Determination of the Initial Apical Canal Diameter by the First File to Bind or Cone-beam Computed Tomographic Measurements Using Micro-computed Tomography as the Gold Standard: An Ex Vivo Study in Human Cadavers

Abstract Introduction This study evaluated the accuracy and reliability of the tactile perception of the first apical binding file (FABF) and cone-beam computed tomographic (CBCT) imaging in estimating the canal diameter at the working length (WL). Methods Ten anterior mandible segments were obtained from cadavers maintained in formalin and scanned using CBCT and high-resolution micro–computed tomographic (micro-CT) imaging. Scans were used to measure the smallest canal diameter of 38 mandibular incisors at 1 mm short of the root apex. After coronal access preparation, the canals of these teeth were explored with a size 08 K-file up to the radiographic apex, and the WL was established 1 mm shorter. Larger K-files were passively introduced in the canal up to the WL until binding was felt and the next instrument size could not reach this point. This instrument was regarded as the FABF. The accuracy and level of agreement (reliability) of the FABF and CBCT imaging in determining the initial apical canal size were determined using the Pearson correlation coefficient and the intraclass correlation coefficient, respectively, considering the micro-CT measurements as the gold standard. Results The Pearson correlation coefficient and the intraclass correlation coefficient were statistically significant when CBCT imaging was compared with micro-CT imaging ( P r = 0.61) and good reliability (0.74). On the other hand, FABF was inaccurate and unreliable ( P > .05). The means of the smallest root canal diameter obtained by micro-CT and CBCT imaging were 0.22 mm (range, 0.14–0.34 mm) and 0.23 mm (range, 0.13–0.37 mm), respectively. The mean of the FABF diameter was 0.15 mm (range, 0.08–0.30 mm). Conclusions Although FABF did not accurately reflect the diameter of the apical canal at the WL, CBCT imaging showed good accuracy and reliability. Data from CBCT imaging regarding the initial apical canal size may be used to plan root canal enlargement.