Fibre Metallurgy

Metallic Materials for Implants – Highly Porous and Degradable

An ongoing medical problem is how best to treat major bone damage. Such damage does not heal spontaneously and requires implants. The best bone replacement is, and always has been, the patient's own bone. However, only limited amounts of this are available and its removal also involves risks. The use of a synthetic bone replacement is also accompanied by various risks. The ideal solution is a degradable material, namely implants which disappear after successful bone healing. 

© Fraunhofer IFAM Dresden
SEM micrograph of magnesium fibers.
© Fraunhofer IFAM Dresden
Metallic fibers (prototype).

Magnesium comes very close to being the ideal material. It degrades in biological surroundings, has excellent biocompatibility, and bonds very readily to bone.

Fraunhofer IFAM in Dresden has developed a magnesium implant material whose structure also gives it other favorable properties. The metallic fiber structures form a highly porous lattice which assists bone growth and also the growth of blood vessels. Such structures are, however, of particular interest due to their reduced stiffness, very closely resembling the biomechanical properties of bone. This stimulates bone growth.

The starting point for the development work was the production of short magnesium fibers via extraction from the melt. These fibers are then homogeneously deposited and sintered. The particular challenge for manufacturing magnesium fiber structures is the sintering, which the material with extremely high oxygen affinity resists due to the stable surface oxides. The heat treatment is hence undertaken in a partial melt phase. Precise knowledge of the melt phase composition is decisive for the sintering result. The best sintering regime was determined using computer simulation methods. The resulting implants possess favorable mechanical properties and also excellent corrosion properties. Multiple depositions of Y2O3 at the grain boundaries allowed for a degradation behavior with reduced corrosion rate to meet the physiological requirements. In the animal model, slow corrosion was measured after 12 weeks but after 24 weeks the majority of the metal implant had disappeared.

As a winner of the Medical Technology Innovation Competition, the research was funded by the BMBF (Federal Ministry of Education and Research). The favorable properties of the implant material have in the meantime also convinced industry, with Botiss Dental GmbH now licensing the patent. The company plans to use this material in oral surgery and is currently evaluating the setting up of a suitable production chain.