• 한국환경보건학회지
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• 제33권1호
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• pp.21-29
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• 2007

Paeonia lactiflora was stepwise extracted with hexane, chloroform, ethyl acetate, butanol and water. Anti-microbial activity of each extract was investigated. Methanol extract of P. lactiflora revealed anti-microbial activity against S. mutans, C. albicans, and S. aureus. Also, hexane fraction revealed anti-bacterial activity against S. mutans and ethyl acetate fraction acted as potent anti-microbial agent on C. albicans and S. aureus. The relative growth ratio(RGR) of hexane fraction of P. lactiflora against S. mutans were determined as 77.8% in concentration of 0.125 mg/ml, 98.46% in 0.25 mg/ml and 100% in 0.5 mg/ml. The ethyl acetate fraction of P. lactiflora revealed RGR against C. albicans as 52.5% in concentration of 0.125 mg/ml, 60.83% in 0.25 mg/ml and 78.33% in 0.5 mg/ml. It indicate that increasing concentration increase RGR. The measured minimal inhibitory concentration(MIC) of hexane fraction on S. mutans KCTC 5316 strain was 0.5 mg/ml and MIC of ethyl acetate fraction on C. albicans KCTC 7270 was 2.0 mg/ml. The experiment of inhibition to growth of KB roll(oral squamous cell carcinoma) result 61.9% in butanol, 76.7% in hexane extract of P. lactiflora. The hexane extract exhibit potent inhibition effect to the growth of KB cell. These results suggest that the hexane extract of Paeonia lactiflora has antimicrobial activity against S. mutans and has preventive effect to dental caries in addition to potent inhibition to KB cell growth.

• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.843-855
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• 1995

Occupational Dentistry was introduced in Korea about 70 years ago. During the colonial period occupied by Japan till 1945, there were few documents about industrial dentistry, furthermore most cases of occupational diseases and accidents might have been concealed intentionally by the colonial government. After being an independent country, several dentists made efforts to set up 'Preventive Dentistry for Workers' performing specific oral health surveys, even though which were stopped by Korean War. In 1960s' and 1970s', some investigations of oral status were carried out intermittently for specific small groups;white-collar workers, mentally retarded person, buddhist monks and crews of ocean liners. At the same time there was important study in Korean history of occupational dentistry, which was 'a comparison of the oral hygiene conditions in the female workers of a spinning factory at intervals of 30 years.' In 1980s', young researchers began to give attention to erosion of the teeth due to sulphuric acid in the acid-related industry and dental caries due to sugar and flour in the sweets industry. After being democratic labor union movement activated in 1987, hidden and suppressed occupational diseases under the military dictatorship were exposed and flushed in the newspapers. It was shocking for all people that 15-year old boy had been dead due to mercury intoxication after 3-month employment in 1988. In 1990s', the activity for studying oral status of workers in their workplaces was launched and 'Occupational Accidents and Diseases in Oral and Maxillofacial Field' was published. And also The Korean Association of Occupationl Dentistry was established. Oral health examination of workers at the time of employment and of workers exposed to 5 special chemicals at the time of routine special health examination was adopted in 1992, and epocally oral health examination was also included in periodic routine examination of workers' health in 1995. So, occupational dentistry in Korea should cope with the changing needs of working environment and the altering scheme of health examination.

• 한국표면공학회지
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• 제38권3호
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• pp.126-135
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• 2005

SKD 11 steel has been widely used for tools, metallic mold and die for press working because of its favorable mechanical properties such as high toughness and creep strength as well as excellent oxidation resistance. The ion nitrided tool steel containing Mo results in improvement of corrosion resistance, strength at high temperature and pitting resistance, especially in $Cl^-$ contained environment. But the Mo addition causes a disadvantage such as lower oxidation resistance at elevated temperature. In this study, several effects of ion-disadvantage on the oxidation characteristics for SKD 11 steel with various oxidation temperature were investigated. SKD 11 steels were manufactured by using vacuum furnace and solutionized for 1 hr at $1,050^{\circ}C$. Steel surface was ion nitrided at $500^{\circ}C$ for 1 hr and 5 hr by ion nitriding equipment. ion nitrided specimen were investigated by SEM, OM and hardness tester. Oxidation was carried out by using muffle furnace in air at $500^{\circ}C,\;700^{\circ}C\;and\;900^{\circ}C$ for 1hr, respectively. Oxidation behavior of the ion nitrided specimen was investigated by SEM, EDX and surface roughness tester. The conclusions of this study are as follows: It was found that plasma nitriding for 5 hr at $500^{\circ}C$, compared with ion nitriding for 1 hr at $500^{\circ}C$, had a thick nitrided layer and produced a layer with good wear, corrosion resistance and hardness as nitriding time increased. Nitrided SKD 11 alloy for 1hr showed that wear resistance and hardness decreased, whereas surface roughness increased, compared with nitrided SKD 11 alloy for 5 hr. The oxidation surface at $900^{\circ}C$ showed a good corrosion resistance.

• 대한간호학회지
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• 제51권5호
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• pp.585-596
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• 2021

Purpose: The purpose of this study was to explore nurses' experience with caring for COVID-19 patients in a negative pressure room amid the spread of the pandemic. Methods: This study was a qualitative research, and focus group interviews were used to collect data. Three focus groups comprising 19 nurses were interviewed from February 17 to 25, 2021. All interviews were recorded and transcribed verbatim with the consent of the participants. The verbatim transcripts were scrutinized using thematic analysis. Results: Two main themes emerged from the analysis: 'Struggling in an isolated space' and 'Limitations of nursing infrastructure and system'. The nurses caring for COVID-19 patients experienced anxiety and fear about the infection, physical exhaustion, emotional burnout, and a sense of duty as a nurse. They also acknowledged the lack of guidelines, increased task and burden, limitations of nursing care, and the demand for improving the limitations of the nursing system. Conclusion: The results of this study demonstrate that nurses caring for COVID-19 patients encounter physical and emotional problems within the limited healthcare system. The study suggests that comprehensive interventions are needed for nurses. Furthermore, detailed guidelines, strengthening of nursing personnel, and improvements to the nursing system are vital to effectively cope with the pandemic. The government and medical institutions should be aware of the needs of nurses and what they are going through, and make efforts to improve the quality of life of healthcare workers and create a safe healthcare environment.

• Journal of Cancer Prevention
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• 제23권4호
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• pp.170-175
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• 2018

Background: Human hepatocellular carcinoma (HCC) is a common liver tumor and the main cause of cancer-related death. Tyrosine kinase inhibitors, such as imatinib and GNF5 which were developed to treat chronic myelogenous leukemia, regulate the progression of various cancers. The aim of this study was to confirm the anti-tumor activity of tyrosine kinase inhibitors through regulation of S-phase kinase-associated protein 2 (Skp2), an important oncogenic factor in various cancer cells, in human hepatocarcinoma SK-HEP1 cells. Methods: Cell viability and colony formation assays were conducted to evaluate the effects of imatinib, GNF5 and GNF2 on the growth of SK-HEP1 cells. Using immunoblot analysis, we assessed change of the activation of caspases, PARP, Akt, mitogen-activated protein kinases, and Skp2/p27/p21 pathway by imatinib and GNF5 in SK-HEP1 cells. Using sh-Skp2 HCC cells, the role of Skp2 in the effects of imatinib and GNF5 was evaluated. Results: Imatinib and GNF5 significantly inhibited the growth of SK-HEP1 cells. Treatment of imatinib and GNF5 decreased Skp2 expression and Akt phosphorylation, and increased the expression of p27, p21, and active-caspases in SK-HEP1 cells. In sh-Skp2 HCC cells, cell growth and the expression of Skp2 were inhibited by more than in the mock group treated with imatinib and GNF5. Conclusions: These results suggest that the anti-growth activity of tyrosine kinase inhibitors may be associated with the regulation of p27/p21 and caspases through Skp2 blockage in HCC cells.

• 융합정보논문지
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• 제11권7호
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• pp.298-306
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• 2021

본 연구목적은 병원 시설 근로자들의 구강 증상에 영향을 미치는 업무 위험요인을 살펴보고자 한다. 연구 방법은 수도권 지역의 대학병원 시설 관리 파견·용역 근로자 627명을 대상으로 2020년 11월 17일~2021년 5월 20일까지 설문조사를 실시하였다. 연구결과 근골격계 질환과 상해 위험이 높은 근로자들에게서 구강 증상이 높게 나타났다. 또한 직무 불안정과 조직 불공정성의 영역에서 구강점막, 악관절 장애, 구강건조증 증상이 높게 나타났으며, 이직 의도와 질병 출근 요인에서 구강건조증 위험도가 가장 높게 나타났다. 근로자들의 업무 위험 요인과 직무스트레스가 증가할수록 구강 증상 위험도가 증가하였다. 추후 병원 시설 근로자들의 구강건강 증진을 위한 구강보건정책 개선 기초 자료로 활용될 것이다.

• Journal of Periodontal and Implant Science
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• 제52권5호
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• pp.411-421
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• 2022

Purpose: In this study, we aimed to evaluate the degree of heat generation when a novel drill design with an irrigation slot was used with metal sleeve-free (MF) and metal sleeve-incorporated (MI) surgical guides in an environment similar to that of the actual oral cavity. Methods: A typodont with a missing mandibular right first molar and 21 bovine rib blocks were used. Three-dimensional-printed MF and MI surgical guides, designed for the placement of internal tapered implant fixtures, were used with slot and non-slot drills. The following groups were compared: group 1, MI surgical guide with slot drill; group 2, MI surgical guide with a non-slot drill; and group 3, MF surgical guide with a slot drill. A constant-temperature water bath at 36℃ was used. The drilling was performed in 6 stages, and the initial, highest, and lowest temperatures of the cortical bone were measured at each stage using a non-contact infrared thermometer. Results: There were no temperature increases above the initial temperature in any drilling procedure. The only significant difference between the non-slot and slot groups was observed with the use of the first drill in the MI group, with a higher temperature in the non-slot group (P=0.012). When the heat generation during the first and the second drilling was compared in the non-slot group, the heat generation during the first drilling was significantly higher (P<0.001), and there was no significant difference in heat generation between the drills in the slot group. Conclusions: Within the limitations of this study, implant-site preparation with the surgical guide showed no critical increase in the temperature of the cortical bone, regardless of whether there was a slot in the drill. In particular, the slotted drill had a cooling effect during the initial drilling.

• Journal of Periodontal and Implant Science
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• 제52권2호
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• pp.127-140
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• 2022

Purpose: In dental avulsion, delayed replantation usually has an uncertain prognosis. After tooth replantation, complex inflammatory responses promote a return to periodontal tissue homeostasis. Various types of cytokines are produced in the inflammatory microenvironment, and these cytokines determine the periodontal tissue response. This study aimed to identify the gene expression profiles of replanted teeth and evaluate the functional differences between immediate and delayed replantation. Methods: Maxillary molars from Sprague-Dawley rats were extracted, exposed to a dry environment, and then replanted. The animals were divided into 2 groups according to the extra-oral time: immediate replantation (dry for 5 minutes) and delayed replantation (dry for 60 minutes). Either 3 or 7 days after replantation, the animals were sacrificed. Periodontal soft tissues were harvested for mRNA sequencing. Hallmark gene set enrichment analysis was performed to predict the function of gene-gene interactions. The normalized enrichment score (NES) was calculated to determine functional differences. Results: The hallmark gene sets enriched in delayed replantation at 3 days were oxidative phosphorylation (NES=2.82, Q<0.001) and tumor necrosis factor-alpha (TNF-α) signaling via the nuclear factor kappa light chain enhancer of activated B cells (NF-κB) pathway (NES=1.52, Q=0.034). At 7 days after delayed replantation, TNF-α signaling via the NF-κB pathway (NES=-1.82, Q=0.002), angiogenesis (NES=-1.66, Q=0.01), and the transforming growth factor-beta signaling pathway (NES=-1.46, Q=0.051) were negatively highlighted. Conclusions: Differentially expressed gene profiles were significantly different between immediate and delayed replantation. TNF-α signaling via the NF-κB pathway was marked during the healing process. However, the enrichment score of this pathway changed in a time-dependent manner between immediate and delayed replantation.

• Safety and Health at Work
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• 제14권1호
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• pp.71-77
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• 2023

Background: This study investigated the relationship between trauma exposure and suicidal ideation. Moreover, this study examines the moderating roles of organizational climate on the association between trauma exposure and suicidal ideation in Korean male firefighters. Methods: A total of 15,104 male firefighters who completed a questionnaire were analyzed. The data were obtained using an online self-administered questionnaire from the Firefighter Research on Enhancement of Safety and Health Study. Poisson regression analysis was performed to determine the effects of trauma exposure on suicidal ideation and the moderating effect of organizational climate. Results: The results showed that 389 firefighters (2.6%) responded that they had experienced suicidal ideation. In the final model, trauma exposure was positively related to suicidal ideation (adjusted risk ratio [aRR], 1.076; 95% confidence interval [CI]: 1.051-1.103), and organizational climate was negatively associated with suicidal ideation (aRR, 0.772; 95% CI: 0.739-0.806). Additionally, the interaction term (trauma exposure × organizational climate) was related to suicidal ideation (aRR, 1.016; 95% CI: 1.009-1.023). Conclusions: This study suggests that trauma exposure might play a significant role in developing suicidal ideation and that positive organizational climate moderates the negative effects of trauma exposure on suicidal ideation among firefighters. It is necessary to perform a follow-up study of various intervention strategies to maintain a healthy organizational climate or work environment. Such interventions should promote lasting trust within teams, provide social support and belonging, and nurture job value.

• 대한소아치과학회지
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• 제51권1호
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• pp.80-87
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• 2024

Silver diamine fluoride, which can arrest dental caries, is alkaline and may cause mild soft tissue irritation. Water-based silver fluoride has a neutral pH, which is closer to the physiological range, and is biocompatible for use in the oral environment. This study aimed to evaluate the effect of water-based silver fluoride on remineralizing early enamel lesions by comparing it with other fluoride agents through microhardness and quantitative light-induced fluorescence measurements. An in vitro study with intact bovine incisors was performed. Artificial enamel lesions were induced and subjected to microhardness and quantitative light-induced fluorescence testing. Specimens were randomly divided into 4 groups for treatment. The specimens in group I were treated with water-based silver fluoride and potassium iodide, group II with silver diamine fluoride and potassium iodide, group III with sodium fluoride varnish, and group IV with distilled water. After 8 days of pH cycling, the specimens were subjected to microhardness and quantitative light-induced fluorescence testing. Water-based silver fluoride and silver diamine fluoride showed the greatest increases in microhardness and quantitative light-induced fluorescence, with no significant differences between the two. Sodium fluoride varnish also exhibited a significant increase in microhardness and quantitative light-induced fluorescence, but the differences were smaller than those for water-based silver fluoride and silver diamine fluoride. Water-based silver fluoride is considered useful in a clinical setting for remineralizing enamel lesions, with the advantages of no risk of tissue burn and improved taste and smell.