Page 31 - My FlipBook

THE CANINES OR CUSPIDS. 29
The croion has a spear-head shape (6), hence the name, cuspid, by
which this tooth is frequently designated, from the Lat. cuspis, '' point,
pointed end," It is constructed essentially for piercing and tearing.
The central cusp or point is braced in all directions ; the edges leading
up to it both mesially and distal (which serve for cutting as well), the
ly
Fig. 15.

The upper canine.
strong labial ridge coming downward from the cervix (c) to the median
ridge leading up on the lingual surface (r/), all support it in the office
of prehension and the laceration of flesh.
The labial face (b) presents the outlines of the spear shape, more or
less rounded in different cases. Starting from the well-defined cusp just
in front of the central axis of the tooth, it widens sharply for about
one-third of its length, whence it narrows gradually to the gum line,
which is fullv rounded. In some cases the mesial and distal anules are
rounded and the outlines are more of a leaf shape {e). The surface
is slightly rounded mesio-distally, so that the sides slope roundlv or
flatly away from the central ridge. This ridge descends from the middle
of the cervical margin, curving slightly forward and then backward to
the point of the cusp (c). This curve recalls the curving shape of this
tooth in the Felidse. It is usually a sharp, prominent ridge, but may
be reduced and rounded so as to be scarcely perceptible. The three lobes
of the surface are imperfectly marked,—the central ridge dominating
and dwarfing the lateral ones. The lateral furrows on each side of
the central ridge separating it from the lateral lobes are more or less
marked, especially toward the edge. Wear reduces in time the prom-
inence of the lobes and ridges and obliterates the furrows.
The Un(juaJ face is of similar spear shape (r/), but is more flat. It is
rarely concave. The thickness of the crown increases gradually to
the lateral prominences, which gives a blade-like edge, then rapidly
to the shoulder at the base. A strong vertical ridge extends from the
cusp to the basal ridge {d), with a slight concave depression on each
side. The basal ridge is well marked and sometimes develops into
a cingule, more or less marked. The marginal ridges lead up on each