A new generation off very strong porcelain materials for fabricating crowns, veneers and inlays helped to advance dentistry in many ways.
The previous generation of metal restorations ( including gold alloys ) would require aggressive reduction of the tooth to allow enough thickness material to provide strength and retention. Cement , the substance used to attach the restoration to the tooth , would provide a simple adhesion , similar to the one that would be provided by a glue.
Porcelain, Zirconia materials that are used now are allowing us to bond the restoration to the tooth and bond is more like a fusion of two objects and one which provides superior strength , fracture resistance and retention. This allowed for a very thin restorations with minimum tooth reduction and great aesthetic qualities. Now these days porcelain , nonmetal restorations are definitely the restorations of choice.