Biocompatibility

The Biocompatibility means the compatibility of artificial materials in direct contact with the human organism and the resistance of materials in the biological environment. These material properties play a role especially for implantology. A lack of biocompatibility can provoke implant rejection.

What is the biocompatibility?

In implantology, artificial materials are permanently introduced into a person's body or should at least remain in the organism for a certain period of time. In connection with the materials used, the term biocompatibility plays an important role. The implanted materials must neither have a negative influence on the tissue or the organism, nor be damaged in the organic environment itself.

Apart from implantology, biocompatibility can also be of relevance. Basically whenever certain materials are in direct contact with people and their environment for a certain period of time.

Medical materials and products are labeled with the property of biocompatibility according to ISO 10993 1-20. For the highest possible biocompatibility, implants made of non-biocompatible materials are coated with biocompatible coatings, for example. Proteins are most often used to ensure surface compatibility. Structural biocompatibility, on the other hand, exists when the internal structure of the implant has been adapted to the structure of the target tissue.

The biocompatibility is ensured in laboratory tests in which medical materials are tested for their compatibility in the human and animal body. The test series for this are lengthy and apply worldwide as a prerequisite for approval for implants and drugs.

Function & task

Implants can now support or even replace body functions. They can just as well have aesthetic benefits and thus contribute to the mental health of patients.

In implantology, the biocompatibility of the implants benefits the patient insofar as the risk of rejection reactions or poisoning is kept as low as possible by testing the materials. Ensuring biocompatibility also prevents symptoms of poisoning or other intolerances in connection with drugs.

If a material or material cannot be classified as compatible in the compatibility test, it is biotolerant, bioinert or bioactive. Biotolerant products can stay in the human body for several months or even years without causing serious damage. In some cases, minor defects occur in the tissue reaction. After the positive test, in addition to the decomposition, cell changes and the toxic effect are excluded during the period of use investigated. Bio-inert products do not cause chemical or biological interactions with tissues. Toxic substances are hardly released into the tissue by these materials.

The interaction between material and body is sufficiently small and only a few substances pass into the body. Biotonized materials are enclosed in non-adherent connective tissue encapsulation, do not trigger any rejection reactions and are resistant to corrosion in the biological environment. The material is usually thermally stable, refractory and passivatable. Medical ceramics, plastics and metals in particular fall into this biocompatibility group.

Bioactive materials play a role primarily in endoprosthetics.Endoprosthetics describe the reaction of a bone to the implant as bioactive if adhesion of the bone to the implant border is possible.

Materials become bioactive through coating. Usually a bioinert material is made bioactive through further processing. The implant material of bioactive substances becomes bone material. In other cases, the term bioactivity is used to describe the active body striving to leave the implant with a certain function over the long term. Carbons, ceramics and bio-glass products are typical materials with bioactivity.

Biocompatibility can also play a role in waste management. In the case of wastewater, for example, biocompatibility is a measure of the biological degradability of polluting substances.

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Illnesses & ailments

The biocompatibility of implants is extremely relevant in connection with various diseases. For example, the use of an implantable cardioverter defibrillator or pacemaker may be necessary for various heart diseases. Implants and biocompatibility in connection with vascular diseases can be just as relevant, since they may require stents or vascular prostheses. Retinal implants serve as visual prostheses for eye diseases. In dentistry, dental implants are used as a fixation for artificial teeth. Other implants serve as a depot for a specific drug.

The biocompatibility in the sense of bioactivity decides in many of these implants to what extent the intervention will be useful for the patient without symptoms. For example, an actually bioactive artificial heart valve is fully accepted by the body. In this way, the organism actively assigns the tasks to the implant that the heart cannot perform itself due to the heart disease. If the bioactivity of the implant is too low, there is no such active transfer of functions by the patient's body. The implant is rejected and the therapeutic approach is unsuccessful.

The rejection of artificial implants due to low bioactivity can be life-threatening, depending on the shape of the implant. In other cases, medical materials cause poisoning or systematic immunological inflammation due to insufficient biocompatibility. Such a connection is almost impossible in modern medicine due to the strict tests for biocompatibility nowadays.