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OPERATIVE DENTISTRY.

CHAPTER I.

MACROSCOPIC ANATOMY OF THE HUMAN TEETH,

By Alton Howard Thompson, D. D, S.

1. Definition,—The teeth may be properly defined as hard, cal-
careous bodies situated in that portion of the alimentary canal near the
anterior or oral extremity. In man they are confined to the oral cavity
and are supported by the maxillary bones only. In the lower verte-
brates they may be scattered over all of the bones and cartilages sur-
rounding the mouth.
2, Function.—The main function of the teeth is the mechanical sub-
division of substances used for food, preparatory to their digestion ; these
orirans therefore beiona: to the alimentarv svstem. The elements of
their function are prehension, incising, crushing, mastication, and insali-
vation. For the performance of these various offices, different forms
of teeth are found in the denture of man. In lower animals food-habit
induces the evolution of many various and extreme forms of the teeth.
The secondary offices of the teeth in man are as adjuncts in vocal-
ization and articulate speech ; they also bear an esthetic relation to the
mouth and face.
Fig. 1.

Il-if I I
The formation of single teeth from the single cone and its repetition in complex teeth.
3, Mechanical Design.—All tooth forms are evolved by modification
from a simple cone, which is the primitive, typal form. The teeth of fishes
and reptiles are but simple cones, and those of higher mammals are
modifications of the sinsfle cone or combinations of two or more cones
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