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CHAPTER X.
MANAGEMENT OF PIT AND FISSURE CAVITIES.
(CLASS ONE.)

Location. Class One cavities occur in the occlusal surfaces of
molars and bicuspids; in the middle and occlusal thirds of the buc-
cal and lingual surfaces of molars and in the lingual surfaces of
nicisors, more frequently in the laterals. (See Figs. 1 and 2.)
The Predisposing Cause of decay in these localities is a fault in
the enamel due to imperfect closure of the enamel plates, affording
a convenient point for the lodgment of food particles and the ac-
tive principles of fermentation which is the exciting cause of all
tooth decay.
Extension for Prevention is Seldom Necessary in this class of
cavities from the fact that the surface of the enamel in the immedi-
ate neighborhood is exposed to the friction of mastication. It is
only necessary to cut away the enamel walls sufficiently to uncover
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the area of affected dentine, and to include in the cavity outline
' all sharp grooves connected with -seat of primary decay to a loca-
tion that will permit a smooth finish to the surface of the filling
and an outline void of angles.
Tendency to Extensive Dentinal Decay must be remembered in
dealing with this class of cavities as the merest opening through
, ,
the enamel will frequently, upon excavation, show an extensive loss
of dentine.
,^.
' Incipient Decays in Occlusal Defects.
\ r ,,
Description. Upon examination it is found that the tine of a
I,
'M sharp exiDlorer Avill pass betAveen the non-united plates of enamel
to the depth of the entire thickness of enamel in one or more points.
A more careful examination may show the surface of the dentine
to be softened to a greater or less extent immediately pulp-wise
from the enamel fault. Such cases demand immediate attention.
Outline Form. To open such cavities there is placed in the en-
gine a discarded No. i/o or 1 round bur which has been made into
a spade drill by flattening on two sides. This drill is made to
travel between the plates of the enamel through a major portion
of the defect, whicU results in Avidening the fissure. This prelimi-
nary step will result in much saving of burs, as a bur which has
been once used on an enamel wall is unfitted to cut dentine. The
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