MRI Detection of Vertical Root Fractures in Endodontically Treated Teeth

Objectives: Vertical root fracture (VRF) is known to occur in root canal treated (RCT) teeth and results in tooth loss. Detecting VRFs early is ideal because surgical intervention could preserve the tooth and prevent patient pain and suffering. Early VRFs are difficult to diagnose with existing imaging modalities and few studies have reported actual fracture sizes. Magnetic Resonance Imaging (MRI) has the potential to identify minute defects in teeth due to beneficial partial volume averaging within voxels without using ionizing radiation. This investigation aims to determine the sensitivity and specificity of MRI compared to cone-beam computed tomography (cbCT) in detecting VRF, using micro-computed tomography (µCT) as the reference standard and to determine the limits of MRI for detecting VRF.
Methods: 115 extracted human teeth were decoronated and the apical 2mm resected. RCT was completed using common techniques. VRFs were induced in 62 teeth using an Instron machine. All teeth were imaged in a phantom using MRI and cbCT. Axial images for MRI and cbCT were presented to three board-certified endodontists. Evaluators determined VRF status with a binary response and confidence assessment for that decision. 30% of images were resampled to calculate inter- and intra-rater reliability. For MRI, the most coronal slice with discernible VRF was measured on correlated µCT to determine the minimum VRF width (µm).
Results: Sensitivity for MRI and cbCT were 0.66 (95%CI:0.53-0.78) and 0.58 (95%CI:0.45-0.70). Specificity was 0.72 (95%CI:0.58-0.83) and 0.87 (95%CI:0.75-0.95). Inter-rater reliability for MRI was k=0.37 and cbCT k=0.49. Intra-rater reliability ranged from k=0.29-0.48 for MRI and k=0.30-0.44 for cbCT. Median VRF width detected using MRI was 56µm (range=20µm-120µm).
Conclusions: MRI demonstrated ability to detect VRF as small as 20 µm. There was no significant difference between sensitivity nor specificity for MRI versus cbCT in detecting VRF, despite the early stage of MRI development.