Zirconia Restorations: Setting Expectations

It seems like whenever I am with a group of dentists discussing the latest and greatest advances in dental technology there are a lot of questions about full contour zirconia crowns. Common questions include:

• In which situations are they most appropriate?
• Why are they so difficult to match to natural teeth or other restorations?
• Why do they look so bright compared to other types of restorations I’ve used?

In my next few articles I’ll provide some background information, discuss indications and review the advantages and disadvantages associated with this material.

Zirconia has been a tremendous addition to the dental laboratory material arsenal. Because of its crystalline structure, it is more fracture resistant than alumina or lithium disilicate ceramics, making it an ideal substitute for metal when a more natural esthetic result is desired.

The primary use of zirconia has been for bridge frameworks or for copings. A feldspathic layering ceramic is then applied to the framework to develop the appropriate color and achieve the desired translucency. Anterior restorations have been highly successful both in esthetics and strength using this process. Posterior restorations have experienced a higher ceramic chipping or fracturing rate when compared to other layered restorations.

Full contour zirconia restorations must be produced using CAD/CAM technology, and recent improvements in software have allowed laboratories to develop more natural tooth morphology than when the material originally came to market. The major downside to zirconia is that it is relatively opaque when compared to other indirect restorative materials, even with the introduction of more “translucent” generations. The upside is that this opacity can help to mask underlying structural discolorations.

In addition, its low thermal conductivity acts as an insulator for those with tooth sensitivity or the potential for its development. Research has also shown that the wear on natural teeth opposing zirconia crowns is less than with feldspathic porcelain restorations.