Perspectives of the Si3N4-TiN ceramic composite as a biomaterial and manufacturing of complex-shaped implantable devices by electrical discharge machining (EDM).

PURPOSE: In this work we investigated the suitability of electroconductive silicon nitride/titanium nitride composite for biomedical implantable devices with particular attention on the processing route that allows the net-shaping of complex components by electrical discharge machining (EDM). METHODS: The composite, constituted mainly of a beta-Si3N4, dispersed TiN grains and a glassy grain boundary phase, exhibited a low density and high hardness, strength and toughness. Bulk, surface characteristics and properties of the Si3N4-TiN composite were analyzed. After the EDM process, the microstructure of the machined surface was examined. RESULTS AND CONCLUSIONS: The obtained results showed that the Si3N4-TiN ceramic composite together with the EDM manufacturing process might potentially play a key role in implantable load-bearing prosthesis applications.

On the possibility of silicon nitride as a ceramic for structural orthopaedic implants. Part II: chemical stability and wear resistance in body environment.

In Part I, the processing, microstructure and mechanical properties of three silicon nitride-based ceramics were examined and their non-toxicity was demonstrated. In this Part II, some features critical to biomedical applications were investigated: (i) the wetting behaviour against aqueous media, including physiological solutions; (ii) the chemical stability in water and in physiological solutions; and (iii) the wear resistance, measured under experimental procedures that simulate the conditions typical of the hip joint prosthesis. The results confirmed that silicon nitride may serve as a biomaterial for bone substitution in load bearing prosthesis.

On the possibility of silicon nitride as a ceramic for structural orthopaedic implants. Part I: processing, microstructure, mechanical properties, cytotoxicity.

Notwithstanding the good combination of mechanical and tribological properties, the suitability of silicon nitride for application as prosthesis in bone reconstruction or in articular joints replacements is still controversial. This study aims to design and produce three different silicon nitride-based ceramics and to test the materials. In this Part I the microstructure and mechanical properties evidence outstanding characteristics and the cytotoxicity studies confirm that all the materials are extremely inert and biocompatible. In Part II, the wear performance and the wettability and chemical stability against different aqueous media and physiological solutions are investigated and discussed.