Page 301 - My FlipBook
P. 301
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enamel has occurred. These areas will become brown or
black with the coming of immunity to the region, and remain
as dark spots in the enamel, and should not be disturbed.
When they begin late, the free margin of the gum has short-
ened so that the beginning is very close to the gingival line,
which soon becomes involved. When they occur late in life
forty to sixty—they most frequently begin just at the gingi-
val line, and often where there has been some recession of
the gums they begin in the cementum. In old age they
usually begin in the cementumi It follows, therefore, that the
position of the area of liability in this class of cavities differs
considerably at different ages of the patient, being well re-
moved from the gingival line in the young, close to the gin-
gival line in the adult, and includes the gingival line in mid-
dle life and old age. At all ages, however, the area of lia-
bility is limited toward the gingival by the free margin of
healthy gum tissue, toward the occlusal by the limit of
habitual uncleanliness of the surface, and toward the mesial
and distal by the margins of the surface, or the angles of
the tooth. In the most highly susceptible persons decay may
pass the angles of the tooth and join with the area of liability
of the proximate surfaces.
The first, appearance of decay in the enamel is usually
in the form of a narrow strip of whitening and softening close
to, and following, the curve of the free border of the gum
margin, or just at that point of the surface that is least per-
fectly cleaned by the friction of mastication. The extent of
the area of beginning decay will correspond with the area of
uncleanliness of the surface. Occasionally this is quite broad
occluso-gingivally, but more generally it is narrow, and not
infrequently it is reduced to a mere line less than a millimeter
in breadth. Mesio-distally, or along the border of the gum,
this line varies much in length, but is rarely less than one-
third the breadth of the surface, more often occupies two-
thirds the breadth and occasionally extends from the mesial
to the distal angle. The first penetration of the enamel is
usually central to this area, but not unfrequently extended
in a line of minute breaks, which unite, as they enlarge, form-
ing an elongated cavity. Unless cavities have gained consid-
erable size before they are seen, there is always a streak of
softened enamel running away from the cavity to the mesial
289
enamel has occurred. These areas will become brown or
black with the coming of immunity to the region, and remain
as dark spots in the enamel, and should not be disturbed.
When they begin late, the free margin of the gum has short-
ened so that the beginning is very close to the gingival line,
which soon becomes involved. When they occur late in life
forty to sixty—they most frequently begin just at the gingi-
val line, and often where there has been some recession of
the gums they begin in the cementum. In old age they
usually begin in the cementumi It follows, therefore, that the
position of the area of liability in this class of cavities differs
considerably at different ages of the patient, being well re-
moved from the gingival line in the young, close to the gin-
gival line in the adult, and includes the gingival line in mid-
dle life and old age. At all ages, however, the area of lia-
bility is limited toward the gingival by the free margin of
healthy gum tissue, toward the occlusal by the limit of
habitual uncleanliness of the surface, and toward the mesial
and distal by the margins of the surface, or the angles of
the tooth. In the most highly susceptible persons decay may
pass the angles of the tooth and join with the area of liability
of the proximate surfaces.
The first, appearance of decay in the enamel is usually
in the form of a narrow strip of whitening and softening close
to, and following, the curve of the free border of the gum
margin, or just at that point of the surface that is least per-
fectly cleaned by the friction of mastication. The extent of
the area of beginning decay will correspond with the area of
uncleanliness of the surface. Occasionally this is quite broad
occluso-gingivally, but more generally it is narrow, and not
infrequently it is reduced to a mere line less than a millimeter
in breadth. Mesio-distally, or along the border of the gum,
this line varies much in length, but is rarely less than one-
third the breadth of the surface, more often occupies two-
thirds the breadth and occasionally extends from the mesial
to the distal angle. The first penetration of the enamel is
usually central to this area, but not unfrequently extended
in a line of minute breaks, which unite, as they enlarge, form-
ing an elongated cavity. Unless cavities have gained consid-
erable size before they are seen, there is always a streak of
softened enamel running away from the cavity to the mesial
289
