An instant mixing toning inkjet 3D printing method and application in the preparation of dentures

Abstract

The application discloses an instant mixing and color adjusting inkjet 3D printing method and application in false tooth preparation, and belongs to the technical field of 3D printing. The method comprises the following steps: preparing multiple color inks added with magnetic particles; constructing a color value-ink ratio database; searching the database according to a target color to determine the proportion formula of required inks; spraying different color inks to corresponding units according to the formula; driving the magnetic particles to move through a magnetic field to make each color ink instantaneously and sufficiently mixed to realize accurate color adjusting; and finally solidifying and forming. The application introduces magnetic particles into inks and combines with an external dynamic magnetic field to solve the technical problem that multiple color inks are difficult to be instantaneously and uniformly mixed in micron-level space in inkjet 3D printing. The method is especially suitable for preparing false teeth with spatial omnidirectional and continuous natural color gradient, and significantly improves the aesthetic effect.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing technology, specifically relating to an instant mixing and color-matching inkjet 3D printing method and its application in denture preparation. Background Technology

[0002] Natural teeth are not uniform in color; instead, they exhibit a distinct spatial color gradient, gradually transitioning from the neck to the incisal edge and from the center to the sides. To improve the aesthetics of dentures and make them closely resemble the color of natural human teeth, many researchers have made numerous attempts in the coloring process during denture fabrication in recent years. For example, lithium disilicate microcrystalline glass-ceramic restorations are formed by cutting or hot-pressing and then manually colored to simulate the spatial color gradient characteristics of natural teeth. However, this method suffers from drawbacks such as uneven coloring and significant color differences between the inner and outer layers. Another example is the invention patent CN120987636A, which describes a method for preparing translucent gradient multicolor zirconia material using photopolymerization. This method utilizes photopolymerization 3D printing technology to achieve layered gradient color changes in zirconia dentures from top to bottom. However, this technology can only achieve unidirectional gradient color changes and cannot achieve simultaneous gradient color changes in multiple spatial directions. Furthermore, the color transitions between layers are not natural and still fall short of the appearance of natural human teeth.

[0003] Inkjet 3D printing (also known as material jetting) is a high-precision additive manufacturing technology that uses multiple nozzles to precisely jet liquid material in micron-sized droplets onto a forming platform, simultaneously performing curing processes such as ultraviolet light curing and thermal curing to stack the materials layer by layer. This technology can achieve simultaneous printing of multiple materials by loading different materials onto different nozzles, and features high printing accuracy and high surface finish. It is particularly advantageous in the field of denture fabrication, where it has more advantages than other 3D printing processes.

[0004] However, in the current process of using inkjet 3D printing technology to prepare dentures, there is still a lack of good solutions on how to make dentures have spatial omnidirectional gradient color changes so that they can closely resemble human natural teeth. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an instantaneous mixing and color-matching inkjet 3D printing method and its application in denture fabrication. The specific technical solution is as follows: An instantaneous mixing and color-matching inkjet 3D printing method, comprising the following steps: S1: Ink preparation, according to specific product requirements, prepare various inks of different colors and add magnetic particles, and load the inks into different printheads; S2: Color gradient control, pre-establish a color value-ink ratio formula database, and find the corresponding color value in the database according to the target color value to obtain the ink ratio formula for the target color value; S3: Inkjet process control, according to the ink ratio formula obtained in S2, control each printhead to spray a quantitative amount of ink to the target position; S4: Color mixing process, apply a magnetic field to the sprayed ink to drive the magnetic particles in the ink to move, so that the ink is mixed; S5: Solidify the ink at the target position, repeat the above process until inkjet printing is completed.

[0006] Preferably, in step S1, preparing inks of different colors involves adding coloring powder of a specific color and proportion to the ink.

[0007] Preferably, in step S2, a color value-ink ratio formula database is pre-established. Specifically, this includes adjusting the proportions of various inks in step S1, printing color blocks, generating a sample set, measuring the measured color value of each color block, establishing a mapping relationship model from ink ratio formula to color value, and storing it as a color value-ink ratio formula database.

[0008] Preferably, in step S3, according to the ink ratio formula obtained in S2, the nozzles are controlled to spray a quantitative amount of ink to the target position. Specifically, this includes constructing a three-dimensional model of the denture, decomposing the model into micro-cubic units, assigning a color value to each unit based on the measured color data of the patient's adjacent teeth, searching the database based on the color value to obtain the corresponding ink ratio formula, thereby obtaining the three-dimensional coordinates and ink ratio formula of each unit, and controlling the spraying position and ink volume of each nozzle accordingly.

[0009] Preferably, in step S4, applying a magnetic field to the ejected ink specifically includes arranging an array of electromagnets on the printing platform, and after each printhead completes ink ejection, controlling the electromagnets to generate a rotating magnetic field or an oscillating magnetic field covering the printing target position.

[0010] Preferably, step S1 further includes a water-soluble support material ink, the composition of which includes one or more of polyvinyl alcohol, polyethylene glycol, and polyacrylic acid, used as a temporary support for the printed structure, which does not contain the constituent materials of the product to be printed, and can be removed by water after printing.

[0011] Preferably, in step S1, a variety of inks of different colors are prepared, specifically including inks No. 1 to No. 5, the specific components of which include lithium silicate glass powder, coloring powder, dispersant, binder, magnetic particles, pH adjuster and solvent.

[0012] Preferably, the inks numbered 1 to 5 are colorless, yellow, magenta, cyan, and black, respectively.

[0013] Preferably, the magnetic particles are any one or a combination of at least two of the following: magnetic iron oxides, cobalt-based materials, and soft magnetic alloy particles.

[0014] A denture, characterized in that it is prepared using the above-mentioned inkjet 3D printing method, has a spatial omnidirectional color gradient variation.

[0015] The beneficial effects of this invention are as follows: To enable the prepared dentures to possess a spatial omnidirectional color gradient, making them more aesthetically similar to the color of natural human teeth, this invention improves the existing inkjet printing process, allowing inkjet printing and color mixing to occur during the printing process, reducing the need for additional color mixing equipment; by pre-establishing a color value-ink ratio formula database, the ink ratio formula can be quickly found and locked according to the color value requirements of each unit of the model to be printed during the printing process; magnetic particles are added to the ink, and the magnetic field drives the magnetic particles to move in the ink, causing different inks to mix, thereby presenting the pre-designed color. The magnetic particles, magnetic field, and base color ink are mixed in different proportions, and the combination of the three achieves the control of multiple colors in inkjet printing, thus enabling precise and flexible control of the color of each unit in each direction of the denture to be printed, thereby producing dentures with omnidirectional color gradient changes. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-section of a denture.

[0017] Figure 2 This is a schematic diagram of the longitudinal section of the denture.

[0018] Figure 3 This is a diagram illustrating the printing process. Detailed Implementation

[0019] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] This invention provides an instant mixing and color-matching inkjet 3D printing method, taking the preparation of dentures as an example.

[0022] S1: Preparation of printing materials (hereinafter referred to as ink).

[0023] Step S1 specifically includes classifying the ink into two categories based on functional requirements: No. 0 water-soluble support material ink and No. 1–5 lithium silicate ink. No. 0 ink is a water-soluble support material ink, composed of one or more water-soluble support materials such as polyvinyl alcohol, polyethylene glycol, and polyacrylic acid. It is used for temporary support of the printed structure and does not participate in the molding process of the denture body. It does not contain lithium silicate glass powder and can be removed by water after printing.

[0024] Inks No. 1–5 are lithium silicate inks, composed of lithium silicate glass powder, coloring powder, dispersant, binder, magnetic particles, pH adjuster, and solvent, prepared by wet ball milling. The preparation method involves sequentially adding lithium silicate glass powder, 0-5 wt% inorganic coloring powder, 0.1-3.0 wt% binder, 0.1-2.0 wt% magnetic particles, and 0.5-3 wt% dispersant to a solvent, adjusting the pH to 9-11, and ball milling to achieve uniform mixing, resulting in a stable dispersed ink with a solid content of 30-60 vol%. The dispersant is one or a combination of several of the following: BYKJET-9133, BYK-111, BYK-110, ammonium citrate, ammonium polyacrylate, sodium polyacrylate, polyacrylic acid, ammonium polymethacrylate, triethanolamine, Span 80, Tween 81, sodium hexametaphosphate, sodium carboxylate, and polyethyleneimine. The binder is one or a combination of thermoplastic resins (such as methylcellulose, ethylcellulose, hydroxyethylcellulose) and photosensitive resins, wherein the thermoplastic resin is suitable for assisting thermosetting molding, and the photosensitive resin is suitable for assisting photocuring molding. The pH adjuster is ammonia or NaOH. The solvent is a mixture of deionized water and an organic solvent, wherein the mixing ratio of deionized water to organic solvent is between 1:8 and 1:1.

[0025] It should be noted that in this embodiment, ink No. 1 is designated as W ink (colorless), meaning that the ink as a whole and the lithium silicate glass powder within it are in an undyed state, and the content of coloring powder is 0, serving as the standard for brightness adjustment. Inks No. 2-5 are designated as colored inks with colors Y (yellow), M (magenta), C (cyan), and K (black). The specific colors of inks No. 2-5 are controlled by adjusting the color and proportion of the coloring powder added to the ink. The coloring powder is a transition metal oxide and rare earth colorant, selected from any one or at least a combination of two of V2O5, NiO, MnO, CuO, Cr2O3, CeO2, Pr2O3, Nd2O3, Er2O3, Tb4O7, Tm2O3, Sm2O3, Dy2O3, Bi2O3, and Yb2O3.

[0026] The magnetic particles in the ink are any one or a combination of at least two of the following: magnetic iron oxides (such as magnetite, ferric oxide), cobalt-based materials (such as cobalt tetroxide), and soft magnetic alloy flakes / particles (Fe-Cr, Fe-Ni). The magnetic particles primarily function to mix the ink during printing; their amount and type should be adjusted flexibly as needed to avoid affecting the overall ink color.

[0027] S2: Color gradient control.

[0028] Color gradient refers to the color gradient created by controlling the color of different spatial units within a denture. The colors of these different spatial units are formed by mixing one or more inks (i.e., base or primary color inks) in a certain proportion. Color control follows the three elements of dental color science: lightness is controlled by the proportion of ink (No. 1 W), saturation is controlled by the ratio of the total amount of colored inks (No. 2-5) to ink (No. 1 W), and hue is adjusted by the ratio of ink (No. 2 Y) to ink (No. 3 M). Ink (C) is used to fine-tune the greenish hue, and ink (K) is used to reduce lightness and enhance color gradation. In practical applications, the VITA 3D-MASTER 26-color shade guide can be used as a reference standard. This shade guide is arranged in three dimensions according to lightness (5 levels), hue (L yellowish, M neutral, R reddish), and saturation (1, 1.5, 2, 2.5, 3). Natural tooth color is mainly concentrated in the yellow-red range. However, this system actually uses continuous color space inkjet printing, and the color output is precisely driven by CIE Lab* color values. The 26 colors are only used as a discrete reference and are not limited by the number of colors. The CIE Lab (also known as CIELAB) is an objective colorimetric system developed by the International Commission on Illumination (CIE) to mathematically describe all colors perceived by the human eye. L* represents lightness (0 for pure black, 100 for pure white), and a* and b* represent the red-green axis (+a for red, -a for green) and the yellow-blue axis (+b for yellow, -b for blue), respectively. These two axes work together to determine the hue and saturation of teeth. Alternatively, the principle of mixing the three primary colors of red, green, and blue can also be used for color mixing.

[0029] The mapping from the target color value to the mixing ratios of the five inks (numbers 1-5) is achieved by consulting a color database. First, the proportions of the five inks are varied, and a large number of standard color patches are printed to generate a sample set. After measuring the actual color value of each patch, a mapping model from the ink ratio formula to the target color is established and stored as a database. If the desired target color value is not obtained, the ink ratios are repeatedly adjusted and printed until the ink ratio formula corresponding to the target color value is obtained. This mapping between the ink ratio formula and the color value is then stored as a color database. During subsequent printing, the ink ratio formula corresponding to the patch closest to the target unit color value is found in the database. This information is used to control the proportion of each ink ejected from the printhead, thus printing the desired color for the target unit.

[0030] S3: Inkjet process control.

[0031] Six independent ink printheads are mounted on the same printhead to form an integrated multi-material printing unit. Printhead 0 is loaded with water-soluble support material, while printheads 1 through 5 are loaded with ink of the corresponding color.

[0032] In the digital processing stage before printing, after adding support structures to the 3D model of the denture obtained from the oral scan, the model is decomposed into tiny cubes (units) to obtain the 3D coordinates of each unit. Each unit corresponds to a spatial unit that can be independently allocated ink. The color of any unit can be designed based on the measured color data of the patient's adjacent teeth. Each unit has an independent CIE L*a*b* color value. The design ratio of each ink layer needs to be implemented to the unit level with precision. Then, the designed color of each unit is converted into different ink mixing ratio data.

[0033] First, an intraoral scanner, along with a spectrophotometer, electronic colorimeter, and camera, is used clinically to acquire complete CIE Lab* point cloud data of adjacent teeth. Each point cloud node records its three-dimensional coordinates and corresponding color value. Referring to the adjacent tooth color data, the color of the denture to be prepared is designed, forming a single-layer unit mesh. Each mesh unit stores a set of Lab target color values. Based on the Lab target color values, a color database is searched. According to the mapping relationship between color values ​​and ink ratios in the database, the ink ratio data corresponding to each unit color value of the denture to be prepared is obtained.

[0034] Based on the three-dimensional coordinates of each unit and its corresponding ink ratio data, printheads 0 to 5 are controlled to perform inkjet operations.

[0035] S4: Color mixing process.

[0036] For inkjet printing, because it uses multiple printheads to supply ink, after printheads 0 to 5 complete their ink ejection at the target printing location, the different inks ejected by each printhead are often stacked in layers at the target location. Because they are not fully mixed, the desired color cannot be obtained. To solve this problem, this invention provides an instant mixing and color matching method. Specifically, during the ink preparation stage, a certain amount of magnetic particle material is added to inks 1 to 5. Simultaneously, an array of electromagnets is arranged above, below, or around the printing platform. After each printhead completes its ink ejection operation, the current in the electromagnets is controlled to generate a rotating or oscillating magnetic field covering the target printing location. This causes the magnetic particles in each ink to move with the magnetic field, thereby fully mixing the inks to achieve the desired color.

[0037] S5: Curing process.

[0038] After the color mixing process is complete, the ink at the target location is cured using a heating module or other curing methods. This process is repeated until the entire denture is inkjet printed. After printing, the denture preform is immersed in water (or an ultrasonic water bath) to dissolve and remove the water-soluble support material. After rinsing with deionized water, it is dried in sections at 60-120 degrees Celsius. If necessary, cold isostatic pressing or hot isostatic pressing is performed to improve the strength and density uniformity of the preform. Finally, after degreasing, crystallization heat treatment (nucleation and crystallization), and sintering densification, the finished denture is obtained.

[0039] The above method, by improving the inkjet 3D printing process, achieves real-time mixing and color adjustment of inks during printing. Furthermore, combined with the inherent characteristics of inkjet 3D printing, it enables the fabrication of dental prostheses with omnidirectional uniform color gradients. Specific implementation methods are as follows: The solid content of the glass-ceramic ink was set at 35 vol%, with 2 wt% coloring powder, 2 wt% BYK-111 as dispersant, 0.5 wt% methylcellulose as binder, and 0.2 wt% cobalt tetroxide as magnetic particles. Specifically, ink No. 1 was a colorless ink; ink No. 2 used iron oxide as coloring powder; ink No. 3 used neodymium oxide as coloring powder; ink No. 4 used cobalt oxide as coloring powder; and ink No. 5 used nickel oxide as coloring powder.

[0040] First, dispersant and binder are added to deionized water. The pH of the system is adjusted to 10 using sodium hydroxide solution. After magnetic stirring and mixing, lithium silicate powder, magnetic particles, and coloring powder are added sequentially. After ball milling, 3D printing ink is obtained. Each ink is loaded into its corresponding container, and the printer is controlled by a computer to output each ink in proportion.

[0041] Before printing the dental restoration, CT technology and an intraoral scanner were used to collect the patient's oral cavity data, and denture design software was used to design the shape of the restoration and establish a digital model of the restoration. Simultaneously, using adjacent teeth as references, complete CIE Lab* point cloud data of the labial surface of the adjacent teeth was obtained using a spectrophotometer, electronic colorimeter, and camera. Then, the database was queried to obtain the ink ratio mapping for the corresponding units. For example, the color values ​​L*68.5, a*5.2, b*23.8 of the central main unit were mapped to 42% for printhead 1, 32% for printhead 2, 18% for printhead 3, 0% for printhead 4, and 5% for printhead 5; the color values ​​L*78.3, a*2.1, b*15.6 of the incisal unit were mapped to 65% for printhead 1, 20% for printhead 2, and 8% for printhead 3. The color values ​​of the cervical unit (L*58.2, a*8.5, b*26.4) are mapped to 24% for nozzle 1, 35% for nozzle 2, 22% for nozzle 3, 0% for nozzle 4, and 15% for nozzle 5. The color values ​​of the edge unit (L*82.1, a*1.8, b*12.3) are mapped to 70% for nozzle 1, 15% for nozzle 2, 5% for nozzle 3, 8% for nozzle 4, and 2% for nozzle 5. All units within a single layer are independently formulated based on measured adjacent tooth data. Fine adjustments to the nozzle ratio between adjacent units achieve a continuous color transition, entirely driven by the patient's natural tooth data. After sintering, the color difference has been verified to be within an acceptable range.

[0042] The results are output as an ink distribution matrix. The color values ​​L*68.5, a*5.2, and b*23.8 of the central main unit are mapped to the following proportions: nozzle 0 sprays 0% of the support material, nozzle 1 sprays 42%, nozzle 2 sprays 32%, nozzle 3 sprays 18%, nozzle 4 sprays 0%, and nozzle 5 sprays 5%, which can be represented as [0,42,32,18,0,5]. The color values ​​L*78.3, a*2.1, and b*15.6 of the cut-end unit are mapped to the following proportions: nozzle 1 sprays 65%, nozzle 2 sprays 20%, nozzle 3 sprays 8%, nozzle 4 sprays 5%, and nozzle 5 sprays 2%, which can be represented as [0,65,20,8,5,2]. The color values ​​of the neck unit are represented as [0,24,35,22,0,15]. The color values ​​of the edge unit are represented as [0,70,15,5,8,2]. Each unit within a single layer has its formula calculated independently based on measured adjacent tooth data. Fine adjustments to the nozzle ratio between adjacent units achieve a continuous color transition. Figure 1 , Figure 2 As shown.

[0043] Figure 1The diagram shows a discrete partitioning scheme for the color distribution of individual cells in a single-layer slice (horizontal, XY direction) of a tooth crown, demonstrating a direct partitioning color matching scheme based on measured data of natural teeth. The outermost and innermost solid arcs in the diagram represent the actual printed outline of the crown; the serrated radial lines are color marking lines pointing to each sector and indicating the six-dimensional ink mixing ratio [0, 1, 2, 3, 4, 5]. This slice is directly divided into functional areas based on measured data of the patient's adjacent teeth, simulating the anatomical characteristic of natural teeth: "deeper color in the center, lighter color at the edges." The upper and lower sector areas correspond to the main body of the tooth. The coloring ink formula [0, 42, 32, 18, 0, 5] is allocated according to CIE Lab* values, i.e., 0% for nozzle 1, 42% for nozzle 2, 32% for nozzle 3, 18% for nozzle 4, and 0% for nozzle 5, to simulate the darker dentin layer. The left and right fan-shaped areas correspond to the cut ends, and the ink matrix [0, 65, 20, 8, 5, 2] is allocated, i.e., printhead 1 0%, printhead 2 65%, printhead 3 20%, printhead 4 8%, and printhead 5 5%, to simulate a highly translucent enamel. The functional areas are directly connected, relying on printing precision to achieve clear boundary demarcation and realize color gradients within the layer. Each fan-shaped area is allocated ink according to a fixed ratio, and all units within the area use the same formula. The visual gradient effect between areas is achieved through formula differences between adjacent levels. Similarly, as... Figure 2 As shown, gradient colors can also be achieved between layers (vertical, Z direction), so this method can prepare a uniform gradient color presentation in omnidirectional (x, y, z) space.

[0044] like Figure 3 As shown, after the ink is ejected at the printing location, the electromagnetic fields arranged around the worktable are controlled by corresponding currents to generate oscillating magnetic fields that reciprocate in a cyclical manner. The magnetic field drives the magnetic particles in the ink to reciprocate, causing the ink within the unit and at the interface of adjacent units to mix. After the ink layer is mixed using the magnetic field, a heating lamp module completes the thermal curing of the ink, completing the printing of one layer. After printing the entire restoration, steps such as support removal, degreasing, and sintering are performed to complete the fabrication of the spatial omnidirectional color gradient denture.

[0045] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A real-time mixing and toning inkjet 3D printing method, characterized in that, The specific steps are as follows: S1: Ink preparation. Based on specific product requirements, prepare inks of different colors and add magnetic particles. Load the inks into different printheads. S2: Color gradient control. A color value-ink ratio formula database is pre-established. The corresponding color value in the database is searched according to the target color value to obtain the ink ratio formula for the target color value. S3: Inkjet process control. Based on the ink ratio formula obtained in S2, control each printhead to spray a quantitative amount of ink to the target position. Specifically, this includes constructing a three-dimensional model of the denture, decomposing the model into micro-cubic units, assigning a color value to each unit based on the measured color data of the patient's adjacent teeth, searching the database based on the color value to obtain the corresponding ink ratio formula, thereby obtaining the three-dimensional coordinates and ink ratio formula of each unit, and controlling the spray position and ink volume of each printhead accordingly. S4: The color mixing process applies a magnetic field to the ejected ink. Specifically, an array of electromagnets is arranged on the printing platform. After each printhead completes ink ejection, the electromagnets are controlled to generate a rotating magnetic field or an oscillating magnetic field that covers the target printing position. This drives the magnetic particles in the ink to move, so that different inks can be mixed to present the pre-designed color. S5: Solidify the ink at the target location, repeat the above process until inkjet printing is completed, and obtain a product with spatial omnidirectional color gradient changes.

2. The instantaneous mixing and toning inkjet 3D printing method as described in claim 1, characterized in that, In step S1, various inks of different colors are prepared by adding coloring powder of specific colors and proportions to the ink.

3. The instantaneous mixing and toning inkjet 3D printing method as described in claim 1, characterized in that, In step S2, a color value-ink ratio formula database is pre-established. Specifically, this includes adjusting the proportions of various inks in step S1, printing color blocks, generating a sample set, measuring the measured color value of each color block, establishing a mapping relationship model from ink ratio formula to color value, and storing it as a color value-ink ratio formula database.

4. The instantaneous mixing and toning inkjet 3D printing method as described in claim 1, characterized in that, Step S1 also includes a water-soluble support material ink, the components of which include one or more of polyvinyl alcohol, polyethylene glycol, and polyacrylic acid, used as a temporary support for the printed structure. It does not contain the constituent materials of the product to be printed and can be removed by water after printing.

5. The instantaneous mixing and toning inkjet 3D printing method as described in claim 1, characterized in that, In step S1, a variety of inks of different colors are prepared, specifically including inks No. 1 to No. 5, the specific components of which include lithium silicate glass powder, coloring powder, dispersant, binder, magnetic particles, pH adjuster and solvent.

6. The instantaneous mixing and toning inkjet 3D printing method as described in claim 5, characterized in that, The inks numbered 1 through 5 are colorless, yellow, magenta, cyan, and black, respectively.

7. The instantaneous mixing and toning inkjet 3D printing method as described in claim 1, characterized in that, The magnetic particles are any one or a combination of at least two of the following: magnetic iron oxides, cobalt-based materials, and soft magnetic alloy particles.

8. A denture, characterized in that, The denture is manufactured using an instant mixing and color-matching inkjet 3D printing method as described in any one of claims 1-7, and has a spatial omnidirectional color gradient variation.

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