Page 162 - My FlipBook

146 THE TREATMENT OF TEETH
therefore to be preferred to those which attain a
rock-like hardness.
The writer tested the cements he is in the habit
of using as follows : a ball of putty-like consistency
was made, immediately dropped into Stephen's ink,
and left there for twenty-four hours ; a slight per-
meation of the cement resulted. Experiment No. 2
—A similar ball was made, and a pin was inserted
into it to hold it while it was varnished ; the
varnish was partially dried with a chip blower, the
pellet was dropped into the ink, and left there for
twenty-four hours ; in this instance no permeation
of the cement resulted. Similar experiments made
with the liquid of this cement, and the powder
of another cement, produced precisely similar re-
sults. Another popular cement was then tried,
with the result that it was completely permeated,
whether varnished or not, and the unvarnished
cement when removed from the ink was found
to be considerably reduced in size. These little
experiments are mentioned merely to show that
a wholesale condemnation of cements because
some of them are readily permeated is hardly
fair. The writer does not for a moment consider
that the cements he tested with such good results
as regards permeability are very much better than
many other makes. They are good cements with