Lithium silicate glass ceramics comprising copper

Abstract

To provide lithium silicate glass ceramics comprising copper.SOLUTION: Lithium silicate glass ceramics and precursors thereof are described, which contain copper and are characterized by very good mechanical and optical properties and in particular can be used as restorative materials in dentistry. The lithium silicate glass ceramics according to the invention contain 0.001 to 1.0 wt.% copper calculated as CuO. In particular, the glass ceramics contain 0.05 to 0.7, preferably 0.06 to 0.5, and particularly preferably 0.07 to 0.35 wt.% copper calculated as CuO.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Background information The present invention relates to a copper-containing lithium silicate glass ceramic, which is particularly suitable for use in dentistry, preferably for producing dental restorations, and to a precursor for producing this glass ceramic. [Background technology]

[0002] Glass ceramics containing copper are known from the prior art.

[0003] German Patent Application Publication No. 10304382 describes a photostructured body made of glass or glass ceramic in which a change in refractive index is induced by light irradiation. The body may optionally contain photosensitive elements such as Cu, Ag, Au, Ce, and Eu to generate appropriate absorption centers. In particular, the body is used as an optical device such as a waveguide and a grating. However, all of the specified glass and glass ceramics contain very high levels of antimony oxide or arsenic oxide, which are harmful to health. Therefore, they are not suitable for use in the medical field, especially in dentistry.

[0004] European Patent Application Publication No. 1985591 describes glass ceramics that can be colored with metal colloids. Possible metal colloidal entities are compounds of the metals Au, Ag, As, Bi, Nb, Cu, Fe, Pd, Pt, Sb, and Sn. The glass ceramics are, in particular, lithium aluminosilicate glass ceramics or magnesium aluminosilicate glass ceramics containing a large amount of aluminum oxide, at least 18.0% by weight, and a considerable amount of antimony oxide and arsenic oxide, which are harmful to health.

[0005] International Publications 03 / 050053 and 03 / 050051 describe antimicrobial glass ceramic powders that can be used in the field of dental care, for example, as components of mouthwash, toothpaste, or dental floss. To enhance antimicrobial properties, antimicrobially active ions such as Ag, Au, I, Ce, Cu, Zn, and Sn may be present. The glass ceramics have alkaline earth alkali silicates and / or alkaline earth silicates, particularly sodium calcium silicate and calcium silicate, as the main crystalline phase.

[0006] International Publication No. 2005 / 058768 discloses a lithium aluminosilicate glass ceramic body particularly suitable for the manufacture of cooking hobs. The body has a surface layer containing a higher content of a crystallization-promoting chemical element from the group of Zn, Cu, Zr, La, Nb, Y, Ti, Ge, V, and Sn, and a higher degree of crystallinity is produced in the surface layer. European Patent Application Publication No. 1688397 describes lithium silicate glass ceramics containing a small amount of zinc oxide and a large amount of 2.0 to 5.0% by weight of a nucleating agent. The nucleating agent for forming lithium metasilicate is selected in particular from P2O5 and compounds of the elements Pt, Ag, Cu, and W, and is preferably P2O5. Therefore, P2O5 is also used as a nucleating agent in all glass ceramics specifically disclosed, which also results in the formation of lithium phosphate as a crystalline phase in addition to lithium silicate. However, lithium phosphate crystals may impair the mechanical and / or optical properties of the lithium silicate glass ceramic. Studies of lithium silicate glass and copper oxide-doped glass ceramics are publicly known from HA Elbatal et al. in the Journal of Non-Crystalline Solids 358 (2012) 1806-1813. However, no mention of any applications of these glasses and glass ceramics as dental materials, let alone as dental restorative materials, has been given. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] German Patent Application Publication No. 10304382 [Patent Document 2] European Patent Application Publication No. 1985591 [Patent Document 3] International Publication No. 03 / 050053 [Patent Document 4] International Publication No. 03 / 050051 [Patent Document 5] International Publication No. 2005 / 058768 [Patent Document 6] European Patent Application Publication No. 1688397 [Non-Patent Document]

[0008] [Non-Patent Document 1] H. A. Elbatal et al., the Journal of Non-Crystalline Solids 358 (2012) 1806 - 1813 [Summary of the Invention] [Means for Solving the Problems]

[0009] In summary, known glass ceramics do not possess the properties desirable for dental restoration materials, or contain a large amount of P2O5, which may lead to the formation of undesirable crystal phases such as phosphate phases or cristobalite, and thus may particularly impair the mechanical and / or optical properties desirable for restoration materials.

[0010] Therefore, the present invention is based on the problem of providing a glass ceramic having a very good combination of mechanical and optical properties, which should be easy to process into dental restorations and thus be excellently suitable as a restorative dental material.

[0011] This problem is solved by the lithium silicate glass ceramics described in claims 1 to 13 and 16. The present invention also applies to the starting glass described in claims 14 to 16, the methods described in claims 17 to 19 and 22, and the uses described in claims 20 and 21. The present invention provides, for example, the following items: (Reclaim) (Item 1) Lithium silicate glass ceramic containing 0.001 to 1.0, particularly 0.05 to 0.7, preferably 0.06 to 0.5, and especially preferably 0.07 to 0.35 wt% copper, calculated as CuO. (Item 2) The glass ceramic according to any one of the above items, wherein the copper is present at least partially as elemental copper. (Item 3) A glass ceramic according to any one of the above items, comprising 67.0 to 89.0, preferably 68.0 to 82.0, and particularly preferably 70.0 to 81.0% by weight of SiO2. (Item 4) A glass ceramic according to any one of the above items, comprising 7.0 to 22.0, preferably 13.0 to 19.0, and particularly preferably 14.0 to 17.0% by weight of Li2O. (Item 5) A glass ceramic according to any one of the above items, comprising 0.002 to 1.5, particularly 0.05 to 1.0, preferably 0.1 to 0.8, and especially preferably 0.1 to 0.6 by weight percent of tin, calculated as SnO. (Item 6) A glass ceramic according to any one of the above items, comprising 0.1 to 6.0, preferably 0.1 to 5.0, more preferably 0.5 to 4.0, and even more preferably 0.9 to 3.0 wt% Al2O3. (Item 7) 1.0 to 11.0, preferably 1.5 to 7.0 wt% of monovalent element oxides Me selected from the group consisting of K2O, Na2O, Rb2O, Cs2O, and mixtures thereof. I A glass ceramic containing 2O, as described in any one of the above items. (Item 8) A glass ceramic according to any one of the above items, comprising 0 to 11.0, particularly 0.5 to 6.0, preferably 1.0 to 4.5, and especially preferably 1.5 to 4.0 by weight % K2O. (Item 9) 0 to 10.0, preferably 1.0 to 9.0, and particularly preferably 2.0 to 7.0 wt% of divalent element oxides Me selected from the group consisting of CaO, MgO, SrO, ZnO, and mixtures thereof. II A glass ceramic containing O, as described in any one of the above items. (Item 10) 0.1 to 12.0, preferably 1.0 to 9.0, and particularly preferably 2.0 to 8.0 wt% of trivalent element oxides Me selected from the group consisting of Al2O3, B2O3, Y2O3, La2O3, and mixtures thereof. III A glass ceramic containing 2O3, as described in any one of the above items. (Item 11) A glass ceramic according to any one of the above items, comprising lithium disilicate or lithium metasilicate as the main crystalline phase, preferably lithium disilicate as the main crystalline phase. (Item 12) A glass ceramic according to any one of the above items, comprising at least 10% by weight, preferably 10 to 50% by weight, of lithium metasilicate crystals. (Item 13) A glass ceramic according to any one of the above items, comprising at least 50% by weight, preferably 50 to 85% by weight, of lithium disilicate crystals. (Item 14) A starting glass containing the glass-ceramic components described in any one of the above items. (Item 15) A starting glass according to any one of the above items, comprising a nucleus for crystallization of lithium metasilicate and / or lithium disilicate. (Item 16) The glass ceramic and the starting glass are in the form of a blank or a dental restoration, as described in any one of the items, as described in the glass ceramic or the starting glass. (Item 17) A method for producing a glass ceramic according to any one of the preceding items, wherein the starting glass according to any one of the preceding items is subjected to at least one heat treatment, particularly in the range of 500 to 1050°C, preferably 650 to 970°C. (Item 18) (a) The starting glass is subjected to heat treatment at a temperature of 400 to 600°C, particularly 450 to 550°C, more preferably 460 to 490°C to form a starting glass having a nucleus. (b) The starting glass having the nucleus is subjected to heat treatment at a temperature of 500 to 1050°C, particularly 650 to 970°C, to form the lithium silicate glass ceramic. A method using any one of the above items. (Item 19) The method according to any one of the above, wherein the starting glass is formed by melting a mixture of starting materials containing an agent for reducing copper cations, preferably an organic compound or a tin compound, more preferably a sugar, SnO, or SnO2. (Item 20) Use of glass ceramic or starting glass according to any one of the above items as a dental material, preferably for coating dental restorations, and particularly preferably for producing dental restorations. (Item 21) Use for producing any one of the aforementioned dental restorations, wherein the glass ceramic or the starting glass is given a desired dental restoration, in particular a bridge, inlay, onlay, veneer, abutment, partial crown, crown, or facet shape by machining. (Item 22) A method for producing dental restorations, particularly bridges, inlays, onlays, veneers, abutments, partial crowns, crowns, or facets, wherein the shape of the desired dental restoration is given to a glass ceramic or starting glass according to any one of the items, by machining, particularly by a CAD / CAM process. [Modes for carrying out the invention]

[0012] Lithium silicate glass ceramics and precursors are described, characterized by their copper content and excellent mechanical and optical properties, and are particularly suitable for use as dental restorative materials. The lithium silicate glass ceramic according to the present invention is characterized by containing 0.001 to 1.0 wt% of copper, calculated as CuO. In particular, the glass ceramic contains 0.05 to 0.7, preferably 0.06 to 0.5, and especially preferably 0.07 to 0.35 wt% of copper, calculated as CuO.

[0013] In a particularly preferred embodiment, copper is present at least partially as elemental copper in the glass ceramic. Its presence can be detected, in particular, by scanning electron microscopy (SEM) or transmission electron microscopy (TEM), or by X-ray diffraction studies. The red coloration of the glass ceramic also indicates the presence of elemental copper.

[0014] Elemental copper is preferably present in the form of particles having an average size D50 of 0.1 to 100 nm, particularly 1 to 70 nm, and especially preferably 2 to 50 nm, as determined from at least three particles by electron microscopy.

[0015] In another preferred embodiment, at least 65%, preferably at least 75%, and particularly preferably at least 90% of the copper particles have a size in the range of 0.1 to 100 nm, particularly 1 to 70 nm, and particularly preferably 2 to 50 nm, as determined from at least three particles by electron microscopy.

[0016] The size of the elemental copper particles is preferably determined by transmission electron microscopy or scanning electron microscopy, and particularly preferably by scanning electron microscopy.

[0017] Surprisingly, the glass ceramic according to the present invention exhibits a favorable combination of mechanical and optical properties desirable for restorative dental materials. The glass ceramic has high strength and fracture toughness, and in particular, the shape of dental restorations can be easily given by machining.

[0018] It is surprising that the use of P2O5 as a conventional nucleating agent in lithium silicate glass ceramics does not necessarily achieve these properties. In the glass ceramic according to the present invention, it is assumed that the present copper acts as a nucleating agent. Furthermore, it is particularly surprising that even small amounts of copper are effective.

[0019] The glass ceramic according to the present invention may also have a very large amount of lithium disilicate crystalline phase, particularly more than 65% by weight, and it is assumed that the presence of copper as a nucleating agent is essentially responsible for this. Such a high content of lithium disilicate crystalline phase cannot normally be formed when P2O5 is used as a nucleating agent.

[0020] Furthermore, the glass ceramic according to the present invention can be produced from the corresponding starting glass by using a very short crystallization time, which is another significant advantage of glass ceramics.

[0021] The glass ceramic according to the present invention preferably also has a very small amount of further crystalline phase, such as lithium phosphate or cristobalite. The formation of large amounts of such further crystalline phases frequently occurs with the use of large amounts of P2O5 as a nucleating agent, and this has been common to date. These further crystalline phases may have a negative effect on the mechanical and / or optical properties of the lithium silicate glass ceramic. Furthermore, lithium is consumed by the formation of lithium phosphate crystals and is therefore no longer available for the formation of lithium silicate. Lithium silicate plays an essential role, especially for the excellent mechanical properties of lithium silicate glass ceramic. Therefore, the glass ceramic according to the present invention is advantageous from this viewpoint as well.

[0022] The glass ceramic according to the present invention contains SiO2 in particular 67.0 to 89.0, preferably 68.0 to 82.0, and especially preferably 70.0 to 81.0% by weight.

[0023] The glass ceramic according to the present invention more preferably contains 7.0 to 22.0, preferably 13.0 to 19.0, and particularly preferably 14.0 to 17.0% by weight of Li2O. It is also assumed that Li2O reduces the viscosity of the glass matrix and therefore promotes the crystallization of the desired crystalline phase.

[0024] In a more preferred embodiment, the glass ceramic according to the present invention contains 0.002 to 1.5, particularly 0.05 to 1.0, preferably 0.1 to 0.8, and especially preferably 0.1 to 0.6% by weight of tin, calculated as SnO.

[0025] Tin, for example, when present in the starting materials used for this purpose, particularly in the form of SnO or SnO2 during the production of glass ceramics, is expected to act as a reducing agent for copper cations and promote the formation of elemental copper in glass ceramics.

[0026] The glass ceramic contains 1.0 to 11.0, preferably 1.5 to 7.0 wt% of monovalent element oxides Me selected from the group consisting of K2O, Na2O, Rb2O, Cs2O, and mixtures thereof. I It is also preferable to include 2O.

[0027] Particularly preferred is the glass ceramic being an oxide of the following monovalent element Me I At least one of 2O, especially all of them: [Table 2] It contains the amount indicated by [the symbol].

[0028] In a particularly preferred embodiment, the glass ceramic according to the present invention contains 0.5 to 6.0, preferably 1.0 to 4.5, and especially preferably 1.5 to 4.0% by weight of K2O.

[0029] Furthermore, the glass ceramic contains 0 to 10.0, preferably 1.0 to 9.0, and particularly preferably 2.0 to 7.0 wt% of divalent element oxides Me selected from the group consisting of CaO, MgO, SrO, ZnO, and mixtures thereof. II It is preferable that it contains O.

[0030] In another preferred embodiment, the glass ceramic contains less than 2.0% by weight of BaO. In particular, the glass ceramic is substantially BaO-free.

[0031] Preferably, the glass ceramic is an oxide of the following divalent element Me II At least one type of O, especially all of them: [Table 3] It contains the amount shown.

[0032] Furthermore, 0.1 to 12.0, preferably 1.0 to 9.0, most preferably 2.0 to 8.0% by weight of an oxide Me of a trivalent element selected from the group consisting of Al2O3, B2O3, Y2O3, La2O3, Ga2O3, In2O3, and mixtures thereof III is preferably included in the glass-ceramic.

[0033] Particularly preferably, the glass-ceramic contains at least one, particularly all, of the following oxides Me of trivalent elements III 2O3: [Table 4] in the amounts indicated.

[0034] In a particularly preferred embodiment, the glass-ceramic contains 0.1 to 5.0, preferably 0.5 to 4.0, more preferably 0.9 to 3.0% by weight of Al2O3.

[0035] Furthermore, 0 to 10.0, particularly preferably 0 to 8.0% by weight of an oxide Me of a tetravalent element selected from the group consisting of ZrO2, TiO2, GeO2, and mixtures thereof IV is preferably included in the glass-ceramic.

[0036] Particularly preferably, the glass-ceramic contains at least one, particularly all, of the following oxides Me of tetravalent elements IV O2: [Table 5] in the amounts indicated.

[0037] In another preferred embodiment, the glass-ceramic contains 0 to 10.0, preferably 0 to 8.0% by weight of an oxide Me of a pentavalent element selected from the group consisting of P2O5, Ta2O5, Nb2O5, and mixtures thereof V 2O5.

[0038] Particularly preferably, the glass-ceramic contains the following oxides Me of pentavalent elementsV At least one type of 2O5, especially all of them: [Table 6] It contains the amount shown.

[0039] In another preferred embodiment, the glass ceramic contains less than 7.5%, particularly less than 3.5%, preferably less than 1.5%, and more preferably less than 0.5% by weight of P2O5, and particularly preferably the glass ceramic is substantially P2O5-free.

[0040] In another embodiment, the glass ceramic contains 0 to 6.0, preferably 0 to 5.0 wt% of a hexavalent element oxide Me selected from the group consisting of WO3, MoO3, and mixtures thereof. VI Contains O3

[0041] Particularly preferred is the following oxide Me VI At least one type of O3, especially all of them: [Table 7] It contains the amount shown.

[0042] In further embodiments, the glass ceramic according to the present invention contains 0 to 1.0, particularly 0 to 0.5% by weight of fluorine.

[0043] At least one, preferably all, of the following ingredients: [Table 8] (In the table, Me I 20, Me II O, Me III 203, Me IV O2, Me V 2O5, and Me VI (O3 has the meaning given above.) Glass ceramics containing the amount shown are particularly preferred.

[0044] In another particularly preferred embodiment, the glass ceramic comprises at least one, preferably all, of the following components: [Table 9] It contains the amount shown.

[0045] Some of the above components can act as colorants and / or fluorescent agents. The glass ceramics according to the present invention may further contain additional colorants and / or fluorescent agents. These may be selected in particular from additional inorganic pigments and / or oxides of elements d and f, such as oxides of Mn, Fe, Co, Pr, Nd, Tb, Er, Dy, Eu, and Yb. In preferred embodiments, Ag, Ag oxide, or Ag halides, such as AgCl, AgBr, or AgI, are used. With the help of these colorants and fluorescent agents, it is possible to easily color the glass ceramics to mimic the desired optical properties of natural dental materials in particular.

[0046] In preferred embodiments of glass ceramics, the molar ratio of SiO2 to Li2O is in the range of 1.5 to 6.0, preferably 1.7 to 5.5, and particularly preferably 2.0 to 4.0.

[0047] The glass ceramic according to the present invention is more preferably composed of lithium disilicate or lithium metasilicate as the main crystalline phase.

[0048] The term "principal crystalline phase" refers to the crystalline phase that has the highest weight proportion of all crystalline phases present in the glass ceramic. The amount of the crystalline phase is determined, in particular, by the Rietveld method. A suitable procedure for quantitative analysis of the crystalline phase using the Rietveld method is described, for example, in the paper by M. Dittmer, "Glaser und Glaskeramiken im System MgO-Al2O3-SiO2mit ZrO2als Keimbildner", University of Jena 2011.

[0049] The glass ceramic according to the present invention preferably contains at least 10% by weight, preferably at least 15% by weight, and particularly preferably at least 20% by weight of lithium metasilicate crystals. Particularly preferably, the glass ceramic according to the present invention contains 10 to 50% by weight, preferably 15 to 45% by weight, and particularly preferably 20 to 40% by weight of lithium metasilicate crystals.

[0050] In another embodiment, the glass ceramic according to the present invention preferably contains at least 50% by weight, preferably at least 55% by weight, and particularly preferably at least 60% by weight of lithium disilicate crystals. Particularly preferably, the glass ceramic according to the present invention contains 50 to 85% by weight, preferably 55 to 80% by weight, and particularly preferably 60 to 78% by weight of lithium disilicate crystals.

[0051] In a preferred embodiment, the lithium disilicate crystals in the glass ceramic according to the present invention have an average size in the range of 10 to 3000 nm, particularly in the range of 50 to 2000 nm, and especially preferably in the range of 100 to 1200 nm.

[0052] The average size of lithium disilicate crystals can be determined from SEM images. For this purpose, the surface of each glass-ceramic is polished (<0.5 μm), etched with 40% HF vapor for at least 30 seconds, and then sputtered with an Au-Pd layer. SEM images from the pre-treated surfaces are recorded using a scanning electron microscope such as a Supra 40VP (Zeiss, Oberkochen, Germany). The SEM images are then processed using a common image processing program to improve the contrast between the crystal and glass phase. From these images, the average size can be determined, for example, using Olympus Stream Motion 2.4 image analysis software (Olympus Corporation, Tokyo, Japan).

[0053] The glass ceramics according to the present invention are characterized in particular by their excellent mechanical and optical properties and can be formed by heat treatment of a corresponding starting glass or a corresponding starting glass having a nucleus. Therefore, these materials can serve as precursors for the glass ceramics according to the present invention.

[0054] The type and, in particular, the amount of the crystalline phase formed can be controlled by the composition of the starting glass, as well as the heat treatment applied to produce the glass ceramic from the starting glass. The examples illustrate this by varying the composition of the starting glass and the heat treatment applied.

[0055] The glass ceramic has a high biaxial fracture strength, preferably at least 200 MPa, and particularly preferably at least 300 MPa. The biaxial fracture strength was determined according to ISO 6872 (2008) (piston-on-three-ball test).

[0056] The glass ceramic is preferably at least 1.5 MPa·m 0.5 Particularly preferably at least 2.0 MPa·m 0.5 Most preferably at least 2.5 MPa·m 0.5 It also possesses high fracture toughness. Fracture toughness was determined according to ISO 6872 (2015) (SEVNB method).

[0057] The glass ceramic has a translucency of at least 50, preferably at least 55, and most preferably at least 60. Translucency was determined in the form of a contrast value (CR value) according to British Standard BS 5612.

[0058] Furthermore, the glass ceramic is preferably 100 g / cm³ 2 It has high chemical stability, measured as acid solubility according to ISO 6872 (2015), with a value of less than 1.

[0059] The specific combination of properties present in the glass ceramic according to the present invention makes it possible to use it as a dental material, and even as a material for producing dental restorations.

[0060] The present invention also relates to precursors of corresponding compositions from which glass ceramics according to the present invention can be produced by heat treatment. These precursors are appropriately configured starting glass and appropriately configured starting glass having a nucleus. The term "corresponding composition" means that these precursors contain the same components as the glass ceramic, in the same amounts, and the components are calculated as oxides, as is common in glass and glass ceramics, with the exception of fluorine.

[0061] Therefore, the present invention also relates to a starting glass containing the components of the glass ceramic according to the present invention.

[0062] Therefore, the starting glass according to the present invention particularly contains appropriate amounts of SiO2, Li2O, and copper, which are necessary for forming the glass ceramic according to the present invention. Furthermore, the starting glass may also contain other components shown above with respect to the glass ceramic according to the present invention. All such embodiments are indicated as preferred components of the starting glass, and these are also preferred components of the glass ceramic according to the present invention.

[0063] Particularly preferably, the starting glass takes the form of a monolithic blank obtained by casting the molten starting glass into a mold.

[0064] The present invention also relates to such starting glasses, including nuclei for crystallization of lithium silicate, particularly lithium metasilicate and / or lithium disilicate.

[0065] In particular, the starting glass is produced by melting a suitable starting material, such as a mixture of carbonates, oxides, and halides, at a temperature of approximately 1400 to 1700°C for 0.5 to 4 hours. The molten material can then be poured into water to produce frit. To achieve particularly high homogeneity, the resulting glass frit is melted again.

[0066] Next, the molten material can be poured into a mold to produce a blank of the starting glass, also known as a solid glass blank or monolithic blank.

[0067] As a starting material, it is particularly preferable to use an agent for reducing copper cations, especially an organic compound, preferably a sugar, a metal powder, preferably Al or Fe powder, or a tin compound, preferably SnO or SnO2. During the formation of glass ceramics, which begins with the melting of the starting glass, this reducing agent is expected to at least partially cause the reduction of existing copper cations, resulting in the favorable formation of elemental copper.

[0068] Accordingly, the present invention also relates to a method for producing glass ceramics according to the present invention, wherein a starting glass is melted from a mixture of starting materials, the mixture contains an agent for reducing copper cations, particularly an organic compound, preferably a sugar, a metal powder, preferably Al or Fe powder, or a tin compound, preferably SnO or SnO2, and the starting glass is subjected to at least one heat treatment.

[0069] In a preferred embodiment, the molar ratio of the agent present for reducing copper cations to copper in the mixture of starting materials is in the range of 0.5 to 200, preferably 1 to 80, and particularly preferably 1 to 30.

[0070] A further precursor starting glass having a nucleus can be initially produced by heat treatment of the starting glass. The lithium silicate glass ceramic according to the present invention can then be produced by heat treatment of this further precursor. Alternatively, the glass ceramic according to the present invention can be formed by heat treatment of the starting glass.

[0071] It is preferable to subject the starting glass to a heat treatment at a temperature of 400 to 600°C, particularly 450 to 550°C, more preferably 460 to 490°C, for a duration of 5 to 120 minutes, particularly 10 to 60 minutes, in order to produce a starting glass having nuclei for the crystallization of lithium silicate.

[0072] It is even more preferable to produce the glass ceramic according to the present invention by subjecting the starting glass or starting glass having a nucleus to a heat treatment at a temperature of 500 to 1050°C, preferably 650 to 970°C, for a duration of 5 seconds to 120 minutes, preferably 1 minute to 100 minutes, more preferably 5 minutes to 60 minutes, and even more preferably 10 minutes to 30 minutes.

[0073] Accordingly, the present invention also relates to a method for producing glass ceramics according to the present invention, comprising subjecting a starting glass or a starting glass having a nucleus to at least one heat treatment in the range of 500 to 1050°C, preferably 650 to 970°C, for a duration of 5 seconds to 120 minutes, preferably 1 minute to 100 minutes, more preferably 5 minutes to 60 minutes, and even more preferably 10 minutes to 30 minutes.

[0074] In a more preferred embodiment, a starting glass or a starting glass having a nucleus can be first subjected to a heat treatment at a temperature of 500 to 800°C, preferably 550 to 800°C, for a duration of 5 seconds to 120 minutes, preferably 1 minute to 100 minutes, most preferably 5 minutes to 60 minutes, and even more preferably 10 minutes to 30 minutes to produce a glass ceramic according to the present invention having lithium metasilicate as the main crystalline phase.

[0075] Next, the glass ceramic according to the present invention, having lithium metasilicate as the main crystalline phase, can be subjected to further heat treatment to convert the lithium metasilicate crystals into lithium disilicate crystals, thereby forming the glass ceramic according to the present invention, particularly having lithium disilicate as the main crystalline phase. Preferably, the glass ceramic is subjected to further heat treatment at a temperature of 800 to 1050°C, preferably 850 to 1030°C, more preferably 900 to 970°C, for a duration of 5 seconds to 120 minutes, preferably 1 minute to 100 minutes, more preferably 5 minutes to 60 minutes, even more preferably 5 minutes to 30 minutes, and most preferably 5 to 10 minutes.

[0076] Appropriate heat treatment conditions can be determined for a given glass ceramic by, for example, performing X-ray diffraction analysis at various temperatures.

[0077] The glass ceramics and glass according to the present invention exist, in particular, as blanks of any shape and size, such as monolithic blanks such as plates, cuboids, or cylinders. In these forms, they can be easily further processed, for example, into dental restorations. They can also take the form of dental restorations such as inlays, onlays, crowns, veneers, facets, or abutments.

[0078] Dental restorations such as bridges, inlays, onlays, crowns, veneers, facets, or abutments can be produced from glass ceramics and glass according to the present invention. Therefore, the present invention also relates to their use for producing dental restorations. Preferably, the glass ceramic or glass is given the desired shape of the dental restoration by machining.

[0079] Machining is typically carried out by a material removal process, particularly by milling and / or grinding. Machining is particularly preferably carried out by a CAD / CAM process. The starting glass, the nucleated starting glass, and the glass ceramic according to the present invention can be used for machining. Preferably, the nucleated starting glass or glass ceramic according to the present invention, having lithium metasilicate as the main crystalline phase, is used. The glass and glass ceramic according to the present invention can be used in particular in the form of blanks.

[0080] Due to the aforementioned properties of the glass ceramics and glass according to the present invention, they are particularly suitable for use in dentistry. Therefore, an object of the present invention is also to use the glass ceramics or glass according to the present invention as dental materials, preferably to produce dental restorations such as bridges, inlays, onlays, veneers, abutments, partial crowns, crowns, or facets.

[0081] Accordingly, the present invention relates to a method for producing dental restorations, particularly bridges, inlays, onlays, veneers, abutments, partial crowns, crowns, or facets, wherein the shape of the desired dental restoration is given to a glass ceramic or glass according to the present invention by machining, particularly by a CAD / CAM process.

[0082] The present invention will be described in more detail below using non-limiting embodiments. [Examples]

[0083] (Examples 1 to 48) Composition and crystalline phase The 48 types of glasses and glass ceramics according to the present invention, having the compositions shown in Table 1, were produced by melting the corresponding starting materials to produce a starting glass, followed by heat treatment for controlled crystallization.

[0084] The applied heat treatment and the properties of the resulting glass ceramic are shown in Table 1. The following meanings apply. T g Glass transition temperature determined by DSC T s and t s Temperature and time applied to melt the starting glass T Kb and t Kb Temperature and time applied for nucleation of the starting glass T C1 and t C1 Temperature and time applied for the first crystallization T C2 and t C2 Temperature and time applied for the second crystallization K IC Fracture toughness measured according to ISO 6872 (2015) (SEVNB method) Chemical stability was measured as mass loss according to ISO 6872 (2015). σ Biax Biaxial fracture strength measured according to ISO 6872 (2015) (piston-on-three-ball test)

[0085] In the examples, starting glass having the composition shown in Table 1 was first prepared from common raw materials in quantities of 100 to 200 g, at a temperature T S Duration t s The material melted, and very good melting was achieved without the formation of bubbles or streaks. In Examples 10, 14, and 48, sugar was also added to the raw materials as a reducing agent.

[0086] Glass frit is made by pouring the starting glass into water and continuing to homogenize it at temperature T as needed. S Duration t s This was produced by a second melting process. Next, the resulting molten material from the starting glass was poured into a graphite mold to produce a monolithic glass block.

[0087] The temperature of the obtained glass block, T Kb Duration tKb The first heat treatment resulted in the relaxation of the glass and the formation of glass with nuclei. Temperature T C1 Duration t C1 Further heat treatment was used to crystallize these nucleated glasses, forming glass ceramics having lithium metasilicate or lithium disilicate as the main crystalline phase, as determined by X-ray diffraction studies at room temperature. In some cases, temperature T C2 Duration t C2 Further heat treatment was carried out, and as a result, a glass ceramic having lithium disilicate as the main crystalline phase was obtained.

[0088] The amount of the crystalline phase was determined by X-ray diffraction. For this purpose, each glass-ceramic powder was prepared by grinding and sieving (<45 μm) and mixed with Al2O3 (Alfa Aesar, product number 42571) as an internal standard in a ratio of 80 wt% glass-ceramic to 20 wt% Al2O3. The mixture was slurryed with acetone to achieve the best possible mixture. The mixture was then dried at approximately 80°C. The diffraction pattern was then recorded using a Bruker D8 Advance diffractometer with CuKα radiation in the range of 10 to 100°²θ and a step size of 0.014°²θ. This diffraction pattern was then analyzed using Bruker's TOPAS 5.0 software with the Rietveld method. The proportion of the phase was determined by comparing the peak intensity with the intensity of Al2O3.

[0089] To determine the biaxial fracture strength according to ISO 6872(2015) (piston-on-three-ball test), the holder was bonded to blocks of relaxed and nucleated glass, and these blocks were subsequently machined using a CAD / CAM grinding unit (Sirona InLab). The grinding process was carried out using a diamond-coated grinding tool. The resulting small plates were subjected to a temperature T C1 Duration t C1The plates were subjected to the heat treatment shown in the table, and then the crystallized plates were polished to a thickness of 1.2 ± 0.2 mm using a diamond wheel. The biaxial fracture strength was determined for the specimens thus prepared.

[0090] High biaxial fracture strengths ranging from 330 to 780 MPa were determined for the generated glass ceramics.

[0091] Fracture toughness was determined according to ISO 6872 (2015) (SEVNB method), ranging from 2 to 3.2 MPa·m. 0,5 The high fracture toughness in the specified range was determined for the generated glass ceramics.

[0092] Chemical stability tests were conducted according to ISO 6872 (2015), and the resulting glass ceramic was found to be 100 g / cm³. 2 It showed an acid solubility of less than [value missing].

[0093] Dental crowns were fabricated from the generated glass and glass ceramics using CAD / CAM-assisted machining, and these crowns were further subjected to final crystallization under the conditions shown in Table 1, as needed. [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5]

Claims

1. Lithium silicate glass ceramics containing 0.001 to 1.0, in particular 0.05 to 0.7, preferably 0.06 to 0.5, particularly preferably 0.07 to 0.35 wt.-% copper, calculated as CuO.

2. 10. The glass-ceramic of claim 1, wherein the copper is at least partially present as elemental copper.

3. 67.0 to 89.0, preferably 68.0 to 82.0, particularly preferably 70.0 to 81.0 wt.-% SiO ２ 2. The glass-ceramic of claim 1, comprising:

4. 7.0 to 22.0, preferably 13.0 to 19.0, particularly preferably 14.0 to 17.0 wt. % Li ２ 2. The glass-ceramic of claim 1 , comprising O.

5. 2. The glass-ceramic according to claim 1, which contains 0.002 to 1.5, in particular 0.05 to 1.0, preferably 0.1 to 0.8, particularly preferably 0.1 to 0.6 wt.-% tin, calculated as SnO.

6. 0.1 to 6.0, preferably 0.1 to 5.0, more preferably 0.5 to 4.0, and even more preferably 0.9 to 3.0 wt. % Al ２ O ３ 2. The glass-ceramic of claim 1, comprising:

7. 1.0 to 11.0, preferably 1.5 to 7.0 wt. % K ２ O, Na ２ O, Rb ２ O, Cs ２ Oxides of monovalent elements selected from the group consisting of O, and mixtures thereof. Ｉ ２ 2. The glass-ceramic of claim 1 , comprising O.

8. 0 to 11.0, in particular 0.5 to 6.0, preferably 1.0 to 4.5, particularly preferably 1.5 to 4.0 wt. % K ２ 2. The glass-ceramic of claim 1 , comprising O.

9. 0 to 10.0, preferably 1.0 to 9.0, particularly preferably 2.0 to 7.0 wt. % of oxides of divalent elements selected from the group consisting of CaO, MgO, SrO, ZnO, and mixtures thereof, Me ＩＩ 2. The glass-ceramic of claim 1 , comprising O.

10. 0.1 to 12.0, preferably 1.0 to 9.0, particularly preferably 2.0 to 8.0 wt. % Al ２ O ３ , B ２ O ３ , Y ２ O ３ , La ２ O ３ and mixtures thereof. ＩＩＩ ２ O ３ 2. The glass-ceramic of claim 1, comprising:

11. 2. The glass-ceramic according to claim 1, comprising lithium disilicate or lithium metasilicate as the predominant crystalline phase, preferably lithium disilicate as the predominant crystalline phase.

12. 2. The glass-ceramic according to claim 1, comprising at least 10% by weight, preferably 10 to 50% by weight, of lithium metasilicate crystals.

13. 2. The glass-ceramic according to claim 1, comprising at least 50% by weight, preferably 50 to 85% by weight, of lithium disilicate crystals.

14. A starting glass comprising components of a glass-ceramic according to any one of claims 1 to 10.

15. 15. The starting glass of claim 14, comprising nuclei for the crystallization of lithium metasilicate and / or lithium disilicate.

16. 14. The glass ceramic according to claim 1 or the starting glass comprising components of the glass ceramic according to claim 1, wherein the glass ceramic and the starting glass are in the form of a blank or a dental restoration.

17. 14. A method for producing a glass ceramic according to claim 1, wherein a starting glass comprising the components of the glass ceramic according to claim 1 is subjected to at least one heat treatment, in particular at a temperature in the range of 500 to 1050°C, preferably 650 to 970°C.

18. (a) the starting glass is subjected to a heat treatment at a temperature of from 400 to 600°C, in particular from 450 to 550°C, more preferably from 460 to 490°C, to form a starting glass having nuclei; (b) the starting glass with the nuclei is subjected to a heat treatment at a temperature of 500 to 1050°C, in particular 650 to 970°C, to form the lithium silicate glass ceramic; 18. The method of claim 17.

19. The starting glass contains an agent for reducing copper cations, preferably an organic compound or a tin compound, more preferably a sugar, SnO, or SnO ２ 20. The method of claim 17, formed by melting a mixture of starting materials comprising:

20. 14. Use of a glass ceramic according to any one of claims 1 to 13 or of a starting glass comprising components of a glass ceramic according to any one of claims 1 to 10 as a dental material, preferably for coating dental restorations, particularly preferably for producing dental restorations.

21. 21. Use for producing a dental restoration according to claim 20, wherein the glass ceramic or the starting glass is given the shape of the desired dental restoration, in particular a bridge, an inlay, an onlay, a veneer, an abutment, a partial crown, a crown or a facet, by machining.

22. 12. A method for producing a dental restoration, in particular a bridge, inlay, onlay, veneer, abutment, partial crown, crown or facet, wherein a starting glass comprising components of a glass ceramic according to any one of claims 1 to 13 or a glass ceramic according to any one of claims 1 to 10 is given the shape of the desired dental restoration by machining, in particular in a CAD / CAM process.