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SENSrTIVE^'ESS OF THE DENTINE. 1007
able pathological change in the dentine itself which presents this hvper-
aesthesia, except a waste of its surface.
Fig. 536 is a sectional view of a central incisor with an erosion at a
which exposes the dentinal fibrils At 6 the layer of odontoblasts are
shown—these line the pulp-cham-
ber—and at c a nerve-branch the Fig. 536.
finer filaments of which are found
ramifying in close conjunction with
the odontoblasts. The processes
from these odontoblasts form the
dentinal fibrils which pass by way
of the dentinal tubules to the per-
iphery of the dentine. The odon-
toblast and its process, the denti-
nal fibril, constitute one cell ; the
protoplasm is united in one life
and whatever markedly affects
the protoplasm of the fibril affects
the protoplasm of the w^hole cell.
For this reason any pathological
changes that may be set in mo-
tion in consequence of irritation
of the dentinal fibrils are found Section of the Crown of an Incisor: n, an erosion
exposing the dentine; b, the layer of odonto-
in the odontoblasts and the tissues
blasts liiiing the pulp-chamber; c, a nerve-
in intimate association with them branch the delicate filaments of which are dis-
trilnited about the layer of odontoblasts; d, (I,
—in that portion of the pulp gingival margin ; E, point at which pathological
changes first occur as the result of irritatiou of
marked e in the figure. Along the dentinal fibrils at a.
the course of the fibril itself no
pathological changes whatever can be discovered, seemingly for the
reason that the hard substance of the dentine—the basis-substance and
the lime salts—is incapable of manifesting vital phenomena, is not liv-
ing protoplasm. This portion of the dentine is essentially fixed mate-
rial. It may be acted upon, but does not in itself act. It is passive.
The changes which occur in the tissues of the pulp in consequence
of distal irritation of the dentinal fibrils are sufficiently discussed in the
paper on Pathology of the Dental Pulp, and will not be repeated here
except for the purpose of illustration. The effect of slight but continu-
ous irritation of the ends of the fibrils is seen in the production of sec-
ondary deposits of dentine, which in those cases in which the area of
irritation is small are not unfrequently confined to the area represented
by the pulpal ends of the fibrils irritated. If the area of irritation is
large, as in most cases of mechanical abrasion, the area of secondary
deposits includes the whole internal surface'of the pulp-chamber. If the
intensity of the irritation of the fibrils be more considerable, the result
will be irritation of the pulp, instead of secondary deposits, or possibly
both, the secondary dentine proper giving place to irregular deposits.
In case the irritation becomes excessive, well-marked hyperemia of the
pulp will occur, which occasionally results in the destruction of that
organ before it is exposed to external influences other than through
the medium of the fibrils.
SENSrTIVE^'ESS OF THE DENTINE. 1007
able pathological change in the dentine itself which presents this hvper-
aesthesia, except a waste of its surface.
Fig. 536 is a sectional view of a central incisor with an erosion at a
which exposes the dentinal fibrils At 6 the layer of odontoblasts are
shown—these line the pulp-cham-
ber—and at c a nerve-branch the Fig. 536.
finer filaments of which are found
ramifying in close conjunction with
the odontoblasts. The processes
from these odontoblasts form the
dentinal fibrils which pass by way
of the dentinal tubules to the per-
iphery of the dentine. The odon-
toblast and its process, the denti-
nal fibril, constitute one cell ; the
protoplasm is united in one life
and whatever markedly affects
the protoplasm of the fibril affects
the protoplasm of the w^hole cell.
For this reason any pathological
changes that may be set in mo-
tion in consequence of irritation
of the dentinal fibrils are found Section of the Crown of an Incisor: n, an erosion
exposing the dentine; b, the layer of odonto-
in the odontoblasts and the tissues
blasts liiiing the pulp-chamber; c, a nerve-
in intimate association with them branch the delicate filaments of which are dis-
trilnited about the layer of odontoblasts; d, (I,
—in that portion of the pulp gingival margin ; E, point at which pathological
changes first occur as the result of irritatiou of
marked e in the figure. Along the dentinal fibrils at a.
the course of the fibril itself no
pathological changes whatever can be discovered, seemingly for the
reason that the hard substance of the dentine—the basis-substance and
the lime salts—is incapable of manifesting vital phenomena, is not liv-
ing protoplasm. This portion of the dentine is essentially fixed mate-
rial. It may be acted upon, but does not in itself act. It is passive.
The changes which occur in the tissues of the pulp in consequence
of distal irritation of the dentinal fibrils are sufficiently discussed in the
paper on Pathology of the Dental Pulp, and will not be repeated here
except for the purpose of illustration. The effect of slight but continu-
ous irritation of the ends of the fibrils is seen in the production of sec-
ondary deposits of dentine, which in those cases in which the area of
irritation is small are not unfrequently confined to the area represented
by the pulpal ends of the fibrils irritated. If the area of irritation is
large, as in most cases of mechanical abrasion, the area of secondary
deposits includes the whole internal surface'of the pulp-chamber. If the
intensity of the irritation of the fibrils be more considerable, the result
will be irritation of the pulp, instead of secondary deposits, or possibly
both, the secondary dentine proper giving place to irregular deposits.
In case the irritation becomes excessive, well-marked hyperemia of the
pulp will occur, which occasionally results in the destruction of that
organ before it is exposed to external influences other than through
the medium of the fibrils.
