• 대한치과기공학회지
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• 제9권1호
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• pp.21-29
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• 1987

The purpose of this investigation was to determine the effect of recasting on the castability and physical properties of the nonprecious metal alloy. Using 2 sorts of the nonprecious metal alloy for production of Crown and Bridge prosthetics, such as 1) sankin C. B 80 metal 2) C & B alloy, the result of experimental research on the castability and hardness according to the recasting, is as followes; 1. The difference of castability between sankin CB80 metal and C & B alloy was statistically significant (p < 0.01) and the difference of castability among the test groups, was statistically significant (p <0.01). 2. In the case of sankin C.B 80 metal, the difference of castability among the New alloy and first mixed alloy and second mixed alloy and old alloy was not significant statistically (p >0.05). 3. In the case of C & B alloy, the difference of castability among the New alloy and mixed alloys and old alloy, was not significant statistically (p >0.05). 4. The difference of hardness between sankin C & B alloy was not significant statistically (p >0.05), but the difference of hardness among the test groups was statistically significant (p <0.01). 5. In the case of Sankin C.B 80 metal, the difference of hardness among the new ally and mixed alloys and old alloy was not significant statistically (p >0.05). 6. In the case of C & B alloy, the difference of hardness between New alloy and mixed alloys was not significant statistically (p >0.05) but the difference of hardness among the old alloy and New alloy and mixed alloys was statistically significant (p <0.01).

• 대한치과기공학회지
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• 제31권1호
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• pp.63-74
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• 2009

Partial or complete prosthesis is needed when teeth are lost due to various kinds of reason. Artificial teeth recover occlusion instead of natural teeth. Artificial teeth are required of esthetics, fragile resistance and abrasive resistance. Artificial tooth is made of acrylic resin or porcelain. Nowadays, acrylic resin artificial teeth are mainly used. Acrylic resin teeth are occluded with natural teeth, gold alloy, Ni-Cr alloy or porcelain etc. Acrylic resin teeth have similar translucency, gloss of natural teeth. And it has good chemical bond with denture base material, but it has low wear resistance. The aim of this study is to compare wear resistance among several denture teeth(Endura, SR-orthosit-PE, Planustar) and between artificial resin denture teeth and opposing 3 restorative materials(gold, Ni-Cr alloy, porcelain). Wear tests were conducted with a rotating wear testing apparatus(pin-on-disk type wear tester) under conditions of rpm 180, 75 minutes and constant loading of 50N. The upper part was the cusp of maxillary first molar and the lower part was a disk type restorative materials. To make similar oral environment, water was supplied continually. The acrylic resin teeth wear was determined by weighing the cusp each 5 minutes during 75 minutes test. Vicker's hardness tester was used to evaluate the surface hardness of test specimens. The SEM was used to evaluate the wear surfaces. The results were as follows: 1. Wear rates of acrylic resin teeth opposing to the restorative materials were high in order of Porcelain, Gold, Ni-Cr alloy (p<.05). 2. Wear resistance rate opposing to the Porcelain disk, was shown in order of Endura, SR-orthosit-PE, Planustar. The wear rate of opposing to porcelain disk was above two times more than that of other groups (p<.05). 3. Wear resistance rates opposing to the Gold, Ni-Cr alloy disk, was shown in order of Endura, SR-orthosit-PE, Planustar (p<.05). 4. A degree of the surface hardness is directly proportional to the degree of wear resistance. There are statistically significant differences between each groups (p<.05).

• 대한치과기공학회지
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• 제41권4호
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• pp.327-335
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• 2019

Purpose: The purpose of this study was to investigate the relationship between periodontal disease, diabetes and chewing problems in Korean adults over the age of 19 using the 6th National Health Nutrition Survey. Methods: Data from the 6th National Health and Nutrition Survey (Ministry of Health & Welfare, 2013; 2014; 2015) were used. In this study, 17,101 adults aged 19 and older were included in the study to determine the relationship between diabetes and chewing problems in Korean adults. Results: Diabetes and chewing problems have been associated with periodontal disease. Diabetes was 0.719 times lower(p<0.001) in periodontal disease than in the case of diabetes. Chewing problem was 1.360 times(p<0.001) periodontal disease prevalence compared to 'not at all uncomfortable'. It was found that the prevalence of periodontal disease was 2.139 times(p<0.001) compared to 'not at all uncomfortable'. It was found that the prevalence of periodontal disease was 2.296 times higher(p<0.001) compared to 'not at all uncomfortable'. It was found that the prevalence of periodontal disease was 2.119 times higher(p<0.001) compared to 'not at all uncomfortable'. Conclusion: Diabetes and chewing problems were found to be related to periodontal disease, and as reported in previous studies, diabetes and chewing problems related to oral disease need to be prevented and treated with regular checkups. In addition, based on the research results, it can be used as basic data for the health business plan that can maintain and manage health.

• 대한치과기공학회지
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• 제35권1호
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• pp.57-64
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• 2013

Purpose: Waste parts of zirconia blocks and powders were remained after CAD/CAM process. In order to make these residual zirconia fit for practical use, zirconia single cores were produced by drain casting process. Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh sieve. Zirconia slip was prepared from waste parts of zirconia by ball milling. Plaster molds for forming cores by slip casting were also prepared. Formed cores were removed from mold after partial drying. Dried cores were biscuit fired at $1,100^{\circ}C$ for 1hour. Biscuit fired cores were treated with tools to control the fitness and thickness. Finished cores were $2^{nd}$ fired at $1,500^{\circ}C$ for 1hour. Microstructure of cross section of core was observed by SEM. Results: When mill pot was filled with 100g of zirconia and alumina mixed powder, 300g of zirconia ball, and 180g of distilled water, the optimum slip for drain casting was obtained. Gypsum plaster for ceramic forming was more suitable then yellow stone plaster for casting process. SEM photograph showed the microstructure of fully dense with uniform grain size of zirconia and well dispersed alumina grains into the zirconia matrix. Conclusion: Zirconia single cores were produced by drain casting process. Drain casting is useful process to make these residual zirconia fit for practical use. Further study will be focused on the preparation of the bridge type cores by casting.

• 대한치과기공학회지
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• 제36권1호
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• pp.51-62
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• 2014

Purpose: Recently our country is rapidly aging population is growing. In the oral cavity of the elderly status of oral health-related quality of life to evaluate any impact. Methods: The survey used structured self administered questionnaires from April to May in 2011 in Daejeon and Chungcheong provinces to 277 people, analysis of the general characteristics of a frequency analysis method, the difference between the quality of life T/F test, whether oral self-according to the quality of life healthy oral health effects of the multiple regression analysis. Results: Award comes on the number of residual value, lower age all the more, smaller monthly income was small, but significant difference between them was no difference between gender. Residual value according to the number of differences in the quality of life of physical pain upper, physical disability, the lower the physical pain, physical disability, psychological disability were significant differences in degradation. Depending on oral maxillary prosthesis fitted to physical pain, psychological discomfort, physical disability, the lower the functional limitation, physical pain, there was a significant difference in physical disability. Conclusion: Status of the oral cavity of the elderly factors affecting the quality of life remaining in the lower dimensions, upper and lower prosthetics, self-aware state of oral health in order to improve the quality of life of elderly oral health education to be strengthened to increase the residual value, reducing their own prosthetic perceived oral health is health, so they feel it should be for the development of health education programs for the elderly should be.

• 대한치과기공학회지
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• 제26권1호
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• pp.97-104
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• 2004

A new Ti-10Ta-10Nb alloy has designed and examined some possibility of forming more passive oxide film by oxidation treatment which is closely related to corrosion resistance and biocompatibility. Ti-6Al-4V and Ti-10Ta-10Nb alloys were prepared by consumable vacuum arc melting and homogenized at 1050$^{\circ}C$ for 24hours. Alloy specimens were oxidized at the temperature range of 400 to 750$^{\circ}C$ for 30minutes, and the oxide films on Ti alloys were analysed by optical microscope, SEM, XPS and TGA. Cytotoxicity test was performed in MTT assay treated L929 fibroblast cell culture by indirect method. It is found out that the oxide film on Ti-10Ta-10Nb alloy is denser and thinner compared to Ti-6Al-4V alloy. The weight gain during the oxidation was increased rapidly at the temperature above 650$^{\circ}C$ for Ti-6Al-4V alloy and above 700$^{\circ}C$ for Ti-10Ta-10Nb alloy respectively. It was analysed that the passive film of the Ti alloys consisted of TiO2 through X-ray photoelectron spectroscopy (XPS) analysis. It is found out by cytotoxicity test that moderate oxidation treatment lowers cell toxicity, and Ti-10Ta-10Nb alloy showed better result compared to Ti-6Al-4V alloy.

• 대한치과기공학회지
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• 제34권2호
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• pp.129-134
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• 2012

Purpose: This study was conducted to investigate the colors of zirconia and veneered ceramics according to the build-up method of veneer porcelain. Methods: The samples were divided into three groups: a group for which a liner was applied to the zirconia surface and dentine coating was built up and burned (Cz1), a group for which the dentine coating was directly built up and burned (Cz2), and a group for which the samples were wash-burned with dentine coating and a dentine coating was built up and burned again (Cz3). The the colors were measured with a Spectrophoto-meter. Results: The average $L^*$ value of the Cz3 group was the highest among the groups at $59.1{\pm}0.5$ (P<0.05), followed by Cz2 at $57.5{\pm}0.8$ and Cz1 at $56.6{\pm}1.3$. The $a^*$ value of Cz3 was negative at $-0.0{\pm}0.0$ and the $a^*$ values of Cz2 and Cz1 were positive at $0.2{\pm}0.1$ and $0.4{\pm}0.0$, respectively (P<0.05). The $b^*$ of Cz1 was the highest at $11.2{\pm}0.6$, followed by Cz3 at $10.8{\pm}0.5$ and Cz2 at $10.5{\pm}0.8$ (P<0.05). Conclusion: Compared to other experimental groups, the Cz3 groups showed the brightest colors with high brightness and relatively low green and yellow levels.

• 대한치과기공학회지
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• 제38권1호
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• pp.1-6
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• 2016

Purpose: The present study was to determine the stress distribution of an abutment screw according to implant abutment material. Methods: This study was a tightening torque 10 Ncm, 20 Ncm, set to 30 Ncm, and a titanium alloy (Ti-6Al-4V), PEEK (polyetheretherketone), Endoligns (60% Carbon Fiber Reinforced PEEK) material of the custom abutment titanium alloy (Ti-6Al-4V) the stress distribution in the material of the abutment screw will be evaluated by the finite element analysis. Results: Abutment screw most stress has been concentrated on the interface between the fixture and the abutment was also part of the interface that the threads are started. Depending on the abutment of the abutment screw Material von Mises stress values are shown differently. 10Ncm T10 under the tightening torque of 294.2 MPa, P10 is 562.8 MPa, appeared to E10 is 295.8 MPa, 20Ncm tightening torque under T20 is 581.1 MPa, P20 is 1125 MPa, E20 was shown to 585.1 MPa, 30Ncm tightening torque under T30 is 918.2 MPa, P30 is 1795 MPa, E30 has appeared 925.1 MPa. Conclusion: If the abutment is used as Endoligns, it was confirmed that the abutment screw exhibits of von Mises stress value is similar to the titanium alloy abutment.

• 대한치과기공학회지
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• 제27권1호
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• pp.9-17
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• 2005

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. But it has been reported recently that the vanadium element expresses cytotoxicity 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. This paper was described the influence of phase changes of Ti-Nb alloys on mechanical properties. Ti-3wt.%Nb($\alpha$type),Ti-20wt.%Nb($\alpha+\beta$type) and Ti-40wt.%Nb($\beta$type) alloys were melted by vacuum arc furnace. The specimens were homogenized at 1050$^{\circ}C$ for 24hr and were then hot rolled to 50% reduction. Each alloys were solution heat treated at $\beta$ zone and $\alpha+\beta$ zone after homogenization and then were aged. The mechanical properties of Ti alloys were analysed by hardness test, tensile test, elongation test and SEM test. The results can be summarized as follows: 1) The higher hardness value of $\alpha+\beta$type alloy was obtained compared to the, $\alpha,\beta$type alloys. 2) The aged treated showed better hardness compared to the solution heat treated, homogenized. 3) In the case of solution and aging treatment at $\beta$region, the $\alpha+\beta$type alloy showed the most highest tensile strength and $\beta$type alloy showed the best elongation.

• 대한치과기공학회지
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• 제33권4호
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• pp.331-337
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• 2011

Purpose: The purpose of this study was to impact of force system change in finger spring that add helical coil one round on orthodontic force. Methods: The following conclusions were drawn from the experiment conducted after bending 90 samples with a CNC wire forming machine while changing the height and lumen size to 1mm - 3mm - 5mm and 2mm - 3mm - 4mm respectively in the coil of the force system in finger spring added with one wheel of helical coil of 18-8 stainless steel round wire (${\Phi}0.5mm$, spring hard) from Jinsung Co. in domestic market under the following conditions: Laboratory name = Instron 5942; Temperature($deg^{\circ}C$) = 18.00; Humidity(%) = 50.00; Rate 1 = 10.00000 mm/min; Compressive extension = 5.0mm. Results: When Coil height is 1, 3, 5mm and lumen size is 2, 3, 4mm reduce finger spring as mean value of compressive extension occasion maximum load(mN) increases as coil height rises, and lumen size grows to 5.0mm. And was expose that compressive load(mN) increases as coil position of finger spring rises and increase as lumen size is decrescent. Conclusion: As the adherence height of coil was raised from 1mm through 3mm to 5mm, compressive load increased. As the lumen size increased from 2mm through 3mm to 4mm, compressive load decreased. Therefore, these results suggest that it is desirable to lower the coil height and enlarge the lumen size to enhance the biomechanical efficiency of finger spring when manufacturing the finger spring for removable orthodontic devices.