Abstract
To investigate potential correlations between objective CBCT image parameters and accuracy in endodontic working length determination ex vivo. Contrast-to-noise ratio (CNR) and spatial resolution (SR) as fundamental objective image parameters were examined using specific phantoms in seven different CBCT machines. Seven experienced observers were instructed and calibrated. The order of the CBCTs was randomized for each observer and observation. To assess intra-operator reproducibility, the procedure was repeated within six weeks with a randomized order of CBCT images. Multivariate analysis (MANOVA) did not reveal any influence of the combined image quality factors CNR and SR on measurement accuracy. Inter-operator reproducibility as assessed between the two observations was poor, with a mean intra-class correlation (ICC) of 0.48 (95%-CI 0.38, 0.59) for observation No. 1. and 0.40 (95%-CI 0.30, 0.51) for observation No. 2. Intra-operator reproducibility pooled over all observers between both observations was only moderate, with a mean ICC of 0.58 (95%-CI 0.52 to 0.64). Within the limitations of the study, objective image quality measures and exposure parameters seem not to have a significant influence on accuracy in determining endodontic root canal lengths in CBCT scans. The main factor of variance is the observer.
Highlights
The success of endodontic treatment, among other factors, is strongly correlated to accurate determination of the endodontic working length[1]
cone-beam computed tomography (CBCT) devices and parameters used for the evaluation are shown in Table 1; the voxel size provided is stated by the corresponding manufacturer
Contrast-to-noise ratio (CNR) ranged from 0.18 (PaX-Duo3D) to 1.94 (3D eXam), while Modulation Transfer Function (MTF) 10% ranged from 1.8 cycles/mm (3D eXam) to 2.8 cycles/ mm (Orthophos SL)
Summary
The success of endodontic treatment, among other factors, is strongly correlated to accurate determination of the endodontic working length[1]. Hardware, exposure parameters, field of view size and reconstruction parameters differ to a great extent between different machines, and no two CBCTs are the s ame[12] These different characteristics affect image quality, dose ranges[13] and probably the interpretation of the images as well. Objective image parameters for CBCT comprise contrast, spatial resolution (SR), noise characteristics and homogeneity/uniformity as well as artifact c haracteristics[13,16] These can be readily measured and image quality objectively determined. The aim of this study was to investigate potential correlations between objective CBCT image parameters and accuracy in endodontic working length determination using a sufficiently large number of experienced observers
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