Aim: this study was conducted to evaluate the routinely used methods for working length determination of root canals and comparing them to the working length obtained from the cone beam computed tomography -CBCT- to assess its efficiency in working length determination through both in-vivo and in-vitro measurements.

Methodology: a total number of 47 root canals of 47single rooted human anterior teeth – 18 upper central incisors, 17 upper lateral incisors, 7 upper canines and 12 lower canines that were diagnosed to be extracted due to grade III mobility.
The sample was collected from 10 patients – 6 males and 4 females where a preoperative periapical radiograph for the desired teeth were taken in addition to the preoperative CBCT, the working length was determined using apex locator and preoperative radiographs (in-vivo) then same teeth were extracted to determine the actual working length (in-vitro).
The working length were recorded and compared to the actual working length of the teeth.

Results: working length measurements using the preoperative CBCT when compared to the actual working length after teeth extraction were considered to be accurate with the mean value difference between the CBCT and the actual working length >0.5mm

Conclusion: under the circumstances of this study, it was concluded that CBCT is considered to be a reliable and accurate method for working length determination with negligible difference from the actual working length of the teeth that was measured in vitro after extraction.

Keywords: Apex Locator, Cone Beam Computed Tomography, Working Length Determination, root canal treatment.