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90 Ot*ERATIVE DENTISTRY
step jjortion should be retentive throughout as it is liable to be
worn aAvay by subsequent wear, growing thinner from year to year,
hence the necessity of retentive form from cavo-surface angle to the
base line angles.
Third Plan of Angle Restoration. (Class Four.)

This plan is the addition to plan one of the lingual step. It is
particularly indicated in eases of long incisors which are quite thin
labio-lingually and subjected to a long sweep of the lower incisors
in the movements of articulation, or what is spoken of as the "scis-
sors bite."
Also Indicated in cases where the axial wall extends out to the
enamel edge on the lingual thus removing the lingual wall.
The Labial Outline is the same as with the first plan of restora-
tion. The step is formed on the lingual by cutting away the enamel
from the lingual surface of the tooth toward the central axial line
for a distance of from one to two millimeters at the incisal edge.
As the gingival is approached the cutting is narrowed to a point
Avhere the marginal ridge may be crossed at right angles to meet
the gingival portion of the outline. This will form a V-shaped axial
Avail of dentine facing the lingual. There should be cut a flat-
floored groove in this dentine parallel Avith the remaining enamel
wall ending in the gingivo-axio-lingual angle which should be an
acute convenience angle. The plan gives great resistance to stress
from lingual pressure.
Fourth Plan of Angle Restoration. (Class Four.)
This plan consists of resorting to all of the features of resistance
and retention embodied in plans two and three by combining both
the lingual and incisal steps. Each of these has been fully de-
scribed and the method of cutting both steps to the same should not
prove hard to accomplish.
By this plan the maximum resistance and retention forms are se-
cured with the minimum loss of dentine. It must be remembered
that resistance to stress is good in proportion to the amount of se-
curing dentine retained, hence it should be sparingly cut away.
The removal of enamel to lay bare dentine Avherein to lay anchor-
age is only harmful from the esthetic standpoint and is of little loss
when taken away from a surface not in view, as is the case when we
cut aAvay a portion of the lingual plate.
Cavities in the Distal of Superior Cuspids. On account of the
peculiar articulation of the lingual surface of superior cuspids this