Page 65 - My FlipBook

EXCAVATION OF CAVITIES PA" CLASSES. 01

The primary physical condition leading to the location
of caries in these positions is a foult, or imperlection in the
enamel — an imperfect closure of the enamel plates — which
leaves an opening of more or less depth as a pit or fissure, and
it is in these that decay starts. The surface of the enamel in
the immediate neighborhood of these is fully exposed to the
friction of mastication and is kept well cleaned. For this
reason there is no disposition to the spreading of the carious
process upon the surface of the enamel. Therefore, these
cavities all belong to the class which do not require extension of
the cavity outiines for the prevention of the recurrence of decay.
All the extension that is necessary is such cutting away of the
cavity walls as will fully uncover the carious area and present a
surface upon which a good, smooth finish of the filling can be
made. In order that this good, smooth finish may be made, it
is necessary that all sharp grooves connecting with the cavity be
cut out to a point where the enamel is sufficiently level.
Pit Cavity in Central Fossa of an Upper First Molar No. I.
Description.— Upon examination a small pit in the enamel
is found and the point of the exploring instrument passes
through it into the dentin, which seems to be softened, show ing
that caries has begun. The surface of the enamel about the pit
is clear and clean. The buccal groove is deep and sharp, but
the mesial and distal grooves are shallow, fairly smooth, and
well closed.
Procedure.— A round bur, A millimeters in diameter, in
the engine, is placed in the pit while in rotation and fairly strong
pressure applied, while the hand-piece is swayed to and fro. In
most cases the bur will cut through the enamel and enter the
cavity within a few seconds. If it does not do so promptly, it
should be removed for a moment and allowed to cool — for heat
will develop quickly — and then reapplied in the same manner.
This should be repeated until the bur passes through the enamel
and enters the softened dentin. Immediately this occurs, the
bur should be removed from the hand-piece and a bur, i mil-
limeter in diameter, chosen. This is passed through the opening
into the dentin in the same way, thus enlarging the opening in
the enamel. This is then exchanged for a larger bur, i i^o mil-
limeters in diameter, which is also passed through the opening.