الفهرس 
Removal ability of different root canal filling materialsOnly 14 pages are availabe for public view
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Abstract
Root canal therapy, despite having a high degree of
success, may not lead to the desired response, and
failure may occur. When root canal therapy fails,
treatment options include conventional retreatment,
periradicular surgery, or extraction. Whenever possible, the
nonsurgical retreatment option is preferred because it is the
most conservative method to solve the problem . The main
goal of retreatment is to regain access to the apical foramen
by complete removal of the root canal filling material,
thereby facilitating sufficient cleaning and shaping of the
root canal system and final proper obturation .
Today it has not been proven that removing all obturation
material will ensure success of endodontic retreatment and
that remaining gutta-percha or sealer will cause the
retreatment to fail. However, removing as much sealer and
core as possible from inadequately prepared and obturated
root canal systems is critical in order to uncover remnants
of necrotic tissue or bacteria that may be responsible for
periapical inflammation and failure .
Many materials are being used for the filling of root canals,
of which gutta-percha with a variety of sealers is the most
common. However, lately, various resin-based root canal
filling materials have been developed to establish a core sealer-dentin continuum to the end of preventing
microleakage and improving the fracture resistance of rootfilled
teeth.
A variety of techniques have been advocated for the
removal of gutta-percha from the root canal system
including manual endodontic hand instruments
facilitated by solvents such as chloroform, xylol,
eucalyptol, halothane, orange oil, or ultrasonics , lasers,
heat carrying instruments , as well as nickel-titanium (Ni-
Ti) rotary instruments, and in recent years, a number of
retreatment file systems were developed.
Several studies have evaluated the efficacy of different
engine-driven nickel-titanium (Ni-Ti) file systems in the
removal of root canal filling materials, whereby these
systems promised reduced working time. Therefore it was
thought that investigation of the applicability of Ni-Ti
rotary instruments with and without solvent in the removal
of different resin-based root canal filling materials, in
comparison to conventional gutta-percha is of great value.