Normally a metal substructure is used for resistance in porcelain applications. However the search for an alternative material to metal has continued for years because this metal substructure causes damage to gums and has aesthetical shortcomings. The replacement of metal by zirconium, which is also used in other medical fields, for porcelain crown production in dentistry has opened a new era. Porcelain crowns which have zirconium substructure are preferred because they do not cause gum problems and allergies, they fully transmit light and they ensure aesthetical teeth as if they are natural due to the cad-cam technique
What are their disadvantages?