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446 DENTAL ANATOMY.
ing, as will be seen by the diagram : the greater width of the superior
central covers the wudth of the inferior central and a small portion of
the inferior lateral ; this brings the superior lateral over the remainder
of the inferior one and the mesial fourth of the inferior cuspid, while
the cusp of the superior cuspid fits into the concave space between the
cusp of the inferior cuspid and the first bicuspid. In like manner, this
Fig. 224.

irregularity of opposition is maintained in all the teeth, so as to give
each tooth a bearing on two teeth, except the superior third molar,
which has but the corresponding tooth in the lower jaw for an antag-
onizer. This irregularity of opposition contributes to the efiiciency of
the teeth in mastication, and is a valuable feature when a tooth is lost
from the arch in either jaw, for by this arrangement the tooth in partial
antagonism with the one lost still maintains a portion of its usefulness
by its occlusion with yet another tooth.
The Deciduous or Temporary Teeth (Fig. 225), twenty in number, are
Fig. 225.
rf^

smaller than the permanent set, though tliey resemble them in their gen-
eral conformation of crown and root, the bicuspids of the permanent set