• The types of porcelain crowns differ in strength and appearance.woman smile image by Julia Britvich from Fotolia.com
  
  For teeth with root canals, decay or large fillings, crowns are a favored way to reinforce the tooth and prevent further damage. Crowns can also cosmetically enhance or repair a smile. Crowns are available in metal, ceramic or porcelain, though porcelain crowns provide a more aesthetically natural look.
  
  

All-Porcelain Crowns

• All-porcelain crowns are the most natural-looking crowns. Because porcelain is a thicker material, it is necessary to remove more tooth to accommodate the fit of the crown. Porcelain crowns have a higher instance of gingival inflammation and require a higher skill level in the lab and dentists that manufacture and install them. All-porcelain crowns are not strong enough for back teeth.
  
  

Porcelain Fused to Metal

• These crowns feature a porcelain cover of metal framework. Porcelain fused to metal crowns don't have the full transparency of all-porcelain crowns because of their inability to transmit light like real teeth, and often have a grayish appearance. They can also show a dark line where teeth meet gums despite the dentist's attempt to hide the metal band beneath the gums. Porcelain fused to metal is stronger than all-porcelain crowns.
  
  

Zirconia

• Similar to the porcelain fused to metal crowns, zirconia crowns are zirconia ceramic base covered in porcelain. Milled by a computerized machine, zirconia is manufactured to match the shade of the tooth and then fused to a porcelain crown. These crowns offer the stability of porcelain fused to metal with the aesthetic of all-porcelain crowns. Unlike all-porcelain crowns, zirconia is stable for front and back teeth.
  
  

Cerec Crowns

• A variation of the all-porcelain crown, Cerec crowns are all ceramic and manufactured in the dentist's office by a computer. These ceramic crowns do have some limitations, but if made by an artistically skilled dentist, they can be just as aesthetically strong. Cerec crowns, like all-porcelain crowns, are better for individuals with metal allergies.