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1.
J Int Med Res ; 52(3): 3000605241240946, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38534086

RESUMO

BACKGROUND: To compare the biomechanical stability of a novel, C-shaped nickel-titanium shape memory alloy (SMA) implant (C-clip) with traditional cerclage wiring in the fixation of a Vancouver B1 (VB1) periprosthetic femoral fracture (PFF). METHODS: In total, 18 synthetic femoral fracture models were constructed to obtain unstable VB1 fracture with an oblique fracture line 8 cm below the lesser trochanter. For each model, the distal portion was repaired using a 10-hole locking plate and four distal bi-cortical screws. The proximal portion was repaired using either three, threaded cerclage wirings or three, novel C-shaped implants. Specimens underwent biomechanical testing using axial compression, torsional and four-point bending tests. Each test was performed on three specimens. RESULTS: The C-clip was statistically significantly stronger (i.e., stiffer) than cerclage wiring in the three biomechanical tests. For axial compression, medians (ranges) were 39 (39-41) and 35 (35-35) N/mm, for the C-clip and cerclage wiring, respectively. For torsion, medians (ranges) were, 0.44 (0.44-0.45) and 0.30 (0.30-0.33) N/mm for the C-clip and cerclage wiring, respectively. For the four-point bending test, medians (ranges) were 39 (39-41) and 28 (28-31) N/mm; for the C-clip and cerclage wiring, respectively. CONCLUSION: Results from this small study show that the novel, C-shaped SMA appears to be biomechanically superior to traditional cerclage wiring in terms of stiffness, axial compression, torsion and four-point bending, and may be a valuable alternative in the repair of VB1 PFF. Further research is necessary to support these results.


Assuntos
Fraturas do Fêmur , Fraturas Periprotéticas , Humanos , Ligas de Memória da Forma , Fraturas do Fêmur/cirurgia , Fêmur/cirurgia , Fraturas Periprotéticas/cirurgia , Fixação Interna de Fraturas/métodos , Placas Ósseas , Fenômenos Biomecânicos
2.
Biomater Adv ; 158: 213774, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38237321

RESUMO

Ni-free Ti-based Shape Memory Alloys composed of non-toxic elements have been studied as promising candidates for biomedical applications. However, high tool wear makes them complex to manufacture with conventional techniques. In this way, Additive Manufacturing technologies allow to fabricate complex three-dimensional structures overcoming their poor workability. Control of composition, porosity, microstructure, texture and processing are the key challenges for developing Ni-free Ti-based Shape Memory Alloys. This article reviews various studies conducted on the Additive Manufacturing of Ni-free Ti-based shape memory alloys, including their processing, microstructures and properties.


Assuntos
Níquel , Ligas de Memória da Forma , Titânio , Comércio , Porosidade
4.
Bioinspir Biomim ; 19(1)2023 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-38016443

RESUMO

Operating outside the spacecraft via remotely controlled structures is an important opportunity in different space applications. The research in this area is focused on designing robots that are sufficiently flexible to allow inspection in locations where access is difficult or impossible for astronauts, while minimizing weight and bulk. The purpose of the research is to design a borescope for space applications with no hinges or other mechanisms, exploiting biomimetic design concepts. This is pursued by giving to the borescope a backbone exoskeleton provided by a continuous structure made of fibre reinforced composite material and using NiTi wires as tendons, taking advantage of their low weight and dimensions, which allow them to be embedded between the composite layers during the lamination process. After a study of the state of the art of flexible structures, concentrated in the medical and robotic fields, the research work unfolded in two phases. In the first design phase, several composite layup solutions were considered and analysed using finite element models, leading to the definition of the borescope geometrical parameters and to an initial estimate of the displacements that can be achieved. In the second experimental phase, seven prototypes were produced and tested, with one or more wires, to validate the design and to search for a configuration that can be actuated in different directions. The borescope prototypes resulted flexible enough to achieve an extended degree of bending and at the same time sufficiently rigid to allow complete rearm of the NiTi wires. The numerical and experimental study led to the definition of the design parameters, the number of wires, and the manufacturing technique to integrate NiTi actuators.


Assuntos
Robótica , Ligas de Memória da Forma , Ligas/química , Robótica/métodos , Biomimética
5.
J Mech Behav Biomed Mater ; 147: 106122, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37778169

RESUMO

In this paper we propose a methodology for a fast numerical determination of low cycle fatigue lifetime of superelastic shape memory alloy structures. This method is based on the observation that generally, in low cycle fatigue, shape memory alloy (SMA) structures are subject to loadings that lead to a confined non-linear behaviour at stress concentration points, such as notches. Numerical fatigue lifetime prediction requires the computation of the mechanical state at critical points. However, classical computational methods, like the non-linear finite element method, lead to a prohibitive computation time in a non-linear cyclic framework. To overcome this issue, we propose to use fast prediction methods, based on localization laws. Following the determination of the stabilized behaviour, an energetic fatigue criterion is applied. The numerical fatigue life prediction model is validated experimentally on SMA endodontic instruments.


Assuntos
Ligas de Memória da Forma , Estresse Mecânico
6.
Macromol Rapid Commun ; 44(22): e2300319, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37657776

RESUMO

Future wearable electronic gadgets offer great potential for using stretchable, strain-sensitive materials to instantly detect human motion and record physiological information. This paper presens a strain/compress sensor made from a Shape memory alloy (SMA) coil spring covered with silver pastes and the composite of carbon nanotubes and Shape memory polymer (SMP). The combination of the shape memory materials that expand or contract automatically by temperature improved the mechanics of the sensor. First, the proposed sensors showed an excellent ability to broad-range strain of 250% and compress of 50% with a relative inductance (∆L/L0 ) range from -35% to 50%, respectively. Durability during 1000 loading and unloading cycles at 200% strain is included. Secondly, by monitoring changes in resistance, inductance, and time, it is determined how many silver layers appropriate for transformation should be in order to improve the recovery time of the SMA coil spring. Moreover, the presence of CNTs in the composite-covered outer of sensors helps to reduce the influence of the relation between resistance and temperature in the range from 30 °C to 110 °C. Finally, a device is suggested for monitoring arm and triceps brachii muscle movements based on the stretchable area as a key parameter.


Assuntos
Nanotubos de Carbono , Materiais Inteligentes , Dispositivos Eletrônicos Vestíveis , Humanos , Ligas de Memória da Forma , Prata
7.
Bioinspir Biomim ; 18(6)2023 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-37726011

RESUMO

Active needles demonstrate improved accuracy and tip deflection compared to their passive needle counterparts, a crucial advantage in percutaneous procedures. However, the ability of these needles to effectively navigate through tissues is governed by needle-tissue interaction, which depends on the tip shape, the cannula surface geometry, and the needle insertion method. In this research, we evaluated the effect of cannula surface modifications and the application of a vibrational insertion technique on the performance of shape memory alloy (SMA)-actuated active needles. These features were inspired by the mosquito proboscis' unique design and skin-piercing technique that decreased the needle tissue interaction force, thus enhancing tip deflection and steering accuracy. The bioinspired features, i.e., mosquito-inspired cannula design and vibrational insertion method, in an active needle reduced the insertion force by 26.24% and increased the tip deflection by 37.11% in prostate-mimicking gel. In addition, trajectory tracking error was reduced by 48%, and control effort was reduced by 23.25%, pointing towards improved needle placement accuracy. The research highlights the promising potential of bioinspired SMA-actuated active needles. Better tracking control and increased tip deflection are anticipated, potentially leading to improved patient outcomes and minimized risk of complications during percutaneous procedures.


Assuntos
Culicidae , Gafanhotos , Animais , Masculino , Humanos , Ligas de Memória da Forma , Agulhas , Pelve
8.
Am J Vet Res ; 84(11)2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37591491

RESUMO

OBJECTIVE: To investigate the feasibility of using shape memory alloy (SMA) implants for atlantoaxial joint stabilization using a rabbit model as a substitute for canines. ANIMALS: 20 rabbit cadavers. METHODS: We prepared rabbit cadavers from the middle of the skull to the third cervical vertebra. The vertebral body and canal sizes of the atlas and axis were compared using CT data from rabbits, normal dogs, and dogs with atlantoaxial instability (AAI) to assess the feasibility of using rabbits as substitutes for toy-breed dogs. The shape memory alloy (SMA) implants were designed to stabilize the atlantoaxial joint without compromising the spinal canal passage for safety and were classified into SMA-1 and SMA-2 based on their design. To evaluate the strength, the ventrodorsal force was measured with atlantoaxial ligaments intact, after removing the ligaments, and after applying conventional wire or SMA implants to stabilize the atlantoaxial joint. The time taken for implant application was measured. RESULTS: No significant difference in vertebral body size of the atlas and axis was observed. A significant difference in vertebral canal size was observed between the animals. In biomechanical testing, the SMA-2 implant provided more stabilization, while the SMA-1 implant had lower strength than the conventional method using wires. The application time of wire was the longest, while that of SMA-1 was the shortest. CLINICAL RELEVANCE: SMA implants provide comparable strength and demonstrate superior efficacy compared to conventional dorsal wire fixation of atlantoaxial stabilization. Therefore, SMA implants can be an effective surgical option for AAI.


Assuntos
Articulação Atlantoaxial , Doenças do Cão , Instabilidade Articular , Coelhos , Cães , Animais , Ligas de Memória da Forma , Articulação Atlantoaxial/cirurgia , Instabilidade Articular/cirurgia , Instabilidade Articular/veterinária , Ligamentos , Cadáver , Doenças do Cão/cirurgia
9.
Int J Med Robot ; 19(5): e2554, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37489047

RESUMO

BACKGROUND: Conventional needles lack active mechanisms for large tip deflection to bypass obstacles or guide through a desired trajectory in needle-based procedures, compromising accuracy and effectiveness. METHODS: An active needle with a shape memory alloy (SMA) actuator was designed and evaluated by demonstrating deflections in tissue-mimicking gels. Finite element simulation and real-time needle tip deflection tracking in tissue-mimicking gels were performed. RESULTS: The active needle deflected 50 and 39 mm at 150 mm insertion depth in the liver and prostate mimicking gels, respectively. Reasonable simulation errors of 16.42% and 12.62% in needle deflections and small root mean squared errors of 1.42 and 1.47 mm in deflection tracking were obtained. CONCLUSIONS: The proposed needle produced desirable large tip deflections capable of bypassing obstacles in the insertion path and tracked a preplanned trajectory with minor errors. The finite element study would help optimise needle designs and predict deflections in soft tissues.


Assuntos
Agulhas , Ligas de Memória da Forma , Masculino , Humanos , Análise de Elementos Finitos , Simulação por Computador , Géis
10.
Environ Sci Pollut Res Int ; 30(49): 107498-107516, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37126160

RESUMO

The near-dry electrical discharge machining processes have been conducted using air-mist or gas mist as a dielectric fluid to minimize the environmental impacts. In this article, near-dry electrical discharge machining (NDEDM) experiments have been performed to improve machining performance using an oxygen-mist dielectric fluid, a copper composite electrode, and Cu-Al-Be polycrystalline shape memory alloy (SMA) work materials. The copper composite electrode is made up of 12 wt% silicon carbide and 9 wt% graphite particles. The oxygen-mist pressure (Op), pulse on time (Ton), spark current (Ip), gap voltage (Gv), and flow rate of mixed water (Fr) were used as process parameters, and the material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) were used as performance characteristics. The global optimal alternative solution has been predicted by the PROMETHEE-II (Preference Ranking Organization METhod for Enrichment Evaluations-II) optimization technique. The best combinations of process parameters have been used to examine the microstructure of composite tools and SMA-machined surfaces by scanning electron microscopy (SEM) analysis. The best global optimum settings (oP: 9 bar, Ip: 60 µs, Ip: 12 A, Gv: 40 V, and Fr: 12 ml/min) are predicted to attain optimum machining performance (MRR: 39.049 g/min, TWR: 1.586 g/min, and SR: 1.78 µm). The tool wear rate of the NDEDM process has been significantly reduced by the copper composite electrode due to increasing microhardness, wear resistance, and melting point. When compared to the pure copper electrode tool, the MRR of NDEDM is improved to 21.91%, while the TWR and SR are reduced to 46.66% and 35.02%, respectively.


Assuntos
Cobre , Ligas de Memória da Forma , Ligas , Eletrodos , Oxigênio
11.
Carbohydr Polym ; 314: 120961, 2023 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-37173015

RESUMO

Nitinol (NiTi shape-memory alloy) is an interesting candidate in various medical applications like dental, orthopedic, and cardiovascular devices, owing to its unique mechanical behaviors and proper biocompatibility. The aim of this work is the local controlled delivery of a cardiovascular drug, heparin, loaded onto nitinol treated by electrochemical anodizing and chitosan coating. In this regard, the structure, wettability, drug release kinetics, and cell cytocompatibility of the specimens were analyzed in vitro. The two-stage anodizing process successfully developed a regular nanoporous layer of Ni-Ti-O on nitinol, which considerably decreased the sessile water contact angle and induced hydrophilicity. The application of the chitosan coatings controlled the release of heparin mainly by a diffusional mechanism, where the drug release mechanisms were evaluated by the Higuchi, first-order, zero-order, and Korsmeyer-Pepass models. Human umbilical cord endothelial cells (HUVECs) viability assay also showed the non-cytotoxicity of the samples, so that the best performance was found for the chitosan-coated samples. It is concluded that the designed drug delivery systems are promising for cardiovascular, particularly stent applications.


Assuntos
Quitosana , Nanoporos , Humanos , Quitosana/química , Ligas de Memória da Forma , Heparina/química , Materiais Revestidos Biocompatíveis/farmacologia , Materiais Revestidos Biocompatíveis/química , Células Endoteliais , Ligas/química , Sistemas de Liberação de Medicamentos , Propriedades de Superfície
12.
Sci Rep ; 13(1): 2134, 2023 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-36747043

RESUMO

Exerting a constant load would likely improve orthosis effectiveness in treating knee lateral deviations during childhood and early adolescence. Shape memory alloys are potential candidates for such applications due to their so called pseudoelastic effect. The present study aims to quantitatively define the applicable mechanical loads, in order to reduce treatment duration while avoiding tissular damage and patient discomfort. This is essential for performing a more efficient design of correction devices. We use a patient-specific finite elements model of a pediatric knee to determine safe loading levels. The achievable correction rates are estimated using a stochastic three-dimensional growth model. Results are compared against those obtained for a mechanical stimulus decreasing in proportion to the achieved correction, emulating the behavior of conventional orthoses. A constant flexor moment of 1.1 Nm is estimated to change femorotibial angle at a rate of (7.4 ± 4.6) deg/year (mean ± std). This rate is similar to the achieved by more invasive growth modulation methods, and represents an improvement in the order of 25% in the necessary time for reducing deformities of (10 ± 5) deg by half, as compared with conventional orthoses.


Assuntos
Articulação do Joelho , Ligas de Memória da Forma , Humanos , Criança , Joelho , Aparelhos Ortopédicos , Braquetes , Fenômenos Biomecânicos
13.
Orthop Surg ; 15(4): 1028-1036, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-36797993

RESUMO

OBJECTIVE: At present, the most commonly used filler polymethyl methacrylate (PMMA) has the disadvantages of monomer toxicity, heat and leakage, and cannot be applied in young people. Therefore, finding a minimally invasive and good tissue-compatible alternative material has been a research hotspot in spine surgery in recent years. The aim of this study is to explore whether the memory alloy stent can avoid the complications of bone cement or not. METHODS: Four non-adjacent vertebral bodies of the thoracic and lumbar spine in the 18 10-month-old pigs were selected as the surgical site and were randomly divided into the scaffold group and the bone cement group. The memory alloy scaffold and PMMA (polymethyl methacrylate) bone cement were placed via percutaneous puncture, and intraoperative fluoroscopy and micro-CT were used to observe the changes in the height of scaffolds and bone cement in the vertebral body immediately, 6 weeks, and 12 weeks after operation, the microstructural parameters of the bone trabeculae (bone volume fraction, bone surface volume ratio, bone trabeculae number) were also measured. RESULTS: The memory alloy stent could expand in the vertebral body, and its height gradually increased with time; additionally, the height of the bone cement mass did not change with time (p = 0.00). New bone trabeculae could grow into the scaffold along the gap, and the volume fraction of bone, the volume ratio of bone surface area, and the number of bone trabeculae increased gradually (p = 0.00). However, the volume fraction of bone, the volume ratio of bone surface area, and the number of trabeculae in the cement block decreased gradually (p = 0.00). CONCLUSIONS: Memory alloy scaffolds have dynamic expansion characteristics in vivo, which can effectively avoid the complications of bone cement. Thus, it is beneficial to explore this minimally invasive treatment for vertebral compression fractures.


Assuntos
Fraturas por Compressão , Cifoplastia , Fraturas por Osteoporose , Fraturas da Coluna Vertebral , Vertebroplastia , Animais , Cimentos Ósseos , Fraturas por Compressão/cirurgia , Vértebras Lombares/cirurgia , Vértebras Lombares/lesões , Fraturas por Osteoporose/cirurgia , Polimetil Metacrilato/química , Estudos Retrospectivos , Ligas de Memória da Forma , Fraturas da Coluna Vertebral/cirurgia , Fraturas da Coluna Vertebral/etiologia , Suínos , Resultado do Tratamento , Corpo Vertebral
14.
Soft Robot ; 10(4): 713-723, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-36779989

RESUMO

The majority of sprawling-posture quadrupedal vertebrates, such as geckos and lizards, adopt a cyclical lateral swing pattern of their trunk that is coordinated with limb movements to provide extraordinary flexibility and mobility. Inspired by the gecko's locomotory gait and posture, a gecko-like robot with a flexible spine driven by shape memory alloy (SMA) springs was proposed in this work. The static parameters of the SMA spring were experimentally measured, and the flexible spine driven by SMA springs can be deflected bidirectionally. A kinematic model of the spine mechanism was established, and the mathematical relationship between the thermodynamic behavior of the SMA springs and spinal deflection was systematically analyzed. When a gecko trots with a lateral swing pattern of its trunk, the body and the spine show a standing wave shape and a single-peak C-type curve, respectively. The lateral spine deflection and trotting gait were combined in a collaborative model of a flexible spine and limbs to describe in detail the specific relationships between leg joint variables and spine deflection angle. Planar motion tests of a prototype robot were also conducted by using four high-speed cameras to record the trajectory of each point of the body, which verified the proposed model. From the acquired results, it was demonstrated that, compared with a rigid body, a robot with a flexible spine has a longer stride length, higher speed, and a greatly reduced turning radius.


Assuntos
Lagartos , Robótica , Animais , Ligas de Memória da Forma , Locomoção , Coluna Vertebral
15.
Int J Mol Sci ; 24(3)2023 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-36768774

RESUMO

Shape memory alloys, especially ferromagnetic shape memory alloys, are interesting new materials for the manufacturing of stents. Iron-palladium alloys in particular can be used to manufacture self-expanding temporary stents due to their optimum rate of degradation, which is between that of magnesium and pure iron, two metals commonly used in temporary stent research. In order to avoid blood clotting upon the introduction of the stent, they are often coated with anticoagulants. In this study, sulfated pectin, a heparin mimetic, was synthesized in different ways and used as coating on multiple iron-palladium alloys. The static and dynamic prothrombin time (PT) and activated partial thromboplastin time (APTT) of the prepared materials were compared to samples uncoated or coated with polyethylene glycol. While no large differences were observed in the prothrombin time measurements, the activated partial thromboplastin time increased significantly with all alloys coated with sulfated pectin. Aside from that, sulfated pectin synthesized by different methods also caused slight changes in the activated partial thromboplastin time. These findings show that iron-palladium alloys can be coated with anticoagulants to improve their utility as material for temporary stents. Sulfated pectin was characterized by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy, and the coated alloys by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).


Assuntos
Anticoagulantes , Ligas de Memória da Forma , Paládio , Propriedades de Superfície , Ligas/química , Ferro , Materiais Revestidos Biocompatíveis/farmacologia , Materiais Revestidos Biocompatíveis/química
16.
Comput Methods Biomech Biomed Engin ; 26(8): 952-959, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35855667

RESUMO

The purpose of this investigation was to assess the effects of changing the Nitinol stent's geometrical characteristics on the superelastic behavior of the stent using the finite element method. Four different geometrical parameters were considered and analyzed in sixteen stents. These geometrical parameters consisted of stent length, number of stent's meanders, inside diameter of the stent and wire diameter. Results showed that decreasing either stent length or the number of stent meanders and increasing either the inside diameter of the stent or wire diameter generally result in more sensible superelastic behavior exposure. The effect of changing stent length is independent of the inside diameter and number of the stent's meanders. Effects of changing inside diameter and number of stent's meanders were exactly dependent together. In addition, increasing wire diameter has a great effect on the maximum force. In conclusion, the results of this study may serve as guidelines for future stent design.


Assuntos
Níquel , Ligas de Memória da Forma , Titânio , Stents , Ligas
18.
Int J Comput Assist Radiol Surg ; 18(1): 29-43, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36269508

RESUMO

PURPOSE: The complex and elaborate structure of the urinary system presents surgeons with difficulty in using a ureteroscope with a fixed optical fiber to reach the targeted calculus. To address this challenge, a robotic device is required to control the direction of laser irradiation position independently in ureteroscopes. METHOD: A continuum robotic device was designed and fabricated. The device is constructed with three slackened shape memory alloy (SMA) wires to control the laser irradiation position of the optical fiber combined with the view of the camera on the tip of the ureteroscope. Kinematics analysis and experimental evaluation reveal the capability of the device. RESULTS: The structure of the device is the same as a single-joint continuum robot. This device is unique because of the tiny diameter of 1.1 mm which can be used inside the ureteroscope through a Ø1.2 mm inner channel into the kidney for transurethral ureterolithotripsy. Kinematic analysis revealed the relationship among space coordinates, angles of bending, and direction and SMA wires length. The maximum bending angle was around 25° when the current value was 350 mA on a single SMA wire. The device could achieve multi-directional bending by allocating the values of current on SMA wires, separately. CONCLUSION: This device offers a major advancement in small size and dexterity in medical robotics. Combined with a proper control system, this device could simplify the operation and improve the efficiency of the transurethral ureterolithotripsy.


Assuntos
Robótica , Humanos , Ligas de Memória da Forma , Fenômenos Biomecânicos , Desenho de Equipamento , Rim
19.
Belo Horizonte; s.n; 2023. 64 p. ilus, graf, tab.
Tese em Português | LILACS, BBO - Odontologia | ID: biblio-1509346

RESUMO

A introdução da liga NiTi na endodontia proporcionou a fabricação de instrumentos com excelentes propriedades mecânicas, e uma das principais características é a possibilidade de alteração das temperaturas de transformação da liga, o qual pode possibilitar a presença de martensita em temperatura ambiente e consequentemente um efeito memória de forma. Entretanto, alguns dos sistemas comercializados atualmente possuem pouca ou nenhuma informação científica relatando suas propriedades mecânicas, características de design e métodos de fabricação. O objetivo deste trabalho foi comparar características geométricas, metalúrgicas e propriedades mecânicas (resistência à torção e flexão) de instrumentos Reciproc Blue (VDW, Munique, Alemanha), e quatro sistemas reciprocantes réplicas. Um total de 39 instrumentos de cada um dos sistemas reciprocantes, Reciproc Blue (RB), Prodesign R (PDR), V File (VF), V+ File (V+) e Univy One (UO) foram utilizados na pesquisa. O programa de Image J foi utilizado para mensuração dos diâmetros a cada milímetro da parte ativa e da área da seção transversal a 3 mm da ponta dos instrumentos. Imagens de MEV da parte ativa foram realizados para avaliar o acabamento superficial dos instrumentos. A composição atômica, fases presentes e temperaturas de transformação foram verificadas através de EDS, DRX e DSC, respectivamente. A flexibilidade foi aferida através de ensaios de dobramento até 45º conforme a especificação ISO 3630-1, e os ensaios de resistência à torção foram realizados de acordo com a especificação Nº28 ANSI/ADA. Todos os instrumentos apresentaram uma quantidade aproximadamente equiatômica de níquel e titânio. A análise qualitativa das fases cristalinas realizada através de ensaios de DRX, demonstrou a predominância de Fase R em todos os grupos, com exceção do grupo UO que apresenta uma mistura de fase R e martensita B19'. Na avaliação da área da seção, o instrumento RB obteve valores intermediários, os instrumentos PDR e V+ possuem menores valores e os instrumentos VF e UO possuem maiores valores. Observou-se grande impacto da geometria sobre as propriedades mecânicas, sendo que aqueles sistemas que apresentavam menor área que RB (PDR, V+) mostraram-se mais flexíveis e menos resistentes à torção (p<0.05), e o instrumento VF que teve maior área apresentou, como esperado, menos flexibilidade (p<0.05) e resistência torcional semelhante (p>0.05). A única exceção se deu com o sistema UO, que embora apresentasse uma maior área de seção, mostrou-se mais flexível e menos resistente à torção, provavelmente por influência da maior quantidade de martensita presente à temperatura ambiente. Nenhum dos instrumentos réplicas avaliados apresentaram características e comportamento mecânico iguais ao sistema padrão RB. Sugere-se que mais estudos devem ser realizados para a comparação do comportamento clínico destes instrumentos.


The introduction of NiTi alloy in endodontics has allowed the manufacturing of instruments with excellent mechanical properties, and one of the main characteristics is the ability to change alloy's transformation temperature, which can enable the presence of martensite at room temperature and consequently favor a shape memory effect. However, some of the currently marketed systems have limited or no scientific information regarding their mechanical properties, design characteristics, and manufacturing methods. The aim of this study was to compare the geometric characteristics, metallurgical aspects, and mechanical properties (torsional and flexural strength) of Reciproc Blue instruments (VDW, Munich, Germany) with four replica-like reciprocating systems. A total amount of 39 instruments from each reciprocating system, namely Reciproc Blue (RB), Prodesign R (PDR), V File (VF), V+ File (V+), and Univy One (UO), were used in the study. The Image J program was used to measure the diameters at every millimeter along the instruments active portion and the cross-sectional area at 3 mm from the instrument tip. SEM images of the active portion were obtained to evaluate the surface finishing of the instruments. Atomic composition, phases present, and transformation temperatures were determined through EDS, XRD, and DSC analyses, respectively. Flexibility was assessed by bending tests up to 45° according to ISO 3630-1 specifications, and torsional strength tests were performed according with ANSI/ADA Specification No. 28. All instruments exhibited an approximately equiatomic composition of nickel and titanium. Qualitative analysis of the crystalline phases using XRD tests demonstrated the predominance of the R-phase in all groups, except for the UO group, which exhibited a mixture of Rphase and B19' martensite. In terms of diameter and cross-sectional area evaluation, the RB instrument obtained intermediate values, while the PDR and V+ instruments had smaller values, and the VF and UO instruments had larger values. A significant impact of geometry on mechanical properties was observed, with systems exhibiting a smaller area than RB (PDR, V+) being more flexible and less torsion-resistant (p<0.05), and the VF instrument with a larger area showed, as expected, less flexibility (p<0.05) and similar torsional resistance (p>0.05). The only exception was the UO system, which, despite having a larger geometric configuration, exhibited greater flexibility and less torsional resistance, likely due to the higher amount of martensite present at room temperature. None of the replica-like instruments evaluated showed identical characteristics and mechanical behavior to the standard RB system. Further studies are suggested to compare the clinical performance of these instruments.


Assuntos
Varredura Diferencial de Calorimetria , Endodontia , Torção Mecânica , Ligas de Memória da Forma , Testes Mecânicos
20.
J Long Term Eff Med Implants ; 33(1): 67-74, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36382706

RESUMO

Nitinol is a shape-memory alloy that has many diverse applications in the field of orthopedics. There have been no previous investigations reporting clinical or radiographic outcomes of the use of nitinol staples in the definitive stabilization of the pubic symphysis. A retrospective chart review was completed on 42 patients who underwent operative stabilization of pubic symphyseal disruption at an urban level-1 trauma center. Patients treated with pelvic staples alone, or in conjunction with traditional plates and screws, were compared with those treated without the use of a shape memory alloys. Thirty-four patients were included for final analysis (8 staples and 26 controls) in this investigation. Three of eight patients in the pelvic staple group had implant failures, with two having a loss of reduction (25%); this was not significantly different from the seven hardware failures (P = 0.61) seen in the control group without any loss of reduction (P = 0.17). Failures in the nitinol staple group occurred earlier at 17.3 days compared with the control group at 101.7 days (P = 0.003). There were no significant differences between groups with regards to any of the other pre- or postoperative variables investigated. The use of nitinol staples vs. traditional plate and screw constructs for stabilizing the pubic symphysis did not result in more clinical failures. The hardware failures identified in the nitinol staple group occurred significantly earlier in the postoperative period, and were associated with a loss of reduction of the pubic symphysis.


Assuntos
Sínfise Pubiana , Humanos , Sínfise Pubiana/diagnóstico por imagem , Sínfise Pubiana/cirurgia , Sínfise Pubiana/lesões , Ligas de Memória da Forma , Fixação Interna de Fraturas/métodos , Estudos Retrospectivos , Placas Ósseas
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