METHOD FOR THE PASSIVATION OF SURGICAL IMPLANTS COMPRISING TITANIUM, AND SURGICAL IMPLANT OBTAINED

Abstract

The present invention discloses a method for the passivation treatment of a surgical implant comprising titanium, characterized in that it comprises the steps of: a) immersing said surgical implant in a solution comprising hydrochloric acid, sulfuric acid and hydrogen peroxide; b) performing at least two washes with an aqueous solution; and c) performing at least one wash with ethanol. In addition, the present invention discloses a surgical implant comprising titanium with bactericidal capacity, characterized in that it comprises a surface layer of titanium oxide with a nanoporosity of between 90 nm and 200 nm.

Claims

1. A method for the passivation of a surgical implant comprising titanium, the method comprising steps of: a) immersing said surgical implant in a solution comprising hydrochloric acid, sulfuric acid and hydrogen peroxide; b) performing at least two washes with an aqueous solution; and c) performing at least one wash with an alcohol.

2. The method according to claim 1, wherein the solution of the step a) also comprises divalent cations.

3. The method according to claim 2, wherein said divalent cations are calcium (Ca.sup.2+) and/or magnesium (Mg.sup.2+).

4. The method according to claim 1, wherein the step a) has a duration of between 30 minutes and 4 hours.

5. The method according to claim 1, wherein said hydrochloric acid has an initial concentration of between 10% and 30% (v/v).

6. The method according to claim 1, wherein the sulfuric acid has an initial concentration of between 90% and 99% (v/v).

7. The method according to claim 1, wherein the hydrogen peroxide has an initial concentration of between 20% and 40% (v/v).

8. The method according to claim 1, wherein the ratio of hydrochloric acid and sulfuric acid to hydrogen peroxide is between 40% and 60% for each by volume.

9. The method according to claim 1, wherein the aqueous solution of step b) is distilled water.

10. The method according to claim 1, wherein the alcohol of step c) is ethanol.

11. The method according to claim 1, wherein the washes of steps b) and c) have a duration between 1 min and 2 min.

12. The method according to claim 1, wherein the washes of steps b) and c) are performed in an ultrasonic bath.

13. A Bactericidal surgical implant comprising titanium, and a surface layer of titanium oxide with a nanoporosity of between 50 nm and 500 nm.

14. A use of a solution comprising hydrochloric acid, sulfuric acid and hydrogen peroxide for the passivation of a surgical implant comprising titanium.

Description

[0037] FIG. 1 is a photograph illustrating a titanium surface showing the passivation layer (titanium dioxide, TiO.sub.2) formed after using a composition according to the prior art, i.e. with a solution of 15% (v/v) nitric acid and 30% (v/v) hydrofluoric acid for 30 seconds.

[0038] FIG. 2 is a photograph illustrating a titanium surface after being treated with a solution according to the present invention.

[0039] FIG. 3 shows scanning electron microscopy (SEM) images illustrated in the top line and fluorescence microscopy images illustrated in the bottom line of Pseudomonas aeruginosa (P. aeruginosa) stained using a live (green)/dead (red) bacterial viability kit.

[0040] FIG. 4 shows scanning electron microscopy (SEM) images illustrated on the top line and fluorescence microscopy images illustrated on the bottom line of Streptococcus sanguinis (S. sanguinis) stained using a live (green)/dead (red) bacterial viability kit.

[0041] FIG. 5 is a photograph illustrating a titanium mesh nanostructure obtained after being treated by means of the method of the present invention.

[0042] FIG. 6 presents scanning electron microscopy (SEM) images showing histologies in dental implants placed in minipig pigs at different implantation times.

[0043] FIG. 7 is a graph representing values of bone-to-implant contact (BIC) osseointegration percentages and total bone area (TBA).

[0044] In the following, the present invention is illustrated by means of examples, which do not constitute a limitation thereof.

EXAMPLES

Example 1: Passivation Treatment of Implants Comprising Titanium

[0045] To perform the study, implants comprising titanium were subjected to three different treatments: (1) control (untreated), (2) with hydrochloric acid (HCl) at a concentration of 1 M and (3) with the solution of the present invention (hydrochloric acid at a concentration of 20% (v/v), concentrated 96% (v/v) sulfuric acid and hydrogen peroxide at a concentration of 30% (v/v)). The ratio of hydrochloric acid and sulfuric acid to hydrogen peroxide is 50% each by volume.

Example 2: Quantitative Analyses of the Bacterial Adhesion Test Performed with the Gram-Negative Strain P. aeruginosa and the Gram-Positive Strain S. sanguinis

[0046] The quantitative analyses of the bacterial adhesion test performed with the Gram-negative strain P. aeruginosa and the Gram-positive S. sanguinis show that there are no significant differences in the number of bacteria adhered to the upper side of the control and hydrochloric acid-treated surfaces, but that there were differences with the meshes treated with the solution of the present invention (Table 2). In fact, for both bacterial strains, the titanium alloy surfaces treated by means of the method of the present invention drastically reduced (by at least an order of magnitude) bacterial adhesion compared to all other groups. Bacteria adhering to the differently treated surfaces can be seen in FIG. 3 for P. aeruginosa and FIG. 4 for S. sanguinis, which corroborates the quantification differences assessed for bacterial adhesion. The live/dead images revealed that the differences in bacterial numbers were mainly related to the prevention of bacterial colonization of the surfaces treated by means of the method of the present invention, as virtually none of the bacteria remaining on the surfaces had compromised membranes (red colour).

TABLE-US-00002 TABLE 2 Quantitative analysis of the number of P. aeruginosa and S. sanguinis bacteria adhering to surfaces of grade V titanium alloys with different passivation treatments. P. aeruginosa S. sanguinis (number of (number of bacteria/mm.sup.2) bacteria/mm.sup.2) Control 7.02 10.sup.5 0.52 10.sup.5 3.52 10.sup.5 0.48 10.sup.5 HCl 5.75 10.sup.5 0.33 10.sup.5 2.25 10.sup.5 0.13 10.sup.5 Composition of the 1.23 10.sup.4 0.02 10.sup.4 5.03 10.sup.3 0.10 10.sup.3 present invention

[0047] The characteristic nanotexture resulting from the passivation treatment of titanium alloy meshes with the solution of the present invention (FIG. 5) was a relevant surface property achieved with the treatment of the present invention compared to the treatment with HCl. The meshes treated with the solution of the present invention showed a sub-microtexture with overlapping nanoporosity between 90 nm and 200 nm. This surface topography was homogeneous and without cracks, suggesting good toughness of the oxide layer formed. The presence of grooves on the treated surfaces could be related to a preferential etching method in areas with high internal energy, such as grain boundaries, dislocation stacking or other metallurgical or crystallographic singularities.

[0048] In the experiments performed, the inventors evaluated the effects of the passivation treatment on bacterial adhesion, as infection is a growing concern for dental meshes. Titanium alloy surfaces treated with the solution of the present invention were found to prevent bacterial adhesion significantly more effectively than untreated and HCl-treated surfaces.

[0049] Furthermore, divalent cations such as calcium and/or magnesium are added to the acidic solution, which impregnate the passivation layer and their release on physiological contact causes the rapid migration of osteoblast precursor proteins. This release of cations causes the rapid adhesion of osteoblasts, subsequent cell proliferation and differentiation, favouring a certain level of osteoconduction, increasing the speed of osseointegration and the level of bone-to-implant contact (BIC).

[0050] FIG. 6 shows the histologies of dental implants that release calcium (BIO) with respect to sand blasting (SB), acid etching (AE) or plasma treatment (PL). The higher bone-to-implant contact (BIC) index and total bone area (TBA) for divalent cation-treated implants may be seen in FIG. 7.