Page 282 - My FlipBook

124 THE TECHNICAX, PROCEDUKES IN FILLING TEETH.

shown in the filled cavity, Figure 126. Often advantage may
be taken of the point where a groove passes the crest of the mar-
ginal ridge (which bounds the occlusal surface) and a good finish
made in a moderately sharp groove. At such a point, instruments
of suitable form to work in the line of the groove may be
used, fashioning the margin of the filling to the form of the
groove. It may then be polished by rotary disks of suitable
form working in the line of the groove.- In many cases of decays
occurring in the upper molars, the cavity in the central fossa,
with the buccal and mesial groove, may be filled sej^arately from
the cavity in disto-lingual groove, that is, without cutting through
the oblique ridge.
Variations. It will often happen that in a cavity having
the superficial appearance of those above described, a consider-
able area of decayed dentin will be found beneath the enamel
after the burs have been passed through into it. In this case,
the overhanging enamel must be chipped away with straight
chisel 10 or 15 and binangle chisel 10-6-6 or 15-8-6, until sound
dentin is reached. When this has been done, the remaining por-
tion of the buccal groove should be cut out as described, first
completing the outline of the cavity. Then the pulpal wall
should be squared up so that its angles with the surrounding
walls are sliarj? and definite, using hoe 12-5-6, or, in some posi-
tions hoe 12-5-12, with a scraping motion. In many cases this
will be as conveniently and accurately done with a square-ended
fissure bur 12, or with an inverted cone bur. In this use of the
bur, the shaft should be held parallel with the long axis of the
tooth so that the square end of the bur will cut the pulpal wall
of the cavity flat and make its angles with the surroimding walls
sharp. Then, if there is remaining decay, this is best removed
with spoons 15-8-12 or 20-9-12, as may best suit the size of the
cavity. Enter the blade beneath the softened material close
against the enamel wall at the lingual or buccal side, as shown
in Figure 132, and force it with a strong thrust in a curved direc-
tion to the other side of the cavity; two or three strokes well
made should be sufficient. The rule will be, however, that such
cavities will not be too deep to square up the whole depth of
the decay in squaring up the pulpal wall in the first cutting.
This will complete both the resistance form and the retention
form. The enamel wall should be finished and cavo-surface
angles beveled the same as before. In many cases the mesial
groove will be so sharp and deep that it will require cutting out
well toward, or even to the mesial marginal ridge. In lower