Deactivation Forces Research Articles

In vitro analysis of prosthetic abutment and angulable frictional implant interface adaptation: Mechanical and microbiological study

The aim of this study was to evaluate, in vitro, the microbiological sealing at the implant and different angles frictional prosthetic abutment interface, submitted or not to mechanical cycling, as well as the deactivation force and evaluation of the implant-abutment interface by scanning electron microscopy. For this study, the sealing capacity of eighty sets of abutments/implants of each angle, with and without mechanical cycling, with internal conical connection (locking tapper) (4.3 mm × 9.0 mm) constituted in Titanium alloy (Ti6Al4V), and stainless steel angled prosthetic abutment was evaluated (18Cr14Ni2.5Mo) according to ASTM F138-13a (Arcsys, FGM, Joinville, Brazil), 6 mm high and 4.2 mm in diameter at the coronary portion, and 3.5 mm high transmucosal, in 4 different angles (0, 5, 10 and 20°). After in vitro tests, 100% biological sealing was observed at the implant / prosthetic abutment interface within cycled and non-cycled conditions, for the straight, 5, 10 and 20° inclination groups. There was no statistically significant difference in the removal force of the prosthetic abutments at different angles, under non-cycled conditions; however, under mechanical loading, the deactivation force was significantly higher for straight prosthetic abutments than with 10 and 20° of angulation. Surface analysis revealed good adaptation between implants and abutments, and the presence of wear areas, independently of mechanical loading. It is concluded that the analysis of implant and prosthetic abutment interface revealed good adaptation between the parts, for all analyzed samples.

Force‐deflection behavior of NiTi archwire at different configurations of bracket system

AbstractNiTi shape memory alloy archwire is widely used in orthodontic treatment, replacing stainless steel for the flat and low deactivation force it can offer. However, the presence of friction at the contact region of wire and bracket may cause the low deactivation force to be ineffective to induce tooth movement. This work evaluated the bending deformation behavior of NiTi archwire in application using conventional orthodontic stainless steel bracket in levelling treatment. Experimental test rig was developed to perform three‐brackets bending test at room temperatures (27 °C). The bracket used was 0.022‐in stainless steel and the archwire was 0.016‐in NiTi round wire. Fabricated polytetrafluoroethylene (Teflon) bracket was used as a control experiment to represent frictionless condition of deformation on three‐bracket bending. Additionally, elastomeric ligature was also used to evaluate the effect of friction produced by the elastomer. Bending tests were done at 3 different deflection magnitudes of 2 mm, 3 mm and 4 mm. The results show that bending deformation behavior of the wire on frictionless Teflon bracket produced a flat force plateau on both activation and deactivation. On the other hand, when stainless steel brackets were used, the force plateau exhibited positive gradient on the activation and negative gradient on the deactivation.

Effects of site-specific substitution to hexacene and its effect towards singlet fission

The singlet fission (SF) process, which is involved in organic solar cell, is a spin allowed and extremely fast internal conversion process by which a photo-excited singlet exciton produces two triplets. To accelerate this fission and to increase the efficiency of solar cell, designing of new materials/molecules is an interesting area of research and our current interest. Several alternate hydrocarbons of the acene series and their derivatives with structural variety are desirable for this purpose. Therefore, we have theoretically modeled and investigated different substituted hexacenes in detail. Different electron donating groups (EDGs) as well as electron withdrawing groups (EWGs) and few groups of other varieties are chosen for site-specific monosubstitution to the hexacene ring for manipulation of their excited singlet-triplet energy levels and thereby to match the SF driving force (Δ) and triplet-triplet annihilation (TTA) deactivation force (Ω). The geometries, electronic structures, frontier molecular orbital (FMO) energies, optimization of excited state and calculation of Δ and Ω of the substituted hexacenes are investigated with Time Dependent Density functional theory (TDDFT) method using B3LYP/6-31G∗ basis set. After a detail theoretical analysis on sixty five (65) hexacene derivatives, the δ-triisopropylsilylethynyl (-TIPS) hexacene and β-NO2 hexacene are predicted to exhibit good SF characteristics.

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.

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.

Deflection test on different orthodontic wire materials sized 0.016 x 0.022 inches

The development of technology in orthodontic field produces some orthodontic wires that have different deflection abilities. Loading force is the force needed to place an orthodontic wire in bracket slot (activation). Unloading force is the force produced by an orthodontic wire to move tooth (deactivation). Deflection test with three-point bending technique is a technique that is often used to determine the magnitude of the activation and deactivation force of orthodontic wire. Stainless steel (SS), nickel titanium (NiTi), copper nickel titanium (CuNiTi), and beta titanium (TMA), are the types of frequently used wires. This study aimed to compare loading and unloading force on the deflection test of SS, NiTi, CuNiTi, and TMA orthodontic wires sized 0.016 x 0.022 inch on the load-deflection graph. This is a laboratoryexperimental research on a total of 16 pieces of SS, NiTi, CuNiTi, and TMA orthodontic wires sized 0.016 x 0.022 inches. The group was divided based on the type of material. The deflection test was performed using a universal testing machine with a press speed of 5 mm/minute. Loading and unloading forces were recorded on deflections of 0.5; 1; and1.5 mm. Statistical tests of differences among groups were carried out by ANOVA analysis (p-value ≤ 0.05) and post-hoc analysis with T-test. There were significant differences in the loading and unloading forces recorded on deflections of 0.5; 1; and 1.5 mm; except for deflections of 0.5 mm of the SS and nickel-titanium wires. The wire deflection force fromthe lowest to the highest was CuNiTi wire, nickel-titanium wire, TMA wire, and stainless-steel wire.

Computational study on the effect of contact friction towards deactivation force of superelastic NiTi arch wire in a bracket system

This study investigated the impact of contact friction towards force-deflection behavior exhibited by superelastic NiTi arch wire during orthodontic treatment. A three-dimensional finite-element model of wire bending in bracket configurations was developed by employing UMAT/Nitinol and contact interaction. This model was used to predict the force response of NiTi wires upon bending at different friction conditions; friction coefficient at the wire-bracket interfaces was varied from 0.0 to 0.5. The force from the finite-element model was validated against experimental work, and good agreement was obtained between the two results. This investigation revealed that the superelastic wires exhibited the forces over a plateau trend in a frictionless bracket system. As the friction coefficient at the wire-bracket interface increased, the force plateau gradually transformed into a slope trend, suppressing the deactivation force to a lower magnitude. Over the increment of the friction coefficients, the rectangular wire registered the largest force reduction and slope variation at a ratio of −12.7 N/μ and −4.6 Nμ mm−1, respectively. Also, under the condition of high contact friction coefficient (μ ≥ 0.4), the deactivation force is suppressed to zero and inhibits tooth movement.

Stress assessment of mandibular incisor intrusion during initial leveling in continuous arch system with different archwire shapes of superelastic nickel-titanium: A three-dimensional finite element study

INTRODUCTION: Orthodontic leveling of mandibular teeth with deep curve of Spee usually creates an intrusive force on mandibular incisors with labial tipping. After placing an archwire, a deactivation force causes tooth movement within the periodontal space which induces the first step and is the first signal for further remodeling processes. This study aimed to investigate stress distribution and types of mandibular incisor movement after initial leveling with different nickel-titanium (Ni-Ti) archwires using finite element analysis. MATERIALS AND METHODS: A three-dimensional finite element model of well-aligned mandibular teeth with a deep curve of Spee was created to investigate intrusive force on mandibular incisors within the periodontal ligament (PDL) space. Round, square, and rectangular superelastic Ni-Ti archwires of 0.016” in height were tested to compare stress magnitude and the pattern of distribution on the root surface and PDL as well as the pattern of tooth displacement between the archwires. RESULTS: Intrusive force by an archwire within the PDL space caused the highest stress at both labial and lingual cervical roots, but much higher stress was found at the labial than the lingual cervical roots. The highest labial stress was more cervical than lingual in all models. Round wires showed much higher stress than either square- or rectangular-shaped archwires. Displacement in the labial direction of round wires moved the farthest, whereas square and rectangular wires showed less labial displacement. CONCLUSIONS: Lower incisor intrusion with round wires produced more stress at the labial cervical root and tipped more labially compared to square and rectangular archwires.

Force‐deflection behaviour of NiTi archwires in a polytetrafluoroethylene (Teflon) bracket system

AbstractIn orthodontic treatment, archwire forces for tooth movement is influenced by the magnitude of friction encountered during the sliding motion of archwire along the bracket slot. Friction will reduce the archwire force, and subsequently modify the constant force delivery trend into a slope. The aim of this work is to investigate the force‐deflection behaviour of nickel‐titanium (NiTi) shape memory alloy archwire on polytetrafluoroethylene (Teflon) as the bracket. Sliding tests was performed to determine the coefficient of friction of polytetrafluoroethylene‐NiTi material combinations. The force‐deflection behaviour was evaluated from a modified bending tests, at two different configurations; commercial stainless‐steel bracket and hand‐made polytetrafluoroethylene bracket. During test, wires were deflected into different deflections (2 mm, 3 mm and 4 mm) by using four commercial NiTi archwires at different sizes and geometry. From the test; coefficient of friction for polytetrafluoroethylene‐NiTi wire was recorded as small as 0.07. On force‐deflection graphs, bending load on 3 mm and 4 mm deflection were observed higher on stainless steel (SS) bracket compared with polytetrafluoroethylene bracket. Due to small coefficient of friction on polytetrafluoroethylene‐NiTi configuration, the NiTi archwire exhibited the activation and deactivation force within the plateau limit. Greater friction on stainless steel‐nickel‐titanium bracket configuration causes wire to release force in a slope trend. This finding highlights the potential of polytetrafluoroethylene as a material in the bracket slot to minimize friction during orthodontic treatment.

Effects of reversing the coiling direction on the force-deflection characteristics of nickel-titanium closed-coil springs.

ObjectiveTo investigate the effects of reversing the coiling direction of nickeltitanium closed-coil springs (NiTi-CCSs) on the force-deflection characteristics.MethodsThe samples consisted of two commercially available conventional NiTi-CCS groups and two reverse-wound NiTi-CCS groups (Ormco-Conventional vs. Ormco-Reverse; GAC-Conventional vs. GAC-Reverse; n = 20 per group). The reverse-wound NiTi-CCSs were directly made from the corresponding conventional NiTi-CCSs by reversing the coiling direction. Tensile tests were performed for each group in a temperature-controlled acrylic chamber (37 ± 1℃). After measuring the force level, the range of the deactivation force plateau (DFP) and the amount of mechanical hysteresis (MH), statistical analyses were performed.ResultsThe Ormco-Reverse group exhibited a significant shift of the DFP end point toward the origin point (2.3 to 0.6 mm), an increase in the force level (1.2 to 1.3 N) and amount of MH (1.0 to 1.5 N) compared to the Ormco-Conventional group (all p < 0.001), which indicated that force could be constantly maintained until the end of the deactivation curve. In contrast, the GAC-Reverse group exhibited a significant shift of the DFP-end point away from the origin point (0.2 to 3.3 mm), a decrease in the force level (1.1 to 0.9 N) and amount of MH (0.6 to 0.4 N) compared to the GAC-Conventional group (all p < 0.001), which may hinder the maintenance of force until the end of the deactivation curve.ConclusionsThe two commercially available NiTi-CCS groups exhibited different patterns of change in the force-deflection characteristics when the coiling direction was reversed.

An In Vitro Comparison of the Forces Released by Closed Nickel–Titanium Springs

The aim of this study was to evaluate the force-release behavior of closed coil nickel-titanium springs of three different commercial brands available on the market, as well those from different batches, tested over multiple distances, according to the number of deactivations. For this in vitro analysis, closed coil nickel-titanium springs of the following numbers and brands: eight, 3 mm GAC® springs; eight, 3 mm springs from TP Orthodontics® and eight, 5 mm springs from MORELLI® were standardized at 200 gf force. Two batches of all three brands were tested and compared. All springs were evaluated on a test machine and extended to a distance of five times beyond their original length. The springs were extended, and the distances of force released were measured and marked at every 20% of the total spring length, during their deactivation, and the process was repeated five times for each spring. The intraclass correlation coefficients showed that the value of 200 gf indicated by the manufacturers was poorly reproduced. The springs did not change their force release after successive extensions. All springs presented higher deactivation force values as their stretching increased. All springs presented the greater release of force as their stretch was increased, but the GAC® brand springs presented a more uniform pattern. TP Orthodontics® springs exhibited an acceptable force release pattern, but MORELLI® springs proved to be far below expected strength. As a clinical consideration of the study, the results obtained in the present research are relevant to the use of nickel-titanium closed springs with regard to the quantity of force released during the mechanics of space closure after extraction (main application of nickel-titanium closed springs), and to the pattern of forces released by springs in view of the real context of gradual closure of spaces after tooth extractions.

Evaluation of the force generated by gradual deflection of 0.016-inch NiTi and stainless steel orthodontic wires in self-ligating metallic and esthetic brackets

BackgroundThe purpose of this study was to evaluate the deflection forces of 0.016-inch Nitinol and stainless steel orthodontic wires, in association to different self-ligating brackets.Material and MethodsSpecimens were mounted in a clinical simulation model and evaluated in a Universal Testing Machine (INSTRON 3342), using a 10N load cell and ISO 15,841, as a protocol. Eight of these models were prepared, each one for the bonding of each set of self-ligating accessories to be tested: Damon Q, Damon Clear (Ormco), In-Ovation R, In-Ovation C (GAC), BioQuick, QuickClear (Forestadent), SmartClip and Clarity SL (3M). Data were subjected to One-way ANOVA, followed by Tukey tests (P<0.05).ResultsElastic deflection results showed that the deactivation forces increased with increase in wire deflection in the different brackets evaluated. For the different combinations, Clarity SL generated the greatest force and Damon Clear presented the lowest force when compared to the other brackets in all alloys and deflections. BioQuick and QuicKlear were those with the most similar behavior with each other.ConclusionsStrength values increased with gradual increase in wire deflection in all evaluated brackets. Clarity SL generated the greatest and Damon Clear the lowest force when compared to the other brackets in all alloys and deflections tested. Key words:Brackets, orthodontic wires, deflection.

Flexural properties of rectangular nickel-titanium orthodontic wires when used as ribbon archwires.

To compare the flexural properties of rectangular nickel-titanium (Ni-Ti) orthodontic wires in occlusoapical and faciolingual orientations using a standardized test method. Twenty-two rectangular Ni-Ti wire groups were tested in occlusoapical (ribbon) orientation: eight conventional Ni-Ti products, five superelastic Ni-Ti products, and nine thermal Ni-Ti products (n = 10 per group). Six products of thermal Ni-Ti wire were tested in faciolingual (edgewise) orientation. A three-point bending test was performed to measure deactivation force at 3.0-, 2.0-, 1.0-, and 0.5-mm deflections of each rectangular wire at 37.0 ± 0.5°C. Analysis of variance and post hoc Student-Newman-Keuls tests were used to compare the mean values of the different groups (α = .05). The ranges of deactivation forces varied greatly with different kinds, sizes, products, and deflections of Ni-Ti wires. One product of conventional and superelastic Ni-Ti wires had steeper force-deflection curves. Four products had similarly shaped flat force-deflection curves, whereas the sixth product had a moderately steep force-deflection curve. Thermal Ni-Ti wires had smaller deactivation forces ranging from 0.773 N (78.8 g) to 2.475 N (252.4 g) between deflections of 1.0 and 0.5 mm, whereas wider ranges of force from 3.371 N (343.7 g) to 9.343 N (952.7 g) were predominantly found among conventional Ni-Ti wires between deflections of 3.0 and 2.0 mm. Clinicians should critically select archwires for use in the occlusoapical orientation not only based on Ni-Ti wire type, size (0.022 × 0.016-in or 0.025 × 0.017-in), and product but also with deactivation deflections from 0.5 and 1.0 mm to obtain light forces in the occlusoapical orientation.

Comparison of the load-deflection characteristics of 0.012″ heat-activated, superelastic and bent superelastic nickel titanium wires

PurposeTo compare the characteristics and load-deflection graphs of 0.012″ heat-activated NiTi, superelastic NiTi and bent (bends placed at 1, 2 and 3mm) superelastic NiTi wires, focusing on force at 0.5mm after deactivation after deflection by 1, 2, 3 and 4mm. Materials and methodsThree-bracket bending tests using a 10N load cell with 1mm/min crosshead speed and 8mm span were performed at 37°C. Three groups of wires, 0.012″ heat-activated NiTi wires (HANT), superelastic NiTi wires (S), and superelastic NiTi wires with bends placed at 1, 2 and 3mm (SB1, SB2 and SB3, respectively) were deflected by 1, 2, 3 and 4mm. Deactivation forces (N) at 0.5mm after deactivation were compared using ANOVA. ResultsBent NiTi wires produced lighter forces than superelastic and heat-activated NiTi wires (P<0.05). Superelastic and heat-activated NiTi wires had linear load-deflection graphs at 1mm deflection. No bent NiTi wires had linear load deflection graphs; hysteresis was observed after 2, 3 and 4mm deflection in all NiTi groups. Increasing the number of bends and deflection appeared to inactivate NiTi wires. ConclusionsAfter any deflection, all bent NiTi wires produce lighter forces at 0.5mm after deactivation than superelastic NiTi and heat-activated NiTi wires. This study indicates bending a NiTi wire close to a displaced tooth with up to 1mm deflection can produce an active light deactivation force to level severely displaced teeth.

Comparative Evaluation of Load-deflection Property of Different Brands of Nickel-titanium Archwires

Context The tooth alignment and leveling constitute the preliminary clinical phase of any orthodontic procedure with fixed appliances. It has been accepted in orthodontics the principle that light and continuous forces would be desirable for physiologic and controlled tooth movement. For this purpose, it has been suggested that nickel-titanium (NiTi) archwires which offer a force-bending curve with a defined baseline and a larger activation range should be used Aims The aim of this study was to evaluate and compare the force versus deflection properties of different brands of NiTi wires available in market. Settings and Design Null hypothesis. There is no difference in force-deflection properties between different brands of same dimension NiTi archwires available in market. A cross-sectional study design was planned. Subjects and Methods Different companies were identified producing their own version or marketing NiTi archwires of the following sizes: 0.016 inch round and 0.016 × 0.022 inch rectangular were selected because all companies produced or marketed these particular sizes, and in addition, these were selected because these wire sizes are commonly used clinically. The three-point bend test was utilized to test the various wires in accordance with the ISO 15841 standard for orthodontic wires with the exception that the bottom support span was 16 mm rather than 10 mm due to fixture limitations. Statistical Analysis Used Data obtained from different brands of wires available in the Indian market Ormco, American Orthodontics, Ortho Organizers, Rocky Mountain Orthodontics 3M and MO which are manufactured in U.S.A, While as Natural, Orthomatix, JJ Orthodontics, Koden, Gdc, Rabbit force, and Optima are manufactered in china. and size 0.016 inch round wire and 0.16x0.022 inch rectangular wires were compared using ANOVA test. Statistical analysis was performed using SPSS 2.1. Results In this study, the data show that minimum force during activation of 0.016 inch round wire at 1 mm was 95 ± 10 g whereas maximum was 165 ± 10 g with a difference of 70 ± 20 g. Whereas at 3 mm activation, minimum force generated was 150 ± 10 g and maximum was 225 ± 10 g with a difference of 75 ± 20 g. In 0.016 × 0.022 inch rectangular wire, minimum activation force at 1 mm deflection was 210 ± 10, whereas maximum was 340 ± 10 with a difference of 130 ± 20 g. For deactivation, the minimum force for 0.016 wire at 1 mm deflection was 40 ± 10, whereas maximum force was 125 ± 10 with a difference of 85 ± 20 g, and for the 0.016 × 0.022 wire, the minimum load at 1 mm deflection was 150 ± 10 g, whereas the maximum was 295 ± 10 g with a difference of 145 ± 20 g. The deactivation force in majority of brands (8) at 1 mm deflection was &lt;80 g whereas at 3 mm, majority brands have force levels &gt;150–195 g. The deactivation force at 3 mm deflection in five brands was between 235 and 335 and five other brands between 335 and 445 whereas at 1 mm, deflection majority of brands was between 170 and 200 g. Conclusion From this data, a comparative evaluation shows that there is a huge difference in force-deflection properties of same dimension wire from different brands, which means that its making the orthodontic treatment more indeterminate; some wires have shown less and some have shown more force. Wires of the same materials, dimensions, but from different manufacturers do not always have the same mechanical properties. There are significant differences in the activation and deactivation forces among the different manufacturers of NiTi archwires. Improvements should be made in the standardization of the manufacturing testing process of NiTi archwires to provide orthodontists with NiTi archwires that have consistent mechanical properties despite the manufacturing brand that produces them.

Evaluation of the mechanical properties and surface topography of as-received, immersed and as-retrieved orthodontic archwires.

Background and aimsThis experimental study mainly aims at comparing the most important mechanical properties of the new orthodontic archwires, those immersed in fluorinated solution, the as-retrieved ones and the intra-oral used ones.MethodsA total of 270 arch wires were tested, using tensile testing and three-point bending tests. The tested archwires were made of Stainless Steel, Nickel Titanium, Beta-Titanium and physiognomic covered Nickel Titanium. The tested archwires were subjected to three types of treatments: immersion into fluorinated solution, immersion into carbonated drinks and intra-oral use.ResultsThe immersion caused variations of the activation and deactivation forces of all arch wires. The most affected arch wires, in terms of bending characteristics, were the intra-oral used ones.ConclusionsThe alteration of mechanical properties of the orthodontic arch wires by their immersion into fluorinated solutions and soft drinks could not be statistically demonstrated.

Quantification of the force systems delivered by transpalatal arches activated in the six Burstone geometries.

To evaluate the force systems produced by transpalatal arches (TPAs) activated according to the six classes of geometries described by Burstone and Koenig. Sixty appliances were tested for first-order activations using a mechanical force testing system. The TPAs were first checked for passivity in sagittal, transverse, and vertical planes at the measuring machine. Then 10 appliances per group were activated using a millimeter template to obtain the six classes of geometries, and the activated appliances were inserted into lingual tubes of the Force System Identification machine that recorded the deactivation forces and moments delivered by both terminal ends of the TPAs. The overall force system with the actual values of forces and moments recorded by each type of activation was illustrated and compared with the mathematical model reported by Burstone and Koenig. Although a great consistency of the direction of forces and moments were observed, the theoretically feasible force systems could not be fully accomplished by the TPA activated for the six classes of geometries. The first-order activations of the TPA can deliver predictable force systems in respect to the direction of forces and moments attainable, but some unexpected forces and moments are also produced. Careful clinical monitoring is, therefore, strongly recommended when using this statically indeterminate system.

Forces in initial archwires during leveling and aligning: An in-vitro study.

Aim:This in-vitro study measured the force deflection behavior of selected initial alignment archwires by conducting three-point bending tests under controlled tests. The study tested three wire designs, namely, co-axial multistranded stainless steel wires, nickel–titanium, and copper–nickel–titanium archwires.Materials and Methods:The archwires were ligated to a specially designed metal jig, simulating the arch. A testing machine (Instron) recorded activation and deactivation forces of different deflections at 37°C. Forces on activation and deactivation were compared by one-way analysis of variance (ANOVA).Results:Significant differences (P < 0.05) in activation and deactivation forces were observed among the tested wires. The co-axial multistranded wire had the lowest mean activation and deactivation forces, whereas conventional nickel–titanium wires had more mean activation and deactivation forces at different deflections.Conclusion:The activation and deactivation forces were higher for nickel–titanium followed by copper–nickel titanium and co-axial wires. The amount of percentage force loss was more for co-axial wire, indicating that these wires are not ideal for initial leveling and aligning.

Comparison and ranking of superelasticity of different austenite active nickel-titanium orthodontic archwires using mechanical tensile testing and correlating with its electrical resistivity

Introduction:The application of light and continuous forces for optimum physiological response and the least damage to the tooth supporting structures should be the primary aim of an orthodontist. Nickel-titanium (NiTi) alloys with their desirable properties are one of the natural choices of the clinicians.Aim:This study was aimed to compare and rank them based on its tensile strength and electrical resistivity.Materials and Methods:The sample consisted of eight groups of 0.017 inch × 0.025 inch rectangular archwires from eight different manufacturers, and five samples from each group for tensile testing and nine samples for electrical resistivity tests were used. Data for stress at 10% strain and the initial slope were statistically analyzed with an analysis of variance and Scheffe tests with P < 0.05. The stress/strain plots of each product were ranked for superelastic behavior. The rankings of the wires tested were based primarily on the unloading curve's slope which is indicative of the magnitude of the deactivation force and secondarily on the length of the horizontal segment which is indicative of continuous forces during deactivation. For calculating the electric resistivity, the change in resistance after inducing strain in the wires was taken into account for the calculation of degree of martensite transformation and for ranking.Results:In tensile testing Ortho Organizers wires ranked first and GAC Lowland NiTi wires ranked last. For resistivity tests Ormco A wires were found superior and Morelli remained last.Conclusion:these rankings should be correlated clinically and need further studies.

Effect of Temperature on Deactivation Force of Three Commercial NiTi Orthodontic Archwires

Objective: The purpose of this study was to investigate the transition temperature range (TTR) and the effect of temperatures at 10, 20, 30, 40, 50 and 60 °C on the deactivation force of three commercially available NiTi archwires. Materials and methods: Three different brands of NiTi archwires, NiTi OR (Ormco), NiTi GH (G&amp;H) and NiTi H (Highland), with a cross sectional area of 0.016 x 0.022 inch2 were analysed for transformation temperature range (TTR) by using differential scanning calorimeter and load-deflection characteristics using a three-point bending test at temperatures of 10, 20, 30, 37, 40, 50 and 60 °C. Statistical Analysis: Descriptive analysis was used to calculate each variable and Kruskal Wallis test was performed to assess the difference in measurements among the three NiTi wires. P&lt;0.05 was considered as statistical significant. Results: TTR showed austenitic temperature finish (Af) at 24.45 °C for NiTi OR, 27.55 °C for NiTi GH and 51.5 °C for NiTi H. The highest deactivation force was found in NiTi H followed by NiTi OR and NiTi GH at the temperatures below and higher than 37°C. There were siginificant differences (p&lt;0.05) in the deactivation force of NiTi OR - NiTi H and NiTi GH - NiTi H at 10 °C and 20 oC, and NiTi GH – NiTi H and NiTi GH – NiTi OR at 30 °C and 37 °C. However, no significant difference was found among all NiTi wires at 40, 50 and 60 oC, except NiTi GH – NiTi H at 60 oC. A close relationship was found between temperature and unloading curves (deactivaton force); increase in the temperature led to an increase in the plateau of delivery deactivation force and decrease in temperature led to a decrease in the plateau of delivery deactivation force. Conclusion: The TTRs of commercial NiTi archwires are variable, expecially the austenitic finish temperature. The deactivation force increases in higher temperature and decreases in lower temperature.