Page 833 - My FlipBook

hyperjEmia of the dental pulp. 843

dental pulp, for the reason that its causes are so constantly present and
their action augmented in every case of filling with metal. It is liable
to occur in the pulp of any tooth, however sound and otherwise
healthy.
Sensitiveness to thermal changes in a certain degree is, as has been
explained above, the normal sensory function of the pulp. In each
instance of the exercise of this function there is an unusual amount of

Hj-pertemia of the Dental Pulp, showing the natural injection of the vessels: a, a, membrana ehoris,
or layer of oduiioblasts; /), b, b, b, vessels distended with blood; c, c, c, c, points from which the
blood has fallen in handling the section.
blood sent to the organ. This, when in a reasonable degree, is purely
physiological—a temporary physiological hypersemia which calls out a
simple warning in the form of an unpleasant sensation, and immediately
passes away. It is evident in this case that no injury results ; but when
this is repeated frequently with a degree of thermal change that is inor-
dinate, the vessels finally fail to contract in a normal manner and remain
overfilled with blood, and at the same time acquire an unusual degree
of susceptibility to thermal influences, so that very slight changes pro-
duce great results. This is evidently in a large degree a nervous jihenom-
enon. The tension of the blood-vessels, the degree of their contraction
upon their contents, is under the control of the nerves of the vaso-motor
system, and in the derttal pulp these are prominently affected by ther-
mal change in such a way tliat the vessels in some degree let go their
grasp on the blood and expand passively before the pressure of the cir-
culation. This condition becomes pathological when the part has become
inordinately excitable by over-stimulation or the vessels fail to resume
their normal tonicity after the momentary excitement has passed.