• The Journal of Advanced Prosthodontics
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• 제11권4호
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• pp.223-231
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• 2019

PURPOSE. The purpose of this study was to evaluate the shear bond strength (SBS) of an indirect resin composite (IRC) to the various resin matrix ceramic (RMC) blocks using different surface treatments. MATERIALS AND METHODS. Ninety-nine cubic RMC specimens consisting of a resin nanoceramic (RNC), a polymer-infiltrated hybrid ceramic (PIHC), and a flexible hybrid ceramic (FHC) were divided randomly into three surface treatment subgroups (n = 11). In the experimental groups, untreated (Cnt), tribochemical silica coating (Tbc), and Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser irradiation (Lsr) with 3 W (150 mJ/pulse, 20 Hz for 20 sec.) were used as surface treatments. An indirect composite resin (IRC) was layered with a disc-shape mold ($2{\times}3mm$) onto the treated-ceramic surfaces and the specimens submitted to thermal cycling (6000 cycles, $5-55^{\circ}C$). The SBS test of specimens was performed using a universal testing machine and the specimens were examined with a scanning electron microscope to determine the failure mode. Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tukey HSD test (${\alpha}=.05$). RESULTS. According to the two-way ANOVA, only the surface treatment parameter was statistically significant (P<.05) on the SBS of IRC to RMC. The SBS values of Lsr-applied RMC groups were significantly higher than Cnt groups for each RMC material, (P<.05). Significant differences were also determined between Tbc surface treatment applied and untreated (Cnt) PIHC materials (P=.039). CONCLUSION. For promoting a reliable bond strength during characterization of RMC with IRC, Nd:YAG laser or Tbc surface treatment technique should be used, putting in consideration the microstructure and composition of RMC materials and appropriate parameters for each material.

• The Journal of Advanced Prosthodontics
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• 제11권2호
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• pp.128-137
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• 2019

PURPOSE. The aim of this study was to compare the effect of different finishing and polishing techniques on water absorption, water solubility, and microhardness of ceramic or glass-polymer based computer-aided design and computer-aided manufacturing (CAD/CAM) materials following thermocycling. MATERIALS AND METHODS. 150 disc-shaped specimens were prepared from three different hybrid materials and divided into five subgroups according to the applied surface polishing techniques. All specimens were subjected up to #4000 grit SiC paper grinding. No additional polishing has been done to the control group (Group I). Other polishing procedures were as follows: Group II: two-stage diamond impregnated polishing discs; Group III: yellow colored rubber based silicone discs; Group IV: diamond polishing paste; and Group V: Aluminum oxide polishing discs. Subsequently, 5000-cycles of thermocycling were applied. The analyses were conducted after 24 hours, 7 days, and 30 days of water immersion. Water absorption and water solubility results were analyzed by two-way ANOVA and Tukey post-hoc tests. Besides, microhardness data were compared by Kruskal-Wallis and MannWhitney U tests (P<.05). RESULTS. Surface polishing procedures had significant effects on water absorption and solubility and surface microhardness of resin ceramics (P<.05). Group IV exhibited the lowest water absorption and the highest microhardness values (P<.05). Immersion periods had no effect on the microhardness of hybrid ceramic materials (P>.05). CONCLUSION. Surface finishing and polishing procedures might negatively affect physical properties of hybrid ceramic materials. Nevertheless, immersion periods do not affect the microhardness of the materials. Final polishing by using diamond polishing paste can be recommended for all CAD/CAM materials.

• 대한치과보철학회지
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• 제49권2호
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• pp.114-119
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• 2011

연구 목적: 미세 인장결합강도 측정을 위한 시편 제작 시 발생하는 스트레스가 결합강도에 어떠한 영향을 미치는 지를 알아보고자 하였다. 연구 재료 및 방법: 원통 모양의 지르코니아 블럭을 다이아몬드 디스크를 이용해 디스크 형태로 자른 후 소결하였다. 소결된 지르코니아 디스크에 소성시 수축을 고려한 적당한 크기의 틀을 제작하여 LAVA ceram (3M ESPE, Seefeld, Germany) 도재를 축성한 후 소성하였다. 먼저 그룹 1은 디스크 모양의 시편을 충분히 물을 뿌려가며 다이아몬드 디스크를 이용하여 $1{\times}1{\times}7\;mm^3$의 막대기 모양으로 저속에서 절단하였다 (n = 15). 그룹 2는 같은 방법으로 $1.2{\times}1.2{\times}7\;mm^3$로 자른 후 두꺼운 다이아몬드 디스크를 이용해 $1{\times}1{\times}7\;mm^3$로 트리밍하였다 (n = 15). 그 후 특별히 제작된 지그에 각각의 시편을 core-veneer의 접착면이 오염되지 않도록 조심히 접착한 후 미세 인장결합강도 측정기 (Instron 8848, $Instron^{(R)}$ Co., Norwood, USA)를 이용하여 미세 인장결합강도를 측정하였다. 측정이 끝난 시편은 파절면을 stereomicroscope (MZ6, Leica Microsystems GmbH, Wetzlar, Germany) 로 30배 확대 관찰하여 파절의 종류를 구분하였다. 결과: 지르코니아 코어와 비니어링 세라믹 간의 평균 미세 인장결합강도는 절단만 시행한 그룹은 $28.8{\pm}7.0\;MPa$, 절단 후 트리밍을 한 그룹은 $11.0{\pm}33\;MPa$로 절단후 트리밍을 한 시편이 유의성 있게 결합강도가 낮아진 것으로 나타났다 (P=.00). 결론: 미세 인장결합강도 측정을 위한 시편 제작 시 가능한 한 스트레스를 가하지 않고 미세 시편을 제작하는 것이 중요하다고 사료된다.

• 한국재료학회지
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• 제12권2호
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• pp.129-134
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• 2002

The optimum condition for fabricating cordierite disc type filter element was deduced. Cordierite monolith was used as starting material for filter element because it has many advantages such as high thermal shock resistance and good catalytic activity compared with $TiO_2$and SiC. The contents of organic additives and foaming agent were optimized to control the porosity and mechanical strength of cordierite filter. Among the required properties to be adopted as filter elements, the pressure drop and NOx removal efficiency were investigated depending on processing variables. It was found that pressure drop depends on particle size distribution of cordierite monolith and organic additives added as forming agent. The pressure drop at 5cm/sec of face velocity was in the range of 15~655mm$H_2O$ at room temperature. The NOx removal efficiency of catalytic filter with $V_2O_5$ as catalyst was over 85% at $450^{\circ}C$.

• 한국세라믹학회지
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• 제33권11호
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• pp.1267-1275
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• 1996

Green sheet was prepared by tape casting in the composition of (1-x)Pb(Mg1/3Nb2/3)O3-PbTiO3 system using Pb(Mg1/3Nb2/3)O3 and PbTiO3 synthesized with PbO, Nb2O5 MgO and TiO2 The densest green sheet was obtained in the weight ratio 70:30 of powder to binder. Green sheet wasmultilayered in metal mould and formed into lamination at 7$0^{\circ}C$, 300kg/cm2 The lamination was sintered at 110$0^{\circ}C$ 2hr, Dielectric constant and Curie temperature of disc type sintered body was highered with increasing the amount of PbTiO3 and was in the range of 19000-21000, -7~45$^{\circ}C$ respectively. Green and sintered relative density of lamination was 61% and 95% respectively.

• 한국세라믹학회지
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• 제20권3호
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• pp.227-235
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• 1983

The dielectric and piezoelectic properties in which $(Zr_{0.52} Ti_{0.48})^{+4}$ ions of $Pb(Zr_{0.52} Ti_{0.48})O_3$ are partially substituted for $W^{+6}$ ions were studied. $ZrTiO_4$ was made by coprecipitation. The specimens of disc shape were sintered respectively at 1180$^{\circ}$to 130$0^{\circ}C$ at an intervals of 2$0^{\circ}C$ for 1 hour. The optimum sintering temperature were found to be between 126$0^{\circ}C$ and 128$0^{\circ}C$. PZT solid solutions sintered had the tetragonal structure with c/a=1.025$\pm$0.005 and theoretical densities incre-ased from 8.02 to 8.17g/cm3 with increasing the amount of the partial substitution of $(Zr_{0.52} Ti_{0.48})^{+4}$ ion for $W^{+6}$ ion The grain size and curie temperature decreased with increasing the amount of $WO_3$ while the dielectric constant increased. When $(Zr_{0.52} Ti_{0.48})^{+4}$ ion was substituted for 1 mole% of $W{+6 ]$ion the planar coupling coefficient$(K_P)$ was as high as 0.58 But as the amount of $WO_3$ increased the mechanical quality factor(Qm) decreased considerably.

• 자동차안전학회지
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• 제12권1호
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• pp.26-32
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• 2020

The luxury car market has been steadily growing for the last 10 years and it might keep expanding in the future. Furthermore, it is expected to be a very competitive market because luxury cars are considred to reflect the technology level of motor companies. For this reason, it is very important for motor companies to improve performances of luxury vehicles. However, it takes years for the companies to increase the technology level for the high performances. In this paper, we aim to analyze the technologies for high quality brake perfomances through investigation of two luxury vehicle models and develop a new high performance brake system. First, we found out a variety of effective factors for the high performances. Second, we conducted the brake performance analysis to figure out the relationship between brake effort and brake feeling. Finally, we develped the new brake system using carbon ceramic composite materials to satisfy the high quality brake performances.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.291-299
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• 2018

PURPOSE. To assess the degree of conversion (DC) and light irradiance delivered to light-cured and dual-cured cements by application of different light sources through various types of monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) materials. MATERIALS AND METHODS. RelyX Ultimate Clicker light-cured and dual-cured resin cement specimens with 1.5-mm thicknesses (n=300, 10/group), were placed under four types of crystalline core structure (Vita Enamic, Vita Suprinity, GC Ceresmart, Degudent Prettau Anterior). The specimens were irradiated for 40 seconds with an LED Soft-Start or pulse-delay unit or 20 seconds with a QTH unit. DC ratios were determined by using Fourier transform infrared spectroscopy (FTIR) after curing the specimen at 1 day and 1 month. The data were analyzed using the Mann-Whitney U test (for paired comparison) and the Kruskal-Wallis H test (for multiple comparison), with a significance level of P<.05. RESULTS. DC values were the highest for RelyX Ultimate Clicker light-cure specimens polymerized with the LED Soft-Start unit. The combination of the Vita Suprinity disc and RelyX Ultimate Clicker dual-cure resin cement yielded significantly higher values at both timepoints with all light units (all, P<.05). CONCLUSION. Within the limitations of this study, we conclude that the DC of RelyX Ultimate Clicker dual-cure resin cement was improved significantly by the use of Vita Suprinity and the LED Soft-Start light unit. We strongly recommend the combined use of an LED light unit and dual-cure luting cement for monolithic ceramic restorations.

• 한국재료학회지
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• 제27권3호
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• pp.132-136
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• 2017

We synthesized potassium hexatitanate, ($K_2Ti_6O_{13}$, PT6), with a non-fibrous shape, by acid leaching and subsequent thermal treatment of potassium tetratitanate ($K_2Ti_4O_9$, PT4), with layered crystal structure. By controlling nucleation and growth of PT4 crystals, we obtained splinter-type crystals of PT6 with increased width and reduced thickness. The optimal holding temperature for the layered PT4 was found to be ${\sim}920^{\circ}C$. The length and width of the PT4 crystals were increased when the nucleation and growth time were increased. After a proton exchange reaction using aqueous 0.3 M HCl solution, and subsequent heat treatment at $850^{\circ}C$, the PT4 crystal transformed into splinter-type PT6 crystals. The frictional characteristics of the friction materials show that as the particle size of PT6 increases, the coefficient of friction (COF) and wear amounts of both the friction materials and counter disc increase.

• The Journal of Advanced Prosthodontics
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• 제6권1호
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• pp.8-13
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• 2014

PURPOSE. The purpose of this study was to evaluate whether surface treatments affect the translucency of laminate veneers with different shades and thicknesses. MATERIALS AND METHODS. A total of 224 disc-shaped ceramic veneers were prepared from A1, A3, HT (High Translucent) and HO (High Opaque) shades of IPS e.max Press (Ivoclar Vivadent) with 0.5 mm and 1.0 mm thicknesses. The ceramics were divided into four groups for surface treatments. Group C: no surface treatments; Group HF: etched with hydrofluoric acid; Group SB: sandblasted with 50-${\mu}m$ $Al_2O_3$; and Group L; irradiated with an Er;YAG laser. A translucent shade of resin cement (Rely X Veneer, 3M ESPE) was chosen for cementation. The color values of the veneers were measured with a colorimeter and translucency parameter (TP) values were calculated. A three-way ANOVA with interactions for TP values was performed and Bonferroni tests were used when appropriate (${\alpha}=0.05$). RESULTS. There were significant interactions between the surface treatments, ceramic shades and thicknesses (P=.001). For the 0.5-mm-thick specimens there were significant differences after the SB and L treatments. There was no significant difference between the HF and C treatments for any shades or thicknesses (P>.05). For the 1-mm-thick ceramics, there was only a significant difference between the L and C treatments for the HT shade ceramics (P=.01). There were also significant differences between the SB and C treatments except not for the HO shades (P=.768). CONCLUSION. The SB and L treatments caused laminate veneers to become more opaque; however, HF treatment did not affect the TP values. When the laminate veneers were thinner, both the shade of the ceramic and the SB and laser treatments had a greater effect on the TP values.