Page 164 - My FlipBook

• 162
It never affects the extreme ends of the roots, but it is
most frequently seen in them near the neck ; and it gene-
rally attacks both the roots and the neck on those sides of
the tooth which form the semicircle or arch of the jaw.
When it makes its first appearance on the surface of any
part of the crown of the tooth which is covered with enamel,
it generally presents itself as a very small speck, though
sometimes as a large, round, or irregular spot.
After the removal of this irregular, broad, or round spot
of caries with the file, it will be generally observed to have
extended superficially only, and to have penetrated in this
manner through a part of the whole enamel. It will next
exhibit on the surface of the bony structure a small spot,
similar to that sometimes observed on the enamel : whence
in either case, it almost invariably proceeds, in a dircet line,
towards the cavity of the tooth. This spot appears in some
cases not larger than a point, although it may already have
penetrated a third or even half of the bony structure of the
affected side of the tooth.
On such parts as are not covered with enamel, the neck
and roots of the tooth, for instance, the spot generally ap-
pears irregular, and extending across a considerable portion
of the surface of the neck, having the appearance of a notch
of an oblong form. The colour of carious spots may be
white, grey, yellow, brown, or black ; the specific appearance
being presumed to depend upon the chemical influence of
the external fluids on the diseased parts.
Sometimes the disease of the crown penetrates very nearly
to the lining membrane of the tooth, before the mortified
bony structure becomes sufficiently soft to allow the escape
of the diseased matter, so as to form a cavity ; but this is
more rarely the case in the roots or neck, which are generally
of a softer or more easily corroded nature. This state