IMPLANTABLE MEDICAL DEVICE COMPRISING A ZIRCONIA LAYER, AND METHOD FOR THE PREPARATION THEREOF

Abstract

The present invention relates to an implantable medical device comprising a layer consisting of or comprising zirconia, and to a method for the preparation thereof.

Claims

1. Implantable medical device comprising, over all or some of its surface, a layer comprising zirconia, said layer having a thickness of between around 50 and 2000 nm, wherein the layer comprises, further to zirconia, at least one element or compound comprising an element chosen from among Mg, Ca, Ag, and Zn, in particular in metal or oxide form, located at least partially on the surface of the layer.

2. Device according to claim 1: wherein said layer has a thickness of between around 100 or 200 and around 2000 nm, in particular between around 500 or 600 and around 800 nm; or comprising a layer comprising zirconia, said layer having, over a part of the surface of said device, a thickness of between around 50 and around 2000 nm, in particular between around 50 and around 1200 nm, and over another part of the surface of said device, a thickness of between around 50 and around 2000 nm, in particular between around 800 and around 2000 nm.

3. Device according to claim 1, wherein zirconia is yttria zirconia, and/or partially or totally in its quadratic, cubic or monoclinic phase, in particular monoclinic.

4. Device according to claim 1, wherein the at least one element or compound comprising an element chosen from among Mg, Ca, Ag, and Zn, is located at least partially on the surface of the layer, over 10 to 30% of said surface.

5. Device according to claim 1, which, in particular its surface, consists of or comprises titanium or aluminium, titanium being in particular grade 4 titanium, or in the form of an alloy, in particular grade 5 titanium or a titanium-niobium alloy.

6. Device according to claim 1, wherein said layer has a roughness Ra of between 0 and 4.0 ?m, in particular of 0.6 to 2.0 ?m, in particular of 1.0 to 1.5 ?m.

7. Device according to claim 1, which is an implant, in particular a dental implant, or a prosthesis, in particular a hip prosthesis, more specifically a cupula, a shoulder prosthesis, or a knee prosthesis.

8. Method for preparing an implantable medical device according to claim 1, comprising a step of depositing, over all or some of the surface of an implantable medical device, a layer comprising zirconia, said layer having a thickness of between around 50 and around 2000 nm, said deposition being carried out by physical vapour deposition (PVD); in the presence of a zirconium target and a target of at least one element or one compound comprising at least one element chosen from among Mg, Ca, Ag, and Zn; or in the presence of a zirconium target, and by bringing the device into contact with at least one element or one compound comprising at least one element chosen from among Mg, Ca, Ag, and Zn, by electrophoresis or by plasma jet, said at least one element or at least one compound comprising at least one element chosen from among Mg, Ca, Ag, and Zn being introduced, in particular in the form of nanoparticles, in the plasma jet formed during the zirconia deposition.

9. Method according to claim 8, wherein the physical vapour deposition is carried out by magnetron cathode spraying.

10. Method according to claim 8, wherein said implantable medical device is in rotation, or not, about at least one axis of rotation during all or some of the deposition.

11. Method according to claim 8, wherein said at least one element or one compound comprising at least one element chosen from among Mg, Ca, Ag, and Zn is deposited: together with zirconia; or after zirconia has been deposited.

12. Method according to claim 8, wherein the variation between the roughness Ra of the initial device and the roughness Ra of the device obtained from the method is less than or equal to around 25%.

Description

EXAMPLES

Example 1: Preparation of an Implantable Medical Device According to the Invention

[0053] An implantable medical device on the market, for example, a dental implant, is prepared according to the following steps: [0054] cleaning with alcohol (pure ethanol); [0055] bathing in an ultrasonic tank with water, for example distilled water; [0056] drying by pure air blowing; [0057] installing the device in the PVD machine; [0058] if necessary, cleaning of the device by pure air blowing; [0059] vacuuming of the PVD machine; [0060] if necessary, plasma stripping of the device.

[0061] Once the device is prepared as indicated above, the layer consisting of or comprising zirconia is deposited on said device as follows: [0062] cleaning of the PVD machine (in particular sandblasting the substrate carrier, screen suppressors, etc.); [0063] implementing the zirconium target, optionally yttria; [0064] implementing the device on the rotary substrate carrier; [0065] vacuuming the machine (for example, 2 to 5.10.sup.?6 mbar); [0066] introducing plasma gas (for example, 30 sccm of argon); [0067] introducing reactive gas (for example, 6 sccm of oxygen); [0068] adjusting the pressure inside the deposition chamber using the butterfly valve (for example, at 0.75 Pa); [0069] switching on the pulsed DC generator (Power=0.5 A?Frequency=100 kHz?Idle time=2 ?s, for example); [0070] if necessary: priming the plasma using an RF generator; [0071] deposition time to be adapted according, in particular, to the thickness of the desired deposition layer (for 100 nm, 1 hour of deposition can be necessary, for example, on a non-industrial machine. For 800 nm, around 8 hours of deposition can be necessary); [0072] end of deposition (by stopping the generator and gas flow, in particular); [0073] stopping of the molecular turbo pump and of the primary pump; [0074] purging of the development chamber; [0075] recovery of the device according to the invention, preferably with gloves.

[0076] The parameters indicated above are given as examples and can be adapted easily by a person skilled in the art, according to the PVD machine used.

[0077] In particular, devices of the invention, have been obtained according to the present example, with a zirconia thickness of 100 nm or of 800 nm, from dental implants on the market:

TABLE-US-00001 Name of the Thickness device of the Reference of the implant used of the zirconia invention which is on the market layer A100 Naturall + of the company ETK? 100 nm A800 Naturall + of the company ETK? 800 nm B100 Natea + of the company ETK? 100 nm B800 Natea + of the company ETK? 800 nm

[0078] Each of the 4 implants above have been completely covered with zirconium oxide over their entirety, by magnetron cathode spraying. To do this, the target corresponded to pure zirconium in metal form. The gas present was oxygen and the substrate was the implant to be sprayed.

[0079] Thus, by ion bombardment on the zirconium target, a zirconium metal vapour is formed, which is oxidised by the oxygen present during its route to the implant. Zirconium oxide is thus fixed to the implant.

Example 2: Tearing Tests Carried Out on the Devices of the Invention

[0080] Two devices of the invention obtained according to example 1, one with a zirconia thickness of 100 nm, the other with a zirconia thickness of 800 nm, have been scratched in the form of a check pattern, using a diamond comb. The scratches are spaced apart by around 750 ?m.

[0081] A piece of adhesive tape is adhered onto the check pattern formed, then torn.

[0082] The check pattern is thus observed under an optical microscope.

[0083] When the check pattern observed under a microscope is intact, the test is successful. When the layer is unstuck, torn in at least one place of the check pattern, the test is not successful.

[0084] For the two devices of the invention, the zirconia layer is fully adherent after the test. No peeling off can be seen. The test is therefore successful and the adherence of the layer is greatly satisfactory as regards the devices of the invention.

Example 3: Roughness Measurements on the Devices of the Invention

[0085] Materials and Methods

[0086] Transverse cross-sections of the devices of the invention, for example of the apical part of a dental implant according to the invention, have been made using a micro-cutting machine. Samples of each device of 4 to 6 mm of thickness have thus been obtained. Each of them has been analysed with a profilometer and with a scanning electron microscope (SEM). This makes it possible, if necessary, to keep the integrity of the devices studied.

[0087] The profilometer (or roughness meter) makes it possible to measure the deviations of 500? to 1 mm of a surface. It is composed of a diamond stylet which is placed and is moved on the sample with a constant force. These physical data are converted into electrical information on a computer. The topography, the surface corrugation and the roughness of the sample are obtained.

[0088] Each measurement is taken over three different zones of each device sample. These measurements are 200 ?m. In order to obtain a value representative of the surface roughness, the mean of the three values obtained has been calculated.

[0089] The measurement is taken on a Dektak Stylus? (Bruker) profilometer according to the standard ISO 4287.

[0090] The scanning electron microscope (SEM) makes it possible to take atomic composition measurements of the devices from the samples. The composition measurements are taken by energy dispersion X-ray spectroscopy or energy dispersive spectroscopy (EDS) by X-ray emission. The impact of the electron beam on the sample produces X-rays characteristic of the elements present on the sample. A qualitative composition measurement spectrum of the sample is obtained, also with the three-dimensional image acquisition.

[0091] Results

[0092] The roughness of the devices A, B, C and D of the invention, mentioned in example 1 has been measured as indicated above.

[0093] A reference implant (outside of the invention), implant on the market without a zirconia layer, has also been considered.

[0094] The results obtained, corresponding to the mean of the three measurements, as indicated above, show that the variation between the roughness Ra of the initial device and the roughness Ra of the device obtained from the method is less than or equal to around 25%, in particular less than or equal to around 20%, in particular less than or equal to around 7%.