Quantitative assessment of cleft volume and evaluation of cleft's impact on adjacent anatomical structures using CBCT imaging.

OBJECTIVES: To determine pre-operative cleft volume and evaluate cleft´s impact on surrounding anatomical structures in children and adolescents with orofacial clefts using cone bean computed tomography (CBCT) imaging. METHODS: The present retrospective study retrieved CBCT examinations of 68 patients from a previous study. The examinations had been exposed either before (n = 53) or after (n = 15) alveolar bone grafting. Pre-operative volume of cleft was determined, and type and location were evaluated. Morphological changes on the adjacent anatomical structures, including the incisive foramen, the nasal septum and floor, and the inferior turbinate, were assessed. RESULTS: Mean bilateral cleft volume was 0.76 cm3, while mean unilateral cleft volume was 1.08 cm3; the difference was significant (p < 0.001). Variation in cleft volume, however, was large. The incisive foramen was not visible in the majority of cases with bilateral clefts (71%); the difference was significant (p = 0.001). In cases with unilateral clefts, the nasal septum in 87% was curved towards the cleft or graft side. Also, the mean size of the widest part of the inferior turbinate was 8.8 mm on the cleft or graft side and 10.4 mm on the non-cleft side. The difference was significant (p < 0.001). CONCLUSIONS: When required, CBCT is a feasible method for quantitatively illustrating alveolar clefts and their impact on the morphological development of surrounding structures. Variation in cleft volume was large.

Effects of premolar extraction and orthodontic treatment in adolescents - a retrospective cephalometric study.

OBJECTIVES: To evaluate the cephalometric effects of premolar extraction on skeletal and dental parameters, and on the soft tissues, in patients subsequently treated with fixed appliances. Prevalence and severity of external apical root resorption due to premolar extraction were also examined. MATERIALS AND METHODS: The dental records of 79 patients treated with fixed appliances were retrieved (groups: extraction, n = 19; non-extraction, n = 60). Pre- and post-treatment statuses of skeletal, dentoalveolar, and soft tissue variables were analyzed on lateral cephalograms to determine change. Periapical radiographs of the maxillary incisors were assessed for external apical root resorption using the Levander & Malmgren index. The t-test, Mann-Whitney U test, chi-squared test, and Kruskal-Wallis test were used to analyze the data. Significance was set at p < .05. RESULTS: Changes in the protrusion and proclination of the incisors and in lip position were significantly different between the groups. Prevalence of external apical root resorption in the two groups was similar. CONCLUSIONS: Our findings suggest that extraction therapy affects dentoalveolar traits but not jaw position, nor the risk of root resorption, in patients treated with fixed appliances.

Comparison of absorbed doses and organ doses measured with thermoluminescent dosimeters and Gafchromic film for cone beam computed tomography examination of the posterior mandibular region in a head phantom.

OBJECTIVES: We aimed to map the correlation between thermoluminescent dosimeters (TLDs) and Gafchromic film for measuring absorbed doses and to compare minimum, maximum, and mean absorbed doses over larger regions of interest and at various craniofacial organs and tissues during cone beam computed tomography (CBCT) exposure of the mandibular third molar region. STUDY DESIGN: We positioned TLDs at 75 measurement points in a head phantom. Gafchromic film was cut to the same shape as the 5 levels of the phantom and was placed on top of the TLDs. Both dosimetry methods thus included the surface of each level simultaneously. CBCT scans were made using a 5 × 5 cm field of view and a rotation angle of 200°. Measurements included absorbed dose distributions, doses at all 75 points, and minimum, maximum, and mean doses within organs and tissues. RESULTS: The correlation of point-dose measurements at all TLD sites with doses measured on film was strong (R2 = 0.9687), with greatest correlation at lower doses (<2 mGy). Large deviations between TLD and film measurements of minimum and maximum doses and absorbed doses to the organs occurred at all 5 levels. TLD positioning failed to cover several organ sites; for these, only absorbed dose measurements from the film were available. CONCLUSIONS: TLDs were unable to sample dose distributions and gradients accurately. The characteristics of Gafchromic LD-V1 film make it a favorable alternative in dental CBCT dosimetry.

Visibility of anatomical landmarks in the region of the mandibular third molar, a comparison between a low-dose and default protocol of CBCT.

OBJECTIVE: Optimization of radiographic examinations is essential for radiation protection. The objective of the study was to investigate the clinical applicability of a low-dose CBCT protocol as compared to the default for pre-surgical evaluation of mandibular third molars. MATERIAL & METHODS: Forty-eight patients (62 teeth) referred for pre-surgical mandibular third molar investigation were recruited after justification for CBCT. Two CBCT scans of each site were made using a default protocol and a low-dose protocol (Veraviewepocs 3D F40, J Morita Corp, Kyoto, Japan). The low-dose protocol had the same tube potential (90 kV) and exposure time (9.4 s) as the default, but with reduced tube current, from 5 mA to 2 mA. Four observers evaluated the visibility of five relevant anatomical variables. Image quality was ranked on a 3-point scale as diagnostically acceptable, doubtful, or unacceptable. The Wilcoxon signed-rank test compared differences between the two protocols. The significance level was set at p ≤ .05. RESULTS: No significant differences were found between the two protocols for any observer regarding the visibility of the relationship and proximity between the roots and the mandibular canal; root morphology; and possible root resorption of the second molar. The periodontal ligament differed significantly in visibility between the two protocols (p ≤ .05). CONCLUSIONS: This study indicates that a low-dose CBCT protocol with a 60% reduction of the tube current provides, in most cases, acceptable image quality for pre-surgical assessment of mandibular third molars. Optimization of CBCT protocols should be a priority according to recommended guidelines.

Do preterm-born children and adolescents have greater need for dental care as compared to full term-born controls?

BACKGROUND: Preterm birth has been shown to cause various long-term health issues. Children who were born preterm have also been observed to have more dental behaviour management problems (DBMP) during dental examinations and treatment than children born full term. It is known that dental radiographic examinations can be uncomfortable and cause anxiety in paediatric patients. Thus, our aims were to retrospectively compare dental care related examinations and treatments carried out in three different age intervals (3-6 years, 7-12 years, and 13-19 years) among preterm- and full-term born children and adolescents. METHODS: The present study included 311 patient files: 122 very preterm-born and 33 extremely preterm-born children and adolescents (< 32 gestational weeks). A matched control group of 156 full term-born children and adolescents (≥ 37 gestational weeks) was analysed for comparison. Various factors, including DBMP, missed appointments, dental caries, and radiographic examinations, were retrieved from the dental records for three age intervals: 3-6 years, 7-12 years, and 13-19 years. RESULTS: Extremely preterm-born children missed significantly more dental appointments and presented with more DBMP during dental examinations and treatment than full term-born children in the 3-6-year age group; the same was observed for the very preterm-born in the 7-12-year age group. No significant differences in DBMP during bitewing and periapical examinations or in number of bitewing, periapical and panoramic radiographs occurred between the groups in any age interval. CONCLUSION: Preterm-born children and adolescents may need more flexibility in booking and receive reminders for scheduled visits with the general dental team. Due to the non-significant differences in dental care related oral examinations and treatments, the same dental care service may be applied to the preterm- and full-term born children and adolescents.

The Changes in Size of Periapical Lesions after Root Canal Treatments Assessed by Digital Periapical Radiography and Cone-Beam Computed Tomography: A 2-Years Prospective Clinical Study.

Background and Objectives: There is limited information regarding comparison of long-term dynamics of periapical bone destruction estimated by digital periapical radiography (DPR) and by cone-beam computed tomography (CBCT). This study aimed to compare the radiographically assessed periapical changes of endodontically treated teeth over 2 years of follow-up and to analyse disagreements in periapical lesion size estimates around the same roots using DPR and CBCT. Materials and Methods: A total of 176 endodontically treated teeth, of 128 patients with apical periodontitis, were assessed by DPR and CBCT, at baseline and after 2 years. All periapical radiolucencies were categorised by severity (S0, S1, S2, S3) concerning their size. Descriptive statistics were used to report distribution of the radiolucencies at baseline and at follow-up, and their size transitions over 2 years. Site-specific comparison of the radiolucencies identified by two methods was performed using Z test and Pearson's chi-square test. Results: majority of the detected radiolucencies were scored as S0: 65% and 68% at baseline; 89% and 83% at follow-up, by DPR and CBCT, respectively. Site-specific score comparison showed that disagreements comprised 18% and 20% of the total number of radiolucencies detected by DPR and CBCT, respectively. There were more disagreements between DPR and CBCT within categories S1 and S2 + S3 compared to S0: at baseline, they comprised 17-33% and after two years 62-95% of all detected radiolucencies within the category. 65% of non-matching score transitions over two years occurred between S0 and S1. The CBCT-based evaluation resulted in negative treatment outcomes for 10 more root canals than the DPR-based result. Conclusions: Most remarkable disagreement between DPR and CBCT recordings was observed within the radiolucency categories S2 and S3. However, the diagnostic accuracy of both radiographic methods was questionable as it resulted in a high proportion of non-matching S0-S1 lesion transitions over 2 years.

Radiographic imaging in relation to the mandibular third molar: a survey among oral surgeons in Sweden.

OBJECTIVES: To query the experience of oral surgeons concerning referral routines and preferences for radiographic imaging modality before surgical removal of mandibular third molars and investigate factors that influence imaging modality preferences. MATERIALS AND METHODS: Members of the Swedish Association of Oral and Maxillofacial Surgeons (n = 280) were invited to participate in a web-based digital survey concerning their experiences and use of three imaging modalities in pre-surgical assessment of mandibular third molar removal. The survey comprised multiple-choice questions and four cases depicted in images; respondents reported whether they would supplement the cases with other images and, if so, from which modality. RESULTS: The response rate was 64%. Panoramic radiographs were most commonly used in pre-surgical planning (response options: always or often), significant difference between professions (p = 0.039), and considered to facilitate treatment planning (87%), as was CBCT (82%); for 51%, CBCT reduced post-operative complications. Preferred modality for localizing the mandibular canal was fairly evenly distributed and for non-complex case, significant difference between subgroups of OMFS surgeons was found (p = 0.003) as to preference for intraoral radiographs. CONCLUSIONS: A majority of respondents received a report within 2 weeks of their referral for CBCT and would read the report and view the images before surgery. Image modality preference differed depending on case complexity, with a greater perceived need for CBCT. Profession and practical experience affected choice. CLINICAL RELEVANCE: Choice of imaging modality in mandibular third molar assessment is also important from dose delivery and social economy standpoints.

Aerodynamic characteristics in upper airways among orthodontic patients and its association with adenoid nasopharyngeal ratios in lateral cephalograms.

BACKGROUND: Adenoid hypertrophy among orthodontic patients may be detected in lateral cephalograms. The study investigates the aerodynamic characteristics within the upper airway (UA) by means of computational fluid dynamics (CFD) simulation. Furthermore, airflow features are compared between subgroups according to the adenoidal nasopharyngeal (AN) ratios. METHODS: This retrospective study included thirty-five patients aged 9-15 years having both lateral cephalogram and cone beam computed tomography (CBCT) imaging that covered the UA region. The cases were divided into two subgroups according to the AN ratios measured on the lateral cephalograms: Group 1 with an AN ratio < 0.6 and Group 2 with an AN ratio ≥ 0.6. Based on the CBCT images, segmented UA models were created and the aerodynamic characteristics at inspiration and expiration were simulated by the CFD method for the two groups. The studied aerodynamic parameters were pressure drop (ΔP), maximum midsagittal velocity (Vms), maximum wall shear stress (Pws), and minimum wall static pressure (Pw). RESULTS: The maximum Vms exhibits nearly 30% increases in Group 2 at both inspiration (p = 0.013) and expiration (p = 0.045) compared to Group 1. For the other aerodynamic parameters such as ΔP, the maximum Pws, and minimum Pw, no significant difference is found between the two groups. CONCLUSIONS: The maximum Vms seems to be the most sensitive aerodynamic parameter for the groups of cases. An AN ratio of more than 0.6 measured on a lateral cephalogram may associate with a noticeably increased maximum Vms, which could assist clinicians in estimating the airflow features in the UA.

Prognostic validity of the Periapical and Endodontic Status Scale for the radiographically assessed 2-year treatment outcomes in teeth with apical periodontitis: a prospective clinical study.

BACKGROUND: Endodontic treatment planning and treatment success evaluation are largely based on radiographic assessment of anatomical and treatment-related parameters of teeth with apical periodontitis (AP). This prospective clinical study aimed to assess radiographically the 2-year endodontic treatment outcomes for teeth with AP, and to evaluate prognostic validity of Periapical and Endodontic Status Scale (PESS). METHODS: A total of 128 patients, representing 176 teeth with AP were examined by cone-beam computed tomography at baseline and at 24 months after endodontic treatment. Treatment outcome was evaluated using estimates of periapical radiolucency and the relationship between anatomical structures and location. The strength of the associations between these and treatment-related parameters was tested by logistic regression analysis. PESS sensitivity and specificity were calculated for every treatment risk group (low, moderate, high) of teeth. RESULTS: One hundred and fifty-seven teeth, representing 350 root canals had a positive treatment outcome, while 19 teeth, representing 53 root canals had a negative treatment outcome at 24 months. The probability of negative outcome was 25 times higher in the moderate/high-risk group than in the mild-risk group of teeth (OR = 25.1; 95%CI [12.2-51.5]). Pre-treatment complications and retreatment cases with radiolucency were associated with negative outcomes (OR = 35.9; 95%CI [12.6-102.4]; OR = 26.437; 95%CI [10.9-64.1], respectively). PESS sensitivity and specificity was over 80% in all risk groups except for high risk group, due to very low number of cases. CONCLUSIONS: Endodontic treatment outcome depends on the severity of periapical changes. The presence of complications and retreatment cases with periapical lesions are associated with negative treatment outcome. The PESS is a valid instrument to predict outcome of teeth with low-moderate treatment risk of AP.

Effect of Rapid Maxillary Expansion on Upper Airway Morphology: A Retrospective Comparison of Normal Patients versus Patients with Enlarged Adenoid Tissue.

Objectives The present study evaluated the effect of rapid maxillary expansion (RME) on the morphology of the upper airway (UA) by calculating cross-sectional areas and volumes and comparing the effect in patients with a normal-sized adenoid with the effect in patients with an enlarged adenoid. Study design: Seventeen patients met the inclusion criteria. We constructed 3D models of the UA on cone-beam computed tomography images to calculate cross-sectional areas and volumes at the levels of the nasopharyngeal, retropalatal, and retroglossal airways. Patients were divided into two groups: group 1 was comprised of patients with an adenoidal nasopharyngeal (AN) ratio < 0.6 and group 2 with an AN ratio ≥ 0.6. Paired samples t-tests assessed any area and volumetric changes of the UA after RME. Changes in degree of nasal obstruction, calculated as the AN ratio, was then compared for the two groups. An independent samples t-test compared volumetric changes in the nasopharynx between the two groups before and after RME. Results Changes in cross-sectional areas and volumes of the UA due to RME were not significant. The effects of RME on AN ratio (11 % vs 0 %) and nasopharyngeal volume (36.8 % vs 5.97%) were somewhat larger in group 2 patients who had adenoid-associated nasal obstruction compared with group 1 patients with a normal-sized adenoid; however, the differences were not significant. Conclusions After RME, the patients with an enlarged adenoid had more increases in nasopharyngeal volume compared with those with normal adenoid, despite there was no significant difference.

Orthodontic appliances and MR image artefacts: An exploratory in vitro and in vivo study using 1.5-T and 3-T scanners.

PURPOSE: The aim of this study was to assess the artefacts of 12 fixed orthodontic appliances in magnetic resonance images obtained using 1.5-T and 3-T scanners, and to evaluate different imaging sequences designed to suppress metal artefacts. MATERIALS AND METHODS: In vitro, study casts of 1 adult with normal occlusion were used. Twelve orthodontic appliances were attached to the study casts and scanned. Turbo spin echo (TSE), TSE with high readout bandwidth, and TSE with view angle tilting and slice encoding for metal artefact correction were used to suppress metal artefacts. Artefacts were measured. In vivo, 6 appliances were scanned: 1) conventional stainless-steel brackets; 2) nickel-free brackets; 3) titanium brackets; 4) a Herbst appliance; 5) a fixed retainer; and 6) a rapid maxillary expander. The maxilla, mandible, nasopharynx, tongue, temporomandibular joints, and cranial base/eye globes were assessed. Scores of 0, 1, 2, and 3 indicated no artefacts and minor, moderate, and major artefacts, respectively. RESULTS: In vitro, titanium brackets and the fixed retainer created minor artefacts. In vivo, titanium brackets caused minor artefacts. Conventional stainless-steel and nickel free brackets, the fixed retainer, and the rapid maxillary expander caused major artefacts in the maxilla and mandible. Conventional stainless-steel and nickel-free brackets caused major artefacts in the eye globe (3-T). TSE with high readout bandwidth reduced image artefacts in both scanners. CONCLUSION: Titanium brackets, the Herbst appliance, and the fixed retainer caused minor artefacts in images of neurocranial structures (1.5-T and 3-T) when using TSE with high readout bandwidth.

The effect of rapid maxillary expansion on the upper airway's aerodynamic characteristics.

BACKGROUND: The effect of rapid maxillary expansion (RME) on the upper airway (UA) has been studied earlier but without a consistent conclusion. This study aims to evaluate the outcome of RME on the UA function in terms of aerodynamic characteristics by applying a computational fluid dynamics (CFD) simulation. METHODS: This retrospective cohort study consists of seventeen cases with two consecutive CBCT scans obtained before (T0) and after (T1) RME. Patients were divided into two groups with respect to patency of the nasopharyngeal airway as expressed in the adenoidal nasopharyngeal ratio (AN): group 1 was comprised of patients with an AN ratio < 0.6 and group 2 encompassing those with an AN ratio ≥ 0.6. CFD simulation at inspiration and expiration were performed based on the three-dimensional (3D) models of the UA segmented from the CBCT images. The aerodynamic characteristics in terms of pressure drop (ΔP), maximum midsagittal velocity (Vms), and maximum wall shear stress (Pws) were compared by paired t-test and Wilcoxon test according to the normality test at T0 and T1. RESULTS: The aerodynamic characteristics in UA revealed no statistically significant difference after RME. The maximum Vms (m/s) decreased from 2.79 to 2.28 at expiration after RME (P = 0.057). CONCLUSION: The aerodynamic characteristics were not significantly changed after RME. Further CFD studies with more cases are warranted.

Evaluation of Panoramic Radiographs in Relation to the Mandibular Third Molar and to Incidental Findings in an Adult Population.

OBJECTIVES: The aim was to evaluate the characteristics of the mandibular third molars, especially in relation to the inferior alveolar nerve. Further aims were to investigate incidental findings in panoramic radiographs in an adult population, and to investigate image quality related to patient positioning. MATERIALS AND METHODS: From a previous study with 451 randomly selected adult participants who lived in Sweden, 442 panoramic radiographs from four dental public health clinics were used. The third molars' characteristics and relation to inferior alveolar nerve were evaluated. Incidental findings and patient positioning were recorded. STATISTICAL ANALYSIS: Frequency analysis was used to investigate the occurrence of all findings and their possible interconnections. Whether the patients' age or gender had an impact or not was also analyzed. RESULTS: The third molars were erupted in vertical position among 73% regardless of age. When retained or semi-retained, they were most commonly in mesioangular positions. The inferior alveolar nerve was located inferior to the roots in 52%, whereas an overlapped position was most common if the third molar was retained (90%), semi-retained (83%) or the age was less than 30 years (66%). Common incidental findings were apical radiolucencies, idiopathic osteosclerosis, and tooth fragments. Suboptimal patient positioning was found in one-third of the radiographs. CONCLUSIONS: Panoramic radiography is a useful method to evaluate third molar prior to surgical removal and may be the only image required. Most incidental findings on panoramic radiographs does not seem to require any further odontological management.

Accuracy of cone-beam computed tomography is limited at implant sites with a thin buccal bone: A laboratory study.

BACKGROUND: To evaluate whether buccal bone thickness (BBT), implant diameter, and abutment/crown material influence the accuracy of cone-beam computed tomography (CBCT) to determine the buccal bone level at titanium implants. METHODS: Two implant beds (i.e., narrow and standard diameter) were prepared in each of 36 porcine bone blocks. The implant beds were positioned at a variable distance from the buccal bone surface; thus, resulting in three BBT groups (i.e., >0.5 to 1.0; >1.0 to 1.5; >1.5 to 2.0 mm). In half of the blocks, a buccal bone dehiscence of random extent ("depth") was created and implants were mounted with different abutment/crown material (i.e., titanium abutments with a metal-ceramic crown and zirconia abutments with an all-ceramic zirconia crown). The distance from the implant shoulder to the buccal bone crest was measured on cross-sectional CBCT images and compared with the direct measurements at the bone blocks. RESULTS: While abutment/crown material and implant diameter had no effect on the detection accuracy of the buccal bone level at dental implants in CBCT scans, BBT had a significant effect. Specifically, when BBT was ≤1.0 mm, a dehiscence was often diagnosed although not present, that is, the sensitivity was high (95.8%), but the specificity (12.5%) and the detection accuracy (54.2%) were low. Further, the average measurement error of the distance from the implant shoulder to the buccal bone crest was 1.6 mm. CONCLUSIONS: Based on the present laboratory study, BBT has a major impact on the correct diagnosis of the buccal bone level at dental titanium implants in CBCT images; in cases where the buccal bone is ≤1 mm thick, detection of the buccal bone level is largely inaccurate.

Comparison of Selected Anatomical and Treatment-related Diagnostic Parameters Estimated by Cone-Beam Computed Tomography and Digital Periapical Radiography in Teeth with Apical Periodontitis.

OBJECTIVES: To compare selected anatomical and treatment-related diagnostic parameters estimated by cone-beam computed tomography and by digital periapical radiography in teeth with apical periodontitis, and to evaluate reliability of different examiners in interpretation of images obtained by both methods. MATERIAL AND METHODS: Teeth with apical periodontitis were evaluated independently by 2 endodontists and 1 radiologist based on 128 cone-beam computed tomography (CBCT) and 162 digital periapical radiography (DPR) images. Anatomical (size, relation with root, location of periapical radiolucency) and treatment-related (canal obturation length, homogeneity, coronal seal) parameters were assessed. Fleiss kappa reflected inter-observer agreement while intra-examiner agreement was estimated by Cohen's kappa. McNemar and McNemar-Bowker tests served for evaluation of differences between CBCT- and DPR-based estimates. RESULTS: Cohen's kappa ranged from 0.62 to 1 for all examiners. Fleiss kappa values were nearly perfect for majority of parameters. Diagnostic discrepancy between methods was found for size of radiolucency that in 15 - 17% cases was larger, and in 25 - 28% smaller in DPR than in CBCT images. DPR revealed 20% of root canals scored as non-obturated while in CBCT - obturation present. Canal obturation was rated as homogenous by CBCT, while absent or non-homogenous by DPR, in 17 - 23%, and 11 - 14% of cases, respectively. Radiologist detected more root perforations in CBCT than in DPR images. CONCLUSIONS: Good intra- and inter-examiner agreement for anatomical and treatment-related diagnostic parameters was achieved using cone-beam computed tomography and digital periapical radiography methods and demonstrated similar diagnostic capability, although variation regarding root perforations and canal obturation quality was observed.

Web-based educational programme for temporomandibular joint assessment with cone-beam computed tomography.

OBJECTIVES: To develop and evaluate an educational web-based programme for temporomandibular joint (TMJ) assessment using cone-beam computed tomography (CBCT). METHODS: A web-based educational programme was designed for TMJ assessment using CBCT images. Fifteen CBCT cases of the TMJ (three-dimensional reconstructed volumes) and an assessment module based on image analysis criteria in the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) were added to the programme. Thirty-six undergraduate dental students were invited to test the programme by assessing all cases twice: before and after 2 months of training. Participants submitted written subjective evaluations of the programme. RESULTS: The web-based programme can be accessed on Malmö University webpage (www.cbct-tmj.mau.se). Despite limited CBCT learning in their undergraduate training and not using the programme in the 2-month interval, the students were able to correctly diagnose 80% of the cases at the second assessment. Their diagnoses, however, did not differ significantly from the first assessment. Overall, the students were satisfied with the programme and considered it user-friendly. CONCLUSION: The web-based educational programme that was developed in the present study and tested by dental students could be a useful educational tool for TMJ assessment using CBCT.

Evaluation of a low-dose protocol for cone beam computed tomography of the temporomandibular joint.

OBJECTIVE: Evaluation of cone beam CT (CBCT) examination with a low-dose scanning protocol for assessment of the temporomandibular joint (TMJ). METHODS: 34 adult patients referred for CBCT imaging of the TMJ underwent two examinations with two scanning protocols, a manufacturer-recommended protocol (default) and a low-dose protocol where the tube current was reduced to 20% of the default protocol. Three image stacks were reconstructed: default protocol, low-dose protocol, and processed (using a noise reduction algorithm) low-dose protocol. Four radiologists evaluated the images. The Sign test was used to evaluate visibility of TMJ anatomic structures and image quality. Receiver operating characteristic analyzes were performed to assess the diagnostic accuracy. κ values were used to evaluate intraobserver agreement. RESULTS: With the low-dose and processed protocols, visibility of the TMJ anatomical structures and overall image quality were comparable to the default protocol. No significant differences in radiographic findings were found for the two low-dose protocols compared to the default protocol. The area under the curves (Az) averaged for the low-dose and processed protocols, according to all observers, were 0.931 and 0.941, respectively. Intraobserver agreement was good to very good. CONCLUSION: For the CBCT unit used in this study, the low-dose CBCT protocol for TMJ examination was diagnostically comparable to the manufacturer-recommended protocol, but delivered a five times lower radiation dose. There is an urgent need to evaluate protocols for CBCT examinations of TMJ in order to optimize them for a radiation dose as low as diagnostically acceptable (the as low as diagnostically acceptable principle recommended by NCRP).

Dose distributions in adult and child head phantoms for panoramic and cone beam computed tomography imaging of the temporomandibular joint.

OBJECTIVES: The aim of this study was to map and compare the distributions of absorbed doses with Gafchromic film for panoramic radiography and cone beam computed tomography (CBCT) examinations of the temporomandibular joint (TMJ) by using adult and child phantoms. STUDY DESIGN: Gafchromic films were placed at 5 selected levels of anthropomorphic head phantoms of an adult and a child. Clinical protocols for panoramic and CBCT imaging of the TMJ were used for three 2-dimensional or 3-dimensional dental x-ray units. Mean absorbed doses in a set of radiosensitive tissues within the oral and maxillofacial regions were estimated. RESULTS: The absorbed doses varied considerably among and within radiosensitive tissues. The bone surface and the salivary glands received the highest absorbed doses compared with other tissues, in both panoramic and CBCT examinations of the TMJ. The radiation burden to the adult phantom was generally higher than that to the child phantom. Small right and left fields of view were associated with lower amounts of radiation, in contrast to a single larger field of view. CONCLUSIONS: The absorbed dose within all radiosensitive tissues varied considerably in relation to examination type, x-ray unit, clinical settings, and patient age. The mean doses were smaller when using 2 (bilateral) 4 × 4 cm volumes than with use of one 14 × 5 cm volume.

Reliability of marginal bone level measurements on digital panoramic and digital intraoral radiographs.

OBJECTIVES: The aim of this study was to evaluate the reliability of bitewing and panoramic radiographs in marginal bone level measurements in terms of inter- and intra-observer agreement. METHODS: Fifty paired bitewing and panoramic images were used. Eight observers measured marginal bone level at the mesial and distal surfaces of tooth 25 and tooth 35. Thus, in total 100 radiographs of 400 measurements were obtained for each observer. To evaluate intra-observer agreement, three observers re-evaluated the radiographs after a minimum of 1 month. Intra-class correlation coefficient (ICC) was applied to evaluate the inter- and intra-observer agreement. The t test was applied to assess possible difference in measurement between bitewing and panoramic radiographs. RESULTS: The mean ICC value of inter-observer agreement was 0.85 for bitewing and 0.66 for panoramic radiographs. The mean intra-observer agreement was 0.92 and 0.76 for bitewing and panoramic radiographs, respectively. There was no statistically significant difference between bitewing and panoramic radiographs in measurements of marginal bone level on maxillary tooth 25, whereas a statistically significant difference was found between the two image modalities on mandible tooth 35. CONCLUSION: Bitewing examination should be the choice of image modality for assessment of marginal bone level at premolar region due to good to excellent reliability and low radiation dose. However if a panoramic radiograph already exists, a rough estimation of marginal bone level at premolar region is clinically acceptable bearing in mind that the bone height of the mandible premolar region might be overestimated as compared to bitewing radiograph.

CBCT of Swedish children and adolescents at an oral and maxillofacial radiology department. A survey of requests and indications.

Objectives: This retrospective study investigated requests and indications for cone-beam computed tomography (CBCT) in children and adolescents over a 3-year period at one oral and maxillofacial radiology department. Specific aims were to determine what technical settings were used, which caregivers write the referrals, and how often and for what reasons re-exposure was necessary.Materials and methods: Patients <19 years of age who had been referred to the department and undergone a CBCT scan during 2015-2017 were included in the study.Results: CBCT were made in 617 of the 3847 eligible referrals. The most common referral was from general practice dentists (GPD) (43%). Mean age of the patients was 12.5 years (range: 6-18). Nineteen different types of requests were identified. The most common request was assessment of an ectopic canine with a question about potential resorption of adjacent teeth (38.6%). Forty (6.5%) of the CBCT needed to be re-taken due to patient motion artefacts.Conclusions: The most common request and indication for CBCT examination of children and young adults were to assess an ectopic canine and determine the presence of resorption of adjacent teeth. Referrals from GPDs were the most frequent and the largest age group was the 11- to 15-year olds. The reason for re-exposures was motion artefacts. High scanning speed to reduce motion artefacts and a half rotation (180°) to reduce the radiation dose to the patient should be preferred. The need for continuous work with quality and systematic monitoring of radiographic procedures at any radiology department should be given high priority.