Sensitivity and Specificity of MRI versus CBCT to Detect Vertical Root Fractures Using MicroCT as a Reference Standard.

INTRODUCTION: Vertical root fracture (VRF) in root-canal-treated teeth frequently results in tooth loss, partly because VRFs are difficult to diagnose and when detected the fracture is often beyond the point of preservation with surgical intervention. Nonionizing magnetic resonance imaging (MRI) has demonstrated the ability to detect small VRFs, but it is unknown how its diagnostic capabilities compare with the current imaging standard for VRF detection, cone-beam computed tomography (CBCT). This investigation aimed to compare the sensitivity and specificity between MRI and CBCT for detecting VRF, using micro-computed tomography (microCT) as a reference. METHODS: A total of 120 extracted human tooth roots were root canal treated using common techniques, and VRFs were mechanically induced in a proportion. Samples were imaged using MRI, CBCT, and microCT. Axial MRI and CBCT images were examined by 3 board-certified endodontists, who evaluated VRF status (yes/no) and gave a confidence assessment for that decision, from which a receiver operating characteristic curve was generated. Intra- and inter-rater reliability were calculated, sensitivity and specificity, and area under the curve. RESULTS: Intra-rater reliability was 0.29-0.48 for MRI and 0.30-0.44 for CBCT. Inter-rater reliability for MRI was 0.37 and for CBCT 0.49. Sensitivity was 0.66 (95% confidence interval [CI], 0.53-0.78) and 0.58 (95% CI, 0.45-0.70), and specificity 0.72 (95% CI, 0.58-0.83) and 0.87 (95% CI, 0.75-0.95) for MRI and CBCT, respectively. Area under the curve was 0.74 (95% CI, 0.65-0.83) for MRI and 0.75 (95% CI, 0.66-0.84) for CBCT. CONCLUSIONS: There was no significant difference in sensitivity or specificity between MRI and CBCT in detecting VRF, despite the early-stage development of MRI.

Minimal Detectable Width of Tooth Fractures Using Magnetic Resonance Imaging and Method to Measure.

INTRODUCTION: Vertical root fracture (VRF) in root canal-treated (RCT) teeth is a common cause of pain, bone resorption, and tooth loss. VRF is also difficult to diagnose and measure. Magnetic resonance imaging (MRI) has the potential to identify VRF due to beneficial partial volume averaging, without using ionizing radiation. This investigation aimed to describe the narrowest VRFs detectable based on MRI, using micro-computed tomography (microCT) as the reference standard and proposes a method using profile integrals to measure the widths of small VRFs. METHODS: VRFs were induced in 62 RCT tooth root samples. All samples were imaged in a phantom using MRI and reference imaging was obtained using microCT. The stacks of 3-dimensional axial MRIs were assessed by 3 board-certified endodontists. Evaluators determined the most coronal slice within the stack that was discernible as the extent of the VRF. This slice was measured on correlated microCT sections to determine the minimum VRF width (µm) detectable using a profile integral-based method to measure small fractures and negate the effects of the point spread function. RESULTS: Using profile integrals to measure VRF width was repeatable and resulted in estimates that were on average 1 µm smaller than known reference widths. Adjusted median VRF width detected using MRI was 45 µm (first quartile: 26 µm, third quartile: 64 µm). CONCLUSION: Using profile integrals is a valid way to estimate small VRF width. The MRI approach demonstrated ability to repeatedly detect VRFs as small as 26 µm.

Accuracy and Reliability of Root Crack and Fracture Detection in Teeth Using Magnetic Resonance Imaging.

INTRODUCTION: Magnetic resonance imaging (MRI) has the potential to aid in determining the presence and extent of cracks/fractures in teeth because of better contrast without ionizing radiation. The objectives were to develop MRI criteria for root crack/fracture identification and to establish reliability and accuracy in their detection. METHODS: MRI-based criteria for crack/fracture appearance was developed by an MRI physicist and a panel of 6 dentists. Twenty-nine human adult teeth previously extracted after a clinical diagnosis of a root crack/fracture were frequency matched to 29 controls. Samples were scanned using an in vivo MRI protocol and the reference standard (ie, ex vivo limited field of view cone-beam computed tomographic [CBCT] imaging). A blinded, 4-member panel evaluated the images with a proportion randomly retested to establish intrarater reliability. Overall observer agreement, sensitivity, and specificity were computed for each imaging modality. RESULTS: Subjectively, MRI has increased crack/fracture contrast and is less prone to artifacts from radiodense materials relative to CBCT imaging. Intrarater reliability for MRI was fair to excellent (κ = 0.38-1.00), and for CBCT imaging, it was moderate to excellent (κ = 0.66-1.00). Sensitivity for MRI was 0.59 (95% confidence interval [CI], 0.39-0.76; P = .46), and for CBCT imaging, it was 0.59 (95% CI, 0.59-0.76; P = .46). Specificity for MRI was 0.83 (95% CI, 0.64-0.94; P < .01), and for CBCT imaging, it was 0.90 (95% CI, 0.73-0.98; P < .01). CONCLUSIONS: Despite advantages of increased contrast and the absence of artifacts from radiodense materials in MRI, comparable measures of sensitivity and specificity (to limited field of view CBCT imaging) suggest MRI quality improvements are needed, specifically in image acquisition and postprocessing parameters. Given the early stage of technology development, there may be a use for MRI in detecting cracks/fractures in teeth.