Accuracy of High-resolution Small-volume Cone-beam Computed Tomography in Detecting Complex Anatomy of the Apical Isthmi: Ex Vivo Analysis.

INTRODUCTION: The purpose of this study was to evaluate the accuracy of small-volume cone-beam computed tomography (CBCT) to detect and measure isthmi in the apical root canals of mandibular molars by using micro-computed tomography (μ-CT) as the reference standard.

METHODS: Forty mandibular first molars selected on the basis of μ-CT scan and presenting isthmi in the apical 3-mm mesial roots were scanned by using the highest-resolution settings of a small-volume CBCT unit. Isthmi lengths were measured and compared between both μ-CT and CBCT images to study the accuracy of CBCT readings. Quantitative data for sensitivity rate were depicted as percentage value with 95% confidence interval. Results were analyzed by using linear regression between true lengths (μ-CT) and CBCT lengths, Bland-Altman plot and t test, at α = 0.05.

RESULTS: CBCT sensitivity for isthmi detection was 65% (95% confidence interval, 0.4667-0.8333). An average of 74.7% of the lengths could be measured, and differences among the lengths in μ-CT and CBCT were significant (P < .05; mean, 0.756 ± 0.655; t test), showing that there was no agreement between both methods.

CONCLUSIONS: Accuracy of identifying apical isthmi of mandibular molars was highly influenced by the evaluation method. Small-volume CBCT imaging could not detect and measure apical isthmi length accurately. Moreover, using high-resolution settings in CBCT, it was not reliable to forecast the actual apical root canal anatomy.