Dental article with a coating comprising nanostructures made of yttria-stabilized zirconia

Abstract

A dental article including a dental article body made of a ceramic material and a coating formed on the surface of said dental article body. The coating includes crystalline nanostructures made of yttria-stabilized zirconia YSZ.sub.1, the crystal habitus of at least a portion of the nanostructures having at least approximately the shape of a regular convex polyhedron.

Claims

1. A dental article comprising a dental article body made of a ceramic material and crystalline nanostructures formed on the surface of the dental article body, the crystalline nanostructures forming nanoscopic peaks projecting outward from the surface of the dental article body, wherein the crystalline nanostructures are made of yttria-stabilized zirconia YSZ.sub.1, the crystal habitus of at least a portion of the nanostructures having at least approximately the shape of a regular convex polyhedron.

2. The dental article according to claim 1, wherein the crystal habitus of at least a portion of the nanostructures has at least approximately the shape of a tetrahedron or an octahedron.

3. The dental article according to claim 1, wherein the nanostructures have a cubic crystallographic structure, a tetragonal crystallographic structure, or a crystallographic structure in an intermediate phase between a tetragonal and a cubic phase.

4. The dental article according to claim 1, wherein the amount of yttria in the yttria-stabilized zirconia YSZ.sub.1 is higher than 3 mol-%.

5. The dental article according to claim 1, wherein the amount of yttria in the yttria-stabilized zirconia YSZ.sub.1 is lower than 12 mol-%.

6. The dental article according to claim 1, wherein the amount of yttria in the yttria-stabilized zirconia YSZ.sub.1 is in a range from 6 to 8 mol-%.

7. The dental article according to claim 1, wherein the nanostructures have a size of less than 200 nm.

8. The dental article according to claim 1, wherein the dental article body is made of zirconia.

9. The dental article according to claim 8, wherein the dental article body is made of yttria-stabilized zirconia YSZ.sub.2, and the percentage of yttrium in the yttria-stabilized zirconia YSZ.sub.1 differs from the percentage of yttrium in the yttria-stabilized zirconia YSZ.sub.2.

10. The dental article according to claim 1, wherein the surface of the dental article body, on which the crystalline nanostructures are formed, is rough.

11. The dental article according to claim 1, wherein the crystalline nanostructures have a thickness of 100 nm at most.

12. A dental implant comprising the dental article according to claim 1.

13. The dental article according to claim 1, wherein the crystalline nanostructures form a nanoscopic roughness on the surface of the dental article body.

14. A process for providing the dental article according to claim 1, the process comprising a. providing the dental article body made of the ceramic material, and b. forming on the surface of the dental article body the crystalline nanostructures made of yttria-stabilized zirconia YSZ.sub.1 by physical vapor deposition using a target made of a zirconium-yttrium alloy or using a target made of zirconium and a target made of yttrium.

15. The process according to claim 14, wherein the crystalline nanostructures are formed by sputter deposition.

16. The process according to claim 14, wherein an oxygen containing gas is used for the physical vapor deposition, a gas containing between 0.5 to 2 vol-% oxygen.

17. The process according to claim 14, wherein the physical vapor deposition is performed at a temperature above room temperature.

18. The process according to claim 14, wherein prior to the physical vapor deposition, the surface of the dental article body is roughened.

19. The process according to claim 18, wherein a microscale roughness is formed on the dental article body prior to step b, the microscale roughness being defined by at least one of surface parameters S.sub.a, S.sub.t and S.sub.sk: i. S.sub.a being the arithmetic mean deviation of the surface in three dimensions and being in the range from 0.1 m to 2.0 m; ii. S.sub.t being the maximum peak to valley height of a profile in three dimensions and being in the range from 0.5 m to 20.0 m; and iii. S.sub.sk being the skewness of the profile in three dimensions and being in the range from 0.01 to 0.6, and by the crystalline nanostructures formed in step b, at least one of S.sub.a, S.sub.t and S.sub.sk is changed by less than 50% at most.

Description

(1) Images of the respective surfaces are shown in the attached figures of which

(2) FIG. 1 shows a FESEM image of the ZLA sample (comparative) at a nominal magnification of 5000 with the scale representing 2 m given in the lower left corner of the image;

(3) FIG. 2 shows a FESEM image of the ZLA masking sample (according to the invention) at a nominal magnification of 5000 with the scale representing 2 m given in the lower left corner of the image;

(4) FIG. 3 shows a high resolution FESEM image of the ZLA masking sample (according to the invention) with the scale representing 50 nm given at the bottom of the image;

(5) FIG. 4 shows a high: resolution FESEM image of the double-blasted ZLA masking sample (according to the invention) with the scale representing 50 nm given at the bottom of the image;

(6) FIG. 5 shows a sectional image of a sample obtained by gas flow sputter deposition as specified above, but using 20 (instead of 6) deposition cycles, with the scale representing 400 nm given at the bottom of the image; and

(7) FIG. 6 shows a sectional image of a sample obtained by gas flow sputter deposition as specified above, but using a flow of the reactive gas of 60 sccm (instead of 40 sccm), with the scale representing 500 nm given at the bottom of the image.

(8) As in particular shown in FIGS. 3 and 4, nanostructures having the crystal habitus of a tetrahedron are achieved by the process of the present invention.

(9) As shown in FIGS. 5 and 6, the nanostructures obtained have on their distal side the shape of the respective sector of a regular convex polyhedron, while having at their proximal side a columnar shape forming a surface oriented tilted columnar structure, which is a result of the nanostructures being conjoined with the surface of the dental article body. In a sectional view, these nanostructures can be described as having the shape of a cauliflower, the stem of which being formed by the columnar portion and the florets by the sector of the regular convex polyhedron.

(10) As also shown in FIGS. 5 and 6, there is no interface between the columnar portion and the substrate, i.e. the dental article body. Rather, the nanostructures protrude from the substrate as a continuous material formation. (The light areas in the images according to FIGS. 5 and 6 relate to a Pt layer deposited for the protection of the nanostructures against the Ga-ion beam of the FIB.)

(11) The biological activity of ZLA and ZLA masking samples has been assessed by a-biological pull-off tests (a-bio) using a dental plastic (Exakto-Form Modellkunststoff, bredent GmbH & Co. KG). Specifically, sample disks of a diameter of 15 mm and a height of 1 mm or 1.5 mm were analysed for their pull-off force at a pull-off speed of 0.83 mm/s. These a-bio pull-off forces were compared to the respective pull-off force determined for the sample in vivo.

(12) The results are shown in Table 5.

(13) TABLE-US-00005 TABLE 5 Pull-off tests (a-biological and in vivo) ZLA ZLA Masking a-bio in vivo a-bio in vivo Average (N) 179 30 171 45 STD (N) 107 13 83 16 a-bio/in 6 4 vivo

(14) According to Table 5, the ZLA Masking sample showed a markedly higher pull-off force in vivo compared to the ZLA sample. Dividing the pull-off force (a-bio) by the pull-off force (in vivo) results for the ZLA Masking sample in a relatively small value of less than 4. Since a small value is indicative of a high biological activity, the results indicate that the process of the present invention leads to an improved biological activity (compared to the untreated sample for which the above division results in a much higher value of about 6).