The Evolution of Zirconia in the Dental Laboratory
- Apr 21, 2018 -
Zirconia restorations have become the material of choice in restorative dentistry today, out pacing the previous porcelain fused to metal champions and reaching nearly 80% of the current crown and bridge prescriptions filled by laboratories. With this generational change in mind, lets take a look at how zirconia evolved.
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.