Zirconia workpiece for dental cutting, including In and Y

Abstract

To provide a technique for giving a zirconia sintered body high light-transmissivity comparable to that of natural tooth enamel.SOLUTION: A zirconia cut body for dental cutting contains, as stabilizers, a yttrium compound and an indium compound, with the content of the yttrium compound being 3.0 mol%-6.0 mol% in terms of oxides and the content of the indium compound being 0.2 mol%-3.0 mol% in terms of oxides, and the total of the yttrium and indium compounds being 5.5 mol%-7.0 mol% in terms of oxides.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a zirconia work piece for dental cutting and a method for manufacturing the same.

Background Art

[0002] In recent years, technology for producing prosthetic devices by cutting using dental CAD / CAM systems has been rapidly spreading. As a result, it has become possible to easily produce prosthetic devices by machining work pieces made of ceramic materials such as zirconia, alumina, and lithium disilicate, and resin materials such as acrylic resin and hybrid resin.

[0003] In particular, zirconia has high strength and is clinically applied in various cases. On the other hand, a finally fired zirconia final fired body (hereinafter also referred to as a zirconia sintered body) that can be used in the oral cavity has a very high hardness and thus cannot be machined using a dental CAD / CAM system. Therefore, a zirconia work piece for dental cutting is calcined at a low firing temperature without final firing and adjusted to a hardness that can be cut.

[0004] When zirconia was first applied as a dental material, although it had high strength, its translucency was low, and it was mainly used as a coping or a frame. In recent years, with the development of zirconia with improved translucency (high-translucency zirconia), its applications have expanded from molar parts to full crowns of anterior teeth. However, even in high-translucency zirconia, the translucency is insufficient to reproduce the enamel of natural teeth. Therefore, in cases where aesthetic properties are particularly required, a natural restoration is produced by building up ceramic material on zirconia. In such a situation, it is desired to obtain a more natural restoration with full contour zirconia, and for this purpose, the development of zirconia with better translucency is required.

[0005] Patent Document 1 discloses a method for producing a zirconia workpiece for dental cutting using zirconia powder containing 3 mol% yttrium with reduced alumina content, and a zirconia sintered body produced from this workpiece. This sintered body maintains high strength while improving translucency, and has therefore been clinically applied to long-span bridges of 4 units or more and full crowns in the posterior region. However, even with this sintered body, the translucency is insufficient, making it difficult to apply to cases where high aesthetics are required, such as in the anterior teeth. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-150063 [Overview of the project] [Problems that the invention aims to solve]

[0007] There was a need for a technology that could impart high translucency to zirconia sintered bodies, similar to that of natural tooth enamel. [Means for solving the problem]

[0008] The inventors of this invention investigated a zirconia workpiece for dental cutting that can impart high translucency to a zirconia sintered body, similar to that of natural tooth enamel.

[0009] The present invention relates to a zirconia workpiece for dental cutting, characterized by containing a yttrium compound and an indium compound as stabilizers, with the yttrium compound present at 3.0 moles to 6.0 moles in oxide terms, and the indium compound present at 0.2 moles to 3.0 moles in oxide terms, and the total of the yttrium compound and indium compound being 5.5 moles to 7.0 moles in oxide terms. In the present invention, the remainder of the component other than the component specified as constituting the zirconia workpiece for dental cutting of the present invention can be composed of zirconia (ZrO2). Furthermore, the zirconia (ZrO2) can be present at 90 moles to 94.5 moles in oxide terms. Furthermore, the combined concentration of yttria and indium can be set to 6.0 moles to 6.7 moles.

[0010] The zirconia workpiece for dental cutting according to the present invention, when formed as a sintered body, can be a zirconia workpiece for dental cutting that has a contrast ratio of 0.68 or less at a sample thickness of 1.0 mm. The zirconia workpiece for dental cutting according to the present invention contains a coloring agent, and when sintered, it can be a zirconia workpiece for dental cutting that has a contrast ratio of 0.68 or less at a sample thickness of 1.0 mm. The zirconia workpiece for dental cutting according to the present invention does not contain a coloring agent, and when formed into a sintered body, it can be a zirconia workpiece for dental cutting that has a contrast ratio of 0.65 or less at a sample thickness of 1.0 mm. The present invention also provides a prosthetic device obtained by sintering a zirconia workpiece for dental cutting according to the present invention. [Effects of the Invention]

[0011] The zirconia workpiece for dental cutting according to the present invention can impart high translucency to the final fired zirconia body, similar to that of natural tooth enamel. [Modes for carrying out the invention]

[0012] The present invention relates to a zirconia workpiece for dental cutting, characterized by containing a yttrium compound and an indium compound as stabilizers, with the yttrium compound present at 3.0 moles to 6.0 moles in oxide terms, and the indium compound present at 0.2 moles to 3.0 moles in oxide terms, and the total of the yttrium compound and indium compound being 5.5 moles to 7.0 moles in oxide terms. In the present invention, the remainder of the component other than the component specified as constituting the zirconia workpiece for dental cutting of the present invention can be composed of zirconia (ZrO2). Furthermore, the zirconia (ZrO2) can be present at 90 moles to 94.5 moles in oxide terms.

[0013] The indium compound is more preferably 0.4 moles to 1.3 moles in terms of indium oxide (In2O3). If the amount of indium oxide is less than 0.2 moles, sufficient light transmission cannot be imparted to the zirconia sintered body. On the other hand, if the amount of indium oxide exceeds 3.0 moles, sufficient light transmission cannot be imparted to the zirconia sintered body.

[0014] There are no restrictions on the state of the indium compound in the zirconia workpiece for dental cutting according to the present invention before it becomes a zirconia sintered body. Specifically, it may be solid-dissolved in zirconia, or it may exist as a separate crystalline or amorphous material from the zirconia as an indium compound.

[0015] Any known indium compound can be used as the indium compound without any limitations. Specifically, the indium compounds used in the present invention include indium oxides, halides, nitrates, sulfates, organic acid salts, etc. Specifically, these include indium oxide, indium nitrate, indium chloride, indium sulfate, etc.

[0016] In the present invention, a method for adding an indium compound to a zirconia workpiece for dental cutting is preferably one that allows for the uniform addition of a specified amount to the zirconia workpiece for dental cutting. For example, a method may be used in which the indium compound is added when manufacturing zirconia particles, or a method may be used in which the zirconia workpiece for cutting is immersed in a solution containing the indium compound.

[0017] When using a method in which a zirconia workpiece for machining is immersed in a solution containing an indium compound, the solvent for the indium solution can be any solvent, but water, alcohol, organic solvents, etc., can be used. Water or ethanol, or a mixture thereof, is particularly preferred because it is readily available and easy to handle.

[0018] The method for preparing a solution containing an indium compound is not particularly limited; any method of preparation that dissolves the indium compound in a solvent is acceptable.

[0019] There are no particular restrictions on the specific atmosphere in which the indium compound-containing solution is impregnated into the zirconia workpiece for machining; atmospheric pressure, reduced pressure, or pressurized pressure are all acceptable. From the viewpoint of shortening manufacturing time, placing the surrounding environment under reduced pressure or pressurized pressure is a preferred method as it promotes the penetration of the indium compound-containing solution. Furthermore, repeating the operation of returning to atmospheric pressure after a reduced pressure operation (reduced pressure / atmospheric pressure operation) or returning to atmospheric pressure after a pressurized operation (pressurized / atmospheric pressure operation) multiple times is effective in shortening the time required for the process of impregnating the indium compound-containing solution into the space inside the zirconia workpiece for dental machining that communicates with the outside of the workpiece.

[0020] The time for immersing the solution containing an indium compound in the zirconia workpiece for dental cutting is not uniformly determined by the relative density and molded body size of the zirconia workpiece for dental cutting, the degree of penetration of the solution containing an indium compound, the immersion method, etc., and can be appropriately adjusted. For example, when immersing, it is usually 1 to 120 hours, when immersing under reduced pressure, it is usually 0.5 to 12 hours, and when contacting under pressure, it is usually 0.2 to 6 hours.

[0021] The yttrium compound contained in the zirconia workpiece for dental cutting in the present invention is more preferably 4.0 mol% to 5.5 mol% in terms of yttrium oxide conversion (Y2O3). When the amount of yttrium oxide is less than 3.0 mol%, it is not preferable because sufficient translucency cannot be imparted after the final firing of zirconia. On the other hand, when the amount of yttria, the amount of yttrium oxide, exceeds 6.0 mol%, it is not preferable because the translucency of the final fired zirconia body tends to decrease. The final firing is a firing process for obtaining a prosthetic device that can be used in the oral cavity, and the final fired body is one obtained by the same firing process as the prosthetic device that can be used in the oral cavity.

[0022] The total amount of the yttrium compound and the indium compound contained in the zirconia workpiece for dental cutting in the present invention is more preferably 6.0 mol% to 6.7 mol% in terms of oxide conversion. When the total amount of the yttrium compound and the indium compound is less than 5.5 mol%, it is not preferable because sufficient translucency cannot be imparted after the final firing of zirconia. On the other hand, when the total amount of the yttrium compound and the indium compound exceeds 7.0 mol%, it is not preferable because sufficient translucency cannot be imparted after the final firing of zirconia. In the present invention, it is preferable that any one of the following three requirements is satisfied: the yttrium compound is 4.0 mol% to 5.5 mol% in terms of yttrium oxide, the indium compound is 0.4 mol% to 1.3 mol% in terms of indium oxide, and the total amount of the yttrium compound and the indium compound is 6.0 mol% to 6.7 mol% in terms of oxide. It is more preferable to satisfy two requirements, and most preferable to satisfy all three requirements. As the number of satisfied requirements increases, the contrast ratio decreases and the light transmittance increases.

[0023] The primary particle size of the zirconia powder used in the production of the zirconia workpiece for dental cutting in the present invention is preferably 1 to 500 nm. When the primary particle size is less than 1 nm, although the light transmittance of the zirconia sintered body is improved, it tends to be difficult to impart sufficient strength. On the other hand, when the primary particle size is larger than 500 nm, it tends to be difficult to impart sufficient strength to the zirconia sintered body.

[0024] The zirconia workpiece for dental cutting in the present invention preferably contains a colorant. Specifically, it is an inorganic colorant. More specifically, it is iron oxide, erbium, cobalt, manganese, chromium, or a rare earth element. Iron oxide is added to impart yellow, and erbium is added to impart red. In addition to these colorants, it is preferable to use elements such as cobalt, manganese, and chromium in combination for color tone adjustment. It is preferable that the present invention colors the tooth color by including a colorant.

[0025] The zirconia workpiece for dental cutting in the present invention may contain a sintering aid. Specifically, for the purpose of improving sinterability and suppressing low-temperature deterioration, it is preferable to contain 0.01 to 0.3% by mass of alumina. When the amount of alumina is lower than 0.01% by mass, it is difficult to obtain sufficient properties even after final firing, and it tends to be unable to impart sufficient strength and light transmittance. On the other hand, when the amount of alumina exceeds 0.3% by mass, although the strength of the zirconia sintered body is improved, it tends to be difficult to impart sufficient light transmittance.

[0026] In the present invention, the relative density of the zirconia sintered body obtained by firing the zirconia workpiece for dental cutting at 1450°C to 1600°C is preferably 98% or more of the theoretical density. The relative density is determined by the ratio of the measured density to the theoretical density. If the relative density is 98% or less, the strength and light transmittance tend to decrease.

[0027] In the present invention, the crystalline phase of the zirconia workpiece for dental cutting is preferably tetragonal and / or cubic. If the crystalline phase is monoclinic, it is undesirable because it is difficult to impart sufficient translucency even after final firing.

[0028] The method for manufacturing a zirconia workpiece for dental cutting in this invention is not particularly limited, and any known manufacturing method can be used without any problems. Specifically, it is preferable to form the workpiece by press molding of zirconia powder. Furthermore, it is even more preferable to form a multi-layered workpiece by press molding zirconia powders of different colors and compositions in multiple stages.

[0029] In the present invention, the zirconia workpiece for dental cutting is preferably one that has been press-formed and then subjected to isotropic pressure by cold isostatic pressing (CIP treatment).

[0030] In the present invention, the maximum load pressure for the CIP treatment is preferably 50 MPa or higher. If the maximum load pressure is less than 50 MPa, it may not be possible to impart sufficient light transmission and strength to the zirconia sintered body.

[0031] In the present invention, the calcination temperature of the zirconia workpiece for dental cutting is preferably 800 to 1200°C. If the calcination temperature is below 800°C, the Vickers hardness and / or flexural strength become too low, making chipping and fracture more likely during cutting. On the other hand, if the calcination temperature is above 1200°C, the Vickers hardness and / or flexural strength become too high, leading to excessive wear of the milling bur of the cutting machine and a tendency for higher running costs.

[0032] In this way, a zirconia workpiece for dental cutting is obtained by the manufacturing method of the present invention. The obtained zirconia workpiece for dental cutting is then cut, machined, and surface polished to the desired size as needed.

[0033] There are no particular limitations on the method for final firing the zirconia workpiece for dental cutting according to the present invention, but a simple and preferred method is firing at atmospheric pressure. There are no particular limitations on the firing temperature, but 1450 to 1600°C is preferred, and 1500 to 1600°C is particularly preferred. There are no particular limitations on the holding time at the firing temperature, but 1 minute to 12 hours is preferred, and 2 to 4 hours is particularly preferred. There are no particular limitations on the heating rate, but 1 to 400°C / min is preferred, and more preferably 3 to 100°C / h is particularly preferred.

[0034] In the present invention, the contrast ratio of the sintered body obtained by the final firing of the zirconia workpiece for dental cutting is preferably 0.68 or less at a sample thickness of 1 mm.

[0035] In the present invention, the contrast ratio of the sintered body obtained by final firing of a zirconia workpiece for dental cutting containing a coloring agent is preferably 0.68 or less at a sample thickness of 1 mm.

[0036] In the present invention, the contrast ratio of the sintered body obtained by final firing of a zirconia workpiece for dental cutting that does not contain a coloring agent is preferably 0.65 or less at a sample thickness of 1 mm.

[0037] There are no particular restrictions on the type of prosthetic device that can be machined using the zirconia workpiece for dental machining of the present invention; any prosthetic device such as inlays, onlays, veneers, crowns, or bridges can be used without any problems. Therefore, there are no particular restrictions on the shape of the zirconia workpiece for dental machining used to manufacture prosthetic devices by machining; any shape of zirconia workpiece for dental machining can be used, such as a block shape corresponding to inlays, onlays, veneers, or crowns, or a disc shape corresponding to bridges. [Examples]

[0038] The present invention will be described in more detail and specifically below with reference to examples, but the present invention is not limited thereto.

[0039] [Indium oxide and yttrium oxide content (mol%) measurement] Test specimens for evaluating indium and yttrium content were prepared by machining each zirconia workpiece into a circular plate shape (φ14 mm × 1.6 mm). The indium and yttrium content on the top and bottom surfaces of each specimen was measured using an X-ray fluorescence analyzer (manufactured by Rigaku Corporation), and the average values ​​of the top and bottom surfaces were defined as the indium and yttrium content. The indium and yttrium content (mol%) is expressed in terms of oxide equivalent.

[0040] [Sintering conditions] A zirconia workpiece for dental cutting was cut to a predetermined shape, and then fired in a firing furnace (firing temperature: 1550°C, heating rate: 5°C / min, holding time: 120 minutes) to produce a sintered zirconia body.

[0041] [Evaluation of light transmittance] Test specimens for evaluating light transmittance were prepared by machining each dental cutting material (zirconia) into a round plate shape (φ14mm × 1.6mm). Each specimen was sintered in a firing furnace. Subsequently, the thickness of each specimen (1.0mm) was adjusted using a surface grinder. Light transmittance was evaluated by measuring the contrast ratio. The contrast ratio was measured using a spectrophotometer (Konica Minolta). The Y value when measuring with a white board placed beneath each specimen was defined as Yw, and the Y value when measuring with a black board placed beneath the specimen was defined as Yb. The contrast ratio was calculated using the following formula. The closer the contrast ratio is to 0, the more transparent the material is; the closer the contrast ratio is to 1, the more opaque the material is. Contrast ratio = (Yb / Yw) (Formula) Furthermore, the contrast ratio was used to evaluate the following ABC scores. Contrast ratio of sintered body without colorants ≤ 0.65:A 0.65 < Contrast ratio of sintered body without coloring agent ≤ 0.68:B Contrast ratio of sintered body without colorants > 0.68:C Contrast ratio of sintered body containing coloring agent ≤ 0.68:A 0.68 < Contrast ratio of sintered body containing colorant ≤ 0.71:B Contrast ratio of sintered body containing coloring agent > 0.71:C In the case of A, it has high transmittance, making it suitable for cases where high light transmittance is required. Among these, those with a low contrast ratio are preferred. In case B, it possesses a degree of translucency that makes it applicable to cases where high translucency is required. In the case of C, the light transmittance is low, making it unsuitable for cases where high light transmittance is required.

[0042] Example 1: Zirconia powder containing 5.5 ml of solid-solution yttria (Zpex SMILE: manufactured by Tosoh Corporation, containing 0.05 mass% alumina) was filled into a mold (φ100 mm) and press-molded (surface pressure: 50 MPa) to obtain a molded body. Furthermore, the molded body was subjected to CIP treatment (maximum load pressure: 200 MPa, load pressure after release: 0 MPa, holding time: 1 minute, number of repetitions: 10). After that, it was calcined in an electric furnace (1000°C, 30 minutes) to produce a zirconia pre-sintered body. The pre-sintered body was immersed in an indium nitrate aqueous solution (indium concentration: 3.86 mass%) at room temperature and atmospheric pressure for 12 hours. After that, the pre-sintered body was removed from the solution and completely dried in a dryer at 120°C to produce a zirconia workpiece for dental cutting. Test specimens were prepared from the zirconia workpieces used for dental cutting by cutting, and then fired in a firing furnace (firing temperature: 1550°C, heating rate: 5°C / min, holding time: 120 minutes) to produce sintered zirconia bodies.

[0043] Example 2: A zirconia sintered body was prepared in the same manner as in Example 1, except that the indium concentration of the indium nitrate aqueous solution was 4.5 mass% (as indium). Example 3: A zirconia sintered body was prepared in the same manner as in Example 1, except that the indium concentration of the indium nitrate aqueous solution was 6.0 mass% (as indium). Example 4: A zirconia sintered body was prepared in the same manner as in Example 1, except that the indium concentration of the indium nitrate aqueous solution was 8.0 mass% (as indium). Example 5: A zirconia sintered body was prepared in the same manner as in Example 1, except that the indium concentration of the indium nitrate aqueous solution was 10.0 mass% (as indium). Example 6: A zirconia sintered body was prepared in the same manner as in Example 1, except that the indium concentration of the indium nitrate aqueous solution was 12.0 mass% (as indium). Example 7: A zirconia sintered body was prepared in the same manner as in Example 1, except that the pre-sintered body was immersed in an indium nitrate-yttrium nitrate aqueous solution (indium concentration: 4.10 mass% as indium, yttrium concentration: 3.07 mass% as yttrium) at room temperature and atmospheric pressure for 12 hours. Example 8: A zirconia sintered body was prepared in the same manner as in Example 1, except that the zirconia powder used was a mixed powder (mixing ratio (mass) 75:25) of zirconia powder containing 5.5 moles of solid-solution yttria (Zpex SMILE: manufactured by Tosoh Corporation, containing 0.05 mass% alumina) and zirconia powder containing 5.5 moles of solid-solution yttria and iron oxide (Zpex Yellow: manufactured by Tosoh Corporation, containing 0.05 mass% alumina).

[0044] Example 9: Zirconia powder containing 3.0 moles of solid-solution yttria: 93.2 g and indium oxide: 6.8 g were mixed in a ball mill to prepare zirconia powder, which was then filled into a mold (φ100 mm) and press-molded (surface pressure: 50 MPa) to obtain a molded body. Furthermore, the molded body was subjected to CIP treatment (maximum load pressure: 200 MPa, load pressure after release: 0 MPa, holding time: 1 minute, number of repetitions: 10). After that, it was calcined in an electric furnace (1000°C, 30 minutes) to produce a zirconia pre-sintered body. Test specimens were prepared from the prepared zirconia workpiece for dental cutting by cutting, and then calcined in a firing furnace (calcination temperature: 1550°C, heating rate: 5°C / min, holding time: 120 minutes) to produce a zirconia sintered body.

[0045] Example 10: A zirconia sintered body was prepared in the same manner as in Example 9, except that 95.5 g of zirconia powder containing 4.0 moles of solid-solution yttria and 4.5 g of indium oxide were mixed in a ball mill to produce zirconia powder.

[0046] Example 11: A zirconia sintered body was prepared in the same manner as in Example 7, except that the concentrations of the indium nitrate-yttrium nitrate aqueous solution were set to 1.71 mass% as indium and 3.07 mass% as yttrium.

[0047] Comparative Example 1: Zirconia powder containing 5.5 moles of solid-solution yttria (Zpex SMILE: manufactured by Tosoh Corporation, containing 0.05 mass% alumina) was filled into a mold (φ100 mm) and press-molded (surface pressure: 50 MPa) to obtain a molded body. Furthermore, the molded body was subjected to CIP treatment (maximum load pressure: 200 MPa, load pressure after release: 0 MPa, holding time: 1 minute, number of repetitions: 10). After that, it was calcined in an electric furnace (1000°C, 30 minutes) to produce a zirconia pre-sintered body. Test specimens were prepared from the prepared zirconia workpiece for dental cutting by cutting, and then calcined in a firing furnace (calcination temperature: 1550°C, heating rate: 5°C / min, holding time: 120 minutes) to produce a zirconia sintered body.

[0048] Comparative Example 2: Zirconia powder containing 5.5 moles of solid-solution yttria (Zpex SMILE: manufactured by Tosoh Corporation, containing 0.05 mass% alumina) was filled into a mold (φ100 mm) and press-molded (surface pressure: 50 MPa) to obtain a molded body. Furthermore, the molded body was subjected to CIP treatment (maximum load pressure: 200 MPa, load pressure after release: 0 MPa, holding time: 1 minute, number of repetitions: 10). After that, it was calcined in an electric furnace (1000°C, 30 minutes) to produce a zirconia pre-sintered body. The pre-sintered body was immersed in an aqueous solution of yttrium nitrate (yttrium concentration: 3.0 mass% as yttrium) at room temperature and atmospheric pressure for 12 hours. After that, the pre-sintered body was removed from the solution and completely dried in a dryer at 120°C to produce a zirconia workpiece for dental cutting. Test specimens were prepared from the zirconia workpieces used for dental cutting by cutting, and then fired in a firing furnace (firing temperature: 1550°C, heating rate: 5°C / min, holding time: 120 minutes) to produce sintered zirconia bodies.

[0049] Comparative Example 3: A zirconia sintered body was prepared in the same manner as in Comparative Example 2, except that the yttrium concentration in the yttrium nitrate aqueous solution was 8.0 mass% (as yttrium). Comparative Example 4: A zirconia sintered body was prepared in the same manner as in Comparative Example 2, except that the yttrium concentration in the yttrium nitrate aqueous solution was 10.0 mass% (as yttrium). Comparative Example 5: A zirconia sintered body was prepared in the same manner as in Comparative Example 1, except that the zirconia powder used was a mixed powder (mixing ratio (mass) 75:25) of zirconia powder containing 5.5 moles of solid-solution yttria (Zpex SMILE: manufactured by Tosoh Corporation, containing 0.05 mass% alumina) and zirconia powder containing 5.5 moles of solid-solution yttria and iron oxide (Zpex SMILE Yellow: manufactured by Tosoh Corporation, containing 0.05 mass% alumina). Comparative Example 6: A zirconia sintered body was prepared in the same manner as in Comparative Example 2, except that the zirconia powder used was a mixed powder (mixing ratio (mass) 75:25) of zirconia powder containing 5.5 moles of solid-solution yttria (Zpex SMILE: manufactured by Tosoh Corporation, containing 0.05 mass% alumina) and zirconia powder containing 5.5 moles of solid-solution yttria and iron oxide (Zpex SMILE Yellow: manufactured by Tosoh Corporation, containing 0.05 mass% alumina). Comparative Example 7: A zirconia sintered body was prepared in the same manner as in Comparative Example 6, except that the yttrium concentration in the yttrium nitrate aqueous solution was 8.0 mass% (as yttrium). Comparative Example 8: A zirconia sintered body was prepared in the same manner as in Comparative Example 6, except that the yttrium concentration in the yttrium nitrate aqueous solution was 10.0 mass% (as yttrium). Comparative Example 9: A zirconia sintered body was prepared in the same manner as in Example 1, except that the indium concentration of the indium nitrate aqueous solution was 0.9 mass% (as indium). Comparative Example 10: A zirconia sintered body was prepared in the same manner as in Example 9, except that 92.8 g of zirconia powder containing 3.0 mole% solid-solution yttria and 7.2 g of indium oxide were used. Comparative Example 11: A zirconia sintered body was prepared in the same manner as in Example 7, except that the concentrations of the indium nitrate-yttrium nitrate aqueous solution were set to 1.71 mass% as indium and 4.30 mass% as yttrium. Comparative Example 12: A zirconia sintered body was prepared in the same manner as in Example 9, except that 95.5 g of zirconia powder containing 5.5 mole% solid-solution yttria and 4.5 g of indium oxide were used. Comparative Example 13: A zirconia sintered body was prepared in the same manner as in Example 6, except that zirconia powder containing 4.0 moles of solid-solution yttria was used.

[0050] Table 1 shows the indium oxide and yttrium oxide content and characteristic test results of the zirconia cut materials for dental machining produced in the examples and comparative examples.

[0051] [Table 1]

[0052] Examples 1 to 11 showed high translucency similar to that of natural tooth enamel, as the total amount of yttrium and indium compounds they contained ranged from 5.5 ml to 7.0 ml.

[0053] Comparative Examples 1-13 either did not contain indium compounds, or the total amount of yttrium and indium compounds they contained was less than 5.5 moles or more than 7.0 moles, and therefore did not have the same high translucency as natural tooth enamel. [Industrial applicability]

[0054] This invention relates to a zirconia workpiece for dental cutting and a method for manufacturing the same, and is a technology applicable in the dental field.

Claims

1. A zirconia workpiece for dental cutting, comprising an yttrium compound and an indium compound as stabilizers, containing the yttrium compound in an amount of 3.0 mol% to 6.0 mol% in terms of oxide, containing the indium compound in an amount of 0.2 mol% to 3.0 mol% in terms of oxide, and characterized in that the total of the yttrium compound and the indium compound is 5.5 mol% to 7.0 mol% in terms of oxide. A zirconia workpiece for dental cutting.

2. The zirconia workpiece for dental cutting according to Claim 1, characterized in that when it is a sintered body, the contrast ratio at a sample thickness of 1.0 mm is 0.68 or less. A zirconia workpiece for dental cutting.

3. The zirconia workpiece for dental cutting according to Claim 1, containing a colorant, and characterized in that when it is a sintered body, the contrast ratio at a sample thickness of 1.0 mm is 0.68 or less. A zirconia workpiece for dental cutting.

4. The zirconia workpiece for dental cutting according to Claim 1, not containing a colorant, and characterized in that when it is a sintered body, the contrast ratio at a sample thickness of 1.0 mm is 0.65 or less. A zirconia workpiece for dental cutting.

5. A prosthetic device obtained by sintering the zirconia workpiece for dental cutting according to any one of Claims 1 to 4.

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