Aligning archwires, the shape of things to come?--a fourth and fifth phase of force delivery

Multi-Force Bio-Active™ Archwires and Various Contemporary NiTi Multi-Force Archwires: Properties and Characteristics-A Review

The manufacturing of orthodontic archwires made from NiTi alloy has undergone numerous changes from the second half of the last century to modern times. Initially, superelastic-active austenitic NiTi alloys were predominant, followed by thermodynamic-active martensitic NiTi alloys, and, finally, the most recent development was graded thermodynamic alloys. These advancements have been the subject of extensive investigation in numerous studies, as they necessitated a deeper understanding of their properties. Furthermore, it is imperative that we validate the information provided by manufacturers regarding these archwires through independent studies. This review evaluates existing studies on the subject with a specific focus on the Bio-active multi-force NiTi archwire, by examining its mechanical, thermal, and physicochemical properties before and after clinical use. This archwire consists primarily of Ni and Ti, with traces of Fe and Cr, which release graduated, biologically tolerable forces which increase in a front-to-back direction and are affected by the temperature of the environment they are in. The review provides information to practicing orthodontists, facilitating informed decisions regarding the selection and use of Bio-active™ archwires for individual patient treatments.

Effects of Clinical Use on the Mechanical Properties of Bio-Active® (BA) and TriTanium® (TR) Multiforce Nickel-Titanium Orthodontic Archwires

Multiforce orthodontic archwires are thermodynamic wires made of nickel-titanium alloy (Ni-Ti). They release biologically tolerable forces along their length, progressively increasing from front to back. The frontal archwires' segments distribute the weakest force: the premolar, the greater, and the molar, the greatest. The aim of the present study was to determine the influence of clinical use on the mechanical properties of two types of multi-force orthodontic archwires (TriTanium^®, American orthodontics; Bio-Active^®, GC) with dimensions of 0.016 × 0.022 inches for periods of up to 8 weeks and over 8 weeks of in-vivo use. A three-point bending test was used, and the data gained is statistically analyzed through a multi-variance comparison Mann-Whitney test. We found that after uses of up to 8 weeks and over 8 weeks, the shape memory effect and superelasticity are preserved, as well as the tendency for differential force release along the length of the archwires is kept.

Nitinol Type Alloys General Characteristics and Applications in Endodontics

A very extensive literature review presents the possibilities and needs of using, in endodontics, the alloys commonly known as nitinol. Nitinol, as the most modern group of engineering materials used to develop root canals, is equilibrium nickel and titanium alloys in terms of the elements’ atomic concentration, or very similar. The main audience of this paper is engineers, tool designers and manufacturers, PhD students, and students of materials and manufacturing engineering but this article can also certainly be used by dentists. The paper aims to present a full material science characterization of the structure and properties of nitinol alloys and to discuss all structural phenomena that determine the performance properties of these alloys, including those applied to manufacture the endodontic tools. The paper presents the selection of these alloys’ chemical composition and processing conditions and their importance in the endodontic treatment of teeth. The results of laboratory studies on the analysis of changes during the sterilization of endodontic instruments made of nitinol alloys are also included. The summary of all the literature analyses is an SWOT analysis of strengths, weaknesses, opportunities, and threats, and is a forecast of the development strategy of this material in a specific application such as endodontics.

What Are the Chances of Resilon to Dominate the Market Filling Materials for Endodontics?

This paper is a literature review with additional virtual analyses of the authors’ own experimental research results. Knowledge from various areas was synergistically combined, appropriately for concurrent engineering, presenting several possible methodological approaches used in research, optimizing the selection of engineering materials and the conditions of their application with particular application in endodontics. Particular attention was paid to the theoretical aspects of filling material strengths, weaknesses, opportunities, and threats SWOT analysis. Attention was paid to the original concepts of Sustainable Dentistry Development in conjunction with Dentistry 4.0, which includes endodontics as an important element. The dentists’ actions, among others, in conservative dentistry, along with endodontics, requires close cooperation with engineers and the enginering sciences. Methods of root canal preparation were described, together with selected tools, including those made of nitinol. Principles concerning the process of cleaning and shaping the pulp complex are presented. The importance of obturation methods, including the Thermo-Hydraulic-Condensation THC technique, and the selection of filling materials with the necessary sealants for the success of endodontic treatment are discussed. The experimental studies were carried out in vitro on human teeth removed for medical reasons, except for caries, for which two groups of 16 teeth were separated. After the root canal was prepared, it was filled with studs and pellets of a filling material based on polyester materials, which has gained the common trade name of resilon or, less frequently, RealSeal (SybronEndo) with an epiphany sealant. The teeth for the first group were obturated by cold lateral condensation. In the second case the obturation was performed using the Thermo-Hydraulic-Condensation technique using System B and Obtura III. The experimental leakage testing was done using a scanning electron microscope SEM and a light stereoscopic microscope LSM, as typical research tools used in materialography. The research results, in a confrontation with the data taken from the literature studies, do not indicate the domination of resilon in endodontics.

Influence of different storage temperatures on the mechanical properties of NiTi, Cu-NiTi and SS orthodontic archwires: An in vitro study

OBJECTIVE

Due to their exceptional temperature sensitivity, the mechanical properties of Nickel-titanium and Copper Nickel-titanium wires may be influenced by their storage temperature. This in turn may have clinical implications and may also affect the outcomes. This study analyzed the influence of storage temperatures on the mechanical properties of orthodontic wires in a laboratory setting.

MATERIALS AND METHODS

Stainless steel (SS), Nickel-Titanium (NiTi), and three variants of Copper-NiTi (Cu-NiTi 27°C, 35°C and 40°C), 0.017×0.025 inches in size were analysed using a three-point bending test in a pre-heated chamber at 36°C. The orthodontic wires were stored for twenty-four hours before the mechanical testing at four different temperatures (5°, 22°, 36° and 60°C).

RESULTS

The obtained results showed that the mechanical forces exerted by 27°C Copper-NiTi exhibit the most stable behaviour after having been stored at different temperatures, whereas 35°C Copper-NiTi showed the highest variability. As to be expected, Stainless steel shows no changes in its bending mechanical properties.

CONCLUSION

Furthermore, the results of this investigation reflect the importance of controlling the storage temperature of orthodontic NiTi and Copper-NiTi wires tested in a research environment in order to avoid unexpected bias.

Initial arch wires used in orthodontic treatment with fixed appliances

BACKGROUND

Initial arch wires are the first arch wires to be inserted into the fixed appliance at the beginning of orthodontic treatment and are used mainly for the alignment of teeth by correcting crowding and rotations. With a number of different types of orthodontic arch wires available for initial tooth alignment, it is important to understand which wire is most efficient, as well as which wires cause least amount of root resorption and pain during the initial aligning stage of treatment. This is an update of the review entitledInitial arch wires for alignment of crooked teeth with fixed orthodontic braces, which was first published in 2010.

OBJECTIVES

To assess the effects of initial arch wires for the alignment of teeth with fixed orthodontic braces, in terms of the rate of tooth alignment, amount of root resorption accompanying tooth movement, and intensity of pain experienced by patients during the initial alignment stage of treatment.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 5 October 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library, 2017, Issue 9), MEDLINE Ovid (1946 to 5 October 2017), and Embase Ovid (1980 to 5 October 2017. The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of initial arch wires to align teeth with fixed orthodontic braces. We included only studies involving participants with upper or lower, or both, full arch fixed orthodontic appliances.

DATA COLLECTION AND ANALYSIS

Two review authors were responsible for study selection, 'Risk of bias' assessment and data extraction. We resolved disagreements by discussion between the review authors. We contacted corresponding authors of included studies to obtain missing information. We assessed the quality of the evidence for each comparison and outcome as high, moderate, low or very low, according to GRADE criteria.

MAIN RESULTS

For this update, we found three new RCTs (228 participants), bringing the total to 12 RCTs with 799 participants. We judged three studies to be at high risk of bias, and three to be at low risk of bias; six were unclear. None of the studies reported the adverse outcome of root resorption. The review assessed six comparisons.1. Multistrand stainless steel versus superelastic nickel-titanium (NiTi) arch wires. There were five studies in this group and it was appropriate to undertake a meta-analysis of two of them. There is insufficient evidence from these studies to determine whether there is a difference in rate of alignment between multistrand stainless steel and superelastic NiTi arch wires (mean difference (MD) -7.5 mm per month, 95% confidence interval (CI) -26.27 to 11.27; 1 study, 48 participants; low-quality evidence). The findings for pain at day 1 as measured on a 100 mm visual analogue scale suggested that there was no meaningful difference between the interventions (MD -2.68 mm, 95% CI -6.75 to 1.38; 2 studies, 127 participants; moderate-quality evidence).2. Multistrand stainless steel versus thermoelastic NiTi arch wires. There were two studies in this group, but it was not appropriate to undertake a meta-analysis of the data. There is insufficient evidence from the studies to determine whether there is a difference in rate of alignment between multistrand stainless steel and thermoelastic NiTi arch wires (low-quality evidence). Pain was not measured.3. Conventional NiTi versus superelastic NiTi arch wires. There were three studies in this group, but it was not appropriate to undertake a meta-analysis of the data. There is insufficient evidence from these studies to determine whether there is any difference between conventional and superelastic NiTi arch wires with regard to either alignment or pain (low- to very low-quality evidence).4. Conventional NiTi versus thermoelastic NiTi arch wires. There were two studies in this group, but it was not appropriate to undertake a meta-analysis of the data. There is insufficient evidence from these studies to determine whether there is a difference in alignment between conventional and thermoelastic NiTi arch wires (low-quality evidence). Pain was not measured.5. Single-strand superelastic NiTi versus coaxial superelastic NiTi arch wires. There was only one study (24 participants) in this group. There is moderate-quality evidence that coaxial superelastic NiTi can produce greater tooth movement over 12 weeks (MD -6.76 mm, 95% CI -7.98 to -5.55). Pain was not measured.6. Superelastic NiTi versus thermoelastic NiTi arch wires. There were three studies in this group, but it was not appropriate to undertake a meta-analysis of the data. There is insufficient evidence from these studies to determine whether there is a difference in alignment or pain between superelastic and thermoelastic NiTi arch wires (low-quality evidence).

AUTHORS' CONCLUSIONS

Moderate-quality evidence shows that arch wires of coaxial superelastic nickel-titanium (NiTi) can produce greater tooth movement over 12 weeks than arch wires made of single-strand superelastic NiTi. Moderate-quality evidence also suggests there may be no difference in pain at day 1 between multistrand stainless steel arch wires and superelastic NiTi arch wires. Other than these findings, there is insufficient evidence to determine whether any particular arch wire material is superior to any other in terms of alignment rate, time to alignment, pain and root resorption.

Effectiveness and efficiency in clinical orthodontic practice

Proffitt et al. have described "effectiveness and efficiency" (E&E) as achieving desired results without wasting the orthodontist's and patients' time. In 1972, Archibald Cochrane published a monograph entitled "Effectiveness and Efficiency," which challenged the medical community to use medical protocols that were evidence-based. As a possible starting point for E&E, the orthodontist could consider an "Evidence-based clinical practice" (EBCP) model, which integrates the best research evidence with clinical expertise and patient values. This model considers scientific or evidence-based orthodontics (EBO) together with patient preferences and patient autonomy, clinical or patient circumstances, and clinical experience and judgment. In this paper, therefore, E&E will be discussed from an EBCP perspective which, for our purposes, includes relevant evidence but also our clinical experience and rationale. We will discuss: wire sequence; NiTi Wire types; space closure by sliding; canine retraction versus en masse retraction, 18" slot versus 22" slot, the Bidimensional System; self-ligating brackets (SL); vertical slot; economic aspects.

Differences in cytocompatibility, dynamics of the oxide layers' formation, and nickel release between superelastic and thermo-activated nickel-titanium archwires

Superelastic (SE) and thermo-activated (TA) nickel-titanium (NiTi) archwires are used in everyday orthodontic practice, based on their acceptable biocompatibility and well-defined shape memory properties. However, the differences in their surface microstructure and cytotoxicity have not been clearly defined, and the standard cytotoxicity tests are too robust to detect small differences in the cytotoxicity of these alloys, all of which can lead to unexpected adverse reactions in some patients. Therefore, we tested the hypothesis that the differences in manufacture and microstructure of commercially available SE and TA archwires may influence their biocompatibility. The archwires were studied as-received and after conditioning for 24 h or 35 days in a cell culture medium under static conditions. All of the tested archwires, including their conditioned medium (CM), were non-cytotoxic for L929 cells, but Rematitan SE (both as received and conditioned) induced the apoptosis of rat thymocytes in a direct contact. In contrast, TruFlex SE and Equire TA increased the proliferation of thymocytes. The cytotoxic effect of Rematitan SE correlated with the higher release of Ni ions in CM, higher concentration of surface Ni and an increased oxygen layer thickness after the conditioning. In conclusion, the apoptosis assay on rat thymocytes, in contrast to the less sensitive standard assay on L929 cells, revealed that Rematitan SE was less cytocompatible compared to other archwires and the effect was most probably associated with a higher exposition of the cells to Ni on the surface of the archwire, due to the formation of unstable oxide layer.

Mechanical properties of NiTi and CuNiTi wires used in orthodontic treatment. Part 2: Microscopic surface appraisal and metallurgical characteristics

Objective

This research aimed at comparing the qualitative chemical compositions and the surface morphology of fracture regions of eight types of Nickel (Ni) Titanium (Ti) conventional wires, superelastic and heat-activated (GAC, TP, Ormco, Masel, Morelli and Unitek), to the wires with addition of copper (CuNiTi 27ºC and 35ºC, Ormco) after traction test.

Methods

The analyses were performed in a scanning electronic microscope (JEOL, model JSM-5800 LV) with EDS system of microanalysis (energy dispersive spectroscopy).

Results

The results showed that NiTi wires presented Ni and Ti as the main elements of the alloy with minimum differences in their composition. The CuNiTi wires, however, presented Ni and Ti with a significant percentage of copper (Cu). As for surface morphology, the wires that presented the lowest wire-surface roughness were the superelastic ones by Masel and Morelli, while those that presented the greatest wire-surface roughness were the CuNiTi 27ºC and 35ºC ones by Ormco, due to presence of microcavity formed as a result of pulling out some particles, possibly of NiTi.⁴ The fracture surfaces presented characteristics of ductile fracture, with presence of microcavities. The superelastic wires by GAC and the CuNiTi 27ºC and the heat-activated ones by Unitek presented the smallest microcavities and the lowest wire-surface roughness with regard to fracture, while the CuNiTi 35ºC wires presented inadequate wire-surface roughness in the fracture region.

Conclusion

CuNiTi 35ºC wires did not present better morphologic characteristics in comparison to the other wires with regard to surfaces and fracture region.

Transition temperature range of thermally activated nickel-titanium archwires

OBJECTIVES

The shape memory resulting from the superelasticity and thermoelastic effect is the main characteristic of thermally activated NiTi archwires and is closely related to the transition temperature range (TTR). The aim of this study was to evaluate the TTR of thermally activated NiTi archwires commercially available.

MATERIAL AND METHODS

Seven different brands of 0.019" x 0.025" thermally activated nickel-titanium archwires were tested as received by differential scanning calorimetry (DSC) over the temperature range from -100 °C to 150 °C at 10 °C/min.

RESULTS

All thermally activated NiTi archwires analyzed presented stage transformation during thermal scanning with final austenitic temperature (Af) ranging from 20.39 °C to 45.42 °C. Three brands of NiTi archwires presented Af close to the room temperature and, this way, do not present properties of shape memory and pseudoelasticity that are desirable in clinical applications.

CONCLUSIONS

The thermally activated NiTi archwires present great variability in the TTR and the elastic parameters of each NiTi archwire should be provided by the manufacturers, to allow achievement of the best clinical performance possible.

Mechanical properties of NiTi and CuNiTi shape-memory wires used in orthodontic treatment. Part 1: stress-strain tests

OBJECTIVE

This research aimed to compare, through traction tests, eight types of superelastic and heat-activated NiTi archwires, by six trade companies (GAC, TP, Ormco, Masel, Morelli and Unitek) to those with addition of copper (CuNiTi 27°C and 35°C, Ormco).

METHODS

The tests were performed in an EMIC mechanical testing machine, model DL10000, capacity of 10 tons, at the Military Institute of Engineering (IME).

RESULTS

The results showed that, generally, heat-activated NiTi archwires presented slighter deactivation loadings in relation to the superelastic ones. Among the archwires that presented deactivation loadings biologically more adequate are the heat-activated by GAC and by Unitek. Among the superelastic NiTi, the CuNiTi 27°C by Ormco were the ones that presented slighter deactivation loadings, being statistically (ANOVA) similar to the ones presented by the heat-activated NiTi archwires from Unitek. When compared the CuNiTi 27°C and 35°C archwires, it was observed that the 27°C presented deactivation forces of, nearly, ⅓ of the presented by the 35°C.

CONCLUSIONS

It was concluded that the CuNiTi 35°C archwires presented deactivation loadings biologically less favorable in relation to the other heat-activated NiTi archwires, associated to lower percentage of deformation, on the constant baselines of deactivation, showing less adequate mechanical behavior under traction, in relation to the other archwires.

A clinical comparison of three aligning archwires in terms of alignment efficiency: A prospective clinical trial

OBJECTIVES

To clinically evaluate the effectiveness of three orthodontic aligning archwires in relation to tooth alignment speed during the initial alignment stage of treatment.

MATERIALS AND METHODS

A consecutive sample of 74 patients requiring lower only or upper and lower fixed orthodontic appliances were randomly allocated into three different archwires (0.014-inch superelastic nickel-titanium [NiTi], 0.014-inch thermoelastic NiTi, or 0.014-inch conventional NiTi). Good quality impressions were taken of the lower arch before archwire placement (T0) and at designated serial stages of alignment (every 2 weeks: T2, T4, T6, …, T16). The change in tooth alignment was measured in millimeters from the resultant casts using Little's irregularity index. Demographic and clinical differences among the three groups were compared with the chi-square or analysis of variance (ANOVA) test. The difference in the change of lower anterior tooth alignment over time among the three groups was explored with a Split Plot ANOVA (SPANOVA, or within- and between-groups ANOVA). The Kruskal-Wallis nonparametric test was used when data were not normally distributed.

RESULTS

The SPANOVA and Wilks Lambda Multivariate test confirmed that the wire type had no influence on the rate of change in alignment (P  =  .98).

CONCLUSION

The three forms of NiTi wires were similar in terms of their alignment efficiency during the initial aligning stage of orthodontic fixed appliance therapy.

Root resorption after leveling with super-elastic and conventional steel arch wires: a prospective study

BACKGROUND

The aim of this prospective study was to compare root resorption after the leveling phase of treatment, performed by either super-elastic or conventional multi-stranded stainless steel arch wires.

METHODS

From a total of 156 future orthodontic patients in a private clinic, 82 were included in the study after excluding those who earlier had orthodontic or endodontic treatment or signs of resorption. Patients were equally arbitrary allocated into two groups, where leveling was performed either with super-elastic heat-activated or conventional multi-stranded stainless steel arch wires. Root length loss was calculated using pre-treatment and post-leveling periapical radiographs.

RESULTS

The use of super-elastic arch wires did not significantly increase the severity of root resorption, except for tooth 31, while it reduced leveling time compared to conventional stainless steel wires. Crossbite of maxillary lateral incisors seemed to be a risk factor for resorption.

CONCLUSION

Incisor root resorption after leveling did not differ significantly between patients treated with super-elastic and conventional stainless steel arch wires, except for a mandibular incisor.

Initial arch wires for tooth alignment during orthodontic treatment with fixed appliances

BACKGROUND

Initial arch wires are the first arch wires to be inserted into the fixed appliance at the beginning of orthodontic treatment and are used mainly for the alignment of teeth by correcting crowding and rotations. With a number of different types of orthodontic arch wires available for initial tooth alignment, it is important to understand which wire is most efficient, as well as which wires cause the least amount of root resorption and pain during the initial aligning stage of treatment. This is an update of the review 'Initial arch wires for alignment of crooked teeth with fixed orthodontic braces' first published in the Cochrane Database of Systematic Reviews 2010, Issue 4.

OBJECTIVES

To assess the effects of initial arch wires for alignment of teeth with fixed orthodontic braces in relation to alignment speed, root resorption and pain intensity.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Oral Health Group's Trials Register (to 2 August 2012), CENTRAL (The Cochrane Library 2012, Issue 7), MEDLINE via OVID (1950 to 2 August 2012) and EMBASE via OVID (1980 to 2 August 2012). We also searched the reference lists of relevant articles. There was no restriction with regard to publication status or language of publication. We contacted all authors of included studies to identify additional studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of initial arch wires to align teeth with fixed orthodontic braces. Only studies involving participants with upper and/or lower full arch fixed orthodontic appliances were included.

DATA COLLECTION AND ANALYSIS

Two review authors were responsible for study selection, validity assessment and data extraction. All disagreements were resolved by discussion amongst the review team. Corresponding authors of included studies were contacted to obtain missing information.

MAIN RESULTS

Nine RCTs with 571 participants were included in this review. All trials were at high risk of bias and a number of methodological limitations were identified. All trials had at least one potentially confounding factor (such as bracket type, slot size, ligation method, extraction of teeth) which is likely to have influenced the outcome and was not controlled in the trial. None of the trials reported the important adverse outcome of root resorption.Three groups of comparisons were made.(1) Multistrand stainless steel initial arch wires compared to superelastic nickel titanium (NiTi) initial arch wires. There were four trials in this group, with different comparisons and outcomes reported at different times. No meta-analysis was possible. There is insufficient evidence from these trials to determine whether or not there is a difference in either rate of alignment or pain between stainless steel and NiTi initial arch wires.(2) Conventional (stabilised) NiTi initial arch wires compared to superelastic NiTi initial arch wires. There were two trials in this group, one reporting the outcome of alignment over 6 months and the other reporting pain over 1 week. There is insufficient evidence from these trials to determine whether or not there is any difference between conventional (stabilised) and superelastic NiTi initial arch wires with regard to either alignment or pain.(3) Single-strand superelastic NiTi initial arch wires compared to other NiTi (coaxial, copper NiTi (CuNiTi) or thermoelastic) initial arch wires. The three trials in this comparison each compared a different product against single-strand superelastic NiTi. There is very weak unreliable evidence, based on one very small study (n = 24) at high risk of bias, that coaxial superelastic NiTi may produce greater tooth movement over 12 weeks, but no information on associated pain or root resorption. This result should be interpreted with caution until further research evidence is available. There is insufficient evidence to determine whether or not there is a difference between either thermoelastic or CuNiTi and superelastic NiTi initial arch wires.

AUTHORS' CONCLUSIONS

There is no reliable evidence from the trials included in this review that any specific initial arch wire material is better or worse than another with regard to speed of alignment or pain. There is no evidence at all about the effect of initial arch wire materials on the important adverse effect of root resorption. Further well-designed and conducted, adequately-powered, RCTs are required to determine whether the performance of initial arch wire materials as demonstrated in the laboratory, makes a clinically important difference to the alignment of teeth in the initial stage of orthodontic treatment in patients.

Efficiency, behavior, and clinical properties of superelastic NiTi versus multistranded stainless steel wires: a prospective clinical trial

OBJECTIVE

To investigate efficiency, behavior, and properties of superelastic NiTi vs multistranded stainless steel wires in Begg and preadjusted edgewise appliance (PEA) under moderate to severe crowding conditions.

MATERIAL AND METHODS

Ninety-six participants (48 male, 48 female), aged 12-18 years old (mean age  =  15.2 ± 1.95), with moderate (≤ 6 mm; mean  =  5.3 ± 0.48) to severe (> 6 mm; mean  =  7.9 ± 0.66) initial crowding were distributed into four groups: superelastic NiTi PEA (n  =  24), superelastic NiTi Begg (n  =  24), multistranded (coaxial) stainless steel PEA (n  =  25), and multistranded (coaxial) stainless steel Begg (n = 23). In this study, 0.16-inch superelastic (austenitic active) NiTi and 0.175-inch multistranded (six stranded, coaxial) stainless steel wires were used in a 0.022-inch slot (Roth prescription) PEA and Begg appliance with a follow-up of six weeks.

RESULTS

Analysis of variance revealed no significant difference in reduction of crowding between superelastic NiTi PEA and multistranded (coaxial) stainless steel PEA groups, but reduction in crowding was significantly greater in the superelastic NiTi Begg group compared with the multistranded (coaxial) stainless steel Begg group with F (3, 44)  =  8.896, P < .001, and effect size (ω) 0.57 in moderate crowding and F (3, 44)  =  122.341, P < .001, and effect size (ω) 0.93 in severe crowding. Linear regression demonstrated significant (P < .05) positive correlation between amount of initial crowding and reduction in crowding in all groups except the multistranded (coaxial) stainless steel Begg group, wherein a negative correlation did exist.

CONCLUSION

Superelastic NiTi performed significantly better than multistranded (coaxial) stainless steel wire in the Begg appliance. However, in PEA, there was no significant difference.

Alignment efficiency and discomfort of three orthodontic archwire sequences: a randomized clinical trial

AIM

To compare the efficiency of orthodontic archwire sequences produced by three manufacturers.

DESIGN

Prospective, randomized clinical trial with three parallel groups.

SETTING

Private orthodontic practice in Caloundra, QLD, Australia.

SUBJECTS AND METHODS

One hundred and thirty-two consecutive patients were randomized to one of three archwire sequence groups: (i) 3M Unitek, 0·014 inch Nitinol, 0·017 inch × 0·017 inch heat activated Ni-Ti; (ii) GAC international, 0·014 inch Sentalloy, 0·016 × 0·022 inch Bioforce; and (iii) Ormco corporation, 0·014 inch Damon Copper Ni-Ti, 0·014 × 0·025 inch Damon Copper Ni-Ti. All patients received 0·018 × 0·025 inch slot Victory Series™ brackets.

OUTCOME MEASURES

Mandibular impressions were taken before the insertion of each archwire. Patients completed discomfort surveys according to a seven-point Likert Scale at 4 h, 24 h, 3 days and 7 days after the insertion of each archwire. Efficiency was measured by time required to reach the working archwire, mandibular anterior alignment and level of discomfort.

RESULTS

No significant differences were found in the reduction of irregularity between the archwire sequences at any time-point (T1: P = 0·12; T2: P = 0·06; T3: P = 0·21) or in the time to reach the working archwire (P = 0·28). No significant differences were found in the overall discomfort scores between the archwire sequences (4 h: P = 0·30; 24 h: P = 0·18; 3 days: P = 0·53; 7 days: P = 0·47). When the time-points were analysed individually, the 3M Unitek archwire sequence induced significantly less discomfort than GAC and Ormco archwires 24 h after the insertion of the third archwire (P = 0·02). This could possibly be attributed to the progression in archwire material and archform.

CONCLUSIONS

The archwire sequences were similar in alignment efficiency and overall discomfort. Progression in archwire dimension and archform may contribute to discomfort levels. This study provides clinical justification for three common archwire sequences in 0·018 × 0·025 inch slot brackets.

A systematic review of clinical trials of aligning archwires

OBJECTIVES

This review aimed to identify the evidence for the efficacy of archwires used in the alignment stage of orthodontic treatment by undertaking a systematic review of the literature.

DATA SOURCES

MEDLINE, the Cochrane Central Register of Controlled trials (CENTRAL), EMBASE, and the meta Register of Controlled Trials were searched up to July 2008. Reference lists of identified articles and relevant review articles were checked for further possible studies.

REVIEW METHODS

Controlled clinical trials and randomised clinical trials that compared aligning archwires and reported objective measures of alignment were selected for inclusion. Validity and quality assessment were undertaken to identify studies with a low risk of bias. Details of the study methodology and the reported results were then abstracted.

RESULTS

100 studies were identified by the searches and 7 of these were identified as meeting the selection criteria. Four studies were deemed, after quality assessment, to have a low risk of bias and data was extracted from these. No two studies shared a common methodology or common reporting of outcome. Meta-analysis was therefore not possible.

CONCLUSIONS

There is insufficient data in these studies to make clear recommendations regarding the most effective archwire for alignment. Recommendations on future study design have been made.

Stiffness and frictional resistance of a superelastic nickel-titanium orthodontic wire with low-stress hysteresis

INTRODUCTION

Stress-induced martensite formation with stress hysteresis that changes the elasticity and stiffness of nickel-titanium (Ni-Ti) wire influences the sliding mechanics of archwire-guided tooth movement. This in-vitro study investigated the frictional behavior of an improved superelastic Ni-Ti wire with low-stress hysteresis.

METHODS

Improved superelastic Ni-Ti alloy wires (L & H Titan, Tomy International, Tokyo, Japan) with low-stress hysteresis were examined by using 3-point bending and frictional resistance tests with a universal test machine at a constant temperature of 35 degrees C, and compared with the former conventional austenitic-active superelastic Ni-Ti wires (Sentalloy, Tomy International). Wire stiffness levels were derived from differentiation of the polynomial regression of the unloading curves, and values for kinetic friction were measured at constant bending deflection distances of 0, 2, 3, and 4 mm, respectively.

RESULTS

Compared with conventional Sentalloy wires, the L & H Titan wire had a narrower stress hysteresis including a lower loading plateau and a higher unloading plateau. In addition, L & H Titan wires were less stiff than the Sentalloy wires during most unloading stages. Values of friction measured at deflections of 0, 2, and 3 mm were significantly (P <.05) increased in both types of wire. However, they showed a significant decrease in friction from 3 to 4 mm of deflection. L & H Titan wires had less friction than Sentalloy wires at all bending deflections (P <.05).

CONCLUSIONS

Stress-induced martensite formation significantly reduced the stiffness and thus could be beneficial to decrease the binding friction of superelastic Ni-Ti wires during sliding with large bending deflections. Austenitic-active alloy wires with low-stress hysteresis and lower stiffness and friction offer significant potential for further investigation.

Pseudoelasticity and thermoelasticity of nickel-titanium alloys: a clinically oriented review. Part II: Deactivation forces

The purpose of this review was to organize a systematic reference to help orthodontists evaluate commonly used orthodontic nickel-titanium alloys. Part I of the article reviewed the data available in the literature regarding the temperature transitional ranges of the alloys. The thermomechanical behavior of these compounds is, in fact, strictly dependent upon the correlation between the temperature transitional range and the oral temperature range. Part II focuses on the mechanical characteristics of the alloys, such as the magnitude of the forces delivered and correlations with the temperature transitional range and oral temperature.

Pseudoelasticity and thermoelasticity of nickel-titanium alloys: a clinically oriented review. Part I: Temperature transitional ranges

The purpose of this review was to organize a systematic reference to help orthodontists evaluate commonly used orthodontic nickel-titanium alloys. Part I of the article reviews the data available in the literature regarding the temperature transitional ranges of the alloys. The thermomechanical behavior of these compounds is, in fact, strictly dependent on the correlation between the temperature transitional range and the oral temperature range. Part II of the article will focus on the mechanical characteristics of the alloys, such as the magnitude of the forces delivered and its correlations with temperature transitional range and oral temperature.

Nickel-titanium alloys: stress-related temperature transitional range

The inducement of mechanical stress within nickel-titanium wires can influence the transitional temperature range of the alloy and therefore the expression of the superelastic properties. An analogous variation of the transitional temperature range may be expected during orthodontic therapy, when the archwires are engaged into the brackets. To investigate this possibility, samples of currently used orthodontic nickel-titanium wires (Sentalloy, GAC; Copper Ni-Ti superelastic at 27 degrees C, 35 degrees C, 40 degrees C, Ormco; Nitinol Heat-Activated, 3M-Unitek) were subjected to temperature cycles ranging between 4 degrees C and 60 degrees C. The wires were mounted in a plexiglass loading device designed to simulate clinical situations of minimum and severe dental crowding. Electrical resistivity was used to monitor the phase transformations. The data were analyzed with paired t tests. The results confirmed the presence of displacements of the transitional temperature ranges toward higher temperatures when stress was induced. Because nickel-titanium wires are most commonly used during the aligning stage in cases of severe dental crowding, particular attention was given to the performance of the orthodontic wires under maximum loading. An alloy with a stress-related transitional temperature range corresponding to the fluctuations of the oral temperature should express superelastic properties more consistently than others. According to our results, Copper Ni-Ti 27 degrees C and Nitinol Heat-Activated wires may be considered suitable alloys for the alignment stage.

An overview of nickel-titanium alloys used in dentistry

The nickel-titanium alloy Nitinol has been used in the manufacture of endodontic instruments in recent years. Nitinol alloys have greater strength and a lower modulus of elasticity compared with stainless steel alloys. The super-elastic behaviour of Nitinol wires means that on unloading they return to their original shape following deformation. These properties are of interest in endodontology as they allow construction of root canal instruments that utilize these favourable characteristics to provide an advantage when preparing curved canals. This review aims to provide an overview of Nitinol alloys used in dentistry in order for its unique characteristics to be appreciated.

Clinical comparison and performance perspective of three aligning arch wires

OBJECTIVES

To clinically evaluate three commonly used orthodontic tooth aligning arch wires: 016 x 022 inch active martensitic medium force nickel titanium, 016 x 022 inch graded force active martensitic nickel titanium, and 0.0155 inch multistrand stainless steel.

DESIGN

A prospective randomized clinical trial.

DATA SOURCE

Measured serial study casts of dental arches for 112 assigned arch wires from 56 consecutive patients. Analysis based on completed records for 98 arch wires and 51 patients.

METHOD

A consecutive sample of 56 patients requiring both upper and lower fixed appliance therapy were randomly allocated two different arch wires from a possible three under trial. Good quality impressions were taken of the dental arches at the designated serial stages of alignment (start, T0; 4 weeks, T4; 8 weeks, T8). The resultant casts were measured on a Reflex Microscope to record the change in individual tooth alignment both in three and two dimensions (horizontal plane only).

RESULTS

The measurement error was within acceptable limits (range, 0.05 to 0.09 mm) and showed no significant bias. ANOVA statistical models were fitted to the data to adjust for a number of variables. No significant difference in aligning capability (p > 0.05), in either two or three dimensions, was demonstrated between the three arch wires in the trial.

CONCLUSION

Heat activated nickel titanium arch wires failed to demonstrate a better performance than the cheaper multistrand stainless steel wires in this randomized clinical trial. The failure to demonstrate in vivo superiority at the clinical level may be due to the confounding effects of large variations in individual metabolic response. Alternatively, it may be that in routine clinical practice NiTi-type wires are not sufficiently deformed to allow their full superelastic properties to come in to play during initial alignment.