The validity of cone-beam computed tomography in measuring root canal length using a gold standard

Introduction
The distance between a coronal reference point and the major apical foramen is important for working length determination. The aim of this in vitro study was to determine the accuracy of root canal length measurements performed with cone-beam computed tomographic (CBCT) scans using a gold standard.

Methods
A total of 162 teeth (198 root canals) in 16 dry human dentulous mandibles were scanned using a 3DX-Accuitomo CBCT scanner (Morita 3DX; J Morita Mfg Corp, Kyoto, Japan). The root canal length was measured with CBCT data. All teeth were extracted atraumatically and endodontically accessed; the root canal length was measured blindly using a #10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) and served as the gold standard.

Results
The mean absolute difference of the CBCT-based root canal length from the gold standard was 0.46 mm (95% confidence interval, 0.41-0.50 mm). Only in 9 of 198 (4.5%) roots did the difference between the CBCT-based root canal length and the gold standard exceed 1 mm.

Conclusions
CBCT-based root canal length measurements are accurate and reliable when compared with a gold standard.