Most dentists think of zirconia as the highest strength, all-ceramic material that they can use to balance esthetics and durability.

It is the material we go to for patients with occlusal risk, for second molars at higher risk of fracture and for all-ceramic bridges.

You have likely heard of flexural strengths of 900-1,400 mPa being thrown around. While this is the flexural strength of a certain category of zirconia, you might not be aware there are different types.

Not all Zirconia has the same strength.

Because dentists have demanded manufacturers make versions that are more esthetic, some types are not as strong and durable as others. The general rule of thumb follows. The prettiest zirconia is the weakest. Conversely, the opaquest zirconia is the strongest. For example, the white opaque zirconia that visible as the substructure on the underside of a bridge is the highest strength and may have flexural strengths of 1,000-1,400 mPa. The other end of the spectrum is the highly esthetic materials we refer to as “translucent,” “crystal” or “esthetic” zirconia, and they may have flexural strength of 500-700 mPa. There is also a category of material with strengths in between.

Because there are many manufacturers and brands, you will want to be familiar with what your lab offers. Ask your lab what types of zirconia they can provide, and their specific strengths. Ask your lab how you should specify which zirconia to use for a given case. This, of course, will be determined by the esthetic and functional demands of the individual situation.

Some labs can note your preferences in their computer. For example, they can note that you always want the middle strength material for second molars, the highest strength for bridges and the prettiest material for premolars.