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224 PREPARATION OF CAVTTTES.
In the foregoing classification the cavities have been arranged pro-
gressively from the simplest (^1) to the most complicated (7').
I. Simple Cavities on Exposed Surfaces.
HK'USPIDS AND MOLARS.
Class A.—Cavities upon the ocdusal surface are very accessible and
in l"ull view, enabling the operator to see every part of the cavity and
affording him i)lenty of room in which to operate. Naturally those
nearest the front, as in the bicuspids, present the advantage of greater
accessibility, but none of them are difficult to prepare and fill except
under unusual conditions.
Usually the first part of a bicuspid crown to become affected by
caries is the fissure between the cusps. Sometimes it presents merely as
a black line into which only the point of an explorer will penetrate
at a later stage the cavity is more fully defined by the greater pro-
gress of caries and the crumbling of the walls of its orifice. In the
first instance the cavity is most readily and comfortably o])cned by
means of the tapering fissure bur shown in Fig. 163. After passing it
into one of the terminal pits of the cavity it may be drawn along toward
the other, opening the fissure quite freely. Once open, the decay may
be removed and the cavity shaped by a suitably sized round bur
(Fii^. 162). As the decay has usually progressed farther in the region
of the terminations of the cavity than in
F^^- 1"^- the space between them, the cavity when
fully formed will be oblong in shape and
contracted in the centre. In Fig. 172,
A shows this form, while B represents
the same surface before being oiierated
^
Cavity in sulcus of a Viii'uspia.
upon.
In preparing the cavity no more sound tooth-structure should be
sacrificed than is absolutely necessary, but every portion of decay should
^^ thoroughly removed and particular attention be given
Fig 173
to opening up the minor fissure terminations as shown at
A a, B B (Fig. 173).
When completed, the cavity should be very slightly
07/
larger within than without, the margins should present
^ no angles, but only a series of curves in outline, and the
The fissure
terminals. marginal edges should be slightly bevelled outwardly.
Bicuspid cavities of this character vary in size according to the extent
of decay, but the essential features in each case are very similar. The
palatal. In the forming of compound terms, where the mesial, or dintal surfaces are
included, these terms precede the others. Where they are not included and the word
occlusal is used, it is given first phice.
224 PREPARATION OF CAVTTTES.
In the foregoing classification the cavities have been arranged pro-
gressively from the simplest (^1) to the most complicated (7').
I. Simple Cavities on Exposed Surfaces.
HK'USPIDS AND MOLARS.
Class A.—Cavities upon the ocdusal surface are very accessible and
in l"ull view, enabling the operator to see every part of the cavity and
affording him i)lenty of room in which to operate. Naturally those
nearest the front, as in the bicuspids, present the advantage of greater
accessibility, but none of them are difficult to prepare and fill except
under unusual conditions.
Usually the first part of a bicuspid crown to become affected by
caries is the fissure between the cusps. Sometimes it presents merely as
a black line into which only the point of an explorer will penetrate
at a later stage the cavity is more fully defined by the greater pro-
gress of caries and the crumbling of the walls of its orifice. In the
first instance the cavity is most readily and comfortably o])cned by
means of the tapering fissure bur shown in Fig. 163. After passing it
into one of the terminal pits of the cavity it may be drawn along toward
the other, opening the fissure quite freely. Once open, the decay may
be removed and the cavity shaped by a suitably sized round bur
(Fii^. 162). As the decay has usually progressed farther in the region
of the terminations of the cavity than in
F^^- 1"^- the space between them, the cavity when
fully formed will be oblong in shape and
contracted in the centre. In Fig. 172,
A shows this form, while B represents
the same surface before being oiierated
^
Cavity in sulcus of a Viii'uspia.
upon.
In preparing the cavity no more sound tooth-structure should be
sacrificed than is absolutely necessary, but every portion of decay should
^^ thoroughly removed and particular attention be given
Fig 173
to opening up the minor fissure terminations as shown at
A a, B B (Fig. 173).
When completed, the cavity should be very slightly
07/
larger within than without, the margins should present
^ no angles, but only a series of curves in outline, and the
The fissure
terminals. marginal edges should be slightly bevelled outwardly.
Bicuspid cavities of this character vary in size according to the extent
of decay, but the essential features in each case are very similar. The
palatal. In the forming of compound terms, where the mesial, or dintal surfaces are
included, these terms precede the others. Where they are not included and the word
occlusal is used, it is given first phice.
