40 years ago, Garvie and his Australian co-workers reported that the stress induced transformation of metastable tetragonal zirconia grains to the monoclinic symmetry could give rise to a powerful toughening mechanism. Their results even led them to consider zirconia systems as analogues of certain steels in terms of mechanical performances, while exhibiting a much superior corrosion and biological performance. This seminal paper generated extraordinary excitement in the ceramic community and led to a large variety of new applications, with a special interest in orthopedics first then in dentistry today. Zirconia in dentistry was first developed for dental restorations, for which translucency and optical properties must be associated to a high mechanical resistance and stability in vivo, and then for implantology where biological integration is emphasized.
Here we show that ‘zirconia’ is not one, but a family of materials, with many different (mechanical/optical) properties. Playing with the microstructure (grain size), alloying (choice of dopant and content) and phase content through processing, it is possible to develop zirconia ceramics with a high degree of translucency and/or high strength and/or a certain transformation-induced plasticity before failure. Thus, 40 years after their inception for structural applications, zirconia ceramics can answer different needs as a function of the targeted application/product. We will thus review the current choice of zirconia ceramics available for dental use and show current trends both for restoration and implantology. In particular, we present our current work on ultrafine yttria-doped zirconia with an excellent balance between translucency-aging resistance-strength and on both ceria-doped and yttria-doped compositions that exhibit some transformation-induced plasticity before failure and strain-accommodation. These new developments may create new opportunities for clinicians in their practice.
About Dr. Jerome Chevalier, DDS :
Born in 1970, Jérôme Chevalier is currently full Professor at the National Institute of Applied Sciences, in France. His research activity is mainly focused on ceramics, from their processing to their mechanical and functional properties. He has published more than 200 international papers with a review process, 8 review papers in journals and encyclopedia, 4 book chapters. He is co-author of 10 patents and his research has led to the commercialization of 6 medical products. More than 14.000 papers have cited his work (Google Scholar). He is highly recognized for his work on the mechanical and fatigue behavior of ceramics, on zirconia, and more generally on ceramics for orthopedic implants, scaffolds for tissue engineering and dental ceramics.