Blanks for preparing dental articles by cutting or grinding

Abstract

1. A blank for cutting or grinding a dental article, the blank having a planar body adapted to be received in a blank holder of a CAM system, the planar body including one or more ceramic or glass-ceramic blank portions and two or more through holes, each through hole adjacent to at least one of the ceramic or glass-ceramic blank portions for receiving a working end of a cutting or grinding tool of the CAM system.

Description

[Technical field]

[0001] The present invention relates to a blank for cutting or grinding a dental article. The present invention also relates to a kit of parts comprising at least two blanks of the present invention of different colors or hues. Furthermore, the present invention relates to a method for preparing the blanks of the present invention. Moreover, the present invention relates to a subtractive method for preparing one or more dental articles, in which the blanks of the present invention are used. Moreover, the present invention relates to a computer-implemented method for preparing a dental article, in which the blanks of the present invention are used. Finally, the present invention relates to a non-transitory computer readable medium comprising a program executable to perform the computer-implemented method for preparing a dental article according to the present invention, and further comprising a digital representation of the blanks of the present invention.

[0002] The blank of the present invention can be used to prepare dental articles by machining using dental CAD / CAM systems.The blank of the present invention allows multiple dental articles to be prepared quickly and efficiently, without being limited to a certain type or shape of dental article, thereby optimizing the service life of cutting or grinding tools, despite the high mechanical strength of the ceramic or glass-ceramic material from which the dental articles are prepared, and at the same time helps to reduce the inventory of blanks, thereby reducing the operating costs associated with CAD / CAM systems. [Background technology]

[0003] The preparation of dental articles from ceramic materials by subtractive methods is known. CAD / CAM systems are used to design dental articles by computer and to produce the design by machining from ceramic or glass-ceramic blanks using milling or grinding machines. For example, the inLab MC X5 (Dentsply Sirona) is a universal manufacturing unit for processing glass-ceramics, zirconia, polymers, composites, waxes and sintered metals. From the prior art, disks with a diameter of about 98 mm are known, which can be mounted in the blank holder of a CAD / CAM system. To secure the disk in the blank holder, an annular adapter is provided around the circumference of the disk. To place the disk in place, the disk may be provided with recesses that engage with protrusions of the blank holder.

[0004] Due to the high mechanical resistance of high density sintered ceramic or glass-ceramic materials, the wear of cutting or grinding tools is excessive and their useful life is limited. As a result, no universal disks made of high density ceramic or glass-ceramic materials are known.

[0005] Rather, pre-sintered ceramic materials are used to mold dental articles, which are then heat treated to prepare the final dental article. For example, U.S. Patent No. 6,354,836 discloses ceramic precursor powders that are mixed with a binder and pressed into a block or similar shape to form a green body. The green body is soft-sintered to a density less than about 85% of the final density. The soft-sintered block can then be cut into a desired shape and sintered to the final density to provide a high-strength dental restoration. However, such a method is still time-consuming, considering the high shrinkage of ceramic materials during sintering and the time required for the heating process.

[0006] In order to reduce the processing time for producing dental molded parts from ceramic blocks, in particular to avoid sintering processes, US 2015 / 0125822 A1 discloses a blank in the form of a disk with at least one preform of a dental crown. The preform in the blank is machined by cutting, sawing, grinding, drilling and / or cutting to prepare a dental crown of the desired shape. The blank of US 2015 / 0125822 A1 is a three-dimensional body that in terms of its dimensions and / or shape / settings approximates or matches the dimensions and / or shape / settings of the dental molded part to be produced. Thus, thanks to the at least partially matched or anticipated dimensions and / or shape of the preform, the preparation of the dental molded part from the blank is facilitated.

[0007] However, the blanks of U.S. Patent Application Publication No. 2015 / 0125822 cannot be used efficiently in practice, given that the preform requires highly accurate placement of the blank in the blank holder, and inaccuracies can result in defective dental articles when the preform is misplaced in the holder.

[0008] Moreover, considering that occlusion depends on tooth size, the preforms contemplated by U.S. Patent Application Publication No. 2015 / 0125822 must be provided in different sizes for each type of dental article to allow for preparation of different sizes of teeth, particularly molars. Considering that tooth color variations already require inventorying multiple different blanks in different colors, the need for preforms for different types and sizes of dental articles requires the dentist to obtain numerous different blanks.

[0009] Moreover, considering that the blanks in the U.S. Patent Application Publication No. 2015 / 0125822 specification must be frequently selected for a particular blank, frequent changing of the blanks is unavoidable, which is time consuming and introduces potential inaccuracies in blank placement.

[0010] EP 2016922 A1 discloses a cluster mill blank that includes a framework configured to engage with a blank holder of an existing CAD / CAM system and a plurality of sub-blanks attached to the framework to form an addressable matrix or cluster blank. The sub-blanks can include a lithium silicate-based glass ceramic that can be machined into dental articles. The blanks disclosed by EP 2016922 are intended to maximize yield per blank and reduce material waste. Summary of the Invention [Problem to be solved by the invention]

[0011] According to a first aspect, the object of the present invention is to provide a blank for cutting or grinding dental articles, which can be used to quickly and efficiently prepare a plurality of dental articles, without being limited to a predetermined shape, thereby optimizing the service life of the cutting or grinding tools, despite the high mechanical strength of the ceramic or glass-ceramic material from which the dental articles are prepared, and at the same time helping to reduce the inventory of blanks, thereby reducing the operating costs associated with CAD / CAM systems.

[0012] According to a second aspect, the object of the present invention is to provide a kit of parts comprising at least two blanks according to the invention, which can be used to quickly and efficiently prepare a plurality of dental articles of different colors, without being limited to a predetermined shape, whereby the blanks optimize the service life of cutting or grinding tools, despite the high mechanical strength of the ceramic or glass-ceramic material from which the dental articles are prepared, and at the same time serve to reduce the inventory of blanks, thereby reducing the operating costs associated with CAD / CAM systems.

[0013] According to a third aspect, it is an object of the present invention to provide a method for preparing blanks, which can be used to prepare blanks quickly and efficiently.

[0014] According to a fourth aspect, it is an object of the present invention to provide a subtractive method for quickly and efficiently preparing a plurality of dental articles, without being limited to a predetermined shape, which reduces wear and increases the useful life of cutting or grinding tools, despite the high mechanical strength of the ceramic or glass-ceramic material from which the dental articles are prepared.

[0015] According to a fifth aspect, it is an object of the present invention to provide a computer-implemented method for preparing dental articles, which can be used to quickly and efficiently prepare a plurality of dental articles, without being limited to a predetermined shape, in which the positioning of the blank is easy or simple and does not result in defects due to inaccuracies in the positioning of the blank, and at the same time, the blank optimizes the useful life of cutting or grinding tools despite the high mechanical strength of the ceramic or glass-ceramic material from which the dental articles are prepared.

[0016] According to a sixth aspect, it is an object of the present invention to provide a non-transitory computer-readable medium that can be used to quickly and efficiently prepare a plurality of dental articles, without being limited to a predetermined shape, in which the positioning of the blank is easy or simple and does not result in defects due to inaccuracies in the positioning of the blank, and at the same time, the blank optimizes the useful life of cutting or grinding tools despite the high mechanical strength of the ceramic or glass-ceramic material from which the dental articles are prepared. [Means for solving the problem]

[0017] According to a first aspect, the present invention provides a blank for cutting or grinding a dental article, the blank having a planar body adapted to be received in a blank holder of a CAM system, the planar body including one or more ceramic or glass-ceramic blank portions and two or more through holes, each through hole adjacent at least one of the ceramic or glass-ceramic blank portions for receiving a working end of a cutting or grinding tool of the CAM system.

[0018] According to a second aspect, the present invention provides a kit of parts comprising at least two blanks as defined by the first aspect of the invention, each blank being colour coded to identify the colour of one or more ceramic or glass-ceramic blank portions.

[0019] According to a third aspect, the present invention provides a method of preparing a blank as defined by the first aspect of the invention, the method comprising forming two or more through holes at two or more predetermined locations on a surface of a planar body adapted to be received in a blank holder of a CAM system.

[0020] According to a fourth aspect, there is provided a subtractive method for preparing one or more dental articles, comprising the steps of: (i) providing a blank as defined by the first aspect of the present invention; (ii) mounting the blank in a blank holder of a CAM system, the CAM system further comprising a milling or grinding machine configured with a cutting or grinding tool having a working end; (iii) placing a working end of a cutting or grinding tool into the preformed through-hole of the blank and adjacent a flat or concave inner wall of the preformed through-hole; and (iv) enlarging the preform through-hole by cutting or grinding the flat or concave inner wall of the preform through-hole with a working end of a cutting or grinding tool so as to prepare at least a portion of the convex contour of the dental article. The present invention provides a method comprising:

[0021] According to a fifth aspect, the present invention provides a computer-implemented method for preparing a dental article, comprising the steps of: (a) determining a type of blank having two or more preformed through holes as defined by a first aspect of the present invention to be mounted on a blank holder of a milling machine of a CAM system; (b) controlling the CAM system so that the working ends of the cutting or grinding tools of the milling machine are received in the preformed through holes of the blank; (c) controlling the working end of the cutting or grinding tool such that the preform through-hole is enlarged by the tool into at least a portion of the convex contour of the dental article. The present invention provides a computer-implemented method comprising:

[0022] According to a sixth aspect, the present invention provides a non-transitory computer readable medium comprising a program executable to perform a computer implemented method for preparing a dental article of the present invention, and further comprising a digital representation of a blank as defined by the present invention.

[0023] The present invention is based on the recognition that excessive tool wear that occurs when a cutting or grinding tool moves along its longitudinal axis through a high density ceramic or glass ceramic blank can cause the useful life (i.e., operational performance) of the cutting or grinding tool to deteriorate or deteriorate prematurely. Thus, the tool cannot quickly drill through the blank even when the lateral parts of the tool remain effective for machining the dental article. Moreover, the present invention is based on the recognition that the useful life of the cutting or grinding tool can be significantly extended by providing two or more through holes in the blank adjacent to the ceramic or glass ceramic blank part for receiving the working end of the cutting or grinding tool of the CAM system, thereby avoiding the tool penetrating along its longitudinal axis while cutting or grinding the hard ceramic or glass ceramic material. [Brief description of the drawings]

[0024] [Figure 1] 1 shows a first embodiment of the blank of the present invention, in which the planar body is a blank portion constructed entirely of a ceramic or glass-ceramic material and has one through hole formed therein. [Diagram 2] 1 shows a first embodiment of a blank of the present invention, with the cut silhouette of a dental article shown on the planar body. [Diagram 3] 1 shows a second embodiment of a blank of the present invention, depicting a blank portion having a planar body constructed from a ceramic or glass-ceramic material and having a plurality of through holes formed therein. [Figure 4] 13 illustrates a third embodiment of a blank of the present invention, in which a planar body includes a plurality of openings for receiving a plurality of blank portions of ceramic or glass-ceramic material, each blank portion adjacent its own dedicated through-hole. [Diagram 5] 13 illustrates a fourth embodiment of the blank of the present invention, in which a planar body includes multiple blank sections of ceramic or glass-ceramic material, each blank section adjacent a through hole shared by multiple blank sections. [Figure 6] FIG. 6 shows the embodiment of FIG. 5, in which the framework of the planar body is shown without a blank portion of ceramic or glass-ceramic material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The term "dental article" is understood to mean an article that can be used in the dental and / or orthodontic field, including dental laboratories. A typical example of a dental article is an indirect dental restoration. The term "indirect dental restoration" includes dental restorations molded outside the patient's oral cavity that can be used in the dental field, such as inlays, onlays, veneers, crowns, bridges, abutments, dental posts, dentures, denture bases and implant parts. For this, the dental restoration must provide sufficient mechanical properties, such as a Vickers hardness (HV1) of at least 400 MPa (ISO 6507-1:2005(E)). The dental restoration can also be composed of a dental support structure and a dental veneer or veneer.

[0026] The term "glass" refers to an amorphous solid, which can also be described thermodynamically as a frozen, supercooled liquid, such as oxide-based glasses, particularly borosilicate glasses, aluminosilicate glasses, or lithium silicate glasses.

[0027] The term "ceramic" refers to inorganic, non-metallic materials. Ceramics are usually hard, porous and brittle and, in contrast to glasses or glass-ceramics, exhibit an essentially purely crystalline structure.

[0028] The term "glass-ceramic" refers to inorganic, non-metallic materials in which one or more crystalline phases are surrounded by a glassy phase.

[0029] The term "machining" refers to cutting, grinding, cutting, engraving or shaping material with a machine.

[0030] A dental ceramic article is classified as "pre-sintered" if it has been heat treated at a temperature range of 900-1100°C for 1-3 hours. Pre-sintered dental ceramic articles usually have a porous structure and their density is at least 10% lower than that of fully sintered dental ceramic articles. Pre-sintered blank parts or dental articles are sometimes called green bodies. The present invention does not concern pre-sintered blank parts having a Vickers hardness (HV1) (ISO 6507-1:2005(E)) of less than 400 MPa.

[0031] The term "sintering" refers to the densification of a porous material, such as a green body, to a less porous material having a higher density.

[0032] The term "casting" refers to a manufacturing process in which a liquid material is poured into a hollow cavity of the desired shape of a mold and then allowed to solidify.

[0033] "Aspect ratio" is a dimensionless shape factor for numerically expressing the shape of a blank, regardless of its size, based on the length and thickness of the blank. For a circular blank, the relevant length is the diameter of the circular planar body. For a non-circular blank, the relevant length is the maximum dimension of the planar body in a direction perpendicular to the thickness of the planar body. The thickness direction coincides with the direction of two or more through holes in the blank.

[0034] Blanks (Mill Blanks) The present invention provides a blank for cutting or grinding a dental article. The dental article may be any indirect restoration, including inlays, onlays, veneers, crowns, bridges, abutments, dental posts, dentures, denture bases, and implant members. Preferably, the dental article is selected from crowns, bridges, inlays, and abutments.

[0035] The blank has a flat body adapted to be received in the blank holder of the CAM system. According to a preferred embodiment, an adapter is provided which holds the flat body at its periphery and is designed to fit snugly into the blank holder of the CAM system. For this, the blank preferably has one or more slots at its periphery for orienting the blank in the blank holder of the CAM system. The blank may comprise further elements which facilitate the orientation of the blank in the blank holder. In particular, in the case of a circular disk, it may comprise recesses which are designed to mate with corresponding protrusions of the blank holder when the blank is mounted in the blank holder.

[0036] The outline of the flat body is not particularly limited and may be selected from a circle, an ellipse, a rectangle, or a polygon.

[0037] According to a preferred embodiment, the flat body of the blank has an aspect ratio (diameter / thickness) of at least 3, more preferably at least 4.

[0038] The plate-like body is preferably a circular disk. Preferably, the disk has a diameter of at least 50 mm, more preferably, the disk has a diameter of at least 70 mm. According to a particular embodiment, the plate-like body is a disk having a diameter of at least 95 mm, in particular 98.5 mm.

[0039] The thickness of the flat body may be in the range of 3 to 35 mm, more preferably 7 to 25 mm, and may be appropriately selected based on the dental article to be prepared from the blank.

[0040] The planar body includes one or more ceramic or glass-ceramic blank parts. According to a particular embodiment, the planar body includes one ceramic or glass-ceramic blank part. Thus, the planar body can consist essentially of a ceramic or glass-ceramic material. The planar body may further include an adapter. The adapter can be fixed to the planar body by any suitable means, including an adhesive. The adapter can be provided around the periphery of the planar body. The material of the adapter is not particularly limited and can preferably be selected from fiber or particle reinforced resin. The ceramic or glass-ceramic blank part can be used to prepare one or more dental articles. The preparation of multiple dental articles from one ceramic or glass-ceramic blank part is preferably performed by placing the cutting silhouette of a first dental article adjacent to the through-hole of the blank part and placing the cutting silhouette of a further dental article adjacent to the through-hole obtained from the preparation of one or more previous dental articles. The cutting silhouette of the dental article is designed and stored for use by the CAD software controlling the CAM machine.

[0041] According to a further particular embodiment, the planar body comprises a framework having a plurality of openings adapted to hold ceramic or glass ceramic blank parts. Thus, the planar body comprises at least two, preferably four or more, individual ceramic or glass ceramic blank parts. Thus, the present invention provides a blank comprising a planar body adapted to engage with a blank holder of an existing CAD / CAM system and a plurality of blank parts contained in the planar body of the blank. The planar body may further comprise an adapter. The adapter may be fixed to the planar body by any suitable means, including adhesive. The adapter may be provided around the periphery of the planar body. The material of the adapter is not particularly limited and may preferably be selected from fiber or particle reinforced resins. The blank may be formed from the individual blank parts using a prefabricated or custom-made framework that allows the individual blanks to be used in different systems. The framework may be made of any suitable material having sufficient strength to hold the blank parts during preparation of the dental article. Examples of suitable materials are ceramic materials, glass ceramic materials, metals, resins, composites and combinations thereof.

[0042] A flat body can include the same individual blank portions of the same size and color, or blank portions of the same size and type but different colors. A flat body can also include the same blank portion material in various sizes and colors, or a variety of different types of blank portions from one or different manufacturers can be assembled on the same framework to form a hybrid blank.

[0043] The blank portion may be permanently or releasably attached to the framework of the planar body by any suitable method, examples of suitable methods include those involving gluing, sintering, soldering, brazing, adhesives, nuts-bolts-washers, knock-down fittings, and screws.

[0044] The blank part does not include a preform that is a three-dimensional body that, in terms of its dimensions and / or its shape / design, approximates or matches the dimensions and / or shape / design of the dental part to be produced. Rather, the overall shape of the blank part, excluding the through-holes, can be selected from simple three-dimensional geometric shapes, including a rectangular prism, a cube, a cylinder, or a polygonal prism, such as a triangular prism, a pentagonal prism, or a hexagonal prism. Rectangular prisms and cylinders are preferred. In the case of a rectangular prism shape, the dimensions of the blank part are preferably in the range of 1-5 cm:1-5 cm:0.5-3 cm. In the case of a cylindrical shape, the dimensions of the blank part preferably match the dimensions of the planar body, preferably in the range of 5-10 cm:0.5-3 cm.

[0045] The blank parts are composed of ceramics or glass ceramics having high hardness. At least one of the blank parts is not a green body. Rather, the blank parts preferably have a Vickers hardness (HV1) of at least 400 MPa (ISO6507-1:2005(E)). More preferably, the blank parts have a Vickers hardness (HV1) of at least 500 MPa, and even more preferably at least 600 MPa. Thus, dental articles prepared based on the ceramic blank parts of the present invention do not need to be sintered to final density after machining (cutting or grinding) to achieve the required mechanical properties. Thus, the design process does not need to take into account the shrinkage of more than 10% involved in conventional cutting and grinding processes of dental articles (where green bodies are used).

[0046] The ceramic materials from which the blank parts of the invention can be manufactured are polycrystalline materials (as such, preferably oxide ceramics) which are particularly suitable as starting materials for the blanks of the invention.

[0047] The term "oxide ceramic" or "oxide ceramics" refers to materials that are distinct from materials referred to as "silicate ceramics." Oxide ceramics are based on simple metal oxides that contain primarily crystalline phases, including aluminum oxide (Al2O3), zirconium dioxide (ZrO2), titanium dioxide (TiO2), and manganese oxide (MgO). Preferably, the oxide ceramics are based on zirconium dioxide.

[0048] Zirconium dioxide may be modified by the addition of suitable metal oxides to stabilize the high temperature modifications of zirconium dioxide at lower temperatures. Suitable metal oxides are, for example, yttrium oxide (Y2O3), calcium oxide (CaO), magnesium oxide (MgO) and cerium oxide (CeO, Ce2O3).

[0049] According to further embodiments, the oxide ceramics can also be mixed oxide ceramics based on aluminum oxide (Al2O3) and zirconium dioxide (ZrO2) as main components, for example mixed oxide ceramics containing 70% to 90% aluminum oxide and the remainder zirconium dioxide, or 70% to 80% zirconium oxide and the remainder aluminum oxide.

[0050] The ceramics are preferably densely sintered and have low residual porosity, specifically, the ceramics can be densely sintered to at least about 90%, preferably 99%, of their maximum or fully sintered density, such that the residual porosity is less than 10%, preferably less than 1%.

[0051] According to a further preferred embodiment, the blank part is made of glass ceramics. The blank part may preferably have the following composition in weight %:

[0052] [Table 1]

[0053] The total is 100% by weight.

[0054] A blank portion can be formed from the glass melt during or after cooling to room temperature, and the blank is then heated to a temperature T W1 At time t W1 (620°C≦T W1 ≦800℃, especially 650℃≦T W1 ≦750℃ and / or 1min ≦t W1 ≦200 min, preferably ≦10 min W1 ≦60 min). The foam body is produced from the blank / heat-treated blank.

[0055] The blanks of the invention can be colored through the use of color additives, such as metal atoms or metal ions of rare earth elements or elements in the d or f blocks of the periodic table.

[0056] The blank portion may be uniformly colored with one color or one hue, but it is also possible to provide different color layers or to color the blank with a gradation in which the color changes continuously from a starting color to a final color.

[0057] The planar body includes two or more through holes, each adjacent to at least one of the ceramic or glass-ceramic blank parts for receiving a working end of a cutting or grinding tool of a CAM system. The through holes may be inside the outline of the blank part or outside the outline of the blank part. In either case, the through holes are such that the working end of the cutting or grinding tool can penetrate the blank part without cutting or grinding along its longitudinal axis. According to a particular embodiment, the through holes are adjacent to one blank part, such that the through holes are used to machine that particular blank part.

[0058] Alternatively, the through-hole may be adjacent to multiple blank portions so that the through-hole can be used to machine each of the multiple blank portions.

[0059] According to further embodiments, the blank portion is adjacent to two or more through-holes, such that any of the through-holes can be used to machine the blank portion. For example, the blank portion can be used to prepare multiple dental articles, with each dental article being prepared using a different through-hole.

[0060] In accordance with a preferred embodiment, the blank has a plurality of preformed through holes distributed over the surface of one or more sintered ceramic blank portions.

[0061] The shape of the through hole is not particularly limited, as long as its size is large enough to receive the working end of a cutting or grinding tool of the CAM system in the through hole. According to a further preferred embodiment, the one or more preformed through holes are circular holes or elongated holes. The diameter of the circular through hole is preferably in the range of 1-20 mm, more preferably 2-10 mm. The length of the elongated hole is preferably in the range of 5-100 mm, more preferably 10-50 mm, and the width of the elongated hole can be selected to be similar to the diameter of the circular through hole. Preferably, the preformed through hole is located at the center of gravity of the disk. Thus, the CAM software can determine the position of the through hole based on the dimensions of the disk, so that the working end of the cutting or grinding tool can be introduced into the through hole by determining the position of the center of gravity of the blank. Specifically, in the case of a cylindrical disk, the center of gravity is the center of the disk.

[0062] For blanks with through-holes that are not in the blank's center of gravity, the detailed positions of the through-holes must be available to the CAM software. According to a preferred embodiment, blanks with through-holes that are not in the blank's center of gravity further include features such as slots for engaging with corresponding features of a blank holder of a CAM system. Preferably, the features are provided on an adapter attached to the periphery of the blank's planar body. The blank can be represented in digital form, including the positions of the through-holes relative to the features, such that the CAM software can derive the positions of the through-holes when the blank is fitted into the blank holder of a CAM system. The representation of the blank preferably represents the surface of the blank or a portion thereof, including the through-holes. According to a preferred embodiment, the surface geometry of the three-dimensional blank is described in a computer-readable format, for example an STL file that encodes the surface geometry by using the concept of tessellation.

[0063] The invention also relates to a non-transitory computer readable medium storing a digital representation of the blank of the invention, including the locations of the through-holes relative to the features. Preferably, the digital representation is in an STL file format.

[0064] Kit of parts According to a second aspect, the present invention provides a kit of parts comprising at least two blanks as defined by the first aspect of the invention, each blank being colour coded to identify the colour of one or more ceramic or glass-ceramic blank portions.

[0065] The color coding is preferably based on a color coding system used in dentistry, such as the VITA shade system.

[0066] How to prepare a blank According to a third aspect, the present invention provides a method of preparing a blank as defined by the first aspect of the invention, the method comprising forming two or more through holes at two or more predetermined locations on a surface of a planar body adapted to be received in a blank holder of a CAM system.

[0067] According to a first embodiment, the planar body is a ceramic or glass ceramic blank part that includes two or more through holes in its contour. The method of the present invention thus includes the step of forming two or more through holes at two or more predetermined locations on a surface of a ceramic or glass ceramic blank part that is adapted to be received in a blank holder of a CAM system. The blank part can be formed by preparing and shaping a pre-sintered ceramic material into the desired shape of the blank part, followed by heat treating the pre-sintered ceramic material. To prepare the final blank part, the two or more through holes can be formed in the pre-sintered material or after sintering. For example, a ceramic precursor powder can be mixed with a binder and pressed into a suitable shape to form a green body. Injection molding, pressing and extrusion are suitable techniques for preparing the green body. The green body can be pre-sintered to a density less than about 85% of the final density. The pre-sintered block can then be machined into the desired shape and sintered to the final density to provide the blank part.

[0068] According to a second embodiment, the planar body includes one or more ceramic or glass-ceramic blank parts. The method of the present invention therefore includes forming two or more through holes at two or more predetermined locations on the planar body adapted to be received in a blank holder of a CAM system. For example, the ceramic or glass-ceramic blank part can be prepared and attached to a framework to provide a through hole adjacent to the ceramic or glass-ceramic blank part in the planar body.

[0069] Subtractive method using blanks According to a fourth aspect, the present invention provides a subtractive method for preparing one or more dental articles, comprising: (i) providing a blank as defined by the first aspect of the present invention; (ii) mounting the blank in a blank holder of a CAM system, the CAM system further comprising a milling or grinding machine configured with a cutting or grinding tool having a working end; (iii) placing a working end of a cutting or grinding tool into the preformed through-hole of the blank and adjacent a flat or concave inner wall of the preformed through-hole; and (iv) enlarging the preform through-hole by cutting or grinding the flat or concave inner wall of the preform through-hole with a working end of a cutting or grinding tool so as to prepare at least a portion of the convex contour of the dental article. The present invention provides a method comprising:

[0070] Preferably, the blank of the first aspect is a disc having a diameter of about 98.5 mm.

[0071] Attachment of the blank to the blank holder of the CAM system can preferably be by means of a slot provided around the periphery of the blank. The blank can be secured by any conventional means used in CAM systems.

[0072] The CAM system further includes a milling or grinding machine configured with a cutting or grinding tool having a working end.

[0073] The working end of a cutting or grinding tool is placed into the preformed through hole of the blank and adjacent to the flat or concave inner wall of the preformed through hole. Preferably, only the lateral portions of the working end of the cutting or grinding tool contact the blank portion. More preferably, the contact of the working end at a given moment is limited to lateral points that are within at least 50% of the maximum tangential velocity of the working end of the cutting or grinding tool.

[0074] The preform through-hole is enlarged by cutting or grinding the flat or concave inner wall of the preform through-hole with the working end of a cutting or grinding tool to prepare at least a portion of the convex contour of the dental article. Thus, when the cutting or grinding tool is placed into the preform through-hole, the through-hole is outside the cut silhouette of the dental article.

[0075] Computer implementation method using blanks According to a fifth aspect, the present invention provides a computer-implemented method for preparing a dental article, comprising the steps of: (a) determining a type of blank having two or more preformed through holes defined by a first aspect, the blank being mounted on a blank holder of a milling machine of a CAM system; (b) controlling the CAM system so that the working ends of the cutting or grinding tools of the milling machine are received in the preformed through holes of the blank; (c) controlling the working end of the cutting or grinding tool such that the preform through-hole is enlarged by the tool into at least a portion of the convex contour of the dental article. The present invention provides a method comprising:

[0076] A type of blank having two or more preformed through holes defined by the first aspect that is mounted on a blank holder of a milling machine of the CAM system is determined, which may be performed by manual user input, by reading a bar code, a database, or by other process that allows the blank to be unambiguously identified.

[0077] According to a preferred embodiment, the CAM system checks whether a digital representation of a blank of a particular type is available, and if a digital representation of a blank of a particular type is not available, the CAM system can download a digital representation of a blank of a particular type over a network such as the Internet, if necessary.

[0078] The CAM system is then controlled such that the working end of the milling machine's cutting or grinding tool is received in the preformed through-holes of the blank. For this, the positions of the two or more through-holes of the blank must be available to the CAM system. It is therefore preferred that the computer system accesses or preferably stores a digital representation of the blank in STL format. Based on the virtual representation of the blank, the CAM system can determine the center of gravity of the blank when the through-holes are placed in the center of the blank. Alternatively, the CAM system can use the digital representation of the blank to derive the positions of the two or more through-holes with reference to features of the blank that are adapted to engage with corresponding features on the blank holder in the positions stored in the CAM system.

[0079] The working end of the cutting or grinding tool is controlled such that the preform through-hole is enlarged by the tool into at least a portion of the convex contour of the dental article.

[0080] Non-Transitory Computer-Readable Medium The present invention further includes a non-transitory computer readable medium. The medium includes a program executable to perform a computer-implemented method for preparing a dental article according to the present invention. The medium further includes a digital representation of a blank defined by the present invention. Preferably, the digital representation is in STL format.

[0081] Based on the digital representation of the blank, the executable program can determine the locations of the through-holes relative to known locations on the blank holder, which are used to orient the blank in the blank holder.

[0082] The invention will now be further described with reference to the drawings.

[0083] FIG. 1 shows a first embodiment of a blank 10 for cutting or grinding dental articles, in which a flat body 12 is a blank part 14 entirely made of ceramic or glass-ceramic material, in which a through hole 20 is formed. The blank 10 has a flat body 12 adapted to be received in a blank holder of a CAM system (not shown). For this purpose, the flat body includes an adapter 15. The adapter 15 is provided around the periphery of the flat body 12. Alternatively, the adapter 15 may be integral with the flat body, for example the periphery of the flat body may be shaped to match the shape of the blank holder. The flat body includes a ceramic or glass-ceramic blank part 14 and a circular through hole 20 adjacent the ceramic or glass-ceramic blank part 14 for receiving the working end of a cutting or grinding tool of the CAM system. The through hole 20 is in the center of gravity of the flat body and within the contour of the blank part. The CAM system can therefore easily determine the position of the through hole regardless of the orientation of the blank in the blank holder.

[0084] FIG. 2 shows a first embodiment of the blank 10 of FIG. 1, in which the flat body 12 is a blank part 14 entirely made of ceramic or glass-ceramic material, in which one through-hole 20 is formed. FIG. 2 shows a cutting silhouette 30 for preparing a dental article 40. In the preparation of the dental article, firstly the working end of a cutting or grinding tool is introduced into the through-hole 20 in order to prepare a first dental article adjacent to the through-hole 20. The preparation of the first dental article increases the through-hole 20, providing access to the cutting silhouette of a second dental article adjacent to the increased through-hole 20. Thus, most or substantially all of the flat body 12 can be consumed starting from the through-hole 20 of the blank 12, while at the same time avoiding excessive wear of the cutting or grinding tool. According to FIG. 2, the through-hole 20 is in the center of gravity of the blank, i.e. in the center of the flat body, which is preferred in view of the fact that at this position the cutting or grinding tool can be easily inserted into the through-hole.

[0085] FIG. 3 shows a second embodiment of a blank 10 of the invention, in which a flat body 12 is a blank portion 14 made entirely of ceramic or glass-ceramic material, in which a number of elongated through-holes 20 are formed. An adapter 15 is provided, which holds the flat body at its periphery and is designed to fit snugly into a blank holder of a CAM system (not shown). The flat body 12 comprises one ceramic or glass-ceramic blank portion 14 and 15 elongated through-holes 20 adjacent the ceramic or glass-ceramic blank portion 14 for receiving the working end of a cutting or grinding tool of the CAM system. The through-holes 20 are distributed throughout the flat body and within the contour of the blank portion. FIG. 3 shows a cutting silhouette 30 for preparing a dental article. In the preparation of the dental article, the working end of a cutting or grinding tool is introduced into one of the elongated through-holes 20 to prepare the dental article adjacent the through-hole 20. Second and further dental articles can also be prepared by introducing the working ends of cutting or grinding tools into different elongated through-holes 20. Thus, by using each of 15 elongated through-holes, most or substantially all of the planar body 12 can be consumed while avoiding excessive wear of the cutting or grinding tools.

[0086] 4 shows a framework 16 of a third embodiment of a blank 10 for cutting or grinding dental articles, in which a planar body 12 comprises a plurality of blank parts (not shown) of ceramic or glass-ceramic material, each blank part adjacent its own elongated through-hole 20 and fixed in a corresponding opening 21 of the framework 16. The framework 16 of the blank 10 is adapted to be received in a blank holder of a CAM system (not shown). For this purpose, the framework comprises an adapter 15, which is provided around the framework 16. The framework 16 comprises 15 openings 21 for arranging 15 ceramic or glass-ceramic blank parts 14 (not shown) adjacent the 15 elongated through-holes 20 for receiving the working end of a cutting or grinding tool of the CAM system. The openings 21 and the elongated through-holes 20 for the ceramic or glass-ceramic blank parts 14 are distributed throughout the planar body. In preparing a dental article, a working end of a cutting or grinding tool is introduced into one of the elongated through-holes 20 to prepare a dental article using the blank portion adjacent to the through-hole 20. Second and further dental articles can also be prepared by introducing a working end of a cutting or grinding tool into a different elongated through-hole 20. Thus, by using 15 ceramic or glass-ceramic blank portions 14 and elongated through-holes, respectively, most or substantially all of the planar body 12 can be consumed while avoiding excessive wear of the cutting or grinding tool.

[0087] 5 shows a fourth embodiment of a blank 10 for cutting or grinding dental articles, in which each blank portion 14 is adjacent to a through hole 20 shared by several blank portions. The blank 10 has a framework 16 of a planar body 12 adapted to be received in a blank holder of a CAM system (not shown). For this purpose, the planar body 12 includes an adapter 15, which is provided around the periphery of the planar body 12. The planar body 12 includes 12 ceramic or glass-ceramic blank portions 14 and two through holes 20, each adjacent to six of the ceramic or glass-ceramic blank portions 14, for receiving the working ends of cutting or grinding tools of the CAM system. Markings in the form of slots 50 for orienting the blank 10 in the blank holder when engaging corresponding protrusions of the blank holder are arranged around the periphery.

[0088] FIG. 6 shows the framework 16 of the embodiment of FIG. 5, in which the planar body framework 16 is shown without the blank portion of ceramic or glass-ceramic material.

Claims

1. A blank for preparing a dental article by cutting or grinding, the blank having a planar body adapted to be received in a blank holder of a CAM system, the planar body including one or more ceramic or glass-ceramic blank portions and two or more through holes, each through hole adjacent at least one of the ceramic or glass-ceramic blank portions for receiving a working end of a cutting or grinding tool of the CAM system; A blank, wherein the flat body has a thickness dimension and a length dimension perpendicular to the thickness, and each through hole is an elongated hole extending along the length of the flat body and penetrating the thickness of the flat body.

2. The blank of claim 1 , wherein the planar body includes between 2 and 50 through holes.

3. The blank of claim 1 or 2, wherein the planar body comprises a single ceramic or glass-ceramic blank portion.

4. The blank of claim 1 or 2, wherein the planar body includes a framework having a plurality of openings adapted to hold ceramic or glass-ceramic blank portions.

5. The blank of claim 4, wherein the framework includes between 2 and 50 openings adapted to hold ceramic or glass-ceramic blank portions.

6. 6. The blank of claim 4 or 5, wherein the framework is made of a material having sufficient strength to hold the ceramic or glass-ceramic blank portions during preparation of a dental article.

7. The blank of any one of claims 4 to 6, wherein each through hole is adjacent to one of the ceramic or glass-ceramic blank portions.

8. The blank of any one of claims 4 to 6, wherein at least one through hole abuts a plurality of said ceramic or glass-ceramic blank portions.

9. A blank according to any one of claims 1 to 8, having one or more slots in the periphery of the planar body for orienting the blank in a blank holder of a CAM system.

10. A kit of parts comprising at least two blanks according to any one of claims 1 to 9, each blank being colour coded.

11. A method for preparing a blank according to any one of claims 1 to 9, comprising the step of forming two or more through holes at two or more predetermined locations on a surface of a flat body adapted to be received in a blank holder of a CAM system.

12. 1. A subtractive method for preparing one or more dental articles, comprising: (i) providing a blank according to any one of claims 1 to 9; (ii) mounting the blank in a blank holder of a CAM system, the CAM system further comprising a milling or grinding machine configured with a cutting or grinding tool having a working end; (iii) placing the working end of the cutting or grinding tool into a preformed through hole of the blank and adjacent a flat or concave inner wall of the preformed through hole; and (iv) enlarging the preform through-hole by cutting or grinding the flat or concave inner wall of the preform through-hole with the working end of the cutting or grinding tool so as to prepare at least a portion of a convex contour of a dental article. The method includes:

13. 1. A computer-implemented method for preparing a dental article, comprising: (a) determining the type of blank having one or more preformed through holes according to any one of claims 1 to 9, which is mounted on a blank holder of a milling machine of a CAM system; (b) controlling the CAM system such that a working end of a cutting or grinding tool of the milling machine is received in a preformed through hole of the blank; (c) controlling the working end of the cutting or grinding tool such that the preform through-hole is enlarged by the cutting or grinding tool into at least a portion of a convex contour of a dental article.

23. A computer-implemented method comprising:

14. A non-transitory computer readable medium comprising a program executable to perform a computer implemented method for preparing a dental article according to claim 13, and further comprising a digital representation of a blank according to any one of claims 1 to 9.

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