EP4313448A1

EP4313448A1 - Composite material comprising a silver infiltration as an antibacterial matrix material especially for biofilm reduction

Info

Publication number: EP4313448A1
Application number: EP22717168.3A
Authority: EP
Inventors: Clemens Meyer-Kobbe
Original assignee: Meko Manufacturing EK
Current assignee: Meko Manufacturing EK
Priority date: 2021-03-24
Filing date: 2022-03-23
Publication date: 2024-02-07
Also published as: WO2022200429A1; EP4063042A1

Abstract

The present invention relates to a composite material made of an open-pored porous, sintered matrix material and elemental silver, wherein the elemental silver is infiltrated into the pores of the open-pored porous, sintered matrix material, the content of silver in the composite material is between 6% by weight and 30% by weight and the open-pored porous, sintered matrix material consists of at least one metal, at least one metal alloy or at least one ceramic, to processes for producing this composite material and to medical implants containing this composite material. The composite material is especially suitable for reduction and avoidance of biofilm formation.

Description

Composite material with silver infiltration as an antibacterial matrix material, in particular for biofilm reduction

description

The present invention relates to a composite material made from an open-pore, porous, sintered matrix material and elemental silver, the elemental silver being infiltrated into the pores of the open-pore, porous, sintered matrix material, the silver content in the composite material being between 6% by weight and 30% by weight. % is, and the open-pored, porous, sintered matrix material consists of at least one metal, at least one metal alloy or at least one ceramic, as well as methods for producing this composite material and medical implants containing this composite material. The composite material is particularly suitable for reducing and avoiding biofilm formation.

The present invention also describes an antibacterial composite material for medical implants, preferably long-term medical implants, in particular for use as bracket material in orthodontics. No surface coating is applied, but antibacterial silver is introduced by means of infiltration, e.g. into the pores of a metal or ceramic sinter. The silver does not form a closed surface, but has a sufficient long-distance effect to prevent biofilm adhesion over a large area.

State of the art

Biofilm formation in the oral environment is one of the central problems in dentistry. Microorganisms trigger caries, periodontal diseases and other dental diseases, which are the main diseases to be treated in dentistry.

Inadequate oral and dental hygiene and the associated biofilm formation leads to tooth decay in patients of all ages, also known as caries for short. According to Wikipedia, tooth decay is “a multifactorial destructive disease of hard tooth tissue, enamel and dentine. It develops with the participation of microorganisms and starts from a tooth surface that has been “decalcified” by the action of acids.”

Biofilm formation also promotes the development of periodontitis, i.e. an inflammatory disease of the entire periodontium including the jawbone. Adult patients in particular are affected by the attachment of Plaque on intraoral surfaces is at increased risk of periodontitis. As a result, chronic periodontitis can develop or worsen, which, if left untreated, can lead to loosening of the teeth due to loss of attachment and, in extreme cases, ultimately to tooth loss.

A close association of this oral plaque accumulation with systemic diseases of the body, such as arteriosclerotic changes in the blood vessels, has also been scientifically proven.

Undesirable biofilm formation is also of immense importance in orthodontics and particularly affects the large patient group of young people in puberty, whose motivation in the field of dental care is often restrained. To make matters worse, young patients are more susceptible to gingivitis, an inflammation of the marginal gums caused by bacteria, due to pubertal hormonal changes.

Adult patients also increasingly want their misaligned teeth to be corrected, since the importance of orthodontic treatment of misaligned teeth and jaws has increased significantly in society. This growth can be explained on the one hand by the increasing health awareness of the population and on the other hand by the extended therapeutic possibilities in the field of orthodontics. Treatments with completely individual lingual appliances now enable precise orthodontic tooth position correction with almost no aesthetic impairments.

Fixed orthodontic appliances, regardless of a buccal or lingual insertion, require a lot of cleaning due to their complex geometry. This goes hand in hand with extremely good patient compliance if the occurrence of undesirable side effects such as demineralization of tooth enamel, the development of caries or periodontal changes is to be reduced. In particular, the development of demineralization (decalcification) of the tooth enamel as a result of biofilm formation in the oral environment is regarded as a central problem in orthodontics.

As the case numbers of patients treated with fixed appliances and the patient age increase, a major focus of clinical research is the occurrence of such, through medical treatment to avoid the (iatrogenic) effects that have arisen during orthodontic therapy.

To date, biofilm avoidance on orthodontic treatment appliances has not been possible, even with very good patient compliance. Tooth cleaning is made more difficult with orthodontic appliances, especially with fixed treatment appliances. Fixed orthodontic

Treatment devices, such as brackets, have niches that are difficult to clean due to their geometry, which can lead to demineralization of the tooth enamel in the area around the brackets if there is insufficient oral hygiene.

You can counteract the formation of biofilms by cleaning your teeth thoroughly several times a day, but without being able to completely eliminate them. A thin enamel membrane made of adsorbed proteins enables early bacterial colonizers to adhere to the enamel immediately after mechanical removal of the biofilm. The plaque then continues to grow due to the accumulation of late colonists. The resulting three-dimensional biofilm structure of bacteria, embedded in a matrix of extracellular polysaccharides, can be very different in relation to each other. Depending on the type of bacteria and the surrounding conditions, the proportion of bacteria in the matrix varies between 2 - 15% by volume or 60 - 70% by volume. In this state, the biofilm can no longer be eliminated by the self-cleaning effects of the oral cavity. The bacteria metabolize carbohydrates into organic acids and an acidic anaerobic environment is created. As a result, calcium and phosphate ions are released from the crystal lattice structure of the tooth enamel. In the long term, this decalcification of the enamel becomes visible as irreversible white spots, so-called "white spot lesions".

The "white spot lesions" are the initial stage of a carious lesion of the tooth. If the acidic environment persists and demineralization processes progress, the initial enamel caries leads to dentine caries.

To make matters worse, regular fixed orthodontic therapy usually lasts around 18-24 months. During the entire treatment period, the brackets are fixed to the teeth and connected to each other with archwires and ligatures. The orthodontic material, which was inserted at the beginning of the treatment, is therefore exposed in the oral cavity and exposed to the intraoral conditions for a very long time. In current medical and dental research, efforts are being made to avoid this microbial colonization on material surfaces in the oral cavity ab initio, ie from the time of insertion.

There are various strategies to minimize the undesired clinical side effects of fixed treatment appliances. In the course of increasing health awareness, preventive treatment concepts for biofilm reduction are becoming increasingly important.

In general, the aim is to counteract the favorable propagation environment for microorganisms in the mouth through improved oral hygiene or to select dental materials with reduced biofilm affinity (in each case depending on the material and its surface) or to provide the orthodontic appliances with bactericidal properties.

The various concepts that exist to reduce demineralization of tooth enamel during orthodontic treatment are presented below. a) Improvement of individual oral hygiene

A preventive approach lies in patient motivation and guidance. The focus here is on improving oral hygiene at home. In addition, the reduction of the oral biofilm is of great importance as part of the professional tooth cleaning that is to be carried out every six months. In addition, an increase in the acid resistance of the tooth enamel can be achieved by regular home and in-office fluoridation. The use of antimicrobial or fluoride-containing mouthwash solutions, which can noticeably reduce the formation of biofilms, is recommended. One of the aims is to effectively reduce the cariogenic bacterium Streptococcus mutans and to have an inhibitory effect on Aggregatibacter actinomycetemcomitans.

However, as explained above, even with good patient compliance and good oral hygiene, biofilm formation can only be reduced but not avoided. b) Fluoride-containing orthodontic adhesives

Fixing adhesives (adhesives for fixing the brackets) that are mixed with fluoride nanoparticles are used. These fluoride-containing fastening materials lead to increased resistance of the Tooth hard substance against an acidic anaerobic environment and thus for less demineralization of the enamel. In the area of fluoride-containing luting composites, a tendency towards less demineralization of the enamel could be determined.

Due to their size, nanoparticles can penetrate cells and are viewed critically due to the lack of known side effects and the often insufficiently researched risks. c) Modification of the immediate area around the bracket

A mechanical-chemical barrier against acid attack can be created by sealing the enamel in the immediate vicinity of the bracket. However, the seals are not very resistant to abrasion and therefore only have a temporary effect. d) Coatings of bracket appliances

Antibacterial coatings on brackets prevent biofilm formation from the start while at the same time ensuring good biocompatibility. The coatings are applied over the entire surface, i.e. the antibacterial top layers have a completely closed surface, which encapsulates the base material, i.e. the actual bracket material.

One method is to seal orthodontic appliances with polytetrafluoroethylene (PTFE) to prevent polysaccharide adhesion. The formation of an adherent biofilm can be greatly minimized. However, due to the prevailing oral conditions, there is rapid abrasion of sealants applied to the surface and thus a rapid loss of the antibacterial effect.

Alternatively, antibacterial coatings applied galvanically or by means of the physical vapor deposition (PVD) process are suitable. Silver was often used as a biocompatible and antibacterial material.

An animal study on rat teeth demonstrated that silver-coated surfaces of orthodontic appliances without additional oral hygiene have an antibacterial effect due to good patient compliance. The study shows that the coating leads to a reduced development of Streptococcus mutans and thus reduces the risk of tooth decay. In general, however, coatings in the mouth are rubbed off and only have a temporary effect.

In addition to pure silver, investigations into the effect of silver nanoparticles in dentistry and orthodontics have been carried out. It has been shown that the addition of 5% or 10% silver/hydroxyapatite nanoparticles to orthodontic luting adhesives inhibits further bacterial growth and thus has an antibacterial effect in the immediate vicinity of the adhesive. The addition of silver nanoparticles in adhesives leads to an inhibition of further growth of Streptococcus mutans.

Chinese patent application CN 111 197 130 A discloses powdered Co-based alloys containing 1-5% by weight of silver, which are used for tooth restorations or dental prostheses. The dental prostheses can be produced from the powdered alloys using 3D printing (selective laser melting).

Chinese patent CN 102 648 876 B discloses an antibacterial orthopedic dental wire made of a titanium-nickel alloy, wherein 0.1 to 20% by weight of granular silver is dispersed in the orthopedic wire. The mass ratio of titanium and nickel in the antibacterial orthopedic wire is 45:55-55:45. The wire can be made from a powdered titanium-nickel-silver mixture by melting, sintering or high-temperature synthesis.

Feilong et al. (Materials & Design 2019, 184, 108190) report on a cobalt alloy with antibacterial properties containing 30 at.% chromium and 5 at.% silver. The alloy is made by sintering a powder mixture of cobalt, chromium and silver.

However, silver nanoparticles are not only incorporated into luting adhesives or cements, but also used as a coating. It has been demonstrated that bacterial adhesion can be prevented on dentine coated with silver nanoparticles.

Silver nanoparticles have a size of up to 100 nm and are therefore able to occur outside of solid and liquid solid states. They can have a cytotoxic effect by affecting the cell cycle, DNA and cell apoptosis. Above a certain concentration, silver nanoparticles have a cell and genotoxic effect on human mesenchymal stem cells character and cause DNA damage, cell death and functional impairment.

Despite the numerous positive studies that prove an antibacterial effect of silver nanoparticles, commercial use in the medical field should therefore be viewed critically due to numerous studies that show that nanoparticles pose a health risk.

However, as described above, pure silver coatings have the disadvantage of low abrasion resistance. A problem for superficially applied coatings within the oral cavity is the high intraoral abrasion load due to strong shearing and muscle forces of the teeth, tongue and perioral muscles as well as the attack by various liquids in the oral cavity. The antibacterial effect is quickly lost as a result of partial damage or extensive abrasion of the usually very thin coatings. The antibacterial protective effect is therefore not permanent.

The serious disadvantage of all surface coatings in dentistry is consequently the high level of abrasion in the oral cavity, which leads to abrasion of the coatings after just a short time.

There are currently no materials or coating techniques with a satisfactory, long-lasting antibacterial effect for treatment appliances in orthodontics to prevent the formation of the initial intraoral biofilm. None of the prevention concepts shown can inhibit increased plaque accumulation over a longer period of time to such an extent that the central problem of the development of “white spot lesions” does not occur with multi-bracket appliances.

For the reasons mentioned, there is a need to develop a medical implant that not only prevents the formation of biofilm, e.g. on orthodontic appliances intraorally, but also has good resistance to shearing forces and abrasion.

The object of the present invention is therefore to provide a material for an implant and an implant that prevents the formation of a biofilm or at least counteracts the formation of it while at the same time being resistant to shearing forces and abrasion in order to achieve a permanent protective effect. According to the invention, this object is achieved by the technical teaching of the independent claims. Further advantageous configurations of the invention result from the dependent claims, the description, the figures and the examples.

It has been found that coatings and even unusually thick coatings of an implant with an antibacterial material or active ingredient only provide short-term protection against the formation of a biofilm, since such coatings are insufficiently stable with respect to the forces acting on them and are abraded.

Surprisingly, however, it was found that a complete coating of an implant with an antibacterial material or active substance is not necessary at all, but rather an infiltration of elemental silver into an open-pored, porous, sintered matrix material leads to a composite material that permanently protects and protects against biofilm formation on the composite material this protection is also not reduced by forces acting on the composite material.

The present invention thus relates to a composite material made from an open-pore, porous, sintered matrix material and elemental silver, the elemental silver being infiltrated into the pores of the open-pore, porous, sintered matrix material, the silver content in the composite material being between 6% by weight and 30% by weight. -% is, and the open-pore, porous, sintered matrix material consists of at least one metal, at least one metal alloy or at least one ceramic.

matrix material

The term “open-pore, porous, sintered matrix material” as used herein refers to the base material made of a metal, a metal alloy or a ceramic, which is produced in a sintering process and in whose pores the elemental silver is infiltrated. The matrix material itself has no antibacterial properties.

"Sintered" here means that a powdery starting material is pressed together to form a sinter with a specific grain size and then shaped into a solid matrix material by heat treatment.

In principle, all metals, metal alloys and ceramics with the following properties are suitable as matrix material: a) Biocompatibility (corrosion-resistant, haemocompatible, non-cytotoxic and genotoxic, non-carcinogenic), b) abrasion resistance that is usual for dental implants, c) sinterability for the production of porous materials, d) low brittleness, ie sufficient ductility not to withstand sudden stress to break.

Preference is given to those metals, metal alloys and ceramics which, in addition to the properties a) to d) mentioned, have a melting point above the melting point of silver (961.8° C.).

Examples of preferred matrix materials are metals and metal alloys approved for implants, such as stainless steel (e.g. 316LVM®, 316L medical), Co-based alloys or CoCr materials (e.g. L605®, Phynox®, MP35N®), nickel free iron-chromium-manganese alloys such as Vasculoy®, cobalt-nickel-chromium alloys such as Duratherm®, iron-chromium-nickel alloys such as Durinox®, iron-cobalt-nickel alloys such as Durnico® and Phytime ®, titanium alloys, tantalum and tungsten as well as ceramics made of aluminum oxide or zirconium dioxide.

Composition of Vasculoy® (weight %)

Composition of Duratherm® 600 (in percent by weight)

Composition of Durinox® (weight %)

Composition of Durnico® (weight %) Composition of Phytime® (weight %)

Metals and metal alloys, preferably austenitic metals and austenitic metal alloys, are therefore suitable as matrix material. Examples are stainless steels, CoCr alloys, iron-chromium-manganese alloys, cobalt-nickel-chromium alloys, iron-chromium-nickel alloys, iron-cobalt-nickel alloys, titanium alloys, tantalum and tungsten, and aluminum oxide ceramics Zirconium dioxide ceramics. The metals, metal alloys and ceramics are suitable as materials for dental implants.

The term "abrasion resistance" or "abrasion resistance" as used herein denotes a high resistance to abrasion, so that scraping and abrasion occur only to a small extent, which is normal in the dental field. A certain abrasion is tolerable and also unavoidable. An advantage according to the invention, however, is that the silver is homogeneously distributed in the matrix material, so that even in the event of abrasion, silver repeatedly comes to the surface, which prevents the formation of a biofilm.

The term "sinterability" as used herein is defined as follows:

The ability to form a workpiece from fine-grained ceramic or metallic materials under high temperatures (but below the melting temperatures of the main components) and often under pressure, so that the shape of the workpiece is retained.

The term "brittleness" as used herein is defined as follows:

Brittleness is a material property that describes the failure or fracture behavior. A brittle material can only be plastically deformed to a small extent and is therefore characterized by low ductility.

The term "porosity" as used herein represents the ratio of the void volume to the total volume of the matrix material and is made up of the sum of the voids that are connected to each other and to the environment (open porosity) and the voids that are not interconnected. It serves as a classifying measure of the actual present cavities. The porosity can be represented by the following formula where V _H denotes the void volume, V the total volume and V _F the net volume of the solid.

The matrix materials used here have a high open porosity; they are therefore »open-pore porous«. A porosity of the matrix material of less than 30%, preferably less than 20%, more preferably less than 15% has proven advantageous. With a porosity of 6% - 10%, corresponding to a silver content of 6% - 10%, the antibacterial effect is reduced and below 6% it is almost non-existent.

Silver as an antibacterial filler

It has been proven that silver has an antibacterial and healing effect when it comes into contact with blood or tissue. The antibacterial effect of silver is based on the permeabilization of the bacterial cell membrane and the formation of intracellular complexes with bacterial enzymes that are difficult to dissolve. This leads to the destruction of the bacterial respiratory chain and the inhibition of the DNA replication of the microorganisms.

Due to the infiltration of silver into the matrix material, the silver cannot be removed completely by abrasion, as would be the case with a coating made of silver or containing silver. Rather, there is always a sufficient concentration of silver on the surface of the composite material so that biofilm formation is prevented or at least greatly reduced in the long term.

According to the invention, the silver must be infiltrated into the pores of the open-pore, porous, sintered matrix material, so that not only does the surface of the matrix material have an antibacterial effect, but a composite material is created which is antibacterial not only on its surface but throughout the entire material. By infiltration of the elemental silver in the open cavities or open pores of the matrix material, a distribution of the silver in the matrix material is achieved such that per arbitrarily selected unit volume of composite material, the same mass of matrix material and the equal masses of silver are included. The deviations in the mass of matrix material and the mass of silver between two arbitrarily chosen volume units of the composite material are not more than 20%. Illustratively, this means the following. If in an arbitrarily chosen unit volume of the composite material of 0.1 mm ³ there is 90% by weight of matrix material and 10% by weight of silver, in any other unit volume of the composite material of 0.1 mm ³ between 8% by weight and 12 Wt .-% silver must be included.

This is illustrated in FIG. 1, which shows a scanning electron micrograph of a cross section of a porous tungsten matrix material. The stored silver is shown in black. The distribution of the silver throughout the tungsten matrix material can be clearly seen.

The elemental silver content in the composite material is between 6% by weight and 30% by weight, more preferably between 7% by weight and 25% by weight, more preferably between 8% by weight and 20% by weight , more preferably between 9% and 17% and most preferably between 10% and 15% by weight silver based on the composite material.

According to the invention, the silver is also infiltrated into the pores of the open-pore, porous, sintered matrix material in such a way that the pores are at least partially filled with elemental silver. In a preferred embodiment, the pores of the matrix material are completely filled with elemental silver. In this way, a long-lasting antibacterial effect and, at the same time, high abrasion resistance can be achieved.

composite material

"Composite material" as used herein means the combination of matrix material and silver, with a certain amount of elemental silver being infiltrated into the pores of the open-pored, sintered matrix material. An antibacterial composite material is thus obtained which is not only antibacterial on its surface but also at any point within the composite material. The composite material in the medical implant therefore has no antibacterial coating.

The composite material is thus a new material made of matrix material and elemental silver distributed therein and not a matrix material with an antibacterial coating. This means that even with abrasion and even with heavy abrasion, the The antibacterial properties of the composite material are retained, since abrasion repeatedly causes silver to come to the surface of the composite material, thereby maintaining the antibacterial effect over the long term.

Coatings as antibacterial surfaces are therefore unsuitable for guaranteeing a long-term antibacterial effect for the aforementioned reasons. The composite material according to the invention combines both properties in an ideal way. It consists of a porous matrix material with infiltrated silver as an intramatrix filler. The matrix material ensures stability and gives the composite material high abrasion resistance, and the infiltrated, homogeneously distributed silver ensures the antibacterial effect not only on the surface of the composite material and maintains the antibacterial effect even in the case of severe abrasion.

In addition, the composite material is neither an alloy nor a mixed crystal of silver and the components of the matrix material. An alloy is a macroscopically homogeneous metallic material made up of at least two elements, at least one of which is a metal, and which together exhibit the metal-typical feature of metal bonding. In the composite material according to the invention, elemental silver is infiltrated into the pores of the matrix material and at least partially fills them. There is therefore no compound in which the silver atoms are integrated into the crystal structure of the matrix material.

The composite material according to the invention thus serves to reduce or prevent the formation and adhesion of a biofilm to the surface of the composite material. Most importantly, the composite serves to permanently reduce or prevent the formation and adhesion of a biofilm to the surface of the composite while the composite is in the body.

Production of the composite material with silver infiltration

The composite material according to the invention can be produced in a sintering process and subsequent silver infiltration.

Thus, a further aspect of the present invention lies in a method for producing the composite material described herein, comprising the following steps:

A) Provision of a granular powder or a granular powder mixture of the matrix material; B) producing a sintered blank from the granular powder or from the granular powder mixture of the matrix material from step A);

C) sintering of the sintered blank according to step B) below the melting temperature of the matrix material to form an open-pore, porous sintered compact with a porosity of 6% to 30%; and

D) infiltration of the open-pored porous sintered body according to step C) with elemental silver until the pores are at least partially filled with elemental silver.

The sintering process can be carried out using a pressed sinter blank, a granular powder or a granular powder mixture of the matrix material, using laser sintering of powder layers of the matrix material, or using a 3D-printed sinter blank.

A sintered blank is pressed from fine-grained metal or ceramic powder or from a mixture of different grain sizes of a metal or ceramic powder. The sintered blank usually already has the desired shape

workpiece or molded part. Through heat treatment with or without applying pressure below the melting temperature, the actual sintering process, the powder particles are connected to one another and the sintered blank is compacted and hardened into a "sintered compact". The starting materials are, to put it colloquially, “baked together”. The sintered matrix material, i.e. the sintered part, must have open porosity.

The porosity of the sintered part must be large enough that silver can infiltrate the matrix material and then there is enough silver in the matrix material or in the composite material to ensure an antibacterial effect. On the other hand, the porosity should only be so large that as little expensive silver as possible is consumed and the abrasion resistance of the matrix material is retained or only slightly reduced.

A porosity of the matrix material of less than 30%, preferably less than 20%, more preferably less than 15% has proven advantageous. With a porosity of 6% - 10%, corresponding to a silver content of 6% - 10%, the antibacterial effect is reduced and below 6% it is almost non-existent.

Thus, a further aspect of the present invention lies in a method for producing the composite material described herein, comprising the following steps: A) Provision of a granular powder or a granular powder mixture of the matrix material;

B) pressing a sintered blank from the granular powder or from the granular powder mixture of the matrix material from step A);

In a preferred embodiment, the method for producing the composite material described herein comprises the following steps:

A) Provision of a granular powder or a granular powder mixture of the matrix material;

C) sintering of the sintered blank according to step B) with or without application of pressure by heat treatment below the melting temperature of the matrix material to form an open-pore, porous sintered compact with a porosity of 6% to 30%; and

The porosity according to step C) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and

12%

The sintered blank is preferably already produced in the shape of the desired workpiece or molded part.

In step D), the pores of the open-pore porous sintered compact according to step C) are preferably completely filled with elemental silver.

The composite material according to the invention can also be produced by means of laser sintering and subsequent silver infiltration:

A more recent method is the production of the sintered parts using what is known as selective laser sintering (SLS), an additive manufacturing method to produce three-dimensional structures by sintering with a laser beam from a powdery starting material. Using a squeegee, a powder or a powder mixture of matrix material is applied to a construction platform in a thin layer over the entire surface. The component contour is gradually sintered or melted into the powder bed layer by layer by rapid lateral deflection of the laser beam in the x and y directions, according to the respective layer contour of the component. The beam energy of the focused laser beam is absorbed by the powder and leads to locally limited sintering of the powder particles. The construction platform is lowered slightly after each laser sintering/melting process and a new layer of powder is applied. The workpiece is thus built up layer by layer. At the end of the process, the remaining powder is simply removed and some of it can be reused for the next run.

By using a powder or a powder mixture as a matrix material, such as stainless steel, an abrasion-resistant, open-pored porous sintered part can be produced. This method offers the advantage of being able to create almost any shape.

Thus, the present patent application relates to a method for producing a molded part from the composite material described herein, comprising the following steps:

B) Application of a thin layer of the powder or the powder mixture from step A) to a construction platform;

C) sintering of the applied thin layer according to step B) by means of a laser;

D) repeating steps B) and C) until the composite material molding is obtained, and

E) infiltrating the molded part with elemental silver until the pores are at least partially filled with elemental silver.

The porosity of the molding is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%.

In step E), the pores of the molding are preferably completely filled with elemental silver. The composite material according to the invention can also be produced using the 3D printing process (binder jetting) and subsequent silver infiltration:

Similar to laser sintering, the binder jetting process creates a molded part in layers from a powdered starting material. The powdered starting material is bonded with a liquid binding agent (binder) at selected points of each powder layer.

In 3D printing, a powder or a powder mixture of matrix material is applied to a construction platform in a thin layer over the entire surface. The powder layer is then bonded with a binder at the points that belong to the workpiece. The binder is applied with a print head. The construction platform is lowered slightly after each binder printing process, and a new layer of powder and additional binder is applied. The workpiece is thus built up layer by layer. At the end of the process, the binder is thermally cured and the remaining loose powder is easily removed and partially reused for the next run. The workpiece can then be debound by thermally driving out the binder or the binder components, with the workpiece being sintered.

C) selectively applying a binder to the applied thin layer of step B);

D1) repeating steps B) and C) until the molded part has been obtained from the composite material,

D2) curing of the applied binder,

D3) removing the remaining loose powder,

D4) sintering of the molded part to form an open-pore, porous sintered part and expulsion of the binder,

E) Infiltration of the open-pored porous sintered body with elemental silver until the pores are at least partially filled with elemental silver. The porosity of the molding according to step D4) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%.

In step E), the pores of the molding according to step D4) are preferably completely filled with elemental silver.

In a preferred embodiment, the method for producing a molded part from the composite material described herein comprises the following steps:

C) selectively applying a binder to the applied thin layer of step B);

D2) curing of the applied binder,

D3) removing the remaining loose powder,

D4) sintering the molding according to step D2) to form an open-pored porous sintered part with a porosity of 6% to 30%, and removing the binder in the process,

E) infiltrating the open-pored porous sintered body according to step D4) with elemental silver until the pores are at least partially filled with elemental silver.

The porosity of the sintered compact according to step D4) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%.

In step E), the pores of the sintered compact according to step D4) are preferably completely filled with elemental silver.

Subsequent infiltration of the pores with elemental silver can be achieved by immersing the sintered part in a silver melt or by galvanic deposition.

Melting down silver:

During melting, the sintered part is immersed in molten silver under negative pressure conditions and silver is thus immersed in the open-pored sintered material infiltrated. The negative pressure ensures that the silver penetrates and fills all pores of the sintered part.

With this method, it is obvious to a person skilled in the art that the matrix material would also melt if it consisted of materials having a melting point below the melting point of silver. Accordingly, in this process, materials must be selected that have a higher melting point than the melting point of silver, i.e. greater than 962 °C.

Thus, one embodiment of the present invention relates to a method for producing the composite material described herein, comprising the following steps:

B) producing a sintered blank from the granular powder or from the granular powder mixture of the matrix material from step A);

C) sintering of the sintered blank according to step B) below the melting temperature of the matrix material to form an open-pored sintered body with a porosity of 6% to 30%; and

D1) immersing the open-pore porous sintered body according to step C) under reduced pressure conditions in molten elemental silver until the pores are filled with elemental silver;

D2) Removal of the sintered part according to step D1) from the liquid silver and cooling to room temperature.

In a preferred embodiment of the present invention, the method for producing the composite material described herein comprises the following steps:

C) sintering of the sintered blank according to step B) with or without application of pressure by heat treatment below the melting temperature of the matrix material to form an open-pored sintered compact with a porosity of 6% to 30%; and

D1) immersing the open-pore porous sintered body according to step C) under reduced pressure conditions in molten elemental silver until the pores are filled with elemental silver; D2) Removal of the sintered part according to step D1) from the liquid silver and cooling to room temperature.

The porosity according to step C) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%.

In step D1), the pores of the open-pore porous sintered compact according to step C) are preferably completely filled with elemental silver.

In a further embodiment, a method for producing a molded part from the composite material described herein comprises the following steps:

D) repeating steps B) and C) until the molded part has been obtained from the composite material,

E1) dipping the shaped part according to step D) into molten elemental silver under vacuum conditions until the pores are filled with elemental silver, and

E2) Removal of the molding according to step E1) from the liquid silver and cooling to room temperature.

The porosity of the molding according to step D) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%.

Preferably, in step E1), the pores of the molding according to step D) are completely filled with elemental silver.

In a further embodiment, the method for producing a molded part from the composite material described herein comprises the following steps:

A) Provision of a granular powder or a granular powder mixture of the matrix material; B) Application of a thin layer of the powder or the powder mixture from step A) to a construction platform;

C) selectively applying a binder to the applied thin layer of step B);

D1) repeating steps B) and C) until the molded part has been obtained from the composite material, and D2) curing the applied binder,

D3) Removal of the remaining loose powder from the molded part according to step

D2),

E1) immersing the open-pored porous sintered body according to step D4) under reduced pressure conditions in molten elemental silver until the pores are filled with elemental silver, and

E2) Removal of the sintered part according to step E1) from the liquid silver and cooling to room temperature.

The porosity of the molding according to step D4) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%.

In step E1), the pores of the molding according to step D4) are preferably completely filled with elemental silver.

C) selectively applying a binder to the applied thin layer of step B);

E1) repeating steps B) and C) until the molded part has been obtained from the composite material,

E2) curing of the applied binder,

E3) removing the loose binder from the molded part according to step E1),

E4) sintering of the molded part according to step E2) to form an open-pored sintered part with a porosity of 6% to 30% and expulsion of the binder, F1) dipping the sintered part according to step E4) into molten elemental silver under reduced pressure conditions until the pores are filled with elemental silver, and

F2) Removal of the sintered part according to step F1) from the liquid silver and cooling to room temperature.

The porosity of the sintered compact according to step E4) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%.

In step F1), the pores of the sintered body are preferably completely filled with elemental silver in accordance with step E4).

Electroplating of silver:

In an alternative embodiment, the infiltration with elementary silver can also be carried out by separating silver from an aqueous solution containing silver ions (silver bath), through which electric current is passed by means of two electrodes (cathode and anode). Elemental silver then infiltrates into the pores of the sinter when it is in contact with the cathode.

Thus, a further embodiment of the present invention relates to a method for producing the composite material described herein, comprising the following steps:

D′1) immersing the open-pore porous sintered body according to step C) in a silver bath and galvanically depositing elemental silver until the pores are at least partially filled with elemental silver;

D'2) Removal of the sintered part according to step D'1) from the silver bath.

In a further embodiment of the present invention, the method for preparing the composite material described herein comprises the following steps: A) Provision of a granular powder or a granular powder mixture of the matrix material;

D'2) Removal of the sintered part according to step D'1) from the silver bath.

12%

Preferably, the sintered blank is already provided in the desired shape

workpiece or molded part.

In step D′1), the pores of the open-pore porous sintered compact according to step C) are preferably completely filled with elemental silver.

In another embodiment, a method of making a

molding from the composite material described herein, the following steps:

E1) immersing the shaped part according to step D) in a silver bath and galvanically depositing elemental silver until the pores are at least partially filled with elemental silver; and

E2) removal of the molding according to step E1) from the silver bath.

The porosity of the molding according to step D) is preferably between 6% and 20%, more preferably between 8% and 15% and even more preferably between 10% and 12%. Preferably, in step E1), the pores of the molding according to step D) are completely filled with elemental silver.

C) selectively applying a binder to the applied thin layer of step B);

D2) curing of the applied binder,

D4),

E1) immersing the open-pored porous sintered body according to step D4) in a silver bath and galvanically depositing elemental silver until the pores are at least partially filled with elemental silver; and E2) removal of the molding according to step E1) from the silver bath.

C) selectively applying a binder to the applied thin layer of step B); D1) repeating steps B) and C) until the molded part has been obtained from the composite material,

D2) curing of the applied binder,

D2),

D4) sintering of the molded part according to step D3) to form an open-pored porous sintered part with a porosity of 6% to 30% and expulsion of the binder,

E1) immersing the sintered part according to step D4) in a silver bath and galvanically depositing elemental silver until the pores are at least partially filled with elemental silver; and E2) removing the sintered part according to step E1) from the silver bath.

In step E1), the pores of the sintered compact according to step D4) are preferably completely filled with elemental silver.

Medical implant

The composite material according to the invention with silver infiltration should preferably be used in orthodontics for braces brackets. Due to the high-strength matrix material, the silver-infiltrated composite material withstands the high abrasive loads in the oral cavity. Surprisingly, the silver in the pores exhibits such a great antibacterial “remote action” that there is very little to no adhesion of a biofilm, even if the silver does not cover the entire surface like a coating. This was clearly demonstrated in a clinical study, as explained below.

The present invention thus preferably relates to dentistry and is intended to reduce or prevent the accumulation of bacteria on surfaces located intraorally (in the oral cavity). A composite material with infiltrated silver was developed for this purpose. The metal or ceramic matrix material ensures abrasion resistance and the infiltrated silver provides the antibacterial effect. The formation of a biofilm and the associated negative consequences for the teeth, the periodontium and other collateral diseases are avoided.

The antibacterial effect of the composite material according to the invention was demonstrated in the field of orthodontics on bracket material for braces. The otherwise resulting three-dimensional biofilm structure of bacteria, embedded in a matrix of extracellular polysaccharides, is prevented as soon as the fixed appliance is inserted. The bacteria that normally metabolize the supplied carbohydrates into organic acids and thereby create an acidic anaerobic environment are not present. As a result, no calcium and phosphate ions are released from the crystal lattice structure of the tooth enamel. The present invention prevents the initial stage of a carious lesion of the tooth. In addition, no whitish irreversible decalcification of the enamel is clinically visible.

The invention on which it is based satisfies the need to carry out gentle orthodontic treatment using preventive treatment concepts as part of increasing health awareness and as a result of clinical necessity.

According to the invention, the bracket material also withstands the highly abrasive loads to which orthodontic appliances are exposed as a result of shearing forces in the oral cavity. In contrast to previous coatings applied to the surface, which are soft and at high risk of abrasion, the composite material developed for e.g. brackets of dental braces itself has antibacterial properties according to the invention. In particular, the brackets made of the composite material according to the invention withstand the strong shearing forces in the oral cavity caused by the tongue and cheek. Unlike superficial coatings, the antibacterial protective effect is permanent. The regular orthodontic treatment time for a fixed therapy is approx. 18 - 24 months. For this entire period, an antibacterial effect to prevent "white spot lesions" has been demonstrated by the composite material.

Previous clinical investigations have clearly shown that the formation of biofilms on the composite material according to the invention with infiltrated silver is greatly reduced or completely prevented. The antibacterial silver works without the need for a closed antibacterial surface coating.

In addition, the investigations of the abrasion behavior have shown that the biofilm formation is significantly reduced over the entire therapy period. The composite material with infiltrated silver withstands the shear forces acting in the oral cavity. Even if the matrix material wears off during long-term use in the oral cavity, the silver infiltration in the base material means that there is always enough silver on the pore surface to ensure the antibacterial effect. This is also the clear advantage over the conventional antibacterial coatings, which do not withstand the abrasive load for long, so that an initially clear antibacterial effect is lost quite quickly. The infiltration and homogeneous distribution of the silver in the matrix material and thus in the composite material guarantees a consistently good and, above all, long-lasting antibacterial effect even in the case of heavy abrasion.

This is the first material available, preferably for dentistry, with a long-term antibacterial effect and high abrasion resistance. Especially in orthodontics and there preferably for multi-bracket appliances, decalcification of the tooth enamel and the resulting caries are avoided, even with long-term use.

Accordingly, the present invention relates to medical implants which contain the composite material according to the invention or consist of the composite material.

The medical implants described herein which consist of the composite material or the medical implants described herein which contain the composite material or components made of the composite material are particularly suitable for being subjected to shear forces and abrasion forces.

These medical implants can be short-term medical implants or long-term medical implants and preferably long-term dental implants.

In dentistry, other applications are also planned for this new composite material, for example anchoring devices such as transpalatal arches and lingual arches, which should also consist of antibacterial materials. Also inserted mini-screws, which are fixed for anchoring with the threads in the jawbone while the screw head remains exposed in the oral cavity, are an important area of application of the present invention. Ceramic tooth inlays and metallic or ceramic tooth crowns are another area of application for the composite material.

Thus, examples of medical implants are in particular dental implants of all kinds such as brackets, orthodontic arches, ligatures and bands, dental anchorage devices such as transpalatal arches and lingual arches, temporary anchorage devices (e.g. minipins, palatal implants, bollard pins), mini screws, dental inlays and metal or ceramic ones ready-made dental crowns.

What the dental appliances, mechanisms and implants mentioned have in common is that they are fixed in the intraoral area for a long period of time (months to years) and are therefore exposed to the oral conditions.

Dental implants such as brackets, transpalatal arches, lingual arches, mini-screws, dental inlays and metal or ceramic dental crowns can be made entirely of the composite material or contain only certain areas that have been made of the composite material. In the case of braces as a dental implant, only the brackets are usually made of the composite material.

Even if the composite material disclosed herein is preferably used for dental implants, other medical products and, above all, other implants that are also exposed to strong forces or pressures can also be manufactured from it. The composite material with infiltrated silver can be used as an implant material in orthopedics to prevent inflammation in knee implants, for example. Examples of other medical products are orthopedic implants such as joint implants, especially knee implants, intervertebral implants, bone wedges or bone screws.

The great advantage of the composite material according to the invention is that this composite material is antibacterial per se and thus an antibacterial coating is unnecessary and thus also a further work step of applying an antibacterial coating to the medical implant or parts thereof.

The present invention is the result of extensive biofilm research. None of the previous materials or material or surface modifications have shown satisfactory long-term antibacterial effects in numerous clinical studies. On the other hand, the composite material with silver infiltration has a strong long-term antibacterial effect and thus prevents or completely prevents the formation of a biofilm. Surprisingly, a closed silver surface is not required as with a coating to comprehensively reduce or prevent biofilm. Even composite materials with a silver content of less than 20%, whose interstices are filled with silver, show an excellent long-term antibacterial effect.

The present invention has pursued a novel approach to effectively reduce the formation of biofilms, e.g. on orthodontic fixed appliances, and to produce a long-term antibacterial effect.

For the composite material with infiltrated silver developed according to the invention, it could be demonstrated that even with silver contents of less than 20%, preferably less than 15%, there are strong antibacterial properties, with silver contents of less than 10%, but a minimum silver content of 6%, there are still sufficient antibacterial properties and these antibacterial property persists even under abrasive conditions. In addition, the composite material is biocompatible.

When used for orthodontic bracket material, the composite material according to the invention differs significantly from the previous bracket materials on the market. Due to its inherent antibacterial effect, additional antibacterial coatings on the brackets are not necessary. The present invention thus combines antibacterial properties with long-lasting antibacterial protection to prevent an intraoral biofilm for the first time.

The invention thus has the following advantages:

• antibacterial effect,

• high abrasion resistance,

• long-lasting antibacterial effect over the entire period of use,

• uniform silver infiltration in the composite material, also in the edge area,

• total modification of the composite material instead of a superficially applied coating,

• no increase in bracket thickness,

• biocompatibility,

• low consumption of antibacterial silver,

• uncomplicated manufacturing process, therefore suitable for production of large quantities. character description

FIG. 1: shows a scanning electron micrograph of a cross section of a porous matrix material (here tungsten) with infiltrated, homogeneously distributed silver (black).

FIG. 2 shows a tooth cleaning machine for determining the abrasion resistance of brackets made of conventional stainless steel and of tungsten with infiltrated, homogeneously distributed silver.

Figure 3 shows the wall thickness before and after abrasion for a bracket material made of conventional stainless steel ("control") and a composite metal made of tungsten as the matrix material with low (Low Ag = 7-9% by weight Ag in the matrix material) and high (High Ag = 9-14% by weight Ag in the matrix material) silver infiltration. A small amount of material removal was observed in the composite material made of tungsten with silver infiltration, as well as for comparison purposes in the samples made of conventional stainless steel brackets ("control" group).

Figure 4: shows a significantly reduced biofilm volume on intraorally worn bracket material made of silver-infiltrated tungsten composite metal (control = stainless steel, low Ag = 7-9% Ag, high Ag = 9-14% Ag in the composite metal.

FIG. 5: Biofilm on bracket samples worn in the mouth according to Example 4 (Low Ag=7-9% Ag, High Ag=9-14% Ag in the composite metal)

examples

Example 1 Production of the Composite Material According to FIG. 1 In the production of the tungsten composite material, various fine-grain fractions of tungsten powder (different grain sizes) were combined and mixed over a longer period of time in order to obtain a uniform distribution of the grain sizes in the powder.

For shaping, the powder mixture was pressed in tools under high pressure to form so-called "green compacts". The green compacts already have the shape of the end product. In the case of the brackets produced, thin discs with a diameter of 20 mm and a wall thickness of 2 mm were produced.

The blanks (green compacts) were then sintered, i.e. "baked" at high temperatures, which are below the melting temperatures of tungsten here. The sintering process takes place in a protective gas atmosphere or in a vacuum.

The finished sinters were then immersed in liquid silver. This is done in a vacuum so that all pores are completely filled with silver.

The silver-containing discs were ground down on both sides to a wall thickness of 0.6 mm and cut to the outer dimensions of the brackets using a laser.

Example 2 Scanning electron microscope image according to FIG. 1 The brackets were attached to a sample holder and placed in the sample chamber of the scanning electron microscope from TESCAN, type Vega3—without further sample preparation. The recording of the sintered structure was created using the so-called BSE method (backscattered electrons), which enables a good material contrast. Thus, in Figure 1, the light areas represent the tungsten grains surrounded by dark (black) silver. Example 3 Abrasion Tests on a Silver-Infiltrated Composite Material In order to test the abrasion resistance, endurance tests were carried out with a tooth cleaning machine on samples made from conventional stainless steel brackets and, for comparison, from a silver-infiltrated composite metal made from silver-infiltrated tungsten (see FIG. 2). The tooth brushing process was simulated for a period of 2 years with rotating toothbrushes, an oscillating linear relative movement between toothbrush and metal surface and the addition of abrasive toothpaste.

A small amount of material removal was observed in the composite material made of tungsten with silver infiltration, as well as for comparison purposes in the samples made of conventional stainless steel brackets ("control" group), see Fig. 3.

The material removal of less than 50 μm in the bracket wall thickness is acceptable for a wearing period of 2 years. The brackets made of composite material are therefore sufficiently resistant to abrasion. The decisive factor is that with each removal, the silver in the pores is exposed, i.e. it is present on the bracket surface and ensures a permanent antibacterial effect.

Example 4: Clinical study to prove the antibacterial effect of brackets In a clinical study, carrier splints were worn intraorally, which were fitted with brackets made of conventional stainless steel and, in comparison, made of composite metal (here tungsten) with silver infiltration.

The new composite material made of tungsten with a silver infiltration that was produced for the study was initially available in discs with a diameter of 19.3 mm and a thickness of 2.0 mm. Using a belt grinder, the blanks were reduced to an average wall thickness of 0.64 mm. The samples were then cut to an edge length of 5.0 x 5.0 mm using a laser.

Test specimens made from conventionally available stainless steel bracket material with material number 1.4456 were used as a control group and cut to the same specimen size. The exact material composition of the

Bonded metal specimens and the control specimen were determined using energy dispersive X-ray spectroscopy (EDX). The surface roughness of the different specimens was measured using confocal laser scanning microscopy (CLSM). This ensured that all samples average roughness (Ra) below the limit value of Ra = 0.2 pm, above which an influence of bacterial adhesion due to a material's surface structure that is too rough can be proven. The differences in biofilm formation could therefore only be attributed to the sample material itself.

For the present study, a toothbrushing machine was designed and built to simulate the abrasive stress on the brackets caused by daily brushing. It was assumed that the brackets were cleaned twice a day for two minutes each time with an average wearing time of 24 months. This period could be reproduced using the designed toothbrushing machine by continuously treating the samples for two hours.

In order to be able to trace the data obtained from the present study exclusively to the newly developed bracket material, the study design created the same starting conditions as possible. Twelve healthy volunteers (six women and six men) aged between 21 and 30 years were included in the clinical study. All twelve subjects could be included in the study in compliance with the test protocol created. By means of a periodontal screening of the twelve subjects, it was verified that the study was being carried out under periodontally healthy oral conditions. Various periodontal indices, including the approximal plaque index as an indicator of the prevailing oral hygiene, were collected. Other risk criteria that change the composition of the microbial flora were excluded. These include pregnancy, smoking, general illnesses, removable dentures and the possible use of antibiotics in the last six weeks before the start of the study.

For the twelve subjects, a plastic mini-splint was manufactured using a deep-drawing process. In order to prevent an incorrect reduction of the biofilm due to existing shearing forces in the oral cavity and rubbing of the cheek and tongue, plastic pads were attached to the miniplast splint in the posterior region. These pads were attached to a retaining wire at a small distance from the miniplast splint using the spray and scatter method, so that saliva circulation between the splint and the holding pad was perfectly possible. The rails were then fitted with the test specimens to be examined. In order to increase the adhesion of the flowable composite as a composite material between the test specimens and the Miniplast splint, the adhesive points on the splints were roughened using sandpaper. On both sides of the rail was randomized A control of conventional stainless steel, a sample of the composite metal (here tungsten) with a silver infiltration of 20% and a sample of the composite metal (here tungsten) with a silver infiltration of 15% are fixed in sequence. The order of the three specimens per side of the splint was randomized, since the biofilm coverage within the oral cavity can vary depending on the position. Thus, a possible effect of the sample position was ruled out.

To determine the wearing time, which enables a reproducible evaluation of the biofilm formed intraorally, a wearing time of 48 hours was determined in several preliminary tests on test persons. During this time, oral hygiene and alcohol consumption had to be suspended in order not to provoke falsification of the biofilm formed by cleaning the test specimens. For eating, the splints were removed for a maximum of 40 minutes and stored in a humid environment.

After the end of the wearing time, the splints were removed from the subjects and the biofilm formed was marked with a live/dead fluorescent stain and fixed with glutaraldehyde. The three-dimensional quantitative analysis of the fluorescence-stained biofilm was performed using confocal laser scanning microscopy (CLSM). The statistical evaluation of the collected data was carried out with the help of the GraphPad Prism software at a significance level of p<0.05.

It could be proven that the bracket samples made of the silver-infiltrated tungsten composite metal showed a significantly reduced biofilm volume compared to the conventional stainless steel bracket material: a) For untreated bracket samples, the biofilm volume for the standard brackets made of stainless steel is 1,000,000 pm ³ on average and for the brackets made of silver-infiltrated composite metal on average only 280,000 pm ³ for LowAg and 120,000 pm ³ for HighAg (see Fig. 3). b) For brackets that have previously been subjected to abrasion in the toothbrushing machine, the average biofilm volume for the standard brackets made of stainless steel is 1,600,000 pm ³ and for the brackets made of silver-infiltrated composite metal on average only ± 420,000 pm ³ for LowAg or 230,000 pm ³ for HighAg (see Figure 4).

Fig. 4 shows that even with bracket material samples that were previously exposed to abrasion in the toothbrush machine (see Fig. 2), there is a significant reduction in the biofilm volume, ie the effect of the silver infiltrated in the matrix material is permanently retained despite abrasion of the edge layer. The antibacterial effect of the silver in the composite material is clearly shown when the biofilm, consisting of a large number of bacteria, is fluorescently stained after the intraoral wearing time and then evaluated under a confocal laser scanning microscope. 5 shows live bacteria in light and dead bacteria in dark.

Closed biofilms form when the standard brackets made of stainless steel are worn in the oral cavity, both for untreated brackets and for brackets that have previously been subjected to abrasion in the toothbrush machine (see Fig. 5 "Control" group).

Flingegen, only slight biofilm formation can be seen in the composite material with little silver (7-9% by weight Ag) and with a lot of silver (9-14% by weight Ag) (see FIG. 5). Even after abrasion in the toothbrush machine, there is only a small amount of biofilm formation, i.e. the silver infiltrated in the material is effective.

This low level of biofilm formation is all the more important because in the clinical study the teeth or bracket samples were not cleaned for 48 hours and yet there is hardly any biofilm.

Claims

patent claims

1. Composite material made of an open-pore, porous, sintered matrix material and elemental silver, the elemental silver being infiltrated into the pores of the open-pore, porous, sintered matrix material, the silver content in the composite material being between 6% by weight and 30% by weight, and the open-pored, porous, sintered matrix material consists of at least one metal, at least one metal alloy or at least one ceramic.

2. Composite material according to claim 1, wherein the metal, the metal alloy or the ceramic has a melting point of over 962° C. and the elemental silver is melted into the pores of the open-pore, porous, sintered matrix material.

3. Composite material according to claim 1, wherein the elemental silver is electrodeposited in the pores of the open-pored, porous, sintered matrix material.

4. Composite material according to any one of claims 1-3, wherein the elemental silver fills the pores of the open-pored, porous, sintered matrix material.

5. Composite material according to one of claims 1-4, wherein the matrix material is selected from the group consisting of or comprising medical stainless steel, CoCr alloys, iron-chromium-manganese alloys, cobalt-nickel-chromium alloys, iron-chromium Nickel alloys, iron-cobalt-nickel alloys, titanium alloys, tantalum, tungsten, ceramics, aluminum oxide and zirconium dioxide.

6. Composite material according to any one of claims 1-5 for reducing or preventing the formation and adhesion of a biofilm on the surface of the composite material.

7. The composite material according to any one of claims 1-6, wherein the silver content in the composite material is between 9% by weight and 17% by weight.

8. A method for producing the composite material according to any one of claims 1 - 7 comprising the following steps: A) Provision of a granular powder or a granular powder mixture of the matrix material;

C) sintering of the sintered blank according to step B) below the melting temperature of the matrix material to form an open-pored sintered body with a porosity of 6% to 30%;

9. The method according to claim 8, wherein step D) comprises the following steps: D1) submerging the open-pore porous sintered body according to step C).

vacuum conditions into molten elemental silver until the pores are filled with elemental silver;

10. The method according to claim 8, wherein step D) comprises the following steps:

silver bath and electrodeposition of elemental silver until the pores are at least partially filled with elemental silver;

D'2) Removal of the sintered part according to step D'1) from the silver bath.

11. Medical implant containing or consisting of the composite material according to any one of claims 1-7.

12. Medical implant according to claim 11, wherein the medical implant is a short-term medical implant or a long-term medical implant.

13. Medical implant according to claim 11 or 12, wherein the medical implant is a dental implant, bracket, orthodontic arch, ligature, band, dental anchorage apparatus, transpalatal arch, lingual arch, temporary anchorage device, mini pin, palatal implant, bollard pin, mini screw, tooth inlay, metal or ceramic ready-made tooth crown.

14. Medical implant according to one of claims 11 - 13, wherein the medical implant is an orthopedic implant, joint implant, intervertebral implant, bone wedge or bone screw.

15. Medical implant according to one of claims 11-14, wherein the composite material in the medical implant has no antibacterial coating.