Page 275 - My FlipBook

VITAL, PHENOMENA IN CAEIES. 145
ments. This sensitiveness varies greatly in different persons
and in different carious cavities in the teeth of the same person.
Therefore, we may recognize subnormal, normal and hypernor-
mal sensitiveness. Similar grades of sensitiveness will be found
if we cut into the dentin of perfectly normal teeth free from all
decay. The great variety of grade of sensitiveness in normal
healthy dentin has seemed to me very remarkable. Some per-
sons have cut into so many teeth that, apparently, were not sen-
sitive at all, that they have expressed a doubt as to whether a
tooth that was perfectly normal was sensitive. Even in these
cases of failure to find sensation at a first cutting, sensation is
usually aroused and it may soon pass the normal point and
become hypersensitiveness.
Sensitiveness to cutting instruments is not materially dif-
ferent in carious teeth from normal sensitiveness of dentin, only
that, in a long rim of cases, it will be found somewhat greater
for equal areas. Those who have had some experience in remov-
ing enamel from living teeth in the preparation of abutments
for bridges, have found that a high degree of sensitiveness has
been quickly developed in a large proportion of cases. This is
so general and creates so much difficulty that most dentists pre-
fer to destroy and remove the pulp before beginning this prep-
aration. Sensitiveness in carious teeth is not greater ; it seems
to be subject to the same degree of increase under similar treat-
ment. Well planned and firm work with sharp cutting instru-
ments arouses the least sensitiveness; dull instruments arouse
much more sensitiveness than sharp ones; burs arouse much
more than hand instruments, and grinding with stones more than
any other form of cutting.
Sensitiveness of dentin is greatest along the dento-enamel
junction, where the fibrils are much branched, and diminishes
perceptibly in the deeper parts. For this reason, practically
the whole work of removing the enamel cap, as in preparing
abutments for bridges, is cutting in the area of most acute sen-
sitiveness. For the same reason, broad, shallow areas of decay,
such as are often found in labial and buccal surfaces, are more
sensitive than those of deeper penetration and less superficial
breadth. In any and all cavities, the more sensitive areas are
along the dento-enamel junction about the circumference. In a
few positions the form of the finished cavity will permit of cut-
ting off the fibrils supplying such a part deeper in the dentin, and
save considerable pain to the patient. A good knowledge of the
histological structure will always indicate these in the particular