• Korean Journal of Materials Research
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• v.29 no.6
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• pp.392-397
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• 2019

A cold roll-bonding process is applied to fabricate an AA6061/AA5052/AA6061 three-layer clad sheet. Two AA6061 and one AA5052 sheets of 2 mm thickness, 40 mm width, and 300 mm length are stacked, with the AA5052 sheet located in the center. After surface treatment such as degreasing and wire brushing, sample is reduced to a thickness of 1.5 mm by multi-pass cold rolling. The rolling is performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at rolling speed of 6.0 m/sec. The roll bonded AA6061/AA5052/AA6061 complex sheet is then hardened by natural aging(T4) and artificial aging(T6) treatments. The microstructures of the as-roll bonded and age-hardened Al complex sheets are revealed by optical microscopy; the mechanical properties are investigated by tensile testing and hardness testing. After rolling, the roll-bonded AA6061/AA5052/AA6061 sheets show a typical deformation structure in which grains are elongated in the rolling direction. However, after T4 and T6 aging treatment, there is a recrystallization structure consisting of coarse equiaxed grains in both AA5052 and AA6061 sheets. The as roll-bonded specimen shows a sandwich structure in which an AA5052 sheet is inserted into two AA6061 sheets with higher hardness. However, after T4 and T6 aging treatment, there is a different sandwich structure in which the hardness of the upper and lower layers of the AA6061 sheets is higher than that of the center of the AA5052 sheet. The strength values of the T4 and T6 age-treated specimens are found to increase by 1.3 and 1.4 times, respectively, compared to that value of the starting material.

• Journal of Korean society of Dental Hygiene
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• v.19 no.4
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• pp.555-564
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• 2019

Objectives: The purpose of this study was to investigate how mental health status affects oral health in the elderly. Methods: The subjects of the study provided the data for the sixth Korea National Health and Nutrition Examination Survey from 2013 to 2015. Four-hundred and twenty-one subjects were selected for the study. All data were analyzed by complex sampling frequency, chi-square test, and composite multiple regression analysis using SPSS 21.0 version. In addition, a significance level of 0.05 was considered. Results: The general factors affecting cases of periodontal disease were general characteristics, mental health status, oral health status, elderly males, household income, education level, daily brushing frequency, speaking, and stress. The effect of periodontal disease was 1.64 times higher in the male group than in the female group (p<0.001). In the household income level, the 'low' group had 1.91 times more periodontal disease, while the 'mid low' group had 1.64 times more periodontal disease than the 'high' group (p<0.05). Periodontal disease was found to be lower in the group that recognized subjective oral health status as 'good' (p<0.05). The study subjects had low levels of periodontal disease when there was no speaking difficulty (p<0.05). Conclusions: Therefore, in order to improve oral health of the elderly, it is necessary to understand the mental health condition of the elderly and prepare proper oral health education programs accordingly. Institutional devices for various oral health projects should be prepared, as well.

• Journal of dental hygiene science
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• v.19 no.3
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• pp.162-169
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• 2019

Background: Oral diseases are caused by various systemic and local factors, the most closely related being the biofilm. However, the challenges involved in removing an established biofilm necessitate professional care for its removal. This study aimed to evaluate and compare the effects of professional self and professional biofilm care in healthy patients to prevent the development of periodontal diseases. Methods: Thirty-seven patients who visited the dental clinic between September 2018 and February 2019 were included in this study. Self-biofilm care was performed by routine tooth brushing and professional biofilm care was provided using the toothpick method (TPM) or the oral prophylaxis (OP) method using a rubber cup. Subgingival bacterial motility and halitosis (levels of hydrogen sulfide, $H_2S$; methyl mercaptan, $CH_3SH$; and di-methyl sulfide, $(CH_3)_2S$) were measured before, immediately after, and 5 hours after the preventive treatment in the three groups. Repeated measures analysis of variance test was performed to determine significant differences among the groups. Results: TPM was effective immediately after the prevention treatment, whereas OP was more effective after 5 hours (proximal surfaces, F=16.353, p<0.001; smooth surfaces, F=66.575, p<0.001). The three components responsible for halitosis were effectively reduced by professional biofilm care immediately after the preventive treatment; however, self-biofilm care was more effective after 5 hours ($H_2S$, F=3.564, p=0.011; $CH_3SH$, F=6.657, p<0.001; $(CH_3)_2S$, F=21.135, p<0.001). Conclusion: To prevent oral diseases, it is critical to monitor the biofilm. The dental hygienist should check the oral hygiene status and the ability of the patient to administer oral care. Professional biofilm care should be provided by assessing and treating each surface of the tooth. We hope to strengthen our professional in biofilm care through continuous clinical research.

• Journal of Korean society of Dental Hygiene
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• v.19 no.1
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• pp.105-116
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• 2019

Objectives: This study aimed to confirm the relationship between toothbrushing practice after lunch and typical oral health behaviors in children and adolescents according to the subject and type of social support. Methods: The study used data from the 2010 Korean Survey on the Health of Youth and Children and selected 8,704 elementary, middle, and high school students as final targets. Multiple logistic regression was conducted to confirm the link between social support and toothbrushing after lunch. Results: The results showed that in elementary and vocational high school students, statistical significance of all social support variables disappeared after controlling for both demographic and social factors and oral symptom experience. However, in the middle school students, the emotional support of the neighbors and the emotional support of the teachers showed statistically significant effect on brushing daily after lunch (p<0.05). In general high school students, there was a significant association between family emotional support and toothbrushing after lunch (p<0.01). Conclusions: The oral health promotion program for children and adolescents needs to be integrated and coordinated with the overall health promotion program. In particular, it is believed that the school-based program can strengthen the practice of health behaviors by inducing behavioral changes based on the formation of healthy relationships and trust of colleagues and teachers. Therefore, it is necessary to develop social network-based programs including social support such as emotional health and healthy relationships that can be applied among children for oral health promotion.

• Journal of the Korea Convergence Society
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• v.10 no.4
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• pp.91-97
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• 2019

The aim of this study was to compare effects of oral health education on oral health behavior according to demographic and dental health-related characteristics in inpatient alcoholics. 62 alcoholic male patients were recruited to 32 patients at education group and 30 at non-education group. To search demographic and dental health-related characteristics, the self-administered structured questionnaires were used, and the survey was conducted before and after the oral health education. The oral health education program was consisted of 40 mins theoretical education and individual tooth brushing training once a week for 4 weeks. The oral health education for alcoholic patients had big effects on oral health behavior. And these results indicate that if oral health program was performed systematically in alcohol counseling centers or alcohol hospitals, more oral health promotion effects will appear.

• The Journal of Advanced Prosthodontics
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• v.13 no.1
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• pp.1-11
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• 2021

PURPOSE. The study compared the color change, lightness, and translucency of hybrid resin ceramics exposed to toothbrush abrasion and surface treatment. MATERIALS AND METHODS. Four hybrid ceramics [Lava Ultimate (LU), Vita Enamic (EN), Shofu HC (SH), and Crystal Ultra (CU)] were compared with a glass-ceramic (Vita Mark II) control. One hundred and twenty specimen blocks were prepared using a precision saw machine. Specimens in each material were divided into four subgroups based on the surface treatment (polishing or staining) and a storage medium (water or citric acid). Simulated tooth brushing with a mixture of 100 RDA (radioactive abrasives) with 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Measurements for the color change, lightness, and translucency were measured after toothbrushing using a spectrophotometer. Statistical analysis compared outcomes using paired t-test, ANOVA, and Tukey post hoc test. RESULTS. The maximum color change was identified in SH (stained acid) [1.44 (0.40)], whereas the lowest was identified in EN (polished water) [0.66 (0.16)] material. The maximum and minimum loss of surface translucency was observed in SH (polished water) [12.3 (0.52)] and EN (stained acid) [6.5 (0.55)] specimens, respectively. Lastly, loss of lightness was the highest in VM (polished acid) [69 (0.95)], whereas the lowest was observed in CU (stained water) [56.7 (0.86)]. CONCLUSION. The comparison presented a significant effect of toothbrush abrasion on translucency and lightness of the hybrid resin ceramics. Color change was not significantly influenced irrespective of the storage medium employed. Surface staining demonstrated the preservation and stability of color and optical properties under the influence of toothbrush abrasion and chemical trauma.

• Journal of Korean Dental Hygiene Science
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• v.3 no.2
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• pp.1-8
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• 2020

This study investigated the relationship between oral health knowledge, behavior and orthodontic satisfaction in orthodontic patients visiting dental hospitals and clinics and provided suggestions to improve orthodontic patients' satisfaction. This study anayzed structured self-administered questionnaires collected from 245 patients who visited 5 dental clinics in Gwangju Metropolitan City. Regarding oral health knowledge, the highest percentage of correct answers was for the item "Cavities heal themselves over time" (97.1%), and the lowest percentage of correct answers was for the item "Cavity bacteria move from tooth to tooth" (16.7%). Five fluoride items showed a lower percentage of correct answers than those for cavity and gingival diseases. Regarding the survey on oral health behavior, the highest score was found for the item "I brush my teeth with a certain method and order" (3.78 out of 5), and the lowest score was found for the item "I use an electric toothbrush" (1.34 out of 5). Regarding the survey on orthodontic satisfaction, the highest score was found for the item "I would recommend receiving medical treatment at the department of orthodontics" (4.23), and the lowest score was found for the item "Orthodontic cost is reasonable" (3.46). While oral health behavior had on orthodontic satisfaction, oral health knowledge had no effect on it. Oral health behaviors should be improved to enhance orthodontic satisfaction. To improve oral health behavior, it is necessary to develop and activate education programs for tooth brushing and oral care for orthodontic patients.

• Oral Biology Research
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• v.42 no.4
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• pp.208-215
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• 2018

The purpose of this study was to identify the risk of dysphagia among patients that visited prosthodontics department, and evaluate the difference in risks arising from oral conditions and disease in order to preliminarily intervene the various influencing factors of dysphagia. A questionnaire was given to patients that were aged 65 years or older who visited the prosthodontics department between September to December 2017. The data was collected and analyzed using the t-test, $x^2-test$ and logistic regression analysis. The mean age of the patients was 75 years. Out of 300 patients, 206 patients (68.7%) had a risk of dysphagia. There were statistically significant differences between the -non-risk and risk groups, which included the number of natural teeth, total number of teeth including prosthesis, denture use, denture discomfort, number of tooth brushing, oral dryness, digestive system diseases, and musculoskeletal diseases. Among these, oral dryness was a risk factor while the total number of teeth, including natural teeth and prostheses, served as a protective factor. More than half of the elderly patients were at risk of dysphagia. Oral dryness is influenced by many factors and it should continuously be managed. Patients should fully recover their masticatory function by preserving the remaining teeth and compensating for the missing teeth. A dental practitioner should be fully aware of the risk of dysphagia in elderly patients and be able to intervene and offer proper patient health care in advance through treatment guidelines and education.

• Journal of Korean society of Dental Hygiene
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• v.20 no.6
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• pp.963-972
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• 2020

Objectives: This study aimed to check the effect of preschool visiting oral health education programs and provide baseline data for an oral health education program that suggests the necessity of oral health education in children's living places. Methods: The preschool visiting oral health education was conducted with the parents of 3-year-old and 4-year-old children at a preschool in the jurisdiction of the Seoul Metropolitan Office of Education, with teachers observing the education, and oral health educators to examine the effect of the oral health education, the effectiveness of the education, the status of oral health care, and the degree of cooperation for the education. Results: Regarding oral health behaviors after the education program, the attitude toward brushing teeth after food intake increased from 2.86 to 3.17 and thinking of the relationship with dental caries and eating food increased from 2.57 to 2.90. The satisfaction with the children's health education was very high at over 4.9 points in most items. The teachers' interest in children's oral care was 4.26 points, and the degree of their cooperation for education was 4.41 points; 96.4% responded that they were willing to conduct reeducation. Conclusions: Children's oral health education should be conducted steadily and repeatedly.

• Journal of dental hygiene science
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• v.21 no.1
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• pp.38-44
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• 2021

Background: Dental caries and periodontal disease are bacterial infectious disease, mainly caused by plaque, a bacterial colony deposited on the tooth surface and gum tissue. Dental plaque disclosants easily stain the dental plaque, making them effective for scaling and tooth brushing education. As the erythrosine typically contained in dental plaque disclosants is highly cytotoxic, a low toxicity additive is needed. In this study, we aimed to examine the natural pigments with negligible cytotoxicity but can effectively stain the dental plaques for use in dental plaque disclosants. Methods: The pigmentation of eight types of natural pigments was tested on bovine tongue and teeth, as well as on head and neck tissue sections of experimental ICR mice. The cytotoxicity of gingival epithelial cells was measured via MTT assay. Pigmentation was performed on the bovine tongue and tooth surface. Pigmentation in the oral environment was observed in four mandibular incisors. A 2 Tone was used as a control. Results: Of the eight types of natural pigments, purple and blue pigments were effective in coloring dental plaques on the enamel surface as well as in the head and neck tissue sections. Additionally, purple and blue pigments were visible on the surface of the bovine tongue. Red, pink, orange, green, purple, and yellow pigments showed strong cytotoxicity, whereas brown and blue pigments had relatively low cytotoxicity. Blue pigment was effective in staining the dental plaque of four mandibular incisors. Conclusion: We suggest that the blue pigment derived from Gardenia jasminoides Ellis (Rubiaceae), which is effective for coloring dental plaques and has low cytotoxicity, is useful as a naturally derived dental disclosant.