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36 MACROSCOPIC ANATOMY OF THE HUMAN TEETH.
being raised with it. The ridges are the mesial and distal marginal
/), which are bowed out round and full and are always
ridges (/, j)ro-
nouuced ; the buccal marginal ridges {/,/), leading down from the buc-
cal cusp to form an angle with the mesial and distal marginal ridges
the basal ridge, when the lingual cingule is lowered (h) ; and the tri-
angular ridge of the buccal cusj), which is always large and when the
inner tubercle is reduced leads down as a high central eminence. The
lingual cingide, as a rule, possesses no triangular ridge.
The central groove usually crosses the central ridge (A-), but not
always, being often bowed around its lower termination. Sometimes the
ridge is crossed by a sulcus. The groove terminates in a sulcus at each
end, with slight triangular grooves branching up on the buccal (!usp.
The necJx is usually oval on section, being much constricted, the crown
flaring upward from the cervical portion, giving the crown the well-
known bell shape. The enamel line dips but slightly, being usually
level on all four sides. The buccal border sometimes presents a prom-
inent ridge.
The root is single, long, tapering and may be nearly round, but is
usually flattened mesio-distally. It is sometimes thick the greater part
of its length, and terminates in an abrupt, round, blunt apex (c, (J). It
is very liable to be crooked. It is rarely bifurcated and does not pre-
sent grooves on its lateral faces.
The pulp canal is constricted and flattened at the neck, and the back-
ward inclination of the teeth makes it difficult to enter. The possibility
of the root being crooked and the peculiarity of its anatomical rela-
tionships ' also increase the uncertainty of treatment, which makes the
pulp canals of the lower bicuspids difficult to deal with.
The lo"wer second bicuspid aj)proximates the first on its distal side.
It resembles the first as regards the general form of
^^*^'- -^- the crown, its tapering bell shape, the constriction of
the neck, and the shape of the root. In all these
features there is little difference between these teeth,
and the description of the first will apply also to the
second bicuspid.
The m.orsal surface (Fig. 20), however, differs very
materially from that of the first. This is circular in
I,
Themorsai surface of outline like the first, and the l)uccal cusp is full and
the lower second bi- i i / \ i i • • t • i i i
cuspid. rounded (a), but the niner cusp is divided by a groove
(6) running over it, into two parts, so that it is really
divided into two tubercles. This makes the lower second bicuspid in its
typal form a tricuspid tooth ; so that it differs from the lower first, which
has but one cusp, and from the others, which have but two cusps. The
^ See page G06, Chapter XXI., on Extraction of Teeth.
36 MACROSCOPIC ANATOMY OF THE HUMAN TEETH.
being raised with it. The ridges are the mesial and distal marginal
/), which are bowed out round and full and are always
ridges (/, j)ro-
nouuced ; the buccal marginal ridges {/,/), leading down from the buc-
cal cusp to form an angle with the mesial and distal marginal ridges
the basal ridge, when the lingual cingule is lowered (h) ; and the tri-
angular ridge of the buccal cusj), which is always large and when the
inner tubercle is reduced leads down as a high central eminence. The
lingual cingide, as a rule, possesses no triangular ridge.
The central groove usually crosses the central ridge (A-), but not
always, being often bowed around its lower termination. Sometimes the
ridge is crossed by a sulcus. The groove terminates in a sulcus at each
end, with slight triangular grooves branching up on the buccal (!usp.
The necJx is usually oval on section, being much constricted, the crown
flaring upward from the cervical portion, giving the crown the well-
known bell shape. The enamel line dips but slightly, being usually
level on all four sides. The buccal border sometimes presents a prom-
inent ridge.
The root is single, long, tapering and may be nearly round, but is
usually flattened mesio-distally. It is sometimes thick the greater part
of its length, and terminates in an abrupt, round, blunt apex (c, (J). It
is very liable to be crooked. It is rarely bifurcated and does not pre-
sent grooves on its lateral faces.
The pulp canal is constricted and flattened at the neck, and the back-
ward inclination of the teeth makes it difficult to enter. The possibility
of the root being crooked and the peculiarity of its anatomical rela-
tionships ' also increase the uncertainty of treatment, which makes the
pulp canals of the lower bicuspids difficult to deal with.
The lo"wer second bicuspid aj)proximates the first on its distal side.
It resembles the first as regards the general form of
^^*^'- -^- the crown, its tapering bell shape, the constriction of
the neck, and the shape of the root. In all these
features there is little difference between these teeth,
and the description of the first will apply also to the
second bicuspid.
The m.orsal surface (Fig. 20), however, differs very
materially from that of the first. This is circular in
I,
Themorsai surface of outline like the first, and the l)uccal cusp is full and
the lower second bi- i i / \ i i • • t • i i i
cuspid. rounded (a), but the niner cusp is divided by a groove
(6) running over it, into two parts, so that it is really
divided into two tubercles. This makes the lower second bicuspid in its
typal form a tricuspid tooth ; so that it differs from the lower first, which
has but one cusp, and from the others, which have but two cusps. The
^ See page G06, Chapter XXI., on Extraction of Teeth.
