*Amorphous and Crystalline Magnesium Alloys for Biomedical Applications DOI: http://dx.doi.org/10.5772/intechopen.94914*

The main problems and research limitations of this concept are as follows:


The major problem concerning all metal biomaterials consists in the adjustment of their mechanical properties to those of the reconstructed tissues. The density of steel is approx. 4 times higher than the density of bone tissue. Steel has several times higher yield point and tensile strength, higher elongation and about 10 times higher Young's modulus. The differences in the mechanical properties of materials and those of the tissues they replace result in inappropriate loading of the tissues surrounding the implant, causing pain and discomfort in patients [22].

The density of magnesium alloys is similar to the density of the human bones, therefore, there is no possibility of stress shielding, as in the case of the previously used implant materials, based on stainless steel and titanium. Stress shielding is a process, in which the bone mass and density decrease near the implant, because it transfers the loads. The density of magnesium alloys is three times lower than that of titanium alloys and five times lower than that of stainless steel and Co-Cr alloys. The modulus of elasticity and fracture resistance are much lower than for the biomaterials used so far [23, 24]. In the 19th and 20th centuries, magnesium alloys were used in medicine (**Table 2**). They were used in the form of scaffolds and to improve healing of wounds or organs. In addition, magnesium and its alloys have


#### **Table 2.**

*Applications of magnesium and its alloys in medicine [25].*

#### **Figure 2.**

*Potential applications of Mg and its alloys in implantology [17–22].*

been used in orthopedic surgery for such elements as screws, plates, fasteners or as stents in the cardiovascular system.

At present, magnesium alloys are mainly considered as potential materials for applications in orthopedic implantology, vascular surgery and laryngeal microsurgery [26–30]. As regards orthopedic implantology, Mg alloys are used as compression screws. MAGNEZIX is the trade name of biodegradable orthopedic screws for human osteosynthesis application [31]. In the literature, there are some reports [32–34] on resorbable stents made of magnesium alloys (their trade name is Lekton Magic, produced by Biotronik company). This material is composed of zirconium (< 5 wt.%), yttrium (< 5 wt.%) and rare earth elements (< 5 wt.%). The stents degrade in a living body with time, but their location can still be identified. Finally, the stent material completely degrades and the space around it is filled with a calcium-apatite complex with an admixture of phosphate elements. The stents were implanted in 20 people and good flow in the implanted blood vessel was achieved after one month. In 2013, Biotronik, a German company, has obtained the CE mark for biodegradable coronary stents made of Mg alloy. It was the leader in development of biodegradable metal coronary stents. The areas of potential applications of magnesium and its alloys in implantology are presented in **Figure 2**.
