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We elucidated the in vivo corrosion mechanism of the biodegradable alloy Mg-10 wt % Ca in rat femoral condyle through transmission electron microscope observations assisted by focused ion beam technique. The alloy consists of a primary Mg phase and a three-dimensional lamellar network of Mg and Mg(2)Ca. We found that the Mg(2)Ca is rapidly corroded by interdiffusion of Ca and O, leading to a structural change from lamellar network to nanocrystalline MgO. In contrast to the fast corrosion rate of the lamellar structure, the primary Mg phase slowly changes into nanocrystalline MgO through surface corrosion by O supplied along the lamellar networks. The rapid interdiffusion induces an inhomogeneous Ca distribution and interestingly leads to the formation of a transient CaO phase, which acts as a selective leaching path for Ca. In addition, the outgoing Ca with P from body fluids forms needle-type calcium phosphates similar to hydroxyl apatite at interior and surface of the implant, providing an active biological environment for bone mineralization.

Original publication

DOI

10.1002/jbm.b.32795

Type

Journal article

Journal

J biomed mater res b appl biomater

Publication Date

11/2012

Volume

100

Pages

2251 - 2260

Keywords

Absorbable Implants, Animals, Bone Substitutes, Calcification, Physiologic, Calcium, Calcium Compounds, Corrosion, Durapatite, Magnesium, Magnesium Oxide, Materials Testing, Nanoparticles, Oxides, Rats