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PORCELAIN INLAYS 199

instances it will be found difficult to tie the inlay
in place without disturbhig the accuracy of the fit.
Judging by what is left on the mixing slab,
Harvard cement, when mixed for setting inlays,
does not become hard under from one to two
hours—depending on the mix—and the maximum
of hardness is not even reached then. The patient
must therefore be warned not to use the teeth in
mastication for a certain time after the inlay is
cemented in place. This cement is not hydraulic
—that is to say, it does not set properly in the
presence of moisture. It must therefore be pro-
tected with a sufficiently thick film of varnish
or other suitable substance that will remain in
place for some hours. It seems an unnecessary
infliction—except, perhaps, in exceptional cases—to
keep the rubber-dam in place for an hour or two,
even if the annoyance is minimised by cutting the
greater part of it away, and tying the remainder
into a kind of little bag that encapsules the tooth.
A small agate pestle and mortar will be found very
useful for remixing any surplus of mixed inlay body
that has become dry. An ordinary watchmaker's
eyeglass (No. 4) will be of great assistance to many
in accurately placing the inlay body in the matrix,
and painting it to exact margins.