Protocol for vat polymerization 3D printing of multi-material prosthetics

Abstract

A protocol for vat polymerization 3-D printing a prosthetic having multiple materials includes designing a model of a prosthetic formed of multiple materials; utilizing slicing software to divide the model of the prosthetic into a plurality of layers forming the prosthetic, and creating printer control set for each layer that defines the type of material forming each layer and the area to be polymerized to form the layer, wherein the printer control sets includes layers of at least two different materials; and printing the prosthesis in a vat polymerization system using the printer control set, wherein the printer will pause at each layer having a material different from the preceding layer, wherein multiple vats of different material are provided wherein the material is replaced to provide for the next layer's newly designated material by replacing the current vat with a separate vat with the material for the next layer.

Description

Protocol for Vat Polymerization 3D Printing of Multi-Material ProstheticsBACKGROUND OF THE INVENTION

[0001] 1. FIELD OF THE INVENTION

[0002] The inventors developed this technology which generally relates to a protocol for 3D printing of multi-material prosthetics, particularly oral prosthetics, although it will have broader applications including protocols for 3D printing prosthetics with embedded substructures.

[0003] 2. BACKGROUND INFORMATION

[0004] A prosthetic within the meaning of this application is an artificial manmade device that replaces a missing body part (generally human body part), which may be lost through trauma, disease, or a condition present at birth such as a congenital disorder. A prosthetic field within the meaning of this application is the area within the body, including related or adjacent tissue within which a prosthetic fits and operates, analogous, roughly, to an operative field in surgery. Prostheses are intended to restore the normal functions of the missing body part to the greatest extent possible. The present invention is described in connection with oral prosthetics, but can have broader application to fitting of any prosthetics associated with surgically altered physiologic parameters.

[0005] An oral prosthetic, also called a dental prosthetic or dental prosthesis, is an intraoral prosthetic used to restore / reconstruct intraoral defects, such as missing teeth, missing parts of teeth, and missing soft or hard structures of the jaw or palate. The prosthetic field for oral prosthetics is the oral cavity and associated body structures. Prosthodontics is the dental specialty that focuses on dental prostheses. Such prostheses are used to rehabilitate mastication (chewing), improve aesthetics, and aid speech.

[0006] An oral prosthetic may be held in place by connecting to teeth, or via dental implants, by suction, or by being held passively by surrounding muscles. Like other types of prostheses, they can either be fixed permanently or removable. Fixed prosthodontics (permanent oral prosthetic) and removable oral prosthetic (such as dentures) are made in many variations. Permanently fixed oral prosthetic or dental prostheses typically use dental adhesive or screws, to attach to teeth or dental implants. Removable oral prosthetic or dental prostheses may use friction against parallel hard surfaces and undercuts of adjacent teeth or dental implants, suction using the mucousretention (with or without aid from denture adhesives), and by exploiting the surrounding muscles and anatomical contours of the jaw to passively hold in place.

[0007] Dentures (also known as false teeth) are a common oral prosthetic constructed to replace missing teeth, and are supported by the surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable (removable partial denture or complete denture). However, there are many denture designs, some which rely on bonding or clasping onto teeth or dental implants (fixed prosthodontics). There are two main categories of dentures, the distinction being whether they are used to replace missing teeth on the mandibular arch or alternatively on the maxillary arch.

[0008] Oral prosthetics have a long history, as early as the 7th century BC, Etruscans made partial dentures out of human or other animal teeth fastened together with gold bands. Wooden full dentures were invented in Japan around the early 16th century. In 1728, Pierre Fauchard proposed dentures using a metal frame and teeth sculpted from animal bone. The first porcelain dentures were made around 1770 (attributed to Alexis Duchateau). In 1791 , the first British patent was granted to Nicholas Dubois De Chemant, who was a previous assistant to Duchateau, for an artificial teeth forming composition, and also springs for fastening or affixing the same “which said teeth may be made of any shade or colour, which they will retain for any length of time and will consequently more perfectly resemble the natural teeth.” In 1820, Samuel Stockton, a goldsmith by trade, began manufacturing high-quality porcelain dentures mounted on 18-carat gold plates. Later dentures (from about the 1850s) were made of Vulcanite, a form of hardened rubber into which porcelain teeth were set. In the 20th century, acrylic resin and other plastics were used.

[0009] 3D printing, also known as additive manufacturing, is the construction of a three- dimensional object from a CAD (computer aided design) model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer control with material being added together (such as plastics, liquids or powder grains being fused), typically layer by layer. By the early 2010s, the phrases “3D printing” and “additive manufacturing” became alternate umbrella terms for additive technologies, one being used in popular language by consumer-maker communities and the media, and the other used more formally by industrial end-use part producers, machine manufacturers, and global technical standards organizations. Peter Zelinski, the editor-in-chief of Additive Manufacturing magazine, pointed out in 2017 that the terms are still often synonymous in casual usage, but some manufacturing industry experts are trying to make a distinction whereby additive manufacturing comprises 3D printing plus other technologies or other aspects of a manufacturing process. Within this application the terms are used interchangeably, although the invention disclosed herein may more commonly be referenced as being directed to 3D printing.

[0010] Additive manufacturing has been established in the dental sector for over 20 years, represented, for example, by the laser sintering (AKA Selective Laser Melting, or SLM) processes such as by Bego Medical (Bremen, Germany) and EOS (Krailing, Germany). Moreover, SLM enjoys worldwide acceptance as the basis for manufacturing metallic structures (such as crowns, bridges, or clasp-retained cast-metal frameworks). Laser sintering has now become a standard process for the production of CoCr crowns and bridges. See Revilla-Lebn M., Meyer M.J., Ozcan M. Metal additive manufacturing technologies. Int. J. Comput. Dent. 2019; 22:55-67. Laser sintering of clasp-retained castmetal frameworks is also well established and clasps are one of the oldest forms of denture retention. See Lehmann K.M., Hellwig E., Wenz H.J. Zahnarztliche Propadeutik. Deutscher Zahnarzte; Kbln, Germany: 2015.

[0011] Stereolithography (SL) has also been used in the dental industry for many years, for example, in the production of surgical templates (drilling guides). Stereolithography is based on point-by-point solidification within a resin vat (epoxy resins, acrylates) by a laser beam or with the aid of blue-light LEDs (also referenced as digital light processing, DLP). Until a few years ago, 3D printers for dental applications were the preserve of industry or large manufacturing centers, given the considerable capital outlays required, but now, many printers have come down to within reach of “regular” or smaller scale dental laboratories. Moreover, industry outsiders are entering the dental market and offering additive manufacturing technologies. Using comparatively inexpensive equipment, dental laboratories currently produce objects made of acrylics or composite resins to be used in the preparatory stages of a workflow, such as jaw models or surgical templates.

[0012] In this digital dental technology, hybrid production is the phase introduced for a combination of additive and subtractive steps with a view to combining the efficiency of additive manufacturing with the precision of CNC milling. See Torii M., Nakata T., Takahashi K., Kawamura N., Shimpo H., Ohkubo C. Fitness and retentive force of cobalt-ch romium alloyclasps fabricates with repeated laser sintering and milling. J. Prosthodont. Res. 2018; 62:342-346. doi: 10.1016 / j.jpor.2018.01.001 ; and Akata T., Shimpo H., Okhubo C. Clasp fabrication using one-process molding by repeated laser sintering and high-speed milling. J. Prosth. Research. 2017; 61 :276-282. doi: 10.1016 / j.jpor.2016.10.002.

[0013] Several 3D printing technologies exist for the additive manufacturing of plastic objects in prosthetic dentistry and exhibit, when compared to each other, different characteristics regarding speed, resolution, size, and process reliability depending on the underlying technology. See Revilla-Leon M., Oczan M. Additive manufacturing technologies used for processing polymers: Current status and potential application in prosthetic dentistry. J Prosthodont. 2019; 28:146-158. doi: 10.1111 / jopr.12801 .

[0014] Currently, stereolithographic processes predominate in the dental sector, including classic stereolithography using a laser source (stereolithography AKA SLA) and the so-called mask exposure processes (digital light processing, DLP). In both processes, the object is solidified by the action of light in a vat of photopolymer. For several years now, 3D printers have been available that use low-cost liquid crystal displays (LCD). The technology is called direct ultraviolet printing (DUP); it uses the LCD displays for pixel-by-pixel exposure of the build platform. UV LEDs with a wavelength range of 395 to 405 nm are usually used for background lighting.

[0015] Direct 3D printing processes (material jetting, MJT) are also used in dental applications. Material extrusion (MEX) processes such as fused-filament fabrication (FFF) or fused deposition modeling (FDM) are currently less implemented on the dental market due to perceived long printing times and lower resolutions of the resulting products. The SLA, DLP, and MJT technologies mentioned appear to be the most commonly implemented technologies for the plastics sector, due to technical and economic consideration. For further background see Brown G.B., Currier G.F., Kadioglu O., Kierl J.P. Accuracy of 3-dimensional printed dental models reconstructed from digital intraoral impressions. Am. J. Orthod. Dentofac. Orthop. 2018; 154:733-739; and Emir F., Ayyildiz S. Accuracy evaluation of complete-arch models manufactured by three different 3D printing technologies: A three- dimensional analysis. J. Prosthodont. Res. 2021 doi: 10.2186 / jpr.JPOR_2019_579; and Etemad-Shahidi Y., Qallandar O.B., Evenden J., Alifui-Segbaya F., Ahmed K.E. Accuracy of 3-Dimensionally printed full-arch dental models: A systematic review. J. Clin. Med. 2020 ;9: 3357. doi: 10.3390 / jcm9103357.

[0016] A noteworthy process in the digital dental manufacturing space is multi-material 3D printing by Stratasys on a POLYJET™ or J750™ brand printer, which allows different colors and materials with different properties to be processed simultaneously in a single build. This has been described (by Joseph Flynt of 3D Insider in January 2021 ) as one of the most advanced ways to 3D print in multiple colors is on the Stratasys J750™ printer. The Stratasys method uses photopolymer resin as raw material. This liquid resin is deposited on a build plate through very small droplets and cured by a flash of UV light. What is unique about Multi- Color Stratasys system or process is that it allows the droplets to be colored before deposition. The result is a full-color 3D print. A special feature in the Stratasys system is multi-material 3D printing, where five different grades of materials can be printed in more than 500,000 colors. See Schweiger J., Edelhoff D., Stimmelmayr M., Guth J.F., Beuer F. Automated production of multilayer anterior restorations with digitally produced dentin cores. Quintessence Dent. Tech. 2015;38: 207-220. See also Schweiger J., Trimpl J., Schwerin C., Guth J.F., Edelhoff D. Biomaterials update— Additive manufacturing: Applications in dentistry based on materials selection. Quintessence Dent. Tech. 2019; 42:50-69. It has been described by Mr. Flynt that the “biggest downside, as you would expect, is that you can’t just buy a POLYJET printer. This type of printer is ridiculously expensive and typically only used in businesses or corporations.”

[0017] It has been noted in this field, see Schweiger J, Edelhoff D, Guth JF. 3D Printing in Digital Prosthetic Dentistry: An Overview of Recent Developments in Additive Manufacturing. J Clin Med. 2021 May 7;10(9):2010., that “Another possible application of multi-material 3D printing in the dental field could be the fabrication of multi-layered dentures made from different materials. With regard to the identical reproduction of natural teeth by crowns or bridges, this technology is currently in the prototype phase. It is based on the tooth-structure database, which allows the multilayer structure of natural teeth to be copied and the data thus generated to be used in an additive manufacturing process. The ultimate aim is to produce biomimetic dental restorations that reflect the multi-layered three-dimensionality as well as the complex mechanical and optical properties of natural teeth. Taking into account the light-optical properties of the different tooth layers (pulp, dentin, and enamel), an identical esthetic reproduction of natural teeth can be achieved.” It is clear that multi-material 3D printing in the dental field is not currently available in cost effective efficient process.

[0018] There is a need to improve 3D printing of medical prosthetics, particularly dental prosthetics, in an effective and cost efficient manner.SUMMARY OF THE INVENTION

[0019] One aspect of the present invention provides a protocol for vat polymerization 3-D printing a prosthetic having multiple materials includes designing a model of a prosthetic formed of multiple materials; utilizing slicing software to divide the model of the prosthetic into a plurality of layers forming the prosthetic, and creating printer control set for each layer that defines the type of material forming each layer and the area to be polymerized to form the layer, wherein the printer control sets includes layers of at least two different materials; and printing the prosthesis in a vat polymerization system using the printer control set, wherein the printer will pause at each layer having a material different from the preceding layer, wherein multiple vats of different material are provided wherein the material is replaced to provide for the next layer’s newly designated material by replacing the current vat with a separate vat with the material for the next layer.

[0020] One aspect of the present invention provides a protocol for 3-D printing via vat polymerization of a prosthetic having a substructure embedded within the prosthetic comprising the steps of: designing a model of a prosthetic having a substructure embedded within the prosthetic; utilizing slicing software to divide the model of a prosthetic having a substructure embedded within the prosthetic into a plurality of layers forming the prosthetic, and creating printer control set for each layer that defines layers in a sequence and include an indication of a layer in which the substructure first appears; and printing the prosthesis in a vat polymerization system using the printer control set, wherein the printer will pause at the layer in the sequence which includes an indication this is the layer in which the substructure first appears, and the substructure will be placed within an operative vat prior to formation of that layer. The prosthetic 3-D printing protocol according to the invention may provide wherein the pause at the layer in the sequence which includes an indication this is the layer in which the substructure first appears includes noting a position of the build plate, moving the build plate to a home position out of the current vat with material forming the preceding layer and returning the build plate to the noted position within the associated vat with the substructure positioned therein.

[0021] One aspect of the present invention provides a protocol for 3-D printing via vat polymerization of a prosthetic having multiple materials comprising the steps of: designing a model of a prosthetic formed of multiple materials; utilizing slicing software to divide the model of a prosthetic formed of multiple materials into a plurality of layers forming the prosthetic, and creating printer control set for each layer that defines at least the type of material forming each layer and the area to be polymerized to form the layer, wherein the printer control sets includes layers of at least two different materials; and printing the prosthesis in a vat polymerization system using the printer control set, wherein the printer will pause at each layer having a material different from the preceding layer and the material in the vat associated with the printer is replaced to provide for the newly designated material for the layer.

[0022] The prosthetic 3-D printing protocol according to the invention may provide wherein multiple vats of different material are provided wherein the material is replaced with the newly designated material for the layer by manually replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer, or by using an automatic vat change out mechanism. The prosthetic 3-D printing protocol according to invention may provide wherein the replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer includes noting a position of the build plate, moving the build plate to a home position out of the current vat with material forming the preceding layer and returning the build plate to the noted position within the separate vat with the material for the next layer. The prosthetic 3-D printing protocol according to the invention may provide wherein the printer verifies the proper vat at least before beginning of forming a layer with a material different from the preceding layer.

[0023] These and other advantages of the present invention will be clarified in the following description of the invention taken together with the attached figures in which like reference numerals represent like elements throughout.BRIEF DESCRIPTION OF THE FIGURES

[0024] Figure 1 is a schematic illustration of a generalized additive manufacturing process.

[0025] Figure 2 is a schematic illustration of a generalized additive manufacturing SLA process of the Prior art.

[0026] Figures 3A-3D are schematic illustrations of generalized additive manufacturing SLA protocol of the present invention.

[0027] Figures 4A-4D are schematic illustrations of generalized additive manufacturing DLP protocol of the present invention

[0028] Figure 5 is a schematic illustration of oral prosthetics formed by the additive manufacturing protocol of the present invention.

[0029] Figure 6 schematically illustrates a printer implementing the protocol of the present invention with an automatic vat change out mechanism in the form of a rotating indexable table with an annular array of four vats each with a specific colors / material.

[0030] Figure 7 a schematic cross sectional illustration of oral prosthetics formed by the additive manufacturing protocol of the present invention each including an embedded substructure.DESCRIPTION OF THE INVENTION

[0031] The various embodiments and examples of the present invention as presented herein are understood to be illustrative of the present invention and not restrictive thereof and are non-limiting with respect to the scope of the invention.

[0032] The present invention relates to a protocol for 3D printing of multi-material prosthetics 70, particularly oral prosthetics 70. The protocol of the present invention may be expanded beyond prosthetics 70, but it has particular application in this field. Figure 1 is a schematic illustration of a generalized additive manufacturing process 10 flowing from a 3D cad model to the 3D printed object 70. In summary the present invention provides a protocol for vat polymerization 3-D printing in a system 60 a prosthetic 70 having multiple materials 74 and 76 includes designing a model 20 of a prosthetic 70 formed of multiple materials; utilizing slicing software 40 to divide the model 20 of the prosthetic 70 into a plurality of layers 72 forming the prosthetic 70, and creating printer control set 50 for each layer 72 that defines the type of material (74 or 76 in one example) forming each layer 72 and the area to be polymerized to form the layer 72, wherein the printer control sets 50 includes layers 72 of at least two different materials (74 and 86 for example); and printing the prosthesis 70 in a vat polymerization system 60 using the printer control set 50, wherein the printer 60 will pause at each layer 72 having a material different (74 or 76 for example) from the preceding layer,wherein multiple vats 80 and 80’ of different material 82 and 82’ are provided wherein the material 82 or 82’ is replaced to provide for the next layer’s newly designated material 82 or 82’ by replacing the current vat 80 or 80’ with a separate vat 80 or 80’ with the material 82 or 82’ for the next layer 72.

[0033] The present invention is directed to vat (80 or 80’) polymerization in system 60, as opposed to those additive manufacturing processes using a material delivering printing head. Vat polymerization 3D printing technologies make use of a (liquid) photopolymer resin (82 or 82’) which is able to cure (solidify) under a light 88 from a light source 84 controlled with a scanner or controller 86. In the world of vat polymerization, there are two main technologies: SLA and DLP (as introduced above). SLA is schematically represented in figures 2 and figures 3A-D while DLP is shown in figures 4A-D. Naturally, both use resin (82 or 82’) and a light source 84 to produce parts, the main difference being the type of light source 84 which is used to cure the resin 82 or 82’.

[0034] As shown in the figures the build plate or platform 92 can move via mechanism 90 up out of the vat 80 or 80’ (most commonly) or down into the vat 80 or 80’ in the build process. The vat 80 or 80’ aligned with the build plate 90 and light source 84 is the “current vat” or the “associated” vat or “active” vat within this application. If designed to move downward (as shown in prior art figure 2) the platform or plate 92 is not preferably mounted for movement through the base of the vat 80 or 80’ as schematically shown because that complicates the switching of vats 80’ for 80. This common simplified schematic representation of a vat polymerization set up shown in figure 2 is illustrative of the single vat systems contemplated and prevalent in the prior art and helps establish the state of the art.

[0035] Additive manufacturing of a 3D object or prosthetic 70, in general and in the present invention, can be divided into major steps along the process 10: (i) designing 20, (ii) printing in system 60, and (iii) post-processing to complete the product 70, which is generally reflected in figure 1 . In the designing step 20, the desired 3D shape is created using CAD (computer automated design) software, such as TINKERCAD, FUSION 360, SOLIDWORKS, AUTOCAD, etc. The designed geometry created in the model 20 is converted into STL (Standard Tessellation Language) format 30 and sliced into 2D images (layers) by slicing software 40. The post processing in the current protocol is conventional and not discussed further herein.

[0036] It can be stated that 3D DLP / LED printers of system 60 basically work with a 3D file which is “water tight” of a “closed model” which has a bottom and top side and connected together with some thickness. A lack of water-tightness, in the context of a CAD file, means that the shape of the file is not closed or "manifold". In short, this means that there are “holes” in the proposed shape of the designed product that exported from the CAD software and such cannot be printed. The file when watertight gets sliced in the proprietary software of the printer or some other software.

[0037] As noted above file then gets “sliced” which means that the layer thickness 72 of the respective properties of the material are properly used for the purpose of printing. The “slicing “ software 40 slices the 3D object 70 and at that point makes a printer control set or “mask” 50 for each layer or slice. This mask or control set 50 includes a representation or a snapshot of the 3D object 70 in horizontal sliced layers 72. These layers 72, when stacked vertically in their entirety make up the 3D object or prosthesis 70. The output file or control set 50 from the slicing software 40 contains the geometrical information related to the sliced layers 72. The materials 82 or 82’ in the vat 80 or 80’ in a layer 72 are photo-initiated which means that the areas of light 88 that are exposed in the mask aspect of control set 50 are “cured” or hardened by the light 88.

[0038] Printing parameters are included in the control set 50 which conventionally include items such as exposure time, which depend on the technique and the specific process, are typically detailed in the printer software in system 60 before printing. Currently, 3D printers often use G-codes generated by the printer software and are compatible with different formats of 3D files. The control set 50 allows the printer controller to form these G-codes which contain all the information required for printing, conventionally including printer movements, sliced images, exposure time, temperature, etc. As detailed below the present invention the control set 50 forming the G-codes further includes the extra information related to material selection (82 or 82’) for each the layers 72 of the prosthesis 70, as well as whether a substructure 78 needs to be positioned in the next layer 72.

[0039] During printing (second step), 2D slices (layers 72) are printed one after the other in the operative or active vat 80, until the final object 70 emerges on the build plate 92 as a compact integrated stack of layers 72. The present invention differs from the conventional process by interrupting or pausing the print at specified layers 72 to swap vats (80 or 8O’) / materials (82 or 82’) and / or position substructures 78 as discussed in detail below,however, overall the layers 72 are still printed one after the other until the final manufactured object 70 is completed.

[0040] This manufactured object 70, also called ‘green body’ at this stage, is then removed from the build plate 92 and subjected to post-processing (third step). Post-processing may be required to remove the excess raw material or impart the final finishing which may depend on the specific AM technology, the material used, and the final application for produced parts. The post processing with the current protocol is the same as the prior art post processing steps.

[0041] In order to understand DLP (such as used in the protocol of figures 4A-4D) properly, it first makes sense to review and describe its predecessor, SLA (such as used in the protocol of figures 3A-3D). 3D printers 60 that employ SLA, or stereolithography, use a build platform or plate 92, an elevator 90 that moves the platform or plate 92 upwards or downwards, a tank 80 filled with resin 82, a light source 84 forming a laser 88 and galvanometers (scanner 86 controlling the laser 88). SLA 3D printers 60 start to work by lowering the build platform or plate 92 into the tank 80 filled with resin 82 with only one layer (equivalent to layer 72) of height left between the bottom of the tank 80 and the build platform or plate 92. Then the galvanometers 86 take over. Galvanometers 86 are mirror-like components used for navigating the laser beam 88 of an SLA printer 60 to the bottom of the tank 80. With the help of G-code, galvanometers 86 navigate the laser beam 88 in a path which represents one layer 72 of a certain part 70. The laser 88 then cures the resin 82 making a solid layer 72 of a part 70. When one layer 72 is complete, the build platform 80 moves up by one layer 72 in height and the process is repeated until the part 70 is complete

[0042] DLP is a “sister technology” to SLA as the only big difference is the light source 84 used to cure the resin 82. As mentioned, SLA printers 60 use lasers 88 combined with galvanometers 86 to cure resin 82. With a DLP 3D printer 60, the light source 84 is a specially developed digital light projector controlled by a controller 86 to project the light for an entire layer 72 which is the main reason DLP is generally considered to be faster than SLA. With SLA, the laser 88 has to individually cure the resin in a “point to point” technique. On the other hand, a DLP projector screen flashes an image 88 of a layer 72 all at once. Thus all points of a layer 72 can be cured simultaneously. In this way, the print speed is increased in comparison to SLA since it takes less time to cure a single layer 72. Since the DLP is a digital technology, the 2D image 88 that is projected via controller 86 is composed of pixels. Whentranslated into three dimensions, they become voxels (with the height of the voxel being the height of the “slice” or layer 72). The light source 84 of a DLP 3D printer 60 itself, an LED screen, means nothing without a digital micro-mirror device (DMD) 86, the “heart” of every DLP chipset. A DMD 86 contains hundreds of thousands or even millions of small micromirrors that direct the light and create the pattern of a layer onto the bottom of the resin tank. The resolution of a printed part 70 using a DLP 3D printer 60 usually corresponds to the number of micro-mirrors inside a DMD device 86.

[0043] It is critical to note that a given vat 80 or 80’ can only hold the liquid of one material and one color (single resin 82 or 82’). The material 82 or 82’ is placed in a vat 80 or 80’ and the printing build plate 92 moves until it is in the material profile proximity to the vat - i.e. 100 micron -100p. The present invention resolves the material limitations of the prior art this by including multiple vats 80 and 80’, one vat 80 and 80’ for each material and / or color variation (resin 82 or 82’) desired in the final part 70. Two vats 80 and 80’ containing different color resin 82 or 82’ are shown for convenience but three or more are possible. With this process a prosthesis 70 can have one portion 74 (made up of a number of layers 72) formed of one material (e.g., resin 82) and a second portion 76 (also made up of a number of layers 72) formed of another material (e.g., resin 82’) allowing better control over the appearance of the prosthetic 70. In the two material examples shown in figures 3A-3D and 4A-4D, the prosthesis 70 is formed of two materials 74 and 76 with each of these portions of the prosthesis formed of multiple layers 72.

[0044] In a manufacturing process of the present protocol, the designed geometry from the model 20 is converted into STL (Standard Tessellation Language) format 30 and sliced into 2D images (layers) by slicing software 40. The object 70 may be “positioned” and include “supports” as known in the art to aid in manufacturing and part handling. In the present protocol the slicing of the object 70 will create layers 72 (450 as a representative example for an oral prosthetic 70) as before except the slicing process will split the file in two, or three, or as many color / material layers 72 needed, which colors / materials (e.g., 82 or 82’) are noted in the slice or mask 50 or g-code for the manufacture of a layer 72.

[0045] In a manufacturing process of the present protocol there is an important step to assure the printer 60 setting matches the material choice for the initial printed layers 72 (say layers 72 numbered 1 -312 for a representative example). In other words the vat 80 of material 82 must match the designated material / color for this print of the initial layers 72. In amanufacturing process of the present protocol the printer 60 may incorporate an RFID reader with RFID identification on the individual vats 80 or 80’ to automatically sense the material 82 or 82’ that is being used and to assure the process will not proceed with non-designated materials.

[0046] The process proceeds when the printer 60 is engaged until the initial set of layers 72 of a first vat 80 is complete (schematically shown in figures 3A and 4A except the entire prosthetic 70 is shown in this schematic. The end of one “set” of layers 72 is referenced as a pause in the present invention. When process reaches the “pause “position for 2nd color / material (i.e. the layer 72 that begins the second material 82’) the print build plate 92 will move to its home position (shown in figures 3B and 4B) and remember the layer 72 the process stopped or paused at (example slice 312). This notation of the pause position is part of what can be referenced as a registration process of registering the semi-finished workpiece (70) with the new vat 80’ containing the new material 82’ (generally a new color).

[0047] In a manufacturing process of the present protocol, following the pause and the movement of the print build plate 92 to the home position, a new vat 80’ with different color (material 82’) will replace previous vat 80 as shown in figures 3C and 4C. Then the print process is reengaged. The reengagement may be automated once the system 60 assures the presence of the proper new vat 80’ in proper position. Then the printer 60 will use mechanism (elevator 90) to move the build platform or plate 92 and associated partially formed product 70 to the paused location, e.g. slice 313, for the new color / material 82’ with the new parameters of the specific material 82’ in the new vat 80’ to be applied.

[0048] The pause, noting position, moving the plate 92 to a retracted home position, removing original vat 80, replacing with second vat 80’, checking the validity and position of a second vat 80’, and returning the plate 92 to the requisite new start position are collectively referenced as the registration process of registering the semi-finished workpiece (70) with the new second vat 80’ containing the second or different material 82’ such as for forming a new color.

[0049] The continuation of the print in printer 60 will happen to completion at slice 450 (for a two material / color piece 70in this example). More vats with more materials may be integrated as needed or desired, and materials can be repeated in different sets of layers, with a registration step for each vat / material. In a manufacturing process of the presentprotocol, the object 70 may now be manufactured in a vat process with two or more colors / materials depending on the necessity of colors in the part 70.

[0050] In a manufacturing process of the present protocol, the software can pre calculate how many colors needed and break it down for the user to manually change the vats 80 and 80’. Alternatively, in a manufacturing process of the present protocol there may be an automated process which will contain stacked, row or array of vats 80, 80’ 80” and 80”” with all the colors / materials 82, 82, 82’, 82” and 82’” of a part 70 in sequence and coupled with an automatic vat change out mechanism 62 operated within the registration process. For a representative example, figure 6 schematically illustrates an automatic vat change out mechanism 62 in the form of a rotating indexable table with an annular array of four vats 80, 80’, 80”, 80’” each with a specific colors / material 82, 82, 82’, 82” or 82’”. The table 62 rotates 64 to move the proper one of the four vats 80, 80’, 80”, 80’” into the work zone below the build plate 92 and above the light source not shown. The table 62 will have locks / detents for assuring the new one of the four vats 80, 80’, 80”, or 80’” is properly positioned as the operative or active or associated vat. This example shows four vats but more or less vats can be easily utilized.

[0051] For retrofitting existing systems, manual vat changing is anticipated. The new process not only brings versatility to a limited machine but also a “new layered” process that can have multiple material strengths with multiple layering.

[0052] The protocol for 3D printing of multi-material prosthetics 70 according to the present invention include the ability to introduce substructures 78 therein. Figure 7 shows a cross section of two material 74, 76 prosthetics 70 each with an embedded substructure 78 one a U shaped embedded support post and the other an h shaped embedded support post. The shape of the substructure 78 can take many forms as desired and there can be more than one embedded within each prosthetic. There is no possibility for substructure manufacturing or adding in the current conventional vat 3d printing. The shape and location of the embedded substructures 78 is first determined by the cad model 20 and will be reflected in the STL file 30. The slicing software 40 creates the slices 72 wherein the mask 50 of the invention includes the location of the material for that slice, together with the notation of the type of material and whether that slice is the first slice containing a substructure 78 (meaning this is the layer 72 in which prior to the formation of which the substructure 78 must be added in the vat 80 or 80’)

[0053] Substructures in the dental arena for prosthesis are very important and warrant discussion. Their importance is to guarantee integration of multiple dental implant locations surgery in the oral cavity, either in the maxilla or the mandible. Substructures 78 is not limited to dental prosthetics but can be used in maxillofacial surgery and even other “replacement surgeries” that need an enhanced or strengthened core or anchor point for the prosthetic. The protocol of the present invention has solved this problem and allows the user to add any kind of material substructure 78 either metal or polymer, milled or printed into ANY 3D printer DLP, LED , FDM-FFF, P3, HARP, LEAP, PpSL, DCM, SLA, MSLA, Binder Jetting, droplet printing new technology, SLS, SLM , MJP, EBM Polyjet and some others. However the process is particularly well suited for vat 80 based printing systems such as 60. This process can embed small multiple parts 78, a single part 78, and can even layer parts that are from a different material into the 3D printing cycle.

[0054] The process of incorporating substructures 78 into the prosthetic 70 is to treat the substructure 78 analogous to new color or new material wherein the system 60 creates a pause when the layer(s) 72 is reached for the insertion of the designated substructure 78.

[0055] Consider the examples shown in figure 7 with the substructures 78 added, when part in software reaches the “pause “ position for the substructure 78 will move to its home position shown in figures 3B and 4B and remember the layer it stopped at (example slice 312). The substructure 78 gets placed by a positioning device in the vat 80 or 80’ or 80” or 80’” (depending upon the material for that layer 72). The protocol will register the semi-finished piece 70 with the substructure 78 in its holder / vat 80 or 80’ by moving to the home position sufficient to mount the substructure and vat / holder, check the presence and position of the new vat and return the semi-finished workpiece to the layer for incorporation of the substructure 78. When the printer 60 resumes operation, which may be a single layer for positioning the substructure 78, the printer 60 will have the plate 92 descend to slice 313 as the substructure 78. The result is the substructure 78 gets cured into the partially printed part.

[0056] As an alternative the substructure 78 may be held in a specialized vat or specialized mini vat, which positions the substructure 78 (i.e.-internal core or bar) in the correct position relative to the STL file and the part which has been printed thus far. A specialized vat may be beneficial for the ability to include precision positioning jigs, with the specialized vat basically used for a substructure 78 fixing layer(s).

[0057] When part in software reaches the next “pause “position such as for 2nd color and or the 3rd position of the process the print build plate 92 will move to its home position and remember the layer 72 it stopped at and continue to next layer 72 (example slice 314) in another registration process and the operator may add a new vat with different color and will replace previous vat. The printer will descend to slice 314 as the new color with the new parameters of the specific material in the vat have been applied. The continuation of the print will happen to completion at slice 450. The object is completed with an embedded substructure 78 and two or more colors / materials depending on the necessity of colors in the part. The substructure 78 can be utilized within only a single material 82 part.

[0058] In a manufacturing process of the present protocol, the process will allow multiple colors with or without automation, with or without pre milled or printed substructures, in printers that have no ability to do this thus far. In a manufacturing process of the present protocol, a cartridge system of vats 80, 80’, 80”, 80”’may be implemented where the machine will stop and allow the operator to change the vat cartridge and also allow a user to remove the plate to clean the part if necessary.

[0059] An alternative to physically implementing multiple separate vats is a system that includes a material adding system for the vats such as a pump that can release enough material into the vat and then pump in a different color / material into a single vat. This system would further include a material removal system such as a vacuum to remove the prior material before adding another material in the vat.

[0060] The above description is representative of the present invention but not restrictive thereof. It will be apparent to those of ordinary skill in the art that various changes may be made to the present invention without departing form the scope thereof.

Claims

CLAIMSWhat is claimed is:

1. A protocol for 3-D printing via vat polymerization of a prosthetic having multiple materials comprising the steps of:A. Designing a model of a prosthetic formed of multiple materials;B. Utilizing slicing software to divide the model of a prosthetic formed of multiple materials into a plurality of layers forming the prosthetic, and creating printer control set for each layer that defines at least the type of material forming each layer and the area to be polymerized to form the layer, wherein the printer control sets includes layers of at least two different materials; c. Printing the prosthesis in a vat polymerization system using the printer control set, wherein the printer will pause at each layer having a material different from the preceding layer and the material in the vat associated with the printer is replaced to provide for the newly designated material for the layer.

2. The prosthetic 3-D printing protocol according to claim 1 , wherein multiple vats of different material are provided wherein the material is replaced to the newly designated material for the layer by replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer.

3. The prosthetic 3-D printing protocol according to claim 2, wherein the replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer is performed manually.

4. The prosthetic 3-D printing protocol according to claim 2, wherein the replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer is performed with an automatic vat change out mechanism.

5. The prosthetic 3-D printing protocol according to claim 2, wherein the replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer includes noting a position of the build plate, moving the build plate to a home position out of the current vat with material forming the preceding layer and returning the build plate to the noted position within the separate vat with the material for the next layer.

6. The prosthetic 3-D printing protocol according to claim 2, wherein the printer verifies the proper vat at least before beginning of forming a layer with a material different from the preceding layer.

7. The prosthetic 3-D printing protocol according to claim 2, further including embedding a substructure within the prosthetic.

8. The prosthetic 3-D printing protocol according to claim 7, wherein the model of a prosthetic formed of multiple materials includes the design of the substructure.

9. The prosthetic 3-D printing protocol according to claim 8, wherein the model printer control sets have the layers in a sequence and include an indication of a layer in which the substructure first appears.

10. The prosthetic 3-D printing protocol according to claim 9, wherein the printer will pause at the layer in the sequence which includes an indication this is the layer in which the substructure first appears, and the substructure will be placed within the operative vat prior to formation of that layer.

11. The prosthetic 3-D printing protocol according to claim 10, wherein the pause at the layer in the sequence which includes an indication this is the layer in which the substructure first appears includes noting a position of the build plate, moving the build plate to a home position out of the current vat with material forming the preceding layer and returning the build plate to the noted position within the associated vat with the substructure positioned therein.

12. The prosthetic 3-D printing protocol according to claim 2, wherein more than two vats are provided.

13. The prosthetic 3-D printing protocol according to claim 2, wherein the prosthetic is an oral prosthetic.

14. A protocol for 3-D printing via vat polymerization of a prosthetic having a substructure embedded within the prosthetic comprising the steps of: a. Designing a model of a prosthetic having a substructure embedded within the prosthetic; b. Utilizing slicing software to divide the model of a prosthetic having a substructure embedded within the prosthetic into a plurality of layers forming the prosthetic, and creating printer control set for each layer thatdefines layers in a sequence and include an indication of a layer in which the substructure first appears; c. Printing the prosthesis in a vat polymerization system using the printer control set, wherein the printer will pause at the layer in the sequence which includes an indication this is the layer in which the substructure first appears, and the substructure will be placed within an operative vat prior to formation of that layer.

15. The prosthetic 3-D printing protocol according to claim 14, wherein the pause at the layer in the sequence which includes an indication this is the layer in which the substructure first appears includes noting a position of the build plate, moving the build plate to a home position out of the current vat with material forming the preceding layer and returning the build plate to the noted position within the associated vat with the substructure positioned therein.

16. The prosthetic 3-D printing protocol according to claim 14, wherein the prosthetic is an oral prosthetic.

17. The prosthetic 3-D printing protocol according to claim 16 wherein the prosthetic has multiple materials and wherein the printer control set for each layer defines the type of material forming each layer and the area to be polymerized to form the layer, wherein the printer control sets includes layers of at least two different materials, and wherein the printer will pause at each layer having a material different from the preceding layer and the material in the vat associated with the printer is replaced to the newly designated material for the layer.

18. The prosthetic 3-D printing protocol according to claim 17, wherein multiple vats of different material are provided wherein the material is replaced to the newly designated material for the layer by replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer.

19. The prosthetic 3-D printing protocol according to claim 18, wherein the printer verifies the proper vat at least before beginning of forming a layer with a material different from the preceding layer.

20. A protocol for 3-D printing via vat polymerization of an oral prosthetic having multiple materials comprising the steps of:A) Designing a model of an oral prosthetic formed of multiple materials;B) Utilizing slicing software to divide the model of an oral prosthetic formed of multiple materials into a plurality of layers forming the oral prosthetic, and creating printer control set for each layer that defines the type of material forming each layer and the area to be polymerized to form the layer, wherein the printer control sets includes layers of at least two different materials;C) Printing the oral prosthesis in an SLA or DLP vat polymerization system using the printer control set, wherein the printer will pause at each layer having a material different from the preceding layer, wherein multiple vats of different material are provided wherein the material is replaced to provide for the newly designated material for the layer by replacing the current vat with material forming the preceding layer with a separate vat with the material for the next layer.

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