Page 40 - My FlipBook

36 THE TECHNICAL PROCEDURES IN FILLING TEETH.

any attempt be made to cut the enamel from without inward with
the bur. Cutting enamel with the bur dulls the blades very
quickly. After the bur has been used for this purpose a few
times, it should be discarded and a new one employed. The
dull bur may be sharpened by the instrument maker.
In squaring out angles of cavities, the inverted cone bur
may often be used to advantage in such positions as are readily
accessible, as in occlusal, labial and buccal cavities. Usually this
is done by flattening the pulpal wall in occlusal cavities, or the
axial wall in buccal or labial cavities. In order to accomplish
this with the bur the approach must be such that the square end
of the bur may be placed in the plane of the pulpal or axial wall
to be formed, or, in other words, the axis of the hand-piece
must be at right angles to the pulpal or axial wall to be formed.
Then the side or periphery of the bur is engaged in the deeper
part of the rounded pulpal or axial wall, and made to cut
toward one of the surrounding walls. This is then repeated in
another direction, and the bur is finally carried in a similar way
around the whole circumference of the cavity in such a way
that its square end leaves the pulpal or axial wall flat, and
its line angles with the surrounding walls are made sharp and
definite.
The right-angle hand-piece is often useful for doing this
work in occlusal cavities in the lower second and third molars,
and occasionally in buccal cavities in these teeth. With it the
proper position of the bur may be obtained in these places that
are not accessible to the straight hand-piece. The right-angle
hand-piece, as at present constructed, is an awkward instrument,
and it should be used only in well chosen positions, inaccessible
to the straight hand-piece.^ In most cases this squaring out of
the pulpal or axial walls to definite angles with the surrounding
walls is done just as easily and quickly with the hoes 12-5-6,
1 2-5- 1 2, or the 8-3-6 or 12, used with a scraping motion.
These instruments will reach any of these positions if the sur-
rounding walls have been properly formed previous to their use.
In making extensions for prevention in any of the axial
surface cavities the small inverted cone burs may be used to
advantage. If, in excavating proximate cavities, we find that

*It is now expected that a contra-angled hand-piece that will be much more useful,
will be on the market soon.