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THE HISTOLOGICAL STRUCTURE OP THE TEETH. 93

The Histological Structure of the Teeth in
Relation to Cavity Preparation.

THE ENAMEL.

ILLUSTRATIONS: FIGURES 100-110.

THE structure of the enamel is of such importance in its rela-
tion to the preparation of cavities for filling that it requires
special study. It is difficult to so prepare specimens of the
enamel that they show its structure well, and when the specimens
are well prepared it requires a large amount of study to gain
that intimate knowledge of it that is necessary to the most intelli-
gent practice in filling operations. On the ordinary hook page,
we can not place photomicrographs that are sufficiently amplified
to show the enamel rods well and at the same time show a suffi-
cient amount of the tooth form to give their relations. There-
fore, the only way to study these effectively is under the micro-
scope itself, hut after the microscopic study, much more can be
done by diagrammatic illustrations.
The enamel, when examined macroscopically, appears as a
very hard, vitreous body, white, or a bluish white, very dense and
brittle, in which no traces of structure can be determined. It
cuts with much difficulty and is inclined to chip and crumble, but
shows decisive cleavage lines. If, however, it is examined with a
good hand magnifying glass, certain striations can be observed
that give a suggestion of histological structure.
Although the enamel seems to be opaque, or slightly trans-
lucent, by ordinary examination, it is found to be almost as trans-
parent as glass when ground into thin, finely polished sections.
When so prepared, very little of the structure can be seen with
the microscope without some preparation that will cause its his-
tological elements to appear. It is largely for this reason that
so little is seen of the structure of enamel in the sections ordi-
narily prepared for microscopic observation.