WO2012161646A2

WO2012161646A2 - A method of producing a multilayered structure

Info

Publication number: WO2012161646A2
Application number: PCT/SE2012/050548
Authority: WO
Inventors: Saeid Kazemi; Reza Kazemi; Nazila HASANZADE
Original assignee: Drsk Development Ab
Priority date: 2011-05-20
Filing date: 2012-05-21
Publication date: 2012-11-29
Also published as: WO2012161646A3

Abstract

A method of producing a multi-layered structure comprising the steps applying a first material having a first set of properties to form a first shape having an interior cavity, applying a second material having a second set of properties to form a first layer covering at least a first section of said first shape,and applying a third material having a third set of properties into said cavity wherein said third material is an electrically conducting material. A multi-layered dental structure comprising a longitudinally extending body made of a first material having a first set of properties and being formed with an interior cavity, a first layer covering at least an upper part of said longitudinally extending body, wherein said first layer is made of a covering material that is harder than said first material, and a filling material within said cavity, wherein said filling material is an electrically conducting material softer than said first material.

Description

A METHOD OF PRODUCING A MULTI-LAYERED STRUCTURE

TECHNICAL FIELD

The present invention relates to a method of producing a multi-layered structure. It also relates to interactive multi-layered models for practicing dental treatments and general medical treatments and methods of

manufacturing such interactive multi-layered models.

Realistic models imitate models of a human or animal body such as teeth and jaws. Also general medical models come as close as possible to normal anatomy. Such models can be used in specific treatment practice in order to diminish the gap between pre-clinic and clinic for medical trainees.

Jaws are the two opposite structures forming the entrance of the mouth. The lower jaw is called mandible which comprises mandible bone with soft tissue around it. Inferior alveolar nerve enters into mandibular canal in the mandible bone and runs forward in the canal under the mandibular teeth. The upper jaw is called maxilla and the teeth located in this jaw are called maxillary teeth.

A tooth is divided into two parts: the crown and the root(s). It comprises four distinct types of tissue: Enamel, Dentin, Pulp and Cementum. Enamel is the outer layer of the tooth which covers the crown of the tooth. Dentin is an intermediate layer in the crown which is located directly beneath the enamel and surrounding the pulp. Dentin in root is located directly beneath the cementum and surrounds the root canals.

Dentinoenamel junction (DEJ) is a surface located inside the crown and is the boundary between the enamel and the underlying dentin. DEJ is sensitive to some stimuli such as touch which can generate pain signals. Pulp is a living tissue and highly sensitive to different stimuli. It is located in the central part of the tooth called the pulp cavity and transmits pain signals toward the nervous system. An elongation of the pulp that extends toward the dentin is called pulp horn. PRIOR ART

Teaching and training aids for the aim of training and simulation of dental students are known from the state of the art.

GB1466907 "Dental Patient Simulator" describes a dental patient simulator comprising a phantom head, jaws and artificial teeth. Document JP5204300 "Model Teeth for Dental Teaching" describes a model of a mandible comprising artificial teeth showing surface anatomy and

mechanical properties similar to natural teeth. WO201 1 104351 "A Dental Model" describes a dental model with a jawbone and teeth arranged in cavities of the jawbone which imitate the characteristics of real teeth and jawbone which allows realistic surgery training in dentistry. Document FR2929740 "Anatomical model of a human jaw for surgery or implantology" describes a model for practicing insertion of a dental implant into the model.

EP1912194 "Multi-layered Model Tooth for Dental Training" describes a multi-layered model tooth for dental training including a crown part artificially produced by simulating an enamel layer as a surface layer and a dentin layer as an inner layer and a root part. Document

WO2004023435 "Tooth model for dentistry practical training" describes a tooth model for dentistry practical training capable of correct shape measurement using laser light. Document US2009239204 "Tooth for jaw tooth model and method of producing the same" relates to a tooth to be used in a jaw tooth model which allows students under dental training to experience tooth treatment.

EP0822786 "Image Sound and Feeling Simulation System for

Dentistry" describes a simulation system comprising some sensors, a data processing unit, a hand piece and some more devices, the whole system imitates the sound and associated hand feeling, when drilling through tooth layers of different hardness. However the simulation system suffers from many limitations. Firstly, using three different 3D sensors require a powerful data processing unit to interpret the incoming signals from sensors, resulting in higher complexity of the system and more problems in support and maintenance. Secondly, although using a processor on a computer machine is an easy way to handle signals coming from the sensors; it always imposes high expenses and dependency to a computer machine which of course acquires significant support. Power consumption is noticeable in long term. Thirdly, required 3D sensors themselves, imposes high expenses to the whole system. Furthermore 3D sensors will easily go out of calibration, which cause handling errors. Fourthly, the simulator is very expensive and will not be cost effective to purchase for most dental institutes. Fifthly, in spite of similarity of the hand and ear feeling to the real dentistry practice the trainee cannot get the feeling of working on a real tooth or patient when looking at the monitor while drilling.

JP2007328083 "Dentition Model" also describes a simulation system comprising teeth model, pressure sensors and a data processing unit. The whole system generates pseudo physical feeling of a patient while drilling teeth in a treatment session using pressure sensors. However this simulator suffers from many limitations. In reality, when drilling a tooth, the pain signal is generated by a touch stimulus while the pressure stimulus on a tooth is not the main stimulus. Secondly, compared to the traditional simulators this simulator commercially should not be cheap at least due to dependency to a computer machine and using piezo film sensors and possibly complicated production procedure. Thirdly, using a processor on a computer machine is imposes high expenses and acquires significant support and furthermore power consumption is noticeable in long term.

WO 2008091434 describes an anesthesia model comprising an artificial model of upper and lower jaws containing sensing means. The sensing means are situated between the upper and lower jaws and are constituted by flexible switch membranes or a position sensor. A

processing means then detects whether injections have been delivered in a suitable area. This anesthesia model suffers from many limitations. Firstly, the system is sensitive to pressure and not touch which is not imitating the real situation. Secondly, it does not disclose any output signal from the detector in the form of pain simulation. Thirdly, there are not any means for simulating pain associated with drilling or injection. JP5027675 describes a simulation system which is able to detect changes of potential when a drill touches two different layers in artificial tooth without a closed circuit. It shows detection of the position, the angle, and depth of a tip of the injector in nerve blocking training. The artificial teeth comprise two sensitive layers. Simulation of anesthetic techniques is also provided. However, the system uses electrostatic energy to generate signals, which is a major disadvantage since it makes the signals

unpredictable and temporary. Once the sensor is touched, it is discharged and must then be charged again.

WO200182266 "System and method for virtual reality training for odontology", US20021 19432 "Methods and apparatus for simulating dental procedures and for training dental students", WO2008066891 "Systems for haptic design of dental restorations", and US201031 1028 "Dental Implant Surgical Training Simulation System" describe systems for virtual training, to acquire procedure movements in odontology, by sensing data

concerning spatial position of a real hand-held element. However the main drawback using the above systems is that the trainee does not have possibility to practice with a physically palpable model.

A system able to generate signals of pseudo pain, block pseudo pain and provide perception of different signals of pseudo pain and accordingly reacting different parts of a jaw model including the jaw bone and teeth is described in SE0801628, "A method and a device for practicing dental treatments". The disclosed system introduces moulding and over moulding as production method. This production system may not be sufficient to provide complicated structures.

The spinal cord, located within the spinal canal, is surrounded by three layers of protective membranes which are called meninges. The outermost meaning is called dura mater. Above the dura mater there is a space called 'Epidural Space' containing fat and the nerve roots exiting from the spinal cord. The epidural space extends along the spine outside the dura mater and is the target of the epidural injection. There are specific treatments in which injection is administrated into specific spaces around spinal cord. For example, in order to administer an injection in epidural space the needle should pass through some different layers until the needle reaches into epidural space. During the practice, the practitioner can be guided by X-Ray.

GB2369714 "An epidural simulator device" describes a model with bone frame to be used for epidural practices. The simulator imitates physical properties of tissues that the trainee is penetrating and passing through. JP2002132138 "Epidural puncture simulator" describes a model to be used for epidural practices. The simulator imitates physical properties of tissues that the trainee is penetrating and passing through. It enables an operator to check a puncture area by inserting a needle tip while making palpation and to catch on the sensation of the needle tip advancing.

WO2007068050 "Simulator and method" describes a haptic simulation apparatus which simulates a medical or surgical procedure to provide interactive training for learning a complete procedure, particularly an epidural anaesthesia, including dextrous and non-dextrous steps. However the limitation of above said simulators is that the trainee cannot get a palpable and real time feedback from a physically palpable model.

In prior art either no interaction or simulation of reaching internal parts by the medical/dental instruments is provided or the interaction and simulation is not realistic to efficiently improve the learning process of the trainee. None of the documents reveal full and realistic interaction or simulation in a physically palpable model when medical/dental instruments are for example touching, cutting, drilling, or penetrating the models.

SUMMARY OF THE INVENTION

The present invention relates to interactive multi-layered models for practicing general and dental medical treatments and methods of

manufacturing such interactive multi-layered models.

A model produced in accordance with the invention comprises at least one multi-layered structure in which at least one layer is made of electrically conductive component in or between different layers. With using various production methods it is possible to produce and embed the multi-layered structure inside the model. Furthermore it is possible to produce unique shapes for each model. The model is realistic in essential specific anatomic details and even very complex anatomic structures such as pulp horn in a tooth can be manufactured in the model. Sensors can be embedded generally in any model of complete or parts of a human or animal body for simulation of a specific medical procedure.

The dental model can comprise at least one multi-layered tooth and at least one multi-layered jaw for practicing dental procedures and treatments such as tooth drilling, giving anesthetic injection, pulp cap, drilling and inserting a tooth implant, impact tooth surgery, periodontal surgery, periapical surgery, inserting bone implants, temporomandibular joint injection and tooth extraction.

When the trainee is practicing treatments with this model, due to its multi-layered structure, the model has the capacity of identifying where the medical tools are touching, moving, or located. The medical tools used can be of various types for instance an injection needle when performing local anesthesia in soft tissue or other tissues, a drilling bur when drilling tooth or bone, surgical knives when cutting the soft tissue, explorers, scalers, probes, and other medical tools.

Identification of stimuli is made in real time and accordingly the model is able to simulate pain, anesthesia or display that the medical tool is getting close, passing by or passing through an anatomic structure or anatomic landmark. The simulation of the function is handled by a standalone processor in an embedded system extendable to be connected into a network.

The interactive multi-layered models manufactured in accordance with the invention comprise multi-layered constructions reflecting the anatomic structure and sensitive layers of normal natural human tooth, jaw, or other parts of human or animal body. The layers in the interactive multi-layered model according to the present invention will have a similar anatomy and hardness/hardness difference between different layers, compared to the corresponding part in natural anatomical counterpart for example the enamel, dentin and pulp in a real tooth. Thereby the trainee is given the possibility to feel and learn the small anatomical aspects of the model in real-time, which is the basis to learn many of medical practices. The model comprises at least one multi-layered structure in which at least one layer is made of electrically conductive components in or between different layers. The conductive layer is attached to a connector which is communicating with a processing unit. The multi-layered sensors can be embedded generally in any model of complete or part of human or animal body for simulation of a specific medical procedure.

The present invention further discloses a method of manufacturing such a model using additive method by using a 3D printer alone and combined with other manufacturing methods such as moulding, and subtractive manufacturing methods. The methods make it possible to manufacture unique anatomical surfaces and internal anatomy for each model.

Furthermore the methods make it possible to manufacture interactive models with complicated anatomic structures and consequently possibilities for the trainees to practice different treatments.

In various embodiments the dental model comprises at least one multi- layered tooth and at least one multi-layered jaw for practicing dental procedures and treatments such as tooth drilling, giving anesthetic injection, pulp cap, drilling and inserting a tooth implant, impact tooth surgery, periodontal surgery, periapical surgery, inserting bone implants,

temporomandibular joint injection, and tooth extraction.

The layered tooth model has the capacity of simulating pain during drilling or touch in pseudo-pain sensitive layers when practicing dental treatments. The layered jaw model will reveal for example where the injection needle, when performing local anesthesia is located in soft tissue or where the drilling bur is located in the hard tissue like a bone when practicing dental treatments such as insertion of dental implants.

The multi-layered models comprise multi-layered constructions reflecting the anatomical structure and pain sensitive layers of a for example normal natural human tooth or jaw. The layers in a multi-layered tooth according to the present invention will have a close morphology and hardness/hardness difference between different layers, compared to the corresponding part in a natural normal tooth i.e. enamel, dentin and pulp. Thereby the dental trainee is given the possibility to feel and learn the small changes in morphology and hardness when drilling in a tooth.

The manufacturing principle for the multi-layered models according to the present invention allows the manufacturing process to be initiated from the middle part to the inner part and then toward the outer part. For example with a multi-layered tooth the manufacturing process can start with forming the layer similar to dentin, followed by the layers similar to pulp and finally over moulding within the layer similar to enamel. Following these steps the resulting model will be more similar to the real anatomy and will have more distinct shapes.

The manufacturing process will also make it possible to form individually shaped models for example a multi-layered tooth with pulp horns. Such a multi-layered tooth will make it possible for the trainee to practice a dental damage which, if not properly treated, will result in severe pain and the performance of root canal therapy. A general advantage of the present invention is the possibility to produce different shapes of dentin and different shapes of pulp which forms the basis for a very realistic training session for the dental trainees.

A multi-layered tooth produced in accordance with the present invention comprises embedded sensors either as layers themselves or part of layers or sensors processed in or between different layers. Embedded sensors are important for the dental trainee or dentist in order to receive an accurate response in real time regarding where the pain is occurring. Accordingly, it is important to include at least one sensor in the component similar to the pulp because when reaching this part of the tooth with the drilling bur, a strong pain sensation is felt by the dental patient.

Additionally it is important to have a sensor in the component similar to the dentin in order for the dental trainee to get a feeling and an

understanding of how deep drilling into the enamel can be performed before exposing the dentin and the same for pulp. Furthermore, a multi-layered tooth with embedded sensors renders the functionality to combine the injection and drilling simulation at the same time for the dental trainees which allows for a more realistic dental training. Another embodiment of such an interactive multi-layered model is a model for practicing drilling and insertion of dental implant. When the trainee wants to insert a dental implant awareness of the anatomic structures associated with the mandible and maxilla is essential. Avoiding life- threatening hemorrhage and nerve and sinus injury is imperative.

Another aspect of the present invention relates to the manufacturing of conducting passages, preferably electrically conducting passages in a nonconductive material. Two or more elements of electrically conducting materials can be electrically connected in a controlled and adjustable way. The material or materials between the conducting materials are made according to specific conditions where channels, void, grooves and/or tubes are incorporated into the nonconductive material.

The manufacturing of the nonconductive material in different shapes are made using additive method by a 3D printer programmed in a way to incorporate channels, voids, grooves and/or tubes according to an exact and predetermined route. The so formed channels, voids, grooves and/or tubes are then filled or injected with a conductive material for example conductive silicone. The resulting material, based on nonconductive material comprising channels, voids, grooves and/or tubes in a predetermined way can be used for exact and accurate transfer of electrical charges from one or more conductive materials to other conductive materials through sections of nonconductive materials.

Still a further aspect of the present invention is to provide a dental model where the crown of the tooth model is attached to the root of the tooth model with a system allowing the crown to be exchanged after dental practicing while the root part is continuously but not permanently attached to the jaw model. Consequently the tooth model is made of two parts. One part is the crown part which is replaceable while the root part normally is attached to the jaw part.

Still another further aspect of the invention is to provide a general medical model for medical trainees to practice epidural anesthesia or for radiologists to practice spinal procedures either an epidural injection or a facet injection. The model consist of one or more layers of bone resembling materials and other relevant parts that should be reached in a controlled way in order to render the medical trainee relevant practice.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above recited and other advantages and objects of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.

Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

Figure 1A, illustrates a longitudinal section of a normal real tooth, Figure 1 B, illustrates a longitudinal section of a multi-layered tooth model (22) produced in accordance with the invention,

Figure 2 shows a human lower jaw,

Figure 3A, illustrates an application of a multi-layered dental system,

Figure 3B, illustrates a sagittal section of a multi-layered jaw model, Figure 4A, 4B illustrate a longitudinal section of an embodiment of implant model,

Figure 5 shows a model for practicing epidural injection

Figure 6A-G show the production steps in accordance with one embodiment of the invention of a multi-layered tooth,

Figure 7A-D show the production steps in accordance with an alternative embodiment of the invention of a multi-layered tooth,

Figure 8A, 8B, 8C illustrate a further aspect of the invention with a replaceable crown,

Figure 9 shows different uniquely shaped artificial models produced in accordance with the invention,

Figure 10 shows a general model manufactured with the properties of having sensors embedded, Figure 1 1 shows a further aspect of the invention with a replaceable artificial crown that can be attached to an artificial root,

Figure 12 shows a further aspect of the invention. DETAILED DESCRIPTION

As shown in Figure 1 A a normal real tooth, (2) is formed with crown (4), root (6) enamel (8), dentin (10), dentino enamel junction (DEJ) (16), pulp (12) which fills the pulp cavity, root canal (14), and pulp horn (18).

In Figure 1 B a multi-layered tooth model (22) is shown with artificial crown (24), artificial root (26) artificial enamel (28), artificial dentin (30), artificial pulp (32) which fills the pulp cavity, artificial root canal (34), artificial dentino enamel junction (DEJ)(36), artificial pulp horn (38), electrically insulating layer (40) between the artificial pulp and artificial dentin, attachment site (42) of the artificial tooth to root, and attachment site (44) between artificial root and artificial jaw.

Figure 2 shows a human lower jaw, containing the mandible bone (46), soft tissue around it (48), mandibular canal (50), and infra alveolar nerve (52) passing through it.

Figure 3A, illustrates an application of a model and shows a

longitudinal section of a system which is able to generate signals (61 ) by multi-layered sensors (58) or tooth model (22) equipped with the multi- layered sensors when they are touched by a tool (64) which is electrically conductive and accordingly sending signals to a central processing unit (59) to provide reaction to different signals.

Figure 3B, illustrates a sagittal section of a jaw model with artificial mandibular bone (54), artificial soft tissue (56), multi-layered sensor (58) including electrically conductive layer (60) with an insulating layer (40) in between, and attachment site (62), it displays that the tool (64) is getting close or passing by artificial infra alveolar nerve.

Figure 4A, 4B illustrate a longitudinal section of an embodiment of implant model. Figure 4A displays that the tool (64) is getting close or passing by an artificial infra alveolar nerve (66) when it touches the first electrically conductive layer (60). Figure 4B displays that the tool (64) is passing through an artificial infra alveolar nerve (66) when it touches another electrically conductive layer (60).

Figure 5 shows a model for practicing epidural injection when the trainee passing through different electrically conductive layers and electrically insulating layers and can find the correct space for injection.

The process of manufacturing multi-layered interactive models can, according to the present invention be performed by using different

technologies in a cost efficient way. The invention is therefore based on implementing one single method or combination of methods to solve the technical challenges of the production of such models. These methods of manufacturing of models have the advantage of being able to either embed prefabricated sensors or manufacture the sensor layer together with other layers in a single step or multiple steps and accordingly connect the sensor layers to a processing unit. The sensor, sensor material or sensor layer is designed to send signals to a processor unit in case of being touched by a dental and/or general medical tool.

In one embodiment according to the present invention, readymade sensors are positioned inside a mould and the same or different materials will cover said sensor partially or completely (Figure 6G, 7D). Yet in another process the sensor material and none sensor materials are positioned beside each other (Figure 7B) in a multi-layered fashion and are manufactured in one single or more than one production cycle(s).

Within the scope of this invention and in order to manufacture a multi- layered model, one of the following methods or combination of the methods of manufacturing multi-layered structures may be used in order to

manufacture one or more of the layers. Furthermore a single layer or multiple layers can be manufactured implementing any of the below mentioned methods and materials. The manufacturing process, when a combination of methods is used, can be based on one or more of the methods in sequential or different orders.

Within the scope of this invention and in order to manufacture a multi- layered tooth model, the preferred method is additive manufacturing which is defined as the process of joining materials to make objects from 3D model data, usually layer upon layer or particle added to particles. Additive method is implemented by a 3D printer (Figure 6A-C, 7A (68)) machine which uses any of the technologies of Selective laser sintering (SLS), Fused deposition modelling (FDM), Stereolithography (SLA), Laminated object manufacturing (LOM), Electron beam melting (EBM), 3D printing (3DP), and Aerosol Jet 3D printing. There are different possibilities with such machines. The first possibility is to manufacture a single layer object. This object thereafter will be embedded inside other material or will embed other material in itself using any of the other methods to manufacture a multi-layered object.

The first possibility with additive methods is to manufacture a single layer object. This object thereafter will be embedded inside other material or will embed other material in itself using any of the other methods to manufacture a multi-layered object. The second possibility is to manufacture a multi-layered component in a single printing cycle with a 3D printing machine which is using different dispensers and each dispenser is dispensing a material different from the other dispenser. The word dispense is used as a general word to express adding material to the part in printing process. Furthermore in the second possibility it is yet possible to use two or more printer machines which are printing concurrently using one common printing area to print different materials. With using any of the second said possibility a multi-layered object is manufactured in a way that material A is partially or completely embedded inside the material B in a single printing cycle. The third possibility is to print the objects with cavities to be filled with other materials such as electrically conductive material.

The above described method can be used alone or in combination of the following methods in order to manufacture one or more of the layers. Furthermore a single layer or multiple layers can be manufactured

implementing any of the below mentioned methods and materials. The manufacturing process, when a combination of methods is used, can be based on the above described additive method together with one or more of the methods in sequential or different orders.

1 . Injection Moulding is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Material is fed into a heated barrel, mixed, and forced into a mould cavity where it cools and hardens.

2. Over moulding (Insert moulding, and Plastic Encapsulation) (Figure 6F, 7C), is placing previously manufactured parts (or section of those parts) into an injection mould and injecting material around it.

Accordingly this is the process of injection a moulding material in and around another component in order to fully or partially encapsulates the component. Inserts can either be incorporated at the time of the moulding process, or be inserted as a post moulding operation.

3. Multi-shot injection moulding which is a method to over mould within a single moulding cycle. This process is an injection moulding process performed multiple times. For example in a two-shot mould, in the first step the first material is injected into a mould to form the initial section of a part. Once formed, a second material is injected into the remaining open space of the mould to form the remainder of the part.

4. Matrix moulding or matrix transfer moulding is a method often used during moulding. As a first step the creation of the rigid outer shell is made and then the softer and more fluid moulding material is introduced between the shells.

5. Rotational moulding: A heated hollow mould is filled with a charge or shot weight of material, and the mould is then slowly rotated (usually around two perpendicular axes) causing the softened material to disperse and stick to the walls of the mould.

6. Compression moulding which is a method of moulding in which the moulding material, generally preheated, is first placed in an open mould cavity. The mould is closed with a top force or plug member, pressure is applied to force the material into contact with all mould areas.

7. Reaction injection moulding (RIM) which is similar to injection

moulding except thermosetting polymers are used.

8. Subtractive manufacturing which is defined as the process of

removing materials to make objects from 3D model data. For example using any cutting instrument like a milling machine or using laser technology in a laser machine to remove the material from inside of a previously produced part.

9. Lamination, Coating, and Metalizing which refers to the placing of a layer over a part. Accordingly, the part will be covered partially or completely by the layer.

For specific applications it is also beneficial to use other methods such as:

• Sandwich injection

• Transfer Moulding

· Compaction plus sintering

• Extrusion moulding

• Blow moulding

• Thermoforming

• Vacuum forming

· Expandable bead moulding

• Foam moulding

• Vacuum plug assist moulding

• Pressure plug assist moulding

• Matched mould

· Film Insert Moulding

The method or combination of the methods for manufacturing layers of an interactive multi-layered model may be properly selected in accordance with the materials to be used. The base material can be chosen or combined from the group comprising: Polylactic Acid (PLA); Polyamide (PA);

Polyaryletherketone (PAEK); Polybutylentereftalat (PBT); Polycarbonate (PC); Polyethylene (PE (LD, MD, HD)); Polyetheretherketone (PEEK);

Polyetherimide (PEI); Polyethersulfone (PES); Polyetylentereftalat (PET); Liquid Crystal Polymer (LCP); Polyoxymethylene (POM); Polypropylene (PP); Polyphenylene amid (PPA); Polyphenylene Sulfide (PPS); Acrylonitrile- Butadiene-Styrene (ABS);PolySulfone (PSU); Polystyrene (PS);

Thermoplastic Elastomers (Ester and Amide based) (TPE); Thermoplastic urethane (TPU); Thermoplastic olefin (TPO);Epoxy 40 plastic (EPI); Silicone rubber (Q); or Silicone plastic (SI); Thermosetting resins such as Duroplast; Composites such as Bisphenol A-Glycidyl Methacrylate (BIS-GMA) and acrylic materials; Porcelains such as ceramics.

Furthermore materials such as DuraForm ® EX Natural; DuraForm ® FR 100 Plastic; Somos™ 201 ; LaserForm ST-100; LaserForm A6; different types of DSM Somos; different types of Somos; different types of ProtoGen TM; different types of NanoForm TM; different types of ProtoCast TM;

different types of DMX-SL TM; WaterClear® Ultra, ProtoTherm TM; different types of Accura; different types of RenShape SLA; digital materials from Objet can be chosen.

Furthermore the material can be chosen from the group comprising:

PRE-ELEC PC1431 , PRE-ELEC PBT 1455, PRE-ELEC PE 1292, PRE- ELEC PE 1294, PREELEC PP 1370, PRE-ELEC PP 1373, PRE-ELEC PP 1375, PRE-ELEC PP 1378, PRE-ELEC PP 1380, PRE-ELEC PP 1382, PRE- ELEC PP 1383, PRE-ELEC PP 1385, 5 PRE-ELEC PP 1387, PRE-ELEC PS 1326, PRE-ELEC 17-031 -HI, PRESEAL TPE 5010, PRESEAL TPE 5020, PRESEAL TPE 6070, PRESEAL TPE 6080, LNP FARADEX AS-1003, LNP FARADEX PS003E, LNP FARADEX DS0036IP, or Loctite 5421 TM, Loctite 5420 TM.

The method or combination of the methods for manufacturing layers of such a model tooth may be properly selected in accordance with the materials to be used. The conductive additive material can be chosen or combined from the group consisting of: carbon powder, carbon fiber, stainless steel grades, carbon nanotubes, nickel, graphite, silver, copper and gold. Volume resistivity of the conductive material in the composition is between 0.0001 to 10000 Ω/cm.

Other additives might be chosen or combined from the groups of Fillers/Extenders, Reinforcements agents, Antistatic Agents, Pigments, in order to change the physical property of the material to be used in the interactive multi-layered model. A combination of the base material mixed with various kinds of one or more types of conductive and non-conductive additives might be used to manufacture the sensor component. Other materials with the required specifications and properties can also be used according to the invention. The invention is not limited to use only the above mentioned methods and materials.

In one embodiment shown in Figures 3B the electrically conductive material of the electrically conductive layer (60) is a compound of the base material and carbon, iron or nickel additive. Alternatively, a carbon or iron based material is combined with a nickel coating. The carbon or iron based material is a composition comprising an electrically conductive material and a polymer base.

Another embodiment of an interactive multi-layered model is a model for practicing epidural injection as shown in Figure 5. Different anatomical layers in natural counterpart are imitated by using the multi-layered structure. One multi-layered sensor which is corresponding to spinal cord, dura matter and epidural space is located in the core of the model inside an artificial vertebral bone. Thereafter a multi-layered sensor is covering the entire part again. The advantage of the model is that the trainee can interactively learn the correct position for the tip of the needle in with a palpable model.

Furthermore in case of the practitioner be guided by X-Ray, lower radiation absorption is foreseen as the practitioner has better practical anatomical view of the area.

An embodiment of the production steps of a multi-layered tooth is shown in Figures 6A-G. Two electrically conductive layers (60), artificial dentin layer (30) and artificial pulp horn (38). Figures 6A, B, C show an additive method implemented by a 3D printer (68) to manufacture electrically conductive artificial dentin (30). Figure 6D shows the artificial tooth after insulating layer (40) is applied by a coating (72) method into cavity inside artificial dentin layer (30). 6E shows dispensing (70) of electrically conductive artificial pulp layer (32), 6F shows injection over moulding the model inside a mould (76), and 6G shows a manufactured artificial tooth (22) with artificial enamel (28).

As shown in Figures 6A-6G the interactive multi-layered model is manufactured with the properties of having sensors embedded in the artificial dentin layer and also in the artificial pulp. The manufacturing process of producing such a tooth model includes the following steps:

1 . Using additive method implemented by a 3D printer (68) to make the artificial dentin layer in a conductive material such as any material or combination of materials from above said lists.

2. Insertion of an insulating layer (40) such as a silicone layer or any material or combination of materials from above said lists inside the cavity in the middle of artificial dentin so called pulp cavity, in order to isolate the artificial dentin layer from the cavity which also will be filled by the electrically conductive artificial pulp. The insulating layer can be applied for example with laminating or coating method (72).

3. Dispensing or injecting (70) a conductive material such as electrically conductive silicone into the cavity of artificial dentin layer (30) to act as artificial pulp (32).

4. Inserting the model into a mould (76) and injection over mould (84) produces an artificial enamel layer (28) around the artificial layers

The advantages of this embodiment of the present invention is that by using an additive method and a 3D Printer, the flexibility in form and design is increased thus allowing the possibility of manufacturing individually shaped tooth models for example including artificial pulp horns for practicing pulp cap procedures or individually shaped dentins for having a more realistic drilling practice. The dental trainee gets real time feedback when exposing the artificial dentin and drilling through the same and when exposing the artificial pulp and drilling through the same. The dental trainee will also feel the structures being similar to the anatomy in a real tooth depending on the chosen materials in the different layers.

In another embodiment of the present invention as shown in Figures 7A-7D the interactive multi-layered model is manufactured with the properties of having sensors embedded in the artificial DEJ layer and also in the artificial pulp. A multi-layered tooth is produced with two conductive layers (60) which are located in artificial pulp layer (32) and artificial DEJ (36).

Figure 7A shows additive method implemented by a 3D printer (68) to manufacture electrically insulating (40) artificial dentin (30). Figure 7B shows dispensing (70) of electrically conductive artificial pulp layer (32) and manufacturing conductive artificial DEJ (36) by coating (72). Figure 7C shows injection overmoulding the model inside a mould (76), and finally 7G shows a manufactured artificial tooth (22) with artificial enamel (28). The

manufacturing process of producing such a tooth model includes the following steps:

1 . Manufacturing artificial dentin layer (30) comprising a cavity using

additive method from a 3D file and in a non-conductive material (40) such as any material or combination of materials from above said lists. An upper section of the cavity forms an artificial pulp 32.

2. Dispensing (70) of a conductive material such as electrically

conductive silicone into the cavity inside artificial dentin

3. Coat, metalize or laminate (72) a conductive layer applied on the top of the artificial dentin layer (30) to act as electrically conductive artificial DEJ (72).

4. Injection (84) over mould into a mould (76) to embed the artificial

dentin layer (30) in between artificial enamel layer (28).

The advantages of this embodiment are the possibility to manufacture distinct shapes of the pulp cavity for each and every model because of using 3D file and additive method. The pulp cavity includes sensors which allow the dental trainee to get real time feedback when drilling exposes the pulp. The dental trainee will also feel the structures being similar to the anatomy in a real tooth depending on the chosen materials in the different layers.

Figures 8A, 8B, 8C illustrate a longitudinal section of a multi-layered tooth model (22) with a replaceable artificial crown (25), artificial root (27) with attachment to replaceable artificial crown, artificial enamel (28), artificial dentin (30), artificial pulp (32), the attachment site (74) between crown and root, and attachment site (44) between artificial root and jaw.

In another embodiment of the present invention as shown in Figure 9 a 3D file (78) comprises data of a unique shape for a model within anatomic normal variation is fed to a software application (80) which can change specific parts of the file in a normal predefined variation. The software application will create modified 3D files (82) which each of them are having slight variation in specific anatomic parts for instance artificial pulp horn. Thereafter the files are 3D printed and each file has a unique anatomic shape. The advantage of this embodiment is that the optimal practice for a trainee is to practice on for example tooth models with different anatomic shape in their structures such as pulp horn or DEJ. Since the tooth anatomy has a normal variation the trainees have the chance to practice that aspect. The same technique can be used to produce models of mandible bone, maxilla bone, vertebral bones with different anatomic shapes internally and externally.

In yet another embodiment of the present invention as shown in Figures 10A-10D a model is manufactured with the properties of having sensors embedded. This embodiment provides production of a model for giving anesthetic injection, drilling and inserting a tooth implant, impact tooth surgery, periodontal surgery, periapical surgery, inserting bone implants, temporomandibular joint injection, tooth extraction, epidural injection, or generally any model which has hard tissue, soft tissue and multi-layered sensors either embedded inside or on the top of both. Manufacturing process of producing such a model includes the following steps:

1 . Production of multi-layered sensor (58) using additive method and a 3D printer, and/or various moulding methods in a material such as conductive rubber material for conductive layers and non-conductive rubber material for insulating layers.

2. Using additive method and a 3D printer or moulding to manufacture artificial bone(55) of any part of the body in a material such as a thermoplastic material.

3. Applying multi-layered sensors (58) inside or over the bone.

4. Making a multi-layered sensor by repeatedly over moulding conductive and non-conductive layers over each other.

In yet another embodiment of the present invention as shown in Figures 1 1 A-1 1 D a tooth model is manufactured with an artificial crown (25) which is replaceable and attached to the artificial root (Fig8C-27). The artificial root (Fig8C-27) is further attached to the jaw model in a way allowing the artificial crown to be replaced without replacing the artificial root. The manufacturing process of producing such a tooth model includes the following steps:

1 . Using a subtractive, additive, and/or moulding method to make the dentin layer (30) of a conductive or non-conductive material.

2. Dispensing (70) a conductive material such as electrically conductive silicone into the pulp cavity (32).

3. Installing an attachment site (74) by insert injection moulding (84). 4. The replaceable crown (25) with different artificial layers comes out from the mould.

5. Manufacturing the root part by the similar techniques as the

replaceable crown part,

The advantages with this embodiment of the present invention are to improve the flexibility related to the choice of manufacturing methods and the need for less material for the production of a tooth model. Furthermore since replacing the new tooth model is more convenient for the trainee the whole practicing process is facilitated. A combination of the base material mixed with various kinds of one or more types of conducting materials might be used to manufacture the sensor component.

Furthermore nonconductive layers of the multi-layered tooth might be chosen from the above mentioned list of the materials. Other materials with the required specifications and properties can also be used according to the invention.

In various embodiments such as shown in Figure 3B and Figure 6B, the electrically conductive material of the electrically conductive layer (60) is either an electrically conductive material and/or an electrically conductive additive such as a compound of the base material and carbon, iron or nickel additive.

An application of an interactive multi-layered model in accordance with the invention is a model for practicing drilling and insertion of dental implant. When the trainee wants to insert a dental implant awareness of the anatomic structures associated with the mandible and maxilla is essential. Avoiding life-threatening hemorrhage and nerve and sinus injury is imperative.

The advantage with this model is that there are multi-layered sensors in critical positions including for instance the mandibular canal (50), c.f.

Figure 2, maxillary sinuses, adjacent roots, mylohyoid ridge, and incisive fossa inside the jaws. If the bur gets close to the critical anatomies the model warns the trainee that the drilling bur is getting close to the critical anatomic structures. Furthermore if exposure of critical structures happens while inserting the implant, the interactive multi-layered model is capable to warn the trainee. The feedback is in real time from the processing unit connected to the model. Another aspect of the model is that the trainee may place implants in a physically palpable model which is taking into account the existing anatomy and the prosthetic objectives.

The present invention also relates to the manufacturing of conducting passages, preferably electrically conducting passages in a nonconductive material. Two or more electrically conductive materials can be connected in a controlled and adjustable way. The material or materials between the electrically conductive materials are made according to specific conditions where channels, void, grooves and/or tubes are incorporated into the nonconductive material.

The present invention also relates to the use of a nonconductive material comprising channels, void, grooves and/or tubes for practicing dental treatments and methods of manufacturing such material for practicing dental treatments. The model can comprise a tooth, a jaw or other models used for practicing dental treatments such as extraction models and implant models.

The manufacturing of the nonconductive material in different shapes are made with a 3D printer programmed in a way to incorporate channels, void, grooves and/or tubes according to an exact and predetermined route. The so formed channels, void, grooves and/or tubes are then filled with a conductive material for example conductive silicone. The resulting material, based on nonconductive material comprising channels, void, grooves and/or tubes in a predetermined way can be used for exact and accurate transfer of electrical charges from one or more sides of nonconductive materials to other sides of the nonconductive materials, c.f. Figure 12.

The material comprise constructions reflecting the anatomical structure and pain sensitive layers of a for example normal natural human tooth or jaw. The layers in a tooth according to the present invention will have a close morphology and hardness/hardness difference between different layers, compared to the corresponding part in a natural normal tooth i.e. enamel, dentin and pulp. Thereby the dental trainee is given the possibility to feel and learn the small changes in morphology and hardness when drilling in a tooth.

While certain illustrative embodiments of the invention have been described in particularity, it will be understood that various other

modifications will be readily apparent to those skilled in the art without departing from the scope defined by the claims appended hereto. Terms in the claims and description must therefore be construed as they would be by the skilled person in view of the overall content of the above specification according to the idea behind the invention.

Claims

1 . A method of producing a multi-layered structure comprising the steps: a) applying a first material having a first set of properties to form a first shape having an interior cavity

b) applying a second material having a second set of properties to form a first layer covering at least a first section of said first shape, and c) applying a third material having a third set of properties into said cavity wherein said third material is an electrically conducting material.

2. A method as claimed in claim 1 , wherein said first material has a hardness comparative to dentin of a tooth and said third material has a hardness comparative to the pulp of a tooth.

3. A method as claimed in claim 1 or claim 2, also comprising applying said third material by injecting it into the said interior cavity.

4. A method as claimed in any of the preceding claims, also comprising applying said second material by over moulding it onto said first shape.

5. A method as claimed in any of the preceding claims, also comprising forming said interior cavity as a longitudinally extending channel with first open end and a second expanded hollow end section.

6. A method as claimed in claim 5, also comprising forming said second hollow end section with irregular hollow narrow ends.

7. A method as claimed in any of the preceding claims, wherein the first material is an electrically conducting material also comprising applying a fourth electrically insulating material to cover at least a substantial part of inside surfaces of said interior cavity, and applying said third material into a remaining volume of said cavity.

8. A method as claimed in claim 7, wherein said first material has a hardness comparative to the dentin layer of a tooth.

9. A method as claimed in any of claims 1 to 6, wherein said first material is an electrically insulating material and the second material is an electrically conducting material, also comprising applying an electrically insulating cover material over at least a substantial part of said first layer, said electrically insulating cover material having a hardness comparative to the dentin layer of a tooth.

10. A method of making a multi-layered structure as claimed in claim 1 , further including the steps: providing a hollow structure between an exterior of the multi-layered structure and said interior cavity and injecting an electrically conducting material into said hollow structure.

1 1 . A multi-layered dental structure, characterized by

a longitudinally extending body made of a first material having a first set of properties and being formed with an interior cavity,

a first layer covering at least an upper part of said longitudinally extending body, wherein said first layer is made of a covering material that is harder than said first material, and

a filling material within said cavity, wherein said filling material is an electrically conducting material softer than said first material.

12. A multi-layered dental structure as claimed in claim 1 1 , wherein said interior cavity is individually shaped.

13. A multi-layered dental structure comprising a crown portion and a root portion, wherein said crown section is provided with at least a first sensor, characterized in

that said crown portion is removably connected to said root portion, that a first electric connecter is provided in the root portion for electrically connecting to said at least first sensor.

14. A multi-layered dental structure as claimed in claim 13, wherein an artificial tooth (22) has one crown portion (24), which appears above the margin of a simulated gum of the an artificial jaw (56) and a root portion (26) which is releasable embedded in artificial bone (54) of said artificial jaw (56).

15. A multi-layered dental structure as claimed in claim 14, wherein said artificial jaw (56) is provided with a plurality of artificial teeth (22) each of said artificial teeth (22) being provided with touch sensors (60) embedded in at least a simulated dentin layer (30) and a simulated pulp layer (32) which both have similar morphology and comparative hardness as natural dentin and pulp layers.

16. A multi-layered dental structure as claimed in claim 15, wherein said touch sensors are layers formed by conductive material.