• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.73-80
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• 2007

Compomer that release fluoride could be used on proximal caries of child effectively. But oral cavity is always wet, so saliva inhibits bonding of tooth and compomer. When the saliva exist on bonding, it can be occured microleakages. The purpose of this study was to evaluate the influence of salivary contamination on compomer restoration and degree of microleakage according to restoration methods. Dyract $AP^{(R)}$ and prime and $bond^{(R)}$ NT was applied by the manufacture s instructions. Elipar Trilight was applied for light curing. Saliva pool was made for reconstruction of oral cavity. Two premolar was embedded in acrylic resin. After class II cavity preperation, Dyract $AP^{(R)}$ was restored under several condition, the specimen was thermocycled 500 times with 30 second dwell time. 0.5% methylene blue was used for microleakage test. Micoleakage was measured by the ratio of the infiltration length to occlusal and gingival side interface. Data were analyzed statistically using Kruskal Wallis Test, Mann-Whitney Test. The Result were as follows ; 1. In occlusal side, there were no statistical differences. 2. In gingival side, there were no statistical differences in Group III ($ContactMatrix^{TM}$, Rubber dam, $Oraseal^{(R)}$), Group IV (No saliva contamination). 3. In gingival side, there were no statistical differences in Group I$(ContactMatrix^{TM})$, II($ContactMatrix^{TM}$, Rubber dam). 4. In gingival side, there were statistical differences in Group I$(ContactMatrix^{TM})$, II($ContactMatrix^{TM}$, Rubber dam).

• Journal of The Korean Association For Science Education
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• v.20 no.4
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• pp.572-581
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• 2000

Teachers' perceptions about curricular objectives are very important to achieve given educational objectives. This study examined teachers' perceptions about priority and hinderance of science objectives. The national science curriculum stated four areas of objectives: inquiry, knowledge, attitude, and STS. A total of 76 elementary and 217 secondary teachers were responded to questionnaire developed for this study. Non-parametric statistics, such as Friedman test, Kruskal-Wallis test, and chi-square test were used by using SPSS/PC program. Teachers in general ranked the inquiry first among the four areas at their perception on the national curriculum, on themselves, and on their instructions. Elementary teachers ranked inquiry higher than secondary science teachers, while secondary science teachers ranked knowledge higher than elementary teachers. As factors hindering teachers from achiving the objectives, elementary teachers pointed out overcrowded classroom and secondary science teachers pointed out college and university entrance examination respectively.

• Journal of dental hygiene science
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• v.15 no.2
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• pp.220-225
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• 2015

This study was conducted to examine O'leary index, patient hygiene performance (PHP) index, and toothbrushing practice assessment in subjects of college students in 20s who had been randomly selected. The purpose of this study is to examine if it is easy for rolling method which is recommended by many dental professionals in Korea to implement and to effectively remove dental plaque. Also, the correlations between dental plaque index and toothbrushing practice assessment with the course of time was confirmed, after instruction session on toothbrushing was provided. STATA 11.0 (StataCorp) was used for analysis. There was no significant difference on the three ways of O'leary index, PHP index, and toothbrushing practice assessment in using rolling method, bass technique and toothpick method when comparing the average resulting from first to third instruction session on toothbrushing. O'leary index, PHP index, and toothbrushing practice assessment were inspected with Kruskal-Wallis test which is used for non-parametric statistics. They were checked three times: the first, before the toothbrushing instruction was given; the second, two weeks after the toothbrushing session was given; and the third, 4 weeks after the session. The results are as follows: O'leary index stood at the lowest in the first experiment but showed the highest in the second (p=0.0001). PHP index was the highest level in the first trial and decreased in the second time, but increased again in the last examination (p=0.0001). Toothbrushing practice assessment also showed a similar tendency with PHP index (p=0.0001). In conclusion, rolling method is not the best option for everyone, and it is thought that more various toothbrushing ways need to be reviewed and recommended to people. Also, institutional framework is required for the continuous education on toothbrushing to be in place as the effectiveness of the education is decreased with time.

• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.121-127
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• 2005

A variety files made of stainless steel (S-S) or nickel-titanium (Ni-Ti) are used during endodontic treatment. The purpose of tt)is study was to evaluate the corrosion susceptibility of S-S and Ni-Ti endodontic files. Three brands of files were used for this study: $K-flex^{(R)}$ S-S files (Maillefer, USA), $Profile^{(R)}$ Ni-Ti files (Maillefer, USA), $K-3^{(R)}$ Ni-Ti files (SybronEndo. USA). 120 files of each brands (21mm, ISO size $\#20$) were divided into 12 groups according to 1) sterilization methods using Autoclave or Ethylene Oxide (E-O) gas, 2) Irrigation solutions using $5.25\%$ NaOCl or Saline, 3) the number of sterilization (1, 5, 10 times), After above procedures, each of the files was inspected by three examiners with a light microscope and camera at X25. Each file was judged and ranked according to the following criteria: 0;, no corrosion, 1; mild corrosion, 2; moderate corrosion, and 3; severe corrosion. The files of high score were examined under the Scanning Electron Microscope. Data were statistically analyzed with the Kruskal-Wallis test (p < 0.05). Most of the ten time-autoclaved files had showed mild to moderate corrosion. But, one or five time-autoclaved files did not show corrosive surface. NaOCl treatment and E-O gas sterilization did not influence on corrosion. There was a significant difference in corrosion susceptibility between sterilization methods and the number of autoclaving. However, there was no significant difference between brands and file materials.

• Journal of dental hygiene science
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• v.18 no.4
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• pp.265-270
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• 2018

The purpose of this study was to investigate the chemical properties of some commercially available mouthwashes and to ascertain whether the mouthwashes accelerated mineral loss in dental enamel. Five commercially available mouthwashes were selected from the three largest malls in Korea: Perio Total 7 Aqua Cool Mint Strong $Fresh^{TM}$ (PS; LG Household & Health Care Ltd.), Garglin $Original^{TM}$ (Dong-A Pharmaceutical Co., Ltd.), Garglin $Zero^{TM}$ (Dong-A Pharmaceutical Co., Ltd.), Listerine Naturals $Citrus^{TM}$ (LC; IDS Manufacturing Ltd.), and Listerine Cool $Mint^{TM}$ (LM; IDS Manufacturing Ltd.). The composition, pH, and titratable acidity of the mouthwashes were investigated. Six bovine teeth specimens were prepared for each mouthwash group. Each of the six specimens was individually immersed in 30 ml aliquots of mouthwash for 1 minute, 30 minutes, 90 minutes, and 120 minutes, and the samples were placed in a $36.5^{\circ}C$ stirred incubator. The degree of mineral loss (${\Delta}F$) of the tooth surface area exposed to mouthwash, compared with normal teeth, was analyzed by quantitative light-induced fluorescence-digital. The difference in ${\Delta}F$ among mouthwash groups was examined by the Kruskal-Wallis H test (${\alpha}=0.05$). The contents of mouthwashes differed between Listerine and other products, and the pH ranged from 4.09 to 6.75. The titratable acidity of PS was the lowest at 0.63 ml and highest at 9.25 ml for LM. Minor mineral loss was observed when dental specimens were immersed in the Listerine products (LC and LM) for more than 90 minutes, but the degree of mineral loss for Listerine products was not statistically significantly different from that for groups without mineral loss. In conclusion, all five commercially available mouthwashes showed no harmful effects on tooth enamel.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.26 no.1
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• pp.17-23
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• 2017

Purpose: This retrospective study is to evaluate whether the timing of implant placement and the result of esthetic outcomes are related. Materials and Methods: Among the patients who had undergone single implant surgery on anterior area from 2010 to 2013 in Veterans Health Service Medical Center, 34 implants in 27 patients (24 male and 3 female) were selected and categorized into 3 groups according to the timing of placement, which are group D (Delay), group E (Early) and group I (Immediate). Aesthetic indices used included the Pink Esthetic Score (PES). It has 7 variables scores, such as mesial papilla, distal papilla, a level of soft-tissue margin, soft-tissue contour, alveolar process, soft-tissue color, and soft-tissue texture. Each variable ranges from 0 to 2, therefore total 14 points are highest. All patients were received by regular follow-up at least 1-year. One examiner measured PES on the intraoral photos. Each patient was considered as a statistical unit for statistical analysis. Statistical analyses were performed using a commercially available statistical software (SPSS Statistics 21.0, IBM Corp., Armonk, NY, USA). Kruskal-Wallis test was used for inter-group comparisons. Statistical significance was set at P<0.05. Result: Mean score in Group D, Group I, and Group E were $11.5{\pm}1.5$, $11.4{\pm}1.8$, and $11.3{\pm}1.8$ respectively. In Kruskal-Wallis test, there are no differences (P=0.989). Conclusion: In this limited study suggests that clinical aesthetic results can be achieved with all treatment protocols. Finally, various factors can be considered to produce the esthetic results.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.3
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• pp.201-206
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• 2020

Purpose: The purpose of this study is to evaluate the antimicrobial activity on the dental bur with fluoride for S. mutans. Materials and methods: 0 ppm, 300 ppm, 500 ppm, 1,000 ppm, 1,450 ppm fluoride ion is added to a specimen. S. mutans was incubated for 24 hours, the number of S. mutans were counted. Kruskal-Wallis and MannWhitney analysis were used SPSS 25.0 (IBM SPSS 25.0, Chicago, IL, USA). Results: The mean S. mutans counts of 0 ppm, 300 ppm, 500 ppm, 1,000 ppm, and 1,450 ppm were 374.0 ± 12.6, 251.0 ± 66.7, 111.4 ± 35.6, 41.6 ± 11.7 and 13.2 ± 4.6, respectively. All groups except the control and 300 ppm showed statistically significant. Conclusion: Thus, more than 500 ppm fluoride ion showed the statistically significant antimicrobial activity. 1,450 ppm group showed the highest antimicrobial activity. This study showed the clinical possibility for dental caries protection and antimicrobial activity of dental bur.

• Culinary science and hospitality research
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• v.19 no.5
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• pp.264-279
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• 2013

This study aimed to analyze the differences between the types of disputes in food service franchises and the relevant corporate information. For this aim, the types of disputes were analyzed on the basis of the cases reported by the Korea Fair Trade Commission, and whether there are any differences from the relevant corporate information was analyzed using SPSS WIN(V.17.0). According to analysis results, the most often seen types of disputes were failure to provide the information disclosure sheet (58.5%) and failure to deposit franchising fee (15.1%). In Kruskal-Wallis test between the type of disputes and related corporate information variables, significant difference was found under significance level p<.05 for sales volume, the establishment period and the number of franchisees, and under p<.1 for the number of full-time employees. In correlation coefficient, the establishment period, the number of full-time employees and the number of franchisees showed positive correlation(p<.05), and the number of full-time employees showed correlation in the number of franchisees and the number of brands under the significance level p<.05. As a solution for the dispute, there should be franchisors' responsibility to comply with the principle of good faith, the authorities' strengthening exemplary transaction criteria and legal systems, as well as experts' consulting for prospective franchisees prior to establishing business.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.4
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• pp.220-227
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• 2019

Purpose: The purpose of this study was to compare the degree of tooth preparation abilities of students according to three self-assessment methods. Materials and Methods: forty-eight sophomores in Kyungpook National University College of Dentistry were divided into three experimental groups. Students performed tooth preparation of the left mandibular first molar for full gold crown. They performed self-assessment using the three methods (visual, digital, and putty index self-assessment group), and reperformed tooth preparation. An intraoral scanner was used to scan each tooth model (prepared tooth and unprepared tooth), and data were acquired in standard tessellation language (STL) file format. The STL files of prepared tooth and unprepared tooth were superimposed using the 3-dimensional analysis software (Geomagic control X). And the reduction amount was measured. In the statistical analysis, all values of reduction amount were analyzed with the Wilcoxon signed rank test and Kruskal-Wallis test (α = 0.05). Results: The three self-assessment methods showed statistically significant differences (P < 0.001). The putty index self-assessment group showed the highest reduction in error than the digital self-assessment method. Conclusion: Within limitations of this study, students showed significant differences in improvement of tooth preparation ability according to the three self-evaluation methods.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.168-175
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• 2020

Purpose: The purpose is to test and evaluate the physical properties of commonly used temporary restoration materials and newly emerged materials. Materials and Methods: Four groups of polymer materials were evaluated: Polymethyl methacrylate (PMMA) 2 groups, Polyetheretherketone (PEEK), Polycarbonate. Four physical properties were tested: surface hardness, bending strength, abrasion resistance during wear, wear behavior. The 3-axis bending strength and Vickers hardness test were measured using a universal testing machines respectively. The microstructure was observed with a scanning electron microscope and weight comparison was evaluated after 100,000 chewing tests using a chewing simulator. Kruskal wallis test was performed to evaluate statistical significance. Results: The four groups showed the highest flexural strength and Vickers hardness of PEEK, followed by PC, PMMA-H, PMMA-T. Microstructure observation also showed the least surface roughness in the PEEK group, followed by PC, PMMA-H, PMMA-T. Conclusion: PC is considered to have sufficient mechanical properties that can be applied to the manufacture of temporary teeth. However, further studies, such as biocompatibility, are considered to be necessary for practical clinical applications.