Retention

RETENTION •         The essential element of retention is two opposing vertical surfaces of the same preparation. •         These may be external surfaces such as the buccal and lingual walls of a full veneer crown (sleeve retention). •         The opposing surfaces can also be internal, such as the buccal and lingual walls of the proximal box of a inlay. •         An intracoronal restoration resists displacement by wedge retention. •         Many restorations are a combination of the two types.