Nickel-titanium Wires Research Articles

A comparison of torque expression between stainless steel, titanium molybdenum alloy, and copper nickel titanium wires in metallic self-ligating brackets

The force moment providing rotation of the tooth around the x-axis (buccal-lingual) is referred to as torque expression in orthodontic literature. Many factors affect torque expression, including the wire material characteristics. This investigation aims to provide an experimental study into and comparison of the torque expression between wire types. With a worm-gear-driven torquing apparatus, wire was torqued while a bracket mounted on a six-axis load cell was engaged. Three 0.019 x 0.0195 inch wire (stainless steel, titanium molybdenum alloy [TMA], copper nickel titanium [CuNiTi]), and three 0.022 inch slot bracket combinations (Damon 3MX, In-Ovation-R, SPEED) were compared. At low twist angles (<12 degrees), the differences in torque expression between wires were not statistically significant. At twist angles over 24 degrees, stainless steel wire yielded 1.5 to 2 times the torque expression of TMA and 2.5 to 3 times that of nickel titanium (NiTi). At high angles of torsion (over 40 degrees) with a stiff wire material, loss of linear torque expression sometimes occurred. Stainless steel has the largest torque expression, followed by TMA and then NiTi.

Orthodontic forces released by low-friction versus conventional systems during alignment of apically or buccally malposed teeth

The aim of the present study was to analyse the forces released by passive stainless steel self-ligating brackets (SLBs) and by a non-conventional elastomeric ligature-bracket system on conventional brackets ([slide ligatures on conventional brackets (SLCB)]) when compared with conventional elastomeric ligatures on conventional brackets (CLCB) during the alignment of apically or buccally malposed teeth in the maxillary arch. An experimental model consisting of five brackets was used to assess the forces released by the three different bracket-ligature systems with 0.012-inch super-elastic (SE) nickel-titanium (NiTi) wires in the presence of different amounts of apical or buccal canine misalignment of the canine (ranging from 1.5 to 6 mm). The forces released by each wire/bracket/ligature combination with the three different amounts of apical or buccal canine misalignment were tested 20 times. Comparisons between the different types of wire/bracket/ligature systems were carried out by means of analysis of variance on ranks with Dunnett's post hoc test (P < 0.05). No difference in the amount of force released in presence of a misalignment of 1.5 mm was recorded among the three systems. At 3 mm of apical misalignment a significantly greater amount of orthodontic force was released by SLB or SLCB when compared with CLCB, while no significant differences were found among the three systems at 3 mm of buccal canine displacement. When correction of a large amount of misalignment (6 mm) was attempted, a noticeable amount of force for alignment was still generated by the passive SLB and SLCB systems while no force was released in presence of CLCB.

Nickel–titanium wire as a flexor tendon suture material: an ex vivo study

Nickel-titanium shape memory alloy (NiTi) is a new suture material that is easy to handle, is strong, and biocompatible. The purpose of this study was to evaluate the material properties and biomechanical behaviour of 150 microm and 200 microm NiTi wires in flexor tendon repair. Braided polyester (4-0 Ethibond) was used as control. Fifty fresh-frozen porcine flexor tendons were repaired using the Pennington modification of the Kessler repair or a double Kessler technique. NiTi wires were stiffer and reached higher tensile strength compared to braided polyester suture. Repairs with 200 microm NiTi wire had a higher yield force, ultimate force and better resistance to gapping than 4-0 braided polyester repairs. Repairs made with 200 microm NiTi wire achieved higher stiffness and ultimate force than repairs made with 150 microm NiTi wire.

Nickel-Titanium Wire in Circumferential Suture of a Flexor Tendon Repair: A Comparison to Polypropylene

Nickel-titanium (NiTi) has been proposed as an alternative material for flexor tendon core suture. To our knowledge, its suitability as a circumferential suture of flexor tendon repair has not been investigated before. The purpose of this ex vivo study was to investigate the biomechanical properties of NiTi circumferential repairs and to compare them with commonly used polypropylene. Forty porcine flexor tendons were cut and repaired by simple running or interlocking mattress technique using 100 microm NiTi wire or 6-0 polypropylene. The NiTi circumferential repairs showed superior stiffness, gap resistance, and load to failure when compared to polypropylene repairs with both techniques. Nickel-titanium wire seems to be a potential material for circumferential repair of flexor tendons.

Evaluation of frictional forces between ceramic brackets and archwires of different alloys compared with metal brackets

The aim of this study was to evaluate, in vitro, frictional forces produced by ceramic brackets and arch wires of different alloys. Frictional tests were performed on three ceramic brackets: monocrystalline (Inspire ICE), polycrystalline (InVu), polycrystalline with metal slot (Clarity), and one stainless steel bracket (Dyna-Lock). Thirty brackets of each were tested, all with .022' slots, in combination with stainless steel and nickel-titanium wires .019' x .025', at 0 degrees and 10 degrees angulation, in artificial saliva. Arch wires were pulled through the slots at a crosshead speed of 10 mm/min. There were statistically significant differences between the groups of brackets and wires studied (p < .05). The polycrystalline brackets with metal slots had values similar to those of conventional polycrystalline brackets, and the monocrystalline brackets had the highest frictional forces. The nickel-titanium wires produced the lowest friction. The addition of metal slots in the polycrystalline brackets did not significantly decrease frictional values. Nickel-titanium wires produced lower friction than those of stainless steel.

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.

Comparison of transition temperature range and phase transformation behavior of nickel-titanium wires

Objective: The aim of this research was to evaluate the mechanical properties (MP) and degree of the phase transformation (PT) of martensitic (M-NiTi), austenitic (A-NiTi) and thermodynamic nickel-titanium wire (T-NiTi). Methods: The samples consisted of 0.016 × 0.022 inch M-NiTi (Nitinol Classic, NC), A-NiTi (Optimalloy, OPTI) and T-NiTi (Neo-Sentalloy, NEO). Differential scanning calorimetry (DSC), three-point bending test, X-ray diffraction (XRD), and microstructure examination were used. Statistical evaluation was undertaken using ANOVA test. Results: In DSC analysis, OPTI and NEO showed two peaks in the heating curves and one peak in the cooling curves. However, NC revealed one single broad and weak peak in the heating and cooling curves. Austenite finishing (Af) temperatures were 19.7℃ for OPTI, 24.6℃ for NEO and 52.4℃ for NC. In the three-point bending test, residual deflection was observed for NC, OPTI and NEO. The load ranges of NC and OPTI were broader and higher than NEO. XRD and microstructure analyses showed that OPTI and NEO had a mixture of martensite and austenite at temperatures below Martensite finishing (Mf). NEO and OPTI showed improved MP and PT behavior than NC. Conclusions: The mechanical and thermal behaviors of NiTi wire cannot be completely explained by the expected degree of PT because of complicated martensite variants and independent PT induced by heat and stress.

NiTi bonded space regainer/maintainer

Early orthodontic interventions are often initiated in the developing dentition to promote favorable developmental changes. Interceptive orthodontic can eliminate or reduce the severity of a developing malocclusion, the complexity of orthodontic treatment, overall treatment time and cost. Premature loss of deciduous tooth or teeth can often destroy the integrity of normal occlusion. There are many space regaining and maintaining devices mentioned in literature. In this article, I present a simple space regaining method by a piece of nickel titanium (NiTi) wire bonded between the teeth in active loop form, and the unique shape memory property of NiTi wire will upright or move the teeth and the lost space can be regained easily.

Corrosion behavior of ion implanted nickel-titanium orthodontic wire in fluoride mouth rinse solutions

This study investigated the corrosion properties of ion implanted nickel-titanium wire (Neo Sentalloy Ionguard) in artificial saliva and fluoride mouth rinse solutions (Butler F Mouthrinse, Ora-Bliss). Non ion implanted nickel-titanium wire (Neo Sentalloy) was used as control. The anodic corrosion behavior was examined by potentiodynamic polarization measurement. The surfaces of the specimens were examined with SEM. The elemental depth profiles were characterized by XPS. Neo Sentalloy Ionguard in artificial saliva and Butler F Mouthrinse (500 ppm) had a lower current density than Neo Sentalloy. In addition, breakdown potential of Neo Sentalloy Ionguard in Ora-Bliss (900 ppm) was much higher than that of Neo Sentalloy although both wires had similar corrosion potential in Ora-Bliss (450 and 900 ppm). The XPS results for Neo Sentalloy Ionguard suggested that the layers consisted of TiO(2) and TiN were present on the surface and the layers may improve the corrosion properties.

Evaluation of NiTi Superelastic Retraction Coil Springs for orthodontic tooth movement in rats

The purpose of this investigation was to assess mechanical properties of Superelastic Retraction Coil Springs for orthodontic use. To reach a goal, a test frame, comprising measuring force transducers was developed. To perform metallographic analyses of the nickel-titanium wire the samples of Superelastic Retraction Coil Springs were observed by scanning electron microscope. For in vivo testing, twenty male Wistar rats, 11-12 weeks of age, were used (Group I with Superelastic Retraction Coil Springs, Group II controls). To simulate human distraction as close as possible, all the applied Superelastic Retraction Coil Springs were modified. The Superelastic Retraction Coil Springs creating a constant force of 25 cN were then attached between the upper left first molars and upper left incisors. Results showed that the reproducible force of 25 cN was shown over a range of 1-11 mm extension. Results also showed that the distance between aforementioned teeth, measured on days 0, 7, 14, 21, 24, 32, 37 and 40, decreased in Group I. Contrary, in Group II the distance between the teeth increased during the study (p<0.001).

Angular deflection of rotary nickel titanium files: a comparative study

A new manufacturing method of twisting nickel titanium wire to produce rotary nickel titanium (RNT) files has recently been developed. The aim of the present study was to evaluate whether the new manufacturing process increased the angular deflection of RNT files, by comparing instruments produced using the new manufacturing method (Twisted Files) versus instruments produced with the traditional grinding process. Testing was performed on a total of 40 instruments of the following commercially available RNT files: Twisted Files (TF), Profile, K3 and M2 (NRT). All instruments tested had the same dimensions (taper 0.06 and tip size 25). Test procedures strictly followed ISO 3630-1. Data were collected and statistically analyzed by means ANOVA test. The results showed that TF demonstrated significantly higher average angular deflection levels (P<0.05), than RNT manufactured by a grinding process. Since angular deflection represent the amount of rotation (and consequently deformation) that a RNT file can withstand before torsional failure, such a significant improvement is a favorable property for the clinical use of the tested RNT files.

Numeric modeling of torque capabilities of self-ligating and conventional brackets

The purpose of this study was to investigate the torque capabilities of conventional and self-ligating brackets by using the finite element method. Three types of brackets were selected: self-ligating Hanson Speed (Strite Industries, Cambridge, Ontario, Canada) and Damon MX (Ormco, Glendora, Calif), and conventionally ligated Discovery (Dentaurum, Pforzheim, Germany). All brackets had a 0.022-in slot size. From the maxillary left incisor to the maxillary right canine, 4 brackets were included in the finite element models generated. Torque of 20 degrees was applied to the maxillary right incisor with 0.46 x 0.64 mm(2) (0.018 x 0.025 in) and 0.48 x 0.64 mm(2) (0.019 x 0.025 in) archwires. Three kinds of wire alloys were used: stainless steel, titanium molybdenum, and nickel titanium. For the conventional Discovery brackets, 2 types of ligation were modeled: elastic and stainless steel wire ligatures. The torque angle/torque moment characteristics in the simulated movement were calculated by using the MSC.Marc/Mentat 2005 FE software package (MSC Software Corporation, Santa Ana, Calif). The torque angle/torque moment curves seemed to be dominated by the characteristics of the wire. The change of wire dimension increased the torque moments less than the change of wire alloy (125% increase for a 0.48 x 0.64 mm(2) instead of a 0.46 x 0.64 mm(2) stainless steel wire, and 220% for a 0.46 x 0.64 mm(2) stainless steel instead of a nickel-titanium wire). The combined change of the wire alloy and wire dimension resulted in a 600% increase for a 0.48 x 0.64 mm(2) stainless steel instead of a 0.46 x 0.64 mm(2) nickel-titanium wire.The play of the 0.46 x 0.64 mm(2) wires was about 9.0 degrees, and the play of the 0.48 x 0.64 mm(2) wires was about 7.5 degrees, with slightly more play for the Damon. The ligation effect of Discovery brackets with elastic and stainless steel ligatures could be compared with the behavior of the Damon. The Speed showed different behavior, with the lowest torquing moments and the smallest torque play. Improving the adaptation of torque movements to the biomechanical reactions of the periodontium is best done by proper selection of both wire dimension and wire alloy. The effect of the bracket system is of minor importance, with the exception of brackets with an active clip (eg, Speed), which had the least play and the lowest torquing moments of all the wires.

Metallurgical Characterization of a New Nickel-Titanium Wire for Rotary Endodontic Instruments

Introduction A novel thermomechanical processing procedure has been developed that yields a superelastic (SE) nickel-titanium (NiTi) wire (M-Wire) that laboratory testing shows has improved mechanical properties compared with conventional SE austenitic NiTi wires used for manufacture of rotary instruments. The objective of this study was to determine the origin of the improved mechanical properties. Method Specimens from 2 batches of M-Wire prepared under different processing conditions and from 1 batch of standard-processed SE wire for rotary instruments were examined by scanning transmission electron microscopy, temperature-modulated differential scanning calorimetry, micro–x-ray diffraction, and scanning electron microscopy with x-ray energy-dispersive spectrometric analyses. Results The processing for M-Wire yields a microstructure containing martensite, that the proportions of NiTi phases depend on processing conditions, and that the microstructure exhibits pronounced evidence of alloy strengthening. Conclusions The presence of Ti 2Ni precipitates in both microstructures indicates that M-Wire and the conventional SE wire for rotary instruments are titanium-rich.

Variation in corrosion resistance of nickel-titanium wires from different manufacturers.

Nickel-titanium (NiTi) wires produced by various manufacturers may have different corrosion resistance in acidic oral environments. The purpose of this study was to investigate the variation during in vitro corrosion resistance of commercial NiTi dental orthodontic wires from different manufacturers using the fast electrochemical technique. The linear polarization test was used to evaluate the corrosion resistance, in terms of polarization resistance (Rp), of as-received commercial NiTi wires in acidic artificial saliva at 37 degrees C. One-way analysis of variance was used to analyze Rp with the wire manufacturer as the variable factor. Atomic force microscopy was used to analyze the three-dimensional surface topography and roughness (Ra). Electron spectroscopy for chemical analysis was used to identify the chemical structure of the passive film on the NiTi wires. The results showed that NiTi wires from different manufacturers had a statistically significant difference in Rp (P < .001). Different surface topography was present among the tested NiTi wires, whereas the same surface chemical structure was observed for the tested NiTi wires. The surface roughness of the commercial NiTi wires with similar surface chemical structure does not correspond with the difference in corrosion resistance.

Comparison of the frictional coefficients for selected archwire-bracket slot combinations in the dry and wet states.

Coefficients of friction were evaluated in the dry and wet (saliva) states for stainless steel, cobalt-chromium, nickel titanium, and beta-titanium wires against either stainless steel or polycrystalline alumina brackets. For both operators' experiments, an 0.010" stainless steel ligature wire pressed each archwire into the 0.018" or 0.022" bracket slot at 34 degrees C. In the dry state and regardless of slot size, the mean kinetic coefficients of friction were smallest for the all-stainless steel combinations (0.14) and largest for the beta-titanium wire combinations (0.46). The coefficients of the polycrystalline alumina combinations were generally greater than the corresponding combinations that included stainless steel brackets. In the wet state, the kinetic coefficients of the all-stainless steel combinations increased up to 0.05 over the dry state. In contrast, all beta-titanium wire combinations in the wet state decreased to 50% of the values in the dry state. The mixed reports that saliva may promote adhesive and lubricious behaviors may have some substance.

Forces Produced by Different Nonconventional Bracket or Ligature Systems during Alignment of Apically Displaced Teeth

To analyze the forces released by four types of passive stainless steel self-ligating brackets (SLBs), and by two nonconventional elastomeric ligature-bracket systems when compared with conventional elastomeric ligatures on conventional stainless steel brackets during the alignment of apically displaced teeth at the maxillary arch. An experimental model consisting of five brackets was used to assess the forces released by the seven different ligature-bracket systems with 0.012'' or 0.014'' superelastic nickel titanium wire in the presence of different amounts of apical displacement of the canine (ranging from 1.5 mm to 6 mm). Comparisons between the different types of bracket/wire/ ligature systems were carried out by means of ANOVA on ranks with Dunnett's post hoc test (P < .05). When correction of a misalignment greater than 3 mm is attempted, a noticeable amount of force for alignment is generated by passive SLBs and nonconventional elastomeric ligature-bracket systems, and a null amount of force is released in the presence of conventional elastomeric ligatures on conventional brackets. When minimal apical displacement is needed (1.5 mm), the differences in performance between low-friction and conventional systems are minimal. These differences become significant when correction of a misalignment of greater than 3.0 mm is attempted.

Distalization of the entire maxillary arch in an adult

Many appliances are available to move maxillary molars distally. First molars have routinely been moved distally with nickel-titanium coil springs and nickel-titanium wire before the eruption of the second molars. However, when first molars are moved distally after the eruption of the second molars, they tend to move slowly, and anchorage loss increases. In adults, the midpalatal area is appropriate for placing titanium miniscrews for orthodontic anchorage. This case report demonstrates the ability of midpalatal miniscrews to control anchorage while distalizing the entire maxillary dentition in an adult, with improvements in lip profile resulting from the retraction of anterior teeth followed by a good response of the lips. This report suggests that absolute anchorage can be established by placing miniscrews in the palate and that miniscrew anchorage can serve as anchorage for the distal movement of an entire arch.

Corrosion Susceptibility and Nickel Release of Nickel Titanium Wires during Clinical Application

Orthodontic wires are exposed to a corrosive intraoral environment and are subject to mechanical and thermal load. This could affect how nickel titanium (NiTi) wires corrode, as they possess temperature- and load-dependent characteristics. It was the scope of this study to determine whether the clinical application of NiTi wires would lead to corrosion defects on the wire surfaces, and whether an influence on the patients' salivary Ni ion concentration would become apparent. A total of 115 wires of different manufacturers (Forestadent Titanol 'Low Force' und 'Martensitic', Ormco Copper Ni-Ti 35 degrees C, Ortho Organizers NiTi) was retrieved after intraoral application lasting 1 to 12 months. The wires were examined after cleaning with a scanning electron microscope. We also analyzed the salivary Ni ion concentration in 18 patients at predefined intervals following a detailed orthodontic treatment protocol during the initial phase of orthodontic therapy. The intervals were: 1) a saliva sample before treatment commenced, 2) after bonding of brackets and bands, 3) 2 weeks after bonding, immediately before and 4) immediately after fitting the archwires, and 5) 4 and 6) 8 weeks after placing the archwires. 16 to 20 brackets and bands were bonded in the upper and lower jaws, while NiTi leveling arches (ODS Euro Arch Opto Therm, 0.40 mm round) were fitted. The saliva samples were quick-frozen and subsequently dried under red light. Dried residuals were dissolved in aqua regia and filled up to 3 ml. The solutions were analyzed using a mass spectrometer (Perkin Elmer Elan 5000). Surface analysis revealed no differences in the degree of corrosion of the different products. In fact, we observed only extremely small and isolated corrosion defects. No statistically-significant differences were noted in the Ni ion concentration at time points 1 (reference value), 3, 5 and 6 (34, 34, 28 and 30 microg/l, respectively). The samples taken immediately after bracket bonding or the NiTi wire application however displayed a significant increase in the salivary Ni ion concentration (2: 78 and 4: 56 microg/l). It was significantly higher after bonding of the steel brackets than after NiTi wire application. Increased Ni ions are released initially after the orthodontic devices have been fitted, but they decay quickly. This is reflected in miniscule corrosion defects as pitting. It is unlikely that orthodontic nickel titanium wires are a relevant additional Ni load for the patient.

In Vitro Frictional Forces Generated by Three Different Ligation Methods

To test the hypothesis that there is no difference between the frictional forces produced by a passive self-ligating bracket (SLB) in vitro and a conventional bracket (CB) used with two types of elastomeric ligatures. The brackets, wires and ligation methods used in vitro were a passive SLB and a CB used with two types of elastomeric ligatures (conventional elastomeric ligature [CEL] and unconventional elastomeric ligatures [UEL]). The bracket ligation systems were tested with two types of wires (0.014'' super elastic nickel titanium wire and 0.019'' x 0.025'' stainless steel wire). Resistance to sliding of the bracket/wire/ligature systems was measured with an experimental model mounted on the crosshead of an Instron testing machine with a 10 N load cell. Each sample was tested 10 consecutive times under a dry state. Frictional forces close to 0 g were recorded in all tests with SLB and in all tests with UEL on CB with both wire types. Resistance to sliding increased significantly (87-177 g) (P < .05) when CEL on CB was used with both wires. UELs may represent a valid alternative to passive SLBs for low-friction biomechanics.

Evaluation of force systems from a “free-end” force system

The purpose of this study was to investigate the biomechanical characteristics of a V-bend wire configuration in a free-end system, ie, with 1 end mounted in an orthodontic tube and the other loosely ligated to a bracket. The effects of V-bend position and size, wire dimension, method of ligation, and the inclusion of a second wire in the system were examined. Samples of various wire configurations were mounted in a bench testing machine to measure moments and forces at both ends in a standardized configuration resembling a 2-premolar extraction clinical case incorporating a special bracket with a second, frictionless slot. The position of the V-bend was altered in 1.0-mm intervals. Moments were created at the posterior end, resulting in intrusive forces anteriorly that induced moments on the anterior block. The sizes of the moments and forces were increased in connection with posterior positioning of the V-bend, increase in the wire dimension and the V-bend sizes, although they were reduced and stabilized by the inclusion of a second nickel-titanium wire. The double wire system created clinically revelant moments and forces. The V-bend in a free-end system can create variable moments and forces that can be used clinically in intrusion and space-closing procedures but should be measured and monitored closely.