• 대한치과기공학회지
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• 제33권4호
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• pp.271-281
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• 2011

Purpose: The aim of this study is to investigate the changes in hardness and microstructure of a dental multipurpose alloy after simulated complete firing with controlled cooling rate and holding time by characterizing the changes in hardness and microstructure after simulated firing with various cooling rates and holding times. Methods: Before hardness testing, the specimens were solution treated and then were rapidly quenched into ice brine. The specimens were completely fired in furnace. Hardness measurements were made using a Vickers microhardness tester. The specimens were examined at 15 kV using a field emission scanning electron microscope. Results: The maximum hardness value was obtained at stage 0 after simulated firing with various cooling rates (quick cooling, stage 0, stage 1, stage 2, stage 3). By the repetitive firing, the hardness of the tested alloy decreased gradually. By holding the specimen at $500^{\circ}C$ for 10-20min after simulated firing, the hardness increased apparently. However, to hold the alloy for long periods of time in the relatively high temperature after simulated firing resulted in the formation of thick oxidation layer. The oxide film formed on the surface of the alloy after simulated complete firing with controlled cooling rate, which was mainly composed of O and Zn. Conclusion: It is reasonable to hold the alloy at $500^{\circ}C$ for 10-20min after complete firing in other to improve the final hardness of the alloy.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2585-2592
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• 2015

3D 프린팅 기술은 최근 치과용 보철물 제작 기술로 도입이 되었다. 본 연구의 목적은 3D 프린팅 기술에 의해 제작된 금속 코어와 상부 도재와의 전단결합강도를 평가하는 것이다. 본 연구를 위해 30개의 금속 코어를 제작하였다(cast 15개, 3D printing 15개). 금속 코어에 치과용 도재를 축성하여 시편 제작을 완료하였다. 완성된 시편의 전단결합강도는 crosshead speed 1mm/min으로 하중을 가하여 측정하였으며, 두 그룹의 전단결합강도 값 사이에는 통계적으로 유의한지 알아보기 위하여 Mann-Whitney test를 이용하였다(유의수준 0.05). 측정이 끝난 후 시편을 대상으로 파절양상을 분석하였다. 본 연구를 위한 실험 설계, 금속 코어 제작, 도재 축성 등의 시편 제작부터 실험 수행과 수행 후 실험 데이터 분석과 통계 분석 그리고 파절된 시편을 대상으로 한 파절 양상 분석까지 총 6개월이 소요되었다. 실험 결과 cast 50.14, 3D printing 54.36 MPa를 갖는 것으로 조사되었고, 통계적으로도 유의하였다. 파절양상은 두 집단 모두 시편의 대부분이 혼합형 파절양상을 보였다. 이와 같은 결과들로 미루어볼 때 3D 프린팅에 의해 제작된 금속도재관 제작을 위한 금속 코어는 임상적으로 허용이 가능할 것으로 사료된다.

• 대한치과기공학회지
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• 제34권2호
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• pp.113-119
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• 2012

Purpose: Zirconia blocks for all ceramic dentures are divided into two groups. One is pre-heated block and the other is binder added block. In this study, the possibility of recycling the remained parts of binder added block after CAD/CAM machining with slip casting process was investigated. Methods: Owing to the binder added block contain large amount of organic matter, Binder burn-out was must be carried out before ball milling for preparing the casting slip. Binder burn-out was accomplished at $600^{\circ}C$ for 10 hours. Ball milling was performed with 5mm zirconia ball and 60mm polyethylene bottle. From 0% to 5% at 1% intervals of alumina was added to zirconia powder for preparing slip. Solid casting was achieved with plaster mold. Cast bodies were dried and sintered at $1,500^{\circ}C$ for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM, EDS and XRD analysis were executed. Results: Optimum slips for casting was prepared with 300g ball, 100g powder, and 180g distilled water. Cast body without alumina showed 26% of linear shrinkage, 6.07 of apparent density, and 470MPa of three point bend strength. On the other hand, as received zirconia block, which was sintered at the same conditions, showed 23% of linear shrinkage, 6.10 of apparent density, and 680MPa of three point bend strength. When 3% of alumina was added to zirconia, sintered body showed 23% of linear shrinkage, 6.10 of apparent density, and 780MPa of three point bend strength. SEM photomicrographs and EDS analysis showed alumina particles uniformly dispersed in zirconia matrix, and XRD analysis showed no phase transformation of tetragonal zirconia particles was occurred when alumina was added. Conclusion: According to the all of this experimental results, 3% of alumina added cast zirconia body showed excellent mechanical properties more than as received binder containing zirconia block.

• 대한치과기공학회지
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• 제19권1호
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• pp.175-184
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• 1997

본 연구는 아동기에 있는 자녀를 둔 부모들로서 치과의원을 내원한 진료환자 중 217명 대상으로 구강건강 실태에 대한 정도를 파악하여 구강보건 관리증진에 도움이 될 수 있는 기초자료 제공목적으로 조사한 바 그 결과를 요약하면 다음과 같다. 1. 구강보건에 관한 기초적 지식 중 유치갯수(20개)에 대한 인지도는 연령별로는 30대(47.6%)에서, 학력별로는 고졸(29.1%)에서 가장 높게 나타났으나 연령별, 학력별 통계상 유의성은 없는 것으로 나타났다. 2. 충치가 발생하는 원인으로 이를 잘 안 닦아서가 44.0%로 가장 많으며 그 다음으로 단 것을 많이 먹기 때문이라고 응답한 비율이 26.4%로 차지하고 있다. 충치예방법으로 불소치약 사용이 26.5%, 당분섭취 제한이 23.3%로 높게 나타났다. 3. 자녀의 치아건강을 위해서는 자주 이를 닦는 것이 중요하다는 빈도가 57.6% 가장 높게 나타나 치아건강에 있어 칫솔질의 중요성을 대부분이 인지하고 있는 것을 알 수 있다. 4. 충치의 보유실태에서는 자녀의 충치발생수가 45.8%로 나타났으며 연령이 적을수록 경험한 빈도가 높으며(P<0.05), 봉하거나 보철을 한 자녀가 84.7%로 나타나 자녀들의 치아건강 관리에 대해 부모들이 많이 신경을 쓰지 못하고 있음을 알 수 있다. 5. 자녀들에 대한 칫솔질 교육과 행동지도에서 잇솔질 시기는 만 2∼3세부터 시키는 것이 적당하다가 42.6%로 나타났으며 칫솔질은 스스로 하게끔 만든다가 80.6%로 통계적으로 유의하게 나타났다.(P<0.05) 6. 구강보건에 대한 정보의 습득경로는 매스컴이 38.95%로 가장 높게 나타났으며 구강보건 교육을 받지 못한 사람이 90.1%로 절대적으로 많았다. 지금까지 체계적인 구강보건 교육이 거의 없었으며 대중매체에 의한 단편적인 지식습득을 하고 있는 것으로 나타나 앞으로 체계적인 구강보건 교육을 통해 인지된 지식을 실천에 옮길 수 있도록 도와주는 일이 구강 보건 전문가들의 과제라 생각된다. 본 연구의 결과로 구강관리에 있어서 부모들의 지식과 실천이 자녀들에 있어 중요한 영향을 미치므로 부모들을 대상으로 체계적인 구강 보건 교육을 실시하는 것이 치과계의 중요한 과제라고 생각된다.

• Tribology and Lubricants
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• 제39권4호
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• pp.148-153
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• 2023

Laser surface dimple patterning is a method of laser surface texturing to reduce lubrication sliding friction. The dimple pattern improves friction properties by reserving lubricant and trapping worn particles. This surface texturing technology can reduce coefficients of friction and extend the service life by applying a uniform load to the surface of the material. This study investigates the friction properties using PMMA, a highly compatible polymer material, as a specimen. We observe the friction properties of untextured specimens by processing specimens with dimple pattern densities of 5 and 10 on the surface area using laser. Dimple pattern density affects the coefficient of friction. We present the following friction property results using a pin-on-disc sliding friction test under saline lubrication. The coefficients of friction for the dimple patterned specimens are lower than those for the untextured specimens. As the normal load and sliding speed increase, the coefficients of friction of the dimple pattern specimens decrease differently from those of the untextured specimens. The specimen with a dimple pattern density of 5 at a normal load of 24.5 N and a sliding speed of 0.22 m/s has the best friction properties. Notably, different friction properties are exhibited depending on the dimple pattern densities.

• 대한기계학회논문집A
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• 제20권3호
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• pp.882-890
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• 1996

Mechanical properties, including Young's modulus, residual stress and rupture strength, of a thermally evaporated gold film have been measured form a blister test. In a theoretical study, the priniple of minimum potential energy and that of virtual work have been applied to the pressurized circular membrane problem, and load-deflection relations have been derived for typical membrane deflection mode of spheroidal shape. In an experimental study, circular gold membranes of 4800 A-thickness and 3.5mm diameter were fabricated by the silicon electropolishing technique. Mecahnical properties of the thin gold films were deduced from the load-deflection curves obtained by the blister test, Young's moduli, obtianed from blister test, have been in the range of 45-70 GPa, while those of bulk gold have been in the range of 78-80 GPa. Residual stresses in the evaporated gold films have been measured as 28-110MPa in tension, The rupture strength of the gold film has turned out to be almost equal to that of dental gold alloy (310-380MPa). It has been demonstrated that the present specimen fabrication method and blister test apparatus have been effective for simultaneous measurement of Young's modulus, residual stress and repture strength of thin solid films. Especially, the electropolishing technique employed here has provided a simple and practical way to fabricate thin membranes in a circular or an arbitrary shape, which could not be obtained by the conventional anisotropic silicon mecromachining technique.

• 대한치과기공학회지
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• 제13권1호
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• pp.37-51
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• 1991

In order to evaluate health status of dental technicians as an individual and a group, this study was conducted with Todai Health Index Questionaire on randomly sampled 277 persons(236 males and 41 females) from Aug. 20 to Oct. 6, in 1990 obtained Following conclusions were drawn. 1. Age composition of the subjects was 136 males(57.6%) in the age of 20$\sim$29 and 28 females(68.3%) in the age of 20$\sim$24. As for working places, 215 males(91.1%) and 38 females (92.7%) were working for dental laboratories and rest of them were at clinics and hospitals. In working years, male technicians who have been working for 5$\sim$10 years amounted to 80 (33.8%) and 12 females(29.3%) were working for 1$\sim$3years. 2. Responses to psychosomatic subjective symptom complaints rated as the highest in multiple subjective symptom(males : 40.00%, females : 41.98%) and those in physical items and mental irritability(male : 24%, female : 25%) and in mental items came next in order. The rate of complaint in depression was higher in female group than in male group (p<0.05). 3. Resonses to psychosomatic subjective symptom complaints in male group were high in the age of 20$\sim$29 and in the age of 20$\sim$24 in female group. The rates of complaint were higher in multiple subjective symptom, respiratory, eye and skin(p<0.05) and digestives(p<0.01) complaints. 4. Responses to psychosomatic subjective symptom complaints were higher among persons working at dental laboratories than at other working places : dental clinics and hospitals in all the items except for respiratory, depression and aggressiveness. Rates of complaints in eye and skin showed significant difference between working places(p<0.05). 5. Those who are engaged in polishing part tended to complain more about psychosomatic subjective symptoms. 6. The higher the level of education is the more they complained the psychosomatic subjective symptoms both in male and female group. In the difference of complaint respones, male group showed high rates of complaint in depression and female group in aggressiveness(p<0.05). 7. Responses to psychosomatic complaints by the length of working service were moderate in males who were working less than 10 years, and they decreased after 10 years of service. Females showed the highest response rate in the group of 3$\sim$5 years service and the lowest response in the group of 5 years service. Male complained more in aggressiveness and female in respiratory and aggressiveness(p<0.05). 8. Responses to psychosomatic subjective symptom complaint varied according to working hours of a day both in male and female group, showing high complaint rates in multiple subjective symptom, respiratory, eye and skin, mouth and anus, digestive, mental irritability and irregular life in male group(p<0.05).

• 치위생과학회지
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• 제8권2호
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• pp.73-80
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• 2008

본 연구는 치위생과 재학생들의 건강증진행위를 조사하여 대학생의 건강증진을 도모하기 위한 기초자료를 제공하고자 경기도에 소재한 4개 대학의 치위생과 재학생 687명을 대상으로 2007년 9월부터 10월까지 설문조사를 실시하였다. SPSS 12.0 program을 이용한 분석한 결과는 다음과 같다. 1. 구강관리행위는 1학년 학생($3.11{\pm}.57$)이 가장 낮은것으로 조사되었으며, 통계적으로 유의한 차이를 보였다(p < .001). 2. 건강증진행위는 건강상태가 나쁘다고 인식하는 경우 영양관리($3.63{\pm}.63$), 사회적지지($2.43{\pm}.60$), 건강에 대한 책임($2.40{\pm}.68$), 자신의 삶에 대한 존중($2.33{\pm}.51$)에서 관리행위정도가 낮은 것으로 조사되었으며, 통계적으로 유의한 차이를 보였다(p < .001, p < 0.01). 3. 부모님의 교육정도에 따른 건강증진행위는 아버지가 중졸이하인 경우($3.62{\pm}.52$) 영양관리가 가장 낮았으며(p < .001), 어머니가 중졸인 경우($2.52{\pm}.52$) 사회적 지지가 낮은 것으로 조사되었으며, 통계적으로 유의한 차이를 보였다(p < .05). 4. 자취를 하는 경우 영양관리($3.66{\pm}.57$)가 가장 낮았으며, 통계적으로 유의한 차이를 보였다(p < .001). 5. 월평균 가계 수입이 100만원 이하에서($2.42{\pm}.62$) 삶의 존중행위가 가장 낮게 조사되었으며, 통계적으로 유의한 차이를 보였다(p < .05). 6. 건강증진행위와 관련 변인간의 상관관계는 건강증진행위가 사회적 지지가 높을수록 삶의 존중이 높았으며, 삶의 존중이 높을수록 스트레스 관리가 잘되고 있는 것으로 조사되었으며, 통계적으로 유의한 차이가 보였다(p < .01).

• 문화기술의 융합
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• 제5권2호
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• pp.123-138
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• 2019

본 연구는 임상실습내용에 따른 실습방법 및 수행정도를 파악하고자 치위생과 학생을 대상으로 진행하였으며 다음과 같은 결론을 얻었다. 감염관리에서는 '진료실 장비 감염 방지하기', '치과진료기구 소독 및 멸균하기'를 가장 많이'수행'하고 있었으며, 예방치과에서는 대부분 '교육하기' 항목에서 '관찰'을 많이 하는 것으로 나타났다. 보존과에서는 '협조하기' 항목에서 '수행'을 많이 하는 것으로 나타났으며, 보철과에서는 '관찰'을 더 많이 하는 것으로 나타났다. 임상실습 경험이 많은 학생일수록 기본진료, 구강악안면방사선과, 예방치과, 보존과, 치주과, 구강외과, 교정과, 구강내과에서 실제적으로 실습생들의 수행 빈도가 증가하는 것으로 나타나 통계적으로 유의한 차이를 보였다(p<0.05). 대부분의 임상실습내용에서 수행하기보다는 관찰하기가 높게 나타나, 실습내용에 대한 학년별 또는 임상실습 경험 횟수별로 명확한 임상실습 내용의 목표설정이 필요할 것으로 사료된다.

• 대한치과기공학회지
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• 제11권1호
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• pp.71-81
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• 1989

This study was aimed for bettering productivity and technical level of the dental 1 aboratory, and helping the dental technician's benefits and rights, and then endowing them some belonged atmospher and stability on their post by Improving job- satisfaction and maintaining the transferability of one's post at a proper limitation. Therefore, 320 dental technicians extracted randomly from all the technicians working at 494 dental laboratories were subjected for this study. The approach to the study was a way through some postal questionaires executed from March 29, 1988 until May 4, the same year, in which total 254 technicians answered, showing 79% resp"nserate. responserate. The data-analysis was done by a model of the dental technician's transferability from their post, as considering Mobley's(1978)-model of post-transferability, and results through the study are as follows : 1. Satisfaction at a given post showed that the married is better than the unmarried(<0.05), and the experienced is better than the inexperienced(P<0.01). 2. Age, sex, educational experience, and one's service-duration did not affect significantly to the respondent's satisfaction on their post, statistically. 3. Satisfaction at a given post differed in adccordance with given conditions of one's post, i. e.,it stowed high when the monthly payment was good(P<0.05), and when too much duty on their job was given, it was the worst as shown in an example of the next order, too much