Zirconia cut object with zirconia δctotal of 5.0 or less and method for manufacturing the same

Abstract

To provide a manufacturing method in which deterioration in compatibility of a dental prosthesis manufactured from a zirconia cut object for dental cutting, when manufacturing the zirconia cut object for dental cutting that has any one or more of a translucent gradation, a color gradation, and an intensity gradation, after complete sintering by impregnating a zirconia calcined body with multiple impregnating liquids; and to provide a zirconia cut object for dental cutting that has any one or more of a translucent gradation, a color gradation, and an intensity gradation, after complete sintering, and suppresses deterioration in the suitability of a manufactured dental prosthesis.SOLUTION: Provided is a manufacturing method comprising impregnating a zirconia calcined body with at least two types of impregnating liquids; at least one of the impregnating liquids containing a zirconium component; when the total metal ion concentration (mass%) contained in each impregnating liquid is Ctotal, the difference of Ctotal between impregnating liquids, ΔCtotal, being 5.0 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a zirconia workpiece for dental cutting and a method for producing the same. [Background technology]

[0002] In recent years, the technology of producing prosthetic devices by cutting using dental CAD / CAM systems has rapidly spread. This has made it possible to easily produce prosthetic devices by processing workpieces made of ceramic materials such as zirconia, alumina, and lithium disilicate, and resin materials such as acrylic resin and hybrid resin.

[0003] In particular, zirconia has been used clinically in a variety of cases due to its high strength. On the other hand, fully sintered zirconia (hereinafter referred to as fully sintered zirconia) is so hard that it cannot be machined using dental CAD / CAM systems. For this reason, zirconia cutting objects for dental machining are not fully sintered, but are pre-fired at a low firing temperature and adjusted to a hardness that allows machining.

[0004] A typical zirconia cutting object for dental cutting is produced by molding zirconia powder by press molding or the like, and then calcining at 800 to 1200°C.

[0005] In recent years, a method of coating and / or impregnating a zirconia workpiece for dental cutting with a solution containing a stabilizer and / or a colorant has been widely used for the purpose of adjusting the color tone and translucency.

[0006] Patent Document 1 discloses a method of impregnating a calcined zirconia body with a plurality of solutions containing a stabilizer and / or a colorant to obtain a gradation in translucency and / or color tone. A fully sintered zirconia body produced by this method has a natural gradation in translucency and color tone. However, this method has a problem that if the metal ion content of each solution is different, the shrinkage rate varies depending on the part of the calcined zirconia body, and compatibility after sintering is deteriorated. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-15364 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a method for producing a zirconia body for dental cutting, which has one or more of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering, by impregnating a zirconia calcined body with a plurality of impregnation liquids, and which suppresses deterioration of the compatibility of a dental prosthesis produced from the zirconia body for dental cutting; and a zirconia body for dental cutting, which has one or more of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering, and which suppresses deterioration of the compatibility of a dental prosthesis produced from the zirconia body for dental cutting. [Means for solving the problem]

[0009] The present inventors have investigated a manufacturing method for suppressing deterioration of the compatibility of a dental prosthesis manufactured from a zirconia cut body for dental cutting, in which a zirconia cut body for dental cutting is manufactured having one or more of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering by impregnating a zirconia calcined body with a plurality of impregnation liquids. As a result, the present inventors have investigated a manufacturing method for suppressing deterioration of the compatibility of a dental prosthesis manufactured from the zirconia cut body for dental cutting, in which a zirconia calcined body is impregnated with at least two types of impregnation liquids, at least one of which contains a zirconium component, and the total of the metal ion concentrations (mass%) contained in each impregnation liquid is C tоtal When the impregnation liquid is tоtal Difference ΔC tоtal It has been found that it is particularly important that the zirconia completely sintered body does not deteriorate in properties and the compatibility of the dental prosthesis is prevented from deteriorating, so that the zirconia completely sintered body does not deteriorate in conformity with the dental prosthesis. The present invention will be described in detail below.

[0010] The method for producing a zirconia workpiece for dental cutting according to the present invention is a method for producing a zirconia workpiece for dental cutting having at least one of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering, comprising the steps of: The method includes a step of impregnating a zirconia calcined body with at least two types of impregnation liquid, At least one of the impregnation solutions contains a zirconium component; The total metal ion concentration (mass%) in each impregnation solution is C tоtal When Between each impregnation liquid, C tоtal Difference ΔC tоtal is less than or equal to 5.0.

[0011] The present invention may include a step of drying the calcined zirconia body impregnated with the impregnation liquid.

[0012] The present invention may include a step of degreasing the calcined zirconia body impregnated with the impregnation liquid.

[0013] In the present invention, at least one of the impregnation liquids may contain transition metal ions.

[0014] In the present invention, at least one of the impregnation liquids may contain rare earth metal ions.

[0015] In the present invention, at least one of the impregnation solutions may contain one or more of aluminum ions, gallium ions, and indium ions.

[0016] In the present invention, the zirconium component contained in the impregnation liquid may be one or more of zirconium oxychloride, zirconium oxyacetate, and zirconyl nitrate.

[0017] In the present invention, at least one of the impregnation liquids may contain urea.

[0018] In the present invention, at least one of the impregnation liquids can include a glycol.

[0019] In the present invention, at least one of the impregnation liquids may contain a hydroxy acid.

[0020] In the present invention, the hydroxy acid may be one or more of citric acid, malic acid, and lactic acid.

[0021] The present invention also provides a zirconia workpiece for dental cutting, in which, between two opposing surfaces, a section from one end to 50% of the distance between the surfaces is designated as section A, and a section from the other end to 50% of the distance between the surfaces is designated as section B, wherein section A includes a region A in which a compound of a stabilizer element is supported within pores, and section B includes a region B in which a zirconium compound is supported within pores, and the concentration of metal ions in region A is different from the concentration of metal ions in region B and / or the type of metal ion in region A is different from the type of metal ion in region B.

[0022] In the present invention, the concentration of the stabilizer contained in the zirconium compound can be lower than the concentration of the stabilizer in the substrate, that is, the zirconia workpiece for dental cutting.

[0023] In the present invention, the stabilizing element can be a rare earth metal.

[0024] In the present invention, the rare earth metal can be yttrium.

[0025] In the present invention, a compound of a coloring element may be supported in the pores of at least one of the regions A and B.

[0026] In the present invention, the coloring element can be a rare earth metal.

[0027] In the present invention, the colouring element can be a transition metal.

[0028] In the present invention, at least one of an aluminum compound and a gallium compound may be supported in the pores of at least one of the regions A and B.

[0029] In the present invention, at least one of a niobium compound and a tantalum compound may be supported in the pores of at least one of the regions A and B.

[0030] In the present invention, the difference in relative density between region A and region B can be less than 0.008. Effect of the Invention

[0031] According to the present invention, a manufacturing method can be provided in which a zirconia calcined body is impregnated with a plurality of impregnation liquids to produce a zirconia body for dental cutting that has one or more of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering, and that suppresses deterioration of the compatibility of a dental prosthesis produced from the zirconia body for dental cutting, and a zirconia body for dental cutting that has one or more of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering and that suppresses deterioration of the compatibility of a dental prosthesis produced from the zirconia body for dental cutting. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The constituent features of the present invention will be specifically described. The present invention is a method for producing a zirconia cutting body for dental cutting, which has at least one of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering, comprising a step of impregnating a zirconia calcined body with at least two kinds of impregnation liquids, at least one of which contains a zirconium component, and the total of the metal ion concentrations (mass%) contained in each impregnation liquid is C tоtal When Between each impregnation liquid, C tоtal Difference ΔC tоtal is 5.0 or less.

[0033] ΔC tоtal is preferably 4.0 or less, and more preferably 2.0 or less. tоtal If ΔC exceeds 5.0, the conformity of the dental prosthesis tends to deteriorate. tоtal When the ratio is 4.0 or less, the prosthesis can be adapted to the abutment tooth with only slight modification after sintering, and when the ratio is 2.0 or less, the prosthesis can be adapted to the abutment tooth with almost no modification after sintering.

[0034] The metal ion in the present invention can be used without any particular limitation as long as it can be dissolved in a solvent.Specific examples include yttrium ion, which is a stabilizer for zirconia, praseodymium ion, neodymium ion, terbium ion, erbium ion, and iron ion, which are used as coloring components, aluminum ion, gallium ion, and indium ion, which are used for the purpose of controlling sintering properties, and niobium ion and tantalum ion, which are used for the purpose of improving fracture toughness.

[0035] The stabilizer in the present invention refers to an oxide and / or metal ions in the oxide that form a solid solution in zirconia crystals and stabilize the tetragonal or cubic crystals of zirconia.

[0036] The colorant in the present invention refers to an oxide and / or a metal ion in the oxide that colors the zirconia after sintering.

[0037] Among the stabilizers are oxides or metal ions that cause coloration of zirconia, such as erbium and neodymium ions, which are both stabilizers and colorants.

[0038] At least one of the metal ions contained in the impregnation liquid can be a transition metal ion. A specific transition metal ion is an iron ion. By including a transition metal ion, it becomes possible to color the zirconia sintered body. The metal ion can be only a transition metal ion.

[0039] At least one of the metal ions contained in the impregnation liquid can be a rare earth metal ion. A specific rare earth metal ion is an yttrium ion. By including a rare earth metal ion, it is possible to improve the translucency of the zirconia sintered body and color the zirconia sintered body. The metal ion can be only a rare earth metal ion.

[0040] At least one of the metal ions contained in the impregnation liquid can be one or more of aluminum ions, gallium ions, and indium ions. By containing any one of aluminum ions, gallium ions, and indium ions, it is possible to improve the sinterability and translucency of the zirconia sintered body. The metal ions can be only aluminum ions, gallium ions, and / or indium ions. The metal ions can be only rare earth metal ions, transition metal ions, aluminum ions, gallium ions, and / or indium ions.

[0041] The metal ion source in the present invention is preferably an organic acid salt of a metal ion, from the viewpoint of low decomposition temperature and little contamination of the firing furnace. Examples include acetates and citrates. The decomposition temperature of an organic acid salt is lower than that of inorganic salts such as halogen compounds, nitrates, and sulfates. If the decomposition temperature is high, pores are left in the sintering process, so that it may be difficult to impart sufficient translucency and strength to the completely sintered zirconia body.

[0042] In the present invention, there is no particular limitation on the metal ion concentration in the impregnation solution, and the metal ion concentration is preferably determined based on the desired amount of metal to be supported and the solubility of the metal ion source in the solvent.

[0043] Although there is no particular limitation on the solvent used in the impregnation liquid in the present invention, it is preferable to use water in terms of ease of availability and handling.

[0044] In the present invention, an acid, a base, or a pH adjuster may be added to the impregnation solution for the purpose of controlling the pH. There is no particular limitation on the acid, base, or pH adjuster used, but organic acids such as acetic acid and citric acid, and ammonia water can be used in order not to leave any residue on the zirconia workpiece for dental cutting.

[0045] The zirconium component contained in the impregnation solution may be one or more of zirconium oxychloride, zirconium oxyacetate, and zirconyl nitrate. Such zirconium components are easy to obtain and handle.

[0046] The impregnation liquid may contain a precipitant. The precipitant is a substance that causes the metal compound to precipitate by performing an operation such as heat treatment after the impregnation liquid has been permeated, and specific examples of the precipitant include urea and hexamethylenetetramine. Urea can be used because it is easy to obtain and handle. This can suppress segregation of the metal compound.

[0047] The amount of precipitant in the impregnation liquid in the present invention is preferably an amount that allows all of the metal ions in the impregnation liquid to be precipitated. If the amount of precipitant is small, the time required to precipitate all of the metal ions tends to be long, and if the amount of precipitant is large, the time required to precipitate all of the metal ions tends to be short, but in either case, the effect of the present invention is not affected. If the amount of precipitant is less than the amount that allows all of the metal ions in the impregnation liquid to be precipitated, the metal ions may not be precipitated in their entirety and may segregate in the subsequent drying step, which is not preferable. If the amount of precipitant is excessive, the effect of the present invention is not affected, but a large amount of precipitant remains after the precipitation step, which is not preferable.

[0048] The impregnation liquid may contain various additives. Examples of additives include glycols, polymers, etc. that adjust the viscosity of the impregnation liquid, and chelating agents that increase the stability of metal ions. Specific examples of the former include ethylene glycol, propylene glycol, polyethylene glycol, etc., and specific examples of the latter include citric acid, ammonium ethylenediaminetetraacetate, etc.

[0049] The zirconium component contained in the impregnation liquid may contain a hydroxy acid. The hydroxy acid may be, for example, citric acid, malic acid, or lactic acid. By containing such a hydroxy acid, segregation of the metal compound after drying can be suppressed.

[0050] The method of permeating the zirconia calcined body with the impregnating liquid is not particularly limited as long as the position and amount of the impregnating liquid in the zirconia calcined body can be controlled. A simple and preferred method is to permeate a specified amount of a first type of impregnating liquid from one end, and then impregnate a specified amount of a second type of impregnating liquid from the same end or the other end.

[0051] The atmosphere during impregnation with the impregnation solution is not particularly limited, and air, inert gas, etc. can be used under normal pressure, reduced pressure, or pressurized conditions. Since no special equipment is required, it is preferable to carry out the impregnation in air at normal pressure.

[0052] There is no particular limit to the metal ion concentration of the impregnation liquid, but for example, in the case of yttrium ions, it can be about 2.0 mass% to 10.0 mass%. If it is less than 2.0 mass%, the amount of supported yttrium is small, and sufficient characteristics may not be obtained. If it is more than 10.0 mass%, the amount of supported yttrium is large, and physical properties may be adversely affected. Since the optimal metal support amount differs depending on the type of metal and the desired characteristics, it is preferable to determine the metal ion concentration of the impregnation liquid based on the desired metal support amount and the solubility of the metal ion source in the solvent.

[0053] The method of impregnating the zirconia calcined body with the impregnating liquid can be any method that can penetrate into the pores of the zirconia body for dental cutting. A simple and preferred method is to immerse the entire and / or part of the zirconia body for dental cutting in the impregnating liquid. In this case, the impregnating liquid can be permeated into the inside by capillary action. The immersion time is 3 minutes or more, and preferably 10 minutes to 10 hours.

[0054] A specific example of using a plurality of impregnation liquids is to impregnate one end with a first type of impregnation liquid, and then impregnate the same end or the other end with a second type of impregnation liquid.

[0055] After the infiltration step, a drying step can be included. The drying step is a step of drying the porous zirconia molded body on which the metal compound has been precipitated. The drying temperature can be 50 to 200°C, and the drying time can be 15 minutes to 20 hours. After drying, the solvent can be sufficiently vaporized. In some cases, the drying step can be followed by a heat treatment step. The drying step can also be included in the heat treatment step.

[0056] After the impregnation step, a degreasing step can be included. The degreasing step is a step for removing unnecessary components such as organic matter contained in the impregnation liquid. The degreasing temperature is 200 to 600°C, and the degreasing time can be 50 to 200 hours. Unnecessary components can be completely removed by degreasing. In some cases, the degreasing step can be followed by a heat treatment step. The degreasing step can also be included in the heat treatment step.

[0057] When the impregnation solution contains a precipitating agent, it is preferable to include a precipitation step after the impregnation in which the precipitating agent is decomposed to precipitate a compound containing metal ions.

[0058] There are no particular limitations on the method for decomposing the precipitant, and examples include hydrolysis by heating and hydrolysis by enzymes, with hydrolysis by heating being preferred due to its simplicity.

[0059] The method of hydrolysis by heating is not particularly limited as long as it can maintain a constant temperature. Examples include methods using an incubator, a dryer, a water bath, and an oil bath.

[0060] In order to prevent the solvent from evaporating during hydrolysis by heating, it is preferable to seal the zirconia calcined body. There are no particular limitations on the method for sealing it, but an example is a method in which the zirconia calcined body is covered with a resin sheet and, if necessary, degassed.

[0061] The temperature of hydrolysis by heating is not particularly limited as long as it is equal to or higher than the decomposition temperature of the precipitant, but if it is too low, a long period of heat treatment is required until the entire amount of the metal compound is precipitated, which is not preferable.Furthermore, if the temperature exceeds the boiling point of the solvent, the solvent evaporates during the heat treatment, which is not preferable, and the supported metal compound segregates.

[0062] The time required for hydrolysis by heating varies depending on the metal ion concentration, precipitant concentration, heat treatment temperature, etc., and must be adjusted appropriately, but is generally about 10 minutes to several days, preferably 10 minutes to 24 hours.

[0063] The thus obtained calcined zirconia body on which the metal compound is precipitated and supported still contains solvent, unreacted materials, by-products, etc., and can be heat-treated. There is no particular restriction on the heat-treatment method, but since no special equipment is required, heat-treatment can be performed in atmospheric air at normal pressure. There is no particular restriction on the heat-treatment temperature, but it can be 500°C to 1200°C. Heat-treatment can remove impurities, organic matter, and odors.

[0064] The method for producing the zirconia object for dental cutting of the present invention can produce, for example, the zirconia object for dental cutting of the present invention. Specifically, the zirconia object for dental cutting of the present invention is a zirconia object for dental cutting, in which, between two opposing surfaces, a section from one end to 50% of the distance between the surfaces is designated as section A, and a section from the other end to 50% of the distance between the surfaces is designated as section B, the section A includes a region A in which a compound of a stabilizer element is supported in the pores, and the section B includes a region B in which a zirconium compound is supported in the pores. In particular, the zirconia object for dental cutting is a zirconia object for dental cutting in which the concentration of metal ions in region A is different from the concentration of metal ions in region B, and / or the type of metal ions in region A is different from the type of metal ions in region B.

[0065] The concentration of the stabilizer contained in the zirconium compound can be made lower than the concentration of the stabilizer in the substrate, zirconia workpiece for dental cutting.

[0066] The stabilizer element is not particularly limited, but may be a rare earth metal, especially yttrium, because it is often used for zirconia cutting objects for dental cutting.Other stabilizer elements may be erbium oxide, neodymium oxide, praseodymium oxide, terbium oxide, etc., which also have the effect of a coloring agent.

[0067] It is preferable that a compound of a coloring element is supported in the pores of at least one of the regions A and B. There is no particular specification for the coloring element, but it can be a rare earth metal and / or a transition metal, and iron, nickel, cobalt, manganese, erbium, praseodymium, terbium, neodymium, vanadium, etc. are preferred because they are often used in dental zirconia.

[0068] At least one of an aluminum compound and a gallium compound may be supported in the pores of at least one of the regions A and B. By supporting these compounds, the sintering behavior of the zirconia workpiece for dental cutting can be changed.

[0069] At least one of a niobium compound and a tantalum compound may be supported in the pores of at least one of the regions A and B. By supporting these compounds, the fracture toughness of the fully sintered zirconia body can be improved.

[0070] The relative density difference between region A and region B is preferably less than 0.008, more preferably less than 0.005, and particularly preferably less than 0.003. If the relative density difference exceeds 0.008, the compatibility of the produced dental prosthesis tends to deteriorate.

[0071] The zirconia powder used in the manufacture of the zirconia cutting object for dental cutting of the present invention can be any known zirconia powder without any restrictions. Specifically, the zirconia powder used in the manufacture of the zirconia cutting object for dental cutting of the present invention is preferably prepared by hydrolysis. More specifically, the method is a method in which a solution in which a zirconium salt and an yttrium compound are mixed and dissolved is heated to carry out a hydrolysis reaction, and the resulting sol is dried and fired to prepare zirconia powder, which is then pulverized and granulated. In addition, by mixing an aluminum compound before this pulverization process, a zirconia powder containing alumina is prepared.

[0072] The primary particle size of the zirconia powder used in the manufacture of the zirconia cutting body for dental cutting of the present invention can be 1 to 500 nm. If the primary particle size is less than 1 nm, the translucency of the zirconia sintered body is improved, but it tends to be difficult to impart sufficient strength to the zirconia sintered body. On the other hand, if the primary particle size is more than 500 nm, it tends to be difficult to impart sufficient strength to the zirconia sintered body.

[0073] The zirconia cutting object for dental cutting in the present invention may contain a coloring agent. Specifically, iron oxide for imparting a yellow color and erbium for imparting a red color may be used. In addition to these coloring agents, coloring agents containing elements such as cobalt, manganese, and chromium may be used in combination to adjust the color tone. The inclusion of a coloring agent in the present invention makes it easy to color the object to a tooth color.

[0074] The relative density of the zirconia sintered body obtained by sintering the zirconia cutting body for dental cutting in the present invention at 1550°C can be 98% or more of the theoretical density. The relative density is calculated by measuring density / theoretical density. If the relative density is less than 98%, the strength and translucency tend to decrease.

[0075] The crystalline phase of the zirconia cutting object for dental cutting in the present invention can be tetragonal and / or cubic. If the crystalline phase is monoclinic, sufficient translucency may not be imparted after complete sintering of the zirconia.

[0076] The manufacturing method of the zirconia cutting object for dental cutting in the present invention is not particularly limited, and any known manufacturing method can be used without any problems. Specifically, it is preferable to mold zirconia powder by press molding. Furthermore, it is also possible to press mold zirconia powders with different colors and compositions in multiple stages to form a multi-layered mold.

[0077] The zirconia workpiece for dental cutting in the present invention can be press-molded and then isostatically pressed by cold isostatic pressing (CIP treatment).

[0078] The maximum load pressure of the CIP treatment in the present invention can be 50 MPa or more. If the maximum load pressure is less than 50 MPa, it may not be possible to impart sufficient translucency and strength to the zirconia sintered body.

[0079] The holding time at the maximum load pressure in the CIP treatment in the present invention is not particularly limited, but can usually be set to 0 to 150 seconds, and can be set to 0 to 60 seconds.

[0080] There is no particular limit to the time required for a series of steps in the CIP process from the start of pressurization to the end of decompression, but it can usually be 30 seconds to 10 minutes, and can be 3 to 7 minutes. If the time is too short, the molded body may be destroyed, and if it is too long, production efficiency will decrease, which is not preferable.

[0081] The pre-sintering temperature of the zirconia cutting object for dental cutting in the present invention is preferably 800 to 1200° C. If the pre-sintering temperature is less than 800° C., the Vickers hardness and / or bending strength will be too low, and chipping or fracture will tend to occur during cutting. On the other hand, if the pre-sintering temperature is 1200° C. or more, the Vickers hardness and / or bending strength will be too high, and the milling bur of the cutting machine will be worn out rapidly, and the running cost will tend to be high.

[0082] The zirconia object for dental cutting of the present invention can be obtained by such a production method. The obtained zirconia object for dental cutting is cut to a desired size, cut, and surface polished as necessary.

[0083] The method for completely sintering the zirconia cutting body for dental cutting of the present invention is not particularly limited, but a simple and preferred method is to sinter it at normal pressure. The sintering temperature is not particularly limited, but can be 1450 to 1600°C, or 1500 to 1600°C. The retention time at the sintering temperature is not particularly limited, but can be 1 minute to 12 hours, or 2 to 4 hours. The heating rate is not particularly limited, but can be 1 to 400°C / min, or 3 to 100°C / h.

[0084] There is no particular restriction on the type of prosthetic device to be cut using the zirconia workpiece for dental cutting of the present invention, and there is no problem with any prosthetic device such as an inlay, onlay, veneer, crown, bridge, etc. Therefore, there is no particular restriction on the shape of the zirconia workpiece for dental cutting from which a prosthetic device is cut, and any shape of zirconia workpiece for dental cutting can be used, such as a block shape corresponding to an inlay, onlay, veneer, crown, etc., or a disk shape corresponding to a bridge. EXAMPLES

[0085] The present invention will be described in more detail and specifically below with reference to examples, but the present invention is not limited thereto.

[0086] (Preparation of zirconia calcined body) 486 g of zirconia powder containing 5.5 mol% of dissolved yttrium was filled into a mold (φ100 mm) and pressed (surface pressure: 50 MPa) to obtain a compact. The compact was subjected to CIP treatment (maximum load pressure: 200 MPa, holding time: 1 minute) and then calcined in an electric furnace (1000°C, 30 minutes) to obtain a calcined zirconia body with a diameter of 98.5 mm and a thickness of 18 mm.

[0087] (Preparation of impregnation solution) The composition of the impregnation liquid is shown in Table 1. Metal salts and additives were added to ion-exchanged water according to the compositions in Tables 1 and 2, and the mixture was stirred for 1 hour to prepare 100 g of a solution, which was used as the impregnation liquid.

[0088] [Table 1]

[0089] [Table 2]

[0090] (Impregnation of zirconia calcined body with impregnation liquid) The zirconia calcined body was placed on a horizontal workbench, and a jig was attached so that the impregnation liquid could be held on the top surface of the zirconia calcined body. A specified amount of impregnation liquid (I) (solution (I)) shown in Table 3 was poured onto the top surface of the zirconia calcined body, and the entire amount was allowed to stand until it was absorbed by the zirconia calcined body. Next, a specified amount of impregnation liquid (II) (solution (II)) shown in Table 3 was poured, and the entire amount was allowed to stand until it was absorbed by the zirconia calcined body. Next, a specified amount of impregnation liquid (III) (solution (III)) shown in Table 3 was poured, and the entire amount was allowed to stand until it was absorbed by the zirconia calcined body. The above operation was performed for all impregnation liquids.

[0091] (Heat treatment after impregnation) When the impregnation liquid (solution) contained urea, heat treatment was performed after impregnation with the impregnation liquid. The impregnated pre-sintered zirconia body was placed in a resin bag and degassed. The degassed pre-sintered zirconia body placed in the resin bag was placed in a dryer and heat-treated at 95°C for 15 hours to precipitate the metal compound. After the heat treatment, the pre-sintered zirconia body was removed from the resin bag and dried (120°C, 1 hour) to obtain a pre-sintered zirconia body supporting the metal compound.

[0092] (Removal of residual organic matter) The calcined zirconia body after the impregnation and / or heat treatment was heat treated (500° C., 30 minutes) in an electric furnace to obtain a zirconia cutting body for dental cutting having the metal compound supported in the pores.

[0093] (Relative density measurement) Using a dental cutting machine (Roland, DWX51D), the surface onto which the impregnation liquid was poured during impregnation was designated as surface B, the opposite surface as surface A, the surface parallel to surface A at a position 1.0 mm from surface A toward surface B as surface C, and the surface parallel to surface B at a position 1.0 mm from surface B toward surface A as surface D. A test specimen measuring 5 mm x 5 mm x 5 mm was prepared from surface C toward surface B, which was used as the test specimen for region A. Similarly, a test specimen measuring 5 mm x 5 mm x 5 mm was prepared from surface D toward surface A, which was used as the test specimen for region B. The relative density of each test specimen was calculated using the following formula. Relative density = (ρ / ρ0) ρ0=100 / [{(A1 / ρA1)+(A2 / ρA2)+···+(An / ρAn)}+{100-(A1+A2+···+An)} / ρ] In the formula, ρ is the measured density of the specimen, ρ is the theoretical density of the specimen, An is the content (wt%) of materials other than zirconia and yttria, ρ An is the theoretical density of materials other than zirconia and yttria, and ρ is the theoretical density of yttria-stabilized zirconia.

[0094] The above ρ varies depending on the content of yttria and the crystal phase of zirconia, but in this specification, the formula described in "Lattice and Density for Y2O3-Stabilized ZrO2," J. Am. Ceram. Soc. 1986, 69(4), 325-332. is used.

[0095] (Evaluation of Supported Elements) Using a dental cutting machine (Roland, DWX51D), the surface on which the impregnation liquid was poured during impregnation was designated as surface B, the opposite surface as surface A, the surface parallel to surface A at a position 1.0 mm from surface A toward surface B was designated as surface C, and the surface parallel to surface B at a position 1.0 mm from surface B toward surface A was designated as surface D. A disk-shaped test specimen of φ25 mm × 2.0 mm was prepared from surface C toward surface B, and was used as the test specimen of region A. Similarly, a disk-shaped test specimen of φ25 mm × 2.0 mm was prepared from surface D toward surface A, and was used as the test specimen of region B. A composition analysis of each test specimen was performed using a fluorescent X-ray analyzer (Rigaku). Measurements were performed on the top and bottom surfaces of each test specimen, and the average value was used as the content ratio of each element in each test specimen. The content ratio (mass%) of all elements is shown in terms of oxide. A similar measurement was also performed on a calcined body that did not use the impregnation liquid (unimpregnated calcined body). Using the obtained results, elements that satisfy the following formula were determined as supported elements. (Content of each element in each test specimen (mass%) × weight of each test specimen (g) - Content of each element in the unimpregnated calcined body test specimen (mass%) × weight of the unimpregnated calcined body test specimen (g)) / (Content of each element in each test specimen (mass%) × weight of each test specimen (g)) > 0.02

[0096] There is no particular limitation on the method for measuring the content (mass%) of substances other than zirconia and yttria contained in the test specimen. In this specification, the content was measured using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation).

[0097] (Measurement of shrinkage rate) Using a dental cutting machine (Roland, DWX51D), a test specimen of 15 mm (x: parallel to face C) x 15 mm (y: parallel to face C) x 2.0 mm (z: perpendicular to face C) was prepared from face C toward face B, and used as a test specimen for the enamel part. Similarly, a face parallel to face A at a position 8.0 mm from face A was designated face E, and a test specimen of 15 mm (x: parallel to face E) x 15 mm (y: parallel to face E) x 2.0 mm (z: perpendicular to face E) was prepared from face E toward face B, and used as a test specimen for the center part. Similarly, a test specimen of 15 mm (x: parallel to face D) x 15 mm (y: parallel to face D) x 2.0 mm (z: perpendicular to face D) was prepared from face D toward face A, and used as a test specimen for the cervical part. The dimensions of each specimen before and after complete sintering were measured using a micrometer, and the shrinkage rate of each part was calculated using the following formula: The specimens were sintered using an Ostromat 674i (manufactured by DEKEMA) (sintering temperature: 1550°C, holding time: 1 hour). Shrinkage rate x = x (mm) before complete sintering / x (mm) after complete sintering Shrinkage ratio y = y (mm) before complete sintering / y (mm) after complete sintering Shrinkage ratio z = z (mm) before complete sintering / z (mm) after complete sintering Average shrinkage rate = (shrinkage rate x + shrinkage rate y + shrinkage rate z) / 3

[0098] (Evaluation of Conformity) A six-piece bridge from the maxillary left canine to the maxillary right canine was cut out of the prepared zirconia dental cutting workpiece using a dental cutting machine (Roland, DWX51D), and then fully sintered using an Ostromat 674i (DEKEMA) (firing temperature: 1550°C, holding time: 1 hour) to produce a six-piece zirconia bridge. The six-piece bridge was attached to a plaster model, and the presence or absence of gaps and wobbling in the margins was confirmed, and the suitability was evaluated according to the following criteria. The inspection and evaluation were performed by five technicians, and the most common evaluation results are shown in Table 3. AA: There are no gaps or looseness in the margins, and the product can be used with little or no additional adjustment. A: There are almost no gaps or looseness in the margins, so it can be used with only minor adjustments. B: There are gaps and stiffness in the margins, but it can be used with some repairs. C: The margins have large gaps or looseness, making the product unusable or requiring significant modification.

[0099] (Esthetic evaluation) A six-piece bridge was cut from the prepared zirconia dental cutting workpiece using a dental cutting machine (Roland, DWX51D) from the left maxillary canine to the right maxillary canine, and then fully sintered (firing temperature: 1550°C, holding time: 1 hour) using an Ostromat 674i (DEKEMA) to produce a six-piece zirconia bridge. The appearance of the six-piece bridge was observed, and the aesthetics were evaluated according to the following criteria. Observations and evaluations were performed by five technicians, and the most common evaluation results are shown in Table 3. ○: Has translucency, color tone, and gradation similar to those of natural teeth, and shows particularly excellent aesthetics. ×: Translucency, color tone, and a part or all of the gradation thereof deviate from those of natural teeth, and excellent aesthetics are not shown.

[0100] Table 3 shows the evaluation results of the zirconia workpieces for dental cutting prepared in the examples and comparative examples.

[0101] [Table 3]

[0102] In Examples 1 to 2 and 7 to 13, at least one of the impregnation solutions contained a zirconium component, and ΔC tоtal Since the difference in shrinkage rate between the enamel part, the central part, and the cervical part was particularly small, the fit was particularly good.

[0103] In Examples 3 and 4, at least one of the impregnation solutions contains a zirconium component, and ΔC tоtal Since the shrinkage rate of the enamel, central, and cervical parts was small, the difference was small, indicating good compatibility.

[0104] In Examples 5 and 6, at least one of the impregnation solutions contains a zirconium component, and ΔC tоtal Since the shrinkage rate was 5.0 or less, the difference in the shrinkage rate between the enamel part, the central part, and the cervical part was not significant, and the prosthesis was shown to be adaptable to a degree that it could be adjusted and used.

[0105] In Comparative Example 1, the impregnation solution did not contain a zirconium component, and ΔC tоtal Since the shrinkage rate exceeded 5.0, there was a large difference in the shrinkage rates of the enamel part, central part, and cervical part, making it difficult to fit them to the plaster cast.

[0106] In Comparative Example 2, at least one of the impregnation solutions contains a zirconium component, but ΔC tоtal Since the shrinkage rate exceeded 5.0, there was a large difference in the shrinkage rates of the enamel part, central part, and cervical part, making it difficult to fit them to the plaster cast.

[0107] In Comparative Example 3, since none of the impregnation solutions contained a zirconium component, ΔC tоtal C of each solution to make it less than 5.0 tоtal was 5.0 or less, and good translucency and color tone were not obtained.

[0108] The present invention relates to a method for suppressing deterioration of the compatibility of a dental prosthesis produced from a zirconia body for dental cutting, in which a zirconia calcined body is impregnated with a plurality of impregnation liquids to produce a zirconia body for dental cutting having one or more of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering, and to a zirconia body for dental cutting produced by the method, and is a technology that can be used in the dental field.

Claims

1. A method for producing a zirconia workpiece for dental machining, which has one or more of a translucency gradation, a color tone gradation, and an intensity gradation after complete sintering, comprising: The method includes a step of impregnating a zirconia calcined body with at least two types of impregnation liquids, At least one of the impregnation solutions contains a zirconium component, The total concentration (mass%) of metal ions contained in each impregnation solution is C ｔоｔａｌ When Between each impregnation liquid, C ｔоｔａｌ The difference ΔC ｔоｔａｌ is 5.0 or less, The zirconium component contained in the impregnation solution is at least one of zirconium oxychloride, zirconium oxyacetate, and zirconyl nitrate.

2. 2. The method according to claim 1, further comprising the step of drying the zirconia calcined body impregnated with the impregnation solution.

3. 2. The method according to claim 1, further comprising the step of degreasing the calcined zirconia body impregnated with the impregnation liquid.

4. The method of claim 1 , wherein at least one of the impregnation solutions contains a transition metal ion.

5. The method of claim 1 , wherein at least one of the impregnation solutions contains rare earth metal ions.

6. 2. The method according to claim 1, wherein at least one of the impregnation solutions contains one or more of aluminum ions, gallium ions, and indium ions.

7. 2. The method of claim 1, wherein at least one of the impregnation solutions contains urea.

8. The method of claim 1 , wherein at least one of the impregnation liquids comprises a glycol.

9. The method of claim 1 , wherein at least one of the impregnation solutions comprises a hydroxy acid.

10. The method according to claim 10, wherein the hydroxy acid is at least one of citric acid, malic acid, and lactic acid.

11. A zirconia workpiece for dental cutting, having two opposing surfaces, a section between one end and 50% of the distance between the surfaces defined as section A and a section between the other end and 50% of the distance between the surfaces defined as section B, wherein section A includes a region A in which a compound of a stabilizer element is supported in pores, and section B includes a region B in which a zirconium compound is supported in pores, and the concentration of metal ions in region A is different from the concentration of metal ions in region B and / or the type of metal ions in region A is different from the type of metal ions in region B, A zirconia workpiece for dental cutting, wherein the difference in relative density between the region A and the region B is less than 0.

008.

12. 12. The zirconia workpiece for dental cutting according to claim 11, wherein the concentration of the stabilizer contained in the zirconium compound is lower than the concentration of the stabilizer in the zirconia workpiece for dental cutting that is the substrate.

13. 12. The zirconia workpiece for dental cutting according to claim 11, wherein the stabilizer element is a rare earth metal.

14. 14. The zirconia workpiece for dental cutting according to claim 13, wherein the rare earth metal is yttrium.

15. 12. The zirconia workpiece for dental cutting according to claim 11, wherein a compound of a coloring element is supported in the pores of at least one of the regions A and B.

16. 16. The zirconia workpiece for dental cutting according to claim 15, wherein the coloring element is a rare earth metal.

17. The zirconia workpiece for dental cutting according to claim 15, wherein the coloring element is a transition metal.

18. 12. The zirconia workpiece for dental cutting according to claim 11, wherein at least one of an aluminum compound, a gallium compound, and an indium compound is supported in the pores of at least one of the regions A and B.

19. 12. The zirconia workpiece for dental cutting according to claim 11, wherein at least one of a niobium compound and a tantalum compound is supported in the pores of at least one of the regions A and B.