Effects of voxel size and resolution on the accuracy of endodontic length measurement using cone beam computed tomography

An accurate determination of the working length is indispensable for successful endodontic treatment. The aim of this study was to determine the influence of the voxel size and resolution of CBCT on measuring root canal working length. Thirty extracted single-rooted permanent teeth were used for this study. The working lengths of the teeth were determined by a researcher inserted a K-file into each canal until the tip became visible through the major foramen. The file was withdrawn until its tip was seen at the level of the coronal-most border of the major foramen under. The rubber stop was adjusted to the occlusal reference and the distance from the stop to the false tip was measured with digital calipers and recorded as the actual working length. The CBCT images were obtained with a Planmeca ProMax 3D Mid (Planmeca, Helsinki, Finland) using four sets of settings: from voxel size 0.5 mm to voxel size 1.0 mm. These measurements were compared with actual lengths (as a control group) using Analysis of Variance and the Dunnett Post Hoc Test. The Pearson correlation coefficient (r) and 95% confidence intervals were calculated to compare all measurement methods. The significance level was set at P < 0.05. No significant difference was found among CBCT groups and working length. A highest correlation was found between the actual length and smallest voxel size and highest CBCT measurements (r = 0.94). CBCT imaging can be used endodontic working length measurement and the smallest voxel size and highest resolution yielded more accurate results.