Imaging Factors Impacting on Accuracy and Radiation Dose in 3D Printing.

OBJECTIVES: To compare reconstructed area and surface roughness of 3D models acquired using nine image acquisition protocols. Radiation dose was also compared among acquisition protocols. METHODS: A dry craniofacial specimen was scanned using three CT devices (a cone beam CT, a 16-channel fan beam CT, and a 64-channel fan beam CT), with three different acquisition protocols each. Nine 3D models were manufactured using polylactic acid. Surface roughness and reconstructed area were determined for each 3D model. The radiation dose during acquisitions was measured using lithium crystals. ANOVA was used to compare the data among the 3D models. Linear function optimization techniques based on stochastic variables were applied to identify the most suitable protocol for use. RESULTS: For surface roughness, statistically significant differences were observed among all 3D models and the specimen. For reconstructed area, CBCT and one CT-16 channel protocols originated 3D models statistically significant different from the specimen. Higher radiation doses were observed with fan beam CT acquisitions. CONCLUSIONS: All three CT devices were suitable for 3D printing when used at full resolution. The highest reconstruct area vs. radiation dose ratio was found for 64-channel CT devices.

Accuracy of detecting and measuring buccal bone thickness adjacent to titanium dental implants-a cone beam computed tomography in vitro study.

OBJECTIVES: The aim of this study was to assess the accuracy of detecting and measuring buccal bone thickness (BBT) adjacent to titanium implants in cone beam computed tomography (CBCT) images. STUDY DESIGN: Titanium implants (1, 2, or 3), abutments, and metal-ceramic crowns were inserted into 40 bone blocks with various BBTs. CBCT images were acquired in various settings: Voxel sizes (0.2 and 0.13 mm) and reconstruction section thicknesses (2.0 and 5.0 mm) were assessed by 3 examiners. True BBT was measured in digital photographs of the bone blocks. Buccal bone detection was evaluated by sensitivity and specificity. BBT was evaluated by 1-way analysis of variance (ANOVA) between the true and the CBCT measurements and by calculating the difference between the true measurement and the CBCT measurement (Di-BBT). RESULTS: Detection of buccal bone exhibited high sensitivity (0.86-1) and low specificity (0.14-1). More implants in the field of view, large voxel size, and thick image reconstruction sections had a negative impact on buccal bone detection. ANOVA showed statistically significantly larger BBT for the CBCT measurements in all settings (1.07-1.21 mm) compared with the true measurements (0.85 mm). Di-BBT was mostly within 0.5 mm. CONCLUSIONS: BBT adjacent to titanium implants is overestimated when evaluated on CBCT cross-sectional images.

Diagnostic accuracy of cone beam computed tomography sections with various thicknesses for detecting misfit between the tooth and restoration in metal-restored teeth.

OBJECTIVE: To evaluate the diagnostic accuracy of cone beam computed tomography (CBCT) sections with various reconstruction thicknesses for detecting misfit between tooth and restoration in metal-restored teeth. STUDY DESIGN: Eighty teeth (perfect fit, 40 of these used with 0.2 mm gap, and 40 with 0.4 mm gap), were imaged with large FOV i-CAT. Images were reconstructed in five thicknesses: 0.2 (voxel size), 1, 2, 5, and 10 mm. Four examiners assessed the presence of gaps using a 5-point scale. Area under the receiver operating characteristics curve (aucROC) for misfit detection was calculated for each variable. A multivariate logistic regression was performed by using misfit detection accuracy as the dependent variable. RESULTS: The score "cannot decide" decreased when the reconstruction thickness was increased. Mean aucROC ranged between 0.60 and 0.72. Logistic regression showed that the presence of a gap and reconstruction thickness had an impact on diagnostic accuracy. CONCLUSIONS: Diagnostic accuracy of CBCT sections was low for detecting misfit in metal-restored teeth.

Development of a new in vitro methodology to simulate internal root resorption.

INTRODUCTION: Studies to evaluate the diagnostic power of imaging examinations to detect root resorption have been based on simulations produced by burs. Standardized, round, and well-outlined access cavities do not reproduce the characteristics of physiological lesions and may facilitate diagnosis, masking the true accuracy of imaging techniques. A methodology to simulate internal root resorption by using acid demineralization was developed. METHODS: Eleven extracted single-rooted teeth were mesiodistally sectioned into homologous halves. Root canals were labeled to ensure restricted and controlled action of fluids. The protocol was composed of 24-hour cycles (5% nitric acid for 12 hours, rinsing with deionized water, and 8% sodium hypochlorite for 10 minutes). At the end of each cycle 1 tooth was removed from treatment, defining an exposure time that cumulated to the last tooth. Electron microscopy imaging was assessed to determine lesion area and depth. RESULTS: Minimum and maximum and areas and depths were 3.14 mm² and 10.34 mm² and 0.22 mm and 1.59 mm, respectively. Resorption simulated by the protocol proposed reproduced lesions of different sizes. CONCLUSIONS: The irregular shape and larger diameter:depth ratio suggest that these lesions are more similar to in vivo internal root resorption, compared with bur-induced lesions.

Planning of dental implant size with digital panoramic radiographs, CBCT-generated panoramic images, and CBCT cross-sectional images.

OBJECTIVES: To compare the implant size (width and length) planned with digital panoramic radiographs, cone beam computed tomography (CBCT)-generated panoramic views, or CBCT cross-sectional images, in four implant systems. MATERIAL AND METHODS: Seventy-one patients with a total of 103 implant sites in the upper premolar and/or lower molar regions were examined with digital panoramic radiography (D-PAN) and (CBCT). A metal ball 5 mm in diameter was placed in the edentulous area for the D-PAN. CBCT data sets were reformatted to a 10-mm thick CBCT panoramic view (CBCT-pan) and 1-mm cross-sections (CBCT-cross). Measurements were performed in the images using dedicated software. All images were displayed on a monitor and assessed by three observers who outlined a dental implant by placing four reference points in the site of the implant-to-be. Differences in width and length of the implant-to-be from the three modalities were analyzed. The implant size selected in the CBCT-cross images was then compared to that selected in the other two modalities (D-PAN and CBCT-pan) for each of the implant systems separately. RESULTS: The implant-to-be (average measurements among observers) was narrower when measured in CBCT-cross compared with both D-PAN and CBCT-Pan. For premolar sites, the width also differed significantly between D-PAN and CBCT-pan modalities. The implant-to-be was also significantly shorter when recorded in CBCT-cross than in D-PAN. In premolar sites, there were no significant differences in implant length among the three image modalities. It mattered very little for the change in implant step sizes whether CBCT-cross was compared to D-PAN or CBCT-pan images. CONCLUSION: Our results show that the selected implant size differs when planned on panoramic or cross-section CBCT images. In most cases, implant size measured in cross-section images was narrower and shorter than implant size measured in a panoramic image or CBCT-based panoramic view.

Detection of vertical root fractures by conventional radiographic examination and cone beam computed tomography - an in vitro analysis.

OBJECTIVES: This study compared the ability of conventional radiographic and cone beam computed tomography (CBCT) examinations to detect vertical root fractures (VRF) in teeth with or without root canal treatment and metallic posts. Furthermore, the influence of using different voxel sizes from CBCT images was assessed. METHODOLOGY: Sixty single-rooted human teeth were randomly divided into two groups: experimental and control. Twenty teeth were endodontically prepared and obturated with gutta-percha, twenty had a metallic postcemented after the filling, and twenty had no preparation. The teeth from the experimental group were fractured. All teeth were radiographed with three different horizontal angles, and after, CBCT images were acquired following three protocols in which the variation was the voxel resolution (0.4, 0.3, and 0.2 mm). Three calibrated examiners assessed the images. RESULTS: Chi-squared test showed no statistical difference among the images in detecting VRFs. The results of the diagnostic performance tests presented similar ability to detect VRFs when conventional radiographic examination was compared with 0.2 and 0.3-voxel CBCTs scans, in roots without endodontic treatment and metallic post. Moreover, specificity, sensitivity, and accuracy findings were similar for both 0.2 and 0.3-voxel resolution scans for teeth that are not root filled. However, it was observed that in teeth with root canal treatment and a post, the accuracy was higher when 0.2-mm voxel resolution was used. CONCLUSION: The radiographic examination with horizontal angle variation should be encouraged as the first complementary approach to assess the presence of VRFs. If conventional imaging is not capable to provide adequate information, CBCT can be indicated if a root fracture is strongly suspected. The root condition should then guide the voxel resolution choice, selecting 0.3-voxel for not root filled teeth and 0.2-voxel for teeth with filling and/or a post.

Comparison between two tomographic sections in the diagnosis of external root resorption.

OBJECTIVES: To assess the accuracy of coronal and sagittal CT sections to detect cavities simulating root resorption. MATERIAL AND METHODS: 60 mandibular incisors were embedded in plaster bases, and cavities with 0.6, 1.2 or 1.8 mm in diameter and 0.3, 0.6 or 0.9 mm in depth (small, medium and large cavities) were drilled on the buccal surfaces with high-speed round burs with diameters of 0.6, 1.2 and 1.8 mm to simulate external inflammatory root resorption. Simulations in the cervical, middle and apical thirds of each tooth root were made randomly. The Dental Scan software was used to obtain 1-mm-thick axial images from direct scanning, which were reconstructed in the coronal and sagittal planes using 3D software (Syngo FastView). Each series was loaded into the software. Fourteen images of each tooth were reconstructed in the coronal plane and 14 in the sagittal plane. A total of 1,652 images were obtained for analysis. Series information, tooth number and the plane reconstructed were stored. The images generated were saved on a CD-ROM together with the visualization software (Syngo FastView). Images were analyzed by a previously calibrated blinded, radiologist. Cochran's Q test was conducted separately for each region analyzed followed by pair-wise comparison by the McNemar test (p=0.05). RESULTS: No statistically significant difference (p>0.05) was observed in the diagnosis of simulated resorption between the apical, middle, and coronal thirds. When the axial plane was assessed separately, diagnoses were statistically different (p<0.05) among the three root thirds. The apical third differed significantly (p<0.05) from the cervical and middle thirds. Diagnostic errors were more often observed in the apical third compared to the cervical and middle thirds. Mid-sized cavities revealed no statistically significant differences (p>0.05) between planes, irrespective of the third in which the resorptions were located. CONCLUSION: When tomographic sections are requested for the diagnosis of buccal or lingual external root resorption, sagittal sections afford the best image characterization of the resorption process.

Oral health and dental anomalies in patients treated for leukemia in childhood and adolescence.

BACKGROUND: This study was conducted to evaluate oral health and dental anomalies in children treated for acute lymphoblastic leukemia (ALL) and to compare results with those of a group of healthy children matched for sex and age. PROCEDURE: Fifty-six children treated for ALL and 56 healthy controls were examined for dental anomalies, and data on decayed, missing, and filled teeth (DMFT) score, visible plaque (VPI), and gingival bleeding (GBI) indices, and saliva flow were collected. Mean age of all children treated for ALL was 5.3 +/- 2.6 years at diagnosis and 11.8 +/- 4.2 at evaluation. Thirty-two were males. RESULTS: Forty-five treated children (80.4%) had at least one dental anomaly, and patients treated with chemotherapy, radiotherapy, and bone marrow transplantation had the greatest mean number of dental anomalies (15.37 +/- 15.03). Patients younger than 5 years at beginning of treatment were also more affected (P = 0.031). Children treated for ALL had a DMFT score of 1.9 +/- 4.0, GBI of 26.5%, VPI of 72.0%, and mean saliva flow of 0.19 ml/min; healthy children had a DMFT score of 1.52 +/- 3.5, GBI of 11.1%, VPI of 53.8%, and mean saliva flow of 0.27 ml/min. CONCLUSION: The treatment of ALL causes a significant increase in the number of dental anomalies. Their GBI and VPI were also elevated. Changes in salivary glands during treatment did not affect saliva flow permanently. Follow-up of these patients by an oral health team is recommended.

Influence of voxel size in the diagnostic ability of cone beam tomography to evaluate simulated external root resorption.

This study assessed in vitro the diagnostic ability of cone beam computed tomography (CBCT) scans with different voxel resolutions in the detection of simulated external root resorption (ERR). For that purpose, 59 teeth were viewed through iCAT tomography (Imaging Sciences International, Inc, Hatfield, PA) following three protocols in which the variation was the voxel resolution (0.4, 0.3, and 0.2mm). A calibrated examiner blinded to the protocol assessed the images through the i-CAT View software (Imaging Sciences International, Inc). The chi-square statistical analysis did not show associations between voxel resolution, section plane, size of cavity, and radicular third. Sensitivity and specificity values were similar. However, likelihood ratio values of 6.4 for a 0.4-mm voxel, 16 for a 0.3-mm voxel, and 12 for a 0.2-mm voxel were found. It was concluded that CBCT is a reliable method for the investigation of simulated ERR, and a 0.3-mm voxel appeared to be the best protocol, associating good diagnostic performance with lower X-ray exposure.

The quad-helix appliance in the primary dentition--orthodontic and orthopedic measurements.

Changes in the midpalatal suture and the alterations in intercanine and intermolar widths with the use of the quad-helix appliance were evaluated. Study casts and occlusal radiographs from 10 patients with a mean age of 4 years and 10 months (SD 11 months) were analyzed. A statistically significant palatal suture widening was observed in all cases. The proportion of dental tipping accomplished with the treatment was greater than opening of the suture.

Dental findings in GAPO syndrome: case report.

This article reports the case of a young female adult with GAPO syndrome who presented as a peculiar dental finding unerupted primary and permanent dentitions, which resembled total anodontia on clinical examination. A cephalometric analysis was performed to investigate the alterations in facial bone development. This is the 9th GAPO syndrome case reported in a Brazilian patient.