What is Zirconia?
Zirconia (ZrO2) is the oxidized form of the metal zirconium (Zr). Dental laboratories use YTZP (yttria-partially stabilized tetragonal zirconia polycrystals). Zirconia exists in several crystal types, and may change depending on the addition of minor compounds. Zirconia is metal-free and is the fastest growing restorative material in dentistry.
How is Zirconia made?
Zirconia powders are combined and pressed together using two different methods:
Hot isostatic pressing - This is a more expensive process, but the results are highly homogenous blanks with extremely even density, incredible strength, translucence, and low, even shrinkage. (1300 MPa)
Cold uniaxial pressing - Results are less homogenous, lower in density, and less strength. (900 MPa)
What are the differences among Zirconias?
Zirconia comes in many qualities for dental use. Zirconia is milled from zirconia blocks. These blocks can vary greatly from each manufacturer - not all milling labs use medical grade zirconia because it is more expensive. Strength of zirconia is also influenced by the processing methods of different manufacturers and techniques applied by dental laboratories. These differences can have a major effect on clinical outcomes such as marginal fit, translucency, strength, and long-term stability.
Strength of Zirconia
Strength value 800 MPa (low) - 1300 MPa (high) is the average range of clinically acceptable zirconia. Many milling labs promote their own zirconia at a lower cost per unit because they use cheaper blocks, which are more prone to breakage. Only six percent of laboratories mill their own - the other 94% outsource. 74% of this outsourcing goes to China and other countries overseas. We do not outsource. Instead, we only use 1300 MPa zirconia and offer a limited LIFETIME guarantee.
Why use Zirconia?
Biocompatible: 30 years in human body
Zirconia is stronger than PFM
No gold cost
Fits are exceptional; margins are razor thin
Highly esthetic and translucent
Blocks out dark underlying tooth structure
Sintered shaded substructure
Costs less than porcelain fused to gold
All Zirconia Is NOT Created Equal!
Don't be fooled by less expensive zirconias of inferior quality. Your patients have confidence in you and expect your best. We want you to have confidence in us and expect our best.
What about shade?
Zirconia blocks are white. Once milled prior to sintering, color needs to be added. There are two ways to do this: dipping or internal shading. Dipping adds some color, but the restoration is still too opaque and monochromatic. Internal staining is done by hand using 16 Vita shades, which give the restoration a nice blend and depth of color. This is the only method we use. It takes more time, but the results are well worth it.
Indications
Singles, bridges, splints, inlays, onlays, and full mouth
Custom abutments for implants
Preparation
Champher is preferable, but other preps (shoulder, knife-edge) will also work
A minimum reduction of 1 mm
Rounded edges
Not necessary to prep subgingival
Cementation
Traditional cements (non-expanding)
Adhesive or self-adhesive resin cements
Zinc phosphate (will diminish aesthetics)
Teeth should be well isolated and the retainer surface left moist, not dry or wet
J&B recommends MonoCem or Unicem