DD222210A1 - METHOD FOR THE PRODUCTION OF IMPLANT MATERIAL AS A HARD AND SOFT TISSUE SET - Google Patents

Abstract

The invention relates to a method for producing an implant material as a hard and soft tissue replacement for the mid-facial skeleton. The implant material can be produced cost-effectively, fully synthetic and thus permanently available. Graphite foil is subjected to a high-temperature treatment at temperatures above 2 300 K, then provided with a surface profiling in the form of alternating Einpraegungen of elevations and depressions on which a pyrolytically deposited hard carbon layer is applied. The material has a very good biocompatibility.

Description

, Method for the distribution of implant material as a H ^ b ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

, Field of application of the invention

The invention relates to a method for the production of implant material, which is suitable for the alloplastic tissue replacement of certain wall structures of the facial skeleton.

Characteristic of the known solutions

For the manufacture or recovery of tissue aggregate for certain wall structures of the mid-aspect skeleton, i.a. of thin bony and connective tissue structures of the nasal cavity system, the orbital walls and the frontal skull base, the following procedures are usedϊ

- Removal of endogenous bone or cartilage from another body region and transplantation into the existing defect »

Chemical denaturation of tissue derived from the hard meninges of human corpses, so-called lyophilized dura mater.

~ Further processing of polymers by known methods of plastic processing.

These known methods for obtaining or producing the implant material have significant disadvantages. When using the body's own implants, a second operation to obtain the implant material is required.

The preparation and storage of iyophilized dura mater is very time consuming and costly. Furthermore, their storage is only limited time possible, so that a constant availability can be guaranteed only with great effort * Although the production of implant material from polymers is expensive, but a major disadvantage is that the tissue compatibility is not always to the required extent given is.-. ; / ... - -

It is also known from other fields of medicine, such as dentistry and orthopedics, to use implant material made of carbon steel. The materials used here are glassy carbon or mechanically very solid carbon materials that can only be applied by means of Zero stress may have a pyrocarbon coating. Such materials may be used as soft and hard tissue substitutes. not be used.

Object of the invention

The aim of the invention is to provide a method for producing a fully synthetic implant material as a hard and soft tissue replacement, which can be produced inexpensively, is virtually unlimited shelf life and thereby has a very high .Biocompatibility «

Explanation of the essence of the invention

The object of the invention is to provide a method for producing a fully synthetic implant material, which makes it possible to use a material from the group of carbon material e as a hard and soft tissue replacement for wall structures of the facial skeleton.

According to the invention, this object is achieved in that commercially available graphite foil, which is completely unsuitable as an implant material, as a starting material for the process according to the invention is used,

Graphite foil is a sheetlike coal ns toffwe'rkst off, the

With layer thicknesses of 0.1 to 1 mm it is characterized by flexibility, easy machinability and by a high gas and liquid impermeability perpendicular to the film plane.

Commercially available graphite foil is unsuitable for medical use because of its preparation and properties. As a result of its production, it may contain 2 to 3% by mass of raineralogical impurities as well as residues of strong acids. Tack resistance and flexibility are inadequate for medical use * Graphite foil tends to break under heavy bending conditions. Furthermore, the surface abrasion resistance is low «

The inventive method is that Graphitfoli © is subjected to a high temperature treatment at temperatures above 2300 K, then a profiling of the surface in the form of alternating impressions of elevations and depressions is such that the additional deformation of the graphite foil at any point exceeds 30 % of the film thickness and Finally, a pyrolytic Hartkohlesohicht is applied.

The pyrolytic hard carbon layer is deposited in a temperature range of 13ΟΟ to 1600 K from hydrocarbons at vapor pressures of 1 to 20 Torr, after the beginning of the coating, the entire apparatus with the prepared graphite foil therein to a vacuum of at least

 5 x 10 torr was brought.

The profiling can be done by embossing with a ribbed roller as a parallel strip arrangement or as a crosswise strip arrangement.

Particularly favorable properties with respect to the deformability of the implant material are achieved if dife surface

  profiling as interrupted high and low embossing takes place in cross grid arrangement.

By the high temperature treatment according to the invention. the nest-like mineralogical impurities as well as any acid residues are completely expelled or reduced to medically harmless values · At the same time the stiffness of the material is considerably improved by a temperature-induced alignment of the graphite fins »

The subsequent surface profiling creates a complex of properties that made the use of the pyrolytic carbon coating to increase strength and simultaneously improve flexibility even smoother, non-profiled graphite foil is already so stiff and stiff with applied pyrocarbon layers of layer thicknesses greater than 0.5-1 Aim it is fragile that an operation is eliminated for the said biomedical purpose.

Due to the type of profiling, the properties of the film can be varied within a wide range of application-specific applications. A parallel profiling results in a very good flexibility and extensibility in the direction perpendicular to the rib arrangement, so that with increasing thickness of the high-strength pyrolytic cover layer large strengths can be realized. However, stiffness and thus the risk of breakage when adapting to the skeletal defect in the direction transverse to the ribs increases considerably. '

Cross-crimping is useful for many purposes because it allows good stiffness to be achieved with high remaining flexibility in all directions. Furthermore, a cross-raster embossing offers advantages in the long-term fixation of the film in the tissue, since the native tissue from both sides grows into the alternating raster subjects and thus causes a firm anchorage »

The embossing is effective only when applied in the form of alternating peaks and valleys without substantial additional densification of the film. The hard carbon layer deposited according to the invention has the particular advantage of high anisotropy of the physical properties. Special importance here has the agreement

  , - 5 -. ·

the coefficient of thermal expansion of the graphite foil backing and the applied pyrocarbon layer. Furthermore, the cover layer has high hardness and abrasion resistance, high purity, high tensile strength and excellent biocompatibility.

embodiment

Me invention will be explained in more detail below in exemplary embodiments.

.Be is pie I ₁ J ₁

Graphite foil of 0.5 tarn thickness and with an ash content of 0.9 % is subjected to a heat treatment at 2500 K for 30 minutes and then provided with a cross pattern grid between 2 staggered rolls such that the crosswise raised and recesses alternate and the annealed Foil does not experience a change in thickness at any point, which is more than 30 % of the initial thickness. Subsequently, the surface profiled foil

-2 under a vacuum of 5x10 Torr to a temperature of

1515 * 2 K heated, awake At this temperature, η-hexane is passed over the film at a pressure of 3 »5 torr for 30 minutes.

After coating, the film has a hard wear resistant surface layer of 2 μm thick, an ash content of less than 0.01% by weight and a tensile strength higher by a factor of 2.5 compared to the starting state, with increased rigidity and well-formed flexibility in all Directions on.

Example 2. .

Graphite foil with a thickness of 0.2 mm is subjected to high-temperature annealing according to Example 1, then provided with a parallel profiling and coated at 1600 K for 90 minutes. The film thickness is then 10 μm. The film has a tensile strength increased by the factor 5, with the flexibility still present in the direction perpendicular to the profile of the profiling ribs.

Claims (4)

Claim of invention. 1. A process for the production of implant material as a hard and soft tissue replacement, characterized in that graphite foil is subjected to a high temperature treatment at temperatures above 2300 K, then a surface profiling in the form of alternating impressions of elevations and depressions is such that the additional deformation of the graphite foil at any Replace 30 % of the film thickness; and, finally, a pyrolytic hard carbon layer is deposited in the temperature range of 1300 to 1600 K from hydrocarbons at steam pressures of 1 to 20 Torr. , . 2. Process for the production of implant material according to item 1, characterized in that the surface profiling takes place as a parallel strip arrangement 3 »Method for the production of implant material ¹ according to: Item 1, characterized in that the surface profiling takes place as a crosswise arrangement of strips, 4 * Procedure for. Production of implant material after. Point 1, characterized in that the surface profiling takes place as interrupted high and low embossing in cross grid arrangement.