Archwire Surfaces Research Articles

A COMPARATIVE STUDY OF THE SURFACE OF FACTORY AND HAND-MADE LOOPS ON TITANIUM-MOLYBDENUM ORTHODONTIC ARCHWIRE

The most important part of the brackets, used in orthodontic treatment, is the archwire, which, when activated, generate light and long-lasting biomechanical forces that make the teeth move. Different manufacturers offer ready-made expensive solutions for orthodontists - archwire with loops along the length of the wire of different shape, which increases the cost of treatment. However, orthodontic practice is strictly individual, depending on the patient’s orthodontic problems, the stages and methods of treatment.Orthodontists often have to choose between expensive archwires with pre-made loops or using an archwire that they can manually bend in the right places depending on the patient’s individual characteristics and specific needs. In this case, the orthodontist’s decision depends on preserving the quality of the archwire surface. The surface roughness of the orthodontic archwire plays an important role in the bracket-archwire complex and is an essential factor that determines the effectiveness of the guided movement of the teeth along the arch. Surface roughness not only affects the efficiency of sliding mechanics, due to frictional effects, but also corrosion behaviour and aesthetics. A comparison of the surface characteristics of Ti-Mo archwire - with factory and hand-made loops is made. The surface of the archwire in the bending zones of the loops was investigated by SEM analysis and Surface roughness analysis. The analysis of the results shows that manual bending practically does not change the surface of the archwire, does not introduce additional defects that increase the contact friction, as well as create conditions for faster deterioration of properties and the undesirable breakage of the archwire. Research results give orthodontists confidence that the manual bending process does not degrade the quality of the archwire surface. The hand-bent archwire preserves the possibility of trouble-free movement in the braces when tightening or loosening during the different stages of treatment.

The effect of salbutamol sulphate inhalation (an anti-asthmatic medication) on the surfaces of orthodontic Archwires.

This study aimed to compare the surface roughness and friction of different orthodontic archwires after exposure to salbutamol sulphate inhalation, an anti-asthmatic medication. Orthodontic archwires (stainless-steel [StSt], nickel-titanium [NiTi], beta-titanium [β-Ti], and copper-NiTi [Cu-NiTi]) were equally divided into two groups. The exposed groups were subjected to 20 mg salbutamol sulphate for 21 days and kept in artificial saliva. The control groups were only kept in artificial saliva. Surface changes were visualized using scanning electron microscopy (SEM). The average surface roughness (Ra) was evaluated using atomic force microscopy (AFM), and friction resistance forces were assessed using a universal testing machine. Statistical analyses were performed using t-tests and ANOVA followed by post hoc tests. Salbutamol sulphate did not change the surface roughness of StSt and NiTi archwires (p > .05). However, the change in the surfaces of β-Ti and Cu-NiTi archwires was significant (p < .001). The frictional forces of exposed StSt, NiTi, and Cu-NiTi archwires did not change (p > .05). However, the frictional forces of β-Ti archwires increased significantly after exposure to salbutamol sulphate (p = .021). Brushing with fluoride after exposure to salbutamol sulphate increased the frictional forces of β-Ti only (p = .002). Salbutamol sulphate inhalation significantly affected the surface texture of β-Ti and Cu-NiTi orthodontic archwires and increased the friction of β-Ti archwires. These deteriorating effects were not detected on the surface of StSt and NiTi archwires. Therefore, we suggest that β-Ti and copper titanium archwires should be used cautiously in individuals under salbutamol sulphate inhalation treatment.

Graphene-Based Coatings for Surface Modification and Their Applications in Fixed Orthodontics: A Scoping Review.

Surface coating technology can assist fixed appliances by reducing friction, improving antibacterial characteristics, and increasing corrosion resistance. The application of functional coatings composed of graphene onto the surfaces of orthodontic brackets and archwires has been shown to enhance their mechanical qualities. The objective of the current study was to carry out a scoping analysis of published recent evidence on the utilization of graphene as a covering material in metallic orthodontic accessories, such as brackets and archwires; Methods: A scoping review was undertaken following the PRISMA-ScR guidelines. PubMed, Embase, the Cochrane Library, Dentistry and Oral Science Source, and Google Scholar were searched between 2003 and 2023; Results: In total, 38 potential references were detected, from which 10 were selected for this review. These articles addressed the benefits of the application of graphene-oxide functional coatings onto the surface of archwires and brackets during fixed orthodontic treatment. Orthodontic graphene-oxide-based coatings provide improved surface characteristics (e.g., reduced friction and anticorrosive effects), antibacterial capabilities, and biocompatibility. These characteristics can increase the effectiveness of orthodontic therapy, improve patient comfort, and lower the likelihood of problems; Conclusion: Orthodontists should be aware of and comprehend the prerequisites for using graphene-oxide-coated archwires and brackets to fulfill needs throughout their clinical practice.

Corrosion of copper nickel titanium archwire in chlorhexidine, sodium fluoride, and chitosan mouthwashes.

Copper (Cu), nickel (Ni), chromium (Cr) ion release, and surface topography change from the orthodontic wire are the initial processes of corrosion that may affect the mechanical properties of the archwire. In this study, we aim to evaluate the effect of CHX, NaF, and chitosan on the corrosion of CuNiTi wire nickel and copper ions released, surface roughness change, and archwire deflection. Ninety samples of CuNiTi Tanzo™ archwires were divided into five groups according to their immersion solution: Artificial Saliva, CHX, NaF, CHX-NaF, and chitosan group. Each group was further divided into three subgroups (n=6) corresponding immersion time, i.e., two, four, and six weeks. The corrosion of the samples was analyzed with an atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM), and universal testing machine (UTM). The amount of nickel ion releases was increasing, but the copper ion releases were reduced by the time of observations. The highest nickel ion was released in the CHX-NaF group and the lowest in the chitosan group for six-week immersion. It also corresponded to the surface topography by SEM analysis which showed the most extended cracks and deep pits in the CHX-NaF group and a smoother surface in the chitosan group. Copper ion release showed the highest ion release in the NaF group and the lowest release in the chitosan group. The unloading force of CuNiTi archwire deflection remains the same at week two and week four for all mouthwashes. The use of mouthwashes that contained CHX, NaF, and chitosan could further alter the passive layer and cause higher nickel and copper ion release and increased CuNiTi archwire surface structure porosity. But there is no distinction between mouthwashes to release the unloading force within two until four weeks.

Corrosion of copper nickel titanium archwire in chlorhexidine, sodium fluoride, and chitosan mouthwashes

Background: Copper (Cu), nickel (Ni), chromium (Cr) ion release, and surface topography change from the orthodontic wire are the initial processes of corrosion that may affect the mechanical properties of the archwire. In this study, we aim to evaluate the effect of CHX, NaF, and chitosan on the corrosion of CuNiTi wire nickel and copper ions released, surface roughness change, and archwire deflection. Methods: Ninety samples of CuNiTi Tanzo™ archwires were divided into five groups according to their immersion solution: Artificial Saliva, CHX, NaF, CHX-NaF, and chitosan group. Each group was further divided into three subgroups (n=6) corresponding immersion time, i.e., two, four, and six weeks. The corrosion of the samples was analyzed with an atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM), and universal testing machine (UTM). Results: The amount of nickel ion releases was increasing, but the copper ion releases were reduced by the time of observations. The highest nickel ion was released in the CHX-NaF group and the lowest in the chitosan group for six-week immersion. It also corresponded to the surface topography by SEM analysis which showed the most extended cracks and deep pits in the CHX-NaF group and a smoother surface in the chitosan group. Copper ion release showed the highest ion release in the NaF group and the lowest release in the chitosan group. The unloading force of CuNiTi archwire deflection remains the same at week two and week four for all mouthwashes. Conclusion: The use of mouthwashes that contained CHX, NaF, and chitosan could further alter the passive layer and cause higher nickel and copper ion release and increased CuNiTi archwire surface structure porosity. But there is no distinction between mouthwashes to release the unloading force within two until four weeks.

Synthesis of coatings on simulated body fluid in presence of Ag nanoparticles on NiTi archwires

In this study, coatings were synthesized on simulated body fluid (SBF) in the presence of silver nanoparticles on the surface of nickel-titanium archwires. The coatings were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray energy dispersive analysis (EDS), fast Fourier transform (FFT), force spectral density (PSD) analysis, surface geometry analysis and particle distribution analysis. The results show the efficiency of the electrostatic interaction of the SBF substrate and Ag nanoparticles in the formation of the coatings. The Ag nanoparticles in the coatings had diameters of approximately 50–150 nm. The pH and temperature conditions within the solution were optimized using a static technique. The functionality of the coatings and their relationship with the dominant wavelength in the force spectral density (PSD) and fast Fourier transform (FFT) analyses; were analyzed. This method opens up a new route for the synthesis of coatings in various body fluids using other biocompatible materials.

Nickel Release and the Viability of Streptococcus mutans Corresponding to Low Risk of Dental Caries in Artificial Saliva Containing Orthodontic Appliances: In Vitro Study.

The aims of this study were to determine the effect of different levels of Streptococcus mutans that correspond to a low risk of dental caries on nickel release and to determine the viability of S. mutans. Simulated fixed orthodontic appliances composed of copper nickel titanium, nickel titanium, or stainless steel were immersed in Klimek artificial saliva for 10 days with or without S. mutans inoculation on day 7. Same levels of S. mutans cultures (4 × 104 cfu/mL) were inoculated into the artificial saliva without orthodontic appliances. Nickel release was detected by inductively coupled plasma mass spectrometry. The archwire surface was analyzed by atomic force microscopy and scanning electron microscopy. The density of S. mutans significantly increased in the artificial saliva without orthodontic appliances (P < .05). Appliances with nickel titanium alloys showed higher nickel release in the artificial saliva with or without S. mutans than those with copper nickel titanium or stainless steel archwires (P < .05). However, S. mutans increased nickel release only in orthodontic appliances with stainless steel archwires (P < .05). Although atomic force microscopy showed that the surface of as-received stainless steel archwires was smoother than that of nickel titanium or nickel titanium archwires, S. mutans increased the surface roughness of only the SS archwires. S. mutans adhered to all archwire types. While corrosion or corrosion-related processes may have decreased the growth capacity of S. mutans, reciprocally, S. mutans influenced corrosion. Rough surfaces can also promote corrosion; therefore, the surface roughness of metal alloy orthodontic appliances should be evaluated to determine their corrosion behavior.

Release of nickel ions and changes in surface microstructure of stainless steel archwire after immersion in tomato and orange juice

Stainless steel archwire is an important component of orthodontic appliances that have the potential to corrode. Consumption of foods and beverages with a low pH, such as fruit-based juices, can trigger the release of nickel ions in stainless steel archwire. This study aimed to determine the difference in the amount of nickel ions release and the surface microstructure of stainless steel archwire after immersed in tomato and orange juice. The sample used is stainless steel archwire with a diameter of 0.016 inches and length of 5 cm immersed in 15 ml of solution and then stored at 37°C in an incubator for 24 hours. The samples were divided into three groups (immersed in tomato juice,orange juice and artificial saliva), each group consisted of 9 samples. The solution was tested using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) to determine the number of nickel ions released. The archwire surface microstructure was tested using a Scanning Electron Microscope (SEM). The results showed that the average amount of nickel ion release in orange juice is more than tomato juice. There was a significant difference between the amount of nickel ion released and surface microstructure on stainless steel archwire after being immersed in tomato and orange juice.

Effect of anodization on friction behavior of β‑titanium orthodontic archwires.

To evaluate the effects of anodization on the friction behavior of beta-titanium (β-Ti) orthodontic archwires in conventional or self-ligating brackets in vitro. β‑Ti archwires (0.018 × 0.025inch) pre- and postanodization were tested in combination with 0.022-inch stainless steel conventional and self-ligating brackets. The surface composition and oxide thickness of the β‑Ti archwires pre- and postanodization were measured using Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). Detailed surface topography and roughness were assessed using atomic force microscopy (AFM). Surface topographies of the β‑Ti archwires pre- and postanodization were examined using scanning electron microscopy (SEM). Friction was measured using auniversal testing machine; the data were statistically analyzed. Postanodization, the identified titanium oxide layer on the surface of the β‑Ti archwires increased in thickness from10 to 100 nm; at the same time, the values for surface roughness were significantly reduced by half (p < 0.001). The archwire surfaces post anodization were harder and had fewer scratches after the friction test. Anodization significantly reduced 23.77% of the static (p < 0.01) and 25.61% of the kinetic (p < 0.001) friction of the β‑Ti archwires in conventional brackets, while it significantly reduced 85.71% of the static and 84.38% of the kinetic friction (p < 0.01) in self-ligating brackets. Anodization reduced the β‑Ti archwire friction, which was particularly more effective in combination with self-ligating brackets. The friction reduction via anodization could be attributed to the increased thickness, surface hardness, and decreased surface roughness of the titanium oxide layer.

Ovrednotenje mikrobne flore pri pacientih s povečanjem dlesni med obravnavo in analiza površine žičnega loka nesnemnega ortodontskega aparata

Gingival enlargement is a common complication of treatment with a fixed orthodontic appliance, biocompatible stainless-steel archwires AISI 304L (SS). Due to the retention areas, dental plaque accumulation is increased, which results in anaerobic conditions, favourable for periodontopathogenic bacteria. Therefore, it is reasonable to assume that periodontopathogenic bacteria can be found in patients with fixed orthodontic appliances. Organic deposits on the surface of archwires were analyzed. Twenty-one patients with fixed orthodontic appliances and gingival enlargement in the upper dental arch were included in the study. For a determination of the periodontopathogenic bacteria Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia and Treponema denticola the molecular microbiological method GenoType Test System was used. For the surface analysis of new and in-vivo exposed SS archwires X-ray Photoelectron Spectroscopy was used. The average probing depth at the baseline was 3.76±0.85 mm. Three types of periodontopathogenic bacteria, namely A. actinomycetemcomitans, T. forsythia and T. denticola, were found to be present. The thickeness of the thin oxide film on new archwires was 8 nm, while organic deposits on the in-vivo exposed archwires was estimated to 60–80 nm. Anaerobic periodontopathogenic bacteria can be found in patients with fixed orthodontic appliances. Therefore, special care is recommended during this kind of treatment.

Comparison of friction coefficient and surface roughness on stainless steel nickel titanium, and nickel-titanium copper wires to standard edgewise brackets: An experimental in vitro study

Aim: The aim of this study was to investigate the friction and the difference in the roughness of the wire on the standard edgewise bracket. Materials and Methods: This was an experimental laboratory study with a posttest only control group design. The number of samples in this research was 21. The samples were divided into three groups (n = 7) consisting of 0.016′′ x 0.022′′ stainless steel archwire (SS group), 0.016′′ x 0.022′′ nickel-titanium archwire (NiTi group), and 0.016′′ x 0.022′′ nickel-titanium copper archwire (NiTiCu group). The bracket used in each group is standard edgewise slot 0.018. Friction coefficient test was conducted by creating an examination tool from acrylic to fixate the bracket with a size of 2cm x 5cm. The bracket was then attached using glue (polyvinyl acetate) and the archwire was fixated to the bracket using power O. After the friction test, three samples were taken from each group to be tested morphology and topography of each type using scanning electron microscope (SEM). Statistical analysis used in this research is using one-way analysis of variance (ANOVA) to find out the comparison of variables and Tukey’s honest significant difference (HSD) to find out the comparison between three groups (P < 0.05). Results: The lowest friction coefficient was found in SS archwire, which consecutively followed by NiTiCu and NiTi. The smoothest archwire surface observed by SEM was SS, followed by NiTiCu and NiTi. Conclusion: SS wire has the smoothest archwire surface and the lowest frictional force, so it is well used for the teeth movement in space closing on edgewise bracket.

Nickel release and the microstructure of stainless steel orthodontic archwire surfaces after immersion in detergent and non-detergent toothpaste: an in vitro study

Background: Stainless steel is a material that can be used in orthodontics for components of dental braces, such as brackets, archwires and molar bands. Orthodontic archwires exposed to toothpaste can release nickel ions that cause hypersensitivity. The excessive use of sodium lauryl sulphate in detergent toothpaste can cause mouth irritation, severe ulceration, decreased salivary solubility and taste sensitivity changes. Purpose: The aim of this study is to compare the nickel ion released by stainless steel archwires after immersion in detergent and non-detergent toothpaste. Methods: Forty stainless steel archwires from Ortho Organizer (0.016 x 0.022in) were divided into two groups (n=20). Group 1 comprised stainless steel archwires immersed in detergent toothpaste. Group 2 consisted of stainless steel archwires immersed in non-detergent toothpaste. These archwires were immersed in 1.5g toothpaste then kept in an incubator at 37°C for around 24 hours. After that, the archwires were removed from the toothpaste, and the toothpaste was dissolved in 25ml of Aquadest. The amount of nickel ion released was examined by using inductively coupled plasma optical emission spectrometry (ICP-OES). After that, the structure of the sample surface was examined with a scanning electron microscope (SEM). A statistical analysis was done using the Shapiro–Wilk normality test (p&gt;0.05). An independent t-test was carried out to compare the two groups (p&lt;0.05). Results: The mean of nickel ion release in group 1 was 0.214±0.319mg/l, and in group 2 it was 0.168±0.107 mg/l. There was no significance between the groups (p=0.323; p&gt;0.05). The SEM images of the archwire surfaces showed that there were more corrosive contour changes in the archwire surface in group 1 than in group 2. Conclusion: There was no difference between the nickel ion released from stainless steel orthodontic archwires after immersion in detergent and non-detergent toothpaste. After immersion in detergent toothpaste, stainless steel archwire surfaces showed more corrosive contour changes than those immersed in non-detergent toothpaste.

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.

Assessment of Streptococcus Mutans Adhesion to the Surface of Biomimetically-Modified Orthodontic Archwires

Bacterial adhesion and biofilm formation on the surfaces of dental and orthodontic biomaterials is primary responsible for oral diseases and biomaterial deterioration. A number of alternatives to reduce bacterial adhesion to biomaterials, including surface modification using a variety of techniques, has been proposed. Even though surface modification has demonstrated a reduction in bacterial adhesion, information on surface modification and biomimetics to reduce bacterial adhesion to a surface is scarce. Therefore, the main objective of this work was to assess bacterial adhesion to orthodontic archwires that were modified following a biomimetic approach. The sample consisted of 0.017 × 0.025, 10 mm-long 316L stainless steel and NiTi orthodontic archwire fragments. For soft lithography, a polydimethylsiloxane (PDMS) stamp was obtained after duplicating the surface of Colocasia esculenta (L) Schott leaves. Topography transfer to the archwires was performed using silica sol. Surface hydrophobicity was assessed by contact angle and surface roughness by atomic force microscopy. Bacterial adhesion was evaluated using Streptococcus mutans. The topography of the Colocasia esculenta (L) Schott leaf was successfully transferred to the surface of the archwires. Contact angle and roughness between modified and unmodified archwire surfaces was statistically significant. A statistically significant reduction in Streptococcus mutans adhesion to modified archwires was also observed.

Evaluation of biofilm accumulation on and deactivation force of orthodontic Ni-Ti archwires before and after exposure to an oral medium: A prospective clinical study.

Background. This in vitro study aimed to evaluate biofilm accumulation on and deactivation force of orthodontic nickeltitanium (NiTi) archwires before and after exposure to an oral medium. Methods. Four commercial brands of orthodontic NiTi 0.016" archwires were examined before and after exposure to the oral medium for 4 weeks. Six archwire segments, 30 mm in length, from each manufacturer were tested in a device with four selfligating brackets, channel 0.022", adapted to a universal test machine to evaluate the deactivation force between 0.5 and 3 mm of deflection. The presence of biofilm on the archwire surfaces was evaluated by scanning electron microscopy, before and after exposure to the oral medium. The Wilcoxon and kappa tests were applied to the biofilm scores, three-way ANOVA for repeated measures (Bonferroni post-test), and linear regression between biofilm and deactivation force. Results. The exposure to the oral medium promoted moderate to severe presence of debris on the archwire surfaces and caused a reduction in deactivation force for the Ormco and GAC brands, while maintaining them with adequate force levels. The MORELLI and ORTHOMETRIC archwires underwent no significant reduction in deactivation force; moreover, these maintained elevated levels of force after exposure to the oral medium. The Spearman test indicated a low correlation between biofilm accumulation and deflection force for the Morelli (R2=0.132 and P=0.683) and Orthometric (R2=0.308 and P=0.330) brands. On the other hand, the GAC (R=0.767 and P=0.004) and ORMCO (R=0.725 and P=0.008) brands exhibited statistically significant correlation between these variables. Conclusion. Exposure to the oral medium for one month might give rise to significant changes in the dissipation of forces of orthodontic NiTi archwires, resulting from biofilm accumulation.

Characterisation of NiTi Orthodontic Archwires Surface after the Simulation of Mechanical Loading in CACO2-2 Cell Culture

Nickel-titanium (NiTi) orthodontic archwires are crucial in the initial stages of orthodontic therapy when the movement of teeth and deflection of the archwire are the largest. Their great mechanical properties come with their main disadvantage—the leakage of nickel. Various in vitro studies measured nickel leakage from archwires that were only immersed in the medium with little or minimal simulation of all stress and deflection forces that affect them. This study aims to overcome that by simulating deflection forces that those archwires are exposed to inside the mouth of a patient. NiTi orthodontic archwires were immersed in CACO2-2 cell culture medium and then immediately loaded while using a simulator of multiaxial stress for 24 h. After the experiment, the surface of the NiTi orthodontic archwires were analysed while using scanning electron microscopy (SEM) and auger electron spectroscopy (AES). The observations showed significant microstructural and compositional changes within the first 51 nm thickness of the archwire surface. Furthermore, the released nickel and titanium concentrations in the CACO2-2 cell culture medium were measured while using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). It was found out that the level of released nickel ions was 1.310 µg/L, which can be assigned as statistically significant results. These data represent the first mention of the already detectable release of Ni ions after 24 h during the simulation of mechanical loading in the CACO2-2 cell culture medium, which is important for clinical orthodontic praxis.

Color stability of esthetic coatings applied to nickel-titanium archwires

Abstract Introduction Color stability is an important feature to be considered when using esthetic coated archwires. Objective To evaluate color changes on the surface of esthetic nickel-titanium archwires coated with Teflon (Ortho Organizers, USA) or epoxy resin (Tecnident, Brazil) after immersion in staining solution. Material and method Twelve 20-mm-long wire segments were used for each type of coating, which were mounted as two test specimens with a width of 7 mm each. The buccal surface of the archwires was evaluated for fluorescence and color measurements both at baseline and after immersion in a staining solution for 21 days using the VITA Easyshade® Compact spectrophotometer (Model DEASYC220). Differences in total color change according to coating type were compared using an independent samples t-test (p&lt;0.05). The surface characteristics of as-received coated archwires were assessed using scanning electron microscopy. Result Color changes were observed on the esthetic coatings, with a significant difference between the two brands analyzed. Surface analysis revealed flaws such as wear, pitting, elevations, lack of material, granulation, grooves, cracks, and lack of standardization in the coating process in all as-received archwires, but flaws were less evident in epoxy-resin coatings. Conclusion The two esthetic coatings did not show color stability, but Teflon coatings showed a more intense color change than epoxy-resin coatings.

Investigation of the Dissolution–Reformation Cycle of the Passive Oxide Layer on NiTi Orthodontic Archwires

Dissolution–reformation cycle of the passive oxide layer on the nickel–titanium (NiTi) orthodontic archwires was investigated, which has recently been recognized as one of the key parameters dictating the biocompatibility of archwires. Specifically, commercially available NiTi orthodontic archwires were immersed in artificial saliva solutions of different pH values (2.3, 3.3, and 4.3) for four different immersion periods: 1, 7, 14, and 30 days. Characterization of the virgin and tested samples revealed that the titanium oxide layer on the NiTi archwire surfaces exhibit a dissolution–reformation cycle within the first 14 days of the immersion period: the largest amount of Ni ion release occurred within the first week of immersion, while it significantly decreased during the reformation period from day 7 to day 14. Furthermore, the oxide layer reformation was catalyzed on the grooves within the peaks and valleys due to relatively larger surface energy of these regions, which eventually decreased the surface roughness significantly within the reformation period. Overall, the current results clearly demonstrate that the analyses of dissolution–reformation cycle of the oxide layer in orthodontic archwires, surface roughness, and ion release behavior constitute utmost importance in order to ensure both the highest degree of biocompatibility and an efficient medical treatment.

In vitro sliding-driven morphological changes in representative esthetic NiTi archwire surfaces.

This study investigated the effects of sliding on the ultrastructure of three representative esthetic superelastic 0.014 inch nickel-titanium (NiTi) archwires. Atomic force microscopy, scanning electron microscopy, and light microscopy were used to estimate the surface roughness of archwires and bracket systems. Energy-dispersive X-ray spectroscopy was used to estimate the molecular differences between coated and uncoated areas. A combination of four different types of 0.014 inch metallic wires and two different types of 0.022 inch × 0.028 inch conventional brackets were evaluated by in vitro sliding tests using a novel self-made tensile-strength tester with a miniature load cell and syringe pump. The NiTi wires included an uncoated NiTi archwire (CO group), epoxy resin-coated NiTi archwire (ER group), Teflon(®) -coated NiTi archwire (TF group), and Ag/biopolymer-coated NiTi archwire (AG group). The brackets included contained stainless steel (SS) and ceramic (CE) brackets. Both ER and TF wire groups exhibited less surface roughness than CO wire groups. The AG group showed the highest surface roughness compared with the others because of its silver particles (P<0.001, ANOVA test). In vitro sliding tests led to a significant increase (P < 0.001, ANOVA test) in the surface roughness of all 0.014 inch NiTi wires regardless of bracket type. The wire groups combined with SS brackets were rougher than those of CE brackets regardless of the coating materials because of exfoliation of the coating materials. The TF-SS group showed the highest increase (fivefold) in surface roughness compared to the others, while the ER groups showed the lowest increase (1.4-fold) in surface roughness compared with the others (P < 0.001, ANOVA test). The results suggested that the sliding-driven surface roughness of superelastic NiTi archwires is directly affected by coating materials. Although the efficiency of orthodontic treatment was affected by various factors, epoxy resin-coated archwires were best for both esthetics and tooth movement when only considering surface roughness.

Influence of Soft Drinks with Low pH on Different Ni-Ti Orthodontic Archwire Surface Patterns

The aim of this study was to determine the influence of soft drinks on the surface of Ni-Ti archwires and their corrosion behavior. Archwires with different patterns (smooth, scratch, dimple, and crack) were selected and characterized by scanning electron microscopy and laser confocal microscopy. Immersion tests were performed in artificial saliva (pH 6.7) with a soft drink with a pH of 2.5 for 28 days. The results showed an increase in the surface defects and/or roughness of the dimple, crack and scratch patterns with the immersion times, and a decrease in corrosion resistance. A relationship between the surface pattern and the extent of the corrosion in Ni-Ti archwires with soft drinks at low pH has been demonstrated. Pattern should be taken into account in future studies, and manufacturing processes that produce surface defects (especially cracks) should be avoided.