Page 22 - My FlipBook

18 THE TECHNICAL PROCEDURES IN FILLING TEETH.

The horizontal plane is at right angles to the long axis of
the tooth, and may be supposed to cut through the crown at
any point in its length.
The axio-mesio-distal plane, or the mesio-distal plane,
passes through the tooth mesio-distally parallel with its long
axis.
The axio-bucco-lingual plane, or the bucco-lingual
plane, passes through the tooth bucco-lingually parallel with its
long axis. In the incisors and cuspids this is the labio-lingual
plane.
The inclination at which walls of cavities are cut, or of the
dentin wall and the enamel wall, when each is specifically
mentioned, is reckoned from these planes of the teeth. When
great accuracy of statement is desired the inclination may be
given in centigrades. More generally the term outward
inclination, or inclined outward, is used, with some word
expressing degree, as slightly, strongly, etc. In this use of
words the wall of the cavity mentioned is always inclined away
from the plane of the tooth in passing from within outward.
The bevel of the cavo-surface angle is always reckoned
from the plane of the enamel wall.
The Use of Divisions of the Surfaces of the Teeth in
Cavity Description.
Whenever we wish to indicate in words the portion of a sur-
face of a tooth involved in decay, or the extent of a cavity, we
may conveniently do so by an imaginary division of the surface
decayed into thirds, fourths or fifths. This division may be
mesio-distally upon a buccal, lingual, or occlusal surface, or
occluso-gingivally upon a buccal, lingual, mesial, or distal sur-
face, or it may be bucco-lingually upon an occlusal, mesial, or
distal surface. In other words, the divisions may be made upon
any one of the planes of the tooth.
For instance, of a cavity in a buccal surface we may say it
involves the middle third mesio-distally and the gingival third
occluso-gingivally. Or if the cavity is broader we may say it
involves the middle three-fifths mesio-distally and the gingival
half of the surface occluso-gingivally.
In this use of words it must be borne in mind that when the
adverbial form is used, it indicates direction. Mesio-distally