• 대한치과기공학회지
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• 제33권4호
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• pp.391-402
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• 2011

Purpose: The purpose of this study was to investigate the factors affecting oral health impact profile. Methods: Subjects included elderly in the metropolitan areas of the cities of Daegu and Gyeong-buk. Statistical analysis was done using the Statistical Package for Social Sciences version 19.0 for Windows. We determined frequencies and percentage, calculating means, and standard deviations, and determining statistical significance using T-tests, analysis of variance, multiple regression analysis. Results: The results of multiple regression analysis between the oral health impact profile and the related factors indicated that Occupation, Economic status are the major component oral health impact profile in general characteristics and the Impediment of oral health promotion behavior is the major component that contribute the oral health impact profile in oral health belief. Conclusion: The comprehensive and reliable research which measures oral health impact profile of elderly is necessary.

• 대한치과기공학회지
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• 제23권2호
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• pp.223-230
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• 2002

Pure titanium and Ti6Al4V alloy have been mainly used as implant materials but the cytotoxicity of V, neurotoxicity of Al resulting in Alzheimer disease had been reported. This paper was described the influence of composition of Ti-Nb alloys with 3 wt%Nb, 20 wt%Nb on the microstructure and corrosion resistance. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at $1000^{\circ}C$ for 24hr. The alloys were rolled in $\beta$ and ${\alpha}+{\beta}$ regions. The corrosion resistance of Ti alloys were evaluated by potentiodymic polarization test in 0.9% NaCl and 5% HCl solutions. The results can be summarized as follows: 1. The microstructure was transformed from $\alpha$ phase to ${\alpha}+{\beta}$ phase by adding Nb 2. The hardness of Ti-20Nb alloy was greater than Cp- Ti, Ti-3Nb alloy. 3. The corrosion resistance of Ti-20Nb alloy was better than that of Cp-Ti, Ti-3Nb alloy in 0.9%NaCl and 5%HCl solutions.

• 대한치과기공학회지
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• 제21권1호
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• pp.67-75
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• 1999

The purpose of this study is to evaluate the friction coefficients between abutment materials and clasp materials, and to an estimation formula for retention force. The coefficients of friction between three clasp materials and four abutment materials were measured under various conditions, polished and sandblasted and wet and dry. The measurement was repeated for each combination up to a total measurement of 1200 times. Estimation formula for retention force is measured as sum of two terms, which the one time is proportional to the product of friction coefficient ${\mu}$ and undercut u and the other term is proportional to u-squared. Two proportional coefficient were obtained by least square method. The results are as follows: 1. Friction coefficients were ranged from 0.08 to 0.53 under various conditions. 2. Friction coefficients of non-metal abutment materials are greater in wet conditions than dry conditions. 3. Friction coefficients of sandblasted clasp against abutment are greater than that of polished clasp. 4. Clasp retention force can be estimated with the model as F=$F_d(3.0{\mu}u+1.5u^2/h)$ with minor error.

• 대한치과기공학회지
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• 제13권1호
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• pp.27-31
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• 1991

The purpose of this study was to evaluate the effect of curing time and curing temperature on the hear - Curing of acrylic resin using ring furnace. Specimens were fabricated from 2 kinds(Laboron, Bertex) heat-cured resin. Total 200 samples were divided into 4 groups(70$^{\circ}C$, 100$^{\circ}C$, 13$^{\circ}C$, 150$^{\circ}C$) and each group was divided into 5 small groups(30 min., 45min., 60min., 75min., 90min.). A microscope(Olympus Coll Co. Japan) was used to examine a randomly selected central zone, midzone and surface for each complete specimen. The results of the experiment were as follows : 1. To obtain non-polymerzation, cure the resin for 30 minutes at 70$^{\circ}C$ and 100$^{\circ}C$ in a ring furnace. 2. To obtain with porosity, cure the resin for 45 minutes, 60 minutes and 75 mintes at 70$^{\circ}C$ and for 90 minutes at 150$^{\circ}C$ in ring furnace. Porosity appears in Laboron for 30 minutes, 45 minutes at 150$^{\circ}C$ in a ring furnace. 3. Every other specimens connot get a sight of special problem with makes eye in the made surface.

• 대한치과기공학회지
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• 제22권1호
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• pp.13-20
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• 2000

This experiment was done to find out how the length and the diameter of the sprue effects the porosity created during the moduling process, which is caused by the metal's shrinking and stretching action. the experiment was done in two groups(A and B), using experimental gold, and made 10 copings for both groups. 1. In group A, The length of the sprues were given the same, but the diameter of the sprue were 6, 8, 10, 12, 18 gauge. As a result, the porosity came out big with 12 and 18 gauge and for 10, 8, 6 gauge, the porosity was hardly seen or none was noticeable. 2. In group B, the diameter was given the sam for the sprues, but the length of the sprues were 5, 10, 15, 20, 25mm. As a result, the porosity came out big with 25, 20, 15mm the porosity was hardly seen or none was noticeable. 3. The diameter needs to be big and the length, short. 4. The appropriate sized sprue must be chosen for each individual tooth, according to it's shape and size.

• 대한치과기공학회지
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• 제14권1호
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• pp.45-54
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• 1992

The purpose of this study was to observe the change of marginal distortion related to heat treatment and surface treatment in. Thirty copings were made on the self-curing resin dies and twenty coping among them were treated by heat and surface grinding. All copings were adapted on the respective dies and then were invested into the plastic boxes with tray resin. Both copiong and die invested in tray resin were cut through labio-lingually by a separating disc. This cross-cutting surface was ground and polished. Specimens were mounted on a light microscope and photographed. Marginal discrepancies were measured on photographes by a scale. The obtained results could be summarized in the followings : 1. In all metal copings, the distortion of cervical margin was shown after heat treatment and surface treatment. 2. There were no statistically significant differences in marginal fitness between shoulder and deep chamfer. 3. There were no statistically significant differences in marginal fitness between labial margin and lingual margin in one die. 4. In case of the copings which were not treated with preheating and were treated with surface grinding, the marginal distortion shows a tendency to increase.

• 대한치과기공학회지
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• 제25권1호
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• pp.89-94
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• 2003

The use of titanium alloys as biomaterials is increasing due to their superior biocompatibility and enhanced corrosion resistance compared to conventional stainless steels and cobalt-based alloys. Ti-6Al-4V ($\alpha+\beta$type) alloy instead of pure titanium ($\alpha$type) is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength and corrosion resistance. It also has similar characteristics to Ti in inducing bony ingrowth. But it has been reported recently that the vanadium element expresses cytotoxicity and carcinogenicity and the aluminium element is related with dementia of Alzheimer type and neurotoxicity. In order to overcome their detrimental effects, $\beta$-phase stabilizer Nb was chosen in the present study. CP-Ti(ASTM grade 2), Ti-3wt.%Nb($\alpha$type), Ti-20wt.%Nb ($\alpha+\beta$type) and Ti-40 wt.%Nb($\beta$type) alloys were melted by vacuum arc furnace. Biocompatibility of Ti-Nb alloys was evaluated by cytotoxicity test. The results can be summarized as follows: 1. For the cytotoxicity test, Ti-Nb alloys showed excellent biocompatibility compared to CP-Ti(ASTM grade 2), 316L STS and Co-Cr alloys.

• 전기학회논문지
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• 제67권10호
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• pp.1375-1381
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• 2018

In this paper, we studied coatings of the DLC thin film for improving loosening torque of dental implant screw. We used a filtered arc ion plating process which can realize the most dense DLC layer by coating the DLC thin film on the surface of the dental abutment screw. It showed both hardness comparable to diamond and low friction coefficient similar to graphite, and to improve the loosening phenomenon by increasing the screw tightening force Cr/CrN, Ti/TiN or Ti/TiN/Cr/CrN buffer layers were deposited for 5 to 10 minutes to improve the adhesion of the DLC thin film to the surface of the Ti (Gr.5), and then the DLC thin film was coated for about 15 minutes. As a result, the Cr/CrN buffer layer exhibited the highest hardness of 29.7 GPa, the adhesion of 18.62N on average, and a very low coefficient of friction of less than 0.2 as a whole. And we measured loosening torque after one million times with masticatory movement simulator. As a result, the values of the coated screw loosening torque were clearly higher than those of the uncoated screw. From this, it was found that the DLC coating was effective methods improving the loosening torque. In addition, it was confirmed that the cytotoxicity test and cell adhesion test showed high biocompatibility.

• 대한치과기공학회지
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• 제21권1호
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• pp.139-144
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• 1999

토양시료로부터 치아우식원인균인 S. mutans에 대하여 항균력을 나타내는 방선균주를 순수분리하여 분리균주를 공시균주로 하여 항생물질 생성에 미치는 환경인자를 규명하였다. 본 공시균주의 항생물질 생성 최적배지조성은 Bacto-soytone 1%, glucose 1%, NaCl 0.5%, $CaCO_3$ 0.1% 였으며 배지의 초기 pH는 7.0이었다. 또한 항생물질은 $28^{\circ}C$에서 진탕배양시 생성의 최적조건이었으며 본 공시균주는 24시간 유도기를 거쳐 배양 72시간째 항생물질의 생성과 더불어 균의 최대증식도를 나타내었다.

• 대한치과기공학회지
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• 제38권4호
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• pp.291-298
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• 2016

Purpose: This study was to evaluate the effect of coloring liquids on the shear bond strength between zirconia and veneering ceramic. Methods: Zirconia(15 mm in diameter, 2.5 mm in thickness; n=40) used in the experiment were divided into 5 groups depending on the coloring liquid. Each specimen were polished using a polishing machine(LaboPol-2, Struers, UK). A cylinder of veneering porcelain(6 mm in diameter, 3 mm in thickness) was fabricated and fired on zirconia surfaces. The shear bond strength was measured using a universal testing machine(Model 4302, Instron, USA). All data were analyzed statistically using a one-way ANOVA and Tukey's multiple comparisons test. After the shear bond test, fracture surfaces were examined by SEM. Results: Colored zirconia showed a higher shear bonding strength than that of uncolored zirconia except for colored zirconia immersed in Zirkonzahn coloring liquid. In particular, colored zirconia immersed in Kuwotech coloring liquid showed the highest shear bond strength. After the shear bond test, mixed failure patterns were mainly observed in the failure between zirconia and veneering ceramic. Conclusion: Coloring liquid enhanced the shear bond strength zirconia and veneering ceramic than uncolored zirconia.