• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.166-182
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• 1998

The purposes of this study are to evaluate the Korean mandibular dental arch and classify the mandibular dental arch shape and size based on the incisal angle, canine angle, inter second molar width and height. In this study the mandibular study models were fabricated using irreversible hydrocolloid impression material from 225 volunteers with a mean age 23.62 (range 19-29). And the study models were measured with 3-dimensional measuring device and the mandibular dental arch was classified by means of K-means clustering method and visual inspection, then obtained data were analyzed with t-test for the statistical analysis. The results were as follows ; 1. The average canine height was 5.19mm(s.d. 1.17) in both sex, 5.34mm in male, and 4.95mnm in female. And the sexual difference was significant($0). 2. The average second molar height was 39.81mm(s.d. 2.44) in both sex, 40.19mm in male, and 39.21mm in female. And the sexual difference was significant($0). 3. The average inter-canine width was 27.16mm(s.d. 1.78) in both sex, 27.41mm in male, and 26.77mm in female. And the sexual difference was significant($0). 4. The average inter-first molar width was 46.93mm(s.d. 2.67) in both sex, 47.72mm in male, and 45.7mm in female. And the sexual difference was significant($0). 5. The inter-second molar width was average 56.09mm(s.d. 3.01) in both sex, 57.24mm in male, and 54.32mn in woma. And the sexual difference was significant($0). 6. The arch form was classified into three shapes based on the incisal and canine angle. V-shape showed $124.88^{\circ}$ of incisal angle and $141.64^{\circ}$ of canine angle, U-shape showed $152.76^{\circ}\;and\;125.35^{\circ}$, and O-shape showed $138.03^{\circ}\;and \;33.66^{\circ}$ respectively. Each shape distribution was that the V-shape was 14.2%, the U-Shape was 14.7%, and the O-shape was 71.1% of the 225 study models. 7. It was thought that the use of second molar width is more reasonable than height for classifying the dental arch size. The arch size was classified into four sizes based on the second molar width. Size 1 showed range of 42.24-48.23mm, size 2 showed 48.24-54.23mm, size 3 showed 54.24-60.23mm, and size 4 showed 60.24-66.23mm respectively. Each arch size distribution was that the size 1 was 1.3%, the size 2 was 27.1%, the size 3 was 63.6%, and the size 4 was 8.0% of the 225 study models.

• Journal of Korean Dental Science
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• v.1 no.1
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• pp.28-34
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• 2008

Objectives. The objectives of this study were: 1) to compare the effect of varying timing of light curing on shear bond strength, and; 2) to compare the shear bond strength of three self-adhesive cements. Materials and methods. A total of 72 extracted non-carious teeth were divided into 24 for Unicem tests, 24 for Maxcem tests, and 24 for Biscem tests; they were assigned 3 * 2 subgroups of 12 teeth each. The specimens were prepared as follows: 1) The calculus and periodontal ligament were removed from the teeth; 2) The teeth were stored in normal saline; 3) The occlusal enamel of each tooth was removed using high-speed coarse diamond burs under water cooling, and; 4) Finally, the teeth were flattened by 600-grit silicone carbide paper disks. Resin blocks were adhered using either Unicem, Maxcem, or Biscem. Light curing timing was divided into two groups: U10, M10, and B10 were exposed to light after 10 seconds, and; U150, M150, and B150 on the other side were exposed to light after 150 seconds. Shear bond strength was measured by a Universal testing machine with cross head speed of 1mm/min. T-test and One way ANOVA were used for the statistical analysis of data. Results. The shear bond strength of U150 was not significantly higher than that of U10 (U150: 20.55.7Mpa, U10: 18.73.80Mpa). On the other hand, the shear bond strength of M150 was significantly higher than that of M10. The shear bond strength of B150 was also significantly higher than that of B10 (M150:14.45.7Mpa, M10: 9.94.2Mpa, B150: 24.38.3Mpa, B10: 17.27.3Mpa). When the light curing timing was 10sec after bonding, the shear bond strength of Unicem was highest; the shear bond strength of Biscem was highest when the light curing timing was 150sec after bonding (U10: 18.73.80Mpa, B150: 24.38.3Mpa). Significance. Since Unicem is less sensitive based on light curing timing, dentists seem to use it without considering the light curing timing. Maxcem showed the lowest bonding strength (especially M10). Thus, when using Maxcem, dentists need to delay the light curing after adhesion.

• The korean journal of orthodontics
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• v.25 no.1 s.48
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• pp.1-12
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• 1995

The purpose of this study was to predict the respose to the chincap therapy from the initial cephalometric measurements and to obtain the indication of chincap therapy. 40 patients selected for this study were classified into two groups by the occlusal stability after completion of permanent dentition and the improvement of facial profile, after chincap therapy. One was good response group which consisted of 25 children and the other was poor response group with 15 patients. Various measurements of the craniofacial structure in the initial lateral cephalogram were calculated and analyzed by t-test and discriminant analysis. The results were as follows: 1. Good response group had more horizontal growth pattern in initial stage of treatment, and the contributing measurements were $Bj\ddot{o}rk$ sum anterior-posterior facial height ratio, genial angle, lower genial angle and occlusal plane to AB plane angle. 2. The critical points and predictive values of the influential skeletal measurements were calculated. 3. The discriminant function was obtained from three major influential measurements; $Bj\ddot{o}rk$ sum, genial angle and occlusal plane to hn plane angle, and this function could discreminate correctly in $85\%$ of this samples.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.94-100
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• 2016

PURPOSE. To evaluate the effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement. MATERIALS AND METHODS. The specimens were prepared to evaluate the bond strength of epoxy resin-based fiber posts (D.T. Light-Post) to dual-curing resin cement (RelyX U200). The specimens were divided into four groups (n=18) according to different surface treatments: group 1, no treatment; group 2, silanization; group 3, silanization after hydrogen peroxide etching; group 4, silanization with warm drying at $80^{\circ}C$ after hydrogen peroxide etching. After storage of the specimens in distilled water at $37^{\circ}C$ for 24 hours, the shear bond strength (in MPa) between the fiber post and resin cement was measured using a universal testing machine. The fractured surface of the fiber post was examined using scanning electron microscopy. Data were analyzed using one-way ANOVA and post-hoc analysis with Tukey's HSD test (${\alpha}=0.05$). RESULTS. Silanization of the fiber post (Group 2) significantly increased the bond strength in comparison with the non treated control (Group 1) (P<.05). Heat drying after silanization also significantly increased the bond strength (Group 3 and 4) (P<.05). However, no effect was determined for hydrogen peroxide etching before applying silane agent (Group 2 and 3) (P>.05). CONCLUSION. Fiber post silanization and subsequent heat treatment ($80^{\circ}C$) with warm air blower can be beneficial in clinical post cementation. However, hydrogen peroxide etching prior to silanization was not effective in this study.

• Journal of Technologic Dentistry
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• v.35 no.3
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• pp.243-257
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• 2013

Purpose: This study aims to analyze the factors affecting the dropout intentions of the dental technology students of a college. Methods: The subject of this study was 76 freshmen and 74 sophomores of dental technician major in an anonymous college. Results from the questionnaire called K-vision diagnosis program were computed by means of t-test, One-Way ANOVA, and correlation analysis. Results: 1. Total points of the drop out intention came to 782.14 points. Of the five categories concerned with the drop out intention, complain in college satisfaction(50.12points) was the highest and department satisfaction(47.51points) was the lowest. Of 16 subcategories, complaining in administrative supporting system proved the highest as 50.80 points and Inquiry to Professor the lowest(45.56 points). 2. Among the general characteristic gender (p<. 01), student group (p<.01), and credit (p<.05) made a meaningful statistical difference; no statistical significance was found in grade, admission, and dwellings. 3. Of the five categories, statistical significance was shown as follows; Department satisfaction (p<.01), College satisfaction (p<.05) under gender, Department satisfaction (p<.05) in grade, Academic integration (p<.01), Department satisfaction (p<.01) in credit. No statistical meaning was found in admission and dwellings. 4. Statistical significance was found under 16 subcategories as follows: Career identification(p<.01), Academic support system(p<.01), Social activity II(p<.05) in gender area, Inquiry to professor(p<.01), Learning(p<.05), Understanding learning I(p<.05) in grade area, Learning(p<.001), Career identification(p<.001), Understanding learning I(p<.01), Understanding learning II(p<.01), Inquiry to professor (p<.01), Learning ability (p<.05), Occupation (p<.05), Social Activity II(p<.05), Administrative support system (p<.05) in student group area, Credit (p<.001), Career identification (p<.01), Understanding learning I(p<.05) in credit area; admission and dwellings was statistically meaningless. 5. Of the 5 categories academic integration (r=.766) was most relevant to the dropout intention of the subjects and followed by department satisfaction (r=.735), college satisfaction (r=.554), service acceptability (r=.373), and statistical significance was shown as p<.01. Conclusion: Considering the results of this study, we are in a pressing need for the introduction of policies and programmes aiming at preventing the dropout rates of the dental technician majors at college. In tandem with this, qualitative and viable human resource management of the dental technicians should be implemented.

• Journal of Information Technology Applications and Management
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• v.15 no.4
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• pp.159-188
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• 2008

This study suggests strategies which can enable to creation of new opportunities of competitive advantages while operating a long lasting and consistent business with major trading partners, based on interorganizational information systems (IOISs) specially established and installed for interorganizational transactions. Nowadays, IOISs based mechanism having been widely expanded as a conventional business infrastructure for the interorganizational transactions and/or exchanges, it is customary difficult to obtain any strongly sound advantage over the competitors who have adopted even the simplest deployment of the IOIS mechanisms. In this connection, this study intends to investigate the interorganizational collaborative activities conducted by under the auspicious of IOISs, focused on the prospect of the exploitation of IOISs rather than the implementation of the IOISs. In this study, we, firstly, suggest the concept of Electronic Collaboration which can be defined by the collaborative activities conducted by IOISs, compared to the ones conducted on off-line. In addition, we suggest the Electronic Collaboration as a multi-dimensional concept, constituted by three sub-constructs, the Electronic Information Sharing (EIS), the Electronic Joint Activity (EJA), and the construction of the Electronic Relational Knowledge Store (ERKS). Secondly, we empirically verify the effects of relational and environmental determinants on the Electronic Collaboration. In this study, the relational determinants relate to the variables created in interorganizational relationship like Trust, Influence, Relational Specific Asset-asset invested for the transaction-, and Continuity of the relationship. On the other hand, the environmental determinants relate to the variables surrounding the relationship which are difficult to control. We consider Product Complexity, Technological Uncertainty, and Market Variability as the domain of the environmental determinants. To test our hypotheses, we conducted both paper-based survey and online-based survey. After refining the data with missing responses, a total of 150 data was used for analysis. The results were as follows : Firstly, it is statistically significant that the Electronic Collaboration is composed of EIS, EJA, and ERKS. In particular, the results imply that the firms are able to accumulate relational knowledge base as well as to exchange information or knowledge, and to conduct joint activities through effort to further expand the Electronic Collaboration. Secondly, we have verified the individual effects of the relational and the environmental determinants on the Electronic Collaboration. Product Complexity has been revealed as the most influential variable affecting the Electronic Collaboration. Next, Interorganizational Trust and Technological Uncertainty, in that order, have been seen to have significant effects on the Electronic Collaboration. In other words, when products or services seem to be difficult to standardize, and the core technologies seem to rapidly change, the need for the Electronic Collaboration increase. In addition, the observation dictates that the interorganizational trust turns out to be a critical variable in building a relationship and in seeking further collaboration. The results, further, illustrate that the environmental determinants are relatively more effective than the relational determinants, which is not consistent with a few prior researches relational determinants emphasized. It is because this study doesn't consider the size of the firm. A few researchers have given an emphasis on the relational determinants like trust and influence, especially from the perspective of small firms in interorganizational relationship. However, in our study, where all the sizes of the firms are contained, electronic collaboration is considerably affected by the environmental determinants.

• Korean Journal of Childcare and Education
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• v.3 no.1
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• pp.17-37
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• 2007

An abundant emotional experience in childhood can be a basis of success of their life. In this research, I set up a hypothesis as follows to see if a group plastic activities are effective for the improvement of children's emotional intelligence and self-emotion awareness ability, self-emotion management ability, self-motivation ability, other's emotion awareness ability and personal relationship skill ability. The research subjects were 40 children of 5 years old(experimental Group: 20, controlled group: 20) in Y kindergarten located in Ulsan. In pretest, we confirmed homogeneity between experiment and control group using child emotional checklist and then applied small group plastic artistic activities to the experiment group. Data analysis was performed with population, percentage, t-test and Cronbach a. The findings of this study were: First, the group plastic artistic activities was effective for the emotional intelligence of children. Second, the small group plastic activities was effective for the self-emotion awareness, self-emotion control and self motivation ability of children. Third, the small group plastic activities was effective for the awareness ability about other's emotion and personal relationship skill ability. The result of this study implies that the small group plastic artistic activities are effective children's emotion and we need to develop the various activity program and practice for children's emotion development.

• Korean Journal of Health Education and Promotion
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• v.21 no.1
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• pp.69-84
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• 2004

This study was conducted to identify actual dental care status, levels of knowledge, attitudes, and behaviors about dental health, and dental health conditions in elementary students; and examine the relationships between the levels of knowledge, attitudes, behaviors, and dental health conditions for 427 students in their sixth grades from six elementary schools in Pusan area from November 1st to December 5th, 2002. The data was collected through a structured study questionnaire and through dental checkups by dentists and was analyzed into frequency, percentage, mean, standard deviation, t-test, one-way ANOVA and Pearson's correlation analysis using SPSS program. The main results of this study were summarized as follows： 1) The levels of knowledge, attitudes, behaviors about dental health was found to be high as mean score 18.75 points (64.7％) in knowledge, 17.86 points (59.5％) in attitudes, and 31.64 points (67.3％) in behaviors. Therefore they were found to care a lot about their dental health. The indices of dental health conditions were found to be low as mean score 0.87 pieces (3.1％) of treated teeth, 1.27 pieces (4.5％) of teeth to be treated, 7.64％ of the DMFT rate and 0.43 points (7.2％) of the simplified oral hygiene index. Therefore their condition of dental health was found to be very clean. 2) The relationships among the knowledge, attitudes, and behaviors about dental health showed a weak level of positive correlations. Among the conditions of dental health, treated teeth and the DMFT rate showed a moderate level of positive correlation； and treated teeth and the simplified oral hygiene index showed weak level of positive correlation. 3) The condition of dental health of the subjects of this study was found to be good and dental care was properly done when there was participation of parents and school health educators in dental care. It tells us that dental education is required not only for children but also for their parents. As there were significant correlations between knowledge, attitudes, and behaviors about children's dental heath, school health educators should encourage students to have continuous dental care habits for lifelong dental health with repetitive education, rather than to deliver simple knowledge to students during dental health education.

• Korean Journal of Community Nutrition
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• v.12 no.4
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• pp.440-448
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• 2007

The objective of this study is to determine the effectiveness of 16-month milk consumption as a part of the health promotion community program for women in Asan. Subjects included 313 women belonging to the milk group (mean age = 69.1, range $47{\sim}89 y$) and 66 women to the control (mean age=43.6, range $20{\sim}69 y$) group. For those in the milk group, one cup (200 ml) of partially lactose-digested low-fat milk was provided everyday for 16 months. Each subject was interviewed to assess calcium intake by a 24-h recall after fasting blood was obtained for analyzing bone turnover markers, and calcaneus broadband ultrasound attenuation (BUA) was measured by quantitative ultrasound (QUS) on the left heel before and after the milk supplementation. After 16 months, the calcium intake levels changed from 55% of recommended dietary allowance (RDA) to 85% RDA in the milk group and from 73% RDA to 84% RDA in the control group. BUA were reduced from $67.9{\pm}8.1$ to $64.7{\pm}17.5$ dB/MHz for milk and from $90.4{\pm}13.0$ to $87.2{\pm}15.2$ dB/MHz for control groups. Paired t-test showed the changes of BUA for both groups (-3.24 and -3.15 dB/MHz for milk and control groups, respectively) were significant, but the two groups did not show any differences in absolute changes. When post-BUA was analyzed after age, initial BUA and menopausal status were controlled as covariates in ANCOVA model, the milk group showed significantly (p < 0.05) smaller changes than the control group (-3.50 vs -6.71 dB/MHz, respectively). According to a multiple regression analysis, milk consumption and initial BUA showed significant interaction meaning that those with lower initial BUA showed higher milk effects. We conclude that one-cup a day milk consumption for 16 month can prevent further bone loss and significantly improve calcium intake.

• Journal of Biosystems Engineering
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• v.36 no.4
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• pp.243-251
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• 2011

Purpose of this study was to analyze power requirement of an agricultural tractor for baler operation. First, a power measurement system was developed and installed in a 75 kW agricultural tractor. Strain-gages with a telemetry system were used to measure torques of transmission and PTO input shafts. An engine tachometer was used to measure rotational speed of transmission and PTO input shafts. The measurement system also included pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to determine power requirements. Second, field experiments were conducted at two PTO speed levels, and proportion of utilization ratio of rated engine power and power consumption of major parts (transmission input shaft, PTO input shaft, main hydraulic pump, and auxiliary hydraulic pump) were analyzed. Results of usage proportion of engine power for PTO speed level 1 and 2 were 4.1 and 2.2%, 31.5 and 16.3%, 49.6 and 59.7%, 14.4 and 20.8%, and 0.4 and 1.0%, respectively, for ratio of measured engine power to rated engine power of less than 25%, 25 ~ 50%, 50 ~ 75%, 75 ~ 100%, and greater than 100%. The results showed that the usage proportion increased in the range with the ratio of power requirement to rated engine power of over than 50% when the PTO gear was shifted from P1 to P2. Averaged engine power requirement for baling operation, tying and discharging operation, and total operation were 43.3, 37.3, and 42.0 kW and 49.0, 37.0, and 47.4 kW, respectively, for PTO speed level 1 and 2. Paired t-test showed significant difference in power consumption of engine, transmission input shaft, and PTO input shaft for different PTO speed levels. Therefore, the power consumption of engine for baler operation increased when the PTO gear was shifted from P1 to P2. It was indicated that the power requirement of tractor was affected by the PTO rotational speed for baler operation.