Effect of Pd and In on mercury evaporation from amalgams

The amount of Hg vapor released from "synthesized" gamma 1 with 1% (wt) Pd was reported to be less than 30% of that from gamma 1 with no Pd. This study tested the hypothesis that Hg evaporation from Pd-containing amalgams decreases with Pd concentration and that In also reduces Hg vapor. Specimens (4 mm dia, 8 mm long) were prepared by triturating Ag-Sn(25%)-Cu(12%) alloy powder containing 0.5-9.0% Pd with pure Hg and by triturating 3% Pd alloy powder with Hg containing 1-5% In (all residual Hg approximately equal to 62%). The total amount (ng/mm2) of Hg vapor released at 37 degrees C from freshly prepared amalgams was measured. Pd (3-9%) in the powder significantly (p < 0.05) decreased Hg vapor release from amalgams during setting. Use of In-containing Hg also reduced Hg vapor release (5% In, p < 0.05). The reduction in the Hg vapor pressure by adding Pd and the rapid oxide film formation on the In-containing amalgam appear to work together to reduce Hg vaporization from these amalgams.