Process for producing a dyed oxide ceramic body

Abstract

The invention relates to a method for producing a dyed oxide ceramic body, wherein an oxide ceramic body with a content of cerium is subjected to a heat treatment under partially reducing conditions, the heat treatment involving both a heat treatment in the presence of a reducing agent and a heat treatment in the presence of an oxidizing agent. The invention also relates to the use of a composition with a content of cerium for producing a dyed oxide ceramic body.

Description

[0001] P 119888 - 1 - 2026-03-24 Ivoclar Vivadent AG

[0002] Method for producing a colored oxide ceramic body

[0003] The present invention relates to a method for producing colored oxide ceramic bodies suitable for dental applications and, in particular, for use as dental restorations. The invention also relates to the use of a composition containing cerium for producing a colored oxide ceramic body.

[0004] Oxide ceramics are highly crystalline ceramic materials based on oxide compounds and containing, at most, a very small proportion of the glass phase. Typical oxide ceramics are based on ZrO₂, Al₂O₃, TiO₂, MgO, as well as combinations, mixed crystals, and composites thereof. Due to their advantageous mechanical properties, oxide ceramics, and especially zirconia ceramics, are widely used, among other things, in the fabrication of dental restorations.

[0005] Dental restorations should not only possess advantageous mechanical properties but also be characterized by the most natural appearance possible. The aim is to mimic the translucency properties of natural tooth material and, furthermore, to achieve the best possible color match between the dental restoration and the remaining natural teeth, and, if applicable, with the color of the oral mucosa, particularly the gums (gingiva). Therefore, for dental restorations that replace both natural teeth and gums, it is necessary to stain the area replacing the teeth in tooth-colored yellow tones and the area replacing the gums, the so-called gingival mask, in gingiva-colored red tones.

[0006] Several approaches are known for coloring oxide ceramics red.

[0007] A red coloration of oxide ceramics can be achieved using color-imparting metal ions, which are introduced in the form of suitable compounds such as metal oxides or other metal salts. Since different metal ions have different color-imparting properties, various colors and shades can be created by mixing different metal ions. However, the toxicity of some metals, such as cadmium and selenium, prevents their use in the fabrication of dental restorations.

[0008] Typically, oxide ceramics, and especially zirconia ceramics, are colored red with erbium ions in the form of erbium compounds, particularly E⁻O₄. Very high concentrations of these erbium compounds are required to achieve a clearly perceptible color. However, using very high concentrations of erbium compounds carries the risk of significantly deteriorating mechanical properties such as flexural strength and fracture toughness compared to untreated oxide ceramics. Furthermore, erbium compounds are very expensive, which is a disadvantage when using them in high concentrations. Finally, even with very high concentrations of erbium compounds, the resulting color is perceived as more of a pink or rose shade and thus differs significantly from the red areas of the gingiva. The addition of other coloring metal ions, such as iron, cobalt, chromium, etc., also contributes to this effect.It is not possible to achieve a satisfactory gingival color in oxide ceramics that corresponds to natural gingiva. Therefore, gingival masks stained with erbium salts must be regularly individualized in a further manufacturing step with gingiva-colored glaze stains (e.g., Ivocolor stains, Ivoclar Vivadent, Liechtenstein) to achieve a color result corresponding to the natural gingiva.

[0009] It is also known to produce red hues in oxide ceramic bodies by introducing cerium ions and subsequently heat-treating the oxide ceramic bodies under reducing conditions, which leads to a conversion of yellow cerium ions. 4+ -ions to red Ce 3+ -ions are coming.

[0010] EP 3345883 A1 describes red-colored zirconia sintered bodies obtained by sintering a cerium oxide-containing zirconia ceramic body in a reducing atmosphere, which can be used as jewelry elements.

[0011] One disadvantage is that the entire oxide ceramic body must be exposed to a reducing atmosphere, which can cause other coloring elements present in the oxide ceramic body to change their oxidation state and color, a change that is usually undesirable. For example, iron ions are frequently used in oxide ceramic bodies for dental applications to produce yellow tones. These iron ions can change color from light yellow or yellow to gray or green during heat treatment under reducing conditions, rendering the oxide ceramic body unusable for dental applications. Furthermore, heat treatments under reducing conditions can also lead to a deterioration of the mechanical properties of an oxide ceramic material.

[0012] The invention therefore aims to provide a method for producing a colored oxide ceramic body, with which clearly perceptible and, in particular, gingival-colored red tones can be generated in the oxide ceramic body without impairing the mechanical properties of the oxide ceramic or significantly altering the colors of other coloring elements, such as those used for coloring the dentin and incisal area. The method should be as simple as possible and be able to be carried out with commonly used equipment and utensils, for example, those typically found in dental laboratories.

[0013] This problem is solved according to the invention by the method for producing a colored oxide ceramic body according to claims 1 to 12. The invention also relates to the colored oxide ceramic body according to claim 13 and the use of a composition containing cerium for producing a colored oxide ceramic body according to claims 14 to 17.

[0014] The inventive method for producing a colored oxide ceramic body is characterized in that an oxide ceramic body containing cerium is subjected to heat treatment under partially reducing conditions, which includes both heat treatment in the presence of a reducing agent and heat treatment in the presence of an oxidizing agent, wherein

[0015] the heat treatment takes place in the presence of an oxidizing agent simultaneously with and / or after the heat treatment in the presence of a reducing agent and wherein

[0016] The heat treatment is carried out in the presence of an oxidizing agent at a lower temperature than the heat treatment in the presence of a reducing agent, provided that it takes place after the heat treatment in the presence of a reducing agent.

[0017] It has been found that the inventive method enables the production of colored oxide ceramic bodies that exhibit excellent mechanical properties and a clearly perceptible and translucent red coloration, and can also imitate the red tones of natural gingiva in the fabrication of dental restorations. Surprisingly, it is even possible to obtain, within the same oxide ceramic body produced according to the invention, both gingiva-colored red tones and other colors particularly important for dental restorations, such as yellow tones caused by iron ions, without the latter undergoing undesirable discoloration, for example, towards gray or green. This allows for the advantageous production of both mixed colors resulting from the combination of several coloring elements and multicolored oxide ceramic bodies with areas of different colors.For the purposes of this invention, the terms "color" and "colored" refer to the color value of a material. Color values ​​can be characterized by the color coordinates L*, a*, and b* in the L*a*b* color space or by a color key commonly used in the dental industry. In the L*a*b* color space, the value L* describes the brightness of a color with values ​​from 0 (black) to 100 (white), the value a* describes the green or red component of a color, with negative values ​​representing green and positive values ​​representing red, and the value b* describes the blue or yellow component of a color, with negative values ​​representing blue and positive values ​​representing yellow. Examples of color keys commonly used in the dental industry are Vitapan classical® and Vita 3D Master®, both from VITA Zahnfabrik H. Rauter GmbH & Co. KG, and Chromascop® from Ivoclar Vivadent AG. Translucency can be characterized by the contrast value CR, where 0% means completely transparent and 100% means completely opaque.

[0018] The terms "red colors" and "red hues" refer to colors with a positive a* value in the L*a*b* color space. The term "tooth-colored" refers specifically to colors with an L* value in the range of 50 to 100, particularly in the range of 80 to 97, an a* value in the range of -10 to 10, particularly in the range of -1 to 5, a b* value in the range of 0 to 50, particularly in the range of 1 to 20, and / or a CR value in the range of 50 to 100%, particularly in the range of 75 to 99%.

[0019] The color coordinates L*, a*, and b* are usually determined according to DIN 5033 and DIN 6174, and the translucency is determined according to BS 5612. The corresponding measurements can be carried out, in particular, using a CM-3700d spectrophotometer (Konica Minolta), preferably according to the specular gloss index (SCI) method. For this purpose, specimens with a thickness of 1.10 ± 0.05 mm and preferably without high-gloss polish are used for the measurements.

[0020] In a preferred embodiment, the oxide ceramic body is further subjected to heat treatment under oxidizing conditions prior to heat treatment under partially reducing conditions. The heat treatment under oxidizing conditions preferably takes place in an oxygen-containing atmosphere. Suitable oxygen-containing atmospheres include, in particular, air, oxygen-enriched air, and oxygen.

[0021] The oxide ceramic body subjected to heat treatment under oxidizing conditions is typically a non-densely sintered and, in particular, a pre-sintered oxide ceramic body, preferably containing pores and / or capillaries. The oxide ceramic body used usually has a relative density in the range of 30 to 90%, particularly in the range of 40 to 80%, and preferably in the range of 50 to 70%, in each case based on the pure density of the oxide ceramic material. Preferably, the oxide ceramic body subjected to heat treatment under oxidizing conditions has the form of a dental restoration. Particularly preferred dental restorations are bridges, inlays, onlays, crowns, veneers, shells, and abutments, and especially bridges comprising two or more units.Suitable oxide ceramic bodies can be obtained, for example, by machining appropriate blanks, especially using a CAD / CAM process.

[0022] The relative density is the ratio of the apparent density of the oxide ceramic material to the pure density of the oxide ceramic material.

[0023] The apparent density of the oxide ceramic material can be determined from the mass of the dry sample (m³) using the immersion method according to ISO 18754. t ), the apparent mass of the sample submerged in an immersion fluid (mi) and the density of the immersion fluid (pi) according to the formula

[0024] m.

[0025] P = - — X A

[0026]

[0027] m t ~ m i

[0028] The calculations are performed. Carbon tetrachloride (CCI4) is preferably used as the immersion fluid.

[0029] The pure density of the oxide ceramic material is determined by grinding the oxide ceramic material into a powder with an average particle size of 10 to 30 pm, particularly 20 pm, based on the number of particles, and then determining the density of the powder using a pycnometer. The particle size can be determined, for example, using the CILAS® Particle Size Analyzer 1064 from Quantachrome GmbH & Co. KG via laser diffraction according to ISO 13320 (2009).

[0030] The heat treatment under oxidizing conditions is preferably carried out at a temperature in the range of 1200 to 1700°C, particularly in the range of 1300 to 1600°C, more preferably in the range of 1350 to 1550°C, and further preferably in the range of 1400 to 1500°C, and most preferably at a temperature of about 1450°C. It is further preferred that the heat treatment under oxidizing conditions be carried out for a duration of 30 to 240 minutes, particularly 60 to 180 minutes, more preferably 90 to 150 minutes, and most preferably about 120 minutes. The heat treatment under oxidizing conditions typically results in dense sintering of the oxide ceramic body. Afterwards, the oxide ceramic material preferably has a relative density of at least 97%, particularly at least 98%, more preferably at least 99%, and most preferably at least 99.5%, in each case based on the pure density of the oxide ceramic material.

[0031] The heat treatment under partially reducing conditions is preferably carried out at a temperature in the range of 700 to 1300°C, particularly in the range of 800 to 1200°C, more preferably in the range of 850 to 1150°C, further preferably in the range of 900 to 1100°C, and most preferably at a temperature of approximately 1100°C. The reducing effect can be controlled, in particular, by the temperature of the heat treatment. It is further preferred that the heat treatment under partially reducing conditions be carried out for a duration of 15 to 180 minutes, particularly 30 to 120 minutes, more preferably 45 to 75 minutes, and most preferably approximately 60 minutes.

[0032] The reducing agent is usually a reducing gas or a substance that can form a reducing gas and / or bind oxygen when heated.

[0033] In a preferred embodiment, the reducing agent is a reducing gas, wherein the gas preferably contains hydrogen and more preferably hydrogen and nitrogen. Mixtures of hydrogen and nitrogen containing approximately 5% by volume of hydrogen, also known as forming gas, are particularly suitable. The reducing effect can be controlled by the amount of gas supplied, and in particular by the flow rate and duration of the gas supply. Preferably, the amount of the effective component of the reducing gas, preferably hydrogen, is 0.05 to 5 l / min, more particularly 0.1 to 1 l / min, and more preferably 0.2 to 0.5 l / min, for a duration of 10 to 180 min, more particularly 20 to 120 min, and more preferably 30 to 90 min.

[0034] In a further preferred embodiment, the reducing agent is a substance that can form a reducing gas and / or bind oxygen upon heating. Examples of suitable such substances are elemental carbon, in particular activated carbon, coal, coke, or graphite; organic compounds; metals, in particular magnesium, aluminum, or copper; and hydrides. The reducing agent is present, in particular, in the form of a powder and preferably in the form of pellets, tablets, or granules. The reducing effect can be controlled by the amount of the reducing agent. In a preferred embodiment, the heat treatment takes place under partially reducing conditions in a sealed container in the presence of a substance that can form a reducing gas and / or bind oxygen upon heating. Examples of suitable containers are crucibles closed with a lid, for example, made of Al₂O₃, ZrÜ₂, or SiC.The reducing effect can be controlled by the amount of reducing agent in the sealed container.

[0035] In a particularly preferred embodiment, the heat treatment takes place under partially reducing conditions in an oxygen-containing atmosphere, particularly air, and in the presence of a substance that can form a reducing gas and / or bind oxygen upon heating, particularly activated carbon. Preferably, the heat treatment takes place in a sealed container in an oxygen-containing atmosphere, particularly air, and in the presence of a substance that can form a reducing gas and / or bind oxygen upon heating, particularly activated carbon, wherein the activated carbon is preferably used in an amount of 0.5 to 50 g / l, particularly 1 to 20 g / l, more preferably 2 to 16 g / l, further preferably 4 to 12 g / l, and particularly preferably 6 to 10 g / l, in each case based on the volume of the container.

[0036] In a further preferred embodiment, the oxide ceramic body is subjected to heat treatment in the presence of an oxidizing agent after heat treatment in the presence of a reducing agent, wherein the heat treatment in the presence of an oxidizing agent is carried out at a lower temperature than the heat treatment in the presence of a reducing agent.

[0037] The heat treatment in the presence of an oxidizing agent is preferably carried out at a temperature in the range of 700 to 1300°C, particularly in the range of 800 to 1200°C, more preferably in the range of 850 to 1150°C, further preferably in the range of 900 to 1100°C, and most preferably at a temperature of about 900°C. It is further preferred that the heat treatment in the presence of an oxidizing agent be carried out for a duration of 15 to 180 minutes, particularly 30 to 120 minutes, more preferably 45 to 75 minutes, and most preferably about 60 minutes. It is further preferred that the heat treatment is carried out in the presence of an oxidizing agent at a temperature that is 25 to 400 K, in particular 50 to 350 K, preferably 100 to 300 K, particularly preferably 150 to 250 K and most preferably about 200 K below the temperature at which the heat treatment is carried out in the presence of a reducing agent.Suitable oxidizing agents include, in particular, air, oxygen-enriched air, and oxygen. In a preferred embodiment, the heating chamber used for heat treatment is perfused during the heat treatment, in the presence of an oxidizing agent, discontinuously or preferably continuously with an oxygen-containing atmosphere, preferably air, oxygen-enriched air, or oxygen, particularly at a flow rate of 0.1 to 50 l / min, preferably 1 to 20 l / min, and most preferably 4 to 8 l / min.

[0038] The process according to the invention is suitable for various types of oxide ceramic materials. Oxide ceramic materials are generally highly crystalline ceramic materials based on oxide compounds and containing, at most, a very small proportion of the glass phase. Typical oxide ceramic materials are based on ZrO₂, Al₂O₃, TiO₂, MgO, combinations thereof, mixed crystals, or composites thereof, in particular ZrO₂ / Al₂O₃ (ZTA), Al₂O₃ / ZrO₂ (ATZ), or ZrO₂ / spinel, wherein spinel is preferably Sr-spinel, Mg-spinel, La-spinel, and / or Ce-spinel. Oxide ceramic materials based on ZrO₂ are preferred according to the invention.

[0039] Particularly preferred are oxide ceramic materials based on zirconium oxide, and especially those based on polycrystalline tetragonal zirconium oxide (TZP). Most preferred are oxide ceramic materials based on zirconium oxide in which the zirconium oxide is stabilized with Y₂O₃, La₂O₅, CeO₂, MgO, and / or CaO, and preferably with 1.5 to 12 mol%, particularly 3 to 5 mol%, of these oxides, based on the zirconium oxide content.

[0040] In a preferred embodiment, at least one region of the oxide ceramic body has a cerium content in the range of 0.001 to 2 mol%, in particular 0.01 to 1 mol%.

[0041] The oxide ceramic body containing cerium used in the process according to the invention can be obtained by bringing a cerium-containing composition into contact with at least a portion of an oxide ceramic body, in particular a non-densely sintered and preferably a pre-sintered oxide ceramic body, which preferably has pores and / or capillaries. The cerium-containing composition is preferably a solution of a cerium salt, preferably cerium nitrate or cerium chloride, in a solvent, in particular water. It is further preferred that the cerium-containing composition is brought into contact with the oxide ceramic body by infiltration, in particular by means of a brush or immersion technique. After the cerium-containing composition has been brought into contact with at least a portion of the oxide ceramic body, the oxide ceramic body is optionally dried.The oxide ceramic body containing cerium can also be obtained by contacting oxide ceramic powder with a composition containing cerium, in particular a solution of a cerium salt, to obtain oxide ceramic powder containing cerium, and then processing this oxide ceramic powder containing cerium into an oxide ceramic body in the usual manner. It is particularly preferred that the oxide ceramic powder is provided as granules and that these granules are sprayed with a solution of a cerium salt, wherein the granules preferably contain pores and / or capillaries, and the solution penetrates these pores and / or capillaries.

[0042] It is further preferred that the oxide ceramic body contains one or more additional coloring elements. Examples of suitable coloring elements are Fe, Er, Cr, Co, Nd, Cu, Mn, and Pr. Particularly preferably, the oxide ceramic body comprises at least two layers and, in particular, at least three layers that differ in color.

[0043] In a preferred embodiment, the oxide ceramic body comprises at least one gingiva-colored layer and at least one further layer, in particular at least one dentin-colored layer and / or an incisal-colored layer. It is preferred that the gingiva-colored layer has a cerium content as described above and that the at least one further layer is wholly or substantially free of cerium. It is further preferred that the gingiva-colored layer contains, in addition to cerium, at least one further coloring element, preferably selected from the group consisting of Nd, Pr, Tb, Co, Cu, Fe, and Mn. It is also preferred that the at least one further layer contains at least one coloring element, preferably selected from the group consisting of Fe, Er, Cr, Co, Nd, Cu, Mn, and Pr.It has surprisingly been shown that the heat treatment according to the invention under partially reducing conditions does not significantly alter the colors of other coloring elements, which are used, for example, for coloring the dentin and incisal area.

[0044] The method according to the invention is particularly suitable for the fabrication of dental restorations. In a preferred embodiment, the colored oxide ceramic body is therefore a dental restoration. Particularly preferred dental restorations are bridges, inlays, onlays, crowns, veneers, shells, and abutments. The method according to the invention is especially suitable for the fabrication of dental restorations, in particular bridges comprising two or more units.

[0045] The invention also relates to a colored oxide ceramic body obtainable according to the inventive method. The invention also relates to the use of a composition containing cerium for the production of a colored oxide ceramic body, wherein the composition containing cerium is brought into contact with at least a part of an oxide ceramic body and the oxide ceramic body brought into contact with the composition containing cerium is subjected to heat treatment under partially reducing conditions, which includes both heat treatment in the presence of a reducing agent and heat treatment in the presence of an oxidizing agent, wherein

[0046] the heat treatment takes place in the presence of an oxidizing agent simultaneously with and / or after the heat treatment in the presence of a reducing agent and wherein

[0047] The heat treatment is carried out in the presence of an oxidizing agent at a lower temperature than the heat treatment in the presence of a reducing agent, provided that it takes place after the heat treatment in the presence of a reducing agent.

[0048] Preferred embodiments of use are as described above for the method according to the invention.

[0049] In particular, the oxide ceramic body that comes into contact with the cerium-containing composition is typically a non-densely sintered and, more specifically, a pre-sintered oxide ceramic body, preferably having pores and / or capillaries. The oxide ceramic body typically has a relative density in the range of 30 to 90%, particularly in the range of 40 to 80%, and preferably in the range of 50 to 70%, in each case based on the pure density of the oxide ceramic material. Preferably, the oxide ceramic body has the form of a dental restoration. Particularly preferred dental restorations are bridges, inlays, onlays, crowns, veneers, shells, and abutments, and especially bridges comprising two or more units.

[0050] Preferably, the oxide ceramic body brought into contact with the cerium-containing composition is further subjected to heat treatment under oxidizing conditions as described above before heat treatment under partially reducing conditions. The heat treatment under oxidizing conditions typically results in dense sintering of the oxide ceramic body. Afterwards, the oxide ceramic material preferably has a relative density of at least 97%, in particular at least 98%, more preferably at least 99%, and most preferably at least 99.5%, in each case based on the pure density of the oxide ceramic material. In a preferred embodiment, the invention thus relates to the use of a cerium-containing composition for the production of a colored oxide ceramic body, in which

[0051] (i) the composition containing cerium is brought into contact with at least part of a non-densely sintered and in particular pre-sintered oxide ceramic body,

[0052] (ii) the oxide ceramic body from step (i) which is brought into contact with the composition containing cerium is subjected to heat treatment under oxidizing conditions, preferably in an oxygen-containing atmosphere and in particular in air, oxygen-enriched air or oxygen, and is preferably densely sintered and

[0053] (iii) the oxide ceramic body subjected to heat treatment under oxidizing conditions from step (ii) is subjected to heat treatment under partially reducing conditions, comprising both heat treatment in the presence of a reducing agent and heat treatment in the presence of an oxidizing agent, wherein

[0054] the heat treatment takes place in the presence of an oxidizing agent simultaneously with and / or after the heat treatment in the presence of a reducing agent and wherein

[0055] The heat treatment is carried out in the presence of an oxidizing agent at a lower temperature than the heat treatment in the presence of a reducing agent, provided that it takes place after the heat treatment in the presence of a reducing agent.

[0056] It is preferred that the composition containing cerium is a solution of a cerium salt, preferably cerium(III) nitrate or cerium(III) chloride, in a solvent, in particular water.

[0057] Furthermore, it is preferred that the composition containing cerium has a cerium content in the range of 0.001 to 2 mol%, in particular 0.01 to 1 mol%.

[0058] In a preferred embodiment, the cerium-containing composition is brought into contact with the oxide ceramic body by infiltration, in particular by means of a brush or immersion technique. After the cerium-containing composition has been brought into contact with at least a portion of the oxide ceramic body, the oxide ceramic body is optionally dried. Figures 1A and 1B illustrate preferred embodiments of the invention. The invention is explained in more detail below with reference to examples.

[0059] Examples

[0060] General procedure: Production of test specimens

[0061] Disc-shaped specimens with a diameter of approximately 10.7 mm and a thickness of approximately 1.35 mm, as well as specimens with a diameter of approximately 16 mm and a thickness of approximately 1.5 mm, were produced from commercially available oxide ceramic discs based on zirconia with 3 mol% Y2O3 (IPS e.max ZirCAD TO, Ivoclar Vivadent, Liechtenstein) using a CAD / CAM milling machine (Programill PM7, Ivoclar Vivadent, Liechtenstein).

[0062] Example 1

[0063] Specimens obtained according to the general procedure were infiltrated for 2 minutes by immersion infiltration with aqueous solutions containing 0.1, 0.5, 1, 2, 10, 20, 30, 40, or 50 wt% cerium(III) nitrate and subsequently dried in a drying cabinet at 80°C for 2 h. The resulting specimens were densely sintered in a dental high-temperature furnace (Programat S1 1600, Ivoclar Vivadent, Liechtenstein) under atmospheric conditions at 1450°C for 2 h. Fig. 2 (top row) shows the resulting densely sintered, light yellow, and translucent specimens, the color intensity of which increases with increasing cerium content.

[0064] The specimens were then heat-treated in an aluminum oxide crucible sealed with an aluminum oxide plate, which was placed in a heating furnace (Cube, Nabertherm, Lilienthal, Germany), in the presence of 1 g of activated carbon at 1100°C for 1 h. Fig. 2 (bottom row) shows the specimens obtained after this heat treatment, the color of which varied from light orange-red to dark red depending on the cerium concentration. Fig. 3 shows that the colors of the specimens produced in this way could be matched to the RAL technical colors.

[0065] The biaxial fracture strength of the specimens thus obtained was determined according to ISO 6872 (2008) (piston-on-three-ball test). The biaxial fracture strength of the specimens infiltrated with an aqueous solution of 10 wt% cerium(1 l) nitrate was 1650 MPa. For comparison, specimens obtained according to the general procedure, which had not been infiltrated with a cerium-containing solution, were densely sintered as described above under atmospheric air at 1450°C for 2 h. The biaxial fracture strength of the specimens thus obtained was 1590 MPa. This shows that the colored oxide ceramic specimens obtained according to the invention do not suffer any loss of strength compared to uncolored oxide ceramic specimens.

[0066] For comparison, test specimens were also infiltrated with an aqueous solution containing 40 wt% erbium(II l) nitrate and treated as described above.

[0067] The color coordinates and translucency values ​​of the test specimens, which were measured according to DIN 5033 and DIN 6174 or BS 5612 using a CM-3700d spectrophotometer (Konica-Minolta) with (SCI) and without (SCE) gloss component, are shown in the following table:

[0068] Concentration Staining Gloss Composition* a* b* Opacity Staining Solution Element component

[0069] [%]

[0070] 0.1 Ce SCI 87.126 6.800 20.609 75.585

[0071] 0.5 Ce SCI 76.227 24.604 32.366 82.104

[0072] 1 Ce SCI 70.275 31.767 34.056 84.454

[0073] 2 Ce SCI 64.425 35.194 32.754 87.556

[0074] 5 Ce SCI 56.649 37.155 25.175 90.892

[0075] 7.5 Ce SCI 52.216 31.947 19.077 93.496

[0076] 10 Ce SCI 52.749 33.029 22.107 94.245

[0077] 20 Ce SCI 46.960 26.248 13.946 97.188

[0078] 30 Ce SCI 44.292 17.205 7.211 98.843

[0079] 40 Ce SCI 42,578 10,647 3,889 99,779

[0080] 40 Er* SCI 85,977 16,967 -1,916 75,562

[0081] 0.1 Ce SCE 86,344 6,807 20,557 75,585

[0082] 0.5 Ce SCE 74,824 25,016 32,643 82,104

[0083] 1 Ce SCE 68,791 32,435 34,549 84,454

[0084] 2 Ce SCE 63,205 35,836 33,162 87,556

[0085] 5 CE SCE 53,716 39,338 26,005 90,892

[0086] 7.5 Ce SCE 49,468 33,823 19,200 93,496

[0087] 10 CE SCE 51,284 33,986 22,339 94,245

[0088] 20 CE SCE 44,738 27,553 13,731 97,188

[0089] 30 CE SCE 40,648 18,780 6,354 98,843

[0090] 40 CE SCE 40,142 11,200 3,016 99,779

[0091]

[0092] 40 Er* SCE 84,743 17,165 -2,257 75,562

[0093]

[0094] *Comparison

[0095] Example 2

[0096] Specimens obtained according to the general procedure were infiltrated for 2 minutes by immersion infiltration with aqueous solutions containing 0.1 to 50 wt% cerium(1 l) nitrate and then dried in a drying oven at 80°C for 2 h. The resulting specimens were densely sintered in a dental high-temperature furnace (Programat S1 1600, Ivoclar Vivadent, Liechtenstein) under an atmospheric atmosphere at 1450°C for 2 h. Fig. 4 (top row) shows the resulting densely sintered, light yellow, and translucent specimens, the color intensity of which increases with increasing cerium content.

[0097] The specimens were then heat-treated in an aluminum oxide crucible sealed with an aluminum oxide plate, which was placed in a heating furnace (Cube, Nabertherm, Lilienthal, Germany), in the presence of 1 g of activated carbon at 900°C for 1 h. Fig. 4 (bottom row) shows the specimens obtained after this heat treatment, the color of which varied from light orange to intense orange to orange-brown depending on the cerium concentration.

[0098] For comparison, test specimens were also infiltrated with aqueous solutions containing 10 or 40 wt% erbium(1 1) nitrate and treated as described above.

[0099] The color coordinates and translucency values ​​of the test specimens, which were measured according to DIN 5033 and DIN 6174 or BS 5612 using a CM-3700d spectrophotometer (Konica-Minolta) with (SCI) and without (SCE) gloss component, are shown in the following table:

[0100] Concentration Staining Gloss Composition* a* b* Opacity Staining Solution Element component

[0101] [%]

[0102] 0.1 Ce SCI 90.507 4.791 16.342 73.265

[0103] 0.5 Ce SCI 86.370 11 .432 25.931 76.634

[0104] 1 Ce SCI 84.435 14.602 29.161 77.990

[0105] 10 Ce SCI 71.502 28.987 42.051 83.881

[0106] 20 Ce SCI 63.802 28.206 36.666 88.169

[0107]

[0108] 10 Er* SCI 92.161 6.341 0.857 72.858

[0109] 40 Er* SCI 87.365 16.800 -2.905 73.866

[0110] 0.1 Ce SCE 89.079 4.782 16.212 73.265

[0111] 0.5 Ce SCE 85.052 11 .530 25.909 76.634

[0112] 1 Ce SCE 83,460 14,715 29,216 77,990

[0113] 10 Ce SCE 70.092 29.586 42.866 83.881

[0114] 20 Ce SCE 62,448 28,851 37,519 88,169

[0115] 10 Er* SCE 90.836 6.356 0.580 72.858

[0116] 40 Er* SCE 86.436 16.939 -3.107 73.866

[0117]

[0118] *Comparison

[0119] Example 3

[0120] A specimen obtained according to the general procedure was infiltrated for 2 minutes by immersion infiltration with an aqueous solution containing 10 wt% cerium(II) nitrate and subsequently dried in a drying oven at 80°C for 2 h. The specimen thus obtained was densely sintered in a dental high-temperature furnace (Programat SI 1600, Ivoclar Vivadent, Liechtenstein) under an air atmosphere at 1450°C for 2 h.

[0121] The specimen was then heat-treated in an aluminum oxide crucible sealed with an aluminum oxide plate, which was placed in a heating furnace (Cube, Nabertherm, Lilienthal, Germany), in the presence of 1 g of activated carbon at 1100°C for 1 h. Fig. 5 (left) shows the specimen obtained in this way, which had an intense red color.

[0122] Finally, the specimen was heat-treated in an oven (Cube, Nabertherm, Lilienthal, Germany) in an atmospheric environment at 900°C, 925°C, or 950°C for 1 hour. Fig. 5 (right) shows the specimens obtained in this way, whose color changed from intense red to a lighter, gingival pinkish-red hue due to the further heat treatment.

[0123] The color coordinates and translucency values ​​of the test specimens, measured according to DIN 5033 and DIN 6174 or BS 5612 using a CM-3700d spectrophotometer (Konica-Minolta) with (SCI) and without (SCE) gloss component, are shown in the following table: Coloring air Gloss component L* a* b* Opacity Element [°C]

[0124] Ce - SCI 51,787 32,091 15,888 92,583

[0125] Ce 900 SCI 58,039 35,697 21,617 89,338

[0126] Ce 925 SCI 59,856 35,613 22,410 88,496

[0127] Ce 950 SCI 75,005 24,730 22,123 84,962

[0128] Ce - SCE 49,670 33,566 16,050 92,583

[0129] Ce 900 SCE 56,585 36,690 21,928 89,338

[0130] Ce 925 SCE 57,993 36,845 22,707 88,496

[0131] Ce 950 SCE 73,738 25,138 22,057 84,962

[0132]

[0133] Example 4

[0134] Specimens obtained according to the general procedure were infiltrated for 2 minutes by immersion infiltration with aqueous solutions containing 10 wt% cerium(II) nitrate and then dried in a drying oven at 80°C for 2 h. The resulting specimens were then densely sintered in a dental high-temperature furnace (Programat SI 1600, Ivoclar Vivadent, Liechtenstein) under an air atmosphere at 1450°C for 2 h.

[0135] The specimens were then heat-treated in an aluminum oxide crucible sealed with an aluminum oxide plate, which was placed in a heating oven (Cube, Nabertherm, Lilienthal, Germany), in the presence of 2 g, 1 g, 0.5 g, or 0.25 g of activated carbon at 1100°C for 1 h. Fig. 6 shows the specimens obtained after this heat treatment, which exhibited a dark red or a lighter, gingiva-like pink color, depending on the amount of activated carbon used.

[0136] The color coordinates and translucency values ​​of the test specimens, which were measured according to DIN 5033 and DIN 6174 or BS 5612 using a CM-3700d spectrophotometer (Konica-Minolta) with (SCI) and without (SCE) gloss component, are shown in the following table:

[0137] Coloring activated charcoal gloss compound* a* b* Opacity element [g] component

[0138] Ce 1 SCI 52.749 33.029 22.107 94.245

[0139] Ce 0.5 SCI 64.917 32.661 21 .161 89.142

[0140]

[0141] Ce 0.25 SCI 57.793 34.751 21 .829 91.447

[0142] Ce 1 SCE 51.284 33.986 22.339 94.245

[0143] Ce 0.5 SCE 56.078 35.870 22.042 91.447

[0144] Ce 0.25 SCE 63.658 33.297 21 .116 89.142

[0145]

[0146] Example 5

[0147] A four-unit bridge with a gingival mask was fabricated from a commercially available zirconia-based oxide ceramic disc containing 3 mol% Y₂O₃ (IPS e.max ZirCAD TO, Ivoclar Vivadent, Liechtenstein) using a CAD / CAM milling machine (Programill PM7, Ivoclar Vivadent, Liechtenstein). The gingival mask was infiltrated by brush infiltration with an aqueous solution containing 20 wt% cerium(III) nitrate and subsequently dried in a drying oven at 80°C for 2 hours.

[0148] The dentin and incisal areas were infiltrated with a commercially available coloring liquid for shade A3 using a brush (IPS e.max coloring liquid A3, Ivoclar Vivadent, Liechtenstein). The bridge was then dried in a drying oven at 80°C for 2 hours and sintered in a dental high-temperature furnace (Programat S1 1600, Ivoclar Vivadent, Liechtenstein) under an air atmosphere at 1450°C for 2 hours.

[0149] The bridge was then heat-treated in an aluminum oxide crucible sealed with an aluminum oxide plate, which was placed in a heating furnace (Cube, Nabertherm, Lilienthal, Germany) in the presence of 1 g of activated carbon at 1100°C for 1 h.

[0150] Afterwards, the bridge was heat-treated in a heating oven (Cube, Nabertherm, Lilienthal, Germany) in an air atmosphere at 900°C for 1 hour.

[0151] Finally, a commercially available glaze (Ivocolor Glaze Paste Fluo, Ivoclar Vivadent, Liechtenstein) was applied to the bridge and fired at 709°C in a kiln (Programat P500, Ivoclar Vivadent, Liechtenstein). Fig. 7 shows the resulting zirconia bridge, which had a dental shade A3 and a gingiva-colored gingival mask. Example 6

[0152] Specimens obtained according to the general procedure were infiltrated for 2 minutes by immersion infiltration with aqueous solutions containing 0.1 wt%, 0.5 wt%, or 1.0 wt% iron(III) nitrate, and then dried in a drying oven at 80°C for 2 h. The resulting specimens were then densely sintered in a dental high-temperature furnace (Programat S1 1600, Ivoclar Vivadent, Liechtenstein) under an atmospheric atmosphere at 1450°C for 2 h. Fig. 8 (top row) shows the specimens obtained in this way, the color intensity of which increases with increasing iron content.

[0153] The specimens were then heat-treated in an aluminum oxide crucible sealed with an aluminum oxide plate, which was placed in a heating furnace (Cube, Nabertherm, Lilienthal, Germany), in the presence of 1 g of activated carbon at 900°C or 1100°C for 1 h. Fig. 8 (middle and bottom row) shows the specimens obtained after this heat treatment, the color of which changed from light yellow to light greenish-gray depending on the temperature of this heat treatment.

[0154] Example 7

[0155] Specimens obtained according to the general procedure were infiltrated by immersion infiltration with aqueous solutions containing 0.5 wt%, 1.0 wt%, or 2.0 wt% cobalt(II) nitrate, and subsequently dried in a drying oven at 80°C for 2 h. The resulting specimens were then densely sintered in a dental high-temperature furnace (Programat S1 1600, Ivoclar Vivadent, Liechtenstein) under an atmospheric atmosphere at 1450°C for 2 h. Fig. 9 (top row) shows the specimens obtained in this way, the color intensity of which increases with increasing cobalt content.

[0156] The specimens were then heat-treated in an aluminum oxide crucible sealed with an aluminum oxide plate, which was placed in a heating furnace (Cube, Nabertherm, Lilienthal, Germany), in the presence of 1 g of activated carbon at 900°C or 1100°C for 1 h. Fig. 9 (middle and bottom row) shows the specimens obtained after this heat treatment, the color of which changed from gray-violet to blue or black-blue depending on the temperature of this heat treatment.

Claims

P 119888 - 19 - 2026-03-24 Ivoclar Vivadent AG Patent claims 1. A method for producing a colored oxide ceramic body, wherein an oxide ceramic body containing cerium is subjected to heat treatment under partially reducing conditions, comprising both heat treatment in the presence of a reducing agent and heat treatment in the presence of an oxidizing agent, wherein the heat treatment takes place in the presence of an oxidizing agent simultaneously with and / or after the heat treatment in the presence of a reducing agent and wherein The heat treatment is carried out in the presence of an oxidizing agent at a lower temperature than the heat treatment in the presence of a reducing agent, provided that it takes place after the heat treatment in the presence of a reducing agent.

2. A method for production according to claim 1, wherein the oxide ceramic body is subjected to heat treatment under oxidizing conditions, preferably in an oxygen-containing atmosphere and particularly in air, oxygen-enriched air or oxygen, prior to heat treatment under partially reducing conditions.

3. Method according to claim 2, wherein the oxide ceramic body which is subjected to heat treatment under oxidizing conditions is a non-densely sintered and in particular pre-sintered oxide ceramic body and this oxide ceramic body is preferably densely sintered by the heat treatment under oxidizing conditions.

4. Method according to claim 2 or 3, wherein the heat treatment is carried out under oxidizing conditions at a temperature in the range of 1200 to 1700°C, in particular in the range of 1300 to 1600°C, preferably in the range of 1350 to 1550°C and more preferably in the range of 1400 to 1500°C and most preferably at a temperature of about 1450°C.

5. A method according to any one of claims 1 to 4, wherein the heat treatment is carried out under partially reducing conditions at a temperature in the range of 700 to 1300°C, in particular in the range of 800 to 1200°C, preferably in the range of 850 to 1150°C, more preferably in the range of 900 to 1100°C, and most preferably at a temperature of about 1100°C.

6. A method according to any one of claims 1 to 5, wherein the reducing agent is a reducing gas or a substance which, upon heating, can form a reducing gas and / or bind oxygen, and in particular is activated carbon.

7. Method according to any one of claims 1 to 6, wherein the heat treatment is carried out under partially reducing conditions in a closed container in the presence of a substance which, when heated, can form a reducing gas and / or bind oxygen, in particular activated carbon.

8. Method according to any one of claims 1 to 7, wherein the heat treatment is carried out under partially reducing conditions in an oxygen-containing atmosphere, in particular air, and in the presence of a substance which, when heated, can form a reducing gas and / or bind oxygen, in particular activated carbon.

9. A method according to any one of claims 1 to 8, wherein the heat treatment is carried out in the presence of an oxidizing agent, followed by the heat treatment in the presence of a reducing agent, and is carried out at a temperature in the range of 700 to 1300°C, in particular in the range of 800 to 1200°C, preferably in the range of 850 to 1150°C, more preferably in the range of 900 to 1100°C and most preferably at a temperature of about 900°C.

10. Method according to any one of claims 1 to 9, wherein at least one region of the oxide ceramic body has a cerium content in the range of 0.001 to 2 mol%, in particular 0.01 to 1 mol%.

11. Method according to any one of claims 1 to 10, wherein the oxide ceramic body further comprises at least one element selected from the group consisting of Fe, Er, Cr, Co, Nd, Cu, Mn and Pr.

12. Method according to any one of claims 1 to 11, wherein the colored oxide ceramic body is a dental restoration, in particular a bridge, inlay, onlay, crown, veneer, shell or abutment, and preferably comprises two or more units.

13. A colored oxide ceramic body obtainable by the method according to any one of claims 1 to 12.

14. Use of a composition containing cerium for the production of a colored oxide ceramic body, wherein the composition containing cerium is brought into contact with at least part of an oxide ceramic body and the oxide ceramic body is subjected to heat treatment under partially reducing conditions, which includes both heat treatment in the presence of a reducing agent and heat treatment in the presence of an oxidizing agent, wherein the heat treatment takes place in the presence of an oxidizing agent simultaneously with and / or after the heat treatment in the presence of a reducing agent and wherein The heat treatment is carried out in the presence of an oxidizing agent at a lower temperature than the heat treatment in the presence of a reducing agent, provided that it takes place after the heat treatment in the presence of a reducing agent.

15. Use according to claim 14, wherein the composition containing cerium is a solution of a cerium salt, preferably cerium(1) nitrate or cerium(1) chloride, in a solvent, in particular water.

16. Use according to claim 14 or 15, wherein the composition containing cerium has a cerium content in the range of 0.001 to 2 mol%, in particular 0.01 to 1 mol%.

17. Use according to one of claims 14 to 16, wherein the composition containing cerium is brought into contact with the oxide ceramic body by infiltration, in particular by means of a brush technique or immersion technique.

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