Convex triangular vs. cylindrical field of view: how does the shape of the FOV affect radiation dose?

OBJECTIVE: To compare the dosimetry between convex triangular fields of view (FOV) and similar dimension cylindrical FOVs of two cone-beam computed tomography (CBCT) models. METHODS: Optically stimulated luminescence dosimeters (OSLDs) were placed in fiducial anatomical locations in an anthropomorphic phantom representing an adult head male for dosimetry scans. Convex triangular FOVs (100 × 80 mm/maxilla-mandible; 100 × 50 mm mandible; 100 × 50 mm/maxilla) from Veraviewepocs 3D R100 (J. Morita, Kyoto, Japan) (R100) and Veraview® X800 (J. Morita, Kyoto, Japan) (X800) and cylindrical FOVs from R100 and X800 (80 × 80 mm/maxilla-mandible; 80 × 50 mm/mandible; 80 × 50 mm/maxilla) were obtained, resulting in 12 different scan protocols. Equivalent doses for each relevant organ/tissue and the effective dose for each protocol were calculated. Mean effective doses were compared by the two-way analysis of variance (ANOVA) with Tukey's post hoc test to evaluate the effect of the FOV and device (α = 0.05). RESULTS: The effective doses ranged between 69 and 324 µSv for the convex triangular FOVs and 76 and 332 µSv for the cylindrical FOVs. Convex triangular FOVs from the R100 device had effective doses 2.3 to 15.3% lower than their corresponding cylindrical FOVs with similar height (p < 0.05), and that difference ranged between 8.8 and 11.8% for the X800 device (p < 0.05). CONCLUSION: Convex triangular fields of view delivered slightly lower effective doses than the cylindrical fields of view of similar dimensions in the R100 and X800 CBCT devices. CLINICAL RELEVANCE: Understanding the influence of the image geometry formation in effective dose allows optimization to reduce patient dose.

Imaging of the upper airway: which method is best for orthodontic assessment?

The objectives of the present study were to compare measurements of pharyngeal airway subregions on lateral cephalometric (LC) and cone beam computed tomographic (CBCT) images in relation to skeletal classes and discuss the advantages and disadvantages of these imaging formats for this type of assessment. The CBCT images were assessed via both multiplanar reconstruction (MPR) and 3-dimensional (3D) reconstruction. The LC and CBCT images from 107 patients were classified according to skeletal class: I, n = 35; II, n = 35; and III, n = 37. Linear measurements of the subdivisions of the upper airway were performed on the LC, MPR, and 3D images. In addition, area and volumetric measurements were performed on the MPR images. The relationships among imaging methods, skeletal class, and pharyngeal thirds were assessed by means of a 1-way analysis of variance (α = 0.05). No statistically significant differences in the linear, area, or volumetric measurements of the upper airway subregions were found among the skeletal classes (P > 0.05). For the linear measurements in the oropharynx and hypopharynx, greater values were observed for the LC images than for the MPR and 3D images (P ≤ 0.05). Based on the study findings, MPR images should be preferred for visualization of the pharyngeal airway subregions. However, LC imaging is preferable to 3D reconstruction.

Is Panoramic Imaging Equivalent to Cone-Beam Computed Tomography for Classifying Impacted Lower Third Molars?

PURPOSE: Preoperative recognition of the relative position of the mandibular third molars may contribute to more reliable treatment planning, avoiding injuries and decreasing surgical and recovery times. The research questions for this study were as follows: 1) Is panoramic radiography (PR) equivalent to cone-beam computed tomography (CBCT) in determining the degree of mandibular third molar impaction? 2) For PR, is the external oblique ridge a more reliable reference to determine the degree of mandibular third molar impaction? MATERIALS AND METHODS: This retrospective case-series study assessed whether the imaging modalities (primary predictor variable) are equivalent in determining the degree of impaction of third molars (primary outcome variable) according to the parameters of the Pell and Gregory classification. Two oral and maxillofacial radiologists evaluated PR and CBCT images presenting at least 1 mandibular third molar. The degrees of impaction related to the ascending ramus and related to the external oblique ridge (secondary outcome variables) also were assessed. The agreement rates between PR and CBCT were presented, and the imaging modalities were compared by the McNemar-Bowker test (α = .05). RESULTS: A total of 173 patients were included (66 male and 107 female patients). Among these patients, 313 mandibular third molars were assessed. In relation to the occlusal plane, the agreement rate between PR and CBCT was 82.1% for Pell and Gregory class A, 90.5% for class B, and 65.6% for class C (P = .116). The overall agreement rate between the classifications in relation to the mandibular ramus on PR and CBCT ranged from 66.8% (considering the ascending ramus, P < .001) to 76.4% (considering the external oblique ridge, P < .001). CONCLUSIONS: PR performs similarly to CBCT in the classification of impaction in relation to the occlusal plane. However, PR shows a tendency to underestimate the space for accommodation of the third molar compared with CBCT. Furthermore, the external oblique ridge is not a reliable alternative landmark on PR.

Relationship of craniofacial morphology in 3-dimensional analysis of the pharynx.

INTRODUCTION: Pharynx dimensions may vary according to the position and morphology of the mandible. The aim of this study was to test the hypothesis that craniofacial morphology affects pharyngeal volume and its cross-sectional areas. METHODS: Seventy-four subjects (38 men, 36 women) aged 18 to 56 years (mean ± SD 32.8 ± 1.8 years) were scanned with a cone-beam computed tomography unit and had facial profile photographs taken. All participants were classified according to skeletal anteroposterior (Class II and Class III) and vertical facial patterns (brachyfacial, mesofacial, and dolichofacial). Facial profile analyses and pharyngeal volume and cross-sectional area determinations were performed. RESULTS: The soft palate cross-sectional area of the oropharynx was significantly greater in the Class III patients. The upper facial third (trichion to soft tissue glabella/facial height) correlated negatively with pharyngeal volume and with soft palate cross-sectional area in the oropharynx. Alternatively, the midfacial third (soft tissue glabella to subnasale/facial height) correlated positively with soft palate cross-sectional area of the oropharynx. No significant differences across sexes and facial patterns regarding pharyngeal volume were found (P >0.05). CONCLUSIONS: The soft palate cross-sectional area is larger in skeletal Class III subjects. It seems that analysis of the facial profile focusing on the proportions of the facial thirds allows for inferences on pharyngeal dimensions. However, anteroposterior skeletal facial type and vertical facial pattern do not seem to affect pharyngeal volume.

Assessment of Volume and Height of the Coronoid Process in Patients With Different Facial Types and Skeletal Classes: A Cone-Beam Computed Tomography Study.

PURPOSE: To determine the height and volume of the mandibular coronoid process (CP) by cone-beam computed tomography (CBCT) and to identify the presence of any correlations of these measurements with age, gender, facial type, and skeletal class. MATERIALS AND METHODS: The sample consisted of 132 patients from a departmental routine patient base. After CBCT, CP height was determined using OnDemand 3D software (CyberMed, Seoul, Republic of Korea), and CP volume was obtained using ITK-SNAP 3.0 software (Cognitica, Philadelphia, PA). Measurements were subjected to analysis of covariance against facial type, skeletal class, gender, and age, with a significance level of 5%. RESULTS: CP height and volume were similar regardless of age, facial type, and skeletal class. However, the 2 measurements were statistically different regarding gender, with larger values for men than for women. CONCLUSIONS: These observations suggest that gender is the only factor influencing the height and volume of the CP.

A novel method of objectively detecting tooth ankylosis using cone-beam computed tomography: A laboratory study.

Purpose: The aim of this study was to objectively detect simulated tooth ankylosis using a novel method involving cone-beam computed tomography (CBCT). Materials and Methods: Tooth ankylosis was simulated in single-rooted human permanent teeth, and CBCT scans were acquired at different current levels (5, 6.3, and 8 mA) and voxel sizes (0.08, 0.125, and 0.2). In axial reconstructions, a line of interest was perpendicularly placed over the periodontal ligament space of 21 ankylosed and 21 non-ankylosed regions, and the CBCT grey values of all voxels along the line of interest were plotted against their corresponding X-coordinates through a line graph to generate a profile. The image contrast was increased by 30% and 60% and the profile assessment was repeated. The internal area of the resulting parabolas was obtained from all images and compared between ankylosed and non-ankylosed regions under different contrast enhancement conditions, voxel sizes, and mA levels using multi-way analysis of variance with the Tukey post hoc test (α=0.05). Results: The internal area of the parabolas of all non-ankylosed regions was significantly higher than that of the ankylosed regions (P<0.05). Contrast enhancement led to a significantly greater internal area of the parabolas of non-ankylosed regions (P<0.05). Overall, voxel size and mA did not significantly influence the internal area of the parabolas (P>0.05). Conclusion: The proposed novel method revealed a relevant degree of applicability in the detection of simulated tooth ankylosis; increased image contrast led to greater detectability.

Monitoring cone-beam CT radiation dose levels in a University Hospital.

OBJECTIVE: To present patient dose levels for different CBCT scanners, acquired by a dose monitoring tool in a University Hospital, as a function of field of view (FOV), operation mode, and patient age. METHODS: An integrated dose monitoring tool was used to collect radiation exposure data [type of CBCT unit, dose-area product (DAP), FOV size, and operation mode] and patient demographic information (age, referral department) performed on a 3D Accuitomo 170 and a Newtom VGI EVO unit. Effective dose conversion factors were calculated and implemented into the dose monitoring system. For each CBCT unit, the frequency of examinations, clinical indications, and effective dose levels were obtained for different age and FOV groups, and operation modes. RESULTS: A total of 5163 CBCT examinations were analyzed. Surgical planning and follow-up were the most frequent clinical indications. For the standard operation mode, effective doses ranged from 35.1 to 300 µSv and 9.26-117 µSv using 3D Accuitomo 170 and Newtom VGI EVO, respectively. In general, effective doses decreased with increasing age and FOV size reduction. CONCLUSIONS: Effective dose levels varied notably between systems and operation modes.Operation mode selection and FOV size were indication-oriented, with larger FOV sizes election serving surgical planning and follow-up. Seeing the influence of FOV size on effective dose levels, manufacturers could be advised to move toward patient-specific collimation and dynamic FOV selection. Systematically monitoring patient doses could be recommended for steering future CBCT optimization.

Filtered back projection vs. iterative reconstruction for CBCT: effects on image noise and processing time.

OBJECTIVES: To assess the effect of standard filtered back projection (FBP) and iterative reconstruction (IR) methods on CBCT image noise and processing time (PT), acquired with various acquisition parameters with and without metal artefact reduction (MAR). METHODS: CBCT scans using the Midmark EIOS unit of a human mandible embedded in soft tissue equivalent material with and without the presence of an implant at mandibular first molar region were acquired at various acquisition settings (milliamperages [4mA-14mA], FOV [5 × 5, 6 × 8, 9 × 10 cm], and resolutions [low, standard, high] and reconstructed using standard FBP and IR, and with and without MAR. The processing time was recorded for each reconstruction. ImageJ was used to analyze specific axial images. Radial transaxial fiducial lines were created relative to the implant site. Standard deviations of the gray density values (image noise) were calculated at fixed distances on the fiducial lines on the buccal and lingual aspects at specific axial levels, and mean values for FBP and IR were compared using paired t-tests. Significance was defined as p < 0.05. RESULTS: The overall mean for image noise (± SD) for FBP was 198.65 ± 55.58 and 99.84 ± 16.28 for IR. IR significantly decreased image noise compared to FBP at all acquisition parameters (p < 0.05). Noise reduction among different scanning protocols ranged between 29.7% (5 × 5 cm FOV) and 58.1% (5mA). IR increased processing time by an average of 35.1 s. CONCLUSIONS: IR significantly reduces CBCT image noise compared to standard FBP without substantially increasing processing time.

Development and validation of a 3D anthropomorphic phantom for dental CBCT imaging research.

BACKGROUND: Optimization of dental cone beam computed tomography (CBCT) imaging is still in a preliminary stage and should be addressed using task-based methods. Dedicated models containing relevant clinical tasks for image quality studies have yet to be developed. PURPOSE: To present a methodology to develop and validate a virtual adult anthropomorphic voxel phantom for use in task-based image quality optimization studies in dental CBCT imaging research, focusing on root fracture (RF) detection tasks in the presence of metal artefacts. METHODS: The phantom was developed from a CBCT scan with an isotropic voxel size of 0.2 mm, from which the main dental structures, mandible and maxilla were segmented. The missing large anatomical structures, including the spine, skull and remaining soft tissues, were segmented from a lower resolution full skull scan. Anatomical abnormalities were absent in the areas of interest. Fine detailed dental structures, that could not be segmented due to the limited resolution and noise in the clinical data, were modelled using a-priori anatomical knowledge. Model resolution of the teeth was therefore increased to 0.05 mm. Models of RFs as well as dental restorations to create the artefacts, were developed, and could be inserted in the phantom in any desired configuration. Simulated CBCT images of the models were generated using a newly developed multi-resolution simulation framework that incorporated the geometry, beam quality, noise and spatial resolution characteristics of a real dental CBCT scanner. Ray-tracing and Monte Carlo techniques were used to create the projection images, which were reconstructed using the classical FDK algorithm. Validation of the models was assessed by measurements of different tooth lengths, the pulp volume and the mandible, and comparison with reference values. Additionally, the simulated images were used in a reader study in which two oral radiologists had to score the realism level of the model's normal anatomy, as well as the modelled RFs and restorations. RESULTS: A model of an adult head, as well as models of RFs and different types of dental restorations were created. Anatomical measurements were consistent with ranges reported in literature. For the tooth length measurements, the deviations from the mean reference values were less than 20%. In 77% of all the measurements, the deviations were within 10.1%. The pulp volumes, and mandible measurements were within one standard deviation of the reference values. Regarding the normal anatomy, both readers considered the realism level of the dental structures to be good. Background structures received a lower realism score due to the lack of detailed enough trabecular bone structure, which was expected but not the focus of this study. All modelled RFs were scored at least adequate by at least one of the readers, both in appearance and position. The realism level of the modelled restorations was considered to be good. CONCLUSIONS: A methodology was proposed to develop and validate an anthropomorphic voxel phantom for image quality optimization studies in dental CBCT imaging, with a main focus on RF detection tasks. The methodology can be extended further to create more models representative of the clinical population.

Is the efficacy of cone beam computed tomography in the diagnosis of tooth ankylosis influenced by dose reduction protocols?

OBJECTIVE: To evaluate the diagnostic efficacy of cone beam computed tomography (CBCT) examinations acquired with varying dose protocols in the diagnosis of simulated tooth ankylosis (TA). STUDY DESIGN: Tooth ankylosis was simulated in 15 of 30 teeth, and CBCT examinations were acquired at 3 mA levels (8, 6.3, and 5) and 3 voxel sizes (0.08, 0.125, and 0.2 mm). Four radiologists independently assessed the presence of TA using a 5-point scale. Sensitivity, specificity, and area under the curve (AUC) obtained through receiver operating characteristic analysis were compared among mA levels and voxel sizes using two-way analysis of variance (α = 0.05). Intra- and interexaminer reliability levels were assessed with the weighted kappa examination. RESULTS: Sensitivity was low (0.32-0.49), and specificity was reasonably high (0.71-0.83). Mean values of AUC were low, ranging between 0.54 and 0.67, which reveals poor overall discrimination between health and disease. The detection of TA was not significantly influenced by mA level or voxel size (P > .05). Intra- and interexaminer agreements ranged from slight to moderate (0.160-0.535) and from fair to substantial (0.236-0.697), respectively. CONCLUSIONS: Despite the limited efficacy of CBCT for TA detection, when indicated as a complementary examination, mA reduction should be considered for dose optimization purposes.

Does the angulation between the maxillary central incisors and the nasopalatine canal differ among sagittal and vertical skeletal patterns? A CBCT study.

OBJECTIVES: To assess the influence of sagittal and vertical skeletal patterns, and sex in the angulation and relationship between the maxillary central incisors and the nasopalatine canal. MATERIALS AND METHODS: Cone-beam computed tomography (CBCT) exams of 172 patients were classified into sagittal (class I, II, and III) and vertical skeletal patterns (mesofacial, brachyfacial and dolichofacial). Hard palate-nasopalatine canal and hard palate-long axis of maxillary central incisors angles were measured in sagittal reconstructions. The obtained angles were used to calculate the angulation between maxillary central incisors and nasopalatine canal by triangle geometric relationship. Analysis of variance (multi-way ANOVA) and Tukey post-hoc test were used for data analysis (α=5%). RESULTS: Sagittal and vertical skeletal patterns, and sex presented a low influence on the angulation of maxillary central incisors and nasopalatine canal. Dolichofacial class II women showed the greatest hard palate-nasopalatine canal angulations (P<0.05) and maxillary central incisors and nasopalatine canal angulations (P<0.05). Mesofacial class II and III men presented the lowest maxillary central incisors and nasopalatine canal angulations (P<0.05). CONCLUSIONS: The sagittal and vertical skeletal patterns, and sex have a low influence on the angulation of the maxillary central incisors and the nasopalatine canal.

Do image enhancement filters in complementary metal oxide semiconductor and photostimulable phosphor imaging systems improve the detection of fractured endodontic instruments in periapical radiography?

OBJECTIVE: The aim of this study was to evaluate the influence of image enhancement filters on detection of fractured endodontic instruments and on image noise and pixel intensity. STUDY DESIGN: In total, 26 mandibular molars (68 root canals), divided into 4 groups (presence/absence of root canal filling, and presence/absence of a fractured endodontic instrument) were radiographed by using a complementary metal oxide semiconductor (CMOS) and a photostimulable phosphor (PSP) system. Images with 4 enhancement filters (Sharpen UM, Edges All, BC Low, and BC High) were compared with nonfiltered images. The area under the receiver operating characteristic curve (Az), sensitivity, and specificity in detection of fractured instruments were compared for each imaging condition. Means and standard deviations (SD) to measure noise and changes in pixel intensity were calculated. Analysis of variance was used to analyze the data. RESULTS: There were no significant differences in Az, sensitivity, and specificity values between nonfiltered and filtered images in detection of instruments in root canals without and with root canal filling (P ≥ .360). SD was reduced by filters in CMOS but not PSP radiographs. Sharpen UM caused more changes in the mean values in both systems. CONCLUSIONS: Filters did not improve diagnostic performance in detecting instruments. Noise and pixel intensity were affected differently.

Influence of the file format and transmission app on the radiographic diagnosis of caries lesions.

OBJECTIVES: This in vitro study aimed to evaluate the influence of the radiographic image file format and the transmission application (app) on the diagnosis of proximal caries lesions. STUDY DESIGN: Twenty bitewing radiographs of 40 posterior human teeth placed in phantoms were acquired using the Digora Toto digital sensor. All images were exported as TIFF (Tagged Image File Format), BMP (Windows Bitmap), PNG (Portable Network Graphics), and JPEG (Joint Photographic Experts Group) and transmitted online via WhatsApp and Messenger. Five examiners evaluated the radiographs with no online transmission and as transmitted through the 2 apps for the presence of proximal caries lesions using a 5-point scale. The reference standard for caries lesions was established using micro-computed tomography. Two-way analysis of variance compared values of sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve (α = .05). The kappa test was used to assess intra- and interexaminer agreement. RESULTS: Sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve values showed no significant differences in the diagnosis of proximal caries lesions between the different image file formats (P ≥ .773) and transmission apps (P ≥ .608). Intraexaminer agreement was substantial (κ = 0.742) and interexaminer agreement was moderate (κ = 0.475). CONCLUSION: The digital file format and transmission app did not influence the radiographic diagnosis of proximal caries lesions.

Influence of different viewing conditions on the detection of fractured endodontic instruments using periapical radiographs at 3 projection angles.

OBJECTIVES: The objective of this study was to assess the influence of ambient lighting levels and horizontal viewing angle (HVA) on the radiographic detection of fractured endodontic instruments in root canals in extracted human mandibular molars. STUDY DESIGN: Thirty-two root canals were selected. Endodontic instrument fracture was induced in 24 canals, and all canals were endodontially treated. Periapical radiographs were obtained at orthoradial, mesioradial, and distoradial projection angles. Five oral radiologists examined the radiographs for detection of fractured endodontic instruments under 3 ambient lighting levels (high, 450 lux; medium, 28 lux; and low, 2.5 lux) and 3 HVAs (90°, 67.5°, and 45°). Area under the receiver operating characteristic curve (AUROC), accuracy, sensitivity, and specificity were calculated and compared by 2-way analysis of variance using Tukey post hoc tests (α = .05). RESULTS: AUROC data indicated that ambient lighting (P = .739) and HVA (P = .238) did not significantly influence the detection of fractured endodontic instruments. Overall mean diagnostic values were 0.745, 0.57, 0.46, and 0.90 for AUROC, accuracy, sensitivity, and specificity, respectively. CONCLUSIONS: The viewing conditions assessed in this study did not influence the radiographic detection of fractured endodontic instruments in root canals.

Image quality optimization of narrow detector dental computed tomography for paediatric patients.

OBJECTIVES: Dental CBCT exposure parameters should be optimized according to patient-specific indications, mainly for children that are most vulnerable to harmful effects of ionizing radiation. The aim of this study was to determine optimized kV settings for paediatric acquisitions for a dental CBCT device. METHODS: Clinical and quantitative evaluations of image quality were performed using 5 and 10 years old (y/o) anthropomorphic phantoms. Technical evaluation was performed with the SEDENTEXCT-IQ phantom. Images were obtained using a PaX-i3D Green CBCT (Vatech, Korea) device, combining tube voltages ranging from 85 to 110 kV and 2 fields of view (FOVs: 21 × 19 and 12 × 9 cm), while maintaining the radiation dose fixed by adjusting the mA accordingly. Clinically, observers assessed images based on overall quality, sharpness, contrast, artefacts, and noise. For quantitative evaluation, mean grey value shift, % increase standard deviation, % beam-hardening and contrast-to-noise ratio were calculated. For technical evaluation, segmentation accuracy, contrast-to-noise ratio and full width at half maximum were measured. Biplot graphs were used to choose representative parameters, from which the best kV was selected for each protocol and evaluation. kV values that had no statistical differences (p > 0.05) with the best kV chosen were considered as having the same quality. RESULTS: Clinically, 95 kV was found as a cut-off value. From the quantitative aspect, 85 kV (p < 0.05) showed the worst quality, except in 12 × 9 cm 5 y/o. Technically, 85 and 110 kV in the large FOV showed significantly worse quality for the large FOV. CONCLUSION: For paediatric indications, 95 kV or higher (and correspondingly low mA values) was found as optimal.

Image quality optimization using a narrow vertical detector dental cone-beam CT.

OBJECTIVES:: To determine the optimized kV setting for a narrow detector cone-beam CT (CBCT) unit. METHODS:: Clinical (CL) and quantitative (QUANT) evaluations of image quality were performed using an anthropomorphic phantom. Technical (TECH) evaluation was performed with a polymethyl methacrylate phantom. Images were obtained using a PaX-i3D Green CBCT (Vatech, Hwaseong, Korea) device, with a large 21 × 19 and a medium 12 × 9 cm field of view (FOV), and high-dose (HD-ranging from 85 to 110 kV) and low-dose (LD-ranging from 75 to 95 kV) protocols, totaling four groups (21 × 19 cm HD, 21 × 19 cm LD, 12 × 9 cm HD, 12 × 9 cm LD). The radiation dose within each group was fixed by adapting the mA according to a predetermined dose-area product. For CL evaluation, three observers assessed images based on overall quality, sharpness, contrast, artefacts, and noise. For QUANT evaluation, mean gray value shift, % increase of standard deviation (SD), % of beam hardening and contrast-to-noise ratio (CNR) were calculated. For TECH evaluation, segmentation accuracy, CNR, metal artefact SD, metal object area, and sharpness were measured. Representative parameters were chosen for CL, QUANT, and TECH evaluations to determine the optimal kV based on biplot graphs. kV values of the same protocol were compared by the bootstrapping approach. The ones that had statistical differences with the best kV were considered as worse quality. RESULTS:: Overall, kV values within the same group showed similar quality (p > 0.05), except for 110 kV in 21 × 19 cm HD and 85 kV in 12 × 9 cm HD of CL score; also 85, 90 kV in 21 × 19 cm HD and 75, 80 kV in 21 × 19 cm LD of QUANT score which were worse (p < 0.05). CONCLUSION:: At a constant dose, low and high kV protocols yield acceptable image quality for a narrow-detector CBCT unit.

Influence of VistaScan image enhancement filters on diagnosis of simulated periapical lesions on intraoral radiographs.

OBJECTIVE:: To evaluate whether image enhancement filters of VistaScan system improve the diagnostic accuracy of simulated periapical lesions. METHODS:: 10 sockets were prepared on bovine ribs to fit a bovine tooth. Bone defects were created and successively enlarged providing four groups (n = 10): Group 0, absence of lesions; Group 1, periapical lesions with 1.6 mm in diameter; Group 2, with 1.8 mm in diameter; and Group 3, with 2.1 mm in diameter. Periapical radiographs were taken using a photostimulable storage phosphor plate and DBSWIN software. VistaScan filters were applied and the images were allocated into seven groups: Nonfiltered, Fine, Caries 1, Caries 2, Endodontic, Periodontal and Noise Reduction. All the 280 images were assessed about the presence or absence of periapical lesions. Pixel intensities standard deviation were compared between nonfiltered and filtered images. Two-Way Analysis of Variance and the post hoc Tukey's test were used to compare area under the ROC curve, sensitivity and specificity. RESULTS:: VistaScan filters showed no significant difference for area under receiver operating characteristic curve (p = 0.124), sensitivity (p = 0.835) and specificity (p = 0.832). Area under receiver operating characteristic curve (p = 0.000) and sensitivity (p = 0.000) in 2.1 mm lesions size were significantly higher than in 1.6 mm and 1.8 mm lesions size. Pixel intensities standard deviation was significantly changed in the filtered images compared to nonfiltered ones (p < 0.01), except for Fine in the bone region (p > 0.05). CONCLUSION:: VistaScan enhancement filters do not influence the diagnostic accuracy of simulated periapical lesions. On the other hand, larger lesions were more frequently detected. The filters change the pixel intensities reducing or intensifying the differences between similar regions.

Effect of micro-computed tomography reconstruction protocols on bone fractal dimension analysis.

OBJECTIVES: To evaluate the influence of the level of three micro-CT reconstruction tools: beam-hardening correction (BHC), smoothing filter (SF), and ring artefact correction (RAC) on the fractal dimension (FD) analysis of trabecular bone. METHODS: Five Wistar rats' maxillae were individually scanned in a SkyScan 1174 micro-CT device, under the following settings: 50 kV, 800 µA, 10.2 µm voxel size, 0.5 mm Al filter, rotation step 0.5°, two frames average, 180° rotation and scan time of 35 min. The raw images were reconstructed under the standard protocol (SP) recommended by the manufacturer, a protocol without any artefact correction tools (P0) and 35 additional protocols with different combinations of SF, RAC and BHC levels. The same volume of interest was established in all reconstructions for each maxilla and the FD was calculated using the Kolmogorov (box counting) method. One-way ANOVA with Dunnet's post-hoc test was used to compare the FD of each reconstruction protocol (P0-P35) with the SP (α = 5%). Multiple linear regression verified the dependency of reconstruction tools in FD. RESULTS: Overall, FD values are not dependent on RAC (p = 0.965), but increased significantly when the level of BHC and SF increased (p < 0.001). FD values from protocols with BHC at 45% combined with SF of 2, and BHC at 30% combined with SF of 4 or 6 had no statistical difference compared to SP. CONCLUSIONS: BHC and SF tools affect the FD values of micro-CT images of the trabecular bone. Therefore, these reconstruction parameters should be standardized when the FD is analyzed.

Impact of COVID-19 pandemic on dental education: perception of professors and students / Impacto de la pandemia COVID-19 en educación dental: percepción de estudiantes y profesores

Abstract The objective of this study was to evaluate perception and feelings experienced by dentistry professors and students about distance learning during the COVID-19 pandemic. Fifty professors and fifty- two students reported the perceptions and implications of distance learning imposed by the pandemic of COVID-19. The participants' answers were analyzed using the qualitative-quantitative method of the collective subject's discourse. The answers were summarized in central ideas, distributed in absolute and relative frequency. The answers with similar central ideas were grouped, obtaining the discourse of the collective subject. The similar central ideas about distance learning addressed by professors and students were: suitable for didactic courses; limited laboratory and clinical courses, and internet access difficulties. Specifically for professors: a complement to classroom teaching; stress and learning with digital technologies; difficulty in reconciling classes with domestic activities; concerns with motivation and interaction with students; asynchronous lectures favor knowledge fixation, and synchronous lectures favor interaction with students; unreliable assessment methods; concern about returning to face-to-face classes. For the students: it was applied to all courses; demotivating; fundamental to guide studies; professors' commitment; long lectures; excessive school activities; difficult attendance control and evaluation; the comfort of being at home; impact on research. Professors considered distance learning as a learning opportunity on how to use digital technologies but too limited for lab and clinical activities and interaction with students. Students found it discouraging due to the absence of practical classes and excessive school activities.

Resumen: Evaluar la percepción y los sentimientos manifestados por profesores y estudiantes de odontología sobre la educación a distancia durante la pandemia por COVID-19. 50 profesores y 52 estudiantes informaron las percepciones e implicaciones del aprendizaje a distancia impuestas por motivo de la pandemia de COVID-19. Respuestas de los participantes fueron analizadas utilizando el método cualitativo-cuantitativo del discurso del sujeto colectivo. Respuestas se agruparon en ideas centrales, obteniendo el discurso del sujeto colectivo y fueron distribuidas en frecuencia absoluta y relativa. Ideas centrales similares entre profesores y estudiantes sobre el aprendizaje a distancia fueron: a) es adecuado para cursos didácticos; b) limitado para cursos de laboratorio y clínicos; c) presenta dificultades devido al acceso a Internet. Específicamente para profesores: a) complemento a la docencia en el aula; b) aumenta el estrés devido a la curva de aprendizaje con tecnologías digitales; c) dificultad para conciliar las clases con las actividades domésticas; d) preocupaciones con la motivación y la interacción con los estudiantes; e) las clases asincrónicas favorecen la fijación del conocimiento y las clases sincrónicas favorecen la interacción con los estudiantes; f) métodos de evaluación poco fiables; y g) preocupación por volver a las clases presenciales. Para los estudiantes: a) se aplicó a todos los cursos; b) desmotivador fundamental para orientar los estudios; c) compromiso de los profesores; d) conferencias largas; e) actividades escolares excesivas; f) difícil control y evaluación de asistencia; g) la comodidad de estar en casa; y h) impacto en la investigación. Profesores consideraron el aprendizaje a distancia como una oportunidad de aprendizaje sobre cómo utilizar las tecnologías digitales, pero demasiado limitado para las actividades de laboratorio y clínicas y la interacción con los estudiantes. Estudiantes lo encontraron desalentador debido a la ausencia de clases prácticas y al exceso de actividades escolares.

Can the Incorporation of a Lead Foil on the Backside of Digital Receptors Produce a Better Endodontic Diagnosis?

ABSTRACT: This study evaluated influence of addition of lead foil coupled to different types of digital receptors on image noise and on diagnosis of fractured instruments in teeth without and with root filling. Twenty-six molars had their root canals (n=67) cleaned and shaped and were divided into groups with and without root filling and with and without fractured instruments. Images were acquired in PSP and CMOS sensor, with and without addition of a lead foil coupled to the digital receptors. Diagnostic values were obtained by the area under the ROC curve, and one-way ANOVA compared the groups. Noise in images was measured by the standard deviation of mean gray values in images with and without the lead foil, and compared by two-way ANOVA (a=0.05). Addition of lead foil did not interfere in the diagnostic accuracy for both digital systems (p>0.05) and did not decrease noise in the images (p>0.05). However, independently of the addition of the lead foil, the phosphor-storage plate presented higher noise compared to the sensor (p ?0.05). Addition of lead foil to the digital receptor did not interfere in image noise and with the diagnostic accuracy for detecting fracured endodontic instrument in ex-vivo conditions.

RESUMEN: Este estudio evaluó la influencia de láminas de plomo acopladas a diferentes tipos de receptores digitales sobre el ruido de la imagen y el diagnóstico de instrumentos fracturados en dientes sin y con obturación radicular. Se limpiaron y moldearon 26 molares (n = 67), se dividieron en grupos con y sin relleno radicular y con y sin instrumentos fracturados. Las imágenes se adquirieron en el sensor PSP y CMOS, con y sin adición de una lámina de plomo acoplada a los receptores digitales. Los valores diagnósticos se obtuvieron por el área bajo la curva ROC y con ANOVA de una vía comparó los grupos. El ruido en las imágenes se midió mediante la desviación estándar de los valores medios de gris en las imágenes con y sin la lámina de plomo, y se comparó mediante ANOVA bidireccional (a = 0,05). La adición de lámina de plomo no interfirió en la precisión diagnóstica de ambos sistemas digitales (p> 0,05) y no disminuyó el ruido en las imágenes (p> 0,05). Sin embargo, independientemente de la adición de la lámina de plomo, la placa de almacenamiento de fósforo presentó mayor ruido en comparación con el sensor (p?0,05). La adición de lámina de plomo al receptor digital no interfirió con el ruido de la imagen y con la precisión diagnóstica para detectar el instrumento endodóntico fracturado en condiciones ex vivo.