SE545198C2 - A Mold Assembly for a Ceramic Dental Restoration - Google Patents

Abstract

A mold assembly, a method for generating the mold assembly, a method for forming a dental restoration with the mold assembly, and a device for pressing a ceramic slip into the mold assembly are disclosed. The mold assembly comprises at least one mold (1) having an inner surface (3) and a first alignment member, at least one die (2) having an outer surface (5) and a second alignment member, at least one inlet (10) for receiving a ceramic material, at least one outlet (11a-11 f) for letting air out of the mold assembly when ceramic material is inserted into the mold assembly. The mold (1) with the inner surface (3) and the die (2) with the outer surface (5) form a cavity with a pre-determined shape when the mold (1) and the die (2) are assembled with the first alignment member and second alignment member in a predetermined relative rotational position.

Description

lO A Mold Assembly for a Ceramic Dental Restoration Field of the lnvention This invention pertains in general to the field of dentistry. More particularly, a mold assembly for molding a ceramic dental restoration, a method for generating the mold assembly, a method for forming a dental restoration with the mold assembly, and a device for pressing a ceramic slip into the mold assembly are disclosed.

Background of the lnvention ln dentistry, a dental restoration made of a ceramic material, such as zirconia or alumina, is many times desirable since it is biocompatible and be made very thin in order to obtain a precise fit. The ceramic dental restoration was traditionally produced by manually adding layer after layer to a base structure. Later production techniques include milling the dental restoration from a block of ceramic material, which may be a green body or be pre-sintered. The dental restoration can be milled to its final shape, or to a base structure to which layers of ceramic material are added manually.

Modern approaches in dentistry include preserving as much as possible of the patients natural teeth when preparing for a dental restoration. This includes preserving or mimicking the shape of the natural tooth. For example, when preparing for a tooth supported dental crown or bridge, a part of one or several teeth are shaped to a stump while the root of the tooth/teeth is/are maintained to support the restoration. The border between a shaped surface and a natural surface of the tooth forms the so-called preparation line. At the preparation line, it is desired to keep as much as possible of the natural tooth. This means that the dental restoration in this area has to be made very thin and at the same time strong, which makes the requirements on the dental restoration challenging. Also, the inner surface of the dental restoration that will sit on the tooth stump has to be very precise to fit accurately.

The shape of the dental restoration is generated from a digital or physical impression of the dentition. Any inaccuracy in the shape of the dental restoration caused in the production chain after the impression has been taken causes the dental restoration to fit sub-optimally on the tooth stump as well as relative to neighboring teeth and antagonistic teeth. Hence, it is desired to have a production chain that generates a dental restoration with a shape that fits into situation captured by the impression and with minimal adjustments needed by the dentist. Any adjustment needed at fitting the dental restoration may make the dental restoration more fragile, sub-optimal in shape, and be more susceptible to future cracking.

Producing a full-contour ceramic dental restoration with milling techniques is challenging. Many times, the thickness of the desired shape at the preparation line is thinner than the minimum size of existing milling tools. This means that the preparation line has to be made wider, resulting in lO removal of a sub-optimal amount of tooth substance and potentially a sub-optimal support for the dental restoration. Also, the movement paths of the milling tool are approximations of the surface shapes, for example at the inner surface of the dental restoration that will sit against the tooth stump. lt is not always possible to mill a shape that is complementary to the shape of the tooth stump since the appropriate milling tools are not available. Such approximations in the milling paths and sub- optimal milling tools result in a dental restoration that may have undesired shapes, imprecise fit, and may be susceptible to future fracture. The dental restoration may also chip at the thinnest structures during milling.

Furthermore, milled ceramic dental restorations are made from a pre-formed ceramic block of material, which is normally a green-body or a pre-sintered body. This milling technique is expensive, time consuming, and generates a lot of waste material. ln fact, the majority of the ceramic block of material is waste material.

Other types of dental restorations than tooth supported dental crowns and bridges are also produced by milling from a block of ceramic material. Such dental restorations include for example abutments for dental implants, inlays, onlays, veneers etc., which are all associated with the challenges described above with regard to tooth supported dental restorations.

Hence, improved ways to produce dental restorations would be advantageous and in particular allowing for improved precision, flexibility, efficiency, durability, fit, environmentally friendly and/or less expensive would be advantageous.

Summary of the lnvention Accordingly, embodiments of the present invention preferably seek to mitigate, alleviate or eliminate one or more deficiencies, disadvantages or issues in the art, such as the above-identified, singly or in any combination by providing, in combination or separately, a mold assembly for molding a ceramic dental restoration, a method for generating the mold assembly, a method for forming a dental restoration with the mold assembly, and a device for pressing a ceramic slip into the mold assembly.

A mold assembly comprises at least one mold having an inner surface, at least one die having an outer surface, at least one inlet for receiving a ceramic material, and at least one outlet for letting air out of the mold assembly when ceramic material is inserted into the mold assembly. The mold with the inner surface and the die with the outer surface form a cavity with a pre-determined shape when the mold and the die are assembled in a predetermined relative rotational position.

The mold comprises a first alignment member, which may be a first anti-rotational feature. The die comprises a second alignment member, which may be a second anti-rotational feature. The first anti-rotational feature and the second anti-rotational feature may have complementary shapes. Additionally or alternatively, the first anti-rotational feature may have a shape that is complementary to a third anti-rotational feature of a holder for holding the mold lO assembly, and the second anti-rotational feature may have a shape that is complementary to the shape of a fourth anti-rotational feature of the holder. The third anti-rotational feature and the fourth anti-rotational feature may be separate portions of the same anti-rotational feature.

The inlet may be located in the mold. The inlet in a first portion may be tapered inwardly from an exterior surface of the mold towards a center of the inlet. Additionally or alternatively, the inlet in a second portion may be tapered outvvardly from a center of the inlet towards the inner surface. The inlet may extend from the exterior surface to the inner surface.

The mold may have a mold duct surface extending from an exterior surface of the mold to the inner surface. The die may comprise a base extending from an exterior surface of the die to the outer surface of the die. The base may comprise a die duct surface. Additionally or alternatively, the base may be configured to be received within a recess of the mold. The mold duct surface may facing the die duct surface, when the mold and the die are assembled, to form at least a portion of the outlet. The mold duct surface may be spaced apart from the die duct surface to form the at least a portion of the outlet.

The mold duct surface may be at least partially tapered from the inner surface towards an exterior surface of the mold. The die duct surface may be at least partially tapered from the outer surface towards the exterior surface of the die.

The mold may comprise a first end surface, a second end surface, a side surface extending between the first end surface and the second end surface. At least one recess may extend in at least one of the first end surface, the second end surface and the side surface. The recess may extend and be contiguous along a portion of the first end surface, along the entire side surface, and a along a portion of the second end surface.

The die and the mold may be made of resin.

A method for generating a mold assembly for molding a ceramic dental restoration comprises obtaining a digital dental restoration having at least a first surface and a second surface, obtaining a digital mold body comprising a digital mold and a digital die forming a mold assembly, positioning the digital dental restoration within the mold body and forming a mold cavity within the mold body having the shape of the digital dental restoration. Positioning the digital dental restoration within the mold body comprises positioning the digital dental restoration relative at least one inlet of the digital mold, whereby the inlet extends from an exterior of the digital mold body into the cavity for receiving a ceramic material in the mold cavity, and positioning the digital dental restoration relative to at least one outlet, whereby the outlet extends from the mold cavity to the exterior of the digital mold body. An interface between the digital mold and the digital die that extends from the mold cavity to the exterior of the digital mold body may have surfaces spaced apart to form a portion of the outlet.

The method for generating a mold assembly for molding a ceramic dental restoration may comprise producing the mold assembly by additive manufacturing in a resin material. lO A method for forming a dental restoration green body with the mold assembly comprises assembling a mold assembly including a mold and a die, heating a chamber containing ceramic material to form a ceramic slip, positioning a nozzle of the chamber in an in|et of the mold assembly, pressing the ceramic slip into a cavity, formed by the mold and the die, of the mold assembly while pressing air, captured in the cavity, through an outlet of the mold assembly. Also, the ceramic slip captured in the cavity to form a dental restoration green body may be cooled, and the dental restoration green body may be removed from the mold assembly, such as when the ceramic slip has been cooled.

A device for pressing a ceramic slip into the mold assembly comprises a heatable chamber for receiving a ceramic material, the chamber having a nozzle, a piston arranged to press the ceramic material, when heated to a ceramic slip, through the nozzle; and a holder configured to receive a mold assembly. The holder has an inner surface and an opening, wherein the inner surface is configured to abut an exterior surface of the mold and an exterior surface of the die while the in|et of the mold assembly is exposed through the opening when the mold assembly is arranged in the holder.

The inner surface of the holder may be tapered outvvardly from a first end to a second end. The opening of the holder may be located at the first end. An external side surface of the mold may be tapered from a first end towards a second end and configured to fit within the holder such that the tapered inner surface of the holder abuts the tapered external side surface of the mold. The die may be configured to abut the second end of the inner surface of the holder.

The holder may comprise a first holder part and a second holder part forming a tubular unit when assembled.

The second holder part may be magnetic. The device may comprise a seat for the holder and a reciprocating magnet. The magnet can be moved in a first direction to be in abutment with the second holder part, and can be moved in a second direction opposite to the first direction to remove the holder from the seat after the magnet has been moved to be in abutment with the second holder part.

Further embodiments of the invention are defined in the dependent claims.

Some embodiments of the invention provide a more efficient method for producing a mold assembly for a producing a dental restoration, and such a dental restoration. The mold assembly has a shape that generates a more desirable interface towards or fit to a patient's dental preparation, neighboring teeth, and opposing teeth. For example, the thickness of the dental restoration at the preparation line can be made thinner than with known production techniques since there is no risk of breaking the material with machining tools. Furthermore, a dental restoration produced with the methods and devices according to embodiments of the invention provides improved fit since the design of the dental restoration does not have to take a minimal size of any machining tools and/or movement paths of such machining tools into consideration. Furthermore, the embodiments of the lO invention provides for increased flexibility to combine ceramic materials having different transiucency and/or colors. lt should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Brief Description of the Drawings These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which Fig. 1a is a side view of the mold assembly; Fig. 1b is a cross-sectional view of the mold assembly; Fig. 2a is a side view of the mold; Fig. 2b is a top view of the mold; Fig. 2c is a bottom view of the mold; Fig. 3a is a side view of the die; Fig. 3b is a top view of the die; Fig. 4 is a cross-sectional view of a dental restoration; Fig. 5a is a cross-sectional view of a mold body; Fig. 5b is a perspective view of a mold body; Fig. 5c is a bottom view of the mold; Fig. 6 is a partial cross-sectional view of the device for pressing a ceramic slip; and Fig. 7 is a cross-sectional view of the holder for holding the mold assembly.

Description of Embodiments Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. ln the drawings, like numbers refer to like elements.

The following description focuses on embodiments of the present inventions applicable to the field of ceramic dental restorations. Embodiments will be described for obtaining a ceramic dental crown that has the shape of a final restoration, also know as a full-contour crown. However, it will be lO appreciated that the invention is not limited to this application but may be applied to other types of dental ceramic restorative components, such as any type of tooth or dental implant supported dental restoration, including for example full or partial dental bridge, coping, abutment, inlay, onlay etc., including the full or partial shape of the final dental restoration.

Figs. 1a-1 b illustrate a mold assembly according to embodiments of the invention. The assembly may be used for molding a ceramic dental restoration, such as from a ceramic slip or slurry. Embodiments for a method of molding the dental restoration with the mold assembly will be further defined below.

The mold assembly comprises at least one mold 1, embodiments of which are illustrated separately in Figs. 2a-2c. The mold assembly also comprises and at least one die 2, embodiments of which are illustrated separately in Figs. 3a-3b. ln the illustrated embodiments, a single mold and a single die are included in the mold assembly. However, in other embodiments, the mold assembly comprises a plurality of molds or mold parts with a single die, a single mold with a plurality of dies or die parts, or a plurality of molds or mold parts in combination with a plurality of dies or die parts. For example, forming a dental restoration in the shape of a dental bridge may include a single mold in combination with a plurality of dies. Other combinations are also foreseeable. ln the following, reference will be made to a single mold and a single die to make the description clear. However, the description of a single mold and a single die is intended to include also embodiments where the mold and/or the die comprise multiple parts.

The mold 1 has an inner surface 3. The die 2 has an outer surface 5. When the mold 1 and the die 2 are in an assembled state, the inner surface 3 and the outer surface 5 may form a cavity 6 for forming the dental restoration. The inner surface 3 of the mold 1 may have a shape that corresponds to an outer shape of the dental restoration, and the outer surface 5 of the die 2 may have a shape corresponding to an inner surface of the dental restoration. The outer surface may be shaped to fit against neighboring and antagonistic teeth. The outer surface 5 may be shaped to fit a tooth stump or a dental implant. Hence, for a single crown, the shape of the cavity corresponds to the shape of the dental restoration. Providing the mold 1 and the die 2 as separate parts enables producing the mold assembly by additive manufacturing without the need for support structures during production, which is othen/vise needed when a structure having a cavity is produced. ln some embodiments, the mold 1, 31 optionally comprise a first alignment member, which may be a first anti-rotational feature 4, 24 as illustrated in Figs. 1a-2b and 5b. The die 2, 32 optionally comprises a second alignment member, which may be a second anti-rotational feature 7, 27 as illustrated in Figs. 1a, 3b, and 5b. The first anti-rotational feature 4 and the second anti- rotational feature 7 may have complementary shapes, as illustrated in Figs. 1a-2b, and Figs. 1a and 3b, respectively. Additionally or alternatively and as illustrated in Fig. 5b, the first anti-rotational feature 24 has a shape that is complementary to a third anti-rotational feature of a holder for holding the mold assembly, and the second anti-rotational feature 27 has a shape that is complementary to lO the shape of a fourth anti-rotational feature of the holder. The third anti-rotational feature and the fourth anti-rotational feature may be separate positions of the same anti-rotational feature. ln some embodiments, such as illustrated in the embodiments of Figs. 1a-2b, the first anti- rotational feature 4 and the second anti-rotational feature 7 have complementary shapes. The anti- rotational features 4, 7 may be sized to be in abutment or substantially in abutment, when the mold 1 and the die 2 are assembled, which enables assembling the mold 1 with the inner surface 3 and the die 2 with the outer surface 5 in a single repetitive relative rotational position to form the cavity 6 with a pre-determined shape when the die 1 and mold 2 are assembled. The first anti-rotational feature 4 may be a protrusion and the second anti-rotational feature may be a recess with a shape that is complementary to the shape of the protrusion (or vice versa), as is illustrated in Figs. 1a, 2a, 2c and 3b. For example, the first anti-rotational feature 4 may be positioned at an end-surface of the mold 1, and the second anti-rotational feature 7 may be located at a base structure 8, such as at a top surface of the base structure 8 facing the end surface of the mold 1 when the mold 1 and the die 2 are in the assembled state, such as illustrated in Fig. 1. The anti-rotational features 4, 7 facilitates producing the mold 1 and the die 2 as separate parts and assemble the parts in a single repetitive position such that the inner surface 3 of the mold 1 and the outer surface 5 of the die 2 are aligned when the mold 1 and the die are in the assembled state. ln other embodiments the anti-rotational features are not included, for example in situations where the preparation line 9 of the dental restoration and of cavity 6 are rotationally asymmetric, wherein the mold 1 and the die 2 can only be assembled in a single rotational position. However, in situations where the preparation line 9 is asymmetric but not pronounced, the anti-rotational features may increase the rotational fit between the mold 1 and the die 2 when assembled, providing increased precision of the dental restoration. ln some embodiments, such as illustrated in the embodiments of Figs. 5a-5c, the first anti- rotational feature 24 has a shape that is complementary to a third anti-rotational feature of a holder for holding the mold assembly, and the second anti-rotational feature 27 has a shape that is complementary to the shape of a fourth anti-rotational feature of the holder. The third anti-rotational feature and the fourth anti-rotational feature may be separate portions of the same anti-rotational feature. The first anti-rotational feature may be a recess and/or a protrusion in a side surface of the mold 31. The second anti-rotational feature 27 may be recess and/or a protrusion in a side surface of the die 32. The holder (as described below) may have a protrusion/recess with a shape that is complementary to the anti-rotational features 24, 27 of the mold 31 and die 32, respectively. Hence, when the mold 31 and the die 31 are assembled with the first alignment member and second alignment member in a predetermined relative rotational position, they are rotationally aligned. For example, the mold 31 and the die 32 may each be rotationally aligned with the other when inserted into the holder comprising an alignment member for rotationally aligning the mold 31 with the die 32 in a predetermined relative rotational position. The predetermined relative position is illustrated in Figs. 1a and 5b, respectively, wherein the outer and the inner surface of the cavity are rotationally lO positioned in a predetermined position. This facilitates inserting the mold assembly in the holder wherein the mold and the die each at the time can be inserted into the holder in a single repetitive position.

Furthermore, the mold may in some embodiments, such as illustrated in the embodiments of Fig. 5b comprise an anti-rotational feature 29 having a compiementary shape to a mating anti- rotation feature of an inner surface of the holder. Hence, the mold 31 may be rotationally fixed in the holder.

Each of the features and alternatives described with regard to and illustrated in the embodiments of Figs. 1a-3b can be combined with each of the features described with regard to and illustrated in Figs. 5a-5c to form individual embodiments.

Furthermore, the mold assembly comprises at least one inlet 10 for receiving the ceramic material. Also, the mold assembly comprises at least one outlet 11a-1 1f for letting air out of the mold assembly when ceramic material is inserted into the mold assembly. ln the illustrated embodiments, the inlet 10 is located in the mold. ln other embodiments, the inlet 10 is located in the die 2. Also, in the illustrated embodiments, a single inlet 10 is shown. Other embodiments include a plurality of inlets 10. The inlet(s) extends from an exterior of the mold assembly into the cavity ln some embodiments, such as illustrated in Figs. 1a-1b, the inlet 10 in a first portion 10a is tapered inwardly from an exterior surface of the mold 1 towards a center of the inlet 10. This facilitates sealing against a nozzle through which the ceramic material is introduced, as will be further explained below. A second portion 10b of the inlet 10 may be straight or parallel cylindrical. ln other embodiments, such as seen in the mold assembly in Figs. 1b and 5, at least a portion of the second portion 10b of the inlet 10 is tapered outvvardly from a center of the inlet 10 and towards the inner surface 3 of the mold 1. ln some embodiments, the inlet has a waist. The outvvard taper or the waist facilitates braking any excess ceramic material remaining in the inlet after the ceramic slip has been introduced and let to solidify.

The die 2 may comprise a base 12, which may extend from the base structure 8. The exterior surface 5 of the die may be located at a top portion of the base 12 facing the mold 1. The base 12 may comprise a base surface extending from the exterior surface 5 of the die 2 to the outer surface of the die 2. At least a portion of the base 12 and the base surface may be tapered outvvardly from the exterior surface 5 of the die 2 towards the outer surface of the die 2. Similarly, the mold may have a recess 13 in which the base 12 is received. The recess of the mold 2 may be tapered corresponding to the tapered surface 12 of the die. Having tapered surfaces facilitates disassembling the die 2 and the mold 1 after ceramic material has been formed in the cavity 6, as will be discussed below.

The outlet 11a-1 1f may comprise one or several duct surfaces. ln some embodiments, the die comprises at least one die duct surface and the mold comprises a compiementary mold duct surface. For example, the mold duct surface may be at least partially tapered from the inner surface lO 3 outvvardly towards and exterior surface of the mold 1. The die duct surface may be at least partially tapered from the outer surface 5 of the die 2 towards the exterior surface of the die. The mold duct surface may extend from an exterior surface of the mold 1 to the inner surface 3. The at least one mold duct surface may at least partially facing the die duct surface, when the mold 1 and the die 2 are assembled, to form the outlet. ln some embodiments, such as is i||ustrated in the embodiments of Fig. 2a-c and Figs. 3a-3b, the die duct surface is formed at least partially by the base 12 of the die 2 and the recess 13 of the mold 1. The base 12 and the recess 13 may be spaced apart when the mold 1 and the die 2 are assembled to form a gap between the mold 1 and the die 2, which forms the duct. The gap may extend circumferentially around the base 12 of the die 2 and the recess 12 of the mold. The gap may have a uniform size. The gap may be sized to let air, captured in the cavity, out of the mold assembly while ceramic material is inserted into the cavity 6. The gap may be sufficiently small to maintain the ceramic material in the cavity 1 when the ceramic slip is pressed into the cavity. The size of the gap, or distance between the mold 1 and the die 2, may be in the range of a 0.01-0.1 mm. For example, the gap may be sized depending on the viscosity of the ceramic slip. ln some embodiments, the gap or duct extends around the periphery of the entire base 12 and the recess 13. Hence, this provides an outlet having a total cross-sectional area sufficient to let air out of the cavity 6 while the ceramic material is captured therein. Also, it prevents capturing of air in pockets. The outlet may start at the preparation line of the die 2 and extend around the entire circumference of the preparation line. This facilitates creating an even surface of the dental restoration with a precise fit against the preparation line of the tooth stump.

The mold 1 may comprises a first end surface 14, such as a top surface, a second end surface 15, such as a base surface, and a side surface 16, which extends between the first end surface 14 and the second end surface15. At least one recess 17a-17c may extend in at least one of the first end surface 14, the second end surface 15 and the side surface 16. The recess may facilitate breaking the mold 1 after the dental restoration has been formed and to remove the dental restoration from the mold 1. Furthermore, the recess, such as located in the second end surface 15 may additionally or alternative form the at least a portion of the mold duct surface, such as i||ustrated in the embodiments of Figs. 2a-2c, where in the mold duct surface comprises the recess 13 spaced apart from the base 12 and the at least one recess in the second end surface 15. Having a plurality of recesses 11a-1 1f in the second end surface 15 of the mold facilitates efficient evacuation of air from the cavity 6 without capturing of air bubbles as ceramic material is formed in the cavity 6. The width and/or the depth of the recess 17a-17c, 34a-34f may be in the range of 2-4mm. ln some embodiments, the recess 17a-17c, 34a-34f is v-shaped with a maximum width/depth of 2-4mm. The number of recesses may e.g. be 4-6. Multiple recesses facilitate controlled removal of the dental restoration from the mold assembly. Breaking the mold, such as with one or several cutting devices, may be made along one or several recesses 17a-17c, 34a-34f. lO The mold 1 and the die 2 may be made of resin, which facilitates producing the mold 1 and the die 2 with additive manufacturing techniques, such as 3D printing techniques. This production technique has a resolution that is higher than using milling techniques, at least for certain shapes. For example, the fissures of a dental restoration, the inner shape of a dental restoration particularly at the border betvveen the a side surface and an end surface to match the shape of a tooth stump, as well as the preparation line of the dental restoration can be produced with higher accuracy than with milling techniques. Hence, the overall resolution of a ceramic dental restoration may be made higher with a mold assembly according to embodiments of the present invention. For example, additive manufacturing can be produced using a liquid resin or a powder material. ln some embodiments, the material of the mold 1 and the die is a high temperature resin, which can tolerate temperatures that are sufficiently high to burn out for example any binder in the ceramic material in order to form a ceramic green body shaped as the dental restoration in the cavity 6, as will be described below. The high temperature resin may e.g. be the High Temp Resin 1L by Formlab. Another alternative high temperature resin is Veroclear RGD 810 by Stratasys.

According to embodiments, a method, which may be a partially or completely computer implemented method, for generating the mold assembly for molding a ceramic dental restoration, comprises obtaining a digital dental restoration 20 having at least a first surface and a second surface 21, 22, as illustrated in Fig. 4. The digital dental restoration 20 may be obtained from a digital impression taken with, e.g. an intra-oral scanner. Alternatively, the digital dental restoration 20 may be obtained from a physical impression of the patients dentition that has been digitized using a 3D scanner, such as a touch probe or laser scanner. The digital dental restoration 20 may be generated using a dental CAD (Computer Aided Design) software, where the dental restoration 20 is designed to fit the situation captured by the impression, such as on one or several a teeth stumps or implants, and fit relative to neighboring and antagonistic teeth. An enlargement factor may be applied to the digital dental restoration 20 in order to take any shrinkage of the final ceramic dental restoration during sintering into account. The enlargement factor is dependent on the actual composition of the ceramic material being used. For example, an enlargement factor in the range of 18-28% may be used for a ceramic material.

According to embodiments of the method, a digital mold body 30 having a predetermined shape may be obtained, such as is illustrated in Figs. 5a-5d. The digital mold body may comprise at least one digital mold 31 and at least one digital die 32 forming a mold assembly. The digital mold 31 and the digital die 32 may initially have pre-determined shapes, which are modified using the digital dental restoration 20. The exterior shape of the digital mold 31 and the digital die 32 may include any of the features discussed above with regard to embodiments of the physical mold assembly, such as the inlet 10, the outlet 11a-11f, the base structure 8, the top surface 14, the base surface 15, the side surface 16, the least one recess 17 and/or the alignment features. The digital mold 31 and the digital lOdie 32, as well as the digital dental restoration may be provided in a 3D file format, such as the STL, 3DS, IGES, STEP, OBJ, FBX, and/or the COLLADA file format.

Furthermore, according to embodiments of the method, the digital dental restoration 20 is positioned within the digital mold body 30 and a mold cavity is formed within the digital mold body based on the shape of the digital dental restoration 30. Hence, the cavity in the digital mold body 30 may also have the shape of the digital dental restoration 20. A 3D model forming the digital dental restoration and one or several 3D models forming the digital model 30 body may be combined or merged such that the surfaces of the digital dental restoration 20 are transferred to the digital mold body 30. Thus, digitally forming a mold cavity according to embodiments of the invention may comprise forming the inner surface 3 of the mold 1 may be based on the first surface of the digital dental restoration 20. Forming the outer surface 5 of the die 2 may be based on the second surface of the digital dental restoration.

According to embodiments of the method, the positioning of the digital dental restoration 20 may comprise positioning the digital dental restoration relative at least one inlet 33 of the digital mold 32. The inlet 33 may extend from an exterior of the digital mold body 30 into the cavity for receiving a ceramic material in the mold cavity. The inlet may be tapered in the first and/or the second portion, as has been described above. Also, the positioning may comprise positioning the digital dental restoration 20 relative to at least one outlet 34a-34f, whereby the outlet extends from the mold cavity to the exterior of the digital mold body 30 when ceramic material is inserted into the mold cavity. Furthermore, embodiments of the method may comprise forming an interface between the digital mold 31 and the digital die 32 that extends from the mold cavity to the exterior of the digital mold body 30. This may comprise forming a tapered base extending from end of the cavity of the mold assembly corresponding to the preparation line 23 of the digital dental restoration 20 to the base structure of the digital die 32. A corresponding opposing tapered surface may be formed in the digital mold 31, as has been described above with regard to embodiments of the physical mold assembly. The tapered surfaces may be spaced apart to form the duct surfaces and the outlet, as has also been described above with regard to embodiments of the physical mold assembly.

Embodiments of the method may comprise producing the mold assembly based on the modified digital dental mold body 30 by additive manufacturing using a resin material, such as has been described above.

Fig. 6 illustrates embodiments of a device 100 for pressing a ceramic material, such as a ceramic slip, into the mold assembly, such as a mold assembly according to the embodiments described above.

The device comprises a chamber 101 for receiving a ceramic material. The chamber comprises a nozzle 102. ln use, the nozzle 102 may be placed at the inlet 10 of the mold assembly to insert the ceramic material in the cavity 6 of the mold assembly. The nozzle 102 may have an exterior end surface that is tapered. The tapered end surface may have the same angle of taper as lOthe taper of the first portion 10a of the inlet 10. Such complementary tapered surfaces provide a seal betvveen the nozzle 102 and the mold assembly during insertion of the ceramic material into the mold cavity 6 when the nozzle is pressed against the mold 1. Furthermore, the chamber 101 may be heatable in order to transform a ceramic material initially in solid form into a ceramic slip. For example, the ceramic material may be supplied as pellets or ingots, where ceramic powder material has been mixed with a binder and formed into the pellets or ingots before it is dried. When the pellets or ingots are heated above the melting temperature of the binder material, they are transformed to the ceramic slip. The chamber 101 may be removable from the device 100. ln order to create the slip, the chamber is removed from the device, filled with pellets or ingots, placed in a heating device, such as an oven and heated to above the melting temperature of the binder in the pellets or ingots, taken out of the heating device, and placed in the device 100 again. Alternatively, the chamberis part of a ceramic extruder for creating the slip. Such a ceramic extruder may use pellets or ingots as the base material, wherein the heating device may be built into the extruder. Thus, the chamber 101 may be permanently mounted in the device 100. As an alternative to pellets or ingots, a ceramic powder may be used. ln embodiments, a piston 103 is arranged press the ceramic material, when heated to a ceramic slip, through the nozzle 102. For example, the piston 103 may be manually, hydraulically and/or pneumatically operated. ln embodiments, a holder 110 may be configured to receive the mold assembly. The holder 110 may have an inner surface 111 and an opening 112. The inner surface 111 may be configured to at least partially abut the exterior surface of the mold assembly, such as the exterior surface of the mold 1 and/or the die 2. At the same, time, the inlet 10 of the mold assembly may be exposed through the opening 112 when the mold assembly is arranged in the holder 110. The holder 100 may be tubular. Also the holder may have one closed end. The holder may made of a material that prevents breaking of the mold assembly while the ceramic material is pressed into the mold assembly, such as made of a metallic or ceramic material. This provides for making the walls of the mold assembly surrounding the cavity 6 of the mold thinner, which reduces required amount of material of the mold assembly with associated reduction in production time, lowered cost, and reduced environmental burden.

The inner surface of the holder 110 may be tapered outvvardly from a first end to a second end. The opening of the holder 110 may be located at the first end, and wherein an external side surface of the mold is tapered from a first end towards a second end and configured to fit within the holder 110 such that the tapered inner surface of the holder 110 abuts the tapered external side surface of the mold 1, and the die 2 abuts the second end of the inner surface of the holder ln some embodiments, such as illustrated in Fig. 7, the holder 110 comprises a first holder part 113 and a second holder part 114 forming a tubular unit when assembled. The second holder part 114 may have threads to be screwed on mating threads on the first holder part lOAlternatively, the first holder part 113 and the second holder part 114 have snap fit features to hold the parts together. ln some embodiments, the second holder part 114 is made of a magnetic material. The device 100 may comprises a seat 115 for the holder 110. A reciprocating magnet 116 may be arranged opposing the second holder part 114, wherein the magnet 116 can be moved in a first direction to be in abutment with the second holder part 114, and can be moved in a second direction opposite to the first direction to remove the holder 110 from the seat 113 after the magnet 116 has been moved to be in abutment with the second holder part 114. The arrangement with a seat 115 for the holder 110 and the magnet 116 may also be employed in embodiments where the holder 110 is made in a single unit or part. ln some embodiments, the inner surface 111 of the holder 110 is tapered outwardly from the opening 112 towards the opposing end, such as towards the second holder 114. ln some embodiments, the inner surface is tapered along the entire surface from the opening 112 to the opposing end, such as to an inner transverse surface of the holder, which may be formed by the second holder part 114. The mold assembly, with the mold 1 and the die 2, may have correspondingly tapered surfaces that are in abutment with the inner surface 111 of the holder when the mold assembly is arranged therein. This facilitates prevention of the mold assemblyjamming in the holder 110, with subsequent risk of fracturing the dental restoration when removing the mold assembly.

Furthemore, the inner surface of the holder may comprise at least one alignment member at the inner surface that has a shape that is complementary to the alignment members of the mold assembly, such as described with regard to the embodiments illustrated in Figs. 5a-5c. Hence, when each of the mold 32 and the die 32 are inserted separately or together into the holder, they are rotationally aligned in a predetermined rotational position.

Embodiments comprise a method for forming a dental restoration green body with the mold assembly, such as according to the embodiments described above. The method comprises assembling the mold assembly, such as by inserting the die 1 into the mold to form the mold cavity 6 having a shape of the dental restoration. The mold assembly may be mounted in the device 100 for pressing ceramic material into the mold assembly, such as have been described above with regard to embodiments of the device 100. Ceramic material in the form of pellets or ingots may be introduced into the chamber 101. Then, the chamber 101 of the device 100 containing ceramic material may be heated to form a ceramic slip from the ceramic material, such as by heating the chamber 101 above the melting temperature of a binder of the ceramic material. Alternatively, a ceramic slip is introduced into the chamber 100, such as using a ceramic extruder.

According to embodiments of the method, the nozzle 102 of the chamber 101 is positioned at the inlet 10 of the mold assembly. A seal may be created betvveen the nozzle 101 and the inlet 10 of the mold assembly by having complementary surfaces of the nozzle 102 and the inlet 10, such as described with regard to embodiments of the inlet 10 and embodiments of the nozzle. The seal may lObe created by pressing the nozzle 101 towards the inlet 10. For example, the end of the chamber 101 opposing the nozzle 102 may be pressed towards the inlet 10 when the chamber 101 and the mold assembly are arranged in the device, such as in a holder 110 described in embodiments above. The pressing the nozzle 102 towards the chamber 101 may be done manually by hand force, pneumatically, or hydraulically, similar to the magnet 116 as described above. Alternatively, the magnet 116 as such is used to press the holder 110 towards the chamber 101 and the nozzle 102, which may be fixed in the device According to embodiments of the method, the ceramic slip in the chamber 101 may be pressed into the cavity 6 of the mold assembly while air, captured in the cavity 6 formed by the mold 1 and the die 2, are pressed through the outlet of the mold assembly.

According to embodiments of the method, the ceramic slip captured in the cavity 6 may be cooled below the melting temperature of the binder of the ceramic material in order to form a dental restoration green body. Once the ceramic material has solidified, the dental restoration green body may be removed from the mold assembly. ln some embodiments, the dental restoration green body is removed by first separating the mold 1 and die 2, wherein the dental restoration green body is captured in the die. Then the dental restoration green body may be removed from the mold 2, such as by breaking the mold in separate pieces. For example, a mold having recesses at the exterior surfaces, as described above with regard to embodiments of the mold 1, may facilitate breaking the mold 1 while not fracturing the dental restoration green body. Finally, the dental restoration green body may be sintered to the final dental restoration.

As can be seen in Fig. 1a, at least one of the mold 1 and the die 2 may have a chamfer 18a, 18b around the perimeter of the mold 1 and/or the die 2. The chamfer 18a of the mold may be located at the intersection of the side surface 16 and the end surface 15 of the mold 1. The chamfer 18b of the die may be located at the intersection of a side surface of the base structure 8 and a top surface of the base structure 8. The chamfer 18a, 18b may extend partially or completely around the perimeter of the mold 1 and/or the die 2, respectively. The chamfer 18a, 18b facilitates separating the die 1 from the mold 2, and particularly reduces the risk of fracturing the dental restoration green body when formed therein.

The ceramic starting material to be supplied in the chamber may be a ceramic compound, such as a zirconium compound. The ceramic compound may be a ceramic injection molding compound. Such injection molding compounds are available by Tosoh Corporation, Japan, in different colors as well with different ceramic materials. The actual ceramic compound can be selected depending on, e.g., type of dental restoration, tooth position, etc.. Certain compounds have a higher strength whereas others have better aesthetics. The ceramic material may be converted into a ceramic slip at a temperature below the melting temperature of the mold assembly. After the dental restoration has been formed and removed from the mold assembly, it may go through a lO dewaxing and sintering process. Finally, the dental restoration may go through a finishing process including, e.g., grinding, polishing, and/or coloring.

As will be apparent, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure.

Conditional language used herein, such as, among others, "can," "could," "might," "may," "e.g.," and the like, unless specifically stated othen/vise, or othen/vise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.

Any process descriptions, elements, or blocks in the flow diagrams described herein and/or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included within the scope of the embodiments described herein in which elements or functions may be deleted, executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those skilled in the art. lt should be emphasized that many variations and modifications may be made to the above-described embodiments, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

The present invention has been described above with reference to specific embodiments. However, other embodiments than the above described are equally possible within the scope of the invention. Different method steps than those described above may be provided within the scope of the invention. The different features and steps of the invention may be combined in other combinations than those described. The scope of the invention is only limited by the appended patent claims.

Claims (15)

1. A mold assembly for molding a ceramic dental restoration, comprising, at least one mold §_fš__iï¿__having an inner surface gjjtfguand a first alignment member, at least one die _having an outer surface =">.=_and a second alignment member, at least one inlett -\§1\“ M; “ v* for receiving a ceramic material, at least one outlet gljlj' '* j¿__for letting air out of the mold assembly when ceramic material is inserted into the mold assembly, wherein the mold ^“ '§__with the innersurface ' i cavity a pre-determined shape when the mold >___:_\and the die the first alignment member and second alignment member in a predetermined relative rotational position.

2. The mold assembly according claim 1, wherein the inlet located in the mold

3. The mold assembly according to any of claims 1 or 2, wherein the inlet a first portion is tapered inwardly from an exterior surface of the mold towards a center of the inlet and the inlet__="_j in a second portion is tapered outvvardly from a center of the inlet towards the inner surfaceíjgšg.

4. The mold assembly according to any of the previous claims, wherein the mold has a mold duct surface extending from an exterior surface of the mold to the inner surface . .\

5. The mold assembly according to claim 4, wherein the die ¿§_'_§___comprises a base " " extending from an exterior surface of the die to the outer surface of the die__{_§_§, the base comprises a die duct surface, and the base; is configured to be received within a recess _of the mold, and the mold duct surface is facing the die duct surface, when the moldiåë xi- n i and the die íšg-aelre assembled, to form said outlet.

6. The mold assembly according to claim 5, wherein the mold duct surface is at least partially tapered from the inner surfacejjšg towards an exterior surface of the mold__¿'_jš__i?¿, and the die duct surface is at least partially tapered from the outer surface towards the exterior surface of the die_g§'_.ïš_}_.

7. The mold assembly according to any of the previous claims, wherein the mold comprises a first end surfaceui: a second end surface_{_fš__í>§_t¿, a side surfaceurjjgjtfgl; extending between the first end surface ° and the second end surface " and at least one recess gjgvextending in at least one of said first end surface; and said side surface__:;_'j;_§§§.

8. The mold assembly according to any of the previous claims, wherein the die__=:_'jš__§ and 'Fx the mold gvare made of resin. lO

9. A method for generating a mold assembly for molding a ceramic dental restoration, comprising obtaining a digital dental restoration having at least a first surface and a second surface; obtaining a digital mold body omprising a digital mold__§ i .___and a digital die ' “ ' forming a mold assembly; positioning the digital dental restoration within the mold bodyg: and forming a mold cavity within the mold body having the shape of the digital dental restoration; wherein said forming a mold cavity comprises forming an inner surface__i§;_“:{_:=_ of the digital mold based on the first surface of the digital dental restoration, and forming the outer surface of the digital u said positioning comprises positioning said digital dental restoration relative at least one inle of the digital moldgjjtfgjgå, whereby the inletuiijgšgjgšgš extends from an exterior of said digital mold body positioning said digital dental restoration relative to at least one outletgl: ' outlet =__extends from the mold cavity to the exterior of the digital mold bodyi forming an interface betiiveen the digital mold the digital die =; t_.__.__that extends from the mold cavity to the exterior of the digital mold

10. The method according to claim 9, comprising producing the mold assembly by additive manufacturing in a resin material.

11. A method for forming a dental restoration green body with the mold assembly of any of claims 1-8, comprising, assembling the mold assembly of any of claims 1-8, heating a chamber gg; \__containing ceramic material to form a ceramic slip; positioning a nozzle - .___=__of the chamber "§_}__in the inlet the mold assembly; pressing the ceramic slip into the cavity of the mold assembly while pressing air, captured in the cavity formed by the mold ¿:§j§_:=__and the di through the outlet gif' “ ' the mold assembly; and cooling the ceramic slip captured in the cavity to form a dental restoration green body;and removing the dental restoration green body from the mold assembly. into the cavity for receiving a ceramic material in the mold cavity, and \ - _of lO

12. A device for pressing a ceramic slip into the mold assembly of any of claims 1-8, wherein the device comprises a heatable chamber ' for receiving a ceramic material, said chamber a nozzle_' " '“ a piston__=_;____ through the nozzle__=:_ a holder an inner surface __i__,.__and an openingi abut an exterior surface of the mold §j§g__and an exterior surface of the die §¿¿__while the inlet the mold assembly is exposed through the opening §§-;f¿__when the mold assembly is arranged in the holder__¿§jš ^~' \. :IS

13. The device according to claim 12, wherein the inner surface of the holder; w tapered outvvardly from a first end to a second end, the opening _-;¿__of the holderijgjg is located at the first end, and wherein an external side surface of the moldurjjg; is tapered from a first end towards a second end and configured to fit within the holder "'“§_such that the tapered inner surface of the holder__s§_1__l' gabuts the tapered external side surface of the mold, and the die §_i_-§j¿__abuts the second end of the inner surface of the holderi

14. The device according to claim 13, wherein the holderg: ïg__comprises a first holder part Égjgand a second holder part___:§j§_ štafter the magnet “\.