The dissolution of nickel from nitinol alloy under different extraction conditions was investigated when biological tests of nitinol medical devices were carried out. It discussed the equivalence of these extraction conditions and found the best extraction conditions. In the experiment, two brands of nitinol were chosen and extracted under different extraction conditions according to GB/T 16886-12. Plasma emission spectrometer was used to analyse the concentration of nickel in extract liquid. The results show that there is no equivalence among these extraction conditions for nitinol materials. And it is suggested that (37 +/- 1) degree C, (72 +/- 2) h could be used as normal extraction condition and (70 +/- 2) degrees C, (24 +/- 2) h as accelerated extraction condition.
Alloys ; chemistry ; Biocompatible Materials ; Materials Testing ; Nickel ; chemistry ; Temperature ; Titanium

The corrosion rates of TiNi, CoCrNiW and CoCrNiMo were measured in Tyrode's solution with potentiodynamic linear polarization, fore-point weak polarization, Cao Chunan weak polarization, transient linear polarization and atomic absorption spectroscopy. Results indicated that corrosion rates of these three alloys were very low due to their excellent corrosion resistance and the corrosion resistance of CoCrNiMo was the best. Corrosion rates of TiNi, CoCrNiW and CoCrNiMo were 0.691, 0.0595, 0.0490 micron/a and 0.0528, 0.0383, 0.0387 micron/a, respectively. The results measured by the first three methods were about ten times of those by the latter two methods, this was related to the applicability of each method and the alloy surface state. Transient linear polarization technique can determine low corrosion rate conveniently and quickly. Atomic absorption spectroscopy method, determining directly the concentration of ion in solution, and thus provide reference for material biocompatibility. And these two methods are properly used in measuring corrosion rates for biomedical materials.
Biocompatible Materials ; chemistry ; Cobalt ; chemistry ; Corrosion ; Materials Testing ; methods ; Nickel ; chemistry ; Spectrophotometry, Atomic ; Titanium ; chemistry

Exposed to neutron flow, the phosphorus implanted TiNi alloy gets radioactive. This radioactive material is used in vascular stent for prevention and cure of restenosis. Phosphorus implantation is carried out in a plasma immerged ion implantation system, and the dose of phosphorus implantation is in the range of 2-10 x 10(17) cm-2. After ion implantation, the alloy is exposed to the slow neutron flow in a nuclear reactor, the dose of the slow neutron is 1.39-5.88 x 10(19) n/cm2. The radioactivity of the TiNi alloy was measured by liquid scintillation spectrometry and radio-chromic-film dosimetry. The result shows that whether the phosphorus is implanted or not, the TiNi alloy comes to be radioactive after exposure to neutron flow. Just after neutron irradiation, the radiation dose of phosphorus implanted TiNi alloy is about one hundred times higher than that of un-phosphorus implanted TiNi alloy. The radiation difference between phosphorus and un-phosphorus implanted alloy decreases as time elapses. Within three months after neutron irradiation, the average half-decay period of phosphorus implanted TiNi alloy is about 62 days. The radiation ray penetration of phosphorus implanted TiNi alloy is deeper than that of pure 32P; this is of benefit to making radiation uniformity between stent struts and reducing radiation grads beyond the edge of stent.
Alloys ; chemistry ; Blood Vessel Prosthesis ; Nickel ; chemistry ; Phosphorus Radioisotopes ; chemistry ; Radiation Dosage ; Titanium ; chemistry

BACKGROUNDThe shape memory effect of nickel-titanium (NiTi) archwires is largely determined by the phase transition temperature. It is associated with a reversible transformation from martensite to austenite. The aim of this study was to characterize austenite, martensite and R phase temperatures as well as transition temperature ranges of the commonly used clinical NiTi orthodontic arch wires selected from several manufacturers.

METHODSDifferential scanning calorimetry (DSC) method was used to study the phase transformation temperatures and the phase transition processes of 9 commonly used clinical NiTi alloys (types: 0.40 mm (0.016 inch), 0.40 mm x 0.56 mm (0.016 inch x 0.022 inch)).

RESULTSThe austenite finish temperatures (Af) of 0.40 mm Smart, Ormco and 3M NiTi wires were lower than the room temperature, and no phase transformation was detected during oral temperature. Therefore, we predicted that these types of NiTi did not possess shape memory property. For 0.40 mm and 0.40 mm x 0.56 mm Youyan I NiTi wires, no phase transformation was detected during the scanning temperature range, suggesting that these two types of wires did not possess shape memory either. The Af of 0.40 mm x 0.56 mm Smart, L&H, Youyan II Ni-Ti wires were close to the oral temperature and presented as martensitic-austenitic structures at room temperature, suggesting the NiTi wires listed above have good shape memory effect. Although the 0.40 mm x 0.56 mm Damon CuNiTi wire showed martensitic-austenitic structures at oral temperature, its Af was much higher than the oral temperature. It means that transformation from martensite to austenite for this type of NiTi only finishes when oral temperature is above normal.

CONCLUSIONThe phase transformation temperatures and transformation behavior varied among different commonly used NiTi orthodontic arch wires, leading to variability in shape memory effect.

Calorimetry, Differential Scanning ; Dental Alloys ; chemistry ; Nickel ; chemistry ; Orthodontic Wires ; Temperature ; Titanium ; chemistry

Various engine-driven NiTi endodontic files have been indispensable and efficient tools in cleaning and shaping of root canals for practitioners. In this review, we introduce the relative terms and conceptions of NiTi file, including crystal phase composition, the design of the cutting part, types of separation. This review also analysis the main improvement and evolution of different generations of engine-driven nickel-titanium instruments in the past 20 years in the geometric design, manufacturing surface treatment such as electropolishing, thermal treatment, metallurgy. And the variety of motion modes of NiTi files to improve resistance to torsional failure were also discussed. Continuous advancements by the designers, provide better balance between shaping efficiency and resistance to of NiTi systems. In clinical practice an appropriate system should be selected based on the anatomy of the root canal, instrument characteristics, and operators' experience.
Dental Alloys/chemistry* ; Dental Instruments ; Equipment Design ; Nickel/chemistry* ; Root Canal Preparation ; Titanium/chemistry*

OBJECTIVEThe aim of this study is to determine the electrochemical corrosion characteristics of Ni-Cr alloys in vitro.

METHODSThe electrochemical corrosion behavior of Ni-Cr alloys was studied by polarization curves in artificial saliva at 36.5 degrees C (pH = 7.0) to measure the corrosion potential and self-corrosion current density. With X-ray photoelectron spectroscopy, the element content was analyzed.

RESULTSIt was found that the dot corrosion voltage of Ni-Cr was -390 mv, and passivation voltage -160 mv. The area of active dissolvation was from -160 mv to -270 mv. The self-corrosion current density is 0.262 micro Acm(-2). From XPS, the content of Ni, Cr, Mo, Fe was increasing gradually, and the content of O, C was decreasing gradually. The content of Ca decreased because Ca existed in the artificial saliva.

CONCLUSIONAfter polarization curve test, Ni-Cr alloy would occur corrosive reaction, and the corrosion product would attach to the surface of the material.

Chromium Alloys ; chemistry ; Corrosion ; Electrochemistry ; In Vitro Techniques ; Nickel ; chemistry ; Saliva, Artificial ; chemistry

Medical metal materials is widely used in medical field due to its excellent properties; the nickel ions leaching from stainless steel because of corrosion have the harmfulness of malformation and cancerization besides allergenicity in human body. Potential harmfulness of nickel in medical metal materials and new trend on research and development are reviewed in this paper, and both the advantage and the long term potential development of nickel-free medical stainless steels are also described on the basis of our own research work.
Corrosion ; Humans ; Materials Testing ; Nickel ; adverse effects ; chemistry ; Stainless Steel ; chemistry ; Titanium ; adverse effects ; chemistry

OBJECTIVEPurpose of the study was to investigate the content of Nickel (Ni) and Chromium (Cr) ion in gingival tissue and blood, and to discuss the reason of gray line in gingival after wearing non-noble Porcelain-Fused-to-Metal crown.

METHODS38 rabbits were selected as experimental animals which were divided into three groups: control group, group 1 (3 months) and group 2 (6 months). The content of Ni and Cr ion in gingival tissue and blood was detected by atomic absorption spectrometer.

RESULTSThe amount of Ni and Cr in group 2 was significantly higher than that in other groups (P < 0.05) . There was no difference between group 1 and control group (P > 0.05) .

CONCLUSIONThe reason of gingival colouration might be the electrochemical corrosion. The metal ion was released in gingival tissue and blood.

Animals ; Chromium ; blood ; chemistry ; Crowns ; Dental Porcelain ; Gingiva ; chemistry ; Hares ; Nickel ; blood ; chemistry

OBJECTIVETo investigate the mechanical properties of Ni-Ti wires with direct electric resistance heat treatment (DERHT) method in three-point bending tests.

METHODSTwo superelastic Ni-Ti wires (wire A: Smart SE, wire B: SENTALLOY SE, 0.406 mm × 0.559 mm) and 2 heat-actived Ni-Ti wires (wire C: Smart SM, wire D: L&H TITAN, 0.406 mm × 0.559 mm) were selected. They were heat-treated using the DERHT method by a controlled electric current (6.36 A) applied for different period of time [0 (control), 1.0, 1.5, 2.0, 2.5 seconds). Then, a three-point bending test was performed under controlled temperature (37°C) to examine the relationships between the deflection and the load in the bending of wires.

RESULTSAfter DERHT treatment, the plateau in the force-deflection curve of superelastic Ni-Ti wires and heat-activated Ni-Ti wires were increased. When the wires were heated for 2.0 seconds and deflected to 1.5 mm, the loading force of A, B, C and D Ni-Ti wires increased from (3.85 ± 0.11), (3.62 ± 0.07), (3.28 ± 0.09), (2.91 ± 0.23) N to (4.33 ± 0.07), (4.07 ± 0.05), (4.52 ± 0.08), (3.27 ± 0.15) N respectively.

CONCLUSIONSDERHT method is very convenient for clinical use. It is possible to change the arch form and superelastic force of NiTi wires. The longer the heating time is, the more the superelastic characteristics of the wires are altered.

Dental Stress Analysis ; Elasticity ; Hot Temperature ; Materials Testing ; Nickel ; chemistry ; Orthodontic Wires ; Stress, Mechanical ; Titanium ; chemistry

OBJECTIVETo evaluate the biological safety of compound galvano-ceramic bridge by measuring the consistency of released nickel ion of the galvano-form slices cohered with Ni-Cr alloy slice specimens which were immersed in artificial saliva.

METHODSSpecimens were divided into five groups with four tests and one control. Test specimens were made into the structure like rectangle sandwich that one side of Ni-Cr alloy was cohered to the center surface of galvano golden base of 0.2 mm and another side was fused porcelain with the thickness of 0.3 mm (group A), 0.5 mm (group B), 1.0 mm (group C), and 0.3 mm (group D). And the Ni-Cr alloys were totally embedded in galvano golden base and firing porcelain. Naked Ni-Cr alloy was taken as control. Group D was immersed into acid artificial saliva (AS) with high fluoride, while others were in acid AS at 37 degrees C for 120 h. Then the consistency of released nickel ion in the solution was measured with inductively coupled plasma-atomic emission spectrometry (ICP-AES).

RESULTSNickel ions detected in the artificial saliva for the groups A, B, C, and D in acid AS with or without high fluoride were all under 0.005 mg/L Significant differences were found between each test group and the control [(0.65 +/- 0.45) mg/L].

CONCLUSIONSGalvano-ceramic bridge, Ni-Cr alloy bridge with fused porcelain and golden base, shows biological safety responsible for the consistency of released nickel ion.

Biocompatible Materials ; chemistry ; Dental Materials ; Materials Testing ; Metal Ceramic Alloys ; chemistry ; Nickel ; analysis