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66 THE TECHNICAL PROCEDURES IN FILLING TEETH.

Parallel walls and a flat pulpal wall as a seat, or a good strong
peripheral ledge in very deep cavities, gives perfect anchorage.
No undercuts are required. All of this done, the cavity should
be swept free of chips and fine dust and is ready for filling. The
use of chip-blower should be sufficiently frequent and thorough
to keep the cavity free from cuttings, and the whole field of
operations cleared of debris during all parts of the operation.
In second and third molars some differences of procedure
and of instrumentation are necessary on account of the differ-
ences of position. Often the bureau not be brought into position
for effective use in squaring up the surrounding and pulpal walls,
and this is done best with the hoes 12-5-6 or 1 2-5-12, or, in some
positions, hoe 12-5-23, used with a scraping motion. In a few
cases the bur may be used effectively in the right-angle hand-
piece, but this is an awkward, and generally ineffective, instru-
ment, and its use instead of hand instruments should be reserved
for cases of the greatest necessity.
The mesial wall, and especially the mesio-buccal angle
of occlusal cavities in the second and third molars, should be so
inclined to the mesial and buccal as to allow of packing gold
against them easily. The amount of this inclination will depend
upon the position and the character of the approach to the
cavity. If the mouth of the patient opens well, giving a good
view, and allows instruments to be placed very nearly parallel
with the long axis of the tooth operated upon, very little inclina-
tion to the mesial and buccal will be required. If, on the other
hand, the mouth does not open well, and the approach of the
instruments must be at a considerable inclination to the distal,
the mesial wall and the mesio-buccal angle must be inclined in
proportion, or sufficiently to allow of mallet force being applied
parallel with the plane of this wall and angle. Any failure in this
will require in filling with gold that the gold be packed against
this wall by lateral hand-pressure, which greatly increases the
difficulty of making a good filling. When the preparation is for
amalgam fillings this is not demanded, but it is still desirable.
When the distal pit in the occlusal surface of the upper
molars is the seat of operation, the procedure is not essentially
different, except that the approach should be rather more from
the buccal. The same instruments and the same methods should
be employed. In these it is very generally necessary to cut out