Journal of Dental Research, Vol 66, 1470-1478, Copyright © 1987 by International & American Associations for Dental Research Online Journals
Surface characterization of amalgams using X-ray photoelectron spectroscopy
T. Hanawa, H. Takahashi, M. Ota, R. F. Pinizzotto, J. L. Ferracane and T. Okabe
This study is the first to report on the use of x-ray photoelectron
spectroscopy (XPS or ESCA) for studying the surface films (less than 10 nm
thick) of aged amalgams. The concentrations and electron binding energies
of the elements on the surfaces of four different amalgams aged for 20 min,
one day, seven days, and 30 days were determined quantitatively. For
comparison, the bulk compositions of the amalgams aged for seven days were
also determined after removal of approximately 5 nm of material from the
surface by argon-ion-sputtering. The XPS data revealed that the surface
films of aged zinc-containing amalgams were not a simple oxide but were
primarily composed of a (hydrated) tin and zinc oxy-hydroxide, whereas, in
the zinc-free amalgams, the surface films were primarily a tin oxide. The
concentration of mercury in this thin surface film after aging was
depleted. This suggests that tin and/or zinc preferentially diffused to the
surface and combined with oxygen, forming a surface film and diluting the
mercury concentration in the surface. Another probable explanation for the
depleted mercury is that a minimal amount of mercury in the surface film
evaporated during the aging.
