Advent of Electrolytic etching of base metal paved a path for development of
A technique for the electrolytic etching of cast base metal  retainers was developed at the University of Maryland by  


Thompson  and  Livaditis.  Etched-cast  retainers  have   definite advantages over cast-perforated restorations: 



Retention is improved because the resin-to-etched metal bond can be substantially stronger than the resin-to-etched  enamel.  The  retainers  can  be thinner yet still resist flexing. 




The oral surface of the cast retainers is highly polished and resists plaque accumulation.
Cast perforated resin bonded fixed dental prosthesis
Maryland Bridge
Rochette Bridge
None of the above