• Imaging Science in Dentistry
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• v.32 no.4
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• pp.213-219
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• 2002

Purpose : Computed radiography (CR) has been used in cephalometric radiography and many studies have been carried out to improve image quality using various digital enhancement and filtering techniques, During CR image acquisition, the frequency rank and type affect to the image quality. The aim of this study was to compare the diagnostic quality of conventional cephalometric radiographs to those of computed radiography. Materials and Methods : The diagnostic quality of conventional cephalometric radiographs (MO) and their digital image counterparts were compared, and at the same time, six modalities (M1-M6) of spatial frequency-processed digital images were compared by evaluating the reproducibility of 23 cephalometric landmark locations. Reproducibility was defined as an observer's deviation (in mm) from the mean between all observers. Results and Conclusion: In comparison with the conventional cephalometric radiograph (MO), Ml showed statistically significant differences in 8 locations, M2 in 9, M3 12, M4 in 7, M5 in 12, and M6 showed significant differences in 14 of 23 landmark locations (p < 0.05). The number of reproducible landmarks that each modality possesses were 7 in M6, 6 in M5, 5 in M3, 4 in M4, 3 in M2, 2 in Ml, and 1 location in MO. The image modality that observers selected as having the best image quality was M5.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.1
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• pp.59-71
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• 1998

The radiation-induced apoptosis was studied for two human cancer cell lines (KB cells, RPMI 2650 cells) and the human gingival fibroblast cell line (HGF-1 cells). The single irradiation of 2, 10, 20Gy was done with 241.5 cGylmin dose rate using the /sup 137/Cs MK cell irradiator. The cells were stained with propidium iodide and examined under the fluoro-microscope and assayed with the flow cytometry a day after irradiation. Also, the LDH assay was done to determine the amount of necrotic cells. The obtained results were as follows: 1. On the fluoro-microscope, many fragmented nuclei were detected in the KB, RPMI 2650, and HGF-1 cells after irradiation. 2. On the DNA content histogram obtained from the flow cytometry, the percentages of the pre-Gl peak of the control and 2, 10 and 20Gy irradiation group were 4.5, 55.0, 52.3, and 66.6％ on KB cells, 2.7, 3.3, 31.8, and 32.6％ on RPMI 2650 cells and 2.8, 21.8, 30.4, and 40.2％ on HGF-1 cells respectively. 3. The number of Gl-stage cells was abruptly decreased after 2Gy irradiation on KB cells and 10Gy irradiation on RPMI 2650 cells, But there was a slight decrease without regard to irradiation dose on HGF-1 cells. 4. There was no significantly different absorbance in extracellular LDH assay along the experimental cell lines.

• Imaging Science in Dentistry
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• v.33 no.2
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• pp.113-119
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• 2003

Purpose : To evaluate the relationship between morphometric analysis of bone microstructure from digital radiographic image and trabecular bone strength. Materials and Methods : One hundred eleven bone specimens with 5 mm thickness were obtained from the mandibles of 5 pigs. Digital images of specimens were taken using a direct digital intraoral radiographic system. After selection of ROI (100 × 100 pixel) within the trabecular bone, mean gray level and standard deviation were obtained. Fractal dimension and the variants of morphometric analysis (trabecular area, periphery, length of skeletonized trabeculae, number of terminal point, number of branch point) were obtained from ROI. Punch sheer strength analysis was performed using Instron (model 4465, Instron Corp., USA). The loading force (loading speed 1 mm/min) was applied to ROI of bone specimen by a 2 mm diameter punch. Stress-deformation curve was obtained from the punch sheer strength analysis and maximum stress, yield stress, Young's modulus were measured. Results: Maximum stress had a negative linear correlation with mean gray level and fractal dimension significantly (p<0.05). Yield stress had a negative linear correlation with mean gray level, periphery, fractal dimension and the length of skeletonized trabeculae significantly (p < 0.05). Young's modulus had a negative linear correlation with mean gray level and fractal dimension significantly (p < 0.05). Conclusions : The strength of cancellous bone exhibited a significantly linear relationship between mean gray level, fractal dimension and morphometric analysis. The methods described above can be easily used to evaluate bone quality clinically.

• Imaging Science in Dentistry
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• v.54 no.1
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• pp.81-91
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• 2024

Purpose: The objective of this study was to propose a deep-learning model for the detection of the mandibular canal on dental panoramic radiographs. Materials and Methods: A total of 2,100 panoramic radiographs (PANs) were collected from 3 different machines: RAYSCAN Alpha (n=700, PAN A), OP-100 (n=700, PAN B), and CS8100 (n=700, PAN C). Initially, an oral and maxillofacial radiologist coarsely annotated the mandibular canals. For deep learning analysis, convolutional neural networks (CNNs) utilizing U-Net architecture were employed for automated canal segmentation. Seven independent networks were trained using training sets representing all possible combinations of the 3 groups. These networks were then assessed using a hold-out test dataset. Results: Among the 7 networks evaluated, the network trained with all 3 available groups achieved an average precision of 90.6%, a recall of 87.4%, and a Dice similarity coefficient (DSC) of 88.9%. The 3 networks trained using each of the 3 possible 2-group combinations also demonstrated reliable performance for mandibular canal segmentation, as follows: 1) PAN A and B exhibited a mean DSC of 87.9%, 2) PAN A and C displayed a mean DSC of 87.8%, and 3) PAN B and C demonstrated a mean DSC of 88.4%. Conclusion: This multi-device study indicated that the examined CNN-based deep learning approach can achieve excellent canal segmentation performance, with a DSC exceeding 88%. Furthermore, the study highlighted the importance of considering the characteristics of panoramic radiographs when developing a robust deep-learning network, rather than depending solely on the size of the dataset.

• Imaging Science in Dentistry
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• v.43 no.1
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• pp.7-15
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• 2013

Purpose: This study was performed to suggest reference line-pair values of panoramic images with clinically desirable qualities using an arch-form phantom stand. Materials and Methods: The line-pair test phantom was chosen. A real skull model was selected for setting the arch-form model of the phantom stand. The phantom stand had slits in four regions (incisor, premolar, molar, TMJ). Four raw images of the test phantom in each region and one raw image of the real skull were converted into 50 test phantom images and 50 skull phantom images with various line-pair values. 50 post-processed real skull phantom images were divided into 4 groups and were randomly submitted to 14 evaluators. Image quality was graded on a 4 point scale (1. good, 2. normal, 3. poor but interpretable, and 4. not interpretable). The reference line pair was determined as the first line-pair value scored less than 2 points. Result: The mean scores tended to decrease as the line-pair values increased. The reference line-pair values were 3.19 LP/mm in the incisor, 2.32 LP/mm in the premolar and TMJ, and 1.88 LP/mm in the molar region. Conclusion: Image quality evaluation methods and criteria should be able to assess various regions considering the characteristics of panoramic systems. This study suggested overall and regional reference line-pair values and established a set of standard values for them.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.157-161
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• 2009

Purpose : This study aimed to investigate the luminal stenosis of the internal carotid artery with calcification detected on panoramic radiographs. Materials and Methods : This study used fifty carotid arteries of 36 dental patients whose panoramic radiograph and computed tomography angiography (CTA) revealed the presence of carotid artery calcification. A neuroradiologist interpreted CTA to determine the degree of stenosis of the internal carotid arteries. The degree of stenosis was stratified in four stages; normal (no stenosis), mild stenosis (1-49%), moderate stenosis (50-69%) and severe stenosis (70-99%). Results : Among the fifty carotid arteries with calcification detected on both panoramic radiography and CTA, 20 carotid arteries (40%) were normal, 29 carotid arteries (18%) had mild stenosis, 1 carotid artery (2%) had moderate stenosis, and there was none with severe stenosis. Conclusion : Sixty percent of the carotid arteries with calcification detected on both panoramic radiography and CTA had internal luminal stenosis, and two percent had moderate stenosis. When carotid atheroma is detected on panoramic radiograph, it is possible that the dental patient has luminal stenosis of the internal carotid artery.

• Imaging Science in Dentistry
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• v.39 no.4
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• pp.199-203
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• 2009

Purpose : To measure dose-width product (DWP) values used for dental panoramic radiography in Anyang city, Korea. Materials and Methods : Thirty-six panoramic dental radiographic sets (17 analogue panoramic sets and 19 digital panoramic sets) in 36 dental clinics in Anyang city were included in the study. Each patient's panoramic exposure parameters were simulated and the panoramic radiation doses were measured at the secondary collimator using a Mult-O-Meter (Unfors Instruments, Billdal, Sweden) at each dental clinic during 2006. The third quartile DWP was determined from 310 surface dose measurements on adult. Results : The third quartile DWP for adult panoramic radiograph was 106.7 mGy mm. For analogue and digital panoramic radiograph, 3/4 DWP were 116.8 mGy mm and 72 mGy mm respectively. The overall third quartile DWP of panoramic radiography was 106.7 mGy mm. Conclusion : The measured 3/4 DWPs were higher than the 3/4 DWP of 65 mGy mm recommended by NRPB. Dentists who are operating above the reference dose should lower their panoramic exposure doses below the recommended reference value by changing the exposure parameters and/or their panoramic equipments.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.1
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• pp.21-28
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• 2019

Objectives: Osteoradionecrosis (ORN) is one of the most severe complications resulting from radiotherapy (RT) in patients with head and neck cancer (HNC). It is characterized by persistent exposed and devitalized bone without proper healing for greater than 6 months after a high dose of radiation in the area. To describe the profile and dental management of ORN in HNC patients undergoing RT in an oncological clinical research center. Materials and Methods: A retrospective descriptive study was performed to analyze dental records from HNC patients with ORN treated at an oncological clinical research center from 2013 to 2017. A total of 158 dental records for HNC patients were selected from a total of 583 records. Afterwards, this number was distributed to three examiners for manual assessments. Each examiner was responsible for selecting dental records that contained an ORN description, resulting in 20 dental records. Results: Mean patient age was 60.3 years with males being the most affected sex (80.0%). The most affected area was the posterior region of the mandible (60.0%) followed by the anterior region of the mandible (20.0%) and the posterior region of the maxilla (10.0%). The factors most associated with ORN were dental conditions (70.0%) followed by isolated systemic factors (10.0%) and tumor resection (5.0%). There was total exposed bone closure in 50.0% of cases. The predominant treatment was curettage associated with chlorhexidine 0.12% irrigation (36.0%). Conclusion: Poor dental conditions were related to ORN occurrence. ORN management through less invasive therapies was effective for the closure of exposed bone areas and avoidance of infection.

• Journal of Dental Anesthesia and Pain Medicine
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• v.21 no.6
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• pp.565-574
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• 2021

Background: Trigeminal neuralgia (TN) is a severe form of pain that affects the daily activities of a patient. Transcutaneous electrical nerve stimulation (TENS) therapy is an emerging option for the treatment of acute and chronic pain. The aim of this study was to evaluate the effect of TENS therapy as an adjunct to drug therapy for the treatment of TN. Methods: A total of 52 patients diagnosed with TN according to the International Classification of Headache Disorders (version 3) were included. Each patient was randomized to either the TENS or placebo TENS groups. Intervention was given in continuous mode and 100-Hz frequency for 20 mins biweekly for 6 weeks. Parameters were measured at baseline, TENS completion and 3 months, 6 months, and 1 year of follow up. The parameters observed were mean carbamazepine dose, mean visual analog scale (VAS) score, mean present pain intensity (PPI) score, and functional outcome. Non-parametric analyses, one-way ANOVA and the Kruskal-Wallis test were applied for intragroup comparisons, while the Mann-Whitney U test and independent t-test were used for intergroup comparisons of variables. The chi-square test was applied to analyze categorical data. Results: Compared to the placebo TENS group, the mean dose of carbamazepine in the TENS group was significantly reduced at TENS completion, as well as at 6 months and 1 year follow up. Changes in mean VAS score, mean PPI score, and functional outcome did not show significant differences between the groups (P>0.05). Conclusion: TENS therapy does not lead to any changes in pain levels but it may reduce the mean dose of carbamazepine when used as an adjunct treatment in patients with TN.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.2
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• pp.161-172
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• 1997

The purpose of this study was to know the proper diagnosis and to establish the treatment plan of cementifying and ossifying fibroma in the jaws through the clinical, raiological, and histopathologic considerations. The authors compared and analyzed the c1inicoradiologic features of the thirteen cases of cementifying and ossifying fibroma, diagnosed at the Dental college hospital in Yonsei university, Seoul, Korea, during the period from 1980 to 1995. The obtained results were as follows : 1. Cementifying and ossifying fibroma occured in the mean age, 44 years, ranged from 29 to 65 years and the male to female ratio was approximately 1:5. 2. Swelling was the most common frequent presenting complaints. Other reported symptoms included pain, tooth mobility and asymptom. 3. The frequency of the lesions was twelve cases in the mandible and one case in the maxilla. And eleven of thirteen cases were distributed on the premolar and molar region. 4. Radiologically, eight of thirteen cases were well defined lesions, five cases were relatively well defined lesions. And nine of thirteen cases were mixed lesions, three cases were radiopaque lesions, and only one case was purely radiolucenct lesion. 5. Histologically, seven of thirteen cases were classified ossifying fibroma, four cases were cemento-ossifying fibroma, and two cases were cementifying fibroma.