Dental materials are getting better all the time. They are more esthetic, easier for the dentist or laboratory technician to sculpt and mold, have more disadvantages once they are placed, and last longer than earlier favorites. Porcelain is the most commonly used dental material today, but zirconia is fast becoming one of the favored dental materials.
Zirconia crowns are milled from a block of zirconia in a soft pre-sintered state. After milling it is sintered (compacted via heat and pressure) in a furnace where it shrinks by about 20 percent and reaches its full strength. Zirconia is the hardest known ceramic in the industry and the strongest material used in dentistry at present. When baked at ultra high temperatures zirconia crowns are nearly indestructible.
Zirconia is strong, tough, durable, and long-lasting
While the advantages of porcelain include its translucency and esthetics (it looks just like a natural tooth) it lacks strength and longevity. Porcelain is known to chip, crack, and break.
Zirconia is nearly indestructible, but monolithic (complete) zirconia crowns tend to lack translucency, fluorescence, and be dense in appearance. However, when layered with feldspathic porcelain they are both strong and esthetic.