Developmental Study of Diopside for Use as Implant Material
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DEVELOPMENTAL STUDY OF DIOPSIDE FOR USE AS IMPLANT MATERIAL
TORU NONAMI TDK Corporation, Materials Research Center, 570-2 Aza-Matsugasita Minami-Hatori, Narita-shi, Chiba-ken, 286, Japan
ABSTRACT Diopside was prepared sintering a powder compact of composition CaMgSi206 at 1573K for 2 hours. The bending strength of this sintered body was 300MPa and fracture toughness was 3.5MPaml/ 2. Diopside was soaked in a simulated body fluid at 309.5K. Three days later diopside formed hydroxyapatite (Hap) all over the surface [1]. Diopside implanted in rabbits came in close contact with the newly grown bone. EPMA spectral diagrams show a change of composition across the junction from the diopside to the newly grown bone [2]. INTRODUCTION Metals and ceramics have been used as materials for artificial bone. Although these materials have high mechanical strength and in vivo stability, they have low biological affinity. Recently, calcium phosphate based ceramics, primarily apatite, and tricalcium-phosphate, bioglass, have thus attracted attention as biologically active materials. However, they have only limited use because of low mechanical strength and toughness [3]. We discovered that diopside in contact with a simulated body fluid forms a
calcium phosphate based compound which covers the surface and shows satisfactory biological activity, in spite of the fact that diopside is not of a calcium phosphate base. EXPERIMENT Peparation of diopside Diopside was prepared by mixing powders (SiO2, CaC03, MgO of stoichiometric ratio). The composition was calcined in air at 1373K for 2 hours and milled in a ball mill for 1 hour. The cake was dried at 393K for 5 hours and pressed at 30MPa. The compacts were heated in air at 1573K for 2 hours. Hap was synthesized by precipitation. It was fabricated by hot-isostatic pressing at 203MPa and 1273K for 2 hours.
The apparent density of diopside was measured in water using the Archimedean technique. The sintered sample was pulverized into powder having a surface area of 5m2 /g which was used for the true density. The relative density was calculated from the apparent and true densities.
Mat. Res. Soc. Symp. Proc. Vol. 252. c1992 Materials Research Society
88
Mechanical property
Bending (flexure) strength was measured by the three-point method on specimens of 3 by 4 by 40mm with 36mm span at crosshead speed of 0.5mm/min. Fracture toughness was measured by the three-point bending method on notched-beam specimens of 3 by 2 by 25mm with 15mm span at crosshead speed of 0.5mm/min. Young's modulus and Poisson's ratio were measured on specimens of 80 by 2 by 20mm using the ultrasonic pulse echo method. Acid resistance A sample having a surface area of 200mm 2 was placed in 200ml of an aqueous solution of lactic acid at pH 4 for 48 hours at 309.5K (in a constant temperature bath) and
was slightly shaken. Immediately thereafter, the sample under test was washed with water, dried, and analyzed for its weight loss. In vitro examination One hundred fifty ml of simulated body fluid comprising an aqueous s
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