Dental prosthesis and manufacturing method thereof, dental prosthesis manufacturing kit, and manufacturing method of coated ceramic article

Abstract

The present invention provides a coated ceramic article such as a dental prosthesis having a body made of a ceramic core and a glass layer covering at least a portion of the surface of the body, in which the bonding strength between the ceramic core and the glass layer is higher than conventional. [Solution] A dental prosthesis having a main body made of a ceramic core and a glass layer covering at least a portion of the surface of the main body, wherein the ceramic core comprises a stabilized zirconia sintered body or a partially stabilized zirconia sintered body that contains a specific stabilizer and zirconium oxide and is substantially free of silicon dioxide components, and a composite formed by combining the sintered body with silicon dioxide, wherein the surface portion of the coating surface of the ceramic core that is covered with the glass layer is formed by the composite, and the ceramic core and the glass layer are bonded together.

Description

[Technical Field]

[0001] The present invention relates to a dental prosthesis and a method for manufacturing the same, a kit for manufacturing a dental prosthesis, and a method for manufacturing a coated ceramic article. [Background technology]

[0002] In particular, in recent years, advances in information and communication technology (ICT) have led to the widespread adoption of computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies in the dental field. For example, when fabricating dental prostheses, CAD / CAM systems are increasingly being used. These systems use intraoral images to machine dental blanks made of nonmetallic materials. Here, a dental blank refers to a workpiece (also called a mill blank) that can be attached to a milling machine in a CAD / CAM system. It typically includes a workpiece to be machined and a holder for attaching it to the milling machine. Commonly known workpieces include solid blocks shaped like rectangular parallelepipeds or cylinders, or solid disks shaped like plates or plates.

[0003] Zirconia-based ceramic materials are often used as non-metallic materials because of their excellent strength and toughness, allowing for the fabrication of aesthetic dental prostheses. Because fully sintered zirconia-based ceramic materials are difficult to machine due to their strength, when using a CAD / CAM system to fabricate dental prostheses (hereinafter referred to as "zirconia prostheses") made of zirconia-based ceramics, a zirconia-based ceramic pre-sintered body pre-sintered at a relatively low sintering temperature is generally used as the machining target for dental zirconia mill blanks (also simply referred to as "zirconia mill blanks"). Based on CAD, which takes into account shrinkage that occurs during high-temperature sintering, the blank is then machined to a shape corresponding to the final prosthesis shape obtained by CAM, and then sintered to produce a dense, high-strength zirconia prosthesis.

[0004] Regarding zirconia-based ceramics, pure zirconia (zirconium oxide) undergoes a phase transition accompanied by a volume change depending on the temperature. Therefore, stress caused by the volume change during the cooling process after sintering can cause cracks and lead to a decrease in strength. To prevent this phase transition, stabilizers such as yttrium oxide, calcium oxide, and magnesium oxide have been added to stabilize zirconia or partially stabilized zirconia, which can exist as a tetragonal or mixed crystal system of tetragonal and cubic crystals stable at high temperatures without transitioning to a monoclinic crystal stable at low temperatures even upon cooling. Such stabilized zirconia or partially stabilized zirconia is also used as the zirconia raw material powder used in zirconia mill blanks, and alumina (an additive) is commonly added to further increase strength. For example, Patent Document 1 describes a raw material powder that can be pressure-sintered to produce a zirconia sintered body that is particularly suited to anterior dentures and has both translucency and strength, and that contains "4.0 mol % to 6.5 mol % of yttria and less than 0.1 wt % of alumina, and has a BET specific surface area of ​​8 to 15 m. 2 / g」。

[0005] Furthermore, zirconia prostheses containing such stabilized zirconia or partially stabilized zirconia are required to have improved adhesive properties to dental adhesives, etc. From this perspective, Patent Document 2 discloses an invention relating to a zirconia prosthesis whose adhesive surface is composited with silicon dioxide, and describes that the zirconia prosthesis can be bonded with high adhesive strength to an adherend such as a tooth using a pretreatment agent containing a silane coupling agent and a dental resin cement.

[0006] Zirconia prostheses, including those made of the above-mentioned stabilized zirconia or partially stabilized zirconia, are often produced by first sintering to produce a ceramic core, and then building up porcelain on the ceramic core and firing it in order to enhance aesthetics or to develop a glossy finish (Non-Patent Document 1). There is no chemical bond between the ceramic core and the porcelain, and a physical method is known to increase the bond strength between them. For example, Patent Document 3 discloses a method in which a zirconia sintered body that will become the ceramic core is sandblasted in advance to increase the physical fit. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-143178 [Patent Document 2] Japanese Patent Application Publication No. 2023-155596 [Patent Document 3] Japanese Patent Application Publication No. 2017-122064 [Patent Document 4] Japanese Patent Application Publication No. 02-21858 [Non-patent literature]

[0008] [Non-Patent Document 1] Dental Technician Special Edition "Zirconia Restoration", Ishiyaku Publishing Co., Ltd., 2010, pp. 44-47 Summary of the Invention [Problem to be solved by the invention]

[0009] The method of fabricating dental prostheses by depositing porcelain to form a glass layer on the surface of a fully sintered ceramic core and then firing it is a useful technique from an aesthetic point of view. However, the fully sintered ceramic core and the porcelain are bonded by a physical interlocking mechanism, and further improvement in the bond strength is required. Therefore, an object of the present invention is to provide a dental prosthesis having a main body made of a ceramic core and a glass layer covering at least a portion of the surface of the main body, in which the bonding strength between the ceramic core and the glass layer is higher than conventional dental prostheses, a method for manufacturing the same, and a method for manufacturing coated ceramic articles such as the dental prosthesis. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to achieve the above object, and as a result have found that by employing a ceramic core having a stabilized zirconia sintered body or a partially stabilized zirconia sintered body that contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide and that is substantially free of silicon dioxide, and a composite of the sintered body and silicon dioxide, a dental prosthesis can be bonded well to a glass layer formed from the porcelain after the porcelain is built up and fired, thereby completing the present invention. The present invention relates to the following [1] to [6].

[0011] [1] A dental prosthesis having a body made of a ceramic core and a glass layer covering at least a part of the surface of the body, The ceramic core comprises a stabilized zirconia sintered body or a partially stabilized zirconia sintered body that contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and that is substantially free of silicon dioxide components, and a composite obtained by combining the sintered body with silicon dioxide, a surface layer portion of the ceramic core that is to be coated with the glass layer is formed from the composite, The ceramic core and the glass layer are bonded together. A dental prosthesis characterized by: [2] A method for producing the dental prosthesis described in [1] above, preparing a zirconia dental mill blank having a cutting portion made of a microporous calcined body of stabilized zirconia or a microporous calcined body of partially stabilized zirconia, which contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and is substantially free of silicon dioxide; a cutting process step of cutting the portion to be cut of the zirconia dental mill blank using a CAD / CAM system to obtain a ceramic core precursor made of the microporous calcined body and having a shape corresponding to a shape of a desired dental prosthesis; a treatment step of impregnating a precursor coating surface of the ceramic core precursor, which corresponds to the coating surface of the ceramic core in the target dental prosthesis, with a treatment liquid comprising an aqueous solution or suspension of an alkali metal silicate, thereby retaining the alkali metal silicate in a surface layer portion of the precursor coating surface; A sintering step in which the ceramic core precursor that has been subjected to the treatment step is heated to 1200 to 1800°C to sinter the ceramic core precursor and convert the surface layer of the precursor coating surface into the composite to obtain the ceramic core; and a baking step in which a ceramic porcelain material containing a glass frit containing silicon dioxide is placed on the surface of the ceramic core obtained in the sintering step that will become the coated surface, and then the porcelain material is heated to 600 to 1000°C to form the glass layer and bond the glass layer to the ceramic core; A method for producing a dental prosthesis according to [1] above, comprising: [3] The microporous calcined body constituting the cutting portion of the zirconia dental mill blank is a microporous calcined body having a relative density of 45 to 65% and pores open to the outside, the treatment liquid is a sodium silicate aqueous solution having a sodium silicate concentration of 15 to 70 mass %, The method for producing a dental prosthesis according to [2] above, wherein in the treatment step, sodium silicate is retained in a surface layer portion of the precursor-coated surface to a depth of 5 to 300 μm. [4] The method for manufacturing a dental prosthesis according to [2] above, wherein the ceramic porcelain material contains glass frit mainly composed of silicon dioxide. [5] A zirconia dental mill blank having a cutting portion made of a microporous calcined body of stabilized zirconia or a microporous calcined body of partially stabilized zirconia, which contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and is substantially free of silicon dioxide components; a treatment liquid comprising an aqueous sodium silicate solution having a sodium silicate concentration of 15 to 70 mass %; a ceramic porcelain material containing a glass frit containing silicon dioxide; A dental prosthesis manufacturing kit comprising: [6] A method for producing a coated ceramic article comprising a body made of a ceramic core, the surface region of which is composited with silicon dioxide, and an inorganic oxide ceramic that is substantially free of silicon dioxide, and a glass layer that covers at least a portion of the surface of the body, comprising: a semi-finished product manufacturing step of processing, as necessary, a microporous formed body made from a molded body of a raw material composition containing inorganic powder that is a raw material for the ceramics made of inorganic oxide, or a heat-treated microporous formed body obtained by heat-treating the microporous formed body, to obtain a semi-finished product having a shape corresponding to that of the main body; a treatment step of permeating a surface layer of a predetermined region on the surface of the semi-finished product with a treatment liquid comprising an aqueous solution of an alkali metal silicate; a sintering step of sintering the semi-finished product after the treatment step to obtain the ceramic core; and a firing step of disposing a ceramic porcelain material containing a glass frit containing silicon dioxide on the surface of the ceramic core obtained in the sintering step and heating the resulting material; 1. A method for producing a coated ceramic article, comprising: [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a coated ceramic article such as a dental prosthesis having a main body made of a ceramic core and a glass layer covering at least a portion of the surface of the main body, in which the bonding strength between the ceramic core and the glass layer is higher than conventional dental prostheses, a method for manufacturing the same, and a method for manufacturing the coated ceramic article such as a dental prosthesis. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically showing a dental prosthesis of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Dental prostheses] Dental prostheses are artificial objects used to replace missing or chipped teeth, and examples include inlays, onlays, crowns, bridges, implant superstructures, and denture bases. During prosthetic treatment, these are used by adhering them to teeth or adherends such as metals and organic-inorganic composite materials using dental adhesives such as dental resin cement. Therefore, the main body of the dental prosthesis (corresponding to the ceramic core in this invention) has an adhesive surface that is bonded to the adherend and a coating surface that is exposed to the surface.

[0015] The dental prosthesis of the present invention is a dental prosthesis having a main body made of a ceramic core and a glass layer covering at least a portion of the surface of the main body. The ceramic core comprises a stabilized zirconia sintered body or a partially stabilized zirconia sintered body that contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide and is substantially free of silicon dioxide components, and a composite of the sintered body and silicon dioxide. The surface layer of the ceramic core that is covered with the glass layer is formed of the composite material, and the ceramic core and the glass layer are fixed to each other.

[0016] A schematic cross-sectional view of a dental prosthesis according to the present invention is shown in Fig. 1. However, the present invention is not limited to the contents of the drawing. The dental prosthesis 10 of the present invention has a ceramic core (main body) 11 and a glass layer 14 that covers at least a portion of the ceramic core (main body) 11. The ceramic core 11 has an outer surface, a coated surface S1, coated with a glass layer 14, and an inner surface, an adhesive surface S2, which is bonded to an adherend such as a tooth or metal. The ceramic core 11 has a sintered body 12, which is either a stabilized zirconia sintered body or a partially stabilized zirconia sintered body, and a composite 13, in which the sintered body is combined with silicon dioxide. Here, the surface layer of the coated surface S1 of the ceramic core 11 is the composite 13. The sintered body 12 in the ceramic core 11 contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and is substantially free of silicon dioxide. The ceramic core 11 and the glass layer 14 are bonded together.

[0017] The dental prosthesis of the present invention has a high bond strength between the ceramic core and the glass layer, and can withstand use in the high-temperature, high-humidity environment of the oral cavity. Although the present invention is not bound by any theory, the reason why the dental prosthesis of the present invention can provide the above-mentioned excellent effects is believed to be as follows. Specifically, the main body of the dental prosthesis, which is made of a ceramic core, includes a stabilized zirconia sintered body or a partially stabilized zirconia sintered body containing zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and substantially no silicon dioxide, and a composite formed by combining the sintered body with silicon dioxide. The surface layer of the ceramic core, which is coated with a glass layer, is formed of the composite, and the ceramic core and the glass layer are bonded together. Here, "bonding" does not mean a simple physical bond such as interlocking, but rather a strong bond between the ceramic core and the glass layer through the diffusion of materials (mainly inorganic oxides such as silicon dioxide) at the interface between the ceramic core and the glass layer, such as adhesion or fusion, due to heating. This bonding allows the ceramic core and the glass layer to exhibit a certain level of strength (e.g., 20 MPa or greater) in a shear bond strength test, as described below.

[0018] A dental prosthesis in which the ceramic core and the glass layer are firmly bonded as described above can be obtained, for example, by the manufacturing method of the present invention described below. The most notable feature of the manufacturing method of the present invention for bonding a ceramic core and a glass layer is that an alkali metal silicate is held in the surface layer of a ceramic core precursor made of a microporous calcined body, and the surface is sintered by heating to 1200 to 1800°C to obtain a coated surface. At this time, silicon dioxide penetrates the surface layer of the coated surface in a complex manner with a predetermined thickness into the body, and is firmly integrated with the body by an anchoring effect to form a composite. As a result, the glass layer formed by baking a ceramic material containing glass frit onto the coated surface of the ceramic core is bonded to the ceramic core.

[0019] The dental prosthesis obtained in this way has sufficient adhesive strength between the ceramic core and the glass layer for use in the oral cavity, and because the composite layer is limited to the outermost surface, it does not adversely affect aesthetics or the overall mechanical strength. Such a composite in a limited area, such as the surface layer of a specific surface region, can be realized by employing the method for manufacturing a dental prosthesis of the present invention. For example, when a general coating method is employed in which a silicon dioxide precursor is applied to the surface of a ceramic (zirconia) sintered body and heat-treated at a relatively low temperature, as described in Patent Document 4, the strong integration due to the anchor effect and chemical bonding described above does not occur, and there is always a concern of a decrease in adhesive strength due to peeling, etc.

[0020] The present invention will be described in detail below. In this specification, unless otherwise specified, the expression "x to y" using numerical values ​​x and y means "greater than or equal to x and less than or equal to y." In such an expression, when a unit is assigned only to the numerical value y, the unit also applies to the numerical value x.

[0021] <Ceramic core> The main body of the dental prosthesis of the present invention is made of a ceramic core, and is basically a zirconia prosthesis having a stabilized zirconia sintered body or a partially stabilized zirconia sintered body and a composite body. The stabilized zirconia sintered body or partially stabilized zirconia sintered body contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and is substantially free of silicon dioxide components. Here, the stabilized zirconia sintered body or partially stabilized zirconia sintered body is a sintered body of crystalline zirconium oxide powder (raw material powder) containing a stabilizer. That is, the raw material powder contains a stabilizer and zirconium oxide. The raw material powder preferably further contains aluminum oxide as an additive. However, silicon dioxide components such as silica are not usually blended into raw material powders, and in the present invention, the stabilized zirconia sintered body or partially stabilized zirconia sintered body that constitutes the portion of the coating surface of the main body of the dental prosthesis excluding the surface layer portion does not substantially contain a silicon dioxide component. Note that "substantially not containing" means that the silicon dioxide component is not contained, or, even if it is contained, the silicon dioxide component content is 0.030% by mass or less, preferably 0.025% by mass or less, based on the total mass of the stabilized zirconia sintered body or partially stabilized zirconia sintered body.

[0022] To explain the raw material powder in more detail, the stabilizer may be any of those conventionally used as stabilizers for zirconium oxide, such as yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, without any restrictions. However, yttrium oxide is particularly preferred, and since it becomes stabilized zirconia or partially stabilized zirconia after sintering, the content of yttrium oxide is preferably 5 to 14 parts by mass per 100 parts by mass of zirconium oxide (0.027 to 0.076 mol per 1 mol of zirconium oxide). The content of the stabilizer is preferably 4 to 14 parts by mass, more preferably 5 to 11 parts by mass, relative to 100 parts by mass of zirconium oxide.

[0023] The aluminum oxide, which is added as needed, functions as a sintering aid for zirconium oxide, and its content is preferably 0.005 to 0.3 parts by mass per 100 parts by mass of zirconium oxide. When the content of aluminum oxide is 0.005 part by mass or more, it becomes easier to obtain the effect as a sintering aid, and when the content is 0.3 part by mass or less, it is possible to suppress a decrease in translucency due to the difference in refractive index with zirconium oxide.

[0024] The stabilizer content and aluminum oxide content per 100 parts by mass of zirconium oxide in the raw material powder are the same as the stabilizer content and aluminum oxide content per 100 parts by mass of zirconium oxide in the stabilized zirconia sintered body or partially stabilized zirconia sintered body.

[0025] The raw material powder is not particularly limited as long as it is easy to handle as a powder, but the average crystallite diameter is preferably 0.001 μm to 50 μm, particularly 0.003 μm to 20 μm, because it is less likely to cause a phase transformation of the oxide crystals and because grain growth does not proceed excessively during sintering. Examples of such raw material powders that can be used include ZpexSmile (manufactured by Tosoh Corporation), Zpex4 (manufactured by Tosoh Corporation), and Zpex (manufactured by Tosoh Corporation). The average crystallite diameter can be measured using a scanning electron microscope (SEM). For example, the primary crystallite diameter (Xi), which is the maximum diameter of 100 crystallites randomly selected on the SEM observation screen, can be measured, and the average crystallite diameter can be calculated based on the measured value using the following formula:

number

[0026] A stabilized zirconia sintered body or a partially stabilized zirconia sintered body means a body in which pore shrinkage and grain growth occur during the sintering process, and which ultimately has "a polycrystalline structure in which tetragonal zirconia grains and cubic zirconia grains, each containing a stabilizer dissolved at a different concentration, are randomly dispersed and adjacent to each other, and when aluminum oxide (alumina) is used as a sintering aid, a dense structure in which alumina grains are dispersed within the polycrystalline structure."

[0027] The main body (ceramic core) of the dental prosthesis of the present invention comprises the above-mentioned stabilized zirconia sintered body or partially stabilized zirconia sintered body, and a composite body in which the sintered body (i.e., the stabilized zirconia sintered body or the partially stabilized zirconia sintered body) is combined with silicon dioxide. In other words, the ceramic core in the dental prosthesis of the present invention has a surface layer of the coating surface formed from the composite. Specifically, the surface layer extending from the surface of the main body (ceramic core) to a depth of 5 to 300 μm, preferably 10 to 200 μm, is selectively composited with silicon dioxide. This composite in the surface layer can be confirmed by analysis using X-ray diffraction (hereinafter sometimes abbreviated as XRD) or electron probe microanalyzer (hereinafter sometimes abbreviated as EPMA). These analyses show that the surface of the main body is at least partially covered with amorphous silicon dioxide, and that a portion of this (on the main body side) forms an amorphous silicon dioxide phase immobilized within pores of complex shape. Furthermore, no alkali metal oxides are detected in the surface layer.

[0028] The structure of this coating surface can also be understood from its formation method (specifically, the treatment and sintering steps in the manufacturing method of the dental prosthesis of the present invention). That is, during the sintering process, alkali metals with melting points lower than the sintering temperature disappear by sublimation or the like, forming amorphous silicon dioxide in the pores and on the surface. At this time, some of the silicon dioxide (especially near the interface) may have formed a complex oxide with components of the (partially) stabilized zirconia. It is believed that cooling after sintering forms a silicon dioxide phase that at least partially covers the surface of the body, with some of this silicon dioxide (on the body side) immobilized within the complex-shaped pores. In this way, the surface coating of the body is formed by disposing a ceramic porcelain containing a glass frit containing silicon dioxide (having Si-OH groups) on the surface of the body, followed by firing to form the glass layer, and the glass layer and the ceramic core are firmly bonded together.

[0029] <Glass layer> In the dental prosthesis of the present invention, at least a portion of the surface of the ceramic core body is coated with a glass layer, which improves the aesthetics of the dental prosthesis and also allows it to exhibit a glossy appearance.

[0030] The glass layer is preferably a layer containing an inorganic oxide as a main component, where the content of the inorganic oxide relative to the total amount of the glass layer is preferably 90% by mass or more, more preferably 95% by mass or more. Examples of the inorganic oxide include silicon dioxide, aluminum oxide, boron oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, and zinc oxide, and one type may be used alone or two or more types may be used in combination. Among the inorganic oxides described above, the glass layer preferably contains at least silicon dioxide. When the glass layer contains silicon dioxide, the bonding strength between the ceramic core and the glass layer is likely to be increased. This is presumably because the silicon dioxide contained in the composite and the glass layer diffuses between them at the interface during heat treatment such as firing. From the viewpoint of improving the bonding strength between the ceramic core and the glass layer, the content of silicon dioxide in the glass layer is preferably 50 to 80 mass %, more preferably 55 to 75 mass %. The glass layer may contain components other than those mentioned above, such as pigments and fluorescent agents, within the range that does not affect the properties of the glass layer.

[0031] The bond strength between the ceramic core and the glass layer can be evaluated by a shear bond strength test, and the shear bond strength is preferably 20 MPa or more, more preferably 25 MPa or more. The higher the shear bond strength, the better, but it is usually 40 MPa or less. The shear bond strength can be measured by the method described in the Examples.

[0032] The thickness of the glass layer is not particularly limited, but is, for example, 10 to 200 μm, and preferably 10 to 100 μm, from the viewpoints of aesthetics and strength, etc. The thickness of the glass layer is the average value measured at 10 equally spaced points.

[0033] [Manufacturing method for dental prostheses] The method for manufacturing a dental prosthesis of the present invention includes the steps of preparing a zirconia dental mill blank (step 1), a cutting step (step 2), a treatment step (step 3), a sintering step (step 4), and a baking step (step 5).

[0034] <Step 1: Step of preparing a zirconia dental mill blank> Step 1 is a step of preparing a zirconia dental mill blank having a cutting portion made of a microporous calcined body of stabilized zirconia or a microporous calcined body of partially stabilized zirconia, which contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and is substantially free of silicon dioxide components.

[0035] A zirconia dental mill blank has at least a portion to be machined, and preferably has a portion to be machined and a holder for attaching the portion to a cutting machine. The zirconia dental mill blank refers to a portion to be machined that is a microporous calcined body of stabilized zirconia or a microporous calcined body of partially stabilized zirconia, containing zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and substantially no silicon dioxide component. Here, "substantially free" means that the silicon dioxide component is not contained, or if it is contained, the silicon dioxide component content is 0.030 mass% or less, preferably 0.025 mass% or less, based on the total mass of the microporous calcined body of stabilized zirconia or the microporous calcined body of partially stabilized zirconia. The part to be machined is generally a (solid) block formed in the shape of a rectangular parallelepiped or a cylinder, or a (solid) disk formed in the shape of a plate or board.

[0036] The microporous calcined body of stabilized zirconia or the microporous calcined body of partially stabilized zirconia is produced from the above-mentioned raw material powder. The term "calcined body" (also referred to as "preliminary sintered body") refers to a state before the material is sintered in the sintering process. During the sintering process, necks are formed where the constituent particles of the raw material powder are partially joined together, and as these necks grow, open pores (i.e., pores open to the outside) originating from the voids between the particles are formed. In the present invention, the term "microporous calcined body" refers to a body in which a large number of these open pores remain.

[0037] The microporous calcined body in the present invention is preferably a microporous calcined body having a relative density of 45 to 65% and pores that are open to the outside. The cutting portion of a commonly available zirconia dental mill blank is made of a microporous calcined body of stabilized zirconia or partially stabilized zirconia having a relative density of 45 to 65% and pores that are open to the outside, so in the present invention, a general zirconia dental mill blank having such a cutting portion can be used without any particular restrictions.

[0038] The relative density is the ratio of actual density to theoretical density (calculated as relative density = (actual density / theoretical density) × 100 (%)), and can be adjusted by controlling the temperature and time of pre-sintering. Furthermore, if pre-sintering is performed to achieve this relative density, the pre-sintered body will typically be microporous, with pores open to the outside. The average pore diameter of these pores is typically within the range of 50 to 200 nm. Here, the average pore diameter refers to the median diameter determined from the pore volume distribution in the pore diameter range of 5 nm to 250 μm obtained by mercury intrusion porosimetry, i.e., measurement using a mercury porosimeter.

[0039] For example, the theoretical density of zirconium oxide varies depending on the type and content of stabilizer and the content of alumina additive, and is 6.10 g / cm, which is the theoretical density of tetragonal zirconia. 3 As the content of these elements increases, the density tends to decrease slightly. For example, Table 1 of Patent Document 1 shows the theoretical density of zirconia containing yttria and alumina, which is reproduced below for reference. The actual density can be determined by density measurement such as the Archimedes method.

[0040] [Table 1]

[0041] Zirconia dental mill blanks are generally produced by molding the above-mentioned raw material powder into a predetermined shape to form a molded body, followed by pre-sintering. If necessary, binders, fine fillers, light-shielding agents, fluorescent agents, etc. may be added to the raw material powder to form a raw material composition, which may then be molded and pre-sintered to produce a microporous pre-sintered body, which serves as the cutting part. When a binder component is added, for example, an acrylic binder, an olefin binder, or wax may be used.

[0042] Molding of such raw material powders or raw material compositions containing the raw material powders is carried out by obtaining a compression-molded body or green body of a predetermined shape using methods such as press molding, extrusion molding, injection molding, and casting. Multi-stage molding may also be used. For example, the raw material powders may be uniaxially pressed and then further subjected to CIP (Cold Isostatic Pressing). In addition, multiple types of raw material powders may be stacked and molded in the molding process. The shape of the compression-molded body or green body may be determined appropriately depending on the shape of the desired mill blank, but is usually disc-shaped (disk type) or rectangular or approximately rectangular parallelepiped-shaped (block type).

[0043] The resulting molded body can be calcined (preliminary sintered) to produce a microporous calcined body. The calcination (preliminary sintering) involves calcining (firing) the compression molded body or green body, after optionally degreasing, at a temperature lower than that of the main sintering. Here, degreasing refers to a process for volatilizing or decomposing and removing moisture, solvents, binders, and the like contained in the compression molded body or green body. Calcination refers to a process for heating inorganic oxide powder particles to cause molecular and atomic diffusion (adhesion and fusion) on the surface, transforming them into a polycrystalline body and improving the strength of the resulting microporous preliminarily sintered body to a level that makes it easy to handle and process. The preliminarily sintering temperature is typically between 600°C and 1200°C, preferably between 800°C and 1000°C.

[0044] The degreasing and / or calcination treatment may be carried out by any conventionally known method without any particular limitations, and may be carried out continuously or in multiple stages. Furthermore, in order to efficiently remove organic substances, it is preferable to carry out the treatment in an oxygen-containing air atmosphere. The degreasing and / or calcination treatment may also be carried out continuously by a method using the same equipment as the preceding molding step, such as the SPS (Spark Plasma Sintering) method or the HP (Hot Press) method.

[0045] <Process 2: Cutting process> Step 2 is a cutting process step in which the portion to be cut of the zirconia dental mill blank is cut using a CAD / CAM system to obtain a ceramic core precursor made of a microporous calcined body having a shape corresponding to the shape of the desired dental prosthesis.

[0046] A CAD / CAM system is a system that uses computer-aided design (CAD) to design desired three-dimensional shape data and then performs computer-aided manufacturing (CAM). As mentioned above, CAD is performed taking into account shrinkage that occurs during high-temperature sintering. The shape of the ceramic core precursor, which is a semi-finished product, is similar to that of the main body, but is larger by the amount of the shrinkage (rate), so it has a surface that corresponds to the bonding surface and a surface that corresponds to the exposed surface.

[0047] Since the zirconia dental mill blank is machined while being joined via a support rod during cutting, after cutting using a CAD / CAM system, the support rod may be removed and the shape may be further modified using a dental laboratory engine or the like, or the surface may be polished. Furthermore, if necessary, the color tone may be adjusted using a penetrating colorant or a clarifying liquid, etc.

[0048] <Process 3: Processing process> Step 3 is a treatment step in which a treatment liquid consisting of an aqueous solution or suspension of an alkali metal silicate is impregnated into the precursor coating surface of the ceramic core precursor, which corresponds to the coating surface of the ceramic core in the desired dental prosthesis, to retain the alkali metal silicate in the surface layer of the precursor coating surface. The alkali metal silicate may be one having a SiO2 / M2O (M represents an alkali metal element) molar ratio of 1.0 to 5.0, either singly or in combination. Sodium silicate and / or potassium silicate are preferred due to their water solubility and availability, and sodium silicate is particularly preferred due to its sintering temperature and melting point. The SiO2 / M2O molar ratio is preferably 2.0 to 4.0.

[0049] The treatment liquid may be a suspension or colloidal dispersion of fine particles of an alkali metal silicate in a dispersion medium, preferably water, but is preferably an aqueous solution from the viewpoint of the permeability into the micropores of the ceramic core precursor. When the treatment liquid is an aqueous solution, the concentration of the alkali metal silicate is preferably 15 to 70 mass %, particularly 25 to 60 mass %, from the viewpoint of the permeability of the treatment liquid. When the treatment liquid is an aqueous sodium silicate solution, various concentrations of water glass are commercially available, so a solution of an appropriate concentration can be used as is, or a high concentration solution can be diluted and used.

[0050] When applying the treatment liquid to the precursor-coated surface of the ceramic core precursor, a general application method, such as application with a coating brush or paintbrush, or spraying, can be used without any particular restrictions. The amount of application is 1 cm per 1 cm of the coating surface. 2 The amount of alkali metal silicate per unit mass is 0.001 to 0.07 g / cm2 in terms of silicon dioxide. 2 , especially 0.003 to 0.06 g / cm 2 It is preferable to set the density to 0.005 to 0.05 g / cm 2By applying such an amount, the treatment solution can be permeated to a depth from the surface layer in the range of 5 to 300 μm, preferably 10 to 200 μm.

[0051] After the treatment step is completed and before proceeding to the sintering step, it is preferable to carry out a drying treatment to remove the dispersion medium and solvent. The drying treatment can be carried out, for example, by leaving it at atmospheric pressure and room temperature.

[0052] <Step 4: Sintering step> Step 4 is a sintering step in which the ceramic core precursor that has undergone the treatment step is heated to 1200 to 1800°C to sinter the ceramic core precursor and convert the surface layer of the precursor coating surface into the composite to obtain the ceramic core. The sintering in this process is not particularly different from the process of sintering a semi-finished product (machined body) when producing a zirconia prosthesis using a conventional zirconia mill blank, except that a ceramic core precursor that has undergone the above-mentioned treatment process is used, and the sintering is carried out at a temperature of 1200 to 1800°C.

[0053] If the sintering temperature is lower than 1200°C, the structure may not be sufficiently densified, and if the sintering temperature is higher than 1800°C, the silicon dioxide may disappear. The sintering temperature is preferably 1250 to 1750°C, more preferably 1300 to 1700°C, because this is expected to result in densification of the zirconia structure and efficient compounding of zirconia and silicon dioxide. Sintering is typically carried out in the atmosphere using a furnace such as a dental firing furnace. The sintering time varies depending on the sintering temperature, but is typically about 10 minutes to 6 hours, preferably about 30 minutes to 4 hours. For example, a good sintered body can be obtained by sintering at 1450°C for 2 hours. In this way, a ceramic core can be obtained in which the surface layer of the coating surface is formed from a composite.

[0054] <Step 5: Baking process> Step 5 is a baking step in which a ceramic porcelain material containing a glass frit containing silicon dioxide is placed on the surface of the ceramic core obtained in the sintering step that will become the coated surface, and then the resulting material is heated to 600 to 1000°C to form the glass layer and bond the glass layer to the ceramic core.

[0055] The ceramic porcelain used in this process includes glass frit containing silicon dioxide. Glass frit is a vitreous inorganic material that is generally known as a material that can impart appearances and functions not present in the substrate by applying it to the surface of the substrate. The glass frit of the present invention contains silicon dioxide. In addition to silicon dioxide, the glass frit may contain one or more inorganic oxides selected from the group consisting of aluminum oxide, boron oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, and zinc oxide. From the viewpoint of increasing the bonding strength between the formed glass layer and the ceramic core, the glass frit preferably contains silicon dioxide as a main component, where "containing silicon dioxide as a main component" means that the silicon dioxide content is 55 mass % or more, preferably 60 mass % or more, based on the total amount of the glass frit.

[0056] The average particle size of silicon dioxide contained in the glass frit is not particularly limited, but is, for example, 0.5 to 150 μm, and preferably 1 to 100 μm. The average particle size is the average value obtained by measuring the particle sizes (maximum diameters) of 100 or more random particles based on an image obtained by an electron microscope (SEM, etc.).

[0057] The ceramic material may contain, in addition to glass frit, water, a solvent, a binder such as a polymer, a pigment (coloring agent), a fluorescent material, an opacifying agent (opacifier), and the like. The form of the porcelain for ceramics is not particularly limited, and it may be in any of powder, paste, or liquid form.

[0058] In step 5, the above-mentioned ceramic porcelain is placed on the surface of the ceramic core that will become the coated surface. The method for placing the ceramic porcelain on the surface of the ceramic core is not particularly limited, and examples thereof include a method in which the ceramic porcelain is applied with a brush.

[0059] After placing the ceramic porcelain on the surface of the ceramic core, it is heated to 600 to 1000°C and fired. This causes the surface of the ceramic core to be coated with a glass layer. During this process, as described above, the silicon dioxide component contained in the composite portion of the ceramic core and the inorganic oxide such as silicon dioxide that constitutes the glass layer diffuse at the interface, thereby bonding the ceramic core and the glass layer together.

[0060] If the heating temperature is lower than 600°C, the glass layer formation speed will be slow, resulting in poor work efficiency, and the bond strength between the glass layer and the ceramic core will tend to be low.If the heating temperature is higher than 1000°C, the aesthetics of the dental prosthesis formed will tend to be poor. From this viewpoint, the heating temperature is preferably 700 to 980°C, and more preferably 800 to 960°C.

[0061] [Dental prosthesis manufacturing kit] When manufacturing the dental prosthesis of the present invention by the manufacturing method of the dental prosthesis of the present invention, it is preferable to use a kit including the zirconia dental mill blank, the treatment liquid, and the ceramic porcelain, in order to smoothly carry out the step of preparing the zirconia dental mill blank, the treatment step, and the firing step.

[0062] [Method for manufacturing coated ceramic articles] Conventionally, the problem of the bond strength between the ceramic core and the glass layer in dental prostheses has been observed not only in zirconia prostheses but also in ceramics made of inorganic oxides that do not substantially contain silicon dioxide. It is believed that the bond strength with the glass layer can be improved by compounding the coating surface of the ceramic core, as performed in the method for producing a dental prosthesis of the present invention. The method for producing a coated ceramic article of the present invention is based on this concept.

[0063] That is, the method for producing a coated ceramic article of the present invention comprises the steps of: A method for producing a coated ceramic article comprising a body made of a ceramic core, the surface layer region of which is composited with silicon dioxide, and an inorganic oxide ceramic that is substantially free of silicon dioxide, and a glass layer that covers at least a portion of the surface of the body, comprising: a semi-finished product manufacturing step of, as needed, processing a microporous formed body made of a molded body of a raw material composition containing inorganic powder that is a raw material for the ceramics made of inorganic oxide, or a heat-treated microporous formed body obtained by heat-treating the microporous formed body, to obtain a semi-finished product having a shape corresponding to that of the main body; a treatment step of permeating a surface layer of a predetermined region on the surface of the semi-finished product with a treatment liquid comprising an aqueous solution of an alkali metal silicate; a sintering step of sintering the semi-finished product after the treatment step to obtain the ceramic core; and The method is characterized by including a baking step in which a ceramic porcelain material containing a glass frit containing silicon dioxide is placed on the surface of the ceramic core obtained in the sintering step and heated.

[0064] In the inorganic oxide that is substantially free of silicon dioxide components, "substantially free of silicon dioxide components" means that the inorganic oxide does not contain any silicon dioxide components, or if it does contain any silicon dioxide components, the content of the silicon dioxide components is 0.030% by mass or less, preferably 0.025% by mass or less, based on the total amount of the inorganic oxide.

[0065] The raw material composition containing the inorganic powder used as a ceramic raw material may be an inorganic powder raw material composition consisting solely of inorganic components, or an organic component-containing raw material composition obtained by adding an organic component such as a binder to the inorganic powder raw material composition. Examples of the microporous molded body include a microporous molded body obtained by compression molding the inorganic powder raw material composition. Examples of the heat-treated microporous molded body include a green body obtained by molding the organic component-containing raw material composition and then degreasing it (a microporous degreased body), and a microporous calcined body obtained by calcining the green body directly or after degreasing. The degree of microporosity is not particularly limited as long as it allows a treatment solution applied to the surface to penetrate into the interior and retain the treatment solution to a predetermined depth from the surface, specifically, a range of 5 to 300 μm, preferably a range of 10 to 200 μm. Typically, the average pore diameter is within a range of 50 to 200 nm.

[0066] In the method for producing a coated ceramic article of the present invention, examples of the inorganic oxide constituting the main body include stabilized zirconia, partially stabilized zirconia, alumina, titania, etc. When a microporous pre-sintered body is used in the semi-finished product production process, the pre-sintering can be performed at a temperature lower than the sintering temperature of the inorganic oxide, as described in the method for producing a dental prosthesis of the present invention. The treatment process can be performed similarly to the treatment process in the method for producing a dental prosthesis of the present invention, and the sintering process can be performed at a sintering temperature that produces a dense sintered body, depending on the type of inorganic oxide. For example, when alumina is used as the inorganic oxide, a calcined body with a relative density of 63% can be obtained by molding alumina powder (Taimicron TM-DAR, manufactured by Taimei Chemical Industry Co., Ltd.) with an average particle size of 0.12 μm and a purity of 99.99% and pre-sintering it at 800°C for 1 hour. Next, a processing step similar to that in the manufacturing method of the dental prosthesis of the present invention is carried out, for example, by sintering at 1400°C for 2 hours, thereby producing a ceramic core composed of the alumina and having a surface region composited with silicon dioxide. In the baking step, a ceramic porcelain material containing a glass frit containing silicon dioxide is placed on the surface of the ceramic core obtained in the firing step and heated. The surface of the ceramic core is the surface that includes the region that has been infiltrated with the treatment solution in the treatment step, and is the surface that has been composited with silicon dioxide. The composition of the ceramic porcelain and the heating conditions after the ceramic porcelain is placed on the surface of the ceramic core are as explained above in the method for manufacturing a dental prosthesis of the present invention. [Example]

[0067] The present invention will be specifically described below with reference to examples and comparative examples, although the present invention is not limited to these examples.

[0068] Example 1 [Manufacturing of ceramic products] As the mill blank, "Katana Zirconia UTML (manufactured by Kuraray Noritake Dental)," a zirconia mill blank having a cutting section made of a partially stabilized zirconia microporous calcined body, was used. Data was created so that a plate-shaped or disc-shaped body of a predetermined size (specifically, a 1 cm x 1 cm x 3 mm plate-shaped body or a disc-shaped body with a diameter of 11 mm and a thickness of 4 mm) would be obtained after sintering, and cutting was performed to produce plate-shaped semi-finished products 1 and 2 of different sizes (corresponding to simulated ceramic core precursors for zirconia prostheses). Next, for each of these plate-shaped semi-finished products 1 and 2, one side was used as a simulated coated surface, and a treatment solution consisting of "No. 3 sodium silicate (manufactured by Toso Sangyo, an aqueous solution of 28 to 30 mass% silicon dioxide and 9 to 10 mass% sodium oxide: SiO2 / Na2O = 3.05)" was applied to the simulated coated surface using a disposable sponge in a thickness of 1 cm. 20.02 g was applied per sample. The sample was then dried at room temperature for 5 minutes and sintered. Sintering was carried out by increasing the temperature from 25°C to 1550°C at a rate of 10°C / min, holding the temperature at 1550°C for 2 hours, and then decreasing the temperature from 1550°C to 25°C at a rate of 10°C / min. Using this method, a zirconia-based ceramic article 1 for analysis was produced, consisting of a 1 cm x 1 cm x 3 mm plate (corresponding to a simulated ceramic core), and a zirconia-based ceramic article 2 for physical property evaluation was produced, consisting of a disk-shaped body with a diameter of 11 mm and a thickness of 4 mm.

[0069] [Analysis of zirconia-based ceramic product 1] One surface layer of the zirconia-based ceramic article 1 was measured using X-ray diffraction (XRD), and the presence of a silicon dioxide layer was confirmed. That is, it was confirmed that the zirconia-based ceramic article 1 (ceramic core) contained a partially stabilized zirconia sintered body and a composite of the sintered body and silicon dioxide. Furthermore, measurement using an electron probe microanalyzer (EPMA) confirmed that the penetration depth of the silicon dioxide was 54 μm, and that no alkali metal oxides derived from alkali metal silicates were detected.

[0070] [Fabrication of Coated Zirconia-Based Ceramic Articles and Evaluation of Shear Bond Strength] The treated surface of the zirconia-based ceramic article 2 (ceramic core) for physical property evaluation samples was smoothed with #600 waterproof paper to define the bonding surface. Next, alumina with a particle size of approximately 50 μm was sprayed onto the bonding surface at an air pressure of 2 atmospheres. This was followed by ultrasonic cleaning with ethanol. A ceramic porcelain (Cerabian ZR, manufactured by Kuraray Noritake) with a diameter of 4 mm was placed on the bonding surface. The temperature was raised from 600°C to 940°C at a rate of 80°C / min, and then fired in a vacuum for 1 minute. This formed a glass layer on the surface of the ceramic core and bonded the ceramic core to the glass layer. The ceramic porcelain used contained a glass frit primarily composed of silicon dioxide. The bonded samples were then stored in water for 24 hours, and the shear bond strength between the zirconia-based ceramic article 2 and the ceramic porcelain was evaluated (n=8) using a universal testing machine (AGS-J, Shimadzu Corporation) at a crosshead speed of 1 mm / min. The shear bond strength was approximately 29.5 MPa. Furthermore, no peeling of the silicon dioxide from the ceramic core body combined with silicon dioxide was observed, and the bond was maintained.

[0071] Comparative Example 1 Zirconia-based ceramic article 3 was manufactured in the same manner as zirconia-based ceramic article 2 described in Example 1, except that a disk-shaped semi-finished product was prepared using "Katana Zirconia UTML (manufactured by Kuraray Noritake Dental)" and the treatment with the treatment solution (coating and drying) was not carried out. Then, the shear bond strength between zirconia-based ceramic article 3 (ceramic core) and a glass layer formed from a ceramic porcelain material by the same method as in Example 1 was evaluated (n=8). As a result, the shear bond strength was approximately 15.2 MPa, and the ceramic core and the glass layer were not adhered to each other. [Explanation of symbols]

[0072] 10 Dental prostheses 11 Ceramic score (main body) 12 Sintered body 13 Complex 14 Glass Layer S1 Coated Surface S2 Adhesive surface

Claims

1. A dental prosthesis having a body made of a ceramic core and a glass layer covering at least a portion of the surface of the body, The ceramic core comprises a stabilized zirconia sintered body or a partially stabilized zirconia sintered body containing zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and substantially no silicon dioxide component, and a composite obtained by combining the sintered body with silicon dioxide, a surface layer portion of the ceramic core that is to be coated with the glass layer is formed from the composite, The ceramic core and the glass layer are bonded together. A dental prosthesis characterized by:

2. A method for producing a dental prosthesis according to claim 1, comprising the steps of: preparing a zirconia dental mill blank having a cutting portion made of a microporous calcined body of stabilized zirconia or a microporous calcined body of partially stabilized zirconia, which contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and is substantially free of silicon dioxide; a cutting process step of cutting the portion to be cut of the zirconia dental mill blank using a CAD / CAM system to obtain a ceramic core precursor made of the microporous calcined body and having a shape corresponding to the shape of a desired dental prosthesis; a treatment step of impregnating a precursor coating surface of the ceramic core precursor, which corresponds to the coating surface of the ceramic core in the target dental prosthesis, with a treatment liquid comprising an aqueous solution or suspension of an alkali metal silicate, thereby retaining the alkali metal silicate in the surface layer of the precursor coating surface; A sintering step in which the ceramic core precursor that has been subjected to the treatment step is heated to 1200 to 1800°C to sinter the ceramic core precursor and convert the surface layer of the precursor coating surface into the composite to obtain the ceramic core; and a baking step in which a ceramic porcelain material containing a glass frit containing silicon dioxide is placed on the surface of the ceramic core obtained in the sintering step that will become the coated surface, and then the porcelain material is heated to 600 to 1000°C to form the glass layer and bond the glass layer to the ceramic core; The method for manufacturing a dental prosthesis according to claim 1 , comprising:

3. the microporous calcined body constituting the cutting portion of the zirconia dental mill blank is a microporous calcined body having a relative density of 45 to 65% and pores that are open to the outside, the treatment liquid is a sodium silicate aqueous solution having a sodium silicate concentration of 15 to 70 mass %, 3. The method for producing a dental prosthesis according to claim 2, wherein in the treatment step, sodium silicate is retained in a surface layer portion of the precursor-coated surface to a depth of 5 to 300 μm.

4. The method for manufacturing a dental prosthesis according to claim 2 , wherein the porcelain for ceramics contains glass frit containing silicon dioxide as a main component.

5. a zirconia dental mill blank having a cutting portion made of a microporous calcined body of stabilized zirconia or a microporous calcined body of partially stabilized zirconia, which contains zirconium oxide and at least one stabilizer selected from the group consisting of yttrium oxide, calcium oxide, magnesium oxide, cerium oxide, and erbium oxide, and is substantially free of silicon dioxide; a treatment liquid comprising an aqueous sodium silicate solution having a sodium silicate concentration of 15 to 70 mass %; a ceramic porcelain material containing a glass frit containing silicon dioxide; A dental prosthesis manufacturing kit comprising:

6. A method for producing a coated ceramic article comprising a body made of a ceramic core, the surface layer region of which is composited with silicon dioxide, and an inorganic oxide ceramic that is substantially free of silicon dioxide, and a glass layer that covers at least a portion of the surface of the body, comprising: a semi-finished product manufacturing step of processing, as necessary, a microporous formed body made from a molded body of a raw material composition containing inorganic powder that is a raw material for the ceramics made of inorganic oxide, or a heat-treated microporous formed body obtained by heat-treating the microporous formed body, to obtain a semi-finished product having a shape corresponding to the main body; a treatment step of permeating a surface layer portion of a predetermined region on the surface of the semi-finished product with a treatment liquid comprising an aqueous solution of an alkali metal silicate; a sintering step of sintering the semi-finished product after the treatment step to obtain the ceramic core; and a firing step of disposing a ceramic porcelain material containing a glass frit containing silicon dioxide on the surface of the ceramic core obtained in the sintering step and heating the resulting material; 1. A method for producing a coated ceramic article, comprising:

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