Uncoated Wires Research Articles

An investigation into the mechanical and aesthetic properties of new generation coated nickel-titanium wires in the as-received state and after clinical use

The purpose of this study was to compare the mechanical, structural, and aesthetic properties of two types of aesthetic coated nickel-titanium (NiTi) wires compared with comparable regular NiTi wires in the as-received state and after clinical use. Sixty one subjects were randomly assigned to four groups (N = 61), two groups of coated wires and two groups of comparable, non-coated controls (n = 15/group). The period in the mouth ranged from 4 to 12 weeks after insertion. In total, 121 wires (61 retrieved and 60 as-received) were used in the study. The percentages of coating retention and loss were extrapolated from scans. A brief survey of five questions with three choices was given to all patients. Differential scanning calorimetry (DSC) and three-point bending tests were done on as-received and used wires. The surface characterization by the percentage of resin remaining indicated that most wires in both test groups lost a significant amount of coating. A patient survey indicated that this was a noticeable feature for patients. DSC analysis of the wires indicated that the metallurgical properties of the coated wires were not similar to the uncoated wires in the as-received condition. Three-point bending results indicate a wide variation in test results with large standard deviations among all the groups. The extent of coating loss requires investigating, as do the biological properties of the detached coating. Both wires lost a significant amount of aesthetic coating after varying periods in the mouth. The metallurgical testing of these findings may indicate that these wires perform differently in the mouth.

Polymer coating of vanadium oxide nanowires to improve cathodic capacity in lithium batteries

Vanadium oxide is a promising next generation cathode material in lithium-based batteries because of its high theoretical energy density. To address the shortcomings of V2O5, which include poor electrical conductivity and stability upon cycling, a core–shell structure consisting of high aspect ratio V2O5 nanowires coated with electroactive polyaniline (PANI) was synthesized. The two step solution-based process involved a facile hydrothermal synthesis of one dimensional V2O5 and subsequent in situ polymerization on the active material surface. Conformal coatings of PANI were achieved at a range of compositions (21–51% by weight) by altering the polymerization conditions. The composite nanowire structure was shown to benefit cycle stability, demonstrating a 90% improvement in discharge capacity over the uncoated wires after 40 cycles at increasing rates of charge. Improvements in rate capability were also correlated with increasing percentages of PANI in the composite, where the 51% PANI composite demonstrated a 57% increase in capacity over an uncoated sample at the high rate of 440 mA g−1 (1 C). Here, we present evidence from galvanostatic cycling experiments that an electroactive polymer coating can enhance the underlying capacity of a cathode material.

The effect of Teflon coating on the resistance to sliding of orthodontic archwires

Teflon is an anti-adherent and aesthetic material. The aim of this study was to evaluate, in vitro, the influence of Teflon coating on the resistance to sliding (RS) of orthodontic archwires. For this purpose, Teflon-coated archwires were examined using frictional resistance tests by means of a universal testing machine and compared with conventional uncoated wires. Twelve types of archwires with round and rectangular sections (0.014, 0.018, and 0.018 × 0.025 inches) and of different materials (stainless steel and nickel-titanium) were tested with two passive self-ligating brackets (SmartClip™ and Opal(®)) and one active self-ligating bracket (Quick(®)). Each archwire-bracket combination was tested 10 times under 8 simulated clinical scenarios. Statistical comparisons were conducted between the uncoated and Teflon-coated archwires using Wilcoxon and Mann-Whitney tests, and linear regression analysis. For all bracket-archwire combinations, Teflon-coated archwires resulted lower friction than the corresponding uncoated archwires (P < 0.01). The results showed that Teflon coating has the potential to reduce RS of orthodontic archwires.

Productivity and Workpiece Surface Integrity When WEDM Aerospace Alloys Using Coated Wires

Following a brief review of recent minimum damage EDM pulse generator developments, experimental data is presented for workpiece productivity & integrity when WEDM Udimet 720 nickel based superalloy and Ti-6Al-2Sn-4Zr-6Mo titanium alloy, using Cu core coated wires (ZnCu50 and Zn rich brass). Up to a 70% increase in productivity was possible compared to when using uncoated brass wires with the same operating parameters. Surfaces measuring ∼ 0.6μm Ra, with near neutral residual stresses and almost zero recast were produced following two trim passes. Cross-sectional micrographs of specimens following rough machining (∼180mm2/min) showed the recast to be < 7μm thick (up to 11μm for uncoated wire), with comparable results for both alloys. Surface cracking, when evident, was restricted to within the recast layer.

Influence of Ni–P coating on fatigue life of an Al 2O 3f/Al composite wire

An Al 2O 3f/Al composite wire was Ni–P coated by means of an electroless plating route. Fatigue life and residual properties of the coated and uncoated composite wires were investigated. It was found that the fatigue life, residual strength and residual modulus of the composite wire could be improved by the Ni–P coating, indicating that Ni–P coating could increase the fatigue resistance of the composite wire. Finite-element analysis (FEA) was performed to understand the mechanism of the prolonged fatigue life. FEA indicated that Ni–P coating could both restore the load-bearing capability of broken surface fibers and reduce the stress and strain concentrations caused by broken fibers, hence resulting in a higher fatigue resistance of the Ni–P coated composite wire than that of the uncoated one.

Mechanical properties of coated superelastic archwires in conventional and self-ligating orthodontic brackets

Coated archwires have been introduced to improve esthetics during orthodontic treatment. Our aim was to investigate the mechanical properties of coated superelastic archwires compared with conventional superelastic archwires with conventional and self-ligating brackets. Four types of orthodontic archwires were investigated, 2 superelastic nickel-titanium and 2 coated Ultraesthetic archwires in 0.016-in and 0.018 x 0.025-in dimensions (all from G&H Wire, Greenwood, Ind). To achieve the same nominal size, the coated archwire is constructed from a smaller archwire that, when coated, reaches the nominal dimensions stated for the archwire. Conventional edgewise Orthos and Damon 2 self-ligating brackets (both from Ormco, Orange, Calif) were used with each wire. All specimens were tested in a universal testing machine in a 3-point bending test at a speed of 1 mm per minute and deflected for 2 mm. Loading and unloading forces were recorded and load-deflection curves plotted. Coated superelastic wires produced statistically significantly lower forces in loading and unloading when compared with the superelastic nickel-titanium wires at most archwire deflections (P <0.01). For nickel-titanium wires, loading values ranged from 189 to 1202 g, whereas the respective values for coated wires were 124 to 772 g. For all wires, an increase in size resulted in an increase in force. Interactions between wire type (coated or uncoated) and bracket type were observed. Ultraesthetic coated archwires produced lower force values in loading and unloading compared with uncoated wires of same nominal size. The Damon 2 self-ligating bracket system produced lower force values in loading and unloading. The lowest forces were generated by the combination of Ultraesthetic coated archwires and Damon 2 self-ligating brackets.

Improved orthodontic stainless steel wires coated with inorganic fullerene-like nanoparticles of WS 2 impregnated in electroless nickel–phosphorous film

Objective To reduce friction between orthodontic stainless wires and bracket by coating the wire with nickel–phosphorous electroless film impregnated with inorganic fullerene-like nanoparticles of tungsten disulfide (IF-WS 2) which are potent dry lubricants. Methods Coating was preformed by inserting stainless steel (SS) wires into electroless solutions of nickel–phosphorus (Ni–P) and IF-WS 2. The coated wires were analyzed by SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectrometer) as well as by tribological tests using a ball-on-flat device. Friction tests simulating archwire functioning of the coated and uncoated wires were carried out by an Instron machine. The adhesion properties of the coated wires after friction were analyzed by a Raman microscope. Results SEM/EDS analysis of the coated wires showed clear impregnation of the IF-WS 2 nanoparticles in the Ni–P matrix. The friction coefficient measured by the ball-on-flat tribometer was significantly reduced (from 0.25 to 0.08). The friction forces as measured with the Instron on the coated wire were reduced by up to 54% (4.00 N ± 0.19 uncoated vs. 1.85 N ± 0.21 coated). Raman spectra showed that even after extensive friction tests the Ni–P with the IF-WS 2 nanoparticles is attached to the underlying stainless steel wire. Conclusions It is proposed that the wires coated with these nanoparticles might offer a novel opportunity to substantially reduce friction during tooth movement. A few tests undertaken to evaluate the toxicity of the fullerene-like nanoparticles have provided indications that they might be biocompatible.

Semi-empirical model of efficiency of wire electrical discharge machining of hard-to-machine materials

In this study, the efficiency of wire electrical discharge machining of hard-to-machine materials was investigated experimentally. Uncoated brass wire, 0.25 mm diameter, zinc oxide coated brass wire and brass CuZn20 coated brass CuZn50 wire were utilized in the conducted research. The following variables were chosen as important WEDM parameters: discharge time t on, average working voltage U. The following properties of machined materials, such as: melting point T t, electrical conductivity σ, thermal conductivity K, thermal expansion coefficient k, density ρ, heat capacit y c p , were selected to develop the semi-empirical model of volumetric efficiency of WEDM . The variation of the WEDM efficiency in cutting different materials and applying different wire electrodes and different process parameters was modelled semi-empirically by employing dimensional analysis.

Surface Modification of Orthodontic Wires with Photocatalytic Titanium Oxide for its Antiadherent and Antibacterial Properties

To test the antiadherent and antibacterial properties of surface modification of orthodontic wires with photocatalytic titanium oxide (TiO(2)). TiO(2) was coated on the surface of the orthodontic wires by a sol-gel thin film dip-coating method. Bacterial adhesion to the wires was evaluated by the weight change of the wires. The antibacterial activity of the surface-modified orthodontic wires was demonstrated by the dilution agar plate method for Streptococcus mutans and spectrophotometry for Porphyromonas gingivalis. The orthodontic wires coated with the photocatalytic TiO(2) showed an antiadherent effect against S. mutans compared with the uncoated wires. The bacterial mass that bound to the TiO(2)-coated orthodontic wires remained unchanged, whereas that of the uncoated wires increased by 4.97%. Furthermore, the TiO(2)-coated orthodontic wires had a bactericidal effect on S. mutans and P. gingivalis, which cause dental caries and periodontitis, respectively. The antiadherent and antibacterial mechanisms of TiO(2) to break down the cell wall of those bacteria were revealed by scanning electron microscopy. The surface modification of orthodontic wires with photocatalytic TiO(2) can be used to prevent the development of dental plaque during orthodontic treatment.

Energy efficient graphite–polyurethane electrically conductive coatings for thermallyactuated smart materials

The concept of graphite–polyurethane coatings as efficient, electrical resistors is the focus of thispaper. A 60–40 graphite–polyurethane mix (weight %) demonstrated an electrical resistivity of40.71 Ω mm. The graphite–polyurethane mix was coated on electrically insulating Kaptontape, which was then wrapped on a nichrome wire (nominal dimensions: 100 mmlength and 1.5 mm diameter). This three-phase assembly was heated by Jouleheating of the graphite–polyurethane layer. Steady state temperatures as high as180 °C were attained under free convection conditions, at a very low power requirement of about2.5 W as opposed to about 18 W for uncoated wires. Interestingly, the effect on transients(heating and cooling times) was not as dramatic. Experiments were also performed undervacuum conditions, following which an analysis is offered regarding the different modes ofheat transfer. These coatings can potentially be used as efficient resistors forhighly conductive, moderately high temperature shape memory alloys (e.g. thecopper–aluminium–nickel system) or electrically insulating shape memory polymers. Anyother thermally activated shape memory alloy (e.g. the popular nickel–titanium system)may also use the coatings as resistors due to the potentially dramatic energy savings thatmay be realized without a dramatic adverse impact on the frequency response.

Enhancement of the Bulbocavernosus Reflex During Intraoperative Neurophysiological Monitoring through the Use of Double Train Stimulation: A Pilot Study

Electrophysiological bulbocavernosus reflex (BCR) testing, during surgeries in which the constituent neural components are at risk, might supplement other low sacral (S2-4) stimulation/recording techniques. However, intraoperative BCR is not always reliably implemented. We proposed to analyze BCR signals in five surgical patients monitored with the novel application of double train stimulation (DTS) to determine if the potential could be enhanced. We prospectively planned a regime of DTS BCR with a series of intertrain delays in five monitored patients at risk for low sacral neural injury. Patients were maintained with propofol, opiate infusion, and low inhalant anesthesia without muscle relaxant. Cutaneous sensory nerves of the penis (or clitoris) were stimulated using two consecutive pulse trains (DTS). Intertrain delays were 75, 100, 125, 150, 175, 200, and 250 ms. For BCR recording, uncoated paired wires were inserted into the external anal sphincter (EAS) bilaterally. For each trial, waveform amplitude, duration, and turn count measures for the first (single train) and second (double train) response were recorded. Percent increase/decrease of the second train response compared to the first train response was calculated. There was at least a 30% increase in measures of amplitude, turn count, and duration of the second train response in 22/28, 22/28, and 14/28 of the total trials respectively. There was an insufficient number of independent observations to determine statistical significance. Intraoperative BCR is currently obtained with some difficulty using pulse train stimulation. Our preliminary evidence has identified BCR waveform enhancement using DTS and suggests that the reliability of intraoperative BCR acquisition may be further improved by the addition of this technique. Our data are insufficient to define the best intertrain interval.

Lubrication performance of diamond-like carbon and fluorinated diamond-like carbon coatings for intravascular guidewires

Diamond-like carbon (DLC) and fluorinated DLC (F-DLC) films were deposited on SUS316L guidewires using radio frequency (RF) plasma enhanced chemical vapor deposition (CVD), and the lubrication performance of DLC- or F-DLC-coated guidewires was then evaluated under in vitro conditions using a novel friction simulator developed for this study. Scanning electron microscopy (SEM) demonstrated that DLC or F-DLC film completely coated the specimens (SUS316L guidewires) and that polishing scars were substantially reduced. In the torturous vessel model, DLC- or F-DLC-coated guidewires exhibited significantly improved lubrication performance (by approximately 30% over that of uncoated wires). DLC and F-DLC films are thus promising candidates for lubricious coating of intravascular guidewires.

Systemic versus local application of gentamicin in prophylaxis of implant-related osteomyelitis in a rat model

Administration of perioperative antibiotic prophylaxis is a routine procedure in orthopedic surgery. Besides systemic prophylaxis, only few techniques are established for local application of antibiotics to reduce infection related to orthopedic implants. The aim of this study was to evaluate the efficacy of locally versus systemically applied gentamicin in a rat model ( n = 60). For local application, the antibiotic was delivered from a biodegradable poly( d, l-lactide) (PDLLA) coating of titanium implants. The efficacy of local prophylaxis was compared to a systemic single shot application of gentamicin as well as a combination of both administrations. Half of the animals received a weight-adopted single shot application of gentamicin 30 min prior to surgery. At surgery, the medullary cavities of the tibiae were contaminated with Staphylococcus aureus (10 2 colony forming units /CFU) and titanium Kirschner wires were implanted into the medullary canals. The implants were either uncoated, PDLLA coated, or coated with PDLLA + 10% w/w gentamicin. The animals were followed up for 42 days. X-ray examinations were performed; body weight, temperature, and the clinical condition were determined. After sacrifice, infection was evaluated by histological and microbiological analysis. All animals treated with uncoated or PDLLA-coated Kirschner wires without systemic application of the antibiotic developed osteomyelitis and all cultures of implants were tested positive on S. aureus. Implant-related osteomyelitis could be prevented by prophylaxis of systemically applied gentamicin in 15% of animals. In contrast, local application of gentamicin delivered from a PDLLA coating was more effective. Onset of infection could be prevented in 90% of animals treated with gentamicin coated Kirschner wires, and in 80% of the animals that were treated with a combination of local and systemic application. The local application from PDLLA-coated implants might support systemic antibiotic prophylaxis in preventing implant-associated osteomyelitis.

Compensation of magnetic field distortions from paramagnetic instruments by added diamagnetic material: Measurements and numerical simulations

In minimally invasive procedures guided by magnetic resonance (MR) imaging instruments usually are made of titanium or titanium alloys (e.g., nitinol), because other more MR-compatible materials often cannot provide sufficient mechanical properties. Artifacts depending on susceptibility arise in MR images due to incorrect spatial encoding and intravoxel dephasing and thereby hamper the surgeon's view onto the region of interest. To overcome the artifact problem, compensation of the paramagnetic properties by diamagnetic coating or filling of the instruments has been proposed in the literature. We used a numerical modeling procedure to estimate the effect of compensation. Modeling of the perturbation of the static magnetic field close to the instruments reflects the underlying problem and is much faster and cost efficient than manufacturing prototypes and measuring artifact behavior of these prototypes in the MR scanner. A numerical model based on the decomposition of the susceptibility distribution in elementary dipoles was developed by us. The program code was written object oriented to allow for both maximum computational speed and minimum random access memory. We used System International units throughout the modeling for the magnetic field, allowing absolute quantification of the magnetic field disturbance. The field outside a simulated needlelike instrument, modeled by a paramagnetic cylinder (out of titan, chi =181.1) of length 8.0 mm and of diameter 1.0 mm, coated with a diamagnetic layer (out of bismuth, chi=-165.0) of thickness 0, 0.1, 0.2, 0.3, and 0.4 mm, was found to be best compensated if the cross-sectional area of the cylinder, multiplied by the absolute susceptibility value of the cylinder material, is equal to the cross-sectional area of the coating, multiplied by the absolute susceptibility value of the coating material. At the extremity of the coated cylinder an uncompensated field distortion was found to remain. We studied various tip shapes and geometries using our computational model: Suitable diamagnetic coating or filling of paramagnetic instruments clearly reduced tip artifacts and diminished the dependency of artifact size on orientation of the instrument with respect to B0 in the numerical studies. We verified the results of the simulations by measuring coated and uncoated titanium wires in a 1.5 T MR scanner.

Gentamicin coating of metallic implants reduces implant-related osteomyelitis in rats

Antibiotic prophylaxis is a routine procedure in orthopedic surgery. Various local antibiotic delivery techniques are used to reduce bone- and soft tissue-related infection. The objective of this study was to evaluate the efficacy of a new biodegradable, gentamicin-loaded poly( d, l-lactide) (PDLLA) coating of orthopedic devices in preventing implant-related osteomyelitis. The medullary cavities of tibiae in 30 Sprague Dawley rats were contaminated with Staphylococcus aureus (10 3 colony forming units). Simultaneously titanium Kirschner wires, uncoated (group II), coated with PDLLA (group III), or coated with PDLLA + 10% gentamicin (group IV), were implanted. Ten animals that received phosphate-buffered saline and uncoated Kirschner wires served as controls (group I). Follow-up was 6 weeks. In weekly intervals X-rays of the tibiae were performed, blood counts were taken, and body temperature and weight were determined. After sacrifice infection was evaluated by histological and microbiological analysis. All animals of groups II and III developed microbiological, histological, and radiological signs of infection, including osseous destruction and soft tissue swelling. All animals of the control group remained sterile. Cultures of implants of group IV showed significantly reduced bacterial growth compared to cultures of groups II and III, and three implants of group IV remained sterile. Further radiological and histological signs of infection were significantly reduced in the gentamicin-coated group compared to groups II and III. No significant differences in body weight, body temperature, and blood parameters between all groups were observed. Local application of antibiotic-coated orthopedic devices containing PDLLA and 10% gentamicin significantly reduced implant-related infection in this animal model.

A novel approach for the adsorption of iodine-125 on silver wire as matrix for brachytherapy source for the treatment of eye and prostate cancer

The adsorption of iodine-125 on silver wire bits coated with palladium to be sealed in titanium capsules as brachytherapy sources was studied. A method was optimized to obtain quantitative adsorption of 125I on the palladium treated silver wires. A comparative evaluation of palladium coated and uncoated (bare) silver wires on the adsorption of 125I was made. While, the adsorption of bare silver wires showed low, inconsistent uptake (∼60%) of 125I with high leachability (∼4%), the Pd coated silver wires showed quantitative and consistent uptake of 125I (∼90%) and exhibited low leachability (0.01%). 125I adsorbed on Pd coated silver wires could be used as a matrix for the preparation of interstitial sources in eye and prostate cancer therapy.

Mechanical properties of electroless Ni/Au wire bonded to an Al pad with the effects of chemical activation

The mechanical properties of electroless nickel (EN) deposited onto pure gold (Au) wire used for the semiconductor industry have been investigated with the effects of the chemical activation, using the electrochemical quartz crystal microbalance (EQCM) technique, tensile, torsion and ball shear (BS) tests, and optical microscopy (OM). The combined results of in situ electrogravimetric curves with ex situ cross-sectional views obtained from the EN/Au composite wire clearly showed that EN deposits with the presence of pre-immersion Au were more rapidly formed on Au wire compared to the absence of the pre-immersion Au. This is presumably due to the surface roughness increased by the hydrogen evolution as validated from OM. The load–displacement curves for the pre-immersion Au-coated and uncoated Au wires prior to EN revealed that the elastic modulus value of the EN outer layer, E Ni, calculated on the basis of a linear elastic deformation model, was higher for the former than the latter. Moreover, it was found from the torsion and BS tests that the shear modulus of the EN, G Ni, and the shear strength of the composite wire bonded to the aluminum (Al) pad with the zincate pretreatment were greater than for wires without this pretreatment; the values increased with increasing zincate immersion time. Consequently, it can be stated that the tensile strength of the EN/Au composite wire and the bonding strength between the wire and the Al pad are effectively increased by the existence of the pre-immersion Au layer and the zincate pretreatment, respectively.

A new electrochemically graded hydroxyapatite coating for osteosynthetic implants promotes implant osteointegration in a rat model.

Hydroxyapatite (HAP) is widely used as an osteoconductive coating for orthopedic implants. So far standard coating methods like plasma spraying produce a relatively thick coating layer (>30 microm). In addition, the chemical structure of the HAP may be altered because of the heating throughout the coating process. This may have negative effects on the coating stability, implant fixation, and induction of bone formation. The relatively thick layer may detach from the implant with the risk of wear debris. In the present study the potential of a newly developed HAP coating of implants on osteointegration was investigated in a rat model. The coating method, based on an electrochemical process, is applied in a graded manner and results in a biodegradable HAP coating with a thickness of approximately 2 mum. Coated versus uncoated titanium Kirschner wires (1.4-mm diameter) were inserted into the medullary cavity of the right femora of 5-month old female Sprague Dawley rats (n=36) in a retrograde fashion. Throughout an experimental period of 2 months the osteointegration was traced radiologically. After this time the animals were sacrificed and the implant integration was tested biomechanically with the use of a push-out test. To analyze the bone-implant interface, histological sections (80 mum) were investigated with an image analyzing system. The biomechanical testing revealed a significantly higher implant fixation in the group treated with the HAP-coated implant (shear strength: 27.8 +/- 6.7 MPa) compared to control (shear strength: 8.08 +/- 3.4 MPa). The histological analyses demonstrated a better ingrowth of the implants in the HAP group with significantly more direct bone-implant contacts compared to the control group. The results demonstrate that the HAP coating promotes implant osteointegration in a rat model.

A new electrochemically graded hydroxyapatite coating for osteosynthetic implants promotes implant osteointegration in a rat model

Hydroxyapatite (HAP) is widely used as an osteoconductive coating for orthopedic implants. So far standard coating methods like plasma spraying produce a relatively thick coating layer (>30 μm). In addition, the chemical structure of the HAP may be altered because of the heating throughout the coating process. This may have negative effects on the coating stability, implant fixation, and induction of bone formation. The relatively thick layer may detach from the implant with the risk of wear debris. In the present study the potential of a newly developed HAP coating of implants on osteointegration was investigated in a rat model. The coating method, based on an electrochemical process, is applied in a graded manner and results in a biodegradable HAP coating with a thickness of approximately 2 μm. Coated versus uncoated titanium Kirschner wires (1.4-mm diameter) were inserted into the medullary cavity of the right femora of 5-month old female Sprague Dawley rats (n=36) in a retrograde fashion. Throughout an experimental period of 2 months the osteointegration was traced radiologically. After this time the animals were sacrificed and the implant integration was tested biomechanically with the use of a push-out test. To analyze the bone-implant interface, histological sections (80 μm) were investigated with an image analyzing system. The biomechanical testing revealed a significantly higher implant fixation in the group treated with the HAP-coated implant (shear strength: 27.8 ± 6.7 MPa) compared to control (shear strength: 8.08 ± 3.4 MPa). The histological analyses demonstrated a better ingrowth of the implants in the HAP group with significantly more direct bone-implant contacts compared to the control group. The results demonstrate that the HAP coating promotes implant osteointegration in a rat model. © John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 168–172, 2002; DOI 10.002/jbm.10130

Corrosion and permanent fracture resistance of coated and conventional orthodontic wires.

The corrosion processes are presumed to have negative consequences on biocompatibility, aesthetic appearance and the frictional behavior between the bracket and the guiding arch during orthodontic treatment. A group of new guiding arches are the coated orthodontic wires. The present in-vitro study investigated the corrosion behavior and permanent fracture resistance of eight coated wires of different dimensions. Five superelastic nickel titanium (NiTi) wires (Titanol Low Force River Finish Gold and Gold 2: Forestadent Corp.; Titanol Superelastic tooth colored: Forestadent Corp.; Bioforce Sentalloy longuard: GAC Corp.; NiTi Imagination: GAC Corp.), two beta-titanium-wires (TMA Low Friction longuard: Ormco Corp.; TMA Low Friction longuard Purple: Ormco Corp.) and one steel wire (Stainless Steel Imagination: GAC Corp.) were selected. For comparison reasons three uncoated arch wires (Rematitan Lite Dimple: Dentaurum Corp.; Titanol Low Force River Finish: Forestadent Corp.; Bioforce Sentalloy: GAC Corp.) were included in the investigation. Surface modifications were made of teflon, polyethylene and by ion implantation. The corrosion processes have been carried out by the use of a specialized electrochemical cell. In a second experimental series the wires were exposed to mechanical stresses. Finally, all wires were examined in a scanning electron microscope. The results indicated that teflon coating prevented the corrosion of the wires. As expected, the beta-titanium wires did not corrode either. The other wires showed rupture potentials between 187 mV and 602 mV (NHE). After mechanical stress testing the wires could be subdivided into three groups. In the first group no differences could be recognized, the second group showed changes in their crystallographic structure and in the last group the teflon coating was peeled off from the surface of the wires.