Synchrotron-based Phase Contrast-enhanced Micro–Computed Tomography Reveals Delaminations and Material Tearing in Water-expandable Root FillingsEx Vivo

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Introduction:This study evaluated the integrity of calcium silicate sealer–based fillings made with hygro-expandable cones (HEC) that are commercially known as CPoint or Smartpoint.Methods:Fourteen human canines were prepared according to a standardized, conventional endodontic treatment protocol and filled with the HEC/calcium silicate sealer. Three-dimensional imaging was performed with laboratory micro–computed tomography (μCT) at its highest resolution and was compared with synchrotron phase contrast-enhanced μCT (PCE-CT) scans of the treatment extending 1–7 mm from the apex. Conventional destructive optical microscopy validated observations by comparison with virtual slices in the tomographic data.Results:Conventional laboratory μCT at 10-μm resolution did not reveal the existing voids and defects within the root canal fillings. PCE-CT revealed elongated interfacial delamination localized mainly at the HEC-sealer interface forming extended through-and-through gaps along the root canal filling.Conclusions:Endodontic studies that use conventional laboratory μCT may underestimate thin defects and delamination within root canal fillings made with HEC because of limited resolution and contrast of laboratory-based broad-spectrum low intensity x-ray sources. These limitations favor use of high-brilliance, monochromatic synchrotron-based PCE-CT to reveal the important micrometer details within large (millimeter sized) samples. PCE-CT revealed the existence of a range of significant structural defects in recently placed HEC fillings, confirmed by optical microscopy after physical sectioning. Substantial delamination spanning 20%–40% of the circumferential interface as well as other structural defects were identified within root canal fillings made of HEC and calcium silicate sealer.HighlightsInternal 3D defects are detected in fillings based on hygro-expandable cones (Cpoint).Such fillings with calcium silicate sealer exhibit delaminations, voids, and tears.These defects are often invisible by laboratory microCT (μCT) due to low contrast.In some specimens, up to 40% of the cone-sealer interface is detached longitudinally.Phase contrast enhanced μCT non-destructively reveals μm-sized voids in root fillings

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