Abstract
Biodegradable materials are of interest for temporary medical implants like stents for restoring damaged blood vessels, plates, screws, nails for fixing fractured bones. In the present paper new biodegradable Zn–2Mg alloy prepared by conventional casting and hot extrusion was tested in in vitro and in vivo conditions. Structure characterization and mechanical properties in tension and compression have been evaluated. For in vivo tests, hemispherical implants were placed into a rat cranium. Visual observation of the living animals, an inspection of implant location and computed tomography CT imaging 12 weeks after implantation were performed. Extracted implants were studied using scanning electron microscopy (SEM) on perpendicular cuts through corrosion products. The behaviour of zinc alloy both in in vitro and in vivo conditions was compared with commercially used Mg-based alloy (Mg–4Y–3RE) prepared by conventional casting and hot extrusion. Both compressive and tensile yield strengths of Zn and Mg-based alloys were similar; however, the brittleness of Mg–4Y–3RE was lower. Zn and Mg-based implants have no adverse effects on the behaviour or physical condition of rats. Moreover, gas bubbles and the inflammatory reaction of the living tissue were not detected after the 12-week period.
Highlights
Biodegradable metals and alloys have attracted great attention in the past few decades as promising alternatives to permanent implant materials, like Ti alloys, Co alloys or stainless steels, and to biodegradable polymeric materials, such as poly-lactic acid (PLLA)
It is obvious that eutectic lamellae typical for the as-cast state [49] are broken down and the eutectic mixture slightly coarsened during hot extrusion at a relatively high temperature
Yield strength and ultimate strength of Zn–2Mg in tension and compression exceed 230 and 360 MPa, respectively, which are considered as sufficient values to ensure mechanical support for healed bone during the regeneration process
Summary
Biodegradable metals and alloys have attracted great attention in the past few decades as promising alternatives to permanent implant materials, like Ti alloys, Co alloys or stainless steels, and to biodegradable polymeric materials, such as poly-lactic acid (PLLA). Biodegradable materials are of interest for temporary medical implants like stents for restoring damaged blood vessels, plates, screws, nails for fixing fractured bones. The biodegradable polymeric materials can be used for coronary stent applications, the main problem is related to the load-bearing applications, where polymeric materials often fail because materials available at present suffer from a low hardness, strength, fracture toughness and wear resistance even when additions of ceramic particles are used. Great attention is devoted to metallic biodegradable materials, which appear more suitable for load-bearing applications. Magnesium, iron and zinc, have been mostly studied up to date concerning the design of biodegradable medical implants because they are relatively non-toxic and essential for proper biological functions of the human body. Iron offers a potential for applications in biodegradable implants
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