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Purpose/Objectives: To understand the professional aspirations of oral and maxillofacial radiologists (OMRs) by exploring their career choices and their association with educational background, engagement in professional activities, professional values, and overall level of career satisfaction. Methods: This prospective cross‐sectional study surveyed board‐certified OMRs in the United States and Canada from September to December 2019. A web‐based questionnaire was created comprising 37 multiple‐choice questions and an open‐ended question focusing on their opinions regarding the profession's future. A thematic approach qualitatively explored open questions. Results: Of the 86 OMRs, 68, 10, and eight were board certified in the United States, Canada, and both countries, respectively. Activities considered "rewarding" included teaching and mentoring (65%) and radiologic reporting (55%). The majority spent approximately 20–30 h/week writing radiographic reports and less than 10 h in research. On an average, OMRs produced 21.9 (SD 12.8) reports per day. Activities considered less rewarding included administrative work (11%) and productivity pressure in institutions. OMRs working in academia reported higher incomes (p < 0.05). Finally, the majority of the OMRs were pleased with their career choices (79%). Conclusions: There is an association between the contemporary OMRs' satisfaction feeling, teaching/mentoring, and the future challenges of participating in multidisciplinary teams. Overall, diverse career choices lead OMRs to be proud of their profession and significantly satisfied. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to determine if image enhancement improves a clinician's ability to identify the presence of calculus on digital radiographs.Methods: Seventy-one hopeless teeth were collected from 34 patients. Teeth were stained with 1% methylene blue, the largest interproximal calculus deposit was scored, and photographs of each interproximal root surface were taken. The surface area of calculus deposit was determined as a percentage of the total interproximal root surface area. Digital radiographs of teeth taken before extraction were modified using the following enhancements: auto-contrast, emboss, invert, and sharpen. Radiographic presence of calculus was determined by two examiners. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each examiner and enhancement. A receiver operating characteristic curve was used to compare differences between the image enhancements in the detection of dental calculus. The kappa statistic was used to compare ratings between examiners.Results: None of the enhanced images were statistically superior to original images in identifying radiographic calculus (P > 0.05). The average sensitivity of digital radiography was 50%, average specificity was 82.2%, PPV was 94%, and NPV 23.2%. A threshold of >30% of interproximal root surface covered with calculus and increasing size of deposits were associated with improved detection (P < 0.05).Conclusions: Digital enhancements do not significantly improve radiographic detection of dental calculus. As area of calculus on the root surface and size of calculus deposits increased, sensitivity of detection also increased. [ABSTRACT FROM AUTHOR]

External cervical resorption (ECR) is a relatively uncommon type of external resorption; its treatment planning and prognosis are largely dependent on the clinician's subjective assessment. This study aimed to provide a volumetric assessment of ECR cases while correlating them to the Heithersay classification, treatment decision, and prognosis determined by 3 calibrated, independent evaluators. A total of 168 ECR cases with corresponding periapical radiographs and cone-beam computed tomographic (CBCT) imaging were included in this study. An oral and maxillofacial radiologist calculated the volume occupied by the resorptive defects in root structures on CBCT imaging using Amira software (Thermo Scientific, Waltham, MA). Also, 3 board-certified endodontists evaluated anonymized and randomized periapical radiographs and corresponding CBCT images in separate sessions. Examiners were asked to provide a Heithersay classification, whether they would surgically repair the ECR lesion, and the expected prognosis of each case. The percentage of radicular volume affected by ECR ranged from 0.5%–58% with a median of 12%. The volumetric quantification of ECR best correlated with classification and prognosis assigned by the independent examiners using CBCT evaluation. The greatest variation in agreement was observed on whether to surgically repair the ECR. However, examiners agreed more uniformly on not to treat when the resorptive port of entry was found on either the lingual or proximal surfaces of the tooth. For the first time, the volumetric quantification of resorptive defects was calculated in vivo and correlated to the Heithersay classification and prognosis. Because the longevity of teeth affected with ECR depends on the integrity of the remaining root, the findings of this study provide important information to help clinicians decide on treatment planning and inform their patients of the expected prognosis. Future studies should focus on automating volumetric assessments of ECR to aid in unbiased chairside treatment planning decisions. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this ex vivo study was to measure the sensitivity, specificity, and receiver operating characteristic (ROC) area under the curve (AUC) of a caries diagnostic system based on photothermal radiometry and modulated luminescence (PTR/LUM) and compare them with the values for digital intraoral radiography (IR) and cone beam computed tomography (CBCT) in detecting recurrent decay.Study Design: Class 2 composite restorations were prepared on 70 proximal surfaces: 35 with caries and 35 without caries. The gingival floor of the restored surfaces was assessed for caries under the restorations using each of the 3 modalities. Statistical calculations and analysis were performed using the R statistical computing environment.Results: The average scores for sensitivity among the 6 observers were 0.89 for PTR/LUM, 0.38 for IR, and 0.40 for CBCT. Sensitivity for PTR/LUM was significantly greater than sensitivity for IR and CBCT. Average scores for specificity were 0.83, 0.80, and 0.70 for PTR/LUM, IR, and CBCT, respectively. CBCT had significantly lower specificity. The AUC was 0.65 for IR and 0.59 for CBCT, which were significantly different. PTR/LUM had moderate intraobserver agreement.Conclusions: PTR/LUM, which involves non-ionizing radiation, can serve as a sensitive adjunct in early caries detection and monitoring. [ABSTRACT FROM AUTHOR]

Objective: We quantitatively compared the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in T1 weighted imaging (WI) and T2 WI sequences in 3 Tesla (T) magnetic resonance imaging (MRI) using zirconium, titanium (grades 4 and 5), and titanium-zirconium alloy implants to evaluate the effect of implant type and imaging sequence.Study Design: MRI was acquired using a 3 T magnet with a 16-channel head coil. Implants of each type were mounted in gel and scanned in axial, coronal, and sagittal planes using fast spin echo sequences in T1 WI (TR = 600, TE = 12 milliseconds) and T2 WI (TR = 3000, TE = 80 milliseconds) sequences. Data were transferred to Synapse 3-D software, and images were measured twice by an oral and maxillofacial radiologist blinded to the type of implants.Results: Zirconium implants resulted in the lowest SNR and CNR values (P < .05). No significant differences were identified between titanium (grades 4 and 5) and titanium-zirconium implants. The T2 WI sequence had a significantly higher SNR and CNR than T1 WI. There was no difference in intraobserver agreement between T1 WI and T2 WI.Conclusions: CNR and SNR at 3 T MRI are dependent on implant type and imaging sequence. Titanium (grades 4 and 5) and titanium-zirconium implants and the T2 WI sequence produced higher SNR and CNR values. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to assess artifacts generated by zirconium, titanium, and titanium-zirconium alloy implants on magnetic resonance imaging(MRI), computed tomography(CT), and cone beam computed tomography(CBCT) and to correlate the findings to the dose-area product and exposure factors on CT and CBCT.Study Design: Three phantoms were built by embedding zirconium, titanium, and titanium-zirconium implants in ultrasound gel. MRI, CT, and CBCT images were acquired by using multiple sequences and settings. For MRI, "artifact" was described as the length of signal void beyond the limits of the implant. For CT and CBCT, "artifact" was calculated by subtracting the gray level of the darkest pixel from the level of the lightest pixel.Results: On MRI, zirconium implants had minor distortion artifacts, whereas titanium and titanium-zirconium implants created extensive artifacts (P < .05). On CT and CBCT, artifacts were less prominent with titanium and titanium-zirconium implants compared with zirconium (P < .05). Titanium grade 5 implants with 0.3 and 0.4 mm3 voxels produced the least severe artifacts.Conclusions: MRI images were less affected by artifacts from zirconium implants, whereas CT and CBCT images showed less severe artifacts from titanium and titanium-zirconium alloy implants. CT generated greater artifacts compared with CBCT. Larger CBCT voxel sizes reduced the dose-area product and the severity of artifacts. [ABSTRACT FROM AUTHOR]

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Objectives: The aim of this study was to evaluate the effect of an optimization filter (OF) and voxel size on the accuracy of root fracture detection.Study Design: Half of 40 endodontically treated roots were fractured, and the other half were left intact. All teeth were randomly placed into 5 bovine ribs. Each rib was scanned with the Planmeca ProMax 3-D using 4 different settings: 75 μm and 100 μm voxel size with and without an OF. Five reviewers reported if a fracture was present by using a 5-point scale. Intra-/interobserver agreement, area under the receiver operative characteristic curve, accuracy, sensitivity, and false-positive rates were analyzed.Results: High κ-values indicated strong intra-/interobserver agreement. There was no significant difference in fracture detection between any of the evaluated techniques.Conclusions: Because of the decreased cost, dose area product, and time required, compared with the other imaging modalities studied, the high-resolution mode (100 μm) without an OF is recommended for root fracture detection in endodontically treated teeth. [ABSTRACT FROM AUTHOR]

Background: To date, limited evidence is available specifically evaluating ridge preservation (RP) and implant placement in molar sites. The primary aim of this study is to radiographically compare alveolar ridge changes with and without RP with cone-beam computed tomography (CBCT).Methods: This parallel, two-arm randomized clinical trial included 40 patients evenly distributed between two treatment groups. After molar extraction, sites were allowed to heal naturally or received RP with freeze-dried bone allograft covered by a non-resorbable dense polytetrafluoroethylene membrane. CBCT scans were taken immediately and 3 months postextraction, and then a dental implant was placed. Width and height measurements were made radiographically.Results: Significantly greater loss in alveolar ridge height was found in molar sites allowed to heal without RP on the buccal aspect of the socket (RP: -1.12 ± 1.60 mm versus no RP: -2.60 ± 2.06 mm, P = 0.01). No significant difference in ridge width loss was found between groups. Two-thirds ridge width reduction was experienced on the buccal aspect in sites without RP, but width loss was evenly distributed between buccal and lingual aspects when RP was performed. Bone grafting at time of placement was required in 25% of implants in the group without RP versus 10% of implants in the RP group.Conclusions: In molar extraction sites without RP, significantly more reduction in ridge height occurred, and the majority of ridge width loss was localized to the buccal aspect. When RP was performed, ridge width loss was not significantly decreased, but the loss was evenly distributed between facial and lingual aspects of the extraction site. [ABSTRACT FROM AUTHOR]

Introduction Cone-beam computed tomographic (CBCT) analysis allows for 3-dimensional assessment of periradicular lesions and may facilitate preoperative periapical cyst screening. The purpose of this study was to develop and assess the predictive validity of a cyst screening method based on CBCT volumetric analysis alone or combined with designated radiologic criteria. Methods Three independent examiners evaluated 118 presurgical CBCT scans from cases that underwent apicoectomies and had an accompanying gold standard histopathological diagnosis of either a cyst or granuloma. Lesion volume, density, and specific radiologic characteristics were assessed using specialized software. Logistic regression models with histopathological diagnosis as the dependent variable were constructed for cyst prediction, and receiver operating characteristic curves were used to assess the predictive validity of the models. A conditional inference binary decision tree based on a recursive partitioning algorithm was constructed to facilitate preoperative screening. Results Interobserver agreement was excellent for volume and density, but it varied from poor to good for the radiologic criteria. Volume and root displacement were strong predictors for cyst screening in all analyses. The binary decision tree classifier determined that if the volume of the lesion was >247 mm 3 , there was 80% probability of a cyst. If volume was <247 mm 3 and root displacement was present, cyst probability was 60% (78% accuracy). Conclusions The good accuracy and high specificity of the decision tree classifier renders it a useful preoperative cyst screening tool that can aid in clinical decision making but not a substitute for definitive histopathological diagnosis after biopsy. Confirmatory studies are required to validate the present findings. [ABSTRACT FROM AUTHOR]

Objective: To evaluate zirconium implant artifact production in cone beam computed tomography images obtained with different protocols.Study Design: One zirconium implant was inserted in an edentulous mandible. Twenty scans were acquired with a ProMax 3D unit (Planmeca Oy, Helsinki, Finland), with acquisition settings ranging from 70 to 90 peak kilovoltage (kVp) and voxel sizes of 0.32 and 0.16 mm. A metal artifact reduction (MAR) tool was activated in half of the scans. An axial slice through the middle region of the implant was selected for each dataset. Gray values (mean ± standard deviation) were measured in two regions of interest, one close to and the other distant from the implant (control area). The contrast-to-noise ratio was also calculated.Results: Standard deviation decreased with greater kVp and when the MAR tool was used. The contrast-to-noise ratio was significantly higher when the MAR tool was turned off, except for low resolution with kVp values above 80. Selection of the MAR tool and greater kVp resulted in an overall reduction of artifacts in images acquired with low resolution.Conclusions: Although zirconium implants do produce image artifacts in cone-bean computed tomography scans, the setting that best controlled artifact generation by zirconium implants was 90 kVp at low resolution and with the MAR tool turned on. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this pilot study was to assess temporomandibular joint disc movement relative to the condyle among centric relation (CR), physiologic rest position (PRP), and maximal intercuspation position (MIP) in healthy patients without signs or symptoms of any temporomandibular disorder. The hypothesis was that as the condyle rotated clockwise or translated anteriorly, the disc would also move in an anterior direction.Material and Methods: Magnetic resonance images were obtained on 20 volunteers in CR, physiologic rest, and MIP. Three investigators measured the location of the disc among the different mandibular positions.Results: Disc location differences between CR and PRP exhibited the widest range of measurement. The largest amount of disc protrusion relative to the condyle was found between CR and PRP on the right side. The largest amount of disc retrusion relative to the condyle was found between CR and MIP on the right side. The hypothesis was not supported by the results.Conclusions: According to the results of this pilot study, the direction of movement of the temporomandibular disc does not correlate with the rotational movement of the condyle in hinge positions.Clinical Implications: Increased knowledge of temporomandibular disc movement among various mandibular positions in asymptomatic patients may help clinicians recognize deviations in symptomatic patients. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to evaluate the effect of milliamperage, number of basis images, and export slice thickness on contrast-to-noise ratio (CNR) and confidence in detecting mandibular canal.Study Design: Two phantoms were used. Each phantom consisted of a dry mandible with an epoxy resin bone tissue substitute block and a water-equivalent block, submerged in water. Each mandible was scanned with a Morita 3D Accuitomo cone beam computed tomography (CBCT) machine (Morita, Kyoto, Japan). Scans were made with 180-degree and 360-degree rotations, at 4, 6, and 8 mA. Each scan was exported in Digital Imaging and Communications in Medicine (DICOM) format at slice thicknesses of 0.125 mm, 0.25 mm, 0.75 mm, and 1.0 mm, resulting in 24 image sets for each phantom. The CNR was calculated. Variables were analyzed using factorial analysis of variance. The scans were also evaluated by five observers who were asked to state their confidence in detecting the mandibular canal on a four-point confidence scale.Results: Increasing the number of basis images, milliamperage, or export slice thickness significantly increased the CNR. Reducing the export slice thickness improved observers' confidence in detecting the mandibular canal.Conclusions: The CBCT acquisition settings should be carefully chosen, depending on specific diagnostic tasks. The lowest slice thickness equal to the voxel size should always be used for exporting CBCT data despite the higher noise. [ABSTRACT FROM AUTHOR]

Introduction After endodontic surgery, radiographic assessment is the method of choice to monitor bone defect healing. Cone-beam computed tomography scans are useful to check and identify the reasons of failure of surgical intervention or confirm healing; however, the artifact generated by some root-end filling material might compromise this task. The objective of the study was to compare the amount of artifacts generated by 4 root-end filling materials and to test multiple exposure settings used with these materials, when the effective dose generated by each protocol was taken into consideration. Methods Twenty central incisors were endodontically treated with retrograde obturation by using amalgam, Biodentine, MTA, and Super-EBA (5 of each). They were placed in a skull with soft tissue simulation and scanned by using the Planmeca Promax Max with different kilovolt peaks (kVp): 66, 76, 84, and 96 with and without the use of metal artifact reduction (MAR) algorithm and with low, normal, and high resolution and high definition. The Dose Area Product was registered, and the effective dose was calculated. Results Amalgam generated the highest amount of artifacts, whereas MAR and low resolution created fewer artifacts than other settings. The artifacts were also reduced with 96 kVp. The effective dose calculated with low resolution was remarkably lower than other resolutions. Conclusions When used as root-end filling material, Biodentine, MTA, and Super-EBA generated fewer artifacts than amalgam. The use of 96 kVp with MAR and low resolution also reduced artifacts on the image and at the same time generated the lowest effective dose. [ABSTRACT FROM AUTHOR]

With the increasing use of digital radiography, the display parameters of the devices used to view radiographs have become important factors in caries detection. Interest in the use of tablet devices for this application has increased due to their availability, portability, and ease of use. However, to be effective in clinical situations, these portable devices must have displays that perform well under multiple lighting conditions and at different angles. The purpose of this study was to assess the utility of the iPad with Retina Display for the detection of Class II caries under common overhead lighting conditions. The device was used in both standing and angled positions by 5 reviewers, and their diagnoses of caries were compared to the diagnoses the same reviewers made using a thin-film transistor flat-panel display (TFT-FPD) in dim lighting conditions. Histological analysis was used as the gold standard to confirm the presence or absence of caries. In a standing position, the tablet device performed as well as the TFT-FPD. When used in the angled position, the tablet performed slightly worse than the TFT-FPD. The findings suggest that if the user can compensate for overhead glare, the tablet device may perform as well as a calibrated, upright display in a dimly lit room. [ABSTRACT FROM AUTHOR]

Background Cleidocranial dysplasia (CCD), also known as cleidocranial dysostosis or osteodental dysplasia, is an autosomal dominant disorder caused by a microdeletion defect in chromosome 6p21. The causative factor of this disorder is a mutation in the gene encoding in the transcription factor core binding factor α 1 ( CBFA1 ), and its incidence is 1 in 100,000 population. The aims of this clinical paper are to illustrate the ways of diagnosing and treating CCD as stated in the literature, and to report the multidisciplinary management of a patient with this condition. Methods Clinical and radiographic examinations are primordial for diagnosis because the most frequent features of CCD are a pathognomonic deformity of the skull (open skull sutures and delayed closing of cranial fontanels, presence of multiple Wormian bones), midfacial hypoplasia, a wide forehead, pronounced frontal bossing and hypertelorism, supernumerary and impacted teeth, hypoplastic or absent clavicles, and short stature. The diagnosis of CCD is obvious when there is a family history. Results Many solutions for the treatment of dental disorders in CCD have been suggested, and the intervention of several dental specialists, namely, the oral surgeon, orthodontist, periodontist, and maxillofacial surgeon, was required to achieve optimal results. Conclusion Orthodontic treatment brought all of the teeth on the arches, and the patient was able to sustain orthognathic surgery to correct the skeletal open bite and Class III relationship. [ABSTRACT FROM AUTHOR]

This article discusses the treatment of a patient with a severely resorbed mandible with six millimeters (mm) or less of bone height. Topics discussed include how the computed tomography (CT) scans of the patient's mandible and the maxilla were performed and how the surgical procedure was carried out including placing the patient in a supine position, degloving the mandible to the mental foramen bilaterally, and screwing the Nobel Bioguide stent with 1.5 mm bone screws onto the mandible.

Objectives: The objective of this study was to compare the accuracy of root fracture detection in endodontically treated teeth using scans acquired with a 180° rotation motion compared with a 360° after which the patient exposure and number of basis images are doubled. Methods: Sixty-six roots were collected and decoronated. All were treated endodontically. One-half of the roots were fractured, resulting in 2 root fragments which were then glued together. The roots were placed randomly in 8 prepared beef rib fragments. Five reviewers independently reviewed the scans twice, at different times. Results: The specificity of the 360° scan was significantly higher than the 180° scan; doubling the basis images leads to a significant decrease in false-positive rates. Accuracy and sensitivity were not significantly different. Conclusions: Only the specificity is improved by the increased rotation and doubling of images. The accuracy and sensitivity are not improved. [Copyright &y& Elsevier]

Objectives: The objectives were to determine whether the images obtained from different cone-beam computerized tomography (CBCT) field of view (FOV) sizes with varying scan time and kilovolt peak using the Picasso Master 3D machine (Vatech, Hwasung, South Korea) differ in contrast-to-noise ratio (CNR). Study Design: A phantom was used. Scans were acquired using the same voxel size, 2 scan times (15 and 24 seconds) for 3 different FOV sizes and 5 different kilovolt peaks. The contrast and CNR were calculated for each FOV. Results: The CNRs were similar for the 2 scan times for all 3 FOV sizes. The CNR was lower in the 20 × 19 cm FOV compared with the other 2 FOVs for both scan times. Conclusions: The CNR does not vary significantly with increasing scan times for all FOV sizes. Smaller FOVs result in enhanced CNR and contrast. [ABSTRACT FROM AUTHOR]

Each of three cone beam computed tomography (CBCT) machines offer a small field of view (FOV); Promax, Accuitomo 3D, and Kodak 9000. The objectives were to determine, when using a small FOV, the difference in contrast-to-noise ratios (CNR) of images obtained from different machines and different scan settings within each machine. A phantom made of a dry mandible with an epoxy resin based substitute (ERBS) block was used. The ERBS block was fixed to the lingual cortex in the posterior left mandible. Water was used to simulate soft tissue. Twenty scans were acquired. CNR was calculated as the difference in density of the ERBS block and a control area divided by the standard deviation of the difference. The CNR obtained from images acquired with the Promax machine (voxel size of 0.2 mm) was higher than the other machines (voxel sizes 0.076, 0.08, or 0.125 mm) when using a small FOV. The Accuitomo 360° scan had higher CNR than the Accu-itomo 180° scan due to the doubling of the number of basis images acquired. Smaller voxel size does not necessarily lead to enhanced CNR. Increasing the number of basis images did increase the CNR. [ABSTRACT FROM AUTHOR]

Background: Because of bone resorption following tooth extraction, preservation of adequate bony dimension is performed often for subsequent treatment with dental implants. This study evaluated a novel, non-invasive treatment using ultrasound to accelerate healing following extraction to minimize alveolar bone loss. The objective of this study was to evaluate the effect of ultrasound on the dimensional healing changes of alveolar bone following tooth extraction using cone-beam volumetric tomography (CBVT). Methods: This randomized, split-mouth trial involved 12 subjects requiring extraction of two contralateral erupted permanent teeth. Baseline CBVT scans were captured 7 to 10 days following extraction, after which time ultrasound therapy commenced in test sites. Ultrasound therapy was delivered for 20 minutes using a piezoelectric transducer for 10 sessions over the subsequent 4 weeks. Follow-up radiographic scans were obtained at 4 weeks and 3 months postextraction. Analyses of variance and covariance were performed to assess dimensional changes over the 3-month healing period. Results: Analysis of dimensional changes in all measures of vertical height and horizontal width demonstrated no statistically significant differences between the ultrasound and control groups from baseline to 3 months postextraction. Evaluation of correlations between dimensional changes demonstrated a moderately strong correlation (r = 0,67; P = 0.023) in the ultrasound group between the change in buccal vertical height and the baseline crestal ridge width. Analysis of the change in buccal vertical height relative to baseline crestal width demonstrated a statistically significant benefit to ultrasound compared to control (P = 0.016). This benefit was more pronounced in wider sockets compared to narrow sockets. Conclusions: In this pilot study, there was no significant benefit to ultrasound in absolute bony dimensional changes following tooth extraction. There was a significant interaction between the treatment rendered (ultrasound versus control) and the change in buccal ridge height relative to baseline ridge width at the crest and 3 mm apical to the crest. This benefit was apparent in wide sockets compared to narrow sockets; however, the clinical importance of these relative dimensional changes in the ultrasound group are difficult to determine given the inclusion of all tooth types in a pilot study with a small sample size. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to investigate the appearance and possible cause of an artifact seen in limited-volume cone-beam CT imaging. Methods: A water-filled plastic cylinder was used as a phantom of the head. A test object was constructed as a bone-equivalent phantom to be imaged. The test object was variously positioned at the center of the phantom and near its margins. CT images of the test object were acquired using a 3DX Accuitomo system. Results: In slice images with the test object positioned near the margin of the phantom, arch-shaped defects or deformities were observed on the side of the object. There was a negative correlation between the artifact and the CT value of the object. The artifact was larger in images scanned with a higher voltage. Conclusion: The probability that this artifact is caused by halation from the image intensifier (II) system is suggested. [Copyright &y& Elsevier]