COMPOSITE PART FOR ENDOSSEOUS IMPLANTATION AND METHOD FOR MANUFACTURING SAME

Abstract

A part adapted for in vivo endosseous implantation made up of a material comprising a thermoplastic organic binder and a fiber charge. The fibers located in a surface layer of the part are mostly delaminated from the binder over all or part of their length. Also, a method for manufacturing such a part.

Claims

1-17. (canceled)

18. A part adapted for in vivo endosseous implantation comprising a material comprising: a thermoplastic organic binder, and a fiber charge; wherein fibers located in a surface layer of said part are mostly delaminated from the binder over all or part of their length.

19. The part according to claim 18, wherein the fiber charge comprises nanofibers or nanotubes.

20. The part according to claim 18, wherein the fiber charge comprises microfibers.

21. The part according to claim 18, wherein the binder comprises polyetheretherketone.

22. The part according to claim 18, wherein the fibers are made of a polymer of a family of aromatic polyamides.

23. The part according to claim 22, wherein the fibers are made of poly(amide-imide).

24. The part according to claim 18, comprising fibers made of calcium silicate (Ca.sub.2SiO.sub.4).

25. The part according to claim 18, wherein the thickness of the surface layer is greater than or equal to 2000 nanometers.

26. The part according to claim 18, wherein the material further comprises a charge of components made from calcium and phosphate.

27. The part according to claim 26, wherein the charge of calcium-based components is made up of tricalcium phosphate Ca.sub.3(PO.sub.4).sub.2 with a hexagonal 0 structure.

28. The part according to claim 26, wherein the material further comprises a zeolite charge.

29. A method for manufacturing the part according to claim 18, comprising the steps of: mixing a thermoplastic polymer and a fiber charge by extrusion and granulation to provide a granulate; molding the part by injection in a mold comprising a cavity with a shape configured for the granulate to provide a blank; and submitting the blank to ultrasonic pickling baths to delaminate the fibers in the surface layer.

30. A method for making a granulate suitable for manufacturing the part according to claim 29, comprising the steps of: mixing by extrusion and granulation of a thermoplastic polymer and a charge comprising calcium-based components to obtain a first granulate; and mixing the first granulate by extrusion and granulation with the fiber charge to obtain a final granulate suitable for injection.

31. The method according to claims 29, wherein the fiber charge ranges between 5% and 15% by mass of a mixture of thermoplastic polymer and the fiber charge.

32. The method according to claims 30 wherein the fiber charge ranges between 5% and 15% by mass a mixture of thermoplastic polymer and the fiber charge.

33. A granulate or compound for manufacturing a part according to claim 26 by plastic injection molding, comprising: a polyetheretherketone (PEEK) polymer binder; a 10% to 20% charge by mass of compounds containing calcium and zeolites; and a 5% to 15% fiber charge.

34. The method according to claim 29, wherein the step of submitting further comprises the steps of, in the stated order: immersing the blank in a bath subjected to ultrasound to reduce particles containing iron; and immersing the blank in a solvent of the binder subjected to ultrasound.

35. The method according to claim 29, wherein the step of submitting further comprises the steps of, in the stated order: immersing the blank in the following baths subjected to ultrasound: Hydrochloric acid; Acetone; Hydrogen peroxide; and rinsing in a bath of water subject to ultrasound between the immersions.

Description

[0047] The invention will now be described in greater detail in the context of preferred embodiments, which are in no way limiting, shown in FIGS. 1 to 4, wherein:

[0048] FIG. 1 is a front view of an endosseous dental implant according to an exemplary embodiment of the invention;

[0049] FIG. 2 shows a detail Y defined in FIG. 1 along a section AA also defined in FIG. 1;

[0050] FIG. 3 represents a detail Z defined in FIG. 2 along a section AA of the surface of an implant according to an exemplary embodiment of the invention during the phases of making and implanting said implant in the bone, in FIGS. 3A to 3E;

[0051] and FIG. 4 is a chart of the different phases of making and implementing an implant according to the invention.

[0052] In FIG. 1, an example of implant (100) with a complex shape can be made cost-effectively using a plastic injection molding method. That exemplary embodiment, which is in no way limiting, represents an application of the invention to the making of a dental implant. Said dental implant comprises an upper part (101) designed to receive superstructures such as a core build-up and a so-called lower part (110) designed to be implanted in bone tissue. The lower part (110) may optionally comprise relief such as ridges adapted to favor its primary mechanical bonding in a location such as a bore made in the receiving bone tissue. The size of such primary bonding ridges or relief features is approximately a millimeter. Said implant is mostly made of thermoplastic polymer with high biocompatibility properties and is suitable for implementation using injection molding techniques. As a non-limiting example, said polymer may be made of polyetheretherketone or PEEK as distributed commercially by VICTREX under the name VICTREX PEEK 150G. Advantageously, the binder may be made of material simultaneously comprising PEEK, charges of compounds containing calcium and zeolites such as the material described in the French patent

[0053] In FIG. 2, according to a first detailed sectional view, the material making up the implant comprises a matrix (210) or binder in PEEK, particles (230) of compounds containing calcium with a diameter of about 1 m (10.sup.6 meter) and reinforcing fibers (220). In this exemplary embodiment, the reinforcing fibers (220) are made of poly(amide-imide), such as fibers available commercially under the name KERMEL TECH from KERMEL, 20 rue Ampere, 68027 Colmar, France. In one exemplary embodiment using microfibers, these have a diameter of approximately 7 m with a length of approximately 700 m (0.7 mm). Because the implant is obtained using a plastic injection method, the injection temperature of the PEEK is equal to or greater than the glass transition temperature of that polymer so that the fibers are easily deformable at the injection temperature and that they follow substantially the flow of material.

[0054] The fiber charge may, in an advantageous embodiment, additionally or exclusively contain calcium silicate fibers (Ca.sub.2SiO.sub.4) (not shown in FIG. 2). The material is rigid at the injection temperature and is thus not deformed at that temperature. Therefore, the calcium silicate fibers are preferably smaller in size, with a diameter of about 1 m and a length of about 10 m to 50 m. In order to prevent jamming during the injection process, the total fraction of fibers, including all fibers, must not exceed 15% by mass.

[0055] Advantageously, the charge of compounds (230) comprising calcium is made of tricalcium phosphate Ca.sub.3(PO.sub.4).sub.2 in phase. The phase of tricalcium phosphate is the crystalline phase with a hexagonal structure that is stable at a low temperature.

[0056] By combining with the moisture contained in the tricalcium phosphate powder, PEEK and possibly zeolites, the compound undergoes a transformation during the injection molding operation according to the following reaction:

4Ca.sub.3(PO.sub.4).sub.2+4(H.sub.2O)=>3((Ca.sub.3(PO.sub.4).sub.2)(OH).sub.2Ca+2HPO.sub.4+O.sub.2

[0057] 3((Ca.sub.3(PO.sub.4).sub.2)OH.sub.2)Ca is hydroxyapatite. This apatite is completely nonstoichiometric, and thus resorptive, giving the material of the implantable part according to the invention integration properties, similar to a transplant, in bone tissue.

[0058] To that end, the powders used during injection are not dehydrated. They can advantageously be rehydrated, or orthophosphoric acid (H.sub.3PO.sub.4) may be added to them to favor that reaction.

[0059] In FIG. 3, the observation of the surface at an ever smaller scale makes it possible to analyze the morphology of the surface depending on the implementation steps of the method and the implantable part in the invention, with the steps of the method stated in FIG. 4.

[0060] In one exemplary embodiment, the implant is obtained by a first step aimed at obtaining a granulate mixing:

[0061] 80% by weight of PEEK

[0062] 10% by weight of tricalcium phosphate (Ca.sub.3PO.sub.4)

[0063] 10% by weight of titanium dioxide (TiO.sub.2)

[0064] All the components are mixed by extrusion at a temperature ranging between 340 C. and 400 C.

[0065] By granulation of the extrusion, a first granulate is obtained, which is mixed with 10% by mass of poly(amide-imide) fibers of the KERMEL TECH type and calcium silicate fibers according to the same extrusion and granulation method.

[0066] The second granulate obtained in this manner is used for plastic injection molding (410) of the implant. Molding takes place at a temperature ranging between 340 C. and 400 C. at a pressure ranging between 70 and 140 MPa, wherein the mold is heated to a temperature above the glass transition temperature of PEEK or a mold pre-heating temperature of approximately 160 C.

[0067] The vitreous transition temperature of fibers of the KERMEL type is 340 C., and they are thus deformable at the injection temperature, which enables them to follow the flow of material and be distributed evenly in the granulate during the extrusion and granulation operation and in the part during the injection molding operation.

[0068] At the end of the molding operation (410) in FIG. 3A, the surface of the implant is substantially smooth and comprises some particles (211) of compounds comprising calcium and zeolites (212) emerging slightly. Fibers (330), calcium silicate in this case, are also present in the vicinity of the surface and possibly emerge slightly from said surface. The surface of the implant also comprises metallic inclusions (340) from contact with the mold and the screw of the injection press.

[0069] At the end of the molding operation, the implant is subjected to a series of chemical etching/pickling baths subjected to ultrasound. For example, the following protocol provides good practical results, with the application of ultrasound at a frequency of 42 kHz:

[0070] HCl 30%: 35 minutes

[0071] H.sub.2O: 10 minutes (or rinsing)

[0072] C.sub.3H.sub.6O (acetone): 35 minutes at the boiling temperature of acetone

[0073] Drying of the implant by acetone evaporation

[0074] H.sub.2O.sub.2 30%: 35 minutes

[0075] NaClO: 35 minutes

[0076] H.sub.2O: 10 minutes (or rinsing)

The implant is then immersed, also under ultrasound, in sterilizing agents:

[0077] GIGASEPT 12%: 35 minutes

[0078] H.sub.2O ppi: 35 minutes

Immersion in the GIGASEPT solution is optional.

[0079] In a first step (420) the implant is subjected to acid etching in hydrochloric acid. Such etching/pickling is chiefly aimed at removing the metallic inclusions. After that etching/pickling operation, the surface of the implant in FIG. 3B is free of metallic inclusions, and also the particles containing calcium that were emergent, leaving corresponding cavities (311) in their place.

[0080] After rinsing, the next step (430) consists in immersing the implant in an acetone bath, also subjected to ultrasound. In FIG. 3C, at the end of that step (430) a thickness of PEEK is dissolved, making initially underlying particles (211, 212) of compounds including calcium and zeolites visible. The ultrasound also tends to delaminate the fibers (330) emerging at the surface from their implantation in the matrix.

[0081] After rinsing, the next step (440) consists in immersing the implant in a hydrogen peroxide bath, also subjected to ultrasound. That bath does not fundamentally modify the morphology of the surface, in FIG. 3D. On the other hand, it has an effect on the surface of the calcium silicate fibers where it tends to form silica (SiO.sub.2) by oxidation at their surface.

[0082] Advantageously, the implant is then inserted in a sterilization sleeve for autoclave treatment. It then undergoes a sterilization cycle at a temperature of about 135 C. for 10 minutes, under pressure of about 2150 hPa. That autoclave sterilization operation contributes to the surface pickling function; it may be associated with ethylene oxide or gamma ray treatment. Further, it favors the crystallization of particles of calcium compounds on the surface. At the end of sterilization, the implant is packaged in sterile packaging and is ready to be implanted in bone tissue.

[0083] During the implantation (450) of said implant in the tissue, organic fluids such as blood will follow by capillarity the delamination between the fibers and the matrix, whether the fibers are KERMEL fibers or calcium silicate fibers, FIG. 3E. In the case of calcium silicate fibers, the silica present on the surface of these fibers absorbs the fluids and thus favors conduction under the surface. On the surface and by conduction by the fibers, under that surface the calcium-based compounds (211) come in contact with these organic fluids. The resorptive nature of these compounds thus favors cell colonization leading to the grafting of the surface of the implant in the bone tissue.

[0084] The application of the surface treatment to an implant of the prior art that only contains calcium phosphate compounds and titanium dioxide in a PEEK matrix makes it possible to obtain a thickness of the surface layer of approximately 1 m. The same treatment applied to an implant with an identical shape but made of material additionally comprising 10% poly(amide-imide) fibers or calcium silicate fibers makes it possible to obtain an active surface layer thickness of 3.6 m.

[0085] The description above illustrates clearly that by its different characteristics and their advantages, this invention achieves its objectives. In particular, it makes it possible to obtain an injection molded and reinforced implant comprising a surface osseointegration layer with thickness that is at least three times the thickness that can be achieved without reinforcement.