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THE DECIDUOUS TEETH. 49

resorbed at from the fifth to the ninth year, when the permanent incisors
come into place, beginning with the lower centrals.
The canines (c) of both jaws are still more reduced from the strong,
Fig. 30.

The deciduous teeth.

full form of their permanent successors, and are but little more
specialized than the incisors. They are of the same general form as
the permanent canines, but much less developed.
But in the deciduous molars are found some important features
which mark distinctive differences. They are of true molar form as
compared with the permanent molars, but they occupy the place of the
bicuspids. There are no bicusjiids in the deciduous set, the molars being
of full molar pattern («, d).
The deciduous molars of both jaws are of irregular, quadrangular
form on the morsal surface, diverging rapidly outward to the neck,
which presents a large buccal ridge standing out at the margin of the
enamel, and is rounded off suddenly to the neck, which is much con-
tracted. This thick ridge is characteristic of the deciduous molars and
is absent in those of the permanent denture. It is somewhat more
prominent and bulging on the buccal than on the other faces. In
adjusting ferrule crowns to these teeth, the gold need not be carried
beyond this ridge but burnished over it slightly.
The morsal surface (e) of the upper deciduous grinders presents the
characteristic pattern of the upper molars, four tubercles, oblique ridges,
etc., but reduced and contracted. A distinctive feature is that the
marginal ridges and angles are more acute and sharp than in the per-
manent molars. Sometimes the two lingual cusps are reduced to one
and the lingual border is rounded and crescentic.
The second molar is larger than the first and the morsal surface is
wider.
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