• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제45권4호
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• pp.199-206
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• 2019

Objectives: In mandibular edentulism, the treatment option with a two-interforaminal implant-retained bridge and a removable partial denture is rarely evaluated in literature. The aim of this in vitro study was to evaluate the stress distribution of this treatment option by comparing it with traditional treatment options with interforaminal implants in the edentulous mandible. Materials and Methods: Two interforaminal implants were placed in a formalin-fixed cadaver mandible, and overdentures with three different types of attachments were fabricated: (1) two ball attachments and an overdenture, (2) a Dolder bar and an overdenture, and (3) screw-retained two-implant inter-canine porcelain fused to a metal bridge and an implant-assisted removable denture (IARD) with precision attachments. Three biting conditions were generated for each denture type, and the strains were documented under vertical loading of 100 N. Results: The calculated strain values from measured strains in all measurement sites and loading conditions for the screw-retained two-implant intercanine porcelain fused to a metal bridge and a cast framework partial denture with precision attachments situation were lower than in the other scenarios (P<0.05). Conclusion: Within the limitations of the present study, it can be concluded that an IARD may be a reasonable and valuable alternative to ball attachments or a bar in two interforaminal implants, especially when the patients prefer to be able to show their teeth even when they take out their removable dentures.

• 한국학교ㆍ지역보건교육학회지
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• 제20권2호
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• pp.37-51
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• 2019

Purpose: This study aims to substantiate a correlation between the period of living alone in a shabby one-room and a depression experience. Methods: We conducted a cross-sectional study using data from the Korea Homeless Survey carried out by the Korea Institute for Health and Social Affairs in 2016. In the study, the data included 485 survey participants who resided in a single room. The period of single-room occupancy being divided into three groups: less than 1 year, 1 to 4 years, and more than 5 years was considered a primary independent variable. The outcome variable which represented a depression experience was measured by CESD-11(The Center for Epidemiological Studies-Depression Scale). We carried out a Chi-square test and multiple logistic regression to evaluate the association. Results: The rate of depression experienced in this population was 77.5%. Almost 83.9% of the participants were reported as being unable to receive the mental health counselling in the last 12 months. After controlling for covariates, subjects who were living in a single room occupancy for 1-5 years(OR=3.89; 95% CI=1.43-10.56) and more than 5 years(OR=2.71; 95% CI= 1.05-6.95) were found to be more likely to experience depression. Conclusions: The results showed that living alone in a shabby one-room had a high correlation with experiencing depression. We proposed that there is a need to develop a new strategy for mental health promotion program for the poor, vulnerable and deprived population.

• Journal of Periodontal and Implant Science
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• 제48권6호
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• pp.383-394
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• 2018

Purpose: The purpose of this study was to evaluate the optimal diabetes duration for bone regeneration experiments in an alloxan monohydrate (ALX)-induced diabetic rabbit calvarial defect model by evaluating the association between diabetes duration and bone healing capacity. Methods: Twenty-four New Zealand white rabbits were used. Twenty-two rabbits were injected with 100 mg/kg of ALX to induce experimental diabetes. These rabbits were divided into 4 groups, including a control group and groups with diabetes durations of 1 week (group 1), 2 weeks (group 2), and 4 weeks (group 3). Calvarial defects were created at 1, 2, and 4 weeks after ALX injection and in the control rabbits. Cone-beam computed tomography (CBCT) scanning was performed on the day of surgery and at 2 and 4 weeks after surgery. The rabbits were sacrificed 4 weeks after surgery, followed by histological and immunofluorescence analysis. Results: The diabetic state of all diabetic rabbits was well-maintained throughout the experiment. Reconstructed 3-dimensional CBCT imaging showed more rapid and prominent bone regeneration in the control group than in the experimental groups. Histological staining showed notable bone regeneration in the control group, in contrast to scarce bone formation in the experimental groups. The appearance and immunoreactivity of receptor activator of nuclear factor-kappa B and osteoprotegerin did not show notable differences among the groups. Conclusion: ALX administration at 100 mg/kg successfully induced experimental diabetes in rabbits. The effect of diabetes on bone healing was evident when the interval between diabetes induction and the intervention was ${\geq}1$ week.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.216-233
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• 2021

In this work, Rhizophora spp. particleboard phantoms were made using SPI-based adhesives, modified with sodium hydroxide and itaconic acid polyamidoamine-epichlorohydrin (0, 5, 10, and 15 wt%). An X-ray computed tomography (CT) imaging system was used to ascertain the CT numbers and density distribution profiles of the particleboards. The SPI-based/NaOH/IA-PAE/Rhizophora spp. particleboard phantoms with 15 wt% IA-PAE addition level had the highest solid content, flexural strength, flexural modulus, and internal bonding strength of 36.06 ± 1.08%, 18.61 ± 0.38 Nmm^-2, 7605.76 ± 0.89 Nmm^-2, and 0.463 ± 0.053 Nmm^-2, respectively. The moisture content, mass density, water absorption, and dimensional stability were 6.93 ± 0.27%, 0.962 ± 0.037 gcm^-3, 22.36 ± 2.47%, and 10.90 ± 0.86%, respectively. The results revealed that the mass attenuation coefficients and effective atomic number values within the 16.59-25.26 keV photon energy region, were close to the calculated XCOM values in water, with a p-value of 0.077. Moreover, the CT images showed that the dissimilarities in the discrepancy of the profile density decreased as the IA-PAE concentrations increased. Therefore, these results support the appropriateness of the SPI-based/NaOH/IA-PAE/Rhizophora spp. particleboard with 15 wt% IA-PAE adhesive as a suitable tissue-equivalent phantom material for medical health applications.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제42권
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• pp.37.1-37.13
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• 2020

Background: The human mandible is variable in shape, size and position and any deviation from normal can affect the facial appearance and dental occlusion. Objectives: The objectives of this study were to determine whether the Sassouni cephalometric analysis could help predict two-dimensional mandibular shape in humans using cephalometric planes and landmarks. Materials and methods: A retrospective computerised analysis of 100 lateral cephalometric radiographs taken at Kingston Hospital Orthodontic Department was carried out. Results: Results showed that the Euclidean straight-line mean difference between the estimated position of gonion and traced position of gonion was 7.89 mm and the Euclidean straight-line mean difference between the estimated position of pogonion and the traced position of pogonion was 11.15 mm. The length of the anterior cranial base as measured by sella-nasion was positively correlated with the length of the mandibular body gonion-menton, r = 0.381 and regression analysis showed the length of the anterior cranial base sella-nasion could be predictive of the length of the mandibular body gonion-menton by the equation 22.65 + 0.5426x, where x = length of the anterior cranial base (SN). There was a significant association with convex shaped palates and oblique shaped mandibles, p = 0.0004. Conclusions: The method described in this study can be used to help estimate the position of cephalometric points gonion and pogonion and thereby sagittal mandibular length. This method is more accurate in skeletal class I cases and therefore has potential applications in craniofacial anthropology and the 'missing mandible' problem in forensic and archaeological reconstruction.

• 한국융합학회논문지
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• 제12권4호
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• pp.87-94
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• 2021

의료기관의 방사선 차폐체의 차폐물질이 친환경소재로 변화되면서 기존 납의 일반된 차폐특성보다 차폐물질의 특성에 따른 방사선 방어가 중요한 요소로 대두되고 있다. 납과 유사한 차폐물질로 대표적인 텡스텐과 황산바륨은 친환경 소재로 시트나, 섬유 형태로 제작되어 사용되고 있다. 이테르븀은 치과 방사선영역에서 불투과성 물질로 불소화합물로 사용되었으며, 에너지대별 차폐특성과 기존 친환경소재의 차폐특성과 비교하여 x-선 차폐영역에서 차폐성능을 평가하고자 한다. 동일한 공정과 조건하에 세 종류의 차폐시트를 제작하여 실험하였으며, 의료방사선 영역에서 텅스텐과 약 5 % 차폐성능 차이가 나타났으며, 황산바륨보다 우수한 차폐성능을 보였다. 차폐시트의 단면 구조에서는 인자의 배열이 일정하지 못하는 큰 단점을 보였다. 따라서 산화이테르븀은 의료방사선 차폐물질로 충분한 가능성을 보였으며, 입자배열 구조와 입자크기 조절로 차폐성능을 향상시킬 수 있을 것으로 사료된다.

• Imaging Science in Dentistry
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• 제52권3호
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• pp.239-244
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• 2022

Purpose: Despite the proliferation of numerous morphometric and anthropometric methods for sex identification based on linear, angular, and regional measurements of various parts of the body, these methods are subject to error due to the observer's knowledge and expertise. This study aimed to explore the possibility of automated sex determination using convolutional neural networks(CNNs) based on lateral cephalometric radiographs. Materials and Methods: Lateral cephalometric radiographs of 1,476 Iranian subjects (794 women and 682 men) from 18 to 49 years of age were included. Lateral cephalometric radiographs were considered as a network input and output layer including 2 classes(male and female). Eighty percent of the data was used as a training set and the rest as a test set. Hyperparameter tuning of each network was done after preprocessing and data augmentation steps. The predictive performance of different architectures (DenseNet, ResNet, and VGG) was evaluated based on their accuracy in test sets. Results: The CNN based on the DenseNet121 architecture, with an overall accuracy of 90%, had the best predictive power in sex determination. The prediction accuracy of this model was almost equal for men and women. Furthermore, with all architectures, the use of transfer learning improved predictive performance. Conclusion: The results confirmed that a CNN could predict a person's sex with high accuracy. This prediction was independent of human bias because feature extraction was done automatically. However, for more accurate sex determination on a wider scale, further studies with larger sample sizes are desirable.

• 정보교육학회논문지
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• 제25권6호
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• pp.1015-1024
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• 2021

엔트리, Machine Learning for Kids, Teachable Machine과 같이 블록 기반 프로그래밍 언어에서 활용할 수 있도록 인공지능을 간단히 학습시킬 수 있는 다양한 플랫폼들이 존재한다. 그러나 이와 같은 플랫폼들은 별도의 메뉴를 통해 인공지능 학습을 진행한 다음, 학습된 모델을 코드 에디터에서 활용하는 방식을 따르고 있다. 이와 같은 방식은 학습되는 과정을 학생들이 더 직관적으로 살펴볼 수 있다는 장점이 있지만, 학습 메뉴와 코드 에디터를 모두 활용해야 한다는 단점도 존재한다. 본 논문에서는 코드 에디터에서 인공지능 학습과 코딩을 모두 진행할 수 있는 인공지능 블록을 개발한다. 본 인공지능 블록은 스크래치 블록으로 제시되지만 실제 학습 과정은 파이썬 서버를 통해 수행된다. 파란색 펜과 빨간색 펜을 분류하는 모델, 덴탈 마스크와 KF94 마스크를 분류하는 모델을 학습하는 과정을 통해 본 블록에 대해 상세히 기술한다. 또, 학습 성능 면에서 Teachable Machine와 큰 차이가 없음을 실험적으로 나타내었다.

• 대한통합의학회지
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• 제11권2호
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• pp.169-179
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• 2023

Purpose : Although human periodontal ligament stem cells (hPDLSCs) are a supportive factor for tissue engineering, oxidative stress during cell culture and transplantation has been shown to affect stem cell viability and mortality, leading to failed regeneration. The aim of this study was to evaluate the antioxidant and protective effects against cell damage of celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, and the antioxidant signal of hPDLSCs in H₂O₂-induced oxidative stress. Methods : To induce oxidative stress in cultured hPDLSCs, H₂O₂ was used as an exogenous reactive oxygen species (ROS). Dose-dependent celecoxib (.1, 1, 10, or 100 µM) was administered after H₂O₂ treatment. WST-1 assay was used to assess cell damage and western blot was used to observe antioxidant activity of hPDLSCs in oxidative stress. Immunohistochemistry was performed for inverting the localization of the SOD and Nrf2 antibody. Results : We found that progressive cell death was induced in hPDLSCs by H₂O₂ treatment. However, low-dose celecoxib reduced H₂O₂-induced cellular damage and eventually enhanced the SOD activity and Nrf2 signal of hPDLSCs. Oxidative stress-induced morphological change in hPDLSCs included lowered the survival and number of spindle-shaped cells, and shrinkage and shortening of cell fibers. Notably, celecoxib promoted cell survival function and activated antioxidants such as SOD and Nrf2 by positively regulating the cell survival signal pathway, and also reduced the number of morphological changes in hPDLS. Immunohistochemistry results showed a greater number of SOD- and Nrf2-stained cells in the celecoxib-treated group following oxidative stress. Conclusion : By increasing SOD and Nrf2 expression at the antioxidant system, the findings suggest that celecoxib enhanced the antioxidative ability of hPDLSCs and protected cell viability against H₂O₂-induced oxidative stress by increasing SOD and Nrf2 expression in the antioxidant system.

• Journal of Oral Medicine and Pain
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• 제47권1호
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• pp.10-26
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• 2022

Purpose: The purpose of this study was to investigate whether various saliva collection methods affect the observed salivary microbiome and whether microbiomes of stimulated and unstimulated saliva and plaque differ in richness and diversity. Methods: Seven sampling methods for unstimulated saliva, stimulated saliva, and plaque samples were applied to six orally and systemically healthy participants. Bacterial 16S ribosomal RNA genes of 10 major oral bacterial species, namely, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, Prevotella intermedia, Prevotella nigrescens, Streptococcus mitis, Streptococcus sobrinus, and Lactobacillus casei, were analyzed by real-time polymerase chain reaction. We comprehensively examined the dependence of the amount of bacterial ribosomal DNA (rDNA), bacterial-community composition, and relative abundance of each species on sample collection methods. Results: There were significant differences in the bacterial rDNA copy number depending on the collection method in three species: F. nucleatum, P. nigrescens, and S. mitis. The species with the highest richness was S. mitis, with the range from 89.31% to 100.00%, followed by F. nucleatum, P. nigrescens, T. denticola, T. forsythia, and P. intermedia, and the sum of the proportions of the remaining five species was less than 1%. The species with the lowest observed richness was P. gingivalis (<0.1%). The Shannon diversity index was the highest in unstimulated saliva collected with a funnel (4.449). The Shannon diversity index was higher in plaque samples (3.623) than in unstimulated (3.171) and stimulated (3.129) saliva and in mouthwash saliva samples (2.061). Conclusions: The oral microbial profile of saliva samples can be affected by sample collection methods, and saliva differs from plaque in the microbiome. An easy and rapid technique for saliva collection is desirable; however, observed microbial-community composition may more accurately reflect the actual microbiome when unstimulated saliva is assayed.