Glass-ceramic dental body, process for preparing the same, and uses thereof

Abstract

To provide a glass-ceramic dental body having one or more material properties that change in a direction of the body.SOLUTION: A glass-ceramic dental body includes three consecutive sections: a section A, a section B and a section C. Each of the sections of the glass-ceramic dental body has a chemical composition that differs from chemical compositions of the other sections. The glass ceramic-dental body may be characterized by a gradient of a mechanical property, an optical property and / or a thermal property in a direction from section C to section A.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a glass-ceramic dental body, such as a glass-ceramic dental blank or a glass-ceramic dental restoration. Furthermore, the present invention relates to a method for preparing the glass-ceramic dental body and to the use of the glass-ceramic dental body in the dental field. [Background technology]

[0002] Dental restorations should ideally have mechanical properties comparable to those of natural teeth to provide long durability of the dental restoration while avoiding excessive wear of adjacent tissues and / or natural teeth. Furthermore, it is desirable for dental restorations to resemble the natural appearance of the patient's teeth. Although the appearance of natural teeth varies, there are some optical properties that can be considered universal for most natural human teeth. Natural teeth usually change in color and / or translucency from the upper incisal or occlusal portion of the tooth to its underlying dentin portion. Between these two portions, the upper incisal or occlusal portion of the tooth often shows some type of gradation or transition in color and translucency.

[0003] Glass ceramic dental restorations are known in the art. Glass ceramic dental restorations are often prepared from glass ceramic dental blanks, such as glass ceramic dental mill blanks or glass ceramic dental press blanks. The glass ceramic dental mill blanks can be machined, usually using CAD / CAM processes, to the desired shape of the dental restoration. The glass ceramic dental press blanks can be hot pressed into a mold with the desired shape of the dental restoration.

[0004] Known glass-ceramic dental bodies, including dental blanks or dental restorations, are often prepared from a single solid glass. The solid glass is exposed to controlled heat to achieve partial crystallization of the solid glass to produce a glass-ceramic having one or more crystalline phases within its amorphous glass phase. Glass-ceramic dental bodies prepared from a solid glass typically have uniform mechanical, optical, and thermal properties. However, glass-ceramic dental bodies with uniform mechanical, optical, and / or thermal properties are often not ideal or acceptable for use in dentistry.

[0005] In the art, there have been efforts to provide glass-ceramic dental bodies by heating different regions of a solid glass at different temperatures, for example using a gradient furnace. This can cause the crystallization of crystalline phases to vary in different regions of the solid glass. As a result, a glass-ceramic dental body is obtained that has one or more non-uniform properties. However, such preparation methods are laborious, and the glass-ceramic dental bodies obtained by such methods may still have insufficient mechanical, optical, or thermal properties.

[0006] EP 2699521 A1 relates to a method for preparing a glass-ceramic body. The method comprises the steps of providing a base glass body and subjecting the base glass body to a heat treatment, whereby a crystalline phase embedded in the glass matrix is ​​formed. The heat treatment comprises a nucleation step followed by multiple crystallization steps at different temperatures, whereby at least two different crystalline phases are formed. EP 3974397 A1 relates to a machinable dental mill block and a method for preparing the same. The method comprises the steps of providing a block having a predetermined shape from a particular glass composition and heat treating the block at a temperature in the range of 760°C to 880°C while applying a temperature gradient to the block in the depth direction.

[0007] There is a need in the art for glass-ceramic dental bodies that have one or more material properties that vary along the body, ideally matching the property transitions in natural teeth and / or allowing for the provision of improved dental restorations, and it is desirable that such glass-ceramic dental bodies be obtainable by relatively simple and reproducible methods. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide a new and improved glass-ceramic dental body.It is an object of the present invention to provide a glass-ceramic dental body having one or more material properties that vary in a direction along the body.It is an object of the present invention to provide a glass-ceramic dental body that does not have the disadvantages of prior art glass-ceramic dental bodies. [Means for solving the problem]

[0009] One or more of the above objectives are solved by glass-ceramic dental bodies and methods for preparing glass-ceramic bodies according to embodiments of the present invention.

[0010] One aspect of the present invention is a method for preparing a cellular membrane comprising: Section A, Section B, and A glass ceramic dental body is provided, the glass ceramic dental body including a section C. Each of the sections has a chemical composition that is different from the chemical composition of the other sections.

[0011] In one preferred embodiment, the glass ceramic dental body has a gradient of mechanical properties (e.g., gradient of biaxial flexural strength and / or fracture toughness (K)) in the direction from section C to section A. IC) gradient), optical property (e.g., gradient in contrast ratio), and / or thermal property (e.g., gradient in coefficient of thermal expansion).

[0012] In one preferred embodiment, the main crystal phase of each of the sections is the same, and the content of the main crystal phase optionally decreases in the direction from section C to section A. In an alternative preferred embodiment, the main crystal phase of section C is different from the main crystal phase of section A. Optionally, the content of the main crystal phase of section C decreases in the direction from section C to section A. Or, the content of the main crystal phase of section A decreases in the direction from section A to section C. In another alternative preferred embodiment, section A is composed of glass, and sections C and B are composed of glass-ceramic material.

[0013] One discovery of the present invention is that it is possible to provide a glass-ceramic dental body having one or more mechanical, optical, and / or thermal properties that vary in the form of a gradient over successive sections, such as biaxial bending strength, fracture toughness, translucency, or thermal expansion coefficient. The glass-ceramic dental body of the present invention can provide, or can be used to provide, a glass-ceramic dental restoration having one or more properties that vary from one zone to another. Thus, the glass-ceramic dental body can provide, or can be used to provide, a dental restoration in which one or more properties are advantageously tailored so that the restoration approaches the properties of natural teeth. For example, a glass-ceramic dental restoration can be provided having an incisal zone that has a higher translucency than its dentin zone. Additionally or alternatively, the thermal properties (e.g., CTE) can be tailored so that different glazings with different thermal properties (e.g., CTE) can be applied to different parts of the restoration.

[0014] One aspect of the present invention provides a method for preparing a glass-ceramic dental body according to an embodiment of the present invention, the method comprising the following steps: providing two or more powders selected from glass powders, glass-ceramic powders, and mixtures thereof; Preparing a compact from the powder; and subjecting the compact to a heat treatment to obtain a glass-ceramic dental body.

[0015] The compact typically includes three successive powder sections: powder section A, powder section B, and powder section C. The weight ratio of two or more powders is different in each of the powder sections.

[0016] It has been found that the glass-ceramic dental body of the invention can be obtained relatively easily. In particular, the method of the invention does not require the simultaneous subjection of different areas of a solid glass to different temperatures. Moreover, such a method would not be suitable for the preparation of a glass-ceramic dental body of the invention, since the solid glass has a uniform chemical composition and therefore cannot be used to obtain different sections with different chemical compositions. Furthermore, the inventors have surprisingly found that two or more glass or glass-ceramic powders with different chemical compositions (e.g. glass or glass-ceramic powders useful for the preparation of glass-ceramics with different types and / or contents of crystalline phases) can be used for the preparation of a dense monolithic glass-ceramic body by heat treatment, in particular sintering. [Brief description of the drawings]

[0017] [Figure 1A] Figure 1 shows the qualitative X-ray diffraction analysis spectra of different sections of the glass-ceramic dental body of Example 5. Figure 1A shows the X-ray diffraction analysis spectrum of section C (bottom layer). [Figure 1B] The spectrum of X-ray diffraction analysis of section B (intermediate layer) is shown. [Figure 1C]Figure 1 shows the spectrum of X-ray diffraction analysis of section A (top layer). The spectrum shows that the ratio of α-quartz (most prominent peak labeled: #) to Li2Si2O5 (most prominent peak labeled: *) peak intensity changes from section C (bottom layer) through section B (middle layer) to section A (top layer). The intensity of Li2Si2O5 decreases from section C (bottom layer) to section A (top layer). The intensity of the α-quartz peak increases from section C (bottom layer) to section A (top layer). The change in peak intensity indicates that the content of Li2Si2O5 decreases from section C (bottom layer) to section A (top layer).

[0018] definition In the context of the present invention, the following terms have the following meanings.

[0019] "Dental body" means a solid, geometrically defined, three-dimensional object of material suitable for use in the fields of dentistry or orthodontics, such as an ingot, block, disc, or for forming a dental restoration. The dental body may be, but is not limited to, a dental blank or a dental restoration. The dental blank may be a dental mill blank or a dental press blank.

[0020] "Dental mill blank" means a solid, geometrically defined, three-dimensional object of material, such as a block or disk, from which dental restorations can be fabricated, typically by machining, such as cutting, milling, grinding, drilling, etc., using CAD / CAM processes.

[0021] "Dental press blank" means a solid, geometrically defined, three-dimensional object of material, such as a block or ingot, from which a dental restoration can be formed by hot pressing the blank into a mold having the shape of the dental restoration.

[0022] As used herein, "dental restoration" refers to an article useful in the dental or orthodontic fields to restore, remodel, support, and / or reconstruct a tooth or a portion thereof, or a group of teeth or portions thereof. A dental restoration may be, but is not limited to, a crown, a partial crown, an abutment, an abutment crown, an inlay, an onlay, a veneer, a shell, or a bridge.

[0023] By "glass-ceramic" dental body is meant a dental body that is partially or completely composed of a glass-ceramic material. For example, a glass-ceramic dental body that is partially composed of a glass-ceramic material can include two sections composed of the glass-ceramic material and one section composed of glass. A glass-ceramic dental body that is completely composed of a glass-ceramic material includes only a section composed of the glass-ceramic material. A glass-ceramic dental body typically does not include or is typically not composed of a glass-matrix composite. A "glass-matrix composite" in the sense of the present disclosure is a material that is obtained by adding crystalline particles to a glass melt or by attaching a glass material to a crystalline material (e.g., by sintering).

[0024] "Glass-ceramic material" means an inorganic, non-metallic solid having a glass phase surrounding one or more crystalline phases. Glass-ceramic materials are typically obtained by controlled nucleation and crystallization of an amorphous base glass. Glass-ceramic materials differ from ceramic materials, which typically do not contain a glass phase. "Glass" means an inorganic, non-metallic solid that is typically hard, brittle, transparent, and essentially devoid of crystalline regions. It can be considered as a thermodynamically unstable frozen melt.

[0025] As used herein, "consecutive sections" means sections that are positioned adjacent to one another. Thus, section A is positioned adjacent to section B, which is positioned adjacent to section C, etc.

[0026] As used herein, "top section" refers to the outermost section of a glass-ceramic dental blank, such as a dental mill blank, which can be used to prepare the incisal or occlusal zone, or a portion thereof, of a dental restoration.

[0027] "Middle section" means a section located between the top section and the bottom section of a glass-ceramic dental blank, such as a dental mill blank. The middle section can be used to prepare a transition zone or part of a dental restoration.

[0028] "Bottom section" means an outermost section of a glass ceramic dental blank, such as a dental mill blank, that is located on the opposite side of the glass ceramic dental blank from the top section. The bottom section can be used to prepare a dentin zone or a portion thereof of a dental restoration.

[0029] The terms "top section," "middle section," and "bottom section" should not be construed as requiring that the glass-ceramic dental blank be positioned (or used) in a particular way or orientation. Any other parts that may additionally be present on the outside of the glass-ceramic dental blank (e.g., a support layer, a protective layer, a printing layer, or a sacrificial layer, such as a retaining pin, or a thin layer of glass-ceramic material) and that are not suitable or intended to be part of a dental restoration formed from the glass-ceramic dental blank should not be understood as or as part of the top section, middle section, or bottom section. For example, a glass-ceramic dental blank (e.g., a dental mill blank) can be attached to one or more of its outsides to a support part, a protective part, and / or a sacrificial part (although this is not required). Such parts can be a support layer, a protective layer, a printing layer, or a sacrificial layer, such as a retaining pin, or a thin layer of glass-ceramic material.

[0030] By "layer" is meant a discrete layer of a glass-ceramic dental body. The discrete layers in a glass-ceramic dental body can be determined by examination under a microscope, such as by single electron microscopy (SEM).

[0031] As used herein, "gradient" refers to the change in the properties of a glass-ceramic dental body (e.g., biaxial flexural strength, fracture toughness (K IC), contrast ratio, coefficient of thermal expansion (CTE), etc.) increase or decrease (e.g., gradually or stepwise) in the direction of the glass-ceramic dental body. Thus, a gradient can be defined as a property value, such as three or more values, that increases or decreases (e.g., gradually or stepwise) in the direction of the glass-ceramic dental body. A property that decreases "from section C to section A" means that the value of the property in section C is higher than the value of the property in section B, which is higher than the value of the property in section A (i.e., section C>section B>section A). When a property increases "from section C to section A," the change in value is reversed (i.e., section C<section B<section A). A gradient can include a property change within a section, such as within section B, in the direction from section C to section A (e.g., stepwise or gradual from one layer to another).

[0032] "Predominant crystalline phase" refers to the crystalline phase of a glass-ceramic dental body or section thereof that has the highest mass fraction of all crystalline phases present in the glass-ceramic dental body or section thereof. Thus, the predominant crystalline phase can be determined for the entire glass-ceramic dental body. In the aforementioned cases, the mass fraction of the crystalline phase is based on the total weight of the glass-ceramic dental body. Additionally or alternatively, the predominant crystalline phase can be determined for a section of the glass-ceramic dental body, such as the bottom section or top section described herein. In the aforementioned cases, the mass fraction of the crystalline phase is based on the total weight of the section. The mass of the crystalline phase can be quantitatively determined using the Rietveld method. The Rietveld method is well known in the art.

[0033] "Quartz" or "quartz crystalline phase" means a crystalline phase selected from the group of α-quartz, α-quartz solid solution, β-quartz solid solution, and mixtures thereof. "Quartz solid solution" refers to a SiO 2 solid solution in which foreign ions are incorporated either in interstitial or lattice sites.2 These hetero ions are Al 3+ In addition, Mg 2+ , Li + , Zn 2+ For example, Al 3+ Zn 2+ and Mg 2+ may be present in the solid solution in the same molar concentration as the combined

[0034] When "comprising" is used herein, it does not exclude the presence of further unspecified elements. When "essentially consisting of" is used herein, it does not exclude the presence of further unspecified elements that do not substantially affect the essential characteristics of the defined subject matter. For example, when a section or layer is defined by its chemical composition, the section or layer may contain unavoidable trace impurities in total of <0.2 wt%, even if this is not explicitly defined. For the purposes of the present invention, the terms "essentially consisting of" and "consisting of" are considered to be specific embodiments of the term "consisting of". Whenever the terms "including" or "having" are used, these terms are meant to be equivalent to "comprising" as defined above.

[0035] The term "obtained" is not necessarily meant to indicate that an embodiment must be obtained by, for example, the sequence of steps following the term "obtained", however, such a limited understanding is always included by the term "obtained" as a preferred embodiment.

[0036] Numbers defined herein are meant to be rounded to their last digit and encompass a range of rounded values ​​according to established rounding rules. For example, the value 3 is meant to encompass values ​​within the range of 2.5 to 3.4, the value 1.5 is meant to encompass values ​​within the range of 1.46 to 1.54, and so on.

[0037] In the following the invention is explained in more detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] I. Glass ceramic dental body The present invention is divided into three consecutive sections: Section A, Section B, and A glass ceramic dental body is provided, the glass ceramic dental body including a section C. Each of the sections has a chemical composition that is different from the chemical composition of the other sections.

[0039] In one preferred embodiment, the glass-ceramic dental body is characterized by one or more gradients in mechanical, optical, and / or thermal properties in the direction from Section C to Section A.

[0040] A glass-ceramic dental body may be further defined by one or more more specific gradients of mechanical, optical, and / or thermal properties. Alternatively or additionally, a glass-ceramic dental body may be defined by its crystalline phase, its chemical composition, and / or its structure and morphology.

[0041] 1. Gradient In one preferred embodiment, the glass-ceramic dental body is characterized by one or more gradients in mechanical, optical, and / or thermal properties from section C to section A. The one or more gradients may include gradients in biaxial flexural strength, fracture toughness (K ICThe gradient may be, but is not limited to, one or more mechanical properties, such as, but not limited to, a gradient of thermal expansion coefficient (CTE), and / or a gradient of machinability. The gradient may be, but is not limited to, one or more optical properties, such as, but is not limited to, a gradient of contrast ratio. The gradient may be, but is not limited to, one or more thermal properties, such as, but is not limited to, a gradient of coefficient of thermal expansion (CTE).

[0042] 1.1 Mechanical property gradients The one or more gradients may be gradients of biaxial bending strength. The biaxial bending strength decreases from section C to section A. The biaxial bending strength can be determined according to DIN EN ISO 6872 (DIN EN ISO 6872:2019). A test specimen for each of the sections can be obtained from the respective sections of the glass-ceramic dental body, for example by milling, cutting and / or sawing with a diamond-coated tool. If the sections have dimensions that are not suitable for preparing suitable test specimens (for example according to DIN EN ISO 6872, in particular according to DIN EN ISO 6872:2019) for determining the biaxial bending strength, suitable test specimens can be prepared from suitable raw materials after analysis of the crystalline phases and / or chemical composition of the respective sections.

[0043] Section C may have a biaxial flexural strength of at least 150 MPa, at least 170 MPa, at least 200 MPa, at least 250 MPa, at least 300 MPa, or at least 350 MPa. Section C may have a biaxial flexural strength of up to 550 MPa, up to 500 MPa, up to 475 MPa, up to 450 MPa, up to 350 MPa, up to 300 MPa, or up to 250 MPa. Section C may have a biaxial flexural strength in the range of 150-550 MPa, in the range of 175-500 MPa, in the range of 200-475 MPa, in the range of 250-450 MPa, in the range of 350-475 MPa, in the range of 250-350 MPa, or in the range of 150-250 MPa. A biaxial flexural strength of at least 200 MPa is typically preferred for section C, as such a biaxial flexural strength is particularly suitable for providing the dentin zone of a dental restoration with good mechanical strength.

[0044] Section C may have a biaxial flexural strength at least 25 MPa, at least 60 MPa, at least 100 MPa, at least 150 MPa, at least 175 MPa, or at least 200 MPa higher than the biaxial flexural strength of section A. Section C may have a biaxial flexural strength up to 400 MPa, up to 350 MPa, up to 300 MPa, or up to 250 MPa higher than the biaxial flexural strength of section A. Section C may have a biaxial flexural strength higher than the biaxial flexural strength of section A by a value in the range of 25-400 MPa, 60-400 MPa, 100-350 MPa, 150-300 MPa, 175-250 MPa, 200-400 MPa, or 60-200 MPa.

[0045] Section B may have a biaxial flexural strength of at least 150 MPa, at least 200 MPa, at least 250 MPa, at least 300 MPa, or at least 350 MPa. Section B may have a biaxial flexural strength of up to 500 MPa, up to 450 MPa, up to 350 MPa, up to 300 MPa, or up to 250 MPa. Section B may have a biaxial flexural strength in the range of 150-500 MPa, 200-450 MPa, 300-450 MPa, 350-450 MPa, 200-400 MPa, 250-400 MPa, or 150-250 MPa.

[0046] Section A may have a biaxial flexural strength of at least 75 MPa, at least 100 MPa, at least 150 MPa, or at least 200 MPa. Section A may have a biaxial flexural strength of up to 350 MPa, up to 300 MPa, up to 250 MPa, or up to 200 MPa. Section A may have a biaxial flexural strength in the range of 75-350 MPa, 100-300 MPa, 150-250 MPa, 200-300 MPa, 100-200 MPa, or 75-200 MPa.

[0047] In one embodiment, section C has a biaxial bending strength in the range of 150-250 MPa, and section A has a biaxial bending strength in the range of 75-200 MPa. In one embodiment, section C has a biaxial bending strength in the range of 250-350 MPa, and section A has a biaxial bending strength in the range of 100-250 MPa. In one embodiment, section C has a biaxial bending strength in the range of 350-475 MPa, and section A has a biaxial bending strength in the range of 150-300 MPa. In one embodiment, section C has a biaxial bending strength in the range of 350-475 MPa, and section A has a biaxial bending strength in the range of 100-200 MPa. In one embodiment, section C has a biaxial bending strength in the range of 250-355 MPa, and section A has a biaxial bending strength in the range of 220-320 MPa. In terms of the gradient of the biaxial bending strength, it will be understood that section B has a biaxial bending strength value that is between the values ​​of sections C and A.

[0048] The gradient or gradients are related to the fracture toughness (K IC ) gradient. Fracture toughness (K IC ) decreases from section C to section A. The fracture toughness (K IC ) can be determined according to the single-edge V-notched beam (SEVNB) method according to DIN EN ISO 6872 and in particular DIN EN ISO 6872:2015. Each specimen of the section can be obtained from the respective section of the glass-ceramic dental body, for example by milling, cutting and / or sawing with a diamond-coated tool. The sections are then subjected to a test for determining the fracture toughness (K IC If the material has dimensions that are not suitable for preparing suitable test specimens (e.g. according to DIN EN ISO 6872, in particular DIN EN ISO 6872:2015) for determining the crystalline phase and / or chemical composition of the respective section, suitable test specimens can be prepared from suitable raw materials after analysis of the crystalline phases and / or chemical composition of the respective section.

[0049] Section C must be at least 1.4MPa* m -1 / 2 , 1.6MPa * m -1 / 2 , at least 1.8 MPa * m -1 / 2 , 2.0MPa * m -1 / 2 , at least 2.2 MPa * m -1 / 2, or at least 2.6MPa * m -1 / 2 Fracture toughness (K IC Section C may have a maximum pressure of 3.4 MPa. * m -1 / 2 , maximum 3.0MPa * m -1 / 2 , max. 2.8MPa * m -1 / 2 , max. 2.6MPa * m -1 / 2 , max. 2.4MPa * m * m -1 / 2 , or up to 2.2MPa * m * m -1 / 2 Fracture toughness (K IC Section C may have a pressure of 1.4 to 3.4 MPa. * m -1 / 2 in the range of 1.6 to 2.8 MPa * m -1 / 2 in the range of 1.8 to 2.6 MPa, more preferably at least * m -1 / 2 Fracture toughness (K IC Section C may have a pressure of 1.4 to 2.0 MPa. * m -1 / 2 Range: 1.6~2.2MPa * m -1 / 2 Range: 2.0~2.6MPa * m -1 / 2 Range: 2.6~3.4MPa * m -1 / 2 Fracture toughness (K IC ) at least 2.0 MPa * m -1 / Fracture toughness (K IC) is typically preferred for section C because such fracture toughness is particularly suitable for providing the dentin zone of a dental restoration with good mechanical strength.

[0050] Section C is the fracture toughness (K IC ) at least 0.4MPa * m -1 / 2 , at least 0.6 MPa * m -1 / 2 , at least 0.8 MPa * m -1 / 2 , at least 1.0 MPa * m -1 / 2 , or at least 1.2 MPa * m * m -1 / 2 High fracture toughness (K IC Section C may have a fracture toughness (K IC ) up to 2.0MPa * m -1 / 2 , maximum 1.8MPa * m -1 / 2 , maximum 1.4MPa * m -1 / 2 , maximum 1.2MPa * m -1 / 2 , or up to 0.8MPa * m * m -1 / 2 High fracture toughness (K IC Section C may have a fracture toughness (K IC ) than 0.4 to 2.0 MPa * m -1 / 2 Range: 0.6~2.0MPa * m -1 / 2 Range: 0.8~1.8MPa * m -1 / 2 Range: 1.0~1.8MPa * m -1 / 2 Range: 1.2~1.8MPa * m -1 / 2 Range: 0.4~1.2MPa * m -1 / 2 or 0.4 to 1.0 MPa * m -1 / 2The fracture toughness (K IC ).

[0051] Section B must be at least 1.2MPa * m -1 / 2 , at least 1.4 MPa * m -1 / 2 , at least 1.6 MPa * m -1 / 2 , at least 1.8 MPa * m -1 / 2 , or at least 2.4 MPa * m -1 / 2 Fracture toughness (K IC Section B may have a maximum pressure of 3.2 MPa. * m -1 / 2 , maximum 2.8Pa * m -1 / 2 , max. 2.6MPa * m -1 / 2 , max. 2.4MPa * m -1 / 2 , or up to 2.2MPa * m * m -1 / 2 Fracture toughness (K IC Section B may have a pressure of 1.2 to 3.2 MPa. * m -1 / 2 Range: 1.4~2.6MPa * m -1 / 2 Range: 1.6~2.4MPa * m -1 / 2 Range: 1.6~2.2MPa * m -1 / 2 Range: 1.2~2.2MPa * m -1 / 2 or 2.4 to 3.2 MPa * m -1 / 2 Fracture toughness (K IC ).

[0052] Section A must be at least 0.5MPa * m -1 / 2 , at least 0.7 MPa * m -1 / 2 , at least 1.2 MPa * m -1 / 2, at least 1.2 MPa * m -1 / 2 , or at least 1.4 MPa * m -1 / 2 , or at least 2.4 MPa * m -1 / 2 Fracture toughness (K IC Section A may have a maximum pressure of 3.0 MPa. * m -1 / 2 , maximum 2.2Pa * m -1 / 2 , maximum 2.0MPa * m -1 / 2 , maximum 1.8MPa * m -1 / 2 , maximum 1.6MPa * m -1 / 2 , maximum 1.2MPa * m -1 / 2 , or up to 1.0MPa * m -1 / 2 Fracture toughness (K IC Section A may have a pressure of 0.5 to 2.2 MPa. * m -1 / 2 in the range of 0.7 to 2.0 MPa * m -1 / 2 More preferably, the range is 0.7 to 1.8 MPa. * m -1 / 2 Fracture toughness (K IC Section A may have a pressure of 0.5 to 1.2 MPa. * m -1 / 2 Range: 0.7~1.4MPa * m -1 / 2 Range: 1.2~1.8MPa * m -1 / 2 Range: 1.4~2.2MPa * m -1 / 2 or 2.4 to 3.0 MPa * m -1 / 2 Fracture toughness (K IC ).

[0053] In one embodiment, section C is 1.2 to 2.0 MPa. * m -1 / 2 Fracture toughness (K IC ) and section A is 0.5 to 1.2 MPa* m -1 / 2 Fracture toughness (K IC In one embodiment, section C has a pressure of 2.0 to 2.6 MPa. * m -1 / 2 Fracture toughness (K IC ) and section A is 1.4 to 2.2 MPa * m -1 / 2 Fracture toughness (K IC In one embodiment, section C has a pressure of 2.2 to 3.0 MPa. * m -1 / 2 Fracture toughness (K IC ) and section A is 0.5 to 1.4 MPa * m -1 / 2 Fracture toughness (K IC In one embodiment, section C has a pressure of 2.6 to 3.4 MPa. * m -1 / 2 Fracture toughness (K IC ) and section A is 2.4 to 3.0 MPa * m -1 / 2 Fracture toughness (K IC ) Fracture toughness (K IC In terms of the gradient of fracture toughness (K IC )

[0054] The gradient or gradients may be a machinability gradient, where the machinability increases from section C to section A.

[0055] 1.2 Gradient of optical properties The gradient or gradients may be contrast ratio gradients. The contrast ratio decreases from section C to section A. The contrast ratio may be determined according to BS 5612, in particular BS 5612:1978. The contrast ratio is typically determined using specimens having a thickness of 2 mm ± 0.02 mm. The specimens may be prepared (e.g. by milling, cutting, and / or sawing with diamond-coated tools) from different sections of the glass-ceramic dental body. Before carrying out the measurements, the surfaces of the specimens may be ground and polished as described in the "Measurement Methods" section. The contrast ratio relates to the ratio of the illuminance (Y) of a material when placed on a black background (Yb) to the illuminance of the same material when placed on a white background (Yw) (CR = Yb / Yw). The contrast ratio can be used to characterize the translucency of a material, i.e. the light transmission of a material expressed as the ratio of the transmitted light intensity to the incident light intensity. A contrast ratio close to 0% can indicate that a given material is almost completely transparent, while a contrast ratio of 100% can indicate that the material is completely opaque. IC If the respective sections have dimensions which make it unsuitable for preparing suitable specimens (e.g. in accordance with BS 5612, in particular BS 5612:1978) for determining the crystal phase and / or chemical composition, suitable specimens can be prepared from suitable raw materials after analysis of the crystalline phase and / or chemical composition of the respective sections.

[0056] Section C may have a contrast ratio of at least 62%, at least 65%, at least 75%, at least 80%, or at least 85%. Section C may have a contrast ratio of up to 94%, up to 92%, up to 85%, up to 75%, or up to 72%. Section C may have a contrast ratio in the range of 62-94%, in the range of 65-92%, in the range of 75-85%, in the range of 80-94%, in the range of 85-92%, in the range of 62-75%, or in the range of 65-72%.

[0057] Section C may have a contrast ratio that is at least 10 percentage points, at least 15 percentage points, at least 20 percentage points, at least 36 percentage points, or at least 42 percentage points higher than the contrast ratio of section A. Section C may have a contrast ratio that is up to 56 percentage points, up to 52 percentage points, up to 35 percentage points, up to 30 percentage points, or up to 26 percentage points higher than the contrast ratio of section A. Section C may have a contrast ratio that is 10 to 56 percentage points, 15 to 52 percentage points, 36 to 56 percentage points, 42 to 52 percentage points, 10 to 35 percentage points, 15 to 30 percentage points, or 20 to 26 percentage points higher than the contrast ratio of section A.

[0058] Section B may have a contrast ratio of at least 40%, at least 45%, at least 50%, at least 55%, or at least 60%. Section B may have a contrast ratio of up to 90%, up to 85%, up to 80%, up to 75%, or up to 65%. Section B may have a contrast ratio in the range of 40-90%, in the range of 45-85%, in the range of 50-80%, in the range of 55-75%, in the range of 60-75%, or in the range of 55-65%.

[0059] Section A may have a contrast ratio of at least 14%, at least 18%, at least 55%, at least 58%, or at least 60%. Section A may have a contrast ratio of up to 80%, up to 74%, up to 70%, up to 65%, up to 30%, or up to 25%. Section A may have a contrast ratio in the range of 14-80%, in the range of 18-74%, in the range of 55-80%, in the range of 58-74%, in the range of 60-70%, in the range of 55-65%, in the range of 14-30%, or in the range of 18-25%.

[0060] In one embodiment, section C has a contrast ratio in the range of 80-94% (e.g., 85-92%) and section A has a contrast ratio in the range of 58-74% (e.g., 60-70%). In one embodiment, section C has a contrast ratio in the range of 62-75% (e.g., 65-72%) and section A has a contrast ratio in the range of 14-30% (e.g., 18-25%). In one embodiment, section C has a contrast ratio in the range of 75-85% and section A has a contrast ratio in the range of 55-65%.

[0061] 1.3 Thermal property gradients The gradient or gradients may be gradients of the coefficient of thermal expansion (CTE). The coefficient of thermal expansion decreases or increases from section C to section A. The coefficient of thermal expansion can be determined using a dilatometer according to DIN EN ISO 6872, in particular DIN EN ISO 6872:2015. A test specimen can be obtained from each of the glass-ceramic dental bodies by milling, cutting and / or soaking the respective sections of the glass-ceramic dental bodies with a diamond-coated tool. If the sections have dimensions that are not suitable for preparing suitable test specimens (e.g. according to DIN EN ISO 6872, in particular DIN EN ISO 6872:2015) for determining the coefficient of thermal expansion, suitable test specimens can be prepared from suitable raw materials after analysis of the crystalline phases and / or chemical composition of the respective sections.

[0062] Each of the sections may have a coefficient of thermal expansion in the range of 5-14 ppm / K. For example, section C may have a coefficient of thermal expansion in the range of 7-13 ppm / K or in the range of 8-12 ppm / K. Section B may have a coefficient of thermal expansion in the range of 6-13 ppm / K or in the range of 7-12 ppm / K. Section A may have a coefficient of thermal expansion in the range of 5-14 ppm / K or in the range of 6-13 ppm / K.

[0063] Section C may have a coefficient of thermal expansion that differs from that of section A by at least 1 ppm / K. Section C may have a coefficient of thermal expansion that differs from that of section A by up to 4 ppm / K or up to 3 ppm / K. Section C may have a coefficient of thermal expansion that differs from that of section A by 1-4 ppm / K or 1-3 ppm / K. In one embodiment, section C has a coefficient of thermal expansion in the range of 7-13 ppm / K (e.g., in the range of 8-12 ppm / K), section A has a coefficient of thermal expansion in the range of 5-14 ppm / K (e.g., in the range of 6-13 ppm / K), and section C has a coefficient of thermal expansion that differs from that of section A by 1-4 ppm / K (e.g., in the range of 1-3 ppm / K).

[0064] In the following, an embodiment of the present invention, referred to herein as "embodiment CTE-1", is described. In embodiment CTE-1, the gradient is the gradient of the coefficient of thermal expansion (CTE), which decreases from section C to section A.

[0065] In CTE-1 embodiments, section C may have a coefficient of thermal expansion of at least 6.6 ppm / K, at least 7.6 ppm / K, or at least 8.2 ppm / K. In CTE-1 embodiments, section C may have a coefficient of thermal expansion of up to 10.6 ppm / K, up to 9.6 ppm / K, or up to 9.0 ppm / K. In CTE-1 embodiments, section C may have a coefficient of thermal expansion in the range of 6.6-10.6 ppm / K, in the range of 7.6-9.6 ppm / K, or in the range of 8.2-9.0 ppm / K.

[0066] In CTE-1 embodiments, section C may have a coefficient of thermal expansion at least 1.0 ppm / K, at least 1.8 ppm / K, or at least 2.2 ppm / K higher than the coefficient of thermal expansion of section A. In CTE-1 embodiments, section C may have a coefficient of thermal expansion up to 4.0 ppm / K, up to 3.2 ppm / K, or up to 2.8 ppm / K higher than the coefficient of thermal expansion of section A. In CTE-1 embodiments, section C may have a coefficient of thermal expansion in the range of 1.0-4.0 ppm / K, in the range of 1.8-3.2 ppm / K, or in the range of 2.2-2.8 ppm / K higher than the coefficient of thermal expansion of section A.

[0067] In CTE-1 embodiments, section B may have a coefficient of thermal expansion of at least 5.2 ppm / K, at least 6.2 ppm / K, or at least 7.0 ppm / K. In CTE-1 embodiments, section B may have a coefficient of thermal expansion of up to 9.2 ppm / K, up to 8.2 ppm / K, or up to 7.6 ppm / K. In CTE-1 embodiments, section B may have a coefficient of thermal expansion in the range of 5.2-9.2 ppm / K, in the range of 6.2-8.2 ppm / K, or in the range of 7.0-7.6 ppm / K.

[0068] In CTE-1 embodiments, section A may have a coefficient of thermal expansion of at least 4.6 ppm / K, at least 5.2 ppm / K, or at least 5.8 ppm / K. In CTE-1 embodiments, section A may have a coefficient of thermal expansion of up to 8.2 ppm / K, up to 7.2 ppm / K, or up to 6.6 ppm / K. In CTE-1 embodiments, section A may have a coefficient of thermal expansion in the range of 4.6-8.2 ppm / K, in the range of 5.2-7.2 ppm / K, or in the range of 5.8-6.6 ppm / K.

[0069] In a more specific embodiment of embodiment CTE-1, section C has a thermal expansion coefficient in the range of 6.6 to 10.6 ppm / K (e.g., in the range of 7.6 to 9.6 ppm / K), section A has a thermal expansion coefficient in the range of 4.6 to 8.2 ppm / K (e.g., in the range of 5.2 to 7.2 ppm / K), and section C has a thermal expansion coefficient that is 1.0 to 4.0 ppm / K (e.g., in the range of 1.8 to 3.2 ppm / K) higher than the thermal expansion coefficient of section A.

[0070] In the following, an embodiment of the present invention, referred to herein as "embodiment CTE-2", is described. In embodiment CTE-2, the gradient is the gradient of the coefficient of thermal expansion (CTE), which increases from section C to section A.

[0071] In CTE-2 embodiments, section C may have a coefficient of thermal expansion of at least 9.2 ppm / K, at least 10.2 ppm / K, or at least 10.6 ppm / K. In CTE-2 embodiments, section C may have a coefficient of thermal expansion of up to 13.2 ppm / K, up to 12.2 ppm / K, or up to 11.8 ppm / K. In CTE-2 embodiments, section C may have a coefficient of thermal expansion in the range of 9.2 to 13.2 ppm / K, in the range of 10.2 to 12.2 ppm / K, or in the range of 10.6 to 11.8 ppm / K.

[0072] In CTE-2 embodiments, section C may have a coefficient of thermal expansion that is at least 0.8 ppm / K, at least 1.0 ppm / K, or at least 1.2 ppm / K lower than the coefficient of thermal expansion of section A. In CTE-2 embodiments, section C may have a coefficient of thermal expansion that is up to 2.5 ppm / K, up to 2.0 ppm / K, or up to 1.8 ppm / K lower than the coefficient of thermal expansion of section A. In CTE-2 embodiments, section C may have a coefficient of thermal expansion that is in the range of 0.8-2.5 ppm / K, in the range of 1.0-2.0 ppm / K, or in the range of 1.2-1.8 ppm / K lower than the coefficient of thermal expansion of section A.

[0073] In CTE-2 embodiments, section B may have a coefficient of thermal expansion of at least 10.0 ppm / K, at least 11.0 ppm / K, or at least 10.4 ppm / K. In CTE-1 embodiments, section B may have a coefficient of thermal expansion of up to 14.0 ppm / K, up to 13.0 ppm / K, or up to 12.6 ppm / K. In CTE-1 embodiments, section B may have a coefficient of thermal expansion in the range of 10.0-14.0 ppm / K, in the range of 11.0-13.0 ppm / K, or in the range of 10.4-12.6 ppm / K.

[0074] In CTE-1 embodiments, section A may have a coefficient of thermal expansion of at least 10.7 ppm / K, at least 11.7 ppm / K, or at least 12.1 ppm / K. In CTE-1 embodiments, section A may have a coefficient of thermal expansion of up to 14.4 ppm / K, up to 13.7 ppm / K, or up to 13.3 ppm / K. In CTE-1 embodiments, section A may have a coefficient of thermal expansion in the range of 10.7 to 14.4 ppm / K, in the range of 11.7 to 13.7 ppm / K, or in the range of 12.1 to 13.3 ppm / K.

[0075] In a more specific embodiment of embodiment CTE-1, section C has a thermal expansion coefficient in the range of 9.2 to 13.2 ppm / K (e.g., in the range of 10.2 to 12.2 ppm / K), section A has a thermal expansion coefficient in the range of 10.7 to 14.4 ppm / K (e.g., in the range of 11.7 to 13.7 ppm / K), and section C has a thermal expansion coefficient that is 0.8 to 2.5 ppm / K (e.g., in the range of 1.0 to 2.0 ppm / K) lower than the thermal expansion coefficient of section A.

[0076] 1.4 Further properties of gradients It is also possible, and sometimes preferred, that a glass-ceramic dental body be characterized by a combination of gradients of one or more of the material properties defined herein. In one embodiment, the glass-ceramic dental body has a gradient of biaxial flexural strength and fracture toughness (K IC In one embodiment, the glass-ceramic dental body is characterized by a combination of gradients of two or more mechanical properties, such as a combination of a gradient of contrast ratio and a gradient of biaxial flexural strength and / or fracture toughness (K IC The optical properties of the material may be characterized by a combination of one or more gradients in mechanical properties and one or more gradients in optical properties, such as a combination of a gradient in optical properties of the material.

[0077] The gradient or gradients may be characterized by a gradual or step change in the respective properties. A gradual change is typically achieved when the glass-ceramic dental body is composed of a section B having a chemical composition that changes gradually in the direction from section C to section A. A step change is typically achieved when the glass-ceramic dental body is composed of a multi-layer structure. The structure of the glass-ceramic dental body is further described elsewhere in this disclosure.

[0078] Additionally or alternatively to multiple gradients, the glass-ceramic dental body may be characterized by its crystalline phase, as will be discussed in more detail in the next section.

[0079] 2.Crystal phase The glass-ceramic dental body has a predominant crystalline phase, which may be, but is not limited to, lithium disilicate, quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), or a stoichiometric or non-stoichiometric lithium alumosilicate (e.g., spodumene or spodumene solid solution).

[0080] The predominant crystalline phase of the glass-ceramic dental body is typically not lithium metasilicate, hi one embodiment, the glass-ceramic dental body does not contain lithium metasilicate crystalline phase in a mass fraction of more than 5 wt.%, or more than 3 wt.%, based on the total weight of the glass-ceramic dental body.

[0081] The sections may comprise different crystalline phases. In one embodiment of the invention, section A may comprise one or more crystalline phases different from the crystalline phase of section C (or vice versa). The crystalline phases of section C, section B, and / or section A may comprise one or more crystalline phases, such as lithium disilicate, lithium silicate, apatite (e.g., fluoroapatite), one or more quartz crystalline phases (e.g., α-quartz, α-quartz solid solution, and / or β-quartz solid solution), stoichiometric lithium aluminosilicates (e.g., eucryptite, spodumene, spodumene solid solution, and / or petalite), non-stoichiometric lithium aluminosilicate phases (e.g., Li with a keatite crystal structure ... 2 O Al 2 O 3 7.5SiO 2 ), cristobalite, lithium phosphate, magnesium silicate (e.g., enstatite), alkali zirconium silicate (e.g., sogdianite or zektzerite), diopside, or wollastonite.

[0082] Each of the sections may include at least one (e.g., one, two, or three) crystalline phases in a content that differs from the content of each crystalline phase in the other sections, including that a section may include 0 wt% of each crystalline phase.

[0083] Each of the sections of the glass-ceramic dental body may be composed of a glass-ceramic material. Thus, in certain embodiments, each of the sections of the glass-ceramic dental body is composed of a glass-ceramic material. Alternatively, section A may be composed of glass. This can be understood as section A being essentially free of liquid crystal phase (0 wt% liquid crystal phase). Section A may be composed of glass, and sections B and C may be composed of glass-ceramic material. Thus, in certain embodiments, section A is composed of glass, and sections B and C are composed of glass-ceramic material.

[0084] Each section of a glass-ceramic dental body composed of a glass-ceramic material can be defined by a predominant crystal phase and, optionally, by one or more minor crystal phases (i.e., one or more crystal phases that are present in the section in a content that is less than the content of the predominant crystal phase).

[0085] A glass-ceramic dental body may be defined by its predominant crystalline phase in section C. The predominant crystalline phase in section C may be lithium disilicate, quartz (e.g., α-quartz, α- or β-quartz solid solution), a stoichiometric lithium aluminosilicate (e.g., eucryptite, spodumene, spodumene solid solution, or petalite), or a non-stoichiometric lithium aluminosilicate (e.g., Li SiO 2 having a keatite crystal structure). 2 O Al 2 O 3 7.5SiO 2 ). In one embodiment, the predominant crystalline phase of section C is lithium disilicate or quartz (e.g., α-quartz, α- or β-quartz solid solution). The predominant crystalline phase of section C is typically (although this is not required) lithium disilicate. The predominant crystalline phase of section C is typically not lithium metasilicate. The predominant crystalline phase of section C may be present in an amount ranging from 20 to 80 wt%, based on the total weight of section C.

[0086] The main crystalline phase of section C may be the only crystalline phase of section C. However, section C typically contains one or more minor crystalline phases. The minor crystalline phase or phases may be lithium disilicate, lithium silicate, apatite (e.g., fluoroapatite), one or more quartz crystalline phases (e.g., α-quartz, α-quartz solid solution, and / or β-quartz solid solution), stoichiometric lithium aluminosilicates (e.g., eucryptite, spodumene, spodumene solid solution, and / or petalite), non-stoichiometric lithium aluminosilicate phases (e.g., Li with a keatite crystal structure). 2 O Al 2 O 3 7.5SiO 2 ), lithium phosphate, magnesium silicate (e.g., enstatite), alkali zirconium silicate (e.g., sogdianite or zexlerite), diopside, or wollastonite.

[0087] A glass-ceramic dental body may be defined by the predominant crystalline phase in its section A. The predominant crystalline phase in section A may be lithium disilicate, apatite, quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), or lithium aluminosilicate (LAS). The apatite may be, but is not limited to, fluoroapatite. The lithium aluminosilicate (LAS) may be eucryptite (LiAlSiO 4 ), spodumene (LiAl(SiO 3 ) 2 ), spodumene solid solution, or petalite (LiAlSi 4 O 10 ) or Li 2 O Al 2 O 3 7.5SiO 2 The lithium aluminosilicate phase may be a non-stoichiometric lithium aluminosilicate phase such as

[0088] The predominant crystalline phase of section A may be the only crystalline phase of section A. However, section A may contain one or more minor crystalline phases. The minor liquid crystal phase or phases may be lithium disilicate, lithium silicate, apatite (e.g., fluoroapatite), one or more quartz liquid crystal phases (e.g., α-quartz, α-quartz solid solution, and / or β-quartz solid solution), stoichiometric lithium aluminosilicates (e.g., eucryptite, spodumene, spodumene solid solution, and / or petalite), non-stoichiometric lithium aluminosilicate phases (e.g., Li 2 O Al 2 O 3 7.5SiO 2 ), lithium phosphate, magnesium silicate (e.g., enstatite), alkali zirconium silicate (e.g., sogdianite or zexlerite), diopside, or wollastonite.

[0089] Section B may have a predominant crystalline phase identical to that of section C or identical to that of section A. Section B may include one or more minor crystalline phases. The one or more minor liquid crystalline phases may be lithium disilicate, lithium silicate, apatite (e.g., fluoroapatite), one or more quartz liquid crystalline phases (e.g., α-quartz, α-quartz solid solution, and / or β-quartz solid solution), stoichiometric lithium aluminosilicates (e.g., eucryptite, spodumene, spodumene solid solution, and / or petalite), non-stoichiometric lithium aluminosilicate phases (e.g., Li 2 O Al 2 O 3 7.5SiO 2 ), lithium phosphate, magnesium silicate (e.g., enstatite), alkali zirconium silicate (e.g., sogdianite or zexlerite), diopside, or wollastonite.

[0090] In certain embodiments, section C has a predominant crystalline phase (e.g., lithium disilicate). The content of each crystalline phase decreases in the direction from section C to section A. This should be understood as meaning that the content of the crystalline phase in section C is higher than the content of the crystalline phase in section B, which is higher than the content of the crystalline phase in section A. This includes that section A may have a predominant crystalline phase different from section C, or that section A has essentially 0 wt% content of the crystalline phase that is the predominant crystal of section C (e.g., when section A is glass or when section A contains only other crystalline phases). It has been found by the inventors that when the content of the predominant crystalline phase in section C decreases in the direction from section C to section A, it is possible to readily provide a glass-ceramic dental body having particularly advantageous properties, such as one or more of the more specific material property gradients defined herein.

[0091] Additionally or alternatively, the amorphous phase (i.e., glass phase) content of the sections may increase in the direction from section C to section A. For example, section C may have a lower amorphous phase content than the amorphous phase content in section B, which may have a lower amorphous phase content than the amorphous phase content in section A. Section A may be comprised of an amorphous phase (i.e., glass) or may be comprised of a glass-ceramic material. Thus, in one embodiment, the glass-ceramic dental body is characterized in that the amorphous phase (i.e., glass phase) content of the sections increases in the direction from section C to section A.

[0092] The crystalline phase(s) (e.g., the primary crystalline phase and any secondary crystalline phase(s)) of Sections C, B, and A may be combined in different ways to provide a glass-ceramic dental body having advantageous properties as described herein. With respect to the liquid crystalline phase, the glass-ceramic dental body may be classified into three types: Type 1: Sections C and A have the same main crystal phase Type 2: Section C and Section A have different predominant crystalline phases Type 3: Glass as Section A

[0093] 2.1 Type 1: Section C and Section A have the same main crystalline phase Section C may have the same predominant crystalline phase as section A. In such cases, the predominant crystalline phase is typically the same for each of the sections of the glass-ceramic dental body. In one embodiment, the predominant crystalline phase of each of the sections is the same (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)), and the content of the predominant crystalline phase decreases from section C to section A. This should be understood as the content of the predominant crystalline phase in the bottom phase is higher than the content of the predominant crystalline phase in section B, which is higher than the content of the predominant crystalline phase in section A.

[0094] In one embodiment, the predominant crystalline phase in each of the sections is the same (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)), with the content of predominant crystalline phase decreasing from section C to section A. The glass-ceramic dental body is characterized by one or more of the following: The gradient of biaxial bending strength decreases from section C to section A. The fracture toughness (K IC ) gradient, A gradient of contrast ratio, decreasing from section C to section A. · The gradient of the coefficient of thermal expansion, decreasing or increasing from section C to section A.

[0095] In one embodiment, the predominant crystalline phase of each of the sections is lithium disilicate. The lithium disilicate content optionally decreases in the direction from section C to section A. In one embodiment, the predominant crystalline phase of each of the sections is lithium disilicate. The lithium disilicate content optionally decreases in the direction from section C to section A. Sections C and B, and optionally section A, contain lithium silicate as one or more quartz crystalline phases, (e.g., α-quartz and / or α-quartz solid solution), and / or one or more minor crystalline phases. In one embodiment, the predominant crystalline phase of each of the sections is lithium disilicate. The lithium disilicate content optionally decreases from section C to section A. The glass-ceramic dental body is characterized by a gradient in biaxial flexural strength, which decreases from section C to section A, and / or a gradient in fracture toughness (K IC ) and this fracture toughness (K IC ) decreases from section C to section A.

[0096] In one embodiment, the predominant crystalline phase of each of the sections is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution). The quartz content optionally decreases from section C to section A. In one embodiment, the predominant crystalline phase of each of the sections is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution). The quartz content optionally decreases from section C to section A. Sections C, B, and A contain lithium disilicate as a minor crystalline phase. Optionally, sections C and B contain a stoichiometric lithium aluminosilicate (e.g., spodumene or spodumene solid solution) as another minor crystalline phase. In one embodiment, the predominant crystalline phase of each of the sections is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution). The quartz content optionally decreases in a direction from section C to section A. The glass-ceramic dental body is characterized by a gradient of contrast ratio, which decreases from section C to section A.

[0097] 2.2 Type 2: Section C and Section A with different main crystalline phases It is also possible that section C has a different predominant crystalline phase (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)) than the predominant crystalline phase of section A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)). In such a case, section C and section B may have the same predominant crystalline phase that is different from the predominant crystalline phase of section A. Alternatively, section A and section B may have the same predominant crystalline phase that is different from the predominant crystalline phase of section C. Thus, the predominant crystalline phase may switch from section C to section B, or from section B to section A. It is also possible that each of the sections has a different predominant crystalline phase.

[0098] If section C has a predominant crystalline phase different from the predominant crystalline phase of section A, the predominant crystalline phase of section C may decrease in content from section C to section A, but is not the predominant crystalline phase of each section. Such a decrease in the crystalline phase that is the predominant crystalline phase of section C from section C to section A is shown, for example, in connection with FIG. 5. Additionally or alternatively, the predominant crystalline phase of section A may decrease in content in the direction from section A to section C, but is not the predominant crystalline phase of each section.

[0099] In one embodiment, the predominant crystalline phase in section C (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)) is different from the predominant crystalline phase in section A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)), and optionally, the content of the predominant crystalline phase in section C decreases in the direction from section C to section A, or the content of the predominant crystalline phase in section A decreases in the direction from section A to section C. In one embodiment, the predominant crystalline phase in section C (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)) is different from the predominant crystalline phase in section A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)), and the content of the predominant crystalline phase in section C decreases in the direction from section C to section A, or the content of the predominant crystalline phase in section A decreases in the direction from section A to section C. In one embodiment, the predominant crystalline phase in section C (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate LAS) is different from the predominant crystalline phase in section A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)), and optionally the content of the predominant crystalline phase in section C decreases in the direction from section C to section A, or the content of the predominant crystalline phase in section A decreases in the direction from section A to section C. The glass-ceramic dental body is characterized by one or more of the following, namely: The gradient of biaxial bending strength decreases from section C to section A. The fracture toughness (K IC ) gradient, A gradient of contrast ratio, decreasing from section C to section A. · The gradient of the coefficient of thermal expansion, decreasing or increasing from section C to section A.

[0100] In one embodiment, the predominant crystalline phase in section C is lithium disilicate and the predominant crystalline phase in section A is apatite (e.g., fluoroapatite) or quartz (e.g., α-quartz or α-quartz solid solution or β-quartz solid solution). In another embodiment, the predominant crystalline phase in section C is β-quartz solid solution and the predominant crystalline phase in section A is α-quartz or α-quartz solid solution.

[0101] In one embodiment, section C has a predominant crystalline phase that is lithium disilicate, and optionally the content of lithium disilicate decreases from section C to section A, and sections B and A have a predominant crystalline phase that is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution). In one embodiment, section C has a predominant crystalline phase that is lithium disilicate, and the content of lithium disilicate decreases from section C to section A, and sections B and A have a predominant crystalline phase that is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution). In one embodiment, section C has a predominant crystalline phase that is lithium disilicate, and optionally the content of lithium disilicate decreases from section C to section A, section C includes one or more quartz crystalline phases (e.g., α-quartz α-quartz solid solution and / or β-quartz solid solution) as a minor crystalline phase, and sections B and A have a predominant crystalline phase that is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), and sections B and A include lithium disilicate as a minor crystalline phase. In one embodiment, section C has a predominant crystalline phase that is lithium disilicate, and optionally the content of lithium disilicate decreases from section C to section A, and sections B and A have a predominant crystalline phase that is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution). The glass ceramic dental body is characterized by a gradient in thermal expansion coefficient, which decreases or increases from section C to section A, and / or a gradient in biaxial flexural strength, which decreases from section C to section A, and / or a gradient in fracture toughness (K IC) and this fracture toughness (K IC ) decreases from section C to section A.

[0102] In one embodiment, sections C and B have a predominant crystalline phase that is lithium disilicate, and optionally the content of lithium disilicate decreases from section C to section A, with section A having a predominant crystalline phase that is apatite (e.g., fluoroapatite). In one embodiment, sections C and B have a predominant crystalline phase that is lithium disilicate, and optionally the content of lithium disilicate decreases from section C to section A, with sections C and B including one or more quartz crystalline phases (e.g., α-quartz and / or one or more quartz solid solutions, such as α-quartz solid solution) as minor crystalline phases, with section A having a predominant crystalline phase that is apatite (e.g., fluoroapatite). In one embodiment, sections C and B have a predominant crystalline phase that is lithium disilicate, and optionally the content of lithium disilicate decreases from section C to section A, with section A having a predominant crystalline phase that is apatite (e.g., fluoroapatite). The glass-ceramic dental body is characterized by a gradient in biaxial flexural strength, which decreases from section C to section A, and / or a decrease in fracture toughness (K IC ) and this fracture toughness (K IC ) decreases from section C to section A.

[0103] 2.3 Type 3: Glass as Section A In another embodiment, section A is composed of glass and sections B and C are composed of glass-ceramic materials. When section A is composed of glass, the predominant crystalline phase may be the same or different for sections C and B of the glass-ceramic dental body. The inventors have found that when section A is composed of glass, it is readily possible to provide a glass-ceramic dental body having particularly advantageous properties, such as one or more of the more specific material property gradients defined herein.

[0104] In one embodiment, section A is composed of glass, the predominant crystalline phase is the same for sections C and B of the glass-ceramic dental body, and optionally the content of the predominant crystalline phase (and considering that section A is essentially free of crystalline phase) decreases from section C to section B. In one embodiment, section A is composed of glass, sections B and C are composed of glass-ceramic material, and the glass-ceramic dental body is characterized by one or more of the following, namely: The gradient of biaxial bending strength decreases from section C to section A. The fracture toughness (K IC ) gradient, A gradient of contrast ratio, decreasing from section C to section A. · The gradient of the coefficient of thermal expansion, decreasing or increasing from section C to section A.

[0105] In one embodiment, section A is comprised of glass, and the predominant crystalline phase of sections C and B is lithium disilicate, optionally with the lithium disilicate content decreasing from section C to section B (and considering section A to be essentially free of crystalline phase). In one embodiment, section A is comprised of glass, and the predominant crystalline phase of sections C and B is lithium disilicate, optionally with the lithium disilicate content decreasing from section C to section A (and considering section A to be essentially free of crystalline phase). The glass-ceramic dental body is characterized by a gradient in biaxial flexural strength that decreases from section C to section A, and / or a gradient in fracture toughness (KIC) that decreases from section C to section A, and / or a gradient in contrast ratio that decreases from section C to section A.

[0106] 2.4 Further specific combinations of crystalline phases The glass-ceramic dental body may be characterized by a particular combination of liquid crystal phases according to the embodiments defined in any one of Tables I-III below.

[0107] The glass-ceramic dental body may include a section having a predominant crystalline phase according to any one of embodiments AA-EE defined in Table I herein below.

[0108] [Table 1]

[0109] The glass-ceramic dental body may include a section having a predominant crystalline phase according to any one of embodiments A-F defined in Table II herein below.

[0110] [Table 2]

[0111] The glass-ceramic dental body may include sections having a predominant crystalline phase and including one or more (or all) minor crystalline phases according to any one of the embodiments a-j defined in Table III hereinbelow.

[0112] [Table 3]

[0113] In any one of embodiments AA through EE of Table I, embodiments A through F of Table II, or embodiments a through j of Table III, the content of the crystalline phase that is the predominant crystalline phase in section C may decrease from section C to section A.

[0114] In addition to or as an alternative to gradients and / or crystalline phases, a glass-ceramic dental body may be characterized by its chemical composition, which is described in more detail in the next section.

[0115] 3.Chemical composition Each of the sections of the glass-ceramic dental body has a chemical composition that is different from the chemical composition of the other sections. The chemical compositions of each of the sections typically differ from one another such that each of the sections includes at least one (e.g., one, two, or three) crystalline phases in a content that is different from the content of each of the crystalline phases in the other sections.

[0116] The chemical composition of each section of the glass-ceramic dental body may be adjusted or selected such that the respective section comprises one or more liquid crystalline phases as defined herein (such as a primary liquid crystalline phase and, optionally, one or more secondary liquid crystalline phases), which may be understood, for example, as being adjusted or selected such that the one or more crystalline phases of section C of the glass-ceramic dental body can be obtained when preparing the glass-ceramic dental body by heating (e.g., sintering or hot compacting) a body of glass powder and / or glass ceramic powder as described herein in connection with the method according to the invention.

[0117] For example, if the chemical composition of a section of a glass-ceramic dental body is adjusted or selected such that the section contains a high purity α-quartz crystalline phase, the chemical composition may be Al 2 O 3 , Ga 2 O 3 , and / or In 2 O 3 The chemical composition of the section of the glass-ceramic dental body should be selected so as to be essentially free of Al. Some residual amounts of the aforementioned components may be unavoidable due to impurities in the raw materials. On the other hand, if the chemical composition of the section of the glass-ceramic dental body is adjusted or selected so that the section contains an α-quartz solid solution crystalline phase, the chemical composition should be selected so as to be essentially free of Al. 2 O 3 (or alternatively, G a 2O 3 Or In 2 O 3 When the chemical composition of a section of a glass-ceramic dental body is adjusted or selected such that the section contains a stoichiometric or non-stoichiometric lithium aluminosilicate crystalline phase, the chemical composition is selected to contain Al 2 O 3 Other embodiments will be apparent to those skilled in the art.

[0118] 3.1 Section C Section C is SiO 2 , Li 2 O, and Li 2 Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 Additionally, section C typically contains a nucleating agent (e.g., P 2 O 5 , and / or a metal such as Cu). Additional components include GeO 2 , CaO, MgO, SrO, ZnO, Y 2 O 3 , Al 2 O 3 , La 2 O 3 , ZrO 2 , or coloring and / or fluorescent components (e.g., selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0119] Section C may comprise (or consist essentially of, or consist of) the following components: 60.0~85.0wt.% SiO 2 , 0.0-10.0wt% GeO 2 , 5.0-20.0wt% Li 2 O. 0.5-15.0wt% Li 2 Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O), 0.0~8.0wt.% P 2 O 5 (For example, 0.5 to 8.0 wt.% P 2 O 5 ), 0.0-12.0 wt.% CaO, MgO, SrO, ZnO, or mixtures thereof; 0.0~20.0wt% Y 2 O 3 , Al 2 O 3 , La 2 O 3 or mixtures thereof, 0.0-12.0wt.% ZrO 2 , 0.0-5.0 wt. % of a coloring and / or fluorescent component, optionally selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof; and 0.0-1.0wt%, optionally 0.0-0.5wt% of other ingredients (e.g., F, B 2 O 3 , metals, and / or residual impurities).

[0120] K 2 O, Na 2 O, Rb 2 O, and Cs 2 Each of K and O may be present in Section C in an amount of 0.0 to 12.0 wt.%. 2 O, Na 2 O, Rb 2 O, and / or Cs 2 SiO is selected to comprise 0.5 to 15.0 wt.% of Section C. 2 The amount of GeO 2 For example, a certain amount of GeO 2 In the presence of SiO 2 The amount of can be reduced by that amount.

[0121] The chemical composition may vary depending on the predominant crystalline phase (and one or more minor crystalline phases) present in section C. The chemical composition of section C may be selected such that section C of the glass-ceramic dental body has a predominant crystalline phase that is lithium disilicate or quartz (e.g., α-quartz, α- or β-quartz solid solution). The chemical composition may be selected such that section C of the glass-ceramic dental body has a predominant crystalline phase and optionally one or more minor crystalline phases as described herein above for section C.

[0122] The components of Section C described herein above may be selected to total 100.0 wt%, based on the total weight of Section C.

[0123] 3.2 Section B Section B is SiO 2 , Li 2 O, and Li 2 Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 Section B typically contains a nucleating agent (e.g., CuO, P 2 O 5 , and / or metals such as Cu). Additional components include F, B 2 O 3 , GeO 2 , CaO, MgO, SrO, ZnO, Y 2 O 3 , Al 2 O 3 , La 2 O 3 , ZrO 2 , or coloring and / or fluorescent components (e.g., selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0124] Section B may comprise (or consist essentially of or consist of) the following components: 55.0-80.0wt.% SiO 2 , 0.0-10.0wt% GeO 2 , 5.0-30.0wt% Li 2 O. 0.5-15.0wt% Li 2 Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O), 0.0~8.0wt.% P 2 O 5 (For example, 0.5 to 8.0 wt.% P 2 O 5 ), 0.0-12.0 wt.% CaO, MgO, SrO, ZnO, or mixtures thereof; 0.0~20.0wt% Y 2 O 3 , Al 2 O 3 , La 2 O 3 or mixtures thereof, 0.0-12.0wt.% ZrO 2 , 0.0-5.0 wt. % of a coloring and / or fluorescent component, optionally selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof; and 0.0-1.0 wt%, optionally 0.0-0.5 wt% of one or more other components (e.g., F, B 2 O 3 , metals, and / or residual impurities).

[0125] K 2 O, Na 2 O, Rb 2 O, and Cs 2Each of K and O may be present in Section B in an amount of 0.0 to 12.0 wt.%. 2 O, Na 2 O, Rb 2 O, and / or Cs 2 % of Section B. 2 The amount of GeO 2 For example, a certain amount of GeO 2 In the presence of SiO 2 The amount of can be reduced by that amount.

[0126] The chemical composition may vary depending on the predominant crystalline phase (and one or more minor crystalline phases) present in section B. The chemical composition of section B may be selected such that section B of the glass-ceramic dental body has a predominant crystalline phase that is lithium disilicate or quartz (e.g., α-quartz, β-quartz solid solution, or α-quartz solid solution). The chemical composition may be selected such that section B of the glass-ceramic dental body has a predominant crystalline phase and optionally one or more minor crystalline phases as described herein above for section B.

[0127] The components of Section B described herein above may be selected to total 100.0 wt%, based on the total weight of Section B.

[0128] 3.3 Section A The chemical composition of section A may vary depending on whether section A is comprised of a glass or a glass-ceramic. If section A is comprised of a glass-ceramic, the chemical composition may vary depending on the predominant crystalline phase (and one or more minor crystalline phases) present in section A.

[0129] The chemical composition of section A may be selected such that section A has a predominant crystalline phase that is lithium disilicate, quartz (e.g., α-quartz, β-quartz solid solution, or α-quartz solid solution). In such a case, section A may be selected such that section A has a predominant crystalline phase that is lithium disilicate, quartz (e.g., α-quartz, β-quartz solid solution, or α-quartz solid solution).2 , Li 2 O, Li 2 Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O), typically containing a nucleating agent (e.g., P 2 O 5 , and / or metals). Additional components include F, B 2 O 3 , GeO 2 , CaO, MgO, SrO, ZnO, Y 2 O 3 , Al 2 O 3 , La 2 O 3 , ZrO 2 , or coloring and / or fluorescent components (e.g., selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0130] In one embodiment, section A is composed of a glass ceramic (e.g., having lithium disilicate or quartz as the predominant crystalline phase). Section A comprises (consists essentially of, or consists of) the following components: 59.0-90.0wt.% SiO 2 , 0.0-15.0wt% GeO 2 , 2.0-20.0wt% Li 2 O. 0.0~15.0wt.% Li 2 Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O), 0.0-9.0wt.% P 2 O 5 , 0.0-12.0 wt.% CaO, MgO, SrO, ZnO, or mixtures thereof; 0.0~20.0wt% Y 2 O 3 , Al 2 O 3 , La 2 O 3 or mixtures thereof, 0.0-12.0wt.% ZrO 2 , 0.0-5.0 wt% of a coloring and / or fluorescent component, optionally selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof, and 0.0-1.0 wt%, optionally 0.0-0.5 wt% of one or more other components (e.g., F, B 2 O 3 , metals, and / or residual impurities).

[0131] In a more specific embodiment, section A is composed of a glass ceramic (e.g., having lithium disilicate or quartz as the predominant crystalline phase). Section A comprises (consists essentially of, or consists of) the following components: 60.0~90.0wt.% SiO 2 , 0.0-5.0wt% GeO 2 , 5.0-20.0wt% Li 2 O. 0.5-15.0wt% Li 2 Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O), 0.5-8.0wt.% P 2 O 5 , 0.0-12.0 wt.% CaO, MgO, SrO, ZnO, or mixtures thereof; 0.0~20.0wt% Y 2 O 3 , Al 2O 3 , La 2 O 3 or mixtures thereof, 0.0-12.0wt.% ZrO 2 , 0.0-5.0 wt. % of a coloring and / or fluorescent component, optionally selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof, and 0.0-0.5 wt. % of one or more other components (e.g., F, B 2 O 3 , metals, and / or residual impurities).

[0132] K 2 O, Na 2 O, Rb 2 O, and Cs 2 Each of K and O may be present in Section A in an amount of 0.0 to 12.0 wt.%. 2 O, Na 2 O, Rb 2 O, and / or Cs 2 % of Section A. 2 The amount of GeO 2 For example, a certain amount of GeO 2 In the presence of SiO 2 The amount of can be reduced by that amount.

[0133] Alternatively, the chemical composition of section A may be selected such that section A of the glass-ceramic dental body has a predominant crystalline phase that is apatite (e.g., fluoroapatite). In such a case, section A may be selected such that section A is composed of SiO 2 , K 2 O, Na 2 O, CaO, and typically a nucleating agent (e.g., P 2 O 5 , and / or metal). Additional components include Li 2 O, TiO 2 , F, B 2 O 3 , GeO2 , CaO, MgO, SrO, ZnO, Y 2 O 3 , Al 2 O 3 , La 2 O 3 , ZrO 2 , or coloring and / or fluorescent components (e.g., selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0134] In one embodiment, section A is composed of a glass ceramic (e.g., having apatite as the predominant crystalline phase). Section A comprises (consists essentially of, or consists of) the following components: 50.0-75.0wt.% SiO 2 , 0.0~12.0wt.% K 2 O. 0.0-12.0wt% Na 2 O. 0.0-12.0 wt% CaO, 0.5-10.0wt.% P 2 O 5 , 0.0-12.0wt% Li 2 O. 0.0-20.0 wt.% SrO, 0.0-8.0 wt.% ZnO, 0.0-8.0wt% Al 2 O 3 , 0.0-8.0wt.% ZrO 2 , TiO 2 or mixtures thereof, 0.0~3.0wt.% F, 0.0~5.0wt.% B 2 O 3 , 0.0-5.0 wt. % of a coloring and / or fluorescent component, optionally selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof; 0.0-1.0 wt%, optionally 0.0-05 wt% of one or more other components (e.g., metals, and / or residual impurities).

[0135] In a more specific embodiment, section A is composed of a glass ceramic (e.g., having apatite as the predominant crystalline phase). Section A comprises (consists essentially of, or consists of) the following components: 50.0-75.0wt.% SiO 2 , 0.0~12.0wt.% K 2 O. 0.0-12.0wt% Na 2 O. 1.0-12.0 wt% CaO, 0.5-8.0wt.% P 2 O 5 , 0.0-12.0wt% Li 2 O. 0.0-20.0 wt.% SrO, 0.0-8.0 wt.% ZnO, 0.0-8.0wt% Al 2 O 3 , 0.0-8.0wt.% ZrO 2 , TiO 2 or mixtures thereof, 0.0~3.0wt.% F, 0.0~5.0wt.% B 2 O 3 , 0.0-5.0 wt. % of a coloring and / or fluorescent component, optionally selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof; 0.0-5.0 wt% of one or more other components (e.g., metals, and / or residual impurities).

[0136] The chemical composition of section A may be selected such that section A of the glass-ceramic dental body has a predominant crystalline phase and optionally one or more minor crystalline phases, as described herein above for section A.

[0137] In yet another alternative, the chemical composition of section A may be selected such that section A is composed of glass. In such a case, section A may be composed of SiO 2 , K 2 O, and Na 2 O. Additional components include Li 2 O, F, B 2 O 3 , CaO, MgO, SrO, ZnO, Al 2 O 3 , or coloring and / or fluorescent components (e.g., selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0138] In one embodiment, section A is composed of glass. Section A comprises (consists essentially of, or consists of) the following components: 59.0-90.0wt.% SiO 2 , 0.0~20.0wt.% E 1 (I) 2 O. 0.0~15.0wt% E 2 (II) O, 0.0~15.0% E 3 (III) 2 O 3 , 0.0~8.0wt.% E 4 (IV)O 2 , 0.0~15.0wt.% E 5 (V) 2 O 5 , 0.0~8.0wt.% E 6 (VI)O 3 , 0.0-2.0 wt% of mixed valence metal oxides, 0.0~5.0wt% F, 0.0-1.0 wt % of one or more other components (e.g., additional coloring and / or fluorescent components, and / or residual impurities); During the ceremony, E 1 (I) 2 O is a monovalent metal oxide (Me 1 (I) 2 O) and mixtures thereof; E 2 (II)O is a divalent metal oxide (Me 2 (II) O) and mixtures thereof; E 3 (III) 2 O 3 is a trivalent metal oxide (Me 3 (III) 2 O 3 ) and mixtures thereof; E 4 (IV)O 2 is a tetravalent metal oxide Me 4 (IV)O 2 and mixtures thereof; E 5 (V) 2 O 5 is a pentavalent metal oxide (Me 5 (V) 2 O 5 ) and mixtures thereof; E 6 (VI)O 3 is a hexavalent metal oxide (Me 6 (VI)O 6 ) and mixtures thereof.

[0139] Monovalent metal oxides (Me 1 (I) 2 O) is Na 2 O, Li 2 OK 2 O, Rb 2 O, Cs2 O, and mixtures thereof.

[0140] Divalent metal oxides (Me 2 (II)O) may be selected from CaO, BaO, MgO, SrO, ZnO, SnO, and mixtures thereof.

[0141] Trivalent metal oxides (Me 3 (III) 2 O 3 ) is Al 2 O 3 , La 2 O 3 , B 2 O 3 , Y 2 O 3 , Yb 2 O 3 , Ga 2 O 3 , In 2 O3, and mixtures thereof.

[0142] Tetravalent metal oxide Me 4 (IV)O 2 is ZrO 2 , TiO 2 , SnO 2 , GeO 2 and mixtures thereof.

[0143] Pentavalent metal oxides (Me 5 (V) 2 O 5 ) is Ta 2 O 5 , Nd 2 O 5 , P 2 O 5 and mixtures thereof.

[0144] Hexavalent metal oxides (Me 6 (VI)O 6 ) is WO 3 , MoO 3 and mixtures thereof.

[0145] Mixed valence metal oxides are mixed trivalent / tetravalent metal oxides (Me 3 / 4 (III, IV) 4 O 7 ) may also be used.

[0146] In a more specific embodiment, section A is composed of glass. Section A comprises (consists essentially of, or consists of) the following components: 60.0~80.0wt.% SiO 2 , 1.0-18.0wt.% K 2 O. 0.5-12.0wt% Na 2 O. 0.0-12.0 wt% CaO, 0.0-12.0wt% Li 2 O. 0.0-8.0 wt.% SrO, ZnO, or mixtures thereof; 0.0-10.0wt% Al 2 O 3 , 0.0~5.0wt.% F, 0.0~10.0wt.% B 2 O 3 , 0.0-15.0wt.% P 2 O 5 , 0.0-5.0 wt. % of a coloring and / or fluorescent component, optionally selected from the group of oxides consisting of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof; 0.0-0.5 wt% of one or more other components (e.g., residual impurities).

[0147] The components of Section A described herein above may be selected to total 100.0 wt%, based on the total weight of Section A.

[0148] In addition to or alternatively to gradients, crystalline phases, and / or chemical composition, a glass-ceramic dental body may be characterized by its structure and / or shape.

[0149] 4. Structure and Shape The glass ceramic dental body is made up of three consecutive sections, namely: Section A, Section B, and Includes Section C. Each of the sections has a chemical composition that is different from the chemical composition of the other sections.

[0150] In one embodiment, the glass-ceramic dental body is constructed of three consecutive sections: Section A, Section B, and Section C.

[0151] 4.1 Dental blanks The glass ceramic dental body may be a glass ceramic dental blank, such as a dental mill blank or a press blank. A dental blank (e.g., a dental mill blank) is characterized by the following: Section A forms the top section of the dental blank; Section B forms the middle section of the dental blank; Section C forms the bottom section of the dental blank.

[0152] The glass ceramic dental blank is not particularly limited with respect to its shape or dimensions, as long as it is suitable for use in preparing a dental restoration (e.g., using a CAD / CAM process or using hot pressing into a mold). The glass ceramic dental blank can have the shape of, but is not limited to, a rectangular block, an ingot, a disk, a cylinder, a dental preform (e.g., an abutment preform, or a tooth sector), a cone, a cone segment, a pyramid, or a pyramid segment. The glass ceramic dental blank may include additional components on the outside of the glass ceramic dental blank that are not part of the sections described herein. For example, the dental blank may include on its outside a retaining pin, a support layer, a protective layer, a printing layer, or a sacrificial layer, such as a (thin) layer of glass ceramic material that is removed (e.g., by milling) when forming a dental restoration from the blank. In one embodiment, the dental blank is a dental mill blank having the shape of a disk, a cylinder, or a rectangular block. The dental mill blank may include a retaining pin for holding the glass ceramic dental mill blank in an apparatus when it is machined using, for example, a CAD / CAM process. The retaining pin is not considered part of the section of the dental mill blank.

[0153] Each section of the glass ceramic dental blank may have a specific height relative to the total height of the glass ceramic dental blank. The total height of the glass ceramic dental blank can be understood as the dimension of the glass ceramic dental blank in the z-direction. The z-direction is the direction that intersects each of the sections. For example, in the case of a rectangular or disc-shaped dental blank, the total height can be determined as the distance of a perpendicular line between the outer surface of the top section and the opposing outer surface of the bottom section. This perpendicular line intersects all of the sections of the dental blank. The height of a section should be understood as the maximum height of the section in the z-direction. This is independent of whether a relative height or an absolute height is defined herein. Thus, the definition of the height of a section (e.g., a relative height or an absolute height) used herein does not necessarily mean that the height of the section is constant, although this is possible.

[0154] Each of the sections may have a substantially constant height. By "substantially constant height" it is meant that the height of the sections does not vary by more than 5% relative to the average height of the sections. The bottom section may have a height in the range of 30-75%, 40-75%, 45-70%, or 50-70% of the total height of the glass ceramic dental blank. The middle section may have a height in the range of 5-40%, 10-30%, or 15-25% of the total height of the glass ceramic dental blank. The top section may have a height in the range of 5-35%, 10-30%, or 15-25% of the total height of the glass ceramic dental blank.

[0155] 4.2 Dental restorations The glass ceramic dental body may be a dental restoration. The dental restoration may have the following features: Section A forms the upper portion of the dental restoration (e.g., part or all of the incisal zone); Section B forms the middle part of the dental restoration (e.g. part or all of the transition zone between the incisal zone and the dentin zone), Section C forms the lower part of the dental restoration (eg, part or all of the dentin zone).

[0156] The dental restoration may be, but is not limited to, a crown, partial crown, abutment, abutment crown, inlay, onlay, veneer, shell, or multi-unit framework, or a bridge (e.g., 2-, 3-, or 4-unit bridge), implant bridge, etc. The dental restoration may have a desired color. The dental restoration may have a color that matches a shade according to the VITA classical A1-D4® shade guide with VITA Bleached Shades manufactured by Vita Zahnfabrik. The shade may be, but is not limited to, A1, A2, A3.5, A4, B1, B2, B3, B4, C1, C2, C3, C4, D1, D2, D3, D4, BL1, or BL2.

[0157] The dental restoration may include a glazing. In one embodiment, the dental restoration includes at least a first glazing and a second glazing. The first glazing has a lower coefficient of thermal expansion than the coefficient of thermal expansion of the second glazing. The first glazing is present on a surface area of ​​the portion of the dental restoration that has a lower coefficient of thermal expansion. The second glazing is present on a surface area of ​​the portion of the dental restoration that has a higher coefficient of thermal expansion. In that context, the terms "lower" and "higher" shall be understood in relation to each other.

[0158] 4.3 Structure The glass-ceramic dental body may have a multi-layer structure. Each of the sections A-C may be composed of one or more layers, such as 2 layers or 1 layer, such as 1-8 layers, 1-6 layers, 1-4 layers, 1-3 layers. Each of the layers may differ in its chemical composition. When the glass-ceramic dental body has a multi-layer structure, the section A may be the layer A, the section C may be the layer C, and the section B may be formed by at least one intermediate layer between the layers A and C. Each layer has a chemical composition different from the chemical composition of the other layers. The at least one intermediate layer may be 2 layers or 1 layer, such as 1-8 layers, 1-6 layers, 1-4 layers, 1-3 layers.

[0159] When the glass-ceramic dental body has a multi-layer structure, one or more gradients described herein may be characterized in that the properties of each of the one or more gradients change from layer to layer in a stepwise manner from Layer C to Layer A. Additionally or alternatively, the content of a crystalline phase (e.g., a predominant crystalline phase in a bottom layer) may change (e.g., decrease) from layer to layer in a stepwise manner from Layer C to Layer A.

[0160] The layers of the glass-ceramic dental body are not particularly limited with respect to their dimensions and shapes. One or more layers may be non-planar. For example, one or more layers may have one or two faces (e.g., an interface between two layers, or an outer surface depending on the location of the layer within the dental body) that are curved, e.g., have a positive or negative curvature (e.g., are convex or concave). It is also possible for one or more layers to have a height that increases uniformly or non-uniformly (e.g., in the form of a cone) over at least a portion of the layer. One or more layers, optionally all layers, may be substantially planar. In that context, the term "substantially planar" means that the layer is planar and within a tolerance of 5% of the average thickness of the layer. The layers of the glass-ceramic dental body may be arranged such that the boundaries of the layers are substantially parallel to each other.

[0161] Alternatively, the glass-ceramic dental body has an intermediate section having a chemical composition that changes gradually in the direction from section C to section A. In this alternative, the glass-ceramic dental body typically does not include separate layers. Sections A and C may have an essentially homogenous chemical composition. This can be understood as sections A and C being portions of the glass-ceramic dental body whose chemical composition does not change in the direction from section C to section A.

[0162] The glass-ceramic dental body is typically a heat-treated (e.g. (fully) sintered or hot compacted) glass-ceramic dental body. The glass-ceramic dental body may be obtained by heat treatment at a maximum temperature in the range of 650-1050°C. The glass-ceramic dental body may be obtained by (fully) sintering at a maximum sintering temperature in the range of 700-1050°C, for example in the range of 780-980°C, for example in the range of 820-940°C. The glass-ceramic dental body may be obtained by hot compacting at a maximum temperature in the range of 650-850°C, for example in the range of 700-800°C, and at a pressure in the range of 5-50 MPa, for example in the range of 10-30 MPa.

[0163] II. Method of Preparing a Glass-Ceramic Dental Body One aspect of the present invention provides a method for preparing a glass-ceramic dental body according to one embodiment of the present invention. The process comprises the following steps: providing two or more powders selected from glass powders, glass-ceramic powders, and mixtures thereof; Preparing a compact from the powder; and subjecting the compact to a heat treatment to obtain a glass-ceramic dental body.

[0164] A compact typically consists of three successive powder sections, namely: Powder Section A, Powder Section B, and Powder section C, including The weight ratio of the two or more powders is different in each of the powder sections.

[0165] 1. Providing a glass powder and / or a glass ceramic powder The method includes providing two or more powders selected from glass powders, glass ceramic powders, and mixtures thereof. The powders differ in their chemical composition. In one embodiment, the two or more powders are two or more glass powders.

[0166] The two or more powders may be two powders (e.g., two glass powders). However, it is also possible to use more than two powders, such as three powders (e.g., three glass powders), or more than three powders. In certain embodiments, two powders (i.e., a first powder and a second powder) are used to prepare the glass-ceramic dental body. In certain other embodiments, three powders (i.e., a first powder, a second powder, and a third powder) are used to prepare the glass-ceramic dental body.

[0167] Each of the glass powders is typically provided by melting chemical starting materials suitable for preparing the glass. The starting materials may be melted at a temperature of 1300-1650°C (e.g., 1450-1650°C) for a period of 30 minutes to 10 hours (e.g., 30 minutes to 3 hours). The melt may be poured into water to freeze the glass. To increase the homogeneity of the glass, the glass may be remelted under the same or similar conditions and re-frozen in water. Each of the resulting glasses may be dried in an oven. Each of the resulting glasses may be milled to obtain a glass powder. The volumetric median particle size d of each of the glass powders is 50 may be in the range of 5 to 30 μm, such as in the range of 10 to 20 μm. 98 may be less than 60 μm, such as less than 50 μm.50 and the volumetric top cut particle size d 98 may be determined, for example, by laser diffraction according to ISO 13320 (ISO 13320:2009).

[0168] Each of the powders may be combined with one or more additives, such as, but not limited to, one or more pigments, one or more fluorescent pigments, one or more pressing aids, and / or one or more binders. Suitable pigments may be, but are not limited to, doped spinel, doped zirconium oxide, zirconium oxide, doped zirconium silicate, doped yttrium silicate, or tin oxide. Suitable pressing aids may be, but are not limited to, polyethylene glycol or stearate. Suitable binders may be, but are not limited to, polyvinyl alcohol and cellulose derivatives, such as sodium carboxymethylcellulose.

[0169] The powder may be provided in dry form, optionally in combination with one or more additives. The powder may be provided in the form of a dry blend together with one or more additives. The dry blend may be a granular mixture or may be in the form of granules. The granules may be prepared by granulating the powder with one or more additives, typically including one or more binders, in a granulation process known in the art. The dry blend may comprise the powder in an amount of at least 90 wt%, based on the total weight of the dry blend. The one or more additives may be present in the dry blend in an amount ranging from 0.1 to 10.0 wt%, such as from 0.3 to 5.0 wt%, based on the total weight of the dry blend. The one or more binders may be present in the dry blend in an amount ranging from 0.1 to 5.0 wt%, such as from 0.3 to 3.0 wt%, based on the total weight of the dry blend. The one or more pressing aids may be present in the dry blend in an amount ranging from 0.1 to 3.0 wt%, such as from 0.1 to 1.0 wt%, based on the total weight of the dry blend.

[0170] Alternatively, the powder may be provided in a liquid form, such as in the form of a suspension, typically in the form of an aqueous suspension, optionally in combination with one or more additives. The suspension may be a slurry. The suspension may include the powder in an amount ranging from 30 to 90 wt%, such as 40 to 70 wt%, based on the total weight of the suspension. The suspension may include one or more additives (e.g., one or more pigments, one or more fluorescent pigments, one or more pressing aids, and / or one or more binders) in an amount ranging from 0.1 to 10.0 wt%, such as 0.3 to 5.0 wt%, based on the total dry weight of the suspension. Suitable pigments, fluorescent pigments, pressing aids, and binders are known to those skilled in the art and may be, but are not limited to, those mentioned above. The one or more binders may be present in an amount ranging from 0.1 to 5.0 wt%, such as 0.3 to 3.0 wt%, based on the total weight of the suspension dry weight. The one or more pressing aids may be present in an amount ranging from 0.1 to 3.0 wt%, such as 0.1 to 1.0 wt%, based on the total dry weight of the suspension. Additionally or alternatively, the suspension may include one or more adjuvants, such as one or more rheology modifiers (e.g., xanthan or starch), one or more dispersing agents (e.g., polymers or lecithin), one or more buffering agents, and / or pH adjusters (e.g., acids such as acetic acid or hydrochloric acid). The suspension may include one or more adjuvants in an amount ranging from 0.1 to 3.0 wt%, based on the total weight of the suspension.

[0171] 2. Preparation of Compacts The method further includes preparing a compact from the powder (e.g., glass powder). The compact may be porous.

[0172] The green body may be prepared by additive manufacturing, such as stereolithography, inkjet printing, screen printing, powder bed printing, or fused deposition modeling (fused filament manufacturing). When the green body is prepared by additive manufacturing, the green body may have the shape of a dental restoration such that the green body can be converted into a dental restoration in a subsequent step by heat treatment (e.g., sintering as described below). Alternatively, the green body may have the shape of a dental blank such that the green body can be converted into a dental blank by heat treatment (e.g., sintering as described below).

[0173] Alternatively, the molded body may be prepared by molding the powder in a suitable mold to obtain a molded body. The molded body typically has a preliminary shape of the dental blank. The preliminary shape may have the desired shape of the dental blank, such as, but not limited to, a disk, a cylinder, or a rectangular block. The preparation of the molded body may differ depending on the form in which the powder is provided. If the powder is provided in dry form, for example in the form of a dry blend with one or more additives, the powder may be introduced into a mold followed by a compacting step (for example a pressing step such as uniaxial pressing). The compacting step may be a cold compacting step. The cold compacting step (for example cold pressing) may be carried out at a temperature below 60°C, for example in the range of 15 to 35°C, and at a pressure of 2 to 30 bar, for example in the range of 5 to 15 bar. Additionally or alternatively, the compacting step may be a hot compacting step. The hot compacting step (e.g. hot pressing step) may be carried out at a temperature in the range of 650-850°C, for example in the range of 700-800°C, and at a pressure in the range of 5-50 MPa, preferably 10-30 MPa. Hot compacting is typically carried out for a period in the range of 0.1-10 minutes, for example in the range of 0.3-5 minutes. The hot compacting step is preferably carried out at atmospheric pressure below ambient pressure, for example below 0.1 bar, such as in the range of 0.01-0.8 bar. Hot compacting may be pressure sintering. After hot compacting, a compacted body may be obtained that is essentially non-porous or does not contain significant porosity.

[0174] If the powder is provided in liquid form, the powder may be introduced into a mold, followed by removal of the liquid. The mold may be a mold suitable for die casting or slip casting. The mold may have pores through which the liquid can be removed. Removal of the liquid may be performed and / or supported by, for example, pressure, suction, and / or freeze drying.

[0175] The compact typically comprises (or may consist of) three successive powder sections, namely: Powder Section A, Powder Section B, and Powder section C.

[0176] The powder sections are prepared such that the weight ratio of two or more powders (eg, two or more glass powders) is different in each of the powder sections.

[0177] When the glass-ceramic dental body has a multi-layer structure, powder sections A-C may be composed of one or more powder layers. For example, a compact may be prepared such that powder section C is powder layer C, powder section B is formed by at least one intermediate powder layer, and powder section A is powder layer A. Powder section B may be formed by 1-8 or more intermediate powder layers (e.g., 1-6 layers, 1-4 layers, 1-3 layers, 2 layers, 1 layer).

[0178] Alternatively, the mold body may be prepared from powders such that powder section C and powder section A comprise an essentially homogenous chemical composition, and powder section B comprises two or more powders in a weight ratio that varies progressively within powder section B in the direction from powder section C to powder section A. Such a gradual variation can be achieved by using deposition or dosing devices known in the art. Such deposition or dosing devices can be adjusted to continuously vary the weight content of the components in the mixture added to the mold.

[0179] 2.1 Two powders When the molded body (e.g., mold body) is prepared from two powders (i.e., a first powder and a second powder), the powder sections are prepared such that the weight ratio of the two powders is different in each of the powder sections. In one embodiment, the molded body (e.g., mold body) is prepared from two glass powders (i.e., a first glass powder and a second glass powder), and the powder sections are prepared such that the weight ratio of the two glass powders is different in each of the powder sections.

[0180] The powder sections are typically prepared such that the weight ratio of the first powder to the second powder decreases in the direction from powder section C to powder section A. This should be understood as the weight content of the first powder decreases in the direction from powder section C to powder section A, and the weight content of the second powder increases in the direction from powder section C to powder section A. Thus, powder section C may contain a greater amount of the first powder than the amount of the first powder in powder section B, and powder section B may contain a greater amount of the first powder than the amount of the first powder in powder section A (and vice versa for the second glass powder). This includes that the second powder may be essentially absent from powder section C (i.e., about 0 wt%) and / or the first powder may be essentially absent from powder section A (i.e., about 0 wt%).

[0181] The weight ratio of the first powder to the second glass powder may vary from a weight ratio of >50:<50, such as >90:<10 (e.g. 100:0), in powder section C to a weight ratio of <50:>50, such as <10:>90 (e.g. 0:100), in powder section A. Thus, the main powders in powder section A (i.e. the powders present in the powder section in an amount of >50 wt%, based on the total weight of the powders) may be different between powder section C and powder section A. However, it is also possible that the main powders are the same in each of the powder sections. In that case, the weight ratio of the first powder to the second powder may vary from a weight ratio of >90:<10 (e.g. 100:0) in powder section C to a weight ratio in the range of >50:<50 to <90:>10 (e.g. 60:40) in powder section A. The weight ratio of the first powder to the second powder in powder section B is between the weight ratio in powder section C and the weight ratio in powder section A.

[0182] For example, the formed body (eg, mold body) may include (or consist of): Powder section A, which is comprised of a second powder (eg, a second glass powder), optionally combined with one or more additives. a powder section B, the powder section B being comprised of a mixture of a first powder (e.g., a first glass powder) and a second powder (e.g., a second glass powder), each optionally combined with one or more additives; and Powder section C, which is comprised of a first powder (eg, a first glass powder), optionally combined with one or more additives.

[0183] When the glass-ceramic dental body has a multi-layer structure, the layers are typically prepared such that the weight ratio of the first powder to the second powder decreases in the direction from powder layer C to powder layer A. This should be understood as the weight content of the first powder decreases in the direction from powder layer C to powder layer A, and the weight content of the second powder increases in the direction from powder layer C to powder layer A. The weight content of the first powder decreases from layer to layer, and the weight content of the second powder increases from layer to layer. Typically, the chemical composition of each layer is essentially homogeneous. Thus, when the molded body includes 1 to 8 intermediate layers (e.g., 1 to 6 layers, 1 to 4 layers, 1 to 3 layers, 2 layers, 1 layer), the weight contents of the first and second powders decrease and increase, respectively, stepwise from layer to layer in the direction from powder section C to powder section A. When the layers include or consist of a mixture of the first and second powders (optionally combined with one or more additives), the powders may be premixed with each other before being introduced into the mold to form the layers.

[0184] In an alternative embodiment, the mold body is prepared from two powders such that powder section C and powder section A comprise an essentially homogenous chemical composition and the weight ratio of the first powder to the second powder gradually decreases in section B in the direction from powder section C to powder section A. The weight content of the second powder gradually decreases in section B in the direction from powder section C to powder section A.

[0185] 2.2 Three powders When the mold body is prepared from three powders (i.e., a first powder, a second powder, and a third powder), the powder sections may be prepared such that the weight ratio of the three powders is different in each of the powder sections. In one embodiment, the mold body is prepared from three glass powders (i.e., a first glass powder, a second glass powder, and a third glass powder), and the powder sections may be prepared such that the weight ratio of the three glass powders is different in each of the powder sections.

[0186] Each powder section can include one of three powders (e.g., one of three glass powders), and thus the weight ratio of the first powder to the second powder to the third powder can be 100:0:0 in powder section C, 0:100:0 in powder section B, and 0:0:100 in powder section A.

[0187] For example, the formed body (eg, mold body) may include (or consist of): Powder section A, which is comprised of a third powder (eg, a third glass powder), optionally combined with one or more additives. a powder section B, which is comprised of a second powder (e.g., a second glass powder), optionally combined with one or more additives; and Powder section C, which is comprised of a first powder (eg, a first glass powder), optionally combined with one or more additives.

[0188] However, it is also possible, and sometimes preferred, that one or more of the powder sections (e.g., at least section B) contain a mixture of two or more of the three powders. This is typically the case when the glass-ceramic dental body has a multi-layer structure with at least four layers, or when the weight ratio of the powders in section B changes gradually.

[0189] When the glass-ceramic dental body has a multi-layer structure, the powder layers may be prepared such that the weight ratios of the three powders are different in each of the powder layers.

[0190] Alternatively, the mold body may be prepared from powders such that powder section C and powder section A comprise an essentially homogenous chemical composition, and powder section B comprises a weight ratio of powders selected from a first powder, a second powder, and a third powder, which weight ratio varies progressively within section B in the direction from powder section C to powder section A.

[0191] 3.Heat treatment of compacts The method further includes subjecting the formed body (eg, mold body) to a heat treatment to obtain a glass-ceramic dental body.

[0192] The heat treatment typically includes a sintering step. During the sintering step, the shaped powder body (e.g., the mold powder body) is densified by applying heat. The sintering step may be a conventional sintering step performed without applying additional pressure. However, it is also possible that the sintering step is pressure sintering. In pressure sintering, the densification of the powder body is promoted by applying pressure. The pressure sintering may be a hot compacting step as described above, or may be performed simultaneously with the hot compacting step. The heat treatment may further include a crystallization step. In the crystallization step, one or more new liquid crystal phases may be created, or one or more existing crystal phases may be converted into another crystal phase. The crystallization step may be performed together with the sintering step, or may be performed separately, such as after the sintering step. If the shaped body includes or is composed of a glass powder, the heat treatment typically further includes a crystallization step.

[0193] The heat treatment may be carried out at a maximum temperature in the range of 700 to 1050° C., such as in the range of 780 to 980° C., for example in the range of 820 to 940° C. The maximum temperature may be held for a period in the range of 5 minutes to 2 hours, such as in the range of 10 minutes to 1 hour, for example in the range of 15 minutes to 45 minutes.

[0194] The heat treatment may comprise one or more heating steps, such as two, three or more heating steps. For example, the heat treatment may comprise a first heating step and a second heating step. The first heating step may start at a temperature in the range of 300-500°C, such as in the range of 350-450°C, and may end at a temperature in the range of 500-700°C, such as in the range of 550-650°C. The end temperature of the first heating step may be held for a period in the range of 5 minutes to 2 hours, such as in the range of 10 minutes to 1 hour, such as in the range of 15 minutes to 45 minutes. The first heating step may have a heating rate in the range of 5-15 K / min. The second heating step may start at the end temperature of the first heating step and may end at the maximum temperature. The second heating step may have a heating rate in the range of 5-15 K / min.

[0195] The heat treatment may be carried out partially or completely at a pressure lower than ambient pressure. In the present disclosure, ambient pressure is defined as 1.013 bar. For example, the heat treatment may be carried out partially or completely at a pressure less than 0.9 bar, for example in the range of 10-300 mbar or 30-120 mbar. The heat treatment is typically followed by a cooling step, which starts at a maximum temperature and ends at a temperature suitable for handling the glass-ceramic dental body (such as removing the glass-ceramic dental body from the sintering furnace).

[0196] The method may include one or more additional method steps that are typical in the art and may be performed before, between, or after the method steps described herein. The additional steps may be, but are not limited to, adjusting the particle size distribution of the powder (e.g., by sieving) and / or preparing the surface of the compact (e.g., mold body) and / or glass-ceramic dental body (e.g., by grinding, lapping or polishing).

[0197] III. Use of Glass-Ceramic Dental Bodies When the glass ceramic dental body is a glass ceramic dental blank (e.g., a dental mill blank), the glass ceramic dental body is useful for preparing a dental restoration, such as the dental restoration described herein. One embodiment of the present invention relates to the use of a glass ceramic dental blank according to an embodiment of the present invention for preparing a dental restoration. One embodiment of the present invention relates to a method for preparing a dental restoration. The method comprises using a glass ceramic dental blank according to an embodiment of the present invention.

[0198] In a preferred embodiment, a method for preparing a dental restoration is provided, comprising machining a glass-ceramic dental mill blank according to an embodiment of the invention to provide a dental restoration, and optionally surface treating the dental restoration.

[0199] Machining of the dental mill blank may be performed by any conventional method for machining glass ceramic dental mill blanks, typically by a CAD / CAM process. Such processes are known in the art. Machining may include, but is not limited to, cutting, drilling, and / or grinding of the glass ceramic dental mill blank. The dental restoration may optionally be subjected to a surface treatment as known in the art, for example by polishing, staining, and / or glazing the surface of the dental restoration. In one embodiment, the dental restoration is surface treated by at least a first glazing and a second glazing. The first glazing has a lower thermal expansion coefficient than the thermal expansion coefficient of the second glazing, and the first glazing is applied to a surface area of ​​the portion of the dental restoration having the lower thermal expansion coefficient. The second glazing is applied to a surface area of ​​the portion of the dental restoration having a higher thermal expansion coefficient. In that context, the terms "lower" and "higher" should be understood in relation to each other.

[0200] Another embodiment of the present invention provides a dental restoration obtained using a glass ceramic dental mill blank according to an embodiment of the present invention. Another embodiment of the present invention provides a dental restoration obtained by a method for preparing a dental restoration according to an embodiment of the present invention.

[0201] IV. Further Non-Limiting Aspects and Embodiments Further non-limiting aspects and embodiments of the present invention are defined in the following paragraphs [1] to

[35] , namely: [1] A glass-ceramic dental body comprising three consecutive sections, namely: Section A, Section B, and Section C, including (or consisting of) A glass-ceramic dental body, wherein each of the sections has a chemical composition that is different from the chemical composition of the other sections. [2] A glass ceramic dental body according to item [1], wherein the glass ceramic dental body is characterized by one or more gradients of mechanical properties in the direction from section C to section A. [3] The glass-ceramic dental body according to paragraph [2], wherein the gradient of the one or more mechanical properties is a gradient of biaxial bending strength, the biaxial bending strength decreasing from section C to section A, and / or a gradient of fracture toughness (K IC ) is the gradient of fracture toughness (K IC ) is reduced from section C to section A, glass ceramic dental body. [4] A glass ceramic dental body according to any one of items [1] to [3], characterized by a gradient of optical properties in the direction from section C to section A. [5] A glass-ceramic dental body according to paragraph [4], wherein the gradient of the optical property is a gradient of the contrast ratio, the contrast ratio decreasing from section C to section A. [6] The glass ceramic dental body according to any one of items [1] to [5], characterized by a gradient of thermal properties in the direction from section C to section A. [7] A glass-ceramic dental body according to paragraph [6], wherein the gradient of thermal properties is a gradient of thermal expansion coefficient, the thermal expansion coefficient decreasing or increasing from section C to section A. [8] A glass-ceramic dental body according to item [7], wherein the thermal expansion coefficient decreases from section C to section A. [9] A glass-ceramic dental body according to paragraph [7], wherein the thermal expansion coefficient increases from section C to section A.

[10] The glass ceramic dental body according to any one of items [1] to [9], wherein the main crystal phases of each of sections C, B, and A are the same.

[11] The glass-ceramic dental body according to item

[10] , wherein the content of the main crystalline phase decreases in the direction from section C to section A.

[12] A glass ceramic dental body according to any one of items [1] to [9], wherein the main crystalline phase of section C is different from the main crystalline phase of section A.

[13] A glass-ceramic dental body according to item

[12] , wherein the content of the crystalline phase which is the predominant crystalline phase in section C decreases in the direction from section C to section A.

[14] A glass-ceramic dental body according to item

[12] , wherein the content of the crystalline phase which is the predominant crystalline phase in section A decreases in the direction from section A to section C.

[15] The glass ceramic dental body according to any one of items [1] to [9], wherein section A is made of glass, and sections B and C are made of glass ceramic.

[16] A glass ceramic dental body according to any one of items [1] to

[15] , wherein section C has a predominant crystalline phase, and the content of this crystalline phase decreases from section C to section B.

[17] A glass-ceramic dental body according to any one of items [1] to

[16] , wherein the main crystalline phase of section C is lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS).

[18] A glass-ceramic dental body according to item

[17] , wherein the predominant crystalline phase of section C is lithium disilicate.

[19] The glass-ceramic dental body according to paragraph

[17] , wherein the predominant crystalline phase in section C is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution).

[20] The glass ceramic dental body according to any one of items [1] to

[19] , wherein the main crystal phase of section C is not lithium metasilicate.

[21] A glass-ceramic dental body according to any one of paragraphs [1] to [9],

[12] to

[14] , and

[16] to

[20] , wherein the main crystalline phase of section A is apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS).

[22] The glass-ceramic dental body according to paragraph

[21] , wherein the predominant crystalline phase in section A is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution).

[23] The glass-ceramic dental body according to item

[21] , wherein the predominant crystalline phase of section A is an apatite (e.g., fluoroapatite).

[24] A glass ceramic dental body according to any one of items [1] to

[23] , wherein section A comprises one or more crystalline phases different from the crystalline phase of section C.

[25] The glass ceramic dental body according to any one of items [1] to

[24] , wherein the glass ceramic dental body is a dental blank such as a dental mill blank or a dental press blank.

[26] A glass-ceramic dental body according to item

[25] , comprising: Section A forms the top section of the dental blank; Section B forms the middle section of the dental blank; Section C is a glass ceramic dental body that forms the bottom section of the dental blank.

[27] The glass ceramic dental body according to any one of items [1] to

[24] , wherein the glass ceramic dental body is a dental restoration.

[28] A glass-ceramic dental body according to item

[27] , comprising: Section A forms the upper portion of the dental restoration, such as part or all of the incisal zone; Section B forms an intermediate portion of the dental restoration, such as part or all of the transition zone between the incisal zone and the dentin zone; Section C is a glass ceramic dental body that forms the lower part of the dental restoration, such as part or all of the dentin zone.

[29] A glass ceramic dental body according to any one of items [1] to

[28] , having a multi-layer structure, wherein section A is layer A, section C is layer C, and section B is formed by at least one intermediate layer between layer A and layer C, each of the layers having a chemical composition different from the chemical composition of the other layers.

[30] A glass ceramic dental body according to any one of items [1] to

[28] , wherein sections A and C have uniform chemical compositions, and section B has a chemical composition that gradually changes in the direction from section C to section A.

[31] A method for preparing a glass ceramic dental body according to any one of items [1] to

[30] , comprising the following steps: providing two or more powders selected from glass powders, glass-ceramic powders, and mixtures thereof; Preparing a compact from the powder; and subjecting the compact to a heat treatment to obtain a glass-ceramic dental body.

[32] The method according to item

[31] , wherein the compact is divided into three successive powder sections, namely: Powder Section A, Powder Section B, and Powder section C, comprising (or consisting of) A method wherein the weight ratio of the two or more powders is different in each of the powder sections.

[33] Use of a glass-ceramic dental body according to any one of items

[25] ,

[26] ,

[28] and

[29] .

[34] A method for preparing a dental restoration, comprising machining a glass-ceramic dental body according to any one of paragraphs

[25] ,

[26] ,

[28] and

[29] to provide a dental restoration, and optionally surface treating the dental restoration.

[35] A dental restoration obtained by using the glass-ceramic dental body according to any one of items

[25] ,

[26] ,

[28] and

[29] or by the method according to item

[34] .

[0202] The present invention is described below by way of specific embodiments that should not be construed as limiting the present invention in any way.

[0203] V. Working Examples Section 1. Measurement method 1.1 Biaxial bending strength The biaxial flexural strength was determined according to DIN EN ISO 6872 (DIN EN ISO 6872:2019). Test specimens were obtained from different sections of the glass-ceramic dental body by cutting the respective sections of the glass-ceramic dental body with a diamond-coated tool.

[0204] 1.2 Fracture toughness K IC Fracture toughness (K IC ) was determined according to the single-edge V-notched beam (SEVNB) method according to DIN EN ISO 6872, in particular DIN EN ISO 6872:2015. Test specimens were obtained from different sections of the glass-ceramic dental body by cutting the respective sections of the glass-ceramic dental body with a diamond-coated tool.

[0205] 1.3 Contrast Ratio The contrast ratio was determined according to BS 5612, in particular BS 5612:1978. The contrast ratio was determined using specimens with a thickness of 2 mm ± 0.02 mm. The specimens were obtained from different sections of the glass-ceramic dental body by cutting the respective parts of the glass-ceramic dental body with a diamond-coated tool. The measurements were performed using a spectrophotometer CM 3700-D (Konica-Minolta). Prior to the measurements, the cut sections were wet ground to a thickness of 2 mm ± 0.02 mm using a rotating diamond grinding disk and 1000 SiC grinding paper, followed by a final surface wet polishing using a diamond grinding disk (20 μm).

[0206] 1.4 Coefficient of Thermal Expansion (CTE) The coefficient of thermal expansion (CTE) was measured using a dilatometer according to DIN EN ISO 6872, in particular DIN EN ISO 6872:2015. Test specimens were obtained from different sections of the glass-ceramic dental body by cutting the respective sections of the glass-ceramic dental body with a diamond-coated tool.

[0207] 2. Working Example 2.1 Preparation of glass powder and glass-ceramic dental body To obtain the glass powders, the individual raw materials for the glass powders were weighed, mixed, and homogenized in a laboratory high-speed mixer. For example, to prepare glass powders GP4, GP10, and GP11 (see glass-ceramic dental body in Example 5), the following raw materials were used: quartz powder (SiO 2 ), lithium carbonate (Li 2 CO 3 ), potassium carbonate (K 2 CO 3 ), aluminum hydroxyhydrate (AlOOH x H 2 O, aluminum phosphate (Al(PO 3 ) 3 ), Magnesium carbonate (MgCO 3 ), calcium carbonate (CaCO3 ), strontium carbonate (SrCO 3 ), zirconium oxide (ZrO 2 ), zinc oxide (ZnO), lanthanum oxide (La 2 O 3 ).

[0208] The raw materials were subsequently melted at a temperature of 1550°C for 1 hour. The melt was shock frozen in water to obtain glass. The glass was dried in an oven at 150°C for 1 hour and then ground in a laboratory mill to obtain glass powder. The powder fraction with a particle size of <45 μm was separated and used to prepare glass powder mould bodies.

[0209] To prepare a multi-layer molded powder body (3 layers), the first powder was introduced into the mold and flattened with a stamp (only the stamp weight without additional external pressure). Subsequently, the second and third powders (in that order) were introduced into the mold and flattened with a stamp. The layered powders were then pressed with a pressure of 10 bar to obtain a molded powder body. The molded body was removed from the mold by rotating it 180° and applying pressure in the opposite direction to push the molded body out of the mold.

[0210] The mould powder body was then fully sintered in a sintering furnace (Programat P500) at 880°C under vacuum. The mould powder body was first inserted into the sintering furnace (preheated to 400°C) and subsequently the furnace pressure was reduced to <0.1 MPa. In the heating step, the temperature was increased to 600°C with a heating rate of 10 K / min and held for 30 min, then to 880°C with a heating rate of 10 K / min and also held for 30 min. Afterwards the heating elements of the furnace were deactivated and the pressure was brought to ambient pressure. The fully sintered glass-ceramic body (see section 2.3: Glass-ceramic dental body) was removed from the furnace at a temperature of about 500°C.

[0211] 2.2 Glass-ceramic dental body The following table shows the chemical composition of glass powders, structures, and example properties for glass-ceramic dental bodies according to embodiments of the present invention. The abbreviation "ss" referring to the crystalline phase means "solid solution".

[0212] 2.1.2 Example 1 [Table 4]

[0213] [Table 5]

[0214] 2.2.2 Example 2 [Table 6]

[0215] [Table 7]

[0216] 2.3.2 Example 3 [Table 8]

[0217] [Table 9]

[0218] 2.4.2 Example 4 [Table 10]

[0219] [Table 11]

[0220] 2.5.2 Example 5 [Table 12]

[0221] [Table 13]

[0222] 2.6.2 Example 6 [Table 14]

[0223] [Table 15]

[0224] 2.7.2 Example 7 [Table 16]

[0225] [Table 17]

[0226] 2.8.2 Example 8 [Table 18]

[0227] [Table 19]

[0228] 2.9.2 Example 9 [Table 20]

[0229] [Table 21]

[0230] 2.10.2 Example 10 [Table 22]

[0231] [Table 23]

Claims

1. A glass ceramic dental body comprising three successive sections, namely: Section A, Section B, and Section C includes: each of said sections has a chemical composition different from the chemical composition of the other sections; The glass-ceramic dental body is characterized by one or more gradients of mechanical, optical, and / or thermal properties in the direction from section C to section A.

2. 2. The glass-ceramic dental body of claim 1, characterized by a gradient in biaxial flexural strength, said biaxial flexural strength decreasing from section C to section A; and / or Fracture toughness (K ＩＣ ) and the fracture toughness (K ＩＣ ) decreases from section C to section A, glass ceramic dental body.

3. 3. The glass-ceramic dental body of claim 1, characterized by a gradient of contrast ratio, said contrast ratio decreasing from section C to section A.

4. 4. A glass-ceramic dental body according to any one of claims 1 to 3, characterized by a gradient in the coefficient of thermal expansion, said coefficient of thermal expansion decreasing or increasing from section C to section A.

5. 5. The glass-ceramic dental body of claim 1, wherein the predominant crystalline phase in each of section C, section B, and section A is the same.

6. 6. The glass-ceramic dental body of claim 5, wherein the content of the primary crystalline phase decreases in a direction from section C to section A.

7. 5. The glass-ceramic dental body according to claim 1, wherein the predominant crystalline phase of section C is different from the predominant crystalline phase of section A.

8. 8. The glass-ceramic dental body of claim 7, the content of the crystalline phase that is the predominant crystalline phase in section C decreases in the direction from section C to section A; or A glass-ceramic dental body, wherein the content of a crystalline phase that is the predominant crystalline phase in section A decreases in a direction from section A to section C.

9. 5. The glass-ceramic dental body according to claim 1, wherein section A is made of glass and sections B and C are made of glass ceramic.

10. 10. The glass-ceramic dental body according to claim 1, wherein section C has a predominant crystalline phase, the content of said crystalline phase decreasing from section C to section A.

11. 11. The glass-ceramic dental body according to claim 1, wherein the predominant crystalline phase of section C is lithium disilicate, quartz, or a stoichiometric or non-stoichiometric lithium aluminosilicate (LAS).

12. 12. The glass-ceramic dental body of claim 11, wherein the predominant crystalline phase of section C is lithium disilicate.

13. 13. A glass-ceramic dental body according to any one of claims 1 to 12, wherein the predominant crystalline phase in section C is not lithium metasilicate.

14. 14. The glass-ceramic dental body according to any one of claims 1 to 4, 7, 8, 10 to 13, wherein the main crystalline phase of section A is apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS).

15. 15. The glass-ceramic dental body of claim 14, wherein the predominant crystalline phase of section A is quartz.

16. 16. A glass-ceramic dental body according to any one of claims 1 to 15, wherein the glass-ceramic dental body is a dental blank, such as a dental mill blank or a dental press blank, and optionally Section A forms a top section of the dental blank; Section B forms a middle section of the dental blank; Section C is a glass ceramic dental body forming a bottom section of the dental blank.

17. 16. A glass-ceramic dental body according to any one of claims 1 to 15, wherein the glass-ceramic dental body is a dental restoration, and optionally further comprising: Section A forms at least a portion of the incisal zone; Section B forms at least a part of a transition zone between the incisal zone and the dentin zone; Section C is a glass-ceramic dental body forming at least a portion of the dentin zone.

18. 18. A glass-ceramic dental body according to any one of claims 1 to 17, having a multi-layer structure, in which section A is layer A, section C is layer C and section B is formed by at least one intermediate layer between layers A and C, each of the layers having a chemical composition different from the chemical composition of the other layers, or A glass-ceramic dental body, wherein sections A and C have a uniform chemical composition, and section B has a chemical composition that varies gradually from section C to section A.

19. A method for preparing a glass-ceramic dental body according to any one of claims 1 to 18, comprising the following steps: providing two or more powders selected from glass powders, glass-ceramic powders, and mixtures thereof; preparing a compact from the powder; and subjecting the shaped body to a heat treatment to obtain a glass-ceramic dental body.

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