Journal Article

An evaluation of the transition temperature range of super-elastic orthodontic NiTi springs using differential scanning calorimetry

O Barwart, JM Rollinger and A Burger

in The European Journal of Orthodontics

Published on behalf of European Orthodontics Society

Volume 21, issue 5, pages 497-502
Published in print October 1999 | ISSN: 0141-5387
Published online October 1999 | e-ISSN: 1460-2210 | DOI: http://dx.doi.org/10.1093/ejo/21.5.497
An evaluation of the transition temperature range of super-elastic orthodontic NiTi springs using differential scanning calorimetry

Show Summary Details

Preview

Differential scanning calorimetry (DSC) was used to determine the transition temperature ranges (TTR) of four types of super-elastic orthodontic nickel-titanium coil springs (Sentalloy). A knowledge of the TTR provides information on the temperature at which a NiTi wire or spring can assume superelastic properties and when this quality disappears. The spring types in this study can be distinguished from each other by their characteristic TTR during cooling and heating. For each tested spring type a characteristic TTR during heating (austenite transformation) and cooling (martensite transformation) was evaluated. The hysteresis of the transition temperature, found between cooling and heating, was 3.4-5.2 K. Depending on the spring type the austenite transformation started (As) at 9.7-17.1°C and finished (Af) at 29.2-37°C. The martensite transformation starting temperature (Ms) was evaluated at 32.6-25.4°C, while Mf (martensite transformation finishing temperature) was 12.7-6.5°C.

The results show that the springs become super-elastic when the temperature increases and As is reached. They undergo a loss of super-elastic properties and a rapid decrease in force delivery when they are cooled to Mf. For the tested springs, Mf and As were found to be below room temperature. Thus, at room temperature and some degrees lower, all the tested springs exert super-elastic properties. For orthodontic treatment this means the maintenance of super-elastic behaviour, even when mouth temperature decreases to about room temperature as can occur, for example, during meals.

Journal Article.  0 words. 

Subjects: Restorative Dentistry and Orthodontics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.