• Journal of Technologic Dentistry
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• v.21 no.1
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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.

• Journal of Technologic Dentistry
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• v.13 no.1
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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.

• Journal of Technologic Dentistry
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• v.22 no.1
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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.

• Journal of Technologic Dentistry
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• v.14 no.1
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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.

• Journal of Technologic Dentistry
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• v.25 no.1
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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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.

• Journal of Technologic Dentistry
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• v.21 no.1
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• pp.139-144
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• 1999

The optimum culture conditions for an antibiotics from Actinomyces sp. were investigated. The optimum composition of medium for antibiotics production was 1% glucose, 1% soybean meal, 0.5% NaCl, 0.1% $CaCO_2$, and the optimum initial pH was 7.0. And the antibiotics showed highest activity when the strain isolated from soil was aerobically cultivated at $28^{\circ}C$ for 72hours under the optimum conditions. A production of the antibiotics from Actinomyces sp. begins at the 36th hours and then reached the maximum at the stationary phase developed at the 72th hours under the optimum conditions.

• Journal of Technologic Dentistry
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• v.38 no.4
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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.

• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.67-73
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• 2012

연구 목적: 임플란트의 하부구조를 상부 구조와 연결하는 레진시멘트의 접착강도를 높이기 위한 기계적 화학적인 표면처리 방법들이 연구 되고 있다. 이 연구에서 다양한 크기의 $Al_2O_3$ sandblasting과 Silano Pen으로 표면처리한 티타늄과 레진 시멘트의 접착강도를 알아보고자 한다. 연구 방법: 12개의 티타늄(Ti-6A1-4V)시편을 디스크 형태로 제작하여 자가중합 수지에 매립하였다. 이들을 각각 6개의 군으로 나누어 $50{\mu}m$, $90{\mu}m$, $110{\mu}m$ 등 3가지 크기의 $Al_2O_3$로 sandblasting 하는 조건과 $Al_2O_3$로 sandblasting한 후 Silano Pen(Bredent, bredent GmbH &Co.KG, Senden, Germany)을 사용한 군으로 나누었다. 표면처리 한 티타늄 표면에 레진시멘트(Duolink dual syringe, Bisco, USA)으로 접착하였다. 그 후 증류수($37^{\circ}C$)에 24시간 보관 후 접착강도 실험을 시행하였고, SEM을 사용하여 표면처리 한 표면과 접착강도 실험 후 파절양상을 관찰하였다. 결과: 통계학적 분석에 따르면 Silano Pen을 사용하여 표면처리한 군들의 접착강도가 높았다(P<0.05). 결론: Silano Pen을 사용하는 것이 티타늄과 레진시멘트의 접착강도를 증가 시킨다.

• Journal of Technologic Dentistry
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• v.5 no.1
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• pp.27-30
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• 1983

This study was undertaken to know the difference that margin fittness in metal bond porcelain crown. When we use porcelain precious metal and non-precious metal as porcelain-fused metal, the results were as following. 1. The precious metal was showed best result in margin fittness and shade. 2. The non-precious metals were showed good results, especially Gemini II was excellent, but that was not good than precious metal. 3. 10k. gold plating on non-precious metal cap showed same result as nonprecious metal in margin fittness, and not good in shade. 4. When we use the non-precious metals at upper part of crown, and using precious metal in 2mm cervical portion, the margin fittness were very good, and the results same as full veneer precious metal.