Method for the production of a blank, blank and a dental restoration

Abstract

The invention relates to a method for the production of a blank of a ceramic material, wherein a first ceramic material and then a second ceramic material of different compositions are filled into a mold and wherein the materials are pressed and after pressing are sintered. Thereby, a layer of the first ceramic material is filled into the mold, a first open cavity is formed in the layer, the second ceramic material is filled into the first open cavity and the materials are pressed together and are then heat-treated. Both the first ceramic material and the second ceramic material contain, or consists of, lithium silicate glass ceramic.

Claims

1. A method for the production of a blank of a ceramic material comprising the steps of: providing a first starting glass composition in percentage by weight: TABLE-US-00010 SiO2 57.5-60.5% Li2O 13.5-20.5% ZrO2  8.5-11.5% P2O5 3.0-7.5% Al2O3 0.5-6.0% K2O 0.5-3.5% CeO2 0.5-2.5% B2O3 0-3% Na2O 0-3% at least one additive  0-4%; and wherein Tb2O3 and/or Er2O3 are added to the first starting glass composition to influence fluorescence; heat treating the first starting glass composition at a temperature between 1350° C. and 1600° C. to form a first melt; quenching the first melt to form a first glass frit; working the first glass frit to form a first glass powder having a grain size ranging from 1 to 150 microns; heat treating the first glass powder at a temperature from 600° C. to 860° C. to form a first lithium silicate glass ceramic powder; providing a second starting glass composition in percentage by weight: TABLE-US-00011 SiO2 57.5-60.5% Li2O 13.5-20.5% ZrO2  8.5-11.5% P2O5 3.0-7.5% Al2O3 0.5-6.0% K2O 0.5-3.5% CeO2 0.5-2.5% B2O3 0-3% Na2O 0-3% at least one additive  0-4%; and wherein Tb2O3 and/or Er2O3 are added to the second starting glass composition to influence fluorescence; and wherein the first starting glass composition is different than the second starting composition; heat treating the second starting glass composition at a temperature between 1350° C. and 1600° C. to form a second melt; quenching the second melt to form a second glass frit; working the second glass frit to form a second glass powder having a grain size ranging from 1 to 150 microns; heat treating the second glass powder at a temperature from 600° C. to 860° C. to form a second lithium silicate glass ceramic powder that is different from the first lithium silicate glass ceramic powder; wherein both the first lithium silicate glass ceramic powder and the second lithium silicate glass ceramic powder include lithium silicate crystals in the range of 10-80% by volume; filling a layer of the first lithium silicate glass ceramic powder into a mold; forming a first open cone-shaped cavity in the layer of the first lithium silicate glass ceramic powder; filling the first cone-shaped open cavity with the second lithium silicate glass ceramic powder; pressing the first and second lithium silicate glass ceramic powders thereby forming a first region corresponding to an area of the first lithium silicate glass ceramic powder and a second region corresponding to an area of the second lithium silicate glass ceramic powder; and sintering the pressed first and second lithium silicate glass ceramic powders; wherein the second lithium silicate glass ceramic powder of the second region is colored and the first lithium silicate glass ceramic powder of the first region is not colored or colored to a lesser degree, so that a higher translucency in the second region relative to the first region results.

2. The method according to claim 1, wherein to produce the first and/or second lithium silicate glass ceramic powders, the first and/or second starting glass composition includes, in percentage by weight: TABLE-US-00012 SiO2 57.5-60.5% Li2O 14.0-16.0% ZrO2  9.0-10.5% P2O5 5.0-6.0% Al2O3 2.5-3.0% K2O 1.0-1.5% CeO2 0.5-1.0% B2O3 2.5-3.0% Na2O 0.1-2.0% V2O5 0.1-0.7% Er2O3   0-1.0% T2O3 0.3-0.5% MnO2    0-0.2%.

3. The method according to claim 1, wherein the first lithium silicate glass ceramic powder has a composition that differs from the second lithium silicate glass ceramic powder in terms of fluorescence and/or color and/or opalescence.

4. The method according to claim 1, wherein after filling of the second lithium silicate glass ceramic powder, a second cone-shaped open cavity is formed therein.

5. The method according to claim 4, further comprising the step of providing a third lithium silicate glass ceramic powder that includes lithium silicate glass ceramic, the third lithium silicate glass ceramic powder having a glass powder/glass particle size between 1 microns and 150 microns, wherein the third lithium silicate glass ceramic powder has a different composition and a lower translucency than the first and second lithium silicate glass ceramic powders.

6. The method according to claim 1, wherein a plurality of first open cone-shaped cavities are formed in the layer of the first lithium silicate glass ceramic powder and into which the second lithium silicate glass ceramic powder is filled.

7. The method according to claim 6, wherein at least some of the plurality of open cone-shaped first cavities have internal geometries that differ from one another.

8. The method according to claim 1, wherein an internal geometry of the first open cone-shaped cavity is geometrically aligned with the course of a dental jaw region to be provided with a restoration that emanates from a jaw region.

9. The method according to claim 1, wherein upon working of a dental restoration out of the blank, a dentin region of the dental restoration is formed at least in regions from the second lithium silicate glass ceramic powder and an incisal region is formed from the first lithium silicate glass ceramic powder.

10. The method according to claim 1, wherein Tb2O3 and Er2O3 are added to the starting glass composition of both the first lithium silicate glass ceramic powder and the second lithium silicate glass ceramic powder to influence fluorescence.

11. The method according to claim 1, wherein to influence the opalescence the crystals have a maximum length extension of between 10 nm and 800 nm.

12. The method according to claim 1, wherein during pressing a recess is formed in the blank that corresponds to a negative form of an implant connection contour.

13. The method according to claim 1, wherein a recess that has a cone-shaped geometry is formed in the blank during pressing, from which the internal cavity of a dental restoration is formed through milling and/or grinding.

14. A dental restoration produced according to the method of claim 1, wherein the dental restoration is of monolithic form and includes at least one first layer of a first ceramic material extending on an incisal side and a second layer of a second ceramic material extending on a dentin side, wherein the first layer has a higher translucency and the first layer differs from the second layer in its color.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details, advantages and features of the invention result not only from the claims and the features disclosed therein—alone and/or in combination—but also from the following description of the example embodiments shown in the drawings.

(2) The following drawings show:

(3) FIG. 1A shows a schematic of a device and process step performed using the device,

(4) FIG. 1B shows another schematic of the device and process step of the present invention performed using the device shown in FIG. 1A,

(5) FIG. 1C shows another schematic of the device and process step of the present invention performed using the device shown in FIG. 1B

(6) FIG. 2 shows FIG. 1A in greater detail,

(7) FIG. 3 shows a blank with regions of different material properties,

(8) FIG. 4 shows a further blank with regions of different material properties,

(9) FIG. 5 shows a schematic of a blank with a tooth to be derived therefrom,

(10) FIG. 6 shows a blank in a top view with a plurality of regions of different material properties,

(11) FIG. 7 shows a further embodiment of a blank of the present invention,

(12) FIG. 8 shows a further embodiment of a blank of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(13) The teaching of the invention is illustrated by reference to the figures, in which the same elements are assigned the same reference numerals, wherein in particular dental restorations are produced from a ceramic material having a monolithic structure such that after full sintering an immediately usable monolithic tooth replacement is available.

(14) To this end, the invention provides for the production of a blank, which has regions of ceramic material with differing compositions and thus properties, through which the particular desired optical properties of the restoration to be produced can be attained, which, as mentioned, offer the possibility of immediate usage of the monolithically fabricated tooth replacement after full sintering without, for example, having to apply a incisal layer by hand and firing.

(15) With reference to FIGS. 1 to 3, the production of a lithium silicate glass ceramic blank will be described from which a dental restoration can be produced, in the example embodiment, a crown. The blank has the shape of a cylinder. Other shapes are possible as cuboids.

(16) Thus a first ceramic material 14 is prepared consisting of lithium silicate glass ceramic. For this a starting glass of the following composition is melted in percentage by weight:

(17) TABLE-US-00005 SiO.sub.2 57.5-60.5%  Li.sub.2O 13.5-20.5%  ZrO.sub.2 8.5-11.5%  P.sub.2O.sub.5 3.0-7.5% Al.sub.2O.sub.3 0.5-6.0% K.sub.2O 0.5-3.5% CeO.sub.2 0.5-2.5% B.sub.2O.sub.3    0-3% Na.sub.2O    0-3% At least one additive     0-4%.

(18) The at least of one additive is at least one from the group of color pigments and/or fluorescence agents. It is in particular provided for the additive to be at least one oxide from the group of rare earth metals or for it to contain such an oxide.

(19) The corresponding mixture of starting materials is then filled into a crucible of fire-resistant material or a noble metal alloy and melted at a temperature between 1350° C. and 1600° C. for a time between 1 and 10 hours, in particular for a time between 4 and 7 hours at a temperature of 1540° C. Homogenization is carried out at the same time, or following on, for example by stirring. The liquid glass so prepared is then quenched in a suitable medium such as a liquid, e.g., water, or high-temperature insulation wool. The quenched glass frit prepared in this way is then dried. It is then milled, for example in a ball mill, and subsequently sieved, wherein a sieve with a mesh size between 50 μm and 250 μm can be used. Where necessary, further milling, for example using a jet mill or Attritor mill, can be carried out.

(20) The grains that have a grain size in the region 1 to 150 μm are in particular selected from the glass powder/glass particle powder so prepared.

(21) To allow the blank to be worked without difficulty, without the molded part derived from the blank being unstable upon sintering to full density, either the frit obtained after melting or the pre-milled or finally milled powder is subjected to a crystallization step. The frit/powder is thereby subject to a preferably multi-stage heat treatment, wherein, for example, a first partial crystallization is carried out from 600° C. to 670° C. for a holding period between 10 minutes and 120 minutes, a second partial crystallization is carried out in the range 730° C. to 780° C. for a holding period between 10 and 60 minutes, and a third partial crystallization step is carried out in the range 800° C. to 860° C. for a time period between 5 minutes and 15 minutes. Where appropriate a further heat treatment can then be carried out for relaxation, for example at a temperature between 350° C. and 500° C. for a time period between 10 and 120 minutes.

(22) It should be noted that crystallization can also be carried out at a later stage, for example after sintering to full density.

(23) The pourable powder or granulate in the form of the first ceramic material 14 is filled into a mold 10 or press mold of a press tool 12.

(24) A binding agent can also be added.

(25) Then, by means of a press plunger 16 an open cavity 18 is formed in the material 14 or in a layer formed from this material. The material 14 is displaced or lightly compacted through the use of the press plunger. Once the cavity 18 is formed (FIG. 1b), the press plunger 16 is removed and a second ceramic material 20 filled into the cavity 18, which largely corresponds in its composition to that of the first material with the limitation that the percentage of coloring substances deviates, so that a desired tooth color is achieved since the dentin of the tooth to be produced is derived from the second ceramic material 20.

(26) After filling of the second ceramic material 20 into the cavity 18 (FIG. 1c), the materials 14, 20, or the layers or regions formed from these, are pressed in the mold 10—by means of a lower or upper punch 22, 24—through which a compaction results. After pressing, the blank 28 has a density of approximately 40-70% of the theoretical density of 2.6 g/cm.sup.3. Pressing is preferably carried out at a pressure between 50 MPa and 400 MPa.

(27) FIG. 2 shows the representation of FIG. 1b) in more detail. It can be seen that the cavity 18 is formed through the press plunger 16 in the first ceramic material 14 respectively in the layer comprising that material. On the base side the mold 10 is limited by the press plunger 22.

(28) As can be seen from FIG. 3, a second cavity 26 can be formed in the second material 20 after its compression by the press plunger 22, 24 or optionally after the pre-sintering, for example by milling.

(29) However, it is also possible to form a corresponding second cavity 26 in the material 20, according to FIG. 1c), which completely fills the bottom-side-open cavity 18, by means of a press plunger that is not shown.

(30) Further, there is the possibility to form a recess or a through-hole emanating from the base or in the base of the blank, which, for example, is designed for a function of the dental restoration or which can be used for subsequent working. There is consequently the possibility of providing an opening in the base which exhibits the negative contour of an implant connection. This is illustrated in FIG. 7. Thus FIG. 7 shows a blank 28 that corresponds for example to FIG. 3 that has a three-dimensional layer structure according to the teaching of the invention. As the drawing makes clear, a recess 126 is formed, emanating from the base of the blank 28 in accordance with the invention, corresponding to the negative shape of an implant connection, naturally taking into account the shrinkage behavior of the blank upon sintering. If necessary, a through-opening 128 can also be formed which after production of the molded parts serves as a screw channel. Naturally it is also possible to form the screw channel after sintering of the blank 28 through milling or grinding. An abutment is then formed from the blank 28 in particular through grinding, for which at least the implant connection is already present.

(31) The shaping for the recess 126/128 can be carried out upon pressing of the blank 28, in that the press tool incorporates a mandrel that corresponds to the desired geometry for the recess 126 or 126/128, which in the example embodiment emanates from the press plunger.

(32) FIG. 8 also shows a blank 28, that has a three-dimensional layer structure as described above. A cone-shaped cavity 130 is formed in the blank 28 emanating from the base upon pressing, to facilitate the milling out/grinding of a dental restoration—in the example embodiment a crown 132—and at the same time to insure that wear of the tool 134 used, in particular a ball head milling or grinding tool is reduced compared to the working of blanks that do not have a corresponding cavity. The advantage of the impressed cone-shaped cavity 130 or recess is that upon usage of a spherical-head milling/grinding tool firstly a cone required for the production of the crown 132 no longer has to be created, and moreover, the working is not initially carried out with the center of the ball head; if there is no corresponding cone then the tool must initially work out the cone with the spherical head, primarily with its center, as a result of which there is greater wear.

(33) The cone-shaped cavity 130 can also be formed upon pressing of the blank 28 through the use of a corresponding mandrel in the press tool.

(34) Irrespective of whether the second cavity 26 or a hole or depression, for example for a screw channel or implant connection, is present or not, a sintering of the blank 28 is carried out after pressing at a temperature in particular in the range between 750° C. and 950° C. for a time period between 5 minutes and 120 minutes. There is initially a debinding and then the pre-sintering. The density of the blank 28 after sintering to full density is approximately 2.6 g/cm.sup.3 and/or >99.9% of the theoretical final density. The breaking strength of the fully sintered or end-sintered blank 28 is greater than 190 MPa.

(35) The blank 28 is provided with a holder 30, so that the blank 28 can be worked for example in a milling or grinding machine to derive a dental restoration such as a tooth crown from the blank 28, as explained with reference to FIG. 5. Thereby, the tooth crown to be produced is at least virtually laid in the blank 28 such that the incisal region extends into the region 32 formed by the first ceramic material 14 and the dentin region in sections extends into the second region 34 formed by the second ceramic material 20. The blank 28 is then worked taking this data into consideration.

(36) FIG. 4 illustrates that after filling of the first cavity 18 in the first ceramic material 14 and filling of the second ceramic material 20 into the cavity 18, optionally a second cavity 36 is formed in accordance with the procedure of FIG. 1b), and then a third ceramic material is filled into the cavity 36, which differs from the second ceramic material in its composition such that it has a different color. A cavity 40 may similarly be formed in the third ceramic material 38—as explained with reference to FIG. 3.

(37) As illustrated in FIG. 5, a dental restoration, in the example embodiment, a tooth 42, is derived through working from the blank 28. For this purpose, with knowledge of the course of the first region 32 of the first ceramic material 14 and the second region 34 of the second ceramic material 20 in the blank 28, the tooth 42 to be produced is virtually laid in the regions 32, 34 such that the incisal region extends in the first region 32 and the dentin 46 extends into the second region 34.

(38) After the so virtually positioned tooth 42 is derived through working from the blank 28, a tooth replacement is available, which in principle can be used directly, and in particular does not require any veneering. A monolithic tooth 42 is prepared on the basis of the teaching of the invention. In this case, the production from the blank 28 through working is made easier in that the second region 34 already has an open cavity 26, as described with reference to FIG. 3 and as can be seen from FIG. 5.

(39) The teaching of the invention introduces the possibility of forming a blank 48 that has a plurality of regions 52, 54, 56, that are made of the second and optionally a third ceramic material, and can have different geometries (FIG. 6), so that corresponding teeth of different shapes can be formed. The second regions 52, 54, 56 formed from the second ceramic material 20 are embedded in the first ceramic material 48, i.e., are surrounded by this, as illustrated in particular through the Figures. The second regions 52, 54, 56 are uncovered on the base side.

(40) As can be seen in particular from FIGS. 2-4, the second regions have external geometries that taper starting from the bottom, i.e., from the base region 35. It may be referred to as a cone-like geometry, wherein the outer contour represents a freeform surface.

(41) The base region 35/the base surface that limits it on the underside merges with the lower side of the base surface 33 of the first region 32.

(42) To prepare the blank sections 52, 54, 56 also referred to as nests, it is necessary—as described with reference to FIG. 1—to have corresponding open cavities in the layer made of the first material 14 and designated as the first region 50, so that the pourable second ceramic material 20 can be filled into the cavities in the manner described above and then the materials 14, 20 can be pressed together, i.e., compacted.

(43) With regard to the blanks 28, 48 it is to be noted that these can have a cuboid shape, for example with the dimensions 18×15×25 mm or a disk shape, for example with a diameter of 100 mm and height of 15 mm, without thereby limiting the teaching of the invention. This brings in particular—as explained by reference to FIG. 6—the advantage that, for example, a plurality of second regions 52, 54, 56—so-called dentin cores—can be formed in a disk-shaped blank, to obtain not only restorations of different geometries, but also with a favorable layer course with respect to translucency and strength.

(44) Since the position of one or more second regions 52, 56, i.e., the nests, optionally with different geometries, is known, they can be stored in a data record. Then, the restorations to be produced, which are available as CAD data sets, are positioned relative to and in the blank sections so that the tooth replacement can be derived from the blank by milling and/or grinding

(45) In other words, teeth of different geometries, for example, can be prepared from a corresponding disc-shaped blank. The schematic clearly shows that the second regions 52, 56 have different dimensions and are intended for dentin cores that have different dimensions.

(46) It was mentioned above that the restorations are derived from the blank that has been pre-sintered or partially sintered, for example through milling, but there is naturally no departure from the invention if the blank is first fully sintered and the tooth replacement then derived. With both embodiments of the invention all advantages resulting from the inventive teaching can be realized.

(47) For the sake of completeness, it is noted that the percentage of lithium silicate crystals in the first and second ceramic materials should lie in the range 10 to 80% by volume. The starting materials may contain compounds which lead to a desired fluorescence and/or coloration.

(48) Thus, for example, Tb.sub.2O.sub.3/Er.sub.2O.sub.3 can be used to influence fluorescence and, for example, MnO, Fe.sub.2O.sub.3, Y.sub.2O.sub.3, V.sub.2O.sub.3, CeO.sub.2 or other rare earth oxides can be used to influence the color.

(49) The amount of lithium disilicate crystals is preferably between 10 to 95 weight percent of the total lithium crystal content. The crystal phase may also include lithium phosphate.

(50) The dentin core designated by the reference numeral 56 is, by way of example, intended for a front tooth and the dentin core designated by the reference numeral 54 is intended for a molar tooth. The not further designated section above the region 54 can be intended for a canine tooth.

(51) The present invention may include one or more of the following features:

(52) 1. A method for the production of a blank (28, 48) of a ceramic material, in particular a blank to be used for the production of a dental restoration (42), wherein a first ceramic material (14) in powder form and then a second ceramic material (20) in powder form of different compositions are filled into a mold (10), wherein the materials are pressed and after pressing are sintered, characterized in that the first or the second or the first and the second ceramic material used contain, or consist of, lithium silicate glass ceramic, that a layer of the first ceramic material (14) is filled into the mold (10), that a first open cavity (18) is formed in the layer, that the second ceramic material (20) is filled into the first open cavity (18), and that the materials are pressed together and are then heat-treated.

(53) 2. The method according to claim 1, characterized in that to produce the first and/or second ceramic material the composition of the starting glass contains, or consists of, in percentage by weight:

(54) TABLE-US-00006 SiO.sub.2 57.5-60.5%  Li.sub.2O 13.5-20.5%  ZrO.sub.2 8.5-11.5%  P.sub.2O.sub.5 3.0-7.5% Al.sub.2O.sub.3 0.5-6.0% K.sub.2O 0.5-3.5% CeO.sub.2 0.5-2.5% B.sub.2O.sub.3    0-3% Na.sub.2O    0-3% At least one additive     0-4%.

(55) 3. The method according to claim 1, characterized in that to produce the first and/or second ceramic material the composition of the starting glass contains, or consists of, in percentage by weight:

(56) TABLE-US-00007 SiO.sub.2 57.5-60.5%  Li.sub.2O 14.0-16.0%  ZrO.sub.2 9.0-10.5%  P.sub.2O.sub.5 5.0-6.0% Al.sub.2O.sub.3 2.5-3.0% K.sub.2O 1.0-1.5% CeO.sub.2 0.5-1.0% B.sub.2O.sub.3 2.5-3.0% Na.sub.2O 0.1-2.0% V.sub.2O.sub.5 0.1-0.7% Er.sub.2O.sub.3 .sup. 0-1.0% Y.sub.2O.sub.3 0.3-0.5% MnO.sub.2 .sup. 0-0.2%

(57) 4. The method according to at least one of the above claims, characterized in that a powder with a mean grain size between 1 μm and 150 μm, in particular between 10 μm and 30 μm, is used as the first and/or second ceramic material.

(58) 5. The method according to at least one of the above claims, characterized in that the first ceramic material has a composition that differs from the second ceramic material in terms of translucency and/or fluorescence and/or color and/or opalescence.

(59) 6. The method according to claim 1, characterized in that after filling of the second ceramic material (18), a second open cavity (26, 36) is formed therein.

(60) 7. The method according to at least one of the above claims, characterized in that that the third ceramic material (38) consists of, or contains, lithium silicate glass ceramic.

(61) 8. The method according to at least one of the above claims, characterized in that a number of first open cavities (18) are formed in the layer of the first ceramic material (14) and into which ceramic material (18), in particular the second ceramic material, is filled.

(62) 9. The method according to at least one of the above claims, characterized in that at least some of the plurality of open first cavities (18) have internal geometries that differ from one another.

(63) 10. The method according to at least one of the above claims, characterized in that the internal geometry of the first open cavity (18) is geometrically aligned with the course of a dental jaw region to be provided with a restoration, such as a tooth stump, or an abutment that emanates from a jaw region.

(64) 11. The method according to at least one of the above claims, characterized in that upon working of the dental restoration out of the blank (28, 48) the dentin region of the dental restoration is formed at least in regions from the second ceramic material (20) and the incisal region is formed from the first ceramic material (14).

(65) 12. The method according to at least one of the above claims, characterized in that Tb.sub.2O.sub.3 and/or Er.sub.2O.sub.3 are added to the starting material to influence fluorescence.

(66) 13. The method according to at least one of the above claims, characterized in that to influence the opalescence the crystals of the crystal phase have a maximum length extension of between 10 nm and 800 nm.

(67) 14. The method according to at least one of the above claims, characterized in that during pressing a recess is formed in the blank (28) that corresponds to a negative form of an implant connection contour (126).

(68) 15. The method according to at least one of the above claims, characterized in that a recess (130) that has a cone-shaped geometry is formed in the blank (28) during pressing, from which the internal cavity of a dental restoration is formed through milling and/or grinding.

(69) 16. A pre-sintered or fully sintered blank (28, 48) for use in producing a dental restoration (42) such as a dental framework, crown, partial crown, bridge, cap, veneer, abutment, pin construction, in particular crown or partial crown, consisting of a ceramic material, that has regions of different compositions, wherein a first region (32, 50) is of a first ceramic material (14) and at least one second region (34) is of a second ceramic material (20) and the regions are adjacent to each other, characterized in that the first or the second, or the first and the second ceramic material contains, or consists of, lithium silicate glass ceramic, that the second region (34, 52, 54, 56) extends within the first region (32) and has an outer geometry that tapers from a basal region (35) or base surface.

(70) 17. The blank according to claim 16, characterized in that the basal region (35)/the base surface of the second region (34) extends in the region of an outer surface (33) of the first region (32), and preferably merges with it.

(71) 18. The blank according to claim 16 or 17, characterized in that the second region (34) commencing from its basal region (35)/its base surface has a cavity (26).

(72) 19. The blank according to at least one of claims 16 to 18, characterized in that the second region (34) has a cone-like geometry on its outer side.

(73) 20. The blank according to at least one of claims 16 to 19, characterized in that a third region (38) extends within the second region (34) and consists of a third ceramic material that has a composition that differs from that of the first and/or second ceramic material (14, 20) and in particular contains, or consists of, lithium silicate glass ceramic.

(74) 21. The blank according to at least one of claims 16 to 20, characterized in that a plurality of second regions (52, 54, 56) are surrounded by the first region (32, 50).

(75) 22. The blank according to at least one of claims 16 to 21, characterized in that at least some of the plurality of second regions (52, 54, 56) differ from one another in their outer geometries.

(76) 23. The blank according to at least one of claims 16 to 22, characterized in that the blank (28, 48) is produced of a lithium silicate glass ceramic of the composition that contains, or consists of, the following in percentage of weight:

(77) TABLE-US-00008 SiO.sub.2 57.5-60.5%  Li.sub.2O 13.5-20.5%  ZrO.sub.2 8.5-11.5%  P.sub.2O.sub.5 3.0-7.5% Al.sub.2O.sub.3 0.5-6.0% K.sub.2O 0.5-3.5% CeO.sub.2 0.5-2.5% B.sub.2O.sub.3    0-3% Na.sub.2O    0-3% At least one additive     0-4%.

(78) 24. The blank according to at least one of claims 16 to 23, characterized in that the blank (28, 48) is produced from lithium silicate starting glass that contains, or consists of, in percentage of weight:

(79) TABLE-US-00009 SiO.sub.2 57.5-60.5%  Li.sub.2O 14.0-16.0%  ZrO.sub.2 9.0-10.5%  P.sub.2O.sub.5 5.0-6.0% Al.sub.2O.sub.3 2.5-3.0% K.sub.2O 1.0-1.5% CeO.sub.2 0.5-1.0% B.sub.2O.sub.3 2.5-3.0% Na.sub.2O 0.1-2.0% V.sub.2O.sub.5 0.1-0.7% Er.sub.2O.sub.3 .sup. 0-1.0% Y.sub.2O.sub.3 0.3-0.5% MnO.sub.2  0-0.2%.

(80) 25. The blank according to at least one of claims 16 to 24, characterized in that the second ceramic material (20) differs from the first ceramic material (14) in coloration, in particular through the addition of at least one oxide from the group MnO, Fe.sub.2O.sub.2, Y.sub.2O.sub.3, V.sub.2O.sub.3, CeO.sub.2, other rare earth oxides.

(81) 26. The blank according to at least one of claims 16 to 25, characterized in that after sintering to full density the restoration (42) produced from the blank (28) has a higher translucency on the incisal side than on the dentin side.

(82) 27. The blank according to at least one of claims 16 to 26, characterized in that the blank (28) has a recess or depression (126) on its bottom side that has a geometry of an implant connection contour.

(83) 28. The blank according to at least one of claims 16 to 27, characterized in that from the depression (126) a through-opening emanates to form a screw channel.

(84) 29. The blank according to at least one of claims 16 to 28, characterized in that the blank (28) on its bottom side has a depression (130) that has a cone-shaped geometry.

(85) 30. A dental restoration (42), in particular crown or partial crown, produced according to at least claim 1, characterized in that the restoration (42) is of monolithic form and consists of at least one first layer (32) of a first ceramic material (14) extending on the incisal side and a second layer (34) of a second ceramic material (20) extending on the dentin side, wherein the first layer has a higher translucency and the first layer differs from the second layer in its color.