The retention of threaded pins in composite resin

The force required to remove three threaded retention pins from composite resin and the pin length for optimum retention were determined. TMS Minuta, TMS Minikin, and TMS Minim pins were tested. Composite resin materials used were representative of large particle, small particle, and microfilled type materials. Results demonstrate that the Minim pin of 2 mm length is the optimum pin for use with large- and small-particle composite resin. However, microfilled composite resin requires a 2.25 mm length of the Minim pin for optimum retention. 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. When these tiny pins are used, the strongest possible composite resin should be selected.