Page 430 - My FlipBook
P. 430
;
440 DENTAL ANATOMY.
projections of the enamel present convex outlines basally, and are
separated from each other by two wide V-shaped notches occupying
the mesial and distal faces.
The labial aspect of the crown is convex from side to side, as well
as from above downward, and is of great'cr vertical than transverse
extent. Upon either side the crown is triangular
Fig. 21
in form, with the apex of the triangle terminating
at each free angle of the cutting extremity, and the
base directed toward the root ; the basal part of the
triangle is interrupted by the V-shaped notch already
alluded to. That lateral surface which is directed
toward the median line (mesial) is comparatively
flat and most produced at the extremity, while the
one which looks away from the median line (distal)
A Left L'pper Central In- is more rounded, having its terminal angle less pro-
cisor of Man : a, external
or labial aspect ; b, inter- duced. The interior or palatine surface is also tri-
nal or lingual aspect.
angular, but the base is formed by the free cutting
edge and the apex turned toward the root. Usually, this surface is
nearly flat, but in some examples it presents a broad central concavity
whose depth may be considerably augmented by the presence of two
marginal ridges meeting at the radicular extremity or apex of the tri-
angle. These ridges, which are homologous with the cinguhim of other
—
teeth, sometimes develop a small cusp at their point of junction, in front
of which there is usually a deep i)it in the enamel " a favorite site for
caries." As a general rule, the cingulum is but faintly marked, and the
posterior or palatine face is slightly concave.
The lateral incisors of the upper jaw are smaller than the median pair,
but have approximately the same form. The labial face is more convex
from side to side, and the outer or distal angle of the cutting edge is
much more rounded off than in the median. The lingual surface may
be slightly concave from above downward, and convex in the opposite
direction, without any trace of the cingulum, or, as is most generally
the case, it is concave, with the cingulum present, and elevated into a
small cusp at the point of junction of the two lateral ridges. The
basilar contour of the enamel covering is the same as in the preced-
ing tooth. The root is more compressed laterally, of relatively greater
length, and tapers more gradually to its termi-
nation, giving to the tooth a more slender and
less robust appearance.
The ])ulp-cavities of these two teeth have sub-
stantially the same shape, and the description of
one will answer for that of both. Its form is
that of an elongated tube, gradually increasing
in diameter from the apical foramen in the apex
A Lower Incisor of Man: of the root to a point which nearly coincides
anterior, and ft, lateral view
with the summit of the V-shaped notch in the
enamel on the lateral surface of the crown, where it becomes contracted
in an antero-posterior direction, but enlarged in its transverse diameter.
It is ]irolonged upon either side into a slight cornua, which reaches but a
short distance bevond the level of the general cavitv : the one which cor-
440 DENTAL ANATOMY.
projections of the enamel present convex outlines basally, and are
separated from each other by two wide V-shaped notches occupying
the mesial and distal faces.
The labial aspect of the crown is convex from side to side, as well
as from above downward, and is of great'cr vertical than transverse
extent. Upon either side the crown is triangular
Fig. 21
in form, with the apex of the triangle terminating
at each free angle of the cutting extremity, and the
base directed toward the root ; the basal part of the
triangle is interrupted by the V-shaped notch already
alluded to. That lateral surface which is directed
toward the median line (mesial) is comparatively
flat and most produced at the extremity, while the
one which looks away from the median line (distal)
A Left L'pper Central In- is more rounded, having its terminal angle less pro-
cisor of Man : a, external
or labial aspect ; b, inter- duced. The interior or palatine surface is also tri-
nal or lingual aspect.
angular, but the base is formed by the free cutting
edge and the apex turned toward the root. Usually, this surface is
nearly flat, but in some examples it presents a broad central concavity
whose depth may be considerably augmented by the presence of two
marginal ridges meeting at the radicular extremity or apex of the tri-
angle. These ridges, which are homologous with the cinguhim of other
—
teeth, sometimes develop a small cusp at their point of junction, in front
of which there is usually a deep i)it in the enamel " a favorite site for
caries." As a general rule, the cingulum is but faintly marked, and the
posterior or palatine face is slightly concave.
The lateral incisors of the upper jaw are smaller than the median pair,
but have approximately the same form. The labial face is more convex
from side to side, and the outer or distal angle of the cutting edge is
much more rounded off than in the median. The lingual surface may
be slightly concave from above downward, and convex in the opposite
direction, without any trace of the cingulum, or, as is most generally
the case, it is concave, with the cingulum present, and elevated into a
small cusp at the point of junction of the two lateral ridges. The
basilar contour of the enamel covering is the same as in the preced-
ing tooth. The root is more compressed laterally, of relatively greater
length, and tapers more gradually to its termi-
nation, giving to the tooth a more slender and
less robust appearance.
The ])ulp-cavities of these two teeth have sub-
stantially the same shape, and the description of
one will answer for that of both. Its form is
that of an elongated tube, gradually increasing
in diameter from the apical foramen in the apex
A Lower Incisor of Man: of the root to a point which nearly coincides
anterior, and ft, lateral view
with the summit of the V-shaped notch in the
enamel on the lateral surface of the crown, where it becomes contracted
in an antero-posterior direction, but enlarged in its transverse diameter.
It is ]irolonged upon either side into a slight cornua, which reaches but a
short distance bevond the level of the general cavitv : the one which cor-
