Influence of Palladium Alloy Elements on Cell Proliferation and Viability

In a preliminary study we reported that elements extracted from two palladium alloys had no significant effect on the proliferation of human gingival fibroblast cells, and the effect on cell viability was marginal (Sun et al., IADR Abstract No. 1839, 2003). Purpose: Verify the effect of elemental release from these two palladium alloys on cytotoxicity using a doubled sample size. Methods: A high-palladium alloy [Freedom Plus (78Pd–8Cu–5Ga–6Sn–2Au–Ru)] and a Pd-Ag alloy [Super Star (60Pd–28Ag–6In–5Sn–Ga–Ru/Re)] (wt. %, both Heraeus Kulzer Jelenko, Armonk, NY) were selected. Forty-eight disk-shaped specimens of each alloy (12.5 mm diameter x 1.3 mm height) were cast and oxidized. The external oxide layers on half of the specimens were removed, and simulated porcelain-firing heat treatment was performed for all specimens. The specimens were placed in 6-well Transwell^TM inserts of cell culture plates and exposed to 5 mL of cell culture medium in an incubator at 37°C and 5% CO₂ for 10 days. Four lines of human gingival fibroblasts were cultured in the medium with elements extracted from the alloys. Fluorescence readings of Alamar Blue that had been added to the cell cultures were recorded at days 1, 3, 7 and 10. At day 10, the numbers of both live and dead cells were counted, and cell viabilities were calculated. Statistical comparisons were performed using ANOVA methods. Results: Extraction of elements from both palladium alloys to the cell culture medium had no significant effect on proliferation of the four lines of human gingival fibroblasts (p > 0.05), and the effect from the oxide layer on their viability was not significant (p > 0.05). Conclusion: The absence of a cytotoxic effect suggests that the biocompatibility of these two palladium alloys is adequate. Supported by NIDCR Grant DE10147.