• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.560-566
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• 2016

In this study, porcelain bonding strength and mechanical properties of sintered Ni-Cr-Ti alloy for dental prosthodontics have been researched experimentally. Mechanical and morphological characteristics of the alloys were examined by Vickers hardness test, tensile and bonding strength test, surface roughness test, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. In the sintered Ni-13Cr-xTi alloys, morphology of sintered alloy showed porous matrix diffused with alloying elements of Cr and Ti, and showed dendritic structure after melting process. From the XRD results, the second phases of NiCr, $Ni_3Cr$, and $Ni_3Ti$ were formed in the case of sintered and melted Ni-13Cr-xTi alloys. The tensile strength and hardness of Ni-13Cr-xTi alloys increased, as Ti content increased. Surface roughness increased, as Ti content increased. The bonding strength between metal and porcelain of Ni-13Cr-5Ti alloy was higher than those of Ni-13Cr and Ni-13Cr-10Ti alloys

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.93-98
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• 2021

Purpose: The aim of this study was to observe the surface roughness and surface topography of cobalt-chrome (Co-Cr) alloys with grinding time in dental barrel finishing. Methods: This study involved two types of Co-Cr alloys. Specimens were manufactured with the dimensions 10×10×2 mm. Each specimen was cast according to the manufacturer's instructions. The cast alloys were polished for 35 minutes at intervals of five minutes in an automatic barrel finishing. Specimens were imaged with a three-dimensional optical microscope to measure surface roughness. Results: BC specimens and GM specimens had the highest roughness (Ra) values in the ungrained control group, and the lowest Ra values were measured 20 minutes after grinding. Conclusion: The best conditions for grinding Co-Cr alloy using a dental barrel finishing were a weight ratio of polishing media, water, and compound of 150 g:200 g:5 g, and a rotation speed of 450 rpm. Grinding time to obtain appropriate surface roughness should be limited to 15 to 30 minutes.

• Journal of Korean Dental Science
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• v.10 no.1
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• pp.10-21
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• 2017

Purpose: The purpose of this study was to investigate the electrochemical characteristics of nanotubular Ti-25Nb-xZr ternary alloys for dental implant materials. Materials and Methods: Ti-25Nb-xZr alloys with different Zr contents (0, 3, 7, and 15 wt.%) were manufactured using commercially pure titanium (CP-Ti), niobium (Nb), and zirconium (Zr) (99.95 wt.% purity). The alloys were prepared by arc melting in argon (Ar) atmosphere. The Ti-25Nb-xZr alloys were homogenized in Ar atmosphere at $1,000^{\circ}C$ for 12 hours followed by quenching into ice water. The microstructure of the Ti-25Nb-xZr alloys was examined by a field emission scanning electron microscope. The phases in the alloys were identified by an X-ray diffractometer. The chemical composition of the nanotube-formed surfaces was determined by energy-dispersive X-ray spectroscopy. Self-organized $TiO_2$ was prepared by electrochemical oxidation of the samples in a $1.0M\;H_3PO_4+0.8wt.%$ NaF electrolyte. The anodization potential was 30 V and time was 1 hour by DC supplier. Surface wettability was evaluated for both the metallographically polished and nanotube-formed surfaces using a contact-angle goniometer. The corrosion properties of the specimens were investigated using a 0.9 wt.% aqueous solution of NaCl at $36^{\circ}C{\pm}5^{\circ}C$ using a potentiodynamic polarization test. Result: Needle-like structure of Ti-25Nb-xZr alloys was transform to equiaxed structure as Zr content increased. Nanotube formed on Ti-25Nb-xZr alloys show two sizes of nanotube structure. The diameters of the large tubes decreased and small tubes increased as Zr content increased. The lower contact angles for nanotube formed Ti-25NbxZr alloys surfaces showed compare to non-nanotube formed surface. The corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface showed longer the passive regions compared to non-treatment surface. Conclusion: It is confirmed that corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface has longer passive region compared to without treatment surface.

• Journal of Technologic Dentistry
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• v.10 no.1
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• pp.47-54
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• 1988

The purpose of this study is to evaluate the castability of Ni-Cr alloys for crown and bridge. New young, Hi-Crown and CB-80 which are widely used in dental laboratory were chosen, casting and increased the temperature of furnace 100$^{\circ}C$ of each 7 grades from 600$^{\circ}C$ to 1200$^{\circ}C$. The results are as follows : 1. CB-80 is the most prominent castability among the three Ni-Cr alloys which are Hi-Crown, New-young and Hi-Cr. 2. The good burning temperatures of casting for CB-8p are 900$^{\circ}C$, 100$^{\circ}C$ and 1100$^{\circ}C$ which are obtained four complate casting body of five former patterns. 3. The most proper burning temperature for three Ni-Cr alloys is 900$^{\circ}C$.

• The Journal of the Korean dental association
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• v.20 no.12 s.163
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• pp.1073-1081
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• 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
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• v.34 no.3
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• pp.237-245
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• 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 Korea Foundry Society
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• v.27 no.3
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

• Journal of Technologic Dentistry
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• v.28 no.1
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• pp.61-66
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• 2006

Titanium alloys have been used for dental materials due to it's very good biocompatibility. Ti-6Al-4V alloy instead of pure titanium 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 carcinogenicity and the aluminium element is related with dementia of Alzheimer type and neurotoxicity. The Ti-Nb alloys has designed and examined corrosion resistance. 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 corrosion resistance of Ti alloys was evaluated by potentiodynamic polarization test in the solution of 0.9% NaCl and 5% HCl. The results can be summarized as follows: 1) For the corrosion test in the solution of 0.9% NaCl and 5% HCl, the corrosion behaviour of Ti-Nb alloys was similar to ASTM grade 2 CP Ti. 2) The corrosion resistance of Ti-20Nb alloy was better than that of CP-Ti, Ti-3Nb, Ti-40Nb alloy in 0.9% NaCl and 5% HCl, solutions.

• Journal of Technologic Dentistry
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• v.34 no.4
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• pp.337-344
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• 2012

Purpose: This study examined the corrosion level by alloy type and pH, and used the corrosion levels as the dental health data. The study utilized one Ni-Cr alloy for the full and removable partial denture metal frameworks and two Ni-Cr alloys for porcelain-fused-to-metal crown, among the non-beryllium dental casting non-precious Ni-Cr alloys. Methods: The alloy specimens were manufactured in $10cm^2$ and stored in the corrosive solution(pH 2.2-4.4) in the electrical water bath($37^{\circ}C$) for seven days. Afterwards, the metal ions were quantitatively analyzed using the ICP. Results: Of the three metal alloys, Bellabond-Plus$^{(R)}$alloy and SOLIBOND N$^{(R)}$alloy, with 22% or higher chrome chemical contents, had higher corrosion resistance than Jdium-100$^{(R)}$alloy with 20% chrome chemical content. In all three alloys, the corrosion of Ni was highest, and metal ion corrosion was higher in the pH 2.2 corrosive solution. Conclusion: Although Ni-Cr alloy was not very corrosive, a Ni-allergic patient should not have Ni-Cr alloy prosthesis. The Ni-Cr alloy for porcelain-fused-to-metal crown should be designed for the dental porcelain to cover the whole crown.

• Journal of Technologic Dentistry
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• v.8 no.1
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• pp.45-50
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• 1986

This study investigated the effect of burnout temperature on the castability of some nickelchromium alloys for porcelain fused to metal system and the effect of beryllium on the castability. Four alloys were evaluated: two contained beryllium(rexillium III, Super I) and two nonberyllium(Unibond, NNB). five burnout temperature, ranging form 100$^{\circ}F$ to 1800$^{\circ}F$, were aet at 200$^{\circ}F$ intervals for this study. The results obtained were as follows: 1. Beryllium-containing alloys were more castable than nonberyllium-containing alloys. 2. There was an optimal burnout temperature of range from 1400$^{\circ}F$ to 1600$^{\circ}F$ for the berylliumcontaining alloys studied. 3. An optimal burnout temperature for the nonberyllium alloys was not established.