Glass ceramic tooth body as well as preparation method and application thereof

Abstract

The present invention provides a glass ceramic dental body comprising three consecutive segments: segment A, segment B, and segment C, where each of the segments has a chemical composition that is different from the chemical composition of the other segments. The glass ceramic dental body may be characterized by a gradient of mechanical, optical, and / or thermal properties in a direction from section C to section A. In addition, a method for producing a glass-ceramic tooth body and a use of a glass-ceramic tooth body are provided.

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). The present invention also relates to a method for preparing a glass-ceramic dental body and the use of the glass-ceramic dental body in the dental field. Background Art

[0002] Ideally, a dental restoration should have mechanical properties comparable to those of natural teeth to provide long-term durability of the dental restoration while avoiding excessive wear on adjacent tissues and / or natural teeth. In addition, it is desirable that the dental restoration resembles the natural appearance of the patient's teeth. Although the appearance of natural teeth can vary, some optical characteristics can be considered common features of most natural human teeth. The color and / or translucency of natural teeth typically vary from the incisal or occlusal part of the tooth to its underlying dentin part. The tooth at the incisal or occlusal part between these two parts typically shows some type of gradient or transition in color and translucency.

[0003] Glass-ceramic dental restorations are known in the art. Glass-ceramic dental restorations are typically prepared from glass-ceramic dental blanks (such as, glass-ceramic dental millblanks or glass-ceramic dental press blanks). The CAD / CAM process can generally be used to machine a glass-ceramic dental millblank into the desired shape of a dental restoration. A glass-ceramic dental press blank can be hot-pressed into a mold of a dental restoration having the desired shape.

[0004] Known glass-ceramic dental bodies, including dental blanks or dental restorations, are typically prepared from a single solid glass. The solid glass is subjected to controlled heating to achieve partial crystallization of the solid glass, thereby producing a glass-ceramic having one or more crystalline phases in its amorphous glassy phase. Glass-ceramic dental bodies prepared from solid glass typically have homogeneous mechanical, optical, and thermal properties. However, glass-ceramic dental bodies having uniform mechanical, optical, and / or thermal properties are generally not ideal or suitable for dentistry.

[0005] Efforts have been made in the art to provide glass-ceramic dental bodies by heating different regions of a solid glass at different temperatures (e.g., using a gradient furnace). Thus, the crystallization of the crystalline phase can be altered in different regions of the solid glass. The result can be a glass-ceramic dental body having one or more non-uniform properties. However, this preparation method is laborious, and the glass-ceramic dental bodies obtained by this method can still have unsatisfactory mechanical, optical, or thermal properties.

[0006] EP 2 699 521 A1 relates to a method for preparing a glass-ceramic body, which method comprises the steps of: providing a base vitreous body and subjecting the base vitreous body to a heat treatment, thereby forming a crystalline phase embedded in a glass matrix. The heat treatment involves a nucleation step followed by several crystallization steps at different temperatures, thereby forming at least two different crystalline phases. EP 3974 397 A1 relates to a machinable dental milling block and a method for preparing the same. The method comprises the steps of: preparing a block having a predetermined shape from a specific glass composition; and subjecting the block to a heat treatment in a temperature range of 760 °C to 880 °C while applying a temperature gradient in the depth direction of the block.

[0007] There is a need in the art for a glass-ceramic dental body having one or more material properties that vary in the direction of the dental body and, desirably, vary in a manner comparable to the property transitions in natural teeth and / or in a manner that allows for the provision of improved dental restorations. It is also desirable to be able to obtain such a glass-ceramic dental body by a relatively simple and reproducible process. SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a new and improved glass-ceramic dental body. An object of the present invention is to provide a glass-ceramic dental body having one or more material properties that change in the direction of the dental body. An object of the present invention is to provide a glass-ceramic dental body that does not have the disadvantages of the glass-ceramic dental bodies of the prior art.

[0009] The glass-ceramic dental body and the method for preparing a glass-ceramic dental body according to embodiments of the present invention solve one or more of the above objects.

[0010] One aspect of the present invention provides a glass-ceramic dental body comprising three consecutive segments:

[0011] Segment A,

[0012] Segment B, and

[0013] Segment C,

[0014] wherein each of the segments has a chemical composition different from that of the other segments.

[0015] In a preferred embodiment, the glass-ceramic dental body is characterized by one or more gradients of mechanical properties (e.g., gradients of biaxial flexural strength and / or fracture toughness (K IC IC

[0016] )), optical properties (e.g., gradient of contrast), and / or thermal properties (e.g., gradient of coefficient of thermal expansion) in the direction from section C to section A.

[0017] In a preferred embodiment, the main crystalline phase is the same for each of the sections, and the content of the main crystalline phase optionally decreases in the direction from section C to section A. In an alternative preferred embodiment, the main crystalline phase of section C is different from the main crystalline phase of section A, and optionally, the content of the crystalline phase that is the main crystalline phase of section C decreases in the direction from section C to section A, or the content of the crystalline phase that is the main crystalline 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 B and C are composed of glass-ceramic.

[0018] One finding 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 (such as biaxial flexural strength, fracture toughness, translucency, or coefficient of thermal expansion) that vary in a gradient form within its continuous sections. 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 region 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 customized in an advantageous manner, such as in a manner that the restoration is closer to the properties of natural teeth. For example, it is possible to provide a glass-ceramic dental restoration having a more translucent incisal region than its dentin region. Additionally or alternatively, the thermal properties (e.g., CTE) can be adjusted in a manner that enables different glazes having different thermal properties (e.g., CTE) to be applied to different parts of the restoration.

[0019] - Providing two or more kinds of powders selected from glass powders, glass-ceramic powders, and mixtures thereof;

[0020] - Preparing a shaped body from the powders; and

[0021] - Heat-treating the shaped body to obtain the glass-ceramic dental body.

[0022] The shaped body generally comprises three successive powder segments: powder segment A, powder segment B and powder segment C, wherein the weight ratio of two or more powders is different in each of the powder segments.

[0023] It has been found that the glass-ceramic dental bodies of the present invention can be obtained in a relatively simple manner. In particular, the method of the present invention does not require different regions of the solid glass to be subjected to different temperatures simultaneously. Such a method is also not suitable for preparing the glass-ceramic dental bodies of the present invention because the solid glass has a homogeneous chemical composition and thus cannot be used to obtain different segments with different chemical compositions. Furthermore, the inventors have surprisingly found that two or more glasses or glass-ceramic powders having different chemical compositions (e.g., glasses or glass-ceramic powders that contribute to the preparation of glass-ceramics having different types and / or contents of crystalline phases) can be used to prepare a dense monolithic glass-ceramic body by heat treatment, and in particular by sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 shows the spectra of qualitative X-ray diffraction analysis of different segments of the glass-ceramic dental body of Example 5. Figure 1A The spectrum of the X-ray diffraction analysis of segment C (bottom layer) is shown. Figure 1B The spectrum of the X-ray diffraction analysis of segment B (intermediate layer) is shown. Figure 1C The spectrum of the X-ray diffraction analysis of segment A (top layer) is shown. The spectra show that the peak intensity ratio of lithium disilicate (lithium metasilicate) (Li 2 Si 2 O 5 ; the most prominent peak is marked as: *) to α-quartz (the most prominent peak is marked as: #) changes from segment C (bottom layer) through segment B (intermediate layer) to segment A (top layer). The intensity of lithium disilicate (Li 2 Si 2 O 5 ) decreases from segment C (bottom layer) to segment A (top layer), and the intensity of the α-quartz peak increases from segment C (bottom layer) to segment A (top layer). The change in peak intensity indicates that the content of lithium disilicate (Li 2 Si 2 O 5 ) decreases from segment C (bottom layer) to segment A (top layer).

[0025] DEFINITIONS

[0026] In the context of the present invention, the following terms have the following meanings:

[0027] "Dental body" refers to a solid, geometrically defined three-dimensional object material (e.g., in the form of an ingot, block, disc, or dental restoration) applicable in the dental or orthodontic field. The dental body can be, but is not limited to, a dental blank or a dental restoration. The dental blank can be a dental milling blank or a dental pressing blank.

[0028] "Dental milling blank" refers to a solid, geometrically defined three-dimensional object material (e.g., a block or disc) that can be processed to form a dental restoration therefrom, typically using CAD / CAM technology, by means of, for example, cutting, milling, grinding, drilling, etc.

[0029] "Dental pressing blank" refers to a solid, geometrically defined three-dimensional object material (e.g., a block or ingot) that can be formed into a dental restoration by hot pressing the blank into a mold having the shape of the dental restoration.

[0030] As used herein, "dental restoration" refers to an article that aids in the restoration, reshaping, supporting, and / or reconstruction of a tooth or part thereof or a group of teeth or part thereof in the dental or orthodontic field. The dental restoration can be, but is not limited to, a crown, partial crown, abutment, abutment crown, inlay, onlay, veneer, shell, or bridge.

[0031] A "glass-ceramic" dental body refers to a dental body that is partially or wholly composed of a glass-ceramic material. For example, a glass-ceramic dental body partially composed of a glass-ceramic material can include two segments composed of a glass-ceramic material and one segment composed of glass. A glass-ceramic dental body wholly composed of a glass-ceramic material includes only segments composed of a glass-ceramic material. A glass-ceramic dental body typically does not contain or is not typically composed of a glass matrix composite. A "glass matrix composite" in the sense of the present disclosure is a material obtained by adding crystalline particles to a glass melt or by attaching (e.g., by sintering) a glass material to a crystalline material.

[0032] "Glass-ceramic material" refers to an inorganic non-metallic solid having a glass phase surrounding one or more crystalline phases. Glass-ceramic materials are typically obtained via controlled nucleation and crystallization of an amorphous base glass. Glass-ceramic materials are different from ceramic materials that typically do not contain a glass phase. "Glass" refers to an inorganic non-metallic solid that is typically hard, brittle, and transparent and that has substantially no crystalline regions. It can be described as a thermodynamically unstable frozen melt.

[0033] As used herein, a "continuous segment" refers to segments arranged adjacent to one another in succession. Thus, segment A is arranged adjacent to segment B, and segment B is arranged adjacent to segment C.

[0034] As used herein, "top section" refers to the outermost section of a glass-ceramic dental blank (e.g., a dental milling blank) that can be used to prepare an incisal or occlusal area or a portion thereof in a dental restoration.

[0035] "Middle section" refers to the section located between the top and bottom of a glass-ceramic dental blank (e.g., a dental milling blank). The middle section can be used to prepare a transition zone or a portion thereof of a dental restoration.

[0036] "Bottom section" refers to the outermost part of a glass-ceramic dental blank (e.g., a dental milling blank) that is located on the opposite side of the glass-ceramic dental blank relative to the top section. The bottom section can be used to prepare a dentin area or a portion thereof of a dental restoration.

[0037] The terms "top section", "middle section", and "bottom section" should not be construed to mean that the glass-ceramic dental blank must be positioned (or used) in a specific manner or orientation. Any other part that may additionally be present on the outside of the glass-ceramic dental blank (e.g., fastening pins, support layers, protective layers, printed layers, or sacrificial layers, such as thin layers of glass-ceramic material) and that is not suitable or not intended to be part of the dental restoration formed from the glass-ceramic dental blank should not be understood as the top section, middle section, or bottom section or as part thereof. For example, a glass-ceramic dental blank (e.g., a dental milling blank) can be attached (although this is not required) to a support part, a protective part, and / or a sacrificial part on one or more of its outsides. Such components can be fastening pins, support layers, protective layers, printed layers, or sacrificial layers, such as thin layers of glass-ceramic material.

[0038] "Layer" refers to a discrete layer of a glass-ceramic dental body. The discrete layers in a glass-ceramic dental body can be determined by microscopy, such as single electron microscopy (SEM).

[0039] As used herein, "gradient" refers to a property of a glass-ceramic dental body (e.g., biaxial flexural strength, fracture toughness (K IC) The contrast, coefficient of thermal expansion (CTE), etc. increase or decrease (e.g., gradually or in a stepwise manner) in the direction of the glass-ceramic dental body. Thus, a gradient (i.e., a value of a property, such as three or more values) can be defined to decrease or increase (e.g., gradually or in a stepwise manner) in the direction of the glass-ceramic dental body. A property that decreases in the "direction from segment C to segment A" means that the value of the property in segment C is higher than the value of the property in segment B, and the value of the property in segment B is higher than the value of the property in segment A (i.e., segment C > segment B > segment A). If the property increases in the "direction from segment C to segment A", the change in value is reversed (i.e., segment C < segment B < segment A). The gradient can include a change of the property within a segment in the direction from segment C to segment A, such as within segment B (e.g., stepwise from one layer to another or gradually).

[0040] "Principal crystalline phase" refers to the crystalline phase of the glass-ceramic dental body or a segment thereof, which has the highest mass fraction among all the crystalline phases present in the glass-ceramic dental body or the segment thereof. Thus, the principal crystalline phase of the entire glass-ceramic dental body can be determined. In such a case, the mass fraction of the crystalline phase is based on the total weight of the glass-ceramic dental body. Additionally or alternatively, the principal crystalline phase of a part of the glass-ceramic dental body, such as the bottom segment or the top segment as described herein, can be determined. In such a case, the mass fraction of the crystalline phase is based on the total weight of the segment. The Rietveld method can be used to quantitatively determine the mass of the crystalline phase. The Rietveld method is well known in the art.

[0041] "Quartz" or "quartz crystalline phase" refers to a crystalline phase selected from α-quartz, α-quartz solid solution, β-quartz solid solution, and mixtures thereof. "Quartz solid solution" refers to a crystalline phase of SiO 2 in which foreign ions are incorporated into interstitial sites or into lattice sites. These foreign ions can be, but are not limited to, Al 3+ and Mg 2+ , Li + and / or Zn 2+ . For example, the molar concentration of Al 3+ present in the solid solution can be the same as the combined molar concentration of Zn 2+ and Mg 2+ .

[0042] In the case of the term "comprising" used herein, the presence of other unspecified elements is not excluded. In the case of the term "consisting essentially of" used herein, the presence of other non-specified elements that do not materially affect the basic characteristics of the defined subject matter is not excluded. For example, when a part or layer is defined by its chemical composition, the part or layer may contain inevitable trace impurities with a total of <0.2 wt.%, even if not explicitly defined. For the purposes of the present invention, the terms "consisting mainly of" and "consisting of" are considered to be specific embodiments of the term "comprising". Whenever the terms "including" or "having" are used, these terms refer to the same as "comprising" defined above.

[0043] The term "obtaining" does not necessarily mean, for example, that an embodiment must be obtained through a series of steps such as those following the term "obtaining", even if the term "obtaining" as a preferred embodiment always includes such a limited understanding.

[0044] The numbers defined herein are rounded to their last digit and the range of the rounded values is included according to the established rounding rules. For example, the value 3 refers to values included between 2.5 and 3.4, the value 1.5 refers to values included between 1.46 and 1.54, and so on.

[0045] Below, the present invention will be described in more detail. Detailed Description

[0046] I. Glass-Ceramic Dental Body

[0047] The present invention provides a glass-ceramic dental body, which comprises three consecutive segments:

[0048] Segment A,

[0049] Segment B, and

[0050] Segment C,

[0051] wherein each of the segments has a chemical composition different from that of the other segments.

[0052] In a preferred embodiment, the glass-ceramic dental body is characterized by one or more gradients of mechanical, optical, and / or thermal properties in the direction from segment C to segment A.

[0053] The glass-ceramic dental body can also be defined by one or more specific gradients of mechanical, optical, and / or thermal properties. Alternatively or additionally, the glass-ceramic dental body can be defined by its crystal phase, its chemical composition, and / or its structure and form.

[0054] 1. Gradient

[0055] In a preferred embodiment, 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. The one or more gradients can be gradients of one or more mechanical properties, such as, but not limited to, a gradient of biaxial flexural strength, a gradient of fracture toughness (K IC ), and / or a gradient of machinability. The one or more gradients can be gradients of one or more optical properties, such as, but not limited to, a gradient of contrast. The one or more gradients can be gradients of one or more thermal properties, such as, but not limited to, a gradient of the coefficient of thermal expansion (CTE).

[0056] 1.1 Gradients of mechanical properties

[0057] The one or more gradients can be a gradient of biaxial flexural strength, wherein the biaxial flexural strength decreases from section C to section A. The biaxial flexural strength can be determined according to DIN EN ISO 6872 (DIN EN ISO 6872: 2019). Test specimens of each of the sections can be obtained from the corresponding sections of the glass-ceramic dental body, for example, by milling, cutting, and / or sawing with a diamond-coated tool. When the dimensions of the sections are not suitable for preparing sufficient test specimens for determining the biaxial flexural strength (e.g., according to DIN EN ISO 6872, and in particular according to DIN EN ISO 6872: 2019), then after analyzing the crystalline phase and / or chemical composition of the corresponding sections, sufficient test specimens can be prepared with suitable raw materials.

[0058] The biaxial flexural strength of section C can be 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. The biaxial flexural strength of section C can be at most 550 MPa, at most 500 MPa, at most 475 MPa, at most 450 MPa, at most 350 MPa, at most 300 MPa, or at most 250 MPa. The biaxial flexural strength of section C can be in the range of 150 to 550 MPa, 175 to 500 MPa, 200 to 475 MPa, 250 to 450 MPa, 350 to 475 MPa, 250 to 350 MPa, or 150 to 250 MPa. For section C, a biaxial flexural strength of at least 200 MPa is generally preferred because such a biaxial flexural strength is particularly suitable for providing good mechanical strength for the dentin region of a dental restoration.

[0059] The biaxial bending strength of section C can be 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 that of section A. The biaxial bending strength of section C can be at most 400 MPa, at most 350 MPa, at most 300 MPa, or at most 250 MPa higher than that of section A. The biaxial bending strength of section C can be 25 to 400 MPa higher, 60 to 400 MPa higher, 100 to 350 MPa higher, 150 to 300 MPa higher, 175 to 250 MPa higher, 200 to 400 MPa higher, or 60 to 200 MPa higher than that of section A.

[0060] The biaxial bending strength of section B can be at least 150 MPa, at least 200 MPa, at least 250 MPa, at least 300 MPa, or at least 350 MPa. The biaxial bending strength of section B can be at most 500 MPa, at most 450 MPa, at most 350 MPa, at most 300 MPa, or at most 250 MPa. The biaxial bending strength of section B can be in the range of 150 to 500 MPa, 200 to 450 MPa, 300 to 450 MPa, 350 to 450 MPa, 200 to 400 MPa, 250 to 400 MPa, or 150 to 250 MPa.

[0061] The biaxial bending strength of section A can be at least 75 MPa, at least 100 MPa, at least 150 MPa, or at least 200 MPa. The biaxial bending strength of section A can be at most 350 MPa, at most 300 MPa, at most 250 MPa, or at most 200 MPa. The biaxial bending strength of section A can be in the range of 75 to 350 MPa, 100 to 300 MPa, 150 to 250 MPa, 200 to 300 MPa, 100 to 200 MPa, or 75 to 200 MPa.

[0062] In one embodiment, the biaxial flexural strength of section C is in the range of 150 to 250 MPa and the biaxial flexural strength of section A is in the range of 75 to 200 MPa. In one embodiment, the biaxial flexural strength of section C is in the range of 250 to 350 MPa and the biaxial flexural strength of section A is in the range of 100 to 250 MPa. In one embodiment, the biaxial flexural strength of section C is in the range of 350 to 475 MPa and the biaxial flexural strength of section A is in the range of 150 to 300 MPa. In one embodiment, the biaxial flexural strength of section C is in the range of 350 to 475 MPa and the biaxial flexural strength of section A is in the range of 100 to 200 MPa. In one embodiment, the biaxial flexural strength of section C is in the range of 250 to 355 MPa and the biaxial flexural strength of section A is in the range of 220 to 320 MPa. Considering the gradient of the biaxial flexural strength, it can be understood that the biaxial flexural strength of section B is a value between section C and section A.

[0063] One or more gradients may be a gradient of fracture toughness (K IC ), where the 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 based on DIN EN ISO 6872, and in particular DIN EN ISO 6872:2015. Test specimens of each of the sections can be obtained from the corresponding sections of the glass-ceramic dental body, for example, by milling, cutting, and / or sawing with a diamond-coated tool. When the size of the section is not suitable for preparing sufficient test specimens for determining the fracture toughness (K IC ) (e.g., according to DIN EN ISO 6872, and in particular DIN EN ISO 6872:2015), then after analyzing the crystal phase and / or chemical composition of the corresponding section, sufficient test specimens can be prepared with suitable raw materials.

[0064] The fracture toughness (K IC ) of section C can be at least 1.4 MPa*m -1 / 2 , at least 1.6 MPa*m -1 / 2 , at least 1.8 MPa*m -1 / 2 , 2.0 MPa*m -1 / 2 , at least 2.2 MPa*m -1 / 2 or at least 2.6 Mpa*m -1 / 2 . The fracture toughness (K IC ) of section C can be at most 3.4 MPa*m -1 / 2 , at most 3.0 Mpa*m -1 / 2, at most 2.8 MPa*m -1 / 2 , at most 2.6 Mpa*m -1 / 2 , at most 2.4 MPa*m -1 / 2 or at most 2.2 Mpa*m -1 / 2 . The fracture toughness (K IC ) of section C can be in the range of 1.4 to 3.4 MPa*m -1 / 2 , preferably 1.6 to 2.8 MPa*m1 / 2 and more preferably at least 1.8 to 2.6 MPa*m -1 / 2 . The fracture toughness (K IC ) of section C can be in the range of 1.4 to 2.0 MPa*m -1 / 2 , in the range of 1.6 to 2.2 MPa*m -1 / 2 , in the range of 2.0 to 2.6 MPa*m -1 / 2 or in the range of 2.6 to 3.4 MPa*m -1 / 2 . For section C, a fracture toughness (K -1 / 2 ) of at least 2.0 MPa*m IC is generally preferred because this fracture toughness is particularly suitable for providing good mechanical strength to the dentin region of a dental prosthesis.

[0065] The fracture toughness (K IC ) of section C can be at least 0.4 MPa*m IC higher than the fracture toughness (K -1 / 2 ) of section A, 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 -1 / 2 . The fracture toughness (K IC ) of section C can be at most 2.0 MPa*m IC higher than the fracture toughness (K -1 / 2 ) of section A, at most 1.8 MPa*m -1 / 2 , at most 1.4 MPa*m -1 / 2 , at most 1.2 MPa*m -1 / 2 or at most 0.8 MPa*m -1 / 2 . The fracture toughness (K IC ) of section C can be 0.4 to 2.0 MPa*m IC higher than the fracture toughness (K -1 / 2 ) of section A, 0.6 to 2.0 MPa*m -1 / 2 , 0.8 to 1.8 MPa*m -1 / 2 , 1.0 to 1.8 MPa*m -1 / 2 , 1.2 to 1.8 MPa*m -1 / 2within the range of 0.4 to 1.2 MPa*m -1 / 2 within the range of 0.4 to 1.0 MPa*m -1 / 2 within the range

[0066] The fracture toughness (K IC ) of section B can be at least 1.2 MPa*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 . The fracture toughness (K IC ) of section B is at most 3.2 MPa*m -1 / 2 , at most 2.8 MPa*m -1 / 2 , at most 2.6 MPa*m -1 / 2 , at most 2.4 MPa*m -1 / 2 or at most 2.2 MPa*m -1 / 2 . The fracture toughness (K IC ) of section B can be within the range of 1.2 to 3.2 MPa*m -1 / 2 within the range of 1.4 to 2.6 MPa*m -1 / 2 within the range of at least 1.6 to 2.4 MPa*m -1 / 2 within the range of at least 1.6 to 2.2 MPa*m -1 / 2 within the range of at least 1.2 to 2.2 MPa*m -1 / 2 within the range of at least 2.4 to 3.2 Mpa*m -1 / 2 within the range

[0067] The fracture toughness (K IC ) of section A can be at least 0.5 MPa*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 . The fracture toughness (K IC ) of section A can be at most 3.0 MPa*m -1 / 2 , at most 2.2 MPa*m -1 / 2 , at most 2.0 MPa*m -1 / 2 , at most 1.8 MPa*m -1 / 2 , at most 1.6 MPa*m -1 / 2 , at most 1.2 MPa*m -1 / 2 or at most 1.0 MPa*m -1 / 2 . The fracture toughness (KIC ) can be in the range of 0.5 to 2.2 MPa*m -1 / 2 , preferably in the range of 0.7 to 2.0 MPa*m1 / 2, and more preferably in the range of at least 0.7 to 1.8 MPa*m -1 / 2 . The fracture toughness (K IC ) of section A can be in the range of 0.5 to 1.2 MPa*m -1 / 2 , in the range of 0.7 to 1.4 MPa*m -1 / 2 , in the range of 1.2 to 1.8 MPa*m -1 / 2 , in the range of 1.4 to 2.2 MPa*m -1 / 2 , in the range of 2.4 to 3.0 MPa*m -1 / 2 .

[0068] In one embodiment, the fracture toughness (K IC ) of section C is in the range of 1.2 to 2.0 MPa*m -1 / 2 and the fracture toughness (K IC ) of section A is in the range of 0.5 to 1.2 MPa*m -1 / 2 . In one embodiment, the fracture toughness (K IC ) of section C is in the range of 2.0 to 2.6 MPa*m -1 / 2 and the fracture toughness (K IC ) of section A is in the range of 1.4 to 2.2 MPa*m -1 / 2 . In one embodiment, the fracture toughness (K IC ) of section C is in the range of 2.2 to 3.0 MPa*m -1 / 2 and the fracture toughness (K IC ) of section A is in the range of 0.5 to 1.4 MPa*m -1 / 2 . In one embodiment, the fracture toughness (K IC ) of section C is in the range of 2.6 to 3.4 MPa*m -1 / 2 and the fracture toughness (K IC ) of section A is in the range of 2.4 to 3.0 MPa*m -1 / 2 . Considering the gradient of the fracture toughness (K IC ), it can be understood that section B has a fracture toughness (K IC ) with a value between that of section C and section A.

[0069] One or more gradients can be a gradient of machinability, where the machinability increases from section C to section A.

[0070] 1.2 Gradient of optical properties

[0071] One or more gradients can be gradients of contrast, where the contrast decreases from section C to section A. The contrast can be determined according to BS 5612, in particular BS 5612:1978. The contrast is typically determined using a test body with a thickness of 2 mm ± 0.02 mm. The test body can be prepared from different sections of the glass-ceramic tooth body (e.g., by milling, cutting, and / or sawing using a diamond-coated tool). Before measurement, the surface of the test body can be ground and polished as described in the "Measurement Method" section of this article. The contrast is related to the ratio (CR = Yb / Yw) of the illuminance (Y) of the material placed on a black background (Yb) to the illuminance (Yw) of the same material placed on a white background (Yw). The contrast can be used to characterize the translucency of the material, i.e., the light transmittance of the material expressed as the ratio of the transmittance to the incident light intensity. A contrast close to 0% can indicate that the given material is almost completely transparent, while a contrast of 100% can indicate that the material is completely opaque. When the size of the section is not suitable for preparing a sufficient test body for determining the contrast (K IC ) (e.g., according to BS 5612, and in particular according to BS 5612:1978), then after analyzing the crystalline phase and / or chemical composition of the corresponding part, a sufficient test body can be prepared from suitable raw materials.

[0072] The contrast of section C can be at least 62%, at least 65%, at least 75%, at least 80% or at least 85%. The contrast of section C can be at most 94%, at most 92%, at most 85%, at most 75% or at most 72%. The contrast of section C can be in the range of 62% to 94%, 65% to 92%, 75% to 85%, 80% to 94%, 85% to 92%, 62% to 75% or 65% to 72%.

[0073] The contrast of section C can be 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 of section A. The contrast of section C can be at most 56 percentage points, at most 52 percentage points, at most 35 percentage points, at most 30 percentage points or at most 26 percentage points higher than the contrast of section A. The contrast of section C is higher than the contrast of section A in the range of 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.

[0074] The contrast of section B can be at least 40%, at least 45%, at least 50%, at least 55% or at least 60%. The contrast of section B can be at most 90%, at most 85%, at most 80%, at most 75% or at most 65%. The contrast of section B can be in the range of 40% to 90%, 45% to 85%, 50% to 80%, 55% to 75%, 60% to 75% or 55% to 65%.

[0075] The contrast of section A can be at least 14%, at least 18%, at least 55%, at least 58% or at least 60%. The contrast of section A can be at most 80%, at most 74%, at most 70%, at most 65%, at most 30% or at most 25%. The contrast of section A can be in the range of 14% to 80%, 18% to 74%, 55% to 80%, 58% to 74%, 60% to 70%, 55% to 65%, 14% to 30% or 18% to 25%.

[0076] In one embodiment, the contrast of section C is in the range of 80% to 94% (e.g., in the range of 85% to 92%) and the contrast of section A is in the range of 58% to 74% (e.g., 60% to 70%). In one embodiment, the contrast of section C is in the range of 62% to 75% (e.g., in the range of 65% to 72%) and the contrast of section A is in the range of 14% to 30% (e.g., 18% to 25%). In one embodiment, the contrast of section C is 75% to 85% and the contrast of section A is 55% to 65%.

[0077] 1.3 Gradient of thermal properties

[0078] One or more gradients can be a gradient of the coefficient of thermal expansion (CTE), where 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 in accordance with DIN EN ISO 6872, and in particular DIN EN ISO 6872:2015. By milling, cutting and / or sawing the corresponding sections of the glass-ceramic dental body using a diamond-coated tool, test specimens can be obtained from each of the sections of the glass-ceramic dental body. When the dimensions of the section are not suitable for preparing a sufficient test specimen for determining the coefficient of thermal expansion (e.g., in accordance with DIN EN ISO 6872, and in particular in accordance with DIN EN ISO 6872:2015), then after analyzing the crystalline phase and / or chemical composition of the corresponding part, sufficient test specimens can be prepared from suitable raw materials.

[0079] The coefficient of thermal expansion of each of the segments can be in the range of 5 to 14 ppm / K. For example, the coefficient of thermal expansion of segment C can be in the range of 7 to 13 ppm / K or in the range of 8 to 12 ppm / K. The coefficient of thermal expansion of segment B can be in the range of 6 to 13 ppm / K or in the range of 7 to 12 ppm / K. The coefficient of thermal expansion of segment A can be in the range of 5 to 14 ppm / K or in the range of 6 to 13 ppm / K.

[0080] The coefficient of thermal expansion of segment C can differ from the coefficient of thermal expansion of segment A by at least 1 ppm / K. The coefficient of thermal expansion of segment C can differ from the coefficient of thermal expansion of segment A by at most 4 ppm / K or at most 3 ppm / K. The coefficient of thermal expansion of segment C can differ from the coefficient of thermal expansion of segment A by in the range of 1 to 4 ppm / K or in the range of 1 to 3 ppm / K. In one embodiment, the coefficient of thermal expansion of segment C can be in the range of 7 to 13 ppm / K (e.g., in the range of 8 to 12 ppm / K), and the coefficient of thermal expansion of segment A can be in the range of 5 to 14 ppm / K (e.g., in the range of 6 to 13 ppm / K), and the coefficient of thermal expansion of segment C differs from the coefficient of thermal expansion of segment A by in the range of 1 to 4 ppm / K (e.g., in the range of 1 to 3 ppm / K).

[0081] Hereinafter, an embodiment of the present invention is described, which is referred to herein as "Embodiment CTE-1". In Embodiment CTE-1, the gradient is a gradient of the coefficient of thermal expansion (CTE), where the coefficient of thermal expansion decreases from segment C to segment A.

[0082] In Embodiment CTE-1, the coefficient of thermal expansion of segment C can be at least 6.6 ppm / K, at least 7.6 ppm / K or at least 8.2 ppm / K. In Embodiment CTE-1, the coefficient of thermal expansion of segment C can be at most 10.6 ppm / K, at most 9.6 ppm / K or at most 9.0 ppm / K. In Embodiment CTE-1, the coefficient of thermal expansion of segment C can be in the range of 6.6 to 10.6 ppm / K, in the range of 7.6 to 9.6 ppm / K or in the range of 8.2 to 9.0 ppm / K.

[0083] In embodiment CTE-1, the coefficient of thermal expansion of section C can be 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 embodiment CTE-1, the coefficient of thermal expansion of section C can be at most 4.0 ppm / K, at most 3.2 ppm / K, or at most 2.8 ppm / K higher than the coefficient of thermal expansion of section A. In embodiment CTE-1, the coefficient of thermal expansion of section C can be in the range of 1.0 to 4.0 ppm / K, 1.8 to 3.2 ppm / K, or 2.2 to 2.8 ppm / K higher than the coefficient of thermal expansion of section A.

[0084] In embodiment CTE-1, the coefficient of thermal expansion of section B can be at least 5.2 ppm / K, at least 6.2 ppm / K, or at least 7.0 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section B can be at most 9.2 ppm / K, at most 8.2 ppm / K, or at most 9.0 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section B can be in the range of 5.2 to 9.2 ppm / K, 6.2 to 8.2 ppm / K, or 7.0 to 7.6 ppm / K.

[0085] In embodiment CTE-1, the coefficient of thermal expansion of section A can be at least 4.6 ppm / K, at least 5.2 ppm / K, or at least 5.8 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section A can be at most 8.2 ppm / K, at most 7.2 ppm / K, or at most 6.6 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section A can be in the range of 4.6 to 8.2 ppm / K, 5.2 to 7.2 ppm / K, or 5.8 to 6.6 ppm / K.

[0086] In a more specific embodiment, the coefficient of thermal expansion of section C can be in the range of 6.6 to 10.6 ppm / K (e.g., in the range of 7.6 to 9.6 ppm / K), and the coefficient of thermal expansion of section A can be 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 the coefficient of thermal expansion of section C is 1.0 to 4.0 ppm / K higher than the coefficient of thermal expansion of section A (e.g., in the range of 1.8 to 3.2 ppm / K).

[0087] Hereinafter, an embodiment of the present invention is described, which is referred to herein as "embodiment CTE-2". In embodiment CTE-2, the gradient is a gradient of the coefficient of thermal expansion (CTE), where the coefficient of thermal expansion increases from section C to section A.

[0088] In embodiment CTE-2, the coefficient of thermal expansion of section C can be at least 9.2 ppm / K, at least 10.2 ppm / K, or at least 10.6 ppm / K. In embodiment CTE-2, the coefficient of thermal expansion of section C can be at most 13.2 ppm / K, at most 12.2 ppm / K, or at most 11.8 ppm / K. In embodiment CTE-2, the coefficient of thermal expansion of section C can be in the range of 9.2 to 13.2 ppm / K, 10.2 to 12.2 ppm / K, or 10.6 to 11.8 ppm / K.

[0089] In embodiment CTE-2, the coefficient of thermal expansion of section C can be 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 embodiment CTE-2, the coefficient of thermal expansion of section C can be at most 2.5 ppm / K, at most 2.0 ppm / K, or at most 1.8 ppm / K lower than the coefficient of thermal expansion of section A. In embodiment CTE-2, the coefficient of thermal expansion of section C can be lower than the coefficient of thermal expansion of section A by 0.8 to 2.5 ppm / K, 1.0 to 2.0 ppm / K, or 1.2 to 1.8 ppm / K.

[0090] In embodiment CTE-1, the coefficient of thermal expansion of section B can be at least 10.0 ppm / K, at least 11.0 ppm / K, or at least 10.4 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section B can be at most 14.0 ppm / K, at most 13.0 ppm / K, or at most 12.6 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section B can be in the range of 10.0 to 14.0 ppm / K, 11.0 to 13.0 ppm / K, or 10.4 to 12.6 ppm / K.

[0091] In embodiment CTE-1, the coefficient of thermal expansion of section A can be at least 10.7 ppm / K, at least 11.7 ppm / K, or at least 12.1 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section A can be at most 14.4 ppm / K, at most 13.7 ppm / K, or at most 13.3 ppm / K. In embodiment CTE-1, the coefficient of thermal expansion of section A can be in the range of 10.7 to 14.4 ppm / K, 11.7 to 13.7 ppm / K, or 12.1 to 13.3 ppm / K.

[0092] In a more specific embodiment CTE-1, the coefficient of thermal expansion of section C can be in the range of 9.2 to 13.2 ppm / K (e.g., in the range of 10.2 to 12.2 ppm / K), and the coefficient of thermal expansion of section A can be 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 the coefficient of thermal expansion of section C is lower than that of section A by 0.8 to 2.5 ppm / K (e.g., in the range of 1.0 to 2.0 ppm / K).

[0093] 1.4 Gradients of Other Characteristics

[0094] It is also possible, and sometimes preferred, that the glass-ceramic dental body is characterized by a combination of gradients of one or more material properties as defined herein. In one embodiment, the glass-ceramic dental body is characterized by a combination of gradients of two or more mechanical properties, such as a gradient of biaxial flexural strength and a gradient of fracture toughness (K IC ). In one embodiment, the glass-ceramic dental body is characterized by a combination of gradients of one or more mechanical properties and gradients of one or more optical properties, such as a gradient of contrast with a gradient of biaxial flexural strength and / or a gradient of fracture toughness (K IC ).

[0095] The characteristic of one or more gradients can be a gradual or stepwise change in the corresponding property. A gradual change is typically achieved when the glass-ceramic dental body is composed of section B having a chemical composition that gradually changes in the direction from section C to section A. A stepwise 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 in other sections of the present disclosure.

[0096] Additionally or alternatively, in addition to one or more gradients, the glass-ceramic dental body can also be characterized by its crystalline phase. This will be described in more detail in the following sections.

[0097] 2. Crystalline Phase

[0098] The glass-ceramic dental body has a main crystalline phase. The main crystalline phase can be, but is not limited to, lithium disilicate, quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), or stoichiometric or non-stoichiometric lithium aluminosilicate (e.g., spodumene or spodumene solid solution).

[0099] The main crystalline phase of the glass-ceramic dental body is typically not lithium metasilicate. In one embodiment, based on the total weight of the glass-ceramic dental body, the glass-ceramic dental body does not contain a lithium metasilicate crystalline phase with a mass fraction greater than 5 wt.% or greater than 3 wt.%.

[0100] The portion of the glass-ceramic dental body may include different crystal phases. In one embodiment of the present invention, segment A may include one or more crystal phases different from those in segment C (and vice versa). The crystal phases in segment C, segment B, and / or segment A may be, but are not limited to, lithium disilicate, lithium silicate, apatite (e.g., fluorapatite), one or more quartz crystal phases (e.g., α-quartz, α-quartz solid solution, and / or β-quartz solid solution), stoichiometric lithium aluminosilicate (e.g., eucryptite, spodumene, spodumene solid solution, and / or petalite), non-stoichiometric lithium aluminosilicate phase (e.g., Li 2 O·Li 2 O·7.5SiO 2 ), cristobalite, lithium phosphate, magnesium silicate (e.g., enstatite), basic zirconium silicate (e.g., sogdianite or zektzerite), diopside, or wollastonite.

[0101] Each of the segments may include at least one (e.g., one, two, or three) crystal phase, the content of which is different from the content of each crystal phase in the other segments. This includes a segment that may include 0 wt.% of the corresponding crystal phase.

[0102] Each of the segments of the glass-ceramic dental body may be composed of a glass-ceramic material. Thus, in certain embodiments, each of the segments of the glass-ceramic dental body is composed of a glass-ceramic material. Alternatively, segment A may be composed of glass. This can be understood as essentially no crystal phase (0 wt.% of crystal phase) being contained in segment A. Segment A may be composed of glass, and segments B and C may be composed of glass-ceramic materials. Thus, in certain embodiments, segment A is composed of glass, and segments B and C are composed of glass-ceramic materials.

[0103] Each segment of the glass-ceramic dental body composed of a glass-ceramic material can be defined by a main crystal phase and optionally one or more minor crystal phases (i.e., one or more crystal phases present in a segment with a content less than that of the main crystal phase).

[0104] The glass-ceramic dental body may be defined by the main crystal phase of its segment C. The main crystal phase of segment C may be lithium disilicate, quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), stoichiometric lithium aluminosilicate (e.g., eucryptite, spodumene, spodumene solid solution, or petalite), or non-stoichiometric lithium aluminosilicate (e.g., Li 2 O·Li 2 O·7.5SiO 2)。In one embodiment, the main crystalline phase of section C is lithium disilicate or quartz (e.g., α - quartz, α - or β - quartz solid solution). The main crystalline phase of section C is typically lithium disilicate (although this is not required). The main crystalline phase of section C is generally not lithium metasilicate. Based on the total weight of section C, the main crystalline phase of section C can be present in an amount in the range of 20 wt.% to 80 wt.%.

[0105] The main crystalline phase of section C can be the sole crystalline phase of section C. However, section C typically includes one or more secondary crystalline phases. The one or more secondary crystalline phases can be but are not limited to lithium disilicate, lithium silicate, apatite (e.g., fluorapatite), one or more quartz crystal phases (e.g., α - quartz, α - quartz solid solution, and / or β - quartz solid solution), stoichiometric lithium aluminosilicate (e.g., eucryptite, spodumene, spodumene solid solution, and / or petalite), non - stoichiometric lithium aluminosilicate phase (e.g., Li 2 O·Li 2 O·7.5SiO 2 ), lithium phosphate, magnesium silicate (e.g., enstatite), alkaline zirconium silicate (e.g., katophorite or arfvedsonite), diopside or wollastonite.

[0106] The glass - ceramic dental body can be defined by the main crystalline phase of its section A. The main crystalline phase of section A can be lithium disilicate, apatite, quartz (e.g., α - quartz, α - quartz solid solution, or β - quartz solid solution), or lithium aluminosilicate (LAS). The apatite can be but is not limited to fluorapatite. The lithium aluminosilicate (LAS) can be stoichiometric lithium aluminosilicate (LiAlSiO 4 ), spodumene (LiAl(SiO) 2 ), spodumene solid solution, or petalite (LiAlSi 4 O 10 ), or non - stoichiometric lithium aluminosilicate phase (such as Li 2 O·Li 2 O·7.5SiO 2 ).

[0107] The main crystalline phase of section A can be the sole crystalline phase of section A. However, section A can also include one or more secondary crystalline phases. The one or more secondary crystalline phases can be but are not limited to lithium disilicate, lithium silicate, apatite (e.g., fluorapatite), one or more quartz crystal phases (e.g., α - quartz, α - quartz solid solution, and / or β - quartz solid solution), stoichiometric lithium aluminosilicate (e.g., eucryptite, spodumene, spodumene solid solution, and / or petalite), non - stoichiometric lithium aluminosilicate phase (e.g., Li 2 O·Li 2 O·7.5SiO2 ), lithium phosphate, magnesium silicate (e.g., enstatite), alkaline zirconium silicate (e.g., mellite or elpidite), diopside or wollastonite.

[0108] Segment B may have the same primary crystal phase as that of segment C or the same primary crystal phase as that of segment A. Segment B may include one or more secondary crystal phases. The one or more secondary crystal phases may be but are not limited to lithium disilicate, lithium silicate, apatite (e.g., fluorapatite), one or more quartz crystal phases (e.g., α - quartz, α - quartz solid solution, and / or β - quartz solid solution), stoichiometric lithium aluminum silicate (e.g., spodumene, petalite, petalite solid solution, and / or eucryptite), non - stoichiometric lithium aluminum silicate phase (e.g., Li 2 O·Li 2 O·7.5SiO 2 ), lithium phosphate, magnesium silicate (e.g., enstatite), alkaline zirconium silicate (e.g., mellite or elpidite), diopside or wollastonite.

[0109] In certain embodiments, segment C has a primary crystal phase (e.g., lithium disilicate), wherein the content of each crystal phase decreases in the direction from segment C to segment A. It should be understood that the content of the crystal phase in segment C is higher than that in segment B, and the crystal phase content in segment B is higher than that in segment A. This includes that segment A may have a different primary crystal phase from segment C, or segment A has a content of the primary crystal phase of segment C of substantially 0 wt.% (e.g., when segment A is glass or when segment A only contains other crystal phases). The inventors have found that when the content of the primary crystal phase of segment C decreases in the direction from segment C to segment A, it is easy to provide a glass - ceramic dental body with particularly advantageous properties, such as one or more of the specific material property gradients defined herein.

[0110] Additionally or alternatively, the content of the amorphous phase (i.e., glass phase) of the segments may increase in the direction from segment C to segment A. For example, the amorphous phase content in segment C may be lower than that in segment B, and the amorphous phase content in segment B may be lower than that in segment A. Segment A may be composed of an amorphous phase (i.e., glass) or may be composed of a glass - ceramic material. Thus, in one embodiment, the glass - ceramic dental body is characterized in that the content of the amorphous phase (i.e., glass phase) of each segment increases in the direction from segment C to segment A.

[0111] One or more crystal phases (e.g., the primary crystal phase and optionally one or more secondary crystal phases) of segment C, segment B, and segment A may be combined in different ways to provide a glass - ceramic dental body with the advantageous properties described herein. For the crystal phases, the glass - ceramic dental body can be divided into the following three types:

[0112] - Type 1: Segment C and segment A having the same main crystal phase

[0113] - Type 2: Segment C and segment A having different main crystal phases

[0114] - Type 3: Glass as segment A

[0115] 2.1 Type 1: Segment C and segment A having the same main crystal phase

[0116] Segment C may have the same main crystal phase as segment A. In this case, for each of the segments of the glass-ceramic dental body, the main crystal phase is generally the same. In one embodiment, the main crystal phase of each of the segments is the same (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)), where the content of the main crystal phase decreases from segment C to segment A. This should be understood to mean that the content of the main crystal phase in the bottom phase is higher than that in segment B, and the content of the main crystal phase in segment B is higher than that in segment A.

[0117] In one embodiment, the main crystal phase of each of the segments is the same (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)), where the content of the main crystal phase decreases from segment C to segment A, and where the glass-ceramic dental body is characterized by one or more of the following:

[0118] · A gradient of biaxial flexural strength, where the biaxial flexural strength decreases from segment C to segment A; and / or

[0119] · A gradient of fracture toughness (K IC )), where the fracture toughness (K IC ) decreases from segment C to segment A;

[0120] · A gradient of contrast, where the contrast decreases from segment C to segment A;

[0121] · A gradient of coefficient of thermal expansion, where the coefficient of thermal expansion decreases or increases from segment C to segment A.

[0122] In one embodiment, the main crystalline phase of each of the segments is lithium disilicate, and the content of lithium disilicate optionally decreases in the direction from segment C to segment A. In one embodiment, the main crystalline phase of each of the segments is lithium disilicate, and the content of lithium disilicate optionally decreases in the direction from segment C to segment A, and segments C and B and optionally segment A include one or more quartz crystalline phases (e.g., α-quartz and / or α-quartz solid solution) and / or lithium silicate as one or more secondary crystalline phases. In one embodiment, the main crystalline phase of each of the segments is lithium disilicate, and the content of lithium disilicate optionally decreases in the direction from segment C to segment A, and the glass-ceramic dental body is characterized by a gradient of biaxial flexural strength, wherein the biaxial flexural strength decreases from segment C to segment A; and / or a gradient of fracture toughness (K IC ), wherein the fracture toughness (K IC ) decreases from segment C to segment A.

[0123] In one embodiment, the main crystalline phase of each of the segments is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), and the content of quartz optionally decreases in the direction from segment C to segment A. In one embodiment, the main crystalline phase of each of the segments is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), and the content of quartz optionally decreases in the direction from segment C to segment A, and segments C, B, and A include lithium disilicate as a secondary crystalline phase, and optionally, segments C and B include stoichiometric lithium aluminosilicate (e.g., spodumene or spodumene solid solution) as another secondary crystalline phase. In one embodiment, the main crystalline phase of each of the segments is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution), and the content of quartz optionally decreases in the direction from segment C to segment A, and the glass-ceramic dental body is characterized by a gradient of contrast, wherein the contrast decreases from segment C to segment A.

[0124] 2.2 Type 2: Segments C and A with different main crystalline phases

[0125] Alternatively, segment C may have a main crystalline phase (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)) different from the main crystalline phase of segment A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminosilicate (LAS)). In this case, segments C and B may have the same main crystalline phase different from the main crystalline phase of segment A. Alternatively, segments A and B may have the same main crystalline phase different from the main crystalline phase of segment C. Thus, the main crystalline phase may be converted from segment C to segment B or from segment B to segment A. Each of the segments may also have a different main crystalline phase.

[0126] When the main crystal phase of segment C is different from that of segment A, the content of the main crystal phase of segment C can decrease from segment C to segment A, but not for each segment. Additionally or alternatively, the main crystal phase of segment A can decrease in the direction from segment A to segment C, but not for each segment.

[0127] In one embodiment, the main crystal phase of segment C (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)) is different from the main crystal phase of segment A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)), and optionally, the crystal phase content of the main crystal phase of segment C decreases in the direction from segment C to segment A, or the crystal phase content of the main crystal phase of segment A decreases in the direction from segment A to segment C. In one embodiment, the main crystal phase of segment C (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)) is different from the main crystal phase of segment A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)), and the crystal phase content of the main crystal phase of segment C decreases in the direction from segment C to segment A, or the crystal phase content of the main crystal phase of segment A decreases in the direction from segment C to segment A. In one embodiment, the main crystal phase of segment C (e.g., lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)) is different from the main crystal phase of segment A (e.g., apatite, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate (LAS)), and optionally, the crystal phase content of the main crystal phase of segment C decreases in the direction from segment C to segment A, or the crystal phase content of the main crystal phase of segment A decreases in the direction from segment A to segment C, and wherein the glass-ceramic dental body is characterized by one or more of the following:

[0128] · A gradient of biaxial flexural strength, wherein the biaxial flexural strength decreases from segment C to segment A; and / or

[0129] · A gradient of fracture toughness (K IC )), wherein the fracture toughness (K IC ) decreases from segment C to segment A;

[0130] · A gradient of contrast, wherein the contrast decreases from segment C to segment A;

[0131] · A gradient of coefficient of thermal expansion, wherein the coefficient of thermal expansion decreases or increases from segment C to segment A.

[0132] In one embodiment, the main crystalline phase of section C is lithium disilicate and the main crystalline phase of section A is apatite (e.g., fluorapatite) or quartz (e.g., α - quartz or α - quartz solid solution or β - quartz solid solution). In another embodiment, the main crystalline phase of section C is β - quartz solid solution and the main crystalline phase of section A is α - quartz or α - quartz solid solution.

[0133] In one embodiment, the main crystalline phase of section C is lithium disilicate, wherein the content of lithium disilicate optionally decreases from section C to section A, and wherein the main crystalline phases of sections B and A are quartz (e.g., α - quartz, α - quartz solid solution or β - quartz solid solution). In one embodiment, the main crystalline phase of section C is lithium disilicate, wherein the content of lithium disilicate optionally decreases from section C to section A, and wherein the main crystalline phases of sections B and A are quartz (e.g., α - quartz, α - quartz solid solution or β - quartz solid solution). In one embodiment, the main crystalline phase of section C is lithium disilicate, wherein optionally the content of lithium disilicate decreases from section C to section A, wherein section C includes one or more quartz crystalline phases (e.g., α - quartz, α - quartz solid solution and / or β - quartz solid solution) as secondary crystalline phases, wherein the main crystalline phases of sections B and A are quartz (e.g., α - quartz, α - quartz solid solution or β - quartz solid solution), and wherein sections B and A include lithium disilicate as a secondary crystalline phase. In one embodiment, the main crystalline phase of section C is lithium disilicate, wherein the content of lithium disilicate optionally decreases from section C to section A, and wherein the main crystalline phases of sections B and A are quartz (e.g., α - quartz, α - quartz solid solution or β - quartz solid solution), and wherein the glass - ceramic dental body is characterized by: a gradient of thermal expansion coefficient, wherein the thermal expansion coefficient decreases or increases from section C to section A; and / or a gradient of biaxial flexural strength, wherein the biaxial flexural strength decreases from section C to section A; and / or a gradient of fracture toughness (K IC ) , wherein the fracture toughness (K IC ) decreases from section C to section A.

[0134] In one embodiment, the main crystalline phase of segment C and segment B is lithium disilicate, wherein the content of lithium disilicate optionally decreases from segment C to segment A, and wherein the main crystalline phase of segment A is apatite (e.g., fluorapatite). In one embodiment, the main crystalline phase of segment C and segment B is lithium disilicate, wherein the content of lithium disilicate optionally decreases from segment C to segment A, wherein segment C and segment B include 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 secondary crystalline phases, and wherein the main crystalline phase of segment A is apatite (e.g., fluorapatite). In one embodiment, the main crystalline phase of segment C and segment B is lithium disilicate, wherein the content of lithium disilicate optionally decreases from segment C to segment A, and wherein the main crystalline phase of segment A is apatite (e.g., fluorapatite), and wherein the glass - ceramic dental body is characterized by: a gradient of biaxial flexural strength, wherein the biaxial flexural strength decreases from segment C to segment A; and / or a gradient of fracture toughness (K IC ) wherein the fracture toughness (K IC ) decreases from segment C to segment A.

[0135] 2.3 Type 3: Glass as segment A

[0136] In another embodiment, segment A is composed of glass and segments B and C are composed of glass - ceramic materials. When segment A is composed of glass, the main crystalline phases of segments C and B of the glass - ceramic dental body can be the same or different. The inventors have found that when segment A is composed of glass, it is easy to provide a glass - ceramic dental body with particularly advantageous properties, such as one or more of the specific material property gradients defined herein.

[0137] In one embodiment, segment A is composed of glass, and the main crystalline phases of segments C and B of the glass - ceramic dental body are the same, wherein the content of the main crystalline phase optionally decreases from segment C to segment B (and decreases to segment A, considering that the glass segment A is substantially free of crystalline phases). In one embodiment, segment A is composed of glass, segments B and C are composed of glass - ceramic materials, and wherein the glass - ceramic dental body is characterized by:

[0138] · A gradient of biaxial flexural strength, wherein the biaxial flexural strength decreases from segment C to segment A; and / or

[0139] · A gradient of fracture toughness (K IC ) wherein the fracture toughness (K IC ) decreases from segment C to segment A;

[0140] · A gradient of contrast, wherein the contrast decreases from segment C to segment A;

[0141] · A gradient of the coefficient of thermal expansion, wherein the coefficient of thermal expansion decreases or increases from section C to section A.

[0142] In one embodiment, section A is made of glass, and the main crystalline phase of section C and section B is lithium disilicate, wherein the content of lithium disilicate optionally decreases from section C to section B (and considering that the glass section A is substantially free of crystalline phase). In one embodiment, section A is made of glass, and the main crystalline phase of section C and section B is lithium disilicate, wherein the content of lithium disilicate optionally decreases from section C to section A (considering that the glass section A is substantially free of crystalline phase), and wherein the glass-ceramic dental body is characterized by: a gradient of biaxial flexural strength, wherein the biaxial flexural strength decreases from section C to section A; and / or a gradient of fracture toughness (K IC ), wherein the fracture toughness (K IC ) decreases from section C to section A; and / or a gradient of contrast, wherein the contrast decreases from section C to section A.

[0143] 2.4 Other specific combinations of crystalline phases

[0144] According to the embodiments defined in any one of Tables I to III below, the glass-ceramic dental body can be characterized by a specific combination of crystalline phases.

[0145] The glass-ceramic dental body can include a section having a main crystalline phase according to any one of embodiments AA to EE defined in Table I below.

[0146] Table I:

[0147] Embodiment Segment C Segment B Segment A Main crystal phase Main crystal phase Main crystal phase AA Lithium disilicate Lithium disilicate Lithium disilicate BB Lithium disilicate Lithium disilicate None (glass) CC Lithium disilicate Quartz Quartz DD Quartz Quartz Quartz EE Lithium disilicate Lithium disilicate Apatite

[0148] The glass-ceramic dental body can include a section having a main crystalline phase according to any one of embodiments A to F defined in Table II below.

[0149] Table II:

[0150]

[0151]

[0152] According to any one of embodiments a to j defined in Table III below, the glass-ceramic dental body can include a section having a main crystalline phase and including one or more (or all) secondary crystalline phases.

[0153] Table III:

[0154]

[0155] In any one of embodiments AA to EE of Table I, embodiments A to F of Table II, or embodiments a to j of Table III, the crystal phase content of the main crystal phase in section C can be reduced from section C to section A.

[0156] Additionally or alternatively, in addition to the gradient and / or crystal phase, the glass-ceramic dental body can also be characterized by its chemical composition. This will be described in more detail in the following sections.

[0157] 3. Chemical Composition

[0158] The chemical composition of each section of the glass-ceramic dental body is different from that of the other sections. The chemical composition of each section is generally different from each other such that each section includes at least one (e.g., one, two, or three) crystal phase with a content different from that of the corresponding crystal phase in the other sections.

[0159] The chemical composition of each section of the glass-ceramic dental body can be adjusted or selected such that the corresponding section includes one or more crystal phases (such as the main crystal phase, and optionally one or more secondary crystal phases) as defined herein. For example, this can be understood as adjusting or selecting the chemical composition of section C in such a way that when preparing the glass-ceramic dental body, e.g., by heating (e.g., sintering or hot pressing) the glass powder and / or glass-ceramic powder, one or more crystal phases of section C of the glass-ceramic dental body can be obtained, as described herein in connection with the method according to the invention.

[0160] For example, when the chemical composition of a section of the glass-ceramic dental body is to be adjusted or selected such that the section includes a high-purity α-quartz crystal phase, then a chemical composition substantially free of Li 2 O, Ga 2 O 3 and / or In 2 O 3 needs to be selected. Due to impurities in the raw materials, some residual amounts of these components may be inevitable. On the other hand, when the chemical composition of a section of the glass-ceramic dental body is to be adjusted or selected such that the section includes an α-quartz solid solution crystal phase, then a chemical composition containing Li 2 O (or alternatively Ga 2 O 3 or In 2 O 3 ) needs to be selected. When the chemical composition of a section of the glass-ceramic dental body is to be adjusted or selected such that the section includes a stoichiometric or non-stoichiometric lithium aluminosilicate crystal phase, then a chemical composition containing Li 2 O needs to be selected. Other examples will be obvious to those skilled in the art.

[0161] 3.1 Section C

[0162] Segment C may include SiO 2 , Li 2 O and alkaline metal oxides other than Li 2 O (e.g., K 2 O, Na 2 O, Rb 2 O and / or Cs 2 O). In addition, segment C typically includes a nucleating agent (e.g., P 2 O 5 and / or a metal such as Cu). Additional components may be, but are not limited to, GeO 2 , CaO, MgO, SrO, ZnO, Y 2 O, Li 2 O, La 2 O 3 , ZrO or coloring and / or fluorescent components (e.g., selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr and mixtures thereof).

[0163] Segment C may include the following components (may consist essentially of or may consist of the following):

[0164] 60.0 wt.% to 85.0 wt.% of SiO 2 ,

[0165] 0.0 wt.% to 10.0 wt.% of GeO 2 ,

[0166] 5.0 wt.% to 20.0 wt.% of Li 2 O,

[0167] 0.5 wt.% to 15.0 wt.% of alkaline metal oxides other than Li 2 O (e.g., K 2 O, Na 2 O, Rb 2 O and / or Cs 2 O),

[0168] 0.0 wt.% to 8.0 wt.% of P 2 O 5 (e.g., 0.5 wt.% to 8.0 wt.% of P 2 O 5 ),

[0169] 0.0 wt.% to 12.0 wt.% of CaO, MgO, SrO, ZnO or a mixture thereof,

[0170] 0.0 wt.% to 20.0 wt.% of Y2 O 3 、 Li 2 O, La 2 O 3 or a mixture thereof,

[0171] 0.0 wt.% to 12.0 wt.% of ZrO 2 ,

[0172] 0.0 wt.% to 5.0 wt.% of a colorant and / or fluorescent component, optionally selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr and mixtures thereof, and

[0173] 0.0 wt.% to 1.0 wt.%, optionally 0.0 wt.% to 0.5 wt.% of other components (such as F, B 2 O 3 , metal and / or residual impurities).

[0174] K 2 O, Na 2 O, Rb 2 O and Cs 2 O may each be present in segment C in an amount of 0.0 wt.% to 12.0 wt.%, wherein the amounts are selected such that K 2 O, Na 2 O, Rb 2 O and / or Cs 2 O accounts for 0.5 wt.% to 15.0 wt.% of segment C. The amount of SiO 2 can be adjusted to the amount of GeO 2 . For example, when a certain amount of GeO 2 is present, the amount of SiO 2 can be reduced by the amount of GeO 2 .

[0175] The chemical composition may vary depending on the main crystalline phase (and one or more secondary crystalline phases) present in segment C. The chemical composition of segment C can be selected in such a way that segment C of the glass-ceramic dental body has a main crystalline phase of lithium disilicate or quartz (e.g., α-quartz, α- or β-quartz solid solution). The chemical composition can be selected in such a way that segment C of the glass-ceramic dental body has a main crystalline phase and optionally one or more secondary crystalline phases, as described above for segment C.

[0176] Based on the total weight of segment C, the components of segment C as described above can be selected so that they add up to 100.0 wt.%.

[0177] 3.2 Segment B

[0178] Segment B may include SiO 2 , Li 2 O and alkaline metal oxides other than Li 2 O (e.g., K 2 O, Na 2 O, Rb 2 O and / or Cs 2 O). Segment B typically includes a nucleating agent (e.g., CuO, P 2 O 5 and / or a metal such as Cu). The additional components may be, but are not limited to, F, B 2 O 3 , GeO 2 , CaO, MgO, SrO, ZnO, Y 2 O 3 , Li 2 O, La 2 O 3 , ZrO 2 or a coloring and / or fluorescent component (e.g., selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0179] Segment B may include the following components (may consist essentially of or may consist of the following):

[0180] 55.0 wt.% to 80.0 wt.% of SiO 2 ,

[0181] 0.0 wt.% to 10.0 wt.% of GeO 2 ,

[0182] 5.0 wt.% to 30.0 wt.% of Li 2 O,

[0183] 0.5 wt.% to 15.0 wt.% of alkaline metal oxides other than Li 2 O (e.g., K 2 O, Na 2 O, Rb 2 O and / or Cs 2 O),

[0184] 0.0 wt.% to 8.0 wt.% of P 2 O 5 (e.g., 0.5 wt.% to 8.0 wt.% of P 2 O 5 ),

[0185] 0.0 wt.% to 12.0 wt.% of CaO, MgO, SrO, ZnO or a mixture thereof,

[0186] 0.0 wt.% to 20.0 wt.% of Y 2 O 3 、Li 2 O、La 2 O 3 or a mixture thereof,

[0187] 0.0 wt.% to 12.0 wt.% of ZrO 2 ,

[0188] 0.0 wt.% to 5.0 wt.% of a colorant and / or a fluorescent component, optionally selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr and mixtures thereof, and

[0189] 0.0 wt.% to 1.0 wt.%, optionally 0.0 wt.% to 0.5 wt.% of one or more other components (such as F, B 2 O 3 , metals and / or residual impurities).

[0190] K 2 O、Na 2 O、Rb 2 O and Cs 2 O may each be present in segment C in an amount of 0.0 wt.% to 12.0 wt.%, wherein the amounts are selected such that K 2 O、Na 2 O、Rb 2 O and / or Cs 2 O account for 0.5 wt.% to 15.0 wt.% of segment C. The amount of SiO 2 can be adjusted to the amount of GeO 2 . For example, when a certain amount of GeO 2 is present, the amount of SiO 2 can be reduced by the amount of GeO 2 .

[0191] The chemical composition may vary depending on the main crystalline phase (and one or more secondary crystalline phases) present in segment B. The chemical composition of segment B can be selected in such a way that segment B of the glass-ceramic dental body has a main crystalline phase of lithium disilicate or quartz (e.g., α-quartz, β-quartz solid solution or α-quartz solid solution). The chemical composition can be selected in such a way that segment B of the glass-ceramic dental body has a main crystalline phase and optionally one or more secondary crystalline phases, as described above for segment B.

[0192] The components of segment B can be selected such that, based on the total weight of segment B, they add up to 100.0 wt.%, as described above.

[0193] 3.3 Segment A

[0194] The chemical composition of segment A can vary depending on whether segment A is made of glass or glass-ceramic. When segment A is made of glass-ceramic, the chemical composition can vary depending on the main crystal phase (and one or more secondary crystal phases) present in segment A.

[0195] The chemical composition of segment A can be selected such that segment A has a main crystal phase of lithium disilicate, quartz (e.g., α-quartz, β-quartz solid solution, or α-quartz solid solution). In this case, segment A can include SiO 2 , Li 2 O, alkali metal oxides other than Li 2 O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O), and typical nucleating agents (e.g., P 2 O 5 and / or metals). Additional components can be, but are not limited to, F, B 2 O 3 , GeO 2 , CaO, MgO, SrO, ZnO, Y 2 O 3 , Li 2 O, 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).

[0196] In one embodiment, segment A is made of glass-ceramic (e.g., lithium disilicate or quartz as the main crystal phase), wherein segment A includes the following components (consisting essentially of or consisting of the following):

[0197] 59.0 wt.% to 90.0 wt.% of SiO 2 ,

[0198] 0.0 wt.% to 15.0 wt.% of GeO 2 ,

[0199] 2.0 wt.% to 20.0 wt.% of Li 2 O,

[0200] 0.0 wt.% to 15.0 wt.% of alkali metal oxides other than Li 2 O (e.g., K 2 O, Na 2 O, Rb 2 O and / or Cs 2 O),

[0201] 0.0 wt.% to 9.0 wt.% of P 2 O 5 ,

[0202] 0.0 wt.% to 12.0 wt.% of CaO, MgO, SrO, ZnO or a mixture thereof,

[0203] 0.0 wt.% to 20.0 wt.% of Y 2 O 3 , Li 2 O, La 2 O 3 or a mixture thereof,

[0204] 0.0 wt.% to 12.0 wt.% of ZrO 2 ,

[0205] 0.0 wt.% to 5.0 wt.% of a colorant and / or a fluorescent component, optionally selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr and mixtures thereof, and

[0206] 0.0 wt.% to 1.0 wt.%, optionally 0.0 wt.% to 0.5 wt.% of one or more other components (e.g., F, B 2 O 3 、metal and / or residual impurities).

[0207] In one embodiment, segment A is composed of a glass-ceramic (e.g., lithium disilicate or quartz as the main crystal phase), wherein segment A comprises the following components (consisting essentially of or consisting of the following):

[0208] 60.0 wt.% to 80.0 wt.% of SiO 2 ,

[0209] 0.0 wt.% to 5.0 wt.% of GeO 2 ,

[0210] 5.0 wt.% to 20.0 wt.% of Li 2 O,

[0211] 0.5 wt.% to 15.0 wt.% of other than Li 2Alkali metal oxides other than O (e.g., K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O),

[0212] 0.5 wt.% to 8.0 wt.% of P 2 O 5 ,

[0213] 0.0 wt.% to 12.0 wt.% of CaO, MgO, SrO, ZnO, or a mixture thereof,

[0214] 0.0 wt.% to 20.0 wt.% of Y 2 O 3 , Li 2 O, La 2 O 3 , or a mixture thereof,

[0215] 0.0 wt.% to 12.0 wt.% of ZrO 2 ,

[0216] 0.0 wt.% to 5.0 wt.% of a colorant and / or a fluorescent component, optionally selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof, and

[0217] 0.0 wt.% to 1.0 wt.%, optionally 0.0 wt.% to 0.5 wt.%, of one or more other components (e.g., F, B 2 O 3 , metals, and / or residual impurities).

[0218] K 2 O, Na 2 O, Rb 2 O, and Cs 2 O may each be present in section A in an amount of 0.0 to 12.0 wt.%, where the amounts are selected such that K 2 O, Na 2 O, Rb 2 O, and / or Cs 2 O accounts for 0.5 wt.% to 15.0 wt.% of section A. The amount of SiO 2 can be adjusted to the amount of GeO 2 . For example, when a certain amount of GeO 2 is present, the amount of SiO 2 can be reduced by the amount of GeO 2 .

[0219] Alternatively, the chemical composition of segment A can be selected such that segment A of the glass-ceramic dental body has a main crystal phase of apatite (e.g., fluorapatite). In this case, segment A can include SiO 2 、K 2 O、Na 2 O、CaO and a typical nucleating agent (e.g., P 2 O 5 and / or metal). Additional components can be, but are not limited to, Li 2 O、TiO 2 、F、B 2 O 3 、GeO 2 、CaO、MgO、SrO、ZnO、Y 2 O 3 、Li 2 O、La 2 O 3 、ZrO 2 or coloring and / or fluorescent components (e.g., selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0220] In one embodiment, segment A is composed of a glass-ceramic (e.g., apatite as the main crystal phase), wherein segment A includes the following components (consisting essentially of or consisting of the following):

[0221] 50.0 wt.% to 75.0 wt.% of SiO 2 ,

[0222] 0.0 wt.% to 12.0 wt.% of K 2 O,

[0223] 0.0 wt.% to 12.0 wt.% of Na 2 O,

[0224] 0.0 wt.% to 12.0 wt.% of CaO,

[0225] 0.5 to 10.0 wt.% of P 2 O 5 ,

[0226] 0.0 wt.% wt.% to 12.0 wt.% of Li 2 O,

[0227] 0.0 wt.% to 20.0 wt.% of SrO,

[0228] 0.0 wt.% to 8.0 wt.% of ZnO,

[0229] 0.0 wt.% to 8.0 wt.% of Li 2 O,

[0230] 0.0 wt.% to 8.0 wt.% of ZrO 2 , TiO 2 or a mixture thereof,

[0231] 0.0 wt.% to 3.0 wt.% of F,

[0232] 0.0 wt.% to 5.0 wt.% of B 2 O 3 ,

[0233] 0.0 wt.% to 5.0 wt.% of a colorant and / or a fluorescent component, optionally selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof, and

[0234] 0.0 wt.% to 1.0 wt.%, optionally 0.0 wt.% to 0.5 wt.% of one or more other components (e.g., metals and / or residual impurities).

[0235] In a more specific embodiment, segment A is composed of a glass-ceramic (e.g., apatite as the main crystal phase), wherein segment A comprises the following components (consisting essentially of or consisting of the following):

[0236] 50.0 wt.% to 75.0 wt.% of SiO 2 ,

[0237] 1.0 wt.% to 12.0 wt.% of K 2 O,

[0238] 1.0 wt.% to 12.0 wt.% of Na 2 O,

[0239] 1.0 to 12.0 wt.% of CaO,

[0240] 0.5 wt.% to 8.0 wt.% of P 2 O 5 ,

[0241] 0.0 wt.% to 12.0 wt.% of Li 2 O,

[0242] 0.0 wt.% to 20.0 wt.% of SrO,

[0243] 0.0 wt.% to 8.0 wt.% of ZnO,

[0244] 0.0 wt.% to 8.0 wt.% of Li 2 O,

[0245] 0.0 wt.% to 8.0 wt.% of ZrO 2 , TiO 2 or a mixture thereof,

[0246] 0.0 wt.% to 3.0 wt.% of F,

[0247] 0.0 wt.% to 5.0 wt.% of B 2 O 3 ,

[0248] 0.0 wt.% to 5.0 wt.% of a colorant and / or a fluorescent component, optionally selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof, and

[0249] 0.0 wt.% to 0.5 wt.% of one or more other components (e.g., metals and / or residual impurities).

[0250] The chemical composition of segment A can be selected in such a way that segment A of the glass-ceramic dental body has a main crystal phase and optionally one or more secondary crystal phases, as described above for segment A.

[0251] Alternatively, the chemical composition of segment A can be selected in such a way that segment A consists of glass. In this case, segment A may include SiO 2 , K 2 O and Na 2 O. The additional components can be, but are not limited to, Li 2 O, F, B 2 O 3 , CaO, MgO, SrO, ZnO, Li 2 O or a coloring and / or fluorescent component (e.g., selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof).

[0252] In one embodiment, segment A consists of glass, wherein segment A includes the following components (consisting essentially of or consisting of the following):

[0253] 59.0 wt.% to 90.0 wt.% of SiO 2 ,

[0254] 0.0 wt.% to 20.0 wt.% of E 1 (I) 2 O,

[0255] 0.0 wt.% to 15.0 wt.% of E 2 (II)O,

[0256] 0.0 wt.% to 15.0 wt.% of E 3 (III) 2 O 3 ,

[0257] 0.0 wt.% to 8.0 wt.% of E 4 (IV)O 2 ,

[0258] 0.0 wt.% to 15.0 wt.% of E 5 (V) 2 O 5 ,

[0259] 0.0 wt.% to 8.0 wt.% of E 6 (VI)O 3 ,

[0260] 0.0 wt.% to 2.0 wt.% of mixed-valence metal oxide,

[0261] 0.0 wt.% to 5.0 wt.% of F,

[0262] 0.0 wt.% to 1.0 wt.% of one or more other components (e.g., other coloring and / or fluorescent components, and / or residual impurities),

[0263] wherein,

[0264] E1(I) 2 O is selected from monovalent metal oxides (Me 1 (I) 2 O) and mixtures thereof,

[0265] E 2 (II)O is selected from divalent metal oxides (Me 2 (II)O) and mixtures thereof,

[0266] E 3 (III) 2 O 3 is selected from trivalent metal oxides (Me 3 (III) 2 O 3 ) and mixtures thereof,

[0267] E 4 (IV)O 2 is selected from tetravalent metal oxides (Me 4 (IV)O 2 ) and mixtures thereof,

[0268] E 5 (V) 2 O 5 selected from pentavalent metal oxides (Me 5 (V) 2 O 5 ) and mixtures thereof, and

[0269] E 6 (VI)O 3 selected from hexavalent metal oxides (Me 6 (VI)O 6 ) and mixtures thereof.

[0270] The monovalent metal oxide (ME1(I) 2 O) may be selected from Na 2 O, Li 2 O, K 2 O, Rb 2 O, Cs 2 O and mixtures thereof.

[0271] The divalent metal oxide (Me 2 (II)O) may be selected from CaO, BaO, MgO, SrO, ZnO, SnO and mixtures thereof.

[0272] The trivalent metal oxide (Me 3 (III) 2 O 3 ) may be selected from 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 O 3 and mixtures thereof.

[0273] The tetravalent metal oxide (Me 4 (IV)O 2 ) may be selected from ZrO 2 , TiO 2 , SnO 2 , GeO 2 and mixtures thereof.

[0274] The pentavalent metal oxide (Me 5 (V) 2 O 5may be selected from Ta 2 O 5 、Nd 2 O 5 、P 2 O 5 and mixtures thereof.

[0275] The hexavalent metal oxide (Me 6 (VI)O 6 ) may be selected from WO 3 、MoO 3 and mixtures thereof.

[0276] The mixed valence metal oxide may be a mixed trivalent / tetravalent metal oxide (ME3 / 4(III,IV)4O7).

[0277] In a more specific embodiment, section A is composed of glass, wherein section A comprises the following components (consisting essentially of or consisting of the following):

[0278] 60.0 wt.% to 80.0 wt.% of SiO 2 ,

[0279] 1.0 wt.% to 18.0 wt.% of K 2 O,

[0280] 0.5 wt.% to 12.0 wt.% of Na 2 O,

[0281] 0.0 wt.% to 12.0 wt.% of CaO,

[0282] 0.0 wt.% to 12.0 wt.% of Li 2 O,

[0283] 0.0 wt.% to 8.0 wt.% of SrO, ZnO or mixtures thereof,

[0284] 0.0 wt.% to 10.0 wt.% of Li 2 O,

[0285] 0.0 wt.% to 5.0 wt.% of F,

[0286] 0.0 wt.% to 10.0 wt.% of B 2 O 3 ,

[0287] 0.0 wt.% to 15.0 wt.% of P 2 O 5 ,

[0288] 0.0 wt.% to 5.0 wt.% of a colorant and / or fluorescent component, optionally selected from the group consisting of oxides of Sn, Ce, V, Mn, Co, Ni, Cu, Fe, Cr, Tb, Eu, Er, Pr, and mixtures thereof,

[0289] 0.0 wt.% to 0.5 wt.% of one or more other components (such as residual impurities).

[0290] Based on the total weight of segment A, the components of segment A as described above can be selected such that they add up to 100.0 wt.%.

[0291] Additionally or alternatively, in addition to the gradient, crystal phase, and / or chemical composition, the glass-ceramic dental body can also be characterized by its structure and / or form.

[0292] 4. Structure and form

[0293] The glass-ceramic dental body comprises three consecutive segments:

[0294] Segment A,

[0295] Segment B, and

[0296] Segment C,

[0297] wherein each of said segments has a chemical composition different from that of the other segments.

[0298] In one embodiment, the glass-ceramic dental body consists of three consecutive segments: segment A, segment B, and segment C.

[0299] 4.1 Dental blank

[0300] The glass-ceramic dental body can be a glass-ceramic dental blank (such as a dental milling blank or a pressing blank). The dental blank (e.g., a dental milling blank) is characterized in that:

[0301] Segment A forms the top segment of the dental blank,

[0302] Segment B forms the middle segment of the dental blank, and

[0303] Segment C forms the bottom segment of the dental blank.

[0304] The glass-ceramic dental blank is not particularly limited in terms of its shape or dimensions, as long as it is suitable for the preparation of dental restorations (e.g., using CAD / CAM technology or hot pressing into a mold). The glass-ceramic dental blank can have, but is not limited to, the form of a rectangular block, ingot, disc, cylinder, dental preform (e.g., abutment preform or tooth sector), cone, conical section, pyramid or pyramidal section. The glass-ceramic dental blank can include additional components outside the glass-ceramic dental blank, which are not part of the sections described herein. For example, the dental blank can include fastening pins, support layers, protective layers, printed layers or sacrificial layers, such as (thin) layers of glass-ceramic material, which are removed (e.g., by milling) when forming a dental restoration from the blank piece. In one embodiment, the dental blank is a dental milling blank in the form of a disc, cylinder or rectangular block. The dental milling blank can include fastening pins for holding the glass-ceramic dental milling blank in the equipment when machining, for example, using CAD / CAM technology. The fastening pins should not be regarded as part of the section of the dental milling blank.

[0305] Each section of the glass-ceramic dental blank can 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 section. For example, for a rectangular or disc-shaped dental blank, etc., the total height can be determined as the distance of the vertical line between the outer surface of the top section and the relative outer surface of the bottom section, and this vertical line intersects all 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 has nothing to do with whether it is a relative height or an absolute height defined herein. Therefore, the definition of the section height used herein (e.g., relative height or absolute height) does not necessarily mean that the height of the section is constant, although this is possible.

[0306] Each of the sections can have a substantially constant height. "Substantially constant height" means that the change in the height of the section relative to the average height of the section does not exceed 5%. Relative to the total height of the glass-ceramic dental blank, the height of the bottom section can be in the range of 30% to 75%, 40% to 75%, 45% to 70% or 50% to 70%. Relative to the total height of the glass-ceramic dental blank, the height of the middle section can be in the range of 5% to 40%, 10% to 30% or 15% to 25%. Relative to the total height of the glass-ceramic dental blank, the height of the top section can be in the range of 5% to 35%, 10% to 30% or 15% to 25%.

[0307] 4.2 Dental Restoration

[0308] The glass-ceramic dental body can be a dental prosthesis. The dental prosthesis can be characterized in that:

[0309] Segment A forms the upper part of the dental prosthesis (e.g., part or all of the incisal region),

[0310] Segment B forms the middle part of the dental prosthesis (e.g., part or all of the transition region between the incisal region and the dentin region), and

[0311] Segment C forms the lower part of the dental prosthesis (e.g., part or all of the dentin region).

[0312] The dental prosthesis can be, but is not limited to, a crown, partial crown, abutment, abutment crown, inlay, onlay, veneer, dental shell or multi-unit framework or bridge (e.g., 2-unit bridge, 3-unit bridge or 4-unit bridge), implant bridge, etc. The dental prosthesis can have a desired color. The color of the dental prosthesis can match the VITA Bleached shade in the VITA classical tooth shade guide produced by Vita Zahnfabrik. The shade can 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.

[0313] The dental prosthesis can include glaze. In one embodiment, the dental prosthesis includes at least a first glaze and a second glaze, wherein the coefficient of thermal expansion of the first glaze is lower than that of the second glaze, and wherein the first glaze is present on the surface region of a part of the dental prosthesis having a lower coefficient of thermal expansion, and the second glaze is present on the surface region of a part of the dental prosthesis having a higher coefficient of thermal expansion. In this case, the terms "lower" and "higher" should be understood in relation to each other.

[0314] 4.3 Structure

[0315] The glass-ceramic dental body can have a multi-layer structure. Each of segments A to C can be composed of one or more layers (such as 1 to 8 layers, 1 to 6 layers, 1 to 4 layers, 1 to 3 layers, such as 2 layers or 1 layer). The chemical composition of each layer can be different. When the glass-ceramic dental body has a multi-layer structure, segment A can be layer A, segment C can be layer C, segment B can be formed by at least one intermediate layer between layer A and layer C, and each layer has a chemical composition different from that of the other layers. The at least one intermediate layer can be 1 to 8 layers, 1 to 6 layers, 1 to 4 layers, 1 to 3 layers, such as 2 layers or 1 layer.

[0316] When the glass-ceramic dental body has a multi-layer structure, the characteristics of one or more of the gradients described herein may lie in that the corresponding properties of one or more of the gradients change in a layer-by-layer manner from layer C to layer A. Additionally or alternatively, the content of the crystalline phase (e.g., the main crystalline phase of the bottom layer) may change (e.g., decrease) in a layer-by-layer manner from layer C to layer A.

[0317] The layers of the glass-ceramic dental body are not particularly limited in terms of their size and shape. One or more of the layers may be non-planar. For example, one or more of the layers may have one or two curved surfaces (e.g., the interface between two layers or the outer surface depending on the position of the layer in the dental body), such as having a positive or negative curvature (e.g., a convex or concave surface). It is also possible for the height of one or more of the layers to increase uniformly or non-uniformly (e.g., in the form of a cone) over at least part of the layer. One or more of the layers, optionally all of the layers, may be substantially flat. In this case, "substantially flat" means that the layer is planar with 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.

[0318] Alternatively, the glass-ceramic dental body has an intermediate section that has a chemically varying composition in the direction from section C to section A. In this alternative, the glass-ceramic dental body generally does not contain discrete layers. Sections A and C may have a substantially homogeneous chemical composition. This can be understood as sections A and C being part of the glass-ceramic dental body where the chemical composition does not change in the direction from section C to section A.

[0319] The glass-ceramic dental body is generally a heat-treated (e.g., (fully) sintered or hot-compacted) glass-ceramic dental body. The glass-ceramic dental body can be obtained by heat treatment in a maximum temperature range of 650 °C to 1050 °C. The glass-ceramic dental body can be obtained by (fully) sintering in a maximum sintering temperature range of 700 °C to 1050 °C (such as 780 °C to 980 °C, such as 820 °C to 940 °C). The glass-ceramic dental body can be obtained by hot pressing in a maximum temperature range of 650 °C to 850 °C (such as 700 °C to 800 °C) and a pressure range of 5 to 50 MPa (such as 10 to 30 MPa).

[0320] II. Method for Preparing a Glass-Ceramic Dental Body

[0321] 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 includes the following steps:

[0322] - Providing two or more powders selected from glass powders, glass-ceramic powders, and mixtures thereof;

[0323] - Preparing a shaped body from the powders; and

[0324] - Heat-treat the formed body to obtain a glass-ceramic dental body.

[0325] The formed body generally includes three successive powder segments:

[0326] Powder segment A,

[0327] Powder segment B, and

[0328] Powder segment C,

[0329] wherein the weight ratios of two or more powders are different in each of the powder segments.

[0330] 1. Provide glass powder and / or glass-ceramic powder

[0331] The method includes the step of providing two or more powders selected from glass powder, glass-ceramic powder, and mixtures thereof. The powders have different chemical compositions. In one embodiment, the two or more powders are two or more glass powders.

[0332] The two or more powders can be two powders (e.g., two glass powders). However, more than two powders can also be used, e.g., 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.

[0333] Each of the glass powders is generally provided by melting chemical starting materials suitable for preparing glass. The starting materials can be melted at a temperature of 1300 °C to 1650 °C (e.g., 1450 to 1650 °C) for a time of 30 min to 10 h (e.g., 30 min to 3 h). The melt can be poured into water to freeze the glass. To improve the uniformity of the glass, the glass can be remelted under the same or similar conditions and refrozen in water. Each of the obtained glasses can be dried in an oven. Each of the obtained glasses can be ground to obtain glass powder. The volume-based median particle size d50 of each of the glass powders can be in the range of 5 to 30 μm, such as in the range of 10 to 20 μm. The volume-based top cut particle size d98 of each of the glass powders can be less than 60 μm, such as less than 50 μm. The volume-based median particle size d50 and the volume-based top cut particle size d98 can be determined, for example, by laser diffraction according to ISO 13320 (ISO 13320:2009).

[0334] Each of the powders can 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 pressure aids, and / or one or more binders. Suitable pigments can be but not limited to, doped spinels, doped zirconia, zirconia, doped zirconium silicate, doped yttrium silicate, or tin oxide. Suitable pressure aids can be but not limited to, polyethylene glycols or stearic acid. Suitable binders can be but not limited to, polyvinyl alcohol and cellulose derivatives, such as sodium carboxymethyl cellulose.

[0335] The powders, optionally combined with one or more additives, can be provided in a dry form. The powders together with one or more additives can be provided in the form of a dry blend. The dry blend can be a mixture of granules or can be in the form of granules. The granules can be prepared by granulating with one or more additives (usually including one or more binders) in a granulation process known in the art. Based on the total weight of the dry blend, the dry blend can include at least 90 wt.% of the powders. Based on the total weight of the dry blend, one or more additives can be present in the dry blend in an amount in the range of 0.1 wt.% to 10.0 wt.%, such as 0.3 wt.% to 5.0 wt.%. Based on the total weight of the dry blend, one or more binders can be present in the dry blend in an amount in the range of 0.1 wt.% to 5.0 wt.%, such as 0.3 wt.% to 3.0 wt.%. Based on the total weight of the dry blend, one or more pressure aids can be present in the dry blend in an amount in the range of 0.1 wt.% to 3.0 wt.%, such as 0.1 wt.% to 1.0 wt.%.

[0336] Alternatively, the powder, optionally in combination with one or more additives, can be provided in liquid form, such as in the form of a suspension, and is typically provided in the form of an aqueous suspension. The suspension can be a slurry. The suspension can include powder in an amount in the range of 30 wt.% to 90 wt.%, such as 40% to 70%, based on the total weight of the suspension. The suspension can include one or more additives (e.g., one or more pigments, one or more fluorescent pigments, one or more compaction aids, and / or one or more binders) in an amount in the range of 0.1 wt.% to 10.0 wt.%, such as 0.3 wt.% to 5.0 wt.%, based on the total dry weight of the suspension. Suitable pigments, fluorescent pigments, compaction aids, and binders are known to those skilled in the art and can be, but are not limited to, those described above. One or more binders can be present in an amount of 0.1 wt.% to 5.0 wt.%, such as 0.3 wt.% to 3.0 wt.%, based on the total weight of the dry weight of the suspension. One or more compaction aids can be present in an amount in the range of 0.1 wt.% to 3.0 wt.%, such as 0.1 wt.% to 1.0 wt.%, based on the total dry weight of the suspension. Additionally or alternatively, the suspension can include one or more adjuvants, such as one or more rheology modifiers (e.g., xanthan gum or starch), one or more dispersants (e.g., polymers or lecithin), one or more buffers, and / or pH regulators (e.g., acids, such as acetic acid or hydrochloric acid), etc. The suspension can include one or more adjuvants in an amount in the range of 0.1 wt.% to 3.0 wt.% based on the total weight of the suspension.

[0337] 2. Preparation of a shaped body

[0338] The method further includes the step of preparing a shaped body from the powder (e.g., glass powder). The shaped body can be porous.

[0339] The shaped body can be prepared by additive manufacturing such as stereolithography, inkjet printing, screen printing, powder bed printing, or fused deposition modeling (fused filament fabrication). When the shaped body is prepared by additive manufacturing, it can have the shape of a dental restoration so that the shaped body can be converted into a dental restoration by heat treatment (e.g., sintering as described below) in a subsequent step. Alternatively, the shaped body can have the shape of a dental blank such that the shaped body can be converted into a dental blank by heat treatment (e.g., sintering as described below).

[0340] Alternatively, a shaped body can be prepared by molding a powder in a suitable mold to obtain a molded body. The molded body typically has a pre-shape of a dental blank. The pre-shape can have the dental blank in a desired form, such as, but not limited to, a disc, a cylinder, or a rectangular block. The preparation of the molded body can depend on the form in which the powder is provided. When the powder is provided in a dry form (e.g., in the form of a dry blend with one or more additives), the powder can be introduced into the mold, followed by a compaction step (e.g., a pressing step, such as uniaxial pressing). The compaction step can be a cold compaction step. Cold compaction (e.g., cold pressing) can be carried out at a temperature below 60 °C (such as in the range of 15 to 35 °C) and at a pressure of 2 to 30 bar (such as in the range of 5 to 15 bar). Additionally or alternatively, the compaction step can be a hot compaction step. The hot compaction step (e.g., a hot pressing step) can be carried out in the range of 650 to 850 °C (such as in the range of 700 to 800 °C) and in a pressure range of 5 to 50 MPa (preferably 10 to 30 MPa). Hot compaction is typically carried out in the range of 0.1 to 10 min, such as in the range of 0.3 to 5 min. The hot compaction step is preferably carried out at an atmospheric pressure below ambient pressure, for example, at an atmospheric pressure of less than 0.1 bar (such as in the range of 0.01 to 0.8 bar). The hot compaction can be pressure sintering. After the hot compaction, a compact can be obtained that is substantially pore-free or does not contain significant porosity.

[0341] When the powder is provided in a liquid form, the powder can be introduced into the mold, followed by removal of the liquid. The mold can be a mold suitable for die casting or slip casting. The mold can have holes through which the liquid can be removed. The removal of the liquid can be carried out and / or supported by, for example, extrusion, suction, and / or freeze-drying.

[0342] The shaped body typically comprises three successive powder segments (or can be composed of three successive powder segments):

[0343] Powder segment A,

[0344] Powder segment B, and

[0345] Powder segment C.

[0346] The preparation of the powder segments is such that the weight ratio of two or more powders (e.g., two or more glass powders) is different in each of the powder segments.

[0347] When the glass-ceramic dental body has a multi-layer structure, the powder segments A to C can be composed of one or more powder layers. For example, a green body can be prepared such that the powder segment C is the powder layer C, the powder segment B is formed by at least one intermediate powder layer, and the powder segment A is the powder layer A. The powder segment B can be formed by 1 to 8 or more intermediate powder layers (e.g., 1 to 6 layers, 1 to 4 layers, 1 to 3 layers, 2 layers, 1 layer).

[0348] Alternatively, the green body can be prepared from powders such that the powder segments C and A comprise substantially homogeneous chemical compositions, and the powder segment B comprises two or more powders, the weight ratio of which varies gradually in the direction from the powder segment C to the powder segment A within the powder segment B. Such a gradual change can be achieved by using deposition or metering devices known in the art. Such deposition or metering devices can be adjusted to continuously vary the weight content of the components in the mixture added to the mold.

[0349] 2.1 Two Powders

[0350] When preparing a green body (e.g., a molded body) from two powders (i.e., a first powder and a second powder), the powder segments are prepared such that the weight ratio of the two powders is different in each of the powder segments. In one embodiment, a green body (e.g., a molded body) is prepared from two glass powders (i.e., a first glass powder and a second glass powder), and the powder segments are prepared such that the weight ratio of the two glass powders is different in each of the powder segments.

[0351] The powder segments are typically prepared such that the weight ratio of the first powder to the second powder decreases in the direction from the powder segment C to the powder segment A. This is to be understood as meaning that the weight content of the first powder decreases in the direction from the powder segment C to the powder segment A, and the weight content of the second powder increases in the direction from the powder segment C to the powder segment A. Thus, the powder segment C can include a higher amount of the first powder than the amount of the first powder in the powder segment B, and the powder segment B includes a higher amount of the first powder than the amount of the first powder in the powder segment A (the reverse being the case for the second glass powder). This includes the second powder being substantially absent from the powder segment C (i.e., about 0 wt.%) and / or the first powder being substantially absent from the powder segment A (i.e., about 0 wt.%).

[0352] The weight ratio of the first powder to the second glass powder can 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 powder of the powder section (i.e., the powder present in the powder section in an amount of >50 wt.% based on the combined weight of the powders) can be different between powder section C and powder section A. However, the main powder can also be the same in each of the powder sections. In this case, the weight ratio of the first powder to the second powder can vary from a weight ratio of >90:<10 (e.g., 100:0) in powder section C to a weight ratio within 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.

[0353] For example, a shaped body (e.g., a molded body) can comprise (or can be composed of)

[0354] powder section A, wherein powder section A is composed of a second powder (e.g., a second glass powder), optionally in combination with one or more additives,

[0355] powder section B, wherein powder section B is composed of a mixture of a first powder (e.g., a first glass powder) and a second powder (e.g., a second glass powder), each powder optionally in combination with one or more additives, and

[0356] powder section C, wherein powder section C is composed of a first powder (e.g., a first glass powder), optionally in combination with one or more additives.

[0357] 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 to mean that 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 layer by layer, and the weight content of the second powder increases layer by layer. Typically, the chemical composition of each layer is substantially homogeneous. Thus, if 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 powder and the second powder respectively decrease and increase in a layer-by-layer decreasing and layer-by-layer increasing manner in the direction from powder section C to powder section A. When the layer comprises a mixture of the first powder and the second powder or is composed of a mixture of the first powder and the second powder (optionally in combination with one or more additives), the powders can be premixed with each other before being introduced into the mold to form the layer.

[0358] In an alternative embodiment, the molded body is prepared from two powders in such a way that powder section C and powder section A have a substantially homogeneous chemical composition, and the weight ratio of the first powder to the second powder gradually decreases within section B in the direction from powder section C to powder section A. The weight content of the second powder gradually decreases within section B in the direction from powder section C to powder section A.

[0359] 2.2 Three powders

[0360] When preparing a molded body from three powders (i.e., a first powder, a second powder, and a third powder), powder sections can be prepared such that the weight ratio of the three powders is different in each of the powder sections. In one embodiment, the molded body is prepared from three glass powders (i.e., a first glass powder, a second glass powder, and a third glass powder), and powder sections can be prepared such that the weight ratio of the three glass powders is different in each of the powder sections.

[0361] Each powder section can include one of the three powders (e.g., one of the three glass powders). 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.

[0362] For example, a shaped body (e.g., a molded body) can include (or can be composed of):

[0363] Powder section A, wherein powder section A is composed of the third powder (e.g., the third glass powder), optionally in combination with one or more additives,

[0364] Powder section B, wherein powder section B is composed of the second powder (e.g., the second glass powder), optionally in combination with one or more additives, and

[0365] Powder section C, wherein powder section C is composed of the first powder (e.g., the first glass powder), optionally in combination with one or more additives.

[0366] However, it is also possible, and sometimes preferred, that one or more powder sections (e.g., at least section B) include 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 4 layers, or when section B has a gradually changing powder weight ratio.

[0367] When the glass-ceramic dental body has a multi-layer structure, powder layers can be prepared such that the weight ratio of the three powders is different in each of the powder layers.

[0368] Alternatively, the molded body can be prepared from the powder in such a way that the powder section C and the powder section A have a substantially homogeneous chemical composition, and the powder section B contains a weight ratio of powder selected from the first powder, the second powder, and the third powder, and this weight ratio of the powder gradually changes in the direction from the powder section C to the powder section A within the section B.

[0369] 3. Heat treatment of the formed body

[0370] The method further includes the step of heat-treating the formed body (e.g., the molded body) to obtain a glass-ceramic dental body.

[0371] The heat treatment generally includes a sintering step. During the sintering step, the formed powder (e.g., the molded powder) is densified by applying heat. The sintering step can be a conventional sintering step carried out without applying additional pressure. However, the sintering step can also be a pressure sintering. In pressure sintering, applying pressure helps the densification of the powder. As described above, pressure sintering can be carried out simultaneously with the hot compaction step. The heat treatment can also include a crystallization step. In the crystallization step, one or more new crystal phases can be generated, or one or more existing crystal phases can be converted into another crystal phase. The crystallization step can be carried out together with the sintering step, or separately as after the sintering step. When the formed body includes or is composed of glass powder, the heat treatment generally also includes a crystallization step.

[0372] The heat treatment can be carried out in a maximum temperature range of 700 to 1050 °C, such as in the range of 780 to 980 °C, such as in the range of 820 to 940 °C. The maximum temperature can be maintained for a period of time in the range of 5 min to 2 hours, such as in the range of 10 min to 1 hour, such as in the range of 15 min to 45 min.

[0373] The heat treatment can include one or more heating steps, such as two, three or more heating steps. For example, the heat treatment can include a first heating step and a second heating step. The first heating step can start in a temperature range of 300 to 500 °C, such as in the range of 350 to 450 °C, and can end in the range of 500 to 700 °C, such as in the range of 550 to 650 °C. The end temperature of the first heating step can be maintained for a period of time in the range of 5 min to 2 hours, such as in the range of 10 min to 1 hour, such as in the range of 15 min to 45 min. The first heating step can have a heating rate in the range of 5 to 15 K / min. The second heating step can start at the end temperature of the first heating step and can end at the maximum temperature. The second heating step can have a heating rate in the range of 5 to 15 K / min.

[0374] The heat treatment can be carried out partially or completely at a pressure below ambient pressure. For the present disclosure, ambient pressure is defined as 1.013 bar. For example, the heat treatment can be carried out partially or completely at a pressure less than 0.9 bar, such as in the range of 10 to 300 mbar or 30 to 120 mbar. The heat treatment is typically followed by a cooling step. The cooling step starts at the highest 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).

[0375] The method can include one or more additional process steps, which are typical in the art and can be carried out before, between, or after the process steps described herein. The additional steps can 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 shaped body (e.g., molded body) and / or the glass-ceramic dental body (e.g., by grinding, lapping, or polishing).

[0376] III. USES OF THE GLASS-CERAMIC BODY

[0377] When the glass-ceramic dental body is a glass-ceramic dental blank (e.g., a dental milling blank), the glass-ceramic dental body is useful for preparing dental restorations, such as the dental restorations 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 comprising using a glass-ceramic dental blank according to an embodiment of the present invention.

[0378] In a preferred embodiment, a method for preparing a dental restoration is provided, wherein the method comprises the steps of: machining a glass-ceramic dental milling blank according to an embodiment of the present invention to provide a dental restoration, and optionally surface-treating the dental restoration.

[0379] The machining of the dental milling blank can be carried out by any conventional process for machining glass-ceramic dental milling blanks and is typically carried out by a CAD / CAM process. Such methods are well known in the art. The machining can include, but is not limited to, cutting, drilling, and / or grinding the glass-ceramic dental milling blank. The dental restoration can optionally be surface-treated by methods well known in the art, for example, by polishing, coloring, 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, wherein the thermal expansion coefficient of the first glaze is lower than that of the second glaze, and wherein the first glaze is applied to the surface area of a part of the dental restoration having a lower thermal expansion coefficient, and the second glaze is applied to the surface area of a part of the dental restoration having a higher thermal expansion coefficient. In this case, the terms "lower" and "higher" should be understood in relation to each other.

[0380] Another embodiment of the present invention provides a dental prosthesis obtained using a glass-ceramic dental milling blank according to an embodiment of the present invention. Another embodiment of the present invention provides a dental prosthesis obtained by a method for preparing a dental prosthesis according to an embodiment of the present invention.

[0381] IV. Other non-limiting aspects and embodiments

[0382] Other non-limiting aspects and embodiments of the present invention are defined in the following items [1] to

[35] :

[0383] [1] A glass-ceramic dental body, the glass-ceramic dental body comprising three consecutive segments (or consisting of three consecutive segments):

[0384] Segment A,

[0385] Segment B, and

[0386] Segment C,

[0387] wherein each of the segments has a chemical composition different from that of the other segments.

[0388] [2] The 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 segment C to segment A.

[0389] [3] The glass-ceramic dental body according to item [2], wherein the one or more mechanical property gradients are gradients of biaxial flexural strength, wherein the biaxial flexural strength decreases from segment C to segment A; and / or a gradient of fracture toughness (K IC ), wherein the fracture toughness (K IC ) decreases from segment C to segment A.

[0390] [4] The glass-ceramic dental body according to any one of items [1] to [3], wherein the glass-ceramic dental body is characterized by a gradient of optical properties in the direction from segment C to segment A.

[0391] [5] The glass-ceramic dental body according to item [4], wherein the gradient of optical properties is a gradient of contrast, wherein the contrast decreases from segment C to segment A.

[0392] [6] The glass-ceramic dental body according to any one of items [1] to [5], wherein the glass-ceramic dental body is characterized by a gradient of thermal properties in the direction from segment C to segment A.

[0393] [7]The glass-ceramic dental body according to item [6], wherein the gradient of the thermal property is a gradient of the coefficient of thermal expansion, and wherein the coefficient of thermal expansion decreases or increases from section C to section A.

[0394] [8]The glass-ceramic dental body according to item [7], wherein the coefficient of thermal expansion decreases from section C to section A.

[0395] [9]The glass-ceramic dental body according to item [7], wherein the coefficient of thermal expansion increases from section C to section A.

[0396]

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

[0397]

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

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

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

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

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

[0398]

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

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

[0399]

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

[0400]

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

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

[0401]

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

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

[0402]

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

[17] , wherein the main crystal phase of section C is lithium disilicate.

[0403]

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

[17] , wherein the main crystal phase of section C is quartz (e.g., α-quartz, α-quartz solid solution, or β-quartz solid solution).

[0404]

[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.

[0405]

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

[12] to

[14] , and

[16] to

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

[0406]

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

[21] , wherein the main crystal phase of section A is quartz (for example, α-quartz, α-quartz solid solution, or β-quartz solid solution).

[0407]

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

[21] , wherein the main crystal phase of section A is apatite (for example, fluorapatite).

[0408]

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

[23] , wherein section A includes one or more crystal phases different from those in section C.

[0409]

[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 milling blank or a dental pressing blank.

[0410]

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

[25] , wherein:

[0411] Section A forms the top section of the dental blank,

[0412] Section B forms the middle section of the dental blank, and

[0413] Section C forms the bottom section of the dental blank.

[0414]

[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.

[0415]

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

[27] , wherein:

[0416] Section A forms the upper part of the dental restoration, such as part or all of the incisal area,

[0417] Section B forms the middle part of the dental restoration, such as part or all of the transition area between the incisal area and the dentin area, and

[0418] Section C forms the lower part of the dental restoration, such as part or all of the dentin area.

[0419]

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

[28] , the glass-ceramic dental body 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, and each of the layers has a chemical composition different from that of the other layers.

[0420]

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

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

[0421]

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

[30] , the method comprising the steps of:

[0422] - providing two or more powders selected from glass powders, glass-ceramic powders, and mixtures thereof;

[0423] - preparing a green body from the powders; and

[0424] - heat-treating the green body to obtain a glass-ceramic dental body.

[0425]

[32] The method according to item

[31] , wherein the green body comprises three consecutive powder sections (or is composed of three consecutive powder sections):

[0426] powder section A,

[0427] powder section B, and

[0428] powder section C,

[0429] wherein the weight ratio of the two or more powders is different in each of the powder sections.

[0430]

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

[25] ,

[26] ,

[28] , and

[29] for preparing a dental prosthesis.

[0431]

[34] A method for preparing a dental prosthesis, wherein the method comprises the step of machining a glass-ceramic dental body according to any one of items

[25] ,

[26] ,

[28] , and

[29] to provide a dental prosthesis, and optionally the step of surface-treating the dental prosthesis.

[0432]

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

[25] ,

[26] ,

[28] , and

[29] or by the method according to item

[34] .

[0433] In the following, the present invention is described by way of specific embodiments which should not be construed as limiting the invention in any way.

[0434] V. Embodiment Section

[0435] 1. Measurement Methods

[0436] 1.1 Biaxial Bending Strength

[0437] The biaxial bending strength is determined in accordance with DIN EN ISO 6872 (DIN EN ISO 6872:2019). The test specimens are obtained by cutting corresponding parts of the glass-ceramic dental body from different sections thereof using a diamond-coated tool.

[0438] 1.2 Fracture Toughness K IC

[0439] The fracture toughness (K IC ) is determined by the single-edge V-notch beam (SEVNB) method in accordance with DIN EN / ISO / 6872, and in particular DIN EN ISO 6872:2015. The test specimens are obtained by cutting corresponding parts of the glass-ceramic dental body from different sections thereof using a diamond-coated tool.

[0440] 1.3 Contrast

[0441] The contrast is determined in accordance with BS 5612, and in particular BS 5612:1978. Test specimens with a thickness of 2 mm ± 0.02 mm are used to determine the contrast. The test specimens are obtained by cutting corresponding sections of the glass-ceramic dental body from different sections thereof using a diamond-coated tool. Measurements are carried out using a spectrophotometer CM 3700-D (Konica-Minolta). Before measurement, the cut parts are wet-ground to a thickness of 2 mm ± 0.02 mm using a rotating diamond grinding disc and 1000 SiC abrasive paper, and then the final surface is wet-polished using a diamond grinding disc (20 μm).

[0442] 1.4 Coefficient of Thermal Expansion (CTE)

[0443] The coefficient of thermal expansion (CTE) is determined using a dilatometer in accordance with DIN EN ISO 6872, and in particular DIN EN ISO 6872:2015. The test specimens are obtained by cutting corresponding sections of the glass-ceramic dental body from different sections thereof using a diamond-coated tool.

[0444] 2. Embodiments

[0445] 2.1 Preparation of Glass Powder and Glass-Ceramic Dental Body

[0446] To obtain glass powder, the individual raw materials of the glass powder are weighed, combined and homogenized in a laboratory speed mixer. For example, to prepare glass powders GP4, GP10 and GP11 (see glass-ceramic dental bodies of Example 5), the following raw materials are used: quartz powder (SiO 2 ), lithium carbonate (Li 2 CO 3 ), potassium carbonate (K 2 CO 3 ), aluminum hydroxide (AlOOH x H 2 O), aluminum phosphate (Al(PO 3 ) 3 ), magnesium carbonate (MgCO 3 ), calcium carbonate (CaCO 3 ), strontium carbonate (SrCO 3 ), zirconium oxide (ZrO 2 ), zinc oxide (ZnO), lanthanum oxide (La 2 O 3 ).

[0447] Subsequently, the raw materials are melted at a temperature of 1550 °C for 1 hour. The melt is shaken and frozen in water to obtain glass. The glass is dried in an oven at 150 °C for 1 hour and then ground in the laboratory to obtain glass powder. The powder fraction with a particle size < 45 μm is separated out and used to prepare the molded body of the glass powder.

[0448] To prepare a multi-layer molded powder (three layers), the first powder is introduced into the mold and flattened with a press mold (only the weight of the press mold, no additional external pressure). Subsequently, the second powder and the third powder (in sequence) are introduced into the mold and flattened with a press mold. Then, the layered powder is pressed at a pressure of 10 bar to obtain a molded powder. The molded body is removed from the mold by rotating the mold 180° and pushing the molded body out of the mold by applying pressure in the opposite direction.

[0449] Then the molded powder is completely sintered in a sintering furnace (Programat P500) under vacuum at 880 °C. First, the molded powder is inserted into the sintering furnace (preheated to 400 °C), and then the pressure in the furnace is reduced to < 0.1 MPa. In the heating step, the temperature is raised to 600 °C at a heating rate of 10 K / min, held for 30 minutes, and then the temperature is raised to 880 °C at a heating rate of 10 K / min, also held for 30 minutes. Subsequently, the heating element of the furnace is deactivated and the pressure reaches ambient pressure. The completely sintered glass-ceramic body (see Section 2.3: Glass-ceramic dental body) is removed from the furnace at a temperature of about 500 °C.

[0450] 2.2 Glass-ceramic dental body

[0451] The following table shows the chemical composition, structure, and properties of the glass powder of a glass-ceramic dental body example according to an embodiment of the present invention. The abbreviation "s.s." related to the crystalline phase indicates "solid solution".

[0452] 2.1.2 Example 1

[0453] Table 1.1: Example 1

[0454]

[0455] * The first crystalline phase shown in each field represents the main crystalline phase of that section.

[0456] Table 1.2: Glass powder for preparing Example 1

[0457] GP1 GP2 GP3 Composition Weight [wt.%] Composition Weight [wt.%] Composition Weight [wt.%] <![CDATA[SiO 2 > 71.5 <![CDATA[SiO 2 > 72.5 <![CDATA[SiO 2 > 73.6 <![CDATA[Li 2 O]]> 10.1 <![CDATA[Li 2 O]]> 10.2 <![CDATA[Li 2 O]]> 10.5 <![CDATA[K 2 O]]> 3.0 <![CDATA[K 2 O]]> 3.0 <![CDATA[K 2 O]]> 3.0 MgO 4.0 MgO 4.0 MgO 4.1 SrO 2.0 SrO 2.0 SrO 2.0 <![CDATA[Li 2 O]]> 2.7 <![CDATA[Li 2 O]]> 1.8 <![CDATA[P 2 O 5 > 3.8 <![CDATA[P 2 O 5 > 3.7 <![CDATA[P 2 O 5 > 3.8 <![CDATA[ZrO 2 > 3.0 <![CDATA[ZrO 2 > 3.0 <![CDATA[ZrO 2 > 3.0

[0458] 2.2.2 Example 2

[0459] Table 2.1: Example 2

[0460]

[0461] * The first crystalline phase shown in each field represents the main crystalline phase of that section.

[0462] Table 2.2: Glass powder for preparing Example 2

[0463]

[0464]

[0465] 2.3.2 Example 3

[0466] Table 3.1: Example 3

[0467]

[0468] * The first crystalline phase shown in each field represents the main crystalline phase of that section.

[0469] Table 3.2: Glass powder for preparing Example 3

[0470] GP4 GP4:GP6 GP6 Composition Weight [wt.%] Composition Weight [wt.%] Composition Weight [wt.%] <![CDATA[SiO 2 > 71.4 <![CDATA[SiO 2 > 71.2 <![CDATA[SiO 2 > 70.8 <![CDATA[Li 2 O]]> 11.8 <![CDATA[Li 2 O]]> 9.5 <![CDATA[Li 2 O]]> 0.4 <![CDATA[K 2 O]]> 2.5 <![CDATA[K 2 O]]> 3.3 <![CDATA[K 2 O]]> 6.3 CaO 1.5 CaO 1.5 CaO 1.8 SrO 2.8 SrO 2.6 SrO 1.9 <![CDATA[Li 2 O]]> 2.7 <![CDATA[Li 2 O]]> 3.7 <![CDATA[Li 2 O]]> 7.7 ZnO 1.4 ZnO 1.7 ZnO 2.7 <![CDATA[B 2 O 3 > 0.0 <![CDATA[B 2 O 3 > 0.3 <![CDATA[B 2 O 3 > 1.5 <![CDATA[CeO 2 > 0.0 <![CDATA[CeO 2 > 0.1 <![CDATA[CeO 2 > 0.5 F 0.0 F 0.1 F 0.6 <![CDATA[Sodium 2 O]]> 0.0 <![CDATA[Sodium 2 O]]> 1.2 <![CDATA[Sodium 2 O]]> 5.8 MgO 1.0 MgO 0.9 MgO 0.0 <![CDATA[P 2 O 5 > 3.8 <![CDATA[P 2 O 5 > 3.0 <![CDATA[P 2 O 5 > 0.0 <![CDATA[ZrO 2 > 1.1 <![CDATA[ZrO 2 > 0.9 <![CDATA[ZrO 2 > 0.0

[0471] 2.4.2 Example 4

[0472] Table 4.1: Example 4

[0473]

[0474]

[0475] The first crystal phase shown in each field represents the main crystal phase of that section.

[0476] Table 4.2: Glass powder for preparing Example 4

[0477] GP7 GP8 GP9 Composition Weight [wt.%] Composition Weight [wt.%] Composition Weight [wt.%] <![CDATA[SiO 2 > 71.5 <![CDATA[SiO 2 > 63.3 <![CDATA[SiO 2 > 68.9 <![CDATA[Li 2 O]]> 14.3 <![CDATA[Li 2 O]]> 28.0 <![CDATA[Sodium 2 O]]> 1.5 <![CDATA[K 2 O]]> 4.0 <![CDATA[K 2 O]]> 2.5 <![CDATA[K 2 O]]> 13.0 <![CDATA[Li 2 O]]> 3.0 MgO 0.2 <![CDATA[Li 2 O]]> 8.6 <![CDATA[P 2 O 5 > 3.2 SrO 0.8 CaO 7.7 <![CDATA[Y 2 O 3 > 4.0 <![CDATA[Li 2 O]]> 1.1 <![CDATA[CeO 2 > 0.3 <![CDATA[P 2 O 5 > 1.7 <![CDATA[La 2 O 3 > 0.1 <![CDATA[CeO 2 > 0.2 <![CDATA[Tb 4 O 7 > 0.1 <![CDATA[ZrO 2 > 0.3 ZnO 1.7

[0478] 2.5.2 Example 5

[0479] Table 5.1: Example 5

[0480]

[0481] The first crystal phase shown in each field represents the main crystal phase of that section.

[0482] Table 5.2: Glass powder for preparing Example 5

[0483]

[0484]

[0485] 2.6.2 Example 6

[0486] Table 6.1: Example 6

[0487]

[0488] The first crystal phase shown in each field represents the main crystal phase of that section.

[0489] Table 6.2: Glass powder for preparing Example 6

[0490] GP12 GP13 GP14 Composition Weight [wt.%] Composition Weight [wt.%] Composition Weight [wt.%] <![CDATA[SiO 2 > 69.5 <![CDATA[SiO 2 > 69.0 <![CDATA[SiO 2 > 68.2 <![CDATA[Li 2 O]]> 10.2 <![CDATA[Li 2 O]]> 10.1 <![CDATA[Li 2 O]]> 10.0 <![CDATA[K 2 O]]> 2.4 <![CDATA[K 2 O]]> 2.4 <![CDATA[K 2 O]]> 2.4 MgO 3.8 MgO 3.7 MgO 3.7 CaO 0.4 CaO 0.4 CaO 0.4 SrO 1.8 SrO 1.8 SrO 1.8 <![CDATA[Li 2 O]]> 5.3 <![CDATA[Li 2 O]]> 6.2 <![CDATA[Li 2 O]]> 7.1 <![CDATA[P 2 O 5 > 3.7 <![CDATA[P 2 O 5 > 3.6 <![CDATA[P 2 O 5 > 3.6 <![CDATA[La 2 O 3 > 0.5 <![CDATA[La 2 O 3 > 0.5 <![CDATA[La 2 O 3 > 0.5 <![CDATA[ZrO 2 > 2.4 <![CDATA[ZrO 2 > 2.3 <![CDATA[ZrO 2 > 2.3 ZnO 0.2 ZnO 0.2 ZnO 0.2

[0491] 2.7.2 Example 7

[0492] Table 7.1: Example 7

[0493]

[0494] The first crystal phase shown in each field represents the main crystal phase of that section.

[0495] Table 7.2: Glass powder for preparing Example 7

[0496]

[0497]

[0498] 2.8.2 Example 8

[0499] Table 8.1: Example 8

[0500]

[0501] *The first crystal phase shown in each field represents the main crystal phase of that section.

[0502] Table 8.2: Glass powder for preparing Example 8

[0503] GP17 GP18 GP19 Composition Weight [wt.%] Composition Weight [wt.%] Composition Weight [wt.%] <![CDATA[SiO 2 > 71.0 <![CDATA[SiO 2 > 70.9 <![CDATA[SiO 2 > 59.3 <![CDATA[Li 2 O]]> 10.1 <![CDATA[Li 2 O]]> 9.9 <![CDATA[Li 2 O]]> 0.4 <![CDATA[K 2 O]]> 3.0 <![CDATA[K 2 O]]> 3.0 <![CDATA[Sodium 2 O]]> 5.9 MgO 3.8 MgO 3.8 <![CDATA[K 2 O]]> 6.4 CaO 0.4 CaO 0.3 CaO 7.2 SrO 1.9 SrO 1.8 SrO 1.9 <![CDATA[Li 2 O]]> 3.2 <![CDATA[Li 2 O]]> 3.2 <![CDATA[B 2 O 3 > 1.5 <![CDATA[P 2 O 5 > 3.7 <![CDATA[P 2 O 5 > 4.2 <![CDATA[Li 2 O]]> 5.8 <![CDATA[La 2 O 3 > 0.5 <![CDATA[La 2 O 3 > 0.5 <![CDATA[P 2 O 5 > 4.5 <![CDATA[ZrO 2 > 2.4 <![CDATA[ZrO 2 > 2.4 F 2.1 ZnO 0.2 ZnO 0.2 <![CDATA[TiO 2 > 1.3 <![CDATA[ZrO 2 > 0.5 <![CDATA[CeO 2 > 0.5 ZnO 2.7

[0504] 2.9.2 Example 9

[0505] Table 9.1: Example 9

[0506]

[0507]

[0508] *The first crystal phase shown in each field represents the main crystal phase of that section.

[0509] Table 9.2: Glass powder for preparing Example 9

[0510] GP20 GP21 GP22 Composition Weight [wt.%] Composition Weight [wt.%] Composition Weight [wt.%] <![CDATA[SiO 2 > 73.9 <![CDATA[SiO 2 > 77.4 <![CDATA[SiO 2 > 79.7 <![CDATA[Li 2 O]]> 12.3 <![CDATA[Li 2 O]]> 9.6 <![CDATA[Li 2 O]]> 7.9 <![CDATA[K 2 O]]> 3.3 <![CDATA[K 2 O]]> 3.2 <![CDATA[K 2 O]]> 3.2 MgO 4.3 MgO 4.3 MgO 4.2 SrO 2.2 SrO 2.1 SrO 2.1 <![CDATA[P 2 O 5 > 4.0 <![CDATA[P 2 O 5 > 3.4 <![CDATA[P 2 O 5 > 2.9

[0511] 2.10.2 Example 10

[0512] Table 101: Example 10

[0513]

[0514] *The first crystal phase shown in each field represents the main crystal phase of that section.

[0515] Table 102: Example 10

[0516] GP24 GP24:GP23 GP23 Composition Weight [wt.%] Composition Weight [wt.%] Composition Weight [wt.%] <![CDATA[SiO 2 > 76.7 <![CDATA[SiO 2 > 77.9 <![CDATA[SiO 2 > 79.4 <![CDATA[Li 2 O]]> 16.0 <![CDATA[Li 2 O]]> 16.3 <![CDATA[Li 2 O]]> 16.5 <![CDATA[K 2 O]]> 3.6 <![CDATA[K 2 O]]> 2.7 <![CDATA[K 2 O]]> 1.8 <![CDATA[Li 2 O]]> 3.7 CuO 0.1 CuO 0.1 Fe 0.1 Fe 0.2 <![CDATA[Li 2 O]]> 2.9 <![CDATA[Li 2 O]]> 2.0

Claims

1. A glass ceramic dental body, comprising three consecutive sections: Section A, Section B, and Section C, in, Each of the segments has a chemical composition that is different from the chemical composition of the other segments, and Therein, the glass ceramic dental body is characterized by one or more gradients of mechanical properties, optical properties and / or thermal properties in the direction from segment C to segment A.

2. The glass ceramic dental body according to claim 1, characterized in that: a gradient in biaxial bending strength, wherein the biaxial bending strength decreases from section C to section A; and / or Fracture toughness K IC The gradient of fracture toughness K IC Decreases from section C to section A.

3. The glass ceramic dental body according to claim 1 or claim 2, characterized in that: A gradient of contrast, wherein the contrast decreases from segment C to segment A.

4. The glass ceramic dental body according to any one of claims 1 to 3, characterized in that: A gradient of the coefficient of thermal expansion, wherein the coefficient of thermal expansion decreases or increases from section C to section A.

5. The glass ceramic dental body according to any one of claims 1 to 4, wherein: The main crystal phase of each of Section C, Section B, and Section A is the same.

6. The glass ceramic dental body according to claim 5, wherein: The content of the main crystal phase decreases in the direction from section C to section A.

7. The glass ceramic dental body according to any one of claims 1 to 4, wherein: The main crystal phase of section C is different from that of section A.

8. The glass ceramic dental body according to claim 7, wherein: The content of the crystal phase as the main crystal phase of section C decreases in the direction from section C to section A, or Here, the content of the crystal phase as the main crystal phase of section A decreases in the direction from section A to section C.

9. The glass ceramic dental body according to any one of claims 1 to 4, wherein: Section A consists of glass, and sections B and C consist of glass ceramic.

10. A glass-ceramic dental body according to any one of the preceding claims, wherein Section C has a main crystal phase, and the content of such crystal phase decreases from section C to section A.

11. A glass-ceramic dental body according to any one of the preceding claims, wherein The main crystalline phase of section C is lithium disilicate, quartz, or stoichiometric or non-stoichiometric lithium aluminum silicate LAS.

12. The glass ceramic dental body according to claim 11, wherein: The main crystalline phase of section C is lithium disilicate.

13. A glass-ceramic dental body according to any one of the preceding claims, wherein The main crystalline phase of section C is not lithium metasilicate.

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 aluminum silicate LAS.

15. The glass ceramic dental body according to claim 14, wherein: The main crystalline phase of section A is quartz.

16. A glass-ceramic dental body according to any one of the preceding claims, wherein The glass-ceramic dental body is a dental blank, such as a dental milled blank or a dental pressed blank, and optionally wherein: Section A forms the top section of the dental blank, Section B forms the middle section of the dental blank, and Section C forms the bottom section of the dental blank.

17. The 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, wherein: Segment A forms at least part of the incisal area, Segment B forms at least part of the transition zone between the incisal zone and the dentin zone, and Segment C forms at least part of the dentin zone.

18. A glass-ceramic dental body according to any one of the preceding claims, having a multi-layer structure, wherein: Segment A is layer A, segment C is layer C and segment B is formed by at least one intermediate layer between layer A and layer C, and each of the layers has a chemical composition different from the chemical composition of the other layers, or Therein, section A and section C have homogeneous chemical compositions, and section B has a chemical composition that gradually changes in a direction from section C to section A.

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

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