It’s technically ingenious. The automatic ‘Crack Stopper’.

With zirconium oxide TZP (“tetragonal zirconia polycrystals”), you now have an extremely strong and fracture tough material that reliably withstands even masticatory loads of 800-900 Newtons in the posterior tooth region. The so-called tetragonal modification, hence the additive TZP, ensures even higher stability with an automatic Crack Stopper. The expansion of fine hairline cracks is prevented by a micro-structural modification that stops the cracking energy. It is simply no longer available for crack expansion.

Fatigue behavior of three all ceramic materials
J. Geis-Gerstorfer, P. Fäßler, R. Kirmeier
(Dental-Clinic, University of Tuebingen, Germany)

Ceramic veneering of Au-alloy and zirconia ceramic
G. Gröger*, M. Rosentritt, M. Behr, G. Handel
Department of Prosthetic Dentistry, University of Regensburg, Germany)