Aim To evaluate the effect of instrumentation using Reciproc Blue (RB; VDW, Munich, Germany) and XP‐endo Shaper (XP‐S; FKG Dentaire, La Chaux‐deFonds, Switzerland) systems on the area of untouched canal wall (AUCW), accumulated hard‐tissue debris (AHTD) and the efficacy of three irrigation protocols on percentage reductions (red%) of AHTD within C‐shaped canals of mandibular molars. Methodology Seventy mandibular molars with C‐shaped canals were scanned, matched and assigned to two shaping groups (n = 35): RB and XP‐S. Following instrumentation, specimens were triple‐matched with respect to the amount of remaining debris and assigned to three irrigation subgroups (n = 10): syringe‐and‐needle irrigation (SNI), XP‐endo Finisher (XP‐F; FKG Dentaire) and passive ultrasonic irrigation (PUI). The AUCW% and AHTD% after instrumentation and the red% of AHTD after irrigation were calculated from micro‐computed tomography. Data were analysed using comparisons for two groups (RB vs. XP‐S) or multiple subgroups followed by pairwise comparison procedures (SNI vs. XP‐F vs. PUI) at α = 0.05. Results For RB and XP‐S, 33.04% and 30.45%, respectively, of the canal wall remained untouched (P > 0.05). For both groups, the apical third had larger AUCW% than the coronal third (P < 0.05). Instrumentation with RB left more debris (2.8%) than XP‐S (1.1%) (P < 0.05). The PUI and XP‐F subgroups had higher mean red% of AHTD than the SNI subgroup; the difference was significant for RB (P < 0.05) but not for XP‐S. Conclusions Both RB and XP‐S systems were associated with similar AUCW after instrumenting C‐shaped canals. RB left significantly greater levels of AHTD compared with XP‐S. PUI and XP‐F irrigation removed more debris than SNI when using the RB system.

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The apical delta is an intricate system within the root canal and incompletely debridement may affect the long-term prognosis of root canal therapy. The aim of the present study is to investigate the morphologic features of apical deltas in human teeth with micro-computed tomography (micro-CT) using a centreline-fitting algorithm. One hundred and thirty-six apical deltas were detected in 1400 teeth. Molars had more apical deltas (15.8%) than anterior teeth (6.3%). In maxillary molars, the mesiobuccal root had a significantly higher prevalence of apical delta than the palatal root or the distobuccal root. The median vertical distance of the apical delta was 1.87 mm with 13% more than 3 mm. The median diameter and length of the apical delta branches were 132.3 and 934.5 μm. Apical delta branches were not straight with cross-sectional shapes being non-circular. These morphological features of apical delta may complicate debridement of the infected root canal system.

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Small organic molecules with carbonyl active site are a prominent member in the family of organic electrode material, due to the reversible reaction and more tunable electrochemical property. However, the dissolution loss is the biggest obstacle in its application. In this work, we tried to address the dissolution issue of 5,7,12,14-pentacenetetrone (PT), a typical quinone-based organic electrode. Highly concentrated electrolyte of 5 M LiTFSI DME was used and it significantly reduced the dissolution and well maintained the capacity after 500 cycles.Besides, through the investigation of the relationship between solvent/electrolyte property and dissolution, and the interaction between electrode and electrolyte, a guiding rule of the dependence of dissolution on polarity was proposed. With the rule, non-polar solvent of hexane was further added as cosolvent and its-adding decreased the polarity and substantially eliminated the dissolution loss. The work supplies a common electrolyte strategy to address the dissolution issue of small organic molecules.