Sintering method of dental zirconia calcined body

Abstract

The present invention relates to a sintering method of a dental zirconia pre-sintered body, characterized by satisfying the following a) to c): a) the average temperature increase rate in the range of room temperature to 1300°C is arbitrary; b) the average temperature increase rate in the range of 1300°C to 1400°C is 3°C / min or less; and c) the average temperature increase rate in the range of 1400°C to the maximum temperature of the present sintering process is 2.5°C / min or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a sintering method of a dental zirconia pre-sintered body. BACKGROUND

[0002] In recent years, a technique of manufacturing a prosthetic device by cutting processing using a dental CAD / CAM system has rapidly spread. By this, a prosthetic device can be easily manufactured by processing a cut body made of a ceramic material such as zirconia, alumina, lithium disilicate, or a resin material such as an acrylic resin, a mixed resin, or the like.

[0003] In particular, since zirconia has high strength, it is clinically applied to various cases. On the other hand, a sintered zirconia that can be used in the oral cavity (hereinafter, referred to as a zirconia sintered body) has very high hardness, and thus cannot be subjected to cutting processing using a dental CAD / CAM system. Therefore, a dental cutting processing zirconia cut body is a cut body (a dental zirconia pre-sintered body) that is not subjected to final sintering but is pre-sintered at a low sintering temperature and adjusted to a hardness that can be subjected to cutting processing.

[0004] First, the initial zirconia used as a dental material has high strength but lower light transmittance than a natural tooth, and is mainly used only as a coping or a frame.

[0005] In recent years, zirconia having improved light transmittance by increasing the concentration of a stabilizer contained in zirconia (high light transmittance zirconia) has been developed, and its use has been expanded from a molar portion to a full crown of a front tooth portion.

[0006] However, even the high light transmittance zirconia has light transmittance that is not sufficient to reproduce the enamel of a natural tooth. Therefore, in a case where esthetics is particularly required, a restoration having light transmittance similar to that of a natural tooth is manufactured by building a ceramic material on zirconia.

[0007] In this case, it is desired to obtain a restoration having light transmittance more similar to that of a natural tooth using a full-contour zirconia, and zirconia having more excellent light transmittance needs to be developed.

[0008] However, even if the concentration of a stabilizer is increased in order to obtain light transmittance superior to that of high light transmittance zirconia, higher light transmittance cannot be obtained.

[0009] This is considered to be because the more the concentration of a stabilizer is increased, the more the grain growth of zirconia is promoted, and there is a tendency that closed pores are increased.

[0010] Inhibition of such closed pores requires a special manufacturing method such as a HIP (hot isostatic pressing) process. Therefore, in the case of manufacturing high light transmittance zirconia having a higher concentration of a stabilizer, a special device such as a HIP device is required.

[0011] Zirconia prostheses in dentistry are manufactured through machining dental zirconia pre-fired bodies, sintering the processed material, and adjustment. Since these operations are primarily performed in dental laboratories, it would be impractical to introduce specialized equipment such as HIP devices into each laboratory if such equipment were used.

[0012] From a manufacturing efficiency perspective, it is desirable to minimize the sintering time required for zirconia. For example, in a dental laboratory with 8-hour operating hours, zirconia can be sintered twice a day if the sintering time is less than 8 hours, but only once a day if the sintering time exceeds 8 hours.

[0013] Patent Document 1 discloses a zirconia sintered body, which is made by using zirconia powder containing 3 mol% yttrium with reduced alumina content to prepare a dental zirconia pre-fired body, and then preparing a zirconia sintered body from this pre-fired body. Because this sintered body maintains high strength while improving translucency, it is clinically used for large-span dental bridges (4 units or more) or full crowns for molars. However, even this sintered body is difficult to apply to cases requiring high aesthetics, such as anterior teeth, due to insufficient translucency.

[0014] Patent Document 2 discloses a fully sintered zirconia body using zirconia powder containing 2–7 mol% yttrium. This sintered body possesses high translucency similar to ceramic or lithium disilicate materials, making it suitable not only for anterior teeth but also for inlays, high-mount inlays, and veneers. However, because this sintered body requires hot isostatic pressing (HIP), it is difficult to fabricate in a typical dental laboratory.

[0015] Existing technical documents

[0016] Patent documents

[0017] Patent Document 1: Japanese Patent Application Publication No. 2010-150063;

[0018] Patent Document 2: Japanese Patent Application Publication No. 2008-222450. Summary of the Invention

[0019] There is a need for a technique to improve the light transmittance of zirconia sintered bodies with high light transmittance without the use of special equipment.

[0020] The inventors have developed a sintering method for dental zirconia pre-sintered bodies that imparts the same high translucency as natural tooth enamel to the zirconia sintered body without the use of special equipment. Therefore, it can improve translucency and does not require a long sintering time.

[0021] The present invention relates to a sintering method for a dental zirconia pre-sintered body containing 5.5 mol% to 7.0 mol% of a stabilizer, which satisfies the following (a) to (c).

[0022] a) The average heating rate in the range of room temperature to 1300℃ is above 9℃ / min.

[0023] b) The average heating rate in the 1300℃~1400℃ range is above 0.6℃ / min and below 3℃ / min.

[0024] c) The average heating rate in the range of 1400℃ to the highest temperature of this sintering process is above 0.5℃ / min and below 2.5℃ / min.

[0025] In this invention, the average heating rate in step a) can be set to 15°C / min or more and 60°C / min or less.

[0026] In this invention, the average heating rate in step b) can be set to 1°C / min or more and 2°C / min or less.

[0027] In this invention, the average heating rate in step c) can be set to 1°C / min or more and 1.5°C / min or less.

[0028] In this invention, the stabilizer can be yttrium oxide.

[0029] The sintering method of the dental zirconia pre-sintered body of the present invention improves light transmittance, thereby enabling the manufacture of zirconia sintered bodies with high light transmittance without the use of special equipment and without the need for long sintering time. Detailed Implementation

[0030] The present invention relates to a sintering method for a dental zirconia pre-sintered body containing 5.5 mol% to 7.0 mol% of a stabilizer, which satisfies the following (a) to (c).

[0031] a) The average heating rate in the range of room temperature to 1300℃ is above 9℃ / min.

[0032] b) The average heating rate in the 1300℃~1400℃ range is above 0.6℃ / min and below 3℃ / min.

[0033] c) The average heating rate in the range of 1400℃ to the highest temperature of this sintering process is above 0.5℃ / min and below 2.5℃ / min.

[0034] In the sintering method of the present invention, the average heating rate in step a) within the range of room temperature to 1300°C is 9°C / min or more, preferably 15°C / min to 60°C / min. When the average heating rate is less than 9°C / min, the overall sintering process time is prolonged and the manufacturing efficiency is reduced. When the average heating rate is 15°C / min or more, even when steps b) and c) are set within the preferred range, the overall sintering process time can be kept to 480 minutes or less, which is therefore particularly preferred. When the average heating rate exceeds 60°C / min, it is not preferred because it may burden the sintering furnace or temporarily exceed the end temperature of step a).

[0035] In the sintering method of the present invention, the average heating rate in step b) within the range of 1300°C to 1400°C is 0.6°C or more and 3°C / min or less, preferably 1°C / min or more and 2°C / min or less. When the average heating rate exceeds 3°C / min, there is a tendency for the light transmittance of the zirconia sintered body to decrease. When the average heating rate is less than 0.6°C / min, the overall sintering time required is extended and the manufacturing efficiency is reduced. Since it is possible to improve light transmittance while shortening the overall sintering time, it is preferable to use an average heating rate of 1°C / min or more and 2°C / min or less. In the dental industry, an average heating rate of 3°C / min or more and 10°C / min or less is generally used.

[0036] In the sintering method of the present invention, the average heating rate in step c) of the range from 1400°C to the highest temperature of the sintering process is 0.5°C / min or more and 2.5°C / min or less, preferably 1°C / min or more and 1.5°C / min or less. When the heating rate exceeds 2.5°C / min, the average heating rate in step c) of the range from 1400°C to the highest temperature of the sintering process is higher than the average heating rate in step b) of the range from 1300°C to 1400°C. In this case, there is a tendency for the light transmittance of the zirconia sintered body to decrease. When the average heating rate is less than 0.5°C / min, the overall sintering process time is extended and the manufacturing efficiency is reduced. Since it is possible to improve light transmittance while shortening the overall sintering process time, it is preferable to use an average heating rate of 1°C / min or more and 1.5°C / min or less. In the dental industry, an average heating rate of 3°C / min or more and 10°C / min or less is generally used.

[0037] There are no particular limitations on the type of stabilizer used in this invention. Examples include yttrium oxide, cerium oxide, calcium oxide, and indium oxide, but yttrium oxide, which is used in many dental zirconia, is preferred.

[0038] The concentration of the stabilizer in this invention, converted to oxides, is preferably in the range of 5.5 mol% to 7.0 mol%, and particularly preferably 6.3 mol% to 6.7 mol%. When the stabilizer concentration is less than 5.5 mol% or more than 7.0 mol%, the effects of the sintering method described in this invention are almost impossible to obtain. In this invention, apart from the specific components constituting the dental zirconia pre-sintered body of this invention, the remaining portion can be composed of zirconia (ZrO2). Furthermore, the zirconia (ZrO2), converted to oxides, can be set to 93 mol% to 94.5 mol%.

[0039] There are no restrictions on the state of the stabilizer in dental zirconia pre-fired bodies. Specifically, it can be dissolved in zirconia or exist as a crystalline or amorphous compound different from zirconia.

[0040] The method of adding a stabilizer to a dental zirconia pre-fired body is preferably a method that can uniformly add a specified amount to the dental zirconia pre-fired body. For example, the stabilizer can be added during the manufacture of zirconia particles, or the dental zirconia pre-fired body can be impregnated in a solution containing a stabilizer.

[0041] When using a method of impregnating a dental zirconia pre-fired body in a solution containing a stabilizer, the solvent for the stabilizer solution can be arbitrary, such as water, alcohol, or organic solvents. From the perspective of ease of availability and processing, water or ethanol, or mixtures thereof, are particularly preferred.

[0042] There are no particular limitations on the preparation method of solutions containing stabilizers. As long as the stabilizer is dissolved in the solvent, any preparation method is acceptable.

[0043] There are no particular restrictions on the specific environment in which the stabilizer-containing solution permeates into the dental zirconia pre-fired body; it works under normal pressure, reduced pressure, and pressurized conditions. From the viewpoint of shortening manufacturing time, placing the surrounding environment under reduced pressure or pressurized conditions promotes the permeation of the stabilizer-containing solution and is therefore the preferred option. Furthermore, repeating the process of reducing pressure and then returning to normal pressure (reduced pressure / normal pressure operation) or pressurizing and then returning to normal pressure (pressurized pressure / normal pressure operation) is effective in shortening the time required to immerse the stabilizer-containing solution into the space located inside the dental zirconia pre-fired body and connected to its exterior.

[0044] The time for impregnating the dental zirconia pre-fired body with the stabilizer-containing solution is not always determined based on the relative density and size of the pre-fired body, the penetration degree of the stabilizer-containing solution, or the impregnation method, but can be appropriately adjusted. For example, in the case of impregnation, it is usually 1 to 120 hours; in the case of impregnation under reduced pressure, it is usually 0.5 to 12 hours; and in the case of contact under pressure, it is usually 0.2 to 6 hours.

[0045] The primary particle size of the zirconia powder used in the manufacture of the dental zirconia pre-sintered body of the present invention is preferably 1 to 500 nm. When the primary particle size is less than 1 nm, there is a tendency to improve the light transmittance of the zirconia sintered body but make it difficult to impart sufficient strength. On the other hand, when the primary particle size is 500 nm or more, there is a tendency to make it difficult to impart sufficient strength to the zirconia sintered body.

[0046] The dental zirconia pre-fired body of the present invention preferably contains a coloring agent. Specifically, it is an inorganic coloring agent. More specifically, it is iron oxide, erbium, cobalt, manganese, chromium, or rare earth elements. Iron oxide is added to impart a yellow color, or erbium is added to impart a red color. In addition to these coloring agents, elements such as cobalt, manganese, and chromium are preferably used in combination to adjust the hue. The present invention preferably uses coloring agents to color teeth.

[0047] The dental zirconia pre-sintered body of the present invention may contain a sintering aid. Specifically, for the purpose of improving sinterability and inhibiting low-temperature degradation, it is preferable to contain 0.01 to 0.3% by weight of alumina. When the alumina content is less than 0.01% by weight, it is difficult to obtain sufficient properties even after final firing, and there is a tendency to fail to impart sufficient strength or translucency. On the other hand, when the alumina content exceeds 0.3% by weight, there is a tendency to improve the strength of the zirconia sintered body but fail to impart sufficient translucency.

[0048] The relative density of the zirconia sintered body, obtained by firing the dental zirconia pre-fired body of the present invention at 1450°C to 1600°C, is preferably 98% or more of the theoretical density. The relative density is determined by dividing the measured density by the theoretical density. When the relative density is below 98%, there is a tendency for a decrease in strength or light transmittance.

[0049] The crystalline phase of the dental zirconia pre-fired body in this invention is preferably tetragonal and / or cubic. A monoclinic crystalline phase is not preferred because it is difficult to impart sufficient light transmittance even after final firing.

[0050] The method for manufacturing the dental zirconia pre-fired body in this invention is not particularly limited; any known manufacturing method can be used without any problems. Specifically, a method of molding zirconia powder by pressure molding is preferred. Furthermore, a method of multi-layer molding by pressure molding zirconia powders with different hues or compositions is more preferred.

[0051] The dental zirconia pre-fired body of the present invention is preferably subjected to isotropic pressing by cold isostatic pressing (CIP treatment) after pressure molding.

[0052] The maximum load pressure of the CIP treatment in this invention is preferably 50 MPa or higher. When the maximum load pressure is less than 50 MPa, it is sometimes impossible to impart sufficient light transmittance and strength to the zirconia sintered body.

[0053] The pre-firing temperature of the dental zirconia pre-fired body in this invention is preferably 800–1200°C. When the pre-firing temperature is below 800°C, the Vickers hardness and / or flexural strength become too low, thus there is a tendency for it to easily break or fracture during machining. On the other hand, when the pre-firing temperature is above 1200°C, the Vickers hardness and / or flexural strength become too high, thus there is a tendency for increased wear on the cutting machine's grinding rod and higher operating costs.

[0054] As described above, a zirconia sintered body is obtained by the manufacturing method of the present invention. The obtained zirconia sintered body is then subjected to morphological correction, color adjustment, and surface polishing as needed.

[0055] There are no particular limitations on the types of prosthetic devices manufactured using the manufacturing method of the present invention; any prosthetic device, such as inlays, onlays, veneers, crowns, and bridges, is acceptable. Therefore, there are no particular limitations on the shape of the dental zirconia pre-fired body used to manufacture the prosthetic device by machining; any shape of dental zirconia pre-fired body, such as a block shape corresponding to inlays, onlays, veneers, crowns, or a disc shape corresponding to bridges, can be used.

[0056] Example

[0057] The present invention will now be described in more detail and specifically through examples, but the present invention is not limited thereto.

[0058] Fabrication of Zirconia Machined Parts (Pre-fired Zirconia for Dental Use)

[0059] (Workpiece 1)

[0060] Zirconia powder containing 6.5 mol% yttrium oxide in solid solution (containing 0.05 wt% alumina) was filled into the mold. In the process, pressure molding (surface pressure: 50 MPa) is applied to obtain a molded body. Then, the molded body undergoes CIP treatment (maximum load pressure: 200 MPa, open load pressure: 0 MPa, holding time: 1 minute). Afterwards, it is pre-fired in an electric furnace (1000°C, 30 minutes) to produce a zirconia cut body.

[0061] (Workpiece 2)

[0062] The zirconia workpiece is prepared in the same manner as workpiece 1, except that it uses zirconia powder containing 5.5 mol% solid solution of yttrium oxide (containing 0.05 wt% aluminum oxide).

[0063] (Workpiece 3)

[0064] The zirconia workpiece is made in the same manner as workpiece 1, except that it uses zirconia powder containing 7.0 mol% solid solution of yttrium oxide (containing 0.05 wt% aluminum oxide).

[0065] (Workpiece 4)

[0066] The zirconia workpiece is prepared in the same manner as workpiece 1, except that it uses zirconia powder containing 6.0 mol% yttrium oxide in solid solution (containing 0.05 wt% alumina).

[0067] (Workpiece 5)

[0068] The zirconia workpiece is prepared in the same manner as workpiece 1, except that it uses zirconia powder containing 6.3 mol% solid solution of yttrium oxide (containing 0.05 wt% aluminum oxide).

[0069] (Workpiece 6)

[0070] The zirconia workpiece is made in the same manner as workpiece 1, except that it uses zirconia powder containing 6.7 mol% yttrium oxide in solid solution (containing 0.05 wt% alumina).

[0071] (Workpiece 7)

[0072] The zirconia workpiece is made in the same manner as workpiece 1, except that it uses zirconia powder containing 5.0 mol% yttrium oxide in solid solution (containing 0.05 wt% alumina).

[0073] (Workpiece 8)

[0074] The zirconia workpiece is prepared in the same manner as workpiece 1, except that it uses zirconia powder containing 7.5 mol% solid solution of yttrium oxide (containing 0.05 wt% aluminum oxide).

[0075] Yttrium oxide content (mol%) determination:

[0076] Zirconia was machined into a circular plate shape using various cutting materials. Test specimens for evaluating yttrium oxide content were prepared. The amount of yttrium oxide on the upper and lower surfaces of each test specimen was measured using a fluorescence X-ray analysis apparatus (manufactured by Rigaku Corporation, Japan), and the average value of the upper and lower surface values ​​was taken as the yttrium oxide content. It should be noted that the yttrium content (mol%) is expressed by conversion to oxides.

[0077] [Sintering conditions]

[0078] Each zirconia body is machined into a specified shape and fired in a sintering furnace according to the sintering schedule shown in Tables 1 to 4 to produce zirconia sintered bodies.

[0079] Table 1

[0080]

[0081] Table 2

[0082]

[0083] Table 3

[0084]

[0085] Table 4

[0086]

[0087] [Evaluation of light transmittance]

[0088] Zirconia was machined into a circular plate shape using various cutting materials. Test specimens for evaluating light transmittance were prepared. Each test specimen was sintered in a firing furnace. Afterwards, the thickness of each test specimen (1.0 mm) was adjusted using a flat grinding disc. It should be noted that light transmittance was evaluated by measuring contrast ratio. Contrast ratio was measured using a spectrophotometer (KONICA MINOLTA, INC.). The Y-value measured when a white board was placed under each test specimen was recorded as Yw, and the Y-value measured when a black board was placed under the test specimen was recorded as Yb. The contrast ratio was calculated using the following formula.

[0089] The closer the contrast ratio is to 0, the more transparent the material is; the closer the contrast ratio is to 1, the less transparent the material is.

[0090] Contrast ratio = (Yb / Yw) (Equation)

[0091] In addition, using the same dental zirconia pre-fired body, the degree of light transmittance improvement for each sintering time was calculated.

[0092] Improvement in light transmittance = (contrast ratio of test specimens sintered according to sintering schedule 9) / (contrast ratio of test specimens sintered according to any of the sintering schedules 1 to 19).

[0093] When the light transmittance improvement is 1.15 or higher, its sintering timetable exhibits particularly high light transmittance improvement performance.

[0094] When the light transmittance improvement is greater than or equal to 1.10 and less than 1.15, its sintering timetable exhibits high light transmittance improvement performance.

[0095] When the light transmittance improvement is greater than or equal to 1.05 and less than 1.10, its sintering time has a slightly higher light transmittance improvement performance.

[0096] When the light transmittance improvement is less than 1.05, the light transmittance improvement performance of its sintering timetable is low or non-existent.

[0097] When the light transmittance improvement is 1.05 or higher, the invention is deemed to have the desired effect.

[0098] Example 1: Sintering a test piece made from a workpiece 1 according to sintering schedule 1.

[0099] Example 2: Sintering the test body made from the workpiece 1 according to sintering schedule 2.

[0100] Example 3: Sintering the test body made from the workpiece 1 according to sintering schedule 3.

[0101] Example 4: Sintering the test piece made from the workpiece 1 according to sintering schedule 4.

[0102] Example 5: Sintering the test piece made from the workpiece 1 according to sintering schedule 5.

[0103] Example 6: Sintering the test body made from the workpiece 2 according to sintering schedule 1.

[0104] Example 7: Sintering the test piece made from the workpiece 3 according to sintering schedule 1.

[0105] Example 8: Sintering the test piece made from the workpiece 4 according to sintering schedule 1.

[0106] Example 9: Sintering the test piece made from the workpiece 5 according to sintering schedule 1.

[0107] Example 10: Sintering the test piece made from the workpiece 6 according to sintering schedule 1.

[0108] Example 11: Sintering the test piece made from the workpiece 1 according to sintering schedule 10.

[0109] Example 12: Sintering the test body made from the workpiece 1 according to sintering schedule 11.

[0110] Example 13: Sintering the test piece made from the workpiece 1 according to sintering schedule 13.

[0111] Example 14: Sintering the test piece made from the workpiece 1 according to sintering schedule 15.

[0112] Example 15: Sintering the test piece made from the workpiece 1 according to sintering schedule 16.

[0113] Example 16: Sintering the test piece made from the workpiece 1 according to sintering schedule 19.

[0114] Example 17: Sintering the test piece made from the workpiece 1 according to sintering schedule 20.

[0115] Comparative Example 1: The test body made from the workpiece 1 was sintered according to sintering schedule 9.

[0116] Comparative Example 2: The test body made from the workpiece 1 was sintered according to sintering schedule 6.

[0117] Comparative Example 3: The test body made from the workpiece 1 was sintered according to sintering schedule 7.

[0118] Comparative Example 4: The test body made from the workpiece 1 was sintered according to sintering schedule 8.

[0119] Comparative Example 5: The test body made from the cut body 2 was sintered according to sintering schedule 9.

[0120] Comparative Example 6: The test body made from the workpiece 3 was sintered according to sintering schedule 9.

[0121] Comparative Example 7: A test piece made from the workpiece 7 was sintered according to sintering schedule 1.

[0122] Comparative Example 8: A test piece made from a cut body 8 was sintered according to sintering schedule 1.

[0123] Comparative Example 9: The test piece made from the workpiece 7 was sintered according to sintering schedule 9.

[0124] Comparative Example 10: The test body made from the cut body 8 was sintered according to the sintering schedule 9.

[0125] Comparative Example 11: The test body made from the cut body 4 was sintered according to sintering schedule 9.

[0126] Comparative Example 12: The test body made from the cut body 5 was sintered according to sintering schedule 9.

[0127] Comparative Example 13: The test piece made from the cut body 6 was sintered according to sintering schedule 9.

[0128] Comparative Example 14: The test body made from the workpiece 1 was sintered according to sintering schedule 12.

[0129] Comparative Example 15: A test piece made from cut body 1 was sintered according to sintering schedule 14.

[0130] Comparative Example 16: The test body made from the cut body 1 was sintered according to sintering schedule 17.

[0131] Comparative Example 17: The test body made from the workpiece 1 was sintered according to sintering schedule 18.

[0132] The results of the characteristic tests of the dental zirconia pre-fired bodies manufactured by the examples and comparative examples are shown in Tables 5 and 6.

[0133] Table 5

[0134]

[0135] Table 6

[0136]

[0137] In Examples 1 to 17, during the sintering of dental zirconia pre-sintered bodies containing 5.5 mol% to 7.0 mol% of stabilizer, the following conditions were met: a) the average heating rate in the range of room temperature to 1300°C was 9°C / min or higher;

[0138] b) The average heating rate in the 1300℃~1400℃ range is above 0.6℃ / min and below 3℃ / min;

[0139] c) The average heating rate in the range of 1400℃ to the highest temperature of this sintering process is above 0.5℃ / min and below 2.5℃ / min, thus showing improved light transmittance and sintering time of less than 8 hours.

[0140] In Comparative Examples 1 to 17, due to conditions other than those mentioned above, the light transmittance was not improved or only slightly improved and / or the sintering time exceeded 8 hours.

[0141] In this specification, when the constituent elements of the invention are described as either singular or plural, or when they are not limited to singular or plural, the constituent elements may be either singular or plural unless understood from the context.

[0142] Although the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes or modifications can be made based on the matters disclosed in this specification. Therefore, the scope of embodiments of the present invention is intended to include any changes or modifications.

[0143] Industrial applicability

[0144] This invention relates to a sintering method for dental zirconia pre-sintered bodies, and is a technology that can be used in the dental field.

Claims

1. A sintering method for a dental zirconia pre-sintered body, wherein, It is a sintering method for dental zirconia pre-sintered bodies containing 5.5 mol% to 7.0 mol% stabilizer. The sintering method satisfies the following a to c: a: The average heating rate in the range of room temperature to 1300℃ is above 9℃ / min; b: The average heating rate in the 1300℃~1400℃ range is above 0.6℃ / min and below 3℃ / min; c: The average heating rate in the range of 1400℃ to the highest temperature of this sintering process is above 0.5℃ / min and below 2.5℃ / min.

2. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, characterized in that, The average heating rate in step a is above 15℃ / min and below 60℃ / min.

3. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, characterized in that, The average heating rate in step b is above 1℃ / min and below 2℃ / min.

4. The sintering method for dental zirconia pre-sintered bodies as described in claim 2, characterized in that, The average heating rate in step b is above 1℃ / min and below 2℃ / min.

5. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, characterized in that, The average heating rate in step c is above 1℃ / min and below 1.5℃ / min.

6. The sintering method for dental zirconia pre-sintered bodies as described in claim 2, characterized in that, The average heating rate in step c is above 1℃ / min and below 1.5℃ / min.

7. The sintering method for dental zirconia pre-sintered bodies as described in claim 3, characterized in that, The average heating rate in step c is above 1℃ / min and below 1.5℃ / min.

8. The sintering method for dental zirconia pre-sintered bodies as described in claim 4, characterized in that, The average heating rate in step c is above 1℃ / min and below 1.5℃ / min.

9. The sintering method for dental zirconia pre-sintered bodies according to any one of claims 1 to 8, characterized in that, The stabilizer is yttrium oxide.

10. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The average heating rate in step b is above 0.6℃ / min and below 3℃ / min.

11. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The concentration of the stabilizer, converted to oxides, is in the range of 6.3 mol% to 6.7 mol%.

12. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, Zirconia, when converted to oxide form, is in the range of 93 mol% to 94.5 mol%.

13. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The stabilizer is dissolved in zirconium oxide.

14. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, Stabilizers exist as crystalline or amorphous compounds, distinct from zirconium oxide.

15. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The stabilizer is included in the dental zirconia pre-fired body by adding the stabilizer during the manufacture of zirconia particles.

16. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The stabilizer is contained in the dental zirconia pre-fired body by impregnating it with a solution containing the stabilizer.

17. The sintering method for dental zirconia pre-sintered bodies as described in claim 16, wherein, The solvents for solutions containing stabilizers are water, organic solvents, and mixtures thereof.

18. The sintering method for dental zirconia pre-sintered bodies as described in claim 16, wherein, The solvents for solutions containing stabilizers are water, ethanol, and mixtures thereof.

19. The sintering method for dental zirconia pre-sintered bodies as described in claim 16, wherein, The environment in which the stabilizer-containing solution permeates into the dental zirconia pre-fired body is under normal pressure, under reduced pressure, and / or under pressure.

20. The sintering method for dental zirconia pre-sintered bodies as described in claim 16, wherein, By repeatedly performing decompression operations followed by restoration to atmospheric pressure (i.e., decompression / atmospheric pressure operation) or pressurization operations followed by restoration to atmospheric pressure (i.e., pressurization / atmospheric pressure operation), a solution containing stabilizers is allowed to permeate the dental zirconia pre-fired body.

21. The sintering method for dental zirconia pre-sintered bodies as described in claim 16, wherein, The solution containing stabilizer is used to impregnate the dental zirconia pre-fired body for 1 to 120 hours.

22. The sintering method for dental zirconia pre-sintered bodies as described in claim 16, wherein, A solution containing stabilizers is allowed to permeate the dental zirconia pre-fired body by immersion under reduced pressure for 0.5 to 12 hours.

23. The sintering method for dental zirconia pre-sintered bodies as described in claim 16, wherein, A solution containing stabilizers is allowed to permeate the dental zirconia pre-fired body by immersion under pressure for 0.2 to 6 hours.

24. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The primary particle size of the zirconia powder used to manufacture dental zirconia pre-fired bodies is 1–500 nm.

25. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, Pre-fired zirconia for dental use contains coloring agents.

26. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The colorant is selected from one or more elements in the group consisting of iron oxide, erbium, cobalt, manganese, chromium, and rare earth elements.

27. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, Dental zirconia pre-fired bodies contain sintering aids.

28. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The dental zirconia pre-fired body contains 0.01 to 0.3% by weight of alumina as a sintering aid.

29. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The relative density of dental zirconia pre-fired body sintered at 1450℃~1600℃ is more than 98% of the theoretical density.

30. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The crystalline phase of dental zirconia pre-fired bodies is tetragonal and / or cubic.

31. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, Dental zirconia pre-fired bodies are formed by pressure molding of zirconia powder.

32. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, Dental zirconia pre-fired bodies are formed by multi-layer molding of zirconia powders with different hues and / or compositions through multi-stage pressure molding.

33. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, After being press-molded, dental zirconia preforms are subjected to isotropic pressing using the cold isostatic pressing method.

34. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The maximum load pressure of dental zirconia pre-fired bodies subjected to isotropic pressing by cold isostatic pressing is above 50 MPa.

35. The sintering method for dental zirconia pre-sintered bodies as described in claim 1, wherein, The dental zirconia pre-fired body was pre-fired at 800–1200°C.

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