1-20. PULPAL REACTION TO DENTAL CARIES
a. The Reason for Pain. When dental decay reaches a depth in the dentin that
is near the pulp tissue inside of the tooth, the pulp tissue can become inflamed. The
inflammation causes the blood vessels to swell and release fluid into the extra cellular
spaces. This swelling is limited by the hard walls of the pulp chamber and root canals
and, as a result, severe pain may result because of the constriction. Pus can
accumulate within the diseased pulp tissue that further accelerates the pathologic
process.
b. The Process of Decay. The reaction of the pulp to dental caries varies. This
reaction generally varies in accordance with the rate of advance of the carious process.
Even before there is significant dentin involvement, the pulp tissue can become irritated
and the irritation causes minor inflammation. This, in turn, stimulates the odontoblasts
to produce secondary dentin in an effort to protect the pulp. If the rate of advance of
caries is slow and the resistance of the patient is high, this deposition of secondary
dentin may prevent the carious process from reaching the pulp tissues for a
considerable time. If it were not for this protective reaction of the odontoblasts, a far
higher percentage of carious lesions would reach the pulp chamber before detection,
causing more injury to the pulp. If not treated or arrested, the carious process can
eventually reach and involve the pulp tissue. As it nears the pulp, the irritation becomes
more severe and direct bacterial invasion occurs. If the resulting inflammation is severe
or of prolonged duration, the pulp tissue may die (necroses) if left untreated.
Section IV. DISEASES OF THE DENTAL PULP
1-21. GENERAL
Pulp is an extremely sensitive tissue that can only elicit pain. It can be subjected
to many irritations resulting from dental caries, exposure to excessive heat or cold, and
mechanical, chemical, or electrical stimulation. In a healthy tooth, the enamel and
periodontal tissues act as mechanical and insulating coverings. If the enamel or
cemental tissues covering the root are damaged or removed, the underlying dentin is
exposed. The dentin then becomes sensitive to external irritants because of the
movement of fluid in and out of the dentinal tubules. This fluid movement causes
stimulation of the sensitive pain receptors inside the dentin pulp. Injuries such as dental
caries, trauma, developmental defects and/or diseases, or dentistogenic (dentist-
caused) injuries can have a negative effect on the pulp. Among the diseases that occur
in the pulp are acute pulpitis, chronic pulpitis, pulp abscesses, hyperplastic pulpitis, and
a number of degenerative changes (diseases) that take place. Acute and chronic
pulpitis and pulp abscesses are commonly encountered in clinical dental practice.
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