Intraradicular bacteria and fungi in root-filled, asymptomatic human teeth with therapy-resistant periapical lesions: A long-term light and electron microscopic follow-up study
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Abstract
Light and electron microscopy were used to analyze nine therapy-resistant and asymptomatic
human periapical lesions, which were removed as block biopsies during surgical treatment
of the affected teeth. The cases that required surgery represented about 10% of all
of the cases which received endodontic treatment and root fillings during the period
1977 to 1984. These cases revealed periapical lesions when they were examined 4 to
10 yr after treatment. The biopsies were processed for correlated light and electron
microscopy. Six of the nine biopsies revealed the presence of microorganisms in the
apical root canal. Four contained one or more species of bacteria and two revealed
yeasts. Of the four cases in which bacteria were found, only in one biopsy could they
be found by light microscope. In the other three specimens, the bacterial presence
could be confirmed only after repeated electron microscopic examination of the apical
root canal by serial step-cutting technique. Among the three cases in which no microorganisms
could be encountered, one showed histopathological features of a foreign body giant
cell granuloma. These findings suggest that in the majority of root-filled human teeth
with therapy-resistant periapical lesions, microorganisms may persist and may play
a significant role in endodontic treatment failures. In certain instances such lesions
may also be sustained by foreign body giant cell type of tissue responses at the periapex
of root-filled teeth.