PRODUCTION OF A FUNCTIONALLY GRADED ARTIFICIAL TOOTH ROOT BY UNIQUE SEQUENCE OF PROCESSES

A unique sequence of processes is used to produce a prototype of a fun ctionally graded artificial tooth root: (1) Dry-jet spraying of the mi xture of Ti and Al2O3 ultrafine particles (UFPs) produced by radio-fre quency plasma onto the surface of a cylindrical Ti rod, where the comp osition of the UFPs is changed gradually in the outward radial directi on from Ti to Al2O3; (2) Temperature-gradient sintering of the deposit ed composite, where the Ti - and the Al2O3 - rich sides are heated sim ultaneously at about 1400 K and 1800 K, respectively; (3) Plasma spray coating of hydroxyapatite (HAP) onto the outermost Al2O3 surface of t he sintered composite. The final product has compressive strength of m ore than 200 MPa and is durable against fatigue test of 10(7) stress c ycles at 1000 N. The adhesion strength between the Ti substrate and th e Ti-Al2O3 functionally graded layer exceeds 65 MPa. No contamination with heavy metals is detected throughout the processes and biological cell growth is confirmed to occur on the HAP surface. With these mecha nical and biochemical properties the composite produced here is consid ered to be highly suitable for an artificial tooth root. A series of p rocesses developed here are expected to be applied to the production o f various kinds of fine-grained functionally graded materials with com plicated forms.