الفهرس 
*Effect on canalOnly 14 pages are availabe for public view
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Abstract
In recent years, patients increasingly expect to retain
their natural teeth and are often reluctant to have their natural teeth extracted. Root canal
retreatment might offer patients a second chance to save their teeth. The success of nonsurgical
root canal treatment is dependent on cleaning and shaping of the root canal space, technical
quality of the root canal filling, and an adequate coronal restoration. Since the main cause of
endodontic failures was found to be inadequate root-filling quality (1), therefore the role of
root canal retreatment was found to be crucial for enhanced treatment outcomes and better success
rates.
The alternatives when root canal treatment fails are conventional root canal retreatment, surgical
retreatment or extraction. Among these alternatives, nonsurgical retreatment offers a more
favorable long-term outcome than the peri-radicular surgery (2). Many techniques have been
advocated for the removal of gutta-percha from the root canal system including ultrasonic
instruments, lasers, hand files, and hand files combined with heat or chemicals.
Removal of gutta-percha by conventional methods by using hand files from the root canal system
might be difficult and time-consuming. For this reason, rotary nickel-titanium (NiTi) files have
been proposed for the removal of the root canal filling, and in recent years, a number of
retreatment file systems were developed.
In the last few years, several retreatment systems were introduced to the market. These systems
consist of 2 or more files. Recently single file concept in cleaning and shaping of root canal was
introduced to decrease time the
consumption. Among those systems are one shape and
wave one. Therefore for the purpose of decreasing the time consumed in retreatment this study was
conducted as it was thought that evaluation of the efficiency of single rotary NiTi file system in
removal of gutta pecha is of a value. This is from the prospective of effect on canal curvature and
the surface topography of the files used.