Claudia Hoffman
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 FTER
the non-surgical root canal therapy is completed, a strong temporary cement
must be placed in the pulp space to prevent leakage and contamination.
As dentists, we have a variety of cements and filling materials available
and we must choose a cement that provides a satisfactory seal. A poor seal
on top of an endodontically treated tooth can allow bacteria and fluid
products from the oral cavity to re-contaminate the pulp space. The cement
must have strength to withstand masticatory forces and preserve a good
seal at the same time.
The most common materials used as temporary fillings
are IRM reinforced zinc oxide cement; Cavit, a mix of zinc oxide, calcium
sulfate, glycol, polyvinyl acetate, polyvinyl chloride, and triethanolamine;
and TERM, a filled composite resin. Of these three options, Cavit and TERM
provide a better seal than IRM at any thickness. IRM has been shown
to have more extensive marginal leakage of fluid than Cavit does. Although
IRM has a bacterial barrier due to the eugenol, that does not prevent other
fluids from leaking in. If Cavit is used, it must be placed at a thickness
of at least 4 mm. If a stronger filling is needed, you can place
glass ionomer on top of the Cavit (Pathways of the Pulp, 8th Ed.).
So the question arises, when should we retreat a
previously endodontically treated tooth if we suspect contamination?
Swanson and Madison (1987) demonstrated that it took only three days for
coronal leakage of a tracer dye to reach the apex. Khayat and Torbinejad
(1993) demonstrated recontamination of obturated root canal systems by
bacteria placed in natural saliva within 30 days. Based on these and other
studies, you should retreat leaking non-surgical root canal therapy cases
if left open for longer than three weeks.
January-March 2006
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A poor seal
on top of an endodontically treated tooth can allow bacteria and fluid
products from the oral cavity to re-contaminate the pulp space.
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