Operative dentistry aje qualtrough, jd satterthwaite la morrow, pa brunton

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Smear layer management
When the blades of any file engage and cut dentine, a smear layer of
organic and inorganic debris forms on the walls of the preparation.
Whether or not to remove the smear layer or leave it intact is still
debated. If the smear layer is removed then a tighter interface between
the obturation materials and the dentine walls is possible. If the smear
layer is left, then the root canal system is incompletely sealed and the
potential for microleakage increases. EDTA in its aqueous form,
flooded into well-shaped preparations has been shown to remove the
inorganic component of the smear layer, and when used in conjunc-
tion with sodium hypochlorite will eliminate the smear layer.
INTER-APPOINTMENT MEDICAMENTS
In asymptomatic teeth in which complications are not anticipated,
cleaning, shaping and filling can be carried out in one visit. However,
as it has been shown that elimination of intra-canal infection cannot be
achieved at one treatment session, the use of intra-canal medicaments
and filling of the canals at a second visit is justified
12
.
Theoretically, therefore, teeth with apical periodontitis should 
have a better prognosis when treated in more than one visit and 
when an intra-canal medicament is placed. However, this hypothesis
is not always supported clinically as some studies indicate that 
teeth with apical periodontitis can perform well when treated in one
visit
12,13
.
The requirements of an inter-appointment medicament are that it
should be:
• Intact for the period of dressing
• Easy to apply and remove
• Antibacterial
• Eliminate any space for bacterial growth
In order to place an inter-appointment medicament, the canal 
is rendered clean and dry following cleaning and shaping before
being filled with the paste material. This may be delivered on a pre-
measured paper point, file or Lentulo spiral filler to the anatomic
apex. Careful application of pressure using a cotton pellet ensures
that the paste is condensed towards the apex. Excess material is 
blotted dry from the pulp chamber and the cavity sealed with a 
temporary cement overlaid with a more rigid material.
POOC03 02/18/2005 04:33PM Page 73

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A variety of materials have been proposed for this purpose 
including antiseptic pastes and other relatively toxic solutions and
tinctures.