Method for producing a blank, blank and a dental restoration

Abstract

The invention relates to a blank of a ceramic material, wherein a first ceramic material and then a second ceramic material of different compositions are filled into a die and wherein the materials are pressed and after pressing are sintered. A layer of the first ceramic material is thereby filled into the die and a first cavity formed in the layer, the second ceramic material is then filled into the first open cavity and the materials pressed together and then heat-treated.

Claims

1. A pre-sintered or fully-sintered blank for use in preparing a dental restoration, the blank having regions of different compositions, wherein the blank comprises one first region of a first ceramic material and at least one second region of a second ceramic material, the first region and the at least one second region being of different compositions and are sited next to one another, wherein the first and second ceramic materials include zirconium dioxide doped with yttrium oxide (Y2O3), and optionally calcium oxide (CaO), magnesium oxide (MgO) and/or ceroxide (CeO2), and wherein the first ceramic material differs from the material of the second ceramic material in terms of color and proportions of stabilized crystal forms present at room temperature, and wherein the at least one second region extends within the first region and has an external geometry that tapers from a base region or a base surface and wherein percentage of yttrium oxide in the second ceramic material lies between 4.5 wt % and 7.0 wt % and in the first ceramic material between 7.0 wt % and 9.5 wt %, wherein the percentage of yttrium oxide in the first ceramic material is greater than in the second ceramic material and wherein the first region of the first ceramic material has a tetragonal crystal phase ranging from 50%-60%.

2. The blank according to claim 1, wherein the base region or the base surface of the at least one second region extends in the region of an outer surface of the first region.

3. The blank according to claim 1, wherein the at least one second region starting from its base region or base surface has a cavity.

4. The blank according to claim 1, wherein the at least one second region has a conus-like geometry on its outer side.

5. The blank according of claim 1, wherein the at least one second region includes a third region extending at least partially therein, the third region including a third ceramic material having a composition different from that of the first and/or second ceramic material.

6. The blank according to claim 1, wherein the composition of the third ceramic material includes zirconium dioxide to which yttrium oxide has been added.

7. The blank according to claim 6, wherein the thermal expansion coefficient of the first region is 0.2 μm/m*K to 0.8 μm/m*K lower than the thermal expansion coefficient of the at least one second and/or third regions.

8. The blank according to claim 1, wherein the at least one second region includes a plurality of second regions surrounded by the first region.

9. The blank according to claim 8, wherein at least some of the plurality of second regions differ from one another in their external geometries.

10. The blank according to claim 1, wherein the second ceramic material differs from the first ceramic material in being colored.

11. The blank according to claim 1, wherein after full sintering the restoration produced from the blank has a higher strength on a dentine side than on an incisal side and/or on the incisal side has a higher translucency than on the dentine side.

12. A dental restoration prepared from a blank according to claim 1, wherein the restoration is formed monolithically and comprises at least one first layer extending on an incisal side of a first ceramic material and a second layer extending on an dentine side of a second ceramic material, wherein the first layer has a higher translucency and/or lower strength than the second layer, and wherein the ceramic materials include zirconium dioxide doped with yttrium oxide (Y2O3), and optionally calcium oxide (CaO), magnesium oxide (MgO) and/or ceroxide (CeO2), and wherein the first ceramic material differs from the material of the second ceramic material in terms of color and proportions of stabilized crystal forms present at room temperature, and wherein percentage of yttrium oxide in the second ceramic material lies between 4.5 wt % and 7.0 wt % and in the first ceramic material between 7.0 wt % and 9.5 wt %, wherein the percentage of yttrium oxide in the first ceramic material is greater than in the second ceramic material.

13. The dental restoration according to claim 12, wherein the thermal expansion coefficient of the first layer is 0.2 μm/m*K to 0.8 μm/m*K lower than the thermal expansion coefficient of the second layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1a shows a schematic of a device and a process step of the present invention performed using the device,

(3) FIG. 1b shows a schematic of another process step of the present invention performed using the device shown in FIG. 1a,

(4) FIG. 1c shows a schematic of another process step of the present invention performed using the device shown in FIGS. 1a and 1b,

(5) FIG. 2 shows FIG. 1b in greater detail,

(6) FIG. 3 shows a blank according to the present invention with regions of different material properties,

(7) FIG. 4 shows another blank according to the present invention with regions of different material properties,

(8) FIG. 5 shows a schematic of a blank according to the present invention with a tooth to be derived therefrom, and

(9) FIG. 6 shows a blank according to the present invention in a top view with a plurality of regions of different material properties.

DETAILED DESCRIPTION OF THE INVENTION

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

(11) To this end, the invention provides for the preparation of a blank, which has regions of ceramic material with differing compositions and thus properties, has desired optical and mechanical properties according to the restoration to be produced, which, as mentioned, offer the possibility of immediate usage of the tooth replacement monolithically fabricated after full sintering without, for example, having to apply incisor material by hand.

(12) Further, specifically desired strength values are attainable in the ranges in which high loads occur. Desired optical properties can be achieved.

(13) With reference to FIGS. 1 to 3, the manufacture of a blank will be described from which a dental restoration can be produced, in the example embodiment, a tooth.

(14) Thus a pourable granulate in the form of a first ceramic material 14 is filled into the die 10 of a pressing tool 12, which is in particular a zirconium dioxide stabilized with yttrium oxide, which can have the following composition in wt %:

(15) TABLE-US-00002 HfO.sub.2 <3.0 Al.sub.2O.sub.3 <0.3 Y.sub.2O.sub.3 7.0 to 9.5 Color-imparting oxides: 0-0.5 Technically caused, unavoidable components ≤0.2 (such as SiO.sub.2, Fe.sub.2O.sub.3, Na.sub.2O) ZrO.sub.2 100 − (Y.sub.2O.sub.3 + Al.sub.2O.sub.3 + HfO.sub.2 + color- imparting oxides + technically caused, unavoidable components)

(16) A binding agent may also be added, but is not taken into consideration in the above percentage by weight values.

(17) However, in particular it is provided for the composition to contain coloring oxides only in small amounts or not at all, for example ≤0.5 wt %, as the first ceramic material 14 is used as an incisor material, so that a high translucency is desired. As a result of the relatively high percentage of yttrium oxide, the tetragonal crystal phase is only 50 to 60% in the incisal region of the produced mold part, i.e., the dental restoration, and the remainder is the cubic and monoclinic crystal phase.

(18) Then, by means of a press plunger 16 an open cavity 18 is formed in a material 14 or in a layer formed from this material. By means of the press plunger, the material 14 is displaced or slightly compacted. After 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 may have one of the following compositions in wt %:

(19) TABLE-US-00003 HfO.sub.2 <3.0 Al.sub.2O.sub.3 <0.3 Y.sub.2O.sub.3 4.5 to 7.0 Color-imparting oxides: 0-1.5 Technically caused, unavoidable components ≤0.2 (such as SiO.sub.2, Fe.sub.2O.sub.3, Na.sub.2O) ZrO.sub.2 100 − (Y.sub.2O.sub.3 + Al.sub.2O.sub.3 + HfO.sub.2 + color- imparting oxides + technically caused, unavoidable components)

(20) Thereby, the coloring oxide or oxides should be present in an amount that results in a desired tooth color, since the dentine of the tooth to be produced is formed from the second ceramic material 20. The relatively low percentage of Y.sub.2O.sub.3 further ensures that the dentine of the fully-sintered tooth replacement has a high tetragonal phase content of at least 85%, preferably at least 90%, thus yielding a high strength.

(21) After filling of the second ceramic material 20 into the cavity 18 (FIG. 1c), the materials 14, 20 respectively the layers or regions formed from these, are pressed in the die 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 3 g/cm.sup.3. Pressing is preferably carried out at a pressure between 1000 bar and 2000 bar.

(22) With regard to the ceramic materials 14, 20 it should also be noted that they have a bulk density between 1 g/cm′ and 1.4 g/cm.sup.3. After pressing, the density is approximately 3 g/cm.sup.3.

(23) FIG. 2 shows the contents 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 the material. On the base side the die 10 is limited by the press plunger 22.

(24) 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.

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

(26) Irrespective of whether the second cavity 26 is present or not, a pre-sintering of the blank 28 is carried out after pressing at a temperature in particular in the range between 800° C. and 1000° C. over a time period between 100 minutes and 150 minutes. There is initially a debinding and then pre-sintering. The density of the blank 28 after the pre-sintering is approximately 3 g/cm.sup.3. The breaking strength of the pre-sintered blank 28 should be between 10 MPa and 60 MPa.

(27) 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 from the blank 28, as explained with reference to FIG. 5. Thereby, the tooth to be produced is at least virtually laid in the blank 28 such that the incisal region runs into the region 32 formed by the first ceramic material 14 and the dentine region in sections runs into the second region 34 formed by the second ceramic material 20. The blank 28 is then worked taking this data into consideration.

(28) 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, a second cavity 36 is filled optionally in accordance with the procedure of FIG. 1b), so that a third ceramic material is filled into the cavity 36 so formed, which differs from the second ceramic material in its composition such that in particular a higher strength can be achieved. A cavity 40 may similarly be formed in the third ceramic material 38—as explained with reference to FIG. 3.

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

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

(31) 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 the third ceramic material, and can have different geometries (FIG. 6), so that corresponding teeth of different geometries can be formed. The so-called second regions 50, 52, 54 formed from the second ceramic material 20 are embedded in the first ceramic material 48, i.e., are surrounded by this, as can be seen in particular also from the Figures. The second regions 50, 52, 54 are uncovered on the base side.

(32) 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. It may be referred to as a conus-like geometry, wherein the outer contour represents a freeform surface.

(33) 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.

(34) 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.

(35) With regard to the physical properties of the materials 14, 20 it is to be noted that in addition to a difference in translucency and strength they should also have different thermal expansion coefficients. In particular, the invention provides for the first ceramic material 14 after full sintering to have a thermal expansion coefficient that is 0.2 μm/m*K to 0.8 μm/m*K lower than the second region 38, 52, 54, 56 formed from the second ceramic material 20. As a result of this a compression stress is generated in the first region 50, i.e., in the incisor material, which leads to an increase in strength.

(36) With regard to the blanks 28, 48 it is to be noted that these can have a cuboid shape, for example the dimensions 18×15×25 mm or a disk shape, for example with a diameter of 100 mm, without thereby affecting 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 dentine cores can be formed in a disk-shaped blank, to yield restorations of different geometries, but with a favorable layer course with respect to translucency and strength.

(37) Since the position of one or more second regions 52, 56, i.e., 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.