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For virtual surgical planning in orthognathic surgery, marking tooth landmarks on CT images is an important procedure. However, the manual localization procedure of tooth landmarks is time-consuming, labor-intensive, and requires expert knowledge. Also, direct and automatic tooth landmark localization on CT images is difficult because of the lower resolution and metal artifacts of dental images. The purpose of this study was to propose an attention-guided volumetric regression network (V 2 -Net) for accurate tooth landmark localization on CT images with metal artifacts and lower resolution. V 2 -Net has an attention-guided network architecture using a coarse-to-fine-attention mechanism that guided the 3D probability distribution of tooth landmark locations within anatomical structures from the coarse V-Net to the fine V-Net for more focus on tooth landmarks. In addition, we combined attention-guided learning and a 3D attention module with optimal Pseudo Huber loss to improve the localization accuracy. Our results show that the proposed method achieves state-of-the-art accuracy of 0.85 ± 0.40 mm in terms of mean radial error, outperforming previous studies. In ablation studies, we observed that the proposed attention-guided learning and a 3D attention module improved the accuracy of tooth landmark localization in CT images of lower resolution and metal artifacts. Furthermore, our method achieved 97.92% in terms of the success detection rate within the clinically accepted accuracy range of 2.0 mm.

Background: Noninfectious myositis (NIM) of the masticatory muscles is uncommon local myalgia disorder persisted by a centrally-mediated neurogenic mechanism. Due to the rarity of this condition and the lack of appropriate data regarding it, diagnosing this pathology when it affects the temporal muscle (TM) is challenging., Case Presentation: Clinical signs and symptoms, diagnostic process, and treatment outcome of 2 rare cases of NIM of the TM were presented. The signs and symptoms of the patients were not pathognomonic. There were restrictions on the mouth opening and lateral excursion of the mandible. The duration of the symptoms may not be chronic. The findings of clinical evaluation may indicate the diagnosis of anterior disc displacement (DD) without reduction of the temporomandibular joint (TMJ) and/or local myalgia. Swelling of the involved muscle could be evident and identified on palpation depending on the involved site of myositis. The axial T2-weighted magnetic resonance (MR) imaging was important for the accurate diagnosis of this rare condition. Application of non-surgical conservative treatment modalities such as administration of non-steroidal anti-inflammatory analgesics for a sufficient period of time, control of oral parafunctional habits, and jaw exercises were effective for the management of NIM of the TM., Conclusion: A thorough clinical examination and MR imaging including the axial T2-weighted view are required for accurate diagnosis and effective management of NIM of the TM., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.)

Cone-beam CT (CBCT) is widely used in dental clinics but exhibits limitations in assessing soft tissue pathology because of its lack of contrast resolution and low Hounsfield Units (HU) quantification accuracy. We aimed to increase the image quality and HU accuracy of CBCTs while preserving anatomical structures. We generated CT-like images from CBCT images using a patchwise contrastive learning-based GAN model. Our model was trained on unpaired CT and CBCT datasets with the novel combination of losses and the feature extractor pretrained on our training dataset. We evaluated the quality of the images generated by our model in terms of Fréchet inception distance (FID), peak signal-to-noise ratio (PSNR), mean absolute error (MAE), and root mean square error (RMSE). Additionally, the structure preservation performance was assessed by the structure score. As a result, the generated CT-like images by our model were significantly superior to those generated by various baseline models in terms of FID, PSNR, MAE, RMSE, and structure score. Therefore, we demonstrated that our model provided the complementary benefits of preserving the anatomical structures of the input CBCT images and improving the image quality to be similar to those of CT images., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The purpose of this study was to propose a continuity-aware contextual network (Canal-Net) for the automatic and robust 3D segmentation of the mandibular canal (MC) with high consistent accuracy throughout the entire MC volume in cone-beam CT (CBCT) images. The Canal-Net was designed based on a 3D U-Net with bidirectional convolutional long short-term memory (ConvLSTM) under a multi-task learning framework. Specifically, the Canal-Net learned the 3D anatomical context information of the MC by incorporating spatio-temporal features from ConvLSTM, and also the structural continuity of the overall MC volume under a multi-task learning framework using multi-planar projection losses complementally. The Canal-Net showed higher segmentation accuracies in 2D and 3D performance metrics (p < 0.05), and especially, a significant improvement in Dice similarity coefficient scores and mean curve distance (p < 0.05) throughout the entire MC volume compared to other popular deep learning networks. As a result, the Canal-Net achieved high consistent accuracy in 3D segmentations of the entire MC in spite of the areas of low visibility by the unclear and ambiguous cortical bone layer. Therefore, the Canal-Net demonstrated the automatic and robust 3D segmentation of the entire MC volume by improving structural continuity and boundary details of the MC in CBCT images., (© 2022. The Author(s).)

Diagnosing osteosarcoma (OS) is very challenging and OS is often misdiagnosed as osteomyelitis (OM) due to the nonspecificity of its symptoms upon initial presentation. This study investigated the possibility of detecting OS-induced trabecular bone changes on panoramic radiographs and differentiating OS from OM by analyzing fractal dimensions (FDs) and degrees of anisotropy (DAs). Panoramic radiographs of patients with histopathologically proven OS and OM of the jaw were obtained. A total of 23 patients with OS and 40 patients with OM were enrolled. To investigate whether there was a microarchitectural difference between OS lesions and normal trabecular areas in each patient, two regions of interest (ROIs) were located on the CT images. Three microarchitectural parameters (box-counting FD, fast Fourier transform-based FD, and DA) were calculated. For both OS and OM, significant differences were found for all three microarchitectural parameters. Compared to normal trabecular bone, trabecular bone affected by OS and OM became isotropic and more complex. When comparing OS and OM, a statistically significant difference was found only in DA. Trabecular bones affected by OS became more isotropic than those affected by OM. Microarchitectural analysis, especially DA, could be useful for detecting OS-induced trabecular alterations and differentiating OS from OM., (© 2022. The Author(s).)

Abstract: Burkitt lymphoma (BL) is a subtype of Non-Hodgkin lymphoma, considered one of the fastest growing human tumors. Due to the highly aggressive nature of BL, a prompt diagnosis and aggressive chemotherapeutic treatment are essential. However, the clinical features of BL often can mimic periodontal disease or dentoalveolar abscess. The aim of this study is to present a case of a 31-year-old male patient who was referred to the department of oral and maxillofacial surgery for severe neurosensory disturbance and pain in the lower jaw. He was misdiagnosed with periodontitis and dental abscess at the local clinic. Based on radiographic findings, he was suspected of hematopoietic malignancy. He was referred to the department of hemato-oncology and diagnosed with BL. This case highlights the essential life-saving role of a maxillofacial surgeon in the early diagnosis of a rare malignancy., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 by Mutaz B. Habal, MD.)

The purpose of this study was to directly and quantitatively measure BMD from Cone-beam CT (CBCT) images by enhancing the linearity and uniformity of the bone intensities based on a hybrid deep-learning model (QCBCT-NET) of combining the generative adversarial network (Cycle-GAN) and U-Net, and to compare the bone images enhanced by the QCBCT-NET with those by Cycle-GAN and U-Net. We used two phantoms of human skulls encased in acrylic, one for the training and validation datasets, and the other for the test dataset. We proposed the QCBCT-NET consisting of Cycle-GAN with residual blocks and a multi-channel U-Net using paired training data of quantitative CT (QCT) and CBCT images. The BMD images produced by QCBCT-NET significantly outperformed the images produced by the Cycle-GAN or the U-Net in mean absolute difference (MAD), peak signal to noise ratio (PSNR), normalized cross-correlation (NCC), structural similarity (SSIM), and linearity when compared to the original QCT image. The QCBCT-NET improved the contrast of the bone images by reflecting the original BMD distribution of the QCT image locally using the Cycle-GAN, and also spatial uniformity of the bone images by globally suppressing image artifacts and noise using the two-channel U-Net. The QCBCT-NET substantially enhanced the linearity, uniformity, and contrast as well as the anatomical and quantitative accuracy of the bone images, and demonstrated more accuracy than the Cycle-GAN and the U-Net for quantitatively measuring BMD in CBCT., (© 2021. The Author(s).)

Objective: This study investigated the association of computed tomography (CT)-verified degenerative condylar changes with disk displacement (DD) and sex., Study Design: Multidetector CT and cone beam CT scans of 165 condyles were evaluated for erosion, osteophyte formation, flattening, subcortical sclerosis, generalized sclerosis, subcortical defects, and loose joint bodies. Disk position was determined using magnetic resonance imaging. The association of degenerative alterations with disk position and sex was analyzed., Results: The risks of erosion, osteophyte formation, and flattening were significantly increased by 3.72, 9.00, and 6.35 times, respectively, in the joints with DD without reduction (DDNR); however, the risks of these changes did not increase significantly in joints with DD with reduction. The risks of extensive erosion and slight and moderate osteophyte formation significantly increased only in the joints with DDNR. The degenerative changes were more likely to exist together in the joints with DDNR than in those with a normal disk position. The association of DD and most degenerative morphologies was not significantly influenced by sex., Conclusions: Erosion, osteophyte formation, and flattening were significantly associated with DDNR, regardless of sex., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background/purpose: There is a paucity of comprehensive information about posterior open bite (POB) in patients with temporomandibular disorders (TMD) because of its rare prevalence. The purpose of this study was to investigate the etiologies, clinical characteristics, and treatment outcomes of patients with TMD presenting POB., Materials and Methods: This study includes a careful review of medical records and imaging findings of 12 patients with TMD (seven men and five women, 50.9 ± 19.2 years, 15-72 years) complaining of POB., Results: In total, 11 had unilateral POB, whereas 1 had bilateral POB. In 11 patients, POB was caused by inflammatory disorders of temporomandibular joint (TMJ). In the remaining one patient, TMJ medial disc displacement (MDD) was responsible for POB. Of 11 patients with inflammatory conditions of TMJ, four patients had unilateral TMJ internal derangement (ID), two had bilateral TMJ ID, and one had rheumatism. POB was resolved in 10 of 11 patients with TMJ inflammation following the administration of non-steroidal anti-inflammatory drugs and self-management instructions. Prosthodontic treatment was needed in one patient to resolve POB. POB was resolved in the patient with TMJ MDD after stabilization splint therapy., Conclusion: POB in patients with TMD was mostly caused by inflammatory disorders of TMJ. TMJ MDD could also be a reason. Although almost all POB was resolved by conservative treatments including medications, the possibility of prosthodontic, orthodontic, or surgical treatments also must be considered., Competing Interests: The authors have no conflicts of interest relevant to this article., (© 2021 Association for Dental Sciences of the Republic of China. Publishing services by Elsevier B.V.)

Objectives: The purpose of this study was to automatically diagnose odontogenic cysts and tumors of both jaws on panoramic radiographs using deep learning. We proposed a novel framework of deep convolution neural network (CNN) with data augmentation for detection and classification of the multiple diseases., Methods: We developed a deep CNN modified from YOLOv3 for detecting and classifying odontogenic cysts and tumors of both jaws. Our data set of 1282 panoramic radiographs comprised 350 dentigerous cysts (DCs), 302 periapical cysts (PCs), 300 odontogenic keratocysts (OKCs), 230 ameloblastomas (ABs), and 100 normal jaws with no disease. In addition, the number of radiographs was augmented 12-fold by flip, rotation, and intensity changes. We evaluated the classification performance of the developed CNN by calculating sensitivity, specificity, accuracy, and area under the curve (AUC) for diseases of both jaws., Results: The overall classification performance for the diseases improved from 78.2% sensitivity, 93.9% specificity,91.3% accuracy, and 0.86 AUC using the CNN with unaugmented data set to 88.9% sensitivity, 97.2% specificity, 95.6% accuracy, and 0.94 AUC using the CNN with augmented data set. CNN using augmented data set had the following sensitivities, specificities, accuracies, and AUCs: 91.4%, 99.2%, 97.8%, and 0.96 for DCs, 82.8%, 99.2%, 96.2%, and 0.92 for PCs, 98.4%,92.3%,94.0%, and 0.97 for OKCs, 71.7%, 100%, 94.3%, and 0.86 for ABs, and 100.0%, 95.1%, 96.0%, and 0.97 for normal jaws, respectively., Conclusion: The CNN method we developed for automatically diagnosing odontogenic cysts and tumors of both jaws on panoramic radiographs using data augmentation showed high sensitivity, specificity, accuracy, and AUC despite the limited number of panoramic images involved.

The purpose of this study was to develop a quantitative AR-assisted free-hand orthognathic surgery method using electromagnetic (EM) tracking and skin-attached dynamic reference. The authors proposed a novel, simplified, and convenient workflow for augmented reality (AR)-assisted orthognathic surgery based on optical marker-less tracking, a comfortable display, and a non-invasive, skin-attached dynamic reference frame. The 2 registrations between the physical (EM tracking) and CT image spaces and between the physical and AR camera spaces, essential processes in AR-assisted surgery, were pre-operatively performed using the registration body complex and 3D depth camera. The intraoperative model of the maxillary bone segment (MBS) was superimposed on the real patient image with the simulated goal model on a flat-panel display, and the MBS was freely handled for repositioning with respect to the skin-attached dynamic reference tool (SRT) with quantitative visualization of landmarks of interest using only EM tracking. To evaluate the accuracy of AR-assisted Le Fort I surgery, the MBS of the phantom was simulated and repositioned by 6 translational and three rotational movements. The mean absolute deviations (MADs) between the simulation and post-operative positions of MBS landmarks by the SRT were 0.20, 0.34, 0.29, and 0.55 mm in x- (left lateral, right lateral), y- (setback, advance), and z- (impaction, elongation) directions, and RMS, respectively, while those by the BRT were 0.23, 0.37, 0.30, and 0.60 mm. There were no significant differences between the translation and rotation surgeries or among surgeries in the x-, y-, and z-axes for the SRT. The MADs in the x-, y-, and z-axes exhibited no significant differences between the SRT and BRT. The developed method showed high accuracy and reliability in free-hand orthognathic surgery using EM tracking and skin-attached dynamic reference.

Panoramic radiography is the most commonly used equipment in the dental field, but there is no comprehensive standard about how to evaluate the spatial resolution of panoramic radiography. In this study, panorama resolution phantoms were developed for evaluation of horizontal and vertical resolution reflecting unique characteristics of panoramic radiography. Four horizontal resolution phantoms of staircase shape were designed to obtain images of horizontal lead line pairs in a 52 mm width. Four vertical resolution phantoms with vertical lead line pairs placed at an oblique angle were also designed. A phantom stand was made. Three machines were evaluated twice by two oromaxillofacial radiologists. The horizontal lead line pairs were readable over the entire measured area at the values of 1.88, 2.32, and 2.58 lp/mm for all machines. A readable area of horizontal 3.19 lp/mm was observed in the lingual side. In the vertical resolution phantoms, it was possible to read a narrower range. By using the panorama resolution phantoms and phantom stand, it was possible to evaluate the resolution of a wide buccolingual width in four significant areas. By evaluating the resolution of the vertical and horizontal compartments separately, it was possible to gain a better understanding of the obtained images.

Rationale: Acantholytic squamous cell carcinoma (ASCC) is an uncommon histopathologic variant of squamous cell carcinoma (SCC), which is the most common malignancy of the oral cavity. Though ASCC showed poor prognosis, the exact diagnosis is challenging., Patients Concerns: A 59-year-old female patient with 1-month long symptoms of pain and burning sensation in the right maxilla., Diagnoses: Incisional biopsy in the maxilla established the pathologic diagnosis of SCC., Intervention: The patient underwent mass resection with near total maxillectomy., Outcomes: The final diagnosis through the microscopic examination was ASCC. Palliative chemotherapy was done to relive the symptoms after the recurrence, however, the patient died of the disease at 8 months after her initial presentation., Lessons: Special attention should be paid to this variant of SCC because most patients with ASCC have a very poor prognosis.

Background: The purpose of this study was to analyze the correlation between spatial resolution and ball distortion rate of panoramic radiography and to elucidate the minimum criterion for ball distortion rate, which is very relevant to clinical readability., Methods: Horizontal and vertical spatial resolution and ball distortion rates were calculated in the same position, such as the incisor, premolar, molar, and temporomandibular joint area with various object depths corresponding to 48 mm. Three devices were evaluated. A region showing spatial resolution above the reference standard was selected, and the ball distortion rate corresponding to the same region was divided into horizontal and vertical phantom groups. The mean and standard deviation of the obtained ball distortion rates were calculated. Student's t-test was used to statistically analyze the mean difference in ball distortion rates between vertical and horizontal phantom groups., Results: In all devices, the horizontal line pair phantom, but not the vertical line pair phantom, was readable in all areas measured at the line pair value of at least 1.88 lp/mm. The line pair value tended to be higher toward the center and lower toward the outside. The ball distortion rate tended to decrease closer to the center and increased further away. In addition, ball distortion rates could not be measured at some areas as they were not recognized as balls due to the high degree of distortion at the outermost and innermost sides. The number of balls satisfying the reference value using the horizontal line pair phantom was 102 (mean of ball distortion rates, 20.98; standard deviation, 15.25). The number of balls satisfying the reference value using the vertical line pair phantom was 49 (mean of ball distortion rates, 16.33; standard deviation, 14.25). However, mean ball distortion rate was not significantly different between the two groups., Conclusions: Image layer of panoramic radiography could be evaluated by the spatial resolution using horizontal and vertical line pair phantoms and by assessing ball distortion rates through a ball-type panorama phantom. A ball distortion rate of 20% could be used as a threshold to evaluate the image layer of panoramic radiography.

Objectives: The aim of this study was to analyze and compare the imaging features of osteomyelitis according to the presence or absence of antiresorptive medications by using computed tomography (CT)., Study Design: We retrospectively reviewed the records of 270 patients with osteomyelitis (83 males and 187 females; average age 66.6 years). CT imaging features were analyzed, and imaging and demographic features were compared between the medication-related osteomyelitis (MROM) group and the medication-unrelated osteomyelitis (MUOM) group., Results: Trabecular defects, cortical defects, sclerosis, and sequestra were detected in the majority of patients, whereas periosteal new bone formation was less common. The MROM group exhibited sequestra and periosteal new bone formation more frequently on CT images, but the size and appearance of the sequestra and type of periosteal new bone were not significantly different between the 2 groups., Conclusions: Sequestra and periosteal new bone formation were characteristic CT features of osteomyelitis more commonly found in the medication-related condition. These findings may be useful in the evaluation of osteomyelitis and medication-related osteonecrosis of the jaw., (Copyright © 2019 Elsevier Inc. All rights reserved.)

We developed an automatic method for staging periodontitis on dental panoramic radiographs using the deep learning hybrid method. A novel hybrid framework was proposed to automatically detect and classify the periodontal bone loss of each individual tooth. The framework is a hybrid of deep learning architecture for detection and conventional CAD processing for classification. Deep learning was used to detect the radiographic bone level (or the CEJ level) as a simple structure for the whole jaw on panoramic radiographs. Next, the percentage rate analysis of the radiographic bone loss combined the tooth long-axis with the periodontal bone and CEJ levels. Using the percentage rate, we could automatically classify the periodontal bone loss. This classification was used for periodontitis staging according to the new criteria proposed at the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions. The Pearson correlation coefficient of the automatic method with the diagnoses by radiologists was 0.73 overall for the whole jaw (p < 0.01), and the intraclass correlation value 0.91 overall for the whole jaw (p < 0.01). The novel hybrid framework that combined deep learning architecture and the conventional CAD approach demonstrated high accuracy and excellent reliability in the automatic diagnosis of periodontal bone loss and staging of periodontitis.

This study aimed to understand long-term changes of the osteoarthritic temporomandibular joint (TMJ) condyle using computed tomography (CT) and to verify its correlation with clinical characteristics of temporomandibular disorders. Eighty-nine patients (152 joints; 76 female, 13 male) who had taken follow-up CTs (mean follow-up period: 644.58 ± 325.71 days) at least once in addition to their initial evaluation were selected. Cross-sectional demographic and clinical data and longitudinal CT images were collected. Data were analyzed by analysis of variance and logistic regression. Overall destructive change index (number of TMJ condyle sections in which destructive change was observed) decreased from 1.56 to 0.66. Improvement was seen in 93 joints (61.2%) and 27 joints (17.8%) worsened. In the pain positive group, both initial and final destructive change index were significantly higher compared to the pain negative group (p = 0.04). Occlusal stabilization splint therapy and nonsteroidal anti-inflammatory drug administration showed a significant effect on improving the prognosis of TMJ osteoarthritis (p = 0.015 and 0.011). In conclusion, TMJ osteoarthritis showed long-term improvement in the majority of cases. TMJ osteoarthritis accompanied by pain showed unfavorable prognosis with additional bone destruction. Occlusal stabilization splint and nonsteroidal anti-inflammatory drug administration were beneficial on the prognosis of TMJ osteoarthritis.

Background: The aim of the present study was to evaluate the effectiveness of intraductal irrigation using normal saline in chronic obstructive sialadenitis., Methods: Patients who had one of the following symptoms were recruited: pain, swelling, stiffness, and dry mouth. A total of 58 salivary glands in 33 patients were diagnosed as having sialadenitis using sialography and ultrasonography. The patients were divided into two groups (swelling group and dry mouth group), according to the major complaint. Repeated intraductal irrigation was performed on each gland. Difference of symptom severity evaluated using numerical rating scale (NRS), and ductal width measured using ultrasonography were compared between the two groups., Results: The average NRS score was significantly decreased from 6.0 to 3.3 after 3-5 visits of intraductal irrigation (P < 0.05). The reduction in NRS was greater in the swelling group than in the dry mouth group, although the difference between the groups was not statistically significant. There was no change of ductal width before and after the irrigation., Conclusions: Intraductal irrigation according to this study method using normal saline is a simple treatment for the patients with chronic obstructive sialadenitis. It provides a conservative treatment option reducing the subjective symptoms.

Objectives: The aim of this study was to investigate the condylar dimensions of the temporomandibular joint (TMJ) with respect to disk displacements and sex by using computed tomography (CT) and magnetic resonance imaging (MRI)., Study Design: Disk displacements were divided into 3 groups based on MRI findings: normal disk position (NR), disk displacement with reduction (DDR), and disk displacement without reduction (DDNR). After the angular and linear condylar dimensions were calculated from CT images, differences in condylar dimensions with respect to disk displacements and sex were analyzed with 2-way analysis of variance., Results: Condylar depth and condylar height were significantly smaller in condyles with DDNR compared with those with NR or DDR (NR = DDR > DDNR). Condylar width gradually decreased significantly from NR to DDNR (NR > DDR > DDNR). The anterior condylar angle was significantly larger in condyles with NR compared with those with DDR or DDNR (NR > DDR = DDNR). Condyles with DDNR exhibited significantly larger horizontal condylar angles than those with NR or DDR (NR = DDR < DDNR). Altered condylar dimensions associated with disk displacement were not significantly different between men and women., Conclusions: Condylar dimensions may be significantly associated with disk displacements of the TMJ, irrespective of sex., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Molar-incisor malformation (MIM) is a recently defined dental abnormality of molar root and incisors, and introduced as one of the causes of periapical and periodontal abscess. The purpose of this study was to investigate the clinical and radiological features of MIM, with special emphasis on various medical history. A total of 38 patients with MIM were included in this study. Radiographic features and clinical data, including medical history, chief complaint, associated complications, treatment, and prognosis, were retrospectively investigated. On radiographs, the affected molars showed short, slender, underdeveloped roots and constricted pulp chambers. All affected incisors and canines exhibited dilacerated short roots, wedge-shaped defect on the cervical part of the crown. Complications included periodontal bone loss (52.6%), endodontic lesion (50.0%), and endodontic-periodontal lesion (28.9%). The medical histories of the patients with MIM indicate that almost all (94.7%) were hospitalized due to problems during the neonatal period. MIM may cause various dental problems, such as periapical and periodontal abscess and early loss of the affected teeth. The early diagnosis of MIM on radiographs and appropriate treatment will contribute to a favorable prognosis, especially for young and adolescent patients.

Monte Carlo (MC) simulation is a simpler radiation dose assessment method than the conventional method, thermoluminescent dosimetry (TLD). MC simulation and TLD were compared as tools to evaluate the effective dose from paediatric panoramic radiography. Various exposure conditions and machine geometries were simulated using the MC method to investigate factors resulting in effective dose reduction. The effective dose of paediatric panoramic radiography was obtained using an MC simulation and its reliability was verified by a comparison with the value obtained using TLD. Next, 7 factors determining the effective dose in the MC simulation were input with 6 equally-spaced values, and a total of 36 simulations were performed to obtain effective dose values. The correlations between each dose-determining factor and the resulting effective dose were evaluated using linear regression analysis. The TLD-measured dose was 3.850 µSv, while the MC simulation yielded a dose of 3.474 µSv. Beam height was the factor that most strongly influenced the effective dose, while rotation angle and focus-to-patient distance were the least influential factors. MC simulation is comparable to TLD for obtaining effective dose values in paediatric panoramic radiography. Obtaining panoramic radiography with a short beam height can effectively reduce the dose in paediatric patients.

Differential diagnosis of Langerhans Cell Histiocytosis (LCH) in the jaw is essential for early treatment including systemic therapy. Records of 17 patients (6 men and 11 women; mean age, 14 years) with histologically confirmed LCH were reviewed. All the lesions occurred in the mandible. Most of the cases (n=12) were intraosseous type LCH, only 5 patients had alveolar type LCH. Patients complained of facial swelling and pain most likely. In the 14 patients who underwent CT and/or MR imaging, all LCH lesions were osteolytic, with a mean size of 23 mm. LCH presented as expansile lesions with periosteal new bone formation, perilesional sclerosis, fluid attenuation/signal within the lesion, and inflammatory changes in adjacent soft tissues on CT/MR images. Considering the major symptoms of LCH were swelling and pain, the differential diagnosis of LCH from osteomyelitis might be more difficult. The differential diagnosis for osteolytic lesions of the jaw with surrounding inflammatory changes should include LCH, especially in young patients.

The present study was conducted to improve human identification based on dental pattern with adopting chronology of dental treatment within the system. Five hundred adult patients were randomly selected, and their initial and recent panoramic radiography images were assumed as antemortem (AM) and postmortem (PM) images, respectively. For each radiographic image, the dental pattern was analyzed. The analysis system was newly developed considering sequence of dental treatment in time order. AM and PM databases were constructed with information of dental patterns, patient age, and gender. For the PM database, age information was stored as the actual age ± 10 years, which was defined as the estimated age. According to dental pattern of PM record, the possible AM records were selected as candidates. Then candidates were sorted in order of dental pattern similarity to the PM record, and the rank of the true AM record was identified. The total 500 AM records were reduced to 14.5 ± 13.4 candidates in average when the dental pattern, gender, and estimated age were considered. When the candidates were sorted in order of similarity, the true AM record received an average ranking of 2.0 ± 2.6. When dental pattern and gender were considered, 46.7 ± 42.3 candidates were selected among 500 records and the true AM record was ranked at 3.0 ± 5.0, in average. The dental pattern analysis adopting dental treatment chronology was contributed to reduce the sample population. This method would become more efficient and comprehensive if the dental pattern analysis process is automatized in the near future., (Copyright © 2019 Elsevier B.V. All rights reserved.)

It is essential to reposition the mandibular proximal segment (MPS) as close to its original position as possible during orthognathic surgery. Conventional methods cannot pinpoint the exact position of the condyle in the fossa in real time during repositioning. In this study, based on an improved registration method and a separable electromagnetic tracking tool, we developed a real-time, augmented, model-guided method for MPS surgery to reposition the condyle into its original position more accurately. After virtual surgery planning, using a complex maxillomandibular model, the final position of the virtual MPS model was simulated via 3D rotations. The displacements resulting from the MPS simulation were applied to the MPS landmarks to indicate their final postoperative positions. We designed a new registration body with 24 fiducial points for registration, and determined the optimal point group on the registration body through a phantom study. The registration between the patient's CT image and physical spaces was performed preoperatively using the optimal points. We also developed a separable frame for installing the electromagnetic tracking tool on the patient's MPS. During MPS surgery, the electromagnetic tracking tool was repeatedly attached to, and separated from, the MPS using the separable frame. The MPS movement resulting from the surgeon's manipulation was tracked by the electromagnetic tracking system. The augmented condyle model and its landmarks were visualized continuously in real time with respect to the simulated model and landmarks. Our method also provides augmented 3D coronal and sagittal views of the fossa and condyle, to allow the surgeon to examine the 3D condyle-fossa positional relationship more accurately. The root mean square differences between the simulated and intraoperative MPS models, and between the simulated and postoperative CT models, were 1.71 ± 0.63 mm and 1.89 ± 0.22 mm respectively at three condylar landmarks. Thus, the surgeons could perform MPS repositioning conveniently and accurately based on real-time augmented model guidance on the 3D condyle positional relationship with respect to the glenoid fossa, using augmented and simulated models and landmarks., (Copyright © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

The purpose of this study was to develop a new method for enabling a robot to assist a surgeon in repositioning a bone segment to accurately transfer a preoperative virtual plan into the intraoperative phase in orthognathic surgery. We developed a robot system consisting of an arm with six degrees of freedom, a robot motion-controller, and a PC. An end-effector at the end of the robot arm transferred the movements of the robot arm to the patient's jawbone. The registration between the robot and CT image spaces was performed completely preoperatively, and the intraoperative registration could be finished using only position changes of the tracking tools at the robot end-effector and the patient's splint. The phantom's maxillomandibular complex (MMC) connected to the robot's end-effector was repositioned autonomously by the robot movements around an anatomical landmark of interest based on the tool center point (TCP) principle. The robot repositioned the MMC around the TCP of the incisor of the maxilla and the pogonion of the mandible following plans for real orthognathic patients. The accuracy of the robot's repositioning increased when an anatomical landmark for the TCP was close to the registration fiducials. In spite of this influence, we could increase the repositioning accuracy at the landmark by using the landmark itself as the TCP. With its ability to incorporate virtual planning using a CT image and autonomously execute the plan around an anatomical landmark of interest, the robot could help surgeons reposition bones more accurately and dexterously., (Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

In this study, correction of the maxillofacial deformities was performed by repositioning bone segments to an appropriate location according to the preoperative planning in orthognathic surgery. The surgery was planned using the patient's virtual skeletal models fused with optically scanned three-dimensional dentition. The virtual maxillomandibular complex (MMC) model of the patient's final occlusal relationship was generated by fusion of the maxillary and mandibular models with scanned occlusion. The final position of the MMC was simulated preoperatively by planning and was used as a goal model for guidance. During surgery, the intraoperative registration was finished immediately using only software processing. For accurate repositioning, the intraoperative MMC model was visualized on the monitor with respect to the simulated MMC model, and the intraoperative positions of multiple landmarks were also visualized on the MMC surface model. The deviation errors between the intraoperative and the final positions of each landmark were visualized quantitatively. As a result, the surgeon could easily recognize the three-dimensional deviation of the intraoperative MMC state from the final goal model without manually applying a pointing tool, and could also quickly determine the amount and direction of further MMC movements needed to reach the goal position. The surgeon could also perform various osteotomies and remove bone interference conveniently, as the maxillary tracking tool could be separated from the MMC. The root mean square (RMS) difference between the preoperative planning and the intraoperative guidance was 1.16 ± 0.34 mm immediately after repositioning. After surgery, the RMS differences between the planning and the postoperative computed tomographic model were 1.31 ± 0.28 mm and 1.74 ± 0.73 mm for the maxillary and mandibular landmarks, respectively. Our method provides accurate and flexible guidance for bimaxillary orthognathic surgery based on intraoperative visualization and quantification of deviations for simulated postoperative MMC and landmarks. The guidance using simulated skeletal models and landmarks can complement and improve conventional navigational surgery for bone repositioning in the craniomaxillofacial area., (Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Objective: The purpose of this study was to evaluate the patient radiation dose based on panoramic radiography and calculated with personal computer-based Monte Carlo (PCXMC) software compared with thermoluminescent dosimetry (TLD) measurement. We also proposed appropriate input values for dose-determining factors in PCXMC., Study Design: Tissue-absorbed doses and the effective dose based on panoramic radiography were measured with TLD and with PCXMC under various conditions. The calculated PCXMC doses were compared with those measured with TLD., Results: The effective doses calculated with PCXMC were higher by 9.55% to 51.24% compared with the doses measured with TLD. Reference points on the Y-axis and Z-axis were the sensitive factors when calculating the effective dose. The differences between the highest and the lowest organ doses were 0.32 and 0.10 mGy, respectively, for PCXMC calculation and TLD measurement., Conclusions: The effective dose calculated with PCXMC was generally higher than the dose measured by using TLD, and the absorbed doses varied by organ more severely in the PCXMC calculations than in the TLD measurements. The effective dose obtained from PCXMC calculations was dependent on input values for dose-determining factors. Standard values for each dose-determining factor required for the application of PCXMC to panoramic radiography were suggested in this study., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Accidental overextension of filling material during endodontic treatment may cause mechanical and chemical irritation of the adjacent tissue. In this case series, seven patients who complained of neurologic complication after overextension of canal filling material during endodontic treatment were presented. Overextensions of filling material into the surrounding tissues, such as the mandibular canal, bone marrow, and submucosal layer, were confirmed with panoramic radiograph and computed tomographic images. When patients complain of neurological disturbances after root canal treatment, proper radiographic images should be taken to verify any overextension of materials and to determine the specific location of the overfilled materials.

Objectives: This study proposed a new automated screening system based on a hybrid genetic swarm fuzzy (GSF) classifier using digital dental panoramic radiographs to diagnose females with a low bone mineral density (BMD) or osteoporosis., Methods: The geometrical attributes of both the mandibular cortical bone and trabecular bone were acquired using previously developed software. Designing an automated system for osteoporosis screening involved partitioning of the input attributes to generate an initial membership function (MF) and a rule set (RS), classification using a fuzzy inference system and optimization of the generated MF and RS using the genetic swarm algorithm. Fivefold cross-validation (5-FCV) was used to estimate the classification accuracy of the hybrid GSF classifier. The performance of the hybrid GSF classifier has been further compared with that of individual genetic algorithm and particle swarm optimization fuzzy classifiers., Results: Proposed hybrid GSF classifier in identifying low BMD or osteoporosis at the lumbar spine and femoral neck BMD was evaluated. The sensitivity, specificity and accuracy of the hybrid GSF with optimized MF and RS in identifying females with a low BMD were 95.3%, 94.7% and 96.01%, respectively, at the lumbar spine and 99.1%, 98.4% and 98.9%, respectively, at the femoral neck BMD. The diagnostic performance of the proposed system with femoral neck BMD was 0.986 with a confidence interval of 0.942-0.998. The highest mean accuracy using 5-FCV was 97.9% with femoral neck BMD., Conclusions: The combination of high accuracy along with its interpretation ability makes this proposed automatic system using hybrid GSF classifier capable of identifying a large proportion of undetected low BMD or osteoporosis at its early stage.

Haemophilic pseudotumour is a rare disease that occurs most often in femur, tibia, ilium or pelvic bone of a patient with haemophilia. Thus far, there have been only 31 reported cases in jaw bones and paranasal sinuses. Among them, the mandible is a more common site than the maxilla or paranasal sinuses. Here, we report a case of haemophilic pseudotumour in two parts of the maxilla. Contrast-enhanced CT showed an expansive and thinly corticated lesion with fluid attenuation at the left anterior maxilla which seemed like a post-operative maxillary cyst, ameloblastoma or odontogenic cyst. In addition, the thickened left palatal process of the maxilla seemed like fibrous dysplasia or intraosseous vascular malformation. Since haemophilic pseudotumour is not pathognomonic in radiological findings, when a patient who suffered from haemophilia or had taken anticoagulating agents has jaw lesion, haemophilic pseudotumour should be included in a differential diagnosis.

Objective: To evaluate the potential feasibility of cone beam computed tomography (CBCT) in the assessment of trabecular bone microarchitecture., Study Design: Sixty-eight specimens from four pairs of human jaw were scanned using both micro-computed tomography (micro-CT) of 19.37-μm voxel size and CBCT of 100-μm voxel size. The correlation of 3-dimensional parameters between CBCT and micro-CT was evaluated., Results: All parameters, except bone-specific surface and trabecular thickness, showed linear correlations between the 2 imaging modalities (P < .05). Among the parameters, bone volume, percent bone volume, trabecular separation, and degree of anisotropy (DA) of CBCT images showed strong correlations with those of micro-CT images. DA showed the strongest correlation (r = 0.693)., Conclusions: Most microarchitectural parameters from CBCT were correlated with those from micro-CT. Some microarchitectural parameters, especially DA, could be used as strong predictors of bone quality in the human jaw., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: To investigate the constancy of the angle between the Frankfort horizontal plane (FH) and the sella-nasion line (SN) using longitudinal data., Materials and Methods: Longitudinal lateral cephalometric data of 223 children (116 girls and 107 boys) from 6 to 14 years of age were used. The angle between FH and SN (SNFH), the distance from FH to the nasion (NFH), the distance from FH to the sella (SFH), and the differences between the NFH and SFH (Δ) were also measured. All data were analyzed statistically using independent t-tests and mixed-effect regression model analysis., Results: The mean SNFH values showed some minor fluctuations, ranging from 9.26° to 9.74° in girls and 8.45° to 8.95° in boys. The mean NFH and SFH values gradually increased according to age irrespective of sex. There were statistically significant differences by sex for all measurements at several ages. The annual change in SFH and Δ showed sexual dimorphism., Conclusions: There are variations among individuals in the angle between the FH and SN. However, within an individual, the angle does not vary significantly over time during the observation period.