Page 32 - My FlipBook

28 OPERATIVE DENTISTRY
the enamel margins, direct the external enamel line and control
the degree of the cavo-surface angle, withont disturbing the gen-
eral retentive form of the cavitj-.
The bevel angle is the angle formed by the junction of the mar-
ginal bevel with the remaining portion of the wall of Avhich it is a
part.
The base of the bevel angle is the remaining portion of the cavity
wall.
The bevel angle is covered when the filling is in position. Its
distance from the enamel margin depends upon the filling material
used, and the location in the cavity outline. To illustrate: With
porcelain inlays and amalgam the bevel angle must be deeply bur-
ied, resulting in a thicker edge of filling material. With cast gold
inlays and platinum combination fillings the bevel angle should be
near the surface, resulting in a short marginal bevel. The distance
of the bevel angle from the cavo-surface angle must not affect the
degree of the latter angle but determines only the length of the
bevel and the thickness of the filling at its margin.
The planes of a tooth are three in number ; horizontal plane, mesio-
distal plane and bucco-lingual plane.
The horizontal plane is at right angles to the long axis of the
tooth.
The mesio-distal plane passes through the tooth from mesial to
distal parallel with the long axis.
The bucco-lingual plane passes through the tooth from buccal to
lingual parallel with the long axis of the tooth. In the six anterior
teeth this plane would be labio-lingual.