Zirconium oxide body to be cut

Abstract

The present invention addresses the problem of providing a zirconium oxide body to be cut for dental cutting, which is capable of reducing the number of types of zirconium oxide bodies to be cut for dental cutting held in a dental workroom or the like in order to obtain a zirconium oxide sintered body having excellent light transmission. As one embodiment of the present invention, provided is a zirconium oxide body to be cut for dental cutting in which zirconium oxide sintered bodies having different optical characteristics are obtained at different sintering temperatures, the different sintering temperatures being selected at least from the range of 1500 DEG C to 1600 DEG C and the range of 1400 DEG C to 1500 DEG C. The present invention also provides a zirconium oxide body to be cut for dental cutting in which the different sintering temperatures can be selected from the range of 1500 DEG C to 1600 DEG C and the range of 1400 DEG C to 1500 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to a dental cutting work zirconia cutting work body. BACKGROUND

[0002] In recent years, a technique of producing a prosthetic device by cutting work using a dental CAD / CAM system (Computer Aided Design / Computer Aided Manufacturing) is rapidly spreading. By this, by working on a cutting work body made of a ceramic material such as zirconia, alumina, lithium disilicate, an acrylic resin, a mixed resin, or the like, a prosthetic device can be easily produced.

[0003] In particular, zirconia is clinically used in various cases because it has high strength. On the other hand, a fully sintered zirconia (hereinafter referred to as a zirconia fully sintered body) has very high hardness, and thus cannot be subjected to cutting work using a dental CAD / CAM system. Therefore, a dental cutting work zirconia cutting work body is a cutting work body that is subjected to pre-sintering at a low sintering temperature by incomplete sintering and adjusted to a hardness that allows cutting work.

[0004] A general dental cutting work zirconia cutting work body is manufactured by molding a zirconia powder by press molding or the like and then pre-sintering at 800°C to 1200°C.

[0005] The characteristics of the dental cutting work zirconia cutting work body, that is, the characteristics of the zirconia fully sintered body, are affected by the characteristics of the zirconia powder used.

[0006] In Japanese Patent Application Publication No. 2022-184793, it is disclosed that by sintering a zirconia pre-sintered body having a specific stabilizer concentration with a specific sintering procedure, a zirconia sintered body having excellent light transmittance can be obtained. SUMMARY

[0007] A zirconia sintered body having excellent light transmittance as described in the above patent document easily reproduces the color tone of a natural tooth, and on the other hand, in cases where the coloring of the abutment tooth is significant, or in cases where the light transmittance of the adjacent teeth is low, color tone adjustment becomes difficult.

[0008] Therefore, it is necessary to separately use dental cutting work zirconia cutting work bodies having different light transmittances depending on the case.

[0009] As such, in dental laboratories and the like, it is necessary to keep various dental cutting work zirconia cutting work bodies corresponding to the required physical properties as stock.

[0010] An object of the present application is to provide a dental cutting work zirconia cutting work body that can reduce the types of dental cutting work zirconia cutting work bodies held by dental laboratories and the like in order to obtain a zirconia sintered body having excellent light transmittance.

[0011] The inventors have studied a zirconia cutter for dental cutting that reduces the variety of zirconia cutters used in dental laboratories and other facilities to obtain sintered zirconia bodies with excellent light transmittance. The results showed that by changing the sintering temperature, sintered bodies with different optical properties can be obtained. The detailed contents of this invention are described below.

[0012] As one embodiment, the present invention provides a zirconia cutter body for dental cutting, which is a zirconia cutter body for dental cutting with different optical properties obtained by different sintering temperatures, wherein different sintering temperatures can be selected from at least the range of 1500°C to 1600°C and the range of 1400°C to 1500°C.

[0013] As one embodiment, the present invention provides a zirconia cutter body for dental cutting, which is a zirconia cutter body for dental cutting with different optical properties obtained by different sintering temperatures, wherein the different sintering temperatures are in the range of 1400°C to 1600°C and have a sintering temperature difference of 50°C to 150°C.

[0014] As one embodiment, the present invention provides a zirconia cutter body for dental cutting, which is a zirconia sintered body with different optical properties obtained by different sintering temperatures. In this embodiment, the difference between the total light transmittance of a 1.0 mm thick sintered body sintered for 1 hour at one different sintering temperature and the total light transmittance of a 1.0 mm thick zirconia sintered body sintered for 1 hour at another different sintering temperature is 0.5% pt or more. The total light transmittance at 700 nm when sintered at any temperature in the range of 1500°C to 1600°C is 37% or more.

[0015] As one embodiment, the present invention provides a zirconia cutter body for dental cutting, which is a zirconia sintered body with different optical properties obtained by different sintering temperatures. In this case, the crystal grain size of the zirconia sintered body produced by sintering for 1 hour at one different sintering temperature is more than 2.0 times that of the zirconia sintered body produced by sintering for 1 hour at another different sintering temperature.

[0016] In this invention, the crystal grain size of the sintered body produced by sintering at 1550°C for 1 hour can be set to 3.0 μm or more.

[0017] In this invention, the stabilizer may be yttrium oxide.

[0018] In the present application, a coloring element can also be contained.

[0019] In the present application, the difference between the total light transmittance under light of wavelength 700 nm of a sintered body having a thickness of 1.0 mm sintered at 1550°C for 1 hour and the total light transmittance under light of wavelength 700 nm of a sintered body having a thickness of 1.0 mm sintered at 1450°C for 1 hour can be set to 0.5% pt or more.

[0020] The dental zirconia cutting tool of the present application can reduce the types of dental zirconia cutting tools held by dental laboratories and the like in order to obtain a zirconia sintered body having excellent light transmittance. DETAILED DESCRIPTION

[0021] In one aspect, the dental zirconia cutting tool of the present application can be understood as a dental zirconia cutting tool that obtains zirconia sintered bodies having different optical properties by sintering under different sintering temperature conditions, wherein the different sintering temperatures are selected from at least one of the range of 1500°C to 1600°C and the range of 1400°C to 1500°C.

[0022] In one aspect, the dental zirconia cutting tool of the present application can be understood as a dental zirconia cutting tool that obtains zirconia sintered bodies having different optical properties by sintering under different sintering temperature conditions, wherein the different sintering temperatures are in the range of 1400°C to 1600°C and have a difference in sintering temperature of 50°C to 150°C.

[0023] In one aspect, the dental zirconia cutting tool of the present application can be understood as a dental zirconia cutting tool that obtains zirconia sintered bodies having different optical properties by sintering under different sintering temperature conditions, wherein the difference between the transmittance of a zirconia sintered body obtained by sintering under a first sintering temperature condition and the transmittance of a zirconia sintered body obtained by sintering under a second sintering temperature condition is 0.5% pt or more and the total light transmittance under 700 nm conditions when sintered under any temperature condition in the range of 1500°C to 1600°C is 37% or more.

[0024] In one aspect, the dental cutting tool zirconia workpiece of the present application can be understood as a dental cutting tool zirconia workpiece of which zirconia sintered bodies having different optical properties are obtained by sintering at different sintering temperatures, wherein the difference between the total light transmittance of a sintered body having a thickness of 1.0 mm produced by sintering for 1 hour at one of the different sintering temperatures and the total light transmittance of a zirconia sintered body having a thickness of 1.0 mm produced by sintering for 1 hour at another of the different sintering temperatures is 0.5%pt or more, and the total light transmittance at 700 nm under the condition of sintering at any temperature in the range of 1500°C to 1600°C is 37% or more.

[0025] In one aspect, the dental cutting tool zirconia workpiece of the present application can be understood as a dental cutting tool zirconia workpiece of which zirconia sintered bodies having different optical properties are obtained by different sintering temperatures, wherein the crystal grain diameter of a zirconia sintered body obtained by sintering at a first sintering temperature condition is 2.0 times or more the crystal grain diameter of a zirconia sintered body obtained by sintering at a second sintering temperature condition.

[0026] In one aspect, the dental cutting tool zirconia workpiece of the present application can be understood as a dental cutting tool zirconia workpiece of which zirconia sintered bodies having different optical properties are obtained by different sintering temperatures, wherein the crystal grain diameter of a zirconia sintered body produced by sintering for 1 hour at one of the different sintering temperatures is 2.0 times or more the crystal grain diameter of a zirconia sintered body produced by sintering for 1 hour at another of the different sintering temperatures.

[0027] In one aspect, the dental cutting tool zirconia workpiece of the present application can be understood as a dental cutting tool zirconia workpiece of which zirconia sintered bodies having different optical properties are obtained by different sintering temperatures.

[0028] The components of the present application are described in detail.

[0029] The dental cutting tool zirconia workpiece of the present application is a dental cutting tool zirconia workpiece for making a prosthetic device by cutting processing. The dental cutting tool zirconia workpiece is a semi-sintered dental cutting tool zirconia workpiece including a ceramic particle-containing semi-sintered body (pre-sintered body, pre-sintered body), and can be manufactured using a known zirconia raw material powder.

[0030] The dental cutting machining zirconia cut body of the present application may, for example, contain zirconia and a stabilizing material composed of an oxide (hereinafter, also referred to simply as "stabilizing material" in the present specification). In the present application, the content of the stabilizer may, for example, be set to 2.0 mol or more and 7.0 mol% or less, and may be set to 5.8 mol% or more and 7.0 mol% or less, in terms of oxide. In the present application, the content of the stabilizing material refers to the value of the ratio of (amount of stabilizing material) / (total inorganic oxide contained in the half-baked body of the ceramic particles) in terms of mol%.

[0031] In the present application, the amount of the stabilizer can be determined by elemental analysis of a test sample. The method of elemental analysis is not particularly limited, and, for example, fluorescent X-ray analysis can be used.

[0032] The dental cutting machining zirconia cut body of the present application can be substantially free of alumina.

[0033] In the present application, "substantially free of alumina" means not containing alumina in an amount that affects the properties of the dental cutting machining zirconia cut body, and the zirconia sintered body obtained by sintering the same, and specifically means a case where the content of alumina is 500 ppm by weight or less of the dental cutting machining zirconia cut body. The content of alumina can be set to 300 ppm or less, and can be set to 200 ppm or less. Depending on the raw material of the zirconia, a trace amount of alumina is sometimes unavoidably contained even in a case where alumina is intentionally not added, and the content of alumina in this case is usually 500 ppm or less. The content of alumina can be determined by various elemental analyses. The method of elemental analysis is not particularly limited, and, for example, fluorescent X-ray analysis can be used. At this time, depending on the measurement conditions and analysis conditions, alumina is sometimes detected in a test sample that does not actually contain alumina, but the content of alumina in this case is usually 500 ppm or less.

[0034] The stabilizer contained in the dental cutting machining zirconia cut body of the present application is not particularly limited, but yttria can be used because it is easy to obtain and is commonly used for dental zirconia. As other stabilizers, ytterbia, erbium oxide, neodymium oxide, praseodymium oxide, terbium oxide, and the like, which also have the effect of a colorant, can also be used. In the present application, the stabilizer can be one or more selected from the group consisting of yttria, magnesia, calcia, scandia, gallia, india, and lanthanide oxides.

[0035] The zirconia body for dental cutting machining of the present application can contain a coloring element. Specifically, iron for imparting yellow color, erbium for imparting red color, and the like can be listed. Further, it is also not a problem to use cobalt, manganese, chromium, and the like in combination with these coloring elements in order to adjust the color tone. The present application can be easily colored to a tooth color by containing a coloring element.

[0036] The stabilizing element compound of the present application can be a compound composed of any one of an oxide, a halogen compound, a nitrate, a sulfate, and an organic acid salt. Further, the coloring element compound of the present application can be a compound composed of any one of an oxide, a halogen compound, a nitrate, a sulfate, and an organic acid salt.

[0037] Specific examples of the water-soluble stabilizing element compound can include yttrium chloride, yttrium nitrate, yttrium acetate, yttrium carboxylate, yttrium sulfate, yttrium carbonate, ytterbium chloride, ytterbium nitrate, ytterbium acetate, ytterbium carboxylate, ytterbium sulfate, ytterbium carbonate, erbium chloride, erbium nitrate, erbium acetate, erbium carboxylate, erbium sulfate, erbium carbonate, neodymium chloride, neodymium nitrate, neodymium acetate, neodymium carboxylate, neodymium sulfate, neodymium carbonate, praseodymium chloride, praseodymium nitrate, praseodymium acetate, praseodymium carboxylate, praseodymium sulfate, praseodymium carbonate, terbium chloride, terbium nitrate, terbium acetate, terbium carboxylate, terbium sulfate, terbium carbonate, and the like.

[0038] Specific examples of the coloring element compound can include iron chloride, iron nitrate, iron acetate, nickel chloride, nickel nitrate, nickel acetate, and the like.

[0039] Among the water-soluble stabilizing element compound and the coloring element compound, an organic acid salt is particularly preferable from the viewpoint of low decomposition temperature and less contamination of the sintering furnace. Specifically, yttrium acetate, yttrium carbonate, and the like can be listed. The organic acid salt decomposes at a lower temperature than inorganic salts such as halogen compounds, nitrates, sulfates, and the like. In the case where the decomposition temperature is high, it leads to the residual pores during sintering, and thus it is difficult to impart sufficient light transmittance and strength to the zirconia full sintered body.

[0040] The content of the water-soluble stabilizing element compound can be set to, for example, 0.1 to 3.5 mol%, or 0.5 to 3.0 mol%. In the present application, the content of the water-soluble stabilizing element compound refers to the value of the ratio expressed in mol% of (the amount of the water-soluble stabilizing element compound) / (the total inorganic oxide contained in the zirconia cutting tool for dental cutting machining).

[0041] In the case where the content of the water-soluble stabilizing element compound is less than 0.1 mol%, it is sometimes difficult to impart sufficient light transmittance to the zirconia cutting tool for dental cutting machining. On the other hand, in the case where it is more than 3.5 mol%, although the light transmittance of the zirconia full sintered body is improved, it is sometimes difficult to impart sufficient strength. In the present application, the water-soluble stabilizing element compound can contain yttria. By containing yttria in the water-soluble stabilizing element compound, the light transmittance can be further improved.

[0042] The zirconia cutting tool for dental cutting machining of the present application can contain an additive other than the stabilizer and the coloring agent. As a specific example of the additive, compounds of gallium, lanthanum, niobium, tantalum, and the like can be listed. By adding these additives, the sintering behavior can be controlled, the light transmittance can be reduced, or the fracture toughness can be improved. These additive materials can or can not be solid-solved in the zirconia.

[0043] The zirconia cutting tool for dental cutting machining of the present application can contain hafnium. The content of hafnium can be set to, for example, 2 wt% or less.

[0044] The zirconia powder used in the production of the zirconia cutting tool for dental cutting machining of the present application can be used without any limitation as long as it is a zirconia powder produced from a publicly known zirconia powder. Specifically, the zirconia powder used in the production of the zirconia cutting tool for dental cutting machining of the present application can be produced by a hydrolysis method. More specifically, it is a method in which a solution in which a zirconium salt and a yttrium compound are dissolved is heated to perform a hydrolysis reaction, the generated sol is dried and fired to produce a zirconia powder, and the powder is pulverized and granulated. In addition, by mixing an aluminum compound before the pulverization process, a zirconia powder containing alumina is produced.

[0045] The primary particle diameter of the zirconia powder used in the production of the zirconia cutting tool for dental cutting machining of the present application is preferably 10 to 500 nm. In the case where the primary particle diameter is less than 10 nm, there is a tendency that it is difficult to impart sufficient strength to the zirconia sintered body. On the other hand, in the case where the primary particle diameter is 500 nm or more, there is also a tendency that it is difficult to impart sufficient strength to the zirconia sintered body.

[0046] The relative density of the zirconia sintered body of the dental cutting tool zirconia sintered body of the present application sintered at 1550°C is preferably 98% or more of the theoretical density. The relative density is obtained by measuring the density / theoretical density. If the relative density is less than 98%, there is a tendency for the strength and light transmittance to decrease.

[0047] The crystal phase of the dental cutting tool zirconia sintered body of the present application is preferably tetragonal crystal and / or cubic crystal. In the case where the crystal phase is monoclinic crystal, the zirconia cannot be fully sintered to impart sufficient light transmittance, and thus is not preferred.

[0048] The dental cutting tool zirconia sintered body of the present application can obtain zirconia sintered bodies having different optical properties by different sintering temperatures.

[0049] The sintering temperature of the dental cutting tool zirconia sintered body of the present application is not particularly limited, and for example, can be selected from the temperature range of 1400°C to 1650°C, can be selected from the temperature range of 1400°C to 1600°C, or can be selected from the temperature range of 1450°C to 1600°C. That is, the "different sintering temperatures" of the present application are not particularly limited, and for example, can be set to two or more temperatures selected from the temperature range of 1400°C to 1650°C, can be set to two or more temperatures selected from the temperature range of 1400°C to 1600°C, or can be set to two or more temperatures selected from the temperature range of 1450°C to 1600°C.

[0050] Specifically, the "different sintering temperatures" of the present application can be set to, for example, two or more temperatures selected from the temperature range of 1400°C to 1450°C, the temperature range of 1450°C to 1500°C, the temperature range of 1500°C to 1550°C, the temperature range of 1550°C to 1600°C, and the temperature range of 1600°C to 1650°C. In addition, the "different sintering temperatures" of the present application can be set to, for example, two or more temperatures selected from the temperature range of 1400°C to 1500°C, the temperature range of 1450°C to 1550°C, the temperature range of 1500°C to 1600°C, and the temperature range of 1550°C to 1650°C.

[0051] In the present application, the temperature range in which the "different sintering temperatures" are selected can be set to temperature ranges that do not overlap with each other except for their end points.

[0052] More specifically, in the case where the "different sintering temperatures" of the present application are two temperatures, for example, one can be selected from the temperature range of 1400°C to 1500°C and the other can be selected from the temperature range of 1500°C to 1600°C, one can be selected from the temperature range of 1450°C to 1550°C and the other can be selected from the temperature range of 1550°C to 1650°C, and one can be selected from the temperature range of 1400°C to 1500°C and the other can be selected from the temperature range of 1550°C to 1650°C. In particular, in the case where the "different sintering temperatures" of the present application are two temperatures, one can be selected from the temperature range of 1400°C to 1500°C and the other can be selected from the temperature range of 1500°C to 1600°C.

[0053] The "different sintering temperatures" of the present application can be set to two or more different temperatures selected from the same temperature range. In this case, the same temperature range can be set to the temperature range of 1400°C to 1650°C, or the temperature range of 1450°C to 1600°C. In addition, the temperature difference of the two or more temperatures can be set to 50°C or more, the range of 50°C to 150°C, the range of 50°C to 100°C, or the range of 100°C to 150°C.

[0054] More specifically, in the case where the "different sintering temperatures" of the present application are two temperatures, the two temperatures can be selected from the temperature range of 1400°C to 1600°C and set to a difference of 50°C to 150°C in the sintering temperature.

[0055] In the present application, the method of making the resulting zirconia sintered body have different optical properties by sintering at different sintering temperatures is not limited. Specifically, by sintering at different sintering temperatures, an element that changes the optical properties of the resulting zirconia sintered body can be added. As examples of such elements, gallium, indium, titanium, scandium, barium, niobium, tantalum, and the like can be listed. In order to add these elements to the zirconia sintered body for dental cutting machining, it can be added by mixing a solution containing these elements into a zirconium oxychloride solution as a zirconia raw material, it can be added by mixing zirconia powder with a compound containing these elements and granulating, or it can be added by permeating a solution containing these elements into the zirconia sintered body for dental cutting machining.

[0056] The optical properties of the zirconia sintered body are affected, for example, by the crystal grain size of the resulting zirconia sintered body. In the present application, the "crystal grain size" refers to the diameter of a circle having the same area as that of the crystal grain (Heywood diameter). The method of measuring the crystal grain size is not limited, and for example, the zirconia sintered body can be subjected to scanning electron microscope (SEM) observation, and the resulting image can be measured using a commercially available particle image analysis software. In such a measurement method, in order to prevent a deviation in the measured value, the crystal grain size is measured from 50 or more crystal grains extracted at random, and the median particle size is taken as the crystal grain size of the sample.

[0057] The stabilizer element such as yttrium also sometimes has an effect on the difference in particle size. Yttrium is generally added in the form of a solution at the time of producing the zirconia powder. The yttrium added like this is present substantially uniformly in the zirconia particles. On the other hand, it is also possible to add by mixing the zirconia powder and the yttria powder, or to add yttrium by permeating a yttrium solution into a zirconia pre-sintered body. The yttrium added like this is present on the outside of the zirconia particles. Such a difference in the distribution of yttrium affects the difference in the crystal grain size of the sintered body, and in the case of adding to the outside of the zirconia particles, the difference in the crystal grain size has a tendency to increase more. That is, the yttrium added to the outside of the zirconia particles functions not only as a stabilizer but also as a particle size difference adjuster.

[0058] The reason for the difference in the difference in the crystal grain size caused by the method of adding yttrium is not clear, but it is possible that it is due to the effect of the mobility of the grain boundary caused by the non-uniform distribution of yttrium. The yttrium added to the outside of the zirconia particles is solid-solved in the zirconia in the sintering. At this time, since yttrium cannot diffuse into the inside of the zirconia particles, the yttrium concentration near the surface of the zirconia particles is higher than that in the inside. On the other hand, in the case of adding yttrium uniformly in the zirconia particles, the difference in the yttria concentration between the surface and the inside of the zirconia particles becomes small. It is considered that the concentration of impurity ions near the grain boundary strongly affects the mobility of the grain boundary, and thus the difference in the difference in the crystal grain size is produced.

[0059] As a specific difference in the crystal grain size that affects the optical properties of the zirconia sintered body, for example, one crystal grain size of the sintered body produced by sintering at a different sintering temperature for 1 hour can be set to be 2.0 times or more of the other crystal grain size. More specifically, for example, the crystal grain size of the sintered body produced by sintering at 1550°C for 1 hour is 2.0 times or more of the crystal grain size of the sintered body produced by sintering at 1450°C for 1 hour, or the crystal grain size of the sintered body produced by sintering at 1500°C for 1 hour is 2.0 times or more of the crystal grain size of the sintered body produced by sintering at 1600°C for 1 hour.

[0060] In a case where the crystal grain diameter of one sintered body produced by sintering at different sintering temperatures for 1 hour is less than 2.0 times the crystal grain diameter of the other, the change in light transmittance, strength, and color caused by the change in sintering temperature is small, and thus it is sometimes not possible to adjust the light transmittance by changing the sintering temperature according to the case. The crystal grain diameter of one sintered body produced by sintering at different sintering temperatures for 1 hour can be set to be 2.3 times or more, 2.5 times or more, or 2.7 times or more the crystal grain diameter of the other. By setting the crystal grain diameter in this relationship, the change in light transmittance, strength, and color caused by the change in sintering temperature becomes large, and thus it is possible to adjust the light transmittance by changing the sintering temperature according to the case.

[0061] The amount of stabilizer in terms of oxides is preferably 5.8 mol% or more. In a case of less than 5.8 mol%, the change in light transmittance, strength, and color caused by the change in sintering temperature is small, and thus there arises a problem that it is not possible to adjust the light transmittance, strength, and color by changing the sintering temperature according to the case. The amount of stabilizer in terms of oxides is preferably 7.0 mol% or less. When the amount of stabilizer in terms of oxides is more than 7.0 mol%, there arises a problem that the light transmittance and / or strength decreases. The amount of stabilizer in terms of oxides can be set to be 6.2 mol% or more and 7.0 mol% or less. By setting to this range, the change in light transmittance, strength, and color caused by the change in sintering temperature becomes large, and thus it is easier to adjust the light transmittance, strength, and color by changing the sintering temperature according to the case.

[0062] One crystal grain diameter of the zirconia sintered body obtained by sintering at different sintering temperatures can be set to be 2.0 μm or more, 3.0 μm or more, or 4.0 μm or more. In this case, the change in light transmittance when the sintering temperature is changed is large, and it is possible to increase the number of cases that can be dealt with by adjusting the sintering temperature.

[0063] In the present application, the difference between the total light transmittance at a wavelength of 700 nm light of a sintered body having a thickness of 1.0 mm produced from one of the zirconia sintered bodies obtained by sintering at different sintering temperatures and the total light transmittance at a wavelength of 700 nm light of a sintered body having a thickness of 1.0 mm produced from the other can be set to be 0.5% pt or more. In this case, by changing the sintering temperature, it is possible to adjust the light transmittance corresponding to the case. The difference in total light transmittance can be set to be 2% pt or more, and further, 3% pt or more. By setting to this difference in total light transmittance, it is possible to increase the adjustment range of the light transmittance.

[0064] In the present application, the total light transmittance at 700 nm under sintering at any temperature in the range of 1500°C to 1600°C can be set to 37% or more, and can be set to 38% or more. In this case, a zirconia sintered body having excellent light transmittance can be obtained.

[0065] The method for producing the dental cutting tool zirconia workpiece of the present application is not particularly limited, and any known production method can be used without any problems. Specifically, a method in which a zirconia powder is molded by press molding is preferred. In addition, a plurality of zirconia powders having different colors and compositions can be press-molded in stages, and multi-layer molding can be performed.

[0066] The dental cutting tool zirconia workpiece of the present application is preferably subjected to isotropic pressurization by a cold isostatic pressing method (CIP treatment) after press molding.

[0067] The maximum load pressure of the CIP treatment of the present application is preferably 50 MPa or more. In the case where the maximum load pressure is less than 50 MPa, it is sometimes not possible to impart sufficient light transmittance and strength to the zirconia sintered body.

[0068] The holding time at the maximum load pressure of the CIP treatment of the present application is not particularly limited, and is generally preferably 0 to 150 seconds, and more preferably 0 to 60 seconds.

[0069] The time taken for the series of processes is not particularly limited, and is generally preferably 30 seconds to 10 minutes, and more preferably 3 minutes to 7 minutes. When the time is too short, the molded body is sometimes broken, and when the time is too long, the production efficiency is poor, and thus is not preferred.

[0070] The pre-sintering temperature of the dental cutting tool zirconia workpiece of the present application is preferably 800°C to 1200°C. In the case where the pre-sintering temperature is less than 800°C, the Vickers hardness and / or the bending strength become too low, and thus there is a tendency that chips and breakage are easily generated during cutting processing. On the other hand, in the case where the pre-sintering temperature is 1200°C or more, the Vickers hardness and / or the bending strength become too high, and thus the consumption of the polishing rod of the cutting machine becomes severe, and there is a tendency that the operating cost becomes high.

[0071] In the manufacturing process of the dental cutting machining zirconia cut body of the present application, a process of infiltrating an infiltration solution containing metal ions can be included. Specifically, at least one of the infiltration solutions is infiltrated into the zirconia pre-sintered body, and the metal compound is loaded into the zirconia fine pores through processes such as drying, degreasing, etc. Thus, the desired part of the dental cutting machining zirconia cut body can be given desired light transmittance, color tone, mechanical properties, etc. Two or more of the infiltration solutions are more preferably used. In this case, by ion diffusion between the infiltration solutions, the zirconia cut body can be given a smooth light transmittance and / or color tone and / or a gradual change in mechanical properties. In addition, in order to perform the ion diffusion, an infiltration solution not containing metal ions can also be used.

[0072] At least one of the metal ions contained in the infiltration solution can be a rare earth metal ion. A specific rare earth metal ion is yttrium ion. By containing a rare earth metal ion, the light transmittance of the zirconia sintered body can be improved, or the zirconia sintered body can be colored. The metal ions can be only rare earth metal ions.

[0073] At least one of the metal ions contained in the infiltration solution can be a transition metal ion. A specific transition metal ion is iron ion. By containing a transition metal ion, the zirconia sintered body can be colored. The metal ions can be only transition metal ions.

[0074] At least one of the metal ions contained in the infiltration solution can be any one of aluminum ion, gallium ion, and indium ion. By containing any one of aluminum ion, gallium ion, and indium ion, the sinterability of the zirconia sintered body can be improved, or the light transmittance can be improved. The metal ions can be only aluminum ion, gallium ion, and / or indium ion. The metal ions can be only rare earth metal ions, transition metal ions, aluminum ion, gallium ion, and / or indium ion.

[0075] The metal ion concentration of the infiltration solution is not particularly limited, and for example, in the case of yttrium ion, it is preferably about 2.0 wt% to about 10.0 wt%, and more preferably about 4.0 wt% to about 10.0 wt%. In the case where the metal ion concentration of the infiltration solution is 2.0 wt% or less, the amount of yttrium loaded is small, and sometimes insufficient properties are not obtained. In the case where the metal ion concentration of the infiltration solution is 10.0 wt% or more, the amount of yttrium loaded is large, and sometimes adversely affects the physical properties. The optimum metal loading amount varies depending on the kind of metal and the desired properties, and thus the metal ion concentration of the infiltration solution is preferably determined in accordance with the desired metal loading amount and the solubility of the metal ion source in the solvent.

[0076] The solvent used in the infiltration solution is not particularly limited, and water is preferably used from the aspects of ease of obtaining and handling.

[0077] In the impregnating solution, an acid or a base, a pH adjuster can be added for the purpose of controlling the pH. The acid or base used is not particularly limited, and from the viewpoint that no residue remains in the porous zirconia shaped body, an organic acid such as acetic acid, citric acid, or the like, aqueous ammonia, or the like is preferably used.

[0078] A precipitant can be contained in the impregnating solution. The precipitant is a substance that precipitates a metal compound by performing a heat treatment or the like after the penetration of the impregnating solution, and specifically, urea, hexamethylenetetramine, or the like can be listed. Since it is easy to obtain and handle, urea is preferred. Thereby, segregation of the metal compound can be suppressed.

[0079] Various additives can be contained in the impregnating solution. As examples of the additives, a glycol, a polymer, or the like that adjusts the viscosity of the impregnating solution, a chelating agent that improves the stability of metal ions can be listed. The former is specifically ethylene glycol, propylene glycol, polyethylene glycol, or the like, and the latter is specifically citric acid, ethylenediaminetetraacetic acid ammonium, or the like. A hydroxy acid can be contained in the impregnating solution. The hydroxy acid can be, for example, citric acid, malic acid, and lactic acid. By containing such a hydroxy acid, segregation of the metal compound after drying can be suppressed.

[0080] As a method of making the impregnating solution penetrate into the zirconia preform, any method can be used without particular limitation as long as the impregnating solution can intrude into the fine pores of the porous zirconia shaped body. A simple and preferred method is a method of immersing the entire and / or a part of the porous zirconia shaped body in the impregnating solution. In this case, the impregnating solution can be made to penetrate into the inside by capillary phenomenon. The time of immersion can be set to 3 minutes or more, and can be set to 10 minutes to 10 hours.

[0081] The impregnating solution can penetrate into the entire of the porous zirconia shaped body, or can penetrate into only an arbitrary part. The method of impregnating into only an arbitrary part is not particularly limited, and as examples, control of the weight, volume of the impregnating solution, control of the impregnation time can be listed.

[0082] Plural kinds of impregnating solutions can also be used for one zirconia preform. As a specific example, a first impregnating solution is made to penetrate from one end, and a second impregnating solution is made to impregnate from the same end or the other end, or the like.

[0083] The environment during impregnation of the impregnation solution is not particularly limited, and atmospheric air, non-reactive gas, or the like can be used under normal pressure, reduced pressure, or pressurized conditions. From the viewpoint of not requiring special equipment, impregnation is preferably performed in atmospheric air. From the viewpoint of shortening the manufacturing time, it is preferable to promote the penetration of the impregnation solution by placing the surrounding environment under reduced pressure or pressurized conditions. Furthermore, repeating the operation of returning to normal pressure after reduced pressure (reduced pressure / normal pressure operation) or the operation of returning to normal pressure after pressurization (pressurization / normal pressure operation) several times is effective for shortening the time for the process of penetrating the impregnation solution. The time for which the impregnation solution is allowed to impregnate the zirconia calcined body cannot be generalized depending on the size of the zirconia calcined body, the degree of penetration of the impregnation solution, and the impregnation method, and 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 pressurization, it is usually 0.2 to 6 hours.

[0084] A drying process is preferably provided after the penetration process. The drying process is a process of drying the porous zirconia shaped body from which the metal compound has been precipitated. The drying temperature is 50°C to 200°C, and the time is preferably 15 minutes to 20 hours. After drying, it is preferable to sufficiently gasify the solvent. Depending on the case, a heat treatment process can be performed after this drying process. The drying process can also be included in the heat treatment process. A debinding process can be provided after the penetration process. The debinding process is a process of removing unnecessary components such as organic matter contained in the impregnation solution. The debinding temperature is 200°C to 600°C, and the time can be 50 hours to 200 hours. By debinding, the unnecessary components can be completely removed. Depending on the case, a heat treatment process can be performed after this debinding process. The debinding process can also be included in the heat treatment process.

[0085] Since solvents, unreacted substances, by-products, and the like remain in the porous zirconia shaped body from which the metal compound has been precipitated and supported as obtained in this way, heat treatment is preferably performed. The method of heat treatment is not particularly limited, and from the viewpoint of not requiring special equipment, heat treatment in atmospheric air at normal pressure is preferable. The heat treatment temperature is not particularly limited, and is preferably 500°C to 1200°C. By heat treatment, removal of impurities, removal of organic matter, and removal of odor can be performed.

[0086] By this manufacturing method, the zirconia shaped body for dental cutting machining of the present application is obtained. The obtained zirconia shaped body for dental cutting machining is cut, machined, and surface-ground to a desired size as needed.

[0087] As a method for completely sintering the dental cutting work zirconia workpiece of the present application, there is no particular limitation, and a simple and preferred method is to perform the firing under normal pressure. The firing temperature is not particularly limited, and is preferably 1450°C to 1600°C. The residence time at the firing temperature is not particularly limited, and is preferably 1 minute to 12 hours, and particularly preferably 2 to 4 hours. The temperature increase rate is not particularly limited, and is preferably 1°C / min to 400°C / min, and more preferably 3°C / h to 100°C / h.

[0088] The kind of the restoration device using the dental cutting work zirconia workpiece of the present application for cutting work is not particularly limited, and any restoration device such as an inlay, an onlay, a veneer, a crown, a bridge, and the like is not problematic. Therefore, the shape of the dental cutting work zirconia workpiece for cutting work for producing the restoration device by cutting work is also not particularly limited, and any shape of the dental cutting work zirconia workpiece such as a block shape corresponding to an inlay, an onlay, a veneer, a crown, and the like, a disc shape corresponding to a bridge, and the like can be used.

[0089] [Example]

[0090] Hereinafter, the present application will be described in more detail and specifically by examples, but the present application is not limited thereto.

[0091] (Production of Zirconia Pre-sintered Body 1)

[0092] A zirconia powder containing 5.2 mol% of yttria solid solution and not containing alumina, 486 g, was filled into a mold (φ 100 mm), and press molding was performed (surface pressure: 50 MPa), thereby obtaining a molded body. The obtained molded body was subjected to CIP treatment (maximum load pressure: 200 MPa, holding time: 1 minute), and then pre-sintering was performed using an electric furnace (1000°C, 30 minutes), thereby obtaining a zirconia pre-sintered body having a diameter of 98.5 mm x thickness of 18 mm.

[0093] (Production of Zirconia Pre-sintered Body 2)

[0094] Except for using a zirconia powder containing 5.2 mol% of yttria solid solution and 0.05 wt% of alumina, the same operation as that for the zirconia pre-sintered body 1 was performed, thereby obtaining a zirconia pre-sintered body.

[0095] (Production of Zirconia Pre-sintered Body 3)

[0096] Except for using a zirconia powder containing 6.5 mol% of yttria solid solution, the same operation as that for the zirconia pre-sintered body 1 was performed, thereby obtaining a zirconia pre-sintered body.

[0097] (Production of Zirconia Pre-sintered Body 4)

[0098] A zirconia powder obtained by performing ball mill mixing using a zirconia powder containing 5.2 mol% of yttria solid-solved and a yttria powder added so that the total yttria concentration is 6.5 mol% and performing spray drying was used, and otherwise, the same operation as the zirconia pre-sinter 1 was performed to obtain a zirconia pre-sinter.

[0099] (Production of Zirconia Pre-sinter 5)

[0100] A zirconia pre-sinter was obtained by the same operation as the zirconia pre-sinter 1 except that a zirconia powder containing 3.0 mol% of yttria solid-solved was used.

[0101] (Production of Zirconia Pre-sinter 6)

[0102] A zirconia pre-sinter was obtained by the same operation as the zirconia pre-sinter 1 except that a zirconia powder containing 4.0 mol% of yttria solid-solved was used.

[0103] (Production of Infiltration Liquid)

[0104] The composition of the infiltration liquid is shown in Table 1. According to the composition of Table 1, metal salts and additives were added to ion-exchanged water, and stirred for 1 hour, whereby 100 g of the infiltration liquid was produced.

[0105] [Table 1]

[0106]

[0107] (Infiltration of Infiltration Liquid into Zirconia Pre-sinter)

[0108] A plastic container was placed on a horizontal workbench, and a zirconia pre-sinter was placed therein. The infiltration liquid was poured so that the liquid surface reached a position of 80% of the thickness of the zirconia pre-sinter, and left to stand for 15 hours.

[0109] (Heat Treatment after Infiltration)

[0110] In the case where urea was contained in the infiltration liquid, heat treatment was performed after the infiltration of the infiltration liquid. The zirconia pre-sinter after the infiltration was put in a resin bag, and degassed. The porous zirconia shaped body put in the resin bag and degassed was set in a drier, and heat-treated at 95°C for 15 hours to precipitate a metal compound. After the heat treatment, the porous zirconia shaped body was taken out of the resin bag, and dried (120°C, 1 hour), whereby a porous zirconia shaped body loaded with a metal compound was obtained.

[0111] (Removal of Residual Organic Matter)

[0112] The zirconia pre-sintered body after impregnation and / or heat treatment is heat-treated in an electric furnace (500°C, 30 minutes) to remove residual organic matter, thereby obtaining a zirconia cuttable body for dental cutting with metal compounds loaded in the fine pores.

[0113] (Repeated soaking)

[0114] In Examples 6 and 13, the process from impregnation to removal of residual organic matter was repeated multiple times.

[0115] (Partial infiltration)

[0116] In Example 11, the zirconia pre-fired body 1 was placed on a horizontal workbench, and a clamp was installed to hold the solution on the top surface of the zirconia pre-fired body 1. 30g of solution 1 was injected into the top surface of the zirconia pre-fired body 1 and allowed to stand until all of it was absorbed by the zirconia pre-fired body, thereby partially impregnating the solution 1.

[0117] (Preparation of test pieces for stabilization material testing and light transmittance testing)

[0118] Using a dental cutting machine (manufactured by Roland Corporation, DWX51D), a test piece with a diameter of 12 mm and a thickness of 2.0 mm was made from the center of a dental cutting zirconia workpiece loaded with a metal compound in a fine hole.

[0119] (Evaluation of stable dosage)

[0120] The molar fraction of stabilizer (stabilizer oxide in the case of yttrium: Y₂O₃) in each test specimen, converted from oxide, was determined using a fluorescence X-ray analysis apparatus (manufactured by Rigaku Corporation, Japan). Within the scope of this example and comparative example, yttrium and ytterbium were used as stabilizers to calculate the stabilizer concentration. For the measurement, the upper and lower surfaces of the test specimen were examined, and their average value was taken as the measured value for that test specimen.

[0121] (Evaluation of light transmittance)

[0122] Each test specimen, after evaluation of stabilizer concentration, was completely sintered in a firing furnace (heating rate: 3℃ / min, firing temperature: high temperature (1500℃~16000℃), low temperature 1400℃~15000℃), holding time: 1 hour). Then, the thickness of each test specimen (1.0 mm) was adjusted using a surface grinder. Transmittance was evaluated based on the transmission spectrum measured using a UV-Vis spectrophotometer (manufactured by Nippon Spectrophotometer, V-750), using the total transmittance under an illumination wavelength of 700 nm.

[0123] Light transmittance is scored according to the following criteria.

[0124] 3: Total light transmittance at 700 nm (high-temperature sintering) ≥ 50% and total light transmittance at 700 nm (low-temperature sintering) > 35%.

[0125] 2: 50% > total light transmittance at 700 nm (high-temperature sintering) ≥ 44% and total light transmittance at 700 nm (low-temperature sintering) > 35%.

[0126] 1: 44% > total light transmittance at 700 nm (high-temperature sintering) ≥ 37% and total light transmittance at 700 nm (low-temperature sintering) > 35%.

[0127] 0: 37% > total light transmittance at 700 nm (high-temperature sintering) or 35% > total light transmittance at 700 nm (low-temperature sintering).

[0128] Further, the difference in light transmittance between the high-temperature sintered body and the low-temperature sintered body was scored according to the following criteria.

[0129] 3: Difference in total light transmittance at 700 nm ≥ 6% pt.

[0130] 2: 6% pt > difference in total light transmittance at 700 nm ≥ 3% pt.

[0131] 1: 3% pt > difference in total light transmittance at 700 nm ≥ 0.5% pt.

[0132] 0: 0.5% pt > difference in total light transmittance at 700 nm.

[0133] (Evaluation of Crystal Grain Size)

[0134] The microstructure of each test body was observed using a scanning electron microscope (manufactured by JEOL Ltd.). The test body was subjected to heat etching after mirror polishing of the test body for evaluation of light transmittance, and was fired at a temperature 50°C lower than the sintering temperature (1550°C or 1450°C) (1500°C or 1400°C) for 10 minutes, and the test body was surface-evaporated with gold. The particle size distribution (heywood diameter, volume distribution) of each test body was measured from the obtained microscope image using image analysis type particle size distribution measurement software (manufactured by MOUNTECH company, Mac-View), and the median particle diameter was taken as the crystal grain size of each test body under the sintering temperature (1550°C or 1450°C) condition.

[0135] (Comprehensive Evaluation)

[0136] Each score of the light transmittance evaluation, the light transmittance difference evaluation, and the three-point bending strength evaluation is comprehensively evaluated according to the following criteria.

[0137] A: light transmittance evaluation score x light transmittance difference evaluation score ≥ 6.

[0138] B: 6 > light transmittance evaluation score x light transmittance difference evaluation score ≥ 1.

[0139] C: light transmittance evaluation score x light transmittance difference evaluation score = 0.

[0140] In the case where the comprehensive evaluation is A, both the light transmittance adjustment function and the light transmittance by changing the sintering temperature are excellent, and at least one of them is particularly excellent, and thus the zirconia can be applied to a variety of uses requiring different light transmittances.

[0141] In the case where the comprehensive evaluation is B, since both the light transmittance adjustment function and the light transmittance by changing the sintering temperature are present, the zirconia can be used for a variety of uses requiring different light transmittances.

[0142] In the case where the comprehensive evaluation is C, at least one of the light transmittance adjustment function and the light transmittance by changing the sintering temperature is insufficient, and thus the zirconia can only be used for a specific use.

[0143] The production conditions and the results of the property tests of the dental cutting zirconia bodies produced in the examples and the comparative examples are shown in Tables 2 and 3.

[0144] [Table 2]

[0145]

[0146] [Table 3]

[0147]

[0148] It was confirmed that in Examples 1 to 15, since both the light transmittance adjustment function and the light transmittance by changing the sintering temperature are present, the zirconia can be used for a variety of uses requiring different light transmittances.

[0149] It was confirmed that in Comparative Example 1, the total light transmittance of both the sintered body at a high temperature and the sintered body at a low temperature is low, and both the sintered body at a high temperature and the sintered body at a low temperature can only be used for a use not requiring light transmittance.

[0150] It was confirmed that in Comparative Examples 2 to 5, the difference in the total light transmittance between the sintered body at a high temperature and the sintered body at a low temperature is small, and the light transmittance cannot be greatly changed, and thus the zirconia cannot be used for a variety of uses requiring different light transmittances.

[0151] It was confirmed that in Comparative Example 6, the sintering temperature in the low-temperature sintering was too low, and thus the light transmittance was low, and in the case where a zirconia sintered body having excellent light transmittance was obtained, it could not be used for a plurality of uses requiring different light transmittances.

[0152] In the present specification, even in the case where a disclosed constitutional element is described as any one of a single or a plurality, or is described without being limited to any one of a single or a plurality, the constitutional element can be any one of a single or a plurality, except in cases where it should be understood otherwise from the context.

[0153] The present application is described with reference to detailed embodiments, but it will be understood by those skilled in the art that various changes or modifications can be made based on the matters disclosed in the present specification. Therefore, the scope of the embodiments of the present disclosure is intended to include any changes or modifications.

[0154] According to the present application, it is possible to provide a zirconia cutting tool for dental cutting machining, which can reduce the types of zirconia cutting tools for dental cutting machining held by dental laboratories and the like in order to obtain a zirconia sintered body having excellent light transmittance.

Claims

1. A zirconia cutter body for dental machining, wherein the zirconia sintered bodies with different optical properties are obtained by sintering at different temperatures, wherein... Different sintering temperatures can be selected from at least the ranges of 1500℃~1600℃ and 1400℃~1500℃.

2. A zirconia cutter body for dental machining, wherein the zirconia sintered bodies with different optical properties are obtained by sintering at different temperatures, wherein... The different sintering temperatures are in the range of 1400℃ to 1600℃ and have a sintering temperature difference of 50℃ to 150℃.

3. A zirconia cutter body for dental machining, wherein the zirconia sintered bodies with different optical properties are obtained by sintering at different temperatures, wherein... The difference in total light transmittance between a 1.0 mm thick sintered body sintered at one different sintering temperature for 1 hour and a 1.0 mm thick zirconia sintered body sintered at another different sintering temperature for 1 hour is greater than 0.5% pt. The total transmittance at 700 nm during sintering at any temperature within the range of 1500℃ to 1600℃ is over 37%.

4. A zirconia cutter body for dental machining, wherein the zirconia sintered bodies with different optical properties are obtained by sintering at different temperatures, wherein... The grain size of zirconia sintered body sintered for 1 hour at one sintering temperature is more than 2.0 times that of zirconia sintered body sintered for 1 hour at another sintering temperature.

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