Image Dental Arts offers a type of crown for your posterior teeth made out of zirconia, which is a very strong ceramic. The zirconia crowns (EZR) are virtually unbreakable and do not require much prepped tooth height.
Porcelain fused to zirconia are beautiful crowns for the anterior (front) teeth and some posterior (back) teeth, but they are more expensive to fabricate. Porcelain fused to zirconia also have more of a tendency to fracture. There are few problems using them on the anterior teeth, but using them on the molars is risky.
The benefit of zirconia crowns (EZR) is a lower cost and a more conservative tooth reduction. The downfall is zirconia crowns are more difficult to adjust and have less translucency. This is why the zirconia crowns (EZR) should only be used in the posterior teeth.