WO2023127561A1 - 良研磨性の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

良研磨性の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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WO2023127561A1
WO2023127561A1 PCT/JP2022/046481 JP2022046481W WO2023127561A1 WO 2023127561 A1 WO2023127561 A1 WO 2023127561A1 JP 2022046481 W JP2022046481 W JP 2022046481W WO 2023127561 A1 WO2023127561 A1 WO 2023127561A1
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Prior art keywords
calcined body
oxide ceramic
dental
alumina
particles
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PCT/JP2022/046481
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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 KR1020247020758A priority Critical patent/KR20240110641A/ko
Priority to JP2023570866A priority patent/JP7792437B2/ja
Priority to US18/723,864 priority patent/US20250186176A1/en
Publication of WO2023127561A1 publication Critical patent/WO2023127561A1/ja
Anticipated expiration legal-status Critical
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    • 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
    • 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
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    • A61C13/00—Dental prostheses; Making same
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    • A61C13/083—Porcelain or ceramic teeth
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    • A61C5/00—Filling or capping teeth
    • A61C5/70—Tooth crowns; Making thereof
    • A61C5/77—Methods or devices for making crowns
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    • 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
    • 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
    • C04B2235/963—Surface properties, e.g. surface roughness

Definitions

  • the present invention relates to a dental oxide ceramics calcined body that contains oxide ceramics and can be satisfactorily polished with a tool, and a method for producing the same.
  • sintered bodies of oxide ceramics have become popular as dental materials.
  • a sintered body of a dental material is used which has been precisely machined in terms of dimensions and surface to match the patient's 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.
  • a semi-sintered zirconia calcined body is cut or ground into a shape close to a 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 machining the resulting cut or ground body at a temperature higher than the sintering temperature.
  • 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 terms of translucency after sintering.
  • it since it is often used as a sintered body except for porous bodies such as heat insulating materials, it is necessary to calcine it. Therefore, it is common practice to sinter a compact to obtain a sintered body.
  • the sintered body since the sintered body has high hardness, it takes a lot of time to polish. In addition, if the surface of the sintered body is chipped (chipped) during polishing of the sintered body, the sintered body must be remanufactured. Therefore, there is room for improvement in terms of productivity and economy.
  • the present inventors have found that if the calcined body can be polished at the stage and the desired surface properties (for example, flatness after polishing) can be imparted, the time and risk can be reduced in polishing after sintering. Found it.
  • Patent Document 1 discloses a method for manufacturing bioactive alumina by molding and polishing, and describes surface polishing of an alumina sintered body.
  • it takes time to polish the sintered body and there is a concern that some particles may fall off, conversely reducing the smoothness of the sintered body.
  • alumina is frequently used as a sintered body except for porous bodies such as heat insulating materials, there is no need to make it into a calcined body. No consideration has been given to sintering after sintering.
  • 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 consider a highly abrasive calcined body. Further, in Patent Document 2, the circularity of the particles was not examined, and the calcined body was not good in polishability due to the large particle size.
  • Patent Document 3 describes the hardness and porosity of abrasive grains suitable for polishing, but does not consider the body to be polished. It cannot be said that appropriate conditions for smoothing the surface of the calcined body (abrasive grain surface) have been found.
  • Patent Documents 1 to 3 there is no consideration of polishing the calcined body to make it smooth and then sintering it, and it was not possible to obtain a smooth sintered body by an economical and easy method. rice field.
  • an oxide ceramic calcined body that has excellent polishability and has aesthetics because the polished surface of the calcined body and the surface of the sintered body after sintering have high flatness, and a manufacturing method thereof.
  • the inventors of the present invention have made intensive studies to solve the above problems, and found that oxide ceramic particles having an average circularity of primary particles of 0.81 or more and a relative density of 43 to 63%.
  • the present inventors have found that the ceramic calcined body has high abrasiveness, and have made further studies based on this finding, thereby completing the present invention.
  • the present invention includes the following inventions.
  • a dental oxide ceramic calcined body containing oxide ceramic particles having an average circularity of primary particles of 0.81 or more and having a relative density of 43 to 63%.
  • Dental oxide ceramics calcined body according to. [9] Any one of [1] to [8], wherein the surface roughness Ra is 1.40 ⁇ m or less after firing under atmospheric pressure to form a sintered body without using hot isostatic pressing. A dental oxide ceramic calcined body as described above. [10] The surface roughness Rz of any one of [1] to [9], wherein the surface roughness Rz is 51 ⁇ m or less after firing under atmospheric pressure to form a sintered body without using hot isostatic pressing. Dental oxide ceramic calcined body.
  • 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 20 to 600 MPa, and a step of firing the obtained compact at 400 ° C. or more and less than 1200 ° C. under atmospheric pressure, Production of a dental oxide ceramic calcined body containing oxide ceramic particles having an average circularity of primary particles of 0.81 or more and a relative density of 43 to 63% Method.
  • an oxide ceramic calcined body that has excellent polishability and aesthetics because the polished surface of the calcined body and the surface of the sintered body after sintering have high flatness, and a method for producing the same.
  • the surface of a calcined body that has been cut or ground by CAD/CAM or the like can be easily polished before sintering, and the surface can be easily smoothed.
  • a calcined body with good smoothness, a sintered body with good smoothness, and a method for producing the same can be provided.
  • alumina has high hardness after sintering, and it is not easy to polish the surface after sintering.
  • the surface smoothness of the sintered body is excellent even in the sintered body by processing the calcined body into a crown shape and then polishing the surface by, for example, polishing the side surface. Furthermore, according to the present invention, it is possible to provide a calcined zirconia body excellent in machinability (cuttability and grindability) and a method for producing the same.
  • FIG. 4 is an optical microscope photograph of the polished surface of the calcined body according to Example 1.
  • the dental oxide ceramic calcined body of the present invention has an average circularity of primary particles of 0.81 or more and a relative density of 43 to 63%.
  • 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 the oxide ceramic particles are solidified in a state in which the oxide ceramic particles are not completely sintered.
  • the calcined body may have a predetermined shape (block shape (for example, disk shape, rectangular parallelepiped shape, etc.), dental product shape (for example, crown shape), etc.).
  • the calcined body may be, for example, a crown-shaped processed body, and when processed, it is referred to as a "processed body” or a "cut or ground 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 fixed particles of oxide ceramics (hereinafter sometimes simply referred to as "oxide ceramic particles"), and the abrasiveness and machinability of the particles depend on the average circularity of the particles. properties (cuttability and grindability) and surface properties (flatness of calcined body and sintered body after polishing) change. If the oxide ceramic particles contained in the calcined body have an average circularity of 0.81 or more, the polishability is high, and the surface roughness Ra and/or Rz after polishing is low. On the other hand, when the average circularity is less than 0.81, the surface roughness Ra and/or Rz increases when the calcined body is polished, or the work time is extended due to excessive hardness.
  • the average circularity is preferably 0.82 or more, more preferably 0.83 or more, and even more preferably 0.84 or more. The method for measuring the average circularity is as described in Examples below.
  • surface roughness Ra means arithmetic mean roughness Ra defined in JIS B 0601:2013.
  • Surface roughness Rz means maximum height roughness Rz defined in JIS B 0601:2013.
  • the surface roughness Ra after polishing is within the desired range (for example, 1.70 ⁇ m or less) before polishing the alumina calcined body, or the surface after polishing
  • the desired range for example, 1.70 ⁇ m or less
  • a pre-polished alumina calcined body having a roughness Rz within the desired range for example, 54 ⁇ m or less
  • the surface roughness of the alumina calcined body of the present invention can be measured by a known method.
  • a stylus method or laser interference may be used, or a cross-section may be photographed with an optical microscope or an electron microscope and image analysis may be performed.
  • the surface roughnesses Ra and Rz are values measured by the measuring method described in Examples below.
  • 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, the number of particles in the calcined body that are in contact with each other decreases, and the calcined body is too soft to be broken during polishing, which is not preferable. In addition, it is not preferable because the Rz increases due to uneven density in the interior of the calcined body. On the other hand, if the relative density exceeds 63%, it is too hard and the working time is extended, which is not preferable. Moreover, chipping increases the surface roughness Ra and/or Rz, which is not preferable.
  • the relative density is 43 to 63%, the surface roughness Ra, Rz and hardness during polishing of the calcined body are moderate, the working time is not increased, the polished surface of the calcined body is highly flat, Even after sintering, the flatness is high, and the sintered body has high aesthetics.
  • the relative density is within the above range, the machinability (cuttability and grindability) is also excellent, the probability of chipping (hereinafter referred to as "chipping rate”) can be reduced, and the sintered body is flat. maintain a high level of quality.
  • the relative density is preferably 45% to 60%, more preferably 48% to 56%, from the standpoint of superior effects of the present invention.
  • 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 necking (sticking) is properly formed is preferably 400°C or higher and lower than 1200°C.
  • the firing temperature in the calcination step (hereinafter also referred to as "calcination temperature”) will be described in detail.
  • the calcined body of the present invention contains adherents of particles made of oxide ceramics (hereinafter sometimes simply referred to as "ceramic oxide particles"), the degree of adherence is determined by the average particle diameter of these particles. change, and the hardness of the calcined body changes.
  • ceramic oxide particles adherents of particles made of oxide ceramics
  • the average primary particle size of oxide ceramic particles contained in the calcined body is preferably 30 to 600 nm, more preferably 40 to 580 nm, even more preferably 60 to 450 nm, and most preferably 80 to 350 nm.
  • the average primary particle size of the oxide ceramic particles is 600 nm or less, it is difficult to absorb small particles with a particle size distribution, and sticking due to the difference in particle size is difficult to occur, the hardness is difficult to increase, and the working time is not increased. Since there is no local presence of coarse particles, chipping is less and the surface roughness Ra and/or Rz can be reduced.
  • the adhesion is not excessively strong, the hardness of the calcined body is not easily increased, the working time is not increased, and the surface roughness Ra and/or Rz can be reduced, which is preferable.
  • 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 polishing tool comes into contact with the calcined body, the pores ensure a room for particles to move, and the polishing resistance is increased. can be reduced, and the surface roughness Ra and/or Rz of the calcined body can be reduced.
  • D10 and D90 in the accumulation of pore distribution (cumulative distribution of pores)
  • D10 and D90 in the accumulation of pore distribution when D10 is 10 nm or more and D90 is 90 nm or less, the amount of tool wear and the chipping rate can be reduced.
  • the median pore diameters corresponding to cumulative 10% and cumulative 90% from the small particle size 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.
  • D10 is 10 nm or more
  • the pores do not become too small for particles having an average primary particle diameter of 30 to 600 nm. can reduce the work time without increasing work time.
  • D10 is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 25 nm or more, from the viewpoint of reducing the chipping rate and surface roughness.
  • D90 is 90 nm or less
  • the chipping rate during polishing can be further reduced, and the surface roughness Ra and/or Rz can be further reduced.
  • D90 is preferably 79 nm or less, more preferably 66 nm or less, and even more preferably 64 nm.
  • the BET specific surface area changes depending on the average circularity of the primary particle size, relative density, average primary particle size, and pore size distribution of the oxide ceramic particles in the calcined body.
  • 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 m 2 /g or more, more preferably 7.5 m 2 /g or more, and 8 m 2 /g or more is more preferable.
  • 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 working time can be 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 polishing time increases and / or the chipping rate tends to decrease.
  • 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. Adhesion to a certain degree is preferable because it can maintain good polishability.
  • a known device can be used to measure the BET specific surface area of the calcined body.
  • 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.).
  • 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
  • the abrasiveness 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 18 MPa or more, and even more preferably 20 MPa or more, in order to ensure a strength that enables machining. .
  • the three-point bending strength of the calcined body is 10 MPa or more, the possibility of breaking the calcined body during polishing can be reduced, which is preferable.
  • the three-point bending strength of the calcined body is preferably 50 MPa or less, more preferably 45 MPa or less, and even more preferably 40 MPa or less in order to facilitate polishing of the calcined body. , 35 MPa or less.
  • the Vickers hardness of the calcined body of the present invention is preferably 350 HV 5/30 or less, more preferably 300 HV 5/30 or less, from the viewpoint of changing the abrasiveness and / or hardness. It is preferably 100 HV 5/30 or less, more preferably 100 HV 5/30 or less.
  • the Vickers hardness is 350 HV 5/30 or less, the machinability (cuttability and grindability) is excellent, the chipping rate is low, and an increase in tool wear can be suppressed.
  • "HV 5/30” means the Vickers hardness when a load (test force) of 5 kgf is held for 30 seconds.
  • the calcined body of the present invention has a Vickers hardness within the above-described predetermined range, so that the chipping rate can be reduced.
  • the method for measuring Vickers hardness in the present invention conforms to JIS Z 2244:2020.
  • the Vickers hardness measurement methods include the following examples.
  • the oxide ceramic particles used in the present invention are not particularly limited, and examples thereof 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.
  • those containing zirconia and/or alumina are preferable, and those containing zirconia and/or alumina as main components are more preferable.
  • the oxide ceramic particles contain alumina as a main component will be described while appropriately explaining the case where the oxide ceramic is zirconia.
  • a composition containing alumina as a main component is preferable because the sintered body can be improved in aesthetics as a dental material and has excellent chemical stability.
  • ⁇ -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.
  • ⁇ -phase alumina ⁇ -alumina
  • the calcined body can be uniformly controlled, and the tool wear amount or chipping rate can be easily reduced.
  • 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.
  • This 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.
  • alumina raw material examples include Sumitomo Chemical Co., Ltd. AA grade ( ⁇ -alumina), AKP grade ( ⁇ -alumina), or NXA grade (“NXA-100”, “NXA-150”, etc.) (both , ultrafine ⁇ -alumina) with a purity of 99.99% or more.
  • the oxide ceramic calcined body of the present invention includes an oxide ceramic calcined body containing alumina or zirconia.
  • the alumina calcined body of the present invention further 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. preferably included.
  • 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. element, more preferably at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ce, Zr, and Y, consisting of Mg, Ce, Zr, and Y More preferably, it contains at least one element selected from the group.
  • magnesium compounds are most preferred. Magnesium compounds include oxides, nitrates, acetates, hydroxides, chlorides and the like.
  • the magnesium compound is not limited as long as it is a magnesium compound that becomes an oxide at a temperature of less than 1200°C when sintered in the atmosphere, but the most preferable ones are magnesium nitrate, magnesium chloride, magnesium hydroxide and magnesium acetate. is mentioned.
  • sintering aids include MgCl 2 , Mg(OH) 2 , CeO 2 , ZrO 2 , Y 2 O 3 and the like.
  • 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.
  • 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 the phase that undergoes a phase transition in the system increases, the chipping rate increases, the polishability decreases, 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.
  • the chipping rate is preferably as low as possible from the viewpoint of reducing the amount of work involved in reworking the cut or ground 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.
  • the method for measuring the chipping rate is as follows. The side surface of a disk with a thickness of 1 mm cut out for measuring the amount of tool wear is imaged with an optical microscope, painted black so that the chipping part is black, and the part other than black is white (binarized) .
  • the chipping rate can be calculated as a percentage of the black area to the sum of the black and white areas.
  • Image analysis software (trade name “Image-Pro Plus”, manufactured by Hakuto Co., Ltd.) can be used for area measurement.
  • Alumina and sintering aid and zirconium oxide and stabilizing agent may be mixed and used as long as they are in small amounts within a range that does not degrade the abrasiveness and aesthetics after sintering.
  • the molar ratio of zirconium oxide to alumina is preferably 99.99-98, more preferably 99.9-99.
  • the molar ratio of zirconium oxide to alumina is preferably 0.01-2, more preferably 0.1-1.
  • 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”. Even when the oxide ceramic is zirconium oxide, it can be implemented as a zirconia composition in the same manner as an alumina 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.
  • the primary particles include alumina particles and sintering aid particles.
  • 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, if there are many secondary particles, sparseness and denseness will occur during press molding, which will be described later.
  • the surface roughness Ra and/or Rz increases after sintered body polishing.
  • the average primary particle size of the primary particles constituting the granules of the alumina composition affects the degree of adhesion during calcination, and affects the hardness of the calcined body.
  • the average primary particle size of the particles is 30 nm or more, the surface area of the primary particles contained in the calcined body does not decrease, the adhesion does not become too strong, and the hardness hardly increases, which is preferable.
  • the average primary particle size of the particles is 600 nm or less, it is preferable because particles with a small particle size distribution are less likely to be absorbed, and the occurrence of local sticking due to the difference in particle size is suppressed, making coarseness and density less likely to occur.
  • the average primary particle size is preferably from 30 to 600 nm, more preferably from 40 to 580 nm, even more preferably from 60 to 450 nm, most preferably from 80 to 350 nm.
  • 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.
  • NXA as the primary particles of alumina particles constituting the granules, which are within the average primary particle diameter of the primary particles of the particles constituting the granules
  • NXA-100 and “NXA-150”
  • a mixture of It may be mixed arbitrarily within the range that satisfies the average circularity and relative density of the oxide ceramic particles in the calcined body. preferable.
  • 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, the polishing time is reduced and/or the chipping rate during polishing is easily reduced, and the surface roughness is reduced. It is possible to further reduce the roughness Ra and / or Rz, or to suppress the occurrence of coarseness and fineness without too little adhesion, to further reduce the chipping rate during polishing of the calcined body, and to further reduce the surface roughness Ra and / or Rz. It is preferable because it can be done.
  • 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 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, and the Vickers hardness or the strength of the calcined body can be increased or decreased. easier to adjust.
  • 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.
  • dental oxide ceramics having a surface roughness Ra of 1.40 ⁇ m or less after firing under atmospheric pressure to form a sintered body without using hot isostatic pressing (HIP) treatment.
  • a calcined body is mentioned.
  • a dental oxide ceramic temporary having a surface roughness Rz of 51.0 ⁇ m or less after firing under atmospheric pressure to form a sintered body without using hot isostatic pressing treatment A baked body is mentioned.
  • the average crystal grain size is 0.3 to 8.0 ⁇ m after firing under atmospheric pressure 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 20 to 600 MPa, and a step of firing at 400 ° C. or more and less than 1200 ° C. under atmospheric pressure, Production of a dental oxide ceramic calcined body containing oxide ceramic particles having an average circularity of primary particles of 0.81 or more and a relative density of 43 to 63% method.
  • 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 circularity of primary particles of 0.81 or more and a relative density of 43 to 63%.
  • 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.
  • the alumina composition can be pulverized (preferably pulverized) to the above-described average primary particle size (pulverization process).
  • Pulverization can be performed, for example, by dispersing the composition and binder in a solvent such as water or alcohol (dispersion step), and then using a ball mill, bead mill, or the like.
  • the composition is pulverized (preferably pulverized) to, for example, 0.05 ⁇ m to 0.6 ⁇ m so that the desired average circularity and relative density can be obtained when the body is produced.
  • 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. After the mixing step and/or the pulverizing step, the mixture can be spray-dried with a spray dryer or the like to form the alumina composition in the form of granules as described above (drying step).
  • 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
  • the average primary particle size of the alumina composition is preferably 30-600 nm, more preferably 40-580 nm, even more preferably 60-450 nm, and particularly preferably 80-350 nm.
  • the average particle size of the alumina composition is preferably 30-600 nm, more preferably 40-580 nm, even more preferably 60-450 nm, and particularly preferably 80-350 nm.
  • 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.
  • 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 may be a uniaxial press.
  • the product obtained by the pressure molding step may be, for example, a columnar molded body obtained by filling a mold with alumina granules and compressing them with a uniaxial pressure press.
  • the higher the contact pressure in press molding the higher the density of the molded product.
  • the relative density of the alumina calcined body obtained by this can also be made high, and average circularity can also be adjusted. On the other hand, if the density of the molded body is too high, the alumina calcined body becomes hard and good machinability cannot be obtained.
  • the surface pressure of press molding is preferably 20 to 600 MPa, more preferably 25 to 400 MPa, and even more preferably 30 to 200 MPa, from the viewpoint of ease of molding.
  • the surface pressure of press molding e.g., uniaxial press
  • the shape retention of the molded body is excellent, and when it is 600 MPa or less, the density of the molded body does not increase too much, making it easier to prevent hardening. .
  • 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 according to the target average circularity, relative density, and the like.
  • the pressure may be 20 to 200 MPa, 25 to 190 MPa, or 30 to 180 MPa, depending on the desired average circularity, 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 alumina calcined body according to the present invention is a precursor of the alumina sintered body described later. Further, the alumina calcined body according to the present invention includes a molded body. For example, it also includes a dental product (eg, crown-shaped prosthesis) in which a calcined alumina disc is processed by a CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) system.
  • CAD/CAM Computer-Aided Design/Computer-Aided Manufacturing
  • 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 in the alumina calcined body of the present invention has a magnesium compound uniformly dispersed in the sintering aid from the viewpoint of the strength and translucency of the sintered body produced from the calcined body described later. is preferred.
  • the calcining temperature in the calcining step affects the average circularity of the oxide ceramic particles contained in the calcined body, and affects the Vickers hardness or the strength of the calcined body.
  • the abrasiveness and hardness of the calcined body change depending on the calcining temperature.
  • the calcining temperature (maximum calcining temperature) in the method for producing the alumina calcined body of the present invention is kept to the extent that sintering does not proceed, so that the shape of the particle surface (spherical shape) remains.
  • a temperature of 400° C. or more and less than 1200° C. is preferable from the viewpoint that the sintered body does not become too hard and the surface roughness and hardness during polishing can be maintained.
  • the calcination increases the average circularity of the oxide ceramic particles during the calcination and does not cause excessive adhesion.
  • the calcining temperature is preferably a temperature at which the average circularity of the oxide ceramic particles contained in the calcined body is 0.81 or more.
  • the calcining temperature does not stick at low temperatures, but sticking starts at high temperatures. , the Vickers hardness or the strength of the calcined body is increased.
  • the calcination temperature is preferably around 1150° C. (1100° C. or more and less than 1200° C.).
  • the average primary particle size of the oxide ceramic particles contained in the alumina composition (for example, a compact) is large and the calcining temperature is 1000° C. or less, the average circularity does not increase, and adhesion between particles does not progress. However, the strength or Vickers hardness of the calcined body is not increased, chipping occurs during polishing, and the surface roughness Ra and/or Rz is lowered.
  • the average primary particle size of the primary particles that make up the granules made of the raw material oxide ceramic composition e.g., alumina composition
  • the average primary particle size of the oxide ceramic particles e.g., alumina particles contained in the calcined body
  • the primary particle size may differ, as described above, the average primary particle size of the primary particles constituting the granules made of the raw material oxide ceramic composition (for example, the alumina composition), the calcining temperature
  • the average primary particle size of the primary particles of the oxide ceramic particles (for example, alumina particles) contained in the calcined body can be adjusted within a desired range by adjusting the progress of adhesion according to the predetermined conditions.
  • the calcination temperature is set so that the average circularity of the oxide ceramic particles contained in the calcined body is 0.81 or more It is preferable that the temperature is such that the relative density of the sintered body is 43 to 63%.
  • the calcination temperature is preferably 600° C. or higher and lower than 1200° C., and more preferably 750° C. or higher and 1150° C. or lower.
  • 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, but the holding time at the maximum calcining temperature is preferably 30 minutes to 6 hours. Further, 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 machine used for machining the calcined body of the present invention is not particularly limited.
  • the cutting or grinding machine may be a desktop machine, a large machining center (general-purpose machine), or the like, depending on the object to be machined.
  • 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.
  • a processing level difference occurs on the surface according to the machining. If the sintered body is sintered while it has a working step, unevenness corresponding to the working step will remain on the surface of the sintered body, so polishing is required before using it as a dental material. Therefore, it is preferable to finish the surface of the calcined body having a step difference by cutting, grinding, or polishing so as to have a smooth surface.
  • the processed body obtained from the alumina calcined body of the present invention can be used as a dental tool with improved surface smoothness.
  • a dental tool for example, a bur and polisher kit suitable for cutting or grinding dental ceramics including porcelain to modify the shape thereof and to improve surface properties by polishing can be used.
  • tools include Kuraray Noritake Dental Co., Ltd.'s Noritake Protech Diamond Point, Carbide Burr, Meister Cone, Rubber Point, Felt Wheel, TWIST DIA's COARSE, MEDIUM, FINE, etc., P.D.R. Point: HP Serapika disk type medium polishing, slanting type medium polishing, disc type finishing polishing, slanting type finishing polishing, etc.
  • the processed body obtained from the alumina calcined body of the present invention may be improved in surface smoothness with a tool.
  • Abrasive powder may be used when polishing a processed body obtained from the alumina calcined body of the present invention with a tool. Examples thereof include Pearl Surface (registered trademark) C and Pearl Surface (registered trademark) F manufactured by Kuraray Noritake Dental Co., Ltd. When an abrasive is used, it becomes a foreign matter during sintering, so it is preferable to wash it.
  • the rotational speed of the tool is preferably 1000 to 7000 rpm. If the number of rotations is less than 1000 ppm, more time is required, and in addition, it is difficult to obtain a smooth surface because the reaction between the rotating tool and the calcined body collides with each other. If the number of rotations is higher than 7000 rpm, the working force of the tool increases, and the calcined body is excessively polished, making it difficult to obtain a desired shape.
  • the rotation speed is more preferably 2000 to 6000 rpm, more preferably 3000 to 5000 rpm.
  • a sintering process is performed. At this time, it is preferable to remove processing dust, because if processing dust adheres to the surface of the workpiece, it affects the shape and appearance after sintering. It is preferable that dust is wiped off with a brush used for painting or the like on the final-polished processed body, and the dust is visually removed.
  • 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 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 increased, and when the alumina calcined body of the present invention is applied to a dental product, the dimensions of the dental product to be used for treatment are determined, and after cutting or grinding, the It is possible to shorten the time until treatment with dental products is possible, and to 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.
  • a method for producing a dental oxide ceramic sintered body which includes the step of polishing any of the dental oxide ceramic calcined bodies described above with a dental polishing instrument.
  • the dental polishing instrument is not particularly limited, and known commercially available products can be used. Polishing conditions are not particularly limited.
  • a dental oxide ceramic sintered body includes a step of sintering the dental oxide ceramic calcined body under atmospheric pressure without using hot isostatic pressing. manufacturing methods.
  • HIP hot isostatic pressing
  • oxide ceramic sintered body will be described using an alumina sintered body as an example in which the oxide ceramic is aluminum oxide.
  • Alumina sintered bodies are obtained by sintering alumina calcined bodies or their processed bodies.
  • the alumina sintered body is alumina particles (powder) that have reached a sintered state.
  • the relative density of the alumina sintered body is preferably 99.5% or more.
  • the relative density of the sintered body can be calculated as a ratio of the actually measured density measured by the Archimedes method to the theoretical density.
  • the relative density is the density d1 of a sintered body obtained by filling a specific mold with granules and applying pressure to a specific shape, and sintering the compact at a high temperature. It means the value divided by the density d2.
  • 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 average grain size of the alumina sintered body can be measured by the following method.
  • An image of the surface of the alumina sintered body is obtained with a scanning electron microscope (trade name “VE-9800”, manufactured by KEYENCE CORPORATION). After describing the grain boundary of each crystal grain in the obtained image, the average crystal grain size is calculated by image analysis. Image analysis software (trade name “Image-Pro Plus”, manufactured by Hakuto Co., Ltd.) is used to measure the average crystal grain size, the captured SEM image is binarized, and the brightness range is adjusted so that the grain boundary becomes clear. Adjust to recognize the particles from the field of view (area).
  • 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.
  • the crystal grain size of all the particles not covering the edge of the image is measured.
  • the average crystal grain size is calculated from the obtained crystal grain size of each grain and the number of crystal grains, and the obtained arithmetic mean diameter is defined as the average crystal grain size in the sintered body.
  • the term "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 grains that do not overlap the image edge is selected in Image-Pro Plus with the option to exclude all boundary grains.
  • 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 5 or more, more preferably 10 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.)
  • CE100 analysis software "Crystal Eye” (manufactured by Olympus Co., Ltd.)
  • * Values can be measured.
  • the contact liquid for example, one having a refractive index nD of 1.60 measured at a measurement wavelength of 589 nm (sodium D line) can be used.
  • the white background means the white part of the hiding rate test paper described in JIS K 5600-4-1:1999, Part 4, Section 1, and the black background means the black part of the hiding rate test paper.
  • the surface roughness Ra of the alumina sintered body is preferably 1.40 ⁇ m or less, more preferably 1.25 ⁇ m or less, further preferably 1.15 ⁇ m or less, in order to more easily reproduce the surface roughness of a natural tooth. 10 ⁇ m or less is particularly preferred.
  • the surface roughness Rz of the alumina sintered body is preferably 51 ⁇ m or less, more preferably 48 ⁇ m or less, still more preferably 42 ⁇ m or less, and particularly preferably 39 ⁇ m or less, in order to more easily reproduce the surface roughness of natural teeth.
  • the methods for measuring the surface roughnesses Ra and Rz are as described in Examples below.
  • the alumina sintered body of the present invention may be a sintered 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, cut or ground bodies, and sintered bodies according to the present invention are not limited to the above unless otherwise specified, and are known. Various manufacturing methods are 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.
  • Alumina granules obtained in Examples and Comparative Examples are filled in a mold, uniaxially pressed at 200 MPa, calcined by mooring at 750 ° C. for 6 hours, and calcined into a disk-shaped 14 mm thick and ⁇ 98.5 mm. made the body. 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.
  • machining pattern (2 mm diameter, not diamond-coated) was cut so as to leave a thin disk with a thickness of 1 mm.
  • a post was cut off from the thin disk with a thickness of 1 mm obtained by processing. Steps derived from CAD/CAM processing were confirmed on the surface of the thin disk.
  • the arithmetic mean roughness Ra was obtained by the following formula using the difference. Also, the maximum height roughness Rz was the maximum value of Zn(X).
  • a disk-shaped calcined body having a thickness of 14 mm and a diameter of 98.5 mm was used in the same manner as the sample used in the surface polishing method. From the disc-shaped calcined body, a sample of 5 mm ⁇ 10 mm ⁇ 50 mm was cut out according to ISO 6872: 2015, and the surface and C surface of the sample (a surface chamfered at an angle of 45 °) (ISO 6872 : 2015, 7.3.1.2.1) was longitudinally faced with 600 grit sandpaper.
  • 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"
  • Examples 1 and 7 > 1000 g of ⁇ -alumina raw material “NXA-100” (average primary particle size: 100 nm, manufactured by Sumitomo Chemical Co., Ltd.) and 0.1 g of magnesium chloride equivalent were weighed, added to 10 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 primary particle size is measured by using a laser diffraction/scattering particle size distribution analyzer (trade name “Partica LA-950”) manufactured by Horiba, Ltd., and irradiating a slurry diluted with ethanol with ultrasonic waves for 30 minutes, followed by It 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 analyzer trade name “Partica LA-950” manufactured by Horiba, Ltd.
  • Example 1 was described as "NXA-100 water level”
  • Example 7 is described as "NXA-100 water level”.
  • an organic binder was added to this slurry.
  • a water-based acrylic binder was used as the organic binder, added in an amount of 2.5% by mass (the content of the organic binder with respect to the entire slurry) relative to the ⁇ -alumina raw material, and stirred for 24 hours with a rotary blade.
  • 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.
  • 350 g of this granule powder was poured into a cylindrical mold with a diameter of 100 mm 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 3° C./min, held at 500° C. for 2 hours to degrease the organic component, and held at the maximum calcination temperature shown in Table 2 for 6 hours.
  • a calcined body was obtained by slowly cooling from the maximum calcining temperature at ⁇ 0.4° C./min.
  • the primary particle size is measured by using a laser diffraction/scattering particle size distribution analyzer (trade name “Partica LA-950”) manufactured by Horiba, Ltd., and irradiating a slurry diluted with ethanol with ultrasonic waves for 30 minutes, followed by It 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 analyzer 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, added in an amount of 2.5% by mass (the content of the organic binder with respect to the entire slurry) relative to the ⁇ -alumina raw material, and stirred for 24 hours with a rotary blade.
  • the slurry after stirring was dried and granulated with a spray dryer to obtain granules.
  • the average particle size of the granules was 40 ⁇ m.
  • 350 g of this granule powder was poured into a cylindrical mold with a diameter of 100 mm 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 3 ° C./min, held at 500 ° C. for 2 hours to degrease the organic component, and further subjected to maximum calcination at 3 ° C./min as shown in Table 2. The temperature was maintained for 6 hours, and then slowly cooled from the calcination temperature at -0.4°C/min to obtain a calcined body.
  • Examples 10 to 13> A calcined body was obtained in the same manner as in Example 3 except that the type and amount of the sintering aid were changed as shown in Table 1.
  • Table 3 shows 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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JP2013119485A (ja) * 2011-12-06 2013-06-17 Pilot Corporation 切削焼結用セラミックス仮焼材料およびその製造方法
WO2018056331A1 (ja) * 2016-09-20 2018-03-29 クラレノリタケデンタル株式会社 ジルコニア組成物、仮焼体及び焼結体並びにこれらの製造方法、並びに積層体
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JP7820618B1 (ja) * 2024-03-29 2026-02-25 クラレノリタケデンタル株式会社 セラミックス仮焼体の製造方法

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