• Journal of Technologic Dentistry
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• v.31 no.2
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• pp.23-30
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• 2009

All-ceramic restorations have gained acceptance among clinicians and patients because of their superior esthetics. Most all-ceramic systems have a 2-layer structure, using a weak veneering ceramic over a strong supporting core. often, failure of all-ceramic restorations occurs when the veneering ceramic fractures, exposing the core material. The purpose of this study was to compare the shear bond strength of heat press ceramic system (Zirpress) to zirconia core with various surface treatments. 10 metal cores and 50 zirconia cores were fabricated and divided into six groups according to surface treatment such as Zirliner application, aluminium oxide blasting, and 9.5% HF etching. Sixty specimens were prepared using Zirpress, veneered 8mm height and 3mm in diameter, over the zirconia cores (n=10). The shear bond strength test was performed in a universal testing machine with a crosshead speed of 1/min. Ultimate shear bond strength data were analyzed with One-way ANOVA and the Scheffe's test (p=.05). Within the limits of this study, the following conclusions were drawn: The mean shear bond strengths (MPa) were: 12.93 for $110{\mu}m$ aluminium oxide blasting/Rexillium III/IPS e.Max Zirpress; 14.92 for $50{\mu}m$ aluminium oxide blasting ${\pm}9.5%$ HF etching/Zirconis core/IPS e.Max Zirpress; 16.37 for $110{\mu}$ aluminium oxide blasting + 9.5% HF etching/Zirconis core/IPS e.Max Zirpress; 12.89 for $200{\mu}$ aluminium oxide blasting + 9.5% HF etching/Zirconis core/IPS e.Max Zirpress; 19.30 for 9.5% HF etching/Zirconis core/IPS e.Max Zirpress; 19.55 for Zirliner/Zirconis core/IPS e.Max Zirpress. The mean shear bond strength for ZNTZH (Zirliner/Zirconis core) and ZNTEH (9.5% HF etching/Zirconis core) were significantly superior to MS110H ($110{\mu}$ aluminium oxide blasting/Rexillium III) and ZS200EH ($200{\mu}$ aluminium oxide blasting + 9.5% HF etching/Zirconis core) (p<0.05).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.693-700
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• 2020

This study compared the accuracy and reliability of definitive casts fabricated from a digital impression and conventional impression technique. A master model with the prepared upper full-arch tooth was used. Samples of ten plaster models and ten polyurethane models were duplicated using a selected standard master model. Six linear measurements were recorded between the landmarks, directly on each of the stone models and the polyurethane models on two occasions by a double examiner. The Wilcoxon signed-rank test, interclass correlation coefficient (ICC), measurement error (MSE), and limit of agreement (LoA) were used for statistical analysis. The ICC ranged from 0.76 to 0.99 when comparing the stone models and polyurethane models. The mean difference between the stone models and polyurethane models ranged from 0.09mm to 0.20mm, suggesting that stone models might be slightly larger than polyurethane models. Based on this study, the accuracy of the polyurethane models in evaluating the performance of an oral scanner and subtractive technology was acceptable. Further studies will be needed on patient subjects under clinical conditions that may involve missing or malpositioned teeth and fixed dental prostheses because this study was limited to use a standard master model and duplicated sample models in a laboratory setting.

• Journal of Technologic Dentistry
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• v.32 no.3
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• pp.195-207
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• 2010

Purpose: The purpose of this study was to observe the microstructural changes of surface in the specimens, performing the shear bond strength testing. The currently most used non-precious alloys are nickel-chromium based alloys with or without beryllium. However, their biocompatibility has been questioned concerning possible damages to the health of the patient and professionals involved in the fabrication of prosthesis caused by long exposure to Ni and Be. An option to nickel-chromium alloys is the cobalt-chromium alloy, an alternative that does not sacrifice the physical properties of the metal porcelain systems. Studies in the animals substantially show that the cobalt-chromium alloys are relatively well tolerated, being therefore more biocompatible than the nickel-chromium alloys. Methods: Non-addition Be to nickel-chromium based alloy(Bellabond plus) and cobalt-chromium alloy which has been widely used(Wirobond C) fused with ZEO light porcelain classified control group and cobalt-chromium alloy which is developing alloy of Alphadent company in Korea(Alphadent alloy) fused with ZEO light porcelain classified experimental group. The specimens of $4mm{\times}4mm{\times}0.5mm$ were prepared as-cast and as-opaque to cast body to analyze the mechanical characteristic change, the microstructure of alloy surface. The phase change was used to observe through XRD analysis and OM/SEM was used to observe the surface of specimens as-cast and as-opaque to cast body. Chemical formation of their elements was measured with EDS. Then hardness was measured with Micro Vicker's hardness tester. Shear bond strength test thirty specimens of $10mm{\times}10mm{\times}2mm$ was prepared, veneered, 3mm high and 3mm in diameter, over the alloy specimens. The shear bond strength test was performed in a universal testing machine(UTM) with a cross head speed of 0.5mm/min. Ultimate shear bond strength data were analyzed with one-way ANOVA and the Scheffe's test (P<0.05). Within the limits of this study, the following conclusions were drawn: The X-ray diffraction analysis results for the as-cast and as-opaque specimens showed that the major relative intensity of Bellabond plus alloy were changed smaller than Wirobond C and Alphadent Co-Cr based alloys. Results: Microstructural analysis results for the opaque specimens showed all the alloys increased carbides and precipitation(PPT). Alphadent Co-Cr based alloy showed the carbides of lamellar type. The Vickers hardness results for the opaque specimens showed Wirobond C and Alphadent Co-Cr based alloys were increaser than before ascast, but Bellabond plus alloy relatively decreased. The mean shear bond strengths (MPa) were: 33.11 for Wirobond C/ZEO light; 25.00 for Alphadent Co-Cr alloy/ZEO light; 18.02 for Bellabond plus/ZEO light. Conclusion: The mean shear bond strengths for Co-Cr and Ni-Cr based alloy were significantly different. But the all groups showed metal-metal oxide modes in shear bond strengths test at the interface.

• Journal of Technologic Dentistry
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• v.9 no.1
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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).

• Journal of Technologic Dentistry
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• v.31 no.1
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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).

• Journal of Technologic Dentistry
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• v.41 no.4
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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.

• Journal of Technologic Dentistry
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• v.35 no.1
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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.

• Journal of Technologic Dentistry
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• v.36 no.1
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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.

• Journal of Technologic Dentistry
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• v.26 no.1
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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.

• Journal of Technologic Dentistry
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• v.34 no.2
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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.