Biomedical Engineering Reference
In-Depth Information
9
Research on Mg-Zn-Ca Alloy as
Degradable Biomaterial
B.P. Zhang
1,2
, Y. Wang
2
and L. Geng
2
1
National Engineering Laboratory for Carbon Fiber Technology,
Institute of Coal Chemistry, Chinese Academy of Sciences
2
School of Materials Science and Engineering, Harbin Institute of Technology
China
1. Introduction
Magnesium and magnesium alloys are light metals, which characterized a low density, high
specific strength and strong specific stiffness. The fracture toughness of magnesium is
greater than that of ceramic biomaterials such as hydroxyapatite. The Young's elastic
modulus and compressive yield strength of magnesium are closer to those of cortical bone.
Especially, Mg
2+
is present in large amount in the human body and involved in many
metabolic reactions and biological mechanisms. The human body usually contains
approximately 35g per 70kg body weight and the human body's daily demand for Mg is
about 350 mg/day. Due to the excellent biomechanical properties and biocompatibility,
magnesium alloys used to be introduced as implants into orthopedic and trauma surgery in
recently years [1~3].Various magnesium alloys have been investigated as biodegradable
materials and some of them have been shown good biocompatibility. For example, AZ31,
AZ91, WE43, LAE442, Mg-Ca and Mg-Zn have been investigated for bone implant
application [4~8]. It has been shown that magnesium enhances osteogenesis response and
increases newly formed bone. However, some magnesium alloys containing aluminum or
heavy metal elements which have latent toxic effects on the human body. Thus, several
problems such as inadequate strength, rapid corrosion and toxic ions must be solved before
this unique metal is widely used in biomedical fields.
It is well known that pure magnesium has poor mechanical properties and the mechanical
properties of magnesium can be effectively improved by the appropriate selection of
alloying elements [1]. But, based on the aforementioned considerations, the range of
alloying elements used in the degradable magnesium alloys is rather limited, Zn, Mn, Ca
and perhaps a very small amount of low toxicity RE can be tolerated in the human body and
can also be retard the biodegradation. Therefore, Mg-Ca binary alloys attract attention of
researchers because Ca is an important element of human bones. The mechanical properties
and biocompatibility of Mg-Ca binary alloy can be adjusted by controlling the Ca content
and processing treatment. However, an inadequate mechanical properties as well as lower
corrosion resistances of Mg-Ca binary alloys are the biggest drawback of these alloys [7][8].
Fortunately, in latest recent years, Mg-Zn system is paid more attention because Zn is one of
abundant nutritional elements in human body [9] [10]. Additionally, it is a great potential
