Initial Mercury Evaporation from Experimental Ag-Sn-Cu Alloys Containing Pd

Objective: This study examined the Hg evaporation from several Ag-Sn-Cu alloy powders with and without Pd. Methods: Four series of alloy powders were fabricated for this project: a) CU series - 1.5% Pd with different Cu concentrations (10-14%); b) 1PD series - 1.0% Pd with different Cu concentrations (10-14%); c) AGSN series- 1.5% Pd with different Ag₃Sn/Ag₄Sn ratios at the same Cu concentration (12%); and d) NOPD series - different Cu concentrations (9-13%) with no Pd. The total amount of Hg release from 10 min after trituration was measured from cylindrical specimens (4x8 mm; n=4) at 37°C using a Hg vapor analyzer (Okabe et al., Dent Mater J 16:191-199, 1997). The results were compared to those from commercial alloys (Tytin, Kerr; Dispersalloy, Caulk; Spheraloy, Kerr). The pooled results of the total amounts of Hg evaporated (ng/mm²) for each series (Mean/SD) were analyzed by ANOVA (α=0.05). Identical letters indicate no statistical differences (p>0.05).

Results: Amalgams from the CU and AGSN series released similar small amounts of Hg vapor.  Amalgams for the NOPD series and Dispersalloy released the largest amounts of Hg. The low-Cu amalgam, Spheraloy, released the lowest amounts of Hg. All high-Cu experimental amalgams with 1.5% Pd exhibited lower Hg release than the commercial high-Cu amalgams. Conclusion: We hypothesize that this reduced Hg vaporization for the 1.5% Pd amalgams and Spheraloy may be due to enhanced oxide formation during setting or a higher concentration of Sn in the γ₁ phase of the amalgam. This study was partially funded by NIH/NIDCR grant DE07644.