Retention of threaded pins in amalgam

The force required to remove three self-threading retention pins from amalgam and the pin length for optimum retention was determined. Link series TMS Minuta, TMS Minikin, and TMS Minim pins were tested; Minim pins were tested at various lengths. The amalgam materials used were representative of a high-copper admixture type and a ternary spherical-type alloy. Results demonstrate that the Minim pin of 2 to 2.5 mm length is the optimum pin for retention in high-copper type amalgam. Minuta and Minikin pins are removed with only a small amount of force and should be used only when clinical prudence requires a small pin; and when used, the strongest possible amalgam should be selected.