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FlQ. 178. Flo. 179.

§

Fig. 181.

Figs. 17S-181. A series ilhistrating cavity preparation in lower first molars.
Fig. 178. The mesial surface of a lower first molar, showing a broad whitened area of begin-
ning decay of enamel stretching bucco-liognally from angle to angle. In the central part of the
area the enamel rods have begun to fall away.
Fig. 179. The form of the prepared cavity, showing the occlusal step to give the necessary
rigidity to the filling, and the outward inclination of the enamel walls of the proximal portion.
Fig. 180. The occlusal surface of the tooth showing rather deep grooves and pita but no
caries is apparent.
Fig. 131. The occlusal surface of the tooth after the filling has been finished, showing the
outline form of the cavity from that view.
21b