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/purpose In cases where oral squamous cell carcinoma (OSCC) invades the jawbone, clinicians frequently observe abnormal attenuation on computed tomography (CT) and pathologic signal intensity (SI) on magnetic resonance (MR) imaging of the affected underlying bone marrow. This study introduced a concept of "underlying bone change" to examine its association with clinicopathological features and prognosis of OSCC, as well as its correlation with medullary invasion. We enrolled 93 consecutive patients diagnosed with OSCC, who underwent mandibulectomy between 2010 and 2016. CT and MR images, along with electronic medical records, were reviewed to evaluate correlations between underlying bone changes, clinicopathological features, five-year overall survival, and medullary invasion. Of the 93 patients, 69 (74.2%) exhibited underlying bone sclerosis on CT, and 74 (79.6%) displayed pathological SI on MR images. These underlying bone changes correlated with the T stage and recurrence, but not with overall survival. Medullary invasion, observed in 61 (65.6%) patients, was strongly associated with T and TNM stages and was linked to poorer overall survival. The underlying bone changes on CT and MR images were positively associated with medullary invasion; however, no significant differences were found in the occurrence of underlying bone changes between the subtypes based on the extent of medullary invasion. Underlying bone changes on CT and MR images can provide valuable insights into the aggressiveness of bone invasion by OSCC. Accurate interpretation of these imaging findings might be crucial for correctly delineating surgical margins and preventing the overestimation of tumor extent. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate a deep convolutional neural network (DCNN) method for the detection and classification of nasopalatine duct cysts (NPDC) and periapical cysts (PAC) on panoramic radiographs. A total of 1,209 panoramic radiographs with 606 NPDC and 603 PAC were labeled with a bounding box and divided into training, validation, and test sets with an 8:1:1 ratio. The networks used were EfficientDet-D3, Faster R-CNN, YOLO v5, RetinaNet, and SSD. Mean average precision (mAP) was used to assess performance. Sixty images with no lesion in the anterior maxilla were added to the previous test set and were tested on 2 dentists with no training in radiology (GP) and on EfficientDet-D3. The performances were comparatively examined. The mAP for each DCNN was EfficientDet-D3 93.8%, Faster R-CNN 90.8%, YOLO v5 89.5%, RetinaNet 79.4%, and SSD 60.9%. The classification performance of EfficientDet-D3 was higher than that of the GPs' with accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 94.4%, 94.4%, 97.2%, 94.6%, and 97.2%, respectively. The proposed method achieved high performance for the detection and classification of NPDC and PAC compared with the GPs and presented promising prospects for clinical application. [ABSTRACT FROM AUTHOR]

An essential step for 3D virtual surgical planning in orthognathic surgery is image segmentation to generate virtual 3D models for virtual osteotomy of the maxillofacial bone in CT images. However, this manual segmentation process is time-consuming and labor-intensive and requires expertise. Also, most conventional automatic segmentation methods can not directly segment the maxillofacial bone for virtual Le Fort I osteotomy. The purpose of this study was to automatically and robustly segment the maxillofacial bone for virtual Le Fort I osteotomy in CT images using a deep multi-scale attentive fusion network (MAFNet). MAFNet consisted of multi-scale encoders (MEs), an atrous feature fusion module (AFFM), a multi-scale spatial attention module (MSAM), and a weighted soft combo loss (SCL) with deep supervision. In performance comparisons, MAFNet outperformed popular segmentation networks by achieving 0.836, 0.951, and 0.929 in terms of F1-score for the maxilla, mandible, and skull segmentation, respectively. In ablation studies, the proposed components and SCL improved segmentation performance by allowing the network to learn multi-scale feature representations and anatomical contexts efficiently. MEs and AFFM captured multi-scale context features and mitigated the loss of spatial information. MSAM emphasized the boundary details, such as an osteotomy line between the maxilla and skull, and suppressed irrelevant background details, such as metal artifacts and soft tissues. SCL with deep supervision helped MAFNet alleviate the class imbalance problem and improve segmentation performance. Therefore, MAFNet outperformed popular segmentation networks and obtained robust segmentation results on challenging CT images including osteotomy lines, metal artifacts, and malocclusions in CT images. • MAFNet predicts the mandible, maxilla, and skull regions for the Le Fort I osteotomy. • Multi-scale encoders are proposed to capture multi-scale context features. • Atrous feature fusion module is proposed to enlarge the receptive field of layers. • Multi-scale spatial attention module is used to focus on the salient regions. • MAFNet shows accurate and robust segmentation for the virtual Le Fort I osteotomy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. 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. 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. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to estimate the prevalence of palatine tonsilloliths and analyze their multidetector computed tomography (CT) imaging features.Study Design: The CT images of 3886 patients (1654 men, 2232 women; mean age, 35.8 years) were reviewed. The distribution, dimension, morphology, and location of each tonsillolith was assessed. The correlation between participant demographic characteristics and the characteristics (prevalence, number, size) of tonsilloliths was determined.Results: The prevalence of palatine tonsilloliths was 30.3%; we identified significant differences in the prevalence and size between men and women. The prevalence of tonsilloliths significantly increased with age (P < .001). The mean number of tonsilloliths per participant was 2.7, and 64.7% of patients had 1 to 2 tonsilloliths. Ovoid-shaped tonsilloliths were the most common (approximately 80%). The centers of the tonsillar crypts contained the majority of the tonsilloliths, 50.3% of which had sizes of 1 to 2 mm.Conclusion: The results, based on a larger sample size compared with previous studies, can be applied as guidelines for the diagnosis of tonsilloliths on CT images. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, we have developed an advanced navigational implant surgery system to overcome some disadvantages of the conventional method and have evaluated the accuracy of the system under in vitro environment. The patient splint for registration and tracking was improvised using a bite splint without laboratory work and the offset of an exchanged drill was calibrated directly without pivoting during surgery. The mean target registration errors (TRE) were 0.35 ± 0.11 mm using the registration body, 0.34 ± 0.18 mm for the registration method with prerecorded fiducials, and 0.35 ± 0.16 mm for the direct calibration of a drill offset. The mean positional deviations between the planned and placed implants in 110 implant surgeries were 0.41 ± 0.12 mm at the center point of the platform and 0.56 ± 0.14 mm at the center point of the apex. The mean angular deviation was 2.64°± 1.31 for the long axis of the implant. In conclusion, the developed system exhibited high accuracy, and the improved tools and simplified procedures increased the convenience and availability. With this advanced approach, it will be possible to complete dental implant surgery during a single visit at local clinics using a navigational guidance involving cone-beam computed tomographic images. [ABSTRACT FROM AUTHOR]

Accurate surgical planning and transfer of the planning in orthognathic surgery are very important in achieving a successful surgical outcome with appropriate improvement. Conventionally, the paper surgery is performed based on a 2D cephalometric radiograph, and the results are expressed using cast models and an articulator. We developed an integrated orthognathic surgery system with 3D virtual planning and image-guided transfer. The maxillary surgery of orthognathic patients was planned virtually, and the planning results were transferred to the cast model by image guidance. During virtual planning, the displacement of the reference points was confirmed by the displacement from conventional paper surgery at each procedure. The results of virtual surgery were transferred to the physical cast models directly through image guidance. The root mean square (RMS) difference between virtual surgery and conventional model surgery was 0.75 ± 0.51 mm for 12 patients. The RMS difference between virtual surgery and image-guidance results was 0.78 ± 0.52 mm, which showed no significant difference from the difference of conventional model surgery. The image-guided orthognathic surgery system integrated with virtual planning will replace physical model surgical planning and enable transfer of the virtual planning directly without the need for an intermediate splint. [ABSTRACT FROM AUTHOR]

We developed a new method to record and reproduce the three-dimensional natural head position (NHP) from a single photograph of a patient's face using a pose from orthography and scaling with iterations (POSIT) algorithm. We attached 4-mm spherical ceramic markers to the patient's face as feature points. A frontal photograph of the patient's NHP was taken using an ordinary digital camera parallel to the global horizon. Computed tomography (CT) was then performed on the patient with the markers. The ceramic marker positions were determined in the 2D image and corresponded to points in the 3D model. The 3D rotation matrix determined using the feature points via the POSIT method was applied to the CT model to reproduce the NHP. A skull phantom was used to evaluate the accuracy and reproducibility of the developed method. The degree difference (°) between the true and POSIT orientations in the roll, pitch, and yaw directions was quantified as the error. The mean accuracy was −0.04 ± 0.15°, −0.17 ± 0.50°, and −0.02 ± 0.37° in the roll, pitch, and yaw directions, respectively. The method developed was highly reproducible during intra-observer and inter-observer variation analyses. The accuracy of the method was clinically acceptable, and the procedure was time- and cost-effective. This method is accurate and inexpensive; additionally, it does not affect the patient's lip position, and we expect it to be routinely used during orthognathic surgery. [ABSTRACT FROM AUTHOR]

Objective: The accuracy and consistency of a new image-guided method for orthognathic surgery using direct and continuous landmark localization was compared with that of a conventional method. Study design: Maxillary and mandibular dental casts mounted on an articulator were used as a surgery phantom. We planned six types of surgeries including translations and rotations. The sequential positions of the landmarks determined before surgery could be traced and the difference between planned and actual positions of the landmarks could be visualized during surgery. The final deviation errors were determined with and without applying the pointing instrument to the landmarks. Results: The mean RMS accuracy of 0.47 ± 0.22 mm by direct localization was significantly higher than that of 1.06 ± 0.49 mm by the manual localization. There were no significant differences in accuracies for surgeries using the direct localization method. Conclusion: The direct and continuous localization method showed higher accuracy and consistency than conventional manual localization in all phantom surgeries. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: The purpose of this study was to investigate the relationship between changes in three-dimensional (3D) facial morphology and mandibular movement after orthognathic surgery. We hypothesized that facial morphology changes after orthognathic surgery exert effects on 3D mandibular movement. Materials and methods: We conducted a prospective follow-up study of patients who had undergone orthognathic surgical procedures. Three-dimensional facial morphological values were measured from facial CT images before and three months after orthognathic surgery. Three-dimensional maximum mandibular opening (MMO) values of four points (bilateral condylions, infradentale, and pogonion) were also measured using a mandibular movement tracking and simulation system. The predictor variables were changes in morphological parameters divided into two groups (deviated side (DS) or contralateral side (CS) groups), and the outcome variables were changes in the MMO at four points. Results: We evaluated 21 subjects who had undergone orthognathic surgical procedures. Alterations in the TFH (total facial height), LFH (lower facial height), CS MBL (mandibular body length), and DS RL (ramus length) were negatively correlated with changes in bilateral condylar movement. The UFH, DS MBL and CS ML (mandibular length) showed correlations with infradentale movement. The CS ML, DS ML, MBL, UFH, and SNB were correlated with pogonion movement. Conclusion: The height of the face is most likely to affect post-operative mandibular movement, and is negatively correlated with movement changes in the condyles, infradentale and pogonion. The changes in CS morphological parameters are more correlated with mandibular movement changes than the DS. The changes in CS MBL and bilateral RL were negatively correlated with condylar movement changes, while the bilateral MBL and CS ML were positively correlated with changes in infradentale and pogonion. [Copyright &y& Elsevier]

Objectives: This study aimed to assess the hard and soft tissue changes in osteomyelitis (OM) of the jaws using CT images. Study Design: The CT images of 153 patients (59 males and 94 females) with OM of the jaws were retrospectively reviewed. The relationships between each space involvement, between space and muscle involvements, between cortical bone defect and space involvement, and between cortical bone defect and muscle involvement were evaluated. Results: The cortical bone defect was more common on the buccal side in the maxilla and on the lingual side in the mandible. The most commonly involved muscle was the buccinator muscle in the maxilla and the masseter muscle in the mandible and the most frequently involved space was the buccal space followed by the masticator space. Conclusions: CT is a useful tool in evaluating both hard and soft tissue changes of OM of the jaws. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to analyze the relationship between mandibular movement and facial morphology parameters measured using 3-dimensional CT data. Materials and Methods: We have developed a mandibular movement tracking and simulation system. The mandibular movement data were acquired from 22 subjects (6 males and 16 females), 3 who had no clinical facial deformities and 19 who had orthofacial deformities. The subjects voluntarily performed maximum mouth opening and closing movements. Three-dimensional maximum linear movements of selected points (bilateral condylions, infradentale, and pogonion) were calculated to represent mandibular movement. Facial morphology values were measured 3-dimensionally from CT data and bilateral morphological values were divided into 2 groups according to the mandibular deviation, the deviated side, and counter-deviated side groups. Correlation coefficients were calculated to evaluate the relationship between mandibular movements and facial morphology. Results: Maximum linear movements of all selected points on the mandible were positively correlated with sella-nasion-point A (SNA) and sella-nasion-point B (SNB). Movements of the infradentale and pogonion were significantly correlated with ramus inclination, lateral mandibular body angle, ramus length, and mandibular body length. Condylar movement was positively correlated with lateral mandibular body angle and mandibular body length. Multiple stepwise linear regression analysis was performed to evaluate the model predicting the effect of morphological values on mandibular movement. Condylar movement was associated with the SNA (R2 value = 0.32 for the deviated side, R2 value = 0.26 for the counter-deviated side), and movement of the infradentale was associated with both SNA and ramus length (R2 value = 0.57). Movement of the pogonion could be predicted by SNA, mandibular length, and condylar head length (R2 value = 0.65). Conclusion: The 3D facial morphology values were associated with variations in mandibular movement, and morphological parameters contributed to predicting the movement of the mandible with different degrees. [Copyright &y& Elsevier]

Objectives: The purpose of this study is to investigate the effects of different bit depths and kilovoltage peak (kVp) values used in intraoral digital radiography on observer performance in detecting subtle radiographic density differences. Study design: Using an intraoral CCD sensor set at 8- or 12-bit depth, kVp set at 60 or 70, and 14 different exposure times, digital radiographs were acquired of a specially designed aluminum step-wedge phantom with small holes of different depths in each step. Ten observers examined all images. Results: The observers counted more holes with the 12-bit images compared with the 8-bit images, particularly at 60 kVp. Significantly more holes were also counted with images taken at 70 kVp compared with those taken at 60 kVp. Conclusion: Regarding the detection of subtle radiographic density differences, 12-bit images and 70 kVp were superior to 8-bit images and 60 kVp. [Copyright &y& Elsevier]

Objectives: To examine the effects of the luminance and bit depth of digital image on observer performance for determination of endodontic file positioning. Study design: Using extracted premolar teeth, no. 08 K-file was placed into the canal and positioned so that the tip was either flush or 1 mm short of the radiologic root apex. The samples were imaged with both conventional and digital radiographs at 8 and 12 bits. Eleven observers read the images under dark and bright condition, and receiver operating characteristics analysis was performed. Additionally, the interpreting time was measured. Results: The 12-bit images showed similar observer performance compared with conventional images, and better than the 8-bit images. The interpretation time for bright condition and 8-bit images was longer than for dark condition and 12-bit images. Conclusion: Twelve-bit digital images were preferred to 8-bit for accurate determination of endodontic file position. [Copyright &y& Elsevier]

Objective: Precise in vivo measurement of the trabecular bone’s mechanical properties is very important for endosseous dental implant treatment and design in clinical practice. The fractal structure of trabecular bone shows directional anisotropy of the architecture, as is shown in most biological fractals. To analyze the anisotropy of the trabecular bone, the fractal geometry technique was applied to 2-dimensional plain radiographs. Study design: The power spectrum was used to calculate the fractal dimensions (FD) of the trabecular bone. The FDs calculated as a function of orientation yielded the fractal information reflecting the spatial characteristics of the trabecular bone in each direction. A polar plot of directional FDs was defined as an ellipse of inertia. The principal loading direction in a local region of the trabecular bone was determined from the minimum moment of inertia for the ellipse of FDs. The anisotropy was calculated directly as the ratio of the 2 principal moments of inertia from the ellipse. Results: The anisotropies were measured for radiographs from the angle and incisor region of 21 human mandibles based on the principal axes of inertia and the best-fitting ellipse. The anisotropy of the angle region was significantly greater than that of the incisor region of the mandibles. Conclusion: The method using directional FDs as determined by the principal axis of inertia measures the anisotropy directly, using 2-dimensional plain radiographs. It can quantify the anisotropy of trabecular bone in vivo. The investigation can be applied to the analysis of the relationships between in vivo 2-dimensional parameters and 3-dimensional mechanical properties, which enables us to predict the bone mechanical properties such as strength in vivo in various regions of the mandible. [Copyright &y& Elsevier]

Objective: We evaluated the influence of surrounding anatomical structures on the registration accuracy of a diagnostically important region, by varying the ROI (region of interest) window used in an automatic ROI-based digital subtraction method. Study design: Pairs of radiographs were taken at 2 molar regions using paralleling techniques of XCP devices (Rinn Co., Elgin, Ill) attached with and without a bite block. The global and local registration accuracies were measured by the RMS (root mean square) of subtraction images for various ROIs. Results: No significant differences were found in global registration accuracies among various ROI sizes in all the paralleling techniques. The local registration accuracies decreased with extension of the ROI size. Conclusion: Registration using an ROI restricted to the anatomical region of diagnostic interest provides higher accuracy than using a larger ROI. [Copyright &y& Elsevier]

Objectives: To investigate the relationship between two-dimensional (2D) and three-dimensional (3D) bone imaging parameters. Study design: Bone specimens were obtained from the mandibles of five male pigs weighing around 110 kg each. A total of 111 samples were measured two-dimensionally with using solid state digital intraoral radiography. Of these 111 samples, 43 were selected for 3D analysis and measured by microcomputed tomography. Through destructive mechanical testing, strength parameters were obtained. Results: Correlations between the 2D and 3D parameters were rare; however, both 2D and 3D parameters separately showed significant correlations with strength. Multiple linear regression analyses using both 2D and 3D parameters together showed greater predictability than those using only 2D or only 3D parameters. Conclusion: Architectural parameters in 2D and 3D independently affect trabecular strength; the combination of the two can be used to improve bone strength predictability. [Copyright &y& Elsevier]

Objective: This study compared the difference between 3 intraoral radiographic techniques on digital subtraction radiography (DSR) in vivo that are commonly used in a clinical setting. Study design: We evaluated and statistically analyzed the errors in the DSR image in 6 regions with 3 radiographic techniques: paralleling technique with a bite block attached to XCP, paralleling technique using XCP, and bisecting-angle technique. Results: The amount of error using the bisecting-angle technique was too large for DSR, compared to that of the paralleling technique with a bite block attached to XCP. In the mandibular anterior region, the paralleling technique using XCP was not different from paralleling technique with a bite block attached to XCP. The lowest degree of error was present in the anterior region whereas the highest was present in the molar region. Conclusion: Bisecting-angle technique should be avoided, and paralleling technique using XCP can be used in the mandibular anterior region for DSR. [Copyright &y& Elsevier]

Keratoameloblastoma is a rare subtype of ameloblastoma. It tends to have a poor prognosis, and therefore a careful diagnosis based on imaging is important in planning appropriate surgical treatment for this distinctive type of ameloblastoma. A unique feature of keratoameloblastoma is atypical calcification inside the mass, such as a ground-glass appearance, internal calcification, or a mixed radiolucent and radiopaque pattern. Because of its poor prognosis and the likelihood of frequent recurrences, surgical resection is considered the treatment of choice. This study reports a new case of keratoameloblastoma with special emphasis on its radiologic features and reviews previously reported cases of keratoameloblastoma. [ABSTRACT FROM AUTHOR]

Objective: To investigate the rotational variations of three-dimensional (3D) trajectories at anatomic landmarks by different mandibular kinematics, we applied principal axes of inertia to the 3D trajectories. The principal rotations were determined directly from the anatomy-based trajectories produced by a patient-specific temporomandibular joint simulation. As a preliminary study, the principal rotations for a pilot group of patients with mandibular deviation were correlated with the deviation. Study design: Three-dimensional mandibular movements from the patients with mandibular deviation were tracked based on a patient-specific splint and an optical tracking system. The dental occlusion recorded on the splint provided synchronization for initial movement in the tracking and the simulation phases. The translation and rotation recorded during tracking were applied sequentially to the mandibular model in relation to a fixed maxilla model. The sequential positions of the points of interest based on the reference coordinate system could also be simulated and traced by the same method. The landmarks selected for analysis were the points of the bilateral condyles and of the mandibular incisor. The moment of inertia tensor was calculated with respect to the 3D trajectory points. Using the unit vectors along the principal axes derived from the tensor matrix, α, β, and γ rotations (horizontal, sagittal, and frontal planes) around the z-, y-, and x-axes, respectively, were determined to represent the principal directions as principal rotations. Results: The measured rotations were correlated with the deviation in 3 orthogonal planes. Under the influence of the mandibular asymmetry, the orientations of the principal axis at the condyles increase counterclockwise in the horizontal plane and clockwise in the frontal plane. At the incisor point, the horizontal and frontal angles increase counterclockwise, but the sagittal angles increase clockwise. The interrelations between different rotations and between landmarks, defined as a correlation coefficient between principal rotations, decrease as the deviation increases. Conclusions: Three-dimensional trajectories at selected landmarks based on the reference coordinate system were evaluated using principal axes of inertia to investigate the functional characteristics of the mandible with a deviation. The movement asymmetry between the condyles increases as the deviation increases in all directions. The principal rotations at the condyles can be explained by those at the incisor with varying degrees despite the deviation. [Copyright &y& Elsevier]

Objective: To characterize the presentation of C-shaped canals in mandibular molars on dental panoramic radiographs. Study design: The sample consisted of 290 patients who had undergone both panoramic dental radiography and computed tomography (CT). Initially the presence of mandibular molars with C-shaped canals was identified on this sample by the use CT. This was used as a ground radiographic truth. Then 3 investigators independently classified the mandibular molars according to their 6 root morphologies on panoramic dental radiographs. The sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) of characteristic findings on panoramic radiographs were calculated. Results: A C-shaped canal was identified in 90 (29%) of 311 mandibular molars. The most common morphology of C-shaped canal molars was 2 separate conical roots (52%); trabecular patterns were relatively common between the roots. In contrast, the most common morphology of molars without C-shaped canals was 2 separate roots that were either divergent or parallel (85%). Conclusion: Panoramic radiography is a good surveying modality to detect C-shaped canals and can be used to determine whether further examination is required before endodontic treatment. [Copyright &y& Elsevier]

Objective: The objective of this study was to evaluate the relationship between sialographic images and clinical symptoms of inflammatory parotid gland diseases. Materials and methods: Clinical symptoms including swelling, pain, the duration of these symptoms, and degree of salivation were examined on 83 parotid glands from 64 patients. Swelling and pain were classified into 4 categories. Duration of any symptom was recorded in months and the degree of salivation was classified into 4 groups by inspection and massage. Sialography was performed and panoramic radiographs were taken later to examine the evacuation state of the contrast medium. The degree of inflammation on sialographic images was evaluated in 3 areas (the main duct, the intraglandular duct, and the parenchyma) by rating 4 grades respectively under the consensus of 3 radiologists. A Fisher''s exact test and a Pearson correlation were used for statistical analyses. Results: The degree of salivation showed significant correlation between the presence of inflammation and the grades of inflammation on sialographic images. There was also a correlation between the grades of inflammation of the sialographic images and the amount of retention of the contrast medium. There was no significant relationship between the grades of inflammation of the sialographic images with swelling or pain. Conclusion: The grade of inflammation of a sialographic image has correlated with a degree of salivation. [Copyright &y& Elsevier]