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82 THE TECHNICAL PROCEDURES IN FILLING TEETH.

instruments will also smooth the lingual portion of the curve at
the incisal angle in many cases. At the incisal angle, the incli-
nation of the enamel wall must generally be strongly toward the
incisal, especially in distal cavities, in order to follow the length
of the enamel rods.
When the trimming is done, note carefully whether the
retentive form has been injured at any important point by
trimming too deeply, and make such corrections as may be
required.
Finally bevel the cavo-surface angle in all parts of the
enamel margin, using the chisel for nearly all this work. At a
few points, especially along the gingival, the hatchet 12-5-6 or
12-5-12, or the 10-6-12 enamel hatchet, will do the work easier.
Make the toilet of the cavity and fill.
General observations on the preparation of prox-
imate cavities in the incisors and cuspids.— In all cases
the enamel margins should be cut sufficiently around the
curves of the surface toward the labial and lingual, that the
margin will be well away from the contact of the two teeth
when the filling has been finished. At the gingival the mar-
gin should be well covered by the gum septum when this is
in its normal position. The gum septum should be carefully
preserved from injury in all parts of the operation, for upon the
health of this tissue depends largely the health and good appear-
ance of the tooth. Toward the incisal the cutting should
always include the normal contact point in distal cavities. In
mesial surfaces the contact point is sometimes so near the incisal
angle that this is impracticable. In these cases, unless strictly
required by the extension of decay, the original contact point
of the enamel should not be removed, but a new contact should be
made by a slight fullness of the filling a little to the gingival of the
position of the original contact, so that the incisal enamel mar-
gin will be held a little apart from contact with the proximating
tooth. A very little space at this point is sufiicient, for the rea-
son that to the incisal of the contact, in the use of the teeth, the
excursions of food constantly cleans the margin of the filling.
In medium and large cavities it is best to cut the labial wall
well over onto the labial surface of the tooth, for the reason that,
if cut only to the mesio-labial or disto-labial angle the light will
not reflect from the surface of the filling and it will appear as a