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

Description

Technical field

[0001] The invention relates to a dental preform, a method of manufacturing such a dental preform and a method of 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 dental preform that is machined. The dental preform is machined by any suitable means and preferably using CAD-CAM technology. Different types of dental preforms are marketed with substantially uniform mechanical characteristics from one end of the preform to the other.

[0003] However, it should be emphasized that the mechanical performance of such preforms is very far from that of a natural tooth, which poses adaptation problems when a dental prosthesis is installed. It can be observed that current composite materials, particularly particulate composites, are not suitable for reproducing the functioning of a natural tooth. The same is true for ceramic preforms, for example lithium disilicate or zirconia preforms. This problem is also present for hybrid ceramics, which are composite materials with a main network and a secondary network. The main ceramic network is infiltrated by a secondary network that is made of polymer. The two networks are completely intertwined. The double ceramic-polymer network structure was designed to ideally combine the good properties of ceramic and composite materials.However, the main ceramic network remains rigid and brittle. It is also not very deformable, which does not allow it to reproduce the mechanical performance of a natural tooth. The toughness of this hybrid material is considered low, which limits its interest.

[0004] It is still possible to form 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 long and relatively expensive.

[0005] WO96 / 26687 discloses a dental post made of composite material with a central core formed by a bundle of fibers. The central core is surrounded by a sheath consisting of at least one layer of fibers. The central core and the sheath are embedded in a curable resin. The fibers of the sheath are oriented at a given angle relative to the fibers of the central core to adjust the longitudinal and transverse tensile strength values ​​of the post.

[0006] Document DE3825601 discloses a dental post having a root portion formed by parallel fibers and a coronal portion formed by obliquely directed fibers. The obliquely directed fibers are directed oppositely and at the same angle to the fibers of the root portion. Document EP 1147748 discloses a dental post having a central portion of composite material around which layers of carbon fiber fabric are wound. The fabric layers are embedded in an epoxy resin. The fabric layers are arranged concentrically around the central portion. Document US2002 / 0123023 discloses a dental post formed by a plurality of glass fibers that are twisted together and embedded in a resin to form a deformable one-piece structure. The post may be terminated by a spacer for receiving a crown.

[0007] There is therefore a need to form a dental preform that better matches the mechanical characteristics of a tooth while being easy to produce. Statement of the invention

[0008] An object of the invention is to overcome these drawbacks, 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 drawbacks tend to be resolved by means of a dental preform as defined in claim 1, comprising: a central portion formed by a plurality of first wire elements and a first resin, the first wire elements extending mainly in a first direction, the first resin mechanically bonding the first wire elements together; a peripheral portion in the form of a ring around the central portion perpendicular to the first direction, the peripheral portion comprising second wire elements and a second resin, the second resin mechanically bonding the second wire elements together, the first wire elements and the second wire elements being mechanically bonded together at least by the first resin and the second resin; dental preform wherein the peripheral portion comprises a plurality of layers arranged one on top of the other perpendicular to the first direction, the layers surrounding the central portion; wherein each layer has at least one turn formed by at least one of the second filamentary elements, the at least one second filamentary element having a longitudinal direction which is offset from the first direction by an angle of between 10° and 80° or between 100° and 170°; wherein the second filamentary elements of two consecutive layers have opposite orientations; and wherein the second filamentary elements of each layer do not belong to a fabric or a woven element;wherein at least several layers of the plurality of layers further have a ply selected from a fabric, a woven element, a ribbon, a braid, the ply being located under or above the second wire elements in said several layers; wherein the ply extends from one end to the other of the dental preform in the first direction and extends over all the layers, the ply being in the form of a spiral in a section plane perpendicular to the first direction, with an alternation between a ply thickness and a second wire element thickness in an observation direction perpendicular to the first direction and directed from the central portion to one end of the peripheral portion. ;

[0010] According to one aspect of the invention, the central portion has wire elements which are, predominantly in volume, the first wire elements.

[0011] Preferably, the central portion comprises exclusively the first wire elements and the first resin.

[0012] In a particular embodiment, the peripheral portion has a gradient of elastic modulus increasing away from the central portion perpendicular to the first direction.

[0013] Advantageously, the peripheral portion has a content of second wire element which increases monotonically away from the central portion perpendicular to the first direction to form the elastic modulus gradient.

[0014] In a particular embodiment, the second resin is doped with particles. The peripheral portion has a ratio of the content of second wire element to the content of particles which increases in the radial direction away from the central portion perpendicular to the first direction to form the gradient of modulus of elasticity.

[0015] Preferably, the ratio of the content of the second wire element to the content of particles increases inversely proportionally to the distance from the central portion to form the gradient of the modulus of elasticity.

[0016] Preferably, a plurality of concentric tubes are formed by the sheet of the plurality of layers from the interface with the central portion to the outer wall of the peripheral portion.

[0017] In a preferred embodiment, each layer comprises several second wire elements wound in turns around the central portion.

[0018] The invention also relates to a manufacturing method which makes it possible to easily form a preform whose mechanical performance is better controlled. This problem tends to be solved by means of a method for manufacturing a dental preform according to claim 7 which comprises the following steps: providing a mandrel extending in a first direction; forming a peripheral portion in the form of a ring around the mandrel perpendicular to the first direction, the peripheral portion having a plurality of layers surrounding the mandrel, the layers being arranged around each other perpendicular to the first direction, each layer comprising at least one second wire element and a second resin, the second resin mechanically bonding the second wire elements together in the peripheral portion; manufacturing method in which the at least one second wire element of each layer has a longitudinal direction which is offset from the first direction by an angle of between 10° and 80° or between 100° and 170°; in which the at least one second wire element of two consecutive layers have opposite orientations;wherein the at least one second wire element of each layer does not belong to a fabric or a woven element; wherein the mandrel is a central portion formed by a plurality of first wire elements and a first resin, the first wire elements extending predominantly in the first direction, the first resin mechanically bonding the first wire elements together, the first wire elements and the second wire elements being bonded together at least by the first resin and the second resin, or wherein the mandrel is removed to define an empty area in the peripheral portion, the empty area being filled by a plurality of first wire elements and a first resin, the first wire elements extending predominantly in the first direction, the first wire elements and the second wire elements being bonded together at least by the first resin and the second resin;wherein at least several layers of the plurality of layers further have a ply selected from a fabric, a woven element, a ribbon, a braid, the ply being located under or above the second wire elements in said several layers; wherein the ply extends from one end to the other of the dental preform in the first direction and extends over all the layers, the ply being in the form of a spiral in a section plane perpendicular to the first direction, with an alternation between a ply thickness and a second wire element thickness in an observation direction perpendicular to the first direction and directed from the central portion to one end of the peripheral portion. ;

[0019] Advantageously, two successive layers share the at least one second wire element. The turns are formed by a honeycomb winding, and preferably the at least one second wire element extends continuously over all the layers of the peripheral portion.

[0020] Preferably, each layer further comprises a sheet formed by a fabric or a woven element whose weft or quasi-weft thread extends in the first direction.

[0021] In a preferred embodiment, the method comprises at least one cutting of an assembly formed by the central portion and the peripheral portion perpendicular to the first direction to define the dimension of the dental preform in the first direction.

[0022] The invention also relates to a method for manufacturing a dental prosthesis whose mechanical performance is better controlled. This problem is resolved by means of a method for manufacturing a dental prosthesis comprising the following steps: a provision of a dental preform of the invention according to any one of the preceding configurations; a machining of the dental preform in which a part of the peripheral portion is completely removed to reach the central portion intended to form a canal anchor, and another part of the peripheral portion is partially removed to form a coronal portion of the dental prosthesis according to a predefined shape.

[0023] Preferably, the method comprises, 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

[0024] Other advantages and characteristics will emerge more clearly from the following description of particular embodiments and implementations of the invention given as non-limiting examples and represented in the appended drawings, in which: there figure 1 schematically illustrates a perspective view of a dental preform; the figure 2 schematically illustrates a perspective view of a dental preform mounted on a gripper; the figure 3 , schematically illustrates another perspective view of a dental preform mounted on a gripper according to another embodiment; the figure 4 schematically illustrates a more detailed view of the central portion of a dental preform; Figure 5 schematically illustrates a step of winding the second wire element to form the peripheral portion of the dental preform; the figure 6schematically illustrates a sectional view of a dental preform; the figure 7 schematically illustrates a view of a device for manufacturing a dental preform. Detailed description

[0025] THE Figures 1, 2 and 3 represent a dental preform 1. The dental preform 1 has a central portion 2 and a peripheral portion 3. The dental preform 1 may be a dental preform to be machined or a generic preform that will be cut to form the dental preforms that will be machined. The preform is made of composite material with at least one resin and at least one wire element. The figure 4illustrates a more detailed view of the dental preform 1 and in particular the central portion 2. The central portion 2 has a plurality of first wire elements 4 and a first resin 5. The first wire elements 4 extend mainly in a first direction AA. The first resin 5 mechanically binds the first wire elements 4 together.

[0026] The first wire elements 4 have first wire elements 4 oriented mainly in the first direction AA, preferably parallel to each other. Preferably, the first wire elements 4 extend continuously from one end to the other of the preform in the first direction AA to facilitate the transmission of forces over the height of the central portion 2. The first wire elements 4 may comprise unidirectional wires, woven elements, fabric, a ribbon, a braid. It is also possible to combine several of these elements, for example wires and braids. A woven element, a fabric, a ribbon or a braid may be formed by several wires or fibers.

[0027] The wires may be silica wires, made of organic material. Preferably, the wires are made of a material chosen from polyethylene, polyetheretherketone PEEK and carbon. The same may be true for the fibers. Preferably, the first wire elements 4 extend continuously over the entire height of the dental preform 1, that is to say in the first direction AA.

[0028] Preferably, the first resin 5 is a polymer resin which is advantageously loaded with particles, preferably micro-particles and / or nano-particles. The threads, fibers, fabrics, ribbons, braids and other elements forming the first wire elements 4 may be covered with an impregnation resin. The impregnation resin may be identical to or different from the first resin 5. The impregnation resin and the first resin 5 are chemically compatible to ensure the mechanical connection between the first wire elements 4. The resins are preferably thermosetting resins.

[0029] The central portion 2 may have any shape in its section plane perpendicular to the first direction AA. Preferably, the central portion 2 has a circular section.

[0030] The central portion 2 has several first wire elements 4 which have a modulus of elasticity greater than the modulus of elasticity of the first resin 5 along the first direction AA. The central portion 2 may also have an additional wire element which has a hardness lower than the hardness of the first wire elements 4 and of the first resin 5 so as to define a preferred etching zone and thus facilitate an intervention up to an infected apex.

[0031] It is advantageous for the central portion 2 to comprise a majority by volume of first wire elements 4 compared to any other wire element to better channel the forces. It is advantageous for the central portion 2 to comprise exclusively the first wire elements 4 and the first resin 5. The forces applied in the central portion 2 are better channeled.

[0032] The peripheral portion 3 completely surrounds the central portion 2 perpendicular to the first direction AA. The peripheral portion 3 forms a ring whose internal part is filled by the central portion 2.

[0033] The peripheral portion 3 comprises second wire elements 6 and a second resin 7. The second resin 7 mechanically bonds the second wire elements 6 together. The first resin 5 and the second resin 7 mechanically bond the first wire elements 4 with the second wire elements 6.

[0034] The peripheral portion 3 comprises a plurality of layers arranged one on top of the other perpendicular to the first direction AA from the central portion 2 and preferably up to the external wall of the dental preform 1. The layers go around the central portion 2. The layers comprise one or more spirals of at least one second wire element 6 and the second resin 7 around the central portion 2. The at least one second wire element 6 forms at least one complete turn around the central portion 2 in an observation along the first direction AA. In a preferred embodiment, a second wire element 6 extends continuously from one end to the other of the dental preform 1 along the first direction AA in the form of a spiral making several complete turns around the central portion 2. Advantageously, a second wire element 6 makes at least two complete turns around the central portion 2.Preferably, the second wire element 1 has a constant or substantially constant winding pitch over the height of the dental preform 1, i.e. along the first direction AA.

[0035] The second wire element(s) 6 of each layer have a longitudinal direction which is offset relative to the first direction AA by an angle of between 10° and 80° or between 100° and 170°. When a second wire element 6 makes a complete turn around the central portion 2, it is offset in one direction or another along the first direction AA. In the embodiment illustrated in Figure 5, the angle made between the longitudinal direction of the second wire element 6 being wound (axis BB) and the first direction AA is between 10° and 80°. In this configuration, at each turn around the central portion 2, the second wire element 6 shifts to the right. In the following layer and in the previous layer, the angle made between the longitudinal direction of the second wire element 6 being wound and the first direction AA is between 100° and 170°, this corresponds to a second wire element 6 whose longitudinal axis has a direction opposite to that of the previous layer. At each turn of the central portion 2, the second wire element 6 shifts to the left. The winding direction is opposite between two consecutive layers.The use of second wireframe elements 6 of two consecutive layers with opposite orientations allows the second wireframe elements 6 of two consecutive layers to define a mesh when observed perpendicular to the first direction AA.

[0036] In each layer, there is at least one second wire element 6, for example a wire, a fiber, a ribbon, a braid which extends from one end to the other of the dental preform 1 in the first direction AA, in the peripheral portion. The at least one second wire element 6 forms a plurality of turns around the central portion 2. Depending on the layers, the turns rotate in opposite directions around the first direction AA. Preferably, in each layer, the second wire elements 6 extend continuously from one end to the other of the dental preform 1 in the first direction AA by forming turns around the central portion 2.

[0037] It is advantageous for the second wire elements 6 to form at least five turns around the central portion 2.

[0038] The second wire element(s) 6 of each layer do not belong to a fabric or a woven element. The second wire element(s) 6 of each layer only define a spiral around the central portion 2. Preferably, the second wire element(s) 6 are only connected by resin in the first direction AA. There is no weft thread or quasi-weft thread as in a woven element to connect them together.

[0039] The second wire elements 6 are wound to form a plurality of turns around the central portion 2. The plurality of turns is in the form of a stack of turns around the central portion 2. The stack of turns comprises several layers of turns arranged on top of each other in a radial direction perpendicular to the first direction AA.

[0040] The second wire elements 6 define a plurality of holes which extend to the central portion 2 in a direction perpendicular to the first direction AA. The holes are filled with the second resin 7. The holes are defined by the multiple layers of turns which are superimposed and they are preferably in the form of diamonds when observed perpendicular to the first direction AA.

[0041] The second wire elements 6 may comprise a unidirectional wire, a woven element, fabric, a ribbon, a braid. The wire may be a silica wire, an organic material. Preferably, the wire is made of a material chosen from polyethylene, polyetheretherketone (PEEK) and carbon. The second wire elements 6 may have a chemical composition identical to that of the first wire elements 4 or a chemical composition different from the latter.

[0042] Preferably, the second resin 7 is a polymer resin which is loaded with particles 7a, preferably micro-particles and / or nano-particles. The threads, fibers, fabrics, ribbons, braids and the elements forming the second wire elements may be covered with a second impregnation resin. The second impregnation resin may be identical to or different from the second resin 7. The second impregnation resin and the second resin 7 are chemically compatible to ensure the mechanical connection between the second wire elements 6. The resins are preferably thermosetting resins.

[0043] The formation of several annular layers arranged around each other and mechanically connected to each other by the second resin 7 makes it possible to effectively modulate the mechanical performance radially or substantially radially perpendicular to the first direction AA. The thickness of a second wire element being small, it is possible to make a large 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. Il It is therefore possible to easily produce a dental preform 1 whose mechanical performance is controlled radially, that is to say as a function of its distance from the central portion 2.

[0044] Modulating the winding characteristics in each layer from the interface with the central portion 2 to the outer wall of the peripheral portion 3 provides great freedom in modulating the mechanical characteristics radially or substantially radially.

[0045] Each layer is formed at least by one or more second wire elements 6 which are wound in a spiral around the central portion 2 and on the lower layer if applicable. The spiral winding present in each layer is defined at least by the following technical characteristics: the number of second wire elements 6 wound in a layer; the intrinsic technical characteristics of the second wire element(s) 6 used with for example the modulus of elasticity, the section, the chemical composition, the surface condition; the winding tension of each wound wire element; the winding pitch, i.e. the offset along the first direction AA when a complete turn is made, which is equivalent to the angle existing between the first direction AA and the longitudinal axis of the second wire element; the use or not of an impregnation resin and the composition of the impregnation resin where appropriate for each wire element.

[0046] The mechanical characteristics of a layer are functions of the winding characteristics as well as the composition of the second resin 7 in said layer.

[0047] In order to form a dental preform 1 which has mechanical characteristics which are close to those of a natural tooth, it is advantageous to form a peripheral portion 3 which has a gradient of modulus of elasticity in 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 moving away from the central portion 2. The modulus of elasticity is advantageously the modulus of elasticity in the first direction AA and / or in the direction perpendicular to the first direction AA.

[0048] Preferably, the gradient of 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 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.

[0049] In an advantageous embodiment, at the outer end of the peripheral portion 3, the modulus of elasticity is greater than 80 GPa and less than 20 GPa in the immediate vicinity or in the central portion 2. Preferably, the modulus of elasticity gradient extends over at least 40 GPa.

[0050] To reduce the propagation of microfractures from the external face of the dental preform 1 towards 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 40 GPa and even more preferably in a linearly decreasing manner.

[0051] 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.

[0052] The gradient of elastic modulus can be obtained by modifying at least one of the following parameters: the number of second wire elements 6 in the layer, the value of the winding pitch, the chemical composition of the second resin 7, the winding voltage of the second wire element 6, the section and / or the chemical composition of the wire element(s) forming the second wire element 6, the surface condition of the second wire element 6.

[0053] The modification of the chemical composition of the second resin 7 or of the second impregnation resin may be a modification of the filler content, for example the microparticle content, the nanoparticle content, the microfiber (whisker) content. The modification of the chemical composition may be a modification of the chemical composition of the fillers. The modifications made to the second resin 7 have the effect of modifying its mechanical characteristics in the direction perpendicular to the first direction AA and in the first direction. For example, to increase the value of the modulus of elasticity by moving away from the central portion 2, it is possible to increase the filler content (the other parameters not having changed) 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 filler content.

[0054] In one embodiment, a layer is formed by several turns from the same wire wound around the central portion 2. In an alternative embodiment, several different wires are wound around the central portion 2. The wires of the same layer may be identical in section and composition. It is also possible to provide wires of the same composition and different sections to use wires having different mechanical performances. IlIt is still possible to use wires having different compositions with identical or different sections to form a layer with wires having different mechanical performances. When the layers are formed by wires having different mechanical performances, the modification of the proportion of wires between two layers makes it possible to modify the value of the modulus of elasticity between two layers, the other parameters being unchanged. Il It is of course possible to modify this parameter and at least one other chosen from the winding pitch and the composition of the second resin 7.

[0055] According to the invention, in addition to the second wire element(s) 6 and the second resin 7, at least one layer has a sheet 8 which goes around the central portion 2. The sheet 8 may be a fabric or a woven element, a ribbon or a braid. The fabric has weft threads 8b and warp threads 8a. The woven element is distinguished from the fabric in that it is devoid of weft threads. There are quasi-weft threads which are oriented like the weft thread of a fabric but which are mechanically distinct. The quasi-weft threads do not join.

[0056] It is particularly advantageous to use plies 8 and in particular plies 8 which have wires or wire elements oriented parallel to the first direction AA. When the preform 1 is used to form a prosthetic element of the inlay-core type, the wires or wire elements oriented in the first direction AA allow a better transfer of forces according to the height of the prosthetic element, that is to say in the direction which connects the root apex to the top of the coronal part. The wires or wire elements improve the characteristics of mechanical resistance and toughness during masticatory forces. Such a gain is observed for forces in the first direction AA or according to an angular offset equal to 45°.

[0057] In this case, it is advantageous to form a preform 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 in the peripheral portion 3 and possibly the diameter of the preform can be chosen according to the tooth to be replaced, for example its dimensions, its position in the mouth and the characteristics of the adjacent teeth.

[0058] It is also possible to form larger dental preforms in the direction perpendicular to the first direction AA and even more preferably in the first direction AA. The preform may 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 direction AA is advantageously greater than 1 cm, more advantageously greater than 2 cm and even more advantageously greater than 3 cm. The dental preforms can then be used to form infrastructures for tooth-supported, attached or joint prostheses, or even implants.

[0059] Preferably, the sheet 8 is a fabric or a woven element whose weft thread or quasi-weft thread is oriented mainly in a direction parallel to the first direction and whose warp threads are arranged perpendicular to the first direction AA.

[0060] The sheet 8 is wider than the second wire element 6 along the first direction AA, preferably slightly wider than the second wire element 6 to remain fully compatible with the winding pitch. Preferably, when several second wire elements are used in the same layer, the sheet 8 extends over a little more than the width occupied by the second wire elements 6. The use of the sheet 8 does not modify the winding characteristics.

[0061] Preferably, the winding of the sheet 8 is carried out so as to have an overlap of the ends of the turns in the first direction AA. The sheet 8 then forms a tube all around the central portion 2 over the entire height of the dental preform 1.

[0062] The second wire element(s) 6 are arranged between two consecutive layers 8. Two turns of two consecutive layers are separated by a layer 8.

[0063] According to the invention, the sheet 8 extends continuously over several successive layers. In other words, the sheet 8 forms several concentric tubes around the central portion 2. The connection between the tubes is made at the two opposite ends of the preform in the first direction AA in an alternating manner between the upper end and the lower end or right and left. According to the invention, the sheet 8 extends continuously over all layers of the peripheral portion 3.

[0064] The sheet 8 can form several complete turns around the central portion 2, for example two complete turns, five complete turns or more than ten complete turns. The number of complete turns can be defined by the final diameter desired for the dental preform.

[0065] According to the embodiments, during winding, the sheet 8 is systematically deposited under or above the at least one second wire element 6 of the layer. In an observation along a section plane perpendicular to the first direction AA, as illustrated in figure 6 and according to the invention, the sheet 8 extends continuously over several layers and is in the form of a spiral. The use of a spiral sheet which extends over all the layers allows for good transmission of forces between the external part of the preform and its central portion. Such a configuration allows the preform to approximate the mechanical functioning of a natural tooth.

[0066] The spiral arrangement of the plies and the second wire elements 6 introduces a clamping effect which makes it possible to form very strong wire elements. The spiral arrangement also makes it possible to improve the toughness of the dental preform which facilitates the blocking of microcracks.

[0067] The spiral arrangement allows for the installation of very long wire elements in a small preform. The length of the wire element, for example a warp wire or a second wire element, may be at least five times the height of the preform, preferably at least 10 times the height, or at least 20 times the height. The length of the wire element, for example a warp wire or a second wire element, may be at least five times the diameter of the preform, preferably at least 10 times the diameter, or at least 20 times the diameter. The use of very long wire elements provides better mechanical strength to the preform.

[0068] The formed dental preform may be a preform to be machined or a preform to be cut. When a preform to be machined is produced, i.e. to be machined without going through a prior cutting step perpendicular to the first direction, it is advantageous for the preform to be of reduced size, for example with a diameter of less than 50 mm. The preform has a volume which is of the same order of magnitude as that of a tooth. A gripper 9 is fixed to the preform to facilitate machining as illustrated in figure 1 . The machining of the preform preferably defines an inlay-core advantageously by a machining technique called CAD-CAM milling. The dental preform can also form a coronal-radicular reconstruction. The preform is then covered by a crown which can be made of ceramic, composite material and preferably zirconia. IlIt is still possible to use the dental preform to form an implant abutment. The mechanical configuration of the preform is particularly advantageous for supporting masticatory forces that are multidirectional. Il It is also possible to form larger preforms, but this poses problems in terms of manufacturing and maintaining the layers on top of each other. Larger preforms can form bridge infrastructures, for example on natural teeth or implants.

[0069] When forming a preform to be machined, the preform must be cut one or more times perpendicular to the first direction AA in order to define a plurality of elementary preforms which will form the preforms to be machined. Il It is advantageous to form a higher preform along the first direction AA to be able to form several preforms to be machined. IlIt is also advantageous to form wider preforms to adapt the preform to uses other than inlay-core formation, for example bridge infrastructures, for example on natural teeth or implants. The cutting step allows the height of the preform to be adapted according to needs. To easily form a preform of significant width, it is preferable to form a preform of significant height which facilitates the good maintenance of the second wire elements and the plies between them on the multiple layers.

[0070] The preform is more deformable than a metallic equivalent, for example, shape memory metal supports. The deformability of the preform is defined by the mechanical performance of the different layers. A preform with large dimensions and a gradient of modulus of elasticity allows the performance of the preform to be better adapted to the constraints of the dental arches. The preform can have a circular or oval section or a shape close to these to better adapt to the shape of the dental arches and thus better adapt the mechanical properties.

[0071] The direct-milling dental preform is machined to form an inlay-core dental prosthesis with a root canal area and a coronal area. The root canal area is intended to be inserted into the dental canal of a dental root of a laboratory model. The coronal area is intended to form the coronal part of the tooth destroyed by caries, for example to support a peripheral prosthetic cap. The dental preform is machined so that the central portion sinks into the dental canal and extends into the coronal part. A part of the peripheral portion 3 is completely removed to form the root canal part. The peripheral portion is machined and partly preserved to form the coronal part which will simulate the dentin of a natural tooth. The peripheral portion is machined to define a shape which approximates the shape of the dentin to be replaced.

[0072] The dental preform 1 is machined using any suitable machining machine, preferably a computer-aided machining machine, for example, with 3 axes to 5 axes. The dental preform 1 is machined to reproduce a predefined shape which is calculated at least from the impression of the tooth to be repaired.

[0073] THE Figures 2 and 3 represent two embodiments where the dental preform 1 has a gripper 9. In the embodiment of the figure 2 , the gripper 9 is fixed on the external side wall of the peripheral portion 3. In the embodiment of the figure 2 , the gripper 9 is fixed on an end face, that is to say a face onto which the first wire elements 4 open.

[0074] The formation of several concentric layers, preferably with turns obtained by winding and advantageously by honeycomb winding, makes it possible to define more precisely the mechanical performances 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.

[0075] This embodiment makes it possible to form a dental preform with mechanical characteristics which are substantially identical all around the central portion depending on the value of the radius. Il It is then possible to define the expected technical characteristics based on the winding characteristics of the layer, which includes the composition of the resin used in the layer.

[0076] The dental preform 1 can be formed in different ways. The peripheral portion 3 is formed on a mandrel 10. In one embodiment, the mandrel 10 is formed by the central portion 2, that is to say the assembly formed by the first wire elements 4 and the first resin 5.

[0077] In another embodiment, the mandrel 10 is another element, i.e. an element which is not part of the dental preform 1, for example a metal mandrel. The peripheral portion 3 is formed around the mandrel 10. Then, the mandrel 10 is removed which forms a hole in the peripheral portion 3. The hole is then filled with the first resin 5 and the first wire elements 4 to form the central portion 2 defined previously. This embodiment is particularly suitable for forming a preform to be cut.

[0078] The mandrel 10 extends along the first direction AA. In one embodiment, the mandrel 10 rotates about the first direction AA which passes through the mandrel 10. In another embodiment, the second wire elements 6 rotate around the mandrel 10.

[0079] The peripheral portion 3 is formed around the mandrel 10 by forming a plurality of layers on top of each other. The peripheral portion 3 is in the form of a ring around the central portion 2 in a section plane perpendicular to the first direction AA. The peripheral portion 3 is formed by depositing one or more second wire elements 6 which surround the mandrel 10 and depositing the second resin 7. The second resin 7 mechanically bonds the second wire elements 6 together.

[0080] The second wire element(s) 6 define a plurality of layers arranged on top of each other perpendicular to the first direction AA. The layers go around the mandrel 10.

[0081] The second wire elements 6 are wound to define the different layers of the peripheral portion 3. The second wire elements 6 of each layer have a longitudinal direction which is offset from the first direction by an angle of between 10° and 80° or between 100° and 170°. The winding is carried out with a certain angular offset from the first direction AA and from the perpendicular to the first direction AA. The second wire elements 6 are preferably wound from one end to the other end of the mandrel 10.

[0082] The formation of the peripheral portion 3 is carried out so that two consecutive layers have second wire elements 6 having opposite orientations. The second wire elements 6 of two consecutive layers define a mesh when observed perpendicular to the first direction AA. Thus, if in a first layer the winding of the second wire elements is carried out “rising” or “dextrorotatory”, the winding of the immediately consecutive lower and upper layers is carried out “descending” or “levorotatory” and vice versa.

[0083] When forming the peripheral portion 3, the second wire elements 3 of each layer do not belong to a fabric or a woven element.

[0084] In order to form the peripheral portion 3 efficiently, it is particularly advantageous to perform a honeycomb winding of the second wire element(s) 6 on the mandrel 10. In a honeycomb winding, one or more second wire element(s) 6 are wound around the mandrel 10 continuously. The wire element(s) 6 are supplied by an arm 11 which moves in one direction from a first stop until it reaches a second stop. Once the second stop is reached, the arm 11 itself moves in the other direction. The movement of the arm 11 is linked to the rotation of the mandrel 10 on itself or to the rotation of the arm around the mandrel 10, but this second embodiment is less advantageous because it is more difficult to implement. The production of the honeycomb winding is known per se and has been used to form electrical inductances.

[0085] Honeycomb winding is particularly advantageous because it allows the turns of each layer to be made quickly and in a controlled manner, and more particularly turns in opposite directions for two consecutive layers. The position of the second wire elements is defined by the position of the movable arm 11, which allows the wire elements to be placed on top of each other in a reproducible manner when the winding pitch is constant between two layers in the same direction.

[0086] Such a winding method allows easy modification of the tension in the second wire elements 6 during winding. Such an embodiment also makes it possible to easily modify the relationship between the movement of the arm 11 and the rotation of the mandrel 10.

[0087] The thickness of the second wire elements 7 being known, it is possible to know the thickness of a layer. If necessary, the thickness of the sheet 8 is also known. To modify the mechanical characteristics of the peripheral portion 3 as a function of its distance from the axis of rotation of the mandrel 10 or from the external surface of the mandrel, it is possible to count the number of turns made and to estimate the corresponding thickness.

[0088] Winding conditions are defined for each turn of the dental preform 1 and the dental preform 1 is formed by winding the second wire elements 6 according to the winding conditions, that is to say by imposing the characteristics of the winding, the composition of the second wire elements 6, the composition of the second resin 7 and the composition of the impregnation resin where applicable.

[0089] There Figure 5illustrates a particular embodiment of the configuration described above with a mandrel 10 rotatably mounted about the first direction AA. Several second wire elements 6 are provided and pass through a die 12 mounted on a movable arm 11. The rotation of the mandrel 10 causes the arm 11 and the dies 12 to move back and forth parallel to the first direction AA. The amount of movement of the arm 11 when one revolution of the mandrel 10 is made defines the value of the angle which exists between the direction AA and the longitudinal axis of the second wire elements 6.

[0090] The second wire elements 6 pass through an impregnation tank 13 which contains an impregnation resin or the second resin 5. By modifying the composition of the resin in the impregnation tank 13, it is possible to modify the composition of the resin as a function of the number of layers deposited, i.e. the number of revolutions of the mandrel 10 from the interface with the mandrel 10. This modification makes it possible to define the gradient of the modulus of elasticity. Preferably, the impregnation tank provides the second resin 7. It is possible to adjust the impregnation rate of the at least second wire element, which makes it possible to define at least in part the thickness of the layer.

[0091] In the embodiment illustrated in Figure 5, three second elementary wire elements are provided and join to form a single second wire element 6. By modulating the number of elementary wire elements which pass through the impregnation tank 13, it is possible to adjust the quantity of second resin 7 which is deposited.

[0092] In an alternative embodiment, the arm 11 only moves the second wire element 6 or the impregnation tank 13 in order to move the second wire element 6 to form the turns.

[0093] In an alternative embodiment illustrated in the figure 7 , each wire is associated with a specific impregnation tank 13.

[0094] There figure 7 illustrates an embodiment close to that of the Figure 5where four wire elements 6 are wound around the mandrel 10. For the sake of clarity, only two wire elements 6 pass through a die 12 mounted on a movable arm 11. The movement of the arm 11 in a back and forth movement is linked to the rotation of the mandrel 10 as before.

[0095] The two wire elements 6 pass through two different impregnation tanks 13 which makes it possible to modify the resin associated with each of the wire elements 6 independently depending on the number of turns of the mandrel 10 made.

[0096] There figure 7 also illustrates the winding of a sheet 8 around the mandrel 10. The sheet 8 and the second wire elements 6 are wound in the same direction. The sheet 8 extends over the entire height of the dental preform 1 or over more than the entire height of the dental preform 1 to be formed, for example over the entire active length of the mandrel 10 in the first direction AA.

[0097] The sheet 8 is wound without a winding pitch in the first direction AA or with a winding pitch compatible with a total covering of the height of the dental preform 1 at each turn. In this embodiment, it is advantageous to use several second wire elements 6 which are distributed over the width of the sheet 8, preferably uniformly distributed over the width of the sheet 8. Each of the second wire elements 6 forms turns around the central portion 2, each of the turns extending from one end to the other of the future dental preform 1 in the first direction AA. The turns are offset from each other in the first direction AA and may extend beyond the height of the preform 1.

[0098] When several second wire elements 6 are used in a layer, it is advantageous to associate a specific impregnation tank for each second wire element to be able to dissociate the composition of the associated second resin and thus better control the evolution of the mechanical characteristics according to the radial direction.

[0099] When several second wire elements 6 are used in a layer, it is advantageous to use an independent arm 11 for each second wire element 6 to be able to separate the winding pitch and thus better control the evolution of the mechanical characteristics according to the radial direction.

[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 wound and polymerized dental preform 1 has a circular section. The mechanical characteristics of the peripheral portion 3 vary according to the distance from the center of the dental preform 1 perpendicular to the first direction AA.

[0102] In a particular embodiment, the dental preform 1 is provided and then a cutting step is carried out so as to define a plurality of elementary preforms from the initial preform. The cutting plane ZZ 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 needs.

[0103] 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 is preferably between 10 mm and 60 mm depending on the prosthetic element to be formed.

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

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

[0106] It is advantageous for the preform to be free of a wire element which extends perpendicular to the first direction AA and radially in the central portion 2.

[0107] During cutting operations perpendicular to the first direction AA or during machining operations, the end zones of the dental preform 1 are removed. The end turns that connect a layer with the consecutive layer going outwards or going inwards are eliminated. These mechanical connection zones between the turns come from a honeycomb winding. The elimination of the end turns means that the turns are only mechanically connected by means of the second resin 7. Without this second resin 7, the turns are mechanically separated from each other.

[0108] Preferably, the dental preform 1 is in the form of a disc with a constant circular section from one end to the other of the preform in the first direction. Alternatively, the section may be a circle with a flat. Other shapes are possible with a constant section from one end to the other of the dental preform 1 in the first direction AA. The dental preform is intended to form a dental prosthesis for installation, preferably, on a laboratory model.

Claims

1. Dental preform (1) comprising: - a central portion (2) formed by a plurality of first wire elements (4) and a first resin (5), the first wire elements (4) extending mostly in a first direction (AA), the first resin (5) mechanically bonding the first wire elements (4) to one another; - a peripheral portion (3) in the form of a ring around the central portion (2) perpendicularly to the first direction (AA), the peripheral portion (3) comprising second wire elements (6) and a second resin (7), the second resin (7) mechanically bonding the second wire elements (6) to one another, the first wire elements (4) and the second wire elements (6) being mechanically bonded to one another at least by the first resin (5) and the second resin (7); dental preform (1) wherein the peripheral portion (3) comprises a plurality of layers arranged on one another perpendicularly to the first direction (AA), the layers passing round the central portion (2); wherein each layer has at least one turn formed by at least one of the second wire elements (6), the at least one second wire element (6) presenting a longitudinal direction that is offset with respect to the first direction (AA) by an angle comprised between 10° and 80° or between 100° and 170°; wherein the second wire elements (6) of two consecutive layers present opposite orientations; wherein the second wire elements (6) of each layer do not belong to a fabric or to a woven element; wherein at least several layers of the plurality of layers further have a sheet (8) chosen from a fabric, a woven element, a strip or a braid, the sheet (8) being situated below or above the second wire-like elements (6) in said several layers; and wherein the sheet (8) extends from one end of the dental preform (1) to the other in the first direction (AA) and extends over all the layers, the sheet (8) being in the form of a spiral in a cutting plane perpendicular to the first direction (AA), with an alternation between a thickness of sheet (8) and a thickness of second wire element (6) in a direction of observation perpendicular to the first direction (AA) and directed from the central portion (2) up to one end of the peripheral portion (3).

2. Dental preform (1) according to claim 1 wherein the central portion (2); has wire elements that are majoritary in volume the first wire elements (4).

3. Dental preform (1) according to claim 2 wherein the central portion (2) only comprises the first wire elements (4) and the first resin (5).

4. Dental preform (1) according to one of claims 1 to 3, wherein the peripheral portion (3) has an increasing elastic modulus gradient when moving away from the central portion (2) perpendicularly to the first direction (AA); wherein the peripheral portion (3) presents a content of second wire elements (6) that is increasing monotonously when moving away from the central portion (2) perpendicularly to the first direction (AA) to form the elastic modulus gradient; and / or wherein the second resin (7) is doped with particles and wherein the peripheral portion (3) presents a ratio of the content of the second wire element (6) over the particle content that is increasing in the radial direction when moving away from the central portion (2) perpendicularly to the first direction (AA) to form the elastic modulus gradient.

5. Dental preform (1) according to claim 4, wherein the second resin (7) is doped with particles and wherein the peripheral portion (3) has a ratio of the content of second wire element (6) to the particle content which is increasing in the radial direction away from the central portion (2) perpendicular to the first direction (AA) to form the elastic modulus gradient and wherein the ratio of the content of second wire element (6) to the particle content is increasing inversely proportional to the distance from the central portion (2) to form the elastic modulus gradient.

6. Dental preform (1) according to one of claims 1 to 5 wherein each layer comprises several second wire elements (6) coiled around the central portion (2).

7. Method for manufacturing a dental preform (1) comprising the following steps: - providing a mandrel (10) extending in a first direction (AA); - forming a peripheral portion (3) in the form of a ring around the mandrel (10) perpendicularly to the first direction (AA), the peripheral portion (3) having a plurality of layers passing round the mandrel (10), the layers being arranged around one another perpendicularly to the first direction (AA), each layer comprising at least one second wire element (6) and a second resin (7), the second resin (7) mechanically bonding the second wire elements (6) to one another in the peripheral portion (3); method for manufacturing wherein the at least one second wire element (6) of each layer presents a longitudinal direction that is offset with respect to the first direction (AA) by an angle comprised between 10° and 80° or between 100° and 170°; wherein the at least one second wire element (6) of two consecutive layers presents opposite orientations; wherein the at least one second wire element (6) of each layer does not belong to a fabric or to a woven element; wherein the mandrel (10) is a central portion (2) formed by a plurality of first wire elements (4) and a first resin (5), the first wire elements (4) extending mostly in the first direction (AA), the first resin (5) mechanically bonding the first wire elements (4) to one another, the first wire elements (4) and the second wire elements (6) being bonded to one another at least by the first resin (5) and the second resin (7), or wherein the mandrel (10) is removed to define an empty area in the peripheral portion (3), the empty area being filled by a plurality of first wire elements (4) and a first resin (5), the first wire elements (4) extending mostly in the first direction (AA), the first wire elements (4) and the second wire elements (6) being bonded to one another at least by the first resin (5) and the second resin (7); wherein at least several layers of the plurality of layers further have a sheet (8) chosen from a fabric, a woven element, a strip or a braid, the sheet (8) being situated below or above the second wire elements (6) in said several layers; wherein the sheet (8) extends from one end of the dental preform (1) to the other in the first direction (AA) and extends over all the layers, the sheet (8) being in the form of a spiral in a cutting plane perpendicular to the first direction (AA), with an alternation between a thickness of sheet (8) and a thickness of second wire element (6) in a direction of observation perpendicular to the first direction (AA) and directed from the central portion (2) up to one end of the peripheral portion (3).

8. Method for manufacturing a dental preform (1) according to claim 7 wherein two successive layers share the at least one second wire element (6) and wherein the turns are formed by a honeycomb winding and preferentially the at least one second wire element (6) extends continuously over all the layers of the peripheral portion (3).

9. Method for manufacturing a dental preform (1) according to one of claims 7 to 8 wherein each layer (6) further comprises a sheet (8) formed by a fabric or a woven element the weft thread or quasi-weft thread of which extends in the first direction (AA).

10. Method for manufacturing a dental preform (1) according to one of claims 7 to 9 comprising at least cutting of an assembly formed by the central portion and the peripheral portion perpendicularly to the first direction (AA) to define the dimension of the dental preform (1) in the first direction (AA).

11. Method for manufacturing a dental prosthesis (1) comprising the following steps: - providing a dental preform (1) according to any one of claims 1 to 6; - milling of the dental preform (1) wherein a part of the peripheral portion (3) is completely eliminated to reach the central portion (2) designed to form a canal anchorage, and another part of the peripheral portion (3) is partially eliminated to form a crown portion of the dental prosthesis (1) according to a predefined shape.

12. Method for manufacturing a dental prosthesis (1) according to the preceding claim comprising, before milling is performed, cutting of the dental preform perpendicularly to the first direction (AA) to define the dimension of the dental preform in the first direction (AA).