Formation and characterization of hydroxyapatite coating layer on Ti-based metal implant by electron-beam deposition
- PDF / 1,029,576 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 32 Downloads / 175 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Formation and characterization of hydroxyapatite coating layer on Ti-based metal implant by electron-beam deposition Jae-Man Choi, Young-Min Kong, Sona Kim, Hyoun-Ee Kim, and Cheol Seong Hwang Creative Research Center for Microstructure Science of Materials and School of Materials Science and Engineering, Seoul National University, Seoul, 151-742, Korea
In-Seop Lee Research Center of Orthopaedic & Rehabilitation Engineering, Inchon, 403-120, Korea (Received 8 February 1999; accepted 14 March 1999)
A hydroxyapatite [HAp; Ca10(PO4)6(OH)2] coating layer was formed on a Ti-based alloy by the electron-beam deposition method. When pure HAp was used as a target for the deposition, an amorphous layer was formed on the metal substrate. By heat treatment in a vacuum at 630 °C, the layer was crystallized into tricalcium phosphate [Ca3(PO4)2]. The crystallization improved the dissolution rate of the layer remarkably; however, at the same time, it deteriorated the bond strength with the substrate. When extra CaO (up to 25 wt%) was added to the target and processed under the same conditions, a layer compositionally close to crystalline HAp was deposited. Before the heat treatment, even though the layer was in amorphous state, the dissolution rate in the physiological solution was extremely low. Furthermore, the bond strength increased remarkably compared to the layer formed by the pure HAp target. Compositional and structural resemblance of the layer with the crystalline HAp was attributed to these improvements in properties.
I. INTRODUCTION
Various metals, such as stainless steel, Co–Cr alloy, or Ti-based alloys, are currently used as implant materials for bones or teeth because of their excellent mechanical properties and machinability.1 However, relatively low biocompatibility is one of the most serious drawbacks of those metals for biomedical applications. To improve the biocompatibility of the metallic implants, hydroxyapatite [HAp; Ca10(PO4)6(OH)2] is generally coated on the surface.2 Because of its chemical and crystallographic similarity with the inorganic component of human bone and teeth, an HAp layer on the implants leads to direct bonding or earlier stabilization of the implants with the surrounding bones or tissues.3,4 Besides the biocompatibility, dissolution rate of the coating layer in a human body solution is also a very important factor that should be considered.2 If the layer is dissolved too fast before the growth of bones or the stabilization of the implants, the coating is simply meaningless. The dissolution rate of crystalline HAp is very low, while that of amorphous HAp generated during the coating process is considerably high.5 Another important property that a coating layer should possess is high bond strength with the metal substrate. If the HAp coating is separated from the implant in vivo, the detached fragments have very adverse effects on the implant or tissues surrounding it.2,6 2980
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 7, Ju
Data Loading...
