Dental preform, method for manufacturing such a preform, and method for manufacturing a dental prosthesis from such a preform

Abstract

A dental preform (1) comprises a central portion (2) comprising a first elementary portion (2a) and a second elementary portion (2b) fixed to each other by a first resin (7) and separated at least by one web (6). The first elementary portion (2a) and the second elementary portion (2b) each comprise a plurality of first filamentary elements (5) and the first resin (4). The first filamentary elements (5) and the web (6) extend predominantly in a first direction (AA). A peripheral portion (3) formed by the web (6) is coiled continuously around the central portion (2) in order to form a spiral. A second resin mechanically binds the multiple layers of the spiraled web (6) and bonds the peripheral portion (3) to the central portion (2).

Description

DENTAL PREFORM, METHOD FOR MANUFACTURING SUCH A PREFORM, AND METHOD FOR MANUFACTURING A DENTAL PROSTHESIS FROM SUCH A PREFORM

[0001] The invention relates to a dental preform, a method for manufacturing such a dental preform and a method for manufacturing a dental prosthesis from such a dental preform. State of the art

[0002] It is known to form at least part of a dental prosthesis from a milled dental preform. The dental preform is milled by any suitable means, preferably using CAD / CAM technology. Various types of dental preforms are commercially available, offering substantially homogeneous mechanical characteristics from one end to the other.

[0003] However, it is important to emphasize that the mechanical performance of such preforms is very different from that of a natural tooth, which poses adaptation problems when a dental prosthesis is fitted. Current composite materials, particularly particle composites, are not suitable for replicating the function of a natural tooth. The same is true for ceramic preforms, such as lithium disilicate or zirconia preforms. This issue also arises with hybrid ceramics, which are composite materials with a primary and a secondary network. The primary ceramic network is infiltrated by a secondary polymer network. The two networks are completely interwoven. The dual ceramic-polymer network structure was designed to ideally combine the desirable properties of ceramics and composite materials.However, the main ceramic matrix remains rigid and brittle. It also has limited deformation, preventing it from replicating the mechanical performance of a natural tooth. The toughness of this hybrid material is considered low, which limits its usefulness.

[0004] It is still possible to create a custom-made dental preform whose mechanical performance has been adapted to the dimensional constraints of the tooth to be replaced. However, this operation is lengthy and relatively expensive.

[0005] A dental preform is described in document FR3129285. This preform has a central portion equipped with unidirectional fibers extending in one direction and mechanically bonded together by a resin. Around this central portion, fibers and a second resin are arranged to form a peripheral portion. The fibers are misaligned from the first direction to wrap around the central portion. The central portion can also be surrounded by a sheet that wraps around it. The misaligned fibers are arranged between the turns of the sheet.

[0006] Even though this preform appears capable of improving mechanical performance compared to prior art, it is clear that this configuration deviates from the behavior of a real tooth in several respects. It also appears that the manufacturing process is difficult to maintain over time.

[0007] Therefore, there is a need to create a dental preform that better matches the mechanical characteristics of a tooth while being easier to produce.

[0008] One object of the invention is to overcome these disadvantages, and more particularly to provide a dental preform which has a gradient of modulus of elasticity between its central portion and its peripheral portion in order to better reproduce the mechanical characteristics of a natural tooth.

[0009] These disadvantages are addressed by means of a dental preform comprising: - a central portion comprising a first elementary portion and a second elementary portion fixed to each other by a first resin and separated at least by a sheet, the first elementary portion and the second elementary portion each comprising a plurality of first wire elements and the first resin, the first wire elements and the sheet extending predominantly in a first direction; - a peripheral portion formed by the sheet wound continuously around the central portion to form a spiral, a second resin mechanically bonding the multiple layers of the spiral sheet and bonding the peripheral portion with the central portion.

[0010] According to one aspect of the invention, the first elementary portion and the second elementary portion each have at least one additional layer extending predominantly in a first direction.

[0011] Preferably, at least one additional layer of the first elementary portion and of the second elementary portion have longitudinal threads extending along the first direction.

[0012] In a particular embodiment, the first elementary portion and the second elementary portion each have wire elements which are predominantly the first wire elements in volume.

[0013] Advantageously, the first elementary portion and the second elementary portion consist exclusively of the first wire elements and the first resin in addition to at least one additional layer.

[0014] In a particular embodiment, at least one additional layer represents less than half the volume of the first elementary portion and the second elementary portion.

[0015] Preferably, the tablecloth is a fabric or woven element and the first direction is the direction of the longitudinal threads.

[0016] In another development, the central portion has a circular section, the sheet extending along a diameter, or the central portion has an oval section, the sheet extending along a small diameter.

[0017] Advantageously, the and directed from the central portion to one end of the peripheral portion.

[0018] The invention also relates to a manufacturing process that allows for the easy formation of a preform with better-controlled mechanical performance. This problem is addressed by a manufacturing process for a dental preform comprising the following steps: - fixing a first elementary portion to a first face of a sheet and fixing a second elementary portion to a second face of the sheet, the first elementary portion and the second elementary portion covering the sheet to define an attachment zone, wherein the first elementary portion, the second elementary portion, and the attachment zone form a central portion, the sheet extending beyond the attachment zone to define an additional zone.in which the first elementary portion and the second elementary portion each comprise a plurality of first filament elements extending predominantly along the first direction and an elementary resin, the elementary resin ensuring the fixation between the first filament elements; - winding the additional portion of the sheet around the central portion to form a peripheral portion, the additional zone forming a spiral around the central portion, the spiral being observed perpendicular to the first direction, a second resin mechanically bonding the multiple layers of the spiral.

[0019] The invention also relates to a method for manufacturing a dental prosthesis that makes it easy to form a prosthesis that better reproduces the characteristics of a real tooth. This problem is addressed by means of a method for manufacturing a dental preform comprising the following steps: - supplying a dental preform according to any of the preceding configurations; - machining the dental preform in which a portion of the peripheral portion is completely removed to reach the central portion intended to form a canal anchor, and another portion of the peripheral portion is partially removed to form a coronal portion of the dental prosthesis according to a predefined shape.

[0020] Preferably, the manufacturing process of a dental prosthesis includes, before machining, cutting the dental preform perpendicular to the first direction to define the dimension of the dental preform along the first direction. Description of the drawings

[0021] Other advantages and features will become clearer from the following description of particular embodiments and implementations of the invention, given by way of non-limiting examples and shown in the accompanying drawings, in which:

[0022] schematically illustrates a cross-sectional view of a dental preform;

[0023] schematically illustrates a cross-sectional view of a central portion of a dental preform with a protruding sheet;

[0024] schematically illustrates another cross-sectional view of another embodiment of a central portion of a dental preform with a protruding sheet;

[0025] schematically illustrates a perspective view of a method of realizing the central portion of a dental preform before the formation of the spiral by the sheet;

[0026] schematically illustrates a cross-sectional view of a dental preform with a central piece made of soft material;

[0027] schematically illustrates a cross-sectional view of a central portion of a dental preform with a protruding sheet and a central piece of soft material. Detailed description

[0028] Figure 1 represents a dental preform. Dental preform 1 has a central portion 2 and a peripheral portion 3. Dental preform 1 can be a preform to be milled or a generic preform that will be cut to form the dental preforms to be milled. Dental preform 1 is intended to be milled to form a dental prosthesis.

[0029] The dental preform 1 is made of composite material with at least one elemental resin 4, at least one filament element 5 and at least one layer 6. The central portion 2 extends along a first direction AA. Preferably, the central portion 2 extends mainly along the first direction AA, that is to say, the largest dimension of the dental preform 1 is along the first direction AA.

[0030] The central portion 2 has a first elementary portion 2a and a second elementary portion 2b. The first elementary portion 2a and the second elementary portion 2b are fixed to each other by means of a sheet 6 and a first resin 7. The first elementary portion 2a and the second elementary portion 2b are arranged opposite each other in a direction perpendicular to the first direction AA.

[0031] Each of the first elementary portion 2a and the second elementary portion 2b possesses a plurality of first filament elements 5 and an elementary resin 4. The first filament elements 5 extend predominantly along the first direction AA. The elementary resin 4 mechanically binds the first filament elements 5 together.

[0032] The first strand elements 5 are preferably parallel to each other and, more preferably, extend exclusively along the first direction AA. Preferably, the first strand elements 5 extend continuously from one end to the other of the dental preform 1 along the first direction AA to facilitate the transmission of forces along the height of the central portion 2. The first strand elements 5 may comprise unidirectional wires, woven elements, fabric, ribbon, or braid. It is also possible to combine several of these elements, for example, wires and braids. A woven element, fabric, ribbon, or braid may be formed from several wires or fibers.

[0033] The wires can be made of silica or organic material. Preferably, the wires are made of a material selected from polyethylene, polyetheretherketone PEEK, and carbon. The same may apply to the fibers. Preferably, the first wire elements 5 extend continuously along the entire height of the dental preform 1, that is, along the first direction AA.

[0034] Preferably, elemental resin 4 is a polymer resin which is advantageously loaded with particles, preferably micro-particles and / or nano-particles.

[0035] Elementary resin 4 can be chosen from PMMA, UDMA, or epoxy resins. It is also possible to have the elemental resin reinforced with fillers, for example, nanoscale graphene elements. A graphene-reinforced PMMA resin can be used.

[0036] The threads, fibers, fabrics, ribbons, braids, and other elements forming the first filament elements 5 can be coated with an impregnation resin. The impregnation resin may be the same as or different from the elemental resin 4. The impregnation resin and the elemental resin 4 are chemically compatible to ensure mechanical bonding between the first filament elements 5. The resins are preferably thermosetting resins.

[0037] The central portion 2 can have any shape in its cutting plane perpendicular to the first direction AA. Preferably, the central portion 2 has a circular, ovoid, or oval cross-section. Figures 1 to 4 illustrate a particular embodiment where the cross-section of the central portion 2 is circular or substantially circular.

[0038] Each of the first elementary portion 2a and the second elementary portion 2b possesses several first filament elements 5 that exhibit a modulus of elasticity greater than the modulus of elasticity of the elementary resin 4 along the first AA direction. Each of the first elementary portion 2a and the second elementary portion 2b may also possess an additional filament element that has a hardness lower than the hardness of the first filament elements 5 and the elementary resin 4 in order to define a preferred etching zone and thus facilitate intervention up to an infected apex.

[0039] It is advantageous that each of the first elementary portion 2a and the second elementary portion 2b has a volumetric majority of first wire elements 5 compared to any other wire element to better channel the forces.

[0040] In one embodiment illustrated in Figure 1, the first elementary portion 2a and / or the second elementary portion 2b consist exclusively of first filament elements 5 extending along the first direction AA and the first resin 4. The forces applied in the first elementary portion 2a and in the second elementary portion 2b are better channeled. In another embodiment illustrated in Figure 1, the first elementary portion 2a and / or the second elementary portion 2b also include one or more layers of an additional layer 8.

[0041] The first elementary portion 2a and the second elementary portion 2b are arranged opposite each other to define an attachment zone 6a for the web 6, and they are fixed to each other on a portion of a web 6 by means of a first resin 7. Advantageously, the first resin 7 is identical to the elementary resin 4. The first resin 7 is compatible with the elementary resin 4. The first resin 7 can be formed from the same resins as those presented for the elementary resin 4.

[0042] It is preferable that the fabric 6 be a woven material. The woven material has longitudinal and transverse threads, which are formed by the warp and weft threads. It is particularly advantageous for the longitudinal or transverse threads to extend mainly, or even exclusively, along the first direction AA. By "threads extend mainly along the first direction AA," it is advantageously understood that the angular offset between the first direction AA and the direction of thread extension is less than or equal to 15°, less than or equal to 10°, or even less than or equal to 5° or less than or equal to 2°.

[0043] The sheet 6 is fixed to the first elementary portion 2a and to the second elementary portion 2b to effect a transfer of forces between the sheet 6 and each of the first elementary portion 2a and the second elementary portion 2b in one direction or the other, as well as between the first elementary portion 2a and the second elementary portion 2b via the sheet 6.

[0044] The layer 6 has a bonding portion 6a which is the portion covered on one side by the first elementary portion 2a and on the other side by the second elementary portion 2b. The layer 6 also has one or at least one additional portion 6b which corresponds to the portion or portions not arranged between the first elementary portion 2a and the second elementary portion 2b.

[0045] The additional portion(s) 6b are in mechanical continuity with the attachment portion 6a by means of the longitudinal or transverse wires which extend along the different portions.

[0046] Preferably, the first elementary portion 2a and the second elementary portion 2b have the same or substantially the same cross-section so that neither the first elementary portion 2a nor the second elementary portion 2b covers the layer 6 outside the attachment zone 6a.

[0047] The facing walls of the first elementary portion 2a and the second elementary portion 2b, which cover layer 6, are preferably plane walls. These plane walls are parallel to the first direction AA and to a second direction BB. These plane walls are perpendicular to a third direction CC, which is the direction from which the first elementary portion 2a faces the second elementary portion 2b.

[0048] It is also advantageous that the dimension of the sheet 6 along the first direction AA be greater than or equal to the dimension of the larger of the first elementary portion 2a and the second elementary portion 2b along the first direction AA and that each end of the sheet 6 along the first direction AA be flush with or extend beyond the ends of the first elementary portion 2a and the second elementary portion 2b.

[0049] Layer 6 extends beyond the attachment zone 6a to form the additional portion 6b, which will define the peripheral portion 3 of the dental preform 1. It is advantageous for layer 6 to extend from one end of the attachment zone 6a to the other along the first direction AA and along a second direction BB perpendicular to the first direction AA. It is even possible for layer 6 to extend beyond the attachment zone 6a at both opposite ends along the second direction BB.

[0050] The peripheral portion 3 completely surrounds the central portion 2 perpendicularly to the first direction AA. The peripheral portion 3 forms a ring whose inner part is filled by the central portion 2.

[0051] The peripheral portion 3 is formed by the wrapping of the additional portion(s) 6b of the sheet 6 around the central portion 2. The sheet extends continuously to form at least one complete turn around the central portion 2. Preferably, the sheet 6 forms several complete turns to form the peripheral portion 3 around the central portion 2.

[0052] The 6th layer can be a fabric or a woven element, a ribbon, or a braid. A fabric has weft and warp threads. A woven element differs from a fabric in that it lacks weft threads. There are quasi-weft threads that are oriented like the weft threads of a fabric but are mechanically distinct. Quasi-weft threads do not intersect.

[0053] It is particularly advantageous to use 6-layer preforms, especially those with wires or wire elements oriented parallel to the first AA direction. When the dental preform 1 is used to create an inlay-core type prosthetic element, the wires or wire elements oriented along the first AA direction allow for better force transfer along the height of the prosthetic element, that is, along the direction connecting the root apex to the crown. The wires or wire elements improve the mechanical strength and toughness characteristics during masticatory forces.

[0054] It has been observed that the presence of layer 6, positioned between the first elementary portion 2a and the second elementary portion 2b, improves the long-term stability of the shape of the dental prosthesis formed from such a dental preform 1. It also appears that the presence of layer 6 allows for a better reproduction of the shape and behavior of a tooth with a root. The dental prosthesis is thus better able to replicate the behavior of a natural tooth.

[0055] In an advantageous embodiment illustrated in Figure 1, one or more additional layers of webs 8 are present between web 6 and the portion containing the elementary resin 4 and the first filament elements 5 of the first elementary portion 2a and the second elementary portion 2b. The addition of at least one additional layer of web 8 allows for a better adaptation of the mechanical characteristics of the apical portion to the mechanical characteristics of a dental root.

[0056] Adding at least one additional layer of fabric helps to better maintain the shape of the part intended to reproduce the effect of the root following the various stresses, particularly the stresses of chewing.

[0057] When transforming the dental preform 1 into a dental prosthesis, it is advantageous to mill the entire peripheral portion 3 and part of the central portion 2 in the apical area. Removing the peripheral portion 3 and part of the central portion 2 results in an apical area that is narrower and more anisotropic in two directions perpendicular to the first direction AA.

[0058] The peripheral portion 3 is formed by a coil of a sheet 6. This configuration tends to form a coronal part whose mechanical behavior is essentially identical for a given load perpendicular to the first direction AA. Conversely, a different behavior is desired in the apical part in order to avoid excessive stress on the area of ​​attachment to the jaw.

[0059] The addition of additional layers 8 improves the mechanical stability of the apical portion and, to a lesser extent, the coronal portion. It is particularly advantageous for the extension axes of the longitudinal wires and the longitudinal wires of the two additional layers 8, separated by layer 6, to be parallel. It is also advantageous for the additional layers 8, arranged in mirror image with respect to layer 6, to be identical.

[0060] It is possible to manufacture such a dental preform 1 efficiently.

[0061] The first elementary portion 2a and the second elementary portion 2b are provided beforehand. The two elementary portions can be formed by any suitable means, for example by pultrusion. The shape of the first elementary portion 2a and the shape of the second elementary portion 2b are chosen according to requirements.

[0062] The first elementary portion 2a and the second elementary portion 2b are then fixed to the first layer 6. More specifically, the two elementary portions 2a and 2b are fixed to the two opposite faces of the first layer 6. The two elementary portions 2a and 2b are fixed by means of a resin 7 and by applying a force F which allows good contact.

[0063] In a case illustrated in the figure, the first elementary portion 2a and the second elementary portion 2b are without additional layers 8 and are fixed directly to the layer 6. In an alternative embodiment illustrated in the figure, the first elementary portion 2a and the second elementary portion 2b have one or more additional layers 8 and the additional layers are arranged between the layer 6 and the first wires 5.

[0064] It is particularly advantageous to fix the first elementary portion 2a and the second elementary portion 2b to the layer 6 by applying bonding pressure in order to reduce the occurrence of bubbles at the bonding interface. This allows for better control of mechanical performance.

[0065] Once the sheet, the first elementary portion 2a and the second elementary portion 2b are glued together, they form the central portion 2 of the dental preform 1. The central portion 2 can be used as a mandrel which rotates on itself and ensures the winding of the additional portion 6b of the sheet 6 around the mandrel to form the peripheral portion 3. As the mandrel makes turns, the thickness of the peripheral portion 3 increases until it reaches the desired thickness.

[0066] Preferably, the central portion 2 is mounted to rotate about an axis of rotation parallel to the first direction AA and passing through the center of the central portion 2. When the central portion 2 has a circular cross-section, the center is the center of the circle. When the central portion 2 has an ovoid cross-section, the center is the intersection of the smaller and larger diameters. When the central position has an arbitrary shape, the center corresponds to the centroid of the cross-section.

[0067] It is advantageous for the first elementary portion 2a and the second elementary portion 2b to extend beyond the first layer 6 to form a mandrel that allows the layer 6 to be wound around the assembly formed by the first elementary portion 2a, the second elementary portion 2b, and the overlapping portion. Alternatively, the mandrel is fixed in place, and a reservoir containing the additional portion of the layer 6 rotates around the mandrel.

[0068] Generally, the additional portion 6b is wound around the mandrel in a spiral. The multiple turns of the layer 6 are secured to each other by a second resin, which ensures the transmission of forces between the turns of the layer and between the layer 7 and the central portion 2. The layer 6 may be impregnated with the second resin, or the second resin may be deposited on the layer before or after its deposition on the layer immediately below. The second resin is preferably compatible with the first resin 7 and / or the elementary resin 4.

[0069] During the formation of the multiple turns of the sheet 6 around the central portion 2, the sheet 6 is subjected to a tensile force which constrains the sheet 6 in tension. The force applied to the multiple turns of the sheet 6 allows the mechanical performance of the dental preform 1 and therefore the mechanical performance of the dental prosthesis 1.

[0070] The tension force applied during the winding of the additional portion 6b applies a centripetal force on the central portion 2.

[0071] Bonding the overlapping portion to the first elementary portion 2a and the second elementary portion 2b prior to winding the additional portion allows for better control over the initial layers of the peripheral portion, i.e., the layers closest to the central portion. The tensile force is more effectively applied to the layers closest to the central portion, resulting in improved control over the mechanical performance of the coronal section.

[0072] In a particular embodiment, the central portion 2 does not have a circular cross-section.

[0073] The first layers are involved in transferring forces to the central portion. These first layers extend over the greatest length of the dental prosthesis because they are the last layers removed during the machining phase. The force applied by the peripheral portion 3 to the central portion is better controlled and more homogeneous all around the central portion 2.

[0074] It is advantageous to form a dental preform 1 whose maximum dimension perpendicular to the first direction AA, for example a diameter, is less than 40 mm. The arrangement of the wire elements in the central portion 2 and the shape of the central portion are chosen according to the tooth to be replaced, for example its dimensions, its position in the mouth and the characteristics of the adjacent teeth.

[0075] It is also possible to form larger dental preforms in the direction perpendicular to the first AA direction, and even more preferably in the first AA direction. The preform can have a diameter greater than 5 cm, advantageously greater than 10 cm, and even more advantageously greater than 20 cm. The thickness in the first AA direction is advantageously greater than 1 cm, more advantageously greater than 2 cm, and even more advantageously greater than 3 cm. These dental preforms can then be used to create frameworks for tooth-supported, removable, or fixed prostheses, or for implants.

[0076] In an observation along a cross-sectional plane perpendicular to the first direction AA, as illustrated in Figure 1, the layer 6 extends continuously over several layers and takes the form of a spiral. The use of a spiral layer extending over several layers, and preferably over all layers, allows for good force transmission between the outer part of the preform and its central portion. Such a configuration allows the preform to approximate the mechanical behavior of a natural tooth.

[0077] The spiral arrangement also helps to improve the toughness of the dental preform, which facilitates the blocking of microcracks.

[0078] It is advantageous for the layer 6 to form at least five turns around the central portion 2.

[0079] Preferably, the second resin 7 is a polymer resin which is loaded with particles 7, preferably micro-particles and / or nano-particles.

[0080] The formation of several annular layers arranged around each other and mechanically linked by the second resin 7 allows for effective modulation of mechanical performance radially or substantially radially perpendicular to the first direction AA. Since the thickness of the layer 6 is small, it is possible to make a significant number of turns around the central portion 2 to form the peripheral portion 3 while remaining within the lateral dimensions of a tooth to be repaired. It is therefore easy to create a dental preform 1 whose mechanical performance is controlled radially, that is, as a function of its distance from the central portion 2.

[0081] The modulation of the winding characteristics in each layer from the interface with the central portion 2 to the outer wall of the peripheral portion 3 offers great freedom in the modulation of the mechanical characteristics in a radial or substantially radial manner.

[0082] In order to form a dental preform 1 with mechanical characteristics approaching those of a natural tooth, it is advantageous to form a peripheral portion 3 with a gradient of modulus of elasticity along a direction perpendicular to the first direction AA. The modulus of elasticity increases in the peripheral portion 3 from the interface with the central portion 2 and away from the central portion 2. The modulus of elasticity is advantageously the modulus of elasticity along the first direction AA and / or along the direction perpendicular to the first direction AA.

[0083] Preferably, the gradient of the modulus of elasticity in the peripheral portion 3 increases monotonically from the interface with the central portion 2 up to at least 50% of the thickness of the peripheral portion 3 and even more preferably over at least 75% of the thickness or even over the entire thickness of the peripheral portion 3. Even more preferably, the gradient of the modulus of elasticity in the peripheral portion 3 increases linearly from the interface with the central portion 2 up to at least 50% of the thickness of the peripheral portion and even more preferably over at least 75% of the thickness or even over the entire thickness of the peripheral portion 3.

[0084] In an advantageous embodiment, at the outer end of the peripheral portion 3, the modulus of elasticity is greater than 80GPa and less than 20GPa in the immediate vicinity or in the central portion 2. Preferably, the gradient of the modulus of elasticity extends over at least 40GPa.

[0085] To reduce the propagation of microfractures from the outer face of the dental preform 1 to the central portion 2, it is advantageous to decrease the value of the modulus of elasticity as one approaches the central portion 2, preferably by at least 40GPa and even more preferably in a linearly decreasing manner.

[0086] To obtain a gradient of the modulus of elasticity over several layers, the winding characteristics evolve from one layer to another or from one set of layers to another.

[0087] The gradient of the elastic modulus can be obtained by modifying the winding voltage of the sheet 6,

[0088] Modifying the chemical composition of the second resin 7 or the second impregnation resin can involve changing the filler content, for example, the microparticle content, the nanoparticle content, or the microfiber (whisker) content. The chemical composition can also be modified by changing the chemical composition of the fillers themselves. Modifications to the second resin 7 alter its mechanical properties in the direction perpendicular to the first direction AA and in the first direction. For example, to increase the modulus of elasticity as one moves away from the central portion 2, it is possible to increase the filler content (while keeping other parameters unchanged) in the layers as one moves away from the central portion 2.It is also possible to modify several parameters between two successive layers, for example the winding pitch and the charge content.

[0089] In an advantageous embodiment, the layer 6 is partially or at least partially polymerized on the central portion 2 during winding, as it is wound. Each portion of the layer 6 is polymerized before being covered by the next layer of layer 6. It is advantageous for the polymerization of the portion of layer 6 to be partial and for several polymerization steps to be carried out successively.

[0090] In one embodiment, the central portion 2 is positioned opposite a polymerization device so as to polymerize a part of the central portion. When the central portion 1 has completed one rotation around it, the newly deposited portion of the web has undergone a first polymerization step. When the central portion 2 completes several rotations, the portion of web 6 deposited during the first rotation undergoes a first polymerization step with the polymerization device directly opposite the portion of web. With the deposition of additional layers of web 6, the first deposited web undergoes additional polymerization steps that facilitate bonding between the different layers while reducing the risk of resin creep due to potential changes in winding conditions as multiple layers of web 6 are deposited.

[0091] Even more advantageously, after the layer is deposited and before the first polymerization step is applied, the layer is subjected to a compaction step which presses the layer against the central portion 2 possibly covered by previous layers.

[0092] The formed dental preform can be a milling preform or a cutting preform. Once the dental preform is cut, it can be milled.

[0093] When creating a preform for machining—that is, machining without a preliminary cutting step perpendicular to the first direction—it is advantageous for the preform to be small, for example, with a diameter less than 50 mm. The preform has a volume roughly equivalent to that of a tooth. A gripper is attached to the preform to facilitate machining. Machining the preform preferably creates an inlay-core, ideally using a CAD / CAM milling technique. The dental preform can also be used to form a core buildup. In this case, the preform is covered by a crown, which can be made of ceramic, composite material, or preferably zirconia. It is also possible to use the dental preform to form an implant abutment. The mechanical configuration of the preform is particularly advantageous for withstanding the multidirectional forces of mastication.It is also possible to form larger preforms, to form bridge infrastructures, for example on natural or implant teeth.

[0094] When forming a preform for milling, it must be cut one or more times perpendicular to the first AA direction to define a plurality of elementary preforms that will form the milling preforms. It is advantageous to form a taller preform along the first AA direction to be able to form several milling preforms. It is also advantageous to form wider preforms to adapt the preform for uses other than inlay-core formation, for example, bridge substructures, for instance, on natural or implant-supported teeth. The cutting step allows the height of the preform to be adapted to the requirements. To easily form a preform of significant width, it is preferable to form a preform of significant height, which facilitates the proper retention of the second wire elements and the layers between them across the multiple layers.

[0095] The preform is more deformable than a metallic equivalent, such as shape-memory metal supports. The preform's deformability is defined by the mechanical properties of its different layers. A preform with large dimensions and a gradient in its modulus of elasticity allows for better adaptation of its performance to the stresses of the dental arches. The preform can have a circular or oval cross-section, or a shape close to these, to better conform to the shape of the dental arches and thus optimize its mechanical properties.

[0096] The preform for direct milling is milled to form an anatomical inlay-core type dental prosthesis with a canal zone and a coronal zone. The canal zone is designed to fit into the root canal of a dental root in a laboratory model. The coronal zone is designed to form the coronal portion of the tooth destroyed by decay, for example, to support a peripheral prosthetic crown. The preform is milled so that the central portion fits into the canal and extends into the coronal zone. Part of the peripheral portion is completely removed to form the canal zone. The peripheral portion is milled and partially retained to form the coronal zone, which will simulate the dentin of a natural tooth. The peripheral portion is milled to define a shape that closely resembles the shape of the dentin to be replaced.

[0097] The dental preform 1 is machined using any suitable machining equipment, preferably a computer-aided machining center (CAD / CAM) machine, for example, a 3-axis to 5-axis machine. The dental preform 1 is machined to reproduce a predefined shape calculated at least from the impression of the tooth to be repaired.

[0098] The formation of several concentric layers, preferably with turns obtained by winding and advantageously by honeycomb winding, allows us to define more precisely the mechanical performance of the peripheral portion 3 for each layer and therefore the evolution of the characteristics as a function of the distance from the central portion 2.

[0099] This embodiment allows for the formation of a dental preform with mechanical characteristics that are virtually identical around the central portion, depending on the radius value. It is then possible to define the expected technical characteristics based on the layer's winding characteristics, including the composition of the resin used in the layer.

[0100] Once the dental preform 1 is fully wound, it is advantageous to carry out the polymerization of the second resin 7 and the second impregnation resin if necessary.

[0101] Preferably, the coiled and polymerized dental preform 1 has a circular cross-section. The mechanical characteristics of the peripheral portion 3 vary with distance from the center of the dental preform 1 perpendicular to the first direction AA.

[0102] In one particular embodiment, the dental preform 1 is provided, and then a cutting step is performed to define a plurality of elementary preforms from the initial preform. The cutting plane is preferably perpendicular to the first direction AA. It is then possible to form an elementary preform with the chosen height (the dimension along the first direction AA) according to the requirements.

[0103] Since the dental preform 1 or the elementary dental preform is intended to be machined to form a dental prosthetic element, the dimension along the first direction AA, i.e. the height, is preferably between 10 mm and 90 mm depending on the prosthetic element to be formed.

[0104] It is advantageous that the dental preform 1 is devoid of a filarial element that extends mainly perpendicularly or perpendicularly to the first direction AA and that is common to the central portion 2 and the peripheral portion 3. The dental preform 4 is devoid of a filarial element that passes through the first filarial elements 4 and between the turns of the sheets 6.

[0105] It is advantageous that the dental preform 1 be devoid of a wire element which extends perpendicularly to the first direction AA and radially in the peripheral portion 3.

[0106] It is advantageous that the preform be devoid of a wire element that extends perpendicularly to the first direction AA and radially in the central portion 2.

[0107] In an embodiment illustrated in Figures 5 and 6, the first elementary portion 2a and the second elementary portion 2b define a central orifice intended to be filled with a soft material. A soft material is one that allows for differential etching compared to the material forming the first elementary portion 2a and the second elementary portion 2b. For example, the soft material is gutta-percha. A reamer can be used to etch the soft material. Because the material of the first elementary portion 2a and the second elementary portion 2b is harder, it limits the movement of the reamer, allowing it to penetrate the depth of a dental restoration safely. This is particularly advantageous when an apex is infected and deep intervention is required.It is advantageous to be able to quickly access the bottom of the reconstruction without having to engrave the first elementary portion 2a and the second elementary portion 2b and risk shifting up to the gum.

[0108] It is advantageous for at least one of the first elementary portion 2a and the second elementary portion 2b to define an opening intended to be filled with a soft material. The opening is preferably defined by both elementary portions, and even more preferably, the two elementary portions define half of the opening. The opening is preferably a through-hole. The opening is located at the upper end of the preform to facilitate subsequent access.

[0109] In this embodiment, the first elementary portion 2a and the second elementary portion 2b define a central orifice, and the sheet 6 is wedged between the soft material and one of the elementary portions. The size of the orifice, as well as the curvature at the ends, allows the sheet 6 to be wedged. It is advantageous that the soft material is preferentially engraved compared to the materials forming the first elementary portion 2a, the second elementary portion 2b, and the sheet 6. This is particularly advantageous when the removal of the soft material is carried out with a reamer.

[0110] When the dental preform has a circular cross-section, it is advantageous for the center of the dental preform to also be the center of the soft material portion.

[0111] The soft material can be a circular rod with a diameter preferably between 0.1 and 1 mm. The soft material is preferably chosen from gutta-percha, polytetrafluoroethylene (PTFE), and polyoxymethylene (POM).

[0112] The dental preform is intended to form a dental prosthesis for installation, preferably, on a laboratory model.

Claims

Dental preform (1) comprising: - a central portion (2) comprising a first elementary portion (2a) and a second elementary portion (2b) fixed to each other by a first resin (7) and separated at least by a sheet (6), the first elementary portion (2a) and the second elementary portion (2b) each comprising a plurality of first wire elements (5) and the first resin (4), the first wire elements (5) and the sheet (6) extending predominantly in a first direction (AA); - a peripheral portion (3) formed by the sheet (6) wound continuously around the central portion (2) to form a spiral, a second resin mechanically bonding the multiple layers of the spiraled sheet (6) and bonding the peripheral portion (3) with the central portion (2). Dental preform (1) according to claim 1 wherein the first elementary portion (2a) and the second elementary portion (2b) each have at least one additional layer (8) extending predominantly in a first direction (AA). Dental preform (1) according to claim 2 wherein at least one additional layer (8) of the first elementary portion (2a) and of the second elementary portion (2b) have longitudinal threads extending along the first direction (AA). Dental preform (1) according to claim 2 in which the first elementary portion (2a) and the second elementary portion (2b) each have wire elements which are predominantly by volume the first wire elements (5). dental preform (1) according to claim 4 wherein the first elementary portion (2a) and the second elementary portion (2b) comprise exclusively the first wire elements (5) and the first resin (4) in addition to at least one additional layer (8). dental preform (1) according to claim 5 wherein at least one additional layer (8) represents less than half the volume of the first elementary portion (2a) and the second elementary portion (2b). Dental preform (1) according to any one of claims 1 to 6, wherein the layer (6) is a fabric or woven element and the first direction (AA) is the direction of the longitudinal threads. Dental preform (1) according to any one of claims 1 to 7, wherein the central portion has a circular cross-section, the sheet (6) extending along a diameter or the central portion has an oval cross-section, the sheet (6) extending along a small diameter.Method for manufacturing a dental preform (1) comprising the following steps: - fixing a first elementary portion (2a) to a first face of a sheet (6) and fixing a second elementary portion (2b) to a second face of the sheet (6), the first elementary portion (2a) and the second elementary portion (2b) covering the sheet (6) to define an attachment portion (6a), in which the first elementary portion (2a), the second elementary portion (2b) and the attachment zone (6a) forming a central portion (2), the sheet (6) extending beyond the attachment zone (6a) to define an additional zone (6b), in which the first elementary portion 2a and the second elementary portion 2b each comprising a plurality of first wire elements (4) extending predominantly along the first direction (AA) and an elementary resin (5), the elementary resin ensuring the attachment between the first wire elements (AA);- wrap the additional portion (6b) of the sheet (6) around the central portion to form a peripheral portion (3), the additional area (6b) forming a spiral around the central portion (2), the spiral being observed perpendicular to the first direction (AA), a second resin (7) mechanically bonding the multiple layers of the spiral.; Method of manufacturing a dental prosthesis (1) comprising the following steps:- supplying a dental preform (1) according to any one of claims 1 to 8;- machining the dental preform (1) in which a part of the peripheral portion (3) is completely removed to reach the central portion (2) intended to form a canal anchor, and another part of the peripheral portion (3) is partially removed to form a coronal portion of the dental prosthesis (1) according to a predefined shape. Method of manufacturing a dental prosthesis (1) according to the preceding claim comprising, prior to machining, a cut of the dental preform (1) perpendicular to the first direction (AA) to define the dimension of the dental preform (1) along the first direction (AA).

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