Journal of Dental Research, Vol 55, 1001-1003, Copyright © 1976 by International & American Associations for Dental Research Online Journals
Influence of amalgam, alloy, and Hg on the in vitro growth of Streptococcus mutans: III. Effect of specimen age and composition
L. J. Nunez, G. Schmalz and J. H. Hembree
We will now summarize the conclusions from parts I, II and III of this
study. A test procedure has been developed that provides a simple, quick,
and nondestructive means of monitoring the in vitro growth of S mutans in
the presence of amalgams and alloys. The spectrophotometric readings are
related in a simple way to growth expressed as dry weight of bacteria and
metabolic products. Results are expressed as growth relative to controls
which represent bacteria growing under identical conditions but not in
contact with metals. The %RA60 value that represents growth after 60 hours
relative to controls is used as a measure of growth in the presence of
alloys or amalgams. Spherical, fine cut, and dispersion alloys were studied
as well as amalgams prepared from these alloys. The dispersion alloy
inhibits growth less than the spherical alloy which in turn inhibits growth
less than the fine cut alloy. The results for amalgams prepared from the
alloys are reversed. At an aging time of two hours, dispersion alloy
amalgams inhibit growth more than spherical alloy amalgams and fine cut
alloy amalgams. Aging time of amalgams greatly influences the growth
inhibition. Immediately after trituration growth is inhibited, but this
inhibition is lost with aging. Different types of amalgams seem to lose
growth inhibition at different rates. Hg composition in the range of 48 to
52% seems to have little effect on growth inhibition. It remains for
clinical studies, which are concerned with the incidence of secondary
caries associated with amalgams, to demonstrate that the age and nature of
the amalgam are significant.
