Surface treatment of mercury-free alloys

Finishing and polishing methods were examined for two metallic direct resto rative materials being proposed as possible alternatives to amalgam, namely a gallium alloy and it consolidated silver alloy. The polished surfaces we re compared to a conventional spherical amalgam (Tytin). After initial surf ace treatment with a 12-fluted tungsten carbide bur in a high-speed dental handpiece, three polishing methods were evaluated: slow-speed polishing bur s, rubber polishing points, and polishing disks (Sof-Lex). Each of these me thods was followed by an additional surface treatment in which a pumice-flo ur/water slurry was applied with a rotary brush and a final surface treatme nt with a zinc-oxide/ethanol slurry that was applied with rotary rubber cup s. The surface roughness was evaluated by profilometric measurements and li ght microscopy. The results showed that the smoothest surfaces for all meta ls were achieved with rotary finishing and polishing disks. Using the rubbe r points resulted in surfaces that were statistically similar to the disk-p olished surfaces on all three materials. The polished surface of gallium al loy was consistently slightly rougher than that of amalgam. The consolidate d silver also presented a consistently rougher surface than did amalgam, al though these differences were not statistically significant. The additional polishing with pumice and zinc oxide improved the luster, but did not sign ificantly improve the measured surface smoothness in any of the restorative materials studied.