Treatment plan for maxillary third molars based on radiological findings varies among oral surgeons: a web-based "paper" clinic study.

OBJECTIVES: To evaluate variation in treatment plans and pathological findings related to maxillary second and third molars based on panoramic (PAN) images and cone beam CT (CBCT) among Danish and Dutch oral and maxillofacial surgeons. STUDY DESIGN: This web-based "paper" clinic contained 10 cases of impacted maxillary third molars comprising clinical information, PAN, and CBCT. Treatment plan and pathological findings were established based on clinical information and PAN, thereafter, based on CBCT by 28 surgeons. Options for treatment plan for third molars were no treatment, or tooth removal. Options for treatment plan for second molars were no treatment, tooth removal, or endodontic and/or filling therapy. The surgeons assessed external root resorption, marginal bone loss, and follicular space. RESULTS: A change in treatment plan between PAN and CBCT was registered between 0% and 43% of the surgeons among the cases. The surgeons did not agree completely on the treatment plan in any of the cases. Variation was present among the surgeons evaluating pathological findings. In several cases, severity of root resorption was rated worse in CBCT than in PAN. CONCLUSIONS: Variation in treatment plan and pathological findings was observed among surgeons. No correlation between change in pathological findings and change in treatment plan was found.

Long-term prognosis for teeth with external cervical resorption based on periapical images and cone beam CT: A clinical study.

AIM: To evaluate whether supplemental information from CBCT changed long-term prognosis for teeth with external cervical resorption (ECR) compared to periapical (PA) images. Furthermore, to assess predictive findings in PA images and evaluate which findings in CBCT affected the long-term prognosis of teeth with ECR. METHODOLOGY: One hundred and ninty-four patients, mean age 41.2, range 13-81, having 244 teeth with ECR were included. An initial long-term prognosis determined either good or poor was established based on intraoral images. Afterwards, the patients underwent CBCT, and final long-term prognosis was decided. From the PA images and CBCT, ECR using Heithersay's classification system, pulp involvement and extension of ECR was assessed. In CBCT, the number of surface lesion(s) was additionally assessed. Descriptive statistics evaluated changes in long-term prognosis after CBCT. Logistic regression analyses tested if findings in PA images and CBCT affected the long-term prognosis. RESULTS: Based on CBCT, out of 244 teeth the long-term prognosis was assessed to be poor for 173 (70.9%) teeth and good for 71 (29.1%) teeth. The long-term prognosis changed in 76 (31.1%) teeth after CBCT; 5 (2.0%) changed from poor to good, and 71 (29%) changed from good to poor long-term prognosis. In 81 (33.2%) teeth the H-class increased, and in 10 (4.1%) teeth the H-class decreased after assessing CBCT. In 70 (28.7%) teeth, there was a change from no pulp involvement to involvement of the pulp after CBCT; eight (3.3%) teeth changed in the opposite direction. H-class 2 and 4 in PA images significantly increased the probability for a change in long-term prognosis compared to an H-class 3 (p < .05). H-class 4, pulp involvement, ECR in the oral 1/3 of the root, and more than two surface lesions seen in CBCT significantly influenced a poor long-term prognosis (p < .05). CONCLUSIONS: Supplemental information from CBCT changed long-term prognosis in almost one third of teeth with ECR. In most cases, the long-term prognosis changed from good to poor. H-class 3 in PA images had a significant influence on change in long-term prognosis. Several findings in CBCT influenced a poor long-term prognosis.

Will supplemental cone beam computed tomography change the treatment plan of impacted maxillary canines based on 2D radiography? A prospective clinical study.

AIM: To evaluate the impact of cone beam computed tomography (CBCT) on treatment planning for impacted maxillary canines; secondly, to identify CBCT factors influencing a change in the treatment plan; and thirdly, to assess 2D radiographic factors that can aid in selecting appropriate candidates for CBCT. MATERIAL AND METHODS: Patients with impacted maxillary canines and an overlap of a neighboring tooth in 2D radiographs and the suspicion of root resorption were referred for CBCT examination. An initial treatment plan was based on 2D radiographs, and the final treatment plan was established after the CBCT examination. Logistic regression analyses and t-tests were performed to evaluate differences in radiographic findings between the groups with and without a change in treatment plan. RESULTS: The study prospectively included 125 impacted canines, and 43 (34.4%) of them had a change in treatment plan after the CBCT examination. The most common change was a modification in the direction of cantilever traction (n = 28; 22.4%), while the least common was the change in decision to remove/keep the canine (n = 4; 3.2%). The size of the alpha and lateral angles had a significant impact on the decision to change the treatment plan. Other radiographic findings did not influence a change in treatment plan. CONCLUSIONS: One-third of the canines had a change in treatment plan after supplemental CBCT examination. Canines with large alpha and lateral angles measured in the panoramic image were found to be significantly more likely to undergo changes in the initial direction of cantilever traction or changes to the canine extraction strategy following CBCT examination.

Jawbone measurements of edentulous sites related to implant planning using magnetic resonance imaging compared to cone beam computed tomography: An ex vivo study.

AIM: 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. MATERIAL AND METHODS: 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. RESULTS: 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). CONCLUSION: 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.

Does cone beam CT change the treatment decision for maxillary second and third molars? A prospective study.

OBJECTIVES: To evaluate whether information from CBCT changes the treatment plan for maxillary second and third molars and to examine clinical and radiographic parameters with an impact on treatment decision. METHODS: This prospective study included 260 maxillary third molars with superimposition onto the second molar in panoramic images (170 patients; mean age 28 years, range 16-63). An initial treatment plan was based on clinical findings and panoramic images. After CBCT, a final treatment plan was decided. Treatment was undertaken based on the final treatment plan. Through logistic regression analyses, impact of clinical and radiographic parameters on change in treatment plan, removal of the third molar vs no treatment, and removal of the second vs third molar were evaluated. RESULTS: The treatment plan changed in 82 cases (32%). Sixteen cases (6%) changed from removal of the third molar to removal of the second molar. Regression analyses showed that severe resorption in the second molar was significantly related to a change in treatment plan. Removal of a third molar was decided in 180 cases and regression analyses identified that mesioangulation of the third molar, marginal bone loss, superficial resorption, and age were significantly related to removal of the third molar vs no treatment. Thirty second molars were removed, and regression analyses showed that severe resorption was significantly related to removal of the second molar instead of the third molar. CONCLUSIONS: Parameters such as resorption evaluated in CBCT can modify the treatment decision, resulting in removal of the second and/or the third molar.

Risk factors observed in 2-dimensional radiographs for permanent injury of the inferior alveolar nerve after removal of mandibular third molars: a case-control study.

OBJECTIVE: To assess whether differences exist in signs observed in 2D radiographs of mandibular third molars between a case group of patients with and a control group without permanent sensory disturbance of the inferior alveolar nerve (IAN) after removal. STUDY DESIGN: Three observers blinded to patient status assessed radiographs from the case group (n=162) and the control group (n=172). Two new signs, craniocaudal relation of the roots and the mandibular canal and position of the canal over the roots; and 4 "classic" signs, interruption of the white borders of the canal, darkening of the roots, narrowing of the canal lumen, and diversion of the canal over the roots were registered. Chi-square tests assessed differences in distribution of radiographic signs between the groups. Odds ratios expressed the association between radiographic signs and permanent sensory disturbance. Inter- and intraobserver reliability values were calculated. RESULTS: We found significantly more teeth with roots positioned inferiorly to the canal borders (P<0.001; OR 4.1-5.3) and with the canal superimposed over the upper or middle third of the roots (P<0.001; OR 2.6-3.9) in the case group than in the control group. Inter- and intraobserver reproducibility was excellent for roots inferior to the canal borders and fair to good for canal superimposition. CONCLUSIONS: Two radiographic signs are valid predictors of permanent sensory disturbance of the IAN in 2D radiographs.

Magnetic resonance imaging artefacts caused by orthodontic appliances and/or implant-supported prosthesis: a systematic review.

OBJECTIVES: Dental materials, including orthodontic appliances and implants, are commonly mentioned as a possible source of artefacts in magnetic resonance imaging (MRI). The aim of the present study was to undertake a systematic review of the relevant literature on MR image artefacts due to dental materials, limited to orthodontic appliances and implant-supported dental prosthesis, on both technical and diagnostic levels. METHODS: The MEDLINE (PubMed) bibliographic database was searched up to September 2020. The search was limited to studies published in English, using the search string: (MRI or magnetic resonance) and (artefact or artifact) and (dental or ortho or implant or restoration or restorative). The studies were assessed independently by three reviewers, focusing on the following parameters: MRI sequences, tested materials, assessed parameters, efficacy level and outcome. RESULTS: The search strategy yielded 31 studies, which were included in this systematic review. These studies showed that metallic dental materials, commonly present in orthodontic appliances and implant-supported dental prosthesis led to diverse types/severities of artefacts in MR images. Fifteen studies were in vivo, based on human subjects. The studies differed substantially in terms of tested materials, assessed parameters, and outcome measurements. CONCLUSIONS: Metallic dental materials cause artefacts of diverse types and severities in MR images of the head and neck region. However, the diagnostic relevance of the investigated artefacts for the diverse MRI applications is yet to be studied.

Alveolar bone measurements in magnetic resonance imaging compared with cone beam computed tomography: a pilot, ex-vivo study.

OBJECTIVES: To compare alveolar bone height and width measurements from zero-echo-time MRI (ZTE-MRI) and cone beam CT (CBCT), in human specimens. MATERIAL AND METHODS: Twenty posterior edentulous sites in human cadaver specimens were imaged with CBCT and ZTE-MRI. Bone height and width at 1, 3, 5, 7 and 9 mm from the top of the alveolar ridge was measured by two trained observers in cross-sections of a site where an implant was to be planned. Twenty percent of the sample was measured in duplicate to assess method error and intra-observer reproducibility (ICC). The differences between CBCT and ZTE-MRI measurements were compared (t-test). RESULTS: Inter- and intra-observer reproducibility was >0.90. The method error (average between observers) for bone height was 0.45 mm and 0.39 mm, and for bone width (average) was 0.52 mm and 0.80 mm (CBCT and ZTE-MRI, respectively). The majority of the bone measurement differences were statistically insignificant, except bone width measurements at 5 mm (p ≤ .05 for both observers). Mean measurement differences were not larger than the method error. CONCLUSION: ZTE-MRI is not significantly different from CBCT when comparing measurements of alveolar bone height and width.

Early detection of external cervical resorption in posterior teeth: a radiographic, cross-sectional study of an adolescent population.

OBJECTIVES: To establish the prevalence and severity of external cervical resorption (ECR) in posterior teeth observed in bitewing (BW) radiographs in an epidemiological study of a 17-year-old patient population from community dentistry. Furthermore, to assess the potential predisposing factors for ECR. METHODS: Posterior BWs from 5596 patients (2717 females, 2879 males; mean age 17.8 years) were assessed by three observers in order to detect ECR (using Heithersay's classification system, severity classes 1-4). When ECR was suspected, cone beam CT (CBCT) was offered to verify diagnosis. Prevalence was estimated based on ECR suspected in BWs and finally in CBCT. Possible predisposing factors (orthodontic treatment, trauma, and periodontal disease) were recorded and assessed for association with ECR. RESULTS: In 41 patients, ECR was suspected in BWs (suspected prevalence 0.73%). 32 patients accepted CBCT examination, of which eight were verified to have ECR (final prevalence 0.18%). In 24 patients, other disease entities and abnormal tooth morphology, that had mimicked ECR in BWs, excluded ECR in CBCT. ECR severity ranged from class 1-3 in BW and 2-4 in CBCT. All but one case had not been diagnosed by the patient's community dentist. No statistically significant association between predisposing factors and ECR was identified. CONCLUSIONS: ECR had low prevalence in this adolescent population, as observed in both BWs and CBCT. Still, early detection of ECR is important for treatment prognosis, and attention should be paid to this disease entity when assessing BWs obtained for other diagnostic purposes. CBCT may subsequently aid in verifying the disease.

Effect of data binning and frame averaging for micro-CT image acquisition on the morphometric outcome of bone repair assessment.

Despite the current advances in micro-CT analysis, the influence of some image acquisition parameters on the morphometric assessment outcome have not been fully elucidated. The aim of this study was to determine whether data binning and frame averaging affect the morphometric outcome of bone repair assessment using micro-CT. Four Wistar rats' tibiae with a surgically created bone defect were imaged with micro-CT six times each, frame averaging set to 1 and 2, and data binning set to 1, 2 and 4, for each of the averaging values. Two-way ANOVA followed by Bonferroni tests assessed the significance of frame averaging and data binning on a set of morphometric parameters assessed in the image volumes (p < 0.01). The effect of frame averaging was not significant for any of the assessed parameters. Increased data binning led to larger trabecular thickness. In contrast, smaller bone volume fraction and bone volume were found as data binning increased. Trabeculae number and trabecular separation were not influenced by any of the parameters. In conclusion, the morphometric outcome of bone repair assessment in micro-CT demonstrated dependency upon data binning, but not frame averaging. Therefore, image acquisition of small anatomical structures (e.g., rat trabeculae) should be performed without data binning.

Reliability of radiographic findings in large FOV CBCTs of mandibular third molars as basis for pre-operative patient information.

OBJECTIVE: The aim of this study was to assess the relation between radiographic findings in large field of view (FOV) cone beam computed tomography (CBCT) exams and clinical findings of mandibular third molars in relation to the pre-operative patient information. MATERIAL AND METHODS: Two hundred and nine mandibular third molars in 134 orthognathic patients examined with CBCT were removed. Three observers assessed tooth- and mandibular canal-related variables in CBCT images, and the findings were correlated to clinical findings during surgery for all observers: tooth angulation, number and morphology of roots and close relationship between the tooth and the mandibular canal. Moreover, positive (PPV) and negative (NPV) predictive values and positive (LR+) and negative (LR-) likelihood ratios were calculated for the canal-related variables. Inter- and intra-observer reproducibility was expressed as percentage accordance and kappa-statistics. RESULTS: Generally, there was high correlation between radiographic and clinical tooth-related variables. The opposite was true for the canal-related variables, since the PPV and LR + were low. The highest PPV and LR + were found when the mandibular canal was positioned between the roots of the third molar. CONCLUSIONS: Tooth-related findings in CBCT are reliable, whereas mandibular canal-related findings should not affect the information provided to the patient pre-operatively.

Impact of cone beam CT on diagnosis of external cervical resorption: the severity of resorption assessed in periapical radiographs and cone beam CT. A prospective clinical study.

OBJECTIVES: To compare the severity of external cervical resorption (ECR) observed in periapical (PA) images and cone beam CT (CBCT) using the Heithersay classification system and pulp involvement; and to assess inter- and intraobserver reproducibility for three observers. METHODS: CBCT examination was performed in 245 teeth (in 190 patients, mean age 40 years, range 12-82) with ECR diagnosed in PA images. Three observers scored the severity of ECR using the Heithersay classification system (severity class 1-4) and pulp involvement (yes/no) in both PA images and CBCT. Percentage concordance and κ-statistics described observer variation in PA images and CBCT for both inter- and intraobserver reproducibility. RESULTS: For all three observers, the ECR score was the same in the two modalities in more than half of cases (average 59%; obs1: 54%, obs2: 63%, obs3: 61%). However, in 38% (obs1: 44%, obs2: 33%, obs3: 36%) of the cases, the observers scored more severe ECR in CBCT than in PA images (p < 0.001). The ECR score changed to a less severe score in CBCT only in 3% (obs1: 1%, obs2: 4%, obs3: 4%). For pulp involvement, 14% (obs1: 7%, obs2: 20%, obs3: 15%) of the cases changed from "no" in PA images to "yes" in CBCT. In general, κ values were higher for CBCT than for PA images for both the Heithersay classification score and pulp involvement. CONCLUSIONS: ECR was generally scored as more severe in CBCT than PA images using the Heithersay classification and also more cases had pulp involvement in CBCT.

Sella Turcica Area and Location of Point Sella in Cephalograms Acquired with Simulated Patient Head Movements.

AIM AND OBJECTIVE: This study assesses changes in the sella turcica area (STA) and location of the cephalometric point sella (S) on lateral cephalograms acquired by charge-coupled device (CCD)-based cephalostats with and without simulated patient head movements. MATERIALS AND METHODS: A real skull was placed on a robot, able to simulate four head movements (anteroposterior translation/lifting/nodding/lateral rotation) at three distances (0.75/1.5/3 mm) and two patterns (returning to 0.5 mm away from the start position/staying at maximum movement excursion). Two ProMax-2D cephalostats (Dimax-3, D-3 or Dimax-4, D-4), and an Orthophos-SL cephalostat (ORT) acquired cephalograms during the predetermined movements ("cases," 48 images/unit) and without movement ("controls," 24 images/unit). Three observers manually traced the contour of sella turcica and marked point sella using a computer mouse. STA was calculated in pixels2 by dedicated software based on the tracing. S was defined by its x and y coordinates recorded by the same software in pixels. Ten percent of the images were assessed twice. The difference between cases and controls (case minus control) for the STA and S (namely Diff-STA and Diff-S) was calculated and assessed through descriptive statistics. RESULTS: Inter- and intraobserver agreement ranged from moderate to good for STA and S. Diff-STA ranged from -42.5 to 12.9% (D-3), -15.3 to 9.6% (D-4), and -25.3 to 39.9% (ORT). Diff-S was represented up to 50% (D-3), 134% (D-4), and 103% (ORT) of the mean sella turcica diameter in control images. CONCLUSION: Simulated head movements caused significant distortion in lateral cephalograms acquired by CCD-based cephalostats, as seen from STA and S alterations, depending on the cephalostat. CLINICAL SIGNIFICANCE: Patient-related errors, including patient motion artifacts, are influential factors for the reliability of cephalometric tracing.

Magnetic Resonance Imaging for the Planning, Execution, and Follow-up of Implant-Based Oral Rehabilitation: Systematic Review.

PURPOSE: To undertake a systematic literature review of magnetic resonance imaging (MRI) employed in the three phases of implant-based oral rehabilitation: planning, execution, and follow-up. MATERIALS AND METHODS: MEDLINE (PubMed) and EMBASE bibliographic databases were searched up to January 2020 for studies assessing the use of MRI alone or in connection with CT and/or CBCT in the planning, execution, or follow-up of dental implant placement and/or bone grafting procedures in the maxilla or the mandible. Included studies were also assessed according to the diagnostic imaging efficacy scale presented by Fryback and Thornbury (F&T). RESULTS: The search strategy yielded 10 studies, which were included in the systematic review. Six studies focused on the implant planning phase, one on the immediate follow-up phase, and three on both planning and follow-up. No studies acquired signal from the bone. There was no consensus on the gold standard, MRI sequence, or field strength (T). One study reached F&T level 1, eight reached level 2, and one reached level 3. CONCLUSION: The possible transition from radiography to ionizing-radiation-free imaging through MRI is still a novelty in dentistry and has yet to establish itself as a viable imaging modality suitable for replacing CT and CBCT. More studies are needed on the accuracy of the diverse MRI possibilities when applied for implant planning, execution, and follow-up before this diagnostic method can be considered as a reality for the clinician.

Radiographic modalities for diagnosis of caries in a historical perspective: from film to machine-intelligence supported systems.

Radiographic imaging for the diagnosis of caries lesions has been a supplement to clinical examination for approximately a century. Various methods, and particularly X-ray receptors, have been developed over the years, and computer systems have focused on aiding the dentist in the detection of lesions and in estimating lesion depth. The present historical review has sampled accuracy ex vivo studies and clinical studies on radiographic caries diagnosis that have compared two or more receptors for capturing the image. The epochs of film radiography, xeroradiography, digital intraoral radiography, panoramic radiography and other extraoral methods, TACT analysis, cone-beam CT and artificial intelligence systems aiding in decision-making are reviewed. The author of this review (43 years in academia) has been involved in caries research and contributed to the literature in all the mentioned epochs.

Effect of a formalin-based fixation method on bone mineral content in human ex-vivo specimens.

OBJECTIVE: Histopathology of formalin-fixated human ex-vivo specimens may be used as reference standard for evaluation of diagnostic index tests like CBCT or MRI. The aim was to estimate changes in bone mineral content (BMC) over time in human ex-vivo bone specimens fixated in a formalin-based solution for 24 h followed by storage in an alcohol-based medium for six months, assessed by dual-energy X-ray absorptiometry (DXA). METHODOLOGY: Bone specimens (n = 19) from human ex-vivo mandibles donated for science were included. BMC was measured by DXA before fixation (D0), after 24 h of immersion fixation in a formalin-based solution (D1), and hereafter every 30 days (M1-M6) during storage in a 30% ethanol-based storage medium for 6 months. Changes in BMC from D0 to D1 and from D0 to M6 were calculated and mean change in BMC estimated. RESULTS: Mean change in BMC from D0 to D1 was -0.73% (95% CI -1.75%; 0.29%), and from D0 to M6 -1.19% (95% CI -2.14%; -0.23%). CONCLUSIONS: No changes in BMC of ex-vivo human bone specimens were found after 24 h formalin-based immersion fixation. After six months storage in an ethanol-based medium, BMC mean loss of 1% was detected. In this range, changes in BMC are not clinically relevant.

Effect of section thickness on cone beam computed tomography-based measurements of intrabony defects compared with clinical measurements.

BACKGROUND: It is unknown whether cone beam computed tomography (CBCT) image reconstruction characteristics, including section thickness, may affect linear bone measurements of periodontal intrabony defects. The aim of this study was to compare intrasurgical and CBCT-based linear measurements of intrabony defects focusing on CBCT section thickness. METHODS: Sixty-six intrabony defects were assessed in 21 patients with chronic generalized severe periodontitis. Linear measurements of alveolar bone (radiographic bone level [rBL]), assessed in CBCT images at diverse section thicknesses: 0.25 mm (voxel size), 1 mm, and 3 mm, were compared with clinical bone level (cBL) measurements obtained intrasurgically. To provide identical reference points for rBL and cBL measurements, individually adjusted grooves on the reference stent were prepared for each periodontal defect site. CBCT measurements were performed in two rounds by two trained observers. Observer agreement was assessed by intraclass correlation coefficients (ICC). ANOVA assessed the difference among cBL and rBL at different section thicknesses. RESULTS: Intra- and inter-observer agreement was excellent (ICC >0.99) and highly significant independent of the observer, evaluation round, and CBCT section thickness. Mean rBL in the diverse CBCT section thicknesses was very close to that measured clinically (cBL). There was no statistically significant difference between cBL and rBL for any section thickness, neither for the overall evaluated sites, nor the maxilla or mandible separately. CONCLUSIONS: No statistically significant difference between clinical and radiographic bone level for 0.25-, 1-, and 3-mm CBCT section thicknesses were observed when assessing intrabony periodontal defects.

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.

Head motion and perception of discomfort by young children during simulated CBCT examinations.

OBJECTIVES: To assess the frequency and characteristics (number, complexity, and distance) of head movements, and the perception of discomfort during simulated CBCT examinations in children, considering units with different patient positioning method and head immobilization device combinations. METHODS: Forty children (20 boys/20 girls, age range 10-14 years) were video-recorded during simulated CBCT examinations. Children were randomly allocated to a sequence of five CBCT units: Newtom-5G, Orthophos-SL, Cranex-3Dx (patient standing/sitting), and X1. The child scored his/her discomfort perception (visual scale) and the preferred/ill-favored unit. Three observers scored the videos (20% in duplicate): child movement (yes/no), number (<3/≥3/continuous), complexity (uniplanar/multiplanar) and distance (<3 mm/≥3 mm). κ statistics provided intra-/interobserver reproducibility. Severe/extreme motion was defined based on movement characteristics. Chi-square tests assessed the frequency differences of severe/extreme motion among the units, age and operator. Logistic regression analyses with severe/extreme motion as outcome were performed. RESULTS: The range of intra- and inter-observer reproducibility for movement observation was 0.78-0.89 and 0.61-0.64, respectively. Between 60% (Newtom-5G) and 100% (X1) of children moved during the examination. Severe/extreme motion was significantly related to unit and age. There was significantly less severe/extreme motion, when the child was in the supine position with a foam headrest as head support. The younger the child, the higher the risk for severe/extreme motion. The majority of the children preferred the unit with the supine position and a foam headrest. CONCLUSIONS: The prevalence of severe and extreme motion was associated with the unit's patient positioning method and head immobilization devices combined, and child age.

Effect of computer-assisted-learning and simulation clinics on dental students' cognitive and performance skills: panoramic image errors related to patient's head position.

OBJECTIVES: To assess dental students' ability to recognize head positioning errors in panoramic (PAN) images after individual learning via computer-assisted-learning (CAL) and in a simulation clinic (SIM). Both cognitive skills and performance in patient examination were assessed. METHODS AND MATERIALS: 60 students (mean age 23.25 years) participated in lectures on the relation between PAN-image errors and patient's head position. Immediately after they took a test, based on which they were randomized to three groups: control (CON) group, CAL group, and SIM group (both CAL and training in a simulation clinic with a phantom). 4-5 weeks after intervention/no intervention, all students individually examined a patient with PAN-exposure. A blinded rater, not knowing group allocation, supervised patient exposure and assessed student's performance (correct/incorrect head position in three planes). 1-2 weeks after, the students scored positioning errors in 40 PAN-images. Differences in cognitive test scores between groups were evaluated by ANOVA and in patient examination by χ2 tests, and within-group differences by sign-tests. RESULTS: No statistically significant difference in cognitive test scores was seen between the SIM and CAL group, while the CON group scored lower (p < 0.003). In all groups, several students positioned the patient incorrectly in the Frankfort horizontal plane. All students performed well in the sagittal plane. Students in SIM group positioned the patient more correctly in the coronal plane. CONCLUSIONS: Training with CAL increased students' cognitive skills compared with a control group. Simulated patient exposure with a phantom increased to some extent their performance skills in examination of patients.