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130 THE TECHNICAL PROCEDLTtES IN FILLING TEETH.

every filling of whatever description that is intended for perma-
nence should be made against clean freshly cut walls. These
need neither washing nor drying. But they should be freed from
all chips and dust as described.
The above will be taken as the method under the varying
conditions named of making the toilet of a cavity whenever, and
wherever, this is mentioned in the following pages. The descrip-
tion of the process will not be repeated, as that given here is
regarded as applying to all possible locations and conditions.

DEEP OCCLUSAL CAVITIES IN MOLABS.

ILLUSTRATIONS: FIGURES 12S137.
Turning now to the management of deep pit cavities in the
occlusal surfaces of molars, we may illustrate the process of
excavation more completely. The operator should have clearly
in liis mind not only the form of the tooth, but every part of its
anatomy clearly outlined, together with the length of the horns
of the pulp in teeth with long, sharp cusps, as compared with the
length of the horns of the pulp in teeth with short, obtuse cusps,
the probable form of these in the child and the reduction of the
size of the pulp and the shortening of its horns that occurs with
age. In the child the pulp will become exposed by a decay of
much less depth than it would do if the patient were thirty or
forty_ years old. It is also much more liable to be exposed in
the preparation of cavities unless these matters are held clearly
in view. In this, the recessional lines of the pulpal horns are
of especial importance and require careful consideration.
Desceiption of case. In Figure 128 an upper molar is rep-
resented with a large pulp chamber and with long puljial horns.
It is split bucco-lingually, exposing a decay, which, under the
conditions, is dangerously deep. It is the first illustration in a
series of ten for the purpose of more fully explaining the steps
in excavating such cavities and avoiding the dangers of pulp
exposure.
Outline fobm. Such a cavity is opened best with chisels,
such as straight chisel 15 and binangle chisel 15-8-6. The instru-
ment should be placed near the margin of the pit and used with
hand pressure, throwing the chips into the cavity as represented
in Figure 128. This should be continued, going partly around
the original oj^ening, as shown in Fig-ure 129, enlarging the open-
ing and substituting the mallet for the hand i:)ressure. This will
give room for the cavity to be cleared of the chips thrown loosely