This review describes the mechanisms responsible for low-temperature degradation (LTD) of zirconia ceramics and its detrimental consequences for biomedical devices. Special emphasis is given to the critical issue of zirconia degradation actually observed for hip prostheses. Experimental methods to accurately measure and predict LTD in a given zirconia ceramic are presented. Different solutions to inhibit LTD or at least reduce its kinetics are reviewed, with the objective of highlighting alternative options for the generation of new zirconia-based biomedical ceramic devices.

Sintering and crystallisation phenomena in powders of a typical bioactive glass composition (45S5 Bioglass®) have been investigated in order to gain further understanding of the processes involved in the fabrication of Bioglass® based glass–ceramic scaffolds for tissue engineering applications. In situ experiments in an environmental scanning electron microscope with a heating stage were carried out to follow the morphology of Bioglass® particles during sintering and crystallisation. Optimal processing parameters for the manufacture of Bioglass® based glass–ceramic scaffolds by the foam-replica technique were determined. To assess the in vitro performance and bioreactivity of Bioglass®-derived glass–ceramic scaffolds, the biodegradation of samples in simulated body fluid (SBF) was investigated using various techniques, including SEM, TEM, XRD and EDX. The mechanism of interaction of the glass–ceramic surface with SBF was determined, which involves (i) preferential dissolution at glass/crystal interfaces, (ii) break-down of crystalline particles into very fine grains through preferential dissolution at crystal structural defects, and (iii) amorphisation of the crystalline structure by introduction of point defects produced during ion exchange. The present report thus offers for the first time a complete assessment of the processing parameters, microstructure, and in vitro performance of Bioglass® derived glass–ceramic scaffolds intended for bone tissue engineering.