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2B MACROSCOPIC ANATOMY OF THE HUMAN TEETH.

incisor tlinii on any other of the anterior teeth. The depression
above it is often the location of a fanlt, a fissnre or j)it, whicli be-
comes the seat of caries. The basal rid^e is
Flo. 13.
sometimes cnt by a fissnre which leads down (jnite
npon the neck of the tooth (Fig. 12,/).
Sometimes the entire surface is full and ronuded
without any concavity whatever.
The memd face (g) is of triangular form similar
05 to that of the central incisor. It is rounded toward
the edge labio-lingually, but flattened at the neck,
'^
with a depression at the enamel line which leads
Showing unusual develop-
i i • i
ment of the cinguie or Upward upou the root. The labial angle is some-
basal talon on an incisor.
^-^^^^^ ^j^^ ^^^^ ^^ ^ depression (h), which o'ives the
(From case reported by Dr. a v /?
w. H. Mitchell, Dental Cos- angle a hook shapc. The depression varies in
. xxxi\
7?io.s ^ . p. o .) width and depth and may become the seat of
caries. The point of contact with the central incisor is at the junction
of the lower with the middle third of the length of the face.
The distal face is more convex in all directions and resembles the
canine in form, being in harmony with the general form of the distal
half of that tooth. From cervix to edge it is rounded and the contact
eminence in the middle third is very fidl [i). From this point it rounds
off rapidly to the edge. The upper third is depressed rapidly toward
the cervix, wdth a considerable depression at the enamel line leading
off to the distal groove on the root.
The cdf/e is divided into two portions by the prominent tubercle
(J)
in the middle which terminates the prominent central ridge of the
labial face. The mesial half is straight, like that of the central.
When worn, these features disappear and the edge becomes almost
straight. The pitch of the edge, like that of the central, is toward
the median line.
The nech is much flattened mesio-distally, and is of a compressed
pear shape, or flattened oval on section. The enamel margin pursues
the same course as on the central incisor, rounding upward toward the
root on the labial and lingual sides and dipping downward on the
distal and mesial. It does not terminate so abruptly as that of the
central incisor, and presents less of a ridge at the gingival margin.
The root is common Iv lono-er than that of the central incisor, is
narrower, flattened mesio-distally (Fig. 12, A, B). It tapers gradually,
not rapidly like the root of the central incisor. It is a flattened oval
on section (e). Sometimes there is a hook at the end, curved distally.
Grooves sometimes occur on the mesial and distal sides.
The j^^dp caned is flattened in conformity to the shape of the root,
but is readily entered if the root be straight.