• 대한치과기공학회지
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• 제45권3호
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• pp.67-73
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• 2023

Purpose: This in vitro study aimed to evaluate the clinical acceptability of precision of fit of the support thickness of Co-Cr alloy copings fabricated using selective laser melting (SLM). Methods: Thirty dental stone models of maxillary left molar abutments were manufactured, images were taken using a scanner, and a computer-aided design program was used to design the form of a conventional metal ceramic crown coping. Overall, 30 single copings were made from Co-Cr alloy using SLM and divided into three support radius groups (0.1, 0.25, and 0.35 mm) of 10 for each. Digitized data were superimposed with three-dimensional inspection software to quantitatively obtain the machinability of a ceramic crown coping, and visual differences were confirmed using a color map. The root mean square values of the ceramic crown coping group were statistically analyzed using one-way analysis of variance (α=0.05). Results: The precision of fit was superior with 0.25 mm compared with 0.1 mm and 0.35 mm, and the results exhibited significant differences (p<0.05). All specimens showed that various support thicknesses did not exceed the clinically permitted value of 120 ㎛, which mean that more than 0.1 mm and 0.35 mm of support radius for SLM was adequate. Conclusion: The support thickness of Co-Cr alloy restoration fabricated using SLM is shown to affect the adaptation.

• 대한치과기공학회지
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• 제35권4호
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• pp.415-424
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• 2013

Purpose: This study is to present a standard value for clinical crown angulation and inclination required in laboratory process and see if the value can be used for actual laboratory process. Methods: In order to find out a standard value for clinical crown angulation and inclination, this study made a study model of normal occlusion of 21 females in twenties. The clinical crown angulation and inclination of both six-maxillary and six-mandibular anterior teeth are measured by Set-up Model Checker. From the measured value above, the mean and standard deviation of the twelve teeth are obtained, and then the mean of the teeth between right and left side is calculated. Results: Each clinical crown angulation of maxillary central incisor, lateral incisor, and canine is like this; $1.0^{\circ}{\pm}1.3^{\circ}$, $3.0^{\circ}{\pm}1.3^{\circ}$, and $5.0^{\circ}{\pm}1.4^{\circ}$. In case of mandibular, each degree is like this; $0.6^{\circ}{\pm}1.1^{\circ}$, $1.5^{\circ}{\pm}1.1^{\circ}$, and $4.1^{\circ}{\pm}1.1^{\circ}$. Each clinical crown inclination of maxillary central incisor, lateral incisor, and canine is like this; $6.1^{\circ}{\pm}1.8^{\circ}$, $4.5^{\circ}{\pm}1.9^{\circ}$, and $-6.2^{\circ}{\pm}1.4^{\circ}$. In case of mandibular, each degree is like this; $0.3^{\circ}{\pm}1.5^{\circ}$, $0.3^{\circ}{\pm}1.8^{\circ}$, and $-7.5^{\circ}{\pm}1.8^{\circ}$. Conclusion: As the result, the mean value for clinical crown angulation and inclination can be referred to actual laboratory process. However, the mean value is different from those of the precedent study and an unsatisfied one for adopting the standard value.

• 치위생과학회지
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• 제7권3호
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• pp.153-159
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• 2007

본 조사는 대학 부설 평생(사회)교육원의 학점은행제 과정에 대한 요구도를 조사하기 위하여 D대학 3년제 보건계열 의료기사 양성학과인 치위생과와 치기공과 3학년 학생들을 대상으로 2007년 3월 26일부터 4월 15일까지 조사를 실시하여 SPSS/WIN 12.0 program을 이용하여 분석한 결과는 다음과 같다. 1. 학사학위 취득 계획을 갖고 있는 조사대상자는 89.7%로 나타났으며, 학사학위 취득에 대한 계획을 갖는 가장 큰 이유로는 개인적 발전을 위해서 라는 응답자가 56.1%이었다(p < 0.05). 2. 조사대상자들은 학사학위 취득 방법에 대한 의견으로 대학부설 평생(사회)교육원의 학점은행제를 73.5%로 가장 많이 선호하고 있는 것으로 나타났으나, 학점은행제에 대한 정보는 주위사람에게 얻는 경우가 54.9% 조사되어 학점은행제를 운영하고 있는 대학들의 적극적인 홍보가 요구되고 있었다. 3. 학점은행제를 통한 학사학위 취득 시 가장 큰 장점은 단 기간에 학위 취득이 가능하다는 것이 34.8%였으며, 가장 큰 단점으로는 학위 취득에 대한 사회적 인식이 낮다가 33.8%로 나타났다. 4. 학점은행제 운영과정에 대한 요구는 기본 이수 과목으로 전공필수과목에 대해 적당하다가 80.3%로 나타났다. 부족한 20학점 이상을 이수하면 학위 취득이 가능한 것에 대해 적당하다는 경우가 79.9%로 나타났다. 그러나 교양학점이 많다고 생각하는 경우도 67.4%로 조사되었으며, 수강료는 학점당 7-8만원에 대해 46.6%가 많다고 생각하고 있었다. 5. 학점은행제 개선 방안으로는 사회적으로 정규대학(교)학위와 동등하게 인정되어야 한다와 적극적인 홍보를 통하여 사회적 인식이 높아져야 한다는 것을 가장 큰 방안으로 생각하고 있으며, 엄격한 학사관리가 필요하다는 의견과 교양학점을 축소시켜야 한다는 의견도 나타났다. 또한 한 기관에서 취득할 수 있는 학점제한을 철폐해야 한다와 교(강)사의 수준을 향상시켜야 하는 것으로 조사되었다.

• 대한치과기공학회지
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• 제31권1호
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• pp.17-21
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• 2009

This experimental study was to determine the fitness on each cervical margin of recast using crown base metal alloy. The alloy used in this experimental study was a Ni-Cr alloy(Wirolloy, Bego, Germany) for the fabrication of full cast crown prosthesis. Twenty-five copings were divided into the five groups. And the group A, B, C, D and E were cording successively according to the frequency of recast to five times. Each specimen was recasted without adding new metal. The experimental results were as follows: 1. The group A and B showed good fitness had subtle differences in each cervical margin adaptation, in other words, the mesio and disto cervical margin showed worse adaptation than the bucco and linguo cervical margin. 2. The group C got good fitness in bucco and linguo cervical margins, but the mesio and disto cervical margin showed inaccurate fitness. And I could not get good casting bodies without adding new metal. 3. The group D and E showed bad fitness for each cervical margin. Therefore the group D and E lost its function as a dental restoration.

• 대한치과기공학회지
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• 제23권2호
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• pp.95-103
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• 2002

For this study, self curing resin and heat curing resin used for existing usual resin denture base in the denture industry were chosen by manufacturer. Curing tests for 30-minute, I-hour, 2-hour and 3-hour were conducted to know the strength of the resins and conduct analysis to get other necessary information. The results obtained are as follows: 1. Heat curing resins show a little differences among the manufacturers. However 30-minute curing resin shows great difference as shown in the fracture strength test. 2. The effect from the granularity of the resins on the fracture strength was found insignificant which means there is no difference between coherence and strength. 3. To summarize the results from each time level, the longer the time is, the more the minute cracks on the surface, which is the cause of reduced strength. From this test, it was identified that in making the denture base for patients in dental clinics, 30-minute curing is most efficient and effective in reducing discoloration and monomers, although long-time curing has been considered to be the principal.

• 대한치과기공학회지
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• 제31권3호
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• pp.59-66
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• 2009

In this study 240 geriatric patients, aged 60 year and over were evaluated using a questionnaire and oral examination for their oral status, demand and satisfaction of prosthesis treatment. 1. The single main complaint was regarding from the existing removable prosthesis. When the complaints were catagorized into larger groups, complaints regarding existing prosthesis were 32% and followed by 30% in caries and endodontic problems. 2. DMFT index woman appeared the man the age when will increase more highly recording where highly and considered statistically. 3. According to the result from questionnaire, 48% of patients wearing removable prosthesis and 43% with fixed prosthesis were not satisfied with existing prosthesis. Thirty-seven percentages of patients were not satisfied with aesthetics and unable to chew food properly. 4. Thirty-nine percentage of patients were wearing removable prosthesis. More complete dentures were found on maxilla and partial dentures on mandible. 5. Seventy-seven percentage of patients requested for new prosthesis and the majority of these patients had complaints of difficulties in chewing and discomfort.

• 대한치과기공학회지
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• 제29권1호
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• pp.35-48
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• 2007

The purpose of this study was to evaluate shade selection using conventional visual assessment in vivo natural teeth and porcelain-fused-to-metal (PFM) crown. Maxillary central incisors, lateral incisors and canines of one hundred twenty four college women were used as vivo natural teeth. Fifty one PFM crown for maxillary central incisor fabricated by dental laboratory were used as experimental materials. Using Vitapan Classical Shade Guides, shade selection of natural teeth was measured by each college woman and shade selection of PFM crown was measured by three ceramists with more than ten years career. Both natural teeth and PFM crown shade selection were measured through Shade Eye-Ex. From the shade selection comparing, following results were obtained. The results were as follows: 1. The shade matching identification of natural teeth between the shade selection using Vitapan Classical Shade Guides and the shade selection using Shade Eye-Ex was 27.4% in maxillary central incisor, 13.7% in lateral incisor and 18.5% in canine. 2. Among the shade selection of PFM crown by three ceramists, the shade evaluation of three ceramists were same only in ten cases. In twenty case, those of two ceramists were same. 3. The shade matching identification of PFM crown between the shade selection using Vitapan Classical Shade Guides and the shade selection using Shade Eye-Ex was 38.6% in average. These results suggest that the shade selection using conventional visual assessment should be dealt with care in clinic and need a credible method for shade matching color.

• 대한치과기공학회지
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• 제24권1호
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• pp.107-126
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• 2002

The first function of occlusion is mastication. Therefore the functional restoration of occlusal surface is very important. The restoration of occlusal surface is three method as wax bite technique, F.G.P. technique, cone technique. Many dental technician is using compound method. I am using compound method of wax bite technique and cone technique. I have knew common point on each teeth during I have waxing up wax pattern. So I studied on the design waxup technique for mandible molar occlusion. The results of the study were as follows; 1. The dam wax up method can restore axial contour of teeth very easy and make short working time of wax pattern. 2. The height of dam must be same with cusp of adjacent teeth. 3. Automatically the contour of tooth is appeared if the contour of dam is relationship with cuspid line of adjacent teeth. 4. The height of contour of buccal, lingual surface is formed natural curve to add fluid wax by gravitation. 5. The development groove of mandible first premolar is appeared V form. 6. The development groove of mandible second premolar is appeared Y form. 7, The development groove of mandible first molar is appeared M form. 8. The development groove of mandible second molar is W form. 9. The embrasure is formed to carve around contact point area as round convex. It affects to axial form of tooth. 10. The buccal, lingual groove of molar is formed parallel with direction of teeth arrangement.

• 대한치과기공학회지
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• 제34권4호
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• pp.361-368
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• 2012

Purpose: The aim of this study was to analysis the composition on the centrifugal casting and the oxide on the casting temperature. Methods: The nickel based alloy were used in this study. Wax pattern specimens (10*10*2) were invested with phosphate-bonded investment in metal rings, the liquid/powder ratio and overall burn-out schedules for these investments were followed in accordance with the manufacturer's instructions. After casting, the alloy specimens were evaluated as regards composition(EPMA). The casting temperatures were as follows: $1400^{\circ}C$ and $1700^{\circ}C$. The quantitative analysis of oxides were scanning electron microscope(SEM), energy dispersive spectroscopy(EDS) and line scanning. Results: Nearer the injection lines showed that there is a large amount of nickel. Quantitative of oxides of Ni-Cr alloy cast from $1400^{\circ}C$ is lager than Ni-Cr alloy cast from $1700^{\circ}C$. Conclusion: Casting when using a centrifugal casting machine centrifugal force affects the composition of the alloy. The higher the temperature, the amount of oxide that is generated many.

• 대한치과기공학회지
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• 제14권1호
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• pp.119-132
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• 1992

This paper aims to investigate the effect of B and Si upon the mechanical properties, microstructure and corrosion resistance of Co-Cr base alloy. Ten groups of alloy ingot ingot with various contents of B and Si were remelted by high frequency electrical induction furnace and cast into tensile specimen of ADA Specification No. 14 Tensile and hardness test were carried out by Amsler and Rockwell hardness tester(R-30N), respectively. The microstructures of specimen were observed by SEM. The results obtained are summarized as follows : 1. As B content is increased, tensile strength, yield strength and Rockwell hardness number(R-30N) are also increased significantly, while the elongation is decreased significantly. 2. As Si contect os increased, no significant chang in tensile strength is noticed, yield strength is slightly decreased, but Rockwell hardness number(R-30N) is moderately in creased, Elongation marks maxium value with 1% Si content while with more than 1% Si it is decreased. 3. As B content is increased corrosion resistance is decreased and is at best with 1.5% B content. Corrosion resistance is increased with the increase of Si content and the alloys with Si over 3.0% showed corrosion resistance. 4. As B content increased, precipitates are increased in number at grain boundaries. The grain size tends to become coarse with the increase of Si content. 5. Co rich-Cr alloy is present through matrix whereas at the grain boundaries Cr base precipitates are primarily formed.