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What is Advent of Electrolytic etching of base metal paved a path for development of and explain in detail?
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.