G. Totten, Portland State University, Portland, OR; C. A. R. De Gouvea, L. Carlos Casteletti, Escola de Engenharia de São Carlos-USP-São Carlos-Brazil, São Carlos, Brazil; A. Lombardi Neto, Escola de Engenharia de São Carlos –USP-São Carlos –SP-Brazil, Sao Carlos, SP, Brazil; A. Itiman Filho, CEFETES, Vitoria, Brazil
Nickel-titanium alloys (Nitinol) with “shape memory” are used in some temperature sensible applications such as “on-off” switches, flow control valves and for biomedical and orthodontic applications, where a combination of resistance, flexibility and biocompatibility are desirable. In the case of self-adjustable orthodontic wires the pseudoelastic property or “shape memory alloy” is important to promote the alignment of the dental arches. When an Nitinol thermo-active arc is placed in the oral environment an austenitic transformation is induced by the temperature variation and the arc tends to gradually change back to its original shape and dislocate the tooth to the intended position. To evaluate the shape memory effect in the Nitinol orthodontic wires, three points bending and microhardness tests were performed on specimes dipped in artificial saliva at temperature of 37±1°C. The results obtained in this work showed that the martensitic to austenitic phase transformation in the thermo-active Nitinol wire resulted in a significant increase in the microhardness and bend resistance.
