Zirconia composite sintered body and dental preservation repair kit including same

Abstract

The present invention provides: a zirconia composite sintered body that can be machined and exhibits exceptional adhesiveness without sandblasting being performed after machining; and a dental preservation repair kit including the zirconia composite sintered body. The present invention relates to a dental zirconia composite sintered body containing monoclinic zirconia, the abundance ratio fm of monoclinic systems represented by formula (1) being higher than 10% and not higher than 60%.　Formula (1): fm = I28 / (I28 + I30) × 100 (In the formula, fm represents the abundance ratio (%) of monoclinic systems, I28 represents the area intensity of a peak around 2θ = 28° where a monoclinic main peak appears in XRD measurement, and I30 represents the area intensity of a peak around 2θ = 30° where a tetragonal or cubic main peak appears in XRD measurement).

Description

Zirconia composite sintered body and dental restoration kit containing same

[0001] The present invention relates to a zirconia composite sintered body and a dental restorative kit containing the same. More specifically, the present invention relates to a machinable zirconia composite sintered body having excellent adhesive properties and a dental restorative kit containing the same.

[0002] Ceramics made from metal oxides have been widely used industrially, and zirconia sintered bodies are particularly used as dental materials for dental prostheses and other applications due to their high strength and aesthetic appeal.

[0003] Zirconia sintered bodies have excellent strength, so when used as dental materials for prostheses, etc., problems such as breakage rarely occur. In addition, zirconia sintered bodies have high translucency and are less likely to become discolored in the oral cavity, so they also have excellent aesthetic properties.

[0004] Regarding the dental material applications, for example, dental prostheses can be manufactured by acquiring intraoral data of a patient and subjecting a dental zirconia material to machining using a CAD / CAM system using the data. Typically, dental zirconia materials machined using a CAD / CAM system are machined into a dental crown shape in a dental laboratory or dental clinic equipped with a CAD / CAM system, and then sintered to be used as a zirconia sintered body.

[0005] Furthermore, various improved zirconia sintered bodies have been proposed in consideration of production efficiency and the like (for example, Patent Documents 1 and 2).

[0006] JP 2021-88501 A JP 2023-37381 A

[0007] Conventionally, zirconia sintered bodies processed into a crown shape and sintered have few surface irregularities, so that the surface of the zirconia sintered body to be bonded to an abutment tooth (hereinafter also referred to as the "bonding surface") is sandblasted to increase the surface area of ​​the bonding surface, thereby achieving clinically sufficient adhesiveness (see, for example, Patent Document 1). Therefore, the zirconia sintered body disclosed in Patent Document 1 did not achieve sufficient adhesive strength unless sandblasted. However, the degree of sandblasting varies depending on the practitioner, and sufficient adhesiveness may not be achieved. Furthermore, the present inventors have found that the zirconia sintered body disclosed in Patent Document 2 also does not achieve sufficient adhesive strength unless sandblasted.

[0008] An object of the present invention is to provide a machinable zirconia composite sintered body that has excellent adhesiveness without requiring sandblasting treatment after machining, and a dental restoration kit including the same.

[0009] As a result of extensive research to solve the above problems, the present inventors have found that the problems can be solved by setting the monoclinic ratio of the machined surface of a zirconia composite sintered body within a specific range. Based on this finding, they have conducted further research and have completed the present invention.

[0010] That is, the present invention includes the following inventions: [1] A monoclinic zirconia containing monoclinic zirconia, and a monoclinic zirconia abundance ratio f represented by the following formula (1) m is more than 10% and not more than 60%. m =I 28 / (I 28 +I 30 )×100 (1) (where f m represents the abundance rate (%) of the monoclinic system, 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 30represents the integrated intensity of the peak near 2θ=30° where the main peak of the tetragonal or cubic system appears.) [2] The dental zirconia composite sintered body according to [1], wherein the monoclinic zirconia is present on the surface. [3] The dental zirconia composite sintered body according to [1] or [2], wherein the surface roughness Ra is 3.0 to 8.0 μm. [4] The dental zirconia composite sintered body according to any one of [1] to [3], wherein the average crystal grain size is 0.5 to 10 μm. [5] The dental zirconia composite sintered body according to any one of [1] to [4], further containing a stabilizer capable of suppressing the phase transition of zirconia. [6] The dental zirconia composite sintered body according to [5], wherein the content of the stabilizer is 1 to 12 mol % relative to a total of 100 mol % of zirconia and the stabilizer. [7] The dental zirconia composite sintered body according to [5] or [6], wherein the stabilizer is yttria. [8] The dental zirconia composite sintered body according to any one of [5] to [7], further comprising Nb2O5 and / or Ta2O5. [9] The dental zirconia composite sintered body according to any one of [5] to [8], further comprising 1 to 9 mol% of Nb2O5 and / or Ta2O5, based on a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5.

[10] The dental zirconia composite sintered body according to [8] or [9], further comprising a capping element or ion.

[11] The dental zirconia composite sintered body according to

[10] , wherein the content of the element or ion derived from the capping agent is more than 0 mol% and not more than 5 mol% based on a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5.

[12] The dental zirconia composite sintered body according to

[10] or

[11] , 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.

[13] The dental zirconia composite sintered body according to

[10] , wherein the element or ion derived from the capping agent is 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.

[14] The dental zirconia composite sintered body according to

[11] , wherein the element or ion derived from the capping agent contains at least one element selected from the group consisting of Li, Na, and K.

[15] The dental zirconia composite sintered body according to any one of [8] to

[14] , further containing TiO2 and / or Al2O3.

[16] A dental restorative kit comprising a combination of the dental zirconia composite sintered body according to any one of [1] to

[15] and a dental cement.

[17] The dental restorative kit according to

[16] , wherein the dental cement contains an acidic component.

[18] The dental restorative kit according to

[17] , wherein the acidic component contains a monomer having an acidic group.

[19] The dental restorative kit according to

[18] , wherein the monomer having an acidic group contains at least one selected from the group consisting of a phosphate group, a pyrophosphate group, a thiophosphate group, a phosphonate group, a carboxylic acid group, and a sulfonic acid group.

[20] A method for bonding the dental zirconia composite sintered body according to any one of [1] to

[15] , which does not include a step of sandblasting, and uses dental cement to bond the dental zirconia composite sintered body.

[0011] According to the present invention, it is possible to provide a machinable zirconia composite sintered body that exhibits excellent adhesion without sandblasting after machining, and a dental restorative kit including the same. Furthermore, since the machinable zirconia composite sintered body of the present invention exhibits excellent adhesion without sandblasting after machining, even higher adhesion (particularly adhesion durability) can be obtained by subjecting it to sandblasting.

[0012] 1 is a partial enlarged view of FIG. 1, showing the results of XRD measurement showing that the dental zirconia composite sintered body according to Example 1 contains monoclinic zirconia after machining.

[0013] The dental zirconia composite sintered body of the present invention (hereinafter also simply referred to as "zirconia composite sintered body") contains monoclinic zirconia and has a monoclinic zirconia abundance ratio f represented by the following formula (1): m (hereinafter also referred to as "monoclinic crystal ratio") is more than 10% and not more than 60%. m =I 28 / (I 28 +I30 )×100 (1) (where f m represents the abundance rate (%) of the monoclinic system, 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 30 represents the area intensity of the peak near 2θ = 30° where the main peak of the tetragonal or cubic crystal system appears.)

[0014] 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 strengthener" refers to a component that functions to improve the mechanical strength of a zirconia composite sintered body. In this specification, "100 mol% total of zirconia, the stabilizer, Nb2O5, and Ta2O5" can be interpreted as "100 mol% total of zirconia and the stabilizer" in the case of a zirconia composite sintered body that does not contain Nb2O5 and Ta2O5. In this specification, the term "(meth)acrylic" is used to encompass both "methacrylic" and "acrylic." The same applies to similar expressions such as "(meth)acrylate," "(meth)acrylic acid ester," "(meth)acrylamide," and "(meth)acryloyloxy." 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, 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" refers to the arithmetic mean roughness defined in JIS B 0601:2013. In this specification, "mean irregularity spacing RSm" refers to the mean irregularity spacing defined in JIS B 0601:2001. In this specification, the upper and lower limits of the numerical ranges (temperature range, content of each component, abundance rate of crystalline system, components, etc., values ​​calculated from these, and each physical property value, etc.) can be combined as appropriate.

[0015] The reason why the zirconia composite sintered body of the present invention has excellent adhesion (especially adhesion durability) without sandblasting after machining is believed to be as follows: In the zirconia composite sintered body of the present invention, fine cracks are generated by the external force applied during machining, and at this time, the crystal system at least on the surface undergoes a phase transition from tetragonal to monoclinic. Therefore, the number of fine cracks is proportional to the monoclinic ratio, and the higher the monoclinic ratio, the more fine cracks there are and the higher the adhesion durability.

[0016] The monoclinic crystal abundance ratio f in the zirconia composite sintered body of the present invention m When the abundance ratio f of the monoclinic system is more than 10% and not more than 60%, excellent adhesiveness (particularly, adhesive durability) can be obtained. m is preferably more than 15%, more preferably 17% or more, even more preferably 18% or more, particularly preferably 20% or more, and most preferably 21% or more, in order to increase the number of fine cracks and improve adhesion (particularly adhesion durability). m is preferably 58% or less, more preferably 55% or less, even more preferably 50% or less, particularly preferably 45% or less, and most preferably 40% or less, in order to have fine cracks in an appropriate range and to achieve better adhesion (particularly adhesion durability). m The measurement method is as described in the Examples below.

[0017] The monoclinic zirconia is preferably present on the surface. In the zirconia composite sintered body, the monoclinic zirconia is present on the surface at the above-mentioned abundance ratio f m The presence of hydroxybenzoates provides superior adhesive properties (particularly adhesive durability).

[0018] The surface roughness Ra is the arithmetic average value of the surface irregularities in the height direction. The surface roughness Ra of the surface of the zirconia composite sintered body of the present invention is preferably 3.0 μm or more, more preferably 3.5 μm or more, even more preferably 4.0 μm or more, and particularly preferably 4.5 μm or more, from the viewpoints of improving the anchoring effect of the adhesive, thereby improving the adhesive strength and providing better adhesion (particularly, adhesion durability). Furthermore, the surface roughness Ra is preferably 8.0 μm or less, more preferably 7.5 μm or less, even more preferably 7.0 μm or less, and particularly preferably 6.5 μm or less, from the viewpoints of preventing the surface from becoming brittle, ensuring the strength required for a dental prosthesis, and providing better adhesion (particularly, adhesion durability). The method for measuring the surface roughness Ra is as described in the Examples below. A large surface roughness Ra means that the surface irregularities are deep, allowing the surface adhesive to penetrate deep into the surface, enhancing the anchoring effect and resulting in higher adhesive strength.

[0019] The mean irregularity spacing RSm is the value measured by the spacing between irregularities when the cross section of the rough surface is viewed from the side. The mean irregularity spacing RSm on the surface of the zirconia composite sintered body of the present invention is preferably 50 μm or more, more preferably 100 μm or more, even more preferably 150 μm or more, particularly preferably 200 μm or more, and most preferably 250 μm or more, from the viewpoint of improving the anchoring effect of the adhesive, improving the adhesive strength, and providing better adhesion (particularly, adhesive durability). Furthermore, the mean irregularity spacing RSm is preferably 700 μm or less, more preferably 600 μm or less, even more preferably 500 μm or less, particularly preferably 450 μm or less, and most preferably 400 μm or less, from the viewpoint of preventing the surface from becoming brittle, ensuring the strength as a dental prosthesis, and providing better adhesion (particularly, adhesive durability). The method for measuring the mean irregularity spacing RSm is as described in the Examples below. A small mean irregularity spacing RSm means that the spacing between irregularities is narrow, the surface is finely roughened, and the specific surface area is large, resulting in a higher adhesive strength.

[0020] The liquid penetration depth on the surface of the zirconia composite sintered body of the present invention is preferably 0.5 mm or more, more preferably 1.5 mm or more, even more preferably 2.0 mm or more, particularly preferably 2.5 mm or more, and most preferably 3.0 mm or more, from the viewpoint of providing gaps through which the adhesive can penetrate and achieving superior adhesion (particularly, adhesive durability). A high penetration depth generates many fine cracks on the surface, allowing a large amount of liquid to penetrate into the fine gaps. In other words, the liquid adhesive penetrates deeper into the surface, enhancing the adhesive's anchoring effect, thereby improving adhesive strength and resulting in superior adhesion (particularly, adhesive durability). Furthermore, the liquid penetration depth on the surface is preferably 7 mm or less, more preferably 6.5 mm or less, even more preferably 6 mm or less, particularly preferably 5.5 mm or less, and most preferably 5 mm or less, from the viewpoint of preventing the surface from becoming brittle, ensuring the strength required for a dental prosthesis, and achieving superior adhesion (particularly, adhesive durability). The method for measuring the penetration depth is as described in the Examples below. By being within the range of the penetration, the monoclinic abundance f m This works in unison with the adhesive, making it possible to achieve both strength and excellent adhesiveness for dental prostheses.

[0021] In this specification, the description of the zirconia composite sintered body of the present invention is applicable to all embodiments unless otherwise specified.

[0022] 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.

[0023] In the zirconia composite sintered body of the present invention, examples of stabilizers capable of suppressing the phase transition of zirconia (hereinafter also referred to as "stabilizers") include calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide (YO), cerium oxide (CeO), scandium oxide (ScO), lanthanum oxide (LaO), erbium oxide (ErO), praseodymium oxide (PrO, PrO), and the like. 11 Examples of suitable stabilizers include oxides such as samarium oxide (SmO), europium oxide (EuO), thulium oxide (TmO), gallium oxide (GaO), indium oxide (InO), and ytterbium oxide (YbO), with YO (yttria) and / or CeO being preferred, and YO being more preferred, because when combined with other components including at least one of NbO or TaO, they provide excellent machinability and strength in the sintered state, and the dental prosthesis obtained after machining has excellent aesthetic properties, being closer to natural teeth. The stabilizers may be used alone or in combination of two or more.

[0024] In the zirconia composite sintered body of the present invention, the stabilizer content is preferably 1 to 12 mol% based on a total of 100 mol% of zirconia, the stabilizer, NbO, and TaO, and more preferably 2 mol% to 10 mol% in terms of easily obtaining sufficient machinability, and even more preferably 3 mol% to 8.0 mol% in terms of more excellent translucency and strength, 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 an embodiment in which the zirconia composite sintered body does not contain NbO and TaO, the stabilizer content refers to the content based on a total of 100 mol% of zirconia and the stabilizer.

[0025] Preferred embodiments of the zirconia composite sintered body of the present invention will be described below.

[0026] In order to achieve excellent machinability in a sintered state, the zirconia composite sintered body of the present invention preferably further contains NbO and / or TaO in addition to zirconia and a stabilizer capable of suppressing the phase transition of zirconia. One preferred embodiment includes a zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, and at least one of NbO and TaO.

[0027] Although the reason why the zirconia composite sintered body of the present invention has excellent machinability in the sintered state while maintaining strength is unclear, it is presumed that this is achieved by improving fracture toughness (IF method) by adding at least one of Nb2O5 and Ta2O5 to zirconia to which a conventional stabilizer has been added, and minimizing hardness by coarsening the microstructure. Also, by adding at least one of Nb2O5 and Ta2O5, fine cracks occur due to a reaction with the stabilizer whenever an external force is applied during machining, and at this time, the crystal system at least on the surface is more likely to undergo a phase transition from a tetragonal system to a monoclinic system, and the desired monoclinic system abundance rate f m It is expected that this will make it easier to adjust the range.

[0028] In the zirconia composite sintered body of the present invention, the content of Nb2O5 or Ta2O5 is preferably 1 to 9 mol%, more preferably 1.5 mol% to 8.5 mol%, based on a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. In order to obtain better machinability in the sintered body, the content is further preferably 2.5 mol% to 8.0 mol%, even more preferably 2.7 mol% to 7.0 mol%, particularly preferably 2.8 mol% to 6.0 mol%, and most preferably 3.0 mol% to 5.5 mol%. If the content of Nb2O5 or Ta2O5 is within the above range, sufficient machinability can be obtained in the sintered body while suppressing the occurrence of defects such as chipping.

[0029] Furthermore, the zirconia composite sintered body of the present invention preferably further contains, in addition to zirconia and a stabilizer capable of suppressing the phase transition of zirconia, an element or ion derived from a capping agent, in order to achieve excellent machinability in the sintered body state. Another preferred embodiment includes a zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, and a capping element or ion. In this embodiment, the zirconia composite sintered body may contain at least one of Nb2O5 and Ta2O5, or may not contain Nb2O5 or Ta2O5.

[0030] Hereinafter, a zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, at least one of NbO and TaO, and a capping element or ion will be described as an example, because it has particularly excellent machinability in the sintered body state. The zirconia composite sintered body of the present invention preferably contains zirconia, a stabilizer capable of suppressing the phase transition of zirconia, at least one of NbO and TaO, and an element or ion derived from the capping agent, because it has particularly excellent machinability.

[0031] 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, 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 at least 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. It is also presumed that the additional addition of a capping element or ion makes it more likely for microcracks to occur each time an external force is applied during machining.

[0032] 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%.

[0033] A zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, at least one of Nb2O5 and Ta2O5, and elements or ions derived from a capping agent has strength and translucency suitable for dental use and also has excellent machinability in the sintered state. The reason why the zirconia composite sintered body can be machined in the sintered state is unclear, but is presumed to be as follows. In zirconia, the stabilizer, and a zirconia composite sintered body (particularly preferably a zirconia composite sintered body containing Nb2O5 and / or Ta2O5), the presence of a capping element or ion at the grain boundaries is presumed to reduce grain boundary strength in the form of a +1-valent cation or a -1-valent anion, thereby acting in a direction that facilitates peeling of the particles, making them easier to cut and improving machinability.

[0034] 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 to 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 in the direction of improving machinability. For example, a +1-valent cation may bond to 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.

[0035] Furthermore, since Nb2O5 and / or Ta2O5 act to coarsen the microstructure and reduce the hardness in the zirconia composite sintered body, the capping element or ion and Nb2O5 and / or Ta2O5 act together to further improve the machinability of the sintered body. Therefore, the capping element or ion and Nb2O5 and / or Ta2O5 act together to further enhance the excellent machinability while maintaining the strength required for artificial teeth, thereby shortening the machining time and suppressing the wear of the machining tool, thereby increasing the number of dental prostheses that can be obtained by continuous machining using a single machining tool.

[0036] In the zirconia composite sintered body of the present invention, the capping element or ion further improves the machinability of the sintered body, acts as a free cutting aid as described above, and does not significantly impair the strength and translucency.

[0037] The content of the capping element or ion contained in the zirconia composite sintered body of the present invention is preferably more than 0 mol% and not more than 5 mol%, and from the viewpoint of providing superior machinability in the sintered body state and enabling a further increase in the number of dental prostheses that can be continuously machined with a single machining tool, the content 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 of the present invention is a Group 17 element or ion, the capping element or ion 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, from the viewpoints of providing superior machinability in the sintered body state and further increasing the number of dental prostheses that can be continuously machined with one machining tool.

[0038] As described above, it is important that the capping element or ion is a +1-valent cation or a −1-valent anion and is present at the grain boundary in order to exhibit appropriate interaction between the charged site at the grain boundary and the adsorption site.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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). The electron affinity (EA) is the energy released when an electron is added to a neutral atom. The 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.

[0043] Specific examples of the capping element include Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F, and from the viewpoint of further improving the machinability of the sintered body, Cu, Ag, Li, Na, K, Rb, Cs, Fr, I, Br, Cl, and F are 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.

[0044] 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.

[0045] As described above, NbO and TaO act to coarsen the microstructure and reduce hardness, and act together with the capping elements or ions to impart excellent machinability. In addition, they can maximize the sintered density through interaction with other components (e.g., TiO, AlO) added to the zirconia composite sintered body and application of HIP, thereby ensuring the aesthetics of natural teeth.

[0046] 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.

[0047] 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 1.0 or more and 1.6 or less, from the viewpoints that the combined action of the capping element or ion and 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.

[0048] In a preferred embodiment of the present invention, the zirconia content is 78 to 97.5 mol%, the stabilizer content is 1 to 12 mol%, the total content of Nb2O5 and Ta2O5 is 1 to 9 mol%, and the stabilizer contains Y2O3 and / or CeO2, and the capping element or ion content is more than 0 mol% and 5 mol% or less, relative to 100 mol% of the total 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 to 3.

[0049] The zirconia composite sintered body may contain a zirconia strengthening agent in order to provide better strength.

[0050] Examples of the zirconia reinforcing agent include TiO2, Al2O3, etc. The zirconia reinforcing agents may be used alone or in combination of two or more.

[0051] One embodiment of the present invention is a zirconia composite sintered body containing zirconia, the stabilizer, and at least one of NbO and TaO, wherein, relative to the total moles of zirconia, the stabilizer, NbO, and TaO, the zirconia composite sintered body further contains a zirconia strengthener in addition to zirconia, the stabilizer, NbO and / or TaO, and a capping element or ion. The zirconia strengthener acts integrally with the capping element or ion in the zirconia composite sintered body containing zirconia, the stabilizer, and NbO and / or TaO to improve the strength of the sintered body.

[0052] In the case of a zirconia composite sintered body containing a zirconia strengthening agent, as described above, the zirconia content, the type and content of the stabilizer, the total content of NbO and TaO, the type and content of the capping element or ion, and the A / B ratio can be appropriately changed.

[0053] 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 5.0 mass%, relative to 100 mass% of the total of zirconia, the stabilizer, 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 is more preferably 0.01 mass% or more and 4.5 mass% or less, and even more preferably 0.5 mass% or more and 4.0 mass% or less.

[0054] The content (mass%) of the zirconia strengthening agent is the external addition rate relative to the total of 100 mass% of zirconia, the stabilizer, NbO, and TaO. Therefore, the content of the zirconia strengthening agent in the zirconia composite sintered body can be calculated from the amount (mass) of the raw material charged when adding it.

[0055] A preferred embodiment includes a zirconia composite sintered body in which the zirconia reinforcement contains TiO2 and the TiO2 content is 0.6 to 3.7 mass %.

[0056] In one preferred embodiment, the ceramic composition contains zirconia, a stabilizer, at least one of Nb2O5 and Ta2O5, and a capping element or ion, and, relative to the total mol of zirconia, the stabilizer, Nb2O5, and Ta2O5, the total of zirconia, the stabilizer, Nb2O5, and Ta2O5 is 100 mol%, the zirconia content is 78 to 97.5 mol%, the stabilizer content is 1 to 12 mol%, the total content of Nb2O5 and Ta2O5 is 1 to 9 mol%, the stabilizer contains Y2O3 and / or CeO2, the zirconia reinforcer contains TiO2, and the TiO2 content is 0.6 to 3.7 mass%, The content of the capping element or ion is more than 0 mol % and 5 mol % or less relative to 100 mol % of the total of zirconia, the stabilizer, Nb2O5, and Ta2O5, and 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 to 3.

[0057] The average crystal grain size of the zirconia composite sintered body of the present invention is preferably 0.3 to 10 μm, and from the viewpoint of superior machinability, strength, and translucency, is more preferably 0.4 to 8 μm, even more preferably 0.5 to 5.0 μm, particularly preferably 0.5 to 4.5 μm, and most preferably 1.0 to 4.0 μm. The method for measuring the average crystal grain size is as described in the Examples below. The average crystal grain size can be measured in the method described in the Examples by adjusting the number of particles so that the number of particles contained in one field of view of an SEM photograph is approximately 50, 100, 200, 500, or 1,000.

[0058] The density of the zirconia composite sintered body is set to 5.5 g / cm because the higher the density, the fewer internal voids there are, the less light scattering occurs, and the more translucency and strength are improved. 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. 3 It 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.

[0059] The method for producing the zirconia composite sintered body of the present invention will be described below using an example in which the zirconia composite sintered body contains zirconia, a stabilizer, and at least one of NbO and TaO. The zirconia composite sintered body of other embodiments can also be produced by the same production method by changing the type and content of the raw material composition so as to obtain the desired zirconia composite sintered body.

[0060] The method for producing a zirconia composite sintered body of the present invention includes, for example, a step of preparing a compact using a raw material composition and a step of sintering the compact. For example, in the production of a zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, and at least one of NbO or TaO, the target compact can be obtained by using a raw material composition containing zirconia, the stabilizer, and at least one of NbO or TaO. For example, in the production of a zirconia composite sintered body containing zirconia, the stabilizer, at least one of NbO or TaO, and an element or ion derived from a capping agent, the target compact can be obtained by using a raw material composition containing zirconia, the stabilizer, at least one of NbO or TaO, and the capping agent.

[0061] 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, and may be in the form of, for example, powder, granules, agglomerates, paste, slurry, or the like.

[0062] In an embodiment in which the resulting zirconia composite sintered body contains a capping element or ion, the raw material composition contains a capping agent. 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., containing 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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).

[0069] 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 that also contain YO can 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 be used in the raw material composition of the present invention.

[0070] 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 to produce 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 (2): y =I 29 / (I 28 +I 29 +I 30 )×100 (2) (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.)

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] In the raw material composition or the molded article of the present invention, the stabilizer (preferably yttria) may not be entirely dissolved in zirconia. In the present invention, the term "solid solution of the stabilizer" means, for example, that an element (atom) (preferably yttrium atom) contained in the stabilizer is dissolved in zirconia.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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. Each of the additives may be used alone or in combination of two or more.

[0085] 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 optionally a capping agent, to water, and then milling the slurry.

[0086] 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.

[0087] Examples of the plasticizer include polyethylene glycol, glycerin, propylene glycol, and dibutyl phthalate.

[0088] 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.

[0089] Examples of emulsifiers include alkyl ethers, phenyl ethers, and sorbitan derivatives.

[0090] Examples of the antifoaming agent include alcohol, polyether, silicone, and wax.

[0091] Examples of pH adjusters include ammonia and ammonium salts (including ammonium hydroxides such as tetramethylammonium hydroxide).

[0092] Examples of the lubricant include polyoxyethylene alkyl ether and wax.

[0093] The solvent used in the wet mixing is not particularly limited as long as it contains water, and an organic solvent may be used, a mixed solvent of water and an organic solvent may be used, or water alone may be used. Examples of organic solvents 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. One organic solvent may be used alone, or two or more organic solvents may be used in combination.

[0094] The raw material composition for the zirconia composite sintered body used in the present invention may contain components other than zirconia, YO, NbO, TaO, capping agent, and zirconia reinforcement, as long as the effects of the present invention are achieved. Examples of such components include colorants (pigments and composite pigments), fluorescent agents, and SiO. Each of the other components may be used alone, or two or more may be mixed.

[0095] 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.

[0096] 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 .

[0097] 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.

[0098] 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.

[0099] 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.

[0100] The pressing pressure in the press molding 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 molded body, 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 molded body are more fully filled, the open porosity can be set lower, and the density of the molded body can be increased. Furthermore, in order to increase the density of the obtained zirconia molded body, a cold isostatic pressing (CIP) treatment may be further performed after uniaxial pressing.

[0101] Next, the resulting molded body is sintered to obtain a zirconia composite sintered body. The sintering temperature (maximum sintering temperature) for obtaining 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. Furthermore, 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. In the method for producing the zirconia composite sintered body of the present invention, the molded body is preferably fired at a maximum sintering temperature of 1300 to 1680°C. The maximum sintering temperature is preferably a temperature in the atmosphere. Furthermore, by lowering the maximum sintering temperature (selecting a low temperature range), the amount of heat is reduced compared to when the high sintering temperature is high (e.g., 1680°C). As a result, the stability of the tetragonal crystal system of zirconia is reduced, making it more likely to change to a monoclinic system, and making it easier to adjust the monoclinic fraction of the surface after processing. From this viewpoint, the maximum sintering temperature may be set to 1580° C. or less, 1550° C. or less, etc. In one preferred embodiment, there is mentioned a method for producing a zirconia composite sintered body, in which a compact is sintered at a maximum sintering temperature of 1300 to 1580° C.

[0102] 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 excellent in bending strength, translucency, and machinability can be produced depending on the stabilizer content. 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.

[0103] In the method for producing a zirconia composite sintered body of the present invention, the heating rate during sintering of the molded body 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 heating 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 heating rate at or above the lower limit, productivity is improved.

[0104] 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, and F-2 (all manufactured by SK Medical Electronics Co., Ltd.).

[0105] 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.

[0106] 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."

[0107] The HIP treatment can be carried out using a known hot isostatic press (HIP) device.

[0108] 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 HIP temperature is preferably 1200° C. or higher, more preferably 1300° C. or higher, and even more preferably 1400° C. or higher. The HIP temperature is also preferably 1700° C. or lower, more preferably 1650° C. or lower, and even more preferably 1600° C. or lower.

[0109] In the method for producing a zirconia composite sintered body of the present invention, the HIP pressure when the primary sintered body is subjected to HIP treatment is not particularly limited, and since a dense sintered body with high strength can be obtained, the HIP pressure 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 HIP pressure is not particularly limited, but can be, for example, 400 MPa or less, 300 MPa or less, or even 200 MPa or less.

[0110] In the method for producing a zirconia composite sintered body of the present invention, when the primary sintered body is subjected to HIP treatment, the heating 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 heating 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 heating rate at or above the lower limit, productivity is improved.

[0111] In the method for producing a zirconia composite sintered body of the present invention, when the primary sintered body is subjected to HIP treatment, the HIP 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.

[0112] In the method for producing a zirconia composite sintered body of the present invention, 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.

[0113] In the method for producing a zirconia composite sintered body of the present invention, 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. An "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%.

[0114] The zirconia composite sintered body of 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.

[0115] 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.

[0116] 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.).

[0117] The zirconia composite sintered body of the present invention has excellent machinability despite being a sintered body, and therefore does not need to be machined in the form of a mill blank of a semi-sintered composite calcined body and then sintered 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 from the raw material composition is calcined to produce a semi-sintered composite calcined body, and the unprocessed composite calcined body is then machined to form a sintered body.

[0118] Furthermore, the zirconia composite sintered body of the present invention contains a predetermined proportion of monoclinic zirconia on the surface by machining, and therefore has excellent adhesiveness without sandblasting after machining, eliminating the need to irradiate the surface of the sintered body with a laser such as an ultrashort pulse laser as in Patent Document 2. In other words, the zirconia composite sintered body of the present invention does not need to have nanopores (open pores) on the surface.

[0119] As another embodiment, there is mentioned a method for producing a zirconia composite sintered body, which includes the steps of: preparing a molded body using 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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 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 "composite calcined body."

[0124] The zirconia composite sintered body of the present invention has excellent strength. The biaxial bending strength of the zirconia composite sintered body of 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 of the present invention has such a biaxial bending strength, it can suppress fracture in the oral cavity 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.

[0125] The zirconia composite sintered body of the present invention preferably has high translucency. * Specifically, in the zirconia composite sintered body of the present invention, the translucency can be evaluated by ΔL (W−B) in a sample having a diameter of 15 mm and a thickness of 1.2 mm. *(W−B) is preferably 10 or more, more preferably 11 or more, even more preferably 12 or more, and particularly preferably 13 or more. * When (W−B) is within the above range, a highly aesthetic zirconia composite sintered body that is closer to natural teeth can be obtained.

[0126] ΔL * (W-B) 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 hiding power 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 hiding power test paper.

[0127] ΔL * There is no particular upper limit to (WB), but it may be, for example, 25 or less, and from the viewpoint of aesthetics, even 20 or less.

[0128] 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)).

[0129] Dental prostheses manufactured using the zirconia composite sintered body of 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.

[0130] The zirconia composite sintered body of the present invention can also be used for applications other than dental applications, and is particularly suitable for zirconia components that require 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 of 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 that are difficult to produce using 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.

[0131] Another embodiment is a dental restoration kit including a combination of any of the above-described dental zirconia composite sintered bodies and dental cement.

[0132] The dental cement is not particularly limited, and any known dental cement can be used, such as those described in JP-A-2002-212019, JP-A-2013-209341, and JP-A-2017-105715.

[0133] The dental cement preferably contains an acidic component.

[0134] The acidic component preferably contains a monomer having an acidic group, since high adhesiveness can be achieved by combining NbO and / or TaO contained in the dental zirconia composite sintered body with, if necessary, a capping element. The monomer having an acidic group may be used alone or in combination of two or more.

[0135] The monomer having an acidic group is preferably a monomer containing at least one selected from the group consisting of a phosphate group, a pyrophosphate group, a thiophosphate group, a phosphonate group, a carboxylic acid group, and a sulfonic acid group, and is preferably a (meth)acrylic monomer having at least one polymerizable group such as a (meth)acryloyloxy group or a (meth)acrylamide group.

[0136] Examples of the phosphate group-containing (meth)acrylic monomer include 2-(meth)acryloyloxyethyl dihydrogen phosphate, 3-(meth)acryloyloxypropyl dihydrogen phosphate, 4-(meth)acryloyloxybutyl dihydrogen phosphate, 5-(meth)acryloyloxypentyl dihydrogen phosphate, 6-(meth)acryloyloxyhexyl dihydrogen phosphate, 7-(meth)acryloyloxyheptyl dihydrogen phosphate, 8-(meth)acryloyloxyoctyl dihydrogen phosphate, 9-(meth)acryloyloxynonyl dihydrogen phosphate, 10-(meth)acryloyloxydecyl dihydrogen phosphate, and 11-(meth)acryloyloxyundecyl dihydrogen phosphate. phosphoric acid group-containing monofunctional (meth)acrylate compounds such as phosphate, 12-(meth)acryloyloxydodecyl dihydrogen phosphate, 16-(meth)acryloyloxyhexadecyl dihydrogen phosphate, 20-(meth)acryloyloxyeicosyl dihydrogen phosphate, 2-(meth)acryloyloxyethylphenyl hydrogen phosphate, 2-(meth)acryloyloxyethyl-2-bromoethyl hydrogen phosphate, 2-(meth)acryloyloxyethyl-(4-methoxyphenyl)hydrogen phosphate, and 2-(meth)acryloyloxypropyl-(4-methoxyphenyl)hydrogen phosphate; phosphoric acid group-containing monofunctional (meth)acrylate monomers such as acid chlorides, alkali metal salts, ammonium salts, and amine salts thereof;Examples of suitable difunctional (meth)acrylate compounds containing a phosphate group include bis[2-(meth)acryloyloxyethyl]hydrogenphosphate, bis[4-(meth)acryloyloxybutyl]hydrogenphosphate, bis[6-(meth)acryloyloxyhexyl]hydrogenphosphate, bis[8-(meth)acryloyloxyoctyl]hydrogenphosphate, bis[9-(meth)acryloyloxynonyl]hydrogenphosphate, bis[10-(meth)acryloyloxydecyl]hydrogenphosphate, and 1,3-di(meth)acryloyloxypropyl dihydrogenphosphate; and difunctional (meth)acrylate monomers containing a phosphate group, such as acid chlorides, alkali metal salts, ammonium salts, and amine salts thereof.

[0137] Examples of the pyrophosphate group-containing (meth)acrylic monomer include bis[2-(meth)acryloyloxyethyl] pyrophosphate, bis[4-(meth)acryloyloxybutyl] pyrophosphate, bis[6-(meth)acryloyloxyhexyl] pyrophosphate, bis[8-(meth)acryloyloxyoctyl] pyrophosphate, bis[10-(meth)acryloyloxydecyl] pyrophosphate, and acid chlorides, alkali metal salts, ammonium salts, and amine salts thereof.

[0138] Examples of the thiophosphate group-containing (meth)acrylic monomer include 2-(meth)acryloyloxyethyl dihydrogen thiophosphate, 3-(meth)acryloyloxypropyl dihydrogen thiophosphate, 4-(meth)acryloyloxybutyl dihydrogen thiophosphate, 5-(meth)acryloyloxypentyl dihydrogen thiophosphate, 6-(meth)acryloyloxyhexyl dihydrogen thiophosphate, 7-(meth)acryloyloxyheptyl dihydrogen thiophosphate, and 8-(meth)acryloyloxyoctyl dihydrogen thiophosphate. thiophosphate, 9-(meth)acryloyloxynonyl dihydrogen thiophosphate, 10-(meth)acryloyloxydecyl dihydrogen thiophosphate, 11-(meth)acryloyloxyundecyl dihydrogen thiophosphate, 12-(meth)acryloyloxydodecyl dihydrogen thiophosphate, 16-(meth)acryloyloxyhexadecyl dihydrogen thiophosphate, 20-(meth)acryloyloxyeicosyl dihydrogen thiophosphate, and acid anhydrides, acid halides (such as acid chlorides), alkali metal salts, and ammonium salts thereof.

[0139] Examples of the phosphonic acid group-containing (meth)acrylic monomer include 2-(meth)acryloyloxyethyl phenyl phosphonate, 5-(meth)acryloyloxypentyl-3-phosphonopropionate, 6-(meth)acryloyloxyhexyl-3-phosphonopropionate, 10-(meth)acryloyloxydecyl-3-phosphonopropionate, 6-(meth)acryloyloxyhexyl phosphonoacetate, 10-(meth)acryloyloxydecyl phosphonoacetate, and acid chlorides, alkali metal salts, ammonium salts, and amine salts thereof.

[0140] Examples of the carboxylic acid group-containing (meth)acrylic monomer include (meth)acrylic acid, 4-[2-[(meth)acryloyloxy]ethoxycarbonyl]phthalic acid, 4-(meth)acryloyloxyethyltrimellitic acid, 4-(meth)acryloyloxybutyloxycarbonylphthalic acid, 4-(meth)acryloyloxyhexyloxycarbonylphthalic acid, 4-(meth)acryloyloxyoctyloxycarbonylphthalic acid, 4-(meth)acryloyloxydecyl Examples of suitable acryloyloxycarbonylphthalic acid include hydroxycarbonylphthalic acid and acid anhydrides thereof; 5-(meth)acryloylaminopentylcarboxylic acid, 6-(meth)acryloyloxyhexane-1,1-dicarboxylic acid, 8-(meth)acryloyloxyoctane-1,1-dicarboxylic acid, 10-(meth)acryloyloxydecane-1,1-dicarboxylic acid, 11-(meth)acryloyloxyundecane-1,1-dicarboxylic acid, and acid chlorides, alkali metal salts, ammonium salts, and amine salts thereof.

[0141] Examples of sulfonic acid group-containing (meth)acrylic monomers include 2-(meth)acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl(meth)acrylate, and acid chlorides, alkali metal salts, ammonium salts, and amine salts thereof.

[0142] Among the monomers having an acidic group, phosphate group-containing (meth)acrylic monomers, pyrophosphate group-containing (meth)acrylic monomers, and carboxylic acid group-containing (meth)acrylic monomers are preferred because they exhibit superior adhesive strength, phosphate group-containing (meth)acrylic monomers and carboxylic acid group-containing (meth)acrylic monomers are more preferred, and phosphate group-containing monofunctional (meth)acrylate monomers are even more preferred. 20 or an alkyl group of C6 to C 20More preferred are phosphate group-containing monofunctional (meth)acrylate monomers having an alkylene group, and carboxylic acid group-containing (meth)acrylate monomers such as 4-(meth)acryloyloxyethyltrimellitic acid and 4-(meth)acryloyloxyethyltrimellitic acid anhydride, and 10-methacryloyloxydecyl dihydrogen phosphate and the like having C8 to C6 as the main chain in the molecule. 12 The most preferred is a phosphoric acid group-containing monofunctional (meth)acrylate monomer having an alkylene group of the formula:

[0143] The dental cement may contain, in addition to the monomer having an acidic group, a hydrophobic crosslinkable monomer without an acidic group (hereinafter also referred to simply as "hydrophobic crosslinkable monomer"). The hydrophobic crosslinkable monomer is a hydrophobic compound that does not have an acidic group in the molecule and has at least two polymerizable groups (e.g., (meth)acryloyloxy groups, (meth)acrylamide groups). Here, "hydrophobic" means that the solubility in water at 25°C is less than 5% by mass.

[0144] The hydrophobic crosslinkable monomer has the effect of improving the handling property and mechanical strength of the dental cement according to the present invention. Examples of the hydrophobic crosslinkable monomer include bifunctional polymerizable monomers of aromatic compounds, bifunctional polymerizable monomers of aliphatic compounds, and trifunctional or higher polymerizable monomers. The hydrophobic crosslinkable monomers may be used alone or in combination of two or more.

[0145] Examples of aromatic compound-based bifunctional polymerizable monomers include 2,2-bis((meth)acryloyloxyphenyl)propane, 2,2-bis[4-(2-hydroxy-3-(meth)acryloyloxypropoxy)phenyl]propane, 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane (average number of moles of ethoxy groups added: 2.6), 2,2-bis(4-(meth)acryloyloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxytetraethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypentaethoxyphenyl)propane, and bifunctional (meth)acrylate compounds such as 2,2-bis(4-(meth)acryloyloxydipropoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxyethoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2-(4-(meth)acryloyloxydipropoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypropoxyphenyl)propane, and 2,2-bis(4-(meth)acryloyloxyisopropoxyphenyl)propane.

[0146] Examples of the aliphatic compound-based bifunctional polymerizable monomer include bifunctional (meth)acrylate compounds such as glycerol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)di(meth)acrylate, and 1,2-bis(3-(meth)acryloyloxy-2-hydroxypropoxy)ethane.

[0147] Examples of the tri- or higher functional polymerizable monomer include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolmethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, N,N'-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetra(meth)acrylate, and 1,7-diacryloyloxy-2,2,6,6-tetra(meth)acryloyloxymethyl-4-oxaheptane.

[0148] The dental cement preferably contains a chemical polymerization initiator. The chemical polymerization initiator can be selected from polymerization initiators generally used in industry, and among these, chemical polymerization initiators used in dental cements are preferably used.

[0149] The chemical polymerization initiator used in the present invention comprises an oxidizing agent and a reducing agent.

[0150] Examples of the oxidizing agent for the chemical polymerization initiator include organic peroxides, azo compounds, inorganic peroxides, etc. The oxidizing agents may be used alone or in combination of two or more.

[0151] Examples of organic peroxides include diacyl peroxides, peroxy esters, dialkyl peroxides, peroxy ketals, ketone peroxides, and hydroperoxides. Specific examples of diacyl peroxides include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and m-toluoyl peroxide. Specific examples of peroxy esters include t-butyl peroxybenzoate, bis(t-butylperoxy)isophthalate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxy-2-ethylhexanoate, and t-butylperoxyisopropyl carbonate. Specific examples of dialkyl peroxides include dicumyl peroxide, di-t-butyl peroxide, and lauroyl peroxide. Specific examples of peroxyketals include 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, and 1,1-bis(t-hexylperoxy)cyclohexane. Specific examples of ketone peroxides include methyl ethyl ketone peroxide, cyclohexanone peroxide, and methyl acetoacetate peroxide. Specific examples of hydroperoxides include t-butyl hydroperoxide, cumene hydroperoxide, p-diisopropylbenzene hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide. Examples of azo compounds include 2,2'-azobisisobutyronitrile and azobisisobutylvaleronitrile. Examples of inorganic peroxides include sodium persulfate, potassium persulfate, aluminum persulfate, and ammonium persulfate.

[0152] Examples of reducing agents for chemical polymerization initiators include aromatic amines having no electron-withdrawing group on the aromatic ring, thioureas, ascorbic acid, etc. The reducing agents may be used alone or in combination of two or more. Examples of aromatic amines having no electron-withdrawing group on the aromatic ring include N,N-bis(2-hydroxyethyl)-3,5-dimethylaniline, N,N-bis(2-hydroxyethyl)-p-toluidine, N,N-bis(2-hydroxyethyl)-3,4-dimethylaniline, N,N-bis(2-hydroxyethyl)-4-ethylaniline, N,N-bis(2-hydroxyethyl)-4-isopropylaniline, N,N-bis(2-hydroxyethyl)-4-t-butylaniline, and N,N-bis(2-hydroxyethyl)-3,5-diisopropylaniline. Examples of aromatic amines that do not have an electron-withdrawing group on the aromatic ring include aniline, N,N-bis(2-hydroxyethyl)-3,5-di-t-butylaniline, N,N-dimethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethyl-m-toluidine, N,N-diethyl-p-toluidine, N,N-dimethyl-3,5-dimethylaniline, N,N-dimethyl-3,4-dimethylaniline, N,N-dimethyl-4-ethylaniline, N,N-dimethyl-4-isopropylaniline, N,N-dimethyl-4-t-butylaniline, and N,N-dimethyl-3,5-di-t-butylaniline. The aromatic amines that do not have an electron-withdrawing group on the aromatic ring may be used alone or in combination of two or more. Examples of thioureas include thiourea, methylthiourea, ethylthiourea, ethylenethiourea, N,N'-dimethylthiourea, N,N'-diethylthiourea, N,N'-di-n-propylthiourea, N,N'-dicyclohexylthiourea, trimethylthiourea, triethylthiourea, tri-n-propylthiourea, tricyclohexylthiourea, tetramethylthiourea, tetraethylthiourea, tetra-n-propylthiourea, tetracyclohexylthiourea, 1-(2-pyridyl)-2-thiourea, 4,4-dimethylethylenethiourea, etc. One type of the thiourea may be used alone, or two or more types may be used in combination.

[0153] Among the oxidizing agents and reducing agents, from the viewpoint of the curability of the composition, a combination of a hydroperoxide (oxidizing agent) and a thiourea (reducing agent), and a combination of a diacyl peroxide and / or an inorganic peroxide (oxidizing agent) and an aromatic amine (reducing agent) having no electron-withdrawing group on the aromatic ring are preferred.

[0154] In order to make the dental cement a dual-cure composition in which polymerization is initiated by light irradiation, a conventionally known photopolymerization initiator may be blended in addition to the chemical polymerization initiator described above. Examples of the photopolymerization initiator include photopolymerization initiators that can be used in dental cements, such as (bis)acylphosphine oxides, water-soluble acylphosphine oxides, thioxanthones or quaternary ammonium salts of thioxanthones, ketals, α-diketones, coumarins, anthraquinones, benzoin alkyl ether compounds, and α-aminoketone compounds. The photopolymerization initiators may be used alone or in combination. Among these, at least one selected from the group consisting of (bis)acylphosphine oxides and α-diketones is preferred. Among these, 2,4,6-trimethylbenzoyldiphenylphosphine oxide is particularly preferred as the (bis)acylphosphine oxide, and camphorquinone is particularly preferred as the α-diketone.

[0155] In the dental cement, the chemical polymerization initiator and / or photopolymerization initiator is preferably used together with a polymerization accelerator. Examples of the polymerization accelerator include aliphatic amines, aromatic tertiary amines having an electron-withdrawing group, sulfinic acid and its salts, sulfur-containing reducing inorganic compounds, borate compounds, barbituric acid derivatives, triazine compounds, copper compounds, tin compounds, vanadium compounds, halogen compounds, aldehydes, and thiol compounds. One type of the polymerization accelerator may be used alone, or two or more types may be used in combination.

[0156] The dental cement preferably contains a filler. Examples of the filler include organic fillers, inorganic fillers, and organic-inorganic composite fillers. One type of filler may be used alone, or two or more types may be used in combination.

[0157] Examples of organic filler materials include polymethyl methacrylate, polyethyl methacrylate, methyl methacrylate-ethyl methacrylate copolymer, cross-linked polymethyl methacrylate, cross-linked polyethyl methacrylate, polyester, polyamide, polycarbonate, polyphenylene ether, polyoxymethylene, polyvinyl chloride, polystyrene, polyethylene, polypropylene, chloroprene rubber, nitrile rubber, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, acrylonitrile-styrene copolymer, and acrylonitrile-styrene-butadiene copolymer. These may be used alone or in combination of two or more. The shape of the organic filler is not particularly limited, and the particle size of the filler can be appropriately selected and used.

[0158] Examples of inorganic filler materials include quartz, silica, alumina, silica-titania, silica-titania-barium oxide, silica-zirconia, silica-alumina, lanthanum glass, borosilicate glass, soda glass, barium glass, strontium glass, glass ceramic, aluminosilicate glass, barium boroaluminosilicate glass, strontium boroaluminosilicate glass, fluoroaluminosilicate glass, calcium fluoroaluminosilicate glass, strontium fluoroaluminosilicate glass, barium fluoroaluminosilicate glass, and strontium calcium fluoroaluminosilicate glass. These may also be used alone or in combination of two or more. The shape of the inorganic filler is not particularly limited, and amorphous fillers, spherical fillers, etc. can be appropriately selected and used. Organic-inorganic composite fillers produced by known methods using the above-mentioned organic fillers and inorganic fillers can be used.

[0159] The present invention includes embodiments in which all or part of the above-described configurations and embodiments 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.

[0160] 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.

[0161] [Examples 1 to 9] Measurement samples for each example were prepared through the steps of preparing a granular raw material composition, preparing a compact, preparing a zirconia composite sintered body (preparation of a primary sintered body, HIP treatment, and tempering treatment), and preparing a desired shape using a wet processing machine. However, in Examples 2 to 9, except that various conditions were changed to those shown in Table 1, the samples were prepared through the following steps in the same manner as in Example 1.

[0162] [Preparation of Granular Raw Material Composition] To prepare the granular raw material composition of each example, commercially available ZrO powder, YO powder, NbO powder, TaO powder, 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 Table 1. 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 to manufacture 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.

[0163] [Preparation of Molded Body] For each Example, a block-shaped molded body was prepared as follows so as to obtain a zirconia composite sintered body sample for evaluating the penetration degree, surface roughness, surface unevenness, and adhesion.

[0164] The block-shaped compact was prepared by placing the raw material composition in a mold having an inner dimension of 19 mm × 18 mm so that the height 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 produce a block-shaped compact.

[0165] [Preparation of primary sintered body] The obtained block-shaped compact was subjected to sintering in the atmosphere for 2 hours at the maximum sintering temperature shown in Table 1 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).

[0166] [Preparation of HIP-treated sintered body] The obtained block-shaped zirconia composite sintered body (primary sintered body) was subjected to a HIP apparatus "O2-Dr. HIP" manufactured by Kobe Steel, Ltd., and held at 150 MPa in an argon atmosphere at the HIP temperature shown in Table 1 for 2 hours, thereby obtaining a sample of a block-shaped zirconia composite sintered body (HIP-treated sintered body).

[0167] [Preparation of zirconia composite sintered body (tempered sintered body)] The obtained block-shaped zirconia composite sintered body (HIP-treated sintered body) was subjected to heating 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 sample block was 15.7 mm wide x 16.5 mm long x 14.5 mm high.

[0168] [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 with a width of 15.7 mm and a height of 14.5 mm was prepared by adhering a metal jig to a surface. Using a CEREC system "MC-XL" (manufactured by Dentsply Sirona), a sample for evaluating the liquid permeability of the sintered body (width 4 mm x length 4 mm x height 10 mm), a sample for evaluating the surface roughness Ra of the sintered body (diameter 10 mm x thickness 5 mm), a sample for evaluating the mean irregularity spacing RSm of the sintered body (diameter 10 mm x thickness 5 mm), and a sample for evaluating the adhesiveness of the sintered body (diameter 10 mm x thickness 5 mm) were processed. The processing program used was the software "inLab (registered trademark) CAM version 20.0.1.203841," with the following settings selected: Manufacture: IVOCLAR VIVADENT, Material name: IPS e. max CAD, Production Method: Grinding, Block size: C16, and the processing tools used were Step Bur 12 and Cylinder Pointed Bur 12S. In Examples 1 and 3 to 9, the machined sintered body was used as the evaluation sample. In Example 2, the machined sintered body was sandblasted with a 50-micron alumina abrasive (manufactured by Morita Corporation) to prepare the evaluation sample.

[0169] [Comparative Examples 1 and 2] Measurement samples for each of the comparative examples were prepared through the following steps: preparation of a granular raw material composition, preparation of a molded body, preparation of a zirconia composite calcined body, preparation of a desired shape using a dry processing machine, and preparation of a zirconia composite sintered body.

[0170] [Preparation of Granular Raw Material Composition] To prepare the granular raw material composition of each example, commercially available ZrO powder and YO powder were mixed so that the content of each component in the sintered zirconia composite sintered body would be the composition shown in Table 1, and water was added to prepare a slurry. The mixture 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 a water-diluted slurry with ultrasonic waves for 30 minutes, followed by ultrasonic irradiation.

[0171] [Preparation of Molded Body] For each example, a block-shaped molded body was prepared as follows so as to obtain a zirconia composite sintered body sample for evaluating the permeability, the surface roughness Ra, the mean irregularity spacing RSm, and the adhesion.

[0172] The block-shaped compact was prepared by placing the raw material composition in a mold having an inner dimension of 19 mm × 18 mm so that the height 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 produce a block-shaped compact.

[0173] [Preparation of Zirconia Composite Calcined Body] The obtained molded body was subjected to a firing furnace "Noritake Katana (registered trademark) F-1" manufactured by SK Medical Electronics Co., Ltd., and was retained in the atmosphere at 1100°C for 2 hours to obtain a zirconia composite calcined body.

[0174] [Preparation of desired shapes using a dry processing machine] The obtained zirconia composite calcined body was processed using a CEREC system "MC-XL" (manufactured by Dentsply Sirona) into a sample for evaluating liquid permeability as a sintered composite body (width 4 mm × length 4 mm × height 10 mm), a sample for evaluating surface roughness Ra as a sintered composite body (diameter 10 mm × thickness 5 mm), a sample for evaluating mean irregularity spacing RSm as a sintered zirconia composite sintered body (diameter 10 mm × thickness 5 mm), and a sample for evaluating adhesion as a sintered composite sintered body (diameter 10 mm × thickness 5 mm), and processed bodies were obtained. The processing program used the software "inLab (registered trademark) CAM version 20.0.1.203841", and the following were selected: Manufacture: KURARAY NORITAKE, Material name: KATANA Zr ONE, Production Method: Milling, Block size: CROWN, and the processing tools used were Shaper 25 and Finisher 10.

[0175] [Preparation of Zirconia Composite Sintered Body] The obtained processed body was subjected to a firing furnace "Noritake Katana (registered trademark) F-1" manufactured by SK Medical Electronics Co., Ltd., and held in the atmosphere for 2 hours at the maximum sintering temperature listed in Table 1 to obtain a composite sintered body. In Comparative Example 1, the composite sintered body was used as an evaluation sample. In Comparative Example 2, the composite sintered body was subjected to sandblasting treatment with a 50-micron alumina abrasive (manufactured by Morita Corporation) to obtain an evaluation sample.

[0176] The content of each component of the zirconia composite sintered body in Table 1 is a value calculated from the amount of raw material charged. The content (mol%) of a capping element or ion (e.g., Na) in Table 1 is the external addition rate relative to a total of 100 mol% of zirconia (the sum of ZrO2 and HfO2), the stabilizer (yttria), Nb2O5, and Ta2O5. The respective contents (mol%) of zirconia, the stabilizer, Nb2O5, and Ta2O5 in Table 1 are the contents of each component relative to a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. The content (mass%) of TiO2 in Table 1 is the external addition rate relative to a total of 100 mass% of zirconia, the stabilizer, Nb2O5, and Ta2O5. In Table 1, 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 %.

[0177] [The proportion of monoclinic crystals in the zirconia composite sintered body f m Measurement method for the monoclinic crystal abundance f m was determined by analyzing the crystalline phase of the zirconia composite sintered body. Specifically, X-ray diffraction (XRD) measurement was performed under the following measurement conditions using a fully automatic horizontal multipurpose X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation) and X-ray analysis integrated software (SmartLab Studio II, manufactured by Rigaku Corporation), and the area intensity of each peak (peak area intensity I) was calculated, and the abundance ratio f of the monoclinic system present on the surface was determined. m was determined (arithmetic mean value of n = 2). X-ray source: Cu Kα (λ = 1.54186 Å) Goniometer length: 300 mm Optical system: focusing method Detector: high-speed one-dimensional X-ray detector (D / teX Ultra 250) Monochromatization: Kβ filter Tube voltage: 45 kV Tube current: 200 mA Scan axis: 2θ / θ Scan speed: 50.00° / min Sampling step: 0.01°

[0178] Monoclinic crystal abundance f m The values ​​of f were calculated from the following formula (1) by assigning each peak to a crystalline phase. The calculation results are shown in Table 1. m =I28 / (I 28 +I 30 )×100 (1) (where f m represents the abundance rate (%) of the monoclinic system, 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 30 (The symbol " represents the integrated intensity of the peak near 2θ = 30°, where the main peak of the tetragonal or cubic system appears.) For the measurements, disc-shaped zirconia composite sintered bodies of each Example and Comparative Example were used as samples. Figure 1 shows the XRD measurement results of the dental zirconia composite sintered body of Example 1 before and after machining. Figure 2 shows a partially enlarged view of Figure 1. As shown in Figures 1 and 2, it was confirmed that the dental zirconia composite sintered body of Example 1 contained monoclinic zirconia after machining.

[0179] [Method for measuring average crystal grain size in sintered body] For the pellet-shaped zirconia composite sintered bodies of each example and comparative example, an image of the surface was taken using a scanning electron microscope (product name "VE-9800", manufactured by Keyence Corporation). After the grain boundaries of each crystal grain were noted on the obtained image, the average crystal grain size was calculated by image analysis. To measure the average crystal grain size, image analysis software (product name "Image-Pro Plus", manufactured by Hakuto Co., Ltd.) was used to binarize the captured SEM image, adjust the brightness range so that the grain boundaries were clearly visible, and recognize the particles from the field of view (area). The crystal grain size obtained using Image-Pro Plus is the average of the lengths 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 was used as the average crystal grain size (by number) in the zirconia composite sintered body. "Particles not on the edge of the image" refers to particles excluding particles whose outlines do not fit within the screen 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 was determined by selecting the option to exclude all particles on all boundary lines in Image-Pro Plus.

[0180] [Method for Measuring Liquid Penetration of Zirconia Composite Sintered Body] The liquid penetration of the zirconia composite sintered body was evaluated using evaluation samples (4 mm × 4 mm × 10 mm) for the zirconia composite sintered body of each Example and Comparative Example. Specifically, the evaluation was performed using the following method. The evaluation sample for the liquid penetration of the zirconia composite sintered body was placed vertically in the center of the bottom of a glass container with a wide opening and a bottom diameter of 5 mm or more, which did not allow liquid to penetrate. A staining solution (e.g., "Crack Finder" product, manufactured by Kuraray Noritake Dental Co., Ltd.) was poured into the evaluation sample to a height of 1 mm vertically from the bottom of the evaluation sample and allowed to stand for 2 minutes. The sample was then lifted vertically from the bottom of the container and the staining solution was washed off with purified water. After washing, the length from the bottom of the evaluation sample to the stained portion remaining after washing was measured (arithmetic mean value for n = 5).

[0181] [Method for measuring surface roughness Ra of zirconia composite sintered body] Surface roughness Ra was evaluated using a sample (diameter 10 mm × thickness 5 mm) for evaluating the surface roughness Ra of the zirconia composite sintered body of each Example and Comparative Example. Specifically, the evaluation was performed by the following method. The surface of each Example and Comparative Example was observed using 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 images were analyzed using image analysis software (product name "VK Analyzer", manufactured by Keyence Corporation) to calculate the surface roughness, which was defined as the surface roughness Ra (arithmetic mean value of n = 3).

[0182] [Method for measuring the mean irregularity spacing RSm on the surface of a zirconia composite sintered body] The mean irregularity spacing RSm was evaluated using samples (diameter 10 mm × thickness 5 mm) for evaluating the mean irregularity spacing RSm of the zirconia composite sintered bodies of each Example and Comparative Example. Specifically, the evaluation was performed by the following method. The surface of each Example and Comparative Example was observed using 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 images were analyzed using image analysis software (product name "VK Analyzer", manufactured by Keyence Corporation) to calculate the mean irregularity spacing, which was designated as the mean irregularity spacing RSm (arithmetic mean value of n = 3).

[0183] [Adhesion Evaluation of Zirconia Composite Sintered Body] Adhesion evaluation samples (10 mm diameter × 5 mm thickness) of the zirconia composite sintered body of each Example and Comparative Example were used to evaluate adhesion. Specifically, the evaluation was performed using the following method. For each zirconia composite sintered body sample of each Example and Comparative Example, the sample was embedded in a stainless steel ring using dental composite resin so that the surface condition (machined surface or sandblasted surface) described in Table 1 was exposed. Next, dental cement (product name "SA Routing Multi" manufactured by Kuraray Noritake Dental Co., Ltd.) paste was applied to one end face (circular cross section) of a stainless steel cylindrical tip (5 mm diameter, 1.0 cm length), and the end face on which the dental cement paste was applied was placed on the embedded sample. A 500 g load was then applied vertically from above the stainless steel cylindrical tip, and the stainless steel cylindrical tip and the margin of the smooth surface were irradiated for 2 to 5 seconds using a dental polymerization light irradiator (trade name "PenCure 2000", manufactured by Morita Corporation) to remove excess cement. The dental polymerization light irradiator was then irradiated for 10 seconds. After 10 minutes, the 500 g load was removed and the specimens were used as test samples. Ten test samples were prepared. The specimens were immersed in water at 37°C for 24 hours, and then their shear bond strength was measured. The shear bond strength was measured using a universal testing machine (trade name "AG-I 100 kN", manufactured by Shimadzu Corporation) at a crosshead speed of 1 mm / min. The arithmetic mean of the measurements for five of the ten specimens was used as the shear bond strength. After immersion in water at 37°C for 24 hours, the shear bond strength evaluated was shown in Table 1 below as "Adhesion X (unit: MPa) after 1 day at 37°C." The remaining five test pieces bonded to dentin were subjected to a thermal cycle (TC) load by alternately immersing them in a water bath at 4°C and a water bath at 60°C for 1 minute each 20,000 times, and then the shear bond strength was measured. The tensile bond strength after this thermal cycle load was used to evaluate adhesion durability. The results are shown in Table 1 below as "Y (unit: MPa) after 20,000 TC cycles." In this test, a "Adhesion X after 1 day at 37°C" of 39 MPa or more and an X / Y (%) of 48% or more were considered to be acceptable.

[0184]

[0185] From the above results, it was confirmed that the machinable zirconia composite sintered body of the present invention has excellent adhesiveness without sandblasting after machining. In Example 2, it was confirmed that by subjecting the body to sandblasting after machining, it has even higher adhesive durability.

[0186] On the other hand, in Comparative Example 1, the initial adhesion was low and the adhesion durability was significantly poor because sandblasting was not performed after machining. In Comparative Example 2, the adhesion durability was not sufficiently improved and the adhesion durability was poor, even though sandblasting was performed after machining.

[0187] The zirconia composite sintered body of the present invention has excellent adhesiveness without sandblasting after machining, and is therefore particularly useful as a dental material for dental prostheses and other dental treatments.

Claims

1. The monoclinic zirconia contains monoclinic zirconia and has a monoclinic abundance ratio f represented by the following formula (1): m is more than 10% and not more than 60%. m = I 28 / (I 28 +I 30 )×100 (1) (where f m represents the percentage of monoclinic crystals, and in the XRD measurement, I 28 represents the integrated intensity of the peak at 2θ = 28° where the main peak of the monoclinic system 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.) 2. The dental zirconia composite sintered body according to claim 1, wherein the monoclinic zirconia is present on the surface.

3. A dental zirconia composite sintered body according to claim 1 or 2, having a surface roughness Ra of 3.0 to 8.0 μm.

4. A dental zirconia composite sintered body according to claim 1 or 2, having an average crystal grain size of 0.5 to 10 μm.

5. A dental zirconia composite sintered body according to claim 1 or 2, further comprising a stabilizer capable of suppressing the phase transition of zirconia.

6. A dental zirconia composite sintered body as described in claim 5, wherein the content of said stabilizer is 1 to 12 mol % in a total of 100 mol % of zirconia and said stabilizer.

7. The dental zirconia composite sintered body according to claim 5, wherein the stabilizer is yttria.

8. The dental zirconia composite sintered body according to claim 5, further comprising Nb2O5 and / or Ta2O5.

9. A dental zirconia composite sintered body according to claim 8, wherein the content of said Nb2O5 and / or Ta2O5 is 1 to 9 mol % in a total of 100 mol % of zirconia, said stabilizer, Nb2O5, and Ta2O5.

10. The dental zirconia composite sintered body according to claim 8, further comprising elements or ions derived from a capping agent.

11. A dental zirconia composite sintered body as described in claim 10, 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.

12. The dental zirconia composite sintered body according to claim 10, 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 smaller first ionization energy than that of a Group 18 element in the same period, and / or an element or ion thereof having a high electron affinity.

13. The dental zirconia composite sintered body according to claim 10, wherein the element or ion derived from the capping agent includes 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.

14. A dental zirconia composite sintered body as described in claim 11, wherein the elements or ions derived from the capping agent include at least one element selected from the group consisting of Li, Na, and K.

15. The dental zirconia composite sintered body according to claim 8, further comprising TiO2 and / or Al2O3.

16. A dental restoration kit comprising a combination of the dental zirconia composite sintered body according to claim 1 or 2 and a dental cement.

17. The dental restoration kit of claim 16, wherein the dental cement comprises an acidic component.

18. The dental restoration kit according to claim 17, wherein the acidic component comprises a monomer having an acidic group.

19. The dental restoration kit according to claim 18, wherein the monomer having an acidic group comprises at least one selected from the group consisting of a phosphate group, a pyrophosphate group, a thiophosphate group, a phosphonic acid group, a carboxylic acid group, and a sulfonic acid group.

20. A method for bonding a dental zirconia composite sintered body as set forth in claim 1 or 2, which does not include a step of sandblasting and involves bonding using dental cement.

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