After canal preparation, three artificial tooth specimens were randomly selected. Micro-CT images were obtained and overlapped to confirm that the prepared canal space in the artificial teeth was consistent (Figure 1 B). A high-resolution micro-CT scanner (SkyScan 1173, Bruker, Billerica, MA, USA) was used to scan the samples. The micro-CT scanner had a pixel size of 11.01 μm; X-ray source voltage, 130 kV; beam current, 60 μA; aluminum filter thickness, 1.0 mm; rotation step, 0.3° per step; and exposure time, 500 ms. Images obtained from the scan were reconstructed using NRecon software version 1.6.6.0 (Bruker microCT, Kontich, Belgium). The range of measurements was 1–5 mm and 5–9 mm from the root apex. The mesial root and distal root were imaged differently, based on the root axis. To evaluate the overall filling state, three-dimensional (3D) images of the filling material were visualized by the surface-rendering program CT-Vol (SkyScan).
The CT-An software (SkyScan) was used to measure the volume of the gap between the filling material and root canal walls, and the voids in the filling material. Three-dimensional image data were obtained after obturation in the x, y, and z axes for the mesial and distal root axes. The most apical 1 mm was not included in the analysis. The area 1–5 mm from the apex constituted the apical area, and the area 5–9 mm from the apex constituted the coronal area. When measuring the voids between the filling material and the root canal wall (Vout), a gray scale ranging between 40–255 was assigned as the volume of the filling material (Vm) and a gray scale ranging between 0–40 was assigned as a void. When measuring voids inside the filling material (Vin), a gray scale ranging between 124–255 was assigned as the volume of the filling material (Vm), and a gray scale ranging between 0–124 was assigned as a void. The percentage of voids (V%) was calculated as follows:
The CT-An software (SkyScan) was used to measure the volume of the gap between the filling material and root canal walls, and the voids in the filling material. Three-dimensional image data were obtained after obturation in the x, y, and z axes for the mesial and distal root axes. The most apical 1 mm was not included in the analysis. The area 1–5 mm from the apex constituted the apical area, and the area 5–9 mm from the apex constituted the coronal area. When measuring the voids between the filling material and the root canal wall (Vout), a gray scale ranging between 40–255 was assigned as the volume of the filling material (Vm) and a gray scale ranging between 0–40 was assigned as a void. When measuring voids inside the filling material (Vin), a gray scale ranging between 124–255 was assigned as the volume of the filling material (Vm), and a gray scale ranging between 0–124 was assigned as a void. The percentage of voids (V%) was calculated as follows:
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