NiTi Orthodontic Archwires Research Articles

Evaluation of titanium dioxide and tantalum pentoxide nanoparticles for coating NiTi archwires in orthodontics: An in vitro study

Background: This study aims to enhance the biocompatibility of Nickel–Titanium (NiTi) alloy by developing a new coating using titanium dioxide (TiO2) and titanium pentoxide (Ta2O5) through direct current (DC) reactive sputtering technology. Materials and methods: Two distinct coating materials, namely, TiO2 and Ta2O5, were used to fabricate NiTi orthodontic archwires with improved surface properties. TiO2 nanoparticles, with thickness ranging from 21.90 nm to 31.93 nm, were deposited onto NiTi alloy substrates through DC reactive sputtering deposition under different power conditions. Results: X-ray diffraction and field emission scanning electron microscopy validated the uniformity and morphology of the coatings. Immersion tests in simulated body fluid (SBF) revealed significant hydroxyapatite layer growth on TiO2-coated NiTi, especially at a sputtering power of 240 W. Reduced nickel ion release was observed on TiO2 nanoparticles with a thickness of 21.90 nm at 50 W sputtering power compared with 31.93 nm-thick nanoparticles at 240 W. Ta2O5 thin films were deposited on NiTi substrates through DC magnetron reactive sputtering at ~100 °C with a deposition power of 50 W. Structural and morphological analyses through optical microscopy and X-ray diffraction, atomic force microscopy, and scanning electron microscopy revealed the homogeneity and low roughness of the coatings. Biocompatibility assessments in artificial saliva and SBF solutions established that Ta2O5-coated NiTi alloys exhibited superior electrochemical behavior, enhanced corrosion resistance, and diminished Ni ion release compared with uncoated specimens. Conclusion: TiO2 and Ta2O5 coatings not only improved the biocompatibility of NiTi orthodontic archwires but also presented a promising path for advanced biomedical applications. These coatings have potential in improving the cellular behavior and performance of NiTi-based orthodontic devices.

Oxidized Ethylene Glycol/ZrO2-coated NiTi Orthodontic Arch Wires: Surface Characterization and Electrochemical and Corrosion Studies

Background: Orthodontic arch wires, typically made of Nickel Titanium (NiTi), are widely utilized in dental procedures for correcting teeth misalignment and jaw issues due to their favorable mechanical attributes and cost-effectiveness. However, these NiTi wires are prone to corrosion in the oral environment, leading to diminished mechanical stability, compromised aesthetics, and potential health concerns for patients. Objective: There is a growing demand to augment the corrosion resistance and stability of orthodontic wires. Hence, this study aimed to address these issues. Herein, zirconium dioxide (ZrO2) and oxidized ethylene glycol (OEG) films were deposited onto NiTi wires to improve the corrosion resistance and stability. Methods: NiTi wires were modified by a two-step process involving electrodeposition of ZrO2 and oxidized ethylene glycol (OEG) film. The surface characterizations of coated material (OEG/ZrO2/NiTi) were carried out by using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), and Electron Microprobe Analysis (EMap) to confirm the elemental composition of the coated NiTi wire. Results: The OEG/ZrO2/NiTi wire exhibited a potentiodynamic polarization resistance of 547037 Ω and higher stability than the bare NiTi wire (396421 Ω). The corrosion rate for OEG/ZrO2/NiTi wire was found to be 0.040 mm/year, which was comparatively lower than a bare NiTi wire (0.069 mm/year). Due to the formation of OEG/ZrO2 film, NiTi wire became electrically insulative and showed a higher impedance than bare NiTi wire. Conclusion: The bilayer coating of ZrO2 and OEG has proven to significantly improve the corrosion resistance and stability of the wires. Thus, these materials can be considered for coating orthodontic arch wires with improved corrosion stability.

DNA fragmentation of lymphocytes and sperm cells induced by nickel released from orthodontic archwires: A preliminary study.

Orthodontic brackets and archwires placed intraorally are subject to corrosion, leading to the release of cytotoxic metal ions. The aim of this study was to determine whether the use of orthodontic NiTi archwires increases systemic Ni levels and cause alterations on the DNA of cells unrelated to the oral environment such as lymphocytes and sperm cells. Human urine, semen and blood samples were collected before (baseline) sham placement of orthodontic archwires and 15 and 30 days after placement. Lymphocytes and sperm cells cells were evaluated by comet assay. Ni concentration levels in urine increased significantly between baseline and 15 days (p<0.01) and 15 and 30 days of exposure (p<0.01). Progressive decrease in sperm viability and motility was observed between the sampling periods. Lymphocytes and sperm cells showed DNA fragmentation. The increase in systemic concentration of nickel induced structural damage in the DNA of lymphocytes and human sperm cells.

Assessment of Nickel Ion Release from NiTi Orthodontic Archwire After Using Magnetized Water as a Mouth Rinse

Objectives This study was to detect whether the magnetized water (MW), when used as a mouth rinse, can influence the release of Nickel (Ni) ions from NiTi (nickel-titanium) archwires. Material and Methods One hundred fifty (0.016” *0.022”) as received orthodontic NiTi archwires were grouped into three chief groups based on the used mouth rinse into MW, Ortho Kin (control positive) (OK) and distilled water (control negative) (DW) groups. Every group contained intervals of five points (24 h, 1 week, 2 week, 3 week and 4 week). Ten archwires were used for each interval. The release Ni was detected at each interval using an atomic absorption spectrometer. The topographic features of orthodontic archwires were examined with a scanning electron microscope and an atomic force microscope. SPSS Statistics software (V.19) was used for statistical analysis. One-way Analysis of Variance (ANOVA) and post hoc Duncan’s multiple range test were used for data analysis with P ≤ 0.05. Results Significantly less amount of Ni ion released in the MW group was recorded from NiTi archwires in comparison with the OK group for all studied intervals. Conclusion MW may be indicated as a suitable adjunct for further commercially available mouth rinses (as OK) throughout orthodontic therapy.

Thermal Behavior Changes of As-Received and Retrieved Bio-Active® (BA) and TriTanium® (TR) Multiforce Nickel-Titanium Orthodontic Archwires.

Multiforce nickel-titanium (NiTi) orthodontic archwires release progressively increasing forces in a front-to-back direction along their length. The properties of NiTi orthodontic archwires depend on the correlation and characteristics of their microstructural phases (austenite, martensite and the intermediate R-phase). From a clinical and manufacturing point of view, the determination of the austenite finish (Af) temperature is of the greatest importance, as in the austenitic phase, the alloy is most stable and exhibits the final workable form. The main purpose of using multiforce orthodontic archwires is to decrease the intensity of the applied forces to the teeth with a small root surface area, such as the lower central incisors, and also provide forces high enough to move the molars. With the optimally dosed forces of multiforce orthodontic archwires in the frontal, premolar and molar segments, the feeling of pain can be reduced. This will contribute to the greater cooperation of the patient, which is of utmost importance to achieve optimal results. The aim of this research was to determine the Af temperature at each segment of as-received and retrieved Bio-Active® and TriTanium® archwires with dimensions of 0.016 × 0.022 inches, investigated by the differential scanning calorimetry (DSC) method. A classical Kruskal-Wallis one-way ANOVA test and multi-variance comparison based on the ANOVA test statistic using the Bonferroni corrected Mann-Whitney test for multiple comparisons were used. The incisor, premolar and molar segments have different Af temperatures, and they decrease from the anterior to posterior so that the posterior segment has the lowest Af. Bio-Active® and TriTanium® with dimensions of 0.016 × 0.022 inches can be used as first leveling archwires by additional cooling and are not recommended for use on patients with mouth breathing.

Thermal Programming of Commercially Available Orthodontic NiTi Archwires.

The shape of superelastic Nickel-Titanium (NiTi) archwires can be adjusted with thermal treatments using devices such as the Memory-MakerTM (Forestadent), which potentially affects their mechanical properties. The effect of such treatments on these mechanical properties was simulated by means of a laboratory furnace. Fourteen commercially available NiTi wires (0.018″ × 0.025″) were selected from the manufacturers American Orthodontics, Dentaurum, Forestadent, GAC, Ormco, Rocky Mountain Orthodontics and 3M Unitek. Specimens were heat treated using different combinations of annealing duration (1/5/10 min) and annealing temperature (250-800 °C) and investigated using angle measurements and three-point bending tests. Complete shape adaptation was found at distinct annealing durations/temperatures for each wire ranging between ~650-750 °C (1 min), ~550-700 °C (5 min) and ~450-650 °C (10 min), followed by a loss of superelastic properties shortly afterwards at ~750 °C (1 min), ~600-650 °C (5 min) and ~550-600 °C (10 min). Wire-specific working ranges (complete shaping without loss of superelasticity) were defined and a numerical score (e.g., stable forces) was developed for the three-point bending test. Overall, the wires Titanol Superelastic (Forestadent), Tensic (Dentaurum), FLI CuNiTi27 (Rocky Mountain Orthodontics) and Nitinol Classic (3M Unitek) proved to be the most user-friendly. Thermal shape adjustment requires wire-specific working ranges to allow complete shape acceptance and high scores in bending test performance to ensure permanence of the superelastic behaviour.

Comparison of the mechanical properties and surface topography of as-received and as-retrieved Copper-Nickel-Titanium arch wires: An ex-vivo study

The mechanical and surface characteristics of Copper NiTi wires following intraoral aging in an important topic. This ex-vivo study is designed to assessthe three most important mechanical properties; torsional stiffness, 3-point bending and surface hardness of the as-received Copper NiTi orthodontic archwires and compare them to the retrieved ones. In this study, 50 round CuNiTi (0.016 inch) and 50 rectangular (0.018×0.025 inch) CuNiTi orthodontic wires (American Orthodontics, Tanzo Copper Nickel Titanium, Sheboygan, WI) were tested. The groups were as follow: 25 as-received 0.016 inch round CuNiTi archwires (group 1), 25 as-retrieved 0.016 inch round CuNiTi archwires (group 2), 25 as-received 0.018×0.025 inch rectangular CuNiTi archwires (group 3), and 25 as-retrieved 0.018×0.025 inch rectangular CuNiTi archwires (group 4). The physical properties of all of the samples were examined using Vickers hardness, bending and torsional tests. The Kolmogorov-Smirnov test was applied to assess the normal distribution of data. An independent t-test was used to compare the variables between the groups. The results showed that the hardness does not significantly differ between the as-received and as-retrieved archwires in both 0.016 and 0.018×0.025 inch archwires (P< 0.05). The bending test of the round wires showed that the values of the activation forces in the as-received ones were significantly higher than those of the as-retrieved (P=0.00). The torsional and bending test results of rectangular wires showed that the amounts of forces exerted from the as-retrieved archwires were significantly higher than the new archwires (P=0.00). Round CuNiTi archwires could be retied in the succeeding visits. However, the bending activation that declines significantly should be took into consideration. On the other hand, since bending and torsion activation of CuNiTi rectangular archwires increased after intraoral use, these wires should be retied cautiously.

Nanotopography Evaluation of NiTi Alloy Exposed to Artificial Saliva and Different Mouthwashes.

Nitinol (NiTi) alloy is a widely used material for the production of orthodontic archwires. Its corrosion behavior in conditions that exist in the oral cavity still remains a great characterization challenge. The motivation behind this work is to reveal the influence of commercially available mouthwashes on NiTi orthodontic archwires by performing non-electrochemical corrosion tests and quantifying the changes in the nanotopography of commercially available NiTi orthodontic wires. In this study, we examined the behavior of NiTi alloy archwires exposed for 21.5 days to different corrosive media: artificial saliva, Eludril®, Aquafresh®, and Listerine®. The corrosion was characterized by contact mode atomic force microscopy (AFM) before and after the corrosion tests. A novel analysis methodology was developed to obtain insight into locations of material gain or material loss based on standard surface roughness parameters Sa, Sdr, Ssk, and S10z. The developed methodology revealed that fluoride-containing mouthwashes (Aquafresh® and Listerine®) dominantly cause material loss, while chloride-containing mouthwash (Eludril®) can cause both material loss and material gain. The sample exposed to artificial saliva did not display significant changes in any parameter.

Analysis of the Hardness, Nano Indentation and Nano Roughness of NiTi Orthodontic Arch wires

Objective: The aim was to observe the modification of NiTi arch wires mechanical characteristics before and after their use and to highlight that when shape memory and super elasticity are stressed, hardness and roughness are also altered. Materials and methods: Samples of used and new 0.016-0.022- and 0.016-inch archwires made by American Orthodontics (AO), AZDent and Ortho Classic (OC) were retrieved from 192 patients. They were analyzed using an Atomic Force Microscope, a hardness tester and SEM. The arches were classified into various categories: the qualitative factors that include manufacturers, type, usage, age, gender, size and location. The quantitative factors include roughness (nm) and hardness (Vickers). The analysis was divided into three parts, comparison of new arches for all three companies, comparison of used arches between all three and comparison between new and used arches company by company. Results: As expected, the acquired results revealed a decrease in the hardness value (ΔHV~50 Vickers) of the retrieved samples after 4–6-week oral installation compared to the control samples, as well as increased surface roughness and porosity. AZDent brand bows have the smallest drop in hardness. The AO brand arches proved to be the roughest while those manufactured by AZDent were the smoothest. It should also be noted that 0.016-0.022 arches showed the most degradation. Conclusion: We was able to demonstrate that the mechanical properties of NiTi arches (shape memory and super-elasticity) appear to differ significantly before and after intra-oral usage. That mean the old arch wires have fewer mechanical properties than the new one and, in this situation, we need to find a solution to avoid this problem.

Assessment of impact of fluoride on mechanical properties of NiTi and Cu NiTi orthodontic archwires

Background: The current study was carried out to assess the impact on the mechanical properties of orthodontic wires such as the NiTi and CuNiTi wires by fluoride available in various prophylactic products. Materials &amp; methods: 80 wire specimens were selected and were divided into two study groups with 20 specimens in each group as follows”: Group A: 0.019 x 0.025 inch NiTi archwires (NT3, American Orthodontics,USA), Group B: 0.019 x 0.025 inch CuNiTi archwires (Tritanium, American Orthodontics,USA). Following fluoride agent was taken as standard for the present study: Phos-Flur gel (Colgate oral pharmaceuticals, New York, USA). From the straight part of the archwire enrolled in the present study, wire specimens of dimensions 0.40 X 0.60 X 20 mm were cut. Control group: 40 specimens consisting of 20 specimens from each wire type; Solution used was deionized water, and Study group: 40 specimens consisting of 20 specimens from each wire group, placed in the Phos-Flur gel. Random selection of the wires was done followed by testing under universal force testing machine. Results: Among the study groups subjects, mean loading force among group A and group B specimens was 596.1 MPa and 368.4 MPa respectively.

Effect of Fluoride Content of Mouthwashes on Superelastic Properties of NiTi Orthodontic Archwires.

The influence of sodium fluoride (NaF) concentration in mouthwashes on the properties of superelastic NiTi orthodontic wires has been studied. In this work, 55.8%Ni and 44.2%Ti (in weight) wires were introduced in commercial mouthwashes with different NaF contents (0, 130, 200 and 380 ppm). The release of Ni2+ and Ti4+ ions was by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) at 1, 4, 7 and 14 days. Superelastic orthodontic wires present at oral temperature the austenitic phase which is transformed into a plastic phase (martensite) by cooling. The temperatures at which this occurs are influenced by the chemical composition. The release of ions from the wire will produce variations in the temperatures and stresses of the stress-induced martensitic transformation. Ms, Mf, As, Af were determined by Differential Scanning Calorimeter (DSC). The transformation stresses (austenite to stress induce martensite) were determined with a servo-hydraulic testing machine at 37 °C. The surfaces for the different times and mouthwash were observed by Scanning Electron Microscope (SEM). The release of Ni2+ in mouthwashes with 380 ppm NaF concentrations reaches 230,000 ppb in 14 days and for Ti4+ 175,000 ppb. When NaF concentrations are lower than 200 ppm the release of Ni and Ti ions is around 1500 ppb after 14 days. This variation in compositions leads to variations in Ms from 27 °C to 43.5 °C in the case of higher NaF concentration. The increasing immersion time and NaF concentrations produce a decrease of Ni in the wires, increasing Ms which exceed 37 °C with the loss of superelasticity. In the same way, the stresses (tooth position corrective) decrease from 270 MPa to 0 MPa due to the martensitic phase. The degradation can produce the growth of precipitates rich in Ti (Ti2Ni). These results are of great interest in the orthodontic clinic in order to avoid the loss of the therapeutic properties of superelastic NiTi due to long immersion in fluoride mouthwashes.

Study of the Corrosion of the Nickel-titanium Orthodontics Archwires in the Mouth

Objective: The corrosion behavior of titanium alloy (NiTi) orthodontic wires shows a high resistance to corrosion in various solutions, such as Ringer's solution, artificial saliva, sodium chloride solution, and others. In these different liquids, NiTi corrosion resistance is higher than that of stainless steel or cobalt-based alloys. These research studies the behavior of the nickel-titanium Orthodontics archwires in the mouth by three methods. Methods: The first testing was the SEM that can perform EPMA (Electro Probing Micro Analysis), microanalysis X, and local and quantitative elementary analysis, and the examination of NiTi are observed in two ways: cross sectional and surface examination. The second one was the electrochemical analysis performed by immersion in an artificial saliva solution consisting of lactic acid at 0.1 moles per liter and sodium chloride at 0.1 mole per liter: Two types of NiTi orthodontic arches were tested. The first ones are from the manufacturer Ortho Classic and were used in the mouth for 4-6 weeks. The second arches are from the manufacturer AZ Dent and were new. The last test was the TEM cartography that shows the atoms and their dispersion on the surface of the wire. Results: The results showed that the presence of corrosion cells in the artificial saliva proved that the NiTi orthodontic archwires were able to initiate the process of corrosion in the mouth, particularly at the point of friction in contact with the braces (Ti6Al4V). Conclusion: The results obtained by the MET on thin sections of orthodontic arches prepared by the FIB method revealed the presence of double or multiple layers of titanium oxide and N-oxide plus aluminum.

Controlling the phase transformation window during stages of hot/cold forging of Ni-rich Ni–Ti alloy

A detailed microstructural analysis during the intermediate stages of fabrication of NiTi orthodontic archwire is carried out in this study. These microstructural findings were related to the phase transformation characteristics such as start and finish transformation temperature, thermal hysteresis, etc. The objective was to monitor the transformation window during the different stages of thermomechanical processing. The casted alloy was further subjected to combinations of hot and cold forging steps with intermediate annealing. Four different sample conditions were prepared. The microstructure development in these samples was studied through electron back-scattered diffraction and synchrotron radiation X-ray diffraction (SR-XRD) techniques. The phase transformation temperatures were determined by differential scanning calorimetric measurements. The microstructures showed grain boundary serrations, very large grains of austenite, twin-like features within austenite grains and mixed-phase distribution of austenite and martensite. The differences in microstructures were also clear in terms of local in-grain misorientation and grain boundary fractions. SR-XRD measurements further revealed possible precipitation of Ni4Ti3 and Ni3Ti. The martensite start temperature (Ms) was seen to be a clear function of high angle grain boundary fraction, while the finish temperature (Mf) showed an inverse trend. The transformation interval, Ms–Mf is related to the stored energy of austenite grains that determines the driving force to overcome the frictional work opposing the movement of the habit plane, while and Af –As largely depends on the elastic energy stored of the martensite plates during its growth. The hysteresis during reverse transformation (M → A) was related to the local in-grain misorientation.

Differences in nickel ions released from nickel-titanium arch wire after immersion in detergent and non-detergent toothpaste

Nickel-titanium (NiTi) arch wire has properties that favor its use during the leveling and aligning phase of orthodontic treatment. This NiTi orthodontic arch wire has the potential to experience nickel ion release. One factor that can cause the release of nickel ions is toothpaste. Nickel ions released can enter the body and cause carcinogenic, mutagenic, cytotoxic, and allergic effects. The purpose of this study was to see the differences of nickel ions released from NiTi orthodontic arch wire after immersion in detergent and non-detergent toothpaste. This was a laboratory experimental research to draft a comparative design. The sample size was 40 pieces of NiTi orthodontic arch wire which were divided into 2 groups, immersion in detergent toothpaste and immersion in non-detergent toothpaste. The sample used was NiTi arch wire solution immersed in toothpaste and distilled water for 24 hours in an incubator at 37 °C then measured using inductively coupled plasma (ICP) mass spectrometer to determine the released nickel ions. Data were analyzed usingMann-Whitney test. The Mann-Whitney test resulted in a value of 0.872 (p≥0.05) which indicates no significant difference between the two groups. The study concluded that there is no difference in the nickel ions released from NiTi orthodonticarchwire after immersion in detergent and non-detergent toothpaste.

Effect of laser welding on mechanical properties of round-rectangular nickel-titanium (NiTi) orthodontic wires

ABSTRACT Objectives. To investigate the welding parameters on preparation of nickel-titanium (NiTi) orthodontic arch wires that can simultaneously level and retract anterior teeth by combining round wire to provide high flexibility with rectangular wire to provide high rigidity. The effects of voltage and number of welding points on tensile strength, transition temperature range (TTR), and penetration of laser beam were investigated. Materials and Methods. 15 mm segments of 0.018 in. round wire and 15 mm of 0.019 × 0.025 in. rectangular wire were laser welded under argon shielding. The laser voltage was varied between 170 and 210 V for one-point and two-point welding. Results. Incomplete welding was found only in one-point welding at low voltage while all others were joined completely. Mean maximum tensile force at fracture was increased with increasing voltage. One-point welding at 210 V gave rise to the highest force at fracture. Differential scanning calorimetry (DSC) of the welded joints showed a lack of the original TTR curve, indicating the loss of superelastic properties. Significance. Laser welding of NiTi orthodontic arch wires with different geometries provided acceptable strength for use in orthodontic treatment.

Changes in the mechanical properties of two nickel-titanium archwires after 3 months of clinical usage

BackgroundNickel-titanium archwires have unique mechanical properties that make them the archwire of choice during the first phase of orthodontic treatment. However, during its clinical use when subjected to oral conditions, these properties can undergo great changes. Materials and methodsA sample of 24 randomly chosen superelastic NiTi orthodontic archwires (12 TE and 12 PSE) with a 0.014-inch round section from the same manufacturer were distributed into four groups of six archwires each. The first two groups were new wires (as-received), which were used as controls (T0), and the other two were collected after 3 months of clinical usage (as-retrieved) in orthodontic patients (T1). Mechanical properties were measured by mechanical tensile testing and three-point bending tests under the same experimental and temperature conditions (36°C) in a universal testing machine. Comparisons between the groups at T0 and T1 were performed with t-tests and Mann-Whitney U tests. A paired t-test and Wilcoxon signed rank sum test were used for intragroup comparisons (T1-T0). ResultsAt baseline, PSE wires presented significantly (P < 0.05) higher load at fracture, range, ultimate tensile strength (UTS), yield strength, springback, maximum tension and flexural ultimate strength (FUS) than those of TE wires. At T1, a significant decrease in load at fracture and UTS in PSE wires and in FUS in TE wires was found. After 3 months of clinical usage, the changes (T1-T0) in the mechanical properties of both alloys were similar. ConclusionsAfter 3 months of clinical usage, wires lost some of their mechanical properties and had less resistance to breakage. However, the as-received differences between both wires were maintained after clinical usage.

Nanoindentation and surface characterization of clinically retrieved multi-force NiTi orthodontic archwires

Nickel-titanium (NiTi) alloys, due to their properties of superelasticity and shape memory effect, have been extensively used in orthodontic treatment. Their superelasticity allows the orthodontist to apply an almost continuously low force with larger activation that reduces tissue trauma and patient discomfort, and thus facilitates tooth movement. The producers usually do not give information about the mechanical properties of the archwires they produce on their packagings or Web pages, which makes it difficult for the dentists to choose the most suitable material and with better cost-benefit for use. In the present work we investigated and compared the mechanical and physicochemical properties of as received and used for 6 and for 9 weeks multi-force NiTi archwires, produced by American Orthodontics under the trademark TriTaniumTM, to evaluate if there are changes in their properties with clinical usage. The mechanical properties were investigated using nanoindentation measurements. The surface morphology and the elemental composition of the archwires were studied by scanning electron microscopy (SEM) and energy-dispersive analysis (EDS), respectively. The comparison of mechanical properties of as received and used for 6 and 9 weeks TriTaniumTM archwires showed that their indentation hardness and modulus decrease with increasing of the time for use. No significant change in the elemental composition of the archwires was observed after their clinical application.

New Bactericide Orthodonthic Archwire: NiTi with Silver Nanoparticles

A potential new bactericide treatment for NiTi orthodontic archwires based in the electrodeposition of silver nanoparticles on the surface was studied. Twenty-five archwires were treated by electrodeposition, obtaining nanoparticles of silver embedded on the archwire surface. These were evaluated in order to investigate the possible changes on the superelastic characteristics (critical temperatures and stresses), the nickel ion release, and the bacteria culture behavior. The chemical composition was analyzed by Energy Dispersive X-Ray Spectroscopy-microanalysis; the singular temperatures of the martensitic transformation were obtained by a flow calorimeter. Induced martensitic transformation stresses were obtained by mechanical testing apparatus. Nickel ion release was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) equipment using artificial saliva solution at 37 °C. Bacterial tests were studied with the most used oral bacterial strains: Streptococcus sanguinis and Lactobacillus salivarius. NiTi samples were immersed in bacterial suspensions for 2 h at 37 °C. Adhered bacteria were separated and seeded on agar plates: Tood-Hewitt (TH) and Man-Rogosa-Sharpe (MRS) for S. sanguinis and for L.salivarius, respectively. These were then incubated at 37 °C for 1 day and the colonies were analyzed. The results showed that the transformation temperatures and the critical stresses have not statistically significant differences. Likewise, nickel ion release at different immersion times in saliva at 37 °C does not present changes between the original and treated with silver nanoparticles archwires. Bacteria culture results showed that the reduction of the bacteria due to the presence to the nanoparticles of silver is higher than 90%. Consequently, the new treatment with nanoparticles of silver could be a good candidate as bactericidic orthodontic archwire.

Thermo-mechanical characterization of NiTi orthodontic archwires with graded actuating forces

Functionally graded NiTi orthodontic archwire was tested to assess the evolution of the actuation force as a function of the temperature. Varying actuation forces on the same orthodontic wire allow the optimization of repositioning of the different types of teeth, according its radicular support. The wire was separated into three segments: Incisive, Premolar and Molar. The functionally graded NiTi orthodontic archwire segments have distinct structural and mechanical behavior as confirmed by differential scanning calorimetry, synchrotron-based X-ray diffraction, and thermomechanical analysis. The mechanical behavior was analyzed by three-point bending tests at four different temperatures (5, 20, 25 and 37 °C). In parallel, three-point bending tests were performed by TMA analysis in a temperature range from 5 °C (from cold water) to 40 °C (hot meal). This study showed the comparison of the different segments on the same archwire, providing a better understanding of the behavior of these functionally graded materials.

In vivo assessment of the corrosion of nickel-titanium orthodontic archwires by using scanning electron microscopy and atomic force microscopy.

This study was undertaken to assess in vivo the corrosion in two commercial nickel-titanium (NiTi) orthodontic archwires removed from the oral cavity of patients using fluoride mouthwashes. Five volunteers took part in this study on the corrosion behavior of two brands of NiTi archwires (3M and AO (brand of archwire)) during use of two mouthwashes with neutral sodium fluoride 1.1%, one with acidulated fluoride 1.1%, and one with placebo and a control group. Each patient used one mouthwash in three different periods of time for 1 min a day for 30 days. The archwires were assessed with scanning electron microscopy and atomic force microscopy for qualitative and quantitative analysis. The values obtained with atomic force microscopy (AFM) were submitted to normality test, two-way analysis of variance, and Tukey's test at a significance level of 5%. The AFM images showed a gradual qualitative increase in the roughness of both types of wire between the treatments: control < placebo < neutral fluoride < acidulated fluoride. The arithmetic average of the roughness and root mean square of the roughness were similar. As for 3M archwires, only the acidulated fluoride group differed statistically from the others. As for AO archwires, the control and placebo groups did not differ from each other, but differed from the other fluoride treatments. The group using neutral fluoride also differed significantly from the acidulated fluoride group. 3M archwires were not affected by daily oral challenges. AO archwires were not affected by daily oral challenges either; their association with fluoride, either neutral or acidulated, increased their roughness.