics comprising zirconium oxide
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C04B35/111—Fine ceramics
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
    • C04B35/486—Fine ceramics
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C2201/00—Material properties
    • A61C2201/002—Material properties using colour effect, e.g. for identification purposes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
    • B28B11/24—Apparatus or processes for treating or working the shaped or preshaped articles for curing, setting or hardening
    • B28B11/243—Setting, e.g. drying, dehydrating or firing ceramic articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B3/00—Producing shaped articles from the material by using presses; Presses specially adapted therefor
    • B28B3/02—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein a ram exerts pressure on the material in a moulding space; Ram heads of special form
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance

Definitions

  • the present invention relates to a dental oxide ceramic calcined body that contains oxide ceramic particles and pores and can be satisfactorily cut and ground by machining, and a method for producing the same.
  • sintered bodies of oxide ceramics have become popular as dental materials.
  • shape of the dental material a sintered body whose dimensions and surface have been processed with high accuracy is used according to the patient and the clinical site. Machining such as CAD/CAM is used for processing into a desired shape.
  • zirconia As oxide ceramics, aluminum oxide (alumina), zirconium oxide (zirconia), etc. are used in dental materials. In particular, zirconia is excellent in strength and relatively excellent in aesthetics, so the demand is increasing especially in conjunction with the recent price reduction.
  • zirconia sintered bodies are too hard to machine and cannot be machined, break during machining, take a long time to machine, and require frequent replacement of machining tools, resulting in productivity and cost problems.
  • the semi-sintered zirconia calcined body is machined into a cut body having a shape close to the desired shape, such as a tooth or a shape simulating a part of a tooth.
  • a zirconia sintered body having a desired shape can be obtained by sintering the obtained machined body at a sintering temperature or higher.
  • a zirconia calcined body is obtained by sintering (hereinafter also referred to as “calcining”) a molded body obtained by forming a raw material powder into a disk shape, a rectangular parallelepiped shape, or the like, in a temperature range that does not lead to sintering.
  • oxide ceramics other than zirconia those using alumina have been proposed, for example, in Patent Documents 1 to 3.
  • Alumina has a different refractive index than zirconia and is advantageous in translucency after sintering. It is common practice to obtain a sintered body by
  • the sintered body since the sintered body has high hardness, it takes a lot of time to polish. Moreover, if the surface of the sintered body is chipped (chipping occurs) during polishing of the sintered body, the sintered body must be remanufactured. Since chipping occurs in common dental oxide ceramic materials, there is room for material improvement. Moreover, since it takes a long time to polish the sintered body, the blade of the cutting tool is worn. Frequent drill replacement is not economical in terms of replacement costs and continuous machining. Therefore, there is room for improvement in terms of productivity and economy.
  • the surface smoothness of the calcined body was not regarded as important.
  • the inventors of the present invention have found that in the cutting process of the calcined body, if chipping occurs and the surface smoothness is low from the stage before sintering, it will take a long time to polish the sintered body after sintering. It was found that the chipping of the sintered body increased or increased.
  • Patent Document 1 describes a highly translucent alumina sintered body suitable for dental applications, since alumina is frequently used as a sintered body except for porous bodies such as heat insulating materials, it is difficult to calcine. Forming a body is not essential, and no consideration has been given to a calcined body.
  • the median diameter D50 of the powder is as large as 0.45 ⁇ m at the minimum, so even if the calcining temperature is adjusted, there is a high probability of chipping when used as a calcined body for dental applications. rice field.
  • Patent Document 2 describes a method for producing an alumina sintered body in which a molded body obtained using alumina powder having an average particle size of 0.2 to 1.0 ⁇ m is fired at 1480 to 1600°C.
  • Patent Document 2 does not suggest a dental application, and does not discuss a calcined body with high machinability in CAD/CAM processing.
  • Patent Document 2 if the alumina powder having an average particle size of 0.7 ⁇ m described in the examples is used as a calcined body, the probability of chipping is high.
  • Patent Document 3 contains a transition metal oxide or the like, has a fracture toughness of 4.5 MPa m 0.5 or more, and has a maximum total light transmittance (thickness 1 mm) for light with a wavelength of 300 to 800 nm. is described as an alumina sintered body in which the is 60% or more.
  • Patent Document 3 does not consider a calcined body with high machinability in CAD/CAM processing.
  • pressure sintering using hot isostatic pressing hereinafter also referred to as “HIP” is essential after firing, and high machinability and high translucency by an easy manufacturing method are required. In terms of compatibility, there was a problem.
  • HIP hot isostatic pressing
  • the present invention provides a dental oxide ceramic calcined body that has excellent machinability, a low probability of chipping, and excellent translucency after sintering, and a method for producing the same. intended to
  • the present inventors have made intensive studies to solve the above problems, and found that dental oxide ceramics having an average primary particle size of 50 to 300 nm and a pore ratio in the calcined body within a specific range In the calcined body, it has excellent machinability, has a low probability of chipping, and furthermore has a high aesthetic appearance after sintering by a simple manufacturing method. Further investigations have led to the completion of the present invention.
  • the present invention includes the following inventions.
  • a dental oxide ceramic calcined body containing oxide ceramic particles having an average primary particle diameter of 50 to 300 nm and pores, and having D10 of 20 nm or more and D90 of 90 nm or less in the cumulative distribution of pores.
  • the dental oxide ceramic calcined body according to [1] which has a relative density of 43 to 63%.
  • a sintering aid is included, and the sintering aid contains at least one element selected from the group consisting of Group 2 elements, Ce, Zr, and Y, [6] or [ 7], the dental oxide ceramic calcined body.
  • the translucency ( ⁇ L) of the sintered body with a thickness of 1.2 mm is 9 or more, and the thickness
  • a dental oxide ceramic calcined body according to any one of [9].
  • a method for producing a dental oxide ceramic calcined body comprising: A step of pressure-molding the oxide ceramic composition at a surface pressure of 5 to 600 MPa, and a step of firing the obtained compact at 400 to 1300 ° C. under atmospheric pressure, A dental oxide ceramic calcined body containing oxide ceramic particles having an average primary particle size of 50 to 300 nm, and having a D10 of 20 nm or more and a D90 of 90 nm or less in the cumulative distribution of pores.
  • a method for producing a sintered body [12] The method for producing a dental oxide ceramic calcined body according to [11], wherein the oxide ceramic particles contain zirconia and/or alumina. [13] The method for producing a dental oxide ceramic calcined body according to [11] or [12], wherein the alumina contains ⁇ -alumina with a purity of 99.5% or more. [14] Dental oxide ceramic sintering, comprising a step of sintering the calcined body according to any one of [1] to [10] under atmospheric pressure without using hot isostatic pressing. body manufacturing method.
  • dental oxide ceramics having excellent machinability, a low probability of chipping (hereinafter also referred to as "chipping rate"), and high translucency after sintering.
  • a calcined body and a method for manufacturing the same can be provided.
  • it has excellent machinability, reduces the amount of tool wear and chipping rate, reduces the replacement of cutting tools (for example, milling burs), increases continuous productivity, and allows rework.
  • a dental oxide ceramic calcined body that is highly productive and economical due to reduced re-production, and a dental oxide ceramic calcined body that does not require HIP treatment and has a uniform shrinkage rate, resulting in high productivity and translucency. can provide an oxide ceramic sintered body for Further, according to the present invention, it is possible to provide a dental oxide ceramic calcined body having a uniform shrinkage rate during sintering and a method for producing the same.
  • FIG. 4 is an optical microscope photograph of the Katana (registered trademark) drill according to Example 1, showing a tool wear amount of 0.07 mm.
  • 10 is an optical micrograph of a Katana (registered trademark) drill according to Comparative Example 2, showing a tool wear amount of 0.21 mm.
  • 1 is an optical microscope photograph of the surface of a machined body having a chipping rate of 3% or less according to Example 1.
  • FIG. 4 is an optical microscope photograph of the surface of a machined body having a chipping rate of 10% or more according to Comparative Example 1.
  • the dental oxide ceramic calcined body of the present invention contains oxide ceramic particles having an average primary particle size of 50 to 300 nm and pores, and the cumulative distribution of pores in the calcined body has a D10 of 20 nm or more and a D90 of 90 nm. It is below.
  • a calcined body can be a precursor (intermediate product) of a sintered body.
  • a calcined body is a product in which oxide ceramic particles are necked (fixed) and solidified in a state in which the oxide ceramic particles are not completely sintered.
  • the calcined body may have a predetermined shape (for example, disk shape, rectangular parallelepiped shape, etc.).
  • the calcined body may be, for example, a processed body processed into a crown shape, and when processed, it is referred to as a "processed body” or a "machined body".
  • the processed body is obtained, for example, by processing an oxide ceramic disc, which is a calcined body, into a dental product (for example, a crown-shaped prosthesis) using a CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) system.
  • CAD/CAM Computer-Aided Design/Computer-Aided Manufacturing
  • the calcined body of the present invention contains particles made of oxide ceramics (hereinafter sometimes simply referred to as "ceramic oxide particles").
  • ceramic oxide particles The hardness of the fired body changes. The smaller the average primary particle size of the oxide ceramic particles, the more likely it is to cause sticking (necking) during calcination.
  • the oxide ceramic particles contained in the calcined body of the present invention have an average primary particle size of 50 to 300 nm from the viewpoint of reducing tool wear and/or chipping in machinability.
  • the average primary particle size of the particles is more than 300 nm, chipping increases due to the local presence of coarse particles.
  • it exceeds 300 nm the crystal grain size after sintering increases, and the translucency and strength of the dental material are lowered, which is not preferable.
  • the particle diameter is less than 50 nm, the number of particles sticking to each other increases, the calcined body becomes hard, and the amount of tool wear increases.
  • the average primary particle size of the particles is 300 nm or less, it is preferable because particles with a small particle size distribution are less likely to be sucked in, sticking due to a difference in particle size is less likely to occur, and tool wear and chipping rate are reduced.
  • the average primary particle diameter of the particles is preferably 60 to 250 nm, more preferably 70 to 200 nm, even more preferably 80 to 180 nm. The method for measuring the average primary particle size in the calcined body is as described in Examples below.
  • the calcined body of the present invention contains continuous pores (pores) inside, so that when a cutting and grinding tool comes into contact with the calcined body, the pores ensure room for particles to move, and cutting And the grinding resistance can be reduced, and the amount of tool wear can be reduced.
  • D10 and D90 are 20 nm or more and D90 is 90 nm or less, so that the amount of tool wear and the chipping rate are reduced. do.
  • the calcined body has more gaps, and the balance between excellent machinability and properties such as translucency as a sintered body after sintering is excellent.
  • the pore diameters corresponding to cumulative 10% and cumulative 90% from the smaller side of the cumulative distribution of pores are referred to as D10 and D90, respectively.
  • a method for measuring the cumulative distribution of pores including D10 and D90 can be measured according to JIS R 1655:2003. Specifically, the method for measuring the cumulative distribution of pores is as described in Examples below.
  • D10 is 20 nm or more
  • the pores do not become too small for particles with an average primary particle diameter of 50 to 300 nm, that is, excessive adhesion can be suppressed, and tool wear can be suppressed. amount can be significantly reduced.
  • D10 is preferably 25 nm or more, more preferably 30 nm or more, still more preferably 36 nm or more, and most preferably 39 nm or more, from the viewpoint of machinability and reduction of chipping rate.
  • D90 is 90 nm or less, there is no coarseness and density in the calcined body for particles with an average primary particle diameter of 50 to 300 nm, or coarse particles are locally present.
  • D90 is preferably 80 nm or less, more preferably 75 nm or less, even more preferably 70 nm or less, and most preferably 66 nm or less.
  • the D10/D90 ratio is preferably 1.0 or less, more preferably 0.9 or less, and 0.8 or less from the viewpoint of reducing the chipping rate. is more preferable, and 0.6 or less is most preferable.
  • the D10/D90 ratio is preferably 0.1 or more, more preferably 0.15 or more, and 0.2 or more from the viewpoint of reducing the chipping rate. is more preferable, and 0.3 or more is most preferable.
  • a preferred embodiment is a dental oxide ceramic calcined body having a D10/D90 ratio of 0.32 to 0.59.
  • the relative density of the calcined body of the present invention can be controlled by the manufacturing method described below. If the relative density is less than 43%, it means that the ratio of pores inside the calcined body is high, and the relative density inside the calcined body becomes uneven and the chipping increases. Furthermore, due to this sparseness and density, the contraction rate during sintering becomes uneven, and the sintered body is deformed to some extent, which increases the need for rework such as cutting. In addition, from the viewpoint of translucency of the sintered body, if the relative density is sparse, the machinability (cuttability and grindability) may be improved, but the ratio of pores inside the calcined body is high.
  • the relative density of the calcined body of the present invention is preferably 43 to 63%. In this range, the overall balance of particles and pores is good, the machinability and translucency after sintering are well balanced, the amount of tool wear and/or chipping rate can be reduced, and the sintered body The translucency of the film can be maintained at a high level. Moreover, since the relative density is within a predetermined range, the overall balance between the particles and the pores is improved, so that the shrinkage rate is uniform and uniform.
  • the relative density is more preferably 45-60%, more preferably 47-57%.
  • the relative density of the calcined body can be calculated from the porosity of the calcined body, and specifically can be measured and calculated using a mercury porosimeter.
  • a mercury porosimeter device a device capable of applying a mercury pressure of 15 to 30,000 psia is preferable, and a device capable of applying a pressure of 0.5 to 60,000 psia is more preferable. From the viewpoint of reducing measurement errors, the pressure resolution is preferably 0.1 psia or more.
  • Mercury porosimeter devices include, for example, AutoPore (registered trademark) IV9500 manufactured by Micromeritics (USA).
  • the density of the calcined body is obtained by filling the granules obtained by drying the raw material into a specific mold (such as a mold), and applying pressure to form a specific shape. It means the density of the calcined body obtained by heating at a temperature at which yttria is moderately solid-dissolved and necking (adhesion) is formed moderately after removing the organic components by using a heat sink.
  • the temperature at which the organic component is removed is not particularly limited as long as it is a temperature at which the organic component such as the binder can be removed.
  • the temperature at which proper necking (sticking) is formed is preferably 400 to 1300°C. The calcination temperature will be described later in detail.
  • the BET specific surface area varies depending on the density including the average primary particle size, fixed state, and relative density.
  • the BET specific surface area can be measured according to JIS Z 8830:2013.
  • the BET specific surface area is measured using a commercially available product such as a fully automatic specific surface area measuring device (trade name “Macsorb (registered trademark) HM model-1200”, BET flow method (single-point method/multi-point method), manufactured by Mountec Co., Ltd.). can be measured
  • the BET specific surface area of the calcined body of the present invention is preferably 5 to 25 m 2 /g, more preferably 7.5 m 2 /g or more, more preferably 8 m 2 /g, from the viewpoint of reducing tool wear and chipping rate. g or more is more preferable.
  • the BET specific surface area is 5 m 2 /g or more, the average primary particle size is not too large, and an increase in the chipping rate can be suppressed, or excessive adhesion does not occur, so an increase in the amount of tool wear can be suppressed.
  • the BET specific surface area is preferably 25 m 2 /g or less, more preferably 22 m 2 /g or less, even more preferably 18 m 2 /g or less.
  • the average primary particle size is not too small, the calcined body does not become too hard, and the tool wear amount and / or chipping rate is easily reduced, or , it is possible to suppress the occurrence of coarseness and fineness without too little sticking, and it is easy to reduce the chipping rate.
  • the "BET specific surface area” is a specific surface area that is measured without distinguishing between primary particles and secondary particles.
  • the numerical difference obtained by subtracting the BET specific surface area of the calcined body from the BET specific surface area of the composition is within 10 m 2 /g.
  • a certain degree of adhesion is preferable because good machinability (cuttability and grindability) can be maintained.
  • the machinability of the calcined body of the present invention is also affected by the strength of the calcined body.
  • the strength of the calcined body according to the present invention can be evaluated, for example, by measuring the bending strength of the calcined body.
  • the three-point bending strength of the calcined body according to the present invention can be measured according to JIS R 1601:2008.
  • the three-point bending strength of the calcined body is preferably 10 MPa or more, more preferably 15 MPa or more, and even more preferably 20 MPa or more, in order to ensure a strength that enables machining. .
  • the post support or sprue
  • the three-point bending strength of the calcined body is preferably 50 MPa or less, more preferably 45 MPa or less, further preferably 40 MPa or less, and 35 MPa or less. is particularly preferred.
  • the Vickers hardness of the calcined body of the present invention is easy from the viewpoint of reducing the amount of tool wear or chipping rate, and when separating the machined body from the fixing frame, which suppresses tool wear and shortens the time.
  • the Vickers hardness is preferably 350 HV 5/30 or less, more preferably 300 HV 5/30 or less, and even more preferably 100 HV 5/30 or less.
  • “HV 5/30” means the Vickers hardness when a load (test force) of 5 kgf is held for 30 seconds.
  • the probability of chipping can be reduced in combination with the predetermined range of the cumulative distribution of pores in the calcined body.
  • the method for measuring the Vickers hardness in the present invention conforms to JIS Z 2244:2020, and will be described in detail in Examples below.
  • the calcined body of the present invention shrinks according to the sintering temperature.
  • the calcined body is obtained through the calcining process.
  • X, Y, and Z directions on average about 1%
  • the sintered body shrinks on average about 20% in the X, Y, and Z directions.
  • the calcined body of the present invention is preliminarily sintered in the X, Y, and Z directions so that it shrinks during firing and the sintered body after sintering has a desired shape.
  • a workpiece can be cut out from the calcined body by CAD/CAM and used.
  • the shrinkage rate from the molded body or calcined body to the sintered body may be different in X, Y, or Z, but for example, the shrinkage rate in the X direction may be locally different in the same calcined body. If there is, for example, in the process in which a processed body obtained by machining such as CAD / CAM becomes a sintered body, local shrinkage occurs and a sintered body with a desired shape cannot be obtained.
  • the shrinkage of Z is uniform.
  • the shrinkage rate when a calcined body becomes a sintered body is larger than the shrinkage rate of a molded body to a calcined body, it is important that the unidirectional shrinkage rate in the calcined body is uniform.
  • the uniformity of the shrinkage rate of the calcined body can be obtained, for example, by cutting out a large number of cubes smaller than the calcined body from the calcined body and firing them, and comparing the shrinkage rate of X, Y, or Z before and after sintering for each cube. can be evaluated by
  • the shrinkage rate of X, Y, or Z and the average value of the shrinkage rate are obtained. Take the difference and use it as the deviation of the shrinkage rate.
  • the absolute value of the shrinkage deviation is preferably within 0.4%. A content of 0.4% or less is preferable because it reduces the risk of local deformation when sintering after cutting into a desired shape as a dental material.
  • the absolute value of the shrinkage rate deviation is preferably within 0.35%, further preferably within 0.3%, and most preferably within 0.25%.
  • the oxide ceramic particles used in the present invention are not particularly limited, and examples include those containing zirconia, alumina, titania, silica, niobium oxide, tantalum oxide, yttria, and the like. Oxide ceramics may be used individually by 1 type, and may use 2 or more types together. Among them, the oxide ceramic particles preferably contain zirconia and/or alumina from the viewpoint of enhancing the aesthetic appearance and strength of the sintered body as a dental material, and those containing zirconia and/or alumina as main components. more preferred.
  • the oxide ceramic particles contain alumina as a main component
  • the oxide ceramic is zirconia
  • the oxide ceramics when a composition containing alumina as a main component is used, the aesthetic properties (mainly translucency) of the sintered body as a dental material can be enhanced, and the chemical stability is also excellent.
  • ⁇ -alumina with a purity of 99.5% or more has few impurities, suppresses the formation of a glass phase at the grain boundaries caused by impurities, and can prevent coarsening of grains.
  • the sintered body is more preferable because it is less likely to deteriorate the aesthetics of the dental material in the sintered body.
  • the calcined body can be uniformly controlled, and the tool wear amount or chipping rate can be easily reduced. It is also preferable because the grain size in the crystal structure in the sintered body can be densified. From the above points, it is particularly preferable that the alumina particles contained in the calcined body of the present invention contain ⁇ -alumina particles with a purity of 99.5% or more.
  • the alumina raw material can be obtained, for example, by the alkoxide method, modified Bayer method, ammonium alum thermal decomposition method, ammonium dawsonite thermal decomposition method, etc., preferably by the alkoxide method.
  • the alkoxide method the purity of the alumina raw material powder can be increased and the particle size distribution can be made uniform.
  • Examples of the above-described alumina raw material include NXA grade (“NXA-100”, “NXA-150”, etc.) manufactured by Sumitomo Chemical Co., Ltd. (both are ultrafine ⁇ -alumina) with a purity of 99.99% or more ⁇ - Alumina is mentioned.
  • the oxide ceramic is aluminum oxide
  • the oxide ceramic is zirconium oxide, it can be similarly implemented as a zirconia composition, unless otherwise specified.
  • the alumina calcined body of the present invention contains a sintering aid (an aid that accelerates and stabilizes sintering of alumina) from the viewpoint of increasing the strength after sintering and particularly from the viewpoint of achieving high aesthetics. is preferred.
  • a sintering aid an aid that accelerates and stabilizes sintering of alumina
  • the sintering aid contained in the alumina calcined body of the present invention is at least one selected from the group consisting of Group 2 elements (Be, Mg, Ca, Sr, Ba, Ra), Ce, Zr, and Y. more preferably contains at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ce, Zr, and Y, and from Mg, Ce, Zr, and Y It is more preferable to contain at least one element selected from the group consisting of: As a sintering aid, among others, magnesium compounds are most preferable. Magnesium compounds include oxides, nitrates, acetates, hydroxides, chlorides and the like.
  • sintering aids examples include MgCl 2 , Mg(OH) 2 , CeO 2 , ZrO 2 , Y 2 O 3 and the like.
  • the magnesium compound of the sintering aid is not limited as long as it is a magnesium compound that becomes an oxide at 1200° C. or less during sintering in the atmosphere, but the most preferable ones are magnesium nitrate, magnesium chloride, and water. Examples include magnesium oxide and magnesium acetate.
  • a sintering aid may be used individually by 1 type, and may use 2 or more types together.
  • the content of the sintering aid in the powder of the alumina raw material according to the present invention is preferably 10 ppm or more and 5000 ppm or less, more preferably 20 ppm or more and 3000 ppm or less, in terms of the above-described element (for example, in terms of Mg element). It is preferably 50 ppm or more and 1500 ppm or less. As used herein, ppm means mass ppm. If the content of the sintering aid (preferably magnesium compound) is low, the color tone of the sintered body tends to be whiter than that of natural teeth, and if the content is too high, the sintered body may be too reddish.
  • the content of the sintering aid preferably magnesium compound
  • the sintering aid increases the sintering density, it exists as a heterogeneous phase at the grain boundary and suppresses the growth and progress of the grain boundary. considered to be excluded from the system.
  • the content of the sintering aid in the alumina powder is calculated in terms of the elements constituting the sintering aid (for example, Mg 10 to 100 ppm, or even 20 to 50 ppm in terms of elements).
  • the content of the sintering aid in the alumina calcined body of the present invention and the later-described alumina composition is the same as the content of the sintering aid in the alumina powder.
  • a preferred embodiment (X-1) includes oxide ceramic particles having an average primary particle size of 50 to 300 nm and pores, a relative density of 43 to 63%, and an accumulation of pores in the calcined body
  • a dental oxide ceramic calcined body having a D10 of 20 nm or more and a D90 of 90 nm or less in the distribution is mentioned.
  • the BET specific surface area is preferably 5 to 25 m 2 /g.
  • the three-point bending strength is preferably 10 to 50 MPa.
  • the Vickers hardness measured according to JIS Z 2244:2020 is preferably 350 HV 5/30 or less.
  • the oxide ceramic particles preferably contain zirconia and/or alumina.
  • Another preferred embodiment (X-2) includes oxide ceramic particles having an average primary particle size of 50 to 300 nm and pores, a BET specific surface area of 5 to 25 m 2 /g, and a calcined body containing A dental oxide ceramic calcined body having a D10 of 20 nm or more and a D90 of 90 nm or less in the cumulative distribution of pores.
  • the three-point bending strength is preferably 10 to 50 MPa.
  • the Vickers hardness measured according to JIS Z 2244:2020 is preferably 350 HV 5/30 or less.
  • the oxide ceramic particles preferably contain zirconia and/or alumina.
  • Another preferred embodiment (X-3) includes oxide ceramic particles having an average primary particle size of 50 to 300 nm and pores, a three-point bending strength of 10 to 50 MPa, and calcination
  • a dental oxide ceramic calcined body having a D10 of 20 nm or more and a D90 of 90 nm or less in the cumulative distribution of pores in the body can be mentioned.
  • the Vickers hardness measured according to JIS Z 2244:2020 is preferably 350 HV 5/30 or less.
  • the oxide ceramic particles preferably contain zirconia and/or alumina.
  • Another preferred embodiment (X-4) includes oxide ceramic particles having an average primary particle size of 50 to 300 nm and pores, and Vickers hardness measured in accordance with JIS Z 2244: 2020 is 350 HV 5/30 or less, and D10 in the cumulative distribution of pores in the calcined body is 20 nm or more and D90 is 90 nm or less.
  • the oxide ceramic particles preferably contain zirconia and/or alumina.
  • Another preferred embodiment (X-5) includes oxide ceramic particles having an average primary particle size of 50 to 300 nm and pores, and the cumulative distribution of pores in the calcined body has a D10 of 20 nm or more. and a dental oxide ceramic calcined body having a D90 of 90 nm or less and an oxide ceramic particle containing alumina.
  • the alumina preferably contains ⁇ -alumina with a purity of 99.5% or higher.
  • Embodiment (X-5) further comprises a sintering aid, wherein the sintering aid contains at least one element selected from the group consisting of Group 2 elements, Ce, Zr, and Y. preferably included.
  • a preferred embodiment (Y-1) is a dental oxide ceramic calcined body containing oxide ceramic particles having an average primary particle size of 50 to 300 nm and pores, and having a relative density of 43 to 63%. is mentioned.
  • the BET specific surface area is preferably 5 to 25 m 2 /g.
  • the three-point bending strength is preferably 10 to 50 MPa.
  • the Vickers hardness measured according to JIS Z 2244:2020 is preferably 350 HV 5/30 or less.
  • it is preferable that the ratio of D10/D90 is 1.5 or less.
  • a sintering aid is further included, and the sintering aid is at least one selected from the group consisting of Group 2 elements, Ce, Zr, and Y. Those containing elements are preferred.
  • the oxide ceramic particles preferably contain zirconia and/or alumina.
  • a calcined dental oxide ceramic containing oxide ceramic particles and pores, and having a D10 of 20 nm or more and a D90 of 90 nm or less in the cumulative distribution of pores in the calcined body body.
  • Another embodiment (Z-2) contains oxide ceramic particles and pores, has a relative density of 43 to 63%, and has a D10 of 20 nm or more and a D90 of 90 nm in the cumulative distribution of pores in the calcined body.
  • the following dental oxide ceramic calcined bodies can be mentioned.
  • any configuration based on the description of this specification and components, and the types and amounts of components can be changed (addition, deletion, substitution, combination) as appropriate.
  • the configuration and components of each calcined body and the values of each characteristic can be changed as appropriate.
  • the calcined bodies of the embodiments (X-1) to (X-5), (Y-1), (Z-1) and (Z-2) are fired at 1400 ° C. or less to obtain sintered bodies.
  • the linear light transmittance at the time may be 0.5% or more.
  • Another preferred embodiment includes a dental oxide ceramic calcined body containing zirconia.
  • zirconia and a stabilizer capable of suppressing the phase transition of zirconia may be used as main components. good.
  • the stabilizer is preferably capable of forming partially stabilized zirconia. Examples of the stabilizer include calcium oxide (CaO), magnesium oxide (MgO), yttria, cerium oxide (CeO 2 ), scandium oxide (Sc 2 O 3 ), niobium oxide (Nb 2 O 5 ), and lanthanum oxide.
  • La2O3 erbium oxide
  • Er2O3 erbium oxide
  • Pr6O11 Pr6O11
  • Pr2O3 praseodymium oxide
  • Sm2O3 samarium oxide
  • Eu2O3 europium oxide
  • thulium oxide Oxides such as (Tm 2 O 3 ) can be mentioned, with yttria being preferred.
  • the zirconia calcined body and its sintered body of the present invention include the stabilization
  • the content of the agent is preferably 3.0 to 8.0 mol%, more preferably 3.2 to 6.5 mol%, and 3.5 ⁇ 6.0 mol% is more preferred, and 3.9 to 5.4 mol% is particularly preferred. If the content of the stabilizer is less than 3.0 mol%, there is a problem that the translucency of the zirconia sintered body is insufficient. There is a problem that the amount of phase transitioning to the system increases, the chipping rate increases, and the strength of the zirconia sintered body decreases.
  • the content of the sintering aid or stabilizer in the calcined body of the present invention and its sintered body can be determined, for example, by inductively coupled plasma (ICP) emission spectrometry, X-ray fluorescence analysis (XRF), Scanning or transmission electron microscope (SEM or TEM) and energy dispersive X-ray analysis or wavelength dispersive X-ray analysis (EDX or WDX), or field emission electron beam microanalysis (FE-EPMA), etc. can be done.
  • ICP inductively coupled plasma
  • XRF X-ray fluorescence analysis
  • SEM or TEM Scanning or transmission electron microscope
  • EDX or WDX energy dispersive X-ray analysis or wavelength dispersive X-ray analysis
  • FE-EPMA field emission electron beam microanalysis
  • the chipping rate of the calcined body is low.
  • a lower chipping rate is preferable from the viewpoint of reducing the amount of work required to rework the cut product as a dental material after firing.
  • the chipping rate is preferably 10% or less, more preferably 7% or less, and even more preferably 3% or less. A method for measuring the chipping rate is as described in the examples below.
  • oxide ceramic composition for producing the oxide ceramic calcined body of the present invention will be described below using an alumina composition, taking as an example the case where the oxide ceramic is aluminum oxide. Unless otherwise specified, "alumina composition” can be read as “oxide ceramic composition”. When the oxide ceramic is zirconium oxide, it can be similarly implemented as a zirconia composition, unless otherwise specified.
  • the alumina composition serves as a precursor of the alumina calcined body of the present invention described above.
  • the alumina composition and the molded body are those before firing, and thus mean those in which the alumina particles are not necked (fixed).
  • the contents of alumina and sintering aid in the alumina composition of the present invention are calculated from the contents of a given alumina calcined body, and the contents of the alumina composition and the alumina calcined body are the same.
  • the form of the alumina composition is not limited, and the alumina composition of the present invention includes powder, a fluid obtained by adding powder to a solvent, and a compact obtained by molding powder into a predetermined shape.
  • the alumina composition of the present invention may be an aggregate of granules. Granules are formed by agglomeration of primary particles.
  • primary particles refer to the smallest unit of bulk.
  • primary particles refer to spherical shapes in an electron microscope (eg, scanning electron microscope).
  • Primary particles include alumina particles.
  • alumina particles and sintering aid particles are included.
  • the particles constituting the granules made of the alumina composition are mainly primary particles.
  • Aggregated primary particles are called secondary particles.
  • the number of primary particles is preferably greater than the number of secondary particles. Since the secondary particles usually have an irregular shape, when there are many secondary particles, the sparseness and density will occur during press molding, which will be described later, and chipping will increase.
  • the particle size of the primary particles constituting the granules made of the alumina composition affects the degree of adhesion during calcination, and affects the hardness of the calcined body. If the average primary particle diameter of the particles is less than 50 nm, the surface area of the primary particles contained in the calcined body is reduced, which increases the adhesion and increases the hardness, which is not preferable. On the other hand, if it is larger than 300 nm, particles with a small particle size distribution tend to be sucked in, causing local sticking due to the difference in particle size, which tends to cause coarseness and density, which is not preferable. 50 to 300 nm is preferred, 60 to 250 nm is more preferred, and 70 to 200 nm is even more preferred.
  • the primary particles constituting the granules made of the alumina composition two types of alumina particles having different average primary particle sizes may be mixed and used.
  • the NXA when used, a mixture of NXA-100 and NXA-150 can be mentioned.
  • the BET specific surface area of the particles constituting the granules made of the alumina composition is preferably 5 m 2 /g or more, and 7.5 m 2 /g or more when measured in accordance with JIS Z 8830:2013. is more preferable, and 8 m 2 /g or more is even more preferable.
  • it is 5 m 2 /g or more, the sinterable temperature is easily lowered, sintering is facilitated, or the sintered body obtained after sintering becomes cloudy and the decrease in translucency is easily suppressed. .
  • the BET specific surface area is preferably 25 m 2 /g or less, more preferably 20 m 2 /g or less, and even more preferably 15 m 2 /g or less.
  • the average primary particle size is not too small, the calcined body does not become too hard, and the tool wear and / or chipping rate is easily reduced, or the adhesion is not too small. It is possible to suppress the occurrence of coarseness and fineness, and it is easy to reduce the chipping rate.
  • alumina in the alumina composition of the present invention 50% or more, preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more of alumina can take the form of granules.
  • the alumina particles constituting the powder should have the above average primary particle size and BET specific surface area.
  • the average particle size (secondary particle size, hereinafter also referred to as “average particle size”) of the granules in the alumina composition of the present invention is preferably 10 ⁇ m or more, more preferably 12 ⁇ m or more, and 14 ⁇ m or more. is more preferred. If the average granule diameter is less than 10 ⁇ m, air is entrapped when the granules are put into a mold, and degassing becomes insufficient during molding, which may make it impossible to produce a uniform and dense molded product. In addition, there is a possibility that granules may be ejected from gaps during molding, resulting in the production of a molded article that does not meet the predetermined required amount.
  • the average particle size is preferably 200 ⁇ m or less, more preferably 190 ⁇ m or less, even more preferably 180 ⁇ m or less, particularly preferably 150 ⁇ m or less, most preferably 100 ⁇ m or less.
  • the average granule diameter exceeds 200 ⁇ m, cavities are likely to be formed inside the granules. Also, when the granules are put into a mold, gaps are likely to occur. Due to these phenomena, degassing becomes insufficient during molding, and there is a risk that a dense molded body cannot be produced. In addition, shrinkage increases during molding, and there is a risk that a molded article having a desired size cannot be produced.
  • the alumina in the alumina composition constitute granules.
  • the average granule size is preferably measured in such a way that the granules are not broken.
  • the average granule size can be measured, for example, by a dry sieving method or a wet sieving method.
  • the dry sieving method can be measured according to the sieving test method described in JIS Z 8815:1994, manual sieving and mechanical sieving can be used, and mechanical sieving is preferred.
  • a sieve used in the sieving method a sieve described in JIS Z 8801-1:2019 test sieve can be used.
  • a low-tap sieve shaker or a sonic vibration sieving measuring device can be used as a measuring device used for the sieving method.
  • the low-tap sieve shaker include “RPS-105M” manufactured by Seishin Enterprise Co., Ltd., and the like.
  • the sonic vibration sieving instrument include "Robot Shifter RPS-01” and “Robot Shifter RPS-02” manufactured by Seishin Enterprise Co., Ltd.
  • the sphericity of the granules in the alumina composition of the present invention is preferably high.
  • By increasing the sphericity of the granules mixing at the interfaces between the layers can be caused when alumina powders with different compositions are layered.
  • the higher the sphericity the higher the packing density.
  • the strength and translucency of the sintered body can be increased by filling alumina granules into a specific mold (mold, etc.) and increasing the packing density, which is the density of a molded body formed into a specific shape by pressure. In addition, even if the mold has corners, it is possible to improve the filling of the corners with the granules.
  • the sphericity of the granules in the alumina composition of the present invention can be expressed, for example, by light bulk density, heavy bulk density, and the like.
  • the light bulk density of the alumina composition of the present invention is preferably 0.6 g/cm 3 or more from the viewpoint of good flow of granules (ease of clogging) for reducing coarseness and fineness of the resulting compact. It is more preferably 0.7 g/cm 3 or more, still more preferably 0.8 g/cm 3 or more, and particularly preferably 0.9 g/cm 3 or more.
  • the light bulk density can be measured according to JIS R 9301-2-3:1999.
  • the stacked bulk density of the alumina composition of the present invention is preferably 0.8 g/cm 3 or more from the viewpoint of good flow of granules (ease of clogging) for reducing coarseness and fineness of the resulting compact. It is more preferably 0.9 g/cm 3 or more, and even more preferably 1.0 g/cm 3 or more.
  • the bulk density can be measured according to JIS R 9301-2-3:1999.
  • the alumina composition of the present invention preferably contains a binder.
  • binder examples include organic binders.
  • organic binders include commonly used acrylic binders, acrylic acid binders, paraffin binders, fatty acid binders, polyvinyl alcohol binders, and the like. Among these organic binders, those having a carboxyl group in the molecular chain or carboxylic acid derivatives are preferred, acrylic binders are more preferred, and water-soluble polyacrylates are even more preferred.
  • the polyacrylic acid salt may be a copolymer of acrylic acid or methacrylic acid and maleic acid, or may contain sulfonic acid, and cations of the salt include sodium, ammonium, and the like.
  • the distance between primary particles in the alumina composition can be adjusted, the cumulative distribution of pores can be adjusted, the relative density can be adjusted, and the Vickers hardness or calcined body It becomes easier to adjust by increasing or decreasing the intensity of the
  • the content of the binder is preferably 1.2 to 2.8% by mass, more preferably 1.5 to 2.5% by mass, and even more preferably 1.8 to 2.2% by mass in the entire alumina composition. .
  • the strength of the calcined body is not too high, and there is no risk of the machined body becoming hard when it is removed. Further, when the content is 2.8% by mass or less, the strength of the calcined body does not decrease excessively, the possibility of the workpiece falling off during cutting can be reduced, and the chipping rate can be easily reduced.
  • the alumina composition of the present invention contains coloring agents (including pigments, composite pigments and fluorescent agents), titanium oxide (TiO 2 ), silica (SiO 2 ), dispersants, antifoaming agents and the like. Additives other than auxiliaries (except CeO 2 , ZrO 2 and Y 2 O 3 ) can be included. These components may be used individually by 1 type, and may be used in mixture of 2 or more types.
  • the pigment for example, at least selected from the group of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Sm, Eu, Gd, and Er Oxides of one element are mentioned.
  • Examples of the composite pigment include (Zr, V) O 2 , Fe(Fe, Cr) 2 O 4 , (Ni, Co, Fe)(Fe, Cr) 2 O 4 ⁇ ZrSiO 4 , (Co, Zn) Al2O4 etc. are mentioned.
  • Examples of the fluorescent agent include Y2SiO5 :Ce, Y2SiO5 :Tb, ( Y, Gd ,Eu) BO3 , Y2O3 : Eu, YAG:Ce, ZnGa2O4 : Zn , BaMgAl 10 O 17 :Eu and the like.
  • the additives may be added during mixing or pulverization, or may be added after pulverization.
  • the translucency ( ⁇ L) of the sintered body with a thickness of 1.2 mm is 9 or more
  • the total light transmittance of the sintered body with a thickness of 1.0 mm is 27% or more in a D65 light source
  • the linear light transmittance is 0.5% or more.
  • the light transmittance ( ⁇ L), total light transmittance, and linear light transmittance measurement methods and suitable ranges are the light transmittance ( ⁇ L), total light transmittance, and linear light transmittance of the alumina sintered body described later. Similar to rate.
  • the number-based average crystal grain size is 0.3 to 8.0 ⁇ m when fired at 1400° C. or less to form a sintered body without using hot isostatic pressing. , dental oxide ceramics calcined body.
  • the method of measuring the average crystal grain size and the preferred range thereof are the same as those for the average crystal grain size of the alumina sintered body, which will be described later.
  • a method for producing a dental oxide ceramic calcined body comprising: A step of pressure-molding the oxide ceramic composition at a surface pressure of 5 to 600 MPa, and a step of firing the obtained compact at 400 to 1300 ° C. under atmospheric pressure, A dental oxide ceramic calcined body containing oxide ceramic particles having an average primary particle size of 50 to 300 nm, and having a D10 of 20 nm or more and a D90 of 90 nm or less in the cumulative distribution of pores.
  • a method for producing a fired body can be mentioned.
  • the oxide ceramic particles contain zirconia and/or alumina. is mentioned. Zirconia and alumina are the same as those of the calcined body described above.
  • the method for producing the oxide ceramic calcined body of the present invention will be described below using a method for producing an alumina calcined body, taking as an example the case where the oxide ceramic is aluminum oxide.
  • the method for producing a zirconia calcined body can also be carried out in the same manner, unless otherwise specified.
  • an alumina calcined body for example, a step of producing an alumina composition containing alumina particles and a sintering aid, and firing (calcining) the alumina composition (for example, a compact) , obtaining an alumina calcined body having an average primary particle diameter of 50 to 300 nm in the calcined body, and a D10 of 20 nm or more and a D90 of 90 nm or less in the cumulative distribution of pores in the calcined body.
  • the content of the sintering aid is preferably 10-5000 ppm.
  • alumina and a sintering aid are mixed in a predetermined ratio to prepare a mixture (mixing step).
  • the sintering aid is magnesium chloride
  • the mixing ratio of alumina and magnesium chloride can be mixed so as to achieve the above content.
  • Mixing may be dry mixing or wet mixing. Since the cumulative distribution of pores can be adjusted and the relative density can be adjusted, the alumina composition can be pulverized (preferably pulverized) to the above average primary particle size (pulverization step).
  • Pulverization can be performed, for example, by using a ball mill, bead mill, or the like after dispersing the composition and binder in a solvent such as water or alcohol (dispersion step).
  • the composition is pulverized (preferably pulverized) to a particle size of 0.05 ⁇ m to 0.3 ⁇ m, for example, because the cumulative distribution of the particles can be adjusted and the relative density can be adjusted.
  • the composition may be subjected to other treatments (classification treatment, water treatment) in order to adjust the particle size.
  • the average primary particle size can be measured by a laser diffraction/scattering particle size distribution measurement method. For example, using a laser diffraction/scattering particle size distribution analyzer (trade name "Partica LA-950") manufactured by Horiba, Ltd., a slurry diluted with water is subjected to ultrasonic irradiation for 30 minutes, and then ultrasonic waves are applied. It can be measured by volume while applying.
  • a laser diffraction/scattering particle size distribution analyzer (trade name "Partica LA-950”) manufactured by Horiba, Ltd., a slurry diluted with water is subjected to ultrasonic irradiation for 30 minutes, and then ultrasonic waves are applied. It can be measured by volume while applying.
  • the mixture can be spray-dried with a spray dryer or the like to make the alumina composition into the above-described granule form (drying step).
  • the average primary particle size of the alumina composition is preferably less than 0.3 ⁇ m, more preferably 0.25 ⁇ m or less, even more preferably 0.2 ⁇ m or less, and 0.15 ⁇ m or less. It is particularly preferred to have By setting the average primary particle size of the alumina composition to less than 0.15 ⁇ m, it is possible to improve the machinability of the calcined body and improve the translucency of the sintered body after sintering.
  • the alumina and sintering aid may be prepared separately.
  • the alumina and the sintering aid are not precipitated at the same time (in the same process), but the alumina preparation process (e.g., manufacturing process) and the sintering aid preparation process (e.g., manufacturing process) are independent of each other. It may also be a separate step.
  • the above-described ⁇ -alumina can be obtained with high purity and a small primary particle size.
  • a sintering aid may be reacted with alumina by heat treatment, and the pulverization and drying steps may be performed using it.
  • Granules or powder can be formed into a compact by applying an external force.
  • the molding method is not limited to a specific method, and a suitable method can be selected according to the purpose.
  • it can be molded by press molding, injection molding, stereolithography, slip casting, gel casting, filter filtration, casting, and the like.
  • you may perform multistep shaping
  • the alumina composition may be press-molded and then CIP-treated, or the press-molding and CIP-molding may be repeated.
  • press molding methods include uniaxial pressing (hereinafter also referred to as “uniaxial pressure pressing”) processing, biaxial pressing processing, CIP (Cold Isostatic Pressing) processing, and the like. These may be performed in combination as appropriate.
  • the molded article of the present invention can have a disk shape, a cuboid shape, or a dental product shape (for example, a crown shape).
  • the pressure molding is a uniaxial press
  • the surface pressure in the uniaxial press is 5 to 600 MPa.
  • the molded body obtained by the pressure molding step may be, for example, a columnar molded body obtained by filling alumina granules in a mold and compacting them with a uniaxial press.
  • the higher the contact pressure in press molding the higher the density of the molded product.
  • the density of the molded body is too high, the alumina calcined body becomes hard.
  • the surface pressure of press molding is preferably 5 to 600 MPa, more preferably 10 to 400 MPa, and even more preferably 15 to 200 MPa, from the viewpoint that the cumulative distribution of pores can be adjusted and the relative density can be adjusted.
  • the surface pressure of the press for example, uniaxial press
  • the surface pressure of press molding may be set to a suitable range of 50 MPa or more, 80 MPa or more, 100 MPa or more, or 150 MPa or more in accordance with the target cumulative distribution of pores, relative density, and the like.
  • the molded body of the present invention also includes a molded body densified by high-temperature pressure treatment such as CIP (Cold Isostatic Pressing) treatment.
  • the water pressure is preferably 50 to 1000 MPa, more preferably 100 to 600 MPa, and even more preferably 150 to 300 MPa from the same viewpoint as above.
  • the contents of alumina and sintering aid in the alumina calcined body of the present invention are the same as the contents in the alumina composition before the alumina calcined body is produced.
  • the sintering aid is preferable because the magnesium compound is uniformly dispersed.
  • the sintering temperature in the calcining step affects the Vickers hardness or the strength of the calcined body. Cumulative distribution and hardness of pores in the calcined body change depending on the calcining temperature combined with alumina particles having a predetermined average primary particle diameter contained in the compact, and the amount of tool wear and/or the chipping rate change.
  • the calcining temperature (maximum calcining temperature) in the method for producing the alumina calcined body of the present invention is determined from the viewpoint that the particles adhere to each other while maintaining an appropriate distance, and the desired cumulative distribution of pores, relative density, etc. can be obtained. It is preferably 400 to 1300°C, more preferably 500 to 1200°C, even more preferably 600 to 1100°C, and particularly preferably 800 to 1000°C.
  • Organic components can also be degreased by processing at the highest calcining temperature. In one embodiment, when the composition or molded body contains an organic component, the organic component is degreased by pre-firing at a temperature lower than the maximum calcining temperature before firing at the maximum calcining temperature.
  • the pre-firing temperature may be any temperature lower than the maximum calcining temperature, preferably 350°C or higher and 650°C or lower, more preferably 400°C or higher and 600°C or lower, and 450°C or higher and 550°C. More preferably:
  • the holding time at the pre-baking temperature is preferably 15 minutes to 4 hours, more preferably 30 minutes to 3 hours, even more preferably 45 minutes to 2 hours.
  • a strut support or sprue
  • the Vickers hardness can be adjusted to a desired range to suppress an increase in the chipping rate.
  • the calcining temperature is 1300° C.
  • the adhesion does not progress too much, so that the workpiece does not become too hard, and it does not take time to separate the workpiece from the frame fixing the workpiece, and Also, since wear of the tool does not increase, an increase in the chipping rate can be suppressed, and the workpiece can be easily separated from the support.
  • Holding at the maximum calcining temperature for a certain period of time is preferable because the hardness of the calcined body falls within a preferable range and the chipping rate may decrease.
  • the calcining conditions depend on the average primary particle size of the calcined body and the density of the calcined body.
  • the holding time at the highest calcining temperature may be 20 minutes to 8 hours, preferably 30 minutes to 6 hours.
  • the rate of temperature increase to the maximum calcination temperature and the rate of temperature decrease from the maximum calcination temperature are preferably 300° C./min or less.
  • the alumina calcined body of the present invention can be machined to produce a processed body.
  • the processing method is not limited to a specific method, and a suitable method can be appropriately selected depending on the purpose.
  • an alumina disc which is also a calcined body, can be cut or ground into the shape of a dental product (eg, a crown-shaped prosthesis) using a CAD/CAM system to produce a processed body.
  • the processed body may be improved in surface smoothness with a tool such as Pearl Surface (registered trademark) (manufactured by Kuraray Noritake Dental Co., Ltd.).
  • a tool such as Pearl Surface (registered trademark) (manufactured by Kuraray Noritake Dental Co., Ltd.).
  • the machine used for machining the calcined body of the present invention is not particularly limited.
  • the cutting machine may be a desktop machine, a large machining center (general-purpose machine), or the like, depending on the object to be cut.
  • a cutting machine for example, desktop machines "DWX-50”, “DWX-4”, “DWX-4W”, “DWX-52D”, “DWX-52DCi” (manufactured by Roland DG Co., Ltd.) etc. Grinding may be used.
  • the tools used in the processing machine used for machining the calcined body of the present invention are not particularly limited. Milling burs and grinding burs recommended by the supplier of the processing machine can be suitably used.
  • milling burs used in cutting machines include Katana (registered trademark) drills.
  • the tools used in machining machines have a lifespan that depends on the conditions of use. For example, when cutting a calcined body, if the drill edge wears (tool wear), the machined surface of the calcined body may crack finely (chipping) or crack greatly, resulting in re-machining. Problems of productivity such as taking time arise.
  • the torque may be detected on the machine side, and a certain torque value may be used as the tool life judgment index (tool replacement judgment index) with a certain torque value as the upper limit of the threshold value. Moreover, it is good also considering processing time as a threshold upper limit.
  • the tool life can be confirmed, for example, by measuring the wear width of the cutting edge of a milling bur for a cutting machine. For example, in the case of a Katana (registered trademark) drill, it can be determined that the tool has reached the end of its service life (time for replacement) when the wear width is 0.21 mm or more.
  • the wear width of the blade is preferably within 0.2 mm. Within 0.15 mm is more preferable, and within 0.1 mm is even more preferable.
  • the method for producing an oxide ceramic sintered body of the present invention will be described below using a method for producing an alumina sintered body, taking as an example the case where the oxide ceramic is aluminum oxide.
  • the alumina sintered body of the present invention can be produced by sintering the alumina calcined body of the present invention and its machined body at a temperature at which the alumina particles are sintered (sintering step).
  • the sinterable temperature (for example, maximum sintering temperature) is preferably above 1300° C. and can be varied depending on the average primary particle size.
  • the sinterable temperature e.g., maximum sintering temperature
  • the sinterable temperature is, for example, preferably higher than 1300°C, more preferably 1350°C or higher, and further preferably 1375°C or higher. preferable.
  • the sinterable temperature is, for example, preferably 1500° C. or lower, more preferably 1450° C. or lower. It is preferable that the rate of temperature increase and the rate of temperature decrease be 300° C./min or less.
  • the holding time at a sinterable temperature is preferably 120 minutes or less, more preferably 90 minutes or less, and further preferably 75 minutes or less. It is preferably 60 minutes or less, particularly preferably 45 minutes or less, and most preferably 30 minutes or less.
  • the holding time is preferably 1 minute or longer, more preferably 3 minutes or longer, and even more preferably 5 minutes or longer.
  • the time of the sintering process for producing the sintered body is shortened without reducing the translucency and strength of the produced alumina sintered body. be able to.
  • the holding time at the maximum sintering temperature for producing the sintered body can be shortened (short-time sintering).
  • the production efficiency can be improved, and when the alumina calcined body of the present invention is applied to a dental product, the dimensions of the dental product used for treatment are determined, and after cutting, the dental product It is possible to shorten the time until the product can be used for treatment, and reduce the time burden on the patient. Also, energy costs can be reduced.
  • the holding time at the sinterable temperature (for example, the maximum sintering temperature) can be, for example, 25 minutes or less, 20 minutes or less, or 15 minutes or less.
  • the rate of temperature increase to the maximum sintering temperature and the rate of temperature decrease from the maximum sintering temperature in the sintering process are preferably set so as to shorten the time required for the sintering process.
  • the heating rate can be set so as to reach the maximum sintering temperature in the shortest time according to the performance of the kiln.
  • the heating rate to the maximum sintering temperature is, for example, 10°C/min or more, 50°C/min or more, 100°C/min or more, 120°C/min or more, 150°C/min or more, or 200°C/min or more. can do.
  • An embodiment includes a method for producing a dental oxide ceramic sintered body, which includes a step of sintering an oxide ceramic calcined body under atmospheric pressure without using hot isostatic pressing. .
  • a special device is not required, and dental oxide ceramics can be easily sintered. body can be manufactured.
  • oxide ceramic sintered body will be described using an alumina sintered body as an example in which the oxide ceramic is aluminum oxide.
  • the alumina sintered body is, for example, alumina particles (powder) that have reached a sintered state.
  • the relative density of the alumina sintered body is preferably 99.5% or more. The same applies to other oxide ceramic sintered bodies.
  • the alumina sintered body of the present invention includes not only a sintered body obtained by sintering molded alumina particles under normal pressure and under no pressure, but also a HIP (Hot Isostatic Press) treatment. Sintered bodies densified by high temperature pressure treatment are also included.
  • HIP Hot Isostatic Press
  • the relative density of the bodies is preferably high.
  • the relative density of the alumina sintered body of the present invention is, for example, preferably over 95%, more preferably 98% or more, and even more preferably 99.5% or more.
  • the alumina sintered body of the present invention contains substantially no voids.
  • the average crystal grain size of the alumina sintered body of the present invention is preferably 0.3 to 8.0 ⁇ m, more preferably 0.4 to 6.0 ⁇ m, more preferably 0.5 to 3, from the viewpoint of excellent translucency and strength. 0.0 ⁇ m is more preferred.
  • the method for measuring the average crystal grain size is as described in Examples below.
  • the content of alumina and sintering aid in the alumina sintered body of the present invention is the same as the content in the composition and/or the calcined body before producing the sintered body.
  • the translucency ( ⁇ L) of the alumina sintered body of the present invention is preferably 9 or more, more preferably 12 or more, further preferably 15 or more, and particularly preferably 20 or more. .
  • Translucency refers to the L* value of lightness (color space) in the L*a*b* color system (JIS Z 8781-4: 2013) for a sample with a thickness of 1.2 mm (sintered body )
  • the L * value measured with a white background is the first L * value
  • the L * value measured with the sample background black is the second L * value and the second L* value is subtracted from the first L* value.
  • composition granules (composition) were press-molded so that the thickness of the sintered body was 1.2 mm, followed by CIP molding. For example, a disk-shaped compact with a diameter of 19 mm can be produced. Next, the molded body is fired under predetermined firing conditions, and the surface is polished with #2000 to prepare a sintered body having a thickness of 1.2 mm as a sample.
  • a color difference meter for example, CE100, analysis software "Crystal Eye” (manufactured by Olympus Co., Ltd.)
  • nD refractive index
  • 589 nm sodium D line
  • the total light transmittance in the D65 light source of the sintered body having a thickness of 1.0 mm is preferably 27% or more, more preferably 40% or more, and 55% or more. is more preferable, and 60% or more is particularly preferable.
  • the method for measuring the total light transmittance is as described in Examples below.
  • the sintered body having a thickness of 1.0 mm preferably has a linear light transmittance of 0.5% or more, more preferably 0.7% or more. It is more preferably 0% or more, and particularly preferably 4.0% or more.
  • the method for measuring the linear light transmittance is as described in Examples below.
  • the alumina sintered body of the present invention may be a molded body having a predetermined shape.
  • the sintered body can have a disk shape, cuboid shape, dental product shape (eg crown shape).
  • the alumina composition, granules, powders, compacts, calcined bodies, machined bodies, and sintered bodies described herein are not limited to the above unless otherwise specified, and various known methods can be used. is applicable.
  • the present invention includes embodiments in which the above configurations are combined in various ways within the scope of the technical idea of the present invention as long as the effects of the present invention are exhibited.
  • the upper limit and lower limit of the numerical range content of each component, each element (average primary particle size, etc.), each physical property, etc.) can be combined as appropriate.
  • a degeneracy filter is applied to the region, each region is degenerated to one or more points, and the Voronoi polygons are generated so that these points become the generating points of the Voronoi polygons.
  • the adjacent particles were separated.
  • one particle may look like a gourd in image processing, but in that case, it was assumed that two circular particles were in contact and looked like one, and were separated into two.
  • a disk-shaped calcined body having a thickness of 14 mm and a diameter of 98.5 mm was produced by the method described in Examples and Comparative Examples below, except that the size of the mold used for pressing the granules was changed. Based on the three-dimensional NC data, this disk-shaped calcined body is milled using a milling machine "DWX-52DC" manufactured by Kuraray Noritake Dental Co., Ltd., using an unused Katana (registered trademark) drill (Kuraray Noritake Dental Co., Ltd.
  • FIG. 2 is an optical microscope photograph showing the amount of tool wear in Example 1
  • FIG. 3 is an optical microscope photograph showing the amount of tool wear in Comparative Example 2.
  • FIG. 4 shows an optical microscope photograph of the surface of the machined body with a chipping rate of 3% according to Example 1
  • FIG. 5 shows the surface of the machined body with a chipping rate of 10% according to Comparative Example 1.
  • 1 shows an optical microscope photograph taken of .
  • the sample is placed so that the widest surface faces the vertical direction (load direction), and a universal testing machine (manufactured by Shimadzu Corporation "AG-I 100 kN") is used to set the span (distance between fulcrums) to 30 mm.
  • a universal testing machine manufactured by Shimadzu Corporation "AG-I 100 kN"
  • Carrier gas Helium (He)
  • Coolant liquid nitrogen ( N2 )
  • the crystal grain size obtained with Image-Pro Plus is obtained by measuring the length of the line segment connecting the contour lines passing through the center of gravity determined from the contour line of the crystal grain at 2-degree increments around the center of gravity and averaging them. It is. In the SEM photographic images (three fields of view) of each example and comparative example, the crystal grain size of all the particles not covering the edge of the image was measured. The average crystal grain size was calculated from the obtained crystal grain size of each grain and the number of crystal grains, and the obtained arithmetic mean diameter was defined as the average crystal grain size in the sintered body.
  • particles that do not overlap the edges of the image means particles excluding particles whose outlines do not fit within the screen of the SEM photograph image (particles whose outlines are interrupted on the upper, lower, left, and right boundaries).
  • the grain size of all particles not overhanging the image edge was selected in Image-Pro Plus with the option to exclude all borderline particles.
  • a disk-shaped calcined body having a thickness of 14 mm and a diameter of 98.5 mm was produced by the method described in Examples and Comparative Examples below, except that the size of the mold used for pressing the granules was changed.
  • the thickness direction was taken as the Z axis, and the X axis and the Y axis were arbitrarily taken from a plane perpendicular to the Z axis.
  • shrinkage factor (S) means the ratio of the size of the workpiece after sintering and shrinking to the size of the workpiece before sintering.
  • the average value of shrinkage can be determined by averaging the shrinkage for each X, Y, or Z. For example, it is the average value of SX1 to SX15.
  • the shrinkage uniformity can be obtained by subtracting the average value of all 15 shrinkage rates at the same position as the side from the shrinkage rate of one side of each cube.
  • the total light transmittance and linear light transmittance in each layer of the alumina sintered body of each example and comparative example were measured by preparing an alumina sintered body by the following method. First, using a mold with a diameter of 30 mm, press molding was performed by adjusting the input amount of the raw material powder in advance so that an alumina sintered body with a thickness of 1.0 mm was obtained. A compact was produced from the raw material powder. A molded body was produced by the method described in each example and comparative example, except that the mold was changed. An alumina calcined body was produced by the method described in each example and comparative example, except that the molded body was used.
  • the obtained alumina calcined body was held at the maximum sintering temperature shown in Table 3 for 2 hours to be sintered to prepare an alumina sintered body.
  • Example 1 100 g of ⁇ -alumina raw material NXA-100 (manufactured by Sumitomo Chemical Co., Ltd.) and 0.1 g of magnesium chloride equivalent were weighed, added to 1 L of ethanol, and ultrasonically dispersed. This and alumina beads were placed in a rotating container, and the alumina raw material containing agglomerated particles was pulverized with a ball mill to mix and pulverize the raw material until the desired average primary particle size was obtained.
  • the average primary particle size is measured by using a laser diffraction/scattering particle size distribution measuring device (trade name “Partica LA-950”) manufactured by Horiba, Ltd., and irradiating a slurry diluted with ethanol with ultrasonic waves for 30 minutes, and then , was measured on a volume basis while applying ultrasonic waves. A desired slurry with almost no secondary agglomeration was obtained with a ball milling time of about 1 hour.
  • a laser diffraction/scattering particle size distribution measuring device (trade name “Partica LA-950”) manufactured by Horiba, Ltd.
  • an organic binder was added to this slurry.
  • a water-based acrylic binder was used as the organic binder, and 2.5% by mass of the organic binder was added to the ⁇ -alumina raw material (the content of the organic binder with respect to the entire slurry), followed by stirring with a rotary blade for 24 hours.
  • the stirred slurry was dried and granulated with a spray dryer to obtain alumina granules.
  • the average particle size of the granules was 40 ⁇ m.
  • the powder composed of the granules was poured into a mold having a predetermined size and uniaxially pressed under atmospheric pressure at a pressure of 150 MPa to obtain a compact.
  • the resulting compact was placed in an electric furnace, heated from room temperature at a rate of 10°C/min, and held at 500°C for 2 hours to degrease the organic component.
  • the temperature was raised to the calcining temperature, held at the calcining temperature for 6 hours, and slowly cooled at -0.4°C/min to obtain a calcined body.
  • the obtained calcined body was sintered at the maximum sintering temperature shown in Table 3 in an air atmosphere for 2 hours to prepare a sintered body.
  • Example 1 A calcined body and a sintered body were obtained in the same manner as in Example 2 except that AA-03 (manufactured by Sumitomo Chemical Co., Ltd.) was used instead of NXA-100 as the ⁇ -alumina raw material.
  • AA-03 manufactured by Sumitomo Chemical Co., Ltd.
  • Comparative Example 2 100 g of the ⁇ -alumina raw material "NXA-100 (manufactured by Sumitomo Chemical Co., Ltd.)" and 0.1 g of magnesium chloride were weighed, added to 1 L of ethanol, and ultrasonically dispersed. This and alumina beads were placed in a rotary container, and the raw materials were mixed and pulverized by ball mill pulverization until the desired primary particle size was obtained. The average primary particle size is measured by using a laser diffraction/scattering particle size distribution measuring device (trade name “Partica LA-950”) manufactured by Horiba, Ltd., and irradiating a slurry diluted with ethanol with ultrasonic waves for 30 minutes. , was measured on a volume basis while applying ultrasonic waves. A desired slurry with almost no secondary agglomeration was obtained with a ball milling time of about 1 hour.
  • a laser diffraction/scattering particle size distribution measuring device (trade name “Partica LA-
  • Example 8 the slurry was stirred in a 2 L beaker with a rotor blade at 200 rpm for 1 hour, then the rotor blade was immediately stopped and left to stand for 15 minutes. It was visually confirmed that white particles had sunk to the bottom of the beaker, and the supernatant was also cloudy.
  • the slurry inside the beaker the upper one-third was sucked out to obtain the slurry of Comparative Example 2, and the lower one-third of the slurry inside the beaker was used as the slurry of Example 8.
  • Table 1 they are distinguished by the operation of water, and Comparative Example 2 is described as "NXA-100 on water” and Example 8 is described as "NXA-100 on water”.
  • an organic binder was added to each of these slurries.
  • a water-based acrylic binder was used as the organic binder, and 2.5% by mass (content of the organic binder with respect to the entire slurry) was added to the ⁇ -alumina raw material, and the mixture was stirred with a rotary blade for 24 hours.
  • the stirred slurry was dried and granulated with a spray dryer to obtain two types of granules.
  • the average particle size of the granules was about 40 ⁇ m for both the “NXA-100 water level” granules and the “NXA-100 water level” granules.
  • the powder composed of the granules was poured into a mold having a predetermined size and uniaxially pressed at a pressure of 150 MPa to obtain a compact.
  • the molded body is placed in an electric furnace, heated from room temperature at a rate of 10 ° C./min, held at 500 ° C. for 2 hours to degrease the organic component, and further calcined at 10 ° C./min to the calcination temperature shown in Table 2.
  • Example 8 and Comparative Example 2 were obtained by raising the temperature to , maintaining the calcining temperature for 6 hours, and slowly cooling from the maximum calcining temperature at ⁇ 0.4° C./min.
  • a sintered body was obtained in the same manner as in Example 1, except that the maximum sintering temperature shown in Table 3 was used.
  • Example 5 a calcined body was obtained in the same manner as in Example 1.
  • Example 6 and 7 calcined bodies were obtained in the same manner as in Example 1 except that the amount of the sintering aid was changed to the amount shown in Table 1.
  • Example 7 using Noritake Katana System Katana (registered trademark) F-1N (manufactured by Kuraray Noritake Dental Co., Ltd.) in an air atmosphere, the same as in Example 1 except that the maximum sintering temperature was changed to that shown in Table 3. to obtain a sintered body.
  • Noritake Katana System Katana (registered trademark) F-1N manufactured by Kuraray Noritake Dental Co., Ltd.
  • Example 9 As shown in Table 2, a calcined body was obtained in the same manner as in Example 1, except that the calcining temperature during calcining was changed. A sintered body was obtained in the same manner as in Example 1, except that the maximum sintering temperature shown in Table 3 was used.
  • Example 10 A calcined body was prepared in the same manner as in Example 1, except that the raw material listed in Table 1 was used instead of NXA-100 as the ⁇ -alumina raw material, and the conditions for producing the calcined body were changed to those listed in Table 2. got In Example 10, the molded body obtained by pressing was placed in an electric furnace, and the temperature was raised from room temperature at a rate of 10 ° C./min to the calcining temperature shown in Table 2. At the calcining temperature It was held for 6 hours and slowly cooled at -0.4°C/min to obtain a calcined body. A sintered body was obtained in the same manner as in Example 1 except that the maximum sintering temperature shown in Table 3 was used.
  • Example 3 A calcined body was obtained in the same manner as in Example 8, except that the manufacturing conditions for the calcined body were changed to those shown in Table 2. Moreover, a sintered body was obtained in the same manner as in Example 8.
  • Example 13 Using a vacuum press molding machine (trade name "250 ton vacuum press molding machine", manufactured by Iwaki Industry Co., Ltd.), the same as in Example 1 except that a molded body was obtained by uniaxial pressure pressing under a reduced pressure of 80 kN. Then, a calcined body and a sintered body were obtained.
  • a vacuum press molding machine (trade name "250 ton vacuum press molding machine", manufactured by Iwaki Industry Co., Ltd.), the same as in Example 1 except that a molded body was obtained by uniaxial pressure pressing under a reduced pressure of 80 kN. Then, a calcined body and a sintered body were obtained.
  • Examples 14 to 18> A calcined body was obtained in the same manner as in Example 1 except that the type and amount of the sintering aid were changed as shown in Table 1. After that, using Noritake Katana System Katana (registered trademark) F-1N (manufactured by Kuraray Noritake Dental Co., Ltd.) in an air atmosphere, the same as in Example 1 except that the maximum sintering temperature was changed to that shown in Table 3. to obtain a sintered body.
  • Noritake Katana System Katana (registered trademark) F-1N manufactured by Kuraray Noritake Dental Co., Ltd.
  • Tables 2 and 3 show the results of each example and comparative example.
  • the dental oxide ceramic calcined body of the present invention can be suitably used for machining such as CAD/CAM.

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