• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.5
• /
• pp.64-69
• /
• 2018

Clear aligners are popular in the field of dental orthodontic treatment because they offer a discreet alternative to braces due to their use of transparent materials. They are formed from flat transparent polymer materials by hot pressed molding. It is necessary to know the mechanical properties of the polymer materials to be able to form the exact shapes of the clear aligners. However, this information is not publicly available. In this study, we present a method to reliably measure the mechanical properties of clear aligner polymer materials and analyze the factors effecting these mechanical properties. First, we surveyed standards related to the mechanical properties of polymer materials to obtain reliable data. Consequently, ISO 527 was selected for use in this study because of the size and thickness of the flat transparent polymer material. The uniaxial tensile tester was constructed and it was verified whether displacement of a crosshead could be regarded as a displacement of gauge-length by optical analysis. Uniaxial tensile tests of three thicknesses from three different companies were performed and each engineering stress-strain curve was measured. Tensile strengths and elastic moduli were obtained by analysis of the stress-strain curves. The tensile strength and elastic modulus of ISO 527 was found to be approximately 50MPa and 2.3GPa, respectively. Both values showed material and thickness dependency.

• Journal of The Korean Society of Integrative Medicine
• /
• v.7 no.4
• /
• pp.203-212
• /
• 2019

Purpose : The purpose of this study was to determine the correlation between the self-esteem of health science college students and their empathy for others. Methods : A survey was administered to 448 students from the five departments of health science (Occupational Therapy, Physical Therapy, Dental Hygienics, Nursing, and Medical Administration) at a college located in Busan, South Korea, between September 28 and November 2, 2017. To measure their self-esteem and empathy for others, the Self-esteem Scale and the Korean Empathy Quotient (K-EQ) Scale were used. Results : There were statistically significant differences in social skills as a sub-item of empathy skills based on age and department, as well as in emotion as a sub-item of empathy skills based on sex. Self-esteem and all the items of empathy showed meaningful differences based on monthly expenses, while self-esteem and cognition as a sub-item of empathy skills displayed significant differences based on source of monthly income. Noteworthy differences were also found in self-esteem and emotion as a sub-item of empathy skills based on satisfaction with current school life. Self-esteem and empathy skills were shown to have a positive correlation. Conclusion : According to the results of this study, self-esteem and empathy skills had a statistically significant correlation. Further research is needed to investigate how health science college students can improve their understanding of themselves and their empathy for others.

• Journal of the Korean Ceramic Society
• /
• v.37 no.4
• /
• pp.354-358
• /
• 2000

Tetragonal (t)-ZrO2/Al2O3 composites doped with Y2O3, Nb2O5, and Fe2O3 ((Y, Nb, Fe)-TZP/Al2O3) were prepared over the range containing Fe2O3 from 0.1 to 0.5 mol% with 0.1 mol% intervals to evaluate the effect of Fe2O3 addition on chromaticity, hydrothermal stability, and mechanical property of the composites. After autoclaving for 20 h at 18$0^{\circ}C$ under 3.5 MPa water vapor pressure, no tlongrightarrowm phase transformation was observed probably due to the preferential solid solubility of Fe2O3 in Al2O3, the presence of the rigid Al2O3 particles, and the inherent phase stability of (Y, Nb)-TZP. The optimized strength and the fracture toughness of the composite were 700 MPa and 8.5 MPa.m1/2, respectively, when 0.1 mol% Fe2O3 was added. The composites have shown a gradual color change from a slightly white ivory to a pale yellowish brown with increasing the Fe2O3 concentration.

• Journal of Oral Medicine and Pain
• /
• v.30 no.3
• /
• pp.361-373
• /
• 2005

Occlusal appliance therapy has been proven to be very useful and effective in reducing signs and symptoms of patients with TMD. However, there are no reports about the masticatory efficiency of the occlusal appliance. The purpose of this study was, first, to investigate the masticatory efficiency of the conventional stabilization appliance experimentally in normal healthy subjects, by comparing it with that of their natural dentition; and, second, to develop a modified stabilization appliance as an attempt to increase masticatory efficiency. Eleven subjects (mean age 25.3 years, range from 23 to 33) participated in this study. Six were men and five were women. They were healthy and had complete or near―complete natural dentition, and did not present with signs or symptoms of TMD. Two kinds of occlusal appliances―the conventional flat maxillary stabilization appliance (i.e., FSA) and a modified maxillary stabilization appliance with additional anatomic structures on its occlusal surface (i.e., ASA)―were made for every subject. Subjects chewed peanuts that were selected as a food to test the three masticatory conditions of the natural dentition, the ASA, and the FSA. The number of chewing strokes was counted during each 1-minute chewing period. Chewed peanut boluses were recovered and their hardness was measured by texture analysis. Statistical tests were performed. The following results were obtained. 1. The masticatory efficiency of the FSA was 38.6 percent that of the natural dentition. The efficiency of the ASA was 78.2 percent that of the natural dentition. 2. The number of chewing strokes in the natural dentition condition was measured to be 1.5 strokes per second. It decreased to 90 percent in the ASA and FSA conditions. These results indicate that the ASA could serve an improved masticatory capacity as well as its therapeutic effects in TMD. A clinical application of the ASA should be considered to extend the management of TMD patients.

• The Journal of Korean Academy of Prosthodontics
• /
• v.40 no.3
• /
• pp.275-286
• /
• 2002

Statement of problem. Surface alteration of the implant screws after function may be associated with mechanical failure. Theses metal fatigue appears to be the most common cause of structural failure. Purpose. The purpose of this study was to evaluate surface alteration of the implant screws after function through the examination of used and unused implant screws in SEM(scanning electron microscope). Materials and methods. In this study, abutment screws(Steri-oss, 3i), gold retaining screw(3i) and titanium retaining screw(3i) were retrieved from patients. New, unused abutment and retaining screws were prepared for control group. Each of the old, used screws was retrieved with a screwdriver. And retrieved implant complex of Steri-oss system was prepared for this study. Then, SEM investigation and EDS analysis of abutment and retaining screws were performed. And SEM investigation of cross-sectioned sample of retrieved implant complex was performed. Results. In the case of new, unused implant screws, as maunfactured circumferential grooves are regularly examined and screw thread are sharply remained. Before ultrasonic cleansing of old, used implant screw, a lot of accumulation and corrosion products were existed. After ultrasonic cleansing of old, used implant screws, circumferential grooves as examined before function were randomly deepened and scratches increased. Also, dull screw thread was examined. More surface alterations after function were examined in titanium screw than gold screw. And more surface alteration was examined when retrieved with driver than retrieved without driver. Conclusions. These surface alteration after function may result in the screw instability. Regularly cleansing and exchange of screws was recommended. We recommend the use of gold screw rather than titanium screw, and careful manipulation of the driver.

• Journal of Digital Convergence
• /
• v.12 no.7
• /
• pp.349-356
• /
• 2014

The present study was aimed to investigate the effects of the application of pulsed electromagnetic fields on the blood components associated hyperlipidemia, antioxidant enzymes and reactive oxygen. The subjects were divided into three groups: General Diet, High fat Diet, High fat diet and pulsed electromagnetic fields. Pulsed electromagnetic field was applied with pulsed electromagnetic energy therapy equipment. The Glucose, free fatty acids, triglycerides, cholesterol and insulin was used to measure hyperlipidemia-related blood components, and the GSH, GRD, XO and MDA was used to measure antioxidant enzymes and reactive oxygen. The applied pulsed electromagnetic field has improved the concentrations of blood components and increasing GSH and GRD, that were decreased due to a high-fat diet and by reducing the increased MDA and XO to a level of general diet group. Therefore, the applied pulsed electromagnetic field can be the effective treatment for changes in the blood composition of hyperlipidemic rats, enhancement of antioxidative activity and the inhibition of reactive oxygen.

• Journal of Digital Convergence
• /
• v.11 no.7
• /
• pp.289-296
• /
• 2013

To propose the way for improving organizational management of small and medium hospitals through analyzing the effect of organizational culture types on organizational commitment and organizational citizenship behavior. A survey was held to the employees of 4 hospitals that could accomodate less than 100 patients located in Daegu and Gyeongbuk for 4 weeks starting November 20, 2012. As result of factor analysis, the organizational culture divided to the four types: adventurous, hierarchical, productive, friendly types. The adventurous and friendly types revealed the positive effect on organizational commitment, and the productive and friendly types revealed it on organizational citizenship behavior. Instead, hierarchical type revealed no effects on the both. Therefore, to improve organizational management in small and medium hospitals, the strengthened efforts to build up friendship and supportive environments for reasonable decision making.

• The Journal of the Convergence on Culture Technology
• /
• v.8 no.5
• /
• pp.1-7
• /
• 2022

Korean medical device industry has laid the foundation for full-fledged growth and development with the G7 medical engineering technology development project that started in 1995, and the medical device production in 2020 increased by 8.52 times and the export by 13.94 times, compared to those in 2001. In early years, electronic medical devices such as ultrasound imaging device contributed greatly to Korean medical industry, but top ranks in medical device production and export in Korea has shifted recently to in vitro diagnostic medical devices and dental implants. However, the share of imported medical devices in the Korean medical device market have not changed much; it still ranges in 60 to 70%, as the Korean medical device industry produces and exports mid- to low-priced medical devices, and technology-intensive and capital-intensive high-priced medical devices are mainly imported. In this paper, we compare the leading medical devices produced by major Korean companies and those by global top medical device companies to suggest strategies for the Korean medical device companies to enter the global market.

• Journal of dental hygiene science
• /
• v.9 no.4
• /
• pp.443-451
• /
• 2009

The purpose of this study was to examine the views of dental hygiene students about the possible countermeasure of domestic hospitals for the opening of the medical market. The subjects in this study were 269 dental hygiene sophomores, juniors and seniors at two different colleges in the region of Busan. The findings of the study were as follows: The opening of the medical market and views of possible countermove, whether they agreed to that or not made a statistically significant difference to their opinions on the necessity of customer-oriented marketing strategy(p=0.023), analysis of foreign medical markets/attempt to make inroads into the markets(p<0.000) and the improvement of the quality of medical services/the diversification of the services(p=0.025). As to an intention of going to a foreign hospital, they had a statistically significantly different intention about whether to go to a foreign hospital regardless of medical bills(p<0.000), whether to consult a doctor in a foreign hospital after going to a domestic hospital first (p<0.000), whether to consider the distance between their houses and a foreign hospital(p=0.05) and whether to take considerations on the assistance of an interpreter(p=0.023). In regard to preference for foreign hospitals, American hospitals ranked first(41.9), followed by Australian hospitals(19.9) and Canadian ones(14.2).

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.4
• /
• pp.197-202
• /
• 2018

This study was conducted to evaluate the distortion and data accuracy that may occur depending on the methods employed by the oral scanner (intra-oral scanner). Deseutap 3D models employing a plaster model used clinically as a scanner to create a standard scan data using the same model, separated by oral scanners in three different ways (AS Group, ZS group, OS group) How to scan each 5 times made the scan data for each group, it shows the 0.121 mm, 0.172 mm AS group, OS group 0.423 mm accuracy in ZS group. The ZS group showed the highest accuracy, with maximum error values of 0.113 mm, 0.169 mm and 0.246 being observed for the ZS, AS and OS group, respectively. The three scanning methods showed a clear differences in accuracy and reproducibility and also appeared to be meaningful in clinical practice.