Question: What does zirconium supported mean?
Answer: In oorder to give more strength to the fragile nature of Porcelain, in all tooth platings (including crone and bridge) zirconium material must be used in substructure because its hard enough and durable.

Question: What are the advantages of using Zirconium?
Answer: Zirconium supported porcelain crone and bridges are as strong as the metal supported ones and last long, if it is correctly crafted and carefully cared by the patient. 
Since the opacity of the zirconium material is equivalent to the real teeth, it does not look inorganic but also look very natural.
Zirconium is also consistent with the gingiva, and does not reflect  any color to the gingiva.  Zirconium is anti-allergenic, due to this characteristics it does not cause gingivitis.  .Unlike with the most metal supported porcelains, gums does not change its color to purpleish/black look with the zirconium.

Question: What are the disadvantages of Zirconium?
Answer: The only disadvantage of Zirconium supported porclains is that they are costlier than metal supported porcelains.

Question: In which circumstances it is best to use zirconium supported porcelains?
Answer: The Zirconium supported porclains are mostly used when excessive teeth material and teeth missing.  Also, it is widely used in frontal parts  of the mouth where esthetics is important.