Precipitation of magnesium apatite on pure magnesium surface during immersing in Hank's solution

A new artificial bone concept by magnesium alloys is proposed to think much importance on its homogenization with a surrounding natural hard and soft tissue. Magnesium is an essential element for human body, so that magnesium bone implants can be expected to be toxicity free even though magnesium dissolved into human soft tissue. In addition, magnesium base artificial bone has vivo-adaptive to growing bone cells once vivo-coating is formed on the surface of magnesium in the inside of soft tissue. In the present paper, its chemical behavior in Hank's solution (HBSS (+)) is described to simulate biochemical reactions of magnesium in the human body. An effect of heat treatment of magnesium on its chemical behavior is also investigated. Specimens of 10 × 20 × 2 mm³ were used for examining chemical behaviors of commercial grade pure magnesium (3N-Mg) in a HBSS (+) for various holding time (25-700h). Specific mass gain of each specimen was measured, the surface microstructure was observed by a scanning electron microscope, identification of reaction products were examined by x-ray diffraction measurements. Chemical compositions of reaction products were also analyzed by an energy dispersion x-ray spectrometry. Mass change of heat-treated 3N-Mg, which was heat-treated at 803 K for 90 ks increased with immersing time in HBSS (+) though that of other heat-treated 3N-Mg unstably decreased in HBSS (+). Magnesium reacted with HBSS (+) and then a magnesium apatite was precipitated on the heat-treated 3N-Mg specimen surface. The magnesium apatite should be described as (Ca_0.86Mg_0.14)₁₀(PO₄)₆(OH )₂.