Empress crown - Empress is strictly speaking not a porcelain, but is more like a glass. It can be called a ceramic material. The Empress material is cast rather than baked as a feldspathic porcelain crown is. The fit of Empress is more precise than the baked feldspathic porcelain. However, the color in Empress is mostly baked on the outside. Empress can be very beautiful. For appearance's sake, some expert cosmetic dentists prefer the feldspathic porcelain, and some prefer the Empress.
Procera crown - Procera is a milled ceramic on the inside with a more traditional porcelain baked onto the outside. The advantage of Procera is its exceptional strength. However, the milled ceramic core is opaque white, so many cosmetic dentists feel that it isn't as natural-looking as the more translucent materials. An advantage of Procera is that it doesn't have to be bonded to the tooth but can be cemented with ordinary crown and bridge cement, a technique familiar to all dentists.
Lava crown - Lava is similar to Procera, but the milled ceramic on the inside is a more translucent Zirconia, rather than an opaque white material. The Zirconia is shaded, and then the final esthetics of the crown are achieved in the baked-on outer layer. The Lava crown can also be cemented with traditional techniques. However, any crown cemented with a traditional crown and bridge cement is going to be susceptible to a compromise in the appearance if that cement line ever shows.
InCeram crown - InCeram is made of a very dense and very tough aluminous porcelain. It also has excellent esthetics, but is more opaque than feldspathic porcelain. InCeram is also strong enough to be cemented with traditional dental cement.
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There are several factors that need to go into the selection of a crown material: strength requirements, esthetic requirements, the abrasivity of the material against the opposing teeth, and the skills of the dentist. There is not a single crown that is clearly superior for all situations. Many cosmetic dentists will have several types that they will use, each for a different situation.
All-porcelain is generally not as strong as porcelain fused to metal. It has to be bonded to the tooth in order to have adequate strength for oral function. The bonding technique is very demanding and technique sensitive.
With porcelain fused to metal, the porcelain has to be opaque in order to block out the appearance of the metal underneath. They all also eventually develop an unsightly dark line at the margin where the edge of the crown meets the tooth.
Some of the all-ceramic systems that have an inner ceramic core with an outer layer of porcelain baked on require more tooth reduction. Grinding away more of the tooth is often not desirable.
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