• 대한치과보철학회지
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• 제33권3호
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• pp.584-609
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• 1995

The purpose of this study was to evaluate the difference of the galvanic corrosion behaviour of the titanium in contact with gold alloy, silva-palladium alloy, and nickel-chromium alloy using the immersion and electrochemical method. And the effects of galvallit couples between titanium and the dental alloys were assessed for their usefulness as materials for superstructure. The immersion method was performed by measuring the amount of metal elementsreleased by Inductivey coupled plasma emission spectroscopy(ICPES) The specimen of fifteen titanium plates, the five gold alloy, five silver-palladium, five nickel-chromium plates, and twenty acrylic resin plates ware fabricated, and also the specimen of sixty titanium plugs, the thirty gold alloy, thirty silver-palladium, and nickelc-hromium plugs were made. Thereafter, each plug of gold alloy, silver-palladium, and nickel-chromium inserted into the the titanium and acrylic resin plate, and also titanium plug inserted into the acrylic resin plate. The combination specimens uf galvanic couples immersed in 70m1 artificial saliva solution, and also specimens of four type alloy(that is, titanium, gold, silver-palladium and nickel-chromium alloy) plugs were immersed solely in 70m1 artificial sativa solution. The amount of metal elements released was observed during 21 weeks in the interval of each seven week. The electrochemical method was performed using computer-controlled potentiosta(Autostat 251. Sycopel Sicentific Ltd., U.K). The wax patterns(diameter 11.0mm, thickness,in 1.5mm) of four dental casting alloys were casted by centrifugal method and embedded in self-curing acrylic resin to be about $1.0cm^2$ of exposed surface area. Embedded specimens were polished with silicone carbide paper to #2,000, and ultrasonically cleaned. The working electrode is the specimen of four dental casting alloys, the reference electrode is a saturated calmel electrode(SCE) and the ounter electrode is made of platinum plate. In the artificial saliva solution, the potential scanning was carried out starting from-700mV(SCE) TO +1,000mV(SCE) and the scan rate was 75mV/min. Each polarization curve of alloy was recorded automatically on a logrithmic graphic paper by XY recorder. From the polarization curves of each galvanic couple, corrosion potential and corrosion rates, that is, corrosion density were compared and order of corrosion tendency was determined. From the experiments, the following results were obtained : 1. In the case of immersing titanium, gold alloy, silver-palladium alloy, and nickel-chromium alloysolely in the artificial saliva solution(group 1, 2, 3, and 4), the total amount of metal elements released was that group 4 was greater about 2, 3 times than group 3, and about 7.8 times than group 2. In the case of group 1, the amount of titanium released was not found after 8 week(p<0.001). 2. In the case of galvanic couples of titanium in contact with alloy(group 5, 6), the total amount of metal elements released of group 5 and 6 was less than that of group 7, 8, 9, and 10(p<0.05). 3. In the case of galvanic couples of titanium in contact with silver-palladium alloy(group 7, 8), the total amount of metal elements released of group 7 was greater about twice than that of group 5, and that of group 8 was about 14 times than that of group 6(p<0.05). 4. In the case of galvanic couples of titanium in contact with nickel-chromium alloy(group 9, 10), the total amount of metal elements released of group 9 and 10 was greater about 1.8-3.2 times than that of group 7 and 8, and was greater about 4.3~25 times than that of group 5 and 6(p<0.05). 5. In the effect of galvanic corrosion according to the difference of the area ratio of cathode and anode, the total amount of metal elements released was that group 5 was greater about 4 times than group 6, group 8 was greater about twice than group 7, and group 10 was greater about 1.5 times than group 9(p<0.05). 6. In the effect of galvanic corrosion according to the elasped time during 21 week in the interval of each 7 week, the amount of metal elements released was decreased markedly in the case of galvanic couples of the titanium in contact with gold alloy and silver-palladium alloy but the total amount of nickel and beryllium released was not decreased markedly in the case of galvanic couples of the titanium in contact with nickel-chromium alloy(p<0.05). 7. In the case of galvanic couples of titanium in contact with gold alloy, galvanic current was lower than any other galvanic couple. 8. In the case of galvanic couples of titanium in contact with nickel-chromium alloy, galvanic current was highest among other galvanic couples.

• 대한치과보철학회지
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• 제34권3호
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• pp.475-488
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• 1996

The opaque porcelain layer of porcelain-fused-to-metal(PFM) restoration is critical for the success of PFM restoration because it is the first layer placed over the treated alloy. But, the methods of opaquing technique have not been confirmed. Usually, the one layer method and two layer method have been used for the application of opaque porcelain. In the past, alloys with porcelain veneers which have been used successfully have contained various precious metals. Recent increase in the cost of precious metals stimulates considerable interest in nonprecious alloys. Although nickel-chromium alloys and nickel-chromium-beryllium alloys have been widely used, the use of cobalt-chromium alloys would be gradually increased with elimination of any potential risk of nickel-related allergic responses and/or beryllium-related toxic responses. This investigation examined one- and two-layer opaque porcelain applications to determine the effect on the bond strength of titanium added cobalt-chromium metal ceramic alloy. Bond strength of Ceramco II porcelain to titanium added cobalt-chromium alloy(2Dentitan) and gold-platinum-palladium alloy(Degudent H) were evaluated by direct shear bond strength test with Instron universal testing machine. The results were as follows; 1. When the mean shear bond strength of each experimental group were compared in $0.25cm^2$ unit area, the titanium added cobalt-chromium alloy/two layer method exhibited the greatest strength(79.7kg), followed by titanium added cobalt-chromium alloy/one layer method(76.2kg), gold-platinum-palladium alloy/two layer method(71.4kg), gold-platinum-palladium alloy/one layer method(64.2kg). 2. No significant differences in bond strength were recorded between the two opaquing techniques for gold-platinum-palladium alloy and titanium added cobalt-chromium alloy. 3. No significant differences in bond strength were recorded between the gold-platinum-palladium alloy and the titanium added cobalt-chromium alloy.

• Corrosion Science and Technology
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• 제6권6호
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• pp.311-315
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• 2007

The anodic polarization behavior of equiatomic TiNi shape memory alloy with pure titanium as a reference material was investigated by means of open circuit potential measurement and potentiodynamic polarization technique. And the structure of passive films on TiNi intermetallic compounds was also conducted using AES and ESCA. While the dissolved Ni(II) ion did not affect the dissolution rate and passivation of TiNi alloy, the dissolved Ti(III) ion was oxidated to Ti(IV) ion on passivated TiNi surface at passivation potential. It has also been found that the Ti(IV) ion increases the steady state potential, and passivates TiNi alloy at a limited concentration of Ti(IV) ion. The analysis by AES showed that passive film of TiNi alloy was composed of titanium oxide and nickel oxide, and the content of titanium was three times higher than that of nickel in outer side of passive film. According to the ESCA analysis, the passive film was composed of $TiO_2$ and NiO. It seems reasonable to suppose that NiO could act as unstabilizer to the oxide film and could be dissolved preferentially. Therefore, nickel oxide contained in the passive film may promote the dissolution of the film, and it could be explained the reason of higher pitting susceptibility of TiNi alloy than pure Ti.

• 한국분말재료학회지
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• 제2권2호
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• pp.142-148
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• 1995

2219 aluminum alloy bonded diamond wheels containing intermetallic compounds were fabricated by powder metallurgy method. Nickel and titanium were added in aluminum matrix piece. The hot pressing condition was $600^{\circ}C$ and 20 Mpa in the furnace of the electric resistance type. The mechanical properties and grinding tests were carried out to confirm the wheel performance. Aluminum oxide ceramics were chosen for use in the grinding tests. The test proved that the heat resistance 2219 aluminum bonded diamond wheel containing 15 wt% nickel and 15 wt% titanium respectively showed the best performance.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.172-177
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• 2015

PURPOSE. The purpose of this study was to evaluate cell toxicity due to ion release caused by galvanic corrosion as a result of contact between base metal and titanium. MATERIALS AND METHODS. It was hypothesized that Nickel (Ni)-Chromium (Cr) alloys with different compositions possess different corrosion resistances when contacted with titanium abutment, and therefore in this study, specimens ($10{\times}10{\times}1.5mm$) were fabricated using commercial pure titanium and 3 different types of Ni-Cr alloys (T3, Tilite, Bella bond plus) commonly used for metal ceramic restorations. The specimens were divided into 6 groups according to the composition of Ni-Cr alloy and contact with titanium. The experimental groups were in direct contact with titanium and the control groups were not. After the samples were immersed in the culture medium - Dulbecco's modified Eagle's medium[DMEM] for 48 hours, the released metal ions were detected using inductively coupled plasma mass spectrometer (ICP-MS) and analyzed by the Kruskal-Wallis and Mann-Whitney test (P<.05). Mouse L-929 fibroblast cells were used for cell toxicity evaluation. The cell toxicity of specimens was measured by the 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyltetrazolium bromide (MTT) test. Results of MTT assay were statistically analyzed by the two-way ANOVA test (P<.05). Post-hoc multiple comparisons were conducted using Tukey's tests. RESULTS. The amount of metal ions released by galvanic corrosion due to contact between the base metal alloy and titanium was increased in all of the specimens. In the cytotoxicity test, the two-way ANOVA showed a significant effect of the alloy type and galvanic corrosion for cytotoxicity (P<.001). The relative cell growth rate (RGR) was decreased further on the groups in contact with titanium (P<.05). CONCLUSION. The release of metal ions was increased by galvanic corrosion due to contact between base metal and titanium, and it can cause adverse effects on the tissue around the implant by inducing cytotoxicity.

• 대한치과교정학회지
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• 제36권5호
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• pp.349-359
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• 2006

니켈-티타늄 합금은 높은 spring-back성질, 초탄성 효과, 형상기억 효과 등의 장점을 가지고 있으나 성형이 어렵다는 단점을 가지고 있다. 본 연구에서는 니켈-티타늄 와이어의 굴곡을 위한 열처리 시에 나타나는 부하-변위 곡선의 변화 및 상전이 온도 변화와 같은 물성 변화 양상을 조사하고자 하였다. 수종의 니켈-티타늄 와이어를 열처리를 시행하지 않은 군, 전기저항 열처리 장치를 이용하여 와이어 단면적에 따라 제조회사에서 권장하는 전류를 기초로 하여 $00.016"\;{\times}\;00.022"$ (5 A, 7 sec), $0.018"\;{\times}\;0.025"$ (6 A, 7 sec) 그리고 $0.0215"\;{\times}\;0.028"$ (7 A, 8 sec) 와이어를 열처리만 시행한 실험군, 열처리를 시행하여 굴곡을 부여한 실험군 그리고 열처리 시간을 1초 증가시켜 굴곡을 부여한 실험군으로 분류하여 3점 굴곡 실험과 시차주사열량측정을 하여 다음과 같은 결과를 얻었다. $0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ 그리고 $0.0215"\;{\times}\;0.028"$ 니켈-티타늄 와이어에서 굴곡을 부여하지 않고 열처리만 시행한 실험군이 열처리를 시행하지 않은 대조군에 비해 부하-변위 곡선이 상방 이동되어 초탄성 현상에 의한 평탄역(loading and unloading plateau)의 힘이 더 증가되었다. $0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ 그리고 $0.0215"\;{\times}\;0.028"$ 와이어에서 열처리만 시행한 실험군이 열처리를 시행하지 않은 군보다 더 낮은 austenite finish ($A_f$) 온도를 보였다. $0.018"\;{\times}\;0.025"$ 및 $0.0215"0.028"$ 와이어에서 열처리를 시행하여 굴곡을 부여한 실험군은 열처리만 시행한 실험군과 열처리를 시행하지 않은 대조군에 비해 부하-변위 곡선이 상방 이동되었으며, 열처리 시간을 1초 증가시켜 굴곡을 부여한 실험군에서 가장 높은 부하-변위 곡선을 나타냈다. $0.018"\;{\times}\;0.025"$ 그리고 $0.0215"\;{\times}\;0.028"$ 와이어에서 $A_f$ 온도는 열처리 시간을 1초 증가시켜 굴곡을 부여한 실험군에서 가장 낮게 관찰되었고 열처리를 시행하여 굴곡을 부여한 실험군, 열처리만 시행한 실험군 그리고 열처리를 시행하지 않은 대조군 순으로 높게 관찰되었다. 이상의 결과를 종합할 때, 임상에서 니켈-티타늄 합금 와이어에 굴곡을 부여하기 위해 열처리하는 경우 초탄성 특성은 유지될 수 있으나, 부하-변위 곡선의 상방 증가가 나타나므로, 와이어에 의한 교정력이 증가될 수 있음에 유의하여야 한다.

• 대한치과보철학회지
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• 제41권1호
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• pp.89-98
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• 2003

Titanium requires special ceramic system for veneering. Low fusing dental ceramics with coefficients of thermal expansion matching that of titanium have been developed. The purpose of this study was determine the bond strengths between cast and noncast pure titanium and two commercial titanium porcelains, and to compare the results with a conventional nickel-chromium alloy-ceramic system. The bond strengths were determined using a 3-point flexure test. Three-point flexure specimens $25{\times}3{\times}0.5mm$ were prepared After removal of ${\alpha}-case$ layer, they were veneered with $8{\times}3{\times}1mm$ of ceramics at the center of the bar. Specimens were tested in a universal testing machine. Within the limits of this study, the following conclusions were drawn: 1. The bond strengths between pure titanium and two commercial porcelains exceeded th lower limit of the bonding strength value in ISO 9693(25MPa). 2. There was no significant difference between cast and noncast titanium-porcelain bonds. 3. There was no significant difference between two commercial titanium porcelains. 4. The bond strengths of the titanium-porcelain systems ranged from 73% to 79% of that of the Ni-Cr-conventional porcelain system.

• 한국재료학회지
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• 제14권12호
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• pp.857-862
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• 2004

Production of titanium powder directly from tantalum oxides ($TiO_2$) pellet through an electronically mediated reaction (EMR) by calciothermic reduction has been investigated. Feed material ($TiO_2\;pellet$) and reductant (Ca-Ni alloy) were charged into electronically isolated locations in a molten calcium chloride ($CaCl_2$) bath at $950^{\circ}C$. The current flow through an external circuit between the feed (cathode) and reductant (anode) locations was monitored during the reduction of $TiO_2$. The current approximately 3.2A was measured during the reaction in the external circuit connecting cathode and anode location. After the reduction experiment, pure titanium powder with low nickel content was obtained even though Ca-Ni alloy was used as a reductant. These results demonstrate that titanium powder can be produced without direct physical contact between the feed and reductant. In certain experimental conditions, pure titanium powder with approximately $99.5\;mass\%$ purity was successfully obtained.

• International Journal of Computer Science & Network Security
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• 제23권2호
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• pp.183-192
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• 2023

Radiofrequency ablation (RFA) is an alternative treatment for liver cancer to the surgical intervention preferred by surgeons. However, the main challenge remains the use of RF for the ablation of large tumours (i.e., tumours with a diameter of >3 cm). For large tumours, RFA takes a large duration in the ablation process compared with surgery, which increases patient pain. Therefore, RFA for large tumours is not preferred by surgeons. The currently materials used in RF electrodes, such as the nickeltitanium alloy (nitinol), are characterized by low thermal and electrical conductivities. On the other hand, the use of materials that have high thermal and electrical conductivities, such as titanium aluminide alloy (gamma titanium), produces more thermal energy for tumours. In this paper, we developed a cool-tip RF electrode model that uses nickel-titanium alloy and replaced it with titanium aluminide alloy by using the finite element model (FEM). The aim of this paper is to study the effect of the thermal and electrical conductivities of gamma titanium on the ablation volume. Results showed that the proposed design of the electrode increased the ablation rate by 1 cm³ /minute and 6.3 cm³/10 minutes, with a decrease in the required time ablation. Finally, the proposed model reduces the ablation time and damages healthy tissue while increasing the ablation volume from 22.5% cm³ to 62.5% cm³ in ten minutes compared to recent studies.

• Restorative Dentistry and Endodontics
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• 제22권2호
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• pp.659-669
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• 1997

The goals of root canal instrumentation are complete debridement of pulp tissue, removal of microbes and affected dentin, and proper cleaning and shaping of the root canal space before obturation. Instrumentation with stainless steel files has been shown to produce undesirable results in canals, regardless of the improved technique or modified file type used. Nickel-Titanium(Ni-Ti) alloy has been shown to be exceptionally elastic, having a lower bending moment and lower permanent set after torsion, compared with similar gauge stainless steel. The purpose of this study was to evaluate the change of root canal prepared by Ni-Ti rotary and stainless steel instruments. Thirty-four single rooted teeth of similar shape and canal size were divided into three groups. The teeth were scanned by computed tomography before instrumentation. In group 1, canals were instrumented using a step-back technique with K-file. In group 2, canals were prepared with K-flex file using the same technique as group 1. Group 3 was prepared with nickel-titanium(Ni-Ti) rotary instrument using a manufacture's instruction. Instrumented teeth were again scanned using computed tomography, and reformated images of the uninstrumented canals were compared with images of the instrumented canals. K-flex file and Ni-Ti file caused significantly less canal transportation than K-file in the 8mm root canal section from the apex(p<0.05). K-flex file and Ni-Ti file produced more centered canal preparation than K-file in the 2mm section(p<0.05). Ni-Ti file maintained more precisely the center of the canal than K-flex file in the 10mm section (p<0.05). There was no difference in the removed volume of canals among each groups.