• 대한치과의사협회지
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• 제50권3호
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• pp.148-154
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• 2012

Mineral trioxide aggregate (MTA) is mainly composed of lime and silica. Its four major phases are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracaclcium aluminoferrite. MTA has relatively long initial setting time (2h 45m) and various additives can be added to reduce setting time. Compressive strength of MTA increases with time and reaches 100 MPa after 28 days. MTA has high pH of 9-12.5 because of the formation of calcium hydroxide during its hydration reaction. MTA has superior sealing ability to amalgam and IRM when it is used in perforation repair or root end filling. MTA is safe in cytotoxicity and genotoxicity and have potential to promote pulpal and periapical hard tissue formation.

• 대한치과재료학회지
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• 제43권1호
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• pp.43-50
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• 2016

The aim of this study was to investigate the effect of multiwall carbon nanotube functionalized with carboxyl group (MWCNT-COOH) on the mechanical properties of dental glassionomer cement (GIC). MWCNT-COOH was prepared by the acid oxidative method. The MWCNT-COOH was incorporated into a commercial GIC powder or liquid at 0.5 wt% or 1.0 wt%. The net setting time of the cements was measured in accordance with ISO 9917 (Dental water-based cement). Specimens for compressive strength ($4mm{\varphi}{\times}6mm$), diametral tensile strength ($6mm{\varphi}{\times}4mm$) and flexure strength with modulus ($2mm{\times}2mm{\times}25mm$) were prepared by mixing with the cement liquid and kept in water bath of $(37{\pm}1)^{\circ}C$. Mechanical tests were conducted in 1 d, 7 d, and 14 days at a cross-head speed of 1 mm/min. Compressive strength of GIC mixed with 0.5 wt% MWCNT-COOH increased significantly at 7 d. However, overall mechanical properties of GIC modified with MWCNT were not significantly increased with a delayed setting time, in comparison with control cement. Overall results indicated that the MWCNT/GIC composite cements showed a limited strengthening effect for dental glassionomer cement.

• The Journal of Advanced Prosthodontics
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• 제13권3호
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• pp.136-143
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• 2021

Purpose. This study aimed to evaluate the effect of repeated use of an implant handpiece under an implant placement torque (35 Ncm) and overloading torque condition (50 Ncm) on an output torque. Materials and Methods. Two types of implant handpiece systems (Surgicpro/X-DSG20L [NSK, Kanuma, Japan] and SIP20/CRB46LN [SAESHIN, Daegu, South Korea]) were used. The output torque was measured using a digital torque gauge. The height and angle (x, y, and z axes) of the digital torque gauge and implant handpiece were adjusted through a jig for passive connection. The experiment was conducted under the setting torque value of 35 Ncm (implant placement torque) and 50 Ncm (overloading torque condition) and 30 times per set; a total of 5 sets were performed (N = 150). For statistical analysis, the difference between the groups was analyzed using the Mann-Whitney U test and the Friedman test was used to confirm the change in output torque (α=.05). Results. NSK and SAESHIN implant handpieces showed significant differences in output torque results at the setting torques of 35 Ncm and 50 Ncm (P<.001). The type of implant handpiece and repeated use influenced the output torque (P<.001). Conclusion. There may be a difference between the setting torque and actual output torque due to repeated use, and the implant handpiece should be managed and repaired during long-term use. In addition, for successful implant results in dental clinics, the output torque of the implant handpiece system should be checked before implant placement.

• Imaging Science in Dentistry
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• 제51권1호
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• pp.1-7
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• 2021

Purpose: The aim of this study was to assess artifacts generated in cone-beam computed tomography (CBCT) of 3 types of dental implants using 3 metal artifact reduction (MAR) algorithm conditions (pre-acquisition MAR, post-acquisition MAR, and no MAR), and 2 peak kilovoltage (kVp) settings. Materials and Methods: Titanium-zirconium, titanium, and zirconium alloy implants were placed in a dry mandible. CBCT images were acquired using 84 and 90 kVp and at normal resolution for all 3 MAR conditions. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the intensity of artifacts for each combination of material and settings. A 3-factor analysis of variance model with up to 3-way interactions was used to determine whether there was a statistically significant difference in the mean intensity of artifacts associated with each factor. Results: The analysis of all 3 MAR conditions showed that using no MAR resulted in substantially more severe artifacts than either of the 2 MAR algorithms for the 3 implant materials; however, there were no significant differences between pre- and post-acquisition MAR. The 90 kVp setting generated less intense artifacts on average than the 84 kVp setting. The titanium-zirconium alloy generated significantly less intense artifacts than zirconium. Titanium generated artifacts at an intermediate level relative to the other 2 implant materials, but was not statistically significantly different from either. Conclusion: This in vitro study suggests that artifacts can be minimized by using a titanium-zirconium alloy at the 90 kVp setting, with either MAR setting.

• Elastomers and Composites
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• 제43권2호
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• pp.88-103
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• 2008

본 연구는 친수성 폴리비닐실록산 치과용 고무인상재를 개발하기 위해 계면활성제의 종류와 함량 및 필러의 배합비를 다르게 하면서 첨가시켜 물성에 미치는 영향을 연구하였다. 계면활성제를 첨가함으로써 친수성이 향상되었으나 점도와 영구변형률을 증가시키고 경화시간을 지연시켰으며 강도를 감소시켰다. 일정이상의 함량에서는 내부에 기포발생과 심한 강도감소를 초래하였다. 특히 Silwet L-77의 첨가는 점도, 압축시 변형률, 기포발생, 경화시간의 증가와 탄성회복률 및 강도의 감소가 두드러졌으나 함량증가에 따른 친수성 향상은 가장 우수하였다. 함량증가에 따른 점도상승, 경화지연, 기포발생 및 친수성은 Span 20을 첨가한 군이 가장 낮았다. 실리카 필러의 20%를 규조토로 대체함으로써 수분접촉각은 증가하였으나 계면활성제 첨가로 인한 경화지연, 기포발생, 강도저하의 문제를 크게 개선할 수 있었다.

• 치위생과학회지
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• 제22권4호
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• pp.256-263
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• 2022

Background: The purpose of this study was to confirm the major motivation for and self-efficacy of career decisions among dental hygiene students and to analyze differences in career decision self-efficacy according to the major motivation. Methods: An online survey was conducted among 194 dental hygiene students. To investigate career decision self-efficacy, 18 questions were posed, including 5 questions on future planning, 4 questions on self-evaluation, 4 questions on job information collection, 3 questions on goal setting, and 2 questions on problem solving. The survey was conducted using a 5-point scale. Results: The motives for choosing a major were a high employment rate (68.6%), a desire to become a professional (36.1%), according to aptitude (27.8%), recommendations by others (26.3%), and according to grades (12.9%). The career decision self-efficacy of the study participants was in the order of self-evaluation factors (3.75 points), problem solving factors a (3.62 points), job information collection factors (3.59 points), future planning factors (3.46 points), goal setting factors (3.44 points) score was high. The career decision self-efficacy scores were higher when the major motivation was "because I want to become a professional" and "because I think I have an aptitude for it." Conclusion: It is necessary to give students who wish to major in dental hygiene an opportunity to consider whether they have an aptitude for it by providing information on not only major subjects but also the duties and roles of dental hygienists. In addition, it is necessary to develop a career education program to help dental hygiene students set their career goals.

• 대한치과보철학회지
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• 제37권6호
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• pp.730-740
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• 1999

The purpose of this study was to investigate setting and thermal expansion of dental soldering investments. In order to compare expansion rates and to investigate the effect of water/powder ratio on expansion, setting and thermal expansion of low dental soldering investments were measured under three different water/powder ratio conditions. standard, 20% decreased and 20% increased. Setting expansion of investments was measured by use of dialgauge method. Each measurement was started two minutes later from the beginning of spatulation and recorded every one minute for one hour. Thermal expansion of cylindrical test specimens, 10mm diameter, 50mm length, was recorded in a thermodilatometer at heating rate of $10^{\circ}C$ per minute from $25^{\circ}C\;to\;700^{\circ}C$. The results of this study were obtained as follows: 1. Setting expansion rates under the standard water/powder ratio condition were 0.198% in Speed-E, 0.090% in Deguvest, 0.080% in CM and Hi-temp. Setting expansion of Speed-E was significantly different from those of CM, Deguvest and Hi-temp, and setting expansion of Deguvest was significantly different from those of CM and Hi-temp(p<.05). 2. Under the decreased water/powder ratio condition, there was significant increase in setting expansion of 4 dental soldering investments (p<.05). 3. There were no significant differences in setting expansions of investments except Hi-temp between standard and increased water/powder ratio condition(p<.05). 4. Thermal expansion rates under the standard water/powder ratio condition were 1.923% in Deguvest, 1.629% in Speed-E, 1.619% in Hi-temp and 1.580% in CM. No significant differences in thermal expansions under the standard water/powder ratio condition existed only between Speed-I and Hi-temp(p<.05) 5. Under the decreased water/powder ratio condition, there was significant increase in thermal expansion of CM and Deguvest but decrease in thermal expansion of Speed-E (p<.05). 6. Under the increased water/powder ratio condition, there was significant decrease in thermal expansion of CM, Deguvest and Speed-I but decrease in thermal expansion of Hi-temp(p<.05).

• 대한치과의사협회지
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• 제10권8호
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• pp.531-534
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• 1972

The author measured exothermic temperature of the 5 kinds of zinc phosphate cement and 3 kinds of copper phosphate cement during setting process. Cements were mixed on the glass slab with flexible steel spatula at room temperature (25.8℃) for one minute (spatulating speed was 100 strokes per minute) and placed in the incubator of which temperature was held at 37℃ and thermometer was inserted into the cement mass. The powder liquid ration was 3.0gm:1ml and 1.5gm:1ml. The results were as follows. 1) The heat generated after mixing these cements was under 47.22℃. 2) The range of thermal change of the zinc phosphate cements during setting process was wider than copper phosphate cements. 3) The exothermic temperature from the thin mix was higher than thick mix. 4) The exothermic temperature of the zinc phosphate cements was higher than copper phosphate cements.

• 한국치위생학회지
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• 제16권6호
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• pp.1079-1092
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• 2016

Objectives: The purpose of the study is to investigate the effect of self-leadership on organizational effectiveness and job performance in the dental hygienist. Methods: A self-reported questionnaire was completed by 281 dental hygienists in Seoul, Incheon, and Gyeonggido from March 1 to 31, 2016. The questionnaire consisted of general characteristics of the subjects, self-leadership, job satisfaction, organizational commitment, job performance. Data were analyzed by t-test, one-way ANOVA, multiple regression analysis using the SPSS 18.0 program. Results: The average of self-leadership was 3.62, self-reward had highest score of 3.84, followed by rehearsal 3.73, self-expectation 3.72, self-goal setting 3.51, constructive thinking 3.48, and self-criticism 3.45. The average of organizational commitment was 3.11, and that of job satisfaction was 3.11 and the average of job performance was 3.70. Among the sub-factors of self-leadership, self-expectation, self-goal setting, constructive thinking showed a positive correlation with organizational commitment and job satisfaction. All sub-factors except for self-criticism showed a positive correlation with job performance. Among the sub-factors of self-leadership, self-expectation (${\beta}=0.350$), constructive thinking (${\beta}=0.124$), self-reward (${\beta}=0.106$), rehearsal (${\beta}=0.102$) showed a significant effect together with job satisfaction (${\beta}=0.187$) on job performance. Also, age, education level, clinical career, the average monthly salary showed a significant effect on job performance. Conclusions: The self-leadership and job satisfaction of in the dental hygienist had influence on job performance. To improve the job performance of dental hygienists, it is necessary to apply self-leadership development program focusing on the strengthening of self-expectation and constructive thinking.

• 한국치위생학회지
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• 제20권4호
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• pp.491-503
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• 2020

Objectives: The purpose of this study is to identify the importance of perception and communication ability among dental hygienists and provide evidence for the activation of communication education necessary to improve communication ability required in the actual dental field. Methods: A questionnaire survey was conducted on 227 members attending conservative education in 2020. Results: The following are mean scores of each area of communication according to importance: message conversion ability, 3.82 points; interpretation ability, 3.74 points; goal setting ability, 3.51 points; self-expression ability, 3.48 points; and role performance ability, 3.46 points. The ability was interpreted in the following order: interpretation ability, 3.61 points; message conversion ability, 3.56 points; role performance ability, 3.43 points; self-expression ability, 3.32 points; and goal setting ability, 3.10 points. The highest score in terms of importance of awareness was 4.27 points, the highest among interpretive abilities, that is, to 'listen carefully to know what the other person intends to say.' When it comes to communication skills, the highest score was 4.12 points for 'a nod or a facial expression of understanding while listening to each other.' Conclusions: In devel oping a training program related to communication for dental hygienists at the clinical site, the curriculum reflecting seven items that needs improvement should be revised; and through this, it is expected that dental hygienists' communication skills will be improved.