Journal of Dental Research, Vol 71, 1417-1422, Copyright © 1992 by International & American Associations for Dental Research Online Journals
The effects of cleaning on the kinetics of in vitro metal release from dental casting alloys
J. C. Wataha, R. G. Craig and C. T. Hanks
University of Michigan School of Dentistry, Ann Arbor 48109-1078.
The kinetics of the release of elements from six dental casting alloys into
cell-culture medium was assessed by means of atomic absorption
spectroscopy. Alloys were evaluated in the polished and polished-cleaned
conditions so that the effects of cleaning could be determined. Auger
scanning microscopy was used for analysis of the surfaces of selected
alloys before and after exposure to the cell-culture medium. Release
patterns for each element were characterized by the shape of the
dissolution vs. time curve, concentration of the element at 12 h as a
percentage of the 72-hour concentration, and the relative slope of the
curve from 48 to 72 h. Three patterns of release were observed for elements
in these alloys. Type I patterns had logarithmic shapes with relatively
large 12-hour concentrations and low 48-72-hour slopes. Type II patterns
had logarithmic shapes but with moderate 12-hour concentrations and
48-72-hour slopes. Type III patterns were polynomial in shape, had
relatively low 12-hour concentrations, and had large 48-72-hour slopes.
Cleaning did not change the pattern of release but did generally
significantly decrease the quantities of elements released (p = 0.05). The
type of dissolution vs. time curve appeared to be dependent upon the
element and the composition of the alloy. When cleaning reduced
dissolution, surface analyses showed that the cleaning process increased
the abundance of elements such as Au and Pd and reduced the abundance of Ag
and Cu. Elements which were released from the alloys were more abundant on
the surface than in the bulk in both polished and polished-cleaned
conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
