Beta-titanium Archwires Research Articles

Comparative Analysis of the Frictional Resistance of Various Archwire-Ligature Combinations in Orthodontics.

Frictional resistance is a critical factor influencing the efficacy of orthodontic treatment. Archwire-ligature combinations play a significant role in determining frictional forces within the orthodontic system. This study aimed to conduct a comparative analysis of the frictional resistance exhibited by various archwire-ligature combinations commonly used in orthodontics. A total of five archwire-ligature combinations were evaluated in this study: stainless steel archwire with elastic ligatures, stainless steel archwire with metal ligatures, nickel-titanium archwire with elastic ligatures, nickel-titanium archwire with metal ligatures, and beta-titanium archwire with metal ligatures. Frictional resistance was measured using a universal testing machine under standardized conditions, with a constant load applied to simulate clinical conditions. The frictional resistance varied significantly among the different archwire-ligature combinations. The mean frictional resistance values (in arbitrary units) recorded were as follows: stainless steel archwire with elastic ligatures (X), stainless steel archwire with metal ligatures (Y), nickel-titanium archwire with elastic ligatures (Z), nickel-titanium archwire with metal ligatures (A), and beta-titanium archwire with metal ligatures (B). Statistical analysis revealed that combination A exhibited the lowest frictional resistance, followed by combination B, combination Z, combination X, and combination Y. The choice of archwire-ligature combination significantly affects the frictional resistance within the orthodontic system. Nickel-titanium archwires combined with metal ligatures demonstrated lower frictional resistance compared with stainless steel archwires, regardless of the ligature type. Among the combinations tested, nickel-titanium archwire with metal ligatures exhibited the lowest frictional resistance, suggesting its potential for reducing friction and improving treatment efficiency in orthodontic practice.

Comparing the Efficacy of Different Archwire Materials in Accelerating Orthodontic Tooth Movement.

Orthodontic treatment is commonly used to correct misaligned teeth and improve dental aesthetics and function. Archwires play a crucial role in this treatment by exerting forces on teeth, prompting them to shift into desired positions. For this experimental study, 60 participants requiring orthodontic treatment were selected and divided into three groups: Group A, treated with stainless steel archwires; Group B, treated with nickel-titanium archwires; and Group C, treated with beta-titanium archwires. Standardized orthodontic procedures were followed for all participants. The rate of tooth movement was measured over a period of 6 months using digital models and a calibrated measurement technique. The study revealed notable differences in the rate of orthodontic tooth movement among the three groups. Group B (nickel-titanium archwires) demonstrated the highest mean rate of tooth movement, with an average of 1.5 mm per month. Group A (stainless steel archwires) exhibited a mean rate of 1.2 mm per month, while Group C (beta-titanium archwires) showed the lowest mean rate at 0.9 mm per month. In conclusion, this study highlights the varying efficacy of different archwire materials in accelerating orthodontic tooth movement. Nickel-titanium archwires exhibited the highest rate of tooth movement compared to stainless steel and beta-titanium archwires.

Comparison of Friction Produced at Backet-Wire Interface in Monocrystalline Ceramic Brackets of 8 Different Brands: An In Vitro Study

ABSTRACT Introduction: The esthetic during the various orthodontic treatments has led to the invention of the brackets. When different ceramic brackets and archwires are used, the different frictional forces may result in the different outputs. Hence, in the present study, we evaluated and compared the frictional resistance between eight standard monocrystalline ceramic bracket models and each of the archwires of four different alloys. Materials and Methods: Frictional force was tested using Instron testing machine, in vitro, for eight types of monocrystalline ceramic bracket, and four types of archwires beta-titanium, NiTi, copper-nickel-titanium, and stainless steel statistical analysis were done using various tools, and significance value of <0.05 was considered. Results: Ormco and AO (Radiance) monocrystalline ceramic brackets created lesser frictional resistance than other monocrystalline ceramic brackets. Stainless steel archwire generates lesser static friction. Beta-titanium archwire created higher static friction. A 0.017 × 0.025 inch stainless steel archwire generates lesser static friction to 0.019 × 0.025 inch TMA. Conclusion: It can be concluded that Ormco and AO (Radiance) monocrystalline ceramic brackets, with stainless steel archwires and of size 0.017 × 0.025 inch, can generate better forces when used for the orthodontic tooth movements.

Evaluation of surface-modified orthodontic wires by different concentration and dipping duration of titanium oxide (TiO2) nanoparticles.

To evaluate in-vitro surface characteristics and frictional properties of orthodontic stainless steel and beta-titanium archwires after surface modification with different concentrations and coating time of titanium oxide (TiO2) nanoparticles by Sol-gel dip coating method. The experiment was carried out with 4 different concentrations (1:2, 1:4, 1:6, and 1:8) and three different dipping durations (24 hours, 48 hours, and 72 hours) over ten main test groups of SS and TMA archwires with uncoated wires acting as control in both dry and wet conditions. Phase analysis and surface characterization of TiO2 was analyzed by X-ray Diffractometry, surface evaluation with the help of scanning electron microscopy (SEM), and frictional characteristics were evaluated. Among all the concentrations 1:6 ratio with 48 hours of dipping duration showed better surface characteristics. A statistically significant difference in frictional coefficient was observed in both SS and TMA wires than their respective controls (p = 0.001). Intragroup comparison among SS and TMA groups showed that groups with 1:6 ratio and 48 hours dipping duration had least frictional coefficient in both dry and wet conditions (p = 0.001). Intergroup comparison between SS and TMA showed that SS group had significantly reduced friction than TMA (p = 0.001) except in few groups. TiO2 nanoparticle with a concentration ratio of 1:6 and 48 hours dipping duration is recommended for surface modification of orthodontic archwires.

Finite element analysis of tie wings rotation: A new phenomenon in orthodontic bracket-archwire contact assembly during simulated torque.

In orthodontics, the torque generated forces from the rectangular archwires refine the teeth position. Literature shows only linear deformation in brackets during torqueing. The objective of this study was to evaluate a new phenomenon of tie wings rotation, an angular deformation in Stainless Steel (SS) brackets with SS and Beta-Titanium (β-Ti) archwires at various angles of twist. Maxillary central incisor SS 0.457 mm × 0.635 mm and 0.558 mm × 0.711 mm brackets, SS and β-Ti archwires of 0.431 mm × 0.635 mm and 0.533 mm × 0.635 mm sizes were used. Finite element analysis was performed in various bracket-archwire assemblies for simulated torque. Palatal root torque was applied and the gingival tie wings rotation was measured at selected points, from 5° to 30° angles of twist. The tie wings rotation for 30° twist with SS 0.533 mm × 0.635 mm archwire in 0.558 mm bracket ranged from 1.32° to 2.55° and with SS 0.431 mm × 0.635 mm archwire in 0.457 mm bracket from 0.71° to 1.73°. Similarly, with β-Ti 0.533 mm × 0.635 mm archwire in 0.558 mm bracket and β-Ti 0.431 mm × 0.635 mm archwire in 0.457 mm bracket, the tie wings rotation ranged from 0.73° to 1.38° and 0.39° to 0.93° respectively. The tie wings rotation were present in all the FE models. Higher archwire size, stiffness, and angles of twist showed increased rotation. Thus, clinicians should be aware of this tie wings rotation during torqueing as an additional factor for torque loss.

Load Deflection Properties of Small Diameter Titanium-Niobium-Tantalum-Zirconium Archwire(An In Vitro Study)

Objectives: This study aimed to evaluate the load deflection properties of new niobium-based beta titanium archwire (Gummetal) in comparison with superelasticnickel titanium (SE-NiTi) and copper NiTinickel titanium (Cu-NiTi) archwires. Methods and Material: Gummetal, superelasticNiTiand copper NiTiarchwire segments of 0.014-inch diameter were examined by three point bending test, using Instron testing machine with 10 Newton (N) load cell. Wire segments were tested at 2 and 4 mmdeflections, and at a temperature of 37±1ᵒC. Oneway analysis of variancewas used to compare the means of the groups at a significance of p ˂ 0.05.Results: At 2 mm deflection, the maximum force values and unloading forces of Gummetalwere significantly higher than those of the control (SE-NiTi and Cu-NiTi) archwires. At 4 mm deflection, there was no significant difference between the maximum force values of Gummetal and SENiTiarchwires, however they were significantly higher than those of Cu-NiTiarchwire. Unloading forces of Gummetalarchwire at 4 mmdeflection were initially significantly higher, then became significantly lower than the control wires at 1 mm unloading deflection point.Conclusions: The present study showed that Gummetalarchwirewas less efficient in providing continuous forcesin comparison with SE-NiTi and Cu-NiTiarchwires.Gummetalarchwire cannot be considered superelastic, and its use in the alignment phase may better be limited to mild crowding cases.

Comparison of frictional resistance between four types of brackets in combination with stainless steel and beta-titanium archwires

Objectives: The objective of the study was to evaluate and compare the frictional resistance generated by four different types of brackets in combination with stainless steel (SS) and titanium molybdenum alloy (TMA) archwires. Materials and Methods: Maxillary premolar brackets were used in this study. These brackets were divided into eight groups comprising seven samples each. Of the eight groups, four groups were combined with SS and four groups were combined with TMA archwires. The testing was done in the presence of human saliva. The static frictional resistance was calculated for each group. One-way ANOVA and post hoc Tukey tests were done to compare the friction generated by each group. Results: There was a statistically significant difference between the friction generated by the monocrystalline brackets and the other bracket groups (P < 0.001). There was no statistically significant difference in static friction generated between self-ligating and conventionally ligated brackets. There was a statistically significant difference between the frictional resistance produced by SS and TMA wires (P = 0.02) with regard to monocrystalline ceramic brackets only. Conclusion: Monocrystalline ceramic brackets (Radiance) were found to generate the highest frictional resistance during sliding mechanics when compared to other brackets in combination with both SS and TMA wires. Self-ligating brackets did not show a statistically significant reduction in friction when compared to conventional ligation. There was a statistically significant difference between SS and TMA wires when used with monocrystalline brackets.

Assessment of the hardness of different orthodontic wires and brackets produced by metal injection molding and conventional methods.

This study was conducted to assess the hardness of orthodontic brackets produced by metal injection molding (MIM) and conventional methods and different orthodontic wires (stainless steel, nickel-titanium [Ni-Ti], and beta-titanium alloys) for better clinical results. A total of 15 specimens from each brand of orthodontic brackets and wires were examined. The brackets (Elite Opti-Mim which is produced by MIM process and Ultratrimm which is produced by conventional brazing method) and the wires (stainless steel, Ni-Ti, and beta-titanium) were embedded in epoxy resin, followed by grinding, polishing, and coating. Then, X-ray energy dispersive spectroscopy (EDS) microanalysis was applied to assess their elemental composition. The same specimen surfaces were repolished and used for Vickers microhardness assessment. Hardness was statistically analyzed with Kruskal-Wallis test, followed by Mann-Whitney test at the 0.05 level of significance. The X-ray EDS analysis revealed different ferrous or co-based alloys in each bracket. The maximum mean hardness values of the wires were achieved for stainless steel (SS) (529.85 Vickers hardness [VHN]) versus the minimum values for beta-titanium (334.65 VHN). Among the brackets, Elite Opti-Mim exhibited significantly higher VHN values (262.66 VHN) compared to Ultratrimm (206.59 VHN). VHN values of wire alloys were significantly higher than those of the brackets. MIM orthodontic brackets exhibited hardness values much lower than those of SS orthodontic archwires and were more compatible with NiTi and beta-titanium archwires. A wide range of microhardness values has been reported for conventional orthodontic brackets and it should be considered that the manufacturing method might be only one of the factors affecting the mechanical properties of orthodontic brackets including hardness.

Force system generated by elastic archwires with vertical V bends: a three-dimensional analysis.

Our previous understanding of V-bend mechanics is primarily from two-dimensional (2D) analysis of archwire bracket interactions in the second order. These analyses do not take into consideration the three-dimensional (3D) nature of orthodontic appliances involving the third order. To quantify the force system generated in a 3D two bracket set up involving the molar and incisors with vertical V-bends. Maxillary molar and incisor brackets were arranged in a dental arch form and attached to load cells capable of measuring forces and moments in all three planes (x, y, and z) of space. Symmetrical V-bends (right and left sides) were placed at 11 different locations along rectangular beta-titanium archwires of various sizes at an angle of 150degrees. Each wire was evaluated for the 11 bend positions. Specifically, the vertical forces (Fz) and anterio-posterior moments (Mx) were analysed. Descriptive statistics were used to interpret the results. With increasing archwire size, Fz and Mx increased at the two brackets (P < 0.05). The vertical forces were linear and symmetric in nature, increasing in magnitude as the bends moved closer to either bracket. The Mx curves were asymmetric and non-linear displaying higher magnitudes for molar bracket. As the bends were moved closer to either bracket a distinct flattening of the incisor Mx curve was noted, implying no change in its magnitude. This article provides critical information on V-bend mechanics involving second order and third order archwire-bracket interactions. A model for determining this force system is described that might allow for easier translation to actual clinical practice.

The effect of buccal-lingual slot dimension size on third-order torque response.

The focus of the presented study was to investigate the effect of buccal-lingual (B-L) orthodontic bracket slot dimension on third-order torque mechanics. Three types of orthodontic brackets and two archwire sizes were considered. Ortho Classic H4 (0.026″ B-L slot, passive), Ormco Damon Q (0.028″ B-L slot, passive), and In-Ovation R (0.028″ slot, active) brackets were tested using 0.017″ × 0.025″ and 0.019″ × 0.025″ beta-titanium archwires. An in vitro orthodontic torque simulator (OTS) was used to rotate archwires relative to a single bracket while recording forces and moments in three directions. For each bracket-archwire combination, a total of n = 47 samples were tested. Repeated measures analysis of variance between brackets was conducted for third-order torque values at 3° increments between 9° and 30° during loading and unloading for each archwire size. Statistically significant differences between H4 and Q brackets were only found for 0.017″ × 0.025″ archwires during loading, and 0.019″ × 0.025″ archwires during unloading. Conversely, differences between H4 and R brackets were found for both archwires during loading and unloading phases. Finally, when using a 0.017″ × 0.025″ archwire the H4 brackets reached the 5 Nmm threshold before R and Q brackets; however, there was little difference found when using a 0.019″ × 0.025″ archwire. The concept of using a smaller B-L bracket slot dimension in orthodontic treatment showed it may theoretically allow for more options, primarily using smaller archwires to correct third-order rotational misalignments. However, it is suspected that bracket material limitations and added loading on the door currently prevent this from being clinically applicable.

Galvanic corrosion between CuNiTi arch wires and other metallic alloys for orthodontic applications

Event Abstract Back to Event Galvanic corrosion between CuNiTi arch wires and other metallic alloys for orthodontic applications Elisa Kassab1, 2 and José P. Gomes1 1 Federal University of Rio de Janeiro, Department of Metallurgy and Materials Science, Brazil 2 Pontifical Catholic University of Rio de Janeiro, Department of Metallurgy and Materials Science, Brazil Introduction: NiTi based alloys are widely used in biomedical applications due to their special mechanical properties, corrosion behaviour and biocompatibility[1]. As orthodontic wires, they deliver light and relative constant force, resulting in a more physiological dental movement. Addition of copper (Cu) as a third element can improve some mechanical properties desirable to their application as orthodontic wires, such as narrowing of stress hysteresis and a more stable stress-strain plateau[2]. However, the better mechanical properties are not accompanied by an increase in the corrosion behaviour. A recent report revealed a lower corrosion resistance of CuNiTi in physiological medium[3]. Using different metals in oral environment, for example as orthodontic arch wires and brackets, may result in galvanic corrosion. The aim of this work is to assess the galvanic corrosion of CuNiTi with other alloys commonly used in dentistry, such as stainless steel (SS) and beta titanium. Materials: The materials used for this work were the following: CuNiTi, SS and beta titanium arch wires. CuNiTi was an 0.18-inch heat activated (35 oC) arch wire from Ormco Corp. (Orange, USA). SS and beta titanium wires were 0.16-inch arch wires ordered from GAC International Inc. (New York, USA). Methods: Electrochemical tests were performed in 0.9% NaCl electrolyte in order to simulate physiological solution. A conventional three electrode cell with a saturated calomel electrode as a reference electrode and platinum as a counter electrode was used. This cell was connected to a potentiostat (Metrohm Autolab). Potentiodynamic polarization was conducted at a scan rate of 20 mV/min starting from -600 mV to 800 mV. Cathodic curves of the materials with higher corrosion potentials (SS and beta titanium) were overlaid with the anodic curve of the CuNiTi. At this intersection point, the value corresponding to x axis was determined as the estimated potential of the galvanic couple (Ecouple) and y axis as the estimated current from the galvanic couple (icouple). Results: Initial results indicate an electrode potential gap between CuNiTi and SS and titanium alloys in 0.9 NaCl solution. This suggests that galvanic corrosion might occur in this environment. Mean Ecouple measured for the CuNiTi/SS couple was -0.1 mV. For CuNiTi/titanium was -0.8 mV. A typical polarization curve for CuNiTi and titanium is shown in Figure 1. Direct galvanic coupling and potentiostatic experiments will be performed for CuNiTi/SS and CuNiTi/titanium couples. Discussion: In dentistry, there are usually two or more different metals together in a potential corrosive environment. Therefore, galvanic corrosion must be investigated. Potentiodynamic curves revealed that for both couples, CuNiTi/SS and CuNiTi/titanium, CuNiTi would act as an anode, and therefore, would corrode faster than it would alone. As a result of corrosion, deterioration of the arch wire surface may occur and the mechanic properties of CuNiTi wires could be altered, delaying orthodontic treatment. Moreover, CuNiTi corrosion might affect the material biocompatibility due to release of potential allergic Ni ion. Conclusion: CuNiTi might be susceptible to galvanic corrosion in oral environment when coupled to more noble materials, such as SS and titanium. This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); and the Fundação Coordenação de Projetos, Pesquisas e Estudos Tecnológicos (Fundação COPPETEC).

Effects of clinical use and sterilization on surface topography and surface roughness of three commonly used types of orthodontic archwires.

To evaluate the changes in surface topography and roughness of stainless steel (SS), nickel-titanium and beta-titanium (β-Ti) archwires after clinical use and sterilization. Thirty wires each of SS, nitinol, and β-Ti (3M Unitek) were tested in as received, as received and autoclaved, and clinically retrieved then autoclaved conditions. A sterilization protocol of 134°C for 18 min was performed using an autoclave. Surface topography of specimens from each subgroup was examined using an environmental scanning electron microscope (ESEM model Quanta 200, The Netherlands) at ×100, ×1000, and ×2500 magnifications. Surface roughness was measured using arithmetic mean roughness (Ra) values obtained from optical profilometric scanning (Taylor Hobson, Leicester, UK). Data were analyzed by one-way analysis of variance and Tukey's post-hoc procedures. Scanning electron microscope images revealed an increase in surface irregularities in SS and nitinol wires after clinical use. There was a significant increase in Ra values of SS orthodontic wires after intra-oral exposure (P = 0.0002). Surface roughness of SS wires increased significantly after clinical use. Autoclave sterilization did not affect considerably on surface characteristics of any archwire.

Comparative Evaluation of Frictional forces between different Archwire-bracket Combinations

Introduction: During sliding mechanics, frictional resistance is an important counterforce to orthodontic tooth movement; whichmust be controlled to allow application of light continuous forces.Objective: To investigate static and kinetic frictional resistance between three orthodontic brackets: ceramic, self-ligating, andstainless steel, and three 0.019×0.025” archwires: stainless steel, nickel-titanium, titanium-molybdenum.Materials &amp; Method: The in vitro study compared the effects of stainless steel, nickel-titanium, and beta-titanium archwires onfrictional forces of three orthodontic bracket systems: ceramic, self-ligating, and stainless steel brackets. All brackets had 0.022”slots, and the wires were 0.019×0.025”. Friction was evaluated in a simulated half-arch fixed appliance on a testing machine. Thestatic and kinetic friction data were analyzed with 1-way analysis of variance (ANOVA) and post-hoc Duncan multiple rangetest.Result: Self-ligating (Damon) brackets generated significantly lower static and kinetic frictional forces than stainless steel (Gemini)and ceramic brackets (Clarity). Among the archwire materials, Beta-titanium showed the maximum amount of frictional forceand stainless steel archwires had the lowest frictional force.Conclusion: The static and kinetic frictional force for stainless steel bracket was lowest in every combination of wire.

Comparative Assessment of Efficacy of Four Different Designs of Retraction Loops made of Beta Titanium Archwire: A Finite Element Study

ABSTRACTObjectiveTo compare the forces, moments and moment/ force (M/F) ratio and load deflection rate of T-loop, keyhole loop, teardrop loop and mushroom loop with the finite element method (FEM).Materials and MethodsFEM was used to compare 3D models of closing loops in rectangular (0.017 × 0.025 inch) beta titanium wire. The T-loop, mushroom loop, keyhole loop and teardrop loop were 7 mm in height. The forces, the moments and the M/F ratios at each tooth node were recorded with an activation of 2 mm.ResultsThe highest force and moments was produced by the keyhole loop and the lowest force was produced by the mushroom loop.ConclusionAll the four retraction loops exerted the greatest force levels at the molar node. The maximum value for M/F ratio is seen at the central incisor followed by lateral incisor, molar and canine node. The keyhole loop demonstrated the least load deflection rate making it the most efficient design.How to cite this articlePatel AS, Ravindranath VK, Karandikar GR, Malik AS. Comparative Assessment of Efficacy of Four Different Designs of Retraction Loops made of Beta Titanium Archwire: A Finite Element Study. J Contemp Dent 2014;4(1): 6-9.

The effect of water storage on the bending properties of esthetic, fiber-reinforced composite orthodontic archwires

To study the effect of water storage on the bending properties of fiber-reinforced composite archwires and compare it to nickel-titanium (NiTi), stainless steel (SS), and beta-titanium archwires. Align A, B, and C and TorQ A and B composite wires from BioMers Products, 0.014-, 0.016, and 0.018-inch, and 0.019×0.025-inch NiTi, 0.016-inch SS, and 0.019×0.025-inch beta-titanium archwires were tested (n=10/type/size/condition). A 20-mm segment was cut from each end of the archwire; one end was then stored in water at 37°C for 30 days, while the other was stored dry. The segments were tested using three-point bending to a maximum deflection of 3.1 mm with force monitored during loading (activation) and unloading (deactivation). Statistical analysis was completed via two-way analysis of variance with wire and condition (dry and water-stored) as factors. In terms of stiffness and force delivery during activation, in general: beta-titanium was >TorQ B>TorQ A>0.019×0.025-inch NiTi and 0.016-inch SS>Align C>0.018-inch NiTi>Align B>0.016-inch NiTi>Align A>0.014-inch NiTi. Water exposure was detrimental to the larger translucent wires (Align B and C, TorQ A and B) because they were more likely to craze during bending, resulting in decreased forces applied at a given deflection. Align A and the alloy wires were not significantly (P>.05) affected by water storage. Overall, the alloy wires possessed more consistent force values compared to the composite wires. Environmental conditions are more likely to affect fiber-reinforced composite archwires compared to alloy wires.

Clinicians' Choices in Selecting Orthodontic Archwires

Abstract Objective: The aim of this study was to assess the choices made by clinicians in selecting archwires during the initial, intermediate and final stages of orthodontic treatment with fixed appliances. Methods: We carried out a questionnaire-based study at the Orthodontics and Pedodontics Clinic Târgu Mureș, between March 2012 and September 2012. The questionnaires consisted of two parts: the first included questions related to the dimension, alloy used in fabrication, section (round or rectangular) and manufacturer of the archwires used by the orthodontists in their orthodontic practice, the second part was concerned with their personal opinion about the physical properties and disadvantages of the archwires. Results: From a total number of 90 distributed questionnaires, 62 were returned. The majority of clinicians are using stainless steel (SS) and nickel-titanium alloy (NiTi) wires in their fixed orthodontic treatments, very few are using beta-titanium (Beta Ti), copper nickel-titanium (Co- NiTi) and esthetic archwires. The preferred dimension seem to be 0.022 inches in the appliance system. Regarding the wire dimensions, 0.014, 0.016 inch wires are mostly used from the round section group and 0.016 × 0.022 inch, 0.017 × 0.025 inch from the rectangular ones. Conclusions: There is a general lack of agreement between the clinicians surveyed regarding the properties of an ideal archwire and the disadvantages of the used wires. The most frequently used alloys seemed to be the SS and NiTi

Evaluation of the Friction of Self-Ligating and Conventional Bracket Systems

This in vitro study evaluated the friction (F) generated by aligned stainless steel (SS) conventional brackets, self-ligating Damon MX(©) brackets (SDS Ormco, Glendora, California, USA), Time3(©) brackets (American Orthodontics, Sheboygan, Wisconsin, USA), Vision LP(©) brackets (American Orthodontics), and low-friction Slide(©) ligatures (Leone, Firenze, Italy) coupled with various SS, nickel-titanium (NiTi), and beta-titanium (TMA) archwires. All brackets had a 0.022-inch slot, and the orthodontic archwires were 0.014-inch, 0.016-inch, 0.014×0.025-inch, 0.018×0.025-inch, and 0.019×0.025-inch NiTi; 0.017×0.025-inch TMA; and 0.019×0.025-inch SS. Each bracket-archwire combination was tested 10 times. In the test, 10 brackets of the same group were mounted in alignment on a metal bar. The archwires moved through all the 10 brackets at a crosshead speed of 0.5 mm/min (each run lasted approximately 5 min). The differences among 5 groups of brackets were analyzed through the Kruskal-Wallis test, and a Mann-Whitney test was calculated as post hoc analysis. The P value was set at 0.05. Coupled with 0.014-inch NiTi and 0.016-inch NiTi, Victory Series(©) brackets generated the greatest F, while Damon MX(©) and Vision LP(©) brackets generated the lowest (P<.05); no significant differences were observed between Time3(©) brackets and Slide(©) ligatures. Coupled with all the rectangular archwires, Victory Series(©) brackets, Slide(©) ligatures, and Vision LP(©) self-ligating brackets generated significantly lower F than did Time3(©) and Damon MX(©) self-ligating brackets (P<.05). These findings suggest that self-ligating brackets are a family of brackets that, in vitro, can generate different levels of F when coupled with thin or thick, rectangular, or round archwires. Clinical conclusions based on our results are not possible due to the limitations of the experimental conditions.

Comparative evaluation of frictional forces in active and passive self-ligating brackets with various archwire alloys

Self-ligating brackets are claimed to eliminate or minimize the force of ligation at the bracket-wire interface; therefore, it is imperative to evaluate the frictional features of contemporary self-ligating brackets with different archwire alloys. This in-vitro study compared the effects of stainless steel, nickel-titanium, and beta-titanium archwires on frictional forces of passive and active self-ligating brackets with a conventional bracket. All brackets had 0.022-in slots, and the wires were 0.019 x 0.025 in. Friction was evaluated in a simulated half-arch fixed appliance on a testing machine. The static and kinetic friction data were analyzed with 1-way analysis of variance (ANOVA) and the post-hoc Duncan multiple range test. Archwire alloy and bracket effects were evaluated with 2-way ANOVA. Static and kinetic frictional forces were lower for both the passive and active designs than for the conventional brackets. Maximum values were seen with the beta-titanium archwires, and significant differences were observed between nickel-titanium and stainless steel archwires. With the passive or active self-ligating brackets, stainless steel wire did not produce a significant difference, but differences were significant with nickel-titanium and beta-titanium wires. When nickel-titanium and beta-titanium wires are used for guided tooth movement, passive appliances can minimize frictional resistance.

Influence of stress and phase on corrosion of a superelastic nickel-titanium orthodontic wire

The purpose of this investigation was to study the effect of stress and phase transformation on the corrosion properties of a superelastic nickel-titanium orthodontic wire. The phase transformation profiles of superelastic nickel-titanium (Sentalloy, GAC International, Bohemia, NY) and beta-titanium (TMA, Ormco, Orange, Calif) archwires were analyzed by using differential scanning calorimetry. The force/deflection behavior of the wires at 37 degrees C was measured in a 3-point bending test per modified American Dental Association specification no. 32. Electrochemical testing consisted of monitoring the open circuit potential (OCP) for 2 hours followed by polarization resistance and cyclic polarization tests on archwire segments engaged in a 5-bracket simulation apparatus with bend deflections of 0.75, 1.5, or 3 mm in artificial saliva at 37 degrees C. Nondeflected segments were also tested. Sentalloy was additionally examined for bending and corrosion at 5 degrees C, where it exists as martensite and is devoid of stress-induced phase transformation. OCP at 2 hours and corrosion current density (i(corr)) were analyzed by using ANOVA and Tukey tests (alpha = .05) (n = 10 per deflection). Significant differences (P < 0.05) in OCP with deflection were found for the TMA and the Sentalloy wires at 5 degrees C, but not for Sentalloy at 37 degrees C. Significant differences (P < 0.05) in i(corr) with deflection were also observed. All 3 wire groups had their lowest mean i(corr) values when not deflected. The i(corr) for superelastic Sentalloy (37 degrees C) peaked at 0.75 mm deflection before the wire's stress-induced phase transformation point and then decreased with further deflection and transformation. The i(corr) values for TMA and Sentalloy at 5 degrees C, both of which do not undergo phase transformation with deformation, continuously increased from 0 to 1.5 mm deflection before decreasing at the 3.0-mm deflection. Stress increased the corrosion rate in nickel-titanium and beta-titanium orthodontic wires. Alterations in stress/strain associated with phase transformation in superelastic nickel-titanium might alter the corrosion rate in ways different from wires not undergoing phase transformation.

Influence of interbracket distances on the resistance to sliding of orthodontic appliances

The influence of interbracket distance (IBD) on the resistance to sliding (RS) was evaluated. Commercially pure titanium brackets (CP-Ti; 0.018- and 0.022-in slots, width = 0.14-in) were tested against 0.016 x 0.022-in rectangular stainless steel (SS), nickel titanium (Ni-Ti), and beta-titanium (beta-Ti) archwires in the dry and wet (human saliva) states. With a custom testing apparatus that simulated a 3-bracket system, the RS was measured at a normal force of 300 cN and at second-order angles (theta) ranging from -9 degrees to +9 degrees. Twenty-three pairs of IBDs (written as IBD1_IBD2) were varied to simulate clinically relevant biomechanical scenarios with IBD ranging from 16 to 7 mm. In the dry state, the kinetic frictional coefficients (micro(k)) were equal to 0.12, 0.23, and 0.24 for the SS, Ni-Ti, and beta-Ti archwires against the CP-Ti brackets, respectively. The presence of saliva slightly increased micro(k). The RS was inversely proportional to the total IBD (IBD(T) = IBD1 + IBD2) regardless of archwire alloy or bracket slot. Elastic binding (BI = RS - frictional force in the passive region) did not depend on the order of the IBDs in the IBD1_IBD2 pair. For a specific archwire-bracket couple, the BI of an IBD1_IBD2 pair is equal to any other pair with an equal IBD(T). Although no significant difference was found between the coefficients of binding (micro(BI)) for SS and beta-Ti archwires, the micro(BI)'s of Ni-Ti archwires were lower and significantly different. The micro(BI) was linearly related (P<.01) to IBD(T) and total archwire beam length (L(T)).