ABSTRACT
Objectives: The shape memory resulting from the superelasticity and thermoelastic effect is the main characteristic of thermally activated NiTi archwires and is closely related to the transition temperature range (TTR). The aim of this study was to evaluate the TTR of thermally activated NiTi archwires commercially available. Material and Methods: Seven different brands of 0.019"x0.025" thermally activated nickel-titanium archwires were tested as received by differential scanning calorimetry (DSC) over the temperature range from -100°C to 150°C at 10°C/min. Results: All thermally activated NiTi archwires analyzed presented stage transformation during thermal scanning with final austenitic temperature (Af) ranging from 20.39°C to 45.42°C. Three brands of NiTi archwires presented Af close to the room temperature and, this way, do not present properties of shape memory and pseudoelasticity that are desirable in clinical applications. Conclusions: The thermally activated NiTi archwires present great variability in the TTR and the elastic parameters of each NiTi archwire should be provided by the manufacturers, to allow achievement of the best clinical performance possible. .
Subject(s)
Nickel/chemistry , Orthodontic Wires , Titanium/chemistry , Transition Temperature , Calorimetry, Differential Scanning , Cold Temperature , Elasticity , Hot Temperature , Materials Testing , Reference ValuesABSTRACT
Este artigo sucintamente descreve a evolução da liga metálica inteligente, com memória de forma na área de Saúde. A confecção de grampos de Judet em nitinol ocorreu no Laboratório de Transformação Mecânica da UFRGS (LdTM) e a simples verificação das qualidades superelásticas e de memória de forma foram contempladas no LdTM e no HCPA pela equipe envolvida no projeto. A título de ilustração, demonstramos com um caso clínico a aplicabilidade do grampo de Judet no cenário de instabilidade da parede torácica, a qual, além de prejudicar a mecânica respiratória, apresenta uma alta taxa de mortalidade. Os resultados preliminares evidenciaram a transformação provocada pelo calor, ocasionando o fechamento das garras dos grampos de Judet, que se manteve firme e sem alteração da consistência com o tempo, permitindo antever sua aplicabilidade num modelo experimental. Grampos de Judet em Nitinol são apresentados teoricamente como vantajosos em relação aos já existentes em aço inoxidável 316L, especialmente pela facilidade de manuseio e possível simplificação do procedimento cirúrgico. Detalhes no acabamento permitem a biocompatibilidade e o engenheiro projetista de materiais deve compatibilizar as ligas de níquel e titânio (NiTi) utilizadas nos grampos. O nitinol possui amplo emprego no cenário médico-odontológico e há normas técnicas bem definidas. A epidemiologia do trauma e a gravidade das lesões associadas à instabilidade da parede torácica evidenciam a oportunidade de estudos nessa direção. Concluímos sobre a necessidade de prosseguir para uma avaliação experimental, agregando a mensuração de parâmetros viscosos e viscoelásticos da mecânica respiratória, especialmente em seu componente de parede torácica (cw).
The aim of this article is to briefly describe the incorporation of nitinol (NiTi) an intelligent nickel-titanium alloy presenting shape memory for use in medical applications. Nitinol Judet staples were developed at the Mechanical Processing Laboratory (LdTM) at Universidade Federal do Rio Grande do Sul. Simple confirmation assays of superelasticity and shape memory were performed at the LdTM and Hospital de Clínicas de Porto Alegre by the project team. A clinical case was used to demonstrate the applicability of nitinol Judet staples in the treatment of flail chest, a condition characterized by respiratory mechanics associated with fairly high mortality. The initial observation revealed a transformation resulting from heat exposure causing the closure of staple prongs. With time, the consistency of the Judet staples remained unchanged, indicating the feasibility of an experimental model employing these staples. The advantages of NiTi-made Judet staples in relation to 316L stainless steel staples are outlined, with emphasis on the ease of use and possible simplification of the surgical procedure. Finishing details ensure biocompatibility, with a focus on specific adaptations in the NiTi alloy employed to manufacture the staples; nevertheless, nitinol is widely employed in medicine and dentistry, with well-defined standards. The epidemiology of trauma and the severity of lesions associated with flail chest provide an opportunity for the proposed studies. The experimental assessment of nitinol Judet staples must now address viscosity and viscoelastic parameters of respiratory mechanics, especially concerning the chest wall.