DE102020101852A1 - Coated medical articles and processes for their manufacture - Google Patents

Abstract

A coated medical article includes a substrate and a coating deposited on the substrate. The coating comprises a non-reflective arc vapor deposited outermost layer of silver. The silver layer in particular has an average roughness of 0.3 to 0.9 μm. A method for producing the coated article by means of electric arc evaporation is also specified. The coated article can in particular be used as a scan abutment.

Description

The invention relates to a coated medical article, in particular a scan abutment, and a method for its production.

CAD / CAM technology is often used to manufacture dental implants. With the help of scan abutments or scan bodies, the implant and remaining tooth situation in the patient's mouth is digitally shaped and the data set obtained in this way is used to manufacture the implants. Scan abutments are cylindrical devices made of a plastic or a metal substrate that are screwed to the implants. The three-dimensional position of the scan abutments connected to the implants in the jaw is measured via an optical scan with the aid of a table or intraoral scanner. The scan abutments are usually made of plastics such as PEEK, which have a non-reflective surface.

However, scan abutments formed from metals or metal alloys cannot be optically detected or only with difficulty. These scan abutments must therefore be surface-treated by a blasting process or provided with a relatively light coating, for example made of zirconium nitride. The scan abutments obtained in this way also have a bright, non-reflective surface.

However, the blasting of the surface results in an undesirable removal of substrate material. In addition, the substrate has to be masked in a complex manner in order to protect the areas of the article that are not to be blasted. The surface obtained by blasting the substrate and coating it with zirconium nitride has a light gray to light yellow appearance. However, white surfaces are advantageous for improved optical detection. Scan abutments made of PEEK or other special plastics are relatively expensive and have a lot-dependent variation of material properties.

Furthermore, scan abutments are known which are provided with a multi-layer coating to improve optical detection. This coating is an economically complex multi-layer system that contains zirconium, zinc, titanium and their oxides.

From the DE 10 2012 018 816 A1 a dental implant is known which has a coating applied by arc deposition (Arc-PVD) which contains zirconium metal or zirconium nitride. After ultrasonic cleaning, the surface of the substrate is pretreated in the gas plasma by ion etching. A zirconium-containing layer is deposited on the pretreated surface using the arc process. The zirconium-containing coating can also be doped with silver. The coating is intended for the prophylaxis of gingivitis and peri-implantitis.

The patent EP 1 361 837 B1 discloses an endoprosthesis with a metallic support structure and a surface which is provided with a bonding layer made of gold and a silver layer galvanically applied to the gold layer. The silver layer is intended to achieve a bactericidal or bacterostatic effect and thus reduce the risk of infection for the person wearing the endoprosthesis.

From the EP 2 240 212 B1 a metallic biomedical article for use in contact with internal human or animal body tissue is known, which has a metal substrate and a first silver-containing metal nitride layer on the metal substrate and a second silver-containing metal nitride layer as an outer surface on the first metal nitride layer, the second silver-containing metal nitride layer having a greater amount of silver than comprises the first silver-containing metal nitride layer. The silver in the metal nitride layer should develop an antibacterial effect.

the EP 2 240 631 B1 discloses a method for the antimicrobial treatment of implant surfaces with silver, the implant being made of titanium or a titanium alloy. The implant surface is anodized in the presence of an electrolyte, the electrolyte comprising a silver-releasing substance and a reducing agent. The silver is obtained at least in part from silver ions which are reduced by the reducing agent. The silver can be incorporated in the form of nanoparticles into the anodizing layer or an oxide layer that is located on the anodizing layer. One variant provides for the silver to be introduced into the titanium surface of the implant by ion implantation before the anodization.

From the WO 2015/107224 A1 a material composite made of a ceramic substrate with an optical functional coating is known, which is deposited by means of a PVD process. To form a coating with increased transmission in the IR range, a first high-index layer made of silicon with an aluminum content of less than 15% by weight is applied to a spinel substrate. On top of this layer is another one high refractive index, dielectric layer made of titanium dioxide. An adhesion-promoting intermediate layer is located between the dielectric base layer and the IR reflective layer. The IR reflective layer can consist of silver (Ag) or one of the known alternative IR reflective materials. A blocker layer made of nickel chromium oxide is applied over the IR reflective layer. The cover layer can consist of silicon nitride. The layers are deposited using the ESV-PVD process (electron beam evaporation) or a sputtering process. The deposition temperature is in the range from 110 to 500 ° C.

It is the object of the present invention to provide a medical article, in particular a scan abutment, with an inexpensive coating that can easily be detected optically. In particular, the coating should have a very bright surface and good adhesion to the substrate.

This object is achieved by a coated medical article according to claim 1 and a method for its production according to claim 8.

Advantageous embodiments are specified in the subclaims, which can optionally be combined with one another.

According to the invention, a coated medical article having a substrate and a coating deposited on the substrate is provided. The coating comprises a non-reflective, outermost silver layer, deposited by arc evaporation, made of pure silver or a silver alloy with up to 10% by weight of additional elements.

A metallic silver coating produced by arc evaporation (Arc-PVD) can be produced quickly, inexpensively and with high process reliability and reproducibility.

With arc evaporation, so-called “droplets” can be formed and deposited on the substrate surface. This mostly undesirable side effect of the arc PVD process is used according to the invention to deposit silver particles on the surface of the metallic silver coating, which thereby receives a microrough, non-reflective surface. The silver particles deposited on the surface of the coating change the refraction of light upon reflection and create an anti-reflective appearance with a white surface.

The coated article is autoclavable and has antibacterial properties.

In particular, the silver layer deposited by arc evaporation has an average roughness R _a of 0.3 μm to 0.9 μm. The measurement of the mean roughness R _a can be done according to DIN EN ISO 4287 be done using tactile measuring devices.

The term “pure silver” describes chemically pure silver with unavoidable impurities.

The silver target used to deposit the silver layer and thus also the silver layer deposited on the substrate preferably consists of pure silver with a purity of 99.99% or more. This avoids contamination in the coating and increases the biocompatibility of the article.

Alternatively, a target made of a silver alloy with up to 10% by weight of additional metallic elements can be used to deposit the silver layer. The additional elements are preferably selected from the group consisting of Ti, Zr, Cr, Nb, Ta and Si and combinations thereof.

The layer thickness of the silver layer can be up to 12 μm, in particular up to 10 μm. The layer thickness of the silver layer is preferably in a range from 1 μm to 3 μm, in particular 1 μm to 2 μm. Thicker layers are not necessary to improve the scannability of the substrate.

The connection of the silver layer to the metal substrate can be improved by depositing a connection layer made of titanium or a titanium alloy on the substrate surface, on which the silver layer is then deposited by arc evaporation. The bonding layer can have a layer thickness of up to 0.5 µm.

Suitable titanium alloys for the tie layer include, but are not limited to, a titanium-aluminum-vanadium alloy such as Ti-3AI-2.5V or Ti-6AI-4V.

A layer of chromium or a chromium alloy can also be used as the connecting layer.

The total layer thickness of the coating, including the connection layer, is therefore preferably in a range from 1.5 to 12.5 μm, in particular 1.5 to 10.5 μm. The total layer thickness is particularly preferably from 1.5 to 3.5 μm, in particular from 1.5 to 2.5 μm. Coatings with a higher layer thickness generate higher costs, are less stable and tend to flake off the substrate.

According to a preferred embodiment, the coating consists of the silver layer and optionally the bonding layer, which can be selected from titanium, a titanium alloy, chromium or a chromium alloy. In this case, there are no further functional layers between the substrate surface and the coating.

The application of the silver layer by means of arc evaporation enables the provision of non-reflective layers with low surface roughness. The mean surface roughness R _a is preferably in a range from 0.3 μm to 0.9 μm, particularly preferably from 0.5 μm to 0.9 μm. The average surface roughness Ra is measured by tactile measurement DIN EN ISO 4287 .

The substrate is preferably a metal substrate, in particular a substrate made of steel, a titanium alloy, a cobalt-based alloy, for example a cobalt-chromium alloy, or a nickel-titanium alloy such as nitinol. A steel suitable as a substrate material for the article according to the invention is, for example, stainless steel 1.4301 (X5CrNi18-10), 1.4404 (X2CrNiMo18-14-3) and 1.4435 (X2CrNiMo18-14-3). Suitable titanium alloys are Ti-3AI-2.5V, Ti-6AI-4V and titanium grade 2 / 3.7035. The substrate material can be selected depending on the intended use of the medical article and is not limited in any way.

• Bereitstellen eines Substrats mit einer Oberfläche
• Bereitstellen eines Targets aus Reinsilber oder einer Silberlegierung mit bis zu 10 Gew.-% an Zusatzelementen;
• Abscheiden einer Silberschicht aus dem Reinsilber oder der Silberlegierung auf wenigstens einem Teil der Substratoberfläche durch Lichtbogenverdampfen bei einer Bias-Spannung von 120 bis 180 V zwischen dem Substrat und dem Target sowie bei einer Temperatur von 280 bis 350 °C,

wobei die Silberschicht unmittelbar nach dem Abscheiden nicht-reflektierend ist.The method according to the invention for producing the coated medical article comprises the following steps:

• Providing a substrate with a surface
• Providing a target made of pure silver or a silver alloy with up to 10% by weight of additional elements;
• Deposition of a silver layer from the pure silver or the silver alloy on at least part of the substrate surface by arc evaporation at a bias voltage of 120 to 180 V between the substrate and the target and at a temperature of 280 to 350 ° C,

the silver layer being non-reflective immediately after deposition.

The use of arc evaporation to deposit a non-reflective silver layer enables a very simple process control with recourse to conventional methods. In contrast to the processes described in the prior art for the deposition of multilayer systems, only a single process step has to be carried out. The coated article obtainable by the process according to the invention shows, in the untreated state, immediately after the deposition of the silver layer, a white surface with a matt, microstructured surface morphology. The coating consists entirely of silver or the silver alloy with up to 10% by weight of additional elements, apart from unavoidable impurities, and shows non-reflective properties that result from the deposition of silver particles on the surface of the coating. In the context of the invention, “immediately after deposition” means that no mechanical post-processing of the coating by blasting or polishing, which would lead to a smoothing of the surface and a silvery appearance, is dispensed with. By dispensing with subtractive processing or post-treatment of the coated surface by blasting, there is also no edge rounding and no material removal, and the component geometry can be retained.

The arc evaporation can be carried out in a commercially available PVD coating system. The arc evaporation is preferably carried out under argon at a chamber pressure in a range from 0.002 to 0.030 mbar (0.2 to 3 Pa), in particular 5 × 10 ^-3 mbar (0.5 Pa).

With the method according to the invention, a coating can be obtained which preferably exhibits adhesive strength DIN EN ISO 26443 of class 0.

To improve the adhesion of the silver layer, the substrate can in particular be provided with a bonding layer made of titanium, a titanium alloy, chromium or a chromium alloy before the deposition of the silver layer. The connection layer can also be deposited on the substrate by arc evaporation using an appropriate metal target. Furthermore, it is possible to pretreat at least part of the substrate surface by blasting with a hard material powder, for example corundum powder, before coating with the silver layer and, optionally, the bonding layer.

The coated medical article can in particular be used as a scan abutment for the intraoral optical scan.

The following description of a preferred embodiment of the invention serves for a more detailed explanation and is not to be understood in a restrictive sense.

Production of a silver coating according to the invention

In the exemplary embodiment described here, a substrate for a scan abutment made of a titanium alloy Ti-6Al-4V was provided with the coating according to the invention.

The substrate surface was cleaned by igniting the plasma and applying a high acceleration voltage to the substrate. First, a 0.5 μm thick Ti bonding layer was deposited on the cleaned substrate surface by arc evaporation from a Ti target. A silver coating according to the invention was also deposited on this bonding layer by arc evaporation in the same coating cycle.

The silver layer was deposited from an Ag target with a purity of 99.99% at a substrate voltage (bias) of 120 to 180 V under argon and at a chamber pressure of about 0.3 Pa. The deposition temperature was about 300 ° C. The current intensity on the silver target was set to about 70 to 90 A. A silver layer with a layer thickness of about 1.5 μm was obtained. The silver layer had a white appearance with a matte, non-reflective surface morphology.

Various measurements to determine the surface roughness, the layer thickness and the adhesive strength were carried out on the coating obtained in this way. The results are shown in the table below. Table: Layer properties parameter procieedings Result Average roughness R _a Tactile measurement according to DIN EN ISO 4287 0.6 µm Layer thickness Dome grind according to DIN EN 1071-2 1.5 µm Adhesive strength Rockwell Test ( DIN EN ISO 26443 ) Class 0

The method according to the invention makes it possible to cost-effectively produce a firm, matt-white silver layer for implants and other medical articles. The coating also shows antibacterial properties.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102012018816 A1 [0006]
• EP 1361837 B1 [0007]
• EP 2240212 B1 [0008]
• EP 2240631 B1 [0009]
• WO 2015/107224 A1 [0010]

Non-patent literature cited

• DIN EN ISO 4287 [0018, 0028]
• DIN EN ISO 26443 [0033, 0040]

Claims (10)

A coated medical article having a substrate and a coating deposited on the substrate, the coating having an arc vapor deposited, non-reflective outermost silver layer of pure silver or a silver alloy with up to 10% by weight of additional elements. Article after Claim 1 , characterized in that the silver layer has an average roughness R _a of 0.3 to 0.9 µm. Article after Claim 1 , characterized in that the silver layer consists of pure silver with a purity of 99.99% or more, or of a silver alloy with up to 10% by weight of additional elements, made up of Ti, Zr, Cr, Nb, Ta and Si as well as combinations thereof existing group are selected. Article after Claim 1 or 2 , characterized in that the silver layer has a layer thickness of 1 µm to 12 µm, preferably 1 µm to 3 µm, more preferably 1 µm to 2 µm. Article according to one of the preceding claims, characterized in that the coating has a class 0 adhesive strength. Article according to one of the preceding claims, characterized in that the substrate is a metal substrate. Article according to one of the preceding claims, characterized in that the article is a scan abutment Method for producing a coated medical article according to one of the preceding claims, comprising the following steps: Providing a substrate with a surface Providing a target made of pure silver or a silver alloy with up to 10% by weight of additional elements; Deposition of a silver layer from the pure silver or the silver alloy on at least part of the substrate surface by arc evaporation at a bias voltage of 120 to 180 V between the substrate and the target and at a temperature of 280 to 350 ° C, the silver layer being non-reflective immediately after deposition. Procedure according to Claim 7 , characterized in that the arc evaporation takes place under argon at a chamber pressure in a range of 0.2 to 3 Pa. Procedure according to Claim 7 or 8th , characterized by depositing a bonding layer made of titanium, titanium alloy, chromium or a chromium alloy on the substrate surface before the silver layer is deposited.