Page 76 - My FlipBook

72 THE TECHNICAL PROCEDURES IN FILLING TEETH.

from angle to angle (nearly — not passing around quite to the
-
actual line of the mesial or distal angle of the tooth, though in
many cases it should).
The incisal wall of this is now broken down with the straight
chisel, and if still further extension to the incisal seems required,
the bur is passed around the incisal wall, cutting away the dentin
from beneath the enamel, which is again chipped away with the
chisel. This cutting should be carried to the incisal until such
portion of the surface as may seem especially liable to future
decay has been removed. Generally, it is not necessary to make
considerable extension in this direction.
Next, attention is turned to the gingival wall. The first cut
has removed all injured enamel in this direction, but the length
of the free gum margin will allow of the cavity being extended
more, without reaching the gingival line, and a finish can be
made against perfect enamel that will be fully covered by the
gum margin. This is just such a wall as is most desirable
in all smooth-surface labial or buccal cavities. Decay
never begins under a covering of healthy gum, and as long as
the margin of the filling is thus protected, and the margin well
made, it is safe; therefore the enamel is carefully planed away to
the proper position with very sharp chisels with a motion along
the length of the wall or from mesial to distal, and from distal
to mesial. In executing this the thumb and palm grasp is to be
preferred.
The dentin wall is now cut back with the same inverted cone
bur used previously or with hoe 6-2-12 or 8-3-12, and slightly
undercut in order that it may be retentive. Any corrections
required in the gingival enamel wall are now made. This
should be inclined strongly to the gingival, the particular
inclination having been determined by observation of the direc-
tion of the enamel rods while trimming away the enamel from
this surface. The incisal wall is also squared up and the dentin
wall slightly undercut— about as an inverted cone bur placed
This is generally
with its flat end on the axial wall would do it.
easier done, however, with hatchet 6-2-23. Then the enamel
wall is finished, .inclining it slightly to the incisal. Its cavo-
surface angle should be slightly beveled by a planing motion
with a very sharp chisel carried very lightly along its length.
The mesial and distal angles of the cavity are similarly finished.