Accuracy of cone-beam computed tomography in the detection of a second mesiobuccal root canal in endodontically treated teeth: an ex vivo study

Introduction
There is a high incidence of a second mesiobuccal root canal (MB2) in maxillary molars. The study aim is to assess the accuracy of cone-beam computed tomographic (CBCT) imaging in detecting a second mesiobuccal root canal in endodontically treated maxillary molars.

Methods
The study sample consisted of 60 extracted maxillary molars, which were endodontically opened and examined under a dental operating microscope for the presence of an MB2. The teeth were then further examined using micro-computed tomographic imaging as the gold standard. Root canals were filled (except the MB2) and were then subdivided into an experimental and a control group. After fixing the teeth in a dry human skull, they were scanned using CBCT imaging (AccuiTomo 170; Morita Inc, Tarumi-cho Suita City, Osaka, Japan). The observers for this study were 2 experienced radiologists blinded to the group allocation of controls and experiments; they evaluated the images twice independently. Sensitivity, specificity, and accuracy were calculated as well as the kappa values for both inter- and intraobserver agreement.

Results
From 30 teeth, which were diagnosed without an MB2 under examination with a dental operating microscope, 6 teeth proved to have an MB2 using μCT (20%). Intraobserver reliability was high for both observers 1 (R = 0.85) and 2 (R = 0.96). Interobserver reliability as assessed by the Cohen kappa was excellent (R = 0.89). CBCT sensitivity for detecting an MB2 was 96%, specificity was 100%, and total accuracy was 98%.

Conclusions
CBCT imaging is a suitable diagnostic technique for detecting a missed MB2 in endodontically treated teeth.