Dental and skeletal training aid and method for producing same

Abstract

The present invention relates to an artificial tooth 10 or bone formed from a unitary 3D printable material. An artificial tooth comprises an outer enamel-like portion 12 and an inner dentine-like por

Description

This invention relates to a dental and skeletal training aid and method for producing same. In particular, the present invention relates to an artificial tooth for dental training, and suitable materials and production processes for 3D printed teeth which provide exceptional realism and tactile feedback for dentistry students and professionals. The present invention also relates to synthetic bone models which may be used as training aids in both the human and veterinary fields. Background The skill of drilling a tooth is a critical part of dentistry. It is covered as a core element of dental training and re-certification. The key aspects of drilling teeth that require continued learning are, how much pressure to apply to the tooth surface (enamel) when initially drilling, then being able to feel a drop in resistance through the drill burr as it transitions between the enamel and dentine layers. Once the enamel has been drilled through, it is common procedure to change the burr type and select a suitable burr for the dentine material. Many of the common day-to-day procedures of tooth repair work is carried out on either the enamel or the dentine layer, thus it is important that the dentist learn how to avoid drilling into the pulp layer. The pulp contains the blood supply and nerve endings for the tooth and should only be accessed via drilling for specific and more complex types of dental surgery. If a dentist were to drill into the pulp layer there would be a significant drop in drilling resistance felt on the burr. Unintentionally drilling into the pulp layer when there is no clinical necessity to do so is a significant error for a dentist. The skill of drilling accurately and understanding the drill resistance tactile feedback between the layers of the tooth is a highly practical skill, meaning it is primarily learned through hands-on experience rather than theoretical knowledge from textbooks or lectures. Dental students, and those re-certifying, practice therefore on a “phantom head” with prosthetic teeth and jaws. EP 1 912 194 describes a two-part moulding technique for creating a multi-layered model tooth for dental training. This document describes that the dentine layer and root part are injection moulded as one part. The enamel layer is then formed using a much harder material that mimics natural enamel and is overmoulded over the first part, resulting in a model tooth that mimics a more real structure. This known two-part injection moulding technique does suffer disadvantages however in terms of the complexity and cost of the manufacturing process. There is therefore a strong commercial and societal need for an artificial tooth that is to be used as a training aid, within a phantom head, with the aim of mimicking the different layers of natural teeth through differential drilling resistance, so that dentistry students and professionals may learn the necessary skills to be able to operate in a clinical environment safely and effectively. Such an artificial tooth for dental training, and suitable materials and production processes for these 3D printed teeth, being also designed for costeffectiveness and ease of manufacture. It is an object of the present invention to provide an innovative dental drilling training aid designed to replicate the differential drilling resistance encountered in natural teeth. It is a further object of the present invention to provide an eloquent way of simulating the various layers of a natural tooth, allowing dentists to develop and hone their drilling skills in a safe and controlled training environment. The goal is to enable dental students and professionals to achieve greater accuracy and sensitivity in their drilling techniques, in distinguishing between enamel, dentine and pulp layers, reducing the risk of accidental errors and enhancing patient safety. It is a further object of the present invention to provide synthetic bone and dental models which may be used as training aids in both the human and veterinary fields. Summary Of The Invention The present invention is described herein and in the claims. According to the present invention there is provided artificial tooth formed from a unitary 3D printable material, the artificial tooth comprising an outer enamel-like portion and an inner dentine-like portion having voids therein. An advantage of the present invention is that such an artificial tooth can be produced more economically and better replicate the various layers of a natural tooth and allow dentists to develop and hone their drilling skills in a safe and controlled training environment. Preferably, the dentine-like portion may be enveloped within the enamel-like portion, and wherein the enamel-like portion and the dentine-like portion together comprise a crown. Further preferably, the voids may be arranged as channels inside the dentine-like portion. In use, the channels may be elongate straight-through channels. Preferably, the channels may be configured in a circular mesh arrangement. Further preferably, the channels may have varying pore sizes along their length and / or individual channels have a distribution of pore sizes. In use, the channels may be configured in a random or quasi-random or repeating pattern. Preferably, the channels may be tortuous and formed by deposition of layers of different perforate patterning that are laterally displaced. Further preferably, the 3D printable material may comprise a Stereolithography (SLA) resin consisting of Urethane Dimethacrylate (UDMA), Isobornyl Methacrylate (IBMA), and a reinforcing agent selected from the group consisting of, but not limited to, any of the following: glass filler, ceramic powder, carbon or graphene. In use, the dentine-like portion may be provided in a sponge-like configuration to mimic the dentine structure of a natural tooth. Preferably, the artificial tooth may further comprise a root portion, wherein the crown being adjacent to, and extending from, the root portion. Further preferably, the root portion may be suitable for insertion into a dummy phantom head for dental training. In use, the voids within the dentine-like portion may provide a realistic drill resistance feedback during dental training. Preferably, the artificial tooth may comprise a separate pulp-like portion formed from a material with a lower resistance to drilling that mimics the pulp structure of a natural tooth. Further preferably, the pulp-like portion may be selected from the group consisting of, but not limited to, any of the following: a wax-type material, 3D printing resin, silicon, rubber or the like. In use, the pulp-like portion may be elongate and positioned generally co-axially with the root portion and extends into the dentine-like portion. Preferably, the artificial tooth is representative of a human or animal tooth. Likewise according to the present invention there is provided a method of 3D printing an artificial tooth having a solid outer enamel-like surface and an inner dentine-like portion comprising voids on a 3D printer having a build platform, a laser and a vat of photosensitive resin, and a digital control system for controlling the movement of the build platform, the laser and / or the vat, the method comprising the steps of: loading a 3D model of the artificial tooth into the digital control system and dividing the 3D model into multiple layers, each layer representing a cross-section of the artificial tooth; for each layer, generating a path for selectively solidifying the photosensitive resin within the vat using a laser, wherein the path includes a continuous path corresponding to the solid enamel-like surface of the tooth, and an infill path corresponding to the inner dentine-like portion, the infill path being generated to create the voids; and continuously lowering the build platform or elevating the vat to allow for the formation of subsequent layers of the artificial tooth and solidifying successive layers of the photosensitive resin by selectively directing the laser in accordance with the 3D model of the artificial tooth. Also according to the present invention there is provided a method of 3D printing an artificial tooth having a solid outer enamel-like surface and an inner dentine-like portion comprising voids on a 3D printer having a print head with a nozzle for depositing a printing material, a build platform, and a digital control system for controlling the movement of the print head, the method comprising the steps of: loading a 3D model of the desired structure into the digital control system and dividing the 3D model into multiple layers, each layer representing a cross-section of the artificial tooth; for each layer, generating a toolpath for the print head to deposit the printing material, wherein the toolpath includes a continuous perimeter path corresponding to the solid enamel-like surface of the tooth, and an infill path corresponding to the inner dentinelike portion, the infill path being generated to create the voids; and controlling the movement of the print head and the deposition of printing material according to the generated toolpath to build up the tooth layer-by-layer. Preferably, the method may further comprise the step of post-processing the 3D printed artificial tooth to remove excess material and / or improve surface and mechanical material properties finish. Further preferably, the printing material may comprise a thermoplastic polymer, a composite material, or a combination thereof. Preferably, the voids within the inner dentine-like portion may be generated to provide a realistic drill resistance feedback during dental training. Further preferably, the method may further comprise the step of adding a second material into a generally axial void created in the infill path, the second material providing a pulplike portion being formed from a material with low resistance to drilling. Also according to the present invention there is provided a multi-layered synthetic bone model for medical training, comprising a 3D printed synthetic bone structure suitable for simulating drilling resistance in human or veterinary medicine. Preferably, the 3D printed synthetic bone structure may be produced through additive manufacturing, enabling realistic tactile feedback during medical training. Further preferably, the synthetic bone structure may include regions with varying drilling resistance to mimic different bone tissues. It is believed that a dental and skeletal training aid and method for producing same in accordance with the present invention at least addresses the problems outlined above. It will be obvious to those skilled in the art that variations of the present invention are possible and it is intended that the present invention may be used other than as specifically described herein. Brief Description Of The Drawings The present invention will now be described by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows various side plan and cutaway views of an artificial tooth for dental training in accordance with the present invention, the artificial tooth being shaped as an incisor; Figure 2 illustrates various side plan and cutaway views of an artificial tooth for dental training in accordance with the present invention, the artificial tooth being shaped as a molar; Figure 3 is a front perspective cutaway view of the artificial tooth for dental training shown in Figure 2; Figure 4 shows various side plan and cutaway views of an artificial tooth for dental training in accordance with a second embodiment of the present invention, the artificial tooth being shaped as an incisor; Figure 5 illustrates various side plan and cutaway views of an artificial tooth for dental training in accordance with the second embodiment of the present invention, the artificial tooth being shaped as a molar; Figure 6 is a front perspective cutaway view of the artificial tooth for dental training shown in Figure 5; Figures 7a and 7b show side plan views of artificial incisor and molar teeth, respectively, for dental training in accordance with the first and second embodiments of the present invention; and Figure 8 is a front perspective cutaway view of a section of artificial bone in accordance with a third embodiment of the present invention. Detailed Description Of The Preferred Embodiments The present invention has adopted the approach of providing an innovative dental drilling training aid designed to replicate the differential drilling resistance encountered in natural teeth. Advantageously, the present invention provides an eloquent way of simulating the various layers of a natural tooth, allowing dentists to develop and hone their drilling skills in a safe and controlled training environment. The goal is to enable dental students and professionals to achieve greater accuracy and sensitivity in their drilling techniques, in distinguishing between enamel, dentine and pulp layers, reducing the risk of accidental errors and enhancing patient safety. Further advantageously, the present invention provides synthetic bone and dental models which may be used as training aids in both the human and veterinary fields. Referring now to the drawings, an artificial tooth 10 according to the present invention is shown in Figures 1 to 3. What is shown in Figures 1 to 3 are side plan and front perspective cutaway views across the interior of the artificial tooth 10 in a plane that passes through the crown 22 of the tooth 10. The outer layer of the artificial tooth 10, which is representative of the enamel layer 12 is formed from a unitary 3D printable material that offers a high level of resistance to drilling. The primary material forming the tooth 10 of the present invention is a Stereolithography (SLA) resin comprising three parts: namely Urethane Dimethacrylate (UDMA), Isobomyl Methacrylate (IBMA) and a reinforcing agent, such as glass filler, ceramic powder, carbon or graphene. This is in no way intended to be limiting and exhaustive. This material is used for the outer enamel layer 12 and the inner dentine layer 14, as described in further detail below. This material offers the most realistic enamel-like resistance when the enamel layer 12 is drilled with dental burrs. The resistance to drilling of the dentine layer 14 is reduced from that of the enamel layer 12, despite being formed of the same base materials. This has been achieved by manufacturing a type of “foam” or “sponge-like” property within the material to reduce its density and thus resistance to drilling. For the purposes of this patent application, the terms “foam” and “sponge” and variations thereof are used interchangeably to signify a solid structure with a significant volume of voids or open spaces, creating a foam- or spongelike appearance and properties. The foaming has been carefully modelled in 3D Computer Aided Design (CAD) to reflect the internal dentine structure of a natural tooth. Thus when drilling, it is possible to feel a drop in resistance for the dentist carrying out the training procedure. The structure can be adjusted to allow a different feel or different decay damage The inner dentine layer 14 comprises the same base materials as the enamel layer 12 but includes a 3D printed sponge structure defining a volume of voids or channels 16 disposed throughout. In one embodiment of the invention, the channels 16 are straight and run longitudinally along the long axis of the artificial tooth 10. Such a structure can be such as to give rise to a drop in burr resistance. The present invention comprises a method for making an artificial tooth 10 by additive manufacturing, or 3D printing, in which perforate layers are superimposed one on another to form a 3D structure having a largely solid outer enamel layer 12 which envelops a dentine layer 14 having channels 16 disposed in its interior. The layers forming the channels 16 can be similar or identical but laterally displaced so as to give rise to tortuous channels. Layers of different perforate patterning could also be alternated to produce intersecting channels. The apertures or channels 16 can have dimensions from as small as can be printed up to the order of about 0.7mm or even larger. Apertures or channels 16 can be configured in a circular mesh arrangement. The channels 16 can have the same, or different, pore sizes or are 3D graduated along their longitudinal length. Alternatively the channels 16 can have a totally randomised pore size or the same pore size along their length. The illustrated sponge structures involve repeating patterns, which are produced by repeated layering of a single or a small number of patterns, but can be random or quasirandom, produced by successive layering of patterns generated by algorithms which, despite being random or quasi-random pattern generators, are constrained to produce continuous, or non-continuous, channels 16. The 3D-printing techniques as described herein can involve the deposition of successive patterned layers of a meltable or softenable material such as a plastic, or laser sintering or fused deposition, or selective curing, as by ultraviolet (UV) radiation, of liquid ink and resins. Figures 4 to 6 show a second embodiment of the training tooth 10. The tooth 10 of the second embodiment is very similar to that of the first embodiment and corresponding features have been given the same reference numerals. The second embodiment differs from the first embodiment in that a separate pulp layer 18 has been created within a void 20 disposed inside the inner dentine layer 14. In this way it is possible to apply a softer material 18 that closely mimics the drilling resistance of pulp. The advantage of this is that a realistic drill resistance feedback between enamel 12, dentine 14 and pulp layers 18 is achievable when the artificial tooth 10 is used on a “phantom head” (not shown). To emulate a natural tooth, the pulp layer 18 is printed in the void 20 which is located at the innermost part of the tooth 10, axially, or near, the axial centre thereof. In one embodiment of the invention, the pulp 18 can be constructed from a soft material with a very low resistance to drilling, such as a wax-type product, 3D printing resin, silicon, rubber or the like. The above list is in no way intended to be limiting and exhaustive. The pulp 18 may be a different colour, for example, red, to better emulate natural teeth. Therefore the tooth 10 of the second embodiment is formed from two 3D printable materials. The present invention also having the capability to simultaneously use two different 3D printable resins during the printing process, which is beneficial for creating multi-material teeth 10 with enhanced quality, functionality and precision. Figure 7 shows side plan views along the long axis of the artificial tooth 10 and illustrates further the anatomical life-like configuration of a human tooth and comprises a crown 22 and an elongate root section or peg 24 that can be received into the jaws of a dummy “phantom head” (not shown). There are numerous ways in which the tooth 10 can be received into the jaws of a dummy “phantom head” (not shown) via the elongate root or peg 24, including interference or friction fits, and the like. The skilled person will equally understand that the present invention the artificial tooth 10 described herein does not necessarily need to be placed inside a phantom head, when in use. A further advantage of the present invention in providing suitable materials and production processes for 3D printed teeth is that the 3D CAD model can be selected to produce molars, premolars, canines and incisors, as and when required. This is not possible with known injection moulding techniques, where a separate mould would be needed for each tooth type. As mentioned above, the above-mentioned artificial tooth 10 is primarily intended for use as a dental training aid for education, training and certification of dentists. The primary purpose is to assist and further develop the exposure of differential drilling to trainee dentist students. Allowing a dental student to be able to learn, refine and perfect their drilling technique on “phantom heads” before being exposed to live patients. The present invention provides an experience and tactile feedback that is exceptionally realistic through the combination of blending a unitary enamel-like outer layer 12 with a complex 3D “foamed” model to represent the dentine later 14, and optionally a second softer material 18 to emulate the pulp. The product has been developed to help training dentists gain a greater drilling skill level before graduating. The increased skills in drilling that the dental students will gain through using the invention will reduce the pressure felt by newly-qualified dentists when facing their first live patient. It is also understood that this invention will reduce the number of newly-qualified dentists that have to re-train and re-certify this aspect of their dentistry practice for accidentally drilling into a patient’s pulp. The present invention can also be used in other applications where it is important to have a differential drilling resistance as either a functional requirement, or as a training aid. The present invention also finds application in the field of veterinary dentistry. In this regard, the artificial tooth 10, and suitable materials and production processes for 3D printed teeth described herein, can be adapted to replicate the characteristics of animal teeth. Another application of the present invention lies in terms of suitable materials and production processes for 3D printed synthetic bones 30 for both human and veterinary medicine. Here, the same purpose of improved training and error reduction can equally be applied to drilling bones in the human or animal body, such as may be undertaken by orthopaedic surgeons, trauma doctors and veterinarians. Figure 8 shows a third embodiment of the invention. The third embodiment differs from the first and second embodiments in that it relates to suitable materials and production processes for synthetic bones 30. As is known to the skilled person, bones are complex natural structures composed of different tissues that provide strength and support, and are crucial for the production of blood cells. Compact bone, forming the outer layer, consists of dense, tightly-packed tissue, contributing to the bone’s hardness. Spongy bone, found inside, has a porous structure, enhancing flexibility and reducing weight. Bone marrow, located within the cavities of bones, produces blood cells and stores fat, and plays a crucial role in haematopoiesis and metabolic functions. Very much like has been described above in relation to the first and second embodiments of the present invention, the artificial bone 30 can be produced having a dense compact bone layer 32 that mimics natural compact bone. A spongy bone layer 34 is achievable by manufacturing the same type of “foam” or “sponge-like” property within the 3D printed material to reduce its density and thus resistance to drilling, and which is equivalent to the dentine layer 14 described above in relation to 3D printed teeth 10. Finally, a separate bone marrow layer 36 can be disposed within spongy bone layer 34. In this way it is possible to apply a softer material 36 that closely mimics the structure of natural bone marrow. Therefore, a dental and skeletal training aid and method for producing same according to the present invention is described. When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and / or “including” when used herein, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, separately, or in any combination of such features, can be utilised for realising the invention in diverse forms thereof. The invention is not intended to be limited to the details of the embodiments described herein, which are described by way of example only. It will be understood that features described in relation to any particular embodiment can be featured in combination with other embodiments. It is contemplated by the inventor that various substitutions, alterations and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. An artificial tooth (10) formed from a unitary 3D printable material, the artificial tooth (10) comprising an outer enamel-like portion (12) and an inner dentine-like portion (14) having voids therein.

2. The artificial tooth (10) of claim 1, wherein the dentine-like portion (14) is enveloped within the enamel-like portion (12), and wherein the enamel-like portion (12) and the dentine-like portion (14) together comprise a crown (22).

3. The artificial tooth (10) of claims 1 or 2, wherein the voids being arranged as channels (16) inside the dentine-like portion (14).

4. The artificial tooth (10) of claim 3, wherein the channels (16) are elongate straight-through channels.

5. The artificial tooth (10) of claims 3 or 4, wherein the channels (16) are configured in a circular mesh arrangement.

6. The artificial tooth (10) of any of claims 3 to 5, wherein the channels (16) have varying pore sizes along their length and / or individual channels (16) have a distribution of pore sizes.

7. The artificial tooth (10) of claim 3, wherein the channels (16) are configured in a random or quasi-random or repeating pattern.

8. The artificial tooth (10) of claim 3, wherein the channels (16) are tortuous and formed by deposition of layers of different perforate patterning that are laterally displaced.

9. The artificial tooth (10) as claimed in any of the preceding claims, wherein the 3D printable material comprises a Stereolithography (SLA) resin consisting of Urethane Dimethacrylate (UDMA), Isobornyl Methacrylate (1BMA), and a reinforcing agentselected from the group consisting of, but not limited to, any of the following: glass filler, ceramic powder, carbon or graphene.

10. The artificial tooth (10) of claim 1, wherein the dentine-like portion (14) being provided in a sponge-like configuration to mimic the dentine structure of a natural tooth.

11. The artificial tooth (10) of claim 2, further comprising a root portion (24), wherein the crown (22) being adjacent to, and extending from, the root portion (24).

12. The artificial tooth (10) of claim 11, wherein the root portion (24) is suitable for insertion into a dummy phantom head for dental training.

13. The artificial tooth (10) of claim 12, wherein the voids within the dentine-like portion (14) provide a realistic drill resistance feedback during dental training.

14. The artificial tooth (10) of claim 1, further comprising a separate pulp-like portion (18) formed from a material with a lower resistance to drilling that mimics the pulp structure of a natural tooth.

15. The artificial tooth (10) of claim 14, wherein the pulp-like portion (18) is selected from the group consisting of, but not limited to, any of the following:a wax-type material, 3D printing resin, silicon, rubber or the like.

16. The artificial tooth (10) of claims 14 or 15, wherein the pulp-like portion (18) is elongate and positioned generally co-axially with the root portion (24) and extends into the dentine-like portion (14).

17. The artificial tooth (10) as claimed in any of the preceding claims, wherein the tooth (10) is representative of a human or animal tooth.

18. A method of 3D printing an artificial tooth having a solid outer enamel-like surface and an inner dentine-like portion comprising voids on a 3D printer having a build platform, a laser and a vat of photosensitive resin, and a digital control system for controlling themovement of the build platform, the laser and / or the vat, the method comprising the steps of:loading a 3D model of the artificial tooth into the digital control system and dividing the 3D model into multiple layers, each layer representing a cross-section of the artificial tooth;for each layer, generating a path for selectively solidifying the photosensitive resin within the vat using a laser, wherein the path includes a continuous path corresponding to the solid enamel-like surface of the tooth, and an infill path corresponding to the inner dentine-like portion, the infill path being generated to create the voids; andcontinuously lowering the build platform or elevating the vat to allow for the formation of subsequent layers of the artificial tooth and solidifying successive layers of the photosensitive resin by selectively directing the laser in accordance with the 3D model of the artificial tooth.

19. A method of 3D printing an artificial tooth having a solid outer enamel-like surface and an inner dentine-like portion comprising voids on a 3D printer having a print head with a nozzle for depositing a printing material, a build platform, and a digital control system for controlling the movement of the print head, the method comprising the steps of:loading a 3D model of the desired structure into the digital control system and dividing the 3D model into multiple layers, each layer representing a cross-section of the artificial tooth;for each layer, generating a toolpath for the print head to deposit the printing material, wherein the toolpath includes a continuous perimeter path corresponding to the solid enamel-like surface of the tooth, and an infill path corresponding to the inner dentinelike portion, the infill path being generated to create the voids; andcontrolling the movement of the print head and the deposition of printing material according to the generated toolpath to build up the tooth layer-by-layer.

20. The method of claims 18 or 19, further comprising the step of post-processing the 3D printed artificial tooth to remove excess material and / or improve surface finish and alter the materials mechanical properties.

21. The method of claims 18 or 19, wherein the printing material comprises a thermoplastic polymer, a composite material, or a combination thereof.

22. The method of any of claims 18 to 21, wherein the voids within the inner dentinelike portion are generated to provide a realistic drill resistance feedback during dental training.

23. The method of any of claims 18 to 22, further comprising the step of adding a second material into a generally axial void created in the infill path, the second material providing a pulp-like portion being formed from a material with low resistance to drilling.

24. A multi-layered synthetic bone model (30) for medical training, comprising a 3D printed synthetic bone structure suitable for simulating drilling resistance in human or veterinary medicine.

25. The multi-layered synthetic bone model (30) of claim 24, wherein the 3D printed synthetic bone structure is produced through additive manufacturing, enabling realistic tactile feedback during medical training.

26. The multi-layered synthetic bone model (30) of claims 24 or 25, wherein the synthetic bone structure includes regions with varying drilling resistance to mimic different bone tissues.17

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