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

Abstract

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.

The Rationale for Silicon Nitride Bearings in Orthopaedic Applications

“…Mazzocchi et al investigated silicon nitride ceramics for their potential use in orthopaedic implants, and validated several properties that are critical to biomedical applications, such as wetting behavior and wear performance that simulates conditions typical of a hip joint prosthesis. 33 In three different silicon nitride ceramic materials prepared, these investigators found a lower contact angle of water when compared to oxide ceramics such as alumina and zirconia. Also, very low friction coefficients were consistently measured with undetectable surface modifications and wear tracks in the silicon nitride materials tested, using a disc-onball model of wear detection.…”

“…Also, very low friction coefficients were consistently measured with undetectable surface modifications and wear tracks in the silicon nitride materials tested, using a disc-onball model of wear detection. 33 …”

“…33 Both weight changes in the specimens, and scanning electron microscopic examination of the exposed surfaces were done to identify morphological and chemical modifications. These experiments showed a very limited surface modification related to exposure to oxygen-containing media; the newly formed phases were limited to the boundary zone, in the nano-scale.…”

“…These experiments showed a very limited surface modification related to exposure to oxygen-containing media; the newly formed phases were limited to the boundary zone, in the nano-scale. 33 Silicon nitride ceramics contain, besides silicon nitride grains, the grain boundary phases formed by sintering additives, and SiO 2 that usually exists on the surface of the starting silicon nitride powders. Independent of additives, during sintering, SiO 2 partially decomposes forming surface gradients, or even leads to metallic Si inclusions in the ceramic.…”

Microhardness and Biocompatibility of Silicon Nitride Ceramic Developed for Dental Applications

“…In addition, because of its excellent physicochemical behavior and biocompatibility, it has been used to fabricate orthopedic and prosthetic implants such as knee and hip-joint replacements [1]. Si 3 N 4 ceramic also has chemical stability and good wetting properties [2] which positively affect the adhesion of the core-veneer interface and lead to higher strength of the material.…”