Method: Sixty NiTi closed-coil springs with 9 mm length and 0,010” lumen diameter (Morelli®, Brasil) were divided into four groups (n=15) and immersed in 20ml of Deionized Water (control), Listerine® (221ppm of sodium fluoride and pH = 4,03), Plax® (225ppm of sodium fluoride and pH = 5,76) and Oral-B® (without fluoride and pH = 4,28) for 1.5 hours at 37oC. After immersion each coil-spring was extended once from its resting length to 12 mm and then was deactivated. All tests were performed in a 37oC. Forces were recorded at the 12 mm extension and deactivation distances of 9 mm, 6 mm, 3 mm, and 1 mm using a universal test machine. Anova and Tukey´s test (p<0.05) were used to analyze the mechanical testing data. Scanning Electron Microscope (SEM) was used to explore the effects on surface topography of the coil-springs.
Result: Mean peak load forces at 12 mm were not significantly different between groups. Significant differences between groups were found only in the final of superelastic plateau (3 mm) and at 1 mm of deactivation in which the Oral B group presented the higher forces.
Conclusion: Despite the differences found all groups studied presented the desirable orthodontic concepts of “physiological load” and “constant force” during the whole phase of deactivation of the springs, not ranging beyond 0.5 N.