• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.1
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• pp.37-42
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• 2010

Purpose: The mental foramen (MF) is an important anatomical structure during local anesthesia and surgical procedures in terms of achieving effective mental nerve blocks and avoiding injuries to the neurovascular bundles. Thus, understanding the anatomic features of the mandibular canal and accessory mental foramen in Korean could contribute to the surgical anatomic assessment. This study was to elucidate frequency, position and course of AMF (accessory mental foramen) in Korean using 3D cone beam computed tomography. Materials and Methods: The CBCT (Conbeam computed tomography) DICOM data (Alphard, Asahi, Japan) from 540 patients in korean were analyzed. We investigated images of 3D CBCT using Ondemand (CyberMed, Korea) software program on the incidence and anatomical characteristics of accessory foramen. Results: The accessory mental foramina were found in 17 patients. Accessory mental foramina exist predominantly in the apical area of the second premolar and posteroinferior area of the mental foramen. The accessory branches of the mandibular canal showed common characteristics in the course of gently sloping posterosuperior direction in the buccal surface area. The size of most AMF was obviously smaller than that of MF. Conclusion: We could identify frequency, position and course of AMF (accessory mental foramen) by the anatomical study of the accessory mental foramen using 3D cone beam CT in Korean.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.2
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• pp.106-111
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• 2012

Purpose: The aim of this sturdy was to assess the prevalence and change in pathologic findings in the maxillary sinus by using preoperative and postoperative cone-beam computed tomography (CBCT). Methods: The subjects included 83 patients with maxillary sinus abnormalities who underwent orthognathic surgery between January 2010 to December 2010. The CBCT analyses were classified according to the thickness of maxillary sinus membrane; Normal (membrane thickness<2 mm), mucosal thickening (membrane thickness ${\geq}2mm$ and <6 mm), partial opacification (membrane thickness>6 mm but not complete), total opacification, and polypoidal mucosal thickening. The diameters of the maxillary sinus ostium on the coronal cross-sectional view were also calculated. Results: Out of 166 maxillary sinuses in 83 patients, 42 (25.3%) maxillary sinuses before surgery and 37 (22.3%) maxillary sinuses after surgery showed abnormalities. A decrease in the diameters of maxillary ostium was observed after surgery (P<0.05). However, there was no significant difference in mucosal thickness both, preoperatively and postoperatively. Conclusion: The orthognathic surgery didn't deteriorate the maxillary sinus abnormaility. Despite the low prevalence of sinus complications in orthognathic surgery, all the patients should be informed of the possibility of sinusitis that could require the surgical intervention before surgery.

• Imaging Science in Dentistry
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• v.47 no.3
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• pp.199-207
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• 2017

Purpose: Evaluation of alveolar bone is important in the diagnosis of dental diseases. The periodontal ligament space is difficult to clearly depict in cone-beam computed tomography images because the reconstruction filter conditions during image processing cause image blurring, resulting in decreased spatial resolution. We examined different reconstruction filters to assess their ability to improve spatial resolution and allow for a clearer visualization of the periodontal ligament space. Materials and Methods: Cone-beam computed tomography projections of 2 skull phantoms were reconstructed using 6 reconstruction conditions and then compared using the Thurstone paired comparison method. Physical evaluations, including the modulation transfer function and the Wiener spectrum, as well as an assessment of space visibility, were undertaken using experimental phantoms. Results: Image reconstruction using a modified Shepp-Logan filter resulted in better sensory, physical, and quantitative evaluations. The reconstruction conditions substantially improved the spatial resolution and visualization of the periodontal ligament space. The difference in sensitivity was obtained by altering the reconstruction filter. Conclusion: Modifying the characteristics of a reconstruction filter can generate significant improvement in assessments of the periodontal ligament space. A high-frequency enhancement filter improves the visualization of thin structures and will be useful when accurate assessment of the periodontal ligament space is necessary.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.1
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• pp.34-40
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• 2012

Purpose: The study was performed to compare patients with anatomical variations in facial asymmetry with patients in the normal range using cone-beam computed tomography (CBCT) and to take the preoperative condition into consideration in the case of a sagittal split ramus osteotomy (SSRO). Methods: The study was conducted on 46 adult patients composed of 2 subdivided groups, an asymmetry group (n=26) and a symmetry group (n=20). The asymmetry group was divided between patients with hemimandibular hyperplasia (HH, n=8) and hemimandibular elongation (HE, n=18). Using cross-sectional computed tomography images, the thickness of cancelleous bone in the buccal area of the mandible, thickness of buccal cortex in the buccal aspect of the mandible, thickness of cancellous bone in the inferior aspect of the mandible, thickness of buccal cortex in the inferior aspect of the mandible, and cross-sectional surface area of the mandible were measured. Results: In the asymmetry group, the cross-sectional area of the mandible including the inferior alveolar nerve positioned on the affected side was significantly different from the symmetry group. Thickness of cancelleous bone in the buccal aspect of the mandible, thickness of cancelleous bone in the inferior aspect of the mandible, and cross-sectional surface area of the mandible in the affected site of hemimandibular hyperplasia was significantly smaller than in the symmetry group. Conclusion: The inferior alveolar nerve runs lower and in a more buccal direction and shows a smaller cross-sectional surface of the mandible in the hemimandibular hyperplasia patients with asymmetry.

• Imaging Science in Dentistry
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• v.44 no.4
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• pp.279-285
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• 2014

Purpose: To assess the influence of anatomic location on the relationship between computed tomography (CT) number and X-ray attenuation in limited and medium field-of-view (FOV) scans. Materials and Methods: Tubes containing solutions with different concentrations of $K_2HPO_4$ were placed in the tooth sockets of a human head phantom. Cone-beam computed tomography (CBCT) scans were acquired, and CT numbers of the $K_2HPO_4$ solutions were measured. The relationship between CT number and $K_2HPO_4$ concentration was examined by linear regression analyses. Then, the variation in CT number according to anatomic location was examined. Results: The relationship between $K_2HPO_4$ concentration and CT number was strongly linear. The slopes of the linear regressions for the limited FOVs were almost 2-fold lower than those for the medium FOVs. The absolute CT number differed between imaging protocols and anatomic locations. Conclusion: There is a strong linear relationship between X-ray attenuation and CT number. The specific imaging protocol and anatomic location of the object strongly influence this relationship.

• Imaging Science in Dentistry
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• v.42 no.2
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• pp.65-70
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• 2012

Purpose : The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Materials and Methods : Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. Results : The effective dose was the highest for Somatom Sensation 10 (425.84 ${\mu}Sv$), followed by AZ3000CT (332.4 ${\mu}Sv$), Somatom Emotion 6 (199.38 ${\mu}Sv$), and 3D eXaM (111.6 ${\mu}Sv$); it was the lowest for Implagraphy (83.09 ${\mu}Sv$). The CBCT showed significant variation in dose level with different device. Conclusion : The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

• Imaging Science in Dentistry
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• v.50 no.4
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• pp.299-307
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• 2020

Purpose: The diagnosis of chronic rhinosinusitis requires a comprehensive knowledge of the signs and symptoms of the disease and an accurate radiographic assessment. Computed tomography (CT) is the superior imaging modality for diagnosis of chronic rhinosinusitis. However, considering the lower dose and higher resolution of cone-beam computed tomography (CBCT) compared to CT, this study aimed to assess the agreement between the findings of CBCT and functional endoscopic sinus surgery (FESS). Materials and Methods: This descriptive prospective study evaluated 49 patients with treatment-resistant chronic rhinosinusitis who were candidates for FESS. Preoperative CBCT scans were obtained before patients underwent FESS. The agreement between the CBCT findings and those of FESS was determined using the kappa correlation coefficient. The frequency of anatomical variations of the paranasal sinuses was also evaluated on CBCT scans. Results: Significant agreement existed between pathological findings on CBCT scans and those of FESS, such that the kappa correlation coefficient was 1 for mucosal thickening, 0.644 for nasal deviation, 0.750 for concha bullosa, 0.918 for nasal polyp, 0.935 for ostiomeatal complex (OMC) obstruction, and 0.552 for infundibulum thickening. Furthermore, 95.9% of patients had 1 or more and 79.6% had 2 or more anatomical variations, of which nasal deviation was the most common (67.3%). Conclusion: Considering the significant agreement between the findings of CBCT and FESS for the detection of pathological changes in the paranasal sinuses, CBCT can be used prior to FESS to detect chronic rhinosinusitis and to assess anatomical variations of the OMC.

• Imaging Science in Dentistry
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• v.51 no.1
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• pp.27-34
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• 2021

Purpose: This study was performed to compare the ability of limited- and large-volume cone-beam computed tomography (CBCT) to display isthmuses in the apical root canals of mandibular molars. Materials and Methods: Forty human mandibular first molars with isthmuses in the apical 3 mm of mesial roots were scanned by micro-computed tomography (micro-CT), and their thickness, area, and length were recorded. The samples were examined using 2 CBCT systems, using the smallest voxels and field of view available for each device. The Mann-Whitney, Friedman, and Dunn multiple comparison tests were performed (α=0.05). Results: The 3D Accuitomo 170 and i-Cat devices detected 77.5% and 75.0% of isthmuses, respectively (P>0.05). For length measurements, there were significant differences between micro-CT and both 3D Accuitomo 170 and i-Cat(P<0.05). Conclusion: Both CBCT systems performed similarly and did not detect isthmuses in the apical third in some cases. CBCT still does not equal the performance of micro-CT in isthmus detection, but it is nonetheless a valuable tool in endodontic practice.

• Restorative Dentistry and Endodontics
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• v.38 no.1
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• pp.55-56
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• 2013

• 대한치주과학회:학술대회논문집
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• 2009.05a
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• pp.40-40
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• 2009