Pin amalgam restoration and pin amalgam foundation

The principles of cavity preparation, retention, pin placement, and finishing of the pin amalgam restoration differ in several respects when applied to the pin amalgam when it is intended to serve as a foundation for a cast restoration. A more conservative extension and removal of undermined enamel is indicated because the amalgam will be covered with a cast restoration. The axial reduction required during crown preparation frequently reduces retention of the pin amalgam foundation; therefore, it is necessary to plan for those alterations during the cavity preparation. The degree of finishing and polishing required is determined by the length of time the pin amalgam foundation is expected to function as an interim restoration.