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Aim To compare the removal of root fillings in extracted teeth using the ProTaper Universal Retreatment system (PTUR) followed by a supplementary preparation with the XP‐Endo Finisher file. Methodology The mesiobuccal root canals of 30 extracted mandibular first molars were instrumented with ProTaper Universal NiTi files up to F2 and filled with one of the following sealers using a single‐cone technique (n = 10): AH Plus, NeoMTA Plus and EndoSequence BC. The root fillings were removed using the PTUR system with additional apical preparation using ProTaper F2 and F3 files. Then, an additional preparation with an XP‐Endo Finisher file was performed. The samples were scanned using micro‐CT before and after retreatment and again after the use of the XP‐Endo Finisher to assess the volume of remaining filling material. Data were analysed by Kruskal–Wallis and Friedman's two‐way analysis of variance tests with Bonferroni correction. Results No significant difference in the initial filling volume was observed amongst the groups (P > 0.05). The amount of filling materials in each group decreased significantly after retreatment with rotary files (P < 0.05). After initial retreatment, the volume of the remaining filling amongst the groups was similar (P > 0.05). Additional preparation with the XP‐Endo Finisher improved the removal of filling materials regardless of the sealer type (P < 0.05). Conclusions In the mesiobuccal root canals of extracted mandibular first molars, additional preparation using an XP‐Endo Finisher file, after using the PTUR system and F3 ProTaper instruments, enhanced the removal of filling materials from root canals.

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At the present time, there is no successful synthetic, off-the-shelf small-caliber vascular graft (<6 mm) for the repair or bypass of the coronary or carotid arteries. This stimulates ongoing investigations to fabricate an artificial vascular graft that has both sufficient mechanical properties as well as superior biological performance. Collagen has long been considered as a viable material to encourage cell recruitment, tissue regeneration, and revascularization, but its use has been limited by its inferior mechanical properties. In this study, novel electrochemically aligned collagen filaments were used to engineer a bilayer small-caliber vascular graft, by circular knitting the collagen filaments and electrospinning collagen nanofibers. The collagen prototype grafts showed significantly greater bursting strength under dry and hydrated conditions to that of autografts such as the human internal mammary artery and the saphenous vein (SV). The suture retention strength was sufficient under dry condition, but that under hydrated condition needs to be further improved. The radial dynamic compliance of the collagen grafts was similar to that of the human SV. During in vitro cell culture assays with human umbilical vein endothelial cells, the prototype collagen grafts also encouraged cell adhesion and promoted cell proliferation compared to the synthetic poly(lactic acid) grafts. In conclusion, this study demonstrated the feasibility of the use of novel collagen filaments for fabricating small caliber tissue-engineered vascular grafts that provide both sufficient mechanical properties and superior biological performance.

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