Orthodontic teeth-straightening means made of shape-memory polymers, and method for the production of same

Abstract

The invention relates to an orthodontic teeth-straightening means, comprising a splint element which contains, or is entirely made from, a thermoplastic polyurethane having shape-memory properties. According to the invention, the thermoplastic polyurethane having shape-memory properties is selected from the group of polyether polyurethanes and contains hard segments which contain polyurethane units that have been obtained by polyaddition of the isocyanate groups of a diisocyanate to the hydroxyl groups of a diol acting as a chain extender, thereby forming urethane groups. The polyether polyurethane also contains soft segments, which contain, or are entirely made from, polyether units in the form of polyalkylene glycols, wherein the polyether units are bonded to isocyanate end groups of the diisocyanate of the hard segments, thereby forming urethane groups with the hard segments. The thermoplastic polyether polyurethane is both thermo-responsive and water-responsive and thus gives the splint element dual-stimuli responsive shape-memory properties.

Description

[0001]Orthodontic tooth regulating device made of shape memory polymers and method for its production. The invention relates to an orthodontic tooth regulating device comprising at least one splint element which, at least in some regions, contains at least one thermoplastic polyurethane with shape memory properties or is formed essentially entirely therefrom. The invention further relates to methods for producing a splint element of such an orthodontic tooth regulating device. Orthodontic treatment methods used to correct tooth misalignments are generally based on tooth movement therapeutically induced by means of various, usually essentially splint-shaped tooth regulating devices.Orthodontic tooth movement is initiated by the sustained application of forces and / or torques. After application of the orthodontic force system, the teeth are deflected within the alveolus as part of their physiological tooth movement. This immediately causes hemodynamic circulatory disturbances in the periodontal space. Local ischemia or hemostasis results in the area of ​​the pressure sores, which can cause localized micronecrosis of the periodontal tissue. The lack of blood supply leads to a sterile inflammatory reaction, which, over the course of approximately 2 to 3 weeks, causes a proliferation of the osteoclasts and osteoblasts responsible for bone remodeling. In addition to the hemodynamic-inflammatory reaction, piezoelectric surface potentials occur due to the deformation of the hydroxyapatite embedded in the bone.which alters the permeability of cell membranes. In particular, the numerous fibroblasts found in the periodontal space experience a deformation of the cytoskeleton due to the membrane-bound integrins. In this way, intracellular signaling chains are activated, which lead to the expression of specific cytokines. These described processes induce orthodontic tissue remodeling, which makes it possible to correct malocclusions. The forces generated by orthodontic appliances must not be too low to result in any change in tooth position, but certain maximum values ​​must not be exceeded, otherwise the periodontal tissue can be irreversibly damaged, which may even lead to tooth loss. For this reason, horizontal tooth movements are usually performed using forces of approximately 0.5 N to approximately 2 N and / or by means of torques of approximately 3 Nmm to approximately 20 Nmm. In this way, the teeth can be moved at a speed of approximately 1 mm to approximately 2 mm per month. The induction of therapeutic tooth movement with fixed orthodontic appliances in the form of so-called multi-bracket appliances, in various modifications, currently still represents the main treatment method for correcting malocclusions. Since the brackets are usually attached to the outside of the teeth, they are perceived as aesthetically compromising not only by the growing group of adult patients, but increasingly also by adolescents. As a result, efforts arose to make the treatment as invisible as possible. This led to the development of aesthetic alternatives and the creation of a new market segment within the orthodontic product range.the so-called "invisible orthodontic treatment appliances." Market-relevant solutions include ceramic brackets, brackets on the inside of the teeth, and, in particular, so-called aligners, which are used to treat malocclusions. Compared to fixed brackets, which are often perceived as uncomfortable by patients, so-called aligner therapy has the advantage of requiring a number of individually manufactured splints made of plastic materials. These splints are preferably transparent and thus largely invisible, and can also be removed and inserted by the patient as needed. The splints, i.e., the so-called aligners, can be produced using modern CAD (computer-aided design) or CAM (computer-aided manufacturing) technologies, for example.During these, any tooth positions or dental arches are transferred into three-dimensional models before they are then corrected, for example, using thermoplastic thermoforming foils. However, the intended tooth movements must be realized in a large number of setup steps, the so-called staging, using a large number of usually between about 30 and up to about 90 models per dental arch, in which the patient's current tooth position must always be taken into account. Technically, this is achieved by the production of individual splints, particularly using the thermoforming process, whereby the splints are not made to fit precisely, but rather in such a way that they exert a therapeutically desired pressure on the respective teeth. In clinical practice, this leads to a majority of relatively small,Pre-programmed tooth position changes within the individual therapy steps, with tooth movements of approximately 0.1 mm to approximately 0.25 mm (translational) and / or up to approximately 3° (rotational), with a recommended patient wearing time of approximately one to three weeks. Currently, the standard materials for aligner therapy are primarily polyethylene vinyl acetate and polyethylene terephthalate glycol (PET-G), with layer thicknesses of approximately 0.5 mm to approximately 1.5 mm. However, such films, including the processes used for their production, have some serious disadvantages. For example, geometric effects, particularly during the deep-drawing process, result in relatively high mechanical strengths of the splints, which can significantly limit the subsequent deflection range of the film. This results, on the one hand, in only limited positional changes,by which a tooth can be moved during a setup step. On the other hand, due to the high strength of the splints, even a reduction in the setup steps to, for example, approximately 0.1 mm to approximately 0.2 mm per tooth can result in the generation of initial, unphysiologically high (compressive) forces. This can lead to the patient feeling high pressure on the teeth to be moved when inserting the foil-like splint. Biomechanical studies examining the effect of the setup steps and the influence of the thickness of aligner foils on the transmitted forces and torques on the teeth have also concluded that the previously recommended setup steps can lead to the development of unphysiologically high forces and torques, even for the thinnest commercially available foils with a thickness of approximately 0.5 mm (see, for example, Hahn W, Fialka-Fricke J, Dathe H, Fricke-Zech S, Zapf A, Gruber R,et al.: "Initial Forces Generated by Three Types of Thermoplastic Appliances on an Upper Central Incisor During Tipping," European Journal of Orthodontics, 2009, 31: 625-631. The polymers of the aforementioned type used for aligners typically exhibit a linear increase in force during elastic deformation and thus also during recovery, which causes the actual tooth movement. Consequently, if a splint is inserted into the patient, very high stresses occur, followed by a rapid decrease in force. For example, a film made of polyethylene terephthalate glycol (PET-G) with a thickness of approximately 0.5 mm generates forces of approximately 2.27 N to approximately 5.31 N during the lip and tongue-side deflection of an upper anterior tooth of 0.25 mm. In contrast, thicker films made of PET-G with a thickness of approximately 0.8 mm lead to even higher forces of between approximately 5.2 N and approximately 7.22 N (cf. e.g. Elkholy F, Panchaphongsaphak T, Kilic F, Schmidt F,Lapatki BG: "Forces and Moments Delivered by PET-G Aligners to an Upper Central Incisor for Labial and Palatal Translation", Journal of Orofacial Orthopedics / Fortschritt der Kieferorthopädie: Organ / Official Journal Deutsche Gesellschaft für Kieferorthopädie, 2015, 76:460-475.]. However, the recommended force for this tooth movement is only approximately 0.35 N to approximately 0.6 N (cf., e.g., Proffit WR, Fields Jr. HW, Sarver DM: "Contemporary Orthodontics", Elsevier Health Sciences, 2006), thus underscoring the need to reduce the forces exerted on the patient's teeth and thus to implement alternative solutions. For larger deflections exceeding approximately 0.15 mm, the splint strength also becomes fully effective.The forces and torques increase significantly. Due to the excessive forces, pronounced hyalinization phases occur in the periodontal ligament as part of the metabolic processes that initiate tooth movement. These phases can even result in a standstill—a so-called cessation—of tooth movement (see, for example, Barbagallo LJ, Jones AS, Petocz P, Darendeliler MA: "Physical Properties of Root Cementum: Part 10. Comparison of the Effects of Invisible Removable Thermoplastic Appliances with Light and Heavy Orthodontic Forces on Premolar Cementum. A Microcomputed-Tomography Study", American Journal of Orthodontics and Dentofacial Orthopedics, 2008, 133: 218-227). The histological phenomenon of hyalinization arises from excessive compression in the area of ​​the periodontal ligament or periodontal space. The vessels in the periodontal space are compressed,Blood circulation is inhibited and disrupted, and the tissue's cellular response to bone remodeling is delayed. As a result, tooth movement slows down or even stops altogether. A further consequence of (excessively) high forces is the increased risk of irreversible pathological root resorption. A comparative split-mouth study aimed to investigate the occurrence of root resorption when using aligners and fixed orthodontic appliances, so-called brackets, for buccal tipping of premolars by 0.5 mm (see the above reference). The study found greater root resorption (irreversible loss of tooth substance at the root tip) in the aligner group than in the bracket group. In order to allow tooth movements to occur within a physiological framework,Small and constant forces have proven particularly suitable. With regard to the quality of the results of treating malocclusion with aligners, studies clearly demonstrate the shortcomings of currently commercially available systems. The effectiveness of tooth movement with aligners therefore still appears inadequate based on current knowledge. Furthermore, results from studies on lingual technology (see, for example, Pauls AH: "Therapeutic Accuracy of Individualized Brackets in Lingual Orthodontics," Journal of Orofacial Orthopedics / Fortschritt der Kieferorthopädie: Organ / Official Journal Deutsche Gesellschaft für Kieferorthopädie, 2010, 71: 348-361) have shown that the accuracy of aligner orthodontics also requires improvement. The activation ranges of commercially available aligner foils are small.so that only small setup steps are possible for programming tooth movement. From an economic perspective, this leads to high material usage and waste, since reducing the setup steps requires more models of the dental arches to be printed and more splints to be processed in the deep-drawing process. As already mentioned, depending on the severity of the malocclusion, an average of 50 to 90 setup steps are required for correction. A material with a larger active working range would promise to influence the number of setup steps and thus achieve sustainable savings in the production of aligners, which should also make it possible to reduce average treatment costs. Furthermore, due to the need for improved quality of the results, further corrections of the tooth positions, so-called refinements, are sometimes necessary.which can further increase treatment costs. Recently, the use of so-called shape memory polymers for the splint elements used in aligner therapy has been suggested to offer great potential, on the one hand, in terms of reducing the number of required setup steps and thus reducing laboratory effort, and on the other hand, in terms of exerting more or less consistently lower forces on the user's teeth. Such shape memory polymers are polymers that typically consist of at least two polymer components or, in particular, of one polymer component with different segments. These include hard segments, which also function as mesh points, and soft segments, which connect the mesh points and are also referred to as switching segments.which are elastic at high temperatures (in this case, they are in amorphous form), while they are rigid at low temperatures (in this case, they are in semi-crystalline or vitrified form). Such shape-memory polymers can be programmed with regard to their shape by heating them to a temperature that corresponds at least to the so-called switching temperature, at which the phase transition (glass transition or melting transition) of the soft or switching segments takes place. At such a temperature, the polymer is then deformed, after which it is cooled, while maintaining the deformation forces, at least to its so-called shape-fixing temperature, which corresponds to the glass transition temperature of the soft or switching segments and can be in the range of the switching temperature.but is usually at least somewhat lower in comparison. The soft or switching segments are then again in a semi-crystalline or vitrified form, so that the shape is retained. This shaping, however, is only temporary insofar as when a shape memory polymer that has been "programmed" to be mechanically deformed in this way is heated to a specific temperature—namely, its switching temperature—the soft segments (switching segments) are converted back into their amorphous form, so that they can no longer counteract the restoring force induced by the hard component (network points), and the shape memory polymer returns to its original shape, thus "reversing" the mechanical deformation. In addition to such shape memory, thermoresponsive shape memory polymers also exhibit temperature memory, which meansWhen the shape memory effect is triggered, the shape recovery begins at approximately the same temperature at which the mechanical deformation was previously introduced into the polymer material. Polymers with semicrystalline network structures, such as thermoplastic polyurethane elastomers, exhibit such material behavior (see, for example, N. Fritzsche, T. Pretsch in Macromolecules 47, 2014, 5952-5959; N. Mirtschin, T. Pretsch in RSC Advances 5, 2015, 46307-46315). The basic principle of using such shape memory polymers for the splint elements used in aligner therapy is that after a thermomechanical pretreatment, the so-called programming, the shape memory polymers react to temperature changes, so that they are able to release forces in a predetermined manner (see, for example, Pretsch T, Müller W.: "Shape Memory Poly(ester Urethane) with Improved Hydrolytic Stability",Polym Degrad Stab, 2010, 95: 880-888; Mya KY, Gose HB, Pretsch T, Bothe M, He C: "Star-Shaped POSS-Polycaprolactone Polyurethanes and their Shape Memory Performance", J Mater Chem, 2011, 21: 4827- 4836; Fritzsche N, Pretsch T: "Programming of Temperature-Memory Onsets in a Semicrystalline Polyurethane Elastomer", Macromolecules, 2014, 47: 5952-5959; Mirtschin N, Pretsch T: "Designing Temperature-Memory Effects in Semicrystalline Polyurethane", RSC Adv, 2015, 5: 46307-46315; Mirtschin N, Pretsch T: "Programming of One- and Two-Step Stress Recovery in a Poly(ester Urethane)", Polymers, 2017, 9: 98 (12 pages). These forces can fundamentally be used to achieve controlled tooth movements. US 2005 / 0003318 A1 describes a splint element of an orthodontic treatment device in the form of an aligner made of a film of shape memory polymers, which is created from a negative impression of the patient's teeth. This is done in such a way thatThe shape of the splint is programmed to the desired tooth position, after which it is deformed to the actual tooth position by heating it to the switching temperature of the shape memory polymer. The switching temperature of the shape memory polymer is in the range of human body temperature, so that the splint can return to its desired position in the patient's oral cavity without exerting excessive pressure on the patient's teeth. A similar aligner splint is disclosed in US 8758 0009 B2, whereby the shape memory polymer film used for the splint has a multi-layer structure.so that each layer is individually programmed and, upon reshaping, is capable of exerting a specific force on the user's teeth. Another orthodontic tooth-regulating device with a splint element made of shape-memory polymers is known from DE 102017 009 287 B4. In this case, the splint element comprises several spaced-apart fastening devices, each of which can be releasably attached to a carrier that can be attached to a patient's tooth, wherein the relative arrangement of the at least two fastening devices can be changed by changing the shape of the shape-memory polymer. US 2006 / 0154195 A1 discloses a variety of shape-memory polymers for use in orthodontic purposes, with the tooth-regulating devices produced therefrom being intended primarily as additional components of conventional splints or brackets.to generate local pressure between different areas of the same. Furthermore, WO 2017 / 079157 A1 deals with aligner splints made of semicrystalline shape memory polymers, which have a switching temperature in the range of human body temperature. DE 102015 108 848 A1 describes an orthodontic tooth-regulating device with a splint element made of an unspecified thermoplastic polymer mixture, which contains, on the one hand, dimensionally stable polymers and, on the other hand, polymers with water-responsive properties. The splint element is to be produced in an initial shape using thermoplastic processing methods according to an actual dental arch model.Upon contact with water, including saliva, it deforms into a subsequent shape corresponding to a target dental arch model. The shape corresponding to the target dental arch model is to be calculated in a manner that is also not further specified, taking into account the shape and wall thickness of the splint element as well as the shape-changing capacity of the water-responsive polymer component. The invention is based on the object of developing an orthodontic tooth-regulating device suitable for aligner therapy, comprising at least one splint element based on thermoplastic polymers with shape memory properties of the type mentioned above, in a simple and cost-effective manner such that precise tooth movement can be induced with a plurality of setup steps, while at least largely avoiding the aforementioned disadvantages.without exerting unphysiologically high forces on the patient's teeth. It is further directed to methods for producing a splint element of such an orthodontic treatment device. The first part of this object is achieved according to the invention in an orthodontic tooth-regulating device of the type mentioned above in that the at least one thermoplastic polyurethane with shape memory properties of the splint element is selected from the group of polyether polyurethanes and - hard segments containing polyurethane units obtained by polyaddition of the isocyanate groups of at least one diisocyanate with the hydroxy groups of at least one diol serving as a chain extender to form urethane groups, and - soft segments containing polyether units in the form of at least one polyalkylene glycol or being formed entirely therefrom,wherein the polyether units are bonded to the hard segments by terminal isocyanate groups of the at least one diisocyanate of the hard segments to form urethane groups, wherein the thermoplastic polyether polyurethane is both thermoresponsive and water-responsive. From a process engineering perspective, a first aspect of achieving this objective provides a method for producing a splint element of an orthodontic tooth-regulating device of the type mentioned at the outset, comprising the following steps: (a) providing at least one film which, at least in some regions, contains at least one thermoplastic polyurethane with shape memory properties or is formed substantially entirely therefrom, wherein the thermoplastic polyurethane with shape memory properties is selected from the group of polyether polyurethanes, and - hard segments which contain polyurethane units,which have been obtained by polyaddition of the isocyanate groups of at least one diisocyanate with the hydroxyl groups of at least one diol serving as a chain extender to form urethane groups, and - soft segments which contain polyether units in the form of at least one polyalkylene glycol or are formed entirely therefrom, wherein the polyether units are bonded to the hard segments by terminal isocyanate groups of the at least one diisocyanate of the hard segments to form urethane groups, wherein the thermoplastic polyether polyurethane is both thermoresponsive and water-responsive; (b) molding the at least one film onto a target toothed rim model to form a splint element,which is in a permanent mold of the thermoplastic polyether polyurethane with shape memory properties; (c) - heating the splint element according to step (b) at least to the switching temperature of the thermoplastic polyether polyurethane with shape memory properties and molding the splint element onto an actual tooth crown model or onto a human tooth crown, after which the splint element is cooled in a temporary mold at least to the shape-setting temperature of the thermoplastic polyether polyurethane, or - placing the splint element according to step (b) in water or an aqueous solution and molding the splint element onto an actual tooth crown model or onto a human tooth crown,after which the splint element is dried in a temporary mold; and (d) removing the splint element in the temporary mold from the actual dental arch model or from the human dental arch. According to a second aspect, the invention provides, in terms of process technology, a method for producing a splint element of an orthodontic tooth-regulating device of the type mentioned above, which comprises the following steps: (a) creating a three-dimensional model of the splint element according to a target dental arch model; (b) inputting the three-dimensional model of the splint element into a 3D printer; (c) melting layers of the splint element in a permanent mold by means of the 3D printer using at least one printing filament or granulate made of a thermoplastic polymer material,which contains at least one thermoplastic polyurethane with shape memory properties or is formed substantially entirely therefrom, wherein the thermoplastic polyurethane with shape memory properties is selected from the group of polyether polyurethanes and - hard segments which contain polyurethane units obtained by polyaddition of the isocyanate groups of at least one diisocyanate with the hydroxy groups of at least one diol serving as a chain extender to form urethane groups, and - soft segments which contain polyether units in the form of at least one polyalkylene glycol or are formed entirely therefrom, wherein the polyether units are bonded to the hard segments with terminal isocyanate groups of the at least one diisocyanate of the hard segments to form urethane groups,wherein the thermoplastic polyether polyurethane is both thermoresponsive and water-responsive; (d) - heating the splint element according to step (c) at least to the switching temperature of the thermoplastic polyether polyurethane with shape memory properties and molding the splint element onto an actual tooth crown model or onto a human tooth crown, after which the splint element is cooled in a temporary mold at least to the shape-setting temperature of the thermoplastic polyether polyurethane, or - placing the splint element according to step (c) in water or an aqueous solution and molding the splint element onto an actual tooth crown model or onto a human tooth crown,after which the splint element is dried in a temporary mold; and (e) removing the splint element in the temporary mold from the actual dental arch model or from the human dental arch. As is known as such for aligner splints made of shape memory polymers according to the prior art, the invention is based on the fact that polymers with thermoresponsive shape memory properties can be easily converted from a permanent mold into a thermoresponsive state of a temporary mold by the thermomechanical treatment also referred to as "programming," in which they then remain until they are again heated at least to their switching temperature. The splint element of the orthodontic device according to the invention, whose total thickness is advantageously between approximately 500 µm and approximately 3 mm,can therefore be temporarily stabilized in a deformed state (corresponding to the actual state of the patient's tooth position) through appropriate programming and is oriented to the dimensions of the patient's current tooth position. Upon heating the splint element at least to the switching temperature of the polymer with shape memory properties and / or with thermoresponsive properties, it returns to its pre-programmed shape (corresponding to the desired state of the patient's tooth position). Due to the material of the splint element made of the at least one polyether polyurethane with shape memory properties according to the invention, the shape change of this polymer is thus variable. However, it can be programmed not only from the actual state of the patient's tooth position to the desired state of a respective setup step, but also to the desired state of a plurality of setup steps.which are then triggered individually and successively by repeated brief heating to the switching temperature range, in order to achieve only a partial recovery (corresponding to one setup step each), until the programmed shape change has been completely reversed and the rail element is back in its permanent shape corresponding to the originally programmed target tooth position. This can be achieved, for example, by carrying out a respective shape recovery of the rail element during a respective setup step just below or in the lower range of the onset of the glass transition temperature of the soft segments made of polyalkylene glycol units, i.e., at the lower end of the switching temperature range, until, in a final setup step, the rail element is heated to or above the upper range of the offset of the glass transition temperature of the soft segments of the polyether polyurethane.to ensure a "final" practically complete shape recovery. In this way, one and the same splint element can be used over a longer treatment period according to the multiple setup steps, and excessive compressive and / or tensile forces acting on the user's teeth are reliably avoided, since the individual setup steps can be selected to be practically as small as desired. Furthermore, it proves particularly advantageous that the soft segments of the thermoplastic polyether polyurethane with shape memory properties are formed according to the invention from polyalkylene glycols, which impart to the polyether polyurethane not only thermoresponsive shape memory properties of the type described above,but also impart water responsiveness. The polyalkylene glycol units of the soft segments, in the event of prolonged contact with the user's water or saliva, are capable of ensuring a moderate shape recovery of the splint element from its temporary shape (corresponding to the programmed actual state of the dental arch) to its permanent shape (corresponding to the target state of the dental arch at the conclusion of the orthodontic treatment step). This ensures that, when the user wears the splint element during one and the same setup step, a more or less continuous reshaping of the splint element "toward" its permanent shape occurs, thus reliably preventingthat excessive forces are acting on the user's tooth crown. The degree of shape recovery of the splint element due to its water responsiveness can also be controlled by the user within certain limits, for example, by placing the splint element in water or an aqueous cleaning solution overnight. The shape recovery is more pronounced the higher the water temperature, i.e., the closer the water temperature is to the switching temperature of the thermoplastic polyether polyurethane with shape memory properties, and / or the longer the splint element is in contact with water. The thermoplastic polyether polyurethane with shape memory properties of the splint element according to the invention is, of course, neither water-soluble nor is it a hydrogel; rather, its shape memory effect is based—as already mentioned—on the glass transition of the soft segments.which contain or consist of polyether units based on polyalkylene glycols. The thermoplastic polyether polyurethane according to the invention with soft segments made of polyalkylene glycol units thus imparts dual stimuli-responsive properties to the splint element of the orthodontic treatment device. On the one hand, it is programmable similarly to conventional shape memory polymers, but on the other hand, a shape recovery - whether complete or particularly successive - is triggered both by single or, in particular, repeated heating to the switching temperature range and by contact with water.i.e., it is both thermoresponsive and water-responsive. Furthermore, the production of the splint element of the orthodontic treatment agent according to the invention is relatively simple and cost-effective: Thus, according to a first embodiment of the manufacturing method according to the invention, at least one film can be provided in step (a), which can be produced by any thermoplastic processing method, such as extrusion, injection molding, hot pressing, or the like, and which, at least in some regions, contains at least one thermoplastic, both thermoresponsive and water-responsive polyurethane with shape memory properties of the type described above, or is essentially formed entirely therefrom. Instead of a single film, a film composite comprising several films, e.g., made of the same or different thermoplastic polymers, can also be provided.For example, film composites made from various polyether polyurethanes according to the invention with shape memory properties can be used, or film composites in which only one or more film layers are formed from such shape memory polymers, in order to be able to specifically adapt, for example, the switching temperature, the shape recovery behavior, etc., to the respective intended use. In a step (b), the film can be molded onto a target gear ring model, which can be done, for example, by deep drawing in the molten state of the thermoplastic polymer material of the rail element. By cutting off the edges of the film, a corresponding rail element can then be obtained in a permanent form of the thermoplastic polyether polyurethane with shape memory properties.which corresponds to the tooth position after completion of a (respective) orthodontic treatment step. During the programming of the splint element into a temporary shape corresponding to the actual tooth position, in a subsequent step (c), the splint element can be heated to at least or even above the switching temperature of the thermoplastic polyether polyurethane with shape memory properties and molded onto an actual dental arch model or onto a human dental arch in order to mechanically deform it into its temporary shape. While continuously molding onto the actual dental arch model or onto the human dental arch, the splint element in its temporary shape is finally cooled to at least the shape-setting temperature of the thermoplastic polyether polyurethane or preferably below it. The programming is thus completed, whereupon the fully programmed,The splint element in the temporary mold can be removed from the actual dental arch model or the human dental arch in a final step (d). Due to the water-responsiveness of the thermoplastic polyether polyurethane with shape memory properties of the splint element according to the invention according to step (c), the latter can instead be immersed in water or an aqueous solution for a sufficient period of time during programming to convert the soft segments of the polyether polyurethane into a glassy state in which they are plastically deformable. The water temperature can be set below the switching temperature of the polyether polyurethane. The splint element pretreated in this way can then be molded onto an actual dental arch model or a human dental arch.after which the splint element is dried in a temporary form (the soft segments are then able to withstand the deformation of the splint element in its temporary form). The latter can be achieved, for example, by exposure to ambient air for a sufficient period of time or, if desired to accelerate the drying process, in a drying chamber or the like. Programming is thus completed, whereupon the fully programmed splint element in the temporary form can be removed from the actual dental arch model or the human dental arch in a final step (d). According to a second embodiment of the manufacturing method according to the invention, the splint element of the orthodontic tooth regulating device can also be produced, in particular, using enamel layers.by plasticizing the at least one thermoplastic polyether polyurethane with shape memory properties of the type described above and depositing it layer by layer using at least one nozzle of a controllably movable print head of a 3D printer to form the rail element in its permanent shape. Such melt-deposition processes, also referred to as "fused deposition modeling" (FDM), "fused filament fabrication" (FFF), or "freeforming," using 3D printers are known as such and represent manufacturing processes in which one or more filaments or granules made of thermoplastic polymers are plasticized in a plasticizing unit of the 3D printer and deposited layer by layer using an outlet nozzle typically provided in the print head of the 3D printer.to create the rail element, which is ultimately formed from a multitude of such layers or "droplets." In the fused layer process using 3D printing, also known as "additive manufacturing," a three-dimensional model of the rail element to be produced is usually created digitally, which can be done particularly using the well-known methods of computer-aided design (CAD). In addition, suitable software, such as a so-called slicer program (e.g., Cura, TMor the like), the three-dimensional model of the rail element to be produced is broken down into a plurality of thin layers, whereupon the plasticized polymer is deposited layer by layer using the outlet nozzle of the correspondingly moved print head in order to build up the rail element layer by layer. Immediately after the polymer plasticized material is discharged from the outlet nozzle of the print head in a more or less strand- or drop-like manner, the curing process begins - or more precisely: the solidification process - whereby the deposited plasticized material solidifies, for example, at ambient temperature or also under active cooling (cf., for example, also DE 102018 003 273 A1).Accordingly, according to the second embodiment of the manufacturing method according to the invention, it can be provided that in a step (a), a three-dimensional model of the rail element is first created in electronic form according to a target sprocket model and, in a step (b), is entered into the control software of a 3D printer. In a subsequent step (c), the molten layering of the rail element in its permanent shape takes place using the 3D printer, wherein at least one printing filament or at least one printing granulate made of at least one thermoplastic polyether polyurethane with shape memory properties of the type described above is used. In this context, it is also conceivable for the rail element to be printed using molten layers onto a core or a support structure made of another, not necessarily polymeric, material.During the programming of the splint element into a temporary shape corresponding to the actual tooth position, the splint element is heated in a subsequent step (d) either at least to or above the switching temperature of the thermoplastic polyether polyurethane with shape memory properties, and the splint element is molded onto an actual tooth crown model or onto a human tooth crown in order to mechanically deform it into its temporary shape. While continuously molding onto the actual tooth crown model or onto the human tooth crown, the splint element in its temporary shape is finally cooled to at least the shape-setting temperature of the thermoplastic polyether polyurethane, or preferably below it.Programming is thus complete, whereupon the fully programmed splint element, in its temporary form, can be removed from the actual dental arch model or the human dental arch in a final step (e). Alternatively, during programming according to step (d), the splint element can also be placed in water or an aqueous solution for a sufficient period of time in this case to convert the soft segments of the polyether polyurethane into a glassy state in which they are plastically deformable. As mentioned above, the water temperature can be set below the switching temperature of the polyether polyurethane.The splint element pretreated in this way can then be molded onto an actual dental arch model or onto a human dental arch, after which the splint element is dried in a temporary mold (the soft segments can then withstand the deformation of the splint element in its temporary form). The latter can be done, for example, by exposure to ambient air for a sufficient period of time or, if desired to accelerate the drying process, in a drying chamber or the like. Programming is thus complete, whereupon the fully programmed splint element in its temporary mold can be removed from the actual dental arch model or the human dental arch in a final step (e).The polyalkylene glycol of the polyether units of the soft segments of the thermoplastic polyether polyurethane according to the invention with shape memory properties, which impart both thermoresponsive and water-responsive properties to the splint element, is preferably a polyalkylene glycol whose monomeric alkylene glycols have between 2 and 5 carbon atoms, in particular polyethylene glycol (PEG) and / or polypropylene glycol (PPG) and / or polytetramethylene ether glycol (PTMEG, polytetrahydrofuran). Furthermore, the polyether units formed by polyalkylene glycol units of the soft segments of the thermoplastic polyether polyurethane preferably have an average molecular weight of at least about 250 g / mol, in particular of at least about 300 g / mol, preferably of at least 350 g / mol, e.g.of at least about 400 g / mol, in order to ensure pronounced thermoresponsive as well as water-responsive properties of the polyether polyurethane with shape memory properties. Furthermore, it can advantageously be provided that the polyether units of the soft segments of the thermoplastic polyether polyurethane, formed from polyalkylene glycol units, have an average molecular weight of at most about 2000 g / mol, in particular of at most about 1600 g / mol, in particular of at most about 1200 g / mol, e.g. of at most about 1000 g / mol, so that the rail element can be designed to be largely transparent for aesthetic reasons.In a further advantageous embodiment, it can be provided that the switching temperature of the thermoplastic polyether polyurethane corresponding to the glass transition temperature of the polyether units formed by polyalkylene glycol units of the soft segments of the thermoplastic polyether polyurethane is more than approximately 37°C, in particular at least approximately 38°C, preferably at least approximately 40°C, e.g., at least approximately 45°C or at least approximately 50°C, in order to prevent, in particular, an unintentional recovery of the shape of the splint element, which exceeds that of a respective setup step, from occurring as a result of the user's body temperature. Similarly, it can prove advantageous if the switching temperature is noticeably higher, e.g., at least approximately 60°C, so that an unintentional recovery of the shape of the splint element is not triggered even if, for example, the user cleans it in warm water.On the other hand, it proves advantageous if the switching temperature is at most about 100°C, in particular at most about 90°C, preferably at most about 80°C, so that during a respective setup step a targeted shape recovery - be it partial or essentially complete - can be brought about at relatively moderate temperatures, e.g. by appropriate heating of the rail element in warm or hot liquid, such as water or the like. In order to ensure pronounced thermoresponsive and water-responsive shape memory properties of the rail element, it has also proven advantageous if the proportion of polyether units of the soft segments formed by polyalkylene glycol units is between about 10 mass% and about 80 mass%, in particular between about 20 mass% and about 70 mass%, preferably between about 30 mass% and about 60 mass%, e.g. between about 35 mass% and about 50 mass%.-%, based on the total mass of the thermoplastic polyether polyurethane. In a further advantageous embodiment, it can be provided that the at least one diisocyanate from which the polyurethane units of the hard segments of the thermoplastic polyether polyurethane with shape memory properties are obtained is selected from the group of aromatic, aliphatic or cycloaliphatic diisocyanates, in particular from the group of isomers or isomer mixtures of methylenediphenyl diisocyanates (MDI), 1,6-hexamethylene diisocyanate (HDI), 4,4'-diisocyanatodicyclohexylmethane (H. 12MDI), isomers or isomer mixtures of toluene diisocyanates (TDI), 1,5-pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), naphthylene diisocyanate (NDI) and polymeric diphenylmethane diisocyanate (PMDI), including mixtures thereof. The at least one diol serving as a chain extender, from which the polyurethane units of the hard segments of the thermoplastic polyether polyurethane with shape memory properties have been obtained, can preferably be selected from the group of alkanediols, in particular from the group of ethanediol (ethylene glycol), 1,3-propanediol (propylene glycol), 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol and 1,12-dodecanediol, including mixtures thereof.The hard segments of the thermoplastic polyether polyurethane according to the invention with both thermo- and water-responsive shape memory properties of the rail element can therefore advantageously consist of at least one aromatic, aliphatic or cycloaliphatic diisocyanate, such as isomers or isomer mixtures of methylenediphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), 4,4'-diisocyanatodicyclohexylmethane (H. 12MDI), isomers or isomer mixtures of toluene diisocyanates (TDI), 1,5-pentane diisocyanate (PDI) or mixtures thereof, and at least one diol serving as a chain extender. The diols serving as chain extenders can be generally known dihydroxy compounds, with particular consideration being given to ethanediol (ethylene glycol), 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol, including mixtures thereof, so that the thermoplastic polyether polyurethane with shape memory properties exhibits no cytotoxicity according to DIN EN ISO 10993-5-2009-10. In addition, additional chain extenders based on diamine compounds can optionally be used. Possible diamine compounds include isophoronediamine, ethylenediamine, 1,2-Propylenediamine, 1,3-propylenediamine, N-methylpropylene-1,3-diamine, N,N'-dimethylethylenediamine, and aromatic diamines such as 2,4-tolylenediamine, 2,6-tolylenediamine, 3,5-diethyl-2,4-tolylenediamine, and 3,5-diethyl-2,6-tolylenediamine, or primary mono-, di-, tri-, or tetraalkyl-substituted 4,4'-diaminodiphenylmethanes, including mixtures thereof. Amino alcohols, such as N-2-(methylamino)ethanol or 3-(methylamino)-1-propanol, and the like, are also suitable as additional chain extenders. Such additional chain extenders can be used individually in combination with the at least one diol or in any mixture with each other and with the at least one diol. However, such diamines would not be suitable as sole chain extenders.because, in contrast to the polyether polyurethane according to the invention, the resulting polyureas could not be processed thermoplastically and also exhibited inadequate shape memory properties. The thermoplastic polyether polyurethane according to the invention with shape memory properties of the splint element therefore contains, on the one hand, hard segments containing polyurethane units obtained by polyaddition of the isocyanate groups (-N=C=O groups) of the at least one diisocyanate with the hydroxyl groups (-OH groups) of at least one diol serving as a chain extender with the isocyanate groups to form urethane groups (-NH-CO-O-). On the other hand, the thermoplastic polyether polyurethane according to the invention contains soft segments containing polyether units in the form of polyalkylene glycol units.wherein the polyether units are bonded to the hard segments, for example, by polyaddition of corresponding (poly)alkylene glycols with the isocyanate groups of the at least one diisocyanate of the hard segments to form urethane groups. Furthermore, according to a further development, the at least one polyether polyurethane with shape memory properties of the splint element can contain at least one additive, which can be selected in particular from the group of biocompatible oils, electromagnetic radiation-absorbing fillers, inductively heatable fillers, dyes and pigments, and reinforcing fibers. While additives in the form of biocompatible oils, for example silicone oil and the like, can improve the biological compatibility of the polymer material of the splint element, it is possible to improve the mechanical,The electrical, magnetic, and / or optical properties of shape memory polymers can be adjusted and adapted to the respective application. In particular, the shape memory properties themselves, such as the recovery rate and / or the recovery temperature, can be modified. Furthermore, fillers that absorb electromagnetic radiation offer the possibility of heating the shape memory polymer using electromagnetic radiation in order to program it or trigger recovery (shape memory effects). The same applies to inductively heatable fillers with regard to heating by exposure to high-frequency alternating magnetic fields. Advantageous fillers for the aforementioned purposes can, for example, have a graphene structure, as found, for example, in graphite, carbon nanotubes (CNTs),Graphene flakes or expanded graphite. Other particles can also be used as fillers, such as magnetic and / or ferromagnetic particles, particularly from the group of Ni / Zn, iron oxide, and magnetite particles. Furthermore, so-called nanoclays can be used as fillers, which can be based, for example, on silicon nitride, silicon carbide, silicon oxide, zirconium oxide, and / or aluminum oxide. Other suitable fillers include oligomeric silsesquioxanes, the above-mentioned graphite particles, graphenes and carbon nanotubes, synthetic fibers, particularly carbon fibers, glass fibers, or Kevlar fibers, but also metal particles, although combinations of such filler materials can of course also be used. Furthermore, it is fundamentally possible to color the shape memory polymers of the rail element using suitable dyes and / or pigments.Food colorings, in particular, have proven particularly suitable due to their excellent physiological compatibility. Furthermore, it is of course conceivable that other additives known from plastics technology could be used, such as lubricants, plasticizers, antioxidants, UV stabilizers, matting agents, antistatic agents, hydrolysis stabilizers, impact modifiers, and the like. The chemical synthesis of the thermoplastic polyether polyurethanes according to the invention with both thermo- and water-responsive shape memory properties of the splint element can, in principle, be carried out using processes known per se, such as the one-shot or prepolymer process.The following describes a purely exemplary synthesis route for producing one embodiment of a thermoplastic polyether polyurethane with shape memory properties according to the invention. Embodiment: Production of a thermoplastic polyether polyurethane with both thermoresponsive and water-responsive shape memory properties: Hard segments: Polyurethane units obtained by polyaddition of a diisocyanate in the form of 4,4'-methylenediphenyl diisocyanate (4,4'-MDI) with a diol serving as a chain extender in the form of 1,4-butanediol (1,4-BD); Soft segments: Polyether units in the form of polypropylene glycol (PPG) with an average molecular weight of 430 g / mol. From the reaction of polypropylene glycol (PPG) with 4,4'-methylenediphenyl diisocyanate (4,4'-MDI) and 1,4-butanediol (1,4-BD) in the molar ratio of PPG : 4,4'-MDI : 1,4-BD = 1 : 2.17 : 2,16 The thermoplastic polyether polyurethane with shape memory properties is synthesized using the prepolymer process. This contains the soft segments based on polypropylene glycol units with an average molecular weight of 430 g / mol. The hard segment content of the resulting polyether polyurethane is approximately 60% by mass, while the soft segment content is approximately 40% by mass, each based on the total mass of the polyether polyurethane. The glass transition range of the soft segments, determined by differential scanning calorimetry (DSC), was determined to be between approximately 45°C and approximately 55°C. This result was confirmed by dynamic mechanical analysis (DMA). From the thermoplastic polyether polyurethane synthesized according to this exemplary embodiment, test specimens and splint elements were produced in accordance with the above first embodiment of the inventive manufacturing process.To demonstrate both thermoresponsive and water-responsive shape memory properties, the splint elements were programmed from their manufacturing-related permanent shape (corresponding to a target toothed rim model) into a temporary shape (corresponding to an actual toothed rim model) by heating them to a temperature above the switching temperature of the thermoplastic polyether polyurethane with shape memory properties (see above) - here: to a temperature of approximately 80°C - using a thermomechanical treatment.plastically deformed and cooled to a temperature below the shape-setting temperature of the thermoplastic polyether polyurethane with shape memory properties—here, approximately 23°C—while maintaining the deformation forces applied for this plastic deformation. The results obtained are explained below with reference to the drawings. Fig. 1 shows a graph of temperature T [°C],The tensile stress σ [MPa] and the strain ε [%] of the programmed thermoplastic polyether polyurethane with shape memory properties over time t [min] during repeated brief heating of a test specimen above the switching temperature – here: to just under 80°C – and cooling below the shape-fixing temperature of the soft or switching segments in the form of polypropylene glycol units to determine the thermomechanical properties of the programmed polyether polyurethane with shape memory properties; Fig. 2 shows a sequence of photographic views of one of the programmed rail elements, each after heating to the switching temperature range corresponding to one of the setup steps, illustrating the successive recovery of the rail element from its temporary shape to its permanent shape.to demonstrate the thermoresponsive shape memory properties of the thermoplastic polyether polyurethane; Fig. 3 shows a sequence of photographic views of one of the programmed splint elements, each at different times during the immersion of the splint element in water at a temperature of approximately 37°C, i.e., significantly below the switching temperature of the soft or switching segments of the thermoplastic polyether polyurethane in the form of polypropylene glycol units, to demonstrate the water-responsive shape memory properties of the thermoplastic polyether polyurethane; and Fig. 4 shows an enlarged photographic view of the splint element, immersed in water at 37°C according to Fig. 3, in its programmed temporary shape at the beginning of immersion (left: "0 min").on the other hand, after 20 hours of immersion in 37°C warm water (right: "20 h"). Figure 1 shows a diagram of the thermomechanical properties of the synthesized polyether polyurethane with shape memory properties. As can be seen from Figure 1, the thermomechanical properties of the polyether polyurethane with shape memory properties were investigated – again at approximately 23°C and at approximately 80°C – by gradually stretching and drawing a test specimen in the form of a tensile bar, respectively, and determining the measurement points after an appropriate equilibration time after each stretching step. The characteristic typical of shape memory polymers can be seen, according to which stretching at low temperatures below the switching temperature (here: approximately 23°C) requires a high tensile stress.whereas the same elongation at high temperatures above the switching temperature (here: approximately 80°C) requires a significantly lower tensile stress. On the other hand, the "cold" polyether polyurethane with shape memory properties could be stretched or deformed significantly less under a given tensile stress than the "warm" polyether polyurethane with shape memory properties under the same tensile stress. Figure 2 shows a sequence of photographic views of a programmed rail element made of the synthesized polyether polyurethane with shape memory properties, each after aThe heating corresponding to a respective setup step to a range of the switching temperature (here: just under 80°C) is shown. The resulting successive deformation of the rail element from its temporary shape (top left) to its permanent shape (bottom right) can be seen. Figure 3 shows a sequence of photographic views of a programmed rail element made of the synthesized polyether polyurethane with shape memory properties, each at different times during the storage of the rail element in water at a temperature of approximately 37°C.i.e., significantly below the switching temperature of the soft or switching segments of the thermoplastic polyether polyurethane in the form of polypropylene glycol units. A more or less continuous reshaping of the splint element from its temporary shape (top left at 0 minutes) to its permanent shape (bottom right at 20 hours) can be seen. Finally, Fig. 4 shows enlarged photographic views of the splint element stored in 37°C water as shown in Fig. 3, on the one hand in its programmed temporary shape at the beginning of storage (left at 0 minutes), and on the other hand after 20 hours of storage in 37°C water (right at 20 hours). Here, too, one can see the reshaping of the splint element—or more precisely, a section of it that has been programmed for a tooth misalignment—from its temporary shape (left) to its permanent shape (right) as a result of 20 hours of contact with water.

Claims

Patent claims 1. Orthodontic tooth regulation device, comprising at least one splint element which at least partially contains at least one thermoplastic polyurethane with shape memory properties or is formed substantially entirely therefrom, wherein the thermoplastic polyurethane with shape memory properties is selected from the group of polyether polyurethanes and - hard segments which contain polyurethane units which have been obtained by polyaddition of the isocyanate groups of at least one diisocyanate with the hydroxy groups of at least one diol serving as a chain extender to form urethane groups, and - soft segments which contain polyether units in the form of at least one polyalkylene glycol or are formed entirely therefrom,wherein the polyether units are bonded to the hard segments by terminal isocyanate groups of the at least one diisocyanate of the hard segments to form urethane groups, wherein the thermoplastic polyether polyurethane is both thermoresponsive and water-responsive.

2. A tooth regulating agent according to claim 1, characterized in that the polyalkylene glycol of the polyether units of the soft segments of the thermoplastic polyether polyurethane is polyethylene glycol (PEG) and / or polypropylene glycol (PPG) and / or polytetra-, methylene ether glycol (PTMEG).

3. A tooth regulating agent according to claim 1 or 2, characterized in that the polyether units of the soft segments of the thermoplastic polyether polyurethane have an average molecular weight of - at least 250 g / mol, in particular of at least 300 g / mol, preferably of at least 350 g / mol, and / or - at most 2000 g / mol, in particular of at most 1600 g / mol, preferably of at most 1200 g / mol.

4. A tooth regulating agent according to one of claims 1 to 3, characterized in that the switching temperature of the thermoplastic polyether polyurethane corresponding to the glass transition temperature of the polyether units of the soft segments is - more than 37°C, in particular at least 38°C, preferably at least 40°C, and / or - at most 100°C, in particular at most 90°C, preferably at most 80°C. 5.Tooth regulating agent according to one of claims 1 to 4, characterized in that the proportion of polyether units of the soft segments is between 10 mass% and 80 mass%, in particular between 20 mass% and 70 mass%, preferably between 30 mass% and 60 mass%, based on the total mass of the thermoplastic polyether polyurethane.

6. Tooth regulating agent according to one of claims 1 to 5, characterized in that the at least one diisocyanate from which the polyurethane units of the hard segments of the thermoplastic polyether polyurethane have been obtained is selected from the group of aromatic, aliphatic or cycloaliphatic diisocyanates, in particular from the group of isomers or isomer mixtures of methylenediphenyl diisocyanates (MDI), 1,6-hexamethylene diisocyanate (HDI), 4,4'-diisocyanatodicyclohexylmethane (H 12MDI), isomers or isomer mixtures of toluene diisocyanates (TDI), 1,5-pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), naphthylene diisocyanate (NDI) and polymeric diphenylmethane diisocyanate (PMDI), including mixtures thereof.

7. A tooth-regulating agent according to any one of claims 1 to 5, characterized in that the at least one diol serving as a chain extender, from which the polyurethane units of the hard segments of the thermoplastic polyether polyurethane are obtained, is selected from the group of alkanediols, in particular from the group of ethanediol (ethylene glycol), 1,3-propanediol (propylene glycol), 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol, including mixtures thereof. 8.Tooth regulating agent according to one of claims 1 to 7, characterized in that the thermoplastic polyether polyurethane contains at least one additive, which in particular is selected from the group. - the biocompatible oils, - the electromagnetic radiation-absorbing fillers, - the inductively heatable fillers, - the dyes and pigments, and - the reinforcing fibers.

9. A method for producing a splint element of an orthodontic tooth-regulating device according to one of claims 1 to 8, comprising the following steps: (a) providing at least one film which, at least in some regions, contains at least one thermoplastic polyurethane with shape memory properties or is formed substantially entirely therefrom, wherein the thermoplastic polyurethane with shape memory properties is selected from the group of polyether polyurethanes, and - hard segments which contain polyurethane units obtained by polyaddition of the isocyanate groups of at least one diisocyanate with the hydroxy groups of at least one diol serving as a chain extender to form urethane groups,and - soft segments which contain polyether units in the form of at least one polyalkylene glycol or are formed entirely therefrom, wherein the polyether units are bonded to the hard segments by terminal isocyanate groups of the at least one diisocyanate of the hard segments to form urethane groups, wherein the thermoplastic polyether poly-, urethane is both thermoresponsive and water-responsive; (b) molding the at least one film onto a target tooth crown model to form a splint element which is in a permanent mold of the thermoplastic polyether polyurethane with shape memory properties;(c) - heating the splint element according to step (b) at least to the switching temperature of the thermoplastic polyether polyurethane with shape memory properties and molding the splint element onto an actual tooth rim model or onto a human tooth rim, after which the splint element is cooled in a temporary mold at least to the shape-setting temperature of the thermoplastic polyether polyurethane, or - placing the splint element according to step (b) in water or in an aqueous solution and molding the splint element onto an actual tooth rim model or onto a human tooth rim, after which the splint element is dried in a temporary mold;and (d) removing the splint element in the temporary mold from the actual dental arch model or from the human dental arch.

10. The method according to claim 9, characterized in that according to step (a), at least one film is used which, at least in some regions, contains at least one thermoplastic polyurethane with shape memory properties according to at least one of claims 2 to 8 or is formed substantially entirely therefrom.

11. A method for producing a splint element of an orthodontic tooth regulating device according to one of claims 1 to 8, comprising the following steps: (a) creating a three-dimensional model of the splint element according to a target dental arch model; (b) inputting the three-dimensional model of the splint element into a 3D printer; (c) melting layers of the splint element in a permanent form by means of the 3D printer using at least one printing filament or granulate made of a thermoplastic polymer material which contains at least one thermoplastic polyurethane with shape memory properties or is formed substantially entirely therefrom, wherein the thermoplastic polyurethane with shape memory properties is selected from the group of polyether polyurethanes and - hard segments which contain polyurethane units,which have been obtained by polyaddition of the isocyanate groups of at least one diisocyanate with the hydroxy groups of at least one diol serving as a chain extender to form urethane groups, and - soft segments which contain polyether units in the form of at least one polyalkylene glycol or are formed entirely therefrom, wherein the polyether units are bonded to the hard segments by terminal isocyanate groups of the at least one diisocyanate of the hard segments to form urethane groups, wherein the thermoplastic polyether polyurethane is both thermoresponsive and water-, is responsive; (d) - heating the splint element according to step (c) to at least the switching temperature of the thermoplastic polyether polyurethane with shape memory properties and molding the splint element onto an actual dental arch model or onto a human dental arch, after which the splint element is cooled in a temporary mold to at least the shape-setting temperature of the thermoplastic polyether polyurethane, or - placing the splint element according to step (c) in water or an aqueous solution and molding the splint element onto an actual dental arch model or onto a human dental arch, after which the splint element is dried in a temporary mold; and (e) removing the splint element in the temporary mold from the actual dental arch model or from the human dental arch. 12.Method according to claim 11, characterized in that according to step (c) a printing filament or granulate is used which contains at least one thermoplastic polyurethane with shape memory properties according to at least one of claims 2 to 8 or is formed substantially entirely therefrom.

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