Page 84 - My FlipBook

o METHODS OF FILLING TEETH.
7
thing is that perfect cohesion is gained by this, and is not obtained if
any other plan be adopted. How often have we all removed some
other mari s filling , taking it away in a solid mass but leaving gold in
the bottom of the undercut ? What does that mean ? It means that
the undercuts were presumably made, to assist in the retention of the
but because of the manner of the no such result
filling, packing gold,
accrued. The explanation lies in this : Gold loses its cohesive prop-
erty in proportion as it is condensed. Thus having partly filled an
undercut, the gold placed therein remaining in position because it is
wedged in, we have before us a small surface of gold presented, and
an undercut lessened in depth. If the next pellet does not cohere,
we would have been as well offwith a shallower undercut. If a pellet
which is too large be now used, the pressure of the plugger begins
to condense it before it is made to touch the gold in the bottom of the
groove, the result being that there is less cohesion, if indeed there is
The with a
any. principle, then, is to begin piece just large enough
to be wedged in without lateral pressure, and to add next a similar
piece, or one even smaller, so that it will readily reach the first, and
cohere with it before any great pressure has been exerted. In other
words, it should be condensed after it has cohered, instead of before.
This one principle observed, will make approximal fillings permanent,
which would fail where it is neglected.
For similar reasons, if a pellet by any accident has become slightly
it should be in the waste-box. It should under
compressed, placed
no circumstances be put with the good gold, and finally used in some
That is an
large cavity. economy which is reprehensible, the more
so because it cannot be detected. I saw this done once in a contour
filling, by a friend for whom I was malleting. I subsequently saw the
same otherwise beautiful, with about of its corner
filling, one-quarter
broken off. I thought at the time that I understood the accident, and
The had a flaw in it, and the flaw was caused
I think so still. filling by
that bit of partly condensed, and, therefore, imperfectly cohesive, gold.
This compression of a pellet before it is brought into contact with
the surface of the already packed gold brings us to another point of
In the surfaces of
great importance. approximal unusually long
we be
bicuspids may compelled to work with insufficient space. I
mean space insufficient for the placing of a pellet of usual size without
The be one in which we would be author-
compression. cavity may
ized to use fairly large pellets ; it may be one in which to use very
small pellets would mean to compel the patient to submit to too long
an operation. Yet we may find that every pellet, as it is pressed to
place either between the teeth or through the possible orifice in the
What must
cutting-surface of the tooth, becomes partly compressed.
be done ? After showing that such pellets do not produce good results,