Linear accuracy of 3D-printed mandibular models fabricated from cone-beam computed tomography scans with two different voxel sizes

To investigate the accuracy and reliability of cone beam computed tomography (CBCT) measurements of buccal alveolar bone height (BBH) and thickness (BBT) using custom acquisition settings. School of Dentistry, Oregon Health & Science University. Twelve embalmed cadavers. Cadaver heads were imaged by CBCT (i-CAT® 17-19, Imaging Sciences International, Hatfield, PA) using a 'long scan' (LS) setting with 619 projection images, 360° revolution, 26.9 s duration, and 0.2 mm voxel size, and using a 'short scan' (SS) setting with 169 projection images, 180° rotation, 4.8 s duration, and 0.3 mm voxel size. BBH and BBT were measured with 65 teeth, indirectly from CBCT images and directly through dissection. Comparisons were assessed using paired t-tests (p≤0.05). Level of agreement was assessed by concordance correlation coefficients, Pearson's correlation coefficients, and Bland-Altman plots. Mean differences in measurements compared to direct measurements were as follows, LS 0.17±0.12 (BBH) and 0.10±0.07 mm (BBT), and SS 0.41±0.32 (BBH) and 0.12±0.11 mm (BBT). No statistical differences were found with any of BBH or BBT measurements. Correlation coefficients and Bland-Altman plots showed agreement was high between direct and indirect measurement methods, although agreement was stronger for measurements of BBH than BBT. Compared to the LS, the similarity in results with the reduced scan times and hence reduced effective radiation dose, favors use of shorter scans, unless other purposes for higher resolution imaging can be defined.

Computed gray levels in multislice and cone-beam computed tomography

Background: To determine the optimal implantation site of orthodontic micro-screws based on cone beam computed tomography (CBCT) analysis in the mandibular anterior tooth region, provide a theoretical basis for orthodontic implant placement and improve post-implantation stability.Methods: Forty patients who underwent CBCT scanning were selected for this study. CBCT scanning was applied to measure the interradicular distance, buccolingual dimension, labial cortical bone thickness and lingual cortical bone thickness between mandibular anterior teeth at planes 2, 4, 6, and 8 mm below the alveolar ridge crest. The data were measured and collected to obtain a comprehensive evaluation of the specific site conditions of the alveolar bone.Results: The interradicular distance, buccolingual dimension and labial cortical bone thickness between the mandibular anterior teeth were positively correlated with the distance below the alveolar ridge crest (below 8 mm). The interradicular distance, buccolingual dimension, labial cortical bone thickness, and lingual cortical bone thickness were all greater than those in other areas between the lateral incisor root and canine incisor root 4, 6, and 8 mm below the alveolar ridge crest.Conclusion: The area between the lateral incisor root and the canine incisor root in planes 4, 6, and 8 mm from the alveolar ridge crest can be used as safe sites for implantation, while 8 mm below the alveolar ridge crest can be the optimal implantation site. An optimal implantation site can be 8 mm below the alveolar ridge crest between the lateral incisor root and the canine incisor root.

Effect of bone thickness on alveolar bone-height measurements from cone-beam computed tomography images

To evaluate the validity and reliability of cone-beam computed tomography (CBCT) masseter muscle segmentation by comparing with the magnetic resonance imaging (MRI) masseter muscle segmentation of the same patients. Seventeen volunteers were included in this study. CBCT and MRI scans of the volunteers were taken, respectively, within one month. The masseter muscles in the CBCT scans were segmented by a generative adversarial network (GAN)-based framework combined with manual check. The masseter muscles in the MRI scans were segmented manually. The segmentations were repeated by the first examiner and a second examiner. For cross-sectional area (CSA), paired t-test, intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to evaluate the validity and reliability of the segmentations. The validity and reliability were also calculated by Dice similarity coefficient (DSC) and average Hausdorff distance (aHD) between different segmentations. Seventeen volunteers were included in this study. CBCT and MRI scans of the volunteers were taken, respectively, within one month. The masseter muscles in the CBCT scans were segmented by a generative adversarial network (GAN)-based framework combined with manual check. The masseter muscles in the MRI scans were segmented manually. The segmentations were repeated by the first examiner and a second examiner. For cross-sectional area (CSA), paired t-test, intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to evaluate the validity and reliability of the segmentations. The validity and reliability were also calculated by Dice similarity coefficient (DSC) and average Hausdorff distance (aHD) between different segmentations. Paired t-test showed that there was no significant difference in CSA between CBCT and MRI masseter segmentations. The ICCs were all larger than 0.95 and the SEM was less than 4.85 mm2 for CSA. The DSC was all larger than 0.95 showing over 95% of similarity between CBCT and MRI masseter segmentations. The aHD was all smaller than 0.09mm showing great consistency of the contour of CBCT and MRI segmentations. Masseter muscle segmentation from CBCT scans was not significantly different from the segmentation from MRI scans. CBCT muscle segmentation showed great validity compared with MRI scans, and great reliability in retests.

BackgroundWith the introduction, development and commercialization of Cone Beam Computerized Tomography (CBCT) technologies in the field of head and neck reconstruction, clinicians now have increased access to the technology. Given the growth of this new user group, there is an increasing concern regarding proper use, understanding, quality and patient safety.MethodsThe present study was carried out to evaluate data acquisition of CBCT medical imaging technology and the accuracy of the scanning at three different machine warming times. The study also compared the accuracy of CBCT at 0.2 mm slice thickness and Computerized Tomography (CT) at 1 mm slice thickness. A control model was CT scanned at five random intervals, at 1 mm slice thickness and CBCT scanned at specialized intervals, at 0.2 mm slice thickness. The data was then converted and imported into a software program where a digital registration procedure was used to compare the average deviations of the scanned models to the control.ResultsThe study found that there was no statistically significant difference amongst the three CBCT machine warming times. There was a statistically significant difference between CT scanning with 1 mm slice thickness and CBCT scanning with 0.2 mm slice thickness.ConclusionsThe accuracy of the i-CAT CBCT scans used in the present study with a parameter at voxel size 0.2, will remain consistent and reliable at any warming stage. Also the difference between the CBCT i-CAT scans and the CT scans was not clinically significant based on suggested requirements of clinicians in head and neck reconstruction.

Objective: The aim of this study was to evaluate the size, shape and location of the mental foramen (MF) and anterior loop (AL) in the Brazilian population through the analysis of cone beam computed tomography (CBCT) and panoramic radiography (PR). Method: We analyzed the location, shape and size of the MF, the distance between the upper wall of the MF and the alveolar crest (AC), the size of the AL and the presence of lingual anastomosis. Results: Fifty PR and CBCT exams were analyzed. In relation to the MF, the most common location was between premolars (56%), the most common shape was the oval shape (83%) and the average size in the PR was 3.63 mm and in the CBCT was3.66 mm. The average distance from the MF to the AC in the PR was 17.29 mm and in the CBCT was 11.48 mm. The average AL size was 3 mm, the smallest being 1 mm and the largest being 5 mm. Static analysis was performed to verify the relationship between the distance from the foramen to the AC with the values ​​that were found in the PR and CBCT, which showed a statistically significant difference (p=<0.001) between them. Lingual anastomosis could be seen in 22% of the analyzed hemimandibles. Conclusion: CBCT is a reliable diagnostic test for planning rehabilitation near the MF. The distance between the implant and the foramen must be analyzed individually.

BackgroundThe mental foramen (MF) represents an anatomical aperture situated on the anterior aspect of the mandible bilaterally and constitutes a significant reference point for surgical procedures. The purpose of this study was to evaluate the usefulness of ultrasonography (USG) in determining the location and dimension of the MF and its distance to the alveolar crest in comparison with cone-beam computed tomography (CBCT).MethodsThe study was conducted on 27 patients (13 males, 14 females) over 18 years of age (19–73 years) who applied to the Department of Dentomaxillofacial Radiology for a CBCT scan before planning of implant procedures. The vertical diameter of the MF and its distance from the alveolar crest were measured on CBCT cross-sectional slices and compared with the measurements obtained by USG.ResultsA total of 54 MFs were evaluated. The measurements of the vertical diameter of MF and its distance to the alveolar crest were consistent between CBCT and USG (P = 0.262 and P = 0.551, respectively). In either technique, the vertical diameter of MF was significantly higher in males whereas the distance to alveolar crest was significantly higher in females (P < 0.001). No significant age differences were observed in USG and CBCT measurements regarding MF diameter and distance to the alveolar crest (P > 0.05)ConclusionsUSG is as accurate as CBCT in measuring MF and associated alveolar crest and has the potential for the localization of vital anatomical structures with the advantage of no concern about ionizing radiation.Trial registrationNot applicable.

Authors' response.

Free AccessLetter to the editorA comparative study of the accuracy and reliability of multidetector CT and cone beam CT in the assessment of dental implant site dimensionsK Kamburoğlu and S YükselK KamburoğluSearch for more papers by this author and S YükselSearch for more papers by this authorPublished Online:28 Jan 2014https://doi.org/10.1259/dmfr/30789406SectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail AboutWe read the article written by AA Al-Ekrish and M Ekram, “A comparative study of the accuracy and reliability of multidetector CT and cone beam CT in the assessment of dental implant site dimensions”,1 with great interest.We would like to congratulate the authors for their effort in the preparation of the manuscript. According to the mentioned study, measurements recorded for both modalities showed high intra and interexaminer reliability. Although cone beam CT (CBCT) measurements were significantly more accurate than those of multi-detector CT (MDCT), both systems showed clinically and statistically significant errors.In this research, the measurements were recorded by two observers. As stated by the authors, CBCT measurements are highly operator dependent and this may explain the lower interexaminer reliability calculated for CBCT compared with MDCT. Interestingly, no specific information was given concerning the specialty and experience of the observers with tomographic slices. When presenting the results (Tables 1–3), which observer was taken into account? Did the authors calculate any intra and interobserver agreement? It is our belief that these agreement calculations should be done and then the results could be presented by evaluating these agreements.The authors had presented the intra and interobserver reliability using correlation and Cronbach's alpha. However, while assessing agreement between two measurement techniques, it is not appropriate to use the correlation analysis. For those types of studies, Bland-Altman2 is a better method of choice. Also, for the evaluation of reliability, Cronbach's alpha is not an appropriate coefficient; Cronbach's alpha is used to rate the internal consistency or the correlation of the items in a test and it is generally used to evaluate the scales. It is appropriate to use intraclass correlation coefficient (ICC) instead of Cronbach's alpha. ICC is used to measure inter-rater reliability for two or more raters.Another drawback of the study design is the wrongly chosen voxel resolution for the Iluma CBCT scanner (Imtek Imaging, 3M Company, St Paul, MN) which was set at 0.3 mm. A similar research article published 2 years earlier, conducted by the authors of the present “letter to the editor”, used the same CBCT unit.3 We found that the accuracy of measurements of various distances surrounding the mandibular canal was highly comparable with that of digital caliper measurements. Our results were obtained from Iluma CBCT scanner images reconstructed at 0.2 mm voxel and two trained oral radiologists served as observers. It would be interesting to know the effects of different voxels in the implant site measurement accuracy.The authors also mentioned in the last paragraph of their discussion that “recording of the ridge dimensions for implant site assessment and placement of implants should be performed by the same operator”. We do not have objection to this idea as long as an oral and maxillofacial radiologist consultation is provided.We believe that the way the authors present their statistical analysis, the sole selection of a 0.3 mm voxel size and the obscure observer performance may mislead the readership with regard to the accuracy of assessment of dental implant site dimensions with CBCT.We hope the authors will consider our constructive comments in their future work.References1 Al-Ekrish AA , Ekram M . A comparative study of the accuracy and reliability of multidetector computed tomography and cone beam computed tomography in the assessment of dental implant site dimensions. Dentomaxillofac Radiol 2011;40:67–75. Link ISI, Google Scholar2 Bland JM , Altman DG . Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1:307–310. Crossref Medline ISI, Google Scholar3 Kamburoğlu K , Kılıç C , Özen T , Yüksel SP . Measurements of mandibular canal region obtained by cone-beam computed tomography: a cadaveric study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107:e34–e42. Crossref Medline, Google Scholar Previous article Next article FiguresReferencesRelatedDetailsCited byComparison of in situ cone beam computed tomography scan data with ex vivo optical scan data in the measurement of root surface areaOral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, Vol. 128, No. 5 Volume 40, Issue 7October 2011Pages: 403-470 2011 The British Institute of Radiology History Published onlineJanuary 28,2014 Metrics Download PDF

To compare measurements on images obtained by magnetic resonance imaging (MRI) and cone beam CT (CBCT) for height, width, and area in alveolar bone sites in human jaw specimens. Forty edentulous alveolar posterior sites in human cadaver specimens were imaged using CBCT scanners, and with zero-echo-time MRI (ZTE-MRI). Semi-automatic volume registration was performed to generate representative coronal sections of the sites related to implant planning. ZTE-MRI sections were also presented after grayscale inversion (INV MRI). Three observers measured bone height, bone width 5 mm from the alveolar crest, and bone area stretching from the width measurement to the top of the alveolar crest in the images. Interobserver agreement was assessed by intra-class correlation coefficients (ICC). The measurements were analyzed using two-way repeated measures ANOVA factoring observer and image type. ICC was >0.95 for bone height, width, and bone area. No significant differences among observers (p = 0.14) or image type (p = 0.60) were found for bone height. For bone width, observer (p = 0.14) was not a significant factor, while ZTE-MRI produced width estimates that were significantly different and systematically smaller than CBCT-based estimates (p ≤ 0.001). Observer (p = 0.06) was not a significant factor regarding the bone area measurements, contrary to the imaging type where ZTE-MRI led to significantly smaller area estimates than CBCT (p ≤ 0.001). Bone height measurements were essentially equivalent using CBCT and MRI. This was found regardless of grayscale choice for the MRI. However, ZTE-MRI resulted in smaller estimates of bone width and area.

A comparative evaluation of Cone Beam Computed Tomography (CBCT) and Multi-Slice CT (MSCT): Part I. On subjective image quality

Objective The aim of this study was to evaluate the effect of voxel size and artefact reduction (AR) on the identification of vertical root fractures (VRFs) in endodontically treated teeth. Methods A total of a hundred sound, extracted human mandibular single-rooted premolars were decoronated, after which root canal preparation was performed, canals were filled with gutta percha by single cone technique. Randomly selected fifty specimens were fractured, repositioned and glued together. The teeth were examined with cone beam computed tomography (CBCT) in five different voxel sizes (0.125, 0.200, 0.250, 0.300, and 0.400 voxels). Two scans were performed for each tooth, one with AR and one without AR. Two radiologists evaluated the CBCT scans. Results All voxel dimensions were successful in detecting VRFs in CBCT scans. But as the voxel size increased, the percentage of detecting VRFs decreased. High accuracy, sensitivity, specificity and predictive values were found for VRF detection on CBCT scans. Accuracy and sensitivity values decreased (from 100 to 82) while voxel dimensions increased (from 0.125 to 0.400). High-resolution images (0.125, 0.200, and 0.250 voxels) caused an increase in sensitivity for detection of VRFs. AR did not affect the accuracy, sensitivity, specificity and predictive values for VRF detection on CBCT scans. Conclusions High-resolution CBCT images resulted in an increase in sensitivity and specificity for detection of VRFs compared with lower-resolution CBCT images. The use of AR did not further improve its diagnostic potential.

To assess the accuracy of measuring the cortical bone thickness adjacent to dental implants using two cone beam computed tomography (CBCT) systems. Ten 4 x 11 mm Astra Tech implants were placed at varying distances from the cortical bone in two prepared bovine ribs. Both ribs were scanned in a reproducible position using two different CBCT scanners. Ten examiners each carried out four measurements on all 10 implants using the two CBCT systems: vertical distance between the top of the implant and the alveolar crest (IT-AC), and thickness of the cortical bone from the outer surface of the implant threads at 3, 6 and 9 mm from the top of the implant. Ground sections were prepared and bone thickness was measured using a light microscope and a graticule to give a gold standard (GS) measurement. The examiner's measurements were significantly different between CBCT systems for the vertical and thickness dimensions (P<0.001) while measuring the cortical bone thickness between 0.3 and 3.7 mm. Within that range, i-CAT NG measurements were consistently underestimated in comparison with the GS. Accuitomo 3D60 FPD measurements closely approximated the GS, except when cortical bone thickness was <0.8 mm. The mean percentage errors from the GS at 3, 6 and 9 mm measurement levels were 68%, 28% and 18%, respectively, for i-CAT NG and 23%, 5% and 6%, respectively, for Accuitomo 3D60 FPD. Within the limitations of this study, it was concluded that i-CAT NG (voxel size 0.3) may not produce sufficient resolution of the thin cortical bone adjacent to dental implants and, therefore, the measurements may not be accurate; whereas, Accuitomo 3D60 FPD (voxel size 0.125) may produce better resolution and more accurate measurement of the thin bone.

Anatomical data of accessory mental foramina (AMFs) were investigated in a Chinese Han population using cone beam CT (CBCT). A retrospective analysis was performed on 527 selected sets of CBCT images. The average frequency and diameter of AMFs, the diameter of the ipsilateral mental foramen (MF), and the center distance and relative position between the AMFs and MF were measured and calculated by three professional dentists. Among the 527 patients, AMFs were identified in 36 cases (frequency 6.83%), of which 68.75% of AMFs were larger than 1 mm. The mean diameters of the AMFs and the ipsilateral MF were 1.32±0.61 mm and 3.26±0.90 mm, respectively. The average distance from the AMFs to the alveolar ridge crest (ARC) was 15.05±3.50 mm, and the average distance to the mandibular plane was 15.87±3.64 mm. The positions of the AMFs relative to the MF varied widely. The AMFs were mostly positioned distal-inferior to the ipsilateral MF and under the mandibular second premolars. Nutrient foramina around the MFs were distinguished from AMFs. The reference plane for measuring AMFs was suggested to be the mandibular plane to increase the repeatability and accuracy of the experiment. Standard planes were proposed to determine the relative position between AMFs and the MFs. Based on our results, we propose that for implant surgeries, the safety region of 2 mm above the MFs should be reevaluated. CBCT examination is recommended before the operation to identify important anatomical structures around the MF region and their variations and set the safety distance on an individual basis.