Micro-CT Study on the Supplementary Effect of XP-Endo Finisher R after Endodontic Retreatment with Mtwo-R.

Background: During the course of a non-surgical orthograde endodontic retreatment, supplementary instrumentation is usually required for better removal of root canal filling material.
Aim: The aim of this study was to assess the effectiveness of XP-Endo Finisher R in endodontic retreatment of oval root canals.
Materials and Methods: The study was performed on extracted mandibular incisors preliminary cut at the cementoenamel junction. The root canals of 12 extracted lower central incisors were initially shaped with the rotary nickel-titanium system XP-Endo Shaper (30/.04) and filled with continuous waves of condensation. Root canal retreatment was performed with the МTwo Retreatment - R1 (15/.05) and R2 (25/.05) files, followed by the XP-Endo Finisher R (30/.00). Three micro-computed tomography scans were performed during the course of the experiment: 1) after the filling of the root canals, 2) after the first retreatment procedures, and 3) after the supplementary shaping. Kolmogorov-Smirnov test for normality and Friedman and Kruskal-Wallis tests for comparison of several independent samples.
Results: There were no statistically significant differences in the percentage of removed obturation material in the different parts of the root canal after the use of Mtwo-R (P = 0.649) and XP-Endo Finisher R (P = 0.934). The additional instrumentation with XP-FR reduced the percentage of the remaining root canal filling insignificantly (P = 0.190).
Conclusions: The combined action of Mtwo-R retreatment files and XP-Endo Finisher R resulted in significant reduction of the amount of root canal filling material. Nevertheless, none of the examined rotary systems guaranteed its complete removal.
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