JP7422995B2 - Method for manufacturing a mill blank for dental processing and method for manufacturing a dental prosthesis - Google Patents

Description

The present invention provides a method for producing a mill blank for dental processing, which is made of a sintered body that does not require special sintering that causes large volumetric shrinkage after cutting, is easy to cut, and has excellent aesthetics. The present invention relates to a method of manufacturing a dental prosthesis using a mill blank for dental processing manufactured by such a manufacturing method.

In recent years, with the development of ICT, computer-aided design (CAD) and computer-aided manufacturing (CAM) have been increasingly introduced in the dental field. For example, in the production of dental crown prostheses, the mainstream method is to cut these materials using a cutting device based on computer-designed data (CAD/CAM). On the other hand, in response to metal allergies and the increasing demand for high aesthetics, materials other than metals are increasingly being used for dental crown prostheses, and zirconia ceramic materials with excellent strength and toughness are being used. There is.

When manufacturing a crown prosthesis made of ceramic material using CAD/CAM technology, a mill blank (or dental mill blank) that can be attached to a cutting machine and has a disc-shaped or rectangular parallelepiped shape is used. It is common to use a solid block molded as a workpiece. Furthermore, dental mill blanks are often joined with retaining pins to secure them to cutting machines, and in this type of form, the dental mill blank that is integrated with the retaining pins is also called a dental mill blank. be. In the present invention, a form integrated with such a holding pin is also referred to as a dental mill blank. The body to be cut (dental mill blank body) is referred to as the part to be cut. As an example of the use of such a dental mill blank, for example, Patent Document 1 discloses a data creation device that creates three-dimensional data about a dental crown prosthesis, a holding part that holds a workpiece, and a Using a specific dental crown prosthesis manufacturing system that includes a cutting device that includes a cutting mechanism for cutting an object, and a control section that controls driving of the holding section and the cutting mechanism, zirconia ceramic A technique has been disclosed in which a dental crown prosthesis of a desired shape is formed by cutting a disc-shaped mill blank made of a material.

For dental mill blanks in which the part to be cut is made of a ceramic material, the part to be cut is generally made of a pre-sintered ceramic material that is easy to process, with emphasis on ease of cutting using CAD/CAM. things are often used. However, when such a dental mill blank is used, it is necessary to completely sinter the sintered ceramic material after cutting and grinding the part to be cut to form a high-strength ceramic. When completely sintering, the occurrence of shrinkage is unavoidable, so cutting and grinding of the dental mill blank is performed assuming this amount of shrinkage, but due to fluctuations in the amount of shrinkage, it is difficult to achieve the desired shape with high precision. It was difficult to obtain a dental crown prosthesis.

As a dental mill blank free from such problems, a mill block has been proposed in which a completely sintered body with improved machinability is used as a part to be cut. That is, Patent Document 2 states, ``100 parts by mass of a metal oxide whose main material is at least one of zirconia, alumina, mullite, and spinel, and 1 part by mass to 23 parts by mass of lanthanum phosphate and/or aluminum phosphate. "Dental processing block" is described. According to Patent Document 2, among the dental processing blocks mentioned above, those containing the lanthanum phosphate and/or aluminum phosphate as crystals having an average particle size of 0.01 μm or more and 1 μm or less are suitable for cutting. - It is said that the grinding process becomes easier, and the coarse lanthanum phosphate and/or aluminum phosphate crystals become less likely to become a starting point of fracture, thereby improving strength.

Japanese Patent Application Publication No. 2018-42895 Patent No. 4870038

The dental processing block (dental mill blank) described in Patent Document 2 has the excellent features described above. However, according to studies by the present inventors, when the sintering temperature is set higher than 1250°C as specifically shown in Cited Document 2 in order to obtain a denser sintered body, lanthanum phosphate and/or Alternatively, the particle size of the aluminum phosphate crystals may increase, causing a visually visible mottled pattern to appear after sintering, or the strength may decrease as the crystals become fracture starting points. There was found.

Therefore, the present invention manufactures a mill blank whose cut part is made of ceramic, which maintains good cutting and workability even when sintered at high temperatures, and does not cause a decrease in aesthetics or strength. The challenge is to provide technology that can.

The present invention solves the above problems by the following technical means.
That is, the first embodiment of the present invention comprises (A) a metal oxide whose main material is at least one of zirconia, alumina, mullite, and spinel, and (B) a metal cation component which is an aluminum cation and/or a lanthanoid metal cation. A method for manufacturing a dental mill blank having a cut portion made of a ceramic containing a certain metal phosphate, the method comprising:
(a) Metal oxide powder mainly composed of at least one of zirconia, alumina, mullite, and spinel: 100 parts by mass, (b1) Organic phosphoric acid compound containing no metal atoms in the molecule: total amount of phosphoric acid groups is 10 (b2) a metal salt other than the metal phosphate (B) containing an aluminum cation and/or a lanthanoid metal cation as the metal cation: (b1) the organic An amount such that the equivalent of the metal salt (mol x ion valence) is 0.9 times equivalent or more and 1.1 times equivalent or less with respect to the equivalent (mol x ion valence) of the phosphoric acid group contained in the phosphoric acid compound, A raw material powder preparation step of preparing a raw material powder composition comprising; a molding step of obtaining a compression molded body or a green body of a predetermined shape using the raw material powder composition; and a compression molded body or green body obtained in the molding step. A sintering step in which the green body is directly sintered at a sintering temperature of 600°C or higher and 1800°C or lower, or after degreasing and/or calcination treatment, it is sintered at a sintering temperature of 600°C or higher and 1800°C or lower; The method is characterized in that it comprises:

When degreasing and/or calcining treatment is performed in the sintering step, the compression molded body or green body is degreased and/or calcined at a temperature of 100°C or more and 1100°C or less and lower than the sintering temperature. Alternatively, it is preferable to carry out the sintering after a calcining treatment.

Further, in the method of the first aspect of the present invention, a fine phase consisting of the metal phosphate salt of (B) is dispersed in a matrix consisting of a sintered body of particles of the metal oxide of (A). A composite ceramic, wherein the fine phase is made of the amorphous and/or crystalline metal phosphate, and the metal phosphate has a crystallite diameter of less than 600 nm as determined by observation with a scanning electron microscope. It is preferable that the method is for manufacturing a dental mill blank having a cut portion made of a composite ceramic.

In a second embodiment of the present invention, the temperature exceeds 1250°C, in which a fine phase consisting of the metal phosphate salt (B) is dispersed in a matrix consisting of a sintered body of metal oxide particles (A). A composite ceramic sintered at a temperature of 1800° C. or lower, wherein the fine phase is composed of the amorphous and/or crystalline metal phosphate, and the phosphorus is determined by observation with a scanning electron microscope. This is a mill blank for dental processing, which has a part to be cut made of a composite ceramic in which the crystallite diameter of the acid metal salt is less than 600 nm.

A third aspect of the present invention is a method for manufacturing a dental prosthesis according to the first aspect of the present invention, wherein the sintering temperature in the sintering step is 600°C or more and 1100°C or less. A step of manufacturing a mill blank for dental processing by a method of the above method; A step of manufacturing a semi-finished dental prosthesis by cutting the part to be cut of the mill blank for dental processing obtained in the above step using CAD/CAM. and sintering the dental prosthesis semi-finished product at a temperature above 1100°C and below 1800°C to obtain a dental prosthesis.

A fourth aspect of the present invention is a method for manufacturing a dental prosthesis, comprising: manufacturing a mill blank for dental processing by the method of the first aspect of the present invention; The method is characterized in that it comprises the step of manufacturing a dental prosthesis by cutting a part to be cut of a mill blank for dental processing using CAD/CAM.

Although the ceramic obtained in the sintering step in the method for producing a mill blank for dental processing of the present invention is not a pre-sintered ceramic but a completely sintered ceramic, it cannot be cut or ground. It's easy. Therefore, the mill blank for dental processing in which the above-mentioned ceramic is used as a cut part can be made into a dental prosthesis without being sintered again after being cut by CAD/CAM. Therefore, compared to a so-called pre-sintered mill blank that requires high-temperature sintering (with shrinkage) after cutting, a dental prosthesis can be manufactured with high precision and efficiency. Moreover, even when the sintered body is sintered at a temperature higher than 1250° C. to increase its strength, the appearance of the sintered body does not have a mottled pattern. As described above, according to the method for producing a mill blank for dental processing of the present invention, a mill blank for dental processing can be manufactured with high precision and efficiency to produce a dental prosthesis with high strength and excellent aesthetics. It becomes possible to do so.

The method for producing a mill blank for dental processing of the present invention comprises: (A) a metal oxide mainly composed of at least one of zirconia, alumina, mullite, and spinel (hereinafter also simply referred to as "matrix metal oxide"); (B) Manufacturing a dental mill blank made of ceramic containing a metal phosphate salt (hereinafter also simply referred to as "aluminum lanthanide phosphate") whose metal cation component is an aluminum cation and/or a lanthanide metal cation. (a) A metal oxide powder mainly composed of at least one of zirconia, alumina, mullite, and spinel, which is a raw material for the matrix metal oxide that is the component (A). (hereinafter also simply referred to as "matrix metal oxide powder") and (b1) an organic phosphoric acid compound (hereinafter also referred to simply as "matrix metal oxide powder") that does not contain a metal atom in its molecule, which is the raw material for the aluminum lanthanoid phosphate, which is the component (B). (hereinafter also simply referred to as "organophosphoric acid") and (b2) a metal salt other than the aluminum lanthanide phosphate of (B) above, which contains an aluminum cation and/or a lanthanide metal cation as a metal cation ( (hereinafter also simply referred to as "aluminum lanthanide salt") in a specific blending ratio, a raw material powder preparation step of preparing a raw material powder composition containing and a sintering step of sintering the compression molded body or green body obtained in the molding process at a specific temperature.

The method of the present invention described above differs from the method disclosed in Patent Document 2 using a raw material powder containing (B) aluminum lanthanide phosphate crystal powder, in that the raw materials (b1) and (b2) In order to generate (B) aluminum lanthanoid phosphate by reacting and decomposing them in the mixing and sintering steps, we use raw material powder containing powder of It is thought that because the crystallite diameter can be kept small, the appearance of the sintered body does not have a mottled pattern, and the aesthetics are improved. In addition, since there are no coarse (B) aluminum lanthanide phosphate crystals that tend to become a starting point for fracture, a decrease in strength is less likely to occur. The reason why the crystal growth of (B) aluminum lanthanide phosphate produced during sintering is suppressed and its crystallite diameter becomes small is because of (b1) and finely dispersed uniformly in the raw material powder during sintering. It is presumed that the organic components of (b2) diffuse while being decomposed and react by associating with each other, so that the crystallites cannot grow large and are kept small.
Hereinafter, each step in the method for manufacturing a dental mill blank of the present invention will be explained in detail.

<Raw material powder preparation process>
In the raw material powder preparation process,
(a) Metal oxide powder (matrix metal oxide powder) mainly consisting of at least one of zirconia, alumina, mullite, and spinel: 100 parts by mass,
(b1) Organic phosphoric acid compound (organic phosphoric acid) that does not contain a metal atom in the molecule: an amount such that the total amount of phosphoric acid groups is 10 mmol or more and 100 mmol or less (hereinafter, “A or more and B or less” is simply “ (b2) A metal salt other than the metal phosphate (B), which contains an aluminum cation and/or a lanthanoid metal cation as a metal cation (aluminum. Lanthanoid salt): The equivalent of the metal salt (mol x ion valence) is 0.9 times to 1. 1 times equivalent amount,
A raw material powder composition containing the following is prepared.

Various raw materials for the raw material powder used in the raw material powder preparation process will be explained below.

1. (a) Matrix metal oxide powder As the matrix metal oxide powder, a metal oxide powder whose main material is at least one of zirconia, alumina, mullite, and spinel is used.

The zirconia powder may have a crystal phase of monoclinic, tetragonal, cubic, or a mixed crystal of one or more of these, but it may contain a stabilizer such as yttria, calcia, magnesia, ceria, or erbium oxide. Partially stabilized zirconia containing tetragonal crystals and having tetragonal crystals as the main component after sintering is suitable for use. The alumina powder may have any crystal structure such as γ, δ, κ, θ, η, α type, etc., but readily available γ-alumina or α-alumina powder is preferred. The mullite powder may contain corundum crystals or glass, but it is preferably composed of approximately 100% mullite crystals. The spinel powder may contain alumina or magnesia, but preferably does not contain these. Among these, it is preferable to use partially stabilized zirconia powder, since it is not only white in color and suitable for dental prostheses, but also difficult to deteriorate at low temperatures and has high strength and toughness.

Matrix metal oxide powders with an average crystallite diameter of 0.001 μm to 50 μm are recommended because they are easy to handle, are difficult to cause phase transformation of oxide crystals, and do not cause excessive grain growth during sintering. is preferably used. It is more preferable to use powder having an average crystallite diameter of 0.003 μm to 20 μm.

The matrix metal oxide may contain a pigment. The pigment is not particularly limited, and known pigments can be used in any combination. For example, erbium oxide, cobalt oxide, iron oxide, etc. can be used. Furthermore, even if the material is white before sintering, it can be colored after sintering and used as a pigment.

2. (b1) Organic phosphoric acid (b1) As the organic phosphoric acid, any organic phosphoric acid compound that does not have a metal atom in its molecule can be used without particular limitation. Here, an organic phosphoric acid compound is defined as having a phosphoric acid group in the molecule in a broad sense, that is, a phosphinic acid group, which is an acidic group derived from phosphoric acid, a phosphonic acid group, a phosphonic acid hydrogen monoester group, or a phosphoric acid dihydrogen monoester group. It means an organic compound having a phosphoric acid group such as a hydrogen monoester group.

Specific examples of (b1) organic phosphoric acid that can be preferably used include 2-acryloyloxyethyl dihydrogen phosphate, 3-acryloyloxypropyl dihydrogen phosphate, 4-acryloyloxybutyl dihydrogen phosphate, 5-acryloyl Oxypentyl dihydrogen phosphate, 6-acryloyloxyhexyl dihydrogen phosphate, 7-acryloyloxyheptyl dihydrogen phosphate, 8-acryloyloxyoctyl dihydrogen phosphate, 10-acryloyloxydecyl dihydrogen phosphate, bis(2 -acryloyloxyethyl) acid phosphate, 2-acryloyloxyethyl phenylphosphonate, 5-acryloyloxypentyl-3-phosphonopropionate, 6-acryloyloxyhexyl-3-phosphonopropionate, bis[2- pyrophosphate] Acryloyloxyethyl], bis[4-acryloyloxybutyl] pyrophosphate, and methacrylates corresponding to these acrylates, vinyl phosphoric acid, and phytic acid. Among these, those whose moieties other than phosphoric acid groups are decomposed and removed during sintering are preferably used. More preferably, 10-methacryloyloxydecyl dihydrogen phosphate and bis(2-methacryloxethyl) acid phosphate are more preferred, since the phosphoric acid groups do not come too close to each other due to steric hindrance or the like.

The content of (b1) organic phosphoric acid in the raw material powder needs to be such that the total amount of phosphoric acid groups is 10 mmol to 100 mmol based on 100 parts by mass of the matrix metal oxide powder (a). Here, phosphoric acid group refers to acidic groups derived from phosphoric acid, such as phosphinic acid group, phosphonic acid group, phosphonic acid hydrogen monoester group, and phosphoric acid dihydrogen monoester group, as described above. means a phosphate group. When the amount of phosphoric acid groups is less than 10 mmol, it is difficult to obtain sufficient machinability. Further, if the content of phosphoric acid groups is more than 100 mmol, pores may remain even after sintering, and sufficient strength may not be obtained. (a) The total amount of phosphoric acid groups based on 100 parts by mass of the matrix metal oxide powder is preferably 15 mmol to 75 mmol.

3. (b2) Aluminum lanthanide salt In the present invention, (b2) metal salt is a metal salt other than the metal phosphate (B), which contains an aluminum cation and/or a lanthanide metal cation as a metal cation (aluminum・Use lanthanide salt). The (b2) metal salt reacts with the (b1) organic phosphoric acid upon contact or at high temperature, and at high temperature, the organic part of (b1) organic phosphoric acid is removed, producing (B) aluminum lanthanoid phosphate. do.

The metal salt is a salt other than aluminum lanthanide phosphate, which contains an aluminum cation and/or a lanthanide metal cation as a metal cation, and which reacts with (b1) organic phosphoric acid upon contact or at high temperature. B) Any metal salt that produces aluminum lanthanide phosphate is not particularly limited, and may be either an inorganic anion salt or an organic anion salt. Specific examples of inorganic anion salts include nitrates, chloride salts, bromide salts, bromates, chlorates, iodide salts, peroxide salts, carbonates, etc. Specific examples include acetate, isopropoxide salt, ethoxy salt, chloranil salt, and acetylacetonate salt. Among these, inorganic anion salts are preferred from the viewpoint of solubility, and nitrates are particularly preferred since the anion portion is easily decomposed and removed during sintering. Examples of metal salts (b2) that can be suitably used include lanthanum nitrate hexahydrate and aluminum nitrate nonahydrate.

(b2) The content of the aluminum lanthanide salt is determined by the total equivalent of the metal salt (total mole x ionic valence) relative to the total equivalent (total mole x ionic valence) of phosphate groups contained in (b1) organic phosphoric acid. ) must be in an amount of 0.9 to 1.1 times equivalent. If it is less than 0.9 times the equivalent, the organic phosphoric acid will be in excess, and phosphorus oxides and phosphorus may be generated by sintering the excess organic phosphoric acid, which may affect the color tone, etc. There is. Furthermore, if the amount exceeds 1.1 times, metal oxides may be generated after sintering, which may affect color tone and the like. (b2) The content of the metal salt is preferably 0.95 times equivalent to 1.05 times equivalent, expressed as the above-mentioned times equivalent.

4. Binder etc. A binder component may be added to the raw material powder as a component other than (a) matrix metal oxide powder, (b1) organic phosphoric acid, and (b2) aluminum lanthanide salt. Whether or not to add a binder component can be appropriately selected depending on the method of molding the sintered body and the like. When adding a binder component, for example, an acrylic binder, an olefin binder, a wax, etc. can be used.

Furthermore, for the purpose of improving fluidity, etc., it is possible to incorporate filler into the raw material powder, which has a sufficiently smaller particle size than that of the mixed powder, within a range that does not affect strength or aesthetic appearance. For example, silica or the like can be added.

5. Preparation method The raw material powder can be easily prepared by weighing each component and mixing them. The mixing method may be either a dry method or a wet method, but it is preferable to use a wet method from the viewpoint of more uniform mixing. As the solvent used in the wet method, for example, water, alcohols such as ethanol, acetone, and other known solvents can be used, but from the viewpoint of safety and ease of solvent removal, it is preferable to use water or alcohols. preferable.

When mixing by a wet method, the solvent may not only be removed in an oven or the like during drying, but also granulated in the raw material powder preparation step. For example, drying may be performed while performing the granulation process using a spray dryer or the like.

<Molding process>
In the molding step, a compression molded body or a green body of a predetermined shape is obtained using the raw material powder composition. At this time, the forming method is not particularly different from the conventional method of obtaining a molded body for a mill blank before sintering or calcination using a conventional powder raw material, except that the above-mentioned raw material powder composition is used as a raw material. Methods known as powder molding methods or green body molding methods, such as molding, extrusion molding, injection molding, cast molding, tape molding, layered molding, powder molding, stereolithography, etc., may be used without particular restrictions. can. Further, multi-stage molding may be performed. For example, the raw material powder composition for sintering of the present invention may be uniaxially press-molded and then further subjected to CIP (Cold Isostatic Pressing) treatment. Moreover, in the molding process, a plurality of types of mixed powders may be layered and molded.

The shape of the compression molded body or green body obtained in the molding process may be determined as appropriate depending on the shape of the intended mill blank, but it is usually disc-shaped or rectangular or approximately rectangular. (block type) etc. are common.

<Sintering process>
In the sintering step, the compression molded body or green body obtained in the molding step is directly sintered at a sintering temperature of 600°C to 1800°C, or after degreasing and/or calcination treatment, Sinter at a sintering temperature of °C.
1. Degreasing and/or Calcination Treatment In the method of the present invention, degreasing and/or calcining treatment can also be performed before sintering in the sintering step. Here, the term "degreasing treatment" refers to a process of removing by volatilization or decomposition of water, solvent, binder, etc. contained in the compression molded body or green body obtained in the above molding process, and the term "calcination treatment" refers to a process of removing moisture, solvent, binder, etc. contained in the compression molded body or green body obtained in the above molding process, and calcination treatment refers to a process of removing moisture, solvent, binder, etc., which is easily processed. It means a treatment that improves strength. These treatments are usually performed at a temperature of 100° C. or higher and 1100° C. or lower and lower than the sintering temperature.

As the method for degreasing and/or calcination treatment, any conventionally known method can be used without particular limitation, and it may be carried out continuously or in multiple stages. Further, in order to efficiently remove organic substances, it is preferable to carry out the process in an air atmosphere containing oxygen. Note that the degreasing and/or calcination treatment may be performed using the same equipment as the molding step that is the preceding step and/or the sintering that is performed thereafter, such as the SPS (Spark Plasma Sintering) method or the like. It can also be carried out continuously by HP (hot press) method or the like.

2. Sintering In the sintering process, the compression molded body or green body obtained in the molding process is directly sintered at a sintering temperature of 600°C to 1800°C, or after degreasing and/or calcination treatment, it is sintered at 600°C. Sinter at a sintering temperature of ~1800°C. Here, sintering (also called firing or sintering) means heating the compression molded body or green body to a temperature below the melting point of the matrix metal oxide by holding it at that temperature (or temperature range) for a certain period of time. Sintering temperature means that powder particles are surface-diffused (adhered, fused) to each other and transformed into a polycrystalline body, and the sintering temperature is maintained at that temperature (or within a certain temperature range) for a certain period of time. , refers to the temperature (or temperature range) at which sintering progresses to a desired degree. If the sintering temperature is less than 600°C, densification is insufficient and the density and strength of the sintered body are low, making it unsuitable for cutting. Furthermore, if the temperature is higher than 1800°C, grain growth may proceed too much, which may result in a decrease in strength.

The sintering is not particularly different from the conventional sintering of matrix metal oxide powders, except that the molded body using the raw material powder composition is sintered at the sintering temperature described above. ) In order to efficiently generate aluminum lanthanoid phosphate and to prevent its crystal growth from proceeding too much, the sintering temperature was set at 1250°C to 1600°C in air, and the sintering was carried out at this temperature for 30 minutes to 4 hours. It is preferable to hold it.

<Method for manufacturing dental processing mill blanks and dental prostheses>
1. One-step method (manufacturing method using a mill blank that does not require resintering)
According to the method of the present invention, by setting the sintering temperature in the sintering step to a high temperature, for example, higher than 1100°C and lower than 1800°C, cutting by CAD/CAM as disclosed in Patent Document 2 is possible. The aluminum lanthanide phosphorus of (B) is contained in a matrix made of a sintered body of matrix metal oxide particles, which is a mill block that is easy to process and does not require any further sintering treatment after the cutting process. A mill blank for dental processing made of a composite ceramic in which acid salt crystals are dispersed can be efficiently manufactured. In addition, a dental prosthesis manufactured using a CAD/CAM system using the dental mill blank has no mottled appearance and has excellent aesthetics.

Such a mill blank for dental processing has a fine phase consisting of (B) aluminum lanthanide phosphate in the matrix, specifically, an amorphous and/or crystalline (B) aluminum lanthanide phosphate. It is made of a composite ceramic in which a fine phase is dispersed in which the (B) aluminum lanthanoid phosphate has a crystallite diameter of less than 600 nm as determined by observation with a scanning electron microscope, and is heated to 1250 °C. This is a material sintered at temperatures exceeding 1,800°C or below that has not been known so far. In addition, because the sintering temperature of the dental processing mill blank is within the above range, it is more compact and has higher density and strength than those sintered at a lower temperature. .

The crystallite diameter of the aluminum lanthanide phosphate (B) determined by observation using a scanning electron microscope (SEM) is a value determined as follows. That is, when the particles of the aluminum lanthanide phosphate (B) observed by SEM are spherical or approximately spherical, it is the maximum diameter of 100 crystal particles randomly extracted on the SEM observation screen. It means a value determined by measuring the primary crystallite diameter (Xi) and calculating the average crystallite diameter using the following formula 1 based on the measured value. In addition, if the particles of the aluminum lanthanide phosphate (B) observed by SEM are amorphous, the maximum diameter is regarded as the primary crystallite diameter (Xi), and the following formula 1 is used as in the case of spherical shapes. It means a value determined by calculating the average crystallite diameter. In addition, in the SEM observation screen of the mill blank for dental processing, each crystal of lanthanoid phosphate and aluminum phosphate is confirmed by using the composition display in the backscattered electron image.

When manufacturing a dental prosthesis using the one-step method, the sintering temperature in the sintering process was set to exceed 1100°C and to be 1800°C or less when manufacturing the mill blank for dental processing using the manufacturing method of the present invention. It is preferable to use a material that has been sintered at 1,300° C. to 1,550° C. from the viewpoint of improving strength and transparency due to high density. Furthermore, cutting using a CAD/CAM system is not particularly different from conventional methods, except that shrinkage due to re-sintering does not need to be considered.

2. Two-step method (manufacturing method using a mill blank that requires resintering)
According to the method of the present invention, by making the sintering temperature in the sintering process relatively low, for example, 600°C to 1100°C, although a resintering process is required for cutting using CAD/CAM, It is possible to efficiently produce a mill blank for dental processing that is easier to cut using CAM and has relatively less shrinkage during resintering. Furthermore, the dental prosthesis semi-finished product obtained by cutting the dental mill blank using CAD/CAM is re-sintered at a temperature exceeding 1250°C for the purpose of further increasing the strength. However, the finally obtained dental prosthesis contains (B) a microphase consisting of aluminum lanthanide phosphate in the matrix, specifically, an amorphous and/or crystalline (B) It is made of a composite ceramic in which fine phases are dispersed, the crystallite size of the aluminum lanthanide phosphate (B) being less than 600 nm as determined by observation with a scanning electron microscope. , the appearance is free of mottled patterns and has excellent aesthetics.

When manufacturing a dental prosthesis using the two-step method, the mill blank for dental processing is one whose sintering temperature in the sintering process is 600°C to 1100°C when manufactured using the manufacturing method of the present invention. It is preferable to use one, and it is more preferable to use one at a temperature of 900°C to 1100°C. Furthermore, cutting using a CAD/CAM system is not particularly different from conventional methods. Furthermore, when a dental prosthesis semi-finished product is completely sintered to obtain a dental prosthesis, the complete sintering temperature is preferably 1100°C to 1800°C, particularly 1300°C to 1550°C.

EXAMPLES Hereinafter, in order to specifically explain the present invention, Examples and Comparative Examples will be given and explained, but the present invention is not limited by these in any way. Below, the abbreviations and abbreviations of the substances used to prepare the samples of each Example and Comparative Example, their structural formulas or substance names, methods for preparing various samples, and various evaluation methods will be explained.

<Raw materials for mill blanks for dental processing>
1. (a) Matrix metal oxide powder - Zpex4: Zirconia manufactured by Tosoh Corporation, average primary particle size 90 nm, yttria content 3.9 mol%
・TZ-6Y: Zirconia manufactured by Tosoh Corporation, average primary particle size 40 nm, yttria content 6 mol%
・AHP200: Alumina manufactured by Nippon Light Metal Co., Ltd., average primary particle size 400 nm
・KM101: Mullite manufactured by Kyoritsu Materials Co., Ltd., average primary particle size 1.9 μm
- SN-1: Spinel manufactured by Tateho Chemical Industry Co., Ltd., average primary particle diameter 360 nm.

2. (b1) Organic phosphoric acid ・MDP (10-methacryloyloxydecyl dihydrogen phosphate): manufactured by Miyoshi Yushi Co., Ltd., molecular weight = 322, number of phosphoric acid groups per molecule: 1
・PM2 (bis(2-methacryloxyethyl) acid phosphate): manufactured by Kyoeisha Chemical Co., Ltd., molecular weight = 322, number of phosphate groups per molecule: 1
・Vinyl phosphoric acid: manufactured by Sigma-Aldrich, molecular weight = 108, number of phosphoric acid groups per molecule: 1
- Phytic acid: manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight = 660, 50% aqueous solution, number of phosphoric acid groups per molecule: 6 .

3. Inorganic phosphoric acid and organic acid compounds other than (b1)
・Orthophosphoric acid: manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., molecular weight = 98, weight percentage 75%, number of phosphoric acid groups per molecule: 1
- CB-1 (2-methacryloyloxyethylphthalic acid): manufactured by Shin Nakamura Chemical Co., Ltd., molecular weight = 278, number of organic acid groups: 1.

4. (b2) Aluminum lanthanoid salt - Lanthanum nitrate hexahydrate: La(NO ₃ ) _{3.6H 2} O, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., molecular weight = 433, metal ion 1 mol per mol.

5. Metal salts other than (b2) - Sodium carbonate: Na ₂ CO ₃ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., molecular weight = 106, 2 mol of metal ions per 1 mol.

6. Solvent, etc. - Ethanol: Manufactured by Fuji Film Wako Pure Chemical Industries, Ltd. - Distilled water: Manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.

<Evaluation method of sintered body>
(1) Visual evaluation of the appearance of the sintered body It was visually confirmed whether a mottled pattern was visible on the appearance of the 1 mm thick sintered body. The judgment criteria are shown below.
○: No mottled pattern is visible when observed through fluorescent light.
×: A mottled pattern is visible when observed through fluorescent light.

(2) Evaluation of the average crystallite diameter of aluminum lanthanide phosphate after sintering Using a scanning electron microscope (SEM) "S-3400N" (manufactured by Hitachi High-Technologies), The average crystallite diameter of the salt crystals was calculated. The average crystallite diameter was calculated by calculating the average diameter of 100 crystalline particles randomly extracted on the SEM observation screen. In addition, in the SEM observation screen of the dental processing mill blank, each crystal of aluminum lanthanide phosphate was confirmed by using the composition display in the backscattered electron image.

(3) Cutting performance evaluation Using Diamond Point HP Form 25 (manufactured by Shofu Co., Ltd.), cutting was performed perpendicularly to the side surface of the sintered body at 10,000 rpm (Utilio (manufactured by Morita Co., Ltd.)) under water cooling, and after 5 seconds The depth of cut was measured.

Example 1
Production of raw material powder composition: 9.9 g of lanthanum nitrate hexahydrate and 100 g of ethanol were weighed and mixed to obtain a lanthanum nitrate solution. 13.6 g of MDP and 40 g of ethanol were weighed and mixed to obtain an MDP solution. A lanthanum nitrate solution and an MDP solution were added to a dispersion in which 100 g of Zpex4 was dispersed in 900 g of ethanol, and the mixture was mixed for 2 hours. Thereafter, the solvent was removed using an evaporator, and then dried at 50° C. for 15 hours using a vacuum drier to produce a raw material powder composition.
Production of sintered body: A disc-shaped compact was obtained by uniaxially pressing 1 g of the obtained raw material powder composition using a press mold with a diameter of 16 mm at a maximum load of 1 t. Thereafter, the molded body was sintered using an electric furnace "Super Burn" manufactured by Motoyama Co., Ltd. at 1450° C. for 2 hours to obtain a sintered body. Table 3 shows the evaluation results of the obtained sintered body.

Examples 2 to 14
A raw powder composition was produced in the same manner as in Example 1, except that the raw materials and amounts of the raw powder composition were changed as shown in Table 1. Using the obtained raw powder composition, the sintering conditions were as shown in Table 1. A sintered body was produced and evaluated in the same manner as in Example 1 except for the changes as shown. The results are shown in Table 3.

Comparative example 1
27.8 g of lanthanum nitrate hexahydrate and 300 g of ethanol were weighed and mixed to obtain a lanthanum nitrate solution. Further, 7.8 g of orthophosphoric acid and 300 g of ethanol were weighed and mixed to obtain a phosphoric acid solution. The phosphoric acid solution was mixed with the lanthanum nitrate solution while stirring. Immediately after mixing, the aqueous solution became cloudy and a lanthanum phosphate solution was obtained. The resulting mixture was subjected to solid-liquid separation using a centrifuge. 900 g of ethanol was added to the sediment, mixed for 1 hour, and solid-liquid separation was performed by centrifugation. After performing the same operation twice, the precipitate was dried at 50° C. for 24 hours to obtain lanthanum phosphate powder. 10.0 g of the obtained powder, 100 g of Zpex4, and 300 g of ethanol were weighed and mixed for 2 hours, solid-liquid separation was performed by centrifugation, and the precipitate was dried at 50 ° C. for 24 hours to prepare a raw material powder composition. did.
Using the obtained raw material powder composition, a sintered body was produced in the same manner as in Example 1 and evaluated. The results are shown in Table 3.

Comparative examples 2 to 10
A raw powder composition was produced in the same manner as in Example 1, except that the raw materials and amounts of the raw powder composition were changed as shown in Table 2. Using the obtained raw powder composition, the sintering conditions were as shown in Table 2. A sintered body was produced and evaluated in the same manner as in Example 1 except for the changes as shown. The results are shown in Table 3.

Comparative example 11
6.7 g of sodium carbonate and 100 g of distilled water were weighed and mixed to obtain a sodium carbonate aqueous solution. 13.6 g of MDP and 40 g of ethanol were weighed and mixed to obtain an MDP solution. An aqueous sodium carbonate solution and an MDP solution were added to a dispersion in which 100 g of Zpex4 was dispersed in 900 g of ethanol, and the mixture was mixed for 2 hours. Thereafter, the solvent was removed using an evaporator, and then dried at 50°C for 15 hours using a vacuum dryer to prepare a raw material powder composition.
Using the obtained raw material powder composition, a sintered body was produced in the same manner as in Example 1 except that the sintering conditions were changed as shown in Table 2, and the sintered body was evaluated. The results are shown in Table 3.

As can be understood from the results of Examples 1 to 14, when the conditions specified in the present invention are met, dental processing is possible where no mottled pattern is seen on the appearance of the sintered body, resulting in excellent aesthetics and excellent machinability. It can be seen that a mill blank can be obtained.

As can be understood from the results of Comparative Examples 1 and 2, the addition of once-isolated lanthanum phosphate powder and the addition of phosphoric acid and lanthanum nitrate provide machinability after sintering, but the lanthanum phosphate does not solidify. Since aggregates are formed and grains grow during sintering, the crystallite size increases after sintering, resulting in a mottled appearance.

As can be understood from the results of Comparative Examples 3 and 11, when the raw material powder composition does not contain (b2) aluminum lanthanide salt, although no mottled pattern appears on the appearance of the sintered body, Since (B) does not contain aluminum lanthanoid phosphate, the machinability is poor.

As understood from the results of Comparative Example 4, when the content of (b1) organic phosphoric acid in the raw powder composition is lower than the conditions specified in the present invention, (B) aluminum in the sintered body - Poor machinability due to low amount of lanthanide phosphate.

As understood from the results of Comparative Example 5, when the content of (b1) organic phosphoric acid in the raw powder composition is higher than the conditions specified in the present invention, (B) aluminum in the sintered body - The amount of lanthanide phosphate becomes too large and grain growth progresses, resulting in a mottled pattern.

As can be understood from the results of Comparative Example 6, when the content of (b2) aluminum lanthanide salt in the raw powder composition is lower than the conditions specified in the present invention, phosphorus oxide is not present in the sintered body. etc., and a mottled pattern appears. On the other hand, as understood from the results of Comparative Example 7, when the content of (b2) aluminum lanthanoid salt in the raw powder composition is higher than the conditions specified in the present invention, oxidation occurs in the sintered body. Lanterns are generated and a mottled pattern appears.

As understood from the results of Comparative Example 8, when the sintering temperature is too high, grain growth progresses, resulting in a mottled appearance. On the other hand, as understood from the results of Comparative Example 9, if the sintering temperature is too low, the sintered body does not have sufficient strength and collapses during cutting.

Furthermore, as understood from the results of Comparative Example 10, when the raw material powder composition does not contain (b1) organic phosphoric acid, no mottled pattern appears on the appearance of the sintered body, but ( B) Poor machinability because it does not contain aluminum lanthanide phosphate.

Claims (5)

A ceramic containing (A) a metal oxide whose main material is at least one of zirconia, alumina, mullite, and spinel; and (B) a metal phosphate whose metal cation component is an aluminum cation and/or a lanthanide metal cation. A method of manufacturing a mill blank for dental processing having a part to be cut, the method comprising:
(a) Metal oxide powder mainly composed of at least one of zirconia, alumina, mullite, and spinel: 100 parts by mass, (b1) Organic phosphoric acid compound containing no metal atoms in the molecule: total amount of phosphoric acid groups is 10 (b2) a metal salt other than the metal phosphate (B) containing an aluminum cation and/or a lanthanoid metal cation as the metal cation: (b1) the organic An amount such that the equivalent of the metal salt (mol x ion valence) is 0.9 times equivalent or more and 1.1 times equivalent or less with respect to the equivalent (mol x ion valence) of the phosphoric acid group contained in the phosphoric acid compound, A raw material powder preparation step of preparing a raw material powder composition comprising;
A molding step of obtaining a compression molded body or a green body of a predetermined shape using the raw material powder composition; and a sintering temperature of 600° C. or higher and 1800° C. or lower for the compression molded body or green body obtained in the molding step. or sintering at a sintering temperature of 600°C or higher and 1800°C or lower after degreasing and/or calcination treatment;
The method characterized in that it comprises. In the sintering step, the compression molded body or green body is degreased and/or calcined at a temperature of 100° C. or higher and 1100° C. or lower and lower than the sintering temperature, and then the sintering is performed. , the method of claim 1. A composite ceramic in which a fine phase made of the metal phosphate salt of the above (B) is dispersed in a matrix made of a sintered body of metal oxide particles of the above (A), wherein the fine phase is amorphous. and/or a dental clinic having a part to be cut made of a composite ceramic made of the crystalline metal phosphate, the crystallite diameter of the metal phosphate being determined by observation with a scanning electron microscope being less than 600 nm. The method according to claim 1 or 2, for producing a mill blank for processing. A method of manufacturing a dental prosthesis, the method comprising:
A step of manufacturing a mill blank for dental processing by the method according to any one of claims 1 to 3, wherein the sintering temperature in the sintering step is 600° C. or higher and 1100° C. or lower;
a step of manufacturing a dental prosthesis semi-finished product by cutting the cut portion of the dental mill blank obtained in the above step using CAD/CAM; and a step of manufacturing the dental prosthesis semi-finished product at a temperature exceeding 1100°C , obtaining a dental prosthesis by sintering at a temperature of 1800° C. or less;
The method, characterized in that it comprises. A method of manufacturing a dental prosthesis, the method comprising:
A step of manufacturing a mill blank for dental processing by the method according to any one of claims 1 to 3; and a step of cutting the part to be cut of the mill blank for dental processing obtained in the step using CAD/CAM to produce a mill blank for dental processing. The process of manufacturing a prosthesis;
The method, characterized in that it comprises.