Method for manufacturing a multi-layer blank with through holes - Patents.com

Abstract

1. A method for forming a multi-layer blank of ceramic material, comprising the steps of: providing a mold including at least one sidewall surrounding a lower press plunger having a movable pin to form a cavity; filling the mold with a first ceramic material; extending the movable pin from a top surface of the lower press plunger into the cavity; pressing the first upper press plunger against the first ceramic material to form a first open cavity with at least a portion of the first upper press plunger in contact with the movable pin to maintain a through hole through the first layer; filling the mold with a second ceramic material of a different composition; extending the movable pin from a top surface of the first layer into the first open cavity; and pressing the second upper press plunger against the second layer to form a second open cavity in communication with the through hole extending through the first and second layers to form the blank.

Description

[Technical field]

[0001] Related Applications This international patent application claims the benefit of and priority to U.S. Non-provisional Patent Application No. 17 / 592,677, filed February 4, 2022, which is incorporated by reference herein for all purposes.

[0002] The present invention relates in particular to a method for producing multi-layer blanks of ceramic material, in particular blanks used for the production of dental restorations, in which a die provided with a through hole is filled with a first ceramic material and then with a second ceramic material of different composition, which materials are pressed and optionally sintered.

[0003] The present invention also relates to blanks for use in the production of dental frameworks, crowns, partial crowns, caps, abutments (e.g. two-piece abutments), Ti bases (or adapters for Ti bases) and / or pre-sintered or fully sintered dental restorations, in particular crowns or partial crowns, made of a ceramic material, in particular containing zirconium dioxide, having regions of different composition and provided with a through hole, and with preformed screw holes. [Background technology]

[0004] US8936848B2 discloses a zirconium dioxide blank used for the production of tooth replacements, which is composed of several layers of different chemical composition, the individual layers having different proportions of yttrium oxide.

[0005] Zirconium dioxide body is L * a * b * They exhibit a decrease or increase in chromaticity along a straight line in color space (US2014 / 0328746A1).

[0006] A zirconium dioxide blank for producing dental objects according to WO 2014 / 062375 A1 has at least two material regions with different proportions of tetragonal and cubic phases, in one region the ratio being greater than 1 and in the other region the ratio being less than 1.

[0007] EP 2 371 344 A1 relates to a ceramic body which is enriched with an antidegradant from the surface to a desired depth. Summary of the Invention [Problem to be solved by the invention]

[0008] Zirconium dioxide is used as a ceramic material for producing dental restorations. For example, a framework may be milled from a zirconium dioxide blank and then sintered. In a subsequent processing step, a veneer is applied manually to the framework, where at least one incisal material is applied and fused. All these process measures are time-consuming and, moreover, do not guarantee that the dental restoration meets the requirements. [Means for solving the problem]

[0009] The object of the present invention is to develop a method of the above-mentioned type in a manner that avoids the drawbacks of the prior art, in particular making it possible to produce dental restorations from ceramic materials that are strong in areas subject to high loads, without laborious finishing, while reducing several additional post-processing steps, while also satisfying aesthetic requirements and simplifying the mounting of the dental restoration in the patient's mouth.

[0010] To this end, it is proposed, inter alia, to fill a layer of a first ceramic material in the die and around the movable pin, in which case a first (or only) layer may be formed through which the through-hole extends. If one or more further layers are desired, a first open cavity may be formed along the exposed surface of the first layer of the first ceramic material. A second ceramic material may be filled in the first open cavity and around the movable pin, and the through-hole may be maintained through both the first and second materials (e.g. the first and second layers) while the first and second materials are pressed together and optionally heat-treated.

[0011] According to the invention, the die is first filled with a layer of injectable material, with the movable pin extending into the cavity of the die. This material may be, for example, 1 g / cm 3 to 1.4 g / cm 3 Especially between 1.15g / cm 3 from 1.35 g / cm 3By using a granular material of zirconium dioxide having a bulk density in the range between 0.01 and 0.05 μm, it is possible to achieve a shade similar to the incisal edge of a natural tooth. After filling with a granular material, preferably having a grain size D50 between 40 μm and 70 μm, a through hole through the material and an open cavity along the exposed surface of the material are formed, for example by a press plunger. This is done, for example, by pushing out and / or lightly compacting a part of the first ceramic material while the movable pin is retracted. Thus, in the recess or cavity thus formed, particularly having a substantially conical geometric shape, the movable pin extends into the cavity to be surrounded by the second ceramic material which is filled in the cavity in preparation for pressing the materials together. Optionally, the pressed first and second materials (e.g. the pressed ceramic blank) can be partially or completely / finally heat treated. The partial and / or complete heat treatment can be performed while the pressed material remains in the die / mold or after it has been removed therefrom. It is understood that when a crown or partial crown or cap is manufactured from the blank, the through hole generally aligns with the conically shaped recess or cavity, which may also generally align with the geometric shape of the stump, abutment, or Ti base.

[0012] It is also possible to form one or more further layers so that the second ceramic material filled in the first open cavity can be provided with a second open cavity. Similarly, the movable pin extends into the second cavity and is surrounded by a third ceramic material that will eventually fill the second cavity while maintaining a through hole. This step can be accompanied by simultaneous pressing of all materials.

[0013] The compaction of the material is carried out independently.

[0014] Compaction may be carried out at a pressure preferably between 2 and 20,000 bar. Preferably, compaction to form one or more internal layers is carried out at a pressure in the range of 2 to 100 bar (e.g., 5 to 50 bar), while final compaction of the block (e.g., all layers) may be carried out at a pressure in the range of 500 to 20,000 bar (e.g., 1000 to 10,000 bar). 3 A density of 0.1 to 0.5 can be achieved.

[0015] Debinding and pre-sintering of the pressed ceramic blank may then be carried out at a temperature ranging between 700° C. and 1100° C., in particular between 850° C. and 1050° C., for a time period ranging between 100 and 150 minutes.

[0016] Debinding and pre-sintering may be carried out in such a manner that a flexural strength, measured according to ISO 6872, of between 10 MPa and 60 MPa, in particular between 15 MPa and 45 MPa, is achieved.

[0017] When a second open cavity is formed in the second ceramic material and filled with a third ceramic material, this composition may differ from that of the second ceramic material, particularly in having a lower translucency and / or a higher bending strength than the second / first material.

[0018] In particular, according to the invention, one or more press tools of the die may be provided with movable pins. The movable pins may extend into (e.g. through) several first open cavities that may be provided in the various layers of the first and second ceramic materials to form and / or maintain the through holes. This results in several separate and separated blank areas, so-called nests, from which several dental restorations can be obtained after pre-sintering, in particular through milling and / or grinding, with threaded holes (e.g. through holes) preformed in the blanks before milling and / or grinding of such blanks. In this regard, the dimensions of the blank areas can be different from each other to obtain restorations of different geometric shapes, and the geometric configuration of the respective root-side / dentin-side material areas can also be different. Thus, it is possible to obtain teeth of various shapes from one blank, depending on the number of nest / blank areas and their geometric shapes, while simplifying / reducing post-processing steps of the blanks and / or supporting the mounting of dental restorations with preformed threaded holes. As already mentioned, it will be appreciated that, although not required, the dentin core may be formed from the second region (e.g., a second further layer / material) and the incisal edge may be formed from the first region (e.g., the first layer / material).

[0019] The present invention is particularly directed to a thermal expansion coefficient of 0.2 μm / m less than that of the first ceramic material. * K~0.8μm / m * K high, providing a coefficient of thermal expansion of the second ceramic material. As a result of the different thermal expansion coefficients of the materials, compressive stresses arise in the first material, i.e. the incisal material, which leads to an increase in the strength of the dental restoration obtained from the blank.

[0020] Furthermore, the ceramic material can be colored to a desired degree, particularly for the first region, such that a more translucent, less colored incisal material is used compared to the second ceramic material.

[0021] If a dental restoration or other shaped body with a screw hole is preferably obtained from a pre-sintered blank with a through hole, it is of course also possible to first partially or fully sinter the blank with the through hole and then further process it to form a shaped body, in particular by milling or grinding.

[0022] Regardless of when the blank with the through hole is sintered, full sintering is provided, which in particular takes place at a temperature in the range of 1300° C. to 1600° C. for a time period between 10 and 250 minutes. Sintering can also take place at slightly higher temperatures.

[0023] If sintering is carried out at a temperature, for example 100° C. higher than that specified by the manufacturer of the starting material, and for a time beyond that recommended by the manufacturer for complete or sufficient sintering, this is called oversintering.

[0024] These values ​​are particularly applicable when the starting material contains substantially more than 80 wt. % zirconium dioxide.

[0025] The zirconium dioxide can be doped with, in particular, yttrium oxide, but also calcium oxide, magnesium oxide and / or cerium oxide.

[0026] For colouring the ceramic material, colour-imparting oxides may be used, in particular from elements selected from the group Pr, Er, Tb, Fe, Co, Ni, Ti, V, Cr, Cu and Mn, preferably Tb2O3, Fe2O3, Er2O3, Co3O4 and / or mixtures thereof.

[0027] The invention is therefore also characterised in that the ceramic material used contains zirconium dioxide, to which yttrium oxide (Y2O3), calcium oxide (CaO), magnesium oxide (MgO) and / or cerium oxide (CeO2), in particular yttrium oxide, is added, the first ceramic material differing from that of the second ceramic material with regard to colour and / or crystalline morphology stabilized at room temperature.

[0028] Further, first and / or second ceramic materials are provided in which the percentage of yttrium oxide in the second material is in the range of 4.5 wt% to 9.5 wt% and / or the percentage in the first material is in the range of 4.5 wt% to 10.5 wt%, and the percentage of yttrium oxide in the first ceramic material may be equal to or higher than the percentage in the second material.

[0029] Thereby, the material of the first region, and also the material of the second region, may be selected such that the ratio of tetragonal to cubic phases of the zirconium dioxide in both regions after pre-sintering is ≧1.

[0030] As base materials for the first and second ceramic materials, the following compositions in wt% are preferred: [Table 1]

[0031] Additional binder may be added, which is not taken into account in the weight percent descriptions above.

[0032] According to the teachings of the present invention, after full sintering, a monolithic dental restoration with a screw hole is obtained, which in principle does not need to be veneered, although this would not depart from the invention.

[0033] A pre-sintered or fully sintered blank with a through hole for use in the manufacture of dental restorations with a screw hole, such as dental frameworks, crowns, partial crowns, caps, abutments (e.g. two-piece abutments), Ti-bases, in particular crowns or partial crowns, with a screw hole extending therethrough, comprises a ceramic material, in particular containing zirconium dioxide, with regions of different composition, a first region consisting of the first ceramic material and at least one second region consisting of the second ceramic material, which regions are adjacent to each other, characterized in that the through hole extends through at least one second region, and the second region extends into the first region such that the first region has an outer geometric shape tapering from the base region. In this regard, the through hole extends through the base region, which extends into a region of the outer surface of the first region, preferably merging with a region of the outer surface of the first region, such that the through hole extends through both regions.

[0034] It is also possible to provide a cavity in a second region extending from the base region.

[0035] Independently, the second region may have a conically extending geometry in its outer geometry.

[0036] It is also possible for a third region to extend into the second region, said third region being composed of a third ceramic material of a composition that deviates from and / or differs from the composition of the second ceramic material.

[0037] According to the invention, it is emphasized that several second regions are surrounded by the first region, in particular some of the plurality of second regions differ in their outer geometric shape, and the through holes preferably extend through each region.

[0038] Thus, for example, crowns or artificial teeth with threaded holes of different geometries can be produced, in which the strength of the dentin region is greater than that of the incisal region. For this purpose, when obtaining a dental restoration with a threaded hole from a blank with a through hole, the dentin is formed in the area of ​​the second region of the blank and the incisal region from the area of ​​the first region, with the through hole extending through the various regions.

[0039] The invention is further characterized in that the blank comprises zirconium dioxide doped with yttrium oxide, the percentage of yttrium oxide in the second or third ceramic material being between 4.5 wt.% and 9.5 wt.% and the percentage in the first ceramic material being between 4.5 wt.% and 10.5 wt.%, the percentage of yttrium oxide in the first ceramic material being equal to or greater than the percentage in the second ceramic material.

[0040] When the percentage of yttrium oxide in the first ceramic material is greater than the percentage in the second ceramic material, the lower yttrium content in the material of the second region may result in higher strength compared to the first region.

[0041] Furthermore, the ceramic material of the second region can be colored and the first region can be colored to a lesser extent or not at all, making it more translucent than the second region.

[0042] A dental restoration having a preformed screw hole, in particular a tooth, crown or partial crown, or cap, each having a preformed screw hole, includes a through hole extending through a first and second layer, the first layer of a first material extending on an incisal side and the second layer of a second ceramic material extending on a root side, the first layer having a higher translucency and / or lower strength than the second layer, and the first layer having a translucency of about 0.2 μm / m or less than the second layer. * K~0.8μm / m * It is characterized by having a low coefficient of thermal expansion.

[0043] The present invention is directed to a dental device and a method for manufacturing the dental device. In one aspect, the present disclosure provides a method for forming a multi-layer blank of ceramic material, comprising the steps of providing a mold including at least one sidewall surrounding a lower press plunger having a movable pin to form a cavity, filling the mold with a first ceramic material in a pourable state to form a first layer, extending the movable pin from an upper surface of the lower press plunger into the cavity before, during, or after filling the mold with the first ceramic material to form the first layer, such that when the movable pin is at least partially extended into the cavity and the first layer is formed, at least a portion of the movable pin extends through the first layer and is surrounded by the first ceramic material, thereby forming a through hole through the first layer, and pressing the first upper press plunger against the movable pin to form a first open cavity, with at least a portion of the first upper press plunger in contact with the movable pin to maintain the through hole through the first layer. pressing an upper press plunger against the first layer; filling the mold with a second ceramic material of a different composition, the second ceramic material being pourably filled into the first open cavity to form the second layer; extending a moveable pin from a top surface of the first layer into the first open cavity before, during or after filling the mold with the second ceramic material to form the second layer, the moveable pin extending at least partially into the first open cavity, such that as the second layer is formed, at least a portion of the moveable pin extends through the second layer and is surrounded by the second ceramic material, thereby extending a through hole through the second layer; and pressing a second upper press plunger against the second layer to form a blank, such that a second open cavity is formed in communication with the through hole extending through the first and second layers.

[0044] In another aspect, the disclosure provides a method for forming a multi-layer blank of ceramic material, comprising the steps of providing a mold including at least one sidewall surrounding a lower press plunger having a moveable pin to form a cavity; extending the moveable pin from an upper surface of the lower press plunger into the cavity; filling the mold with a first ceramic material, the first ceramic material being pourably filled into the mold and around the moveable pin to form a first layer having a through hole; pressing the first upper press plunger against the first layer such that a first open cavity is formed, with at least a portion of the first upper press plunger in contact with the moveable pin to maintain the through hole in the first layer; the second ceramic material is pourably filled into the first open cavity and around the movable pin to form the second layer while maintaining through holes in both the first and second layers; and pressing a second upper press plunger against the second layer to form a second open cavity in communication with the through holes extending through the first and second layers, the second open cavity and the through hole defining a threaded hole of the blank, the threaded hole having a generally cylindrical lower portion and an upper portion having a molded portion with an anti-rotation feature (e.g., an abutment or Ti-based connection / fitting portion).

[0045] In another aspect, the disclosure provides a method for forming a multi-layer blank of ceramic material, comprising the steps of: providing a mold including at least one sidewall surrounding a lower press plunger having a movable pin to form a cavity; extending the movable pin from an upper surface of the lower press plunger into the cavity; filling the mold with a first ceramic material, the first ceramic material being pourably filled into the mold and around the movable pin to form a first layer having a through hole; pressing the first upper press plunger against the first layer and an upper portion of the movable pin such that a first open cavity is formed, with at least a portion of the first upper press plunger in contact with an upper portion of the movable pin to maintain the through hole of the first layer; and, with the first ceramic material of the first layer being compacted by the first upper press plunger, the movable pin being partially retracted into the lower press plunger by pressing movement of the first upper press plunger; removing the first upper press plunger to expose at least a portion of a first open cavity formed therein; extending a movable pin into the first open cavity; filling the mould with a second ceramic material of a different composition than the first ceramic material, the second ceramic material being pourably filled into the first open cavity and around the movable pin to form the second layer while maintaining through holes in both the first and second layers; pressing the second upper press plunger against the second layer and a top of the movable pin to form a blank, the first and second ceramic materials being compacted while at least a portion of the movable pin is partially retracted into the lower press plunger by pressing movement of the second upper press plunger.

[0046] In yet another aspect, any of the aspects of the invention may be further characterized by one or any combination of the following features: the lower press plunger is movable and assists in pressing the first layer, the second layer, or both; at least a portion of the upper press plunger contacts the movable pin to maintain a through hole extending through the first and second layers; the movable pin contacts a lower end of the first upper press plunger or the second upper press plunger during each pressing step to assist in maintaining a through hole through the first layer or the first and second layers. the movable pin is generally cylindrical in shape with a tapered free end that tapers toward the blank; an upper end of the movable pin remains in contact with either the first upper press plunger or the second upper press plunger during each pressing step to assist in maintaining a through hole through each layer; the second upper press plunger includes a lower portion that is pressed into at least a portion of the second ceramic material to define at least a portion of the second open cavity, the lower portion of the second upper press plunger including an upper seat shaped to provide an anti-rotation feature along a surface of the through hole in the blank; The upper end has a shape corresponding to a distal end of a lower portion of the second upper press plunger, and the upper end of the movable pin and the distal end of the lower portion of the second upper press plunger communicate with each other during the pressing step to assist in maintaining a through hole extending through the first and second layers; the second upper press plunger includes a lower portion that is pressed into at least a portion of the second ceramic material to define at least a portion of the second open cavity, and the lower portion of the second upper press plunger has a shape that imparts an upper conical portion and a lower cylindrical end portion along a surface of the through hole in the blank. an upper conical portion of the through hole in the blank defines a seating portion for receiving an attachment instrument for securing a restoration formed from the blank to the abutment, the seating portion including an anti-rotation feature for preventing rotation of the attachment instrument; an upper portion of the moveable pin has a shape corresponding to a lower cylindrical portion of the first upper press plunger or the second upper press plunger to assist in maintaining the through hole extending through the first and second layers; partially or fully sintering the blank; (i) extending the moveable pin into the second open cavity;(ii) filling the mold with a third ceramic material, of a different composition than the second ceramic material, the third ceramic material being pourably filled into the second open cavity and around the movable pin to form a third layer while maintaining the through holes of the first, second, and third layers; (iii) pressing a third upper press plunger against the third layer to form a third open cavity in communication with the through holes extending through the first, second, and third layers to form a blank, the third upper press plunger including a lower portion pressed into at least a portion of the third ceramic material to define at least a portion of the third open cavity, the lower portion of the third upper press plunger in communication with the movable pin pressing the through hole of the blank into a shape generally defining an upper conical portion and a lower cylindrical end portion. imparting; an upper conical portion of the through hole in the blank defining a seating portion to receive an attachment tool for securing a restoration formed from the blank to the abutment, the seating portion including an anti-rotation feature to prevent rotation of the attachment tool; a second upper press plunger including a lower portion that is pressed into at least a portion of the second ceramic material to define at least a portion of the second open cavity, the lower portion of the second upper press plunger in communication with the moveable pin imparting a shape to the through hole in the blank generally defining an upper conical portion and a lower cylindrical end portion; an upper conical portion of the through hole in the blank defining a seating portion to receive an attachment tool for securing a restoration formed from the blank to the abutment, the seating portion including an anti-rotation feature to prevent rotation of the attachment tool, or any combination thereof;

[0047] It should be understood that the above-mentioned aspects and examples are not limiting, as there are others present with the present invention as shown and described herein, for example, any of the above-mentioned aspects or features of the present invention can be combined to form other unique configurations as described herein, shown in the drawings, or in other manners.

[0048] Further details, advantages and features of the invention emerge not only from the claims and the features disclosed therein alone and / or in combination, but also from the following description of exemplary embodiments shown in the drawings. [Brief description of the drawings]

[0049] [Figure 1A] 1 is a cross-sectional view of a device according to the method of the present invention carried out using the device. [Figure 1B] 4A-4C are cross-sectional views of a device according to another step of the method of the present invention carried out using the device. [Figure 1C] 4A-4C are cross-sectional views of a device according to another step of the method of the present invention carried out using the device. [Figure 1D] 4A-4C are cross-sectional views of a device according to another step of the method of the present invention carried out using the device. [Figure 2A] 4A-4C are cross-sectional views of a device according to another step of the method of the present invention carried out using the device. [Figure 2B] 4A-4C are cross-sectional views of a device according to another step of the method of the present invention carried out using the device. [Figure 2C] 4A-4C are cross-sectional views of a device according to another step of the method of the present invention carried out using the device. [Figure 2D] 4A-4C are cross-sectional views of a device according to another step of the method of the present invention carried out using the device. [Figure 2E] 4A-4C are cross-sectional views of a device according to an alternative step of the method of the present invention carried out using the device. [Diagram 3] FIG. 2 shows a blank having a preformed through hole according to the present invention with regions of different material properties. [Figure 4A] 1 is a schematic diagram of a blank with a preformed through hole according to the present invention and a front tooth obtained therefrom. [Figure 4B] 1 is a schematic diagram of a blank with a preformed through hole according to the present invention and a molar tooth obtained therefrom. [Diagram 5]FIG. 13 shows another blank having preformed through holes according to the present invention, with regions of different material properties. [Figure 6A] 4A-4C are cross-sectional views of an alternative device according to another step of the method of the present invention carried out using the device. [Figure 6B] FIG. 6B is another cross-sectional view of the alternative device shown in FIG. 6A. [Figure 7A] 11 is a front view of another alternative device according to another step of the method of the present invention performed using the device. FIG. [Figure 7B] FIG. 7B is an enlarged front view of the alternative device shown in FIG. 7A. [Figure 7C] FIG. 7B is an enlarged top view of the alternative device shown in FIG. 7A. [Figure 8] FIG. 2 is a top view of a blank according to the present invention having multiple regions of different material properties, each region having a preformed through hole. [Figure 9] FIG. 2 is a top view of a holding device for mounting a plurality of blanks having preformed through holes according to the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The teachings of the present invention are explained with reference to the drawings, in which like elements are essentially given the same reference numerals, in particular a dental restoration is manufactured from a ceramic material having a monolithic structure such that after full sintering a ready-to-use monolithic tooth replacement is available.

[0051] For this purpose, the invention provides for the production of blanks having regions of ceramic material with different compositions and therefore properties, with the desired optical and mechanical properties depending on the restoration to be produced, which makes it possible to immediately use a monolithically produced tooth replacement after full sintering, as mentioned above, for example without the need to apply incisal material manually.

[0052] Furthermore, particularly desirable strength values ​​can be achieved in areas where high loads occur. Desired optical properties can be realized.

[0053] With reference to the drawings, the manufacture of a blank from which a dental restoration can be manufactured, which in an exemplary embodiment is a crown or an abutment crown (eg for attachment to an abutment or Ti base) will be described.

[0054] The method includes providing a die (mold) 10 having at least one wall 11 surrounding the press tool to define an open cavity. The press tool may include one or more movable press tools (plungers) and optionally one or more stationary press tools. It is understood that the one or more movable press tools may be movable along at least one wall and / or relative to an opposing movable or stationary press tool (when included). In one embodiment, the press tool includes at least one lower press tool and at least one upper press tool, where at least one of the lower press tool and upper press tool is movable. Preferably, but not necessarily, the press tool may include at least one movable lower press tool (plunger) and at least one movable upper press tool (plunger) configured to operatively move independently of one another (if required).

[0055] The press tool may further include at least one movable pin 23 that is independently movable (and / or presses) relative to the one or more movable or stationary press tools. The movable pin 23 may be provided in any shape and / or size such that it can occupy a portion of the cavity 13 when extending from the one or more movable or stationary press tools. In one exemplary embodiment, the movable pin 23 may have a generally cylindrical (e.g., rod-shaped) shape such that the resulting block may include a through hole.

[0056] As mentioned above, the press tool may include at least one movable pin 23. It is therefore understood that the movable pin 23 may be provided on at least one of the one or more movable press tools and / or the optional one or more stationary press tools (when included). For example, the press tool may include a stationary lower press tool with a movable pin 23 and a movable upper press plunger that may be configured to move independently towards or away from the stationary lower press tool. Preferably, but not necessarily, the press tool includes multiple movable press plungers, such as a lower press plunger and an upper press plunger, which may be configured to be independently movable relative to each other (e.g., towards or away from each other). In this example, although not necessarily, the lower press plunger may include the movable pin 23. However, it is further understood that other combinations / orientations of the one or more movable press plungers and / or the optional one or more stationary press tools may be provided in various configurations, and at least one of the one or more movable press plungers and the optional one or more stationary press tools may include at least one movable pin 23.

[0057] 1A, a cross section of a die 10 is provided that may include at least one wall 11 that defines a cavity 13 surrounding a movable lower press plunger 16, which may independently include a movable pin 23. The lower press plunger 16 has a top surface 17 that defines at least one surface of the resulting block, in addition to an upper portion 27 of the movable pin 23 (in a first position, e.g., in a non-extended position). In this example, the top surface 17 and the upper portion 27 of the movable pin 23 in a non-extended position may define a generally flat surface. However, it is understood that the top surface of the lower press tool (whether movable or stationary) may have any shape or topological geometry.

[0058] As mentioned above, the movable pin 23 may be provided in a generally rod-shaped form such that when it extends from the lower press plunger 16 (first extended position), a portion of the cavity 13 is occupied by the extended portion of the movable pin 23 (FIG. 1B). When the movable pin 23 is placed in the first extended position, injectable grains in the form of a first ceramic material 14 are filled into the cavity 13 of the die 10 surrounding the movable pin 23 to form a first layer 25 (FIG. 1D). Preferably, an upper portion 27 of the movable pin 23 may extend from the upper surface 17 of the lower press plunger to a distance that exceeds the level at which the first material 14 is filled into the cavity 13. However, it is understood that the upper portion 27 of the movable pin 23 may move to an extended position that is lower than the height of the first material 14 after the filling of a portion of the cavity 13. It is further contemplated that the cavity 13 may be filled with the first ceramic material 14 before and / or while the movable pin 23 is extended into the cavity 13 (e.g., from a non-extended position that is generally horizontal / flush with the surrounding portion of the upper surface 17 of the lower press tool).

[0059] In another example, as shown in Figures 6A-6B, a moveable pin 90 according to the present invention may be provided. The moveable pin 90 may include a tapered end 92, as opposed to the moveable pin 23 having a generally flat end 27. When included, an alternative second upper press plunger 94 may also be provided having a lower extension 95 that extends towards the lower press plunger 16. The lower extension 95 has a seat 40 and a distal end 96. The distal end 96 of the alternative second upper press plunger 94 preferably mates with the tapered end 92 of the moveable pin 90 to aid in the movement of either the moveable pin 90 and / or the alternative second upper press plunger 94 during the formation of the blank. It will be appreciated that this corresponding configuration helps to keep the distal end 27 engaged with the tapered end 92 during movement, reducing or eliminating disengagement (e.g., horizontally or otherwise) between the moveable pin 90 and the alternative second upper press plunger 94. It will be appreciated that other similar corresponding configurations may be provided at the distal end 27 of the alternative second upper press plunger 94 and the tapered end 92 of the moveable pin 90 .

[0060] The first ceramic material 14, in particular zirconium dioxide stabilized with yttrium oxide, may have the following composition in wt %: [Table 2]

[0061] Binders may also be added, but are not taken into account in the above weight percentage values.

[0062] However, since a high translucency is desired, especially when the first ceramic material 14 is used as an incisal material, compositions are provided which contain only small amounts or no coloring oxides, e.g. ≦0.5 wt %. A relatively high proportion of yttrium oxide may result in only 50-60% tetragonal phase, the rest being cubic and monoclinic crystalline phases, in the incisal region of the produced molded part, i.e. dental restoration.

[0063] As shown in Figures 1C-1D, the first upper press plunger 18 forms an open cavity 19 in the material 14 or in a layer formed from this material. The first upper press plunger 18 pushes the movable pin 23 toward the upper surface 17 of the lower press plunger 16 (or independently retracts) to displace or slightly compact the material 14. In so doing, a through hole 21 is formed that communicates with the cavity 19. The compaction / pressing to form the first cavity 19 may be performed in a die at a pressure greater than 2 bar, preferably greater than 7 bar. Furthermore, the compaction / pressing to form the first cavity 19 may be performed in a die at a pressure less than 100 bar, preferably less than 50 bar. It is understood that the compaction / pressing to form the first cavity 19 may be performed in a die at a pressure in the range of 2-100 bar, preferably 7-50 bar. It will be appreciated that any intermediate layers (except the last layer) may be compacted / pressed with a pressure similar to that applied during the formation of the first layer.

[0064] After the first layer 25 is formed (e.g., compacted / pressed), the first upper press plunger 18 may be removed from the cavity 19 (FIG. 1D) with at least a portion of the movable pin 23 remaining within the first layer 25 to prevent material 14 from entering the through hole 21. Optionally, or in addition to the pressing movement of the first upper press plunger 18, the movable lower press plunger 16 may assist in the compaction of the first material 14 by moving towards the first upper press plunger 18. It will be appreciated that the movable pin 23 is configured to move independently of the lower press plunger 16 to ensure that the through hole 21 is maintained during the movement of the lower press plunger 16. For example, while the lower press plunger 16 is moving towards the first upper press plunger 18, the movable pin 23 may be retracted (and / or pushed) in a direction opposite to the movement of the lower press plunger 16, through its own independent movement and / or through the movement of the first upper press plunger 18 as it moves towards the lower press plunger 16. It is further contemplated that the movable pin 23 may be movable independently of the first upper press plunger 18 and / or the lower press plunger 16, or in combination with, or through the movement of (or contact with) at least one of the first upper press plunger 18 and the lower press plunger 16. While the movable pin 23 is retracted from the cavity 19 towards the upper surface 17 of the lower press tool, at least some contact is maintained between the upper portion 27 of the movable pin 23 and the first upper press plunger 18 to prevent or substantially prevent the first material 14 from entering the through hole 21. In another non-limiting example, as the first upper press plunger 18 displaces / compresses the first material 14 (towards the lower press tool), it may push an upper portion 27 of the movable pin 23, causing the movable pin 23 to retract towards the first surface 17 of the lower press tool to define the cavity 19.

[0065] Once the first layer has been formed through compaction of the first material 14 and (partial) retraction of the movable pin 23, the first upper press plunger 18 may be removed (or partially removed) from the cavity 19. During or after removal of the first upper press plunger 18 to expose the cavity 19, the movable pin 23 may extend upward from the first layer 25 to occupy a portion of the cavity 19 (FIG. 2A). Optionally, the second ceramic material 20 may be filled into the cavity 19 surrounding the extended movable pin 23 to begin the formation of the second layer 29 (FIG. 2B). It is understood that the movable pin 23 may extend into the cavity 19 a distance such that the top 27 of the movable pin 23 may be located just above (or at the same height as) at least a portion of the surface 31 of the second material 20 when the second ceramic material 20 is filled into the cavity 19. In an alternative embodiment, the top 27 of the movable pin 23 remains generally flush with the exposed surface 26 of the compacted first layer 25, and after filling the cavity 19 with the second material 20, the movable pin 23 extends until the top 27 of the movable pin 23 penetrates the surface 31 of the second material, and the through hole 21 through the second layer 29 (not shown) can be extended and maintained.

[0066] The second material 20 may have one of the following compositions in wt %: [Table 3]

[0067] In that regard, since the dentin of the produced tooth is formed from the second ceramic material 20, one or more coloring oxides may be present in an amount that provides the desired tooth color. Furthermore, due to the relatively low percentage of Y2O3, the dentin of the fully sintered tooth replacement will have a high tetragonal phase content of at least 50%, preferably at least 60%, and therefore high strength.

[0068] Preferably, the movable pin 23 is extended prior to filling of the cavity 19. After filling the cavity 19 with the second ceramic material 20 surrounding the movable pin 23, the material 14, 20, or a layer or region formed therefrom, is pressed into the die 10 by a press tool that may further include a second movable upper press tool (plunger) 30 (FIG. 2C). The second upper press plunger 30 includes a lower surface 32 that may be configured in any general shape of any size and defines a second cavity 36 that is formed in the second layer as a result of compaction. Preferably, the second cavity 36 communicates with the through hole 21, so that the through hole 21 may be further extended into the second layer 29. This may be accomplished through pressing of the second material by the second upper press plunger 30 while a portion of the second upper press plunger 30 remains generally in contact with the movable pin 23 (FIG. 2D). More specifically, as the second press plunger 30 moves toward the lower press tool, the second press plunger 30 pushes the movable pin 23 toward the upper surface 17 of the lower press tool (or the movable pin 23 retracts independently), so that the through hole 21 can extend into the second layer 29 while being generally maintained in both the first layer 25 and the second layer 29 during the pressing / compaction step.

[0069] When the second material 20 is compacted by the second upper press plunger 30 (with the aid of a lower press tool, which may be movable or stationary), a second cavity 36 may be formed in the second layer 29 due to the shape of the lower surface 32 of the upper press plunger 30 and the extended movable pin 23. In one embodiment shown in FIG. 2C, the second upper press plunger 30 may include an extension 33 defined by the lower surface 32 of the second upper press plunger 30. Here, the extension 33 may define a generally "screw" shaped contour / profile having a lower cylindrical portion 38 and an upper seating portion 40, although as previously mentioned, other shapes and sizes for defining the portion of the lower surface 32 are contemplated. Preferably, the distal end 35 of the lower cylindrical portion 38 is configured to be complementary to (and / or mate with) the shape / size of the upper portion 27 of the moveable pin 23 such that communication / contact between the distal end 35 and the upper portion 27 assists in continuing the through hole 21 from the first layer 25 through at least a portion of the second layer 29. It is understood that the remaining portion of the lower surface 32 of the second upper press plunger 30 may be generally flat to assist in forming a generally flat outer wall of the cube-like shaped block of the present invention.

[0070] As shown in Figure 2D and alternatively in Figure 2E, the lower portion 38 of the second upper press plunger can be of various lengths, so that when the second pressing step is completed or substantially completed, the distal end 35 of the lower portion 38 can extend through only a portion of the first layer 25 and the second layer 29 (e.g., only through the second layer) as shown in Figure 2D, or can extend through both the first layer 25 and the second layer 29 as shown in Figure 2E. In either case, or if the distal end 35 of the lower portion 38 extends to different depths in the mold, the moveable pin 23 is appropriately positioned in the mold to ensure that the upper end of the moveable pin 23 remains in contact with the distal end 35 of the lower portion 38 of the second upper press plunger 30 during the pressing step to maintain a through hole through the first and second ceramic materials.

[0071] It is understood that the upper seat 40 of the second upper press plunger 30 may define a geometry that receives the top of an attachment tool, such as a screw, or the top (metal) portion of the lower section of a two-piece abutment (e.g., Ti-based). Preferably, but not necessarily, the upper seat 40 (e.g., seat and / or screw seat) includes a contour configured to form an anti-rotation feature provided in the connecting geometry of the blank (e.g., zirconia block with through holes) to prevent the abutment or two-piece abutment (e.g., the zirconia portion surrounding the metal portion of the Ti-based) from rotating relative to each other.

[0072] In one non-limiting example as shown in Figures 7A-7C, an alternative second upper press plunger 70 may include a conically and / or cylindrically shaped extension 72 having an anti-rotation feature 74. The anti-rotation feature 74 may extend outward (e.g., radially) from an outer surface 76 of the second upper press plunger 70 as shown in Figure 7C. As shown in Figure 7B, the anti-rotation feature 74 may further extend downward along a top 78 of the extension 72 of the second press plunger 70. The anti-rotation feature 74 may be configured in any shape and / or size to prevent the abutment or two-piece abutment (e.g., a zirconia portion surrounding a Ti-based metal portion) from rotating relative to one another. Other non-limiting examples of anti-rotation shapes may include, but are not limited to, polygonal shapes such as hexagons and / or other shapes.

[0073] As previously mentioned, the second upper press plunger 30 may be introduced into the die 10 and cooperate with the lower press tool to compact the powder, thereby forming the second layer 29 in addition to the already formed first layer 25. After pressing, the blank 44 has a density of approximately 3 g / cm 3The compaction / pressing to form the resulting block may be performed in a die at a pressure of more than 500 bar, preferably more than 100 bar. Furthermore, the compaction / pressing to form the resulting block may be performed in a die at a pressure of less than 20,000, preferably less than 10,000 bar. It is understood that the compaction / pressing to form the resulting block may be performed in a die at a pressure in the range of 500-20,000, preferably 1000-10,000 bar.

[0074] The resulting blocks may have a generally cube-like shape, but this is not required. When included, the resulting blocks may have a length greater than 5 mm, preferably greater than 8 mm. Furthermore, it is understood that the resulting blocks may have a length less than 75 mm, preferably less than 60 mm. It is understood that the resulting blocks may have a length between 5 and 75 (e.g. 30) mm, preferably between 8 and 60 (e.g. 20) mm. Furthermore, the resulting blocks may have a width greater than 5 mm, preferably greater than 8 mm. Furthermore, it is understood that the resulting blocks may have a width less than 75 mm, preferably less than 60 mm. It is understood that the resulting blocks may have a width between 5 and 75 (e.g. 30) mm, preferably between 8 and 60 (e.g. 20) mm. Finally, the resulting blocks may have a height greater than 2 mm, preferably greater than 5 mm. Furthermore, the resulting blocks may have a height less than 55 mm, preferably less than 45 mm. It will be appreciated that the resulting block may have a height of from 2 to 55 (eg 30) mm, preferably from 5 to 45 (eg 21) mm.

[0075] Regarding the ceramic materials 14, 20, they have a density of 1 g / cm 3 to 1.4 g / cm 3 It should also be noted that after pressing, the density may be approximately 3 g / cm. 3 It could be.

[0076] 1C-1D, it can be seen that the cavity 19 can be formed in the first ceramic material 14 by the upper press plunger 18 and can be comprised of a first layer 25 containing the material and a through hole 21 formed from the movable pin 23. The base side wall 11 of the die 10 can be limited by the lower press plunger 16.

[0077] 2D, a second cavity 36 may be formed in the second material 20 and the through hole 21 may continue to extend after compaction by the press plungers 16, 18 to form a block with a through hole. The block may then optionally be pre-sintered and / or fully sintered and / or optionally milled.

[0078] Regardless of whether the second cavity 36 is present or not, the pre-sintering of the blank (i.e. after pressing) may be carried out at a temperature in the range of 850° C. to 1050° C. for a time of 100 to 150 minutes. Debinding is carried out first, followed by pre-sintering. The density of the blank after pre-sintering is approximately 3 g / cm. 3 The flexural strength of the pre-sintered blank 28 may be between 15 MPa and 45 MPa.

[0079] As will be explained with reference to Fig. 4, in order to obtain a dental restoration with a screw hole 48 (not shown), such as a tooth 49, from the blank 44 with the preformed through hole 42, the blank 44 may further be provided with a fixed (or removably fixed) holder 46 (Fig. 3), thus allowing the blank 44 with the preformed through hole 42 to be machined, for example in a milling or grinding machine. Thereby, the tooth to be manufactured can be at least virtually placed in the blank 44 with the preformed through hole 42 such that the incisal region extends into the region 52 formed by the first ceramic material 14 and the dentin region partially extends into the second region 54 formed by the second ceramic material 20. Taking this data into account, the blank 44 with the preformed through hole 42 can then be machined.

[0080] 4A, a dental restoration with a screw hole according to the invention, in an exemplary embodiment a tooth 62, is obtained from a blank 44. For this purpose, with knowledge of the transition of a first region 63 from the first ceramic material 14 and a second region 65 from the second ceramic material 20, the regions 63, 65 of the blank 44 of the tooth 62 to be manufactured can be virtually positioned such that the incisal edge 60 extends into the first region 63 and the dentin 66 extends into the second region 65.

[0081] After removing the tooth 62 thus virtually arranged from the blank 44, a tooth replacement is available which in principle can be used directly, in particular without the need for a veneer. Based on the teaching of the present invention, a monolithic tooth 62 can be produced with a screw hole 64. In this case, production from the blank 44 is easier, since the first region 63 and the second region 65 already have the screw hole 64 for optionally connecting to an implant (not shown).

[0082] 4B, a dental restoration with a screw hole according to the invention, in an exemplary embodiment a molar tooth 62', is obtained from the blank 44. For this purpose, with knowledge of the transition of a first region 63' from the first ceramic material 14 and a second region 65' from the second ceramic material 20, the regions 63', 65' of the blank 44 of the tooth 62' to be manufactured can be virtually positioned such that the incisal edge 52 extends into the first region 63' and the dentin 54 extends into the second region 65'.

[0083] After removing the molar 62' thus virtually positioned from the blank 44, a tooth replacement is available which in principle can be used directly, in particular without the need for a veneer. Based on the teaching of the present invention, a monolithic tooth 62' with a screw hole 42 can be produced. In this case, production from the blank 44 is easier, since the first region 63' and the second region 65' already have the screw hole 42 for optionally connecting to an implant (not shown).

[0084] 5 illustrates that after filling the first cavity 19 with the first ceramic material 14 and filling the cavity 19 with the second ceramic material 20, the second cavity 22 so formed may optionally be filled according to the invention with a third ceramic material having a composition different from that of the second ceramic material, thereby achieving particularly higher strengths. A through hole 48 may likewise be formed through the third ceramic material 24, as described herein.

[0085] The teachings of the present invention introduce the possibility of forming a blank 58 having a plurality of regions 52, 54, 56 with different geometries, made of a second ceramic material and optionally a third ceramic material, with a through hole 53 extending through each region 52, 54, 56 (FIG. 8), so that corresponding teeth of different geometries can be formed. The so-called second regions 52, 54, and 56, formed from the second ceramic material 20, each with a through hole 53, can be embedded, i.e. surrounded, by the first ceramic material 14, as can be seen in particular in the drawing. The second regions 52, 54, and 56 are not covered on the base side.

[0086] As can be seen especially in Figures 2D, 3 and 8, the second region has an outer geometry that starts tapering from the bottom, i.e. from the base region through which the through hole extends, which may be described as a conical geometry, and the outer contour represents a freeform surface.

[0087] Base region 67 is a base surface defined below and merges below base surface 61 of first region 25 (FIG. 3).

[0088] To produce the blank areas 52, 54, 56, also called nests, with through holes 53, it may be necessary to provide corresponding open cavities in a layer made of the first material 14, designated as the first region 50, as described with reference to Figures 1A-1D, to fill the cavities with the injectable second ceramic material 20 in the manner previously described, and then to press, i.e. compact, the materials 14, 20 together.

[0089] With regard to the physical properties of the ceramic materials 14, 20, in addition to differences in translucency and strength properties, it may further be advantageous or preferable for them to have different coefficients of thermal expansion. In particular, the present invention provides for a ceramic material 14 having a coefficient of thermal expansion after full sintering that is 0.2 μm / m less than the first regions 52, 54, 56 formed from the second ceramic material 20. * K~0.8μm / m * 5. Providing a first ceramic material 14 with a lower K. This results in compressive stresses in the first region 50, i.e. the incisal material, which leads to an increase in strength (FIG. 5).

[0090] Concerning the blanks, it is noted that these can have a cube-like shape, for example with dimensions 18x15x25 mm, or a disk shape, for example with a diameter of 100 mm, without affecting the teaching of the present invention. This offers the advantage that, as explained in particular with reference to Figure 6, for example several second regions 52, 54, 56, so-called dentin cores, can be formed in the disk-shaped blank in order to obtain restorations with different geometric shapes but with favourable layer transitions in terms of translucency and strength.

[0091] As the positions of one or more second regions 52, 56, i.e. nests, optionally of different geometric shapes, are known, they can be stored in the data record. The restoration to be manufactured, available as a CAD data set, is then positioned relative to and within the blank area, so that a tooth replacement can be obtained from the blank by milling and / or grinding.

[0092] In Fig. 9, a holder 80 is provided that includes a plurality of blanks 82 (removably secured thereto) having preformed through holes 84 in accordance with the present invention. It is understood that the plurality of blanks 82 may be the same or different and may include multiple layers of different compositions with preformed through holes extending through each blank 82. For example, one or more blanks of the plurality of blanks 82 may have the same or different shapes and / or sizes. Additionally, one or more blanks may have multiple layers with different compositions per layer or per block. It is further understood that the blanks 82 may be removably mounted to a mount 80, which may also be removably mounted to a milling and / or grinding machine (not shown).

Claims

1. 1. A method for forming a multi-layer blank of a ceramic material, comprising: providing a mold including at least one sidewall surrounding a lower press plunger having a moveable pin to form a cavity; filling the mold with a first ceramic material, the first ceramic material being pourably filled into the mold to form a first layer; extending the movable pin from an upper surface of the lower press plunger into the cavity before, during, or after filling the mold with the first ceramic material to form the first layer, such that when the movable pin is at least partially extended into the cavity and the first layer is formed, at least a portion of the movable pin extends through the first layer, thereby being surrounded by the first ceramic material and forming a through hole through the first layer; pressing a first upper press plunger against the first layer such that a first open cavity is formed, with at least a portion of the first upper press plunger contacting the movable pin to maintain the through hole through the first layer; filling the mold with a second ceramic material of a different composition, the second ceramic material pourably filling the first open cavity to form a second layer; before, during, or after filling the mold with the second ceramic material to form the second layer, extending the movable pin from a top surface of the first layer into the first open cavity, such that the movable pin extends at least partially into the first open cavity and, upon formation of the second layer, at least a portion of the movable pin extends through the second layer, thereby being surrounded by the second ceramic material and the through hole is extended through the second layer; pressing a second upper press plunger against the second layer to form the blank such that a second open cavity is formed in communication with the through hole extending through the first and second layers; The method includes:

2. The method of claim 1 , wherein the lower press plunger is movable and assists in pressing the first layer, the second layer, or both.

3. The method of claim 1 , wherein at least a portion of the first and second upper press plungers contact the movable pin to maintain the through hole extending through the first and second layers.

4. 2. The method of claim 1, wherein the movable pin is generally cylindrical in shape with a tapered free end that contacts a lower end of the first upper press plunger or the second upper press plunger during the respective pressing steps to assist in maintaining the through hole through the respective first layer or first and second layers.

5. 2. The method of claim 1, wherein an upper end of the movable pin remains in contact with the first upper press plunger or the second upper press plunger during each pressing step to help maintain the through hole through each layer.

6. 2. The method of claim 1, wherein the second upper press plunger includes a lower portion that is pressed into at least a portion of the second ceramic material to define at least a portion of the second open cavity, the lower portion of the second upper press plunger including an upper seat shaped to provide an anti-rotation feature along a surface of the through hole in the blank.

7. 7. The method of claim 6, wherein an upper end of the movable pin has a shape corresponding to a distal end of the lower portion of the second upper press plunger, and wherein the upper end of the movable pin and the distal end of the lower portion of the second upper press plunger communicate with each other during the pressing step to assist in maintaining the through hole extending through the first and second layers.

8. 2. The method of claim 1, wherein the second upper press plunger includes a lower portion pressed into at least a portion of the second ceramic material to define at least a portion of the second open cavity, the lower portion of the second upper press plunger having a shape that imparts an upper conical portion and a lower cylindrical end portion along a surface of the through hole in the blank.

9. 9. The method of claim 8, wherein an upper conical portion of the through hole in the blank defines a seating portion to receive an attachment instrument for securing a restoration formed from the blank to an abutment, the seating portion including an anti-rotation feature to prevent rotation of the attachment instrument.

10. The method of claim 8 , wherein an upper portion of the movable pin has a shape that corresponds with the lower cylindrical portion to assist in maintaining the through hole extending through the first and second layers.

11. The method of claim 1 further comprising the step of partially or fully sintering the blank.

12. extending the movable pin into the second open cavity; filling the mold with a third ceramic material of a different composition than the second ceramic material, the third ceramic material being pourably filled into the second open cavity and around the movable pin to form a third layer while maintaining the through holes of the first, second and third layers; pressing a third upper press plunger against the third layer to form a third open cavity in communication with the through hole extending through the first, second, and third layers to form the blank, the third upper press plunger including a lower portion pressed into at least a portion of the third ceramic material to define at least a portion of the third open cavity, the lower portion of the third upper press plunger in communication with the moveable pin imparting a shape to the through hole of the blank generally defining an upper conical portion and a lower cylindrical end portion; The method of claim 1 further comprising:

13. 13. The method of claim 12, wherein the upper conical portion of the through hole in the blank defines a seating portion to receive an attachment instrument for securing a restoration formed from the blank to an abutment, the seating portion including an anti-rotation feature to prevent rotation of the attachment instrument.

14. 1. A method for forming a multi-layer blank of a ceramic material, comprising: providing a mold including at least one sidewall surrounding a lower press plunger having a moveable pin to form a cavity; extending the movable pin from a top surface of the lower press plunger into the cavity; filling the mold with a first ceramic material, the first ceramic material being pourably filled into the mold and around the movable pin to form a first layer having a through hole; pressing a first upper press plunger against the first layer such that a first open cavity is formed, with at least a portion of the first upper press plunger contacting the movable pin to maintain the through hole in the first layer; extending the movable pin into the first open cavity; filling the mold with a second ceramic material of a different composition, the second ceramic material pourably filling into the first open cavity and around the moveable pin to form the second layer while maintaining the through holes of both the first and second layers; pressing a second upper press plunger against the second layer to form a second open cavity in communication with the through hole extending through the first and second layers, the second open cavity and the through hole defining a threaded hole in the blank, the threaded hole having a generally cylindrical lower portion and an upper portion having a screw seat with an anti-rotation feature; The method includes:

15. 15. The method of claim 14, wherein the lower press plunger is movable and assists in pressing the first layer, the second layer, or both.

16. The method of claim 14 further comprising the step of partially or fully sintering the blank.

17. 1. A method for forming a multi-layer blank of a ceramic material, comprising: providing a mold including at least one sidewall surrounding a lower press plunger having a moveable pin to form a cavity; extending the movable pin from a top surface of the lower press plunger into the cavity; filling the mold with a first ceramic material, the first ceramic material being pourably filled into the mold and around the movable pin to form a first layer having a through hole; a step of pressing the first upper press plunger against the first layer and the upper part of the movable pin to form a first open cavity, with at least a part of the first upper press plunger in contact with the upper part of the movable pin to maintain the through hole of the first layer, and a step of partially retracting the movable pin into the lower press plunger by pressing movement of the first upper press plunger, with the first ceramic material of the first layer being compacted by the first upper press plunger; removing the first upper press plunger to expose at least a portion of the formed first open cavity; extending the movable pin into the first open cavity; filling the mold with a second ceramic material of a different composition than the first ceramic material, the second ceramic material being pourably filled into the first open cavity and around the movable pin to form the second layer while maintaining the through holes in both the first and second layers; pressing a second upper press plunger against the second layer and an upper portion of the movable pin to form the blank, the second upper press plunger forming a second open cavity communicating with the through hole extending through the first and second layers, the first and second ceramic materials being compacted while at least a portion of the movable pin is retracted into the lower press plunger by the pressing movement of the second upper press plunger when the second upper press plunger is pressed against the second layer and the upper portion of the movable pin; The method includes:

18. 18. The method of claim 17, wherein the second upper press plunger includes a lower portion pressed into at least a portion of the second ceramic material to define at least a portion of the second open cavity, the lower portion of the second upper press plunger in communication with the movable pin imparting a shape to the through hole of the blank generally defining an upper conical portion and a lower cylindrical end portion.

19. 20. The method of claim 18, wherein the upper conical portion of the through hole in the blank defines a seating portion to receive an attachment instrument for securing a restoration formed from the blank to an abutment, the seating portion including an anti-rotation feature to prevent rotation of the attachment instrument.

20. The method of claim 19 further comprising the step of partially or fully sintering the blank.

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