• Journal of Microbiology and Biotechnology
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• v.28 no.4
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• pp.645-651
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• 2018

The carcinogenicity of chemicals in the environment is a major concern. Recently, numerous studies have attempted to develop methods for predicting carcinogenicity, including rodent and cell-based approaches. However, rodent carcinogenicity tests for evaluating the carcinogenic potential of a chemical to humans are time-consuming and costly. This study focused on the development of an alternative method for predicting carcinogenicity using quantitative PCR (qPCR) and colon cancer stem cells. A toxicogenomic method, mRNA profiling, is useful for predicting carcinogenicity. Using microarray analysis, we optimized 16 predictive gene sets from five carcinogens (azoxymethane, 3,2'-dimethyl-4-aminobiphenyl, N-ethyl-n-nitrosourea, metronidazole, 4-(n-methyl-n-nitrosamino)-1-(3-pyridyl)-1-butanone) used to treat colon cancer stem cell samples. The 16 genes were evaluated by qPCR using 23 positive and negative carcinogens in colon cancer stem cells. Among them, six genes could differentiate between positive and negative carcinogens with a p-value of ${\leq}0.05$. Our qPCR-based prediction system for colon carcinogenesis using colon cancer stem cells is cost- and time-efficient. Thus, this qPCR-based prediction system is an alternative to in vivo carcinogenicity screening assays.

• The Journal of Advanced Prosthodontics
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• v.3 no.2
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• pp.57-62
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• 2011

MATERIALS AND METHODS. Ceramics have a long history in fixed prosthodontics for achieving optimal esthetics and various materials have been used to improve ceramic core strength. However, there is a lack of information on how color is affected by fabrication procedure. The purpose of this study was to evaluate the effects of various dentin ceramic thicknesses and repeated firings on the color of zirconium oxide all-ceramic system (LavaTM) fabricated using CAD/CAM technology. MATERIALS AND METHODS. Thirty disc-shaped cores, 12 mm in diameter with a 1 mm thickness were fabricated from zirconium oxide based all ceramic systems ($Lava^{TM}$, 3M ESPE, St Paul, MN, USA) and divided into three groups (n = 10) according to veneering with dentin ceramic thicknesses: as 0.5, 1, or 1.5 mm. Repeated firings (3, 5, 7, or 9) were performed, and the color of the specimens was compared with the color after the initial firing. Color differences among ceramic specimens were measured using a spectrophotometer (VITA Easyshade, VITA Zahnfabrik, Bad $S{\ddot{a}}ckingen$, Germany) and data were expressed in CIELAB system coordinates. A repeated measures ANOVA and Bonferroni post hoc test were used to analyze the data (n = 10, ${\alpha}=.05$). RESULTS. $L^{\ast}a^{\ast}b^{\ast}$ values of the ceramic systems were affected by the number of firings (3, 5, 7, or 9 firings) (P<.001) and ceramic thickness (0.5, 1, or 1.5 mm) (P<.001). Significant interactions were present in $L^{\ast}a^{\ast}b^{\ast}$ values between the number of firings and ceramic thickness (P<.001). An increase in number of firings resulted in significant increase in $L^{\ast}$ values for both 0.5 mm and 1.5 mm thicknesses (P<.01, P=.013); however it decreased for 1 mm thickness (P<.01). The $a^{\ast}$ values increased for 1 mm and 1.5 mm thicknesses (P<.01), while it decreased for 0.5 mm specimens. The $b^{\ast}$ values increased significantly for all thicknesses (P<.01, P=.022). As the dentin ceramic thickness increased, significant reductions in $L^{\ast}$ values (P<.01) were recorded. There were significant increases in both $a^{\ast}$ and $b^{\ast}$ values (P<.01) as the dentin ceramic thickness increased. CONCLUSION. The number of firings and dentin ceramic thickness have a definite effect on the final color of all ceramic system tested. The mean ${\Delta}E$ value increased as the dentin ceramic thicknesses increased for zirconium-oxide based all ceramic specimens tested. However, the mean ${\Delta}E$ values were less than 3.7${\Delta}E$ units which is rated as a match in the oral environment.

• Journal of Periodontal and Implant Science
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• v.44 no.2
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• pp.79-84
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• 2014

Purpose: While single-species biofilms have been studied extensively, we know notably little regarding multispecies biofilms and their interactions. The purpose of this study was to develop and evaluate an in vitro multispecies dental biofilm model that aimed to mimic the environment of chronic periodontitis. Methods: Streptococcus gordonii KN1, Fusobacterium nucleatum ATCC23726, Aggregatibacter actinomycetemcomitans ATCC33384, and Porphyromonas gingivalis ATCC33277 were used for this experiment. The biofilms were grown on 12-well plates with a round glass slip (12 mm in diameter) with a supply of fresh medium. Four different single-species biofilms and multispecies biofilms with the four bacterial strains listed above were prepared. The biofilms were examined with a confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM). The minimum inhibitory concentrations (MIC) for four different planktonic single-species and multispecies bacteria were determined. The MICs of doxycycline and chlorhexidine for four different single-species biofilms and a multispecies biofilm were also determined. Results: The CLSM and SEM examination revealed that the growth pattern of the multispecies biofilm was similar to those of single-species biofilms. However, the multispecies biofilm became thicker than the single-species biofilms, and networks between bacteria were formed. The MICs of doxycycline and chlorhexidine were higher in the biofilm state than in the planktonic bacteria. The MIC of doxycycline for the multispecies biofilm was higher than were those for the single-species biofilms of P. gingivalis, F. nucleatum, or A. actinomycetemcomitans. The MIC of chlorhexidine for the multispecies biofilm was higher than were those for the single-species biofilms of P. gingivalis or F. nucleatum. Conclusions: To mimic the natural dental biofilm, a multispecies biofilm composed of four bacterial species was grown. The 24-hour multispecies biofilm may be useful as a laboratory dental biofilm model system.

• Journal of Korean society of Dental Hygiene
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• v.17 no.1
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• pp.49-62
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• 2017

Objectives: This study was conducted to suggest the necessity of education about toothpaste usage to infants, preschoolers, and their parents. Also, another purpose is to provide basic data that is necessary for oral health education about accurate cognition and usage of toothpaste. Methods: From October to December 2015, we conducted a survey on parents of 0~4 years old infants and preschoolers about toothpaste usage based on the data of a questionnaire with a total of 505 subjects. The survey questions were composed of general characteristics of infants, preschoolers and their parents, and toothpaste usage. Results: Usage frequency of toothpaste for infants and preschoolers increased with age (p<0.001), and infants and preschoolers in homes with monthly income under 4 million won showed high frequency of toothpaste usage (p<0.001). Toothpaste mouth rinsing of infants and preschoolers increased with age (p<0.001), while on the other hand, toothpaste swallowing decreased (p<0.001). Conclusions: In this study, it was shown that the factors that effect toothpaste usage in infants and preschoolers were age and average monthly income of the family. This suggests the necessity of oral health education to parents about usage of toothpaste in infants and preschoolers.

• Journal of Periodontal and Implant Science
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• v.42 no.1
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• pp.13-19
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• 2012

Purpose: The aim of this study was to examine whether a previous peri-implantitis site can affect osseointegration, by comparing implant placement at a site where peri-implantitis was present and at a normal bone site. A second aim of this study was to identify the tissue and bone reaction after treating the contaminated implant surface to determine the optimal treatment for peri-implant diseases. Methods: A peri-implant mucositis model for dogs was prepared to determine the optimal treatment option for peri-implant mucositis or peri-implantitis. The implants were inserted partially to a length of 6 mm. The upper 4 mm part of the dental implants was exposed to the oral environment. Simple exposure for 2 weeks contaminated the implant surface. After 2 weeks, the implants were divided into three groups: untreated, swabbed with saline, and swabbed with $H_2O_2$. Three implants from each group were placed to the full length in the same spot. The other three implants were placed fully into newly prepared bone. After eight weeks of healing, the animals were sacrificed. Ground sections, representing the mid-buccal-lingual plane, were prepared for histological analysis. The analysis was evaluated clinically and histometrically. Results: The untreated implants and $H_2O_2$-swabbed implants showed gingival inflammation. Only the saline-swabbed implant group showed re-osseointegration and no gingival inflammation. There was no difference in regeneration height or bone-to-implant contact between in situ implant placement and implant placement in the new bone site. Conclusions: It can be concluded that cleaning with saline may be effective in implant decontamination. After implant surface decontamination, implant installation in a previous peri-implant diseased site may not interfere with osseointegration.

• Journal of dental hygiene science
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• v.12 no.3
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• pp.217-225
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• 2012

The purpose of this study is to measure the relation of employment stress and self-esteem in some health college students and to consider a proper means for the solution. The population of the research is some randomly chosen health college students located in Seoul City during the period from May 10 to June 11 2010, and the sample of 295 students were recruited as the analysis object group. The data on general characteristics and employment stress were collected by a questionnaire survey. The collected data were analyzed with the SPSS WIN 12.0 program. The following shows the results of this study. 1. Employment stress was low in high group of satisfaction in campus life. It was statistically significant(p<0.001). 2. Mean scores of total self-esteem in study population were 3.1 and positive self-esteem level(3.76) were higher than negative ones (2.44)(p<0.001). 3. The relation between employment stress and selfesteem(r=0.132) revealed significant correlation. 4. In regression analysis, home economy, competence for a schoolwork, satisfaction in campus life, self-esteem(p<0.001) were proved as significant factors that is related to the employment stress. In other words, It is significant statistically that the lower home economy, competence for a schoolwork, satisfaction in campus life, self-esteem, the higher employment stress level. I suggest with the result of the study that for coping effectively employment stress of health college students, we will need to open an educational development considering self-esteem and an exclusive employment counsel window for better administrationwelfare service in campus, to expand industry-academic cooperation in community. Because of students are independent responsibility of employment, active effort must take precedence in order for the solution of problem by themselves. Also, we will need to create better academic environment and show more concern, consideration, love in family.

• Journal of dental hygiene science
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• v.12 no.3
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• pp.209-215
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• 2012

Somok, the heart wood of Caesalpinia sappan is used in traditional Chinese medicine. This study was performed to investigate the effect of growth and culture conditions of brazilin from C. sappan against S. mutans ATCC 25175. The bacteria were cultured in brain heart infusion (BHI) broth, and then incubated under 5% $CO_2$ at $37^{\circ}C$ for 18-24 hours. The effect of brazilin against S. mutans was confirmed under the changes of the culture conditions, such as growth curve and the change of pH, protein, and total carbohydrate. The growth of S. mutans in control medium was the highest at 24 hr, while brazilin-added medium (0.3 mg/ml) showed maximum growth at 32 hr. The pH values of the control medium was 5.25 at 16 hr, but the media supplemented with brazilin (0.3 mg/ml) was 7.0 at 16 hr. The amounts of total carbohydrate of the control medium was 11 mg/ml at 8 hr, but the brazilin-added media (0.3 mg/ml) was 18 mg/ml at 8 hr. In the protein change of the culture medium, the control culture broth and the brazilin supplemented-cultures was 2.4 mg/ml and 2.54 mg/ml at 24 hr, respectively. Polysaccharide contents of the control medium and test media were 3 mg/ml and 2 mg/ml at 8 hr, respectively. Thus, the application of C. sappan can be considered a useful and practical material for the prevention of dental caries.

• Journal of Environmental Health Sciences
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• v.43 no.5
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• pp.401-411
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• 2017

Objectives: The purpose of this study was to investigate the factors affecting the use of oral hygiene products in infants. Methods: From October 2015 to December 2015, astructured questionnaire survey was conducted for infants and parents about the infants' oral hygiene product use from 0 to 4 years of age in Seoul and other metropolitan areas. Results: The use of oral tissues for infants and children was more frequent in infants, with less than four uses of oral tissues per 10 infants. The overall amount of toothpaste usage among infants was lower than those of infants whose parents are high school or college graduates. The number of oral tissues used per infant per week was less among infants who sucked less than 4 times per 10 infants. The frequency of use of infant mouthwash per week in every 10 infants was less than those who swallow mouthwash less than once. The number of mouth rinses after the use of oral tissues for infants was high in boys, and the number of infants who sucked oral tissues was less than 4 times when used 10 times. The number of mouth rinses after the use of toothpaste was less for infants with college-graduate parents. The factors affecting the number of mouth rinsings after using oral tissues for infants were gender and sucking frequency. Conclusions: In this study, the oral hygiene products for infants were found to differ and affect the usage, the frequency of use, and the number of mouth rinses according to the general characteristics of infants' and parents and the use of oral hygiene products.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.2
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• pp.212-234
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• 1999

Dental restorative materials must have the physical properties to withstand wear and corrosion. Base metal alloys possess better mechanical properties and lower price than the gold alloys. For these reasons such alloys have largely replaced the precious metal alloys. One aspect to con-sider is the release of metal substances to oral environment. The release of elements from dental alloys is a continuing concern because the elements may have the potentially harmful biological effects on local tissues. The purpose of this study was to minimize metal release on the nonprecious metal surfaces by ion beam assisted deposition(IBAD) of titanium nitride (TiN) Ni-Cr-Be alloys with and without TiN coatings were secured in an wear test machine opposing ruby ball to determine their relative resistance to wear with loom, 200m, 300m and 400m sliding distance. And the corrosion behavior of the Ni-Cr-Be alloys with and without TiN coatings and 3 dental noble alloys have been studied. Potentiodynamic curves were used to analyse the corrosion characteristics of the alloys. The measurement of the released Ni and Cr ions was conducted by analysis of the electrolyte solution with atomic absorption spectroscopy. The results were as follows : 1. The critical sliding distance that wore down TiN coatings of $2.5{\mu}m$ thickness in this study condition was 300m. 2. Ion beam assisted deposition of TiN showed a good surface modification with respect to the properties of wear and corrosion resistance. 3. X-ray diffraction showed that the strongest peak of TiN is TiN(111) in the coatings. 4. The release of Ni and Cr ions from alloys measured by means of atomic absorption spectroscopy was reduced by ion beam assisted deposition of TiN.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4354-4359
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• 2010

The study performed questionnaire to the patients receiving implant operation, who visited dental clinics and hospitals(2 hospitals and 5 clinics) from Jul. 1, 2009 to Sep. 12, 2009 in order to study the factors giving effects to patient's satisfaction in the selection of implant. 145 questionnaire papers collected from patients were analyzed with SPSS12.0 program. The result revealed that the satisfaction with implant operation was usually normal when implant was operated because of tooth extraction due to dental caries and periodontal disease and it was usually high when implant was operated because of wound(P<0.05). When considering each cause of tooth extraction, the satisfaction with pronunciation function was usually normal(P<0.001), the satisfaction with functional part including foreign body sense was very low when the cause of operation was periodontal disease(P<0.01). The satisfaction with hospital environment depending on the cause of hospital selection was usually high when hospital was selected because of doctor's fame. It was low when hospital was selected because it was close to home(P<0.001). The satisfaction with the number of hospital visits depending on the number of implanted teeth was usually low when many teeth were implanted(P<0.01). The analysis on the satisfaction with tooth shape and color showed that the satisfaction was high when '1~2' teeth and 'more than 6' teeth were implanted(P<0.05). In order to improve patient's satisfaction with implant, it is necessary to recognize individual's oral status and request correctly. It is determined that proposal of operation period, number of hospital visits, function and expected aesthetic satisfaction degree will contribute to the improvement of mutual reliance between doctor and patient and post-operation satisfaction degree.