This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Objectives: The purpose of this study was to examine the effect of problem-based learning (PBL) on dental education to dental students. The following were investigated in this study: 1. Does PBL improve the ability of self-directed learning? 2. Does PBL change communication ability? 3. Does PBL change the strategy of problem solving? Methods: The participants of this study were 39 students in the experimental group and 68 students in the control group. The measurement tools of this study were self-directed learning, communication, and problem solving abilities tests designed by the Korean Educational Development Institute. The data was analyzed by the two-way ANOVA and ANOVA with repeated measures. Results: In self-directed learning ability during 3 semesters, the experimental group showed a U-shape change but the control group showed a reverse U-shape change. In the experimental group, the selfdirected learning ability was decreased after one year (after the first and second semester). The level of communication ability decreased every day during the three semesters monitored in both the control and experimental groups. The level of communication ability in the experimental group continuously decreased during the three semesters, with the exception of one semester. Finally, for the problem solving ability during the three semesters, the experimental group showed a reverse U-shape change while the control group showed a U-shape change. In the experimental group, there was no change after two semesters. Conclusions: On the basis of the findings in this study, the following conclusions can be made. First, problem-based learning has a positive educational effect compared to didactic-based learning within one year. Second, the appropriate length of PBL is two semesters, or one year. It could be recommended that dental education in Korea should be combined or hybridized with PBL; for example, PBL could be used in combination with brief lectures or block lectures by teachers.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives:This study aimed to analyze the variables affecting the survival of the four permanent first molars in an adult Korean population using logistic regression analysis. Methods: The Korean government has been collecting oral health data at the national level at 3-year intervals since 2000. In addition, a national survey was conducted in 2006 among 15,777 persons aged 2-95 years who were stratified by age, gender, and region. The relationship between each of nine objective variables and tooth survival was analyzed by frequency, cross-tabulation, and logistic regression analysis, with age, gender, and economic status as functional variables. The inclusion level was α=0.05 and the exclusion level was α=0.10. The nine variables were age, occupational status, monthly family income, gender, frequency of brushing the teeth, snack intake per day, presence of diabetes, education level, and smoking (packs per year). Results: The survival rate of the molars decreased with increased age. In individuals who engaged in farming, stock breeding, and fishing, the rate was 2-5 times lower than that of individuals in higher positions in terms of jobs and society. Furthermore, the survival rate for smokers was 5-10 percent lower, compared with non-smokers. Conclusions: The most significant predictor of the survival rate of the four permanent molars in Korean adults was age, followed by jobs, smoking, and gender.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Objectives: The purpose of this study was to develop and appraise an oral health literacy assessment tool for upper elementary school students. Methods: Twenty-eight preliminary assessment items were developed on the basis of various types of oral health education literature for children. They contained verbal and functional sections and they were classified into 2 cognitive processes (literal and inferential). The questionnaires were analyzed using the testAn v.1.0 program for identified Cronbach's a, item discrimination, and difficulty through classical test theory. A final evaluation tool was developed and selected by conducting three surveys and 20 items. Results: The final survey was completed by 132 fifth and sixth grade elementary school students in Seoul. The Cronbach's a value, item discrimination, and difficulty were .71, .38, and .75, respectively. The mean score for oral health literacy of children was 14.9 (±3.2, theoretical range: 0-20, 75% correct answers). Conclusions: These results suggest that this tool could be relied on to help determine the level of oral health literacy in children and in preparing appropriate oral health education programs for children.

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