RU2604085C1 - Method of formation of nanostructured biologically inert coating on titanium implants - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medical equipment, namely technology of making bioinert nanostructured oxide coating on intraosseous parts of titanium implants. Method includes air-abrasive treatment, etching in solution of acids and gas-thermal oxidation. Air-abrasive treatment is carried out with alumina powder with particle size of 100-200 mcm at pressure of air medium 0.2-0.3 MPa. Etching of implant is performed in water solution of HF (5-8 wt%) + HNO₃ (15-19 wt%) for 0.1-0.2 minutes. Gas-thermal oxidation is performed by induction of heating in air atmosphere to temperature of 800-900 °C at current frequency on inductor of 90±10 kHz and specific consumption of electric power 0.2-0.4 W/kg. Then implant is held for 0.5-2 minutes and cooled in air.

EFFECT: formation of oxide coating on titanium implant surface with thickness of 3-10 mcm is provided, which consists of oxide crystals with size of up to 70±10 nm, with help of high-efficiency and resource-saving method.

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Description

The invention relates to the field of medical equipment, and in particular to a technology for the formation of bioinert nanostructured oxide coatings on the intraosseous parts of titanium implants.

It is believed that the interaction of the implant surface material and bone tissue occurs at the nanometer level of mineralized collagen fibrils [N. Wang, N. Li, W. Lii, J. Li, J. Wang, Z. Zhang, et al., Effects of TiO ₂ nanotubes with different diameters on gene expression and osseointegration of implants in minipigs, Biomaterials 32 (2011) 6900 -6911; Mendonca G. et al. Advancing dental implant surface technology-from micron-to nanotopography // Biomaterials. - 2008. - T. 29. - No. 28. - C. 3822-3835].

At present, the following technological processes are used to form a heterogeneous surface on titanium intraosseous implants, characterized by the presence of micro- and nanoscale structural elements: treatment by concentrated energy flows, thermal spraying, electrochemical and gas-thermal oxidation. Known methods for forming a micro- and nanostructured surface on titanium are characterized by a significant duration of the process, its technological complexity or toxicity of the substances used, which contributes to the search for new ways to solve the existing problem.

A known method of hardening metal products to obtain nanostructured surface layers [patent RU for invention No. 2527511 / Ya.A. Chetokin, D.V. Pugashkin // Method of hardening metal products to obtain nanostructured surface layers. - 2014]. The formation of a nanoscale surface coating is carried out by treating the surface of metal products with an alloy alloy used in finely divided powder form. Then, prepared areas of the surface are exposed to laser radiation produced by a focused optical thermal beam of a high-energy quantum generator, moving the laser beam in increments of 25 microns. After that, the surface of the workpiece is cooled by a stream of compressed air with a temperature of 20 ° C under a pressure of 8 kPa. Upon cooling, the alloying alloy crystallizes on the metal surface of the product.

The main disadvantage of this method is the technological complexity of a uniform surface treatment.

There is also a known method for producing a nanostructured coating in the process of thermal spraying [RU patent for the invention No. 2542218 / L.Yu. Botashev, N.U. Bisilov, R.S. Malsugenov // Method for producing a nanostructured coating. - 2015]. A high-temperature gas stream is formed in the combustion chamber of the atomizer by burning fuel in an oxidizing agent. The source material is supplied into the combustion chamber in the form of a powder. The length of the chamber is selected from the condition of ensuring the evaporation of the powder material by exposure to a high-temperature gas stream. The resulting gas stream after exiting the combustion chamber is accelerated in the nozzle and cooled to form nanoparticles, using a nozzle the length of which is selected from the condition of cooling the gas stream to a temperature below the melting temperature of the starting material. The gas stream is cooled by mixing with a cold inert gas stream.

The main disadvantage of this method is the technological complexity of the process of thermal spraying.

There is also a method of obtaining a biocompatible coating on implants made of titanium and its alloys [RU patent for invention No. 2323267 / I.V. Rodionov, K.G. Butovsky, O.V. Beydik, Yu.V. Seryanov // Method for producing a biocompatible coating on implants made of titanium and its alloys. - 2008], which allows the formation of porous metal oxide layers on the surface of implanted structures. According to the method, the process of oxidation of titanium and its alloys is carried out at a temperature of 600-1000 ° C for 1.5-2 hours in a gas medium supplied under a pressure of 1.2-1.3 atm and consisting of a mixture of inert (argon, neon, helium ) and oxidizing (oxygen, carbon dioxide) gases in the following ratio of components: 60-70% and 40-60%, respectively.

The main disadvantages of the method are the technological complexity and the long duration of the oxidation process.

Closest to the proposed method is a method of creating a nanostructured bioinert porous surface on titanium implants [RU patent for the invention No. 2469744 / F.M. Abdullaev // Method for creating a nanostructured bioinert porous surface on titanium implants. - 2012], which allows one to obtain a porous nanostructured oxide film 1–10 μm thick, consisting of open nanotubes of titanium oxides with pore sizes of 40–140 nm. The implant surface is sequentially treated by sandblasting, etching in a solution of acids HF (2-3 wt.%) Or HF (2-3 wt.%) + HNO ₃ (5-30 wt.%), Or HNO3 + HCl (10 -30 wt.%), Firing-degassing in vacuum at a temperature of 300-770 ° C, preliminary anodization (electrochemical oxidation) at a voltage of 30-90 V, removal of the oxide film by etching in a solution of HF (2-20 wt.%) Or HF (2-3 wt.%) + HNO ₃ (5-30 wt.%), Single-phase or biphasic anodization by constant or pulsed (0.5 Hz) current in a 5-20% aqueous solution of oxalic acid when forming m voltage of 25-130 V and firing in an oven for structuring crystals and removing liquid from surface pores at a temperature of 300-550 ° C.

The main disadvantage of this method is the duration of the process, due to the need for vacuum firing-degassing, preliminary electrochemical oxidation and removal of the oxide film by etching, as well as firing in an oven for structuring crystals and removing liquid from surface pores.

The objective of the invention is to provide a technologically simple and high-performance and resource-saving method of forming a nanostructured bioinert coating on titanium implants.

The problem is solved in that in the method of forming a nanostructured bioinert coating on titanium implants, including air-abrasive treatment, etching in an acid solution and gas-thermal oxidation, after air-abrasive processing and etching, the oxidation process is carried out by induction heating in an air atmosphere to a temperature of 800- 900 ° C at a current frequency at the inductor of 90 ± 10 kHz and a consumed specific electric power of 0.2-0.4 W / kg, then it is held for 0.5-2 minutes and cooled to zduhe. The invention is also claimed in which, along with the above-described features, air-abrasive treatment is carried out with an electrocorundum powder with a dispersion of 100-200 μm at an air pressure of 0.2-0.3 MPa.

In addition, a method is also claimed in which, along with the above-described features, the implant is etched in an aqueous solution of HF (5-8 wt.%) + HNO ₃ (15-19 wt.%) For 0.1-0.2 minutes.

The technical result is the formation on the surface of titanium implants of an oxide coating with a thickness of 3-10 microns, consisting of oxide crystals of sizes up to 70 ± 10 nm, using a high-performance and resource-saving method.

The invention is illustrated by the figures, which represent: the process of thermal oxidation (Fig. 1), micro- and nanoscale surface morphology of the formed oxide coating (Fig. 2a and 2b, respectively), as well as the morphology of the surface structure of the oxide coating (Fig. 3a and 3b) and samples of technically pure titanium (Figs. 3c and 3d) after in vitro tests for 7 days.

In FIG. 1 positions 1-5 are indicated:

1 - implant;

2 - ceramic oxidation chamber;

3 - water-cooled inductor;

4 - power source;

5 - oxide coating.

The proposed method is as follows.

The titanium implant is subjected to air-abrasive powder treatment with electrocorundum powder with a fineness of 100-200 microns at an air pressure of 0.2-0.3 MPa. Then the surface is cleaned of technological impurities and etched in an aqueous solution of acids HF (5-8 wt.%) + HNO ₃ (15-19 wt.%) For 0.1-0.2 minutes. After that, the implant is washed in distilled water and dried in air. The implant 1 is placed in a ceramic oxidation chamber 2 (repeating the shape of the product), on the external surface of which is placed a water-cooled inductor 3 connected to a power source 4 (Fig. 1). After that, the implant 1 is subjected to induction heating at a current frequency of 90 ± 10 kHz at the inductor and a specific electric power consumption of 0.2-0.4 W / kg to a temperature of 800-900 ° C, followed by exposure for 0.5-2 minutes, subsequent cooling in air (Fig. 1). As a result, an oxide coating 5 is formed on the surface of the product (Fig. 1).

Technological modes of air-abrasive treatment, etching and thermal oxidation were determined by conducting research using scanning electron microscopy. The given limits of the values of technological modes of air-abrasive processing provide the formation of a given microrelief of the implant surface.

The given limits of the values of the technological regimes of thermal thermal oxidation provide the formation of titanium oxide coating with a thickness of 3-10 microns, consisting of oxide crystals up to 70 ± 10 nm in size.

When a current of less than 80 kHz is supplied to the inductor, the electric efficiency of the induction heating device and the processing process itself decreases. When a current of more than 100 kHz is applied to the inductor, there is no improvement in the efficiency of the processing process and a decrease in the power factor is observed.

The limiting values of the consumed specific electric power (0.2-0.4 W / kg) are due to the fact that when the specific electric power is less than 0.2 W / kg, it will be difficult to heat small titanium products to a predetermined temperature due to radiation losses. With a specific electric power of more than 0.4 W / kg, the likelihood of overheating of titanium and, as a result, the appearance of cracks in the surface layer increase.

When the heating temperature is less than 800 ° C and the duration of the gas thermal oxidation process is less than 0.5 minutes, an oxide coating is formed that does not have a nanostructured surface morphology. When the heating temperature is more than 900 ° C and the duration of the heat treatment is more than 2 minutes, oxide coatings are formed on the titanium surface, which have low values of adhesive-cohesive strength.

Examples of the method.

Example 1. A dental cylindrical implant with a diameter of 3.7 mm and a length of 10 mm, made of technical titanium grade VT1-00, is subjected to air-abrasive powder treatment of electrocorundum with a dispersion of 100-200 microns at an air pressure of 0.2 MPa. Then the product is cleaned of technological pollution by ultrasonic cleaning in an aqueous 4-6% solution of surface-active substances (for example, Sulfonol-P). Washed in distilled water, followed by drying in air. Then the implant is subjected to etching in an aqueous solution of acids HF (5 wt.%) + HNO ₃ (1 wt.%) For 0.1 minutes and washed with distilled water, followed by drying in air. After that, the implant is placed in a quartz oxidation chamber with an inner diameter of 5 mm and a length of 20 mm. Then the implant is subjected to induction heating to a temperature of 850 ° C and incubated for 0.5 minutes at a current frequency at the inductor of 90 ± 10 kHz. After the process of gas thermal oxidation, the implant is cooled in air to room temperature.

Example 2. A rod clamp for external transosseous osteosynthesis with a diameter of 4 mm and a length of 50 mm, made of technical grade VT6 titanium, is subjected to air-abrasive powder treatment with electrocorundum powder with a dispersion of 100-200 microns at an air pressure of 0.3 MPa for 2 minutes. The surface of the fixative is cleaned of technological contaminants by ultrasonic cleaning in an aqueous 4-6% solution of surfactants (for example, Sulfonol-P) and washed with distilled water, followed by drying in air. Then the implant is subjected to etching in an aqueous solution of acids HF (8 wt.%) + HNO ₃ (16 wt.%) For 0.2 minutes, washed with distilled water and dried in air. After that, the implant is placed in a quartz oxidation chamber with an inner diameter of 6 mm and a length of 60 mm. The implant is subjected to induction heating to a temperature of 900 ° C and incubated for 1 minute at a current frequency at the inductor of 90 ± 10 kHz. After the process of gas thermal oxidation of the implant is cooled in air to room temperature.

To confirm the formation of nanostructured bioinert coatings on the surface of titanium implants as a result of the treatment described in the proposed method, morphology studies and biocompatibility tests were carried out.

We studied samples of VT6 titanium alloy with oxide coatings formed by the method described in Example 2. The structural state of the coatings was studied by scanning electron microscopy (SEM) using an MIRA II LMU electron microscope. The biocompatibility of the coated samples was tested in vitro. As control samples, we used VT1-00 grade titanium plates subjected to air-abrasive treatment. For the study, human dermal fibroblasts isolated by migration from normal skin fragments were used. The cultivation duration was 7 days, which is considered sufficient for the stages of adhesion and the beginning of proliferation. Further, coatings with cells were subjected to fixative treatment with formaldehyde and subsequent study using SEM.

The results of scanning electron microscopy showed that the surface microstructure is a relief of the initial metal base after air-abrasive treatment, etching and oxidation. The nanoscale study revealed the surface structure of the oxide coating, represented by rounded grains and pores, with linear dimensions up to 70 ± 10 nm (Fig. 2).

Verification of in vitro biocompatibility of oxide coatings formed by the proposed method showed that fibroblast cells are more stably attached to the coating surface (Fig. 3a, b) than on the surface of control samples made of technical titanium (Fig. 3c, d), which indicates a high the level of biocompatibility of oxide coatings obtained by the proposed method.

From the results it follows that the proposed method allows the formation of nanostructured bioinert coatings on titanium implants.

Claims (3)

1. A method of forming a nanostructured bioinert coating on titanium implants, including air-abrasive treatment, etching in an acid solution and gas-thermal oxidation, characterized in that after air-abrasive processing and etching, the gas-thermal oxidation is carried out by induction heating in an air atmosphere to a temperature of 800- 900 ° C at a current frequency at the inductor of 90 ± 10 kHz and a consumed specific electric power of 0.2-0.4 W / kg, and then kept for 0.5-2 minutes and cooled down in the air. 2. The method of forming a nanostructured bioinert coating on titanium implants according to claim 1, characterized in that the air-abrasive treatment is carried out with electrocorundum powder with a dispersion of 100-200 microns at an air pressure of 0.2-0.3 MPa. 3. The method of forming a nanostructured bioinert coating on titanium implants according to claim 1, characterized in that the implant is etched in an aqueous solution of HF (5-8 wt.%) + HNO ₃ (15-19 wt.%) For 0.1 -0.2 minutes.

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