Zirconia Oxide

From WikiDent

Zirconia exists in 3 major phases:[1]

• Monoclinic - stable, low temperature phase (below 1170˚C)
• Tetragonal - phase at temperatures between 1170˚C and 2370˚C
• Cubic - stable only at temperatures above 2370˚C

By adding yttria as a stabilizer, the tetragonal phase can be stabilized at room temperature. This phase change produces transformation toughening. When a crack initiates between crystals, the stress induces a phase change from tetragonal to monoclinic. As a result, there is a 1% - 5% volumetric increase surrounding the crack which produces resistance to the crack propagation.[2]

This stabilized zirconia is known as, yttria-stabilized tetragonal zirconia polycrystal or Y-TZP. This ceramic is the strongest available in dentistry, reportedly producing a flexural strength between 1000 MPa and 1500 MPa.

References

Papanagiotou HP, Morgano SM, Giordano RA, Pober R. In vitro evaluation of low-temperature aging effects and finishing procedures on the flexural strength and structural stability of Y-TZP dental ceramics. J Prosthet Dent. 2006 Sep;96(3):154-64.

See Also

• Low-Temperature Degradation
• Transformation Toughening