JP2023163322A - Method for producing zirconia composite ceramic and method for producing zirconia ceramic prosthesis for dental use - Google Patents

Abstract

To provide a method for efficiently producing zirconia composite ceramics having high bending strength, which can be suitably used as a zirconia ceramic prosthesis for dental use.SOLUTION: In a method for producing a zirconia composite ceramic, a "composite zirconia temporary sintered body" is prepared, is cut using a CAD/CAM system as necessary, and is then actually sintered at a temperature of 1,250-1,800°C. Thereafter, it is slowly cooled to a specific primary cooling temperature in a range of 400-900°C at 100-900°C/hour. Subsequently, it is cooled to 50°C or less at 1,000-9,000°C/hour. The composite zirconia temporary sintered body comprises a temporary sintered body of a stabilized or partially stabilized zirconia powder containing zirconium oxide, a stabilizing agent consisting of yttrium oxide, and an aluminum oxide additive as a main structure, which is composited with a silicon dioxide component such as fine particles of silicon dioxide.SELECTED DRAWING: None

Description

The present invention relates to a method for manufacturing zirconia composite ceramics and a method for manufacturing a dental zirconia ceramic prosthesis.

In recent years, with the development of ICT, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies have been increasingly introduced in the dental field. For example, regarding the production of a dental crown prosthesis, a dental prosthesis is produced by cutting a dental blank made of a non-metallic material using a CAD/CAM device based on a photographed image of the oral cavity. CAM systems are becoming widely used. Here, the blank for dental machining refers to an object to be cut (also called a mill blank) that can be attached to a cutting machine in a CAD/CAM system, and usually includes a part to be cut and a part to be cut. It has a holding part for making it attachable to a processing machine. As the part to be cut, a (solid) block formed in the shape of a rectangular parallelepiped or cylinder, or a (solid) disk formed in the shape of a plate or disk is generally known.

As the non-metallic material, zirconia-based ceramic materials are often used because they have excellent strength and toughness and can produce highly aesthetic dental prostheses. Completely sintered zirconia-based ceramic materials are difficult to cut due to their strength, so a dental prosthesis made of zirconia-based ceramics (hereinafter also referred to as "zirconia prosthesis") was created using a CAD/CAM system. In such cases, the part to be cut of the zirconia dental mill blank (also simply referred to as "zirconia mill blank") is generally a zirconia ceramic pre-sintered body pre-sintered at a relatively low sintering temperature. It is used in many ways. Then, based on CAD that takes into account shrinkage that occurs when performing main sintering at high temperatures, cutting is performed using CAM into a shape that corresponds to the shape of the final prosthesis, and then main sintering is performed. A zirconia prosthesis with high density and high strength has been produced by this process.

Regarding zirconia-based ceramics, pure zirconia (zirconium oxide) undergoes a phase transition accompanied by a change in volume depending on the temperature, so during the cooling process after sintering, stress caused by the change in volume can cause cracks to occur, leading to a decrease in strength. There is. In order to prevent this phase transition, stabilizers such as yttrium oxide, calcium oxide, and magnesium oxide are added to create a monoclinic crystal that is stable at high temperatures without transforming into a monoclinic crystal that is stable at low temperatures even when cooled. Stabilized or partially stabilized zirconias have been developed that can exist as tetragonal or mixed tetragonal and cubic crystal systems. Stabilized zirconia or partially stabilized zirconia is also used as the zirconia raw powder used in zirconia mill blanks, and it is generally used with alumina (additive) added to increase strength. has been done. For example, Patent Document 1 describes a raw material powder that can be sintered under pressure to produce a zirconia sintered body that has both translucency and strength that are particularly suitable for anterior dentures. A zirconia powder containing 0.5 mol % or less of yttria and less than 0.1 wt % of alumina and having a BET specific surface area of 8 to 15 m ² /g is described.

By the way, as shown in Non-Patent Document 1, a sintered body of (partially) stabilized zirconia containing yttria (yttrium oxide) as a stabilizer can be made from tetragonal zirconia by adjusting the amount of yttria added. It is known that the abundance ratio with cubic zirconia changes, and the strength and transparency change accordingly. In other words, as the yttria content increases, the content of cubic crystals, which contribute to improved transparency, increases, and correspondingly, the content of tetragonal crystals, which contribute to high strength, decreases, so there is a so-called trade-off between high strength and high transparency. It becomes a relationship. For this reason, when manufacturing prosthetics that require high transparency, such as for front teeth, transparency is given priority, and "partially stabilized zirconia with an yttria content of 5 mol% or more", which has slightly lower strength, is used. It is common to

On the other hand, when manufacturing molar prostheses or long span bridges that require high strength, "stabilized zirconia or partially stabilized zirconia with an yttria content of 3.5 mol% or less", that is, tetragonal zirconia, is used. However, due to the phase transformation from tetragonal to monoclinic in the presence of moisture, the crystal lattice volume increases and cracks occur, causing low-temperature deterioration, which reduces strength and durability. Problems have been pointed out (see Patent Document 2). According to Patent Document 2, stabilized zirconia or A technique has been disclosed in which partially stabilized zirconia is blended with strontium aluminate, spinel, etc., particularly preferably at a content of 4 to 6% by volume, and then pre-sintered after molding. Further, Patent Document 2 states that a completely sintered body obtained by sintering the thus obtained temporary sintered body is a zirconia oxide matrix having an average particle size of 0.1 to 2.0 μm. It has a structure in which a secondary phase made of the above-mentioned strontium aluminate, spinel, etc. having a particle size of preferably 0.2 to 0.5 μm is dispersed in the phase, and has a hardness (compared to a case without a secondary phase). It has been shown that fracture toughness is improved by optimizing the amount depending on the type of secondary phase, and that residual strength after damage (Vickers hardness indenter) is improved. Improvement in initial bending strength has not been studied.

Further, Patent Document 3 describes a dental prosthesis made of stabilized zirconia or partially stabilized zirconia obtained by main sintering a molded body made of zirconia powder, without impairing its inherent aesthetics, and with a manufacturing burden. As a technique for improving adhesion without particularly increasing the adhesion, a catalyst consisting of tetraethylorthosilicate (TEOS) and aluminum nitrate nonahydrate is applied to the surface layer of a stabilized or partially stabilized zirconia pre-sintered body. A technique has been disclosed in which a penetrant consisting of a sol etc. mixed with water is infiltrated, the main sintering is performed, and then the surface layer is etched, but the bending strength of the material obtained in this way is not clear. Not considered.

Furthermore, Patent Document 4 discloses that a zirconia dental restoration having a highly translucent outer surface can be produced from a zirconia mill blank in a short time by omitting the glazing treatment of the zirconia dental restoration obtained after complete sintering. As a manufacturing technique, glass is present in at least a part of the outer surface of a porous dental zirconia restoration produced by cutting from a mill blank in a region within a depth of 5 μm, and then a predetermined heating profile and cooling are performed. A method of sintering with a sintering protocol including a profile is described. However, even in Patent Document 4, the bending strength of the material obtained in this way is not studied.

International Publication No. 2015/098765 pamphlet Patent No. 6333254 Special Publication No. 2007-534368 Special Publication No. 2021-515754

Seiji Ban, “Complete Guidebook for CAD/CAM Materials: Clinically Useful Material Selection and Adhesion Operations,” published by Ishiyaku Publishing Co., Ltd., December 20, 2017, p. 18-20

As described above, when producing a prosthesis for anterior teeth where aesthetics (transparency) is important, it is common to use low-strength zirconia, and even higher strength is required. Further, even in tetragonal zirconia having high strength, further increase in strength is required due to problems with strength durability due to low temperature deterioration.

Therefore, the present invention provides a method for efficiently manufacturing a zirconia composite ceramic having high bending strength, which can be suitably used as a dental zirconia ceramic prosthesis, and a method for efficiently manufacturing a zirconia composite ceramic having high bending strength using a CAD/CAM system. An object of the present invention is to provide a method for efficiently manufacturing a dental prosthesis made of zirconia composite ceramics.

The present invention solves the above problems, and the first form of the present invention includes: 100 parts by mass of zirconium oxide, 4 to 14 parts by mass of a stabilizer made of yttrium oxide, and 0.0 parts by mass of an aluminum oxide additive. 005 to 0.3 parts by mass, and silicon dioxide or its precursor: 0.05 to 5.0 parts by mass (however, parts by mass of the precursor of silicon dioxide represent parts by mass in terms of silicon dioxide). , and a preliminary sintered body preparation step of preparing a composite zirconia temporary sintered body containing the zirconium oxide temporary sintered body as a main structure;
A sintering step of sintering the composite zirconia pre-sintered body prepared in the pre-sintered body preparation step at a temperature of 1250 to 1800°C; and a cooling step of cooling the sintered body sintered in the sintering step. A method for producing zirconia-based ceramics, comprising the steps of:
In the cooling step, the sintered body is cooled at a cooling rate of 100 to 900 (°C/hour) {=1.7 to 15.0°C/min} at a predetermined temperature selected from the range of 400 to 900°C. A first cooling process in which the sintered body is cooled to the primary cooling temperature in the first cooling process is cooled to a temperature of 1000 to 9000 (°C/hour) {=17.0 to 150.0 ℃/min} cooling rate until the temperature reaches 50℃ or less,
This is a method for producing zirconia composite ceramics, which is characterized by the following.

In the method for manufacturing zirconia composite ceramics of the first embodiment (hereinafter also referred to as "method for manufacturing zirconia composite ceramics of the present invention"), the pre-sintered body preparation step includes:
(A) A first raw material containing a zirconia base powder containing 100 parts by mass of zirconium oxide, 4 to 14 parts by mass of a stabilizer consisting of yttrium oxide, and 0.005 to 0.3 parts by mass of an aluminum oxide additive. A step of forming a composition into a predetermined shape and then pre-sintering it at 600-1200°C to obtain a microporous pre-sintered body having a relative density of 45-65% and having pores opening toward the outside. ; and a step of sorbing 0.05 to 5.0 parts by mass of silicon dioxide fine particles per 100 parts by mass of zirconium oxide into the pores of the microporous pre-sintered body obtained in the above step,
A step of preparing a composite zirconia temporary sintered body in which fine particles of silicon dioxide are sorbed into the pores of the microporous temporary sintered body, or (B) Zirconium oxide: 100 parts by mass, yttrium oxide. A zirconia base powder containing 4 to 14 parts by mass of a stabilizer consisting of 4 to 14 parts by mass and 0.005 to 0.3 parts by mass of an aluminum oxide additive; "Precursor of silicon dioxide" consisting of "amorphous silicon dioxide particles having a particle size of 1 to 500 nm" and/or "a silicon dioxide source material consisting of a silicon-containing substance that can be converted into a silicon dioxide compound by sintering": 0. A raw material composition preparation step of preparing a second raw material composition in which 05 to 5.0 parts by mass are uniformly dispersed;
a molding step of molding the second raw material composition to obtain a molded body having a predetermined shape; and a pre-sintering step of pre-sintering the molded body at 600 to 1200°C;
Preferably, this is a step of preparing a composite zirconia temporary sintered body made of the temporary sintered body obtained in the above-mentioned temporary sintering step.

A second form of the present invention is zirconium oxide: 100 parts by mass, a stabilizer consisting of yttrium oxide: 4 to 14 parts by mass, an aluminum oxide additive: 0.005 to 0.3 parts by mass, and silicon dioxide or its like. Precursor: 0.05 to 5.0 parts by mass (however, the parts by mass of the silicon dioxide precursor represent parts by mass in terms of silicon dioxide), and the presintered body of zirconium oxide is the main structure. By cutting a zirconia dental mill blank having a cut part made of a composite zirconia temporary sintered body using a CAD/CAM system, a shape corresponding to the shape of the intended dental prosthesis can be obtained. A cutting process to obtain a semi-finished product having;
A dental zirconia ceramic prosthesis comprising: a sintering step of sintering the semi-finished product obtained in the above step at a temperature of 1250 to 1800°C; and a cooling step of cooling the sintered body sintered in the sintering step. A method of manufacturing,
The cooling step is a first cooling step in which the sintered body is cooled at a cooling rate of 100 to 900° C./hour until it reaches a primary cooling temperature, which is a predetermined temperature selected from the range of 400 to 900° C. , a second cooling step in which the sintered body cooled to the primary cooling temperature in the first cooling step is cooled to 50° C. or less at a cooling rate of 1000 to 9000° C./hour,
This is a method for manufacturing a dental zirconia ceramic prosthesis (hereinafter also referred to as "method for manufacturing a dental zirconia prosthesis of the present invention"), which is characterized by the following.

According to the method for producing zirconia composite ceramics of the present invention, the characteristics of conventional stabilized or partially stabilized zirconia of not causing a phase transition accompanied by a large volume change during the cooling process after sintering can be maintained. It becomes possible to improve the bending strength of the sintered body.

Furthermore, according to the method for manufacturing a dental zirconia prosthesis of the present invention, it is possible to obtain a dental zirconia prosthesis that has both high translucency and high strength.

As a result of studies to solve the above problems, the present inventors have found that in the case of a zirconia composite ceramic in which an appropriate amount of amorphous silica is present at the grain boundaries of stabilized zirconia or partially stabilized zirconia, , strength is improved without reducing transparency, and such a zirconia composite ceramic is made of a pre-sintered body of a raw material powder composition that is a raw material for stabilized zirconia or partially stabilized zirconia, and silicon dioxide or We have already reported that it can be obtained by sintering a composite zirconia temporary sintered body that is a composite of its precursor (a compound that converts into silicon dioxide when fired) (Patent application 2020 -188760 and patent application 2021-129542).

Specifically, "crystalline zirconium oxide powder containing a stabilizer and an aluminum oxide additive is formed into a predetermined shape and then pre-sintered at 600 to 1200°C, so that the relative density is 45 to 65%. A microporous temporary sintered body is obtained, and this is immersed in a sol in which fine particles of silicon dioxide are dispersed in a dispersion medium, and the fine particles of silicon dioxide are sorbed into the pores of the temporary sintered body, and then dispersed. Composite zirconia pre-sintered body obtained by "method of removing the medium" (hereinafter also referred to as "immersion method"), or "silicon dioxide or its precursor (a compound that is converted to silicon dioxide by firing)" A composite zirconia pre-sintered body obtained by "a method of pre-sintering a raw material powder composition that is a raw material for stabilized zirconia or partially stabilized zirconia" (hereinafter also referred to as "pre-addition method"). It has been reported that by sintering at a temperature of 1250 to 1800°C, the biaxial bending strength is improved compared to the case without silicon dioxide.

The present invention has discovered that the biaxial bending strength of the resulting zirconia composite ceramic is influenced by the cooling conditions after sintering these composite zirconia pre-sintered bodies, and has also achieved high biaxial bending strength. This was achieved by discovering a cooling method.

The reason why the biaxial bending strength of the zirconia composite ceramic obtained by sintering the composite zirconia pre-sintered body is improved is that the present inventors' analysis revealed that in the zirconia composite ceramic, silicon dioxide It was confirmed that silicon dioxide exists at the grain boundaries between adjacent zirconia crystal grains and/or at the grain boundaries between adjacent zirconia crystal grains and aluminum oxide crystal grains. It seems that further increase in strength was achieved by reducing the amount of carbon, suppressing the propagation of cracks, or increasing the interfacial strength especially in cubic crystals. In addition, the reason why high strength was achieved by adopting the cooling method in the manufacturing method of zirconia composite ceramics of the present invention is that cracks etc. are prevented in the sintered body by slow cooling to a predetermined temperature and then rapid cooling. In addition to preventing this from occurring, silicon dioxide is rapidly cooled to form low-density silicon dioxide glass, and compressive stress is inherent in the zirconia composite ceramic, thereby increasing its strength.

Hereinafter, a method for producing a zirconia composite ceramic of the present invention, a method for producing a zirconia composite pre-sintered body by the dipping method of the present invention, a method for producing a zirconia composite pre-sintered body by the pre-addition method of the present invention, and dental zirconia ceramics. The method for manufacturing the prosthesis will be explained in detail.

In this specification, unless otherwise specified, the notation "x to y" using numerical values x and y means "more than or equal to x and less than or equal to y." In such a notation, when a unit is attached only to the numerical value y, the unit shall also be applied to the numerical value x.

1. Method for manufacturing zirconia composite ceramics of the present invention The method for manufacturing zirconia composite ceramics of the present invention has a main structure consisting of a pre-sintered body of zirconium oxide to become stabilized zirconia or partially stabilized zirconia, and silicon dioxide or its After preparing a composite zirconia temporary sintered body containing a predetermined amount of the precursor (temporary sintered body preparation process) and main sintering it (sintering process), it is cooled according to a predetermined cooling profile (cooling process). It has major characteristics.
Each of the above steps will be explained in detail below.

1-1. Temporary Sintered Body Preparation Step In the temporary sintered body preparation step, zirconium oxide: 100 parts by mass, stabilizer made of yttrium oxide: 4 to 14 parts by mass, aluminum oxide additive: 0.005 to 0.3 parts by mass, and silicon dioxide or its precursor: 0.05 to 5.0 parts by mass (however, the parts by mass of the silicon dioxide precursor represent parts by mass in terms of silicon dioxide), and the zirconium oxide is calcined. A composite zirconia pre-sintered body containing the compact as a main structure is manufactured.

The composite zirconia temporary sintered body prepared in the temporary sintered body preparation step is not particularly limited as long as it satisfies the above conditions, but it may be manufactured by the above-mentioned "immersion method" or the above-mentioned "pre-addition method". Preferably.

In other words, the preliminary sintered body preparation process is
(A) A first raw material containing a zirconia base powder containing 100 parts by mass of zirconium oxide, 4 to 14 parts by mass of a stabilizer consisting of yttrium oxide, and 0.005 to 0.3 parts by mass of an aluminum oxide additive. By molding the composition into a predetermined shape and pre-sintering it at 600 to 1200°C, a microporous pre-sintered body (hereinafter referred to as (also referred to as "microporous temporary sintered body for adsorption") (hereinafter also referred to as "microporous temporary sintered body for adsorption manufacturing process"); 05 to 5.0 parts by mass of silicon dioxide fine particles are sorbed into the pores of the microporous pre-sintered body obtained in the above step (hereinafter also referred to as "sorption step"),
A composite zirconia pre-sintered body in which fine particles of silicon dioxide are sorbed into the pores of the microporous pre-sintered body is prepared, or (B) a stable zirconia sintered body consisting of 100 parts by mass of zirconium oxide and yttrium oxide; A zirconia base powder containing 4 to 14 parts by mass of a curing agent and 0.005 to 0.3 parts by mass of an aluminum oxide additive, and an average primary particle diameter of 1 to 500 nm as measured by dynamic light scattering. "Silicon dioxide precursor" consisting of "amorphous silicon dioxide particles" and/or "silicon dioxide source material consisting of a silicon-containing substance that can be converted into a silicon dioxide compound by sintering": 0.05 to 5 A raw material composition preparation step of preparing a second raw material composition in which 0 parts by mass are uniformly dispersed;
a molding step of molding the second raw material composition to obtain a molded body having a predetermined shape; and a pre-sintering step of pre-sintering the molded body at 600 to 1200°C;
Preferably, a composite zirconia temporary sintered body made of the temporary sintered body obtained in the above temporary sintering step is prepared.

In short, in the method using the "immersion method" described in (A) above, the first raw material composition containing zirconia base powder is molded into a predetermined shape and then pre-sintered to form a microporous pre-sintered compact for adsorption. A composite zirconia temporary sintered body in which a microporous temporary sintered body for adsorption and silicon dioxide fine particles are composited is prepared by adsorbing silicon dioxide fine particles thereon. In the method using the "pre-addition method", a second raw material composition containing a zirconia base powder and a "silicon dioxide precursor" is formed into a predetermined shape and then pre-sintered to form a composite zirconia pre-sintered compact. Prepare. It is clear from the manufacturing method that the composite zirconia pre-sintered body prepared in (A) has a basic structure of a pre-sintered body of zirconia base powder, but the pre-sintering conditions in (B) are ( Since the pre-sintering conditions are basically the same as those in A), and the amount of "silicon dioxide precursor" contained in the second raw material composition is small, the composite prepared in (B) It can be said that the zirconia pre-sintered body also has a basic structure of a pre-sintered body of zirconia-based powder.

In view of these commonalities, first we will explain the common matters regarding (A) and (B) above. The zirconia base used in the first raw material composition and the second raw material composition As the powder, any powder that can be used as a zirconia raw material powder used in conventional zirconia mill blanks can be used without particular limitation. Use zirconium oxide particles (particles made of stabilized zirconia or partially stabilized zirconia) in which the stabilizer is dissolved in solid solution and have tetragonal or mixed crystallinity of tetragonal and cubic crystals. It is preferable to use a material with an average crystallite diameter of 0.001 μm to 50 μm, particularly 0.003 μm to 20 μm, because crystal phase transformation is difficult to occur and grain growth does not progress too much due to sintering. It is preferable. Furthermore, from the viewpoint of ease of handling the powder, the average secondary particle diameter of the zirconium oxide powder in the zirconia base powder is preferably 0.01 to 500 μm, particularly 0.05 to 100 μm. The average crystallite diameter is preferably from 0.001 μm to 50 μm, particularly from 0.003 μm to 20 μm, because phase transformation of the oxide crystals is difficult to occur and because grain growth does not progress too much due to sintering.

The amount of each component in the zirconia base powder relative to 100 parts by mass of zirconium oxide is preferably 5.5 to 12 parts by mass for yttrium oxide, and 0.05 to 0.1 part for aluminum oxide additive. Parts by mass are preferred.

The first raw material composition and the second raw material composition 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. Furthermore, as other components, a binder, a fine filler, a light shielding agent, a fluorescent agent, etc. can be included. 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.

The molding of each raw material composition in (A) and (B) above is suitably performed by forming the first or second raw material composition into a compression molded body or a green body of a predetermined shape. The molding method at this time is not particularly different from the molding method used to manufacture conventional zirconia mill blanks, and includes press molding, extrusion molding, injection molding, cast molding, tape molding, layered manufacturing, and powder molding. A method known as a powder molding method or a green body molding method, such as molding or stereolithography, can be used without particular limitation. Further, multi-stage molding may be performed. For example, the raw material powder 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 appropriately determined depending on the shape of the target object, but for example, when manufacturing a mill blank, it is usually a disk-shaped body (disk type), Alternatively, a rectangular parallelepiped or approximately rectangular parallelepiped shape (block type) is common.

In pre-sintering, the compression molded body or green body obtained in the above molding is sintered at a lower temperature than the main sintering process to perform degreasing treatment and calcining treatment to form a microporous pre-sintered body. obtain. Here, the degreasing treatment refers to a treatment for removing by evaporation or decomposition the water, solvent, binder, etc. contained in the compression molded body or green body obtained by the above-mentioned molding, and the calcination treatment refers to a treatment for removing moisture, solvent, binder, etc. by evaporation or decomposition by heating. It causes the diffusion (adhesion, fusion) phenomenon of molecules and atoms on the surface of the metal oxide powder particles, changing them into a polycrystalline body, and also improves the strength of the resulting microporous pre-sintered body, making it easier to handle and This refers to processing that improves the strength to the point where it can be easily processed. This pre-sintering temperature is usually 600°C to 1200°C, and if the pre-sintering temperature is lower than 600°C, it may not be possible to obtain the strength to maintain the shape during the sorption process. If the temperature is higher than 1200° C., the density of the microporous temporary sintered body becomes high, and the sol may not be able to penetrate sufficiently, so that high strength may not be obtained.

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 is performed by a method using the same equipment as the molding step, which is the previous step, such as the SPS (Spark Plasma Sintering) method or the HP (Hot Press) method. It can also be done continuously.

In the pre-sintering or pre-sintering step in (A) and (B) above, the pre-sintered body of zirconium oxide contained as the main structure in the composite zirconia pre-sintered body, specifically the pre-sintered body of zirconia base powder. A sintered body is formed. This zirconium oxide pre-sintered body (also a microporous pre-sintered body for adsorption) is a microporous pre-sintered body with a relative density of 45 to 65% and pores that open toward the outside. It is. In (B), the raw material to be pre-sintered (second raw material composition) contains a small amount of "silicon dioxide precursor", so the degree of microporosity and relative density may vary slightly, but the yield can be reduced. It is not significantly different from the value of worn microporous pre-sintered.

Note that the relative density is the ratio of the actual density to the theoretical density {calculated by relative density = (actual density / theoretical density) x 100 (%)}, and it is determined by controlling the pre-sintering temperature and pre-sintering time. It can be adjusted by If the relative density is outside the above range, it will be difficult to obtain a zirconia composite presintered body by the dipping method. Further, if the temporary sintering is performed to obtain such a relative density, the temporary sintered body usually becomes microporous with pores opening toward the outside. The average pore diameter of these pores is usually in the range of 50 to 200 nm. Here, the average pore diameter means the median diameter determined from the pore volume distribution in the range of pore diameters from 5 nm to 250 μm obtained by mercury porosimetry, ie, measurement using a mercury porosimeter.

In addition, the theoretical density varies depending on the type and content of the stabilizer and the content of the aluminum oxide additive, and as the content increases from 6.10 g/ ^cm3 , which is the theoretical density of tetragonal zirconia, it slightly decreases. There is a tendency to decrease. For example, Table 1 of Patent Document 1 shows the theoretical density of zirconia containing yttria and alumina, and is reproduced below for reference.

The matters common to (A) and (B) have been described above, but (A) and (B) differ in the method of compounding with silicon dioxide or its precursor. Therefore, the sorption process in (A) and the raw material composition preparation process in (B), which are the differences, will be explained below.

In the sorption step (A), 0.05 to 5.0 parts by mass of silicon dioxide fine particles are added to 100 parts by mass of zirconium oxide into the pores of the microporous pre-sintered body obtained by pre-sintering. Sorpt. At this time, the microporous temporary sintered body may be newly produced according to the method described above, but it contains a stabilizer consisting of yttrium oxide and aluminum oxide within the above range, and , Check the relative density by measuring the density using the Archimedes method, etc., and if the value is within the above range, use the conventional commercially available zirconia mill blank for the workpiece as is. It may also be used as a microporous pre-sintered body for adsorption.

The method of sorbing silicon dioxide fine particles into the pores of the microporous temporary sintered body in the sorption step is a method in which the silicon dioxide fine particles are sorbed into the pores of the microporous temporary sintered body. If so, the microporous pre-sintered body is immersed in a sol in which fine particles of silicon dioxide are dispersed in a dispersion medium (hereinafter also referred to as "silicon dioxide sol") for a certain period of time, and then the dispersion medium is A method that removes is preferred.

The silicon dioxide sol is not particularly limited as long as it is a liquid in which silicon dioxide is dispersed as a main component. A silicon dioxide sol in which silicon dioxide fine particles are dispersed in a dispersion medium is preferred, and a silicon dioxide sol in which water or alcohol is used as a dispersion medium is particularly preferred. Here, the term "main component" refers to a component containing 80% by mass or more based on the total mass of oxides dispersed in the silicon dioxide sol.

In the silicon dioxide sol, the concentration of silicon dioxide dispersed in the silicon dioxide sol is preferably 0.03 to 0.9% by mass, more preferably 0.05 to 0.5% by mass. If the concentration of silicon dioxide is lower than 0.03% by mass, it may not be possible to obtain sufficient strength as a dental sintered body after main sintering, and if it is higher than 0.9% by mass, oxidation may occur. There is a possibility that transparency will decrease due to the difference in refractive index with zirconium, a possibility that sufficient strength as a dental sintered body cannot be obtained due to the low strength of silicon dioxide, and aggregation of silicon dioxide may occur. There is a possibility that the fine pores between the primary particles may not be impregnated.

Furthermore, the silicon dioxide fine particles contained as a main component in the silicon dioxide sol must necessarily have a size that allows them to enter the pores of the microporous pre-sintered body, and the average primary particle diameter thereof is as described above. It is preferable that the average pore diameter of the microporous pre-sintered body is smaller than the average pore diameter measured by mercury intrusion method, and it is preferably 2 to 100 nm, particularly 10 to 30 nm, while satisfying this condition. When the primary particle size of silicon dioxide fine particles is smaller than 2 nm, it is difficult to maintain a highly dispersed state and there is a possibility of agglomeration during the sorption process, and when the primary particle size is 100 nm or more, the microporous temporary The silicon dioxide fine particles cannot be impregnated into the inside of the sintered body, and there is a possibility that sufficient strength as a dental sintered body cannot be obtained.

Note that the primary particle diameter of the silicon dioxide fine particles is a value determined by a nitrogen adsorption method. That is, it means the average particle diameter calculated based on the specific surface area S determined by the nitrogen adsorption method of the dry powder obtained by drying the medium and the density of silicon dioxide.

The silicon dioxide sol may contain additives such as a binder, a dispersant, an emulsifier, and a pH adjuster in order to prevent precipitation of silicon dioxide fine particles.The additives may be used singly or in combination of two or more. May be used together.

Examples of the binder include polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, carboxymethylcellulose, polyacrylic acid, acrylic binder, wax binder, polyvinyl butyral, polymethyl methacrylate, ethylcellulose, polyethylene glycol, glycerin, propylene glycol, dibutylphthalic acid. Examples include.

Examples of dispersants include ammonium polycarboxylate, ammonium polyacrylate, acrylic copolymer resin, acrylic ester copolymer, polyacrylic acid, bentonite, carboxymethylcellulose, anionic surfactant, and nonionic surfactant. agents, oleic glycerides, amine surfactants, oligosaccharide alcohols, etc.

Examples of emulsifiers include alkyl ethers, phenyl ethers, sorbitan derivatives, and ammonium salts.

Examples of the pH adjuster include ammonia, ammonium salts, alkali metal salts, and alkaline earth metal salts.

Furthermore, the silicon dioxide sol may contain a zirconia coloring component or a fluorescence imparting component. Examples of coloring components include iron ions and cobalt ions, and examples of fluorescence-imparting components include bismuth ions and neodymium ions.

The method of immersing the microporous temporary sintered body in silicon dioxide sol for a certain period of time is not particularly limited as long as the silicon dioxide sol permeates into the pores of the microporous temporary sintered body. It may be under normal pressure or under pressurized pressure. The immersion time can also be freely selected as long as the time allows the silicon dioxide sol to sufficiently penetrate into the pores of the microporous temporary sintered body. The immersion temperature can be freely selected as long as it is a temperature that allows the silicon dioxide sol to sufficiently penetrate into the pores of the microporous pre-sintered body. It is preferable that there be.

The method for removing the dispersion medium is not particularly limited as long as it is a method that can remove the solvent of the silicon dioxide sol, but it is possible to easily remove the solvent while maintaining the shape of the microporous temporary sintered body. From a certain point of view, it is preferable to employ a reduced pressure drying method and/or a heat drying method. Here, the reduced pressure drying method is a method of removing the dispersion medium under reduced pressure of, for example, 800 hectopascals or less, and the heat drying method is a method of removing the dispersion medium at a temperature of room temperature or higher, and the reduced pressure By heating at a temperature lower than the boiling point of the dispersion medium, removal (drying) of the dispersion medium can be performed at a temperature lower than the boiling point of the dispersion medium.

Further, the calcination treatment may be performed again together with the drying step, and may be performed simultaneously or in multiple stages.

Next, the raw material composition preparation step (B) will be explained. In the raw material composition preparation step, the average primary particle diameter of the zirconia base powder measured by a dynamic light scattering method is 1 to 500 nm. A silicon dioxide precursor made of a silicon dioxide source material made of amorphous silicon dioxide particles and/or a silicon-containing substance that can be converted into a silicon dioxide compound by sintering: 0.05 to 5.0 parts by mass is uniform Prepare a raw material composition that is dispersed in

When using amorphous silicon dioxide particles, from the viewpoint of effectiveness, it is measured by a dynamic light scattering method (for example, using ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd. as a measuring device and using water as a dispersion medium). Amorphous nano silicon dioxide particles having an average primary particle diameter of 5 to 100 nm, particularly 5 to 50 nm are preferable.

When using the silicon-containing substance as a silicon dioxide precursor, the silicon-containing substance is not particularly limited as long as it can be converted into a silicon dioxide compound by sintering, and inorganic or organic silicon compounds can be used. can. It is preferable to use an organosilicon compound from the viewpoint that it can be easily converted into a silicon dioxide compound by sintering. As such an organosilicon compound, an organosilicon compound having an Si--O bond and having a molecular weight of 500 or less in terms of one molecule of silicon is suitable. Examples of organosilicon compounds that can be suitably used include tetraethoxysilane, tetramethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, triethylsiloxane, hexamethylcyclotrisiloxane, and silicone oil. It is particularly preferred to use tetraethoxysilane and/or tetramethoxysilane because of their high silicon content.

Further, the amorphous silicon dioxide particles and/or the silicon dioxide precursor (hereinafter also collectively referred to as "silicon dioxide precursor etc.") contained in the zirconia composite pre-sintered body obtained in (B). The content should be 0.05 to 5.0% by mass, more preferably 0.09 to 1.0% by mass in terms of silicon dioxide based on the mass of the zirconia composite pre-sintered body. It is 5% by mass. If the content of the silicon dioxide source material is lower than 0.05% by mass in terms of silicon dioxide, there is a possibility that sufficient strength as a dental sintered body will not be obtained after main sintering, and 5.0% by mass If the amount is larger than that, there is a possibility that the transparency will be reduced due to the difference in refractive index with zirconium oxide, and that sufficient strength as a dental sintered body may not be obtained due to the low strength of silicon dioxide.

The method of mixing the zirconia base powder and the silicon dioxide precursor, etc. may be any method that can prepare a raw material composition in which the zirconia base powder, the silicon dioxide precursor, etc. are uniformly dispersed. Although not particularly limited, the raw material composition is prepared by mixing the zirconia base powder and the silicon dioxide precursor etc. in the presence of a dispersion medium, and the raw material composition containing the obtained dispersion medium is mixed with the dispersion medium. Wet preparation is preferred, which removes.

The method of mixing the zirconia base powder and the silicon dioxide precursor, etc. includes a slurry or a dispersion liquid in which the zirconia base powder is dispersed in a dispersion medium, and a solution of an organosilicon compound and/or the nanoparticles in the dispersion medium. It is more preferable to mix a sol in which silicon dioxide particles are dispersed. The dispersion medium used in the wet preparation is not limited as long as it is a solvent in which the silicon dioxide precursor etc. can be dispersed or dissolved. For example, known solvents such as water, alcohols such as ethanol, and acetone can be used, but safe It is preferable to use water or alcohols from the viewpoint of stability and ease of solvent removal. Furthermore, since the raw material composition can be easily handled during the molding process, a mixing method that does not break down the secondary particles of the zirconia base powder during preparation is more preferred. Specifically, methods such as wet stirring, shaking, vibration, and ultrasonic waves can be employed, but mixing by wet stirring and shaking is more preferable.

The method for removing the dispersion medium from the raw material composition containing the dispersion medium is not particularly limited as long as the dispersion medium can be removed. It is preferable to employ a drying method and/or a heating drying method. Here, the vacuum drying method is a method in which a solvent is removed under a reduced pressure of, for example, 800 hectopascals or less, and the heat drying method is a method in which a solvent is removed at a temperature higher than room temperature. By heating, the organic solvent can be removed (drying) at a temperature lower than the boiling point of the organic solvent. From the viewpoint of not requiring treatment at high temperatures, even when a heat drying method is employed, it is preferable to dry at a temperature of 100° C. or lower by appropriately using a reduced pressure drying method. Furthermore, granulation may be performed together with drying using spray drying or the like.

1-2. Sintering Step In the sintering step, the composite zirconia pre-sintered body prepared in the above-mentioned calcined body preparation step is sintered at a temperature of 1250 to 1800°C.

The main sintering is preferably performed at a temperature of 1300°C or higher and 1700°C or lower, more preferably 1400°C or higher and 1600°C or lower. If the main sintering temperature is 1250°C or lower, sufficient sintering density, transparency, and strength may not be obtained, and if the sintering temperature is higher than 1800°C, the zirconium oxide There is a possibility that sufficient strength cannot be obtained due to excessive grain growth.

As the sintering method, conventionally known methods can be used without particular limitation, and the holding time at the sintering temperature is preferably 30 minutes to 4 hours.

1-3. Cooling process: In the cooling process, the sintered body sintered in the sintering process is heated to a temperature in the range of 400 to 900°C at a cooling rate of 100 to 900°C (°C/hour) {=1.7 to 15.0°C/min}. A first cooling step in which the sintered body cooled to the primary cooling temperature in the first cooling step is cooled to a predetermined temperature selected from 1000 to 9000° C./hour. A second cooling step is included in which the temperature is cooled to 50° C. or lower at a cooling rate of {=17.0 to 150.0° C./min}.

(1) First cooling process In the first cooling process, the sintered body sintered in the sintering process is heated to a predetermined temperature selected from the range of 400 to 900°C at a cooling rate of 100 to 900 (°C/hour). Cool until a certain primary cooling temperature is reached. Here, the cooling rate is the difference (°C) between the temperature of the sintered body (heating temperature) at the time of stopping heating in the sintering process and the primary cooling temperature. Means the average cooling rate divided by the time (hours) it takes to reach the cooling temperature.

The first cooling method is not particularly limited as long as it satisfies the above conditions, but since it involves high temperature conditions, a method of cooling in a sintering furnace is preferred, taking into account safety and the like.

The cooling rate in the first cooling step is preferably 350 to 800 (°C/hour), more preferably 450 to 750 (°C/hour). If the cooling rate is slower than 100°C/hour, the compressive stress that is expected to be applied to the sintered body will be removed by heat, and there is a possibility that a sufficient strength improvement effect will not be obtained. It takes a long time. If the cooling rate is faster than 900° C./hour, various members such as the sintered body and the sintered plate may not be able to cope with the thermal history and may be damaged due to extremely rapid cooling in the second cooling step.

Further, the primary cooling temperature in the first cooling step is preferably 400 to 750°C, more preferably 400 to 550°C. If the primary cooling temperature is lower than 400°C, silicon dioxide may not become low-density silicon dioxide glass, and the inherent compressive stress may not be sufficient, so a sufficient strength improvement effect may not be obtained. If the next cooling temperature is higher than 900° C., various members such as the sintered body and the sintered plate may not be able to cope with the thermal history and may be damaged due to extremely rapid cooling in the second cooling step.

(2) Second cooling process In the second cooling process, the sintered body cooled to the primary cooling temperature in the first cooling process is cooled at a cooling rate of 1000 to 9000°C (°C/hour) until the temperature reaches 50°C or less. Cooling. Here, the cooling rate is the average cooling rate obtained by subtracting 50℃ from the primary cooling temperature (℃) divided by the time (hours) from reaching the primary cooling temperature to reaching 50℃. means.

The method of second cooling is not particularly limited as long as the above conditions are achieved, but since the temperature inside the sintering furnace is high and it is difficult to increase the cooling rate, A preferred method is to take it out of the furnace and cool it in the atmosphere at room temperature.

The cooling rate in the second cooling step is preferably 1000 to 3000 (°C/hour), more preferably 1200 to 2500 (°C/hour). If the cooling rate is slower than 1000° C./hour, the compressive stress expected to be applied to the sintered body is removed by heat, and there is a possibility that a sufficient strength improvement effect cannot be obtained. If the cooling rate is faster than 9000° C./hour, various members such as the sintered body and the sintered plate may not be able to cope with the thermal history and may be damaged due to extremely rapid cooling.

2. Method for manufacturing a zirconia dental prosthesis The method for manufacturing a zirconia dental prosthesis of the present invention is different from the conventional method for manufacturing a zirconia prosthesis in which a zirconia mill blank is cut using a CAD/CAM system and then sintered. , a zirconia mill blank having a cut portion made of a composite zirconia pre-sintered body prepared in the pre-sintered body preparation step in the "method for producing zirconia composite ceramics of the present invention" was used, and further after main sintering. The present invention is characterized in that a cooling profile similar to that of the cooling step in the "method for producing zirconia composite ceramics of the present invention" is adopted for cooling. Since the obtained zirconia prosthesis is made of the zirconia composite ceramic obtained by the "method for producing zirconia composite ceramics of the present invention", it has higher strength than conventional zirconia prosthetics. For example, the biaxial bending strength of the material constituting the zirconia prosthesis obtained by the method for manufacturing a dental zirconia prosthesis of the present invention measured according to JIS T6526:2018 is as high as 800 to 2000 MPa, and is set to 1100 to 2500 MPa. It is also possible. Therefore, the method for manufacturing a dental zirconia prosthesis of the present invention is suitable as a method for manufacturing a prosthesis that requires high strength, such as a long span bridge.

Note that the zirconia dental mill blank having a cut part made of the composite zirconia pre-sintered body is different from the zirconia mill blank except that the material of the cut part is the composite zirconia pre-sintered body. There is no particular difference; for example, the part to be cut is preferably a block (solid) formed into a cylindrical shape, or a disk (solid) formed into a plate or disc shape, and this can be cut as necessary. It may have a holding part to enable it to be attached to a machine. Furthermore, a method for obtaining a semi-finished product having a shape corresponding to the shape of the intended dental prosthesis by cutting the zirconia mill blank using a CAD/CAM system can be carried out in the same manner as the conventional method. I can do it. Further, the obtained semi-finished product may be cut using a CAD/CAM system, and then the shape may be further modified using a technical engine or the like, or the surface may be polished. Further, if necessary, the color tone may be adjusted using a penetrating coloring agent, a clarifying liquid, or the like.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.

First, the raw materials used in each example and comparative example and their abbreviations and abbreviations will be explained.

1. Zirconia base powder ・ZpexSmile: Zirconium oxide manufactured by Tosoh Corporation, aluminum oxide content 0.05% by mass, yttrium oxide content 9.3% by mass, theoretical density: 6.050g/cm ³
・Zpex4: Zirconium oxide manufactured by Tosoh Corporation, aluminum oxide content 0.05% by mass, yttrium oxide content 6.9% by mass, theoretical density: 6.078g/cm ³
・Zpex: Zirconium oxide manufactured by Tosoh Corporation, aluminum oxide content 0.05% by mass, yttrium oxide content 5.3% by mass, theoretical density: 6.093g/cm ³
- TZ-8YSB: Zirconium oxide manufactured by Tosoh Corporation, aluminum oxide content 0.005% by mass or less (below the detection limit), yttrium oxide content 13.74% by mass, theoretical density: 6.011 g/cm ³ .

2. Silicon dioxide sol ・LUDOX-LS: Silicon dioxide sol manufactured by Sigma-Aldrich, content 30% by mass, primary particle size 12 nm, dispersion medium water ・LUDOX-SM: Silicon dioxide sol manufactured by Sigma-Aldrich, content 30% by mass, primary Particle size 7 nm, dispersion medium water.

3. Silicon dioxide precursor, etc. ・LUDOX-LS: Silicon dioxide sol manufactured by Sigma-Aldrich, content 30% by mass, primary particle diameter 12 nm, dispersion medium water ・TEOS: Tetraethoxysilane Si (OC ₂ H ₅ ) ₄ , Tokyo Chemical Industry Co., Ltd. Co., Ltd., molecular weight calculated as one molecule of silicon: 208 g/mol.

4. Dispersion medium - Distilled water: Manufactured by Fuji Film Wako Pure Chemical Industries, Ltd. - Ethanol: Manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.

Example 1 (Example using composite zirconia pre-sintered body obtained by dipping method)
(1) Production and evaluation of microporous temporary sintered body for adsorption 1.5 g of ZpexSmile (first raw material composition) was uniaxially pressed using a press mold with a diameter of 20 mm at a maximum load of 200 MPa to form a disk. A shaped body (thickness: 1.45 mm) was obtained. Thereafter, the molded body is pre-sintered using a ring furnace at 1000°C for 30 minutes to obtain a microporous pre-sintered body for adsorption (thickness: 1.45 mm). ) was obtained. The density was calculated from the mass and volume of the obtained disc-shaped microporous temporary sintered body, and the relative density was determined by dividing this by the theoretical sintered density, which was 49.8%.

Separately, a disk-shaped microporous temporary sintered body with a thickness of 5 mm was prepared in the same manner except that the amount of powder used was changed to 6.5 g, and then a prismatic sintered body with a size of 5 mm x 5 mm x 5 mm was prepared. A sample was cut out to prepare an average pore diameter measurement sample, and the average pore diameter was measured, and the average pore diameter was found to be 103 nm. The average pore diameter was determined using a fully automatic multifunctional mercury porosimeter (“POREMASTER” manufactured by Quantachrome), with a mercury surface tension of 480 erg/cm ² , a contact angle of 140°, a discharge contact angle of 140°, and a pressure of 480 erg/cm 2 . It was performed at 0 to 50,000 psia.

(2) Sorption process and evaluation of the obtained composite zirconia temporary sintered body A silicon dioxide sol was prepared by mixing 0.03 g of LUDOX-LS and 10 mL of ion-exchanged water. The microporous temporary sintered body for adsorption obtained in the manufacturing process of the microporous temporary sintered body for adsorption was immersed in the prepared silicon dioxide sol at room temperature and normal pressure (25°C, 1 atm), and left still for 1 hour. After that, it was taken out from the silicon dioxide sol and dried on a hot stirrer set at 120° C. for 20 minutes to obtain a composite zirconia temporary sintered body. A field emission electron probe microanalyzer (FE-EPMA) analysis was performed on a composite zirconia pre-sintered body separately prepared in the same manner, and the silicon dioxide content was determined to be 0.24% by mass based on the results. Met.

(3) Sintering process, cooling process, and evaluation of the obtained zirconia composite ceramics The obtained composite zirconia temporary sintered body was heated in an electric furnace from room temperature to 1450°C for 3 hours, and then heated to 1450°C for 2 hours. After holding for a period of time, it is slowly cooled in a sintering furnace at a rate of 600°C/hour to the primary cooling temperature of 500°C, and when it reaches 500°C, it is taken out to room temperature and rapidly cooled to below 50°C at a rate of 1500°C/hour. As a result, zirconia composite ceramics were obtained. When the biaxial bending strength and transparency of the obtained zirconia composite ceramic were evaluated as follows, the biaxial bending strength was 1065 MPa, and the contrast ratio: Yb/Yw was 0.648.

[Evaluation of biaxial bending strength]
Using a testing machine manufactured by Shimadzu Corporation, measurements were performed in accordance with JIS T6526:2018 under the conditions of a crosshead speed of 1.0 mm/min, a support circle diameter of 10 mm, and an indenter diameter of 1.4 mm. Further, the biaxial bending strength was calculated using the following formula.
δ=-0.2387×P×(X-Y)/b ²
X=(1+ν)×ln[(r2/r3) ² ]+[(1−ν)/2]×(r2/r3) ²
Y=(1+ν)×[1+{ln(r1/r3) ² }]+(1-ν)×(r1/r3) ²
δ [MPa]: Biaxial bending strength
P[N]: Testing power
b [mm]: Test piece thickness
ν: Poisson's ratio (0.31)
r1 [mm]: Support circle radius
r2 [mm]: Indenter radius
r3 [mm]: Test piece radius.

[Transparency evaluation]
This sintered body was polished to a thickness of 1 mm using water-resistant abrasive paper #800, #1500, and #3000, and then Superstar V (manufactured by Nippon Dental Industry Co., Ltd.), which is an abrasive for porcelain, hybrid resin, and zirconia, was applied. Both sides were polished to a mirror finish to prepare a sample for transparency evaluation. Transparency was determined by measuring the spectral reflectance of the above sample with a black background and a white background using a spectrophotometer (Tokyo Denshoku, spectrophotometer TC-1800MKII). Evaluation was made using the contrast ratio: Yb/Yw, which is the value (Yb) divided by the Y value (Yw) for a white background. Note that the smaller Yb/Yw is, the more transparent the material is.

Examples 2 to 7 and Comparative Examples 1 to 4
A microporous temporary sintered body and a composite zirconia temporary sintered body were prepared in the same manner as in Example 1, except that the type of zirconia base powder, the type and amount of silicon dioxide sol, and the cooling conditions were changed as shown in Tables 2 and 3. A sintered body and a zirconia composite ceramic were manufactured and evaluated in the same manner as in the examples. The evaluation results are shown in Table 5. In addition, "↑" in Tables 2 and 3 means "same as above", and "cooling temperature" in "primary cooling step" means "primary cooling temperature".

Example 8 (Example using composite zirconia pre-sintered body obtained by pre-addition method)
(1) Production and evaluation of composite zirconia temporary sintered body After weighing 30 g of ZpexSmile and 150 g of distilled water, 0.2 g of LUDOX-LS was added and mixed using a stirrer for 10 minutes. Thereafter, water was removed by reducing the pressure at 50° C. using an evaporator to obtain a raw material composition powder (second raw material composition).

A disk-shaped molded body (thickness: 1.45 mm) was obtained by uniaxially pressing 1.5 g of the obtained raw material composition powder using a press mold with a diameter of 20 mm at a maximum load of 200 MPa. Thereafter, the molded body was pre-sintered using a ring furnace at 1000° C. for 30 minutes to obtain a composite zirconia pre-sintered body (thickness: 1.45 mm). Separately, the pre-sintered composite zirconia produced in the same manner was analyzed using an X-ray fluorescence spectrometer (XRF), and based on the results, the content of the silicon dioxide source material in terms of silicon dioxide was determined to be 0.21 mass. %Met.

(2) Sintering process, cooling process, and evaluation of the obtained zirconia composite ceramic The obtained composite zirconia temporary sintered body was sintered in the same manner as in Example 1 to obtain a zirconia composite ceramic. When the biaxial bending strength of the obtained zirconia composite ceramic was evaluated, the biaxial bending strength was 1044 MPa.

Examples 9-10 and Comparative Examples 5-7
Composite zirconia pre-sintering was carried out in the same manner as in Example 8, except that the type of zirconia base powder, the type and amount of silicon dioxide precursor, the type of dispersion medium, and the cooling conditions were changed as shown in Tables 6 and 7. A body and a zirconia composite ceramic were manufactured and evaluated in the same manner as in Example 8. The evaluation results are shown in Table 8.

As understood from the results of Examples 1 to 10, when zirconia composite ceramics are manufactured by a method that satisfies the conditions specified in the present invention, a sintered body with high strength can be obtained, and the same amount of yttrium oxide can be obtained. It can be seen that the strength improvement rate in biaxial bending strength is 15% or more compared to the conventional zirconia sintered body containing a stabilizer consisting of the following and an aluminum oxide additive. On the other hand, in Comparative Examples 1, 2, and 5, in which the primary cooling temperature was less than the prescribed lower limit, and in Comparative Example 3, in which the cooling rate of the primary cooling step was less than the prescribed lower limit, biaxial bending of the main sintered body There is a tendency for the strength to be slightly improved compared to conventional zirconia sintered bodies containing the same amount of yttrium oxide stabilizer and aluminum oxide additive, but the strength improvement rate is less than 15%. be. Further, in Comparative Example 4 in which the content of aluminum oxide is less than the lower limit defined by the present invention, no improvement in biaxial bending strength is observed. Furthermore, in Comparative Example 6, where the content of silicon dioxide is higher than the upper limit specified by the present invention, the silicon dioxide becomes a brittle layer, resulting in a decrease in biaxial bending strength. In Comparative Example 7, where the content was less than the prescribed lower limit, a sufficient strength improvement effect could not be obtained because the content of silicon dioxide was small.

Reference Examples 1 to 5 (Examples in which conventional zirconia sintered bodies were manufactured using conventional temporary sintered bodies that were not composited with silicon dioxide components)
In Reference Example 1, a composite zirconia pre-sintered body and a zirconia composite ceramic were obtained in the same manner as in Example 1, except that 10 mL of ion-exchanged water not containing silicon dioxide was used instead of the silicon dioxide sol for immersion. Further, in Reference Examples 2 to 5, composite zirconia pre-sintered bodies and zirconia composite ceramics were produced in the same manner as in Reference Example 1, except that the type of zirconia base powder and the cooling conditions were changed as shown in Table 4. Regarding the zirconia base powder, preliminary sintering conditions, main sintering conditions, and cooling conditions, Reference Example 1 is the same as Example 1, Reference Example 2 is the same as Comparative Example 2, and Reference Examples 3 and 4 are the same as Example 1. The same as Examples 6 and 7, respectively. Table 5 shows the evaluation results of the obtained composite zirconia pre-sintered body and zirconia composite ceramics.

As shown in Table 5, the biaxial bending strength of the sintered bodies obtained in Example 1 and Examples 6 and 7 was improved by 15% or more. Moreover, as is clear from the comparison between Reference Examples 1 and 2, when silicon dioxide is not included, no improvement in biaxial bending strength is observed even when the cooling conditions of the present invention are used.

Claims (3)

Zirconium oxide: 100 parts by mass, stabilizer consisting of yttrium oxide: 4 to 14 parts by mass, aluminum oxide additive: 0.005 to 0.3 parts by mass, and silicon dioxide or its precursor: 0.05 to 5. 0 parts by mass (however, the parts by mass of the silicon dioxide precursor represent parts by mass in terms of silicon dioxide), and the composite zirconia pre-sintered body contains the pre-sintered body of the zirconium oxide as a main structure. Temporary sintered body preparation process for preparing the body;
A sintering step of sintering the composite zirconia pre-sintered body prepared in the pre-sintered body preparation step at a temperature of 1250 to 1800°C; and a cooling step of cooling the sintered body sintered in the sintering step. A method for producing zirconia-based ceramics, comprising the steps of:
The cooling step is a first cooling step in which the sintered body is cooled at a cooling rate of 100 to 900° C./hour until it reaches a primary cooling temperature, which is a predetermined temperature selected from the range of 400 to 900° C. , a second cooling step in which the sintered body cooled to the primary cooling temperature in the first cooling step is cooled to 50° C. or less at a cooling rate of 1000 to 9000° C./hour,
A method for producing zirconia composite ceramics, characterized by: The provisional sintered body preparation step
(A) A first raw material containing a zirconia base powder containing 100 parts by mass of zirconium oxide, 4 to 14 parts by mass of a stabilizer consisting of yttrium oxide, and 0.005 to 0.3 parts by mass of an aluminum oxide additive. A step of forming a composition into a predetermined shape and then pre-sintering it at 600-1200°C to obtain a microporous pre-sintered body having a relative density of 45-65% and having pores opening toward the outside. ; and a step of sorbing 0.05 to 5.0 parts by mass of silicon dioxide fine particles per 100 parts by mass of zirconium oxide into the pores of the microporous pre-sintered body obtained in the above step,
A step of preparing a composite zirconia temporary sintered body in which fine particles of silicon dioxide are sorbed into the pores of the microporous temporary sintered body, or (B) Zirconium oxide: 100 parts by mass, yttrium oxide. A zirconia base powder containing 4 to 14 parts by mass of a stabilizer consisting of 4 to 14 parts by mass and 0.005 to 0.3 parts by mass of an aluminum oxide additive; "Precursor of silicon dioxide" consisting of "amorphous silicon dioxide particles having a particle size of 1 to 500 nm" and/or "a silicon dioxide source material consisting of a silicon-containing substance that can be converted into a silicon dioxide compound by sintering": 0. A raw material composition preparation step of preparing a second raw material composition in which 05 to 5.0 parts by mass are uniformly dispersed;
a molding step of molding the second raw material composition to obtain a molded body having a predetermined shape; and a pre-sintering step of pre-sintering the molded body at 600 to 1200°C;
A step of preparing a composite zirconia temporary sintered body made of the temporary sintered body obtained in the temporary sintering step,
A method for producing a zirconia composite presintered body according to claim 1. Zirconium oxide: 100 parts by mass, stabilizer consisting of yttrium oxide: 4 to 14 parts by mass, aluminum oxide additive: 0.005 to 0.3 parts by mass, and silicon dioxide or its precursor: 0.05 to 5. 0 parts by mass (however, the parts by mass of the silicon dioxide precursor represent parts by mass in terms of silicon dioxide), and the composite zirconia pre-sintered body contains the pre-sintered body of the zirconium oxide as a main structure. A cutting process in which a semi-finished product having a shape corresponding to the shape of the intended dental prosthesis is obtained by cutting a zirconia dental mill blank having a part to be cut consisting of a body using a CAD/CAM system. ;
A dental zirconia ceramic prosthesis comprising: a sintering step of sintering the semi-finished product obtained in the above step at a temperature of 1250 to 1800°C; and a cooling step of cooling the sintered body sintered in the sintering step. A method of manufacturing,
The cooling step is a first cooling step in which the sintered body is cooled at a cooling rate of 100 to 900° C./hour until it reaches a primary cooling temperature, which is a predetermined temperature selected from the range of 400 to 900° C. , a second cooling step in which the sintered body cooled to the primary cooling temperature in the first cooling step is cooled to 50° C. or less at a cooling rate of 1000 to 9000° C./hour,
A method for manufacturing a dental zirconia ceramic prosthesis, characterized by: