Effect of voxel size in cone-beam computed tomography on surface area measurements of dehiscences and fenestrations in the lower anterior buccal region

Abstract

Objectives This study aims to assess whether different voxel sizes in cone-beam computed tomography (CBCT) affected surface area measurements of dehiscences and fenestrations in the mandibular anterior buccal region. Materials and methods Nineteen dry human mandibles were scanned with a surface scanner (SS). Wax was attached to the mandibles as a soft tissue equivalent. Three-dimensional digital models were generated with a CBCT unit, with voxel sizes of 0.200 mm (VS200), 0.400 mm (VS400), and 0.600 mm (VS600). The buccal surface areas of the six anterior teeth were measured (in mm2) to evaluate areas of dehiscences and fenestrations. Differences between the CBCT and SS measurements were determined in a linear mixed model analysis. Results The mean surface area per tooth was 88.3 ± 24.0 mm2, with the SS, and 94.6 ± 26.5 (VS200), 95.1 ± 27.3 (VS400), and 96.0 ± 26.5 (VS600), with CBCT scans. Larger surface areas resulted in larger differences between CBCT and SS measurements (− 0.1 β, SE = 0.02, p < 0.001). Deviations from SS measurements were larger with VS600, compared to VS200 (1.3 β, SE = 0.05, P = 0.009). Fenestrations were undetectable with CBCT. Conclusions CBCT imaging magnified the surface area of dehiscences in the anterior buccal region of the mandible by 7 to 9%. The larger the voxel size, the larger the deviation from SS measurements. Fenestrations were not detectable with CBCT. Clinical relevance CBCT is an acceptable tool for measuring dehiscences but not fenestrations. However, CBCT overestimates the size of dehiscences, and the degree of overestimation depends on the actual dehiscence size and CBCT voxel size employed.

Effect of hydration on the anatomical form of human dry skulls

“…For this reason, it should be considered in such studies to www.nature.com/scientificreports/ acquire the gold standard references either after hydration, e.g. through a short water embedding session, or to use soft tissue simulation materials that do not contain high amounts of water, such as acrylic or wax 2,3,6 . A shortcoming of the latter approach might be the damage of the specimens during the placement or the removal of the soft-tissue simulant, whereas water embedding for long periods might also cause permanent damage.…”

“…Human subjects are rarely used for research purposes, due to ethical considerations, especially when repeated exposures are required to test various imaging protocols. For this reason, dry human cadaveric specimens are often used instead in ex vivo experimentation to develop and validate X-ray imaging techniques 2,3 . A limitation of this approach stems from the fact that no soft tissues are present, which affects the resulting image, and thus, the applicability of outcomes in actual clinical conditions 4 .…”

“…The accuracy of radiographic imaging techniques is often tested through the comparison of a reference three-dimensional (3D) digital model with a model acquired through the radiographic method in question. The reference model depicts the object as closely to reality as possible, and in modern research, it is often acquired through direct surface scanning of the object of interest using accurate structured-light scanners 3,7 . The latter option offers the advantage of being free from segmentation error, which is always present when segmenting 3D surface models from radiographic images (computed tomographies or cone beam computed tomographies) 7,8 .…”

“…Due to the above considerations, in radiological research a common strategy in diagnostic accuracy studies is the comparison of direct surface scans of dry skeletal structures, with radiographic images of the same objects, which are though embedded in liquid materials for soft-tissue simulation 2,3,[5][6][7] . However, potential water absorption during the dry bone hydration process might affect the anatomical form of the tested bony specimens (e.g., slight changes in size or shape), which might impact the accuracy outcomes 12 .…”

Bone Remodeling during Orthodontic Movement of Lower Incisors—Narrative Review

“…Last but not least, described studies most often used CBCTs with a voxel size of 0.23–0.377mm [ 23 , 24 , 25 , 26 , 29 , 31 , 34 ] or 0.15 mm [ 27 ]. Regarding the dimensions of buccal and lingual bone thickness in anterior region of the mandible, changes in these values after orthodontic treatment may not be detected [ 54 , 55 , 56 ]. It should be noted that the chance of a false positive detection of a dehiscence increases with larger voxel size.…”