| Budget Amount *help |
¥13,600,000 (Direct Cost: ¥13,600,000)
Fiscal Year 2000: ¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥10,200,000 (Direct Cost: ¥10,200,000)
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| Research Abstract |
The purpose of this work is to clarify the mechanism of apatite formation on various bioactive materials in biomimetic process using SBF.
Titanium and tantalum metals were subjected to NaOH and subsequent heat treatments to form amorphous sodium titanate or sodium tantalate on their surfaces. An Na_2O-SiO_2 glass was prepared by conventional melting-quenching technique. The metals and glass were soaked in simulated body fluid (SBF) with ion concentrations nearly equal to those in blood plasma for various periods. Changes in surface structure due to soaking in SBF were analyzed by X-ray photoelectron spectroscopy and transmission electron microscopy accompanied with energy-dispersive X-ray spectrometry. Changes in element concentrations of SBF due to soaking of the metals and glass were examined by inductively coupled plasma atomic emission spectroscopy.
The metals and glass were found to release Na^+ ions in SBF to form functional groups such as Ti-OH, Ta-OH and Si-OH groups on their surfaces. These functional groups, immediately after their formation, combined with Ca^<2+> ions in the fluid to form calcium compounds such as amorphous calcium titanate, calcium tantalate and calcium silicate. Later, these calcium compounds combined with phosphate ions in the fluid to form an amorphous calcium phosphate with low Ca/P atomic ratio. Thereafter, this amorphous calcium phosphate increased its Ca/P ratio and incorporated minor components such as Na^+ and Mg^<2+> to eventually transform into bonelike apatite crystal.
These results indicate that functional groups on bioactive materials, such as Ti-OH, Ta-OH and Si-OH groups, induce apatite formation not directly, but through formations of calcium compounds such as amorphous calcium titanate, calcium tantalate and calcium silicate, and subsequently amorphous calcium phosphate.
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