Nickel-titanium Archwires Research Articles

Coated nickel titanium archwires and their uncoated counterparts: In-vitro contemporary comparison of unloading forces

To compare the unloading forces between aesthetic nickel titanium (NiTi) wires coated with rhodium and epoxy resin, as well as their uncoated equivalents. Additionally, intragroup comparisons between the different deactivation forces were evaluated, and the inner alloy cores were determined. Forty-four 0.018" NiTi wire segments were equally divided into 4 groups: E- NiTi coated with epoxy resin, C- NiTi uncoated, R- heat-activated NiTi coated with rhodium, and T- heat-activated NiTi uncoated. The unloading values were recorded at 0.5, 1, 2, and 3mm using a 3-point bending test, according to the method in ISO Standard 15.841. Cross-sectional scanning electron microscopy was used to assess the inner alloy core thickness of the wires. The intergroup comparison was successively: at 0.5mm: E (1.21)>C (0.60)=R (0.63)=T (0.58); at 1mm: E (1.30)=C (1.23)>R (0.91)=T (0.80); at 2mm:C (1.93)>E (1.36)=R (1.20) and R (1.20)=T (1.00) and E (1.36)>T (1.00); at 3mm:C (2.44)>R (2.02)>E (1.62)=T (1.68). The intragroup comparisons showed for all groups that the forces were statistically higher at 3mm than the other deactivations (p<0.01). Group E presented a reduced inner alloy core (.0155). The unloading forces demonstrated variability between the wires tested and between the different deactivations. Therefore, depending on the type of movement required and the periodontal conditions, orthodontists should pay attention during archwire selection.

A clinical comparison of the effectiveness of two types of orthodontic aligning archwire materials: a multicentre randomized clinical trial.

To compare the heat-activated nickel titanium (HANT) with superelastic nickel-titanium (SENT) archwires in terms of their effectiveness of aligning teeth, possibility of inducing root resorption, and perception of pain. Orthodontic patients aged 12 years or over with mandibular anterior crowding of 3-6 mm, who required treatment without extractions were randomly allocated (a simple non-stratified randomization) to the HANT and SENT archwires groups with a 1:1 allocation ratio. The archwire sequence in both groups was 0.014-inch and 0.016-inch, respectively. Each archwire was placed for 4 weeks. The outcome measures included the amount of crowding assessed blindly using Little's irregularity index (LII), apical root resorption, and pain perception. The effectiveness of alignment was tested using 2 × 2 mixed factorial analysis of variance (ANOVA) model, while root resorption and pain perception were tested by the Mann-Whitney U-test and Wilcoxon signed-rank test (P < 0.05). Thirty-four patients were randomized and recruited from four centres, of those 31 were analysed (15 participants for the HANT and 16 for the SENT groups) with an overall mean age of 19.13 ± 5.73 years. The total reduction in the LII was 2.69 mm and 2.74 mm for the HANT and SENT groups, respectively. This did not reach the level of statistical (P = 0.809) or clinical significance. Similarly, root resorption and pain perception showed non-significant difference between groups. However, there was a slight increase in root resorption with the SENT group. A long-term evaluation of root resorption is required. Both HANT and SENT archwires were equally effective in the aligning stage of orthodontic treatment. Root resorption with SENT wires should be monitored throughout treatment. The trial was registered with ClinicalTrials.gov on 18 September 2019, registration number: NCT04090931.

Combined orthodontic and surgical treatment of impacted maxillary canine in young patient with class II malocclusion: A case report

The impaction of maxillary canines is one of the biggest challenges in orthodontics practice. This case report describes successful surgical and orthodontic approach to the treatment of palatally impacted maxillary canine in a 14-year-old boy. Intraoral clinical examination revealed an absence of the upper right canine, an ectopic position of the upper left canine and crowding in the maxillary arch. The impaction of right maxillary canine and class II malocclusion were confirmed by lateral cephalogram, orthopantomogram and cone beam computed tomography. In the first phase, a transpalatal arch to the upper first molar teeth was applied, first premolars were extracted, and brackets were placed on all teeth and nickel-titanium arch wire was applied. The initial orthodontic phase was soon thereafter followed by the surgical exposure and orthodontic traction of the impacted canine using ligature wire attached from the button with chain to the open coil on the arch wire. The orthodontic treatment took two years with satisfactory aesthetic and functional results at the end. This clinical case has shown that adequate treatment of impacted maxillary canine can be achieved by using combined surgical technique and appropriate orthodontic approach.

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.

A comparative assessment of clinical efficiency between premium heat-activated copper nickel-titanium and superelastic nickel-titanium archwires during initial orthodontic alignment in adolescents: a randomized clinical trial

BackgroundTo compare the clinical efficiency of premium heat-activated copper nickel-titanium (Tanzo Cu-NiTi) and NT3 superelastic NiTi during initial orthodontic alignment.Subject and methodsA total of 50 patients were randomly allocated to 1 of 2 different archwire types (group 1, Tanzo Cu-NiTi; group 2, NT3 superelastic NiTi). Eligibility criteria included Class I or Class II malocclusion, moderate maxillary anterior crowding, and healthy periodontal condition. Impressions of the upper arches were taken before archwire placement (T0) and at every 4 weeks (T1, T2, T3, and T4). For T1 and T2 stages, 0.014-in., and for T3 and T4 stages, 0.018-in. archwires were used. The primary outcome was the alignment efficiency assessed using Little’s irregularity index. The secondary outcomes were arch width and incisor inclination changes. Data were analyzed using independent samples t test, repeated measures ANOVA, and Mann-Whitney U test. Marginal models were established for the estimation of coefficients.ResultsThe anterior irregularity index reduction was mostly observed between T0 and T2 periods, which were respectively − 7.40 ± 0.50 mm (p < 0.001; 95% CI, − 8.94, − 5.85) and − 6.80 ± 0.55 mm (p < 0.001; 95% CI, − 8.49, − 5.12) for groups 1 and 2 (p < 0.001). With both wires, Little’s irregularity index decreased over time, and the difference between the groups was not significant (p = 0.581; estimated effect size, 0.011). No statistically significant difference was found between the groups in terms of intercanine and intermolar width and incisor inclination changes.ConclusionThere were no significant between-group differences in alignment efficiency, arch width, and incisor inclination change. There was an increased alignment with 0.014-in. compared with 0.018-in. diameter archwire.

Can 3D imaging and digital software increase the ability to predict dental arch form after orthodontic treatment?

This study aimed to evaluate the ability of dental clinicians to predict posttreatment dental arch forms in patients with malocclusion with the aid of 3D imaging and digital software in comparison with a conventional method. Pretreatment and posttreatment dental plaster casts of 100 patients (200 maxillary models and 200 mandibular models) were selected. Three orthodontists selected the best-fitted archwires among 5 commercially available preformed nickel-titanium archwires using 2 methods. In the conventional method, they fit the archwires to pretreatment casts, and in the digital method, they fit the scanned wire to a 3D digital model, using Ortho-Aid, a locally developed 3D software, using clinical bracket points as reference for wire fitness. The predicted posttreatment archwire in each method was compared with the best-fit archwire on the actual posttreatment model of each patient in both methods, and the level of agreement was calculated. The interobserver agreement between the 3 orthodontists in each method was evaluated using intraclass correlation coefficient and the Dahlberg formula. Orthodontists predicted the final treatment outcome in 50% of cases using the conventional method and 58% using the digital method. However, the range of method error was significantly higher in the conventional method (0.425-3.853mm for the conventional vs 0.451-0.584mm for the digital). Although the clinicians' ability to predict the final dental arch form after orthodontic treatment and the agreement between clinicians increased by the use of digital equipment, orthodontists can predict the final arch form in about 60% of patients.

Evaluation of friction on self-ligating and conventional brackets associated with different types of archwires submitted to sliding mechanics

Aim: The aim of this study was to verify the frictional force during sliding mechanics in orthodontic tooth movement, using conventional metal brackets of the active and passive self-ligating types with stainless steel and copper nickel titanium archwires. Methods: This experimental in vitro study was conducted with conventional metal (Morelli, Sorocaba, SP, Brazil) brackets, active self-ligated (SLI Morelli, Sorocaba, SP, Brazil) and passive self-ligated (SLP Morelli, Sorocaba, SP, Brazil), with slot 0.022 x 0.028 inches and Roth prescription. The brackets were tested with rectangular section 0.019 x 0.025 inch copper nickel titanium and stainless steel archwires. For each type of bracket, 10 sets of plate/bracket/archwire segment (n=10) were fabricated. Non-parametric Kruskal Wallis and Dunn tests were used for comparison between types of brackets and Wilcoxon tests for comparison between types of archwires. Results: The results showed that the frictional force values were higher with copper nickel titanium than with stainless steel archwires (p&lt;0.05). When copper nickel titanium archwires were used, the active self-ligating brackets showed higher frictional force values than the other types, followed by the conventional brackets. Lower frictional force values were observed with passive self-ligating brackets. For stainless steel archwires, no difference was observed between conventional and active self-ligating brackets, the passive self-ligating type presented lower frictional force values than the others. Conclusion: It was concluded that the higher frictional force was observed when active self-ligating brackets were associated with copper nickel titanium archwires. Lower frictional force was verified between passive self-ligating brackets combined with stainless steel archwires.

Functional properties of superelastic orthodontic nickel-titanium archwires with protective titanium nitride coatings

Today there are many manufacturers of orthodontic archwires composed of a nickel-titanium (TiNi) alloy with different elastic-force characteristics. A limited number of orthodontic archwires is available for initial tooth alignment, since reactive stresses do not always satisfy the condition 160 ≤ σc ≤ 200 MPa. The use of orthodontic archwires with polymer coatings having better aesthetics is increasing. However, they show excessive wear and color change during a long-term orthodontic treatment. The aim of this paper is to study and optimize the functional characteristics of superelastic archwires composed of Ti-50.8 аР % Ni alloy with TiN coatings deposited at varying deposition times. A three-point bending test was carried out to evaluate the functional properties. The distance between the supporters was 10 mm. The archwires were subjected to bending at a temperature of 23 ± 3 °C. Each test was continued until deformation of 1.5; 3; 4.5 and 6 % was reached. It has been found that titanium nitride coatings deposited on the Ti-50.8 at. % Ni surface alloy by the vacuum-plasma method act as the barrier layer to prevent the release of nickel ions into biological environment. Heat treatment (~400 °C) during deposition allows the required elastic-force characteristics and functional properties of the material to form. The optimal reactive stress (160-200 MPa) and the reverse martensitic transformation temperature occurred near room temperature can be obtained due to an appropriate selection of the deposition parameters. In the martensitic phase at room temperature, the archwire can be deformed. When the archwire sample is placed in oral cavity and heated to temperatures above 30 °C the material is in the superelastic state. Further research is needed in terms of coating stability during deformation when the material in superelastic state, as well as conducting corrosion testing, studying biocompatibility of archwire samples with titanium nitride coatings in order to successfully implement the proposed technology in dental practice. The prototypes of orthodontic TiNi archwires with protective and decorative TiN coatings will be obtained for medical application.

Comparison of cold-hardening bending and direct electric resistance heat treatment on the mechanical properties and transformation temperature of NiTi archwire: An in vitro study

The aim of this investigation was (1) to compare the effects of cold-hardening bending and direct electric resistance heat treatment (DERHT) methods; and (2) to compare the effects of offsets and angulations on the mechanical properties and thermal analysis of NiTi alloy archwire. Nickel-titanium (NiTi) archwires (Ormco, Glendora, CA), 0.016×0.022-inch, were bent by cold-hardening bending and DERHT methods into 1-mm, 2-mm, or 3-mm offset for a 3-point bending test, and at angles of 30°, 45°, or 60° to the horizontal plane for testing the change in transformation temperature (Af) measured by differential scanning calorimetry (DSC). The data were analysed using ANOVA followed by the Scheffe post-hoc test. The 3-point bending test results of the cold-hardening bending and DERHT methods were not significantly different between the 1-mm, 2-mm and 3-mm offset groups (95% CI: -0.05 to 0.97; P=0.082, 95% CI: -0.65 to 0.74; P=0.983 and 95% CI: -0.61 to 0.98; P=0.813, respectively). Increasing the offset resulted in a significantly decreased force in the 3-point bending test (P<0.001). The Af temperatures of the cold-hardening bending and DERHT methods were not significantly different for the 30°, 45°, and 60° bending angulations (95% CI: -1.93 to 1.39; P=0.876, 95% CI: -1.2 to 0.87; P=0.878, 95% CI: -2.24 to 1.18; P=0.636, respectively). Af temperatures were not influenced by different bending angulations. NiTi archwire shape can be modified by using both cold-hardening and DERHT bending methods, because the mechanical properties and Af temperature are not affected. However, the bending distance has an effect on the mechanical properties.

A comparative study of initial changes in pulpal blood flow between clear aligners and fixed orthodontic appliances

The objective of this study is to evaluate and compare the initial changes of pulpal blood flow (PBF) using clear aligner and fixed orthodontic treatment. A total of 45 subjects were subdivided into 2 groups: group 1; 25 subjects treated with preadjusted edgewise fixed appliance with 0.014″ nickel titanium as the alignment archwire and group 2; 20 subjects treated using clear aligner. In both groups, PBF was measured for the maxillary right and mandibular left teeth using Laser Doppler flowmetry at different time intervals (20minutes, 48hours, 72hours, and 1month) after the fitting of the nickel titanium archwire in group 1 and after the delivery of the second aligner in group 2. A repeated-measures analysis of variance and a Bonferroni post-hoc comparison test were applied to determine differences at the various time intervals. The PBF decreased in both types of appliances after force application. The maximum reduction in PBF was reached after 72hours. It returned to its normal values within 1month. The differences in PBF between the 2 groups did not reach any statistical significance. PBF in orthodontically treated teeth decreased 20minutes after orthodontic force application in both fixed and clear aligner appliances. In both treatment groups, most changes occurred within 48hours of force application. PBF returned to its normal values within 1month. Changes in PBF in both treatment groups were comparable.

Finite element study of controlling factors of anterior intrusion and torque during Temporary Skeletal Anchorage Device (TSAD) dependent en masse retraction without posterior appliances: Biocreative hybrid retractor (CH-retractor).

To evaluate, using the finite element method (FEM), the factors that allow control of the anterior teeth during en masse retraction with the Biocreative hybrid retractor (CH-retractor) using different sizes of nickel-titanium (NiTi) archwires and various gable bends on the stainless-steel (SS) archwires. Using FEM, the anterior archwire section, engaged on the anterior dentition, was modeled in NiTi, and another assembly, the posterior guiding archwire, was modeled in SS. Two dimensions (0.016 × 0.022- and 0.017 × 0.025-inch NiTi) of the anterior archwires and different degrees (0°, 15°, 30°, 45°, and 60°) of the gable bends on the guiding wire were applied to the CH-retractor on the anterior segment to evaluate torque and intrusion with 100-g retraction force to TSADs. Finite element analysis permitted sophisticated analysis of anterior tooth displacement. With a 0° gable bend all anterior teeth experienced extrusion. The canines showed a larger amount of extrusion than did the central and lateral incisors. With a gable bend of >15°, all anterior teeth exhibited intrusion. Bodily movement of the central incisor required a 30°∼45° gable bend when using anterior segments of 0.016 × 0.022-inch NiTi and 15°∼30° gable bend with the 0.017 × 0.025-inch NiTi. With the CH-retractor, varying the size of the NiTi archwire and/or varying the amount of gable bend on the SS archwire affects control of the anterior teeth during en masse retraction without a posterior appliance.

Effects of Fluoride on NiTi Orthodontic Archwires: An X-ray Diffraction Study:

Objective: To explore the changes in nickel-titanium (NiTi) archwires after exposure to fluoride-containing acetic acid solutions. Materials and methods: Preformed rectangular NiTi wires were immersed in either an acidulated fluoride solution, a neutral fluoride solution or distilled water (control) for 1.5 hours at 37°C. After immersion, the unloading force values at four deflection points were measured by three-point bending test. Scanning electron microscopy and X-ray diffraction analysis were also performed to characterize the effects of the fluoride exposure on the wire. Results: Unloading force values of NiTi orthodontic wires were significantly decreased after exposure to both fluoride solutions (p < 0.001). Corrosive changes in surface topography were observed for both fluoride solutions. Wires exposed to acidic fluoride appeared as more severely affected. X-ray diffraction analysis showed no change in crystal lattice of NiTi wires in both solutions. Conclusion: The results suggest that using topical fluoride agents with NiTi wire could decrease the functional unloading mechanical properties of the wire and contribute to prolonged orthodontic treatment.

Comparison of Mechanical Properties of Plain and Reversed Curve Nickel-Titanium Archwires

In orthodontics, nickel-titanium wires are used for teeth alignment and leveling. For leveling the curve of Spee, reversed curve archwires are often used to increase the vertical force needed to correct a deep bite.Objectives: The aims of this study were to investigate and compare the mechanical properties (unloading force, stiffness, springback, and surface hardness) of the pre-formed plain and reversed curved NiTi archwires.Materials and Methods: NiTi wires of dimensions 0.016x0.022 inch were divided into two groups, Group 1 - plain and Group 2- reversed curve NiTi archwires. For each type of the archwire, load-deflection curve obtained from a three-point bending test, performed by a Texture Analyser (TA.XT.plus, Stable Micro System, United Kingdom) with 5 kg load cell at room temperature, was used to analyze unloading force, springback, and stiffness. Surface hardness was measured by Vickers micro-hardness tester. Kruskal-Wallis test was used to analyze the variables of this study.Results: The results showed that the unloading force of each deflection point of the reversed curve NiTi archwire was more than the plain archwire. The means of unloading force, stiffness, and springback were 2.42 N, 2.76 N; 0.28 N/mm, 0.49 N/mm; and 2.94 mm, 2.98 mm for the plain archwire and reversed curve NiTi archwire, respectively. The properties of reversed curve NiTi archwire were significantly higher (p&lt;0.05) than the plain NiTi archwire, except the springback. The surface hardness of the plain archwire was significantly higher (p&lt;0.05) than reversed curve NiTi archwire in each segment.Conclusion: The reversed curve NiTi archwire had more unloading force and stiffness than plain NiTi archwire. For the correction of deep curve of Spee in orthodontic treatment, clinicians must be aware of the vertical force needed during intrusion of lower incisors or the wires should be used in the later leveling and aligning stage.

Effects of low-level laser therapy and mechanical vibration on orthodontic pain caused by initial archwire.

The aim of this study was to evaluate the effects of mechanical vibration and low-level laser therapy on orthodontic pain after placement of the initial archwire. Sixty subjects with 3-6mm maxillary dental crowding, a nonextraction fixed treatment plan, and no medical history were included in this study. The subjects were randomly divided into 3 groups, equally distributed by sex. In each subject, preadjusted edgewise appliances were placed in the maxillary arch from the left first molar to the right first molar, and a 0.014-inch round nickel-titanium archwire was fully engaged with elastomeric ties and cut at the end of first molar bondable tube. In group 1 (mean age 13.98±2.68y), mechanical vibration was performed 3 times: immediately, 24hours, and 48hours after engagement of the initial archwire. In group 2 (mean age 14.86±2.06y), low-level laser therapy was applied once: immediately after the insertion of the initial archwire. Group 3 (mean age 14.41±1.78y) served as the control group. Pain scores were determined with the use of a visual analog scale (VAS). Although no statistically significant differences were found among the groups (P >0.05), the mean VAS scores for the mechanical vibration group were consistently lower than those of the control and low-level laser therapy groups at all measured time points. The mechanical vibration group had lower, though nonsignificant, VAS scores for all measured time points. Additional clinical trials are recommended for more definitive conclusions.

Long-term evaluation of metal ion release in orthodontic patients using fluoridated oral hygiene agents: An in vivo study

ObjectiveTo investigate levels of nickel and chromium in gingival crevicular fluid from subjects undergoing orthodontic treatment with and without using fluoridated toothpaste and mouthwash over a 6-month period. Materials and methodsSixty subjects divided into two groups of 30 each served as the experimental group with and without using fluoride agents for oral hygiene care along with fixed appliance treatment. Gingival crevicular fluid was collected in fluoridated and nonfluoridated groups before, and at 7 days, 30 days, and 6 months after commencing orthodontic treatment. Levels of nickel, chromium, titanium, and manganese were evaluated using inductively coupled plasma mass spectrometry. ResultsNo changes in metal levels at any time were observed in the untreated control group. Nickel levels were elevated to 101.78 μg/L in the fluoridated group at 30 days posttreatment, indicating heavy leaching from nickel-titanium archwires (Friedman P < 0.001). Results returned to baseline in both groups at 6 months. Mean differences for chromium, titanium, and manganese ion release were not statistically significant at 30 days. Titanium showed elevated levels at 30 days in both tested groups, but levels were lesser than nickel. ConclusionsArchwires are susceptible to corrosion when exposed to fluoride agents during orthodontic therapy causing release of metal ions into the mouth with the possibility of systemic absorption. Long-term consequences of metal ion release into the oral cavity require further investigation.

What are the best materials to use for the first arch wire in orthodontic treatment?

Data sources Six electronic databases/registries including Medline, Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Oral Health's Trials Register, Embase, World Health Organization International Clinical Trials Registry Platform and The US National Institutes of Health Trials Registry (ClinicalTrials.gov) were searched up to October 2017. No restrictions of language or publication date were set.Study selection Only randomised controlled trials (RCTs) assessing the efficiency of initial arch wires to align teeth with fixed orthodontic braces in either or both upper and lower arches.Data extraction and synthesis Two reviewers abstracted data independently. Risk of bias was assessed using the Cochrane Collaboration Risk of Bias tool. Rate of alignment was considered the main outcome. Root resorption and pain level were considered adverse effects. Meta-analysis was performed when possible. Results Twelve RCTs involving 799 participants were included. Three studies were judged at high RoB, six were unclear and three were at low RoB. There was insufficient evidence to determine if there is a difference in the alignment rate between Multistrand stainless steel (MSS) and superelastic nickel-titanium (SNT) arch wires (mean difference (MD) -7.5 mm per month, 95% confidence interval (CI) -26.27 to 11.27; one study), between MSS and thermoplastic NiTi (TNT) arch wires, between conventional Niti (CNT) and TNT arch wires, between CNT and TNT arch wires and between SNT and TNT arch wires. In regards to pain level only two comparisons were assessed (MSS vs. SNT and SNT vs. TNT). The first one did not show meaningful differences while in the second insufficient evidence was identified. Conclusions In general terms there is insufficient evidence that any particular material is clinically superior to any other in regards to alignment rate, pain or root resorption.

Biomechanical analysis of initial incisor crowding alignment in the periodontally reduced mandible using the finite element method.

To reduce remaining plaque niches due to dental malocclusion after periodontal treatment and to avoid reinflammation of periodontitis, severe anterior crowding can be treated orthodontically. The treatment indication is motivated by aesthetic and functional needs. In this study the biomechanical behaviour of crowded lower front teeth in reduced periodontium is analysed. Using the finite element (FE) method, amodel of the mandible was constructed with an anterior crowding of 4 mm and avertical bone loss of 4 mm in the front tooth area. A0.3 mm (0.012″) round superelastic nickel titanium (NiTi) arch wire was fitted to an ideal positioned teeth set-up and was inserted into the brackets of teeth 34 to 44 in the crowded model. The premolars were used as the anchorage unit. Material parameters were adopted from previous investigations, including bone (homogenous, isotropic, E = 2GPa), teeth (E = 20GPa) and healthy periodontal ligament (PDL, bilinear elastic; E1 = 0.05 MPa; E2 = 0.2 MPa; ε12 = 7%). All simulations were compared to simulations with aphysiological periodontal model to assess the effect of bone loss at teeth 42 to 32. Additionally, the influence of three arch wire materials (nonsuperelastic NiTi, superelastic NiTi and stainless steel) were analysed in areduced model, including only brackets in position of the crowded front teeth, wire and ligatures. Wire force levels and stresses were determined to assess the influence of material variation. Initial tooth mobility is increased by afactor of 2.5 in case of amoderate periodontal defect. Front teeth with reduced attachment display increased strains in the periodontal ligament up to afactor of 2. Forces in the model with reduced periodontium were decreased by afactor of 2. Comparing different aligning arch wires, stainless steel appears to have the highest force and stress levels. Force levels of this alloy were 7.5times higher than with the superelastic NiTi wire. Force levels of nonsuperelastic NiTi appeared to be 1.8times higher than superelastic NiTi. Calculated stresses with stainless steel were 5times higher than with the nonsuperelastic NiTi and 10times higher than with superelastic NiTi. Periodontally reduced incisors 42 to 32 are associated with an increased load on periodontal tissue and increased level of tooth mobility during fixed orthodontic treatment. This has to be considered by reducing orthodontic force levels and by selecting mechanics that reduce the load to the tissue.

Clinically relevant sample size calculations for trials.

An orthodontist attends the scientific orthodontic congress and passing by the company exhibitions receives a free sample of a novel orthodontic archwire introduced in the market for initial alignment/levelling with favourable performance over conventional superelastic nickel-titanium archwires. This novel archwire should increase according to the manufacturer’s claims alignment efficacy and halve the pain for the patient. After using the free sample wire on a patient and observing that the patient felt little to no pain during the alignment/levelling phase, the orthodontist decides to venture into unknown territory and find out if this holds true for most of her patients by doing a randomised clinical trial in her practice.

Effect of Surface Treatment on Physical and Mechanical Properties of Nickel-Titanium Orthodontic Archwires by Fine Particle Shot Peening Method

Surface treatment on metal can alter physical and mechanical properties. Understanding the physical and mechanical properties of the archwires is essential for the management of orthodontic treatment. Methods: This study used digital micrometer, universal testing machine, and surface hardness tester for measuring dimension, unloading force, and surface hardness of two different type of nickel-titanium (Ni-Ti) archwires: commercially available Ni-Ti (NT-N) and surface treated Ni-Ti by fine particle shot peening (FPSP) method (NT-F). Statistical analysis was undertaken using a paired T-test (α=0.05). Results: No significant difference was found on both vertical and horizontal dimensions of NT-N and NT-F (p= 1.00 and 0.796 respectively). For bending and surface hardness test, significance difference was found (p&lt;0.001 and p&lt;0.001 respectively). Conclusions: The NT-F archwire provided lower unloading force and surface hardness but there was no change in size when compared with NT-N.

Frictional and Mechanical Properties of Surface Modified Nickel-Titanium Orthodontic Archwires

The purpose of this study was to investigate the surface hardness, frictional force and load-deflection characteristic of three types of nickel-titanium archwires; DLC-coated, CH4-PBII and CF4-PBII NiTi orthodontic archwires. The NiTi wires were deposited with DLC films and were implanted with CH4 and CF4 using Plasma-Based Ion Implantation and Deposition (PBIID) method. These archwires and upper canine brackets with slot dimension of 0.022-inch were used in this study. Surface hardness of three types of surface modified NiTi orthodontic archwires was measured using atomic force microscopy (AFM). Frictional resistance was determined using a Universal Testing Machine with a load cell of 50 N. The custom-fabricated friction-testing device was designed and bonded each bracket in an accurate position. Load-deflection characteristic was evaluated by conducting the three-point bending test with universal testing machine. The results showed that DLC-coated NiTi wires had the lowest mean of frictional force followed by CH4-PBII, CF4-PBII and conventional NiTi wires. DLC-coated NiTi wires had the highest mean of surface hardness and there was no significant difference in the unloading force at 0.5, 1.0, 2.0 and 3.0 mm of the load-deflection graphs between different types of NiTi orthodontic archwires. The results can be concluded that the surfaces of nickel-titanium orthodontic archwires can be successfully modified by the PBIID method to increase surface hardness and reduce frictional force between stainless steel brackets and NiTi archwires. The load-deflection characteristics of three types of surface modified archwires remain unchanged.