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.

Atomic force microscopy study on the effect of different irrigation regimens on the surface roughness of human root canal dentin.

Background: Endodontic irrigants could alter the mechanical properties of root canal dentin, such as its roughness. Aim: To compare the effect of various irrigation protocols on root canal dentin roughness with respect to their application time, concentration, and additional ultrasonic activation. Materials and Methods: Forty single-rooted, non-endodontically treated upper incisors were decoronated and further sectioned longitudinally in a buccolingual direction. The surfaces of all eighty samples were polished and randomly segregated to eight equal groups (n = 10): Group A: 2% NaOCl/2 min followed by 17% EDTA/2 min; Group B: 2% NaOCl/5 min followed by 17% EDTA/5 min; Group C: 5.25% NaOCl/2 min followed by 17% EDTA/2 min; Group D: 5.25% NaOCl/5 min followed by 17% EDTA/5 min; Group E: 2% NaOCl solution, ultrasonically activated for 2 min; Group F: 5.25% NaOCl, ultrasonically activated for 2 min; Group G: 2% NaOCl/2 min followed by 17% EDTA/2 min, both ultrasonically activated; Group H: Control group (distilled water). Results: All irrigation regimens increased root dentin surface roughness in comparison with the control group. The analysis of the values revealed significant differences between the arithmetical average roughness values (Ra) in the groups (p < 0.001). A statistically significant increase in the Ra parameter was observed in groups E, F, G, and D. The irrigation protocol in Group A showed a significantly smoother dentin surface than those with the ultrasonic activation. Conclusion: All tested irrigants increased root canal dentin roughness and the effect was time and concentration-dependent. The ultrasonic activation of the disinfection solutions roughened the root dentin surface significantly.