Establishment of narrow root fracture models using modified temperature cycling method and diagnosis using different cone-beam CT units

Abstract AimUsing modified thermal cycling method to establish narrow root fracture models and evaluate the diagnosis efficiency of them using four different cone-beam CT (CBCT) units.MethodologyFifty-six intact teeth were selected and the crowns of the teeth were embedded using general purpose acrylic resin. 50 VRF models were established by soaking these teeth in liquid nitrogen and hot water cyclically; 6 teeth were used as negative control. All the 56 teeth were scanned with the smallest voxel size of four different CBCT units (NewTom VGi, Planmeca Promax 3D Max, Kavo 3D eXam and Soredex Scanora3D). The CBCT images were evaluated for the presence or absence of fracture lines. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and area under the receiver operating characteristic curve (AUC) were calculated for the diagnosis of FLs using the four CBCT units. After that, 10 VRF teeth were randomly selected and the roots were sliced using slow-speed saw to obtain horizontal root sections with thickness of 2mm from enamel-cemental junction to the root apex and 25 root sections were finally obtained. Scanning electron microscope (SEM) was used to measure the width of the fracture lines (FLs) for each root section at one side.ResultsFifty narrow root fracture models were successfully established. There were totally 50 positive VRF models with 83 FLs and 6 negative VRF models. The diagnosis sensitivity was 0.24, 0.38, 0.29 and 0.19, the diagnosis specificity was 0.45, 0.16, 0.55, and 0.75, and the AUC was 0.60, 0.52, 0.59 and 0.61 for NewTom VGi, Planmeca Promax 3D Max, Soredex Scanora-3D and Kavo 3D eXam respectively. Randomly selected 10 models were sliced and 25 root sections with 45 FLs were acquired. The width of FLs was from 3.43μm to 143μm; 32.06% were less than 25μm, only 9.6% were from 75 to 150μm with SEM.ConclusionsThe modified temperature cycling method is a simple and effective method to establish narrow root fracture models, the diagnosis efficiency for these narrow fracture lines were quite poor using all the four different CBCT units.