Method for manufacturing dental prosthesis

Abstract

The present invention provides a method for manufacturing a dental prosthesis in which defective baking of a porcelain material is suppressed by using a zirconia composite sintered body that contains Nb2O5 and / or Ta2O5. The present invention relates to a method for manufacturing a dental prosthesis, the method comprising a step for performing a heat treatment or a polishing treatment as a pretreatment on a zirconia composite sintered body that contains Nb2O5 and / or Ta2O5, and a step for building up a porcelain material on the pretreated zirconia composite sintered body and performing firing.

Description

Manufacturing method of dental prosthesis

[0001] The present invention relates to a method for manufacturing a dental prosthesis. More specifically, the present invention relates to a method for manufacturing a dental prosthesis using a zirconia composite sintered body containing NbO or TaO, in which poor porcelain bonding is suppressed.

[0002] Traditionally, metals have been commonly used for dental products (e.g., prosthetics such as veneers, dental crowns, crowns, and dental implants). However, metals have the drawback of being unaesthetic, and metal elution can cause allergies. Therefore, to solve the problems associated with the use of metals, ceramic materials such as aluminum oxide (alumina) and zirconium oxide (zirconia) have been used in dental products instead of metals. Zirconia sintered bodies, in particular, are excellent in aesthetics and strength, and demand for them is increasing, especially due to the recent decline in prices.

[0003] To improve the aesthetics of the oral cavity, it is necessary to make the appearance of dental products similar to that of natural teeth. However, it can be difficult to reproduce the same appearance as natural teeth, particularly the transparency, gloss (luster), and color tone, using a zirconia sintered body itself. Therefore, instead of exposing the zirconia sintered body, a veneer crown has been used in which a ceramic material called porcelain (e.g., Patent Document 1) is baked onto the exposed surface of a frame (substrate) formed from a zirconia sintered body, thereby reproducing the same appearance as natural teeth. Such dental products are called porcelain-fused-to-zirconia crowns (PFZ).

[0004] As shown in Patent Document 1, when building up porcelain on a zirconia sintered body, it was known that sandblasting the zirconia sintered body, which is the base material, to form irregularities on the surface and increase wettability before building up the porcelain would distribute the porcelain more uniformly on the base material and make firing easier. Also known was a method in which the zirconia sintered body, which is the base material, is not treated in any way when building up the porcelain, and the porcelain is built up directly on the base material.

[0005] Furthermore, since the zirconia sintered body has high hardness after being completely sintered, it is almost impossible to process it with a dental processing machine. For example, if a cubic zirconia sintered body is machined to obtain a zirconia sintered body having a shape that matches the shape of a patient's teeth, the metal processing tool will be worn out significantly and it will take an enormous amount of time to produce even just one dental prosthesis.

[0006] For these reasons, when using zirconia sintered bodies for dental material applications, they are usually not fully sintered, but rather a calcined body in a semi-sintered state that is easy to process is processed into the shape of the desired dental prosthesis, and then further sintered to produce a sintered body processed into the shape of the intended dental prosthesis. After that, the sintered body having the shape of the dental prosthesis is subjected to slight adjustment processing so that it fits comfortably in the patient's oral cavity when placed in the dental clinic. Therefore, the treatment period from the start of treatment to the completion of treatment, including visits to the dental clinic, often takes more than one month.

[0007] If the zirconia sintered body could be machined to a large extent, the treatment period from the start to the completion of treatment could be significantly shortened. From this perspective, zirconia sintered bodies have been proposed that have excellent machinability in the sintered body state and can be machined into the desired shape of a dental prosthesis from a prismatic or disc-shaped mill blank (for example, Patent Document 2, etc.).

[0008] Patent Document 2 discloses a processable zirconia, which is a sintered body formed to contain a tetragonal zirconia composite powder containing 79.8 to 92 mol% ZrO2, 4.5 to 10.2 mol% YO3, 3.5 to 7.5 mol% Nb2O5 or 5.5 to 10.0 mol% Ta2O5, and a TiO2 nanopowder whose mass ratio to the zirconia composite powder is more than 0 mass% and 2.5 mass% or less, and a method for producing the same.

[0009] JP 2017-122064 A JP 2015-127294 A

[0010] However, the present inventors have newly discovered a problem in that the porcelain does not bond to the substrate, whether the zirconia sintered body having the composition disclosed in Patent Document 2 is subjected to sandblasting as in Patent Document 1 and then porcelain is built up on the zirconia sintered body as a substrate, or the zirconia sintered body is not subjected to any treatment and then porcelain is built up on the zirconia sintered body as is as a substrate. In particular, this problem has been found to be more pronounced when so-called "glaze firing" is performed, in which a thin layer of porcelain is built up on a substrate (including coating or spraying with a spray-type porcelain) and then fired as a finishing step in the production of a prosthesis.

[0011] An object of the present invention is to provide a method for producing a dental prosthesis in which poor porcelain firing is suppressed by using a zirconia composite sintered body containing Nb2O5 and / or Ta2O5.

[0012] As a result of extensive research into solving the above problems, the present inventors have found that the problems can be solved by subjecting a zirconia composite sintered body containing NbO and / or TaO to a heat treatment or polishing treatment. Based on this finding, the inventors have conducted further research and have completed the present invention.

[0013] That is, the present invention encompasses the following inventions: [1] A method for manufacturing a dental prosthesis, comprising the steps of: subjecting a zirconia composite sintered body containing Nb2O5 and / or Ta2O5 to a heat treatment or polishing treatment as a pretreatment; and building up porcelain on the pretreated zirconia composite sintered body and firing it. [2] The method for manufacturing a dental prosthesis as set forth in [1], wherein the heat treatment is performed at a temperature of 150°C or higher and 1550°C or lower. [3] The method for manufacturing a dental prosthesis as set forth in [1], wherein in the polishing treatment, the surface roughness Ra of the zirconia composite sintered body after the polishing treatment is 8.0 μm or less. [4] The method for manufacturing a dental prosthesis according to [1] or [2], wherein the zirconia composite sintered body contains zirconia and a stabilizer capable of suppressing a phase transition of zirconia, and wherein, in a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, the zirconia content is 78 to 97.5 mol%, the stabilizer content is 1 to 12 mol%, and the Nb2O5 and / or Ta2O5 content is 1 to 9 mol%. [5] The method for manufacturing a dental prosthesis according to [4], wherein the zirconia composite sintered body further contains elements or ions derived from a capping agent. [6] The method for manufacturing a dental prosthesis according to [5], wherein the content of elements or ions derived from the capping agent is more than 0 mol% and not more than 5 mol%, relative to a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. [7] The method for manufacturing a dental prosthesis according to [5] or [6], wherein the element or ion derived from the capping agent is an element or ion thereof belonging to Periods 2 to 7 of the periodic table and having a first ionization energy smaller than that of Group 18 elements of the same period, and / or an element or ion thereof having a high electron affinity. [8] The method for manufacturing a dental prosthesis according to [5] or [6], wherein the element or ion derived from the capping agent comprises at least one element or ion thereof selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F. [9] The method for manufacturing a dental prosthesis according to [5] or [6], wherein the element or ion derived from the capping agent comprises at least one element or ion thereof selected from the group consisting of Li, Na, K, Rb, Cs, and Fr.

[10] A method for manufacturing a dental prosthesis according to any one of [4] to [9], wherein the ratio A / B is 0.9 or more and 3 or less, where A is the content of the stabilizer and B is the total content of Nb2O5 and Ta2O5 by mol%.

[11] A method for manufacturing a dental prosthesis according to any one of [4] to

[10] , wherein the stabilizer contains Y2O3 and / or CeO2.

[12] A method for manufacturing a dental prosthesis according to any one of [4] to

[11] , further comprising a zirconia reinforcement, wherein the content of the zirconia reinforcement is more than 0% by mass and 6.0% by mass or less, relative to 100% by mass of the total of zirconia, the stabilizer, Nb2O5, and Ta2O5.

[13] A method for manufacturing a dental prosthesis according to

[12] , wherein the zirconia reinforcement contains TiO2 and / or Al2O3.

[14] The method for manufacturing a dental prosthesis according to

[13] , wherein the zirconia reinforcement contains TiO2 and the TiO2 content is 0.6 to 4.5 mass%.

[15] The method for manufacturing a dental prosthesis according to any one of [1] to

[14] , wherein the zirconia composite sintered body has an average crystal grain size of 0.5 to 5.0 μm.

[0014] According to the present invention, a method for producing a dental prosthesis in which poor porcelain firing is suppressed can be provided by using a zirconia composite sintered body containing Nb2O5 and / or Ta2O5.

[0015] Fig. 1 is a photograph illustrating the frontal and occlusal views of anterior teeth, premolars, and molars. Fig. 2 is a photograph showing the evaluation results of glaze firing of a dental prosthesis obtained in Example 1 of the present invention. Fig. 3 is a photograph showing the evaluation results of glaze firing of a dental prosthesis obtained in Comparative Example 1 of the present invention.

[0016] The method for producing a dental prosthesis of the present invention includes the steps of: performing a heat treatment or a polishing treatment as a pretreatment on a zirconia composite sintered body containing NbO and / or TaO; and building up a ceramic layer on the pretreated zirconia composite sintered body and firing it.

[0017] As used herein, the term "green body" refers to a body that has not yet reached either a semi-sintered state (calcined state) or a sintered state. In other words, a green body is distinguished from a calcined body and a sintered body in that it is a green body formed by molding and then unsintered. As used herein, a "zirconia composite calcined body" refers to a body in a semi-sintered state in which the raw material powders, such as zirconia, are necked (adhered) and are not completely sintered. As used herein, a "zirconia composite sintered body" refers to a body in a sintered state in which the raw material powders, such as zirconia, are completely sintered. In a zirconia composite sintered body, the raw material powders, such as zirconia, solidify or dissolve with each other through sintering, increasing the relative density and promoting densification. As used herein, "zirconia" refers to zirconium(IV) oxide (ZrO), containing a trace amount (0.5% by mass to 3% by mass) of HfO relative to the amount of ZrO. Because HfO2 is difficult to separate, terms such as "zirconia" and "zirconia powder" refer to both ZrO2 and HfO2. Also, powders in which a stabilizer is dissolved in zirconia are included in the term "zirconia powder." In this specification, "in the atmosphere" refers to standard atmospheric pressure (1 atm). In this specification, "zirconia strengthening agent" refers to a component that improves the mechanical strength of a zirconia composite sintered body. In this specification, "build-up" refers to the application of a porcelain material to a substrate using a brush or the like, and includes the application of a porcelain material to a substrate or the application of a spray-type porcelain material to a substrate. The content (mass%) of the zirconia strengthening agent is the external addition rate relative to the total of zirconia, the stabilizer, Nb2O5, and Ta2O5 (100 mass%). Therefore, the content of the zirconia strengthening agent in a zirconia composite sintered body can be calculated from the amount (mass) of the raw materials used when adding the zirconia strengthening agent. In this specification, the content of each component in the zirconia composite sintered body can be calculated from the amount of raw material charged. In this specification, the machining includes cutting and grinding. The machining may be either wet machining or dry machining, and is not particularly limited.In this specification, "surface roughness Ra" means the arithmetic mean roughness in accordance with JIS B 0601: 2013. In this specification, the upper and lower limits of the numerical ranges (temperature range, content of each component, abundance rate of crystalline system, value calculated from components, etc., and each physical property, etc.) can be combined as appropriate.

[0018] The reason why the method for manufacturing a dental prosthesis of the present invention can suppress poor porcelain bonding to the zirconia composite sintered body as a substrate is unclear, but it is thought to be as follows. Because the zirconia composite sintered body as a substrate contains NbO and / or TaO, unlike zirconia sintered bodies obtained by machining a conventional calcined body, heat treatment or polishing of the zirconia composite sintered body modifies the state of the substrate surface after processing, thereby creating a state in which porcelain is easily bonded (high chemical affinity between the substrate surface and the porcelain). More specifically, for example, in a substrate containing NbO and / or TaO, hydrophilic groups on the substrate surface generated by wet processing are dehydrated and hydrophobized by heat treatment or polishing, which is thought to contribute to the improvement of poor porcelain bonding.

[0019] The heat treatment temperature in the method for manufacturing a dental prosthesis of the present invention is preferably 150°C or higher and 1550°C or lower, since this makes it easier to prevent poor porcelain adhesion. Compared to anterior teeth, which have many flat surfaces and simple shapes, premolars have many curved surfaces and also have complex shapes such as fossae and grooves visible in occlusal view, making it more difficult to prevent poor porcelain adhesion. Furthermore, as shown in Figure 1, molars, like premolars, have many curved surfaces, and the fossae and grooves visible in occlusal view have more complex shapes than premolars. Furthermore, the increased number of cusp tips results in a complex shape with greater differences in height between the fossae and grooves and the cusp tips, making it even more difficult to prevent poor porcelain adhesion. The heat treatment temperature is more preferably 180° C. or higher, even more preferably 200° C. or higher, and particularly preferably 250° C. or higher, from the viewpoint of easily preventing poor porcelain bonding regardless of the shape of the dental prosthesis, even if the dental prosthesis has parts with complex shapes such as many curved surfaces and many grooves in occlusal view.Furthermore, the heat treatment temperature is more preferably 1500° C. or lower, even more preferably 1450° C. or lower, and particularly preferably 1400° C. or lower, from the viewpoint of easily preventing poor porcelain bonding regardless of the shape of the dental prosthesis, even if the dental prosthesis has parts with complex shapes such as many curved surfaces and many grooves in occlusal view.

[0020] The heat treatment time in the method for producing a dental prosthesis of the present invention is preferably 10 seconds or more, more preferably 30 seconds or more, from the viewpoint of easily preventing poor porcelain adhesion, and is even more preferably 50 seconds or more, particularly preferably 1 minute or more, from the viewpoint of easily preventing poor porcelain adhesion regardless of the shape of the dental prosthesis, even if the dental prosthesis has a complex shape with many curved surfaces and many grooves in the occlusal view. The upper limit of the heat treatment time is not particularly limited as long as the effects of the present invention are achieved, but is preferably 120 minutes or less, more preferably 60 minutes or less, even more preferably 30 minutes or less, and particularly preferably 10 minutes or less, from the viewpoint of time constraints when actually performing the work in a clinical setting.

[0021] The heating device used for the heat treatment is not particularly limited as long as it can adjust the temperature range and heat treatment time to the above range, and a known heating device (e.g., a firing furnace, etc.) can be used. The heat treatment can also be performed in a vacuum state. By using a vacuum state, the heat treatment temperature can be set lower.

[0022] In the polishing treatment, the surface roughness Ra of the zirconia composite sintered body after the polishing treatment is preferably 8.0 μm or less, from the viewpoint of easily preventing poor porcelain bonding, and is more preferably 7.5 μm or less, even more preferably 5.0 μm or less, and particularly preferably 2.0 μm or less, from the viewpoint of easily preventing poor porcelain bonding regardless of the shape of the dental prosthesis, even if the dental prosthesis has complex shapes such as many curved surfaces and many grooves in the occlusal view. The lower limit of the surface roughness Ra is not particularly limited, but may be 0.001 μm or more. In the method for manufacturing a dental prosthesis of the present invention, completely opposite to the conventional method of roughening the surface by sandblasting, poor porcelain bonding can be prevented by polishing the surface so that the surface roughness Ra is within the above-mentioned range.

[0023] The polishing device and tool used in the polishing treatment are not particularly limited as long as they can adjust the surface roughness Ra to the above-mentioned range, and known polishing devices and tools can be used.

[0024] The shape of the zirconia composite sintered body in the method for producing a dental prosthesis of the present invention is preferably a machined shape so that it can be used as a dental prosthesis after building up porcelain and firing it.

[0025] Furthermore, in the method for manufacturing a dental prosthesis of the present invention, the heat treatment or polishing treatment is preferably performed as a pretreatment immediately before porcelain deposition. In other words, it is preferable not to perform an additional treatment after the heat treatment or polishing treatment to deposit porcelain, since this facilitates preventing poor porcelain deposition regardless of the shape of the dental prosthesis, even if the dental prosthesis has many curved surfaces, many grooves in the occlusal view, etc. When the heat treatment or polishing treatment is performed at such timing, even if the zirconia composite sintered body as the base material is first sandblasted to form surface irregularities, further heat treatment or polishing treatment can prevent poor porcelain deposition. Therefore, the method for manufacturing a dental prosthesis of the present invention may further include a sandblasting treatment before the heat treatment or polishing treatment. A preferred embodiment of the method for manufacturing a dental prosthesis includes a pretreatment before (preferably immediately before) depositing porcelain on a zirconia composite sintered body containing NbO and / or TaO, where the pretreatment is a heat treatment or polishing treatment. In the method for manufacturing a dental prosthesis of the present invention, the thickness of the porcelain to be built up is not particularly limited as long as the effects of the present invention are achieved, but for example, when performing glaze firing, the thickness of the porcelain after sintering may be 200 μm or less, 100 μm or less, or 50 μm or less. By setting the thickness of the porcelain within this range, a dental prosthesis with superior aesthetics can be obtained due to the properties of the porcelain.

[0026] The zirconia composite sintered body used in the method for manufacturing a dental prosthesis of the present invention contains Nb2O5 and / or Ta2O5. The zirconia composite sintered body used in the method for manufacturing a dental prosthesis of the present invention can also be the processable zirconia described in Patent Document 2. Specific examples of the zirconia composite sintered body include tetragonal composite zirconia containing 79.8 to 92 mol% ZrO2, 4.5 to 10.2 mol% YO3, and 3.5 to 7.5 mol% Nb2O5 or 5.5 to 10.0 mol% Ta2O5, and a sintered body formed so as to contain TiO2 in a mass ratio of more than 0 mass% and not more than 2.5 mass% relative to the composite zirconia.

[0027] In the zirconia composite sintered body of the present invention, the zirconia content is preferably 78 to 97.5 mol % relative to a total of 100 mol % of zirconia, the stabilizer, NbO, and TaO. From the viewpoint of achieving better translucency and strength, the zirconia content is more preferably 79 mol % or more and 96 mol % or less, even more preferably 80 mol % or more and 94 mol % or less, and particularly preferably 81 mol % or more and 93 mol % or less.

[0028] Examples of stabilizers capable of suppressing the phase transition of zirconia include calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide (Y2O3), cerium oxide (CeO2), scandium oxide (Sc2O3), lanthanum oxide (La2O3), erbium oxide (Er2O3), and praseodymium oxide (Pr2O3, Pr6O 11 Examples of the stabilizer include oxides such as samarium oxide (SmO), europium oxide (EuO), thulium oxide (TmO), gallium oxide (GaO), indium oxide (InO), and ytterbium oxide (YbO), and from the viewpoints of superior effects of the present invention and particularly superior aesthetics, YO (yttria) and / or CeO are preferred. The stabilizers may be used alone or in combination of two or more.

[0029] In the zirconia composite sintered body of the present invention, the content of the stabilizer is preferably 1 to 12 mol% based on a total of 100 mol% of zirconia, the stabilizer, NbO, and TaO, and is more preferably 2 mol% to 10 mol% in terms of easily obtaining sufficient machinability. From the viewpoint of more excellent translucency and strength, the content is even more preferably 3 mol% to 8.0 mol%, even more preferably 3.5 mol% to 7.5 mol%, particularly preferably 3.8 mol% to 7.0 mol%, and most preferably 4.0 mol% to 6.5 mol%. In one preferred embodiment, the stabilizer capable of suppressing the phase transition of zirconia contains YO and / or CeO, and the total content of YO and CeO is 2 mol% to 10 mol%. In another preferred embodiment, the stabilizer capable of suppressing the phase transition of zirconia contains Y2O3, and the Y2O3 content is 2 mol% or more and 10 mol% or less. In any of the above-mentioned embodiments, the Y2O3 and CeO2 contents can be appropriately changed within the ranges described in this specification. For example, in order to achieve better translucency and strength, the total content of Y2O3 and CeO2 may be 2.5 mol% or more and 10 mol% or less, or 3 mol% or more and 9 mol% or less.

[0030] Furthermore, the reason why the zirconia composite sintered body of the present invention has excellent machinability in a sintered state while maintaining strength is not clear, but it is presumed that this is achieved by improving fracture toughness (IF method) by additionally adding at least one of Nb2O5 and Ta2O5 to zirconia to which a conventional stabilizer has been added, and by minimizing hardness by coarsening the microstructure.

[0031] Furthermore, in the zirconia composite sintered body of the present invention, the content of Nb2O5 or Ta2O5 is 1 to 9 mol%, preferably 1.5 mol% to 8.5 mol%, based on a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. From the viewpoint of superior machinability, the content is more preferably 2.5 mol% to 8 mol%, and even more preferably 3 mol% to 7 mol%. If the Nb2O5 or Ta2O5 content is less than 1 mol%, sufficient machinability is difficult to obtain. If the Nb2O5 or Ta2O5 content exceeds 9 mol%, chipping occurs in the resulting zirconia composite sintered body, making it difficult to obtain sufficient physical properties. Furthermore, in a preferred embodiment, in terms of superior machinability, it is preferable that the total content of NbO and TaO in the zirconia composite sintered body of the present invention be within the above-mentioned range of each content (e.g., 1 mol% or more and 9 mol% or less).

[0032] As described above, NbO and TaO act to coarsen the microstructure and reduce hardness, and act together with the capping element or ion to impart excellent machinability. In addition, they maximize the sintered density through interaction with other components (e.g., TiO, AlO) added to the zirconia composite sintered compact and application of HIP, thereby ensuring the aesthetics of natural teeth in the resulting dental prosthesis.

[0033] The content of each of the above-mentioned components, zirconia, stabilizer, NbO, and TaO, is a percentage relative to a total of 100 mol% of zirconia, stabilizer, NbO, and TaO, and the total of zirconia, stabilizer, NbO, and TaO does not exceed 100 mol%. For example, if the raw material composition contains NbO but does not contain TaO, the content of each of the components, zirconia, stabilizer, and NbO means a content percentage relative to a total of 100 mol% of zirconia, stabilizer, and NbO.

[0034] Furthermore, when the content of the stabilizer is A mol % and the total content of Nb2O5 and Ta2O5 is B mol %, the ratio A / B is preferably 0.9 or more and 3 or less, more preferably 0.95 or more and 2 or less, from the viewpoint of machinability, and is even more preferably 1 or more and 1.6 or less, from the viewpoints that the effect of the capping element or ion acting together with Nb2O5 and / or Ta2O5 is enhanced, better machinability can be imparted, wear of the processing tool can be suppressed, and the number of dental prostheses obtained by continuous processing using one processing tool can be further increased.

[0035] In another preferred embodiment, the zirconia composite sintered body includes zirconia, a stabilizer capable of suppressing the phase transition of zirconia (hereinafter also referred to simply as "stabilizer"), and Nb2O5 and / or Ta2O5, and the zirconia content is 78 to 97.5 mol%, the stabilizer content is 1 to 12 mol%, and the Nb2O5 and / or Ta2O5 content is 1 to 9 mol%, based on a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. The preferred embodiment may also be a method for producing a dental prosthesis that does not contain elements or ions derived from a capping agent described below.

[0036] Another preferred embodiment includes a method for producing a dental prosthesis, wherein the zirconia composite sintered body contains zirconia, a stabilizer, and Nb2O5 and / or Ta2O5, and the total of the zirconia, the stabilizer, Nb2O5, and Ta2O5 is 100 mol %, wherein the zirconia content is 78 to 97.5 mol %, the stabilizer content is 1 to 12 mol %, the Nb2O5 and / or Ta2O5 content is 1 to 9 mol %, and the zirconia composite sintered body further contains elements or ions derived from a capping agent.

[0037] In this specification, the term "capping element or ion" refers to an element or ion derived from a capping agent that caps the ends of bonds in a zirconia composite sintered body made of a zirconia composite oxide containing NbO and / or TaO, thereby weakening the strength (hereinafter also referred to as "grain boundary strength") of the crystal interface (hereinafter also referred to as "grain boundary"). The capping agent can cap a portion of the grain boundary. "Capping" refers to the presence of a target element or ion (capping element or ion) at the grain boundary by bonding to the bonds of the zirconia composite oxide in place of the metal element. It is presumed that the presence of the capping element or ion at the grain boundary in the form of a +1-valent cation or a -1-valent anion causes electrostatic repulsion between the capped cations or anions, thereby weakening the grain boundary strength.

[0038] The contents of zirconia, stabilizer, NbO, and TaO in the zirconia composite sintered body can also be measured by, for example, inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence analysis, etc. The content (mol%) of the element or ion derived from the capping agent is the external addition rate relative to the total of zirconia, the stabilizer, NbO, and TaO, which is 100 mol%. Therefore, the content of the element or ion derived from the capping agent in the zirconia composite sintered body can be calculated by converting the amount (mass) of the raw material charged when added into mol%.

[0039] In the zirconia composite sintered body containing a capping element or ion, the presence of the capping element or ion at the grain boundary is presumably such that the capping element or ion acts in a direction that makes it easier for the grains to peel off by reducing the grain boundary strength in the form of a +1-valent cation or a -1-valent anion, making it easier to cut, and improving the machinability of the sintered body.

[0040] The capping element or ion becomes a +1-valent cation or a -1-valent anion at the grain boundary of the zirconia composite sintered body and bonds with a bond possessed by the zirconia composite oxide. This bond causes electrostatic repulsion between the cations or anions, weakening the grain boundary strength while maintaining the strength and translucency properties of the particles constituting the zirconia composite sintered body, and acting to improve the machinability of the sintered body. For example, a +1-valent cation may bond with the other bond of an oxygen atom bonded to a metal element (e.g., Zr, Hf, Y, Nb, or Ta) contained in the zirconia composite oxide in place of the metal element. Alternatively, a -1-valent anion may bond to an OH2 bonded to a metal element (e.g., Zr, Hf, Y, Nb, or Ta) contained in the zirconia composite oxide. + Furthermore, a form in which a −1-valent anion is bonded to a cation derived from a metal element (for example, Zr, Hf, Y, Nb, or Ta) contained in the zirconia-based composite oxide and bonded to another metal element is also conceivable.

[0041] Furthermore, since Nb2O5 and / or Ta2O5 act to coarsen the microstructure and reduce hardness in the zirconia composite sintered body, the capping element or ion and Nb2O5 and / or Ta2O5 act together to improve machinability. Therefore, the capping element or ion and Nb2O5 and / or Ta2O5 act together to further enhance excellent machinability while maintaining the strength required for artificial teeth, thereby shortening the machining time and suppressing wear of the machining tool, thereby increasing the number of dental prostheses that can be obtained by continuous machining using a single machining tool.

[0042] In the zirconia composite sintered body of the present invention, the capping element or ion further improves the machinability and acts as a free cutting aid as described above, without significantly impairing the strength and translucency.

[0043] The content of the capping element or ion contained in the zirconia composite sintered body used in the present invention is preferably more than 0 mol% and not more than 5 mol%, and from the viewpoint of being more excellent in machinability and being able to further increase the number of dental prostheses that can be continuously machined with one machining tool, it is more preferably 0.05 mol% or more and 3 mol% or less, even more preferably 0.06 mol% or more and 2.5 mol% or less, particularly preferably 0.07 mol% or more and 1.0 mol% or less, and most preferably 0.08 mol% or more and 0.34 mol% or less. Furthermore, when the capping element or ion contained in the zirconia composite sintered body used in the present invention is a Group 17 element or ion, the content is more preferably 0.2 mol% or more and 5 mol% or less, even more preferably 0.3 mol% or more and 4 mol% or less, particularly preferably 0.4 mol% or more and 3.5 mol% or less, and most preferably 0.5 mol% or more and 3.0 mol% or less, in terms of superior machinability and the ability to further increase the number of dental prostheses that can be continuously machined with one machining tool.

[0044] As mentioned above, the presence of capping elements or ions at the grain boundaries results in +1 cations or -1 anions, which can provide suitable interactions between the charged sites at the grain boundaries and the adsorption sites.

[0045] The capping element or ion is preferably an element or ion thereof belonging to Periods 2 to 7 of the periodic table and having a smaller first ionization energy than Group 18 elements of the same period, an element or ion thereof having a high electron affinity, nitrate ion, hypochlorite ion, chlorite ion, chlorate ion, perchlorate ion, bromate ion, permanganate ion, metaborate ion, or cyanide ion. A preferred embodiment includes a zirconia composite sintered body in which the element or ion thereof derived from the capping agent is an element or ion thereof belonging to Periods 2 to 7 of the periodic table and having a smaller first ionization energy than Group 18 elements of the same period, and / or an element or ion thereof having a high electron affinity.

[0046] Suitable examples of elements belonging to Periods 2 to 7 of the periodic table and having a first ionization energy smaller than that of Group 18 elements in the same period include Cu, Ag, Li, Na, K, Rb, Cs, and Fr, from the viewpoints of easier formation of +1-valent cations and superior machinability.

[0047] As elements with high electron affinity, Group 17 elements are preferred, since −1-valent anions are more easily obtained and machinability is superior. Preferred Group 17 elements are At, I, Br, Cl, and F.

[0048] The first ionization energy is the energy required to remove one electron from a neutral atom and ionize it. This can be the same as the first ionization energy described in "Schreiber-Atkins Inorganic Chemistry (Vol. 1), 4th Edition, Part I, Fundamentals, 1. Atomic Structure." The first ionization energy can be converted to units of "KJ / mol" using the unit "eV" described in "Schreiber-Atkins Inorganic Chemistry (Vol. 1), 4th Edition, Appendix 2," where 1 eV = 96.485 KJ / mol. The first ionization energy can also be determined using photoelectron yield spectroscopy (PYS). Electron affinity (EA) is the energy released when an electron is added to a neutral atom. Electron affinity can be measured by the difference in the energy gap from the ionization potential. The ionization potential is defined as the energy difference between the highest-energy occupied orbital of a compound's molecules and the vacuum level, and its value is measured using ultraviolet photoelectron spectroscopy. The first ionization energy and electron affinity may be determined using data stored in the NIST Chemistry WebBook (https: / / webbook.nist.gov / chemistry / ) (select "Ionization Energy" or "Electron Affinity" from "Ion energetics properties"). The first ionization energy and electron affinity are sufficient if they allow comparison of the likelihood of an element becoming a +1-valent cation or a -1-valent anion with other elements to be compared, and therefore the measurement methods described above can be used as appropriate.

[0049] Specific examples of the capping element include Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F. In terms of further improving machinability, Cu, Ag, Li, Na, K, Rb, Cs, Fr, I, Br, Cl, and F are preferred, and Li, Na, K, Rb, Cs, and Fr are more preferred. In a preferred embodiment, the element derived from the capping agent includes at least one element selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F, and the ion of the element is at least one +1-valent cation or −1-valent anion selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, I, Br, Cl, and F. In another preferred embodiment, the zirconia composite sintered body may include a zirconia composite sintered body in which the element or ion derived from the capping agent contains at least one element or ion thereof selected from the group consisting of Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F. The capping element or ion may be used alone or in combination of two or more.

[0050] As described above, the capping element or ion and NbO and / or TaO act together without impairing the effect of the stabilizer, so the stabilizer is not particularly limited and the effects of the present invention can be achieved.

[0051] In the zirconia composite sintered body containing a capping element or ion, the type of the stabilizer, the zirconia, and the content of the stabilizer can be the same as those in the above-described embodiment.

[0052] In zirconia composite sintered bodies containing capping elements or ions, the content of NbO or TaO is 1 to 9 mol%, preferably 1.5 mol% to 8.5 mol%, based on a total of 100 mol% of zirconia, the stabilizer, NbO, and TaO. In order to function in unison with the capping elements or ions and achieve superior machinability, the content is more preferably 2.5 mol% to 8 mol%, and even more preferably 3 mol% to 7 mol%. If the NbO or TaO content is less than 1 mol%, sufficient machinability is difficult to obtain. Furthermore, if the NbO or TaO content exceeds 9 mol%, chipping and other defects occur in the resulting zirconia composite sintered body, making it difficult to obtain sufficient physical properties. Furthermore, in a preferred embodiment, in terms of better machinability, it is preferable that the total content of NbO and TaO in the zirconia composite sintered body containing the capping element or ions is within the above-mentioned respective content ranges (e.g., 1 mol% or more and 9 mol% or less).

[0053] In a preferred embodiment of the present invention, the ceramic composition comprises zirconia, a stabilizer capable of suppressing a phase transition of zirconia, and Nb2O5 and / or Ta2O5, wherein, in a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, the content of zirconia is 78 to 97.5 mol%, the content of the stabilizer is 1 to 12 mol%, the content of Nb2O5 and / or Ta2O5 is 1 to 9 mol%, and further comprises a capping element or ion, the stabilizer comprises Y2O3 and / or CeO2, and the content of the capping element or ion is more than 0 mol% and 5 mol% or less, relative to a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, When the content of the stabilizer is A mol % and the total content of Nb2O5 and Ta2O5 is B mol %, the zirconia composite sintered body has an A / B ratio of 0.9 or more and 3 or less.

[0054] Other zirconia composite sintered bodies usable in the present invention include zirconia composite sintered bodies containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, a capping element or ion, and a zirconia strengthener. In a zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, and NbO and / or TaO, the zirconia strengthener acts together with the capping element or ion to improve the strength of the sintered body.

[0055] In the case of a zirconia composite sintered body containing a zirconia strengthener, as described above, the zirconia content, the type and content of the stabilizer, the content of NbO and / or TaO, the type and content of the capping element or ion, and the A / B ratio can be appropriately changed.

[0056] In a zirconia composite sintered body containing a zirconia toughener, the content of the zirconia toughener is preferably more than 0 mass% and not more than 6.0 mass%, relative to a total of 100 mass% of zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO, and TaO. In view of the fact that the zirconia toughener acts as a unit when combined with a capping element or ion and provides superior strength, the content of the zirconia toughener is more preferably 0.01 mass% or more and not more than 5.5 mass%, and even more preferably 0.5 mass% or more and not more than 5.0 mass%.

[0057] Examples of the zirconia reinforcing agent include TiO2, Al2O3, etc. The zirconia reinforcing agent may be used alone or in combination of two or more.

[0058] Another example of the zirconia composite sintered body that can be used in the present invention is a zirconia composite sintered body in which the zirconia strengthening agent contains TiO2 and the TiO2 content is 0.6 to 4.5 mass%.

[0059] Another zirconia composite sintered body used in the present invention comprises zirconia, a stabilizer capable of suppressing the phase transition of zirconia, and Nb2O5 and / or Ta2O5, wherein, relative to a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, the zirconia content is 78 to 97.5 mol%, the stabilizer content is 1 to 12 mol%, the Nb2O5 and / or Ta2O5 content is 1 to 9 mol%, and further comprises a capping element or ion, the stabilizer contains Y2O3 and / or CeO2, the zirconia strengthening agent contains TiO2 and the TiO2 content is 0.6 to 4.5 mass%, and the capping element or ion content is more than 0 mol% and not more than 5 mol% relative to a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, When the content of the stabilizer is A mol % and the total content of Nb2O5 and Ta2O5 is B mol %, the zirconia composite sintered body has an A / B ratio of 0.9 or more and 3 or less.

[0060] The average crystal grain size of the zirconia composite sintered body used in the present invention is preferably 0.5 to 5.0 μm, more preferably 0.5 to 4.5 μm, and even more preferably 0.7 to 4.0 μm, from the viewpoint of superior machinability, strength, and translucency. The average crystal grain size can be measured, for example, by the following method. First, an image of the surface of a pellet-shaped zirconia composite sintered body is obtained using a scanning electron microscope (product name "VE-9800", manufactured by Keyence Corporation). The grain boundaries of each crystal grain are recorded in the obtained image, and the average crystal grain size is calculated by image analysis. The average crystal grain size is measured using image analysis software (product name "Image-Pro Plus", manufactured by Hakuto Co., Ltd.). The captured SEM image is binarized, the brightness range is adjusted so that the grain boundaries are clearly visible, and the particles are recognized from the field of view (area). The crystal grain size obtained using Image-Pro Plus is the average length of the line segments connecting the outlines of the crystal grains passing through the center of gravity, measured at intervals of two degrees from the center of gravity. The arithmetic mean value of the crystal grain size of all particles not on the edge of the SEM photograph (three fields of view) of each example and comparative example is used as the average crystal grain size (by number) in the sintered body. "Particles not on the edge of the image" refers to particles that do not fit within the outline of the SEM photograph (particles whose outlines are interrupted at the top, bottom, left, and right boundary lines). The crystal grain size of all particles not on the edge of the image can be selected in Image-Pro Plus using the option to exclude all particles on boundary lines. The average crystal grain size can be measured by adjusting the number of particles in one field of view of an SEM photograph image to be about 50 or more, 100 or more, 200 or more, or 600 or more (e.g., 800, 1000, etc.) in the method described in the Examples.

[0061] The density of the zirconia composite sintered body according to the present invention is set to 5.5 g / cm because the higher the density, the fewer the internal voids, the less light scattering occurs, the better the translucency and the better the strength. 3 It is preferable that the density is 5.7 g / cm or more. 3 More preferably, it is 5.9 g / cm or more. 3It is more preferable that the zirconia composite sintered body is substantially free of voids. The density of the composite sintered body can be calculated by dividing the mass of the composite sintered body by the volume of the composite sintered body.

[0062] As described above, the zirconia composite sintered body used in the present invention can be the workable zirconia described in Patent Document 2, and the workable zirconia can be produced in accordance with the production method described in Patent Document 2.

[0063] A method for producing a zirconia composite sintered body used in the method for producing a dental prosthesis of the present invention when the zirconia composite sintered body contains a capping element or ions will be described below.

[0064] Examples of methods for producing a zirconia composite sintered body containing a capping element or ion include a method for producing a zirconia composite sintered body, the method comprising: preparing a compact using a raw material composition containing zirconia, a stabilizer capable of suppressing a phase transition of zirconia, and Nb2O5 and / or Ta2O5, wherein the total of the zirconia, the stabilizer, Nb2O5, and Ta2O5 is 100 mol %, and wherein the zirconia content is 78 to 97.5 mol %, the stabilizer content is 1 to 12 mol %, and the Nb2O5 and / or Ta2O5 content is 1 to 9 mol %, and the capping agent is further contained; and sintering the compact.

[0065] The raw material composition for the zirconia composite sintered body includes zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, and a capping agent. The raw material composition for the zirconia composite sintered body may be in a dry state, a liquid-containing state, or a liquid-contained state. The raw material composition may be in the form of, for example, powder, granules, a granulated material, a paste, a slurry, or the like.

[0066] The raw material composition contains a capping agent so that the resulting zirconia composite sintered body contains a capping element or ion. The capping agent is not particularly limited as long as it is a compound that can become a monovalent ion (a +1-valent cation or a -1-valent anion) in a solvent containing water, and examples thereof include hydroxides, salts, halides (fluorides, chlorides, bromides, iodides), cyanides, etc. that contain an element or ion derived from the capping agent. Each of the capping agents may be used alone, or two or more may be used in combination.

[0067] Examples of hydroxides containing capping elements or ions include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, francium hydroxide, etc. Examples of salts containing capping elements or ions include carbonates, bicarbonates, nitrates, hypochlorites, chlorites, chlorates, perchlorates, bromates, permanganates, metaborates, sulfide salts, and cyanide salts.

[0068] Examples of carbonates containing capping elements or ions include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, francium carbonate, cesium carbonate, etc. Examples of bicarbonates containing capping elements or ions include lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, francium bicarbonate, cesium bicarbonate, etc. Examples of nitrates containing capping elements or ions include calcium nitrate, strontium nitrate, iron (II) nitrate, iron (III) nitrate, cobalt (II) nitrate, magnesium nitrate, gallium nitrate, yttrium (III) nitrate, lanthanum (III) nitrate, praseodymium nitrate, neodymium (III) nitrate, manganese (II) nitrate, europium nitrate, copper (II) nitrate, thorium nitrate, aluminum nitrate, nickel (II) nitrate, chromium (III) nitrate, titanium (IV) nitrate, zirconium nitrate, zirconium oxynitrate (IV) hydrate (ZrO(NO3)2.xH2O), cerium (III) nitrate, tin nitrate, bismuth (III) nitrate, scandium (III) nitrate, indium (III) nitrate, and hafnium (IV) nitrate. Examples of hypochlorites containing capping elements or ions include sodium hypochlorite and calcium hypochlorite. Examples of chlorites containing capping elements or ions include sodium chlorite, potassium chlorite, lithium chlorite, calcium chlorite, magnesium chlorite, barium chlorite, copper(II) chlorite, copper(III) chlorite, silver chlorite, and nickel chlorite. Examples of chlorates containing capping elements or ions include calcium chlorate, barium chlorate, cobalt chlorate, nickel chlorate, magnesium chlorate, zinc chlorate, and copper chlorate. Examples of perchlorates containing capping elements or ions include iron(III) perchlorate, barium perchlorate, calcium perchlorate, cobalt perchlorate, nickel perchlorate, magnesium perchlorate, beryllium perchlorate, aluminum perchlorate, and cerium perchlorate. Examples of bromates containing capping elements or ions include neodymium bromate, lanthanum bromate, and praseodymium bromate.Examples of permanganates containing capping elements or ions include calcium permanganate (VII), potassium permanganate (VII), and sodium permanganate (VII). Examples of metaborates containing capping elements or ions include sodium metaborate and barium metaborate. Examples of sulfide salts containing capping elements or ions include copper (I) sulfide. Examples of cyanide salts containing capping elements or ions include barium cyanide, sodium cyanide, potassium cyanide, and calcium cyanide.

[0069] Examples of fluorides containing capping elements or ions include lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, francium fluoride, beryllium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, scandium (III) fluoride, yttrium (III) fluoride, lanthanum (III) fluoride, cerium (III) fluoride, neodymium (I) fluoride, and II), titanium fluoride (III), titanium fluoride (IV), zirconium fluoride (IV), hafnium fluoride (IV), tantalum fluoride (V), manganese fluoride (II), manganese fluoride (III), iron fluoride (II), iron fluoride (III), copper fluoride (II), zinc fluoride (II), aluminum fluoride, chromium fluoride (III), bismuth fluoride (III), indium fluoride, tin fluoride, and the like.

[0070] Examples of chlorides containing capping elements or ions include zirconium oxychloride, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, francium chloride, beryllium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride, scandium (III) chloride, yttrium (III) chloride, lanthanum (III) chloride, cerium (III) chloride, praseodymium chloride, neodymium (III) chloride, samarium chloride, europium chloride, titanium (III) chloride, titanium (IV) chloride, zirconium (IV) chloride, hafnium (IV) chloride, tantalum (V) chloride, manganese chloride, iron (II) chloride, iron (III) chloride, cobalt (II) chloride, nickel (II) chloride, copper (I) chloride, copper (II) chloride, zinc (II) chloride, aluminum chloride, gallium chloride, bismuth (III) chloride, indium (I) chloride, indium (III) chloride, and tin (II) chloride.

[0071] Examples of bromides containing capping elements or ions include lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, francium bromide, beryllium bromide, magnesium bromide, calcium bromide, strontium bromide, barium bromide, scandium(III) bromide, yttrium(III) bromide, cerium(III) bromide, neodymium(III) bromide, titanium(IV) bromide, zirconium(IV) bromide, tantalum(V) bromide, manganese(II) bromide, iron(II) bromide, iron(III) bromide, cobalt(II) bromide, nickel(II) bromide, copper(I) bromide, copper(II) bromide, zinc(II) bromide, chromium(III) bromide, bismuth(III) bromide, vanadium(III) bromide, indium(III) bromide, and tin bromide.

[0072] Examples of iodides containing capping elements or ions include lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, francium iodide, beryllium iodide, calcium iodide, magnesium iodide, strontium iodide, barium iodide, scandium (III) iodide, yttrium (III) iodide, lanthanum (III) iodide, cerium (III) iodide, neodymium (III) iodide, titanium (IV) iodide, ), zirconium iodide (IV), hafnium iodide (IV), tantalum iodide (V), manganese iodide (II), iron iodide (II), iron (III), cobalt iodide (II), nickel iodide (II), copper iodide (I), zinc iodide (II), aluminum iodide, chromium iodide (III), vanadium iodide (II), bismuth iodide (III), indium iodide (III), tin iodide, and tin iodide (IV).

[0073] Regarding zirconia, commercially available zirconia powder can be used. Examples of commercially available zirconia powder include zirconia powder (trade name "Zpex (registered trademark)" (Y2O3 content: 3 mol%), "Zpex (registered trademark) 4" (Y2O3 content: 4 mol%), and "Zpex (registered trademark) Smile (registered trademark)" (YO content: 5.5 mol%), "TZ-3Y" (YO content: 3 mol%), "TZ-3YS" (YO content: 3 mol%), "TZ-4YS" (YO content: 4 mol%), "TZ-6Y" (YO content: 6 mol%), "TZ-6YS" (YO content: 6 mol%), "TZ-8YS" (YO content: 8 mol%), "TZ-10YS" (YO content: 10 mol%), and "TZ-3Y-E" (YO content: 3 mol%) Examples include "TZ-3YS-E" (YO content: 3 mol%), "TZ-3YB-E" (YO content: 3 mol%), "TZ-3YSB-E" (YO content: 3 mol%), "TZ-3YB" (YO content: 3 mol%), "TZ-3YSB" (YO content: 3 mol%), "TZ-3Y20AB" (YO content: 3 mol%), "TZ-8YSB" (YO content: 8 mol%), and "TZ-0" (YO content: 0 mol%); all manufactured by Tosoh Corporation. The commercially available zirconia powder also contains HfO. Commercially available products containing YO may also be used. As the zirconia powder, a zirconia powder in which Y2O3 is uniformly dispersed and solid-solved, such as the commercially available TZ series (product names including "TZ"), can also be used in the raw material composition of the present invention.

[0074] There are no particular limitations on the method for producing the zirconia powder, and known methods such as a breakdown process in which coarse particles are pulverized into fine powder, or a building-up process in which zirconia is synthesized from atoms or ions through a nucleation and growth process can be used.

[0075] The type of zirconia powder in the raw material composition is not particularly limited. When the zirconia powder contains zirconia but no stabilizer, or when the stabilizer content is increased as needed, stabilizer particles can be added separately. The stabilizer particles are not particularly limited as long as they can adjust the stabilizer content in the zirconia composite sintered body to the above-mentioned predetermined range. For example, a commercially available product may be used as the stabilizer particles, or a commercially available powder may be crushed using a known crushing and mixing device (such as a ball mill) before use.

[0076] The stabilizer may be either a stabilizer that is not solid-dissolved in zirconia or a stabilizer that is solid-dissolved in zirconia. In a preferred embodiment, a method for producing a zirconia composite sintered body includes a stabilizer (preferably YO) that is not solid-dissolved in zirconia in the raw material composition, because this is one factor that makes it easy to obtain the desired zirconia composite sintered body. The fact that the stabilizer includes one that is not solid-dissolved in zirconia can be confirmed, for example, by an X-ray diffraction (XRD) pattern.

[0077] When a peak attributable to the stabilizer is confirmed in the XRD pattern of the raw material composition or the molded body, it means that the stabilizer is present in the raw material composition or the molded body without being solid-dissolved in zirconia. When the entire amount of the stabilizer is solid-dissolved in zirconia, basically, no peak attributable to the stabilizer is confirmed in the XRD pattern. However, depending on conditions such as the crystalline state of the stabilizer, even if no stabilizer peak is present in the XRD pattern, the stabilizer may not be solid-dissolved in zirconia.

[0078] A case where the stabilizer contains a stabilizer that is not solid-dissolved in zirconia will be described below, taking as an example a case where the stabilizer is yttria.

[0079] In the raw material composition or the molded body of the present invention, the abundance rate f of yttria that is not dissolved in zirconia (hereinafter sometimes referred to as "undissolved yttria") is ycan be calculated based on the following formula (1): y =I 29 / (I 28 +I 29 +I 30 )×100 (1) (where f y represents the proportion (%) of undissolved yttria, and in the XRD measurement, I 28 represents the integrated intensity of the peak at around 2θ = 28° where the main peak of the monoclinic system appears, and I 29 represents the area intensity of the peak at 2θ=29° where the main peak of yttria appears, and I 30 represents the area intensity of the peak near 2θ = 30° where the main peak of the tetragonal or cubic crystal system appears.)

[0080] When a stabilizer other than yttria is used in combination, I 29 By substituting the peak of another stabilizer in place of yttria, the formula can also be applied to calculate the undissolved fraction of stabilizers other than yttria.

[0081] Undissolved yttria abundance f y From the viewpoint that the desired zirconia composite sintered body can be easily obtained, the abundance ratio f of undissolved yttria is preferably greater than 0%, more preferably 1% or more, even more preferably 2% or more, and particularly preferably 3% or more. y The upper limit may be, for example, 25% or less, but preferably depends on the content of yttria in the raw material composition or the compact.

[0082] For example, when the content of yttria in the raw material composition or the molded article of the present invention is 3 mol % or more and 8 mol % or less, the following applies: When the content of yttria is 3 mol % or more and less than 4.5 mol %, f y When the yttria content is 4.5 mol % or more and less than 5.8 mol %, f y When the content of yttria is 5.8 mol % or more and 8 mol % or less, f y can be 25% or less.

[0083] For example, when the content of yttria is 3 mol% or more and less than 4.5 mol%, f y is preferably 2% or more, more preferably 3% or more, even more preferably 4% or more, and particularly preferably 5% or more. When the yttria content is 4.5 mol% or more and less than 5.8 mol%, f y is preferably 3% or more, more preferably 4% or more, even more preferably 5% or more, even more preferably 6% or more, and particularly preferably 7% or more. When the yttria content is 5.8 mol% or more and 8 mol% or less, f y is preferably 4% or more, more preferably 5% or more, even more preferably 6% or more, even more preferably 7% or more, and particularly preferably 8% or more.

[0084] In the raw material composition or molded article of the present invention, the stabilizer does not have to be entirely dissolved in zirconia. In the present invention, the term "solid solution of the stabilizer" means, for example, that elements (atoms) contained in the stabilizer are dissolved in zirconia.

[0085] The NbO and / or TaO added to the raw material composition of the present invention is not particularly limited as long as the content of NbO and / or TaO contained in the zirconia composite sintered body can be adjusted to the above-mentioned range. The NbO and / or TaO are not particularly limited, and for example, commercially available products may be used, or the powder of the commercially available product may be crushed in a known crushing and mixing device (such as a ball mill) before use.

[0086] Examples of the step of preparing the raw material composition include a method of wet-mixing the raw materials of the raw material composition (zirconia, a stabilizer, and, if necessary, other components (at least one of NbO and TaO, a capping agent (e.g., a compound that can become a monovalent ion in a solvent containing water), a zirconia reinforcement agent, etc.)) in a solvent containing water to obtain the raw material composition.

[0087] The method for wet-mixing the raw materials in a solvent containing water is not particularly limited. For example, the raw materials may be wet-pulverized and mixed in a known pulverizing and mixing device (such as a ball mill) to form a slurry, and then the slurry may be dried and granulated to prepare a granular raw material composition.

[0088] In the wet mixing step, additives such as a binder, a plasticizer, a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, a lubricant, etc. may be further contained. Each of the additives may be used alone or in combination of two or more.

[0089] The binder may be added to a slurry obtained by adding a primary powder consisting of a mixture of zirconia, Y2O3, Nb2O5 and / or Ta2O5, and a capping agent to water, and then milling the slurry.

[0090] The binder is not particularly limited, and known binders can be used, such as polyvinyl alcohol binders, acrylic binders, wax binders (paraffin wax, etc.), methyl cellulose, carboxymethyl cellulose, polyvinyl butyral, polymethyl methacrylate, ethyl cellulose, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, atactic polypropylene, and methacrylic resins.

[0091] Examples of the plasticizer include polyethylene glycol, glycerin, propylene glycol, and dibutyl phthalate.

[0092] Examples of dispersants include ammonium polycarboxylate (e.g., triammonium citrate), ammonium polyacrylate, acrylic copolymer resin, acrylic acid ester copolymer, polyacrylic acid, bentonite, carboxymethyl cellulose, anionic surfactants (e.g., polyoxyethylene alkyl ether phosphate esters such as polyoxyethylene lauryl ether phosphate esters), nonionic surfactants, olein glyceride, amine salt surfactants, oligosaccharide alcohols, and stearic acid.

[0093] Examples of emulsifiers include alkyl ethers, phenyl ethers, and sorbitan derivatives.

[0094] Examples of the antifoaming agent include alcohol, polyether, silicone, and wax.

[0095] Examples of pH adjusters include ammonia and ammonium salts (including ammonium hydroxides such as tetramethylammonium hydroxide).

[0096] Examples of the lubricant include polyoxyethylene alkyl ether and wax.

[0097] The solvent used in the wet mixing is not particularly limited as long as it contains water, and an organic solvent, a mixed solvent of water and an organic solvent, or water alone may be used. Examples of the organic solvent include ketone solvents such as acetone and ethyl methyl ketone; and alcohol solvents such as ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, glycerin, diglycerin, polyglycerin, propylene glycol, dipropylene glycol, polypropylene glycol, ethylene glycol, diethylene glycol, polyethylene glycol, polyethylene glycol monomethyl ether, 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol.

[0098] The raw material composition for the zirconia composite sintered body used in the present invention may contain ZrO2, YO3, Nb2O5, Ta2O5, a capping agent, and, if necessary, other components in addition to the zirconia reinforcement, as long as the effects of the present invention are achieved. Examples of such other components include colorants (pigments and composite pigments), fluorescent agents, and SiO2. Each of the other components may be used alone, or two or more may be used in combination.

[0099] Examples of the pigment include an oxide of at least one element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, Tb, and Er (specifically, NiO, Cr2O3, etc.), preferably an oxide of at least one element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, and Tb, and more preferably an oxide of at least one element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Sm, Eu, Gd, and Tb. However, YO and CeO may be excluded from the pigment.

[0100] Examples of the composite pigment include (Zr, V) O 2 , Fe(Fe, Cr) 2 O 4 , (Ni, Co, Fe)(Fe, Cr) 2 O 4 .ZrSiO 4 , and (Co, Zn)Al 2 O 4 .

[0101] Examples of the fluorescent agent include Y2SiO5:Ce, Y2SiO5:Tb, (Y, Gd, Eu)BO3, Y2O3:Eu, YAG:Ce, ZnGa2O4:Zn, and BaMgAl. 10 O 17 : Eu, etc.

[0102] Next, the obtained raw material composition is molded to produce a molded body. The molding method is not particularly limited, and known methods (for example, press molding) can be used.

[0103] When a zirconia molded body is produced by a method including a step of press-molding a raw material composition, the specific method of press-molding is not particularly limited, and the press-molding can be carried out using a known press-molding machine. Specific examples of the press-molding method include uniaxial pressing.

[0104] The pressing pressure is set to an optimum value depending on the size, open porosity, biaxial bending strength, and particle size of the raw material powder of the target compact, and is usually 5 MPa to 1000 MPa. By increasing the pressing pressure during molding in the above-mentioned production method, the pores of the obtained compact are more fully filled, the open porosity can be set lower, and the density of the compact can be increased. Furthermore, in order to increase the density of the obtained zirconia compact, a cold isostatic pressing (CIP) treatment may be further performed after uniaxial pressing.

[0105] Next, the obtained compact is sintered to obtain a zirconia composite sintered body. The sintering temperature (maximum sintering temperature) at which the compact is sintered to obtain the zirconia composite sintered body is, for example, preferably 1300°C or higher, more preferably 1350°C or higher, even more preferably 1400°C or higher, even more preferably 1450°C or higher, and particularly preferably 1500°C or higher. The sintering temperature is, for example, preferably 1680°C or lower, more preferably 1650°C or lower, and even more preferably 1600°C or lower. The method for producing the zirconia composite sintered body used in the present invention preferably includes a step of sintering the compact at a maximum sintering temperature of 1300 to 1680°C. The maximum sintering temperature is preferably a temperature in the atmosphere.

[0106] The holding time (holding time) at the maximum sintering temperature varies depending on the temperature, but is preferably 30 hours or less, more preferably 20 hours or less, even more preferably 10 hours or less, even more preferably 5 hours or less, particularly preferably 3 hours or less, and most preferably 2 hours or less. Furthermore, the holding time can be 25 minutes or less, 20 minutes or less, or 15 minutes or less. The holding time is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. According to the manufacturing method of the present invention, a zirconia composite sintered body with excellent bending strength, translucency, and machinability can be produced depending on the content of the stabilizer, NbO, and / or TaO. Furthermore, the sintering time may be shortened as long as the effects of the present invention are obtained. By shortening the sintering time, production efficiency can be improved and energy costs can be reduced.

[0107] In the method for producing a zirconia composite sintered body, the temperature rise rate during sintering of the compact is not particularly limited, but is preferably 0.1°C / min or more, more preferably 0.2°C / min or more, and even more preferably 0.5°C / min or more. The temperature rise rate is preferably 50°C / min or less, more preferably 30°C / min or less, and even more preferably 20°C / min or less. By setting the temperature rise rate at or above the lower limit, productivity is improved.

[0108] A common dental zirconia firing furnace can be used in the step of sintering the green body. Commercially available dental zirconia firing furnaces may be used. Examples of commercially available dental zirconia firing furnaces include Noritake Katana (registered trademark) F-1, F-1N, F-2, and F-2N (all manufactured by SK Medical Electronics Co., Ltd.).

[0109] Furthermore, the step of sintering the compact preferably includes a step of hot isostatic pressing (HIP) treatment in addition to sintering at the maximum sintering temperature. The HIP treatment can further improve the translucency and strength of the zirconia composite sintered body.

[0110] Hereinafter, the sintered body obtained by sintering at the maximum sintering temperature will be referred to as a "primary sintered body," and the sintered body after HIP treatment will be referred to as a "HIP-treated sintered body."

[0111] The HIP treatment can be carried out using a known hot isostatic press (HIP) device.

[0112] The temperature of the HIP treatment is not particularly limited, but since a dense zirconia composite sintered body with high strength can be obtained, the temperature of the HIP treatment is preferably 1200° C. or higher, more preferably 1300° C. or higher, and even more preferably 1400° C. or higher. The temperature of the HIP treatment is preferably 1700° C. or lower, more preferably 1650° C. or lower, and even more preferably 1600° C. or lower.

[0113] In the method for producing the zirconia composite sintered body, when the primary sintered body is subjected to the HIP treatment, the pressure of the HIP treatment is not particularly limited, and since a dense sintered body with high strength can be obtained, the pressure of the HIP treatment is preferably 100 MPa or more, more preferably 125 MPa or more, and even more preferably 130 MPa or more. In addition, the upper limit of the pressure of the HIP treatment is not particularly limited, but can be, for example, 400 MPa or less, 300 MPa or less, or even 200 MPa or less.

[0114] In the method for producing the zirconia composite sintered body, when the primary sintered body is subjected to HIP treatment, the temperature rise rate is not particularly limited, but is preferably 0.1°C / min or more, more preferably 0.2°C / min or more, and even more preferably 0.5°C / min or more. The temperature rise rate is preferably 50°C / min or less, more preferably 30°C / min or less, and even more preferably 20°C / min or less. By setting the temperature rise rate at or above the lower limit, productivity is improved.

[0115] In the method for producing a zirconia composite sintered body used in the present invention, when the primary sintered body is subjected to HIP treatment, the HIP treatment time is not particularly limited, and since a dense zirconia composite sintered body with high strength can be obtained, the HIP treatment time is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. Moreover, the HIP treatment time is preferably 10 hours or less, more preferably 6 hours or less, and even more preferably 3 hours or less.

[0116] In the method for producing the zirconia composite sintered body, when the primary sintered body is subjected to HIP treatment, the pressure medium is not particularly limited, and from the viewpoint of low influence on zirconia, at least one pressure medium selected from the group consisting of oxygen gas, oxygen mixed gas, air, and inert gas (e.g., nitrogen gas, argon gas, etc.) can be selected as the pressure medium. When the primary sintered body is HIP treated in an oxygen mixed gas atmosphere, the oxygen concentration is not particularly limited, but can be, for example, more than 0% to 20% or less. When an oxygen mixed gas is used, at least one inert gas (e.g., nitrogen gas, argon gas, etc.) can be selected as the gas other than oxygen.

[0117] In the method for producing the zirconia composite sintered body, if the HIP treatment is performed in a reducing atmosphere, such as using an inert gas, black discoloration may occur due to oxygen defects. In this case, to remove the black discoloration, it is preferable to include a heat treatment step (hereinafter also referred to as "tempering treatment") in air or an oxygen-rich atmosphere at 1650°C or less after the HIP treatment step. From the viewpoint of efficient heat treatment, it is more preferable to perform the heat treatment in an oxygen-rich atmosphere. In this specification, "oxygen-rich atmosphere" means that the oxygen concentration is higher than that of air. The oxygen-rich atmosphere is not particularly limited as long as the oxygen concentration is more than 21% and less than or equal to 100%, and can be appropriately selected from this range. For example, the oxygen concentration may be 100%.

[0118] The zirconia composite sintered body used in the present invention is not particularly limited as long as it exhibits the effects of the present invention, and may be a primary sintered body, a HIP-treated sintered body, or a sintered body after tempering. A preferred embodiment is a zirconia composite sintered body that is a sintered body after tempering.

[0119] The temperature of the heat treatment in the air or in an oxygen-excess atmosphere can be appropriately changed depending on the aesthetics of the zirconia composite sintered body (e.g., the shade of a dental prosthesis). In a preferred embodiment, the temperature of the heat treatment in the air or in an oxygen-excess atmosphere is preferably 1650°C or less, more preferably 1600°C or less, and even more preferably 1550°C or less, from the viewpoint of the aesthetics of the zirconia composite sintered body. In another preferred embodiment, the temperature of the heat treatment in the air or in an oxygen-excess atmosphere is preferably 1400°C or less, more preferably 1300°C or less, and even more preferably 1200°C or less, from the viewpoint of the aesthetics of the zirconia composite sintered body. Furthermore, in any embodiment, the temperature of the heat treatment is preferably 500°C or more, more preferably 600°C or more, and even more preferably 700°C or more.

[0120] A general dental zirconia firing furnace can be used for the tempering treatment. Commercially available dental zirconia firing furnaces may be used. Examples of commercially available dental zirconia firing furnaces include Noritake Katana (registered trademark) F-1, F-1N, and F-2 (all manufactured by SK Medical Electronics Co., Ltd.).

[0121] The zirconia composite sintered body used in the present invention has excellent machinability despite being a sintered body, so there is no need to machine a semi-sintered calcined body in the form of a mill blank and then sinter it to form a sintered body. On the other hand, a method for producing a zirconia composite sintered body may also be a method in which a molded body obtained using the raw material composition is calcined to produce a semi-sintered calcined body, and the unprocessed calcined body is then machined to form a sintered body.

[0122] Another example of a method for producing a zirconia composite sintered body is a method for producing a zirconia composite sintered body, which includes the steps of: preparing a molded body from the raw material composition; calcining the obtained molded body to obtain a zirconia composite calcined body (calcining step); and sintering the zirconia composite calcined body.

[0123] In order to ensure blocking, the firing temperature (calcination temperature) in the calcination step is, for example, preferably 800°C or higher, more preferably 900°C or higher, and even more preferably 950°C or higher. The calcination temperature is, for example, preferably 1200°C or lower, more preferably 1150°C or lower, and even more preferably 1100°C or lower. The calcination temperature is preferably, for example, 800°C to 1200°C. At such a calcination temperature, it is believed that the dissolution of the stabilizer does not progress significantly in the calcination step.

[0124] The density of the zirconia composite calcined body is 2.7 g / cm 3 The density of the zirconia composite calcined body is preferably 4.0 g / cm 3 Preferably, 3.8 g / cm or less 3 More preferably, 3.6 g / cm 3 The following is more preferable. When the density is within this range, processing can be easily performed. The density of the composite calcined body can be calculated, for example, by dividing the mass of the composite calcined body by the volume of the composite calcined body.

[0125] The three-point bending strength of the zirconia composite calcined body is preferably 15 to 70 MPa, more preferably 18 to 60 MPa, and even more preferably 20 to 50 MPa. The bending strength can be measured using a test piece measuring 5 mm thick, 10 mm wide, and 50 mm long, in accordance with ISO 6872:2015, except for the size of the test piece. The test piece's face and C-face (the surface where the corners of the test piece are chamfered at a 45° angle) are surface-finished in the longitudinal direction with 600-grit sandpaper. The test piece is positioned so that the widest surface faces vertically (the load direction). In the bending test, the span is 30 mm, and the crosshead speed is 1.0 mm / min.

[0126] The step of sintering the zirconia composite calcined body can be carried out by the same method and under the same conditions (temperature, pressure, etc.) as those used in the step of sintering the molded body described above. Therefore, in the embodiment of the production method using the zirconia composite calcined body, the "molded body" can be read as the "calcined body."

[0127] The zirconia composite sintered body used in the present invention has excellent strength. The biaxial bending strength of the zirconia composite sintered body used in the present invention is preferably 300 MPa or more, more preferably 350 MPa or more, even more preferably 400 MPa or more, even more preferably 450 MPa or more, and particularly preferably 500 MPa or more. When the zirconia composite sintered body used in the present invention has such a biaxial bending strength, it can suppress intraoral fracture when used, for example, as a dental prosthesis. There is no particular upper limit to the biaxial bending strength, but the biaxial bending strength can be, for example, 1200 MPa or less, or even 1000 MPa or less. The biaxial bending strength of the zirconia composite sintered body can be measured in accordance with ISO 6872:2015.

[0128] The zirconia composite sintered body used in the present invention preferably has high translucency. Translucency can be evaluated by ΔL*. Specifically, regarding translucency, the zirconia composite sintered body used in the present invention preferably has ΔL* of 10 or more, more preferably 12 or more, even more preferably 13 or more, and particularly preferably 14 or more, at a diameter of 15 mm and a thickness of 1.2 mm. When ΔL* is within the above range, a zirconia composite sintered body with high translucency can be obtained.

[0129] ΔL* refers to the difference between the lightness (first L* value) of the same sample on a white background and the lightness (second L* value) of the same sample on a black background. Specifically, it refers to the difference between the L* value on a white background (JIS Z 8781-4:2013 Colorimetry - Part 4: CIE 1976 L*a*b* color space) and the L* value on a black background. The white background refers to the white portion of the opacity test paper described in JIS K 5600-4-1:1999, Part 4, Section 1, and the black background refers to the black portion of the opacity test paper.

[0130] There is no particular upper limit to ΔL*, but it can be, for example, 25 or less, and from the viewpoint of aesthetics, even 20 or less.

[0131] The ΔL* of a zirconia composite sintered body having a diameter of 15 mm and a thickness of 1.2 mm can be measured using a spectrophotometer, for example, a dental colorimeter (Crystal Eye CE100-CE / JP, 7-band LED light source, analysis software Crystal Eye (manufactured by Olympus Corporation)).

[0132] Furthermore, when the zirconia composite sintered body used in the method for producing a dental prosthesis of the present invention contains zirconia and a stabilizer capable of suppressing the phase transition of zirconia, and the total of zirconia, the stabilizer, NbO, and TaO is 100 mol%, the zirconia content is 78 to 97.5 mol%, the stabilizer content is 1 to 12 mol%, and the NbO and / or TaO content is 1 to 9 mol%, the zirconia composite sintered body can be produced in the same manner as the method for producing a zirconia composite sintered body described above when the zirconia composite sintered body contains a capping element or ion, except that the raw material composition does not contain a capping agent. Furthermore, depending on the content of each component and / or the crystal system of zirconia, the zirconia composite sintered body can also be produced in accordance with the production method disclosed in WO 2021 / 132644.

[0133] Dental prostheses manufactured using the zirconia composite sintered body used in the present invention include, for example, crown restorations such as inlays, onlays, veneers, crowns, core-integrated crowns, and bridges, as well as abutments, dental posts, dentures, denture bases, and implant components (fixtures and abutments). Machining is preferably performed using, for example, a commercially available dental CAD / CAM system. Examples of such CAD / CAM systems include the "CEREC System" manufactured by Dentsply Sirona Dental Systems Inc. and the "Katana (registered trademark) System" manufactured by Kuraray Noritake Dental Co., Ltd.

[0134] The zirconia composite sintered body used in the present invention can also be used for applications other than dental applications, and is particularly suitable for zirconia components requiring irregular or complex shapes and strength. Compared to sintered bodies produced solely by existing manufacturing methods (e.g., injection molding, CIP, slip casting, or 3D printing), the zirconia composite sintered body used in the present invention can be processed as is. Therefore, for example, it is economical when the desired zirconia component can be obtained in a short time. For complex-shaped components difficult to produce by conventional manufacturing methods, it is possible to obtain zirconia components that maintain high strength by eliminating the need to mechanically fit multiple components. Furthermore, since the sintered body can be processed as is, a sintering process is not required when dimensional precision is required, and uneven firing shrinkage is eliminated, resulting in highly accurate zirconia components. Specifically, it can be used as a method for producing jewelry, engine and interior components for mobility such as aircraft and automobiles, display panel frames, building components, electrical appliance components, household goods components, and toy parts. The zirconia component may also be fitted with a different material to form a composite component.

[0135] The present invention includes embodiments in which all or part of the above configurations are combined in various ways within the scope of the technical concept of the present invention, as long as the effects of the present invention are achieved.

[0136] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples, and many modifications within the scope of the technical concept of the present invention are possible by those skilled in the art.

[0137] [Examples 1 to 20 and Comparative Examples 1 to 6] Measurement samples for each of the Examples and Comparative Examples were prepared through the steps of preparing a granular raw material composition, preparing a compact, and preparing a sintered body (preparing a primary sintered body, HIP treatment, and tempering treatment).

[0138] [Preparation of Granular Raw Material Composition] To prepare the granular raw material compositions of each Example and Comparative Example, commercially available ZrO powder, YO powder, NbO powder, or TaO powder, and optionally a capping agent and TiO powder were mixed so that the content of each component in the sintered zirconia composite sintered body would be the composition shown in Tables 1 to 3. Water was added to prepare a slurry, which was then wet-pulverized and mixed in a ball mill until the average particle size was 0.13 μm or less. A binder was added to the pulverized slurry, which was then dried in a spray dryer to prepare a granular raw material composition (hereinafter also simply referred to as the "raw material composition"). This was used in the production of the molded body described below. The average particle size was measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer (Partica LA-950: manufactured by Horiba, Ltd.) by irradiating the water-diluted slurry with ultrasound for 30 minutes, followed by ultrasonic irradiation.

[0139] [Preparation of Molded Body] For each Example and Comparative Example, a block-shaped molded body was prepared as follows to obtain a sintered body sample for evaluating surface roughness and glaze firing. First, the raw material composition was placed in a mold with inner dimensions of 19 mm x 18 mm so that the thickness of the zirconia composite sintered body after sintering would be 14.5 mm. Next, the raw material composition was press-molded using a uniaxial press molding machine at a surface pressure of 200 MPa for 90 seconds to prepare a block-shaped molded body.

[0140] [Preparation of primary sintered body] The obtained block-shaped compact was subjected to sintering in the atmosphere at a maximum sintering temperature of 1550°C for 2 hours using a sintering furnace "Noritake Katana (registered trademark) F-1" manufactured by SK Medical Electronics Co., Ltd., to obtain a sample of a block-shaped zirconia composite sintered body (primary sintered body).

[0141] [Preparation of HIP-treated sintered body] The obtained block-shaped zirconia composite sintered body (primary sintered body) was subjected to heating in an argon atmosphere at 1450°C and 150 MPa for 2 hours using a HIP apparatus "O2-Dr. HIP" manufactured by Kobe Steel, Ltd., to obtain a sample of a block-shaped zirconia composite sintered body (HIP-treated sintered body).

[0142] [Preparation of zirconia composite sintered body (tempered sintered body)] The obtained block-shaped zirconia composite sintered body (HIP-treated sintered body) was subjected to sintering at 700°C for 60 hours in a Noritake Katana (registered trademark) F-1 firing furnace manufactured by SK Medical Electronics Co., Ltd., to obtain a block-shaped zirconia composite sintered body (tempered sintered body) sample. The size of the obtained block-shaped sample was 15.7 mm wide x 16.5 mm long x 14.5 mm high.

[0143] [Fabrication of desired shapes using a wet processing machine] For each example of a block-shaped zirconia composite sintered body (sintered body after tempering treatment), a sample was prepared by adhering a metal jig to a surface measuring 15.7 mm wide x 14.5 mm high. The sample was then processed into the shapes of an anterior tooth, a premolar, and a molar using a CEREC system "MC-XL" (manufactured by Dentsply Sirona) as a sample for evaluating glaze firing. The processing program used the software "inLab (registered trademark) CAM version 20.0.1.203841", and the manufacturer was IVOCLAR VIVADENT, and the material name was IPS e. Max CAD, Production Method: Grinding, Block size: C16 were selected, and Step Bur 12 and Cylinder Pointed Bur 12S were used as machining tools.

[0144] [Pretreatment of substrate (zirconia composite sintered body)] The machined sintered bodies were prepared by the method described in the above [Preparation of desired shape using a wet processing machine], and in Examples 1 to 7, 12, 13, 15, and 17 to 19, the machined sintered bodies were subjected to the heat treatments listed in Table 1. In Examples 8 to 11, 14, 16, and 20, the machined sintered bodies were subjected to a polishing treatment. The dental polishing equipment used in the polishing treatment was "EVE Diapol Twist Medium" (manufactured by EVE) in Example 8, "Pearl Surface Z" (manufactured by Kuraray Noritake Dental Co., Ltd.) in Examples 9, 11, 14, 16, and 20, and "Meister Cone S-Green" (manufactured by Kuraray Noritake Dental Co., Ltd.) in Example 10.

[0145] [Method for measuring surface roughness Ra of sintered body] The surface roughness Ra of the crown-shaped sintered bodies of Examples 8 to 11, 14, 16, and 20, which had been subjected to the above-mentioned pretreatment, was evaluated. Specifically, the evaluation was carried out by the following method. The surface of the crown-shaped sintered body was observed with a color 3D laser microscope (product name "VK-9710", manufactured by Keyence Corporation) under the following conditions: Measurement pitch: 2 μm Measurement distance: 1058 μm The obtained image was analyzed with image analysis software (product name "VK Analyzer", manufactured by Keyence Corporation) to calculate the surface roughness, which was taken as the surface roughness Ra (arithmetic mean value of n = 3).

[0146] [Evaluation of Glaze Firing] The porcelain materials listed in Tables 1 to 3 were applied to the sintered bodies of the Examples that had undergone the above pretreatment and the sintered bodies of the Comparative Examples that had not undergone processing, as described above, and then fired. First, the porcelain materials were applied or sprayed onto the crown-shaped sintered bodies according to the method specified in the instruction manual for each porcelain material. The porcelain material was applied so as to cover the entire surface of the substrate, preventing partial exposure of the substrate surface. The thickness of the applied porcelain was adjusted to 10 to 50 μm after firing. The porcelain materials were then fired in a dental firing furnace (product name "Cerafusion BX," manufactured by SK Medical Electronics Co., Ltd.) according to the firing program specified in the instruction manual for each porcelain material. The surfaces of the resulting evaluation samples were observed to check for any firing defects, and the results are shown in Tables 1 to 3.

[0147] The glaze firing was evaluated according to the following criteria: P: No separation of the glaze porcelain from the substrate was observed in the frontal and occlusal views. F: Separation of the glaze porcelain from the substrate was observed in the frontal or occlusal views. "P" means Pass, and "F" means Fail.

[0148] The content of each component of the sintered body in Tables 1 to 3 is a value calculated from the amount of raw material charged. The content (mol%) of capping elements or ions (e.g., Na) in Tables 1 to 3 is the external addition rate relative to the total 100 mol% of zirconia (total of ZrO2 and HfO2), the stabilizer (yttria), Nb2O5, and Ta2O5. The content (mol%) of zirconia (total of ZrO2 and HfO2), the stabilizer, Nb2O5, and Ta2O5 in Tables 1 to 3 is the content of each component relative to the total 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. The content (mass%) of TiO2 and Al2O3 in Tables 1 to 3 is the external addition rate relative to the total 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. In Tables 1 to 3, "A / B" represents the ratio of A to B when the content of Y2O3 is A mol % and the total content of Nb2O5 and Ta2O5 is B mol %.

[0149]

[0150]

[0151]

[0152] From the above results, it can be seen that the zirconia composite sintered bodies according to Examples 1 to 20 were able to satisfactorily bond porcelain not only to anterior teeth and premolars, but also to dental prostheses having complex shapes such as many curved surfaces and many grooves in occlusal view, as shown in Fig. 2A or 2B, and the dental prostheses were excellent in aesthetics. In contrast, the zirconia composite sintered bodies according to Comparative Examples 1 to 6 exhibited poor aesthetics, with the glaze porcelain peeling from the substrate observed in the frontal or occlusal view, as shown in the area circled in black in Fig. 3A or 3B.

[0153] The zirconia composite sintered body used in the present invention has suitable strength and translucency, and is excellent in machinability, and is particularly useful as a dental material for dental prostheses and the like for dental treatment applications.

Claims

1. A method for manufacturing a dental prosthesis, comprising: performing a heat treatment or a polishing treatment as a pretreatment on a zirconia composite sintered body containing Nb₂O₅ and / or Ta₂O₅; and building and firing a ceramic material on the zirconia composite sintered body that has undergone the pretreatment.

2. The method for manufacturing a dental prosthesis according to claim 1, wherein the temperature of the heat treatment is 150°C or higher and 1550°C or lower.

3. The method for manufacturing a dental prosthesis according to claim 1, wherein in the polishing treatment, the surface roughness Ra of the zirconia composite sintered body after the polishing treatment is 8.0 µm or less.

4. The zirconia composite sintered body contains zirconia and a stabilizer capable of suppressing the phase transition of zirconia. In a total of 100 mol% of zirconia, the stabilizer, Nb₂O₅, and Ta₂O₅, the content of zirconia is 78 to 97.5 mol%, the content of the stabilizer is 1 to 12 mol%, and the content of Nb₂O₅ and / or Ta₂O₅ is 1 to 9 mol%. The method for manufacturing a dental prosthesis according to claim 1 or 2.

5. The method for manufacturing a dental prosthesis according to claim 4, wherein the zirconia composite sintered body further contains an element or ion derived from a capping agent.

6. The method for manufacturing a dental prosthesis according to claim 5, wherein the content of the element or ion derived from the capping agent is more than 0 mol% and 5 mol% or less with respect to a total of 100 mol% of zirconia, the stabilizer, Nb₂O₅, and Ta₂O₅.

7. The method for manufacturing a dental prosthesis according to claim 5, wherein the element or ion derived from the capping agent belongs to the 2nd to 7th periods of the periodic table, and is an element or its ion having a first ionization energy smaller than that of the element of Group 18 in the same period, and / or an element or its ion having a high electron affinity.

8. The method for manufacturing a dental prosthesis according to claim 5, wherein the element or ion derived from the capping agent contains at least one element or its ion selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F.

9. The method for manufacturing a dental prosthesis according to claim 5, wherein the element or ion derived from the capping agent contains at least one element or its ion selected from the group consisting of Li, Na, K, Rb, Cs, and Fr.

10. The manufacturing method of the dental prosthesis according to claim 4, wherein when the content rate of the stabilizer is Amol%, and the total content rate of Nb2O5 and Ta2O5 is Bmol%, the ratio of A / B is 0.9 or more and 3 or less.

11. The manufacturing method of the dental prosthesis according to claim 4, wherein the stabilizer contains Y2O3 and / or CeO2.

12. The manufacturing method of the dental prosthesis according to claim 4, further comprising a zirconia strengthening agent, wherein the content rate of the zirconia strengthening agent is more than 0 mass% and 6.0 mass% or less with respect to the total 100 mass% of zirconia, the stabilizer, Nb2O5 and Ta2O5.

13. The manufacturing method of the dental prosthesis according to claim 12, wherein the zirconia strengthening agent contains TiO2 and / or Al2O3.

14. The manufacturing method of the dental prosthesis according to claim 13, wherein the zirconia strengthening agent contains TiO2, and the content rate of TiO2 is 0.6 to 4.5 mass%.

15. The manufacturing method of the dental prosthesis according to claim 1 or 2, wherein the average crystal grain size of the zirconia composite sintered body is 0.5 to 5.0 μm.

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