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What is transformation toughening? Does it have clinical relevance?

Transformation Toughening

Both yttria-stabilised and alumina-stabilised composite materials can be subject to so-called transformation toughening, which affect their stability and longevity in vivo.

The phenomenon of transformation toughening discovered by Garvie et al. (1975) is a stress-induced transformation from the metastable tetragonal phase to the more stable monoclinic phase. The transformation process is accompanied by a volume expansion of approximately 3–4% (Chevalier et al. 2009). This reduces the driving force that contributes to crack propagation in the material (Green et al. 1989) and leads to an increase in strength compared to non-transformable ceramics (Chevalier et al. 2020).

Stress-induced transformation toughening is particularly important for zirconium dioxide implants, as they are exposed to high chewing forces. Under mechanical stress (e.g. chewing, implant loading), transformation toughening has a crack-inhibiting effect and can help zirconium dioxide implants remain stable and fracture-resistant (Chevalier & Gremillard 2008; Chevalier et al. 2009). This is consistent with the results obtained using atomic force microscopy to observe transformation toughening in cerium dioxide-stabilised zirconium dioxide: The stress-induced transformation from the tetragonal to the monoclinic phase near crack tips contributes to toughness by generating compressive forces that inhibit cracking (Deville et al. 2005).

 

References

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 Society103(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 society92(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., El Attaoui, H., & Chevalier, J. (2005). Atomic force microscopy of transformation toughening in ceria-stabilized zirconia. Journal of the European Ceramic Society25(13), 3089-3096.

C. Garvie, R. H. J. Hannink, and R. T. Pascoe, ‘‘Ceramic Steel,’’ Nature, 258, 703–4 (1975).

Green, D. J.; Hannink, R.; Swain, M. V. (1989). Transformation Toughening of Ceramics. Boca Raton: CRC Press. ISBN 0-8493-6594-5.

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