Removable Partial Denture Attachment
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.
Extracoronal Attachment for Removable Partial Denture uses mechanical resistance to displacement through components placed or attached to external surfaces of an abutment tooth or teeth. Extracoronal attachments are traditionally easier to insert and remove. This type of attachment for removable partial denture is used for patients with limited manual dexterity, or the prosthesis has a difficult path of insertion and removal.
OSO is an extracoronal attachment which provides free movement in all planes. It utilizes replaceable O ring. It is a resilient attachment with vertical and hinge stress breaking action for free end removable partial dentures. OSO O-Ring System for RPD is economical and easy to use.
Photo shows the abutment – Fixed Partial Denture with the O-SO distal extension attachment. FPD with lingual shoulder for the lingual bracing arm.
OSO and other extracoronal precision attachments are normally resilient to allow free movement of the prosthesis to distribute potentially destructive forces or loads away from the abutments to supportive bone and tissue. Three distinctive movements are defined in function: