Surface Modification of Bio-Active Ceramic (Artificial Bone) by Ion Implantation
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SURFACE MODIFICATION OF BIO-ACTIVE CERAMIC (ARTIFICIAL BONE) BY ION IMPLANTATION G.H.Takaoka, R.Tanaka, H.Usui, S.K.Koh, M.I.Current(a), I.Yamada, S.Akamatsu and T.Kokubo* Ion Beam Engineering Experimental Laboratory, Kyoto University, Kyoto, Kyoto-Fu 606-01, Japan * Institute of Chemical Research, Kyoto University, Uji, Kyoto-Fu 611, Japan ABSTRACT Glass-ceramics (A-W) containing apatite and wollastonite phases have been developed that show good bio-compatibility and rapidly form chemical bonds with living bone. The glass-ceramic (A-W) was implanted with 200 keV Zr and Ar ions at doses of 1El5 to 1E17 ions/sq.cm. It was found that the Zr ion implantation was effective for obtaining high mechanical strength in simulated body fluid. The increase of the mechanical strength can be considered to be due to the formation of Zr and 0 bonds by ion implantation. The bioactivity of the implanted ceramics remained, and was improved after soaking in the simulated body fluid. In the case of Ar ion implantation, the fracture strength was not improved. However, the bioactivity was strong and improved with increase of the time soaked in the simulated body fluid. INTRODUCTION Glass-ceramics (A-W) containing apatite and wollastonite, which can form chemical bonds with living bone in the body fluid, have attracted much interest in biological applications [1]. In addition, surface modificatio.t of ceramics by ion implantation has recently been studied by an increasing number of investigators in an attempt to improve mechanical properties such as surface hardness, surface fracture-toughness and bulk fracture-stress [2-5]. For improving the mechanical properties, radiation effects such as implantation-induced residual stress and surface amorphization play an important role [6]. In another approach for enhancement of the mechanical properties, ZrO is utilized, and it has a great influence on the chemical durability. However, the addition of ZrO2 as a component material of glass ceramic by using the conventiona melting method has a limitation, and the maximum concentration is less than 15 wt.%. We have been investigating the effects of Zr ion implantation into glass ceramics for surface treatment [7]. Implantation of various ions into ceramics as well as metals and semiconductors can alter crystallographic, mechanical and electrochemical properties. In this paper, we investigate the fracture strength and the bioactivity of glass ceramics (A-W) implanted with different doses of Zr, Kr and Ar ions. We also discuss the effect of Zr ion implantation based on the Monte-Carlo (TRIM-91) calculations. EXPERIMENTAL PROCEDURE The target material was glass-ceramic (A-W) containing oxyfluoroapatite [Ca 1 0 (PO4) 6 (O,F2 )] and wollastonite (CaO.SiO2 ) as the crystalline phases. The A-W ceramic also has an amorphous phase consisting of CaO, SiO2 and MgO. The chemical composition in wt. % is CaO (44.68 %); SiiO2 (34.03 %); P 20 5 (16.21 %); MgO (4.58 %); CaF2 (0.50 %). The size of the A-W bars was 20mm x 5mm x 5mm. They were polished with No. Mat. Res.
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