This study aimed at assessing the performance of Reciproc Blue (RB) and XP Endo Shaper (XPS), used for canal retreatment on extracted teeth, in terms of debris extrusion and obturating materials removal. Thirty mandibular premolars were prepared to ProTaper X2 file, obturated using warm vertical compaction, and then incubated for 28 days at 100% humidity at 37°C. Teeth were randomly assigned into two groups, according to the system used for retreatment (RB and XPS). During retreatment, debris extruded beyond the apex was collected in preweighed Eppendorf tubes, and the retreatment time was measured. Afterward, the teeth were longitudinally sectioned to assess the remaining obturating materials. Data were statistically analyzed using the Mann–Whitney test and chi-square test at a 95% confidence level. All the samples had extruded debris at varying weights ranging from 0.125 mg to 3.680 mg. XPS extruded less debris than RB, but no difference was detected (Mann–Whitney test; P > 0.05 ). RB and XPS required 54.9 ± 17.9 and 22.3 ± 9.3 seconds to perform retreatment procedures, respectively (Mann–Whitney test; P < 0.05 ). The sealer was found in all the samples. Compared to the RB group, fewer samples with remaining gutta-percha were found in the XPS group (Chi-square test; P < 0.05 ). None of the files fractured during the retreatment procedure. The tested files appear to extrude debris beyond the apex. Although XPS was able to remove the gutta-percha completely from the majority of the canals, it was unable to remove the sealer.

The apically extruded debris caused by TruNatomy System (TRN), RACE EVO system (RE) and VDW Rotate (VR) systems in mandibular anterior teeth with ribbon-shaped root canals were compared. The root canals (n = 20 in each group) were irrigated with NaOCl 2.5%, and the extruded debris was collected at pre-weighted Eppendorf tubes. The amount of apically extruded debris (mg) and the treatment time (s) were recorded. Tukey pairwise comparisons were performed to compare groups with a 95% confidence level. VR had significantly less debris extrusion values and treatment time than RE and TRN (P < 0.05). Although no difference was observed between RE and TRN in terms of apically extruded debris (P > 0.05), a significant difference in favour of RE was observed in terms of treatment time (P < 0.05). All the instruments extruded debris at varying weights.

The purpose of this study was to evaluate the effect of calcium hydroxide [Ca(OH)2] on dentine composition and root fracture resistance. Root canals of fifty extracted mandibular premolars were prepared and divided into five groups (N = 10). Canals were filled with non‐setting Ca(OH)2 or left empty and were subsequently stored in phosphate buffered saline for 7, 14, 30, or 90 days, respectively. Ca(OH)2 was then washed out, and roots were separated from the crowns and subjected to fracture strength test. Fractured fragments were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). The results showed a significant and progressive reduction in fracture resistance the longer the duration of exposure to Ca(OH)2, and the fracture resistance in teeth exposed for 90 days was significantly lower than in any other group. SEM revealed cracks in the dentine surfaces that had been exposed to Ca(OH)2. FTIR showed a significantly lower mineral to matrix ratio in roots exposed to Ca(OH)2 for 30 and 90 days than seen in roots exposed for a shorter duration. XRD analysis revealed a reduction in dentine crystallinity. It was concluded that Ca(OH)2 significantly reduced the fracture resistance of the roots overtime. Exposure to Ca(OH)2 reduced the mineral to matrix ratio and crystallinity of the dentine.

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