Attachments for Removable Partial Dentures can be categorized into: intracoronal attachment or extracoronal attachment, rigid attachment or resilient attachment, and precision attachment or semi-precision attachment.
Let’s limit the discussion on the first 2 categories of attachments mentioned, the intracoronal attachment and extracoronal attachments. Intracoronal attachment for removable partial denture is either cast or attached totally within the natural contours of an abutment tooth or teeth. Typically, it is composed of prefabricated key and keyway with opposing parallel walls, which serve to limit movement and resist removal of removable partial denture through friction. The principle of internal attachment was formulated by Dr. Herman E.S. Chayes in 1906.

O-SO distal extension attachment male component on the proximal of the Fixed Partial Denture
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