Ambient light exposure of photostimulable phosphor plates: is there a safe limit for acceptable image quality?

OBJECTIVES: To subjectively assess radiographs obtained with photostimulable phosphor (PSP) plates exposed to clinical levels of ambient light prior to read-out to potentially set a safe limit for acceptable image quality. METHODS AND MATERIALS: Six dental regions of a dry human skull were X-rayed using PSP plates from VistaScan and Express under four exposure times: 0.1, 0.2, 0.32, and 0.4 s. Before read-out, the PSP plates were exposed to ambient light for 0, 5, 10, 30, 60, and 90 s. Six observers were asked to classify the 288 resulting radiographs as acceptable or unacceptable based on the identification of anatomical structures and global image quality. The number of answers classifying radiographs as unacceptable was used to calculate a rejection rate; a pairwise comparison for better image quality was further conducted among radiographs considered acceptable. Reproducibility was tested by having 25% of all experimental groups reassessed. RESULTS: Intra- and interobserver agreement ranged from 0.87 to 1.00 and from 0.81 to 0.92, respectively. Exposure of PSP plates to ambient light increased rejection rates mostly as of 10 s. In the pairwise comparison, subtle differences were observed between radiographs obtained with PSP plates not exposed and those exposed to ambient light for 5 s. CONCLUSIONS: Ambient light exposure of PSP plates impairs the image quality of radiographs. A safe limit of ambient light exposure of 5 s for VistaScan and Express should be considered. Ambient light exposure of PSP plates within safe limits can avoid retakes and reduce unnecessary patient exposure to X-rays.

Root Curvature in Non-Syndromic Oral Clefts: A Case-Control Study in a Brazilian Population.

OBJECTIVE: This study assesses the degree of root curvature in patients with non-syndromic cleft lip and/or palate (NSCL/P). DESIGN: Retrospective. Case-control study. SETTING: Root curvature was assessed in lower premolars and molars in 800 panoramic radiographs: 400 from patients with cleft and 400 from healthy control individuals. Root curvature was classified according to its angulation, as well as its apical, medial, or coronal localization. RESULTS: The frequency of mild curvature in the NSCL/P group compared to the control group was higher in premolars especially in the left second premolar in cleft palate (OR: 6.91; 95% CI: 3.23-14.77; P < .0001). The frequency of moderate curvature in molars was significantly higher in the cleft group, with the highest risk in the right first molar in the cleft lip group (OR: 2.74; 95% CI: 1.67-4.52; P < .0001). Inclination was more frequently observed in the apical third of the root in the group with cleft, whereas for the control group, the curvature was more frequent in the medial third. In patients with cleft, the OR of curvature in the apical third was significant in premolars (left lower second premolar: Cleft lip, OR: 1.91; 95% CI: 1.04-3.52; P = .03; right lower second premolar: Cleft lip, OR: 1.91, 95% CI: 1.04-3.50; P = .03, cleft lip and palate, OR: 1.75; 95% CI: 1.12-2.73; P = .01). CONCLUSION: The results of the current study indicate differences in root curvature in patients with non-syndromic cleft lip and/or palate, which should be considered during the dental treatment planning of patients.

How is the use of digital dental radiology in a developing country? An overview of Brazil / ¿Cómo es el uso de la radiología dental digital en un país en vías de desarrollo? Una visión general de Brasil

Abstract The aim of this study was to assess the use of digital dental radiology in Brazil, by focusing on the use of image receptors, imaging exams and digital image enhancement tools, also assessing the methods of professional image transfer. Questionnaires were distributed in person on dental meetings and digitally via messaging (WhatsApp®) and mailings list. The sample of this cross-sectional study consisted of 478 questionnaires. Most participants were woman (n=315, 65.9%), with average age of 33.8±9.2 years. Descriptive and frequency analysis was performed. Chi-square and Fisher's exact tests were used (α=0.05). Most dentists worked at shared dental clinics (34.7%) and use digital image receptors (51.1%), but a representative percentage (48.9%) still exclusively use radiographic films. Photostimulable phosphor plate is the most used digital image receptor. Among extraoral exams, panoramic radiography (PAN) is the most used. Regarding dental specialties, oral radiologists and oral and maxillofacial surgeons mostly use cone-beam computed tomography (p<0.001). Most dentists who use digital systems make use of digital image enhancement tools (87.8%), mainly contrast, zoom, brightness and measurements. The most common method of professional image transfer (professional-professional and professional-patiens) is by email, with few dentists using online app and social media (26%). Therefore, while most Brazilian dentists use digital imaging systems, a significant percentage still exclusively use radiographic films. The most extraoral imaging exams used is PAN. Regarding image enhancement tools, brightness and contrast adjustments, zoom and measurements are the most applied. Finally, dentists generally use email for professional image transfer.

Resumen El objetivo de este estudio fue evaluar uso de la radiología dental digital en Brasil, centrándose en uso de receptores de imagen, exámenes de imágenes y herramientas de mejora de imagen digital, evaluando también los métodos de transferencia de imagen profesional. Cuestionarios se distribuyeron de forma presencial en reuniones odontológicas y de forma digital a través de mensajería (WhatsApp®) y lista de correo. Muestra de este estudio transversal estuvo compuesta por 478 cuestionarios. Mayoría de los participantes eran mujeres (n=315, 65,9%), con edad promedio de 33,8±9,2 años. Se realizó un análisis descriptivo y de frecuencias. Se utilizaron las pruebas Chi-cuadrado y exacta de Fisher (α=0,05). La mayoría de los odontólogos trabajaban en clínicas dentales compartidas (34,7%) y utilizan receptores de imágenes digitales (51,1%), pero un porcentaje representativo (48,9%) todavía utiliza exclusivamente películas radiográficas. Placa de fósforo fotoestimulable es el receptor de imagen digital más utilizado. Entre los exámenes extraorales, la radiografía panorámica (PAN) es la más utilizada. En cuanto a las especialidades odontológicas, los radiólogos orales y los cirujanos orales y maxilofaciales utilizan mayoritariamente la tomografía computarizada de haz cónico (p<0,001). Mayoría de los odontólogos que utilizan sistemas digitales utilizan herramientas de mejora de imagen digital (87,8%), principalmente contraste, zoom, brillo y medidas. Método más común de transferencia de imágenes profesionales (profesional-profesional y profesional-pacientes) es por correo electrónico, con pocos dentistas que utilizan aplicaciones en línea y redes sociales (26%). Por lo tanto, mientras que la mayoría de dentistas brasileños utilizan sistemas de imágenes digitales, un porcentaje significativo aún utiliza exclusivamente películas radiográficas. Examen de imagen extraoral más utilizado es el PAN. En cuanto a las herramientas de mejora de imagen, los ajustes de brillo y contraste, el zoom y las medidas son las más aplicadas. Finalmente, los dentistas generalmente usan el correo electrónico para la transferencia de imágenes profesionales.

Cone beam CT optimisation for detection of vertical root fracture with metal in the field of view or the exomass.

Dose optimisation has been revisited in the literature due to the frequent use of cone beam computed tomography (CBCT). Although the reduction of the field-of-view (FOV) size has shown to be an effective strategy, this indirectly increases the negative effect from the exomass. The aim of this study was to evaluate the diagnostic accuracy of an optimised CBCT protocol in the detection of simulated vertical root fracture (VRF) in the presence of metal in the exomass and/or inside the FOV. Twenty teeth were endodontically instrumented and VRF was induced in half of them. All teeth were individually placed in a human mandible covered with a soft tissue equivalent material, metallic materials were placed at different dispositions in the exomass and/or endomass, and CBCT scans were obtained at two dose protocols: standard and optimised. Five radiologists evaluated the images and indicated the presence of VRF using a 5-point scale. Area under the ROC curve (AUC), sensitivity, and specificity were calculated and compared using ANOVA (α = 0.05). Overall, AUC, sensitivity, and specificity did not differ significantly (p > 0.05) between the dose protocols. In conclusion, optimised dose protocols should be considered in the detection of simulated VRF irrespective of the occurrence of artefacts from metallic materials in the exomass and/or inside the FOV.

Influence of metal artefact reduction tool on the detection of vertical root fractures involving teeth with intracanal materials in cone beam computed tomography images: A systematic review and meta-analysis.

BACKGROUND: The effectiveness of the metal artefact reduction (MAR) tool for the detection of vertical root fracture (VRF) by cone beam computed tomography (CBCT) images is controversial. OBJECTIVE: To evaluate the effectiveness of the MAR tool on VRF detection involving teeth with intracanal materials in CBCT images. METHODOLOGY: In September 2019, an electronic search was performed in six databases (PubMed, Scopus, Web of Science, Cochrane, Lilacs and Embase). The electronic search was updated in May 2020 through searches in Google Scholar and references of included studies (embracing the electronic and gray literature searches). No language or year restrictions were applied. Independently, two reviewers examined titles, abstracts and full texts according to the eligibility criteria that were as follows: diagnostic studies that evaluated the effectiveness of the MAR tool on the diagnosis of VRF in human teeth (laboratory or in vivo studies) on CBCT images. The risk of bias was evaluated using the Quality Assessment Tool for Diagnostic of Accuracy Studies-2 (QUADAS-2). For conducting the meta-analysis, the values of sensitivity, specificity, diagnostic odds ratio (DOR) and area under the ROC curve (AUC) were obtained, considering the subgroups with and without MAR active. The Grading of Recommendation, Assessment, Development and Evaluation instrument was applied to assess the level of evidence across the studies using GRADEpro software. RESULTS: A total of 8 laboratory studies were included in both systematic review and meta-analysis. The values of sensitivity, specificity, DOR and AUC to VRF diagnosis with and without MAR active were, respectively, 0.586 and 0.603; 0.699 and 0.713, 3.037 and 3.767; 0.67 and 0.71. The quality of the evidence suggested low confidence in estimating the outcomes. DISCUSSION: The MAR tool decreased slightly the diagnostic values of VRF involving teeth with intracanal materials in laboratory studies. However, it is important to highlight that most studies had an uncertain risk of bias. CONCLUSIONS: Although a low level of evidence and high heterogeneity were observed in the included studies, the meta-analysis revealed better diagnosis values for VRF detection when the MAR was deactivated when analysing extracted teeth in a laboratory setting. REGISTRATION: PROSPERO-CRD42020145222. FUNDING: This study was financed in party by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil (CAPES).

Influence of voxel size on cone beam computed tomography artifacts arising from the exomass.

OBJECTIVES: The objective of this study was to evaluate the influence of voxel size on artifacts arising from the exomass in cone beam computed tomography (CBCT). STUDY DESIGN: An imaging phantom was scanned using 2 CBCT units, each adjusted to 2 voxel sizes: 0.2 and 0.3 mm. From 1 to 3 metal inserts of titanium, cobalt-chromium, or amalgam were placed in the exomass and additional CBCT scans were acquired. Mean voxel gray values were obtained from 16 homogeneous areas of the phantom and averaged, and the standard deviation was calculated to obtain voxel gray value variability. The data were analyzed using 2-way analysis of variance, Tukey, and Dunnett tests (α =.05). RESULTS: Overall, mean voxel gray values and voxel gray value variability did not differ significantly between CBCT scans obtained with voxel sizes of 0.2 and 0.3 mm for either CBCT model tested (P > .05). Despite some exceptions in which significant differences were observed between the 2 voxel sizes (P < .05), the mean voxel gray values and voxel gray value variability resulting from different metal compositions and, in most situations, for different numbers of metal inserts in the exomass were not affected. CONCLUSION: Voxel size has little influence on exomass-related CBCT artifacts.

Does dose optimisation in digital panoramic radiography affect diagnostic performance?

OBJECTIVES: To compare the overall diagnostic performance of digital panoramic radiographs obtained with low-dose protocols and to estimate the absorbed dose in the head and neck. MATERIALS AND METHODS: Forty-eight panoramic radiographs were obtained from eight imaging phantoms using six exposure protocols of progressively lower tube voltages (kVp) and currents (mA), as follows: (1) 70 kVp and 12.5 mA, (2) 66 kVp and 10 mA, (3) 66 kVp and 8 mA, (4) 66 kVp and 5 mA, (5) 66 kVp and 4 mA and (6) 66 kVp and 3.2 mA. Five oral radiologists independently evaluated the images and reported all detectable radiographic findings. Intra-examiner reproducibility was assessed by re-evaluation of 25% of the images. The data were analysed using the McNemar and weighted Kappa tests. Absorbed doses of the six protocols were obtained from thermoluminescent dosimeters placed inside a Rando phantom and compared using one-way ANOVA with post hoc Tukey (α = 0.05). RESULTS: The overall diagnostic performance of panoramic radiographs obtained with low-dose protocols did not differ from that of panoramic radiographs obtained with the highest dose (p > 0.05). Moreover, substantial agreement was observed between all protocols. Protocol 1 resulted in the highest absorbed dose and protocols 4, 5 and 6 in the lowest absorbed doses, with the difference being significant (p ≤ 0.05). CONCLUSION: Although digital panoramic radiography is considered a relatively low-dose examination, the radiation dose can be further reduced without negatively affecting its overall diagnostic performance. CLINICAL RELEVANCE: Considering the risks associated with X-rays, digital panoramic radiographs can be obtained at even lower exposure levels.

Do the tube current and metal artifact reduction influence the diagnosis of vertical root fracture in a tooth positioned in the vicinity of a zirconium implant? A CBCT study.

AIM: To evaluate the influence of the tube current and metal artifact reduction (MAR) tool on the diagnosis of vertical root fractures (VRF) in a tooth adjacent to a zirconium implant, in cone-beam computed tomography (CBCT) images. METHODOLOGY: Thirty single-rooted teeth (15 with VRF and 15 control group) were individually positioned in a mandible, and scanned with the OP300 CBCT unit. Images were acquired using a standardized protocol: 5 × 5 cm field of view, 0.08-mm voxel size, and 90 kVp. Each tooth was scanned with and without a zirconium implant in its vicinity, using different tube currents (4 mA, 8 mA, and 10 mA) and conditions of MAR (enabled × disabled). Diagnostic values were calculated for each protocol, and compared by multi-way analysis of variance. RESULTS: The ROC curve and sensitivity values did not differ significantly among the tube currents, regardless of the presence of the implant and MAR condition (p > 0.05). There were also no significant differences among the tube currents for the specificity values (p > 0.05); however, the specificity differed significantly between the "with implant" and "without implant" conditions, within the same MAR condition and tube current (p < 0.05). Specificity was significantly lower when the implant was present (p < 0.05). CONCLUSION: The presence of a zirconium implant impairs the diagnosis of VRF in teeth adjacent to the artifact-generator material. Neither the tube current nor the MAR tool is effective in improving this diagnostic task. Therefore, in this clinical scenario, the use of the lowest tube current (4 mA), without MAR activation, is recommended. CLINICAL RELEVANCE: Considering that the tube current is one of the main factors that influence the radiation dose and image quality in CBCT, and that metal artifacts negatively influence the diagnosis of VRF in areas adjacent to the artifact-generator material, it is important to evaluate the effect of this energetic parameter in the diagnosis of VRF in teeth adjacent to zirconium implants.

Objective assessment of the combined effect of exomass-related- and motion artefacts in cone beam CT.

OBJECTIVES: To assess quantitatively the combined effect of exomass-related- and motion artefacts on voxel value parameters in cone beam CT (CBCT). METHODS: A cylindrical phantom was manufactured, containing 21 tubes filled with a radiopaque solution, allowing the inclusion of three titanium implants in the periphery to induce exomass-related artefacts. The phantom was mounted on a robot simulating 0.75-, 1.5-, and 3 mm movements (nodding/lateral rotation/tremor). CBCT images with/without exomass and with/without movements were acquired in duplicate in three units: Cranex 3Dx, Orthophos SL-3D, and X1 (with motion-artefact correction). A cylindrical volume of interest was defined in each tube and voxel value mean and standard deviation were assessed. For each CBCT volume, the 21 mean voxel values were averaged providing the overall mean voxel value (MVV), and the standard deviation (among the 21 values) was calculated providing overall voxel value inhomogeneity (VVI). The standard deviation from each of the 21 volumes-of-interest were averaged, providing overall image noise (IN). The effect of the diverse tested situations was inferred from a repeated-measures analysis of variance, followed by Sidak's test (α = 0.05). RESULTS: Overall, images acquired with exomass showed significantly (p ≤ 0.05) lower MVV, and higher VVI and IN. Motion artefacts aggravated exomass-related alterations. MVV and VVI were mostly affected by 3 mm nodding movements. Motion-artefact correction eliminated the deleterious effect of movement. CONCLUSIONS: CBCT voxel-value parameters are altered by exomass-related artefacts, and this finding is aggravated in the presence of motion artefacts. Motion-artefact correction effectively eliminated the deleterious impact of movement.

Mapping the expression of beam hardening artefacts produced by metal posts positioned in different regions of the dental arch.

OBJECTIVES: To objectively assess the expression and direction of artefacts in the vicinity of metal posts positioned in different mandibular regions. MATERIALS AND METHODS: A human mandible had two sockets prepared-anterior and posterior regions-to accommodate a single-rooted tooth. Two CBCT units, Picasso Trio and OP300, were used. CBCT images of the tooth without metal post, and with silver-palladium, nickel-chromium, or cobalt-chromium posts (experimental groups) were individually acquired. Then, 8 lines of interest (LOIs) were determined around the root canal, in an axial reconstruction: 4 in orthogonal (buccal, lingual, mesial, and distal) directions, and 4 in oblique (mesiobuccal, distobuccal, mesiolingual, and distolingual) directions. The mean of gray values was measured for each LOI. RESULTS: For the OP300, in general, all experimental groups showed greater expression of hyperdense streaks in orthogonal LOIs and greater expression of hypodense streaks in oblique LOIs. For the Picasso Trio, for both mandibular regions, the buccal LOI showed greater expression of hypodense streaks; conversely, greater expression of hyperdense streaks was observed in the distal and distobuccal LOIs in the anterior region and in the mesiolingual LOI in the posterior region. The silver-palladium group showed significantly greater expression of beam hardening artefacts in the posterior region of the mandible, regardless of the CBCT unit (p < 0.05). The mandibular posterior region showed significantly lower gray values than the anterior region (p < 0.05). CONCLUSION: The expression and direction of artefacts produced in the vicinity of metal posts vary according to the mandibular region, composition of the post, and CBCT unit. CLINICAL RELEVANCE: The mapping of artefacts produced by metal posts reveals the root regions with greater expression of hypodense and hyperdense artefacts, which may contribute to recognizing regions more likely to mimic or hide root fracture lines.

Effect of digital enhancement on the radiographic assessment of vertical root fractures in the presence of different intracanal materials: an in vitro study.

OBJECTIVES: To evaluate the effect of enhancement tools of intraoral digital radiographs on the assessment of vertical root fracture (VRF) and to quantify the resultant image noise. MATERIALS AND METHODS: Thirty single-rooted human teeth (15 control and 15 fractured) were each radiographed in four intracanal conditions: no filling, gutta-percha, metal post, and fiberglass post, totaling 120 original images. Two filters were applied to the original images-Sharpen filter (SF) and Edge Enhancement filter (EE), and brightness and contrast were adjusted in four combinations (B&C1 to 4), resulting in 840 images. Five oral radiologists analyzed the images for VRF detection. Pixel intensity was obtained in two regions from the radiographs. Diagnostic values were calculated and compared by two-way ANOVA, and the SD values of pixel intensity values were compared by one-way ANOVA (α = 0.05). RESULTS: There were no significant differences in accuracy for VRF detection between the experimental groups (p > 0.05). Teeth with metal post presented the lowest sensitivity (p < 0.05) for all experimental conditions, except for SF and EE (p > 0.05). B&C2, B&C3, and B&C4 had higher specificity than SF (p ≤ 0.05) for all intracanal conditions. Analysis of pixel intensity showed that all enhanced images presented statistically significant higher noise compared to those of the original images (p ≤ 0.05). CONCLUSION: Digital enhancement tools in digital radiography increase image noise; however, they can be used without compromising VRF detection. CLINICAL RELEVANCE: The use of digital enhancement does not impair the detection of VRF and, therefore, can be applied for this purpose according to the observer preference.

Does the metal artifact reduction algorithm activation mode influence the magnitude of artifacts in CBCT images?

PURPOSE: This study was conducted to assess the effectiveness of a metal artifact reduction (MAR) algorithm activated at different times during cone-beam computed tomography (CBCT) acquisition on the magnitude of artifacts generated by a zirconium implant. MATERIALS AND METHODS: Volumes were obtained with and without a zirconium implant in a human mandible, using the OP300 Maxio unit. Three modes were tested: without MAR, with MAR activated after acquisition, and with MAR activated before acquisition. Artifacts were assessed in terms of the standard deviation (SD) of gray values and the contrast-to-noise ratio (CNR) in 6 regions of interest with different distances (10 to 35 mm, from the nearest to the farthest) and angulations (70° to 135°) from the implant region. RESULTS: In the acquisitions without MAR, the regions closer to the implant (10 and 15 mm) had a higher SD and lower CNR than the farther regions. When MAR was activated (before or after), SD values did not differ among the regions (P>0.05). The region closest to the implant presented a significantly lower CNR in the acquisitions without MAR than when MAR was activated after the acquisition; however, activating MAR before the acquisition did not yield significant differences from either of the other conditions. CONCLUSION: Both modes of MAR activation were effective in decreasing the magnitude of CBCT artifacts, especially when the effects of the artifacts were more noticeable.

Age and sex estimation based on pulp cavity volume using cone beam computed tomography: development and validation of formulas in a Brazilian sample.

OBJECTIVES: To develop and validate formulas for age and sex estimation based on the pulp cavity volume of teeth using cone beam CT. METHODS: The sample was composed of 116 cone beam CT scans from Brazilian individuals of both sexes, ranging in age from 13 to 70 years. A total of 232 teeth (upper central incisors and canines) were evaluated. Two calibrated examiners determined pulp cavity volumes using the ITK-SNAP software. Pearson's correlation test was used to assess the correlation between chronological age and pulp volume. Linear and logistic regression models were developed for age and sex estimation, respectively, and were validated in another sample of 72 teeth. RESULTS: Pearson's correlation coefficients between age and pulp volume were negative and significant (p < 0.0001) for both teeth (r = -0.8782 for central incisors and r = -0.8738 for canines). The age estimation formulas showed good determination coefficients (adjusted R² = 0.7614 to 0.8367). For sex estimation, when the age was known, the coefficients were also good (adjusted R² = 0.649 to 0.812). However, when the age was unknown, the coefficients of the sex estimation formulas were low (adjusted R² = 0.047 to 0.393). Validation showed high accuracy of age estimation in individuals older than 35 years, as well as high accuracy of sex estimation when the age was known. CONCLUSIONS: Our formulas provided excellent results and can be applied to the Brazilian population. The best results were observed for age estimation in females and for sex estimation when the age was known.

Influence of brightness and contrast adjustments on the diagnosis of proximal caries lesions.

OBJECTIVES: To assess the influence of brightness and contrast adjustments of digital radiographs on the diagnosis of proximal caries lesions, and to compare with observers' preferences for subjective image quality. METHODS: 80 proximal surfaces of posterior teeth were radiographed using an intraoral digital system (Digora Toto, Soredex, Finland). Initial images and four different combinations of brightness and contrast for each radiography were analysed. Five observers scored the images for the presence and extension of caries lesions. Micro-CT images were used as gold standard. In a second stage, the observers were asked which of the radiographs they preferred for the assessment of caries lesions. RESULTS: No differences were found between the original and adjusted radiographic images regarding the area under the receiver operating characteristic curve, sensitivity, and specificity (p > 0.05). There was a significant difference between the micro-CT and the intraoral radiographs (p < 0.0001). Images with high brightness and low contrast presented higher number of true negative cases, but also a decrease in caries detection. On the other hand, there were more cases of overestimation of the presence and extension of caries lesions in images with low brightness and high contrast. The subjective evaluation of image quality showed that radiographs with lower brightness and higher contrast tended to be preferred by observers. CONCLUSIONS: Brightness and contrast adjustments in digital intraoral radiographs within the range tested in this study do not significantly influence the diagnosis of proximal caries lesions, although observers tend to prefer lower brightness and higher contrast images.

Magnitude of cone beam CT image artifacts related to zirconium and titanium implants: impact on image quality.

OBJECTIVES: To evaluate the magnitude of artifacts related to titanium and zirconium implants at different distances and angulations and their impact on cone beam CT(CBCT) image quality. METHODS: CBCT images were obtained before and after the insertion of titanium and zirconium implants in a mandible on different CBCT units: Picasso Trio, ProMax 3D and 3D Accuitomo 80. Artifact was assessed by measuring the standard deviation (SD) of gray values and contrast-to-noise ratio (CNR) of 11 regions of interest (ROIs) at different distances (1.5 cm, 2.5 cm and 3.5 cm) and angulations (65°, 90°, 115° and 140°) from implant region. RESULTS: For titanium images, SD values did not differ from those of images without implant in all ROIs; however, some effect occurred in Picasso images as higher values were observed in ROIs closer to the implant (p < 0.05). Zirconium images showed higher SD values than the others in some ROIs for Picasso and ProMax (p < 0.05). In ProMax, the difference was observed even in the farthest ROIs from the implant. CNR values were not influenced by the ROI in Picasso, but presented lower values in ROIs closer to the zirconium implant for ProMax and Accuitomo. CONCLUSIONS: The quantity and magnitude of artifacts in CBCT are influenced by the type of implant and CBCT unit. Although they are more pronounced in regions closer to the implant and located at 90° in relation to the mandibular long axis, they can reach as far as 3.5 cm from the artifact-generator object.

Metallic materials in the exomass impair cone beam CT voxel values.

OBJECTIVES: To assess the influence of artefacts arising from metallic materials in the exomass on cone beam CT (CBCT) voxel values. METHODS: CBCT scans were taken of a phantom composed of 16 tubes filled with a homogeneous hyperdense solution and metallic materials of different compositions (titanium, cobalt-chromium and amalgam) and numbers (one, two and three). The phantom was centred in a 5 × 5 cm field of view such that the metallic materials were located in the exomass, using three CBCT units. Voxel values were obtained from the 16 homogeneous areas and averaged. Also, standard deviation was calculated to measure voxel value variability. Analysis of variance in a factorial scheme with additional treatment 3 × 3 + 3 (material × number + control) was performed, followed by Tukey's test for multiple comparisons, and Dunnett's test for comparisons with the control groups, at a level of significance of 5%. RESULTS: Metallic material in the exomass significantly reduced the mean voxel value in the CS9300 and Picasso Trio units, and increased voxel value variability in all CBCT units. Amalgam was the material that induced significantly greater reduction of the mean voxel value in the CS9300 and Picasso Trio units, and significantly greater increase in the NewTom Giano. Voxel value variability was significantly greater for amalgam in all conditions. The presence of one cylinder induced significantly less pronounced effects on the mean voxel value and voxel value variability. CONCLUSIONS: Artefacts arising from metallic materials in the exomass have a negative influence on CBCT voxel values.

Evaluation of a metal artefact reduction tool on different positions of a metal object in the FOV.

OBJECTIVES: To evaluate the action of a metal artefact reduction (MAR) tool when artefact-generator metal object is at different positions in the field of view (FOV). METHODS: A cylindrical utility wax phantom, with a metal alloy sample inside, was made. The phantom was positioned centrally and peripherally in the FOV for image acquisition, with and without the MAR tool activation. The standard deviation values (image noise levels) from areas around the metal sample and the control area were obtained. The numbers were compared by Student's t-test (α = 0.05). RESULTS: When the tool was activated, a significant difference of image noise was observed for central and peripheral positioning, for both control area (p = 0.0012) and metal area (p = 0.03), and a smaller level of noise was observed for images with phantoms in central positioning. A decrease in image noise with the tool activated was found only in phantoms with the metal object positioned centrally in the FOV. CONCLUSIONS: For the MAR tool to be effective, the artefact-generator object needs to be in the central region of the FOV.

Comparison of panoramic radiography and CBCT to identify maxillary posterior roots invading the maxillary sinus.

OBJECTIVES: Given the limitations of panoramic radiography for assessing topographic relationship of maxillary teeth with sinus floor, the purpose of this study was to assess signs on panoramic radiography that could predict root protrusion into the sinus. METHODS: A total of 46 individuals (330 maxillary posterior teeth) who underwent panoramic radiography and CBCT were enrolled. The relationship between the posterior teeth and the maxillary sinus and panoramic radiography signs (projection of the root apices, interruption of the maxillary sinus floor, lamina dura, darkening in the root apices, and superiorly curving sinus floor enveloping the associated tooth root) associated with protrusion of root apices into the sinus were evaluated. RESULTS: There were differences between the imaging modalities about the positioning of the root apices regarding the sinus (p < 0.05). Only the projecting of the root apices and the interruption of the sinus floor on panoramic radiography were predictors for the root protrusion (p < 0.05). No significant association was observed for the other panoramic radiography signs (p > 0.05). CONCLUSIONS: The root projection into the sinus and the interruption of the sinus floor are indicative signs of root protrusion into the sinus on CBCT.

Influence of scan mode (180°/360°) of the cone beam computed tomography for preoperative dental implant measurements.

OBJECTIVE: The aim of this study was to evaluate the effect of scan mode of the cone beam computed tomography (CBCT) in the preoperative dental implant measurements. MATERIAL AND METHODS: Completely edentulous mandibles with entirely resorbed alveolar processes were selected for this study. Five regions were selected (incisor, canine, premolar, first molar, and second molar). The mandibles were scanned with Next Generation i-CAT CBCT unit (Imaging Sciences International, Inc, Hatfield, PA, USA) with half (180°) and full (360°) mode. Two oral radiologists performed vertical measurements in all selected regions; the measurements of half of the sample were repeated within an interval of 30 days. The mandibles were sectioned using an electrical saw in all evaluated regions to obtain the gold standard. The intraclass correlation coefficient was calculated for the intra- and interobserver agreement. Descriptive statistics were calculated as mean, median, and standard deviation. Wilcoxon signed rank test was used to determine the correlation between the measurements obtained in different scan mode with the gold standard. The significance level was 5%. RESULTS: The values of intra- and interobserver reproducibility indicated a strong agreement. In the dental implant measurements, except the bone height of the second molar region in full scan mode (P = 0.02), the Wilcoxon signed rank test did not show statistical significant difference with the gold standard (P > 0.05). CONCLUSIONS: Both modes provided real measures, necessary when performing implant planning; however, half scan mode uses smaller doses, following the principle of effectiveness. We believe that this method should be used because of the best dose-effect relationship and offer less risk to the patient.

In vitro comparison of cone beam computed tomography with different voxel sizes for detection of simulated external root resorption.

The present study compared the efficacy of cone beam computed tomography using different voxel sizes in the diagnosis of simulated external root resorption. The presence or absence of simulated defects on buccal, mesial and distal root surfaces of 20 premolars was evaluated. The defects were small (0.26 mm in diameter and 0.08 mm deep), medium (0.62 mm in diameter and 0.19 mm deep) and large (1.05 mm in diameter and 0.24 mm deep), equally distributed on each root surface. Images were obtained using Classic i-CAT cone beam computed tomography with different voxel sizes: 0.12, 0.20, 0.25 and 0.30 mm. Five oral radiologists evaluated the images. Accuracy, sensitivity, specificity, positive and negative predictive values were determined. The sensitivity decreased and specificity increased as voxel size increased. Accuracy values were the highest for the smallest voxel size (0.12 mm). The results for voxel sizes 0.20 mm and 0.25 mm were similar. Positive and negative predictive values were similar in all protocols, except with 0.30 mm, in which they were the lowest. In conclusion, external root resorption was more easily diagnosed when a smaller voxel size was used.