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CHAPTER V

PREPARATION OF CAVITIES

No attempt will be made here to enter into an extended
discussion of the causes of decay of the teeth. Matters of
this nature are fully covered in works on dental pathology.

The following, however, is a brief statement of the manner in
which cavities of decay are produced.
Causes of Decay.—Cavities occur in teeth as a result of
decay beginning on their surface. Decay is largely the result

of the fermentation of food debris. Fermentation is a de-
composition of carbohydrates (starches, sugars, etc.). Food
debris accumulates because of neglect in the application of the
ordinary rules of cleanliness to the care of the teeth. Fer-
mentation of food debris is due to the constant presence of
germs in the mouth. The action of certain of these germs

on the fermentable material produces lactic acid. Lactic
acid dissolves out the lime salts, of which the major part of
the tooth is composed. Other germs, constantly present,
liquefy the organic material, which constitutes the remainder

of the tooth. The result is a cavity of decay.
Definition.—By ^'preparation of cavities" is meant those
procedures incident to the removal of decay and the shaping
of the cavity, so that when filled, the tooth will be restored,
as far as possible, to its original form and strength, and be
immune from future decay in the same location.
Nomenclature.—A system of words, sounds or signs by

which individuals of the same race, profession, or calling, are
enabled to understand each other. The profession of dentis-
try has a nomenclature of its own.- A study of the nomencla-
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