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THE MOLARS. 41

the two fossse on to the cusps, dividing the triangular from the marginal
ridges.
The neck of this tooth is of rounded rhomboid form on section (o),
widest at the buccal side. The enamel is almost level on all four sides,
dipping downward slightly on the mesial and distal. A depression
occurs at the bifurcation of the buccal roots, and an inward inclination
on the mesial and distal sides.
The roots are three in number (Fig. 21), two on the buccal side,
which are small and flat or round, and one on the lingual side, which is
large and rounded. The roots are usually separated, but may be found
united, by a septum of cementum, in various directions. The mesio-
buccal root is the larger of the two buccal roots, and forms a second
turning-point or spring of the arch. All the roots are slightly bent
and may be very crooked.
The pulp chamber branches into three canals, one in each root. The
lingual canal is large and open and is readily entered. The canals of the
two buccal roots are small and fine, and, with the possibility of crooked-
ness in the roots, present the most difficult problems as to treating and
filling found in the whole denture.
The upper second molar is similar to the first in some respects but
very diiferent in others. It is rather smaller, is not usually full and
square, but disposed to become rhomboid in form (Fig. 23, o, 6), by
disto-mesial compression.
The buccal face is similar to that of
the first molar, and the same description
will apply to it. If any difference is
found it is that the face is strongly com-
pressed from front to back, and the disto-
lingual cusp is more reduced as a con-
stant feature.
The linqual face (c) is diiferent from ^_, ^ f
•^ •^ ^ ' The upper second molar.
,
that of the first molar in that by the sup-
pression of the disto-lingual tubercle (d) and the distal lobe, the mesio-
lingual lobe is enlarged so that it occupies the entire fiice, which is full,
rounded, and convex (<'). It is rarely divided into two lobes as in the
first molar, owing to the enlargement of the mesial lobe and the pushing
backward of the oblique ridge, which throws the lingual groove on to
the disto-lingual angle {(I) ; or the groove may be absent altogether.
The mesial and distal faces are similar in form to those of the first
molar, being perhaps more flattened.
The morsalface is similar to that of the first molar, except that the
tubercles are less pronounced and the distal ones are reduced in height
to accommodate the u])war