The Evolution of Zirconia in the Dental Laboratory

The Introduction of Zirconia

The first use of zirconia was in a high strength ceramic family named In-Ceram, by Vita Zahnfabrik. Zirconia was a constituent of the highest strength In-Ceram intended to be used as a posterior restorative. It was combined with alumina to achieve a flexural strength of 700MPa, nearly double that of the glass ceramic materials. The one drawback: though strong, it was not very translucent, and therefore was relegated to posterior crowns and bridges.

The introduction of CAD CAM milling put automation within reach of virtually every dental laboratory and the industry went for it in a big way. When CAD CAM met millable zirconia, a revolution happened. Suddenly, restorative materials could be made easily and had flexural strengths that exceeded 1,000MPa. Unfortunately they too  were not very translucent, so most labs offered a porcelain-veneered zirconia to their dentist-accounts. This was ideal for anterior or posterior use, since these veneering materials offer natural esthetics.

These presintered yttrium partially-stabilized zirconium oxide materials were introduced by 3M Lava, Vita, Dentsply and a host of other companies. Their popularity started growing immediately as an esthetic substructure, owing to the controlled fit and ease-of-manufacture. But the one limiting factor of these strong materials was the lack of their optical vitality. It was for this reason ceramists preferred to build and layer conventional porcelain onto zirconia, where they could replicate natural dentition. For the first time, laboratories had a restoration that offered reasonable esthetics.Both postieror and anterior without the use of alloy substructures.

For several years, zirconia was the non-metal substructure of choice – especially in the posterior area of the mouth.

The Monolithic Crown

Some labs began using zirconia as full-contour crowns or bridges with no porcelain veneer. It was shaded before sintering and for better esthetics stained and glazed after. The new full-contour crowns became known as monolithic restorations. they were easy, fast and very strong, so they quickly found their place as an accepted posterior crown or bridge material.

In 2016, research carried out by many dental companies and universities produced an even more esthetic version which most companies call their “anterior” zirconia. This version is much more translucent but has two shortcomings.

they offer flexural strengths of only 550MPa to 750MPa

the esthetics are somewhat compromised by a lower value (greyer) appearance.

Even with these limitations, this new class of zirconia was welcomed eagerly by dental labs looking for something better looking. Yes, the new materials are better looking than the previous iterations of zirconia, but with a significant limitation. While it is great for single anterior crowns – or even short anterior bridges - in the posterior it can only be used as single crowns.

The Professional Zirconia

Now the newest generation of zirconia has just become available. It achieves what has been desired since zirconia was introduced. It is a natural-looking anterior restorative material with posterior strength. Historically, the use of zirconia was an either/or choice that was often frustrating and clinically limiting. Today, that choice is no longer necessary.

This new generation zirconia offers a desirable level of optical value (greyness) and a more natural, vital appearance. When combined with a flexural strength of over 1,000 MPa, the ideal, professional zirconia is born. From single anterior or posterior crowns to multi-unit bridgework, laboratories will be able to feel comfortable with this material anywhere in the mouth – including posterior bridges that are larger than 3 units.

This new professional level zirconia will help you to reduce your disc inventory, improve esthetics, and improve your posterior to anterior transitions. Keep your eyes open for the introduction of this material by your favorite manufacturer!