Page 53 - My FlipBook

LEAKAGE.
39
quently hide a portion of the cavity should it encroach upon the
approximal surface. In favorable cases I have filled the portion along
the festoon, and then have removed the in onier to reach that
clamp
which it covered. is an
part It exception, however, when this can
be done without the ingress of moisture. Another class of cavities
where this clamp cannot be employed is where there has been extreme
recession of the gum about the neck of a long cuspid, followed by
caries which reaches the receded The bow limits the
gum-margin.
distance to which the clamp may be made to reach.
For teeth other than the cuspids the How cervix clamp, No. 125, is
the best, known to me. The inventor has
recognized the fact that a
clamp for these cases should have three bearings upon the tooth, be-
cause of the fact that the palatal jaw will not bite on a line with the
labial. Being bowed over the cutting- edge of the tooth, it has the
same limitation as the Evans.
I will dismiss the subject of clamps by saying that, excepting festoon
cavities, the clamp should preferably be placed upon a tooth other
than the one to be filled ; also, in applying a clamp care should be
taken not to press too hard against the sensitive gum, and especially
not to bite the gum itself, as is often done on the palatal side.
Leakage. When we recall that the dam is placed over teeth for
the purpose of keeping out moisture, it is plain that when leakage
occurs our object has been frustrated either wholly or in part. Much
has been written to account for the failure of the
gold fillings along
border. I think cent, of these failures be
gingival ninety per may
attributed to the Moisture is dammed
leakage during operation. easily
up in a dry mouth, but in one abundantly supplied with saliva the
greatest skill is required to keep a cavity absolutely dry, so dry that
at no time after placing the dam can even a trace of moisture be
observed.
It will profit us to consider somewhat carefully this subject of leak-
in relation to failure at the
age, especially gingival margin.
Let us suppose that the cavity is in the approximal surface of a
central incisor, and so closely approaches the gum that a ligature is
needed to bring the gingival border into view. Before placing the
dam the parts are all wet ; so after the dam has been placed this moist-
ure must be wiped away, and this is done. The dentist then proceeds
to prepare the cavity, when, after using a chip-blower, he is surprised
to find that some of the 'dust still adheres near the upper border.
This shows that there was moisture. He concludes that he had not
wiped it thoroughly dry, and does so now. He uses the engine-bur
a second time, and when the dust has been blown away there is still
the same evidence of moisture. Having thoroughly dried the part
before, he is now satisfied that there is a leak. Examination shows