WO2022171723A1

WO2022171723A1 - Method of producing a shaped ceramic body, in particular a dental shaped ceramic body

Info

Publication number: WO2022171723A1
Application number: PCT/EP2022/053204
Authority: WO
Inventors: Christoph Lauer; Berthold Reusch; David Figge
Original assignee: Pritidenta Gmbh
Priority date: 2021-02-11
Filing date: 2022-02-10
Publication date: 2022-08-18
Also published as: DE112022001012A5; EP4291542A1

Abstract

The present invention relates to a method for producing a shaped ceramic body, in particular a dental shaped ceramic body, which allows physical properties of the shaped body to be deliberately adjusted. According to the method, a porous shaped ceramic body is treated with at least one chelate ligand-containing fluid. The invention further relates to a shaped ceramic body that can be obtained in accordance with the method according to the invention. The invention also relates to the use of the shaped ceramic body according to the invention for producing dental restorations such as an inlay, onlay, veneer, crown, bracket, bridge, or scaffold, abutment or implant.

Description

Process for the production of a ceramic shaped body, in particular a dental ceramic shaped body

Technical field of the invention

The present invention relates to a method for producing a ceramic shaped body, in particular a dental ceramic shaped body, which enables the specific adjustment of physical properties of the shaped body, a porous ceramic shaped body being treated with a fluid containing at least one chelating ligand. In addition, the invention relates to a ceramic shaped body which is obtained by the process according to the invention. In addition, the invention relates to the use of the ceramic molding according to the invention for the production of tooth restorations, such as an inlay, onlay, veneer, a crown, bracket, bridge or a framework, abutment or implant.

Background of the Invention

The demand for cost-effective, aesthetic dental materials has increased dramatically in restorative dentistry in recent decades. Most patients want their dental restorations to resemble natural tooth structure, color and translucency of a natural tooth.

A natural tooth does not have a uniform color and translucency. In addition, each tooth is individual in its three-dimensional form. Therefore, the fabrication of dentures, such as bridges, requires three-dimensional coloring and translucency. Each artificial tooth should be clearly different in color from the neighboring tooth. The color gradient within a tooth should be homogeneous from the enamel to the gingival preparation line (dentin). Tooth enamel (enamel) is more translucent and less intense in color than dentin. Therefore, the top enamel of a tooth looks lighter and more translucent than the bottom of a tooth. In general, a process for the production of dental restorations consists of several sub-steps. In a first step, the starting material is pressed into a green body. This is usually followed by a pre-firing and white firing, which results in a stable dental molding, the so-called dental blank or dental blank. This is processed further, in particular using CAD/CAM milling processes. The dental ceramic mold is then densely sintered to form the final tooth restoration.

The use of ceramic or metal powders for the production of dental restorations, ie dental prostheses or entire teeth, such as implants or inlays, onlays, veneers, crowns or bridges, has been known for a long time. Likewise, composite materials made of ceramic and metal, so-called cermets, are generally known. Oxide ceramics are primarily used as the framework material for dental restorations, as they are characterized by excellent biocompatibility, high strength and outstanding mechanical properties. Preferred starting materials are ceramic powders and/or ceramic granules based on Zr02, Al2O3, zirconium dioxide-reinforced aluminum oxide (ZTA), aluminum oxide-reinforced zirconium oxide (ATZ), B4C, SiC, S13N4 or T1O2. The zirconium oxide is stabilized with CaO, Y2O3, La2O3, CeO2, MgO, Er2O3, Pr2O3 and/or Nb2Os.

A particularly preferred ceramic material is zirconium oxide partially or fully stabilized with Y2O3, CeO2 or Er2O3. In the pre-sintered state, it can be easily and inexpensively processed using CAD/CAM milling processes. In the final sintered state, it has high strength, which is why it can be used for all indications, depending on the zirconium oxide ceramic.

A disadvantage of dental zirconium oxides was their lack of translucency, which led to unsatisfactory optical results, especially in the incisal area of front or side teeth. This disadvantage could be eliminated with highly translucent zirconium oxide fully stabilized with 5 mol% yttrium. In the meantime, multi-translucent materials are known in which a translucency progression that approximates that of natural teeth can be achieved by horizontally layering different layers of differently stabilized zirconium oxide powder.

Dental ceramic moldings with a color gradient that resembles the color gradient of a natural tooth can be produced using a number of methods. In a commonly used method, a color gradient is created in a dental ceramic body via a horizontal layering process in the powder state before the dental body is pressed. For this purpose, powders in commercially available colors are mixed with one another in specific proportions in order to achieve natural tooth colors. In order to be able to show the gradient of the natural tooth colour, the upper layer of the blank is often colored less intensively than the lower one. As described, for example, in EP 2 024 300 B1 and EP 1 900 341 B1, these layers can vary in structure, number and extent, but they always remain horizontally or slightly wavy layered blanks.

Another option for producing a colored round or a colored blank starts after the CAD/CAM milling of the round or the block. The dental framework ceramics, such as a single crown, are immersed in coloring liquids in a dipping process. Due to its porosity and the associated capillary forces, the white body is very absorbent and draws the coloring solution into itself. The color can be adjusted via the infiltration time, since shorter infiltration times result in lighter colors and longer infiltration times in darker ones. DE 11 2009 001 253 B4 describes that the coloring ions can optionally be precipitated in a second step after the infiltration. In general, however, it is complicated to achieve the exact desired coloring using the dipping process. A major disadvantage of the method described in DE 11 2009 001 253 B4 is that no color gradient can be produced and that the reproducibility of the coloring is low.

EP 3 178 462 A1 and EP 3 178463 A1 describe a method with which color gradients can be set in dental ceramic moldings. For this purpose, in a first step, a porous dental ceramic, ie a blank, is introduced into a loading body material device specially designed for this purpose and which maintains capillary pressure and is loaded with a staining solution. This step is called the loading step. In a second step, the distribution step, the dyeing liquid is distributed and dried in the blank by means of a convection flow. The convection flow is generated by setting the environmental parameters, such as humidity, in a direction-dependent manner. At least one surface is sealed to adjust the directional dependency. After the distribution step, the remaining dye liquid must be dried by gentle heating. The coloring ions present as salts in the ceramic are then burned out converted to oxides. A dental ceramic blank with an aesthetic color gradient is thereby obtained. In addition, a dental ceramic blank with a two- or three-dimensional color gradient can be produced with this method.

Significant disadvantages of this method are the high processing costs with capillary pressure-maintaining loading body material device, convection flow via targeted drying via adjustment of the environmental parameters, further careful drying and final burning out of the dyeing liquid. In addition, due to the high process complexity and the small process window, it is not easy to ensure the reproducibility of the staining.

One of the greatest disadvantages of the process described in EP 3 178 462 A1 and EP 3 178 463 A1 is the extremely long and uneconomical process duration of several weeks. This results from the second step, the distribution step. The so-called distribution step involves extremely slow drying, which takes place in a special device, the capillary pressure-maintaining loading body material vessel. Only one side of the dental blank can dry in this container, since the other three sides are sealed. During this distribution step, the ambient temperature and the humidity of the room must be precisely controlled so that the ceramic does not dry too quickly despite the capillary pressure-maintaining loading body material vessel.

US 2014/0178834 A1 describes a method for the selective treatment of certain parts of the surface of pre-sintered dental ceramics, which already have the shape of an artificial tooth when used. In this procedure, a non-water based staining solution is selectively applied to only a portion of the outer surface of the tooth mold using a special application apparatus. A major disadvantage of this method is that only the surface of the tooth mold is colored and a special application device is required for this. Therefore, with this method, a dental ceramic with a color gradient which is stepless in the volume and which resembles the color gradient of a natural tooth is not obtained. Due to the fact that the solutions are only introduced on the surface, no other physical properties of the pre-sintered dental ceramic can be adjusted with this method. In addition, there is a significant advantage that the volume of pre-infiltrated blanks can be made by the manufacturer and are not required by the user/customer. is disadvantageous also the use of non-water-based solutions, which are less convenient to dispose of and can be harmful to health

US 2015/0307406 A1 describes a method for coloring part of the surface of a technical ceramic body which contains aluminum oxide as the main component and is already in its final form apart from the sintering shrinkage. This process can be used to produce two- or multicolored technical ceramic bodies. The aim of this process is to obtain a sharp separation between the color zones of the technical ceramic body. The method is therefore not suitable for the production of ceramic bodies with a continuous color gradient in terms of volume, which is similar to the color gradient of a natural tooth. The method described in US 2015/0307406 A1 is mainly used for coloring components of components of watches.

There is therefore a need for a simpler, more economical and better controllable method with which the physical properties of a ceramic molding can be adjusted in a targeted manner. In particular, the process should make it possible to introduce a reproducible and controllable color gradient into a ceramic molded body, the continuity of which is comparable to a color gradient that can be produced from colored powders using horizontal layering processes and can then be processed subtractively, e.g. with CAD/CAM.

Summary of the Invention

The present invention relates to a method for producing a ceramic shaped body, in particular a dental ceramic shaped body, which enables the physical properties of the shaped body to be adjusted in a targeted manner, comprising the following steps:

(a) applying one or more boundary(s) to the area(s) of a porous ceramic body whose physical properties are not to be altered, and/or applying one or more boundary(s) to the or the area(s) to be treated of a porous ceramic shaped body whose physical properties are to be changed;

(b1) treating the porous ceramic shaped body obtained after step (a) with a fluid containing at least one chelate ligand; (b2) optionally treating the porous ceramic shaped body obtained after step (b1) with a second or further, preferably with two to ten further fluid(s) containing at least one chelating ligand (steps (b2) to (b10), preferably steps ( b2) to (b6)), wherein in steps (b1) to (b10) the fluid(s) containing at least one chelate ligand(s) is/are mixed with the area(s) to be treated of the porous ceramic shaped body interacts (s) that the fluid(s) containing the chelate ligand(s) completely moves into the area(s) to be treated of the porous ceramic body(s), or interacts (s) in such a way that the desired interaction depth of the fluid(s) containing at least one chelating ligand is reached in the region of the porous ceramic molded body to be treated;

(c) removing the one or more spatial boundaries, if any; and

(d) burning out and/or drying the at least one chelating ligand-containing fluid or fluids.

In one embodiment of the method described herein, the desired depth of interaction of the fluid(s) containing at least one chelating ligand is/are achieved in three dimensions in the region of the porous shaped ceramic body to be treated.

In a preferred embodiment of the method described herein, the depth of interaction is at least ten percent of the volume of the porous ceramic body.

In one embodiment of the method described herein, a shaped body with an open porosity of 10% to 70%, preferably from 35% to 55%, is used as the porous ceramic shaped body, the average pore size of which is from 1 nm to 1 μm, preferably from 10 nm to 250 nm, particularly preferably from 10 nm to 100 nm.

In one embodiment of the method described herein, a shaped body based on Zr02, Al2O3, zirconium dioxide-reinforced aluminum oxide (ZTA), aluminum oxide-reinforced zirconium oxide (ATZ), B4C, SiC, S13N4 or TiC is used as the porous ceramic shaped body, more preferably on the based on Zr02, AI2O3, ZTA or ATZ, where the Zr02 is combined with CaO, Y2O3, La2O3, CeO 2 , MgO, EG 2 O 3 , Sa 2 O 3 , GCI 2 O 3 and/or Nb 2 O s , Ta 2 O s is stabilized, particularly preferably on the basis of Y 2 O 3 stabilized ZrO 2 .

In one embodiment of the method described herein, a porous ceramic molded body is used

(i) already contains a tooth-colored, powder-technologically layered coloring that is specifically changed by the method described herein; or

(ii) already contains a gradient in terms of translucency, color, strength and/or yttrium content, the porous ceramic molding only being given a coloring and color gradient similar to that of natural teeth as a result of the method described herein; or

(iii) does not contain any coloring similar to tooth color and only obtains a coloring with a layer-free color gradient and a color progression similar to that of natural teeth as a result of the method described herein; or

(iv) does not contain a coloring similar to tooth color and only acquires a monochromatic coloring through the process described herein.

In one embodiment of the method described herein, the fluid(s) containing at least one chelate ligand(s) contain(s) metal ions, preferably of the alkaline earth metals, the rare earth elements and/or the subgroup elements of the periodic table of the elements, which or are suitable for the porous to color ceramic moldings and/or to change their translucency and/or fluorescence, particularly preferably metal ions of at least one of the elements bismuth, cerium, calcium, chromium, cobalt, iron, erbium, copper, manganese, neodymium, nickel, praseodymium, or strontium terbium.

In one embodiment of the method described herein, the fluid(s) containing at least one chelate ligand(s) contain(s) metal ions, preferably of the alkaline earth metals, the rare earth elements and/or the subgroup elements of the periodic table of elements, which are suitable, the machinability, fracture toughness To change hardness or strength of the porous ceramic molding, preferably metal ions of at least one of the elements cerium, calcium, gadolinium, magnesium, niobium, samarium, vanadium, tantalum, ytterbium or yttrium.

In one embodiment of the method described herein, the fluid(s) containing at least one chelate ligand(s) contains at least one chelate Ligand selected from the group of acetylacetone, ethylenediamine, 2-(2-aminoethylamino)ethanol, diethylenetriamine, iminodiacetic acid, triethylenetetramine, triaminotriethylamine, nitrilotriacetic acid and salts thereof,

Bis(salicylidene)ethylenediamine, ethylenediaminotriacetic acid and its salts, ethylenediaminetetraacetic acid (EDTA) and its salts,

Diethylenetriaminepentaacetic acid (DTPA) and its salts,

Triethylenetetraminehexaacetic acid (TTHA) and its salts, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and its salts, oxalic acid and its salts (oxalates), tartaric acid and its salts (tartars), Citric acid and its salts (citrates), dimethylglyoxime, 8-hydroxyquinoline, 2,2'-bipyridine, 1,10-phenanthroline, dimercaptosuccinic acid and 1,2-bis(diphenylphosphino)ethane, preferably at least one chelating ligand from the group of acetic acid and their salts, oxalic acid and its salts, tartaric acid and its salts and citric acid and its salts.

In one embodiment of the method described herein, the fluid(s) containing at least one chelating ligand(s) contain(s) at least one carbonate salt of the metal ions of the elements mentioned herein, and citric acid or a salt of citric acid.

In one embodiment of the method described herein, the fluid(s) containing at least one chelating ligand is a coloring fluid.

The porous shaped ceramic body obtained after step (a) is preferably treated with three to six coloring fluids containing at least one chelating ligand (steps (b1) to (b3) to steps (b1) to (b6)).

In one embodiment of the method described herein, steps (b1) to (b10) are performed sequentially, each after the coloring fluid of the previous step has been completely or almost completely introduced; or the steps (b1) to (b10) are carried out sequentially, each after the coloring fluid of the previous step has been introduced completely or almost completely; or different areas of the porous ceramic shaped body are treated with two to ten coloring fluids containing at least one chelating ligand. In one embodiment of the method described herein, the viscosity of the fluid(s) containing at least one chelating ligand is from 1 mPas to 5 Pas, preferably from 2 mPas to 800 mPas, preferably containing the fluid(s). fluid(s) containing at least one chelate ligand, one or more viscosity-influencing substances.

In one embodiment of the method described herein, the fluid containing at least one chelate ligand also contains one or more viscosity-influencing substances, such as glucose, starch, konjac gluconomannan, cellulose ether, agar-agar, carrageenan, pectin, or fructose, preferably glucose, cellulose ether , starch and konjac gluconomannan.

In one embodiment of the method described herein, the fluid(s) containing one or more chelating ligands is/are applied to the ceramic shaped body in steps (b1) to (b10) using an automated application method, preferably using an inkjet method .

In addition, the present invention relates to a ceramic shaped body, preferably a dental ceramic shaped body, obtainable by a method described herein.

Another object of the present invention is the use of a ceramic molded body described herein for the production of dental restorations, such as an inlay, onlay, veneer, a crown, bracket, bridge or a framework, abutment or implant.

Description of the figures

FIG. 1 shows a schematic representation of an embodiment of the process according to the invention, as carried out in Examples 1 and 2.

FIG. 2 shows a blank with a continuous color gradient that was produced using the method according to the invention. The production of the blank is described in Example 1. The height positions 1 to 5 schematically show the removal points of the color plates, whose CIELAB values are summarized in Table 1. 3 shows the spatial demarcation (area a) on a blank (area b). Region a was treated with solution 4 according to the method of the invention as described in Example 2. Area b was left untreated.

Detailed Description of the Invention Definitions

In the present application, including the patent claims, the following terms have the following meanings.

The terms "ceramic molding", "dental ceramics", "ronde" or "blank" "porous molding" designate a blank that can be further processed. The term “dental ceramic shaped body” is understood to mean a blank that can be shaped further into a tooth restoration or that itself already has the shape of a tooth restoration. This is porous ceramic in the white state, i.e. porous ceramic that has been pre-sintered at temperatures of 700 °C to 1200 °C. The porous shaped body is well suited for use in subtractive shaping processes such as CAD/CAM. In addition, the porous, pre-sintered ceramic has an open porosity sufficient for infiltration, so that sufficient coloring with the coloring fluid or fluids is possible. As a rule, the open porosity of the porous ceramic shaped body is from 10% to 70%, preferably from 35% to 65%. The average pore size of the pores is from 1 nm to 1 μm, preferably from 10 nm to 250 nm, particularly preferably from 10 nm to 150 nm.

The term "blank" is understood to mean a 3-dimensional disc made from a material from which a tooth restoration can be made, for example by means of CAD/CAM processing.

The term “flake” means a thin disc with a thickness of 1 mm to 2 mm. This can be used for color and translucency measurements.

The terms "color" and "colored" are understood to mean color, brightness and translucency of a material, body or layer. For example, colors can be characterized quantitatively by their Lab value, which is also referred to as CIEL ^* a ^* b ^* . The CIELAB color space is a color space created in 1976 by the International Commission on Illumination (CIE). L ^* denotes the lightness, the a ^* value describes the green to red color scale and the b ^* value describes the blue to yellow. According to the invention, changes in these values describe color changes. Alternatively, colors can also be qualitatively characterized by a color code commonly used in the dental industry. Examples of such color codes are the Vitapan classic(R) and the Vita 3D Master(R), both from VITA Zahnfabrik H. Rauter GmbH & Co. KG, and the Chromascop(R) from Ivoclar Vivadent AG. The term "VITA tooth shade(s)" means, for example, the gradual 16 VITA classical A1-D4 shade guide for the exact determination of the tooth shade and the 32 3D master shade guide VITA basic colors. The arrangement of the shades in the VITA classical shade family is as follows: A1, A2, A3, A3.5, A4 (reddish-brownish), B1, B2, B3, B4 (reddish-yellowish), C1, C2, C3, C4 (greyish shades), D2, D3, D4 (reddish-grey).

In the context of the method according to the invention, “layer-free color gradient” means that in a disc that is e.g. CAM milling is the case. However, “stainless shade gradient” does not mean a linear shade gradient, as this would be contrary to the nature of the tooth.

The term "coloring fluid" or "coloring fluids" means a fluid, preferably a liquid, which contains ions of alkaline earth metals, rare earths (lanthanides) and/or transition metals with atomic numbers 21-30, 39-48, 72- 80, 83 contains. These are dissolved in a polar solvent such as water, in an organic solvent such as aliphatic alcohols, preferably isopropanol, or mixtures thereof. The coloring liquid, preferably a coloring solution, can optionally contain complexing agents, substances that influence viscosity and/or pH.

The term "translucency" is understood to mean the ability of a material, e.g.

The term "interaction depth" is understood to mean the volume fraction of the porous ceramic shaped body in which the or the at least one Fluid(s) containing chelate ligands penetrates based on the volume of the porous ceramic molded body lying below the application surface of the fluid(s) containing chelate ligands.

Process according to the invention for the production of a ceramic shaped body

As stated above, none of the processes described in the prior art are optimally suited for the technically simple and cost-effective production of ceramic moldings with physical properties that can be set in a targeted manner, especially not for the production of dental moldings.

There is therefore a need for a simpler, more economical and better controllable method with which the physical properties of a ceramic molding, such as color, translucency, fluorescence, machinability, fracture toughness, hardness or strength, can be adjusted in a targeted manner. In particular, the method should make it possible to introduce a reproducible and controllable color gradient into a ceramic molded body, the continuity of which is comparable to a color gradient that was produced from colored powders by means of horizontal layering processes.

The object of the present invention is therefore to provide a simpler, more economical and better controllable process which enables the production of ceramic shaped bodies with specific physical properties. In particular, the method should enable the production of ceramic moldings with a reproducible and easily controllable color gradient without having the disadvantages of the known methods. Above all, a method with shorter durations should be provided.

It has now been found that this object is achieved by a method for producing a ceramic shaped body, in particular a dental ceramic shaped body, which enables the physical properties of the shaped body to be set in a targeted manner and comprises the following steps:

(a) applying one or more boundary(s) to the region(s) of a porous ceramic body whose physical properties are not to be altered, and/or applying one or more boundary(s) to the or the to treated area(s) of a porous ceramic body whose physical properties are to be modified;

(b1) treating the porous ceramic shaped body obtained after step (a) with a fluid containing at least one chelate ligand; (b2) optionally treating the porous ceramic shaped body obtained after step (b1) with a second or further, preferably with two to ten further fluid(s) containing at least one chelating ligand (steps (b2) to (b10), preferably steps ( b2) to (b6)), wherein in steps (b1) to (b10) the fluid(s) containing at least one chelate ligand(s) is/are mixed with the area(s) to be treated of the porous ceramic shaped body interacts (s) that the fluid(s) containing chelate ligand(s) completely moves into the area(s) to be treated of the porous ceramic shaped body(s), or interacts (s) in such a way that the desired depth of interaction of the fluid(s) containing at least one chelating ligand is/are reached in the region of the porous shaped ceramic body to be treated;

(c) removing the one or more spatial boundaries, if any; and

Surprisingly, it was found that with the method according to the invention, the duration of the method can be greatly reduced. While the method described in EP 3 178 462 A1 and EP 3 178 463 A1 takes about two weeks due to the distribution step, i.e. due to the extremely long drying time, the method according to the invention can be carried out in one to two days.

The treatment of the ceramic shaped body with a fluid containing at least one chelate ligand reduces the mobility of the ions used for the specific adjustment of the physical properties, so that the viscosity of the fluid is increased. The treated porous ceramic moldings obtained according to steps (b1) to (b10), if applicable, can therefore be immediately burned out and/or dried.

In particular, in contrast to the method described in DE 3 178 462 A1 and EP 3 178 463 A1, the method according to the invention does not contain a distribution step. Due to the missing distribution step, this has The method according to the invention has the advantages that it is more controllable, has a significantly shorter process time, and is simpler, since a loading body material device can be dispensed with.

A further advantage of the method according to the invention, which results from the treatment with a fluid containing at least one chelating ligand and the resulting lower mobility of the ions, is that the adjustment of the physical properties, in particular a layer-free color gradient, is better and much easier to control.

In a preferred embodiment of the method described herein, the interaction depth is at least 10 percent of the volume of the porous ceramic shaped body, preferably at least 20 percent of the volume of the porous ceramic shaped body, preferably at least 30 percent of the volume of the porous ceramic shaped body, more preferably at least 40 percent of the volume of the porous ceramic body.

In a very particularly preferred embodiment of the method described herein, the depth of interaction is at least 20 percent of the volume of the porous ceramic shaped body,

An additional advantage of the method according to the invention is a simplification with regard to the starting materials, since any color can be set starting from white powder.

The starting material used in the process according to the invention is ceramic moldings with an open porosity of 10% to 70%, for example 15% to 65%, 20% to 60%, 25% to 55%, 30% to 55%, preferably of 35% to 55% used. The average pore size of the ceramic shaped body is from 1 nm to 1 μm, preferably from 10 nm to 250 nm, preferably from 10 nm to 150 nm.

A shaped body based on ZrO 2 , Al 2 O 3 , reinforced with zirconium dioxide is suitable as a porous ceramic shaped body for the method according to the invention Aluminum oxide (ZTA), aluminum oxide-reinforced zirconium oxide (ATZ), B4C, SiC, S13N4 or T1O2, more preferably based on Zr02, Al2O3, ZTA or ATZ, the Zr02 each having CaO, Y2O3, La2O3, CeO2, MgO, Er 2 O 3 , Sa 2 O 3 , Gd 2 O 3 and/or Nb 2 O s , Ta 2 O s is stabilized, particularly preferably on the basis of Y 2 O 3 stabilized ZrO 2 . The stabilizer content is from 2 mol% to 16 mol%.

The porous molded body that is used as the starting material can (i) already contain a powder-technologically layered coloring that is similar to tooth color, which is specifically changed by the method described herein. For example, a blank that has already been precolored can be used as the starting material, such as a porous ceramic molding made from the commercially available starting material ^priti® multidisc Zr02 multicolor Extra Translucent Alight from pritidenta GmbFI, Leinfelden-Echterdingen, Germany.

Alternatively, the porous molded body that is used as the starting material can (ii) already contain a gradient in terms of translucency, color, strength and/or yttrium content. In this case, the porous shaped body only acquires a coloring and color gradient similar to that of natural teeth as a result of the method described here.

According to a further alternative embodiment, the porous molded body used as the starting material (iii) may not contain a coloring similar to tooth color and only obtained by the method described herein coloring with a layer-free color gradient and a color gradient similar to that of natural teeth.

According to a further alternative embodiment, the porous shaped body which is used as starting material can (iv) contain no coloring and only obtain a monochromatic coloring by the process described herein.

The fluid(s) containing at least one chelate ligand(s) preferably contains metal ions of the alkaline earth metals and/or the rare earth elements and/or the subgroup elements of the periodic table of the elements, which or which are suitable for coloring the porous ceramic molded body and/or its translucency To change and / or fluorescence, particularly preferably metal ions of at least one of the elements bismuth, calcium, cerium, chromium, cobalt, iron, erbium, copper, manganese, neodymium, nickel, praseodymium, strontium or terbium. Preferably that contains or the fluid(s) containing at least one chelating ligand at least one of the following metal ions: calcium, cobalt, iron, erbium, manganese, neodymium and/or praseodymium. The metal ions are used in the form of commercially available salts. Sulfate salts, chloride salts, citrate salts, carbonate salts or nitrate salts of the metal ions mentioned herein are preferably used.

In one embodiment of the method described herein, the fluid(s) containing at least one chelating ligand(s) contain(s) metal ions, preferably of the alkaline earth metals and/or the rare earth elements and/or the subgroup elements of the periodic table of the elements, which are suitable for machinability To change fracture toughness, hardness or strength of the porous ceramic molding, preferably metal ions of at least one of the elements cerium, calcium, gadolinium, magnesium, niobium, samarium, vanadium, tantalum, ytterbium or yttrium. Particularly preferably, the fluid or fluids containing at least one chelating ligand contains metal ions of at least one of the elements niobium, tantalum, samarium or yttrium.

In one embodiment of the method described herein, the fluid(s) containing at least one chelate ligand(s) contains at least one chelate ligand selected from the group consisting of acetylacetone, ethylenediamine, 2-(2-aminoethylamino)ethanol, diethylenetriamine, and iminodiacetic acid , triethylenetetramine, triaminotriethylamine, nitrilotriacetic acid and its salts,

Diethylenetriaminepentaacetic acid (DTPA) and its salts,

Triethylenetetraminehexaacetic acid (TTHA) and its salts, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and its salts, oxalic acid and its salts (oxalates), tartaric acid and its salts (tartars), Citric acid and its salts (citrates), dimethylglyoxime, 8-hydroxyquinoline, 2,2'-bipyridine, 1,10-phenanthroline, dimercaptosuccinic acid and 1,2-bis(diphenylphosphino)ethane, preferably at least one chelating ligand from the group of acetic acid and their salts, oxalic acid and its salts, tartaric acid and its salts and citric acid and its salts. The chelating ligands are commercially available.

In a particularly preferred embodiment of the method described herein, the fluid(s) containing at least one chelate ligand(s) contains at least one carbonate salt of the metal ions mentioned herein, and Citric acid or a salt of citric acid. Calcium carbonate, cobalt carbonate, iron carbonate, erbium carbonate, neodymium carbonate, manganese carbonate and/or praseodymium carbonate and citric acid are particularly preferred.

The fluid(s) containing at least one chelating ligand used as starting material can be prepared by dissolving a corresponding salt containing the metal ions mentioned herein in a suitable solvent, preferably in water or in isopropanol. Sulfate salts, carbonate salts or nitrate salts of the metal ions mentioned herein are preferably used. Then the chelating ligand is added.

Alternatively, the chelating ligand can first be dissolved in a solvent and then a corresponding salt containing the metal ions mentioned herein can be dissolved in the corresponding solvent.

In a particularly preferred embodiment, a fluid containing at least one chelating ligand is produced from neodymium carbonate and/or praseodymium carbonate and citric acid.

The first fluid containing at least one chelating ligand and the second or further fluid containing at least one chelating ligand can be identical or different. For example, they may contain different concentrations of metal ions, different chelating ligands, or different types of metal ions.

A further advantage of the method according to the invention is therefore that the starting materials used are more environmentally friendly and not harmful to health in comparison to the prior art methods described herein. When burned out in step (c), the carbonate anion burns to form CO2 and water and therefore not to form toxic end products.

In a preferred embodiment of the method described herein, the fluid(s) containing at least one chelating ligand is a coloring fluid.

In step (a), the one or more boundary(s) can be applied to the shaped ceramic body by means of suitable adhesive tape or slipping over will. The one or more boundary(s) are preferably applied in such a way that the fluid(s) containing chelate ligand(s) interacts exclusively with the region(s) of the porous ceramic shaped body(s) to be treated.

Commercially available materials such as adhesive tape, insulating tape or adhesive tape are preferably used as the material for the boundaries. Limitations made of, for example, silicone rubber or silicone or PTFE can also be used.

In one embodiment of the method described herein, steps (b1) to (b10) are performed sequentially, each after the coloring fluid of the previous step has been completely or almost completely introduced;

In a further alternative embodiment, in steps (b1) to (b10), different areas of the porous ceramic shaped body can be treated with the coloring fluids containing at least one chelate ligand.

In a particularly preferred embodiment, the porous molding obtained after step (a) is treated with three to six coloring fluids containing a chelating ligand (steps (b1) to (b3) to steps (b1) to (b6)).

In a particularly preferred embodiment, the method according to the invention comprises steps (a), (b1), (b2), (b3), (c) and (d).

The interaction time of a coloring fluid with the porous ceramic shaped body at room temperature is from 5 minutes and 16 hours, preferably from 5 minutes to 10 hours, more preferably from 10 minutes to 8 hours, more preferably from 10 minutes and 5 hours.

The interaction time of the coloring fluid with the porous ceramic can be shortened by changing the ambient temperature, humidity and/or by applying a vacuum to the opposite surface of the introduction of the coloring fluid.

After the interaction time, the one or more fluids fill up to 100% of the open pores of the porous ceramic body, preferably from 55% to 99% and from 5% to 33%. In a preferred embodiment, steps (b1) to (b10) are carried out by means of infiltration, the successive infiltration of differently colored fluids being particularly preferred. This embodiment was carried out in Example 1 by way of example.

In contrast to the method described in EP 3 178 462 A1 and EP 3 178 463 A1, in the method according to the invention the gradient of the physical properties, preferably the color gradient, is not set by means of a distribution step, but by targeted infiltration.

In one embodiment of the method described herein, the one or more chelating ligand-containing fluid(s) in steps (b1) to (b10) is/are applied to a ceramic molded body using an automated application method, preferably using an inkjet method.

A more precise and reproducible color gradient can be set by precisely adjusting the color of the individual fluids by selecting and concentrating the ions. In addition, in contrast to the method described in EP 3 178 462 A1 and EP 3 178463 A1, the color gradient is not dependent on the tightness of the capillary pressure-maintaining loading body material container, the ambient temperature and humidity. This makes the method according to the invention much more reproducible and easier to control.

It is particularly advantageous that in the method according to the invention, due to the complexing of the ions and the increased viscosity, the ions hardly run and therefore have a small radius of movement. This is just big enough to create a smooth (color) gradient, as shown in example 1.

The amount of fluid required for a desired color gradient can be calculated using the following formula (1). It is advantageous that an excess can be avoided by precisely calculating the infiltration quantity, so that the method according to the invention is more economical and resource-saving than the known methods. This is not the case with the methods described in EP 3 178 462 A1 and EP 3 178463 A1, since the ceramic has to be introduced into a loading body material vessel that maintains capillary pressure, in which the ceramic is soaked from below from a liquid reservoir. Here, a waste of liquid is unavoidable. Formula (1) can be used to calculate how much mass (nif) of a fluid is necessary for the targeted, spatial change of a physical property (e.g. color) if the volume of the porous ceramic body (V _p ), the density of the porous ceramic body (p _p ), the theoretical density of the densely sintered material constituting the porous body in the white state (p _d ) and the density of the fluid used is known pj).

The basis for this is that the ions bound to the chelate ligand hardly move after the infiltration. It is therefore sufficient to indicate the volume that you want to change specifically as a percentage (x):

Formula (1) ui _f = mass of the fluid to be used [g]

V _p = volume of the porous body (ceramic) [cm ³ ]

PP = density of the porous body [g/cm ³ ]

P _d = theoretical density of the densely sintered material [g/cm ³ ]

P _f = density of the fluid used [g/cm ³ ] x = desired volume [%] of the changed physical properties; depth of interaction

In one embodiment, the goal is to color an entire blank with a uniform gradient using three fluids. For this, each of the three fluids should fill a third of the pore volume. The amount of the three fluids calculated in this way can be filtered in one after the other.

A further advantage of the method according to the invention is that the gradient, preferably the color gradient, can be easily changed, for example by choosing solution 1 with x=50%, solution 2 with x=30% and solution 3 x=20%. In this way, a stronger gradient can be created with a larger, weakly colored area, e.g. in the enamel area.

The viscosity of the fluid(s) containing at least one chelate ligand can be from 1 mPas to 5 Pas, preferably from 2 mPas to 800 mPas, preferably containing the fluid(s) containing at least one chelate ligand Fluid(s) one or more viscosity-influencing substances. In one embodiment of the method described herein, the fluid containing at least one chelate ligand also contains one or more viscosity-influencing substances such as glucose, starch, konjac gluconomannan, cellulose ether, agar-agar, carrageenan, pectin, or fructose, preferably glucose, cellulose ether , starch and konjac gluconomannan. The viscosity-influencing substances are commercially available. They are known to be harmless from the food industry, for example.

In a further embodiment, the excess fluid or fluids containing at least one chelate ligand can be removed before steps (c) and (d).

In step (c), the one or more spatial boundaries are removed prior to step (d). Alternatively, the one or more spatial boundaries can also be burned in step (d).

In step (d), the fluid containing at least one chelate ligand can be burned out at temperatures from 20°C to 800°C.

The burnout and/or drying of the at least one chelating ligand-containing fluid or fluids can take place immediately after infiltration or after a rest period of up to 96 hours at room temperature.

The process according to the invention can be completed after a process time of 24 hours.

In a particularly preferred embodiment, the ceramic molding according to the invention has a layer-free color gradient, from light in the enamel area to dark in the dentin area. For samples with a thickness of 1 mm, the L ^* value ranges from L ^* = 95 (light) to L ^* = 60 (dark). Another object of the present invention is the use of a ceramic molded body described herein for the production of dental restorations, such as an inlay, onlay, veneer, a crown, bracket, bridge or a framework, abutment or implant.

examples

1. Production of a dental disc with a layer-free color gradient

A commercially available, white disc with a diameter of 98.5 mm and a height of 18 mm made of 4 mol% yttrium-stabilized zirconium oxide (pritidenta GmbH, Leinfelden-Echterdingen, Germany) was covered with commercially available adhesive tape with a 3-4 mm overlap at the edge, so that a the head sides of which was bordered like a tube (step (a)).

Thereafter, the blank obtained after step (a) with 23.14 g of a solution (amount calculated according to formula 1, corresponds to 1/3 of the volume) of 0.4% by weight praseodymium carbonate (ChemPur GmbH, Karlsruhe, Germany) and 99 6% by weight of citric acid (solution 1) treated (step (b1)). The coloring fluid was placed in the area covered by scotch tape and allowed to soak in completely. After infiltration with solution 1, the surface was completely dry again. In a second step (b2), which can take place immediately after the first or with a time delay, 23.14 g of a solution containing 0.8% by weight of praseodymium carbonate and 99.2% by weight of citric acid (solution 2) were again applied and waited until it was fully retracted. In a third step (b2), 23.14 g of a solution containing 1.2% by weight of praseodymium carbonate and 98.8% by weight of citric acid are applied (solution 3) and allowed to soak in completely. After three hours, solutions 1-3 were completely absorbed. The cumulative interaction depth of solutions 1 -3 is almost 100%.

Then the scotch tape was removed and the liquid burned out of the blank. For this purpose, the blank was placed in a commercially available muffle furnace (LT 15/11, Nabertherm GmbH, Lilienthal, Germany) and burned out with a holding time of one hour at 180° C., 340° C. and 450° C. respectively. The heating rate was 1 °C ^* min- ¹ . The entire coloring process, including the burnout, was completed within 24 hours. The blank was then mounted in a CNC milling machine (350i, imes icore, Eiterfeld, Germany) in the holder provided and cylindrical plates were formed, which after sintering had a diameter of 14 mm and a height of 1 mm horizontally from five different height positions milled out of the blank. These height positions were evenly spaced along the height of the 18 mm disc, with height position 1 near the top edge (incisal, region of solution 1) and height position 5 near the bottom edge (dentine, region of solution 3) (Fig. 2 ). In addition, a vertical, rectangular disk, which extends over the maximum area that can be milled, was milled out (Fig. 2).

The cylindrical plaques were measured spectroscopically over black and white background (Spectrophotometer CM-3610A, Konica Minolta Sensing Europe B.V.). The color values (CIELAB color space) are listed in Table 1.

Table 1: Lab color values of height positions 1-5

Figure 2 shows the rectangular disc, which was milled parallel to the color gradient and thus represents it best. FIG. 2 and the CIELAB values for the height positions in Table 1 show that the blank produced using the method according to the invention has a layer-free color gradient.

2. Re-staining of a dental blank in the incisal area

An already precolored disc ( ^priti® multidisc Zr02 multicolor Extra Translucent Light, pritidenta GmbH, Leinfelden-Echterdingen, Germany) was provided with a local, cylindrical boundary (diameter 26 mm) on the top surface (FIG. 3). 2 g of a solution of 2.5% by weight neodymium carbonate and 97.5% by weight citric acid were introduced into this cylindrical boundary (area a) (solution 4). After the solution was fully absorbed, approximately 12 minutes, the cylindrical barrier was removed and the blank was placed burned out. For this purpose, the blank was placed in a commercially available muffle furnace (LT 15/11, Nabertherm GmbH, Lilienthal, Germany) and burned out with a holding time of one hour at 180 °C, 340 °C and 450 °C. The heating rate was 1 °C*min- ¹ . The entire process of targeted coloring and burning out was thus completed within 24 hours. The depth of interaction in area a was about 35%.

A platelet with the same dimensions as in application example 1 was separated from the surface of area a. A small cylindrical plate was also separated superficially from an untreated area (area b) of the blank. Both were measured spectroscopically. The values are listed in Table 2.

Table 2: Lab color values of areas a and b

Claims

patent claims

1. A method for producing a ceramic shaped body, in particular a dental ceramic shaped body, which enables the targeted adjustment of physical properties of the shaped body, comprising the following steps:

(b1) treating the porous ceramic shaped body obtained after step (a) with a fluid containing at least one chelate ligand;

(b2) optionally treating the porous ceramic shaped body obtained after step (b1) with a second or further, preferably with two to ten further fluid(s) containing at least one chelating ligand (steps (b2) to (b10), preferably steps ( b2) to (b6)), wherein in steps (b1) to (b10) the fluid(s) containing at least one chelate ligand(s) is/are mixed with the area(s) to be treated of the porous ceramic shaped body interacts (s) that the fluid(s) containing the chelate ligand(s) completely moves into the area(s) to be treated of the porous ceramic body(s), or interacts (s) in such a way that the desired interaction depth of the fluid(s) containing at least one chelating ligand is reached in the region of the porous ceramic molded body to be treated;

(c) removing the one or more spatial boundaries, if any; and (d) burning out and/or drying the at least one chelating ligand-containing fluid or fluids.

2. The method according to claim 1, wherein the desired depth of interaction of the fluid(s) containing at least one chelating ligand is achieved in three dimensions in the region of the porous ceramic shaped body to be treated.

3. The method according to claim 1 or 2, wherein a shaped body with an open porosity of 10% to 70%, preferably from 35% to 55% is used as the porous ceramic shaped body, the average pore size of which is from 1 nm to 1 pm, preferably from 10nm to 250nm.

4. The method according to any one of claims 1 to 3, wherein a shaped body based on Zr02, Al2O3, zirconium dioxide-reinforced aluminum oxide (ZTA), aluminum oxide-reinforced zirconium oxide (ATZ), B4C, SiC, S13N4 or T1O2 is used as the porous ceramic shaped body. more preferably based on ZrO2, Al2O3, ZTA or ATZ, the ZrO2 being stabilized with CaO, Y2O3, La2O3, CeO2, MgO, Er2O3, Sa2O3, Gd2O3 and/or Nb2O5, Ta2Os, particularly preferably based on Y2O3 stabilized Zr02.

5. The method according to any one of claims 1 to 4, wherein the porous ceramic shaped body

(i) already contains a tooth-colored, powder-technologically layered coloring, which is selectively changed by the method according to one of claims 1 to 4; or

(ii) already contains a gradient in terms of translucency, color, strength and/or yttrium content, the porous ceramic shaped body only being given a coloring and color gradient similar to that of natural teeth by the method according to one of claims 1 to 4; or

(iii) contains no coloring similar to that of a tooth and is only obtained by the method according to one of claims 1 to 4 with a coloring with a layer-free color gradient and a color progression similar to that of natural teeth; or (iv) does not contain a coloring similar to tooth color and is only given a monochromatic coloring by the method according to one of claims 1 to 4.

6. The method according to any one of claims 1 to 5, wherein the fluid(s) containing at least one chelate ligand(s) preferably contains metal ions of the alkaline earth metals, rare earth elements and/or subgroup elements of the periodic table of the elements are to color the porous ceramic molding and / or to change its translucency and / or fluorescence, particularly preferably metal ions of at least one of the elements bismuth, cerium, calcium, chromium, cobalt, iron, erbium, copper, manganese, neodymium, nickel, praseodymium, strontium or terbium.

7- The method according to any one of claims 1 to 6, wherein the fluid(s) containing at least one chelate ligand(s) preferably contains metal ions of alkaline earth metals, rare earth elements and/or subgroup elements of the periodic table of the elements, which are suitable to change the machinability, fracture toughness, hardness or strength of the porous ceramic molding, preferably metal ions of at least one of the elements cerium, calcium, gadolinium, magnesium, niobium, samarium, vanadium, tantalum, ytterbium or yttrium.

8. The method according to any one of claims 1 to 7, wherein the fluid(s) containing at least one chelate ligand(s) contains at least one chelate ligand selected from the group consisting of acetylacetone, ethylenediamine, 2-(2-aminoethylamino)ethanol, diethylenetriamine, iminodiacetic acid,

Triethylenetetramine, triaminotriethylamine, nitrilotriacetic acid and its salts, bis(salicylidene)ethylenediamine, ethylenediaminotriacetic acid and its salts, ethylenediaminetetraacetic acid (EDTA) and its salts, diethylenetriaminepentaacetic acid (DTPA) and its salts, triethylenetetraminehexaacetic acid (TTHA) and its salts, 1,4, 7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and its salts, oxalic acid and its salts (oxalates), tartaric acid and its salts (tartars), citric acid and its salts (citrates), dimethylglyoxime, 8- Hydroxyquinoline, 2,2'-bipyridine, 1,10-phenanthroline, dimercaptosuccinic acid and 1,2-bis(diphenylphosphino)ethane contain(s), preferably at least one chelate ligand from the group of acetic acid and its salts, oxalic acid and their salts, tartaric acid and its salts and citric acid and its salts.

9. The method according to any one of claims 1 to 8, wherein the fluid(s) containing at least one chelate ligand(s) contains at least one carbonate salt of the metal ions of the elements mentioned in one of claims 6 or 7, and citric acid or a salt of citric acid ( en).

10. The method according to any one of claims 1 to 9, wherein the fluid(s) containing at least one chelate ligand(s) is a coloring fluid to six coloring fluids containing a chelating ligand (steps (b1) to (b3), to steps (b1) to (b6)).

11. The method according to any one of claims 1 to 10, wherein steps (b1) to (b10) are carried out in succession, each after the coloring fluid of the previous step has been introduced completely or almost completely; or wherein steps (b1) to (b10) are performed in succession, each after the coloring fluid of the previous step has been completely or almost completely introduced; or wherein different locations of the porous ceramic body are treated with from two to ten coloring fluids containing a chelating ligand.

12. The method according to any one of claims 1 to 11, wherein the viscosity of the fluid(s) containing at least one chelate ligand is from 1 mPa·s to 5 Pa·s, preferably from 2 mPa·s to 800 mPa·s, the fluid(s) containing at least one chelate ligand preferably contain one or more viscosity-influencing substances.

13. The method according to any one of claims 1 to 12, wherein the fluid containing at least one chelate ligand additionally contains one or more viscosity-influencing substances such as glucose, starch, konjac gluconomannan, cellulose ether, agar-agar, carrageenan, pectin or fructose, preferably glucose, cellulose ethers, starch and konjac gluconomannan.

14. The method according to any one of claims 1 to 13, wherein the one or more chelating ligand-containing fluid (s) in steps (b1) to (b10) with an automated application process, preferably with an inkjet process are applied to a ceramic molding.

15. Ceramic molding, preferably dental ceramic molding, obtainable by a process of claims 1 to 14.

16. Use of a ceramic molding according to claim 15 for the production of tooth restorations, such as an inlay, onlay, veneer, a crown, bracket, bridge or a framework, abutment or implant.