Phase transformation and slow crack growth study of Y-TZP dental ceramic

The aim of this study was to understand the phase transformation in yttria-stabilized tetragonal zirconia (Y-TZP) dental ceramic and its effect on slow crack growth (SCG) behavior in oral environment. The SCG behavior of Y-TZP dental ceramic was investigated in air and in water at 37 °C by static fatigue testing on pre-cracked specimens. Additionally, Confocal Raman spectroscopy has been used for the quantitative assessments of phase transformation zones at the crack tip. Environmental metastability of Y-TZP dental ceramic took place a stress/water induced tetragonal - to - monoclinic (t→m) phase transformation and proceed with time. The SCG behavior in water at 37 °C is a result of cracking through a zone of monoclinic material ahead of the crack tip. The crack growth rate is proportional to the probability of successful completion of water/stress induced t→m phase transformation. The Raman spectroscopic assessment provides a new angle of view in understanding the SCG behavior of zirconia dental ceramics in different environments.