الفهرس 
Non surgical RCT retreatment versus surgical retreatmentOnly 14 pages are availabe for public view
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Abstract
The clinical success rate of endodontic retreatments has been estimated to vary between 50% and 90%, depending on the effective elimination of necrotic tissue, bacteria, and infected obturation material such as gutta-percha and cements from root canal. [1] [75] [76]
Various nickel-titanium (Ni-Ti) rotary endodontic instruments have been developed to facilitate cleaning and shaping of root canals. In order to improve safety preparation and to prepare more appropriate shapes, advanced instrument designs with non-cutting tips, radial lands, varying tapers and rake angles, and changing pitch lengths have been developed. [22]
This study aimed to compare the efficiency of two Ni-Ti retreatment rotary files (D-RaCe & R-Endo) and the effect of the multiple uses on that efficiency and on the surface topography of the files.
Eighty mesiobuccal canals of mandibular human molars were equally divided between D-RaCe and R-Endo groups, and further subdivision into 2 groups according to the no of uses of the file. Canals were cleaned, shaped and obturated. Retreatment was carried out using D-RaCe and R-Endo.The roots were then sectioned and the sections with more residual of gutta-percha were examined under stereomicroscope and image analysis was carried out to calculate the percent of the residual filling material surface area.
Also the files that reach the full working length in each group (DR2-R3) were examined under SEM to investigate surface topography.
The results of this study showed that the time needed to complete the retreatment was faster with the D-RaCe in the first and the 5th use. D-RaCe rotary retreatment system leaved less residual filling material than R-Endo after the multiple uses. Both systems were affected by the number or retreated canals and the canal portion with the highest residual filling material in the apical third. The study of the surface topography showed more disturbances in the D-RaCe system after the multiple uses,.