Micro-computed tomography: a new tool for experimental endodontology

Aim Micro-computed tomography (MCT) using cone-beam geometry is a method of producing true 3D images of the structure of small samples. A prototype MCT unit was adapted for imaging teeth to examine whether it could be used to quantify the instrumentation of root canals. Methodology Ten mandibular first molar teeth that had intact crowns and fully formed roots were scanned using MCT at a resolution of 0.081 mm and 3D-rendered images created; root canals were segmented from this. Reproducibility of MCT was verified for root canal shape and size. Access cavities were prepared into the pulp space and root canals enlarged to a continuously tapering preparation using a crowndown technique. Each tooth was scanned again to allow comparison of pre- and post-instrumentation images. The roots were then sectioned at five predetermined horizontal levels for video-digitized measurement of dimensions of roots and root canals. The video images had a resolution of 0.025 mm. Video-digitized images of the physical cut surfaces were compared with equivalent MCT reconstructed images. The total area of the root canals (internal) and root (external) at each level were calculated from both MCT reconstructions and video-digitized images, and compared. Results There was a highly significant correlation between MCT and video images for both external and internal areas (r = 0.94). Rendered 3D images were constructed to show the root canal systems of teeth. The total volumes of the apical 7.5 mm of root canals were calculated from rendered images of nine teeth before and after instrumentation. The mean amount of dentine removed by instrumentation was 3.725 mm(3), which was 28% of the original canal volume. Conclusions Micro-computed tomography was shown to be accurate for experimental endodontology.