Pre-colored slurry for ceramic multi-color inkjet 3D printing

Abstract

To provide a method and apparatus of producing a dental restoration by jet-printing using a three-dimensional printing method, enabling the ceramic dental restoration to be produced with a natural appearance and faithful reproduction of the original color.SOLUTION: A method of producing a dental restoration by jet-printing, includes the steps of jet-printing (S101) a dentin core of the dental restoration using a plurality of opaque ceramic slurries having different colors from each other, and jet-printing (S102) the tooth enamel of the dental restoration using a translucent ceramic slurry.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a dental prosthesis by jet printing and a manufacturing apparatus for manufacturing a dental prosthesis by jet printing.

Background Art

[0002] Today, a solvent-based ceramic slurry that has been colored in various ways in advance, for example, a slurry made of zirconium dioxide, is selectively applied in the form of droplets in multiple layers stacked one on top of the other using an inkjet printing method and dried. However, the processing of highly filled ceramic slurries requires high performance requirements regarding particle size, degree of filling, viscosity, abrasiveness, and corrosiveness for the printing heads used. Inkjet printing of aqueous slurries provides an alternative to solvent-based slurries.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to manufacture a ceramic dental prosthesis using a three-dimensional printing method so as to have a faithful and natural appearance in the original color.

Means for Solving the Problems

[0004] The above technical problems are solved by the subject matter of the independent claims. Technically preferred embodiments are the subject matter of the dependent claims, the detailed description of the invention, and the attached drawings.

[0005] According to a first aspect, there is provided a method for manufacturing a dental prosthesis by inkjet printing, the method including the steps of inkjet printing a dentin core of a dental prosthesis using a plurality of opaque ceramic slurries having mutually different colors; and inkjet printing an enamel of the dental prosthesis using a translucent ceramic slurry. As the ceramic slurry, an aqueous or solvent-based slurry can be used. For this method, a limited number of pre-colored slurries are provided in order to reduce the number of required print heads and achieve a high aesthetic and functional quality of the dental prosthesis despite this reduction.

[0006] An opaque slurry is a non-translucent slurry that does not transmit any light after a sintering process. In contrast, a translucent slurry is a slurry that partially transmits light after a sintering process but does not allow a clear image or shape to be recognized. The opposite (relative) property to translucency is opacity (non-translucency). If a sintered slurry, i.e., a finished ceramic, has a high translucency, then the ceramic has a low opacity in the dental prosthesis, and vice versa. Before the sintering process, the optical properties of the corresponding slurries are generally different. Translucency or opacity is finally formed in the sintered ceramic only by the chemical composition of the slurry associated with the sintering process. That is, the optical properties of translucency or opacity are the result of the sintering process.

[0007] The opaque slurry contains, for example, 1.5 to 4.5 mol%, preferably 2 to 4 mol%, and most preferably 2.5 to 3.5 mol% of Y 2 O 3 -stabilized Z r O 2 particles.

[0008] The translucent slurry contains, for example, 4.0 to 8.0 mol%, preferably 4.0 to 7.0 mol%, and most preferably 4.0 to 6.0 mol% of Y 2 O 3 -stabilized Z r O2 It contains particles.

[0009] According to a technically preferred embodiment of this method, the yttrium content of the translucent ceramic slurry is higher than that of one of the opaque ceramic slurries. Thereby, for example, a technical advantage is achieved in that a slurry highly suitable for forming various regions having different degrees of translucency, i.e., high in enamel and low in the dentin core, in a sintered dental prosthesis is used.

[0010] According to another technically preferred embodiment of this method, the dentin core of the dental prosthesis is additionally jet-printed using a colored translucent slurry. Thereby, for example, a technical advantage is achieved in that the natural appearance of the dental prosthesis is further improved.

[0011] According to another technically preferred embodiment of this method, a color scheme having a limited color space for the slurries for the dentin core is formed. The limited color space is adapted for coloring the dental prosthesis. When using a color scheme that covers the entire color space, a larger number of print heads are required. The production of such various slurries is also costly. That is, for example, a technical advantage is achieved in that the number of print heads and the number of slurries maintained as inventory can be reduced.

[0012] According to another technically preferred embodiment of this method, by mixing at least two types of slurries, one region of the dental prosthesis having an intermediate color value and / or an intermediate translucency value is created. Thereby, for example, a technical advantage is achieved in that a dental prosthesis having a color value or an opacity value that does not match that of the slurries used can be manufactured.

[0013] According to another technically preferred embodiment of this method, mixing is performed by creating a two-dimensional dithering pattern for a layer of a dental prosthesis. The dithering pattern suggests how different slurries are arranged in a two-dimensional plane to create intermediate color values and / or intermediate transparency values. Thereby, for example, a technical advantage is achieved that a dental prosthesis having a natural appearance can be manufactured.

[0014] According to another technically preferred embodiment of this method, different two-dimensional dithering patterns are used in successive layers of the dental prosthesis. Thereby, for example, a technical advantage is achieved that the occurrence of stripe or ripple patterns in the dental prosthesis is prevented.

[0015] According to another technically preferred embodiment of this method, one printing head is assigned to each storage tank of the slurries. Thereby, for example, a technical advantage is achieved that the dental prosthesis can be printed in a simple and fast manner.

[0016] According to another technically preferred embodiment of this method, the dental prosthesis is sintered in a sintering kiln. Thereby, for example, a technical advantage is achieved that a dental prosthesis having high strength can be manufactured.

[0017] According to another technically preferred embodiment of this method, a drying and / or debinding process is performed on the manufactured dental prosthesis before the sintering process. This drying and / or debinding process can be performed in an independent thermal process or be a process step preposed within the sintering process. Usually, drying is performed at a temperature of 25°C to 200°C, more preferably 30°C to 180°C, and most preferably 40°C to 150°C. Additionally in that case, the humidity can be adjusted to 10 to 90%, more preferably 15 to 85%, and most preferably 20 to 80%. Generally, the debinding treatment is performed at a temperature of 50°C to 600°C, more preferably 100°C to 600°C, and most preferably 200°C to 600°C. The heating rate is 0.1 to 10 K / min, more preferably 0.2 to 10 K / min, and most preferably 0.5 to 10 K / min.

[0018] According to a second aspect, the above-described technical problem is solved by a manufacturing apparatus for manufacturing a dental prosthesis by inkjet printing, which has a plurality of storage tanks containing opaque ceramic slurries having different colors for the dentin core and at least one storage tank containing a translucent ceramic slurry for the enamel. This manufacturing apparatus uses a three-dimensional multicolor printing method by material jetting of the ceramic slurry. By this manufacturing apparatus, the same technical advantages as the method according to the first aspect described above are achieved.

[0019] According to a technically preferred embodiment of this manufacturing apparatus, the manufacturing apparatus is provided with one separate printing head for each storage tank. Thereby, for example, the technical advantage that the dental prosthesis can be printed in a simple and fast manner is achieved.

[0020] According to another technically preferred embodiment of this manufacturing apparatus, the manufacturing apparatus is provided with storage tanks for at least two types of slurries, for example, storage tanks for 5, 6, 7, or 8 types of slurries. Thereby, for example, the technical advantage that a dental prosthesis with a natural appearance can be manufactured using a small number of printing heads and storage tanks is achieved.

[0021] According to another technically preferred embodiment of this manufacturing apparatus, a color scheme is formed that has a restricted color space for the various colors of the slurry for the dentin core. Thereby, for example, a technical advantage is achieved in that a smaller number of print heads or storage tanks can be used compared to the case of a complete color scheme.

[0022] According to another technically preferred embodiment of this manufacturing apparatus, the manufacturing apparatus includes a dithering module for calculating color intermediate values or translucency intermediate values by mixing at least two types of slurries. Thereby, for example, a technical advantage is achieved in that a dental prosthesis having a color value or opacity value that does not match that of the slurry used can be manufactured.

[0023] According to another technically preferred embodiment of this manufacturing apparatus, the dithering module is configured to use different two-dimensional dithering patterns in successive layers of the dental prosthesis. Thereby, for example, a technical advantage is achieved in that the occurrence of stripe or ripple patterns in the dental prosthesis is prevented.

[0024] According to a third aspect, the above-described technical problem is solved by an inkjet printing system including: a manufacturing apparatus for manufacturing a dental prosthesis by inkjet printing; at least one of a plurality of opaque ceramic slurries having different colors for printing the dentin core; and a translucent ceramic slurry for printing the enamel. By this inkjet printing system, the same technical advantages as those of the method according to the first aspect described above are achieved.

[0025] According to a technically preferred embodiment of this inkjet printing system, at least one of the plurality of opaque ceramic slurries and / or the translucent ceramic slurry is stored in a storage tank. Thereby, for example, a technical advantage is achieved in that the opaque ceramic slurry and / or the translucent ceramic slurry can be stored safely.

[0026] According to another technically preferred embodiment of this inkjet printing system, the storage tank is replaceable. Thereby, for example, a technical advantage that the solution can be easily changed is achieved.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0028] Next, embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] In FIG. 1, different parts of the tooth 105 are shown. The tooth 105 has an inner dentin core 101 and an outer enamel 103. There is an intermediate region 115 between the dentin core 101 and the enamel 103.

[0030] For the base coloring of the tooth 105, a turbid color, that is, an opaque dentin core 101 is required. The dentin core is visible through the incisal enamel 103. The enamel 103 is translucent. Translucent means partial light transmittance of an object. In order to make the dental prosthesis have an appearance as close to natural as possible, the above structure of the tooth 105 is also applied to the artificial dental prosthesis. Therefore, materials having various optical properties are used in the manufacture of dental prostheses.

[0031] Figure 2 schematically shows a dental prosthesis 100. The dental prosthesis 100 functions as a denture and is formed, for example, as a bridge, crown, veneer, inlay, onlay, abutment, partial or complete denture. The dental prosthesis 100 is composed of, for example, differently colored ceramic slurries, and the slurries contain a small amount of coloring components such as Fe 2 O 3 , Cr 2 O 3 , Mn 2 O 3 , Tb 2 O 3 , Pr 2 O 3 , Er 2 O 3 , Co 3 O 4 , NiO, TiO 2 , CeO 2 etc. Therefore, when the dental prosthesis 100 is three-dimensionally manufactured using an inkjet printing method, the slurry is selectively applied to the corresponding locations.

[0032] The dental prosthesis 100 is formed from successive layers printed one on top of the other. In that case, the ceramic powder of the slurry can be supplied in a given color and translucency in advance. By mixing the slurries, the target tooth color and target translucency of the dental prosthesis 100 within the corresponding spatial region are obtained.

[0033] After selectively applying a layer of the slurry by an inkjet printing method and evaporating water or a solvent, the layer is dried without cracking. What remains is a porous white body layer, which has a layer thickness of 1 μm to 50 μm and a density of at least 2.5 g / cm 3 . This process is repeated until the entire dental prosthesis 100 is three-dimensionally constructed layer by layer.

[0034] Figure 3 shows a schematic view of a manufacturing apparatus 200 for manufacturing a dental prosthesis 100 by inkjet printing of an aqueous or solvent-based slurry 109. A pre-colored slurry 109 is processed in order to additively machine a ceramic multi-material and multi-color dental prosthesis 100 by inkjet printing.

[0035] The manufacturing apparatus 200 comprises a plurality of storage tanks 107 containing ceramic slurries 109 for the dentin core 101, each having different optical properties. In addition, the manufacturing apparatus 200 comprises at least one storage tank 107 containing a translucent ceramic slurry 109 for manufacturing the enamel 103. A manufacturing apparatus for manufacturing a dental prosthesis by inkjet printing; at least one of a plurality of opaque ceramic slurries for printing dentin; and a translucent ceramic slurry for printing enamel, in combination, constitute an inkjet printing system.

[0036] In order to three-dimensionally construct the dental prosthesis 100 layer by layer, the ceramic slurries 109 are applied as a plurality of layers in droplet form using a print head 111 to which each ceramic slurry 109 is assigned. The print head 111 is operable in two directions and can therefore print the slurry 109 at any position. The slurry 109 is typically used with a droplet volume of 10 to 100 picoliters for selective material application, thereby eliminating the time-consuming debinding process. An electrically controlled piezoelectric element is used to eject the droplets. Alternatively, a bubble jet method can also be used.

[0037] The manufacturing apparatus 200 provides a reduced number of pre-colored and yttrium-doped neutral base slurries 109 in order to minimize the number of print heads 111 and yet achieve the aesthetics and functionality of the dental prosthesis 100.

[0038] Pre-colored slurries 109 are combined to mix the required tooth color. In that case, a subtractive color system, which spans a limited dental color space (dental color gamut), is used. Therefore, color synthesis, three-dimensional halftoning, or dithering of the slurries 109 pre-colored in different ratios is created within a specific dental color space (color gamut) that covers all common tooth colors but not all colors.

[0039] In that case, the slurries 109 pre-colored differently are selectively applied within one layer according to a 3D dithering algorithm executed by the dithering module 113. Therefore, the dithering module 113 includes a processor for executing the 3D dithering algorithm and a digital data memory for storing the calculated mixing ratio and the dithering algorithm. The processor includes any hardware system, component, or mechanism for processing data, signals, or other information. The processor can include a central data processing unit (CPU), a system with multiple data processing units (MPU), a dedicated electric circuit for executing functions, and other systems. The data memory can include a hard disk, a flash memory card, a random access memory (RAM), or a read-only memory (ROM).

[0040] During dithering, slurries 109 of various colors are selectively applied within the printing plane in a specific ratio and a two-dimensional printing pattern using an inkjet printing method. In addition, the 3D dithering algorithm calculates so that non-identical two-dimensional dithering patterns are applied one above the other in multiple layers. Thereby, optical effects such as stripes or ripple patterns in the case of a vertical surface can be prevented. Color synthesis, three-dimensional halftoning, or dithering of the slurries 109 pre-colored in different ratios is generated within the range of a specific dental color space (color gamut), but the color gamut covers all common tooth colors but not all colors in general.

[0041] FIG. 4 shows a block diagram of a method for manufacturing a dental prosthesis 100 by inkjet printing. In step S101, a dentin core 101 of the dental prosthesis 100 is inkjet printed using a plurality of opaque ceramic slurries 109 having different colors. In step S102, an enamel 103 of the dental prosthesis 100 is inkjet printed using a translucent ceramic slurry 109. Thereafter, the dental prosthesis 100 thus constructed is sintered in a sintering furnace.

[0042] There are slurries 109 used for constructing the enamel 103 at the incisal edge and slurries 109 used for constructing the dentin core 101. The difference between those slurries 109 lies in the translucency of the material, and the translucency for the enamel 103 is several times higher than that for the dentin core 101.

[0043] For example, the slurry 109 can be used in seven different base colorings, two of which are prepared for the enamel 103 and one additional carrier material 110 is prepared for the support structure. The carrier material pertains to organic components such as wax, paraffin, or carbon black slurry, etc.

[0044] 1 White, high translucency (Incisal edge / Incisal region), high Y-doping component 2 Yellow-brown, high translucency (Incisal edge / Incisal region), high Y-doping component 3 White, opaque, high strength (Dentin region) 4 Pink, translucent, strong (Dentin region, also suitable for incisal edge detailing) 5 Gray, translucent, strong (Dentin region, also suitable for incisal edge detailing) 6 Yellow, translucent, strong (Dentin region) 7 Yellow-brown, opaque, high strength (Dentin region) 8 Carrier material

[0045] According to another embodiment, there is only one type of translucent slurry 109 and five different types of slurry 109 prepared for coloring in the dentin core 101. In that case, a technical advantage is obtained that seven printing heads 111 (including the portion of the carrier material 110) are sufficient.

[0046] 1 Incisal edge, high translucency (8 - 9Y) (Incisal end / Incisal region) 2 White, opaque, high strength (Dentin region) 3 Pink, translucent, strong (Dentin region, also suitable for detailed formation of incisal edge) 4 Gray, translucent, strong (Dentin region, also suitable for detailed formation of incisal edge) 5 Yellow, translucent, strong (Dentin region, also suitable for detailed formation of incisal edge) 6 Yellow - brown, opaque, high strength (Dentin region) 7 Carrier material

[0047] The dentin core 101 is important for basic coloring, and the dentin core is visible through the enamel 103. In extreme cases, the enamel is colorless and highly translucent. Therefore, specially pre - colored and yttrium - doped slurries 109 are provided for coloring and the unique dental core / shell structure (dentin / enamel).

[0048] ZrO 2 In the case of the slurry 109, ceramic powders differently yttrium - doped (3 mol% yttrium - 3Y - TZP, 4 mol% yttrium - 4Y - TZP, 5 mol% yttrium - 5Y - TZP) can be used for different strengths. In that case, yttrium doping becomes a factor in the degree of translucency. Differently yttrium - doped ceramic powders have different characteristics.

[0049] 3Y - TZP = low translucency / high strength 4Y-TZP = Medium translucency / Medium strength 5Y-TZP = High translucency / Low strength

[0050] On the other hand, when using slurries 109 that are differently pre-colored and all have different translucencies and / or mechanical properties, a unique print head 111 is assigned to each of those slurries 109. For example, when using a common four-color color scheme to cover the entire color space and, in addition, using three patterns of slurries with different translucencies or strengths, 3×4 = 12 types of slurries 109 are required among 12 print heads. Manufacturing those different slurries 109 is also complex.

[0051] It is necessary to adapt the pre-colored slurries 109 with different yttrium contents to have consistent sintering characteristics. Adjustment of the sintering characteristics of individual layers can be carried out by adding a sintering activator or a sintering inhibitor to the coloring solution according to the purpose. The sintering activator is, for example, Zn in the form of a soluble salt 2 + ions or Mg 2 + ions, and can be added to the coloring solution, for example, as Zn(NO 3 ) 2 ·6H 2 O or Mg(NO 3 )·H 2 O, etc. The sintering inhibitor is, for example, Al in the form of a soluble salt 3 + or Y 3 + , and can be added to the coloring solution, for example, as Al(NO 3 ) 3 ·9H 2 O or Y(NO 3 ) 3 ·6H 2 O, etc.

[0052] All features described and illustrated in connection with the individual embodiments of the present invention can be the subject of the present invention in various combinations, thereby achieving effective advantages simultaneously.

[0053] All method steps can be carried out using an apparatus suitable for carrying out each method step. All functions carried out by the features in question can be method steps in this method.

[0054] The protection scope of the present invention is defined by the appended claims and is not limited by the features described or illustrated in the description.

Explanation of Signs

[0055] 100 Dental prosthesis 101 Dentin core 103 Enamel 105 Tooth 107 Storage tank 109 Slurry 110 Carrier material 111 Print head 113 Dithering module 115 Intermediate region

Claims

1. jet printing a dentin core of a dental prosthesis using a plurality of opaque ceramic slurries having mutually different colors; jet printing enamel of a dental prosthesis using a translucent ceramic slurry. A method for producing a dental prosthesis by jet printing.

2. 2. The method of claim 1, wherein the yttrium content of the translucent ceramic slurry is higher than the yttrium content of one of the opaque ceramic slurries.

3. 3. The method according to claim 1 or 2, wherein the dentin core of the dental prosthesis is additionally jet-printed with a pigmented translucent slurry.

4. 4. The method according to claim 1, wherein the various colors of the slurry for the dentin core form a color scheme having a limited color space.

5. 5. A method according to any one of claims 1 to 4, in which an area of ​​the dental prosthesis having an intermediate colour value and / or an intermediate translucency value is produced by mixing at least two slurries.

6. 6. The method of claim 5, wherein the blending is performed by creating a two-dimensional dithering pattern for one layer of the dental prosthesis.

7. 7. The method of claim 6, wherein different two-dimensional dithering patterns are used in successive layers of the dental prosthesis.

8. 8. A method according to claim 1, wherein a print head is assigned to each slurry storage tank.

9. 9. A method according to any one of claims 1 to 8, wherein the produced dental prosthesis is subjected to a drying and / or debinding step prior to the sintering process.

10. 10. A method according to any one of claims 1 to 9, wherein the dental prosthesis is sintered in a sintering kiln.

11. a plurality of storage tanks containing opaque ceramic slurries having mutually different colors for the dentin core; At least one storage tank containing a translucent ceramic slurry for enamel. A manufacturing device that produces dental prostheses by jet printing.

12. 12. The manufacturing apparatus of claim 11, wherein the manufacturing apparatus comprises a separate print head for each storage tank.

13. 13. The manufacturing apparatus according to claim 11 or 12, wherein the various colors of the slurry for the dentin core form a color scheme having a limited color space.

14. 14. The manufacturing apparatus according to any one of claims 11 to 13, further comprising a dithering module for calculating intermediate colour values ​​or intermediate translucency values ​​by mixing at least two types of slurries.

15. 15. The manufacturing apparatus of claim 14, wherein the dithering module is configured to use different two-dimensional dithering patterns in successive layers of the dental prosthesis.

16. A manufacturing apparatus for manufacturing dental prostheses by jet printing; at least one of a plurality of opaque ceramic slurries having mutually different colors for printing the dentin core; A semi-transparent ceramic slurry for printing enamel. Jetting printing system.

17. The jetting printing system of claim 16 , wherein at least one of the plurality of opaque ceramic slurries and / or the translucent ceramic slurry is stored in a storage tank.

18. 20. The jetting printing system of claim 17, wherein the storage tank is replaceable.

Images