What is low temperature degradation? Does it have clinical relevance?

Both yttria-stabilised and alumina-stabilised composite materials can be subject to so-called transformation toughening and/or low-temperature degradation (LTD), which affect their stability and longevity in vivo.

While transformation toughening increases crack resistance through controlled stress-induced phase transformation, low-temperature degradation in the presence of water or water vapour leads to uncontrolled transformations that cause surface damage and microcracks and ultimately impair the mechanical properties of zirconia (Chevalier & Gremillard 2009; Chevalier et al. 2011).

Degradation resistance can be significantly improved by adding alumina to 2.5 mol% yttriua-stabilised zirconia. Yttria-stabilised zirconia with a higher alumina content shows less formation of monoclinic phases after ageing tests, which means improved stability (Kern & Gadow 2013) . This is consistent with the results of the study by Deville et al. (2018): Composites with zirconia content ranging from 2.5 wt% to pure 3Y-TZP with higher alumina content show slower ageing rates compared to pure Y-TZP ceramics. Furthermore, Begand et al. (2005) point out that hydrothermal treatment or ageing of ATZ has no significant effect on strength, phase composition and surface properties.

References

Begand, S., Oberbach, T. & Glien, W. (2005). ATZ – Ein neues keramisches Material mit einem hohen Potenzial in der Gelenkendoprothetik*. Materials Testing, 47(4), 207-209. https://doi.org/10.3139/120.100649

Chevalier, B. Cales, and J. M. Drouin, "Low Temperature Aging of Y-TZP Ceramics," J. Am. Ceram. Soc., 82, 2150-4 (1999).

Chevalier, J., Liens, A., Reveron, H., Zhang, F., Reynaud, P., Douillard, T., ... & Courtois, N. (2020). Forty years after the promise of «ceramic steel?»: Zirconia‐based composites with a metal‐like mechanical behavior. Journal of the American Ceramic Society, 103(3), 1482-1513.

Chevalier, J., Gremillard, L., Virkar, A. V., & Clarke, D. R. (2009). The tetragonal‐monoclinic transformation in zirconia: lessons learned and future trends. Journal of the american ceramic society, 92(9), 1901-1920.

Chevalier J, Loh J, Gremillard L, Meille S, Adolfson E. Low-temperature degradation in zirconia with a porous surface. Acta Biomater. 2011 Jul;7(7):2986-93. doi: 10.1016/j.actbio.2011.03.006. Epub 2011 Mar 15. PMID: 21414426.

Chevalier, J., & Gremillard, L. (2008). Zirconia ceramics. In Bioceramics and their clinical applications (pp. 243-265). Woodhead Publishing.

Chevalier J. What future for zirconia as a biomaterial? Biomaterials 2006;27:535−543.

Chevalier, J. M. Drouin, and B. Cales, "Low Temperature Aging Behavior of Zirconia Hip Joint Heads," Bioceramics, 10, 135-8 (1997) ISBN 0080426921.

Deville, S., Chevalier, J., Fantozzi, G., Bartolomé, J. F., Requena, J., Moya, J. S., ... & Dı́az, L. A. (2003). Low-temperature ageing of zirconia-toughened alumina ceramics and its implication in biomedical implants. Journal of the European Ceramic Society, 23(15), 2975-2982.

Deville, S., El Attaoui, H., & Chevalier, J. (2005). Atomic force microscopy of transformation toughening in ceria-stabilized zirconia. Journal of the European Ceramic Society, 25(13), 3089-3096.

Kern, F. R. A. N. K., & Gadow, R. A. I. N. E. R. (2013). Mechanical properties and low temperature degradation resistance of 2.5 Y-TZP–alumina composites. Materiały Ceramiczne, 65(3), 258-266.