• The Journal of the Korean dental association
• /
• v.20 no.12 s.163
• /
• pp.1073-1081
• /
• 1982

The purpose of this study was to measure and compare the tensile strengths, elongation and Vicker's hardness values by heat treatments of three·commercial dental casting gold-silver-palladium alloys(Type A,B and G-50 alloys) used in Korea. Instron universal testing instrument and Vicker's hardness tester were used to determine their physical properties. The following results were obtained with the alloys tested. 1. It was determined that the tensile strengths generally tended to increase as the hardened condition (55.50 - 72.98 Kg/mm₂)than in softened condition (28.75 - 41.16 Kg/mm₂). 2. The results indicated that the elongation was the highest in the softened condition(12.30 - 27.0 %), and was the smallest in the hardened condition (3.6 - 5.8 %). 3. It was found that the Vicker's hardness number was the greatest in type G-50 hardened alloys (304.0), and the smallest in the type A softened alloys (130.0).

• Journal of Technologic Dentistry
• /
• v.17 no.1
• /
• pp.10-25
• /
• 1995

The purpose of this study is to get the difference of the castability in the production of partial denture between Precious Metal Alloys and Base Metal Alloys accompanied with the frequency of reuse. As materials for an experiment, we selected Baker-444 and Soo-444 and Soo-sung as Precious Metal Alloys, New Crown and Chrome Cobalt as Base Metal Alloys. And we tired to case all of them seven times. The experimental results were as follows : 1) In the probability of segments, Baker-444 showed 100$\pm$0.00%, Soo-sung 97.24$\pm$1.58%, New Crown 95.63$\pm$4.28%, and Chrome Cobalt 91.03$\pm$7.76%. Consequently, Precious Metal Alloys were decidely superior to Base Metal Alloys in the castability. 2) In the view of the acheived result, burn-out temperature and smocking time had greatly affected the castability. 3) After casting, Precious Metal Alloys were much less than Base Metal Alloys in the quantity of consumption. It made much difference from the the compiled stastics(p<0.01)

• Journal of Technologic Dentistry
• /
• v.37 no.4
• /
• pp.235-242
• /
• 2015

Purpose: The aims of this study are compare with microstructure and mechanical properties of Co-Cr-Mo alloys fabricated by powder metallurgy(P/M) process and casting process respectively. Methods: Microstructure and micro-hardness were tested by SEM and Vickers Hardness Tester. The sintered specimen was produced by furnace-coolling after sintering, however the casting specimen were produced thru air-cooling and water-cooling after the casting. For observation of phase transformation during sintering, DSC analyzing was carried out. Results: Mean pore size of sintered Co-Cr-Mo alloy was $4.32{\mu}m$ and that of casting alloy was $1.63{\mu}m$. Hardness of sintered alloy was lower than water-quenched casting alloy. Conclusion: Proper sintering temperature of Co-Cr-Mo alloy was above $1,200^{\circ}C$ and pore size of casting specimen were finer than sintered specimen, but hardness were similar.

• Journal of Technologic Dentistry
• /
• v.28 no.1
• /
• pp.27-41
• /
• 2006

The physical property and phase transformation in a commercial dental casting high gold alloy was investigated as a function of ageing temperature and time using microvickers hardness tester, X-ray diffraction, optical and electron microscopy and EPMA analyser. 1. With increasing ageing time, the hardness of solution-treated gold alloys increased slowly at the initial stage of ageing treatment at an ageing temperature of $300{\sim}400^{\circ}C$, and it reached a maximum value of hardness at the medium stage. Finally, it decreased gradually during further ageing. The maximum value of hardness at was similar with that of the conventional materials and suitable for using as the crown & bridge. 2. During isothermal ageing at a temperature range of $300{\sim}400^{\circ}C$, three phases consisting of the Au-rich ${\alpha}_1$phase with a face-centered cubic structure, the Pt3Zn ${\alpha}_2$phase with an ordered AuCu3(L12) type(f.c.c.) and the Pt-rich ${\alpha}_3$phase with face-centered cubic structure in solution-treated gold alloys were transformed into different three phases consisting of the ${\alpha}_1$phase, the ${\alpha}_3$phase and the PtZn $\beta$phase with an ordered AuCu I(L10) type. 3. The hardening of gold alloys was attributed to the lattice strains of the matrix resulting from the transformation of the ${\alpha}_2$phase to the $\beta$phase. 4. The softening of gold alloys during over-ageing was attributed to the coarsening of the nodules consisting of the $\beta$phase and ${\alpha}_1$matrix.

• Journal of Technologic Dentistry
• /
• v.8 no.1
• /
• pp.51-55
• /
• 1986

The castability of base metal alloys for dental casting in influenced by burn-out temperature and recent percentage. Burn-out temperatures for casting are set at 200$^{\circ}F$ interval from 1000$^{\circ}F$ to 1800$^{\circ}F$. According to recast metal percent in new cast alloy metal alloys are tested. The results are as followings: 1. In the new alloy(100%), the castability is the most. 2. The burn-out temperature in 1600$\sim$1800$^{\circ}F$, castability of 100% new alloy was more four times than of 50% new alloy plus 50% recast alloy. The using of 50% new alloy and 50% recast alloy, therefore, was unlike in castability. 3. The burn-out temperature in 1600$^{\circ}F$, castability of 100% new alloy was more than four times in soaking 20 minutes, but there was no any difference at 18700$^{\circ}F$. 4. It is investigated that the optimal burn-out temperature is 1600$^{\circ}F$ for the C & B alloy.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.12
• /
• pp.434-439
• /
• 2020

Selective laser melting (SLM) manufactures an alloy using laser as a heat source, and has recently been introduced in the dental industry. However, there is a lack of analytical research on metal-ceramic restorations achieved by SLM. This study evaluates and compares the metal-ceramic bond strength of Co-Cr alloys produced by selective laser melting and casting methods. Co-Cr samples required for this study were produced through the sintering process of ceramics, by applying the SLM and CAST methods. The metal-ceramic bond strength was measured by applying the shear bond strength test. In order to determine the area fraction of adherent ceramic, Si content of the specimen was measured using scanning electron microscopy SEM/ EDS. Results of the metal-ceramic bond strength and AFAC were analyzed by t-test (α = 0.05). No significant difference was observed comparing the bond strength of SLM and CAST Co-Cr alloys (P> 0.05). However, the SLM group had much better ceramic adherence than the CAST group (P < 0.001). Moreover, oxidation characteristics were similar for both SLM and CAST Co-Cr alloys, but metal structures were different. These results imply that although the bond of ceramic and Co-Cr alloy is not related to the manufacturing method, SLM alloys impart better ceramic adherence. This indicates that alloys made with SLM can be used to fabricate upper implant prostheses in the future. In particular, it is expected to overcome the shortcomings of the CAST method, and save time and cost.

• The Journal of the Korean dental association
• /
• v.10 no.11
• /
• pp.749-752
• /
• 1972

• Journal of Technologic Dentistry
• /
• v.35 no.4
• /
• pp.343-352
• /
• 2013

Purpose: The purpose of this study was to investigate to effect of the ZrN coated on corrosion resistance and physical property of dental Co-Cr alloys using various instruments. Methods: The specimens were used, respectively, for experiment, Arc Ion plating was carried out for dental casting alloys using ZrN coated materials with nitrogen gas. ZrN coated surface of each specimen was observed with field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), vickers hardness tester, and electrochemical tester. Results: The current density of ZrN coated specimen was smaller than that of non-coated specimen in 0.9% NaCl solution. Pit nucleated at scratch of specimen. The pitting corrosion resistant |$E_{max}-E_{rep}$| increased in order of ZrN coated (110 mV), and non-coated wire (100 mV). Conclusion: The corrosion potential of the ZrN coated specimen was comparatively high. the surface of ZrN coated specimen was more smooth than that of other kinds of non-coated specimen. ZrN coated surface showed higher hardness than that of non-coated surface.

• Journal of Technologic Dentistry
• /
• v.34 no.3
• /
• pp.237-245
• /
• 2012

Purpose: This study was conducted to evaluate the corrosion resistance of metal ions of alloys and use the results as the dental health data. These were performed by examining the corrosion levels of Co-Cr alloys for the full and removable partial denture metal frameworks and porcelain-fused-to-metal crown, among the dental casting nonprecious alloys. Methods: The alloy specimens (N = 10) were manufactured in $15mm{\times}10mm{\times}1.2mm$ and stored in two types of corrosive solutions at $37^{\circ}C$ for seven days. The metal ions were quantitatively analyzed using the Inductively Coupled Plasma-Atomic Emission Spectrometer. Results: Of the three Co-Cr alloys, the Co ion concentration of the porcelain-fused-to-metal alloy was 1.512 ${\mu}g/cm^2$, which indicated the highest metal ion dissolution. The metal corrosion was higher in the more acidic pH 2.2 solution compared with the pH 4.4 solution. In all three Co-Cr alloys, Co ion dissolution was predominant in the two corrosive solutions. Conclusion: The corrosion resistance of the three Co-Cr alloys was high, indicating a good biocompatibility.

• Journal of Technologic Dentistry
• /
• v.42 no.2
• /
• pp.65-71
• /
• 2020

Purpose: To know the transmittance of light when wearing shading goggles and to protect eyes from blue light emitted from dental scanner when using CAD/CAM works or inducing polymerization reactions of dental resin with curing unit and infrared light occurred when melting Dental precious metal and non-precious metal alloys. Methods: By measuring and comparing the average transmittances of blue light, visible light and infrared ight by using UV-Vis Spectrophotometer analysis measuring instrument, I compared 3 GREEN Color Goggles worn when casting Dental precious metal and non-precious metal alloys, and compared each of YELLOW, ORANGE Color Goggles worn when using Dental CAD/CAM scanners and Light Curing(LED) the Dental resin. Results: In blue light range, YELLOW Color Goggles are more effective than ORANGE Color Goggles. In infrared light range, No.12 Goggles are more effective than No.10 and No.11 Goggles. Conclusion: When wearing blue light shading goggles to avoid harmful blue light occurred in using dental scanner and curing light, and when wearing infrared light shading goggles to avoid harmful infrared light during casting, to avoid the Side Effects like transmittance rate of blue light and infrared light goggles becomes too high to block appropriate amount of harmful light or too low that causing lower image clarity.