Alloy particle shape and sensitivity of high-copper amalgams to manipulative variables.

Compressive strength, dimensional change during hardening and residual mercury content of three high-copper spherical particle amalgams (Tytin, Logic and Valiant), two admix amalgams (Dispersalloy and Permite C) and a conventional lathe-cut amalgam (New True Dentalloy) were determined as a function of condensation pressure and trituration time. The properties of the three amalgams containing non-spherical particles were markedly dependent on condensation pressure in the range 3 MPa to 14 MPa. Specimens condensed at 3 MPa showed substantially lower strength, greater expansion during hardening and higher residual mercury contents than did specimens condensed at 14 MPa. The three high-copper spherical particle amalgams, on the other hand, were comparatively insensitive to condensation pressure. Variations in trituration time between 5 and 12 seconds had little effect on the properties of any of the amalgams.