Page 156 - My FlipBook

124 PREPARATION OF CAVITIES

val margin trimmers, depending on the location. Hatchet
and hoe excavators are also of value for cutting dentin.

2. Remove the Decay.—Complete removal of decay is
essential. If the minutest portion be left un sterilized, decay
will continue, producing irritation of the pulp via the dentinal
fibrillae, and finally result in the undermining of the filling.
Although during the performance of the first step, viz.:
establishment of the outline form, much of the carious mat-

ter will be removed, it should be done, not with that idea pri-
marily in view, as is so frequently the case with inexperienced
operators, but it should be merely incidental to the operation
of placing the cavity margins in their proper location.
During the progress of caries, decalcification by lactic
acid precedes invasion by micro-organisms. This being the

case, the deepest portion of the dentin may have been
^' affected'^ to some extent, though not necessarily decayed

and "infected.''^ Discoloration also frequently precedes the
process of decay. Therefore, the dentist is in some instances
justified in leaving portions of discolored or partially afiected
dentin on the walls of cavities to avoid possible exposure of
the pulp. In such cases the cavity should be thoroughly
sterilized. However, in every instance it is necessary to
remove the smallest trace of infected and decayed dentin to
prevent the continuance of decay under the filling and to

avoid irritation and inflammation of the pulp.
The method of removal oj decay depends on the character
of the tissue, the size and location of the cavity and the
sensitivity of the dentin.

I. Shallow Cavities on Exposed Surfaces.—The dentin is
usually very sensitive in these cavities. Remove it with
hatchet or hoe excavator, or the round bur. Do not tem-
porize, but make decisive cuts, removing the decayed matter
as quickly and in as large bulk as possible.