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

Titanium and titanium alloys in dentistry: current trends, recent developments, and future prospects

Many implant materials have been used in various dental applications depending on their efficacy and availability. A dental implant must possess the required characteristics, such as biocompatibility, corrosion & wear resistance, adequate mechanical properties, osseointegration, etc., to ensure its safe and optimum use. This review analyzes various aspects of titanium (Ti) and Ti alloys, including properties, manufacturing processes, surface modifications, applications as dental implants, and limitations. In addition, it also presents a perception of recent advances in Ti-based implant materials and the futuristic development of innovative dental implants.

Ion Release and Surface Changes of Nickel-Titanium Archwires Induced by Changes in the pH Value of the Saliva-Significance for Human Health Risk Assessment

The aim of this study was to explore whether changes in the salivary pH influence mechanical properties, surface roughness, and ion release from NiTi archwires with various surface coatings, and discuss the clinical significance of the findings. The uncoated, rhodium-coated, and nitrified NiTi wires were immersed into artificial saliva of different pH values (4.8, 5.1, 5.5, and 6.6). Released nickel and titanium ions were measured with inductively coupled plasma-optical emission spectroscopy at the end of 28 days. Atomic force microscopy was used to measure the arithmetic average surface roughness R_a, the root-mean-square roughness R_q, and the maximum height of the asperities R_Z. The nanoindentation hardness (H_IT) and Young's modulus (E_IT) measurements were performed. The change in the pH of artificial saliva is inversely proportional to the release of titanium from both coated and uncoated wires, and the release of nickel from uncoated wires. The surface roughness parameters of both coated and uncoated wires are unaffected by the change in the pH of artificial saliva. The change in the pH of saliva has minor influence on the hardness and Young's modulus of elasticity of both coated and uncoated wires. The concentration of released metal ions measured was below the recommended upper limit for daily intake; nevertheless, hypersensitivity effects cannot be excluded, even at lower concentrations and at low pH.

An Insight into Geometries and Catalytic Applications of CeO2 from a DFT Outlook

Rare earth metal oxides (REMOs) have gained considerable attention in recent years owing to their distinctive properties and potential applications in electronic devices and catalysts. Particularly, cerium dioxide (CeO2), also known as ceria, has emerged as an interesting material in a wide variety of industrial, technological, and medical applications. Ceria can be synthesized with various morphologies, including rods, cubes, wires, tubes, and spheres. This comprehensive review offers valuable perceptions into the crystal structure, fundamental properties, and reaction mechanisms that govern the well-established surface-assisted reactions over ceria. The activity, selectivity, and stability of ceria, either as a stand-alone catalyst or as supports for other metals, are frequently ascribed to its strong interactions with the adsorbates and its facile redox cycle. Doping of ceria with transition metals is a common strategy to modify the characteristics and to fine-tune its reactive properties. DFT-derived chemical mechanisms are surveyed and presented in light of pertinent experimental findings. Finally, the effect of surface termination on catalysis by ceria is also highlighted.

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.

Short-term "in vivo" study on cellular DNA damage induced by acrylic Andresen activator in oral mucosa cells

OBJECTIVES

To analyse through comet assay and micronucleus test the viability and DNA damage occurred in buccal mucosa epithelial cells after a short-term exposure to Andresen activator resin monomers.

SETTING AND SAMPLE POPULATION

Test group consisting of 26 subjects was treated with Andresen activator; 16 subjects who had never undergone orthodontic treatment were enrolled in the control group.

MATERIAL & METHODS

Buccal mucosa samples were collected before treatment and after 7, 15, 30, 60 and 90 days. The analyses performed on the cells included the following: cellular viability, comet assay and micronucleus test. Mean ± SD were calculated for cellular viability, tail moment, tail intensity, tail length, micronuclei, binuclear and bud cells. Significance (P < 0.05) was evaluated with Dunnett's test.

RESULTS

Cellular viability did not change during observational time, and its trend was similar to the controls. Tail moment and tail intensity significantly increased after 30 and 60 days, respectively, whereas tail length remained unchanged over time in the test group; the same parameters did not change in the control group. In the test group, micronuclei, binuclear and bud cells significantly increased after 30, 60 and 90 days, respectively.

CONCLUSION

The resin monomers of the Andresen activator cause genotoxic effects detectable through comet assay and micronucleus test, but they do not produce clear cytotoxic effects after a 90 days exposure.

Effect of pH, fluoride and hydrofluoric acid concentration on ion release from NiTi wires with various coatings

Aim was to determine effect of pH, fluoride (F^-) and hydrofluoric acid concentration (HF) on dynamic of nickel (Ni²⁺) and titanium (Ti⁴⁺) ions release. Nickel-titanium wires with untreated surface (NiTi), rhodium (RhNiTi) and nitride (NNiTi) coating were immersed once a week for five min in remineralizing agents, followed by immersion to artificial saliva. Ion release was recorded after 3, 7, 14, 21 and 28 days. Pearson correlations and linear regression were used for statistical analysis. Release of Ni²⁺ from NiTi and NNiTi wires correlated highly linearly positively with HF (r=0.948 and 0.940, respectively); for RhNiTi the correlation was lower and negative (r=-0.605; p<0.05). The prediction of Ti⁴⁺ release was significant for NiTi (r=0.797) and NNiTi (r=0.788; p<0.05) wire. Association with F^- was lower; for pH it was not significant. HF predicts the release of ions from the NiTi wires better than the pH and F^- of the prophylactic agents.

Evaluation of corrosion resistance and surface characteristics of orthodontic wires immersed in different mouthwashes

BACKGROUND

Patients use mouthwashes in addition to mechanical cleaning during orthodontic treatment. The effects of mouthwashes on the archwires have not been examined yet.

OBJECTIVE

To compare the corrosion resistance of four different arch wires and corrosion effects of different mouthwashes to formulate a biocompatible and mechanically useful arch wire and mouthwash combination.

METHODS

Each group comprised of 4 wire samples of 2 cm 0.016 × 0.022 inch. 1st group: ion implanted nickel titanium (INT), 2nd group: nickel titanium, without ion implantation (NT), 3rd group: micro layered esthetic nickel titanium (ENT), 4th group: stainless steel (SS) wires. They were immersed inside 2 ml of artificial saliva solutions (AS) for the control, or AS (9%) combined with 1 of the 3 mouthwashes (91%) for study groups, for 24 hours. These mouthwashes were essential oil (EO), chlorhexidine (CHX), sodium-fluoride (NaF). An electrochemical analyzer was used for electrochemical impedance spectroscopy measurements.

RESULTS

High corrosion resistance was obtained for ENT than the other wires. The corrosion potentials are 0.007, -0.042, 0.074 and -0.015 V (Ag/AgCl) for ENT, INT, SS and NT in the artificial salivary, respectively. In NaF containing mouthwash Rp value of ENT is significantly high in comparison to others. The impedance responses of all materials increased significantly in the presence of NaF mouthwash as well as in the CHX mouthwash. Low frequencies are seen at all materials in EO mouthwash. Diameters of loops are 22, 5.9, 5.9 and 3.7 MΩ at ENT, INT, SS and NT.

CONCLUSIONS

In this study, micro layered esthetic nickel titanium wires are found biocompatible among other wires and NaF and CHX mouthwashes can be recommend for their good corrosion resistance during fixed orthodontic therapy.

In vitro biocompatibility of nickel-titanium esthetic orthodontic archwires

OBJECTIVE

To investigate the cytotoxicity of nickel-titanium (NiTi) esthetic orthodontic archwires with different surface coatings.

MATERIALS AND METHODS

Three fully coated, tooth-colored NiTi wires (BioCosmetic, Titanol Cosmetic, EverWhite), two ion-implanted wires (TMA Purple, Sentalloy High Aesthetic), five uncoated NiTi wires (BioStarter, BioTorque, Titanol Superelastic, Memory Wire Superelastic, and Sentalloy), one β-titanium wire (TMA), and one stainless steel wire (Stainless Steel) were considered for this study. The wire samples were placed at 37°C in airtight test tubes containing Dulbecco's Modified Eagle's Medium (0.1 mg/mL) for 1, 7, 14, and 30 days. The cell viability of human gingival fibroblasts (HGFs) cultured with this medium was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Data were analyzed by a two-way analysis of variance (α  =  .05).

RESULTS

The highest cytotoxic effect was reached on day 30 for all samples. The archwires exhibited a cytotoxicity on HGFs ranging from "none" to "slight," with the exception of the BioTorque, which resulted in moderate cytotoxicity on day 30. Significant differences were found between esthetic archwires and their uncoated pairs only for BioCosmetic (P  =  .001) and EverWhite (P < .001).

CONCLUSIONS

Under the experimental conditions, all of the NiTi esthetic archwires resulted in slight cytotoxicity, as did the respective uncoated wires. For this reason their clinical use may be considered to have similar risks to the uncoated archwires.

Surface treatment influences electrochemical stability of cpTi exposed to mouthwashes

The role of surface treatment on the electrochemical behavior of commercially pure titanium (cpTi) exposed to mouthwashes was tested. Seventy-five disks were divided into 15 groups according to surface treatment (machined, sand blasted with Al2O3, and acid etched) and electrolyte solution (artificial saliva — control, 0.12% chlorhexidine digluconate, 0.05% cetylpyridinium chloride, 0.2% sodium fluoride, and 1.5% hydrogen peroxide) (n = 5). Open-circuit-potential and electrochemical impedance spectroscopy were conducted at baseline and after 7 and 14 days of immersion in each solution. Potentiodynamic test and total weight loss of disks were performed after 14 days of immersion. Scanning electron microscopy, energy dispersive spectroscopy, white light interferometry and profilometry were conducted for surface characterization before and after the electrochemical tests. Sandblasting promoted the lowest polarization resistance (Rp) (P b .0001) and the highest capacitance (CPE) (P b .006), corrosion current density (Icorr) and corrosion rate (P b .0001). In contrast, acid etching increased Rp and reduced CPE, independent to the mouthwash; while hydrogen peroxide reduced Rp (P b .008) and increased Icorr and corrosion rate (P b .0001). The highest CPE values were found for hydrogen peroxide and 0.2% sodium fluoride. Immersion for longer period improved the electrochemical stability of cpTi (P b .05). In conclusion, acid etching enhanced the electrochemical stability of cpTi. Hydrogen peroxide and sodium fluoride reduced the resistance to corrosion of cpTi, independent to the surface treatment. Chlorhexidine gluconate and cetylpyridinium chloride did not alter the corrosive behavior of cpTi.

In vitro evaluation of biocompatibility of Ti-Mo-Sn-Zr superelastic alloy

Shape memory alloys (SMAs) including superelastic alloys have unique properties such as shape memory and superelasticity, thus they are recognized as very useful biomaterials. These properties are very advantageous for medical use, and actually the SMA wires have been widely used in medical field. However, biocompatibility of nickel-titanium (Ni-Ti) alloy, which is the only practical SMA at present, has been questioned because of its high nickel content. The aim of this study was to evaluate the biocompatibility of a newly developed Ni-free Ti-based SMA for medical use. The newly developed SMA made of Ti-Mo-Sn-Zr system was processed into a disk of 15.1 mm in diameter. Pure titanium of the same shape was prepared as control. All the disk surfaces were polished using emery papers, #120, #400, and #600. Scanning electron microscopy and a 3D optics profiler were used to evaluate the surface of the materials. In vitro evaluations included colony examination for evaluation of the cell cytotoxicity, DNA quantification for the cell proliferation, Alamar blue assay for metabolic activity, FDA staining for the live cell imaging, and cell cycle analysis, using Chinese hamster fibroblastic V-79 cells and mouse osteoblastic MC3T3-E1 cells. In colony examination and DNA quantification, there was no significant difference between the Ti-Mo-Sn-Zr and the pure titanium. In FDA staining, cultured cells on the Ti-Mo-Sn-Zr alloy showed the same biocompatibility as those on the pure titanium. The present results suggest that the newly developed Ti-Mo-Sn-Zr alloy showed the high biocompatibility comparable to pure titanium and can be used as efficient biomaterial for medical use.

Gradient control of the adhesive force between Ti/TiO2 nanotubular arrays fabricated by anodization

The poor control of the adhesion of TiO2 nanotubes (TNTs) layers to a non-anodized titanium (Ti) substrate has limited their widespread application, because the stripping mechanism has not yet been revealed. Here, we report a novel method to control the detachment of TNTs by post-treatment of the as-fabricated samples in protic and aprotic solvents with different polarities. Post-treatment using an organic solvent of lower polarity increases the adhesion of the tube layer, in contrast to the spontaneous detachment of the TNT layer after treatment using a solvent of higher polarity. The structure and the composition at the rupture interface were studied to explore the mechanism of the stripping behavior. Based on our experimental results and previous studies, a hypothesis of a hydrogen-assisted cracking (HAC) mechanism was proposed to explain the mechanism of TNTs' natural detachment and the control over of TNTs' stripping behaviors by post-treatment, in which the presence of protons at the interface between the TNT layer and the Ti substrate play an important role in controlling the two layers' cohesion. In summary, this method and mechanism hold promise to be used as a tool for the design and fabrication of TNT-related materials in future.

Influence of electrolytic treatment time on the corrosion resistance of Ni-Ti orthodontic wire

The purpose of this study was to examine the use of electrolytic treatment, which can improve the corrosion resistance of Ni-Ti orthodontic wires, to minimize adverse effects. Electrolytic treatment of Ni-Ti wires was performed in a solution composed of glycerol and lactic acid for 5, 15, or 30 min. The anodic polarization test, three-point bending test, and X-ray photoelectron spectroscopic analysis of the wire surface were performed to explore an optimal treatment condition. Breakdown potentials of treated wires increased with increasing treatment time and higher corrosion resistance was obtained by performing the electrolytic treatment for more than 5 min. The relative concentration of nickel in the layer was decreased in inverse proportion to the treatment time. The results suggest that the commercial Ni-Ti wire with low corrosion resistance can be improved by the electrolytic treatment for more than 5 min.

Effects of intraoral aging on surface properties of coated nickel-titanium archwires

OBJECTIVE

To evaluate the effects of intraoral aging on surface properties of esthetic and conventional nickel-titanium (NiTi) archwires.

MATERIALS AND METHODS

Five NiTi wires were considered for this study (Sentalloy, Sentalloy High Aesthetic, Superelastic Titanium Memory Wire, Esthetic Superelastic Titanium Memory Wire, and EverWhite). For each type of wire, four samples were analyzed as received and after 1 month of clinical use by an atomic force microscope (AFM) and a scanning electronic microscope (SEM). To evaluate sliding resistance, two stainless steel plates with three metallic or three monocrystalline brackets, bonded in passive configuration, were manufactured; four as-received and retrieved samples for every wire were pulled five times at 5 mm/min for 1 minute by means of an Instron 5566, recording the greatest friction value (N). Data were analyzed by one-way analysis of variance and by Student's t-test.

RESULTS

After clinical use, surface roughness increased considerably. The SEM images showed homogeneity for the as-received control wires; however, after clinical use esthetic wires exhibited a heterogeneous surface with craters and bumps. The lowest levels of friction were observed with the as-received Superelastic Titanium Memory Wire on metallic brackets. When tested on ceramic brackets, all the wires exhibited an increase in friction (t-test; P < .05). Furthermore, all the wires, except Sentalloy, showed a statistically significant increase in friction between the as-received and retrieved groups (t-test; P < .05).

CONCLUSION

Clinical use of the orthodontic wires increases their surface roughness and the level of friction.

Effect of chlorhexidine-containing prophylactic agent on the surface characterization and frictional resistance between orthodontic brackets and archwires: an in vitro study

Background

The purpose of this study was to assess the surface characterization and frictional resistance between stainless steel brackets and two types of orthodontic wires made of stainless steel and nickel-titanium alloys after immersion in a chlorhexidine-containing prophylactic agent.

Methods

Stainless steel orthodontic brackets with either stainless steel (SS) or heat-activated nickel-titanium (Ni-Ti) wires were immersed in a 0.2% chlorhexidine and an artificial saliva environment for 1.5 h. The frictional force was measured on a universal testing machine with a crosshead speed of 10 mm/min over a 5-mm of archwire. The surface morphology of bracket slots and surface roughness of archwires after immersion in chlorhexidine were also characterized using a scanning electron microscope (SEM) and an atomic force microscope (AFM), respectively.

Results

There was no significant difference in the frictional resistance values between SS and Ni-Ti wires immersed in either chlorhexidine or artificial saliva. The frictional resistance values for the SS and Ni-Ti wires immersed in 0.2% chlorhexidine solution were not significantly different from that inartificial saliva. No significant difference in the average surface roughness for both wires before (as-received) and after immersion in either chlorhexidine or artificial saliva was observed.

Conclusions

One-and-half-hour immersion in 0.2% chlorhexidine mouthrinse did not have significant influence on the archwires surface roughness or the frictional resistance between stainless steel orthodontic brackets and archwires made of SS and Ni-Ti. Based on these results, chlorhexidine-containing mouthrinses may be prescribed as non-destructive prophylactic agents on materials evaluated in the present study for orthodontic patients.