Zirconia-based ceramic green compact, method for producing the same, dental zirconia mill blank made of the zirconia-based ceramic green compact, and method for producing dental prosthesis using the dental zirconia mill blank

Abstract

To provide a zirconia-based ceramic calcined body used as a dental zirconia mill blank that can suppress chipping and cracking due to accidental loads such as loads and drops during cutting while maintaining good cutting workability.SOLUTION: Provided is for example, a stabilized zirconia or partially stabilized zirconia powder with an alumina additive added for high strength used as a raw material powder for conventional zirconia-based calcined ceramics. Amorphous silicon dioxide covers a neck, which serves as a joint between crystalline zirconium oxide particles, by calcining a powder containing 0.05-5.0 pts.mass of a silicon dioxide source material consisting of amorphous silicon dioxide particles or the like with an average primary particle size of 1-500 nm to 100 pts.mass in terms of silicon dioxide at 600-1200°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a zirconia-based ceramic green compact, a method for manufacturing the same, a dental zirconia mill blank made of the zirconia-based ceramic green compact, and a method for manufacturing a dental prosthesis using the dental zirconia mill blank, and the like.

Background Art

[0002] In recent years, with the development of ICT, the introduction of computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies has been progressing in the dental field. For example, regarding the production of dental crown prostheses, a CAD / CAM system that forms a dental prosthesis by cutting a dental processing blank made of a non-metallic material using a CAD / CAM device from a photographed image in the oral cavity has been increasingly used. Here, the dental processing blank means a workpiece (also called a mill blank) that can be attached to a cutting machine in a CAD / CAM system, and usually has a portion to be cut and a holding portion for attaching it to the cutting machine. As the portion to be cut, a (solid) block formed in the shape of a rectangular parallelepiped or a cylinder, or a (solid) disk formed in a plate-like or disk-like shape is generally known.

[0003] As a non-metallic material, zirconia-based ceramic materials are often used because they can produce dental prostheses with excellent strength, toughness, and high aesthetic properties. Since fully sintered zirconia-based ceramic materials are difficult to machine due to their strength, when manufacturing dental prostheses made of zirconia-based ceramics (hereinafter also referred to as "zirconia prostheses") using a CAD / CAM system, a zirconia-based ceramic green compact sintered at a relatively low sintering temperature is generally used as the machined part of the dental zirconia mill blank (simply also referred to as "zirconia mill blank"). Then, based on CAD considering shrinkage and the like that occur during full sintering at high temperature, it is machined into a shape corresponding to the shape of the finally obtained prosthesis by CAM, and then full sintering is performed to produce a densified and high-strength zirconia prosthesis.

[0004] Regarding zirconia-based ceramics, pure zirconia (zirconium oxide) undergoes a phase transition accompanied by volume change depending on temperature, so cracks may occur due to stress caused by volume change during the cooling process after sintering, leading to a decrease in strength. And in order to prevent such a phase transition, stabilizers such as yttrium oxide, calcium oxide, and magnesium oxide are added so that it can exist as a tetragonal crystal stable at high temperature or a mixed crystal system of tetragonal crystal and cubic crystal without transforming into a monoclinic crystal stable at low temperature even when cooled. Stabilized zirconia or partially stabilized zirconia has been developed. Such stabilized zirconia or partially stabilized zirconia is also used as the zirconia raw material powder used for zirconia mill blanks, and those added with alumina (additive) for further strengthening are generally used. For example, Patent Document 1 describes, as a raw material powder capable of providing a zirconia sintered body having both translucency and strength particularly suitable for anterior tooth dentures by sintering at atmospheric pressure, "yttria exceeding 4.0 mol% and not exceeding 6.5 mol%, containing less than 0.1 wt% of alumina, and having a BET specific surface area of 8 to 15 m 2 / g, characterized zirconia powder".

[0005] Furthermore, Patent Document 2 discloses a technique for improving the adhesiveness of a dental prosthesis made of stabilized zirconia or partially stabilized zirconia obtained by subjecting a molded body made of such zirconia powder to full sintering. An impregnating agent composed of a sol obtained by mixing a catalyst composed of tetraethyl orthosilicate (TEOS) and aluminum nitrate nonahydrate in water is impregnated into the surface layer portion of a stabilized or partially stabilized zirconia green compact, followed by full sintering, and then the surface layer portion is etched.

[0006] By the way, in a zirconia mill blank made of a zirconia-based ceramic green compact, there has been pointed out a problem that cracks and chips are likely to occur due to tightening stress when installing it in a CAM device or vibrations during cutting (see Patent Document 3). According to Patent Document 3, it is said that the above problem can be solved by covering the outer peripheral portion joined to the CAM device with a cylindrical resin adapter.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] According to the technology disclosed in Patent Document 3, by using a resin adapter, it is possible to prevent cracks and chips from occurring during attachment to a CAM device or during cutting, but it does not increase the strength of the stabilized or partially stabilized zirconia green compact itself. Therefore, it is impossible to prevent cracks and chips from occurring due to loads during the production or handling of the stabilized or partially stabilized zirconia green compact, or due to accidental drops. Further, when the firing temperature of the zirconia mill blank is increased to improve the strength by densification, the machinability deteriorates.

[0009] Therefore, an object of the present invention is to provide a zirconia-based ceramic green compact capable of suppressing the occurrence of chips and cracks due to accidental loads such as loads during cutting and drops while maintaining good machinability, a method for manufacturing the same, and further, a dental zirconia mill blank made of the zirconia-based ceramic green compact and a method for manufacturing a dental prosthesis using the dental zirconia mill blank.

Means for Solving the Problems

[0010] The present invention solves the above problems, and a first aspect of the present invention is a zirconia-based ceramic green compact having a network skeleton with open pores as a basic structure, in which adjacent crystalline zirconium oxide particles are interconnected via a neck portion, containing a stabilizer, an aluminum oxide additive, and amorphous silicon dioxide, the content of the stabilizer and the aluminum oxide additive with respect to 100 parts by mass of the total mass of the crystalline zirconium oxide particles constituting the network skeleton is 4 to 14 parts by mass of the stabilizer and 0.005 to 0.3 parts by mass of the aluminum oxide additive, respectively, the content of the amorphous silicon dioxide with respect to 100 parts by mass of the total mass of the crystalline zirconium oxide particles, the stabilizer, and the aluminum oxide additive is 0.05 to 5.0 parts by mass, at least a part of the amorphous silicon dioxide covers the surface of the neck portion of the network skeleton and a relative density defined as a ratio of the density of the zirconia-based ceramic green compact to the theoretical density of a fully sintered body that contains crystalline zirconium oxide particles, a stabilizer, and an aluminum oxide additive, does not contain amorphous silicon dioxide, and the contents of the stabilizer and the aluminum oxide additive relative to the total mass of the crystalline zirconium oxide particles are the same as those in the zirconia-based ceramic green compact, is 45 to 65%, It is the above-mentioned zirconia-based ceramic green compact characterized by the above.

[0012] In the zirconia-based ceramic green compact of the above form (hereinafter, also referred to as "the green compact of the present invention"). It is preferable that the amorphous silicon dioxide adheres so as to cover the surface of the neck portion in the network skeleton.

[0013] The second aspect of the present invention is a method for manufacturing the green compact of the present invention, 100 parts by mass of crystalline zirconium oxide powder, 4 to 14 parts by mass of stabilizer, and 0.005 to 0.3 parts by mass of aluminum oxide additive, 100 parts by mass of base powder that gives stabilized zirconia or partially stabilized zirconia by complete sintering, amorphous silicon dioxide particles having an average primary particle diameter of 1 to 500 nm measured by the dynamic light scattering method and / or a silicon source material composed of a silicon-containing substance that can be converted into a silicon dioxide compound by firing: 0.05 to 5.0 parts by mass in terms of the total mass part of silicon dioxide, and a raw material composition preparation step of preparing a raw material composition in which the base powder and the silicon source material are uniformly dispersed; A molding step of molding the raw material composition to obtain a molded body having a predetermined shape; and A green sintering step of sintering the molded body at 600 to 1200 ° C; including In the green sintering step, a network skeleton having open pores in which the particles constituting the crystalline zirconium oxide powder are interconnected via neck portions is formed, and a zirconia-based ceramic green compact in which amorphous silicon dioxide adheres to the surface of the network skeleton is obtained. It is characterized by the above-mentioned method.

[0014] In the manufacturing method of the above-described form (hereinafter, also referred to as "the method for manufacturing a green compact of the present invention"), in the step of preparing the raw material composition, amorphous nanosilica particles having an average primary particle diameter of 5 to 100 nm measured by the dynamic light scattering method and / or an organosilicon compound having a molecular weight of 500 or less in terms of 1 molecule of silicon are used as the silicon dioxide source material. In the step of preparing the raw material composition, the base powder and the silicon dioxide source material are mixed in the presence of a dispersion medium to prepare the raw material composition, and after removing the dispersion medium from the obtained raw material composition containing the dispersion medium, the molding step is performed, which is preferable. Further, in the preferred embodiment, it is preferable to mix a slurry or dispersion in which the base powder is dispersed in the dispersion medium, a solution of the organosilicon compound having a molecular weight of 500 or less in terms of 1 molecule of silicon, and / or a sol in which the nanosilica particles are dispersed in the dispersion medium.

[0015] The third form of the present invention is a dental zirconia mill blank (hereinafter, also referred to as "the zirconia mill blank of the present invention") characterized by having a machined portion configured by the green compact of the present invention.

[0016] The fourth form of the present invention is a step of obtaining a semi-finished product having a shape corresponding to the shape of a target dental prosthesis by machining the machined portion of the zirconia mill blank of the present invention using a CAD / CAM system; and Zirconia-based ceramic green compact and a step of sintering the semi-finished product obtained in the above step at a temperature exceeding 1200 °C and not exceeding 1800 °C to obtain a dental zirconia ceramic prosthesis; This is a method for manufacturing a dental zirconia ceramic prosthesis (hereinafter, also referred to as "the prosthesis of the present invention") including the above steps.

[0017] The fifth aspect of the present invention is a method for manufacturing a zirconia composite ceramic, which has a basic structure in which aluminum oxide crystal grains as additives are dispersed in a polycrystalline structure in which the same or different zirconia crystals solid-solved with a stabilizer are joined, and further contains silicon dioxide. The method includes a main sintering step of sintering the zirconia-based ceramic green compact of the present invention at a temperature exceeding 1200°C and not exceeding 1800°C (hereinafter, also referred to as "the main sintering body manufacturing method of the present invention").

Advantages of the Invention

[0018] The green compact of the present invention has excellent characteristics of good machinability and being less likely to chip or crack. Further, according to the method for manufacturing the green compact of the present invention, the green compact of the present invention can be efficiently manufactured.

[0019] And, since the machined part of the zirconia mill blank of the present invention is composed of the zirconia-based ceramic green compact of the present invention having such characteristics, it is possible not only to prevent the occurrence of cracks and chips due to clamping stress when installing in a CAM device or vibration during cutting without using a resin adapter, but also to be less likely to be damaged by accidental loads during handling.

[0020] Furthermore, the zirconia composite ceramic obtained by the main sintering body manufacturing method of the present invention has a characteristic that its biaxial flexural strength is significantly higher than that of a stabilized or partially stabilized zirconia main sintering body not containing silicon dioxide. The dental zirconia ceramic prosthesis produced using the zirconia mill blank of the present invention also has such characteristics.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0022] The reason why the green compact of the present invention exhibits the above-described effects is not necessarily clear, and the present invention is not restricted by any logic. However, as a result of scanning electron microscope observation, the surface of the neck portion in the network skeleton having open pores in which adjacent crystalline zirconium oxide particles are interconnected via the neck portion was covered with amorphous silicon dioxide. Therefore, it is presumed that the formation of a slight glass layer in the neck portion, which is likely to be a fracture origin, makes it difficult for stress concentration to occur, or that the stress is relaxed during the branching and propagation of fine cracks generated by stress within the ultrafine particles of amorphous silicon dioxide. And, since the formed glass layer is extremely small in amount and the aggregate of ultrafine particles of amorphous silicon dioxide is not high in strength, it is presumed that no decrease in machinability occurred.

[0023] Hereinafter, the present invention will be described in detail. In this specification, unless otherwise specified, the notation "x to y" using numerical values x and y means "x or more and y or less". In such a notation, when a unit is attached only to the numerical value y, the unit is also applied to the numerical value x.

[0024] 1. Green Compact of the Present Invention Except for containing a predetermined amount of amorphous silicon dioxide, the green compact of the present invention is the same as the green compact (conventional green compact) of "stabilized zirconia or partially stabilized zirconia powder to which an alumina additive is added for strengthening (conventional raw material powder)" used as the machined part of a conventional zirconia mill blank, and contains crystalline zirconium oxide particles, a stabilizer, and an alumina additive, and the content ratios thereof are also within the range of those in the conventional green compact. And its basic structure is also the same as the basic structure of the conventional green compact. That is, the green compact of the present invention has a network skeleton with open pores, in which adjacent crystalline zirconium oxide particles are interconnected via neck portions, as its basic structure. The existence form of the stabilizer and the alumina additive in this network skeleton does not change particularly from that in the conventional green compact. For example, the stabilizer basically exists in a solid solution in the crystalline zirconium oxide particles, and the alumina particles constituting the alumina additive are incorporated into the network in a form that replaces the crystalline zirconium oxide particles, and a part thereof adheres to the network surface. Also, in some cases, a part of the alumina exists in a solid solution or precipitates in the crystalline zirconium oxide particles.

[0025] The green compact of the present invention contains a predetermined amount of amorphous silicon dioxide, specifically 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the total mass of the crystalline zirconium oxide particles, the stabilizer, and the alumina additive, and the maximum feature lies in that the amorphous silicon dioxide covers the surface of the neck portion of the network skeleton. As shown in Comparative Example 7 described later, even when the amorphous silicon dioxide is contained in the above range of 0.05 to 5.0 parts by mass, if the aggregates of the amorphous silicon dioxide are locally dispersed and do not cover the surface of the neck portion, the chipping resistance cannot be improved.

[0026] Note that the fact that amorphous silicon dioxide covers the surface of the neck portion of the network skeleton means that a part of the amorphous silicon dioxide is in contact with and covers the surface of the neck portion, and it may be present on the surfaces other than the neck portion. The state of existence of amorphous silicon dioxide in such a green compact of the present invention can be confirmed by observation with a scanning electron microscope (SEM). For example, as shown in FIG. 1, a form in which a large number of ultrafine particles of amorphous silicon dioxide aggregate and adhere so as to cover the surface of the neck portion of the network skeleton (in FIG. 1, ultrafine particles of amorphous silicon dioxide having a particle diameter of about 10 nm cover the surface of the neck portion, and the neck portion with the covered surface occupies most of the neck portion), or, as shown in FIG. 2, a form in which the surface of the neck portion is included or coated (in FIG. 2, highly transparent amorphous silicon dioxide covers the neck portion, and the number of neck portions with the covered surface occupies at least 30% of the total number of neck portions).

[0027] In the green compact of the present invention, when observed with a scanning electron microscope (SEM), the amorphous silicon dioxide is not unevenly distributed greatly (for example, there is no amorphous silicon dioxide in a spherical region with a diameter of 10 μm or more), nor is it sparsely present, and it is distributed over the entire network even with some degree of coarseness or fineness. For example, in a magnified view of 50,000 times, it is preferable that the surfaces of 20% or more, particularly 50% or more, and most preferably 70% or more of the total number of neck portions that are present in a large number in the network are covered with amorphous silicon dioxide.

[0028] Hereinafter, the components, composition, and structural characteristics of the green compact of the present invention will be described in detail.

[0029] In the green compact of the present invention, as the crystalline zirconium oxide particles, stabilizer, and aluminum oxide additive, the same ones as those in the conventional green compact can be used without particular limitation. However, the stabilizer needs to be contained in an amount of 5 to 14 parts by mass, preferably 5.5 to 12 parts by mass, based on 100 parts by mass of zirconium oxide. The aluminum oxide additive needs to be contained in an amount of 0.005 to 0.3 parts by mass, preferably 0.005 to 0.1 parts by mass, based on 100 parts by mass of zirconium oxide.

[0030] Amorphous silicon dioxide needs to be 0.05 to 5.0 parts by mass based on 100 parts by mass of the total mass of the crystalline zirconium oxide particles, stabilizer, and aluminum oxide additive. When the content of amorphous silicon dioxide is less than 0.05 part by mass, the effect of improving chipping resistance may not be obtained. When the content is more than 5.0 parts by mass, not only may the amorphous silicon dioxide part become a low-strength part in the green compact and the chipping resistance may decrease, but also since the strength of amorphous silicon dioxide is lower than that of zirconia after sintering, the strength may decrease and it may not be suitable as a dental prosthesis. From such a viewpoint, the content of amorphous silicon dioxide within the above criteria is preferably 0.1 to 3.0 parts by mass, more preferably 0.1 to 1.0 parts by mass.

[0031] The silicon dioxide contained in the green compact of the present invention needs to be amorphous. As shown in Comparative Example 6 described later, even when silicon dioxide is contained in an amount of 0.05 to 5.0 parts by mass within the above criteria and is crystalline, the chipping resistance cannot be improved.

[0032] The amorphous silicon dioxide in the present invention means silicon dioxide that, when measured using an X-ray diffractometer for (1) the calcined body of the present invention and (2) a calcined body that does not contain silicon dioxide and has the same contents of the stabilizer and aluminum oxide additive with respect to the total mass of the crystalline zirconium oxide particles, shows no distinct diffraction peaks derived from silicon dioxide crystals (such as quartz and cristobalite) in the diffraction pattern obtained in (1), and shows no difference other than the halo peak derived from amorphous silicon dioxide when compared with the diffraction pattern obtained in (2).

[0033] From the viewpoint of machinability, the calcined body of the present invention has a relative density of 45 to 65% is , particularly preferably 48 to 55%. Here, the relative density is defined as the ratio of the density of the zirconia-based ceramic calcined body: d (g / cm T ) to the theoretical density of a fully sintered zirconia-based ceramic that contains crystalline zirconium oxide particles, a stabilizer, and an aluminum oxide additive and does not contain amorphous silicon dioxide, and in which the contents of the stabilizer and aluminum oxide additive with respect to the total mass of the crystalline zirconium oxide particles are the same as those in the zirconia-based ceramic calcined body, that is, a fully sintered zirconia composed of zirconium oxide, a stabilizer, and an aluminum oxide additive and having the same composition: d 3 (g / cm 3 ), calculated as (d / d T ) × 100 (%).

[0034] The theoretical density of the above-mentioned fully sintered zirconia varies depending on the type and content of the stabilizer and the content of the alumina additive, and tends to slightly decrease as these contents increase from the theoretical density of 6.10 g / cm 3 of the tetragonal zirconia fully sintered body. For example, Table 1 of Patent Document 1 shows the theoretical density: d T of yttria and alumina-containing zirconia, which is reproduced below.

[0035]

Table 1

[0036] 2. Method for manufacturing green compact of the present invention The method for manufacturing a green compact of the present invention is as follows Base powder comprising 100 parts by mass of crystalline zirconium oxide powder, 4 to 14 parts by mass of stabilizer, and 0.005 to 0.3 parts by mass of aluminum oxide additive, which gives stabilized zirconia or partially stabilized zirconia by complete sintering: 100 parts by mass, and silicon dioxide source material comprising silicon dioxide and / or silicon-containing substance that can be converted into silicon dioxide compound by firing: 0.05 to 5.0 parts by mass in terms of total parts by mass of silicon dioxide, and a raw material composition preparation step of preparing a raw material composition in which the base powder and the silicon dioxide source material are uniformly dispersed; A molding step of molding the raw material composition to obtain a molded body having a predetermined shape; and A green sintering step of sintering the molded body at 600 to 1200 °C; including In the green sintering step, a zirconia-based ceramic green compact is obtained in which particles constituting the crystalline zirconium oxide powder are interconnected via neck portions to form a network skeleton having open voids, and amorphous silicon dioxide adheres to the surface of the network skeleton. This is the gist of the present invention

[0037] These steps will be described in detail below

[0038] 2-1. Raw material composition preparation step In the raw material composition preparation step, a raw material composition in which a base powder composed of crystalline zirconium oxide powder, a stabilizer, and an aluminum oxide additive and a silicon dioxide source material are uniformly dispersed is produced

[0039] (1) Base powder The base powder consists of 100 parts by mass of crystalline zirconium oxide powder, 4 to 14 parts by mass of a stabilizer, and 0.005 to 0.3 parts by mass of an aluminum oxide additive, and means a powder composition that provides stabilized zirconia or partially stabilized zirconia by complete sintering.

[0040] The above-mentioned crystalline zirconium oxide powder is not particularly limited as long as it consists of crystalline zirconium oxide particles. However, it is preferable to use crystalline zirconium oxide particles (particles composed of stabilized zirconia or partially stabilized zirconia) in which the stabilizer is solid-solved and has a tetragonal crystal structure or a mixed crystal structure of tetragonal and cubic crystals. For the reasons that the phase transformation of the crystal hardly occurs and the grain growth does not proceed too much due to sintering, it is preferable to use those having an average crystallite size of 0.001 μm to 50 μm, particularly 0.003 μm to 20 μm. Also, from the viewpoint of ease of handling the powder, the average secondary particle size of the crystalline zirconium oxide powder of the base powder is preferably 0.01 to 500 μm, particularly 0.05 to 100 μm.

[0041] As the stabilizer, those conventionally used as stabilizers for zirconium oxide such as yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, erbium oxide, etc. can be used without limitation, but yttrium oxide is particularly preferable. In addition, as described above, the stabilizer is preferably blended in a form solid-solved in the crystalline zirconium oxide powder. The content of the stabilizer needs to be 4 to 14 parts by mass with respect to 100 parts by mass of the crystalline zirconium oxide powder, and preferably 5 to 11 parts by mass. When the content of the stabilizer is less than 4 parts by mass, it may not become stabilized zirconia or partially stabilized zirconia upon complete sintering. When the content is more than 14 parts by mass, the zirconia sintered body after complete sintering may not have sufficient strength and may not be suitable for dental prostheses.

[0042] The aluminum oxide additive is included in the base powder as a sintering aid. Its content needs to be 0.005 to 0.3 parts by mass, preferably 0.005 to 0.1 parts by mass, based on 100 parts by mass of the crystalline zirconium oxide powder. When the content of the aluminum oxide additive is less than 0.005 parts by mass, the effect as a sintering aid may not be obtained. When the content is more than 0.3 parts by mass, the light transmittance may decrease due to the difference in refractive index from zirconium oxide, and the zirconia sintered body after complete sintering may not be suitable for dental prostheses.

[0043] The base powder can appropriately contain "other components" such as pigments, binders, fine fillers, light-shielding agents, fluorescent agents, etc., according to its use and the like.

[0044] As the pigment, inorganic pigments such as erbium oxide, cobalt oxide, iron oxide, manganese oxide, etc. can be preferably used. Also, those that are white before sintering but can be colored after sintering and used as pigments can be used. As the binder component, acrylic binders, olefin binders, waxes, etc. can be preferably used and are appropriately selected and used according to the molding method and the like.

[0045] (2) Silicon dioxide source material The silicon dioxide source material means amorphous silicon dioxide particles with an average primary particle diameter of 1 to 500 nm measured by the dynamic light scattering method and / or silicon-containing substances that can be converted into silicon dioxide compounds by firing, and can be used without particular limitation as long as it becomes amorphous silicon dioxide during the calcination process.

[0046] When using amorphous silicon dioxide particles as the silicon dioxide source material, from the perspective of the effect, it is preferably amorphous nanosilica particles with an average primary particle diameter of 5 to 100 nm, particularly 5 to 50 nm, measured by the dynamic light scattering method (for example, using ELSZ - 2000ZS manufactured by Otsuka Electronics Co., Ltd. as the measuring device and water as the dispersion medium).

[0047] When a silicon-containing substance is used as the silicon dioxide source material, the silicon-containing substance is not particularly limited as long as it can be converted into a silicon dioxide compound by firing, and inorganic or organic silicon compounds can be used. From the viewpoint of being easily convertible into a silicon dioxide compound by firing, it is preferable to use an organic silicon compound. As such an organic silicon compound, an organic silicon compound having an Si—O bond and a molecular weight of the organic silicon compound in terms of one molecule of silicon of 500 or less is suitable. Examples of the organic silicon compound that can be preferably used include tetraethoxysilane, tetramethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, triethylsiloxane, hexamethylcyclotrisiloxane, silicone oil, and the like. From the viewpoint of having a high silicon content, it is particularly preferable to use tetraethoxysilane and / or tetramethoxysilane.

[0048] (3) Preparation method In the raw material composition preparation step, a raw material composition in which the base powder and the silicon dioxide source material are uniformly dispersed is produced. The preparation method at this time is not particularly limited as long as it is a method in which the base powder and the silicon-containing compound are uniformly dispersed. However, wet preparation is preferred in which the base powder and the silicon dioxide source material are mixed in the presence of a dispersion medium to prepare the raw material composition, and the dispersion medium is removed from the obtained raw material composition containing the dispersion medium.

[0049] As a method for mixing the base powder and the silicon dioxide source material, it is more preferable to mix a slurry or dispersion in which the base powder is dispersed in a dispersion medium, a solution of an organosilicon compound, and / or a sol in which the nanosilica particles are dispersed in a dispersion medium. The dispersion medium used in the wet preparation is not limited as long as it is a solvent in which the silicon dioxide source material can be dispersed or dissolved. For example, water, alcohols such as ethanol, and known ones such as acetone can be used, but it is preferable to use water or alcohols from the viewpoints of safety and ease of solvent removal. Furthermore, since amorphous silicon dioxide easily adheres to the surface of the network skeleton in which crystalline zirconium oxide powder is formed after the calcination step, a mixing method that does not break the secondary particles of the zirconia powder during preparation is more preferable. Specifically, methods such as stirring, shaking, vibrating, and ultrasonic waves under wet conditions can be adopted, but mixing by stirring and shaking under wet conditions is more preferable.

[0050] 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. However, from the viewpoints of the short time required for solvent removal and the ability to remove almost all of the solvent, it is preferable to adopt a vacuum drying method and / or a heat drying method. Here, the vacuum drying method is a method of removing the solvent under reduced pressure, for example, at 800 hectopascals or less, and the heat drying method is a method of removing the solvent at a temperature of room temperature or higher. By heating under reduced pressure, the organic solvent can be removed (dried) at a temperature lower than the boiling point of the organic solvent. From the viewpoint of not requiring treatment at a high temperature, even when adopting the heat drying method, it is preferable to dry at a temperature of 100°C or lower by appropriately combining with the vacuum drying method, etc. Furthermore, granulation may be performed together with drying using spray drying or the like.

[0051] 2-2. Forming step In the forming process, the raw material composition produced in the raw material composition preparation process is formed to produce a formed body having a predetermined shape. At this time, the forming method is not particularly different from the conventional method of obtaining a formed body for a mill blank before sintering or calcination using a conventional raw material composition, and powder forming methods or green body forming methods such as press forming, extrusion forming, injection molding, casting, tape casting, forming by laminated manufacturing, forming by powder forming, forming by stereolithography, etc. can be used without particular limitation. Also, multi-step forming may be performed. For example, after uniaxially press-forming the raw material composition, it may be further subjected to CIP (Cold Isostatic Pressing) treatment. Also, in the forming process, a plurality of types of raw material compositions may be laminated and formed.

[0052] The shape of the formed body obtained in the forming process may be appropriately determined according to the shape of the target mill blank, but usually, a disk-shaped one (disk type), or a rectangular parallelepiped or substantially rectangular parallelepiped shape (block type), etc. are common.

[0053] 2-3. Calcination process In the calcination process, the calcined body of the present invention is obtained by sintering the formed body obtained in the forming process at a temperature in the range of 600 to 1200 °C, which is a temperature lower than the full sintering treatment. Before the calcination process, a debinding treatment may be performed at a temperature below 600 °C if necessary. Here, the debinding treatment means a treatment for volatilizing or decomposing and removing moisture, solvent, binder, etc. contained in the formed body obtained in the forming process. Also, the calcination process may be performed in multiple steps with sequentially increasing temperature, and the debinding treatment may be performed in the low-temperature calcination process.

[0054] In the pre-sintering process, heating causes diffusion (adhesion, fusion) of molecules and atoms on the surface of the crystalline zirconium oxide particles that make up the crystalline zirconium oxide powder, and a network skeleton with open pores (composed of polycrystals) is formed in which the particles that make up the crystalline zirconium oxide powder are interconnected via neck portions. And at this time, simultaneously, when the silicon-containing substance is used as the silicon dioxide source material, the silicon-containing substance is converted into amorphous silicon dioxide on the surface of the crystalline zirconium oxide particles and the neck portions are covered with amorphous silicon dioxide. Also, when the amorphous silicon dioxide particles are used as the silicon dioxide source material, the amorphous silicon dioxide particles attached to the surface of the crystalline zirconium oxide particles aggregate at the neck portions and cover the surface thereof.

[0055] When the pre-sintering temperature is lower than 600 °C, there is a possibility that the strength required to maintain the shape during processing cannot be obtained. When it is higher than 1200 °C, the density of the pre-sintered body of the present invention becomes high, and there is a possibility that good machinability cannot be obtained. From the viewpoint of improving the strength of the obtained pre-sintered body to a strength that is easy to handle and process, the pre-sintering temperature is preferably 800 to 1150 °C.

[0056] As the method for debinding and / or pre-sintering treatment, conventionally known methods can be used without particular limitation, and they may be carried out continuously or in multiple steps. However, when an organosilicon compound is used as the silicon dioxide source material, it is preferably carried out in an air atmosphere containing oxygen from the viewpoint of removing organic substances. Note that the debinding and / or pre-sintering treatment can also be carried out continuously by a method using the same apparatus as the molding process in the previous step, for example, the SPS (Spark Plasma Sintering) method, the HP (Hot Press) method, or the like.

[0057] Note that the component composition of the calcined body of the present invention is determined by the composition of the raw material composition, and the form of amorphous silicon dioxide in the calcined body of the present invention is determined by the present calcination step. Although the form of amorphous silicon dioxide can be confirmed quantitatively to some extent by SEM observation, there is a limit to its accuracy. Therefore, it can be said that the calcined body of the present invention is the calcined body obtained by the production method of the present invention.

[0058] 3. Zirconia mill blank of the present invention The zirconia mill blank of the present invention has no particular difference from the conventional zirconia mill blank except that the calcined body of the present invention is used for the machined part.

[0059] The shape of the zirconia mill blank of the present invention may be appropriately determined according to the shape of the target mill blank. Since it is used for dentistry, a disk-shaped one (disk type), a rectangular parallelepiped or substantially rectangular parallelepiped-shaped one (block type), etc. are common.

[0060] 4. Manufacturing method of prosthesis of the present invention The manufacturing method of the prosthesis of the present invention is By machining the machined part of the zirconia mill blank of the present invention using a CAD / CAM system, a semi-finished product having a shape corresponding to the shape of the target dental prosthesis is obtained; and Zirconia-based ceramic green compact A sintering step of sintering the semi-finished product obtained in the above step at a temperature exceeding 1200°C and not exceeding 1800°C to obtain a dental zirconia ceramic prosthesis; is characterized by including

[0061] In the step of obtaining the semi-finished product composed of the above Zirconia-based ceramic green compact By machining the machined part of the zirconia mill blank of the present invention using a CAD / CAM system, a semi-finished product having a shape corresponding to the shape of the target dental prosthesis is obtained, and the above Zirconia-based ceramic green compactA semi-finished product consisting of is obtained. Since it is necessary to attach the zirconia mill blank to the CAM device during cutting, the shape of the mill blank is preferably a (solid) block shape or plate shape formed into a rectangular parallelepiped or cylindrical shape, or a (solid) disk shape formed into a plate or disk shape, and may have a holding part for attaching it to a cutting machine as necessary.

[0062] The obtained semi-finished product may be further modified in form or polished on the surface using a dental engine or the like after cutting using a CAD / CAM system. Also, if necessary, the color tone may be adjusted using a penetrating type colorant, a transparentizing liquid, or the like.

[0063] In this sintering step, the semi-finished product obtained in the step of obtaining the semi-finished product made of the composite material is sintered at a temperature exceeding 1200°C and not exceeding 1800°C to be changed into a dental zirconia ceramic prosthesis. This sintering is preferably carried out at 1200 to 1800°C, and more preferably at 1400 to 1600°C. If the sintering temperature is 1200°C or lower, sufficient sintering density, translucency, and strength may not be obtained. If the sintering temperature is higher than 1800°C, sufficient strength may not be obtained due to excessive grain growth of zirconium oxide.

[0064] 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.

[0065] Also, after this sintering step, a shape correction step using a diamond bar or the like and a polishing step using a diamond paste or the like may be performed. Furthermore, in order to make the color tone closer to that of natural teeth aesthetically, a ceramic material or the like may be baked on the surface of the dental zirconia ceramic prosthesis of the present invention.

[0066] 5. Method for manufacturing the main sintered body of the present invention The method for manufacturing the main sintered body of the present invention is A method for manufacturing a zirconia composite ceramic having a basic structure in which aluminum oxide crystal grains as additives are dispersed in a polycrystalline structure in which the same or different zirconia crystals solid-dissolved with a stabilizer are joined, and further containing silicon dioxide. Characterized in that it includes a main sintering step of sintering the green compact of the present invention at a temperature exceeding 1200 °C and not exceeding 1800 °C.

[0067] The zirconia composite ceramic produced by the main sintering body manufacturing method of the invention has a basic structure of a polycrystalline structure in which zirconia crystals are joined, further contains silicon dioxide, and the silicon dioxide is unevenly distributed at the grain boundaries. Further, compared with zirconia ceramics having the same content of the stabilizer and the aluminum oxide additive, it has the feature that the biaxial bending strength measured according to JIS T6526:2018 is significantly high.

Example

[0068] The green compact of the present invention mainly has a basic structure having amorphous silicon dioxide on the surface layer of the neck portion of the network skeleton having open voids between adjacent crystalline zirconium oxide particles, and its manufacturing method also mainly has the feature of manufacturing the green compact of the present invention. Further, the manufacturing method of the patchwork of the present invention and the main sintering body manufacturing method of the present invention both mainly have the feature of obtaining a zirconia composite ceramic having a specific mechanical strength by sintering the green compact of the present invention. Therefore, the green compact manufacturing method of the present invention for obtaining the green compact of the present invention and the main sintering body manufacturing method of the present invention will be specifically described by showing examples and comparative examples. However, the present invention is not limited to these examples.

[0069] First, the raw materials used in each example and comparative example and their abbreviations, symbols, etc. will be described.

[0070] 1. 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: 6.050 g / cm 3 , average secondary particle size: 17 μm · Zpex4: Zirconium oxide manufactured by Tosoh Corporation, aluminum oxide content 0.05% by mass, yttrium oxide content 6.9% by mass, theoretical density: 6.078 g / cm 3 , average secondary particle size: 17 μm · TZ-3YSB-E: Zirconium oxide manufactured by Tosoh Corporation, aluminum oxide content 0.26% by mass, yttrium oxide content 5.2% by mass, theoretical density: 6.085 g / cm 3 , average secondary particle size: 20 μm.

[0071] 2. Silicon dioxide source materials · LUDOX-LS: Silicon dioxide sol manufactured by GRACE, content 30% by mass, primary particle size 12 nm, dispersion medium water · LUDOX-SM: Silicon dioxide sol manufactured by GRACE, content 30% by mass, primary particle size 7 nm, dispersion medium water · TEOS: Tetraethoxysilane Si(OC2H5)4, manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight per silicon atom 208 g / mol · KF-96A-6CS: Silicone oil manufactured by Shin-Etsu Chemical Co., Ltd., molecular weight per silicon atom 74 g / mol · Decamethylcyclopentasiloxane: Manufactured by TCI, molecular weight per silicon atom 74 g / mol · Sodium metasilicate: Manufactured by FUJIFILM Wako Pure Chemical Corporation, molecular weight per silicon atom 284 g / mol · TiO2sol: Titanium dioxide sol manufactured by Osaka Gas Chemical Co., Ltd., content 5% by mass, primary particle size 3 nanometers, dispersion medium water · HZ-NB: Tetrabutoxyzirconium Zr(OC4H9)4, manufactured by Kitakyo Chemical Industry Co., Ltd. · Crystalline silica: Quartz sand, manufactured by FUJIFILM Wako Pure Chemical Corporation · QS-102: Dry silica powder (amorphous, average particle diameter: 12 nm, average secondary particle diameter: 70 μm), manufactured by Tokuyama Corporation.

[0072] 3. Dispersion medium · Distilled water: manufactured by Fujifilm Wako Pure Chemical Corporation · Ethanol: manufactured by Fujifilm Wako Pure Chemical Corporation.

[0073] Example 1 (1) Process for producing a green compact and evaluation of the obtained green compact 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. Then, using an evaporator, water was removed by reducing the pressure at 50 °C to obtain a composite material powder.

[0074] 1.5 g of the obtained composite material powder was uniaxially pressed at a maximum load of 200 MPa using a press mold with a diameter of 20 mm to obtain a disk-shaped compact (thickness: 1.45 mm). Then, the compact was semi-sintered at 1000 °C for 30 minutes using a ring furnace to obtain a semi-sintered body (thickness: 1.45 mm). When the density was calculated from the mass and volume of the obtained disk-shaped semi-sintered body and divided by the theoretical sintered density to obtain the relative density, it was 49.8%. Furthermore, regarding the obtained semi-sintered body, when the crystallinity of the contained silicon dioxide and the chipping resistance of the semi-sintered body were evaluated as follows, the state of existence of silicon dioxide was ○, silicon dioxide was amorphous, and the chipping resistance was ○.

[0075] [Evaluation of crystallinity of silicon dioxide] Using an X-ray diffractometer manufactured by Rigaku Corporation, measurement was performed under the conditions of a measurement range of 2θ 10 to 70 deg., a step width of 0.05 deg., and a scan speed of 40 deg / min. The obtained spectrum was compared with the spectrum of a semi-sintered body consisting only of the base powder, and those showing no difference other than the halo peak indicating the presence of amorphous were regarded as amorphous, and those showing a difference were regarded as crystalline.

[0076] [Evaluation of Chipping Resistance] Five green compacts were prepared, and the appearance of the specimens after dropping the disc-shaped green compacts from a height of 20 cm while keeping them parallel to the ground was evaluated. The evaluation criteria are shown below. Evaluation Criteria ○: None of the five specimens showed cracks or chips. △: Four or three specimens showed no cracks or chips. ×: Two or fewer specimens showed no cracks or chips.

[0077] Separately, green compacts were obtained in the same manner except that the amount of powder used was changed to 6.5 g, the pressing die used was changed to 15.5 mm × 19.5 mm × 20.5 mm, and the green sintering time was changed to 2 hours. When the machinability of the obtained prismatic green compacts was evaluated as follows, the machinability was ○.

[0078] [Evaluation of Machinability] Pins for attaching to the cutting machine were adhered to the surface with the smallest surface area of the obtained prismatic green compacts. Then, cutting was performed into a molar crown shape using a cutting machine manufactured by Roland, and the machinability was evaluated. The evaluation criteria are shown below. Evaluation Criteria ○: Cutting was performed without problems. ×: Problems occurred and cutting could not be performed. Here, problems refer to damage to the part to be cut, damage to the bar, errors in the program of the processing machine, etc.

[0079] (2) Evaluation of the Full Sintering Process and the Obtained Full Sintered Body The obtained green compacts were sintered in an electric furnace under the conditions of 1450 °C for 2 hours to obtain full sintered bodies. When the biaxial flexural strength of the obtained full sintered bodies was evaluated as follows, the biaxial flexural strength was 1044 MPa.

[0080] [Evaluation of Biaxial Flexural Strength] Using a testing machine manufactured by Shimadzu Corporation, measurements were carried out 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 a indenter diameter of 1.4 mm. Also, 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]: Test force b [mm]: Specimen thickness ν: Poisson's ratio (0.31) r1 [mm]: Support circle radius r2 [mm]: Indenter radius r3 [mm]: Specimen radius Examples 2 to 15 and Comparative Examples 1 to 6 The base powder type, the type and blending amount of the silicon dioxide source material, the type of the dispersion medium, and the temperature of the green compact were changed as shown in Tables 2 and 3, and the green compact and the sintered body were produced in the same manner as in Example 1, and the evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 5. In Tables 2 and 3, "↑" means "the same as above".

[0081] Comparative Example 7 30 g of ZpexSmile and 0.20 g of QS-102 were weighed and mixed for 10 minutes by dry vibration by hand to obtain a raw material composition.

[0082] The obtained raw material composition was used to produce a green compact and a sintered body in the same manner as in Example 1, and the evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 5.

[0083] As can be understood from the results of Examples 1 to 15, when a green compact satisfying the conditions defined in the present invention is manufactured, silicon dioxide present on the surface of the neck portion in the crystalline zirconia network structure similar to FIG. 1 is confirmed, and a green compact having sufficient machinability and chipping resistance is obtained, and further, it can be seen that a sintered compact having higher strength is obtained.

[0084] On the other hand, in Comparative Example 1 where the content of the silicon dioxide source material is less than the lower limit defined in the present invention, since the content of amorphous silicon dioxide is small, only a very small amount of silicon dioxide was confirmed to be present on the surface of the neck portion in the crystalline zirconia network structure, but a sufficient effect of improving chipping resistance was not obtained. On the other hand, in Comparative Example 2 where the content of the silicon dioxide source material is more than the upper limit defined in the present invention, not only sufficient chipping resistance was not obtained but also the biaxial flexural strength decreased. Further, Comparative Example 3 with a high green compacting temperature is an example in which the density of the green compact was improved by raising the green compacting temperature. Although the chipping resistance was improved, the machinability decreased.

[0085] In Comparative Examples 4 and 5 where a compound other than the silicon dioxide source material was used for the base powder, chipping resistance was not obtained. Further, in Comparative Example 6 where crystalline silicon dioxide was used as the silicon dioxide source material, it did not become amorphous after green compacting and chipping resistance was not obtained. Comparative Example 7 in which a silicon-containing compound was added in the state of aggregates although it is amorphous is an example in which QS-102 composed of aggregated particles (secondary particles) of amorphous silica was so-called dry blended to prepare a raw material powder. As a result of SEM observation, amorphous silica was dispersed in the matrix composed of the network skeleton in the state of aggregated secondary particles (the primary particles did not exist so as to cover the surface of the neck portion), and chipping resistance was not obtained.

[0086] Reference Examples 1 to 3 (Examples of manufacturing a conventional zirconia sintered body using a conventional green compact) In Reference Example 1, a calcined body and a sintered body were obtained in the same manner as in Example 1, except that a silicon dioxide source material was not used. In Reference Examples 2 and 3, a calcined body and a sintered body were produced in the same manner as in Reference Example 1, except that the type of base powder was changed as shown in Table 4. Note that for the base powder composition, the calcination conditions, and the sintering conditions, Reference Example 1 was the same as Example 1, and Reference Examples 2 and 3 were the same as Examples 12 and 15, respectively. Table 5 shows the evaluation results of the obtained calcined bodies and sintered bodies.

[0087] As shown in Table 5, the calcined bodies obtained in Examples 1, 12, and 15 have equivalent machinability while having improved chipping resistance, and furthermore, the biaxial flexural strength of the sintered bodies is significantly improved in all cases.

[0088] [Table 2]

[0089] [Table 3]

[0090] [Table 4]

[0091] [Table 5] [Description of Symbols]

[0092] 1... Network skeleton 2... Crystalline zirconium oxide (primary) particles 3... Amorphous silicon dioxide 4... Open pores

Claims

1. A zirconia-based ceramic green compact having a network skeleton with open pores, in which adjacent crystalline zirconium oxide particles are interconnected via neck portions, containing a stabilizer, an aluminum oxide additive, and amorphous silicon dioxide, wherein the contents of the stabilizer and the aluminum oxide additive with respect to 100 parts by mass of the total mass of the crystalline zirconium oxide particles constituting the network skeleton are, respectively, stabilizer: 4 to 14 parts by mass and aluminum oxide additive: 0.005 to 0.3 parts by mass, wherein the content of the amorphous silicon dioxide with respect to 100 parts by mass of the total mass of the crystalline zirconium oxide particles, the stabilizer, and the aluminum oxide additive is 0.05 to 5.0 parts by mass, at least a part of the amorphous silicon dioxide covers the surface of the neck portion of the network skeleton, a relative density defined as the ratio of the density of the zirconia-based ceramic green compact to the theoretical density of a fully sintered body containing crystalline zirconium oxide particles, a stabilizer, and an aluminum oxide additive and not containing amorphous silicon dioxide, and having the same contents of the stabilizer and the aluminum oxide additive with respect to the total mass of the crystalline zirconium oxide particles as in the zirconia-based ceramic green compact, is 45 to 65%, The zirconia-based ceramic green compact characterized by the above.

2. The zirconia-based ceramic green compact according to claim 1, wherein the amorphous silicon dioxide is adhered so as to cover the surface of the neck portion in the network skeleton.

3. A method for producing the zirconia-based ceramic green compact according to claim 1 or 2, Crystalline zirconium oxide powder: 100 parts by mass, stabilizer: 4 to 14 parts by mass, and aluminum oxide additive: 0.005 to 0.3 parts by mass, a base powder that provides stabilized zirconia or partially stabilized zirconia by complete sintering: 100 parts by mass, and amorphous silicon dioxide particles having an average primary particle diameter of 1 to 500 nm measured by the dynamic light scattering method and / or a silicon source material composed of a silicon-containing substance that can be converted into a silicon dioxide compound by firing: 0.05 to 5.0 parts by mass in terms of total parts by mass of silicon dioxide, and a raw material composition preparation step of preparing a raw material composition in which the base powder and the silicon source material are uniformly dispersed; A molding step of molding the raw material composition to obtain a molded body having a predetermined shape; and A preliminary sintering step of sintering the molded body at 600 to 1200 °C; including, In the preliminary sintering step, particles constituting the crystalline zirconium oxide powder are interconnected via a neck portion to form a network skeleton having open pores, and a zirconia-based ceramic preliminary sintered body having amorphous silicon dioxide adhered to the surface of the network skeleton is obtained, The method as described above, characterized by this.

4. In the raw material composition preparation step, amorphous nanosilica particles having an average primary particle diameter of 5 to 100 nm measured by the dynamic light scattering method and / or an organosilicon compound having a molecular weight of 500 or less in terms of 1 molecule of silicon are used as the silicon source material, and in the raw material composition step, the base powder and the silicon source material are mixed in the presence of a dispersion medium to prepare the raw material composition, After removing the dispersion medium from the obtained raw material composition containing the dispersion medium, the molding step is performed, The method for manufacturing a zirconia-based ceramic preliminary sintered body according to claim 3.

5. Mixing a slurry or dispersion in which the base powder is dispersed in a dispersion medium, a solution of the organosilicon compound having a molecular weight of 500 or less, and / or a sol in which the nanosilica particles are dispersed in a dispersion medium, the method for producing a zirconia-based ceramic green compact according to claim 4.

6. A dental zirconia mill blank, characterized by having a machined portion configured by the zirconia-based ceramic green compact according to claim 1 or 2.

7. A step of obtaining a semi-finished product made of the zirconia-based ceramic green compact, which has a shape corresponding to the shape of a target dental prosthesis, by machining the machined portion of the dental zirconia mill blank according to claim 6 using a CAD / CAM system; and A final sintering step of sintering the semi-finished product obtained in the above step at a temperature exceeding 1200°C and not exceeding 1800°C to obtain a dental zirconia ceramic prosthesis. A method for producing a dental zirconia ceramic prosthesis, comprising the above steps.

8. A method for producing a zirconia composite ceramic, having as a basic structure a structure in which aluminum oxide crystal grains as an additive are dispersed in a polycrystalline structure in which the same or different zirconia crystals in which a stabilizer is solid-solved are joined, and further containing silicon dioxide, comprising: A final sintering step of sintering the zirconia-based ceramic green compact according to claim 1 or 2 at a temperature exceeding 1200°C and not exceeding 1800°C. A method for producing a zirconia composite ceramic, characterized by the above.

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