Periapical lesions resulting from necrotic dental pulp are
among the most frequently occurring pathologies found in
alveolar bone. Exposure of the dental pulp to bacteria and
their by-products, acting as antigens, may elicit nonspecific
inflammatory responses as well as specific immunological
reactions in the periradicular tissues, and cause the
periapical lesion (1,2).
Apical periodontitis is usually produced by an intraradicular
infection. Treatment consists of the elimination of the infectious
agents by root canal treatment, allowing healing of
the lesion . However, when the infection is not completely
eliminated, the periapical lesion remains, being considered a
treatment failure. Even when the canal is correctly cleaned
and filled, it is possible that the periapical periodontitis
will persist, observing a radiotransparent image which may
be asymptomatic. This is due to the complex root canal system,
with accessory canals, ramifications and anastomoses,
which cannot be accessed, cleaned or filled by conventional
techniques. Furthermore, extraradicular factors such as
periapical actinomycosis, foreign body reaction to extruded
root canal filling, other foreign materials or endogenous
cholesterol crystals can interfere with post-treatment healing
of apical periodontitis.
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