الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
The aim of this study was to evaluate the efficacy of ProTaper Universal retreatment rotary files and Hedström hand files for the removal
of Gutta-percha/AHPlus and Resilon/Epiphany filling materials during root canal retreatment. Materials and Methods: Eighty extracted human singlerooted teeth were instrumented with K-files and irrigated with 2.5% NaOClfollowed by 17% EDTA and the last flush before obturation was by saline.The samples were divided into 2 main groups with 40 specimens each and
filled with Gutta-percha/AHPlus sealer or with Resilon/Epiphany sealer.
According to retreatment method, each main group was further subdivided
into 2 subgroups of 20 specimens each, where Hedström hand files or
ProTaper Universal retreatment rotary files were used. The time needed to
eliminate the filling material was recorded. Root canal walls were examined
using stereomicroscope and direct digital radiographs to evaluate the
material remnants on each root third. Student’s t-test was used to
determine significant differences between mean values of time and
remaining material (P ≤ 0.05).