O presente estudo avaliou a influência do hipoclorito de sódio a 1% e 2,5% na qualidade do acabamento superficial e na resistência à corrosão de duas limas endodônticas: Race® e Hyflex® através de ensaio eletroquímico de polarização potenciodinâmica cíclica (EPPC) e imagens obtidas por microscopia eletrônica de varredura (MEV). Para o EPPC foram utilizados vinte limas de cada marca comercial (#25, conicidade 0.04 e 25 mm de comprimento). Dez dos vinte instrumentos foram individualmente fixados pelo cabo a uma ponta de fio de cobre 0,12 mm de 20 cm de comprimento e posicionado no interior de uma célula eletroquímica com 500 mL de solução de hipoclorito de sódio (NaClO) 1% (Fórmula&Ação) à temperatura ambiente controlada em 23 ºC (±2) até cobrir a parte ativa do instrumento. Os registros foram feitos com o potenciostato da PAR modelo 273A. O ensaio foi repetido nos mesmos padrões para as outras dez limas da mesma marca comercial com o NaClO 2,5%. Além do EPPC, as limas foram submetidas a exames e análises em MEV antes e depois do teste de corrosão para a obtenção de fotomicrografias dos 3 (três) mm finais de cada lima com o intuito de estabelecer parâmetros para a avaliação final. Das fotomicrografias obtidas, 72 foram escolhidas, inseridas no Power Point sem legenda original de identificação, numeradas aleatoriamente para avaliação e projetadas num monitor para 06 avaliadores orientados e calibrados. Os dados obtidos foram tabulados e submetidos aos testes estatísticos pertinentes (Friedman, Wilcoxon e Mann-Whitney). A lima Hyflex® apresentou uma quantidade maior de alterações superficiais (ranhuras, manchas e materiais depositados) antes e depois do ensaio sendo mais suscetível à corrosão. Race® apresentou uma superfície mais polida e regular. Em relação a concentração do NaClO, percebeu-se que os defeitos presentes se tornavam mais evidentes para a concentração maior (2,5%). Nas duas concentrações os itens que apresentaram diferença significativa foram bordas, ranhuras, microcavidades, rebarbas e material depositado. Concluiuse que o acabamento superficial e a concentração da solução de NaClO influenciam a resistência à corrosão dos instrumentos de NiTi. A lima Race® apresentou menor corrosão e melhor acabamento de superfície do que a lima Hyflex® nas condições experimentais testadas. / The present paper evaluated the influence of 1% and 2.5% sodium hypochlorite in the quality of the surface finishing and resistance to corrosion of two endodontic files: Race® and Hyflex® by electrochemical test of cyclic power dynamics polarization (EPPC) and images obtained by scanning electronic microscopy (SEM). Twenty files of each commercial brand (#25, 0.04 taper and 25 mm length) were used in EPPC. Ten from the twenty instruments were individually fixed by the handle to a copper wire tip (0.12 mm diameter and 20 cm length) and placed in the interior of an electrochemical cell with 500 mL sodium hypochlorite solution (NaCIO) 1% (Fórmula e Ação) at the environment temperature controlled in 23ºC (±2) until covering the active part of the instrument. Recordings were made with a PAR potentiostat model 273A. The test was repeated in the same pattern to the other ten files from the same commercial brand with NaClO 2.5%. Besides EPPC, the files were submitted to the scanning electronic microscopy (SEM) test before and after the corrosion test to obtain photomicrographs of the final 3 mm of each file in order to establish the parameters for final evaluation. From the obtained photomicrographs, 72 were chosen and inserted in the Power Point without the original identification legend, randomly numbered for evaluation and projected on the screen to the 06 guided and calibrated evaluators. Data obtained were tabbed and submitted to the relevant statistical tests (Friedman, Wilcoxon and Mann-Whitney). The Hyflex® file showed a higher amount of surface alterations (grooves, stains and deposited materials) before and after the test, being more susceptible to corrosion. Race® showed a more polished and regular surface. As to the NaClO concentration, it was seen that the present defects became more evident in the higher concentration (2.5%). In the two concentrations, the items that presented significant differences were edges, grooves, micro cavities, margins and deposited materials. Conclusion was that surface finishing and the concentration of the NaClO solution influenced the resistance to corrosion of NiTi instruments. The Race® file showed the least corrosion and the best surface finishing compared to the Hyflex® file under the tested experimental conditions.

Abstract Whenever a foreign material is implanted into a human body an implant–tissue interface area forms between them. In this microenvironment, interactions take place between the implant and the surrounding tissue. The implantation of a biomaterial into tissue results in injury and initiation of the inflammatory response. This host response to biomaterials is an unavoidable series of events that occur when tissue homeostasis is disturbed by the implantation process. In bone tissue, biocompatible implants must initially be capable of strong bone implant contact and subsequently, allow the normal bone remodeling cycle around the implant. NiTi is a metal alloy composed of approximately a 50:50 ratio of nickel and titanium. It possesses shape memory and superelasticity properties, which make it an interesting biomaterial. NiTi has two phases: austenite and martensite. A decrease in temperature or applied stress induce the austenite-to-martensite transformation. Heating or removing the stress restores the parent austenite phase. The alloy in its martensite structure can be reshaped and strained several times more than a conventional metal alloy without irreversible deformation of the material. The alloy returns to its original shape as it changes from martensite-to-austenite. This transformation is seen as the macroscopic shape memory effect. This study further investigated the biocompatibility of NiTi, especially the bone cell response to both austenite and martensite. Different surface treatments were investigated in order to improve and possibly even control NiTi's bioactivity as a bone implant material. Osteoclasts grew and attached well on the austenite NiTi phase, but the results indicated that the biocompatibility of martensite NiTi was compromised. Oxidation of the NiTi surface improved osteoblast attachment and viability. This was due to the formation of a TiO2 surface layer of moderate thickness. Coating the NiTi surface with the extracellular matrix protein fibronectin was shown to enhance osteoblast proliferation and increase the number of cells in the G1 cell cycle stage. Austenite was more prone to show these effects than martensite. A sol-gel derived titania-silica surface treatment was observed to increase the bone implant contact of functional NiTi intramedullary nails. The surface treatment was most effective with the constant bending load provided by the NiTi nail.

Magister Chirurgiae Dentium (MChD)

Actuator applications of shape memory alloys have typically been limited by their phase transformation temperatures to around 100 degrees C. However, recently with a focus on aerospace and turbomachinery applications there have been successful efforts to increase the phase transformation temperatures. Several of these alloy development efforts have involved ternary and quaternary elemental additions (e.g., Pt, Pd, etc.) to binary NiTi alloys. Experimentally assessing the effects of varying composition and thermo-mechanical processing parameters can be cost intensive, especially when expensive, high-purity elemental additions are involved. Thus, in order to save on development costs there is value in establishing a methodology that facilitates the fabrication, processing and testing of smaller specimens, rather than larger specimens from commercial billets. With the objective of establishing such a methodology, this work compares thermo-mechanical test results from bulk dog-bone tensile Ni29.5Ti50.5Pd20 samples (7.62 mm diameter) with that of thin wires (100 μm-150 µm diameter) extracted from comparable, untested bulk samples by wire electrical-discharge machining (EDM). The wires were subsequently electropolished to different cross-sections, characterized with Scanning Electron Microscopy, Transmission Electron Microscopy and Energy Dispersive X-Ray Spectroscopy to verify the removal of the heat affected zone following EDM and subjected to Laser Scanning Confocal Microscopy to accurately determine their cross-sections before thermo-mechanical testing. Stress-strain and load-bias experiments were then performed on these wires using a dynamic mechanical analyzer and compared with results established in iv previous studies for comparable bulk tensile specimens. On comparing the results from a bulk tensile sample with that of the micron-scale wires, the overall thermomechanical trends were accurately captured by the micron-scale wires for both the constrained recovery and monotonic tensile tests. Specifically, there was good agreement between the stress-strain response in both the martensitic and austenitic phases, the transformation strains at lower stresses in constrained recovery, and the transformation temperatures at higher stresses in constrained recovery. This work thus validated that carefully prepared micron-diameter samples can be used to obtain representative bulk thermo-mechanical properties, and is useful for fabricating and optimizing composition and thermomechanical processing parameters in prototype button melts prior to commercial production. This work additionally assesses potential applications of high temperature shape memory alloy actuator seals in turbomachinery. A concept for a shape memory alloy turbine labyrinth seal is also presented. Funding support from NASA’s Fundamental Aeronautics Program, Supersonics Project (NNX08AB51A) and Siemens Energy is acknowledged.

A heightened interest in intelligent material systems has occurred in recent years due to their remarkable adaptive abilities. Intelligent materials systems, which contain sensors and actuators coupled by means of active control, frequently utilize composite materials as the skeletal structure. In order for composite materials to be utilized in intelligent material systems to their utmost capability, many material properties, including the interfacial shear strength between the embedded sensor or actuator and the matrix must be thoroughly understood.. Investigations were performed in order to examine the effects of different variables on the interfacial characteristics between a nitinol fiber and a composite matrix. First, rough, clean fiber surfaces were found to provide the best adhesion to the matrix due to the mechanical interaction of the matrix with the rough surface finish. Second, it was determined that the interfacial shear strength is not dependent upon embedded fiber length. Third, a very small diameter fiber will break before pulling out of the matrix, but overall, large fibers have a greater interfacial strength. Fourth, it was found that the initial prestrain on the fiber during processing had no effect on the interfacial shear strength of the fiber to the matrix. Fifth, it was determined that fatigue does not degrade the shear strength of any of the different initial pres trains. Finally, it was found that a coating that does not adhere well to the fiber neither macroscopically degrades nor enhances interfacial strength. / Master of Science

NiTiCu is a shape memory alloy that regains its original shape after large amount of shape changing deformation when heated above a critical temperature called reverse martensitic trans-formation temperature( Af). When external load is applied on the sample in twinned martensite phase at low temperature, it deforms by detwinning, accommodating large amount of strains. When it is heated above Af, the shape recovers by transformation of the martensite to austenite phase. However, the amount of shape recovery degrades over time due to internal factors such as precipitates, residual strains and thermal history as well as external factors such as stresses. Severe localized stresses induced by contacts result in plastic deformation that affect the reverse martensitic transformation and hence the shape recovery. In this work, we study how varying levels of contact stresses induced in NiTiCu thin film affect its shape recovery. NiTiCu thin films of six different compositions are deposited on Si(100) wafer by co-sputtering from elemental targets. After deposition, the films are annealed at 500 C for 4 h to make them crystalline. The composition of the films varied linearly with applied power to the targets. Uniformity in composition over a 4 inch substrate area is achieved by substrate rotation. All the films show ne grain microstructure after annealing. The subsurface of the Ni-rich films is columnar. Ni-rich films have annealing cracks and the crack width increases with Ni composition in the films. The roughness of as-deposited films is found to be more for Ni-rich films compared to Ti-rich films. The roughness of the Ni-rich and Ti-rich films increased after annealing. From the X-ray diffraction studies, it was observed that the films are nanocrystalline. Indentation is carried out using a Berkovich diamond indenter with spherical apex, at nine different locations with loads ranging from 0.25 mN to 25 mN. A predefined array is chosen for indentation such that the larger indents act as a guide to precisely locate minute indents generated at lower loads, with residual depth as small as 10 nm, for imaging in high-resolution microscopes like Scanning Electron Microscope as well as in Atomic Force Microscope . In Ti60 (a Ti-rich) lm, the residual indents generated at loads greater than 10 mN show radial cracks originating at corners. Average crack length increases with the maximum load used for generating the indent. Sequential sectioning of Ti48 (a Ni-rich) lm using Focused Ion Beam microscope, revealed that the cracks originate at the lm-substrate interface and reach the surface. In Ti48 lm, residual indents do not show any indentation cracks. The indentation stresses are accommodated by breaking of the columnar structure and the voids between them. Delamination of the film from the substrate is observed on either sides of the indent in both the Ti60 and Ti48 films. The hardness of the films is high at low loads and decrease as the load increases. The deformation by indentation at lower loads is mainly due to detwinning as only the apex of the indenter, which is nearly spherical, is in contact with the sample and the resulting stresses are low. As the load increases, the deformation starts getting accommodated through dislocations along with detwinning as the stress beneath the indenter increases. Spherical cavity model extended to SMA shows that inner hemisphere near the tip contains dislocations where stresses are very high, surrounded by detwinned region with stresses that are relatively low. When the sample is heated above reverse martensitic transformation temperature to induce shape recovery in the indents, only the detwinned region recovers to the original shape. Recovery ratio, quantification of shape recovery, is calculated from the depth of the indents before and after heating. Recovery ratio in Ti60 films is found to be large at low loads and decreases with increase in load. The decrease in shape recovery in Ti60 is attributed to the increase in the amount of plastic deformation at the expense of detwinning. Three-dimensional mapping of the surfaces shows that the recovery ratio is high at the apex of the indent at the maximum depth and reduces towards the edges of the indent. There is no evident recovery in Ti48 films. The shape recovery of SMAs can be achieved by Joule heating. When electric current is passed through the material, it heats up by Joule heating because of the intrinsic resistivity. The resistivity and hence the resistance would get effected by the dislocation based plastic deformation induced by the contact. This might result in shape recovery through resistive heating. Towards understanding this, the effect of contact stresses on electrical contact resistance is studied. Experimental setup is designed, developed and calibrated for studying the variation of electrical contact resistance of the NiTiCu thin films as a function of load. Electrical contact resistance is found to decrease with increase in applied load. Contact stresses in sub-micron NiTiCu thin films are simulated by carrying out nanoindentation at different loads. The recovery ratio is high when the stresses induced by the contact is less, at lower loads. The shape recovery ratio is reduced when the induced contact stresses in-creases. There is no shape recovery at the sharp edges of the indentation where contact stresses are very high. Hence, by carefully designing the features to reduce the stress concentrations, the performance of the device can be improved.

No description available.

O objetivo do presente trabalho foi avaliar, ex vivo, a eficiência dos sistemas rotatórios ProTaper Universal Retreatment Files e Mani Retreatment Files na desobturação de raízes mesiais de molares inferiores, obturadas pela técnica de ondas contínuas de condensação, determinando-se o volume percentual de material obturador remanescente no sistema de canais radiculares, utilizando-se a microtomografia de raios-X. Um total de 18 molares inferiores portadores de dois canais radiculares mesiais que possuíam curvatura entre 25° e 35° e raio de curvatura menor que 10mm, foram preparados até o instrumento 35/.04 Mtwo. Em seguida foram obturados com guta percha e cimento endodôntico AH-Plus pela técnica de ondas contínuas de condensação e mantidos em estufa a 37°C por sete dias. Imagens microtomográficas dos dentes obturados foram realizadas utilizando o microtomógrafo SkyScan 1172 e parâmetros de 100kV e 100A, gerando imagens de tamanho de 11,88m. Em seguida, os dentes foram divididos aleatoriamente em dois grupos experimentais de acordo com o tipo de instrumento de retratamento avaliado, ProTaper Retreatment Universal Files (PR) e Mani Retreatment Files (MR). De início, a desobturação dos canais radiculares foi realizada com a utilização de brocas de largo associadas a uma gota de solvente para que então os instrumentos de cada sistema fossem utilizados até que a desobturação até o nível do comprimento real de trabalho, fosse alcançada. Após novo escaneamento, as imagens foram reconstruídas utilizando-se o software NRecon e analisadas pelo software CTAn, permitindo a obtenção dos dados quantitativos das amostras. Empregou-se o teste t de Student para determinar a ocorrência de diferença estatística entre os grupos experimentais (p < 0.05). Os volumes, inicial e final médios (mm3) de material obturador remanescente foram de 17,72 e 2,12 para o grupo PR e de 16,61 e 3,71 para o grupo MR, respectivamente. O grupo PR apresentou o menor volume percentual médio de material obturador remanescente (12,76 ± 6,93%), quando comparado ao MR (23,54 ± 10,60%), observando-se diferença estatisticamente significante. Nenhum dos dois sistemas testados, foi capaz de remover completamente o material obturador do interior dos canais radiculares. O sistema rotatório ProTaper Universal Retreatment Files mostrou-se mais eficiente que o sistema Mani Retreatment Files na desobturação de canais mesiais de molares inferiores, obturados pela técnica de ondas contínuas de condensação. As características dos sistemas rotatórios de retratamento podem interferir no volume percentual de material obturador remanescente e conseqüentemente na sua eficiência de desobturação. / The objective of this study was to evaluate, ex vivo, the efficiency of rotary ProTaper Universal Retreatment Files and Mani Retreatment Files in removal procedure of the mesial roots of mandibular molars, obturated by the technique of continuous wave of condensation, determining the volume percentage of material remaining filling in root canals, using the X-Ray micro-CT. A total of 18 mandibular molars with two root canals which had mesial curvature between 25° and 35° and the radius of curvature smaller than 10mm, were prepared by the instrument Mtwo size/taper 35/.04. They were then filled with gutta-percha and sealer Ah-Plus by the technique of continuous wave of condensation and maintained at 37°C for seven days. Micro-CT images of the teeth was carried out using the device SkyScan 1172 on 100kV and 100A as parameters, generating images size 11.88 micrometers. Then the teeth were randomly divided into two groups according to the type of instrument retreatment evaluated ProTaper Universal Retreatment Files (PR) and Mani Retreatment Files (MR). Initially, the procedure for remove the root canal obturation was performed with Largo burs associated with a drop of solvent so that the instrument of each system could be used until the complete removal procedure was reached. After re-scanning, the images were reconstructed with the software used NRecon and analyzed by CTAn software, allowing to obtain quantitative data of the samples. We used the Student t test to determine the occurrence of significant differences between experimental groups (p <0.05). The mean initial and final volumes (mm3) of the remaining filling material were 17.72 and 2.12 for the P group and 16.61 to 3.71 for group MR, respectively. The PR group had the lowest average volume percentage of remaining filling material (12.76 ± 6.93%) when compared to MR (23.54 ± 10.60%), with a statistically significant difference. Neither of the systems tested were able to completely remove the filling material inside the root canals. The rotary system ProTaper Universal Retreatment Files was more efficient than the system Mani Retreatment Files in removal procedure of mesial canals, filled with the technique of continuous wave of condensation. The characteristics of rotary retreatment system may interfere with the volume percentage of remaining filling material and consequently the efficiency of removal procedure.

Os efeitos mecânicos exercidos sobre os dentes pela deformação do fio de níqueltitânio dependem de sua rigidez e das características dos braquetes. Os fatores associados ao braquete são a largura, que influencia o comprimento de fio interbraquetes e o coeficiente de atrito. O objetivo desta pesquisa foi comparar a influência dos braquetes autoligáveis passivos Damon, Easy Clip e Smart Clip, sobre as forças, momentos e binding produzidos pela deformação do fio Contour NiTi .014. Metodologia: um dispositivo de simulação clínica com 3 braquetes .022x.028 de aço, correspondentes ao canino e pré-molares, foi acoplado à maquina de tração universal Instron para registro das forças e ao dinamômetro Lutron para registro dos momentos na unidade de ancoragem. A deformação de primeira ordem do fio superelástico Contour NiTi .014 foi propiciada pelo deslocamento do braquete do primeiro pré-molar fixo à máquina Instron. Foi utilizada célula de carga de 500 Newtons e velocidade de 0,05mm/segundo durante a deformação. As forças e momentos foram registrados até deslocamento máximo de 4,5 mm e durante retorno à zero. Foram realizadas dez repetições para cada modelo de braquete. O registro do binding foi obtido em teste separado por meio da tração contínua do fio Contour NiTi durante deformação de primeira ordem até 4,8 mm e retorno até zero. Os efeitos mecânicos foram comparados com deformação de 4 mm. Resultados: na unidade de movimentação as forças de ativação apresentaram diferenças significantes (Damon 224, Easy Clip 241 e Smart Clip 299 cN) enquanto as forças de desativação foram menores no Damon (62 Cn) e semelhantes entre os braquetes Easy Clip (71 cN) e Smart Clip (76 Cn). Na unidade de ancoragem os momentos de ativação apresentaram diferenças significantes (Damon 314, Easy Clip 356 e Smart Clip 438 cN/mm) enquanto os momentos de desativação foram semelhantes entre os braquetes Damon e Easy Clip (239/242 cN/mm) e significativamente maiores no Smart Clip (317 cN/mm). Os valores de binding na ativação e desativação foram semelhantes. O percentual de histerese das forças foi 70% e dos momentos 28%. Conclusões: 1) as forças de desativação produzidas pelo fio Contour NiTi .014 foram semelhantes, o que indicou equivalência mecânica entre os braquetes Damon, Easy Clip e Smart Clip na unidade de movimentação; 2) os momentos de desativação produzidos pelo fio Contour NiTi .014 foram semelhantes entre os braquetes Damon e Easy Clip, e maiores no Smart Clip, o que indicou equivalência mecânica apenas entre os braquetes Damon e Easy Clip na unidade de ancoragem ; 3) a medição das forças de atrito por meio da tração contínua do fio ortodôntico não se mostrou adequada para medir o binding associado à força de desativação; 4) a histerese acentuada observada no início da desativação das forças foi influenciada pela superelasticidade do fio e pelo binding na unidade de ancoragem. / Bracket characteristics and wire stiffness dictate the mechanical effects that nickel titanium wire deformation will cause upon teeth. The main variables associated to bracket characteristics include bracket length (that influence interbracket distance), and coefficient of friction. The purpose of this research was to compare how self ligated brackets such as Damon, Easy Clip and Smart Clip influence moments, forces, and binding produced by the deformation of a .014 Niti Contour wire. Methods: a clinical simulation device with three .022x.028 stainless steel brackets representing canine and bicuspids was attached to an Instron universal traction machine in order to register the forces, and to a Lutron dynamometer to register the moments produced on the anchor unit. The displacement of the first bicuspid fixed on the Instron machine produced a first order deformation on the superelastic .014 Niti Contour wire. A load cell of 500 Newtons under a speed of 0,05mm/second was used during the deformation. Forces and moments were registered up to 4,5mm maximum displacement and during the return to zero. For each bracket model ten repetitions were performed. Binding registration was obtained on a separate test, by continuous traction of the Contour Niti wire during first order deformation up to 4,8mm and back to zero. The mechanical effects were compared with a 4mm deformation. Results: on the moving unit, the activation forces presented significant differences (Damon 224, Easy Clip 241 and Smart Clip 299cN), while the deactivation forces were smaller on Damon (62cN) and similar on the Easy Clip (71cN) and Smart Clip (76 cN). The activation moments on the anchor unit presented significant differences (Damon 314, Easy Clip 356 and Smart Clip 438 cN/mm), while the deactivation moments were similar in the Damon (239 cN/mm) and Easy Clip (242 cN/mm) brackets, and significantly larger on Smart Clip (317cN/mm). Activation and deactivation binding values were similar. The hysteresis percentage on forces was 70% and on moments 28%. Conclusions: 1) the forces produced by the .014 Contour Niti at the movement unit are similar among the Damon, Easy Clip and Smart Clip brackets; 2) the moments produced by the .014 Contour Niti at the anchor unit are similar between Damon and Easy Clip brackets, while the Smart Clip produces larger moments; 3) the method of measuring friction forces by continuous traction of the orthodontic wire is not adequate to measure the binding associated with deactivation forces; 4) hysteresis observed at the beginning of deactivation is influenced by binding.

Objetivos: O objetivo desta pesquisa foi comparar a resistência ao deslocamento de fios de níquel e titânio superelásticos termoativados sobrepostos, em braquetes ortodônticos metálicos autoligáveis passivos. Material e Métodos: Foram utilizadas três espessuras de fios de níquel e titânio superelásticos termoativados (NiTi-TA): 0,014 sobreposto ao 0,016 e 0,020 (FlexyNiTi Thermal - Orthometric, Marília, SP, BR), associados a dois tipos de braquetes metálicos autoligáveis passivos: SmartClip SL3® (3M Unitek, Monrovia, CA, EUA) e OrthoClip SLB® (Orthometric, Marília, SP, BR). Um dispositivo que continha 5 braquetes de cada tipo (do incisivo central superior direito ao 2º pré-molar superior direito) foi desenvolvido para realização dos testes. O braquete do canino foi colado em uma barra de aço inoxidável móvel que permitia alterar sua posição vertical, enquanto os demais braquetes foram colados a uma barra fixa de acrílico. As forças obtidas por meio do deslocamento vertical do braquete do canino de 0mm para 1,5mm, 3,0 mm, 4,5mm e 6,0 mm foram registradas. O ambiente de teste foi seco com temperatura controlada de 36,5º C ± 1º C. Um total de 160 testes foi realizado na máquina de ensaios universal Instron. Os testes estatísticos de Shapiro-Wilk, teste t de Student não pareado e ANOVA com testes post-hoc de Tukey foram aplicados aos dados (p<0,05). Resultados: A distribuição normal da amostra foi confirmada, e os testes paramétricos demonstraram que houve diferenças estatisticamente significativas no braquete SmartClip SL3® quando associados aos fios de NiTi-TA 0,020 e 0,014 sobreposto ao 0,016 nas alturas de 1,5mm (p=0,003) e 6mm (p0,0001). Porém, não foram encontradas diferenças estatísticas nas alturas de 3mm (p=0,76) e 4,5mm (p=0,09). No braquete OrthoClip SLB® houve diferenças estatisticamente significativas entre os fios de NiTi-TA 0,020 e 0,014 sobreposto ao 0,016 em todas as alturas avaliadas (p0,0001). Na comparação entre os braquetes, quando associados ao fio 0,020 de NiTi-TA houve diferenças estatisticamente significativas na altura de 1,5mm; 3mm e 6mm (p0,0001). No entanto, na altura de 4,5mm as diferenças não foram significativas estatisticamente (p=0,32). Quando associados aos fios de NiTi-TA 0,014 e 0,016 sobrepostos, as diferenças em todas as alturas avaliadas foram significativas estatisticamente (1,5mm - p=0,0006; nas demais alturas p0,0001). Conclusão: Nos braquetes SmartClip SL3®, em desnivelamentos de 1,5mm, os fios de NiTi-TA 0,014 e 0,016 sobrepostos apresentaram menor resistência ao deslocamento, enquanto que na altura de 6mm a menor resistência foi obtida com o fio de NiTi-TA 0,020. Nas demais alturas não houve diferenças estatísticas entre os fios. Para os braquetes OrthoClip SLB®, os fios de NiTi-TA 0,014 e 0,016 sobrepostos apresentaram menor resistência ao deslocamento em todas as alturas avaliadas. Na comparação entre os dois tipos de braquetes, associados ao fio de NiTi-TA 0,020 na altura de 1,5mm, o braquete OrthoClip SLB® apresentou menor resistência ao deslocamento, ao passo que nas alturas de 3mm e 6mm foi o braquete SmartClip SL3®. Na altura de 4,5mm não foram encontradas diferenças estatisticamente significativas entre os dois braquetes avaliados. / Objective: The objective of this research was to compare the displacement resistance of overlapped heat-activated superelastic nickel titanium wires, in passive self-ligating metallic brackets. Material and Methods: Three thicknesses of heat-activated superelastic nickel titanium wires (NiTi-TA) were used: 0.014 overlapped with 0.016 and 0.020 (FlexyNiTi Thermal - Orthometric, Marília, SP, BR), associated with two types of passive self-ligating metallic brackets: SmartClip SL3® (3M Unitek, Monrovia, CA, EUA) and OrthoClip SLB® (Orthometric, Marília, SP, BR). A device with 5 brackets of each type (from right central incisor to the second maxillary premolar) was developed for this research. The canine bracket was attached to a sliding stainless steel bar which allowed the alteration of its vertical position, while the remaining brackets were attached to a fixed acrylic bar. The forces generated by means of the canine bracket vertical displacement from 0mm to 1.5mm; 3.0mm; 4.5mm and 6.0mm were recorded. The test environment was dry with a controlled temperature of 36.5º C ± 1º C. A total of 160 tests were carried out in the Instron Testing Machine. The Shapiro-Wilk test, non-paired Student t-test and ANOVA with Tukey post hoc test were applied to the data (p<0.05). Results: The normal distribution was confirmed, and the parametric tests showed that there were statistically significant differences in the SmartClip SL3® when associated with the NiTi-TA 0.020 and 0.014 wires overlapped to the 0.016 wire in the height of 1.5mm (p=0.003) and 6mm (p<0.0001). However, statistically significant differences were not found in the heights of 3mm (p=0.76) and 4.5mm (p=0.09). For the OrthoClip SLB® brackets, there were statistically significant differences between the NiTi-TA 0.020 and 0.014 wires overlapped with the 0.016 wire in all the heights assessed (p<0.0001). In the comparison between the brackets when associated with the NiTi-TA 0.020 wire, there were statistically significant differences in the heights of 1.5mm, 3mm and 6mm (p<0.0001). However, in the height of 4.5mm the differences were not statistically significant (p=0.32). When associated with the overlapped NiTi-TA 0.014 and 0.016 wires, the differences in all assessed heights were statistically significant (1.5mm - p=0.0006; other height - p0.0001). Conclusion: For the SmartClip SL3® brackets, with 1.5mm of displacement, the overlapped NiTi-TA 0.014 and 0.016 wires showed less displacement resistance, while in the height of 6mm the least displacement resistance was found with the NiTi-TA 0.020. In the remaining heights, there were no statistically significant differences between the wires. For the OrthoClip SLB® brackets, the overlapped NiTi-TA 0.014 and 0.016 wires showed the least displacement resistance in all the assessed heights. In the comparison between the two types of brackets, associated with the NiTi-TA 0.020 wire, for the height of 1.5mm, the OrthoClip SLB® bracket showed less displacement resistance, while for the heights of 3mm and 6mm the SmartClip SL3® brackets showed less displacement resistance. For the height of 4.5mm there were no statistically significant differences found between the assessed brackets.