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IRREGULARITY. 27

for green stain, therapeutic treatment must be com-

bined with the operative; but only the latter will be
here described, which has for its object the removal
of the deposit, and the rendering of the eroded sur-
face smooth and polished. There are two or three
methods of accomplishing this object. When the
erosion is but slight, it will be effected with Arkansas-
stone, or pulverized pumice and water applied with
a wooden polisher of the proper form till the stain
disappears, and with the subsequent use of the
burnisher with a solution of soap. But when the
erosion is too extensive to be thus reduced, it must be

cut down with a file, and then finished with stone and
burnisher, as before. And when the erosion is extreme,
a cutting-instrument must precede the file.

IRREGULARITY.

By this term we imply those variations from a

beautiful and natural position, in which the teeth are
so frequently found. The principal cause of irregu-
larity is a disproportion between the actual size of the
arch, and the size required for the accommodation of
the teeth. When this disproportion exists, the teeth
which are first erupted, occupy very nearly their
proper position; but those which come in afterward,
are more or less disarranged, in proportion to the pre-