Comparison of Reproducibility of Linear Measurements on Digital Models among Intraoral Scanners, Desktop Scanners, and Cone-beam Computed Tomography

Abstract

Purpose: Intraoral scanners, desktop scanners, and cone-beam computed tomography (CBCT) are being used in a complementary way for diagnosis and treatment planning. Limited patient-based results are available about dimen sional reproducibility among different three-dimensional imaging systems. This study aimed to evaluate dimension al reproducibility among patient-derived digital models created from an intraoral scanner, desktop scanner, and two CBCT systems. Materials and Methods: Twenty-nine arches from sixteen patients who were candidates for implant treatments were enrolled. Different types of CBCT systems (KCT and VCT) were used before and after the surgery. Polyvinylsiloxane impressions were taken on the enrolled arches after the healing period. Gypsum casts were fabricated and scanned with an intraoral scanner (CIOS) and desktop scanner (MDS). Four test groups of digital models, each from CIOS, MDS, KCT, and VCT, respectively, were compared to the reference gypsum cast group. For comparison of linear measurements, intercanine and intermolar widths and left and right canine to molar lengths were measured on indi vidual gypsum cast and digital models. All measurements were triplicated, and the averages were used for statistics. Bland–Altman plots were drawn to assess the degree of agreement between each test group with the reference gyp sum cast group. A linear mixed model was used to analyze the fixed effect of the test groups compared to the refer ence group (α=0.05). Result: The Bland–Altman plots showed that the bias of each test group was –0.07 mm for CIOS, –0.07 mm for MDS, 2 J Korean Dent Sci 2022;15(1):1-8 Deuk-Won Jo, et al: Comparison of Reproducibility of Digital Models Deuk-Won Jo, et al: Comparison of Reproducibility of Digital Models Introduction Digital workflows in dentistry have been enor mously evolved and grown over the past decades. These days, three-dimensional (3D) digital dental models can be rendered using intraoral scanners (IOS), desktop scanners (DS), and computed tomog raphy. Clinicians use these imaging systems in a complementary way for diagnosis and treatments. IOS and DS use light source for imaging and en coded coordinates are created as a form of polygons. Cone-beam computed tomography (CBCT) use ra diation as an imaging source, and the rendering sys tem builds a 3D image based on relative voxel posi tions. Because of the difference in the imaging source and image rendering procedure, a dimensional discrepancy exists between digital models created by different imaging systems. Despite the inevitable dimensional deviations developed during image scanning and processing according to the imaging methods, IOS and DS are in active use in the clinic1-3). Digital models derived from CBCT are also used for the diagnosis and treat ment planning despite that the image deterioration of occlusal surface and artifacts limit its use4-6). There fore, many studies have tested the trueness and precision to verify the reproducibility of 3D digital imaging methods1-6). Trueness is defined as the close ness to the real value, and precision is defined as the consistency of the deviations among the measured values within a test group. In most of the studies exploring the reproducibility of the digital imaging method, a superimposition of the test model on the reference model has been preferred1,3,6-8). The superimposition method is an ef ficient and useful way to analyze an average amount of shell/shell deviation and overall distortion ten dency through a color-coded map. However, con verting the dataset format from the digital imaging and communications in medicine (DICOM) format of the CBCT dataset to STL format can make it dif ficult to compare the CBCT derived model to the ref erence. An additional dimensional deviation can de velop due to the beam hardening effect in a normal anatomic structure such as enamel and restorations9) . Even though several technical trials have been made to improve the image quality of CBCT10,11), artifacts development in CBCT images makes it challenging to compare CBCT to optical scanners4,12). Knowing the dimensional compliance among dif ferent 3D imaging systems is important for their combined utilization. Comparing the linear mea surements with other diagnostic tools is the fun damental way to prove the credibility of data13,14). Even though the linear measurement method does not provide 3D information, this method enables direct comparisons among multiple digital models. Therefore, this study aimed to evaluate dimensional reproducibility among digital models derived from IOS, DS, and CBCT. In addition, the reproducibility of two CBCT systems equipped with different image acquisition methods and rendering was evaluated. The null hypothesis was that no significant dimen sional differences exist among digital models created by other imaging systems. –0.21 mm for VCT, and –0.25 mm for KCT. The linear mixed model did not show significant differences between the test and reference groups (P>0.05). Conclusion: The linear distances measured on the digital models created from CIOS, MDS, and two CBCT systems showed slightly larger than the references but clinically acceptable reproducibility for diagnosis and treatment plan ning.