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PORCELAIN INLAYS 195

leads him to consider that maintenance of integrity
of margins (meaning resistance of margins to decay)
will principally depend on the preservation of the
cement joint. The closer the fit of the inlay the
less chance there is for particles of food to collect in
the disintegrated joint, and the probabilities are that
the closer the joint the less rapidly the cement will
be dissolved. The writer has seen cases where decay
has rapidly attacked the margins, but this was due
to the overlooking of a defect in the enamel near to
the margin. He has seen exactly the same thing
with gold fillings. As an illustration of this, he
may say that he inserted a contour gold filling
in an upper bicuspid, the margins of which were
well extended for prevention. Six months after-
wards a pin-point cavity of decay was discovered
near the cervico- palatal angle. This decayed point
was close to the enamel margin of the filling, but
had not extended to the filling. The decayed part
was cut out, extended to the filling, and filled.
In another six months an exactly similar point of
decay was found midway between the cervical and
occlusal margins, also on the palatal side. This
was cut out, extended to the filling (it was close
to the filling, but had certainly not commenced at
the margin), and filled. Here are two causes of
failure, both on the same side of the filling,